Can walking motions improve visually induced rotational self-motion illusions in virtual reality?

PubMed

Riecke, Bernhard E; Freiberg, Jacob B; Grechkin, Timofey Y

2015-02-04

Illusions of self-motion (vection) can provide compelling sensations of moving through virtual environments without the need for complex motion simulators or large tracked physical walking spaces. Here we explore the interaction between biomechanical cues (stepping along a rotating circular treadmill) and visual cues (viewing simulated self-rotation) for providing stationary users a compelling sensation of rotational self-motion (circular vection). When tested individually, biomechanical and visual cues were similarly effective in eliciting self-motion illusions. However, in combination they yielded significantly more intense self-motion illusions. These findings provide the first compelling evidence that walking motions can be used to significantly enhance visually induced rotational self-motion perception in virtual environments (and vice versa) without having to provide for physical self-motion or motion platforms. This is noteworthy, as linear treadmills have been found to actually impair visually induced translational self-motion perception (Ash, Palmisano, Apthorp, & Allison, 2013). Given the predominant focus on linear walking interfaces for virtual-reality locomotion, our findings suggest that investigating circular and curvilinear walking interfaces offers a promising direction for future research and development and can help to enhance self-motion illusions, presence and immersion in virtual-reality systems. © 2015 ARVO.

Demonstrating Circular Motion with a Model Satellite/Earth System

ERIC Educational Resources Information Center

Whittaker, Jeff

2008-01-01

A number of interesting demonstrations of circular and satellite motion have been described in this journal. This paper presents a variation of a centripetal force apparatus found in G.D. Freier and F.J. Anderson's "A Demonstration Handbook for Physics," which has been modified in order to demonstrate both centripetal force and satellite motion.…

Determination of the Static Friction Coefficient from Circular Motion

ERIC Educational Resources Information Center

Molina-Bolívar, J. A.; Cabrerizo-Vílchez, M. A.

2014-01-01

This paper describes a physics laboratory exercise for determining the coefficient of static friction between two surfaces. The circular motion of a coin placed on the surface of a rotating turntable has been studied. For this purpose, the motion is recorded with a high-speed digital video camera recording at 240 frames s[superscript-1], and the…

Determination of the static friction coefficient from circular motion

NASA Astrophysics Data System (ADS)

Molina-Bolívar, J. A.; Cabrerizo-Vílchez, M. A.

2014-07-01

This paper describes a physics laboratory exercise for determining the coefficient of static friction between two surfaces. The circular motion of a coin placed on the surface of a rotating turntable has been studied. For this purpose, the motion is recorded with a high-speed digital video camera recording at 240 frames s-1, and the videos are analyzed using Tracker video-analysis software, allowing the students to dynamically model the motion of the coin. The students have to obtain the static friction coefficient by comparing the centripetal and maximum static friction forces. The experiment only requires simple and inexpensive materials. The dynamics of circular motion and static friction forces are difficult for many students to understand. The proposed laboratory exercise addresses these topics, which are relevant to the physics curriculum.

Physical Sensing of Surface Properties by Microswimmers--Directing Bacterial Motion via Wall Slip.

PubMed

Hu, Jinglei; Wysocki, Adam; Winkler, Roland G; Gompper, Gerhard

2015-05-20

Bacteria such as Escherichia coli swim along circular trajectories adjacent to surfaces. Thereby, the orientation (clockwise, counterclockwise) and the curvature depend on the surface properties. We employ mesoscale hydrodynamic simulations of a mechano-elastic model of E. coli, with a spherocylindrical body propelled by a bundle of rotating helical flagella, to study quantitatively the curvature of the appearing circular trajectories. We demonstrate that the cell is sensitive to nanoscale changes in the surface slip length. The results are employed to propose a novel approach to directing bacterial motion on striped surfaces with different slip lengths, which implies a transformation of the circular motion into a snaking motion along the stripe boundaries. The feasibility of this approach is demonstrated by a simulation of active Brownian rods, which also reveals a dependence of directional motion on the stripe width.

Crankshaft motion in a highly congested bis(triarylmethyl)peroxide.

PubMed

Khuong, Tinh-Alfredo V; Zepeda, Gerardo; Sanrame, Carlos N; Dang, Hung; Bartberger, Michael D; Houk, K N; Garcia-Garibay, Miguel A

2004-11-17

Crankshaft motion has been proposed in the solid state for molecular fragments consisting of three or more rotors linked by single bonds, whereby the two terminal rotors are static and the internal rotors experience circular motion. Bis-[tri-(3,5-di-tert-butyl)phenylmethyl]-peroxide 2 was tested as a model in search of crankshaft motion at the molecular level. In the case of peroxide 2, the bulky trityl groups may be viewed as the external static rotors, while the two peroxide oxygens can undergo the sought after internal rotation. Evidence for this process in the case of peroxide 2 was obtained from conformational dynamics determined by variable-temperature (13)C and (1)H NMR between 190 and 375 K in toluene-d(8). Detailed spectral assignments for the interpretation of two coalescence processes were based on a correlation between NMR spectra obtained in solution at low temperature, in the solid state by (13)C CPMAS NMR, and by GIAO calculations based on a B3LYP/6-31G structure of 2 obtained from its X-ray coordinates as the input. Evidence supporting crankshaft rotation rather than slippage of the trityl groups was obtained from molecular mechanics calculations.

Physical Sensing of Surface Properties by Microswimmers – Directing Bacterial Motion via Wall Slip

PubMed Central

Hu, Jinglei; Wysocki, Adam; Winkler, Roland G.; Gompper, Gerhard

2015-01-01

Bacteria such as Escherichia coli swim along circular trajectories adjacent to surfaces. Thereby, the orientation (clockwise, counterclockwise) and the curvature depend on the surface properties. We employ mesoscale hydrodynamic simulations of a mechano-elastic model of E. coli, with a spherocylindrical body propelled by a bundle of rotating helical flagella, to study quantitatively the curvature of the appearing circular trajectories. We demonstrate that the cell is sensitive to nanoscale changes in the surface slip length. The results are employed to propose a novel approach to directing bacterial motion on striped surfaces with different slip lengths, which implies a transformation of the circular motion into a snaking motion along the stripe boundaries. The feasibility of this approach is demonstrated by a simulation of active Brownian rods, which also reveals a dependence of directional motion on the stripe width. PMID:25993019

Numerical simulation of temperature at drilling micro-hole on moving CO2 laser irradiated sticking plaster

NASA Astrophysics Data System (ADS)

Rao, Zhiming; He, Zhifang; Du, Jianqiang; Zhang, Xinyou; Ai, Guoping; Zhang, Chunqiang; Wu, Tao

2012-03-01

This paper applied numerical simulation of temperature by using finite element analysis software Ansys to study a model of drilling on sticking plaster. The continuous CO2 laser doing uniform linear motion and doing uniform circular motion irradiated sticking plaster to vaporize. The sticking plaster material was chosen as the thermal conductivity, the heat capacity and the density. For temperatures above 450 °C, sticking plaster would be vaporized. Based on the mathematical model of heat transfer, the process of drilling sticking plaster by laser beams could be simulated by Ansys. The simulation results showed the distribution of the temperature at the surface of the sticking plaster with the time of vaporizing at CO2 laser to do uniform linear motion and to do uniform circular motion. The temperature of sticking plaster CO2 laser to do uniform linear motion was higher than CO2 laser to do uniform circular motion in the same condition.

The transformation of regular circular motion into straight motion according to Nasir al din al-Tusi - a genious model for the conscious preservation of a defect of Ptolemy's lunar theory (German Title: Die Umwandlung gleichförmiger Kreisbewegung in geradlinige Bewegung nach Nasir al din al-Tusi - Ein geniales Modell zur bewußten Beibehaltung eines Mangels der Ptolemäischen Mondtheorie)

NASA Astrophysics Data System (ADS)

Hein, Olaf; Mader, Rolf

Nasir al din al-Tusi (1201-1274) was one of the most important universal scholars of Islam. As a convinced Aristotelian, he rejected Ptolemy's modifications of the Aristotelian dogma of uniform circular motion. He created a theory of lunar motion which is only based on uniform circular motion, and which results in the same representation of lunar motion as conceived by Ptolemy. He successfully attempted to consciously preserve, and not to correct, an error of Ptolemy's theory (the doubling of the earth-moon distance in the syzygies as compared to the quadratures). We explain the Tusi mechanism and point out its philosophical consequences (the unwanted dissolution of the difference between the extra- and intralunar world).

Articulated Multimedia Physics, Lesson 10, Circular Motion.

ERIC Educational Resources Information Center

New York Inst. of Tech., Old Westbury.

As the tenth lesson of the Articulated Multimedia Physics Course, instructional materials relating to circular motion are presented in this study guide. The topics are concerned with instantaneous velocity, centripetal force, centrifugal force, and satellite paths. The content is arranged in scrambled form, and the use of matrix transparencies is…

Classifying Motion.

ERIC Educational Resources Information Center

Duzen, Carl; And Others

1992-01-01

Presents a series of activities that utilizes a leveling device to classify constant and accelerated motion. Applies this classification system to uniform circular motion and motion produced by gravitational force. (MDH)

A computational model for reference-frame synthesis with applications to motion perception.

PubMed

Clarke, Aaron M; Öğmen, Haluk; Herzog, Michael H

2016-09-01

As discovered by the Gestaltists, in particular by Duncker, we often perceive motion to be within a non-retinotopic reference frame. For example, the motion of a reflector on a bicycle appears to be circular, whereas, it traces out a cycloidal path with respect to external world coordinates. The reflector motion appears to be circular because the human brain subtracts the horizontal motion of the bicycle from the reflector motion. The bicycle serves as a reference frame for the reflector motion. Here, we present a general mathematical framework, based on vector fields, to explain non-retinotopic motion processing. Using four types of non-retinotopic motion paradigms, we show how the theory works in detail. For example, we show how non-retinotopic motion in the Ternus-Pikler display can be computed. Copyright © 2015 Elsevier Ltd. All rights reserved.

Topology of the Relative Motion: Circular and Eccentric Reference Orbit Cases

NASA Technical Reports Server (NTRS)

FontdecabaiBaig, Jordi; Metris, Gilles; Exertier, Pierre

2007-01-01

This paper deals with the topology of the relative trajectories in flight formations. The purpose is to study the different types of relative trajectories, their degrees of freedom, and to give an adapted parameterization. The paper also deals with the research of local circular motions. Even if they exist only when the reference orbit is circular, we extrapolate initial conditions to the eccentric reference orbit case.This alternative approach is complementary with traditional approaches in terms of cartesian coordinates or differences of orbital elements.

Seeing Circles and Drawing Ellipses: When Sound Biases Reproduction of Visual Motion

PubMed Central

Aramaki, Mitsuko; Bringoux, Lionel; Ystad, Sølvi; Kronland-Martinet, Richard

2016-01-01

The perception and production of biological movements is characterized by the 1/3 power law, a relation linking the curvature and the velocity of an intended action. In particular, motions are perceived and reproduced distorted when their kinematics deviate from this biological law. Whereas most studies dealing with this perceptual-motor relation focused on visual or kinaesthetic modalities in a unimodal context, in this paper we show that auditory dynamics strikingly biases visuomotor processes. Biologically consistent or inconsistent circular visual motions were used in combination with circular or elliptical auditory motions. Auditory motions were synthesized friction sounds mimicking those produced by the friction of the pen on a paper when someone is drawing. Sounds were presented diotically and the auditory motion velocity was evoked through the friction sound timbre variations without any spatial cues. Remarkably, when subjects were asked to reproduce circular visual motion while listening to sounds that evoked elliptical kinematics without seeing their hand, they drew elliptical shapes. Moreover, distortion induced by inconsistent elliptical kinematics in both visual and auditory modalities added up linearly. These results bring to light the substantial role of auditory dynamics in the visuo-motor coupling in a multisensory context. PMID:27119411

Measuring the circular motion of small objects using laser stroboscopic images.

PubMed

Wang, Hairong; Fu, Y; Du, R

2008-01-01

Measuring the circular motion of a small object, including its displacement, speed, and acceleration, is a challenging task. This paper presents a new method for measuring repetitive and/or nonrepetitive, constant speed and/or variable speed circular motion using laser stroboscopic images. Under stroboscopic illumination, each image taken by an ordinary camera records multioutlines of an object in motion; hence, processing the stroboscopic image will be able to extract the motion information. We built an experiment apparatus consisting of a laser as the light source, a stereomicroscope to magnify the image, and a normal complementary metal oxide semiconductor camera to record the image. As the object is in motion, the stroboscopic illumination generates a speckle pattern on the object that can be recorded by the camera and analyzed by a computer. Experimental results indicate that the stroboscopic imaging is stable under various conditions. Moreover, the characteristics of the motion, including the displacement, the velocity, and the acceleration can be calculated based on the width of speckle marks, the illumination intensity, the duty cycle, and the sampling frequency. Compared with the popular high-speed camera method, the presented method may achieve the same measuring accuracy, but with much reduced cost and complexity.

Wiimote Experiments: Circular Motion

ERIC Educational Resources Information Center

Kouh, Minjoon; Holz, Danielle; Kawam, Alae; Lamont, Mary

2013-01-01

The advent of new sensor technologies can provide new ways of exploring fundamental physics. In this paper, we show how a Wiimote, which is a handheld remote controller for the Nintendo Wii video game system with an accelerometer, can be used to study the dynamics of circular motion with a very simple setup such as an old record player or a…

Wiimote Experiments: Circular Motion

NASA Astrophysics Data System (ADS)

Kouh, Minjoon; Holz, Danielle; Kawam, Alae; Lamont, Mary

2013-03-01

The advent of new sensor technologies can provide new ways of exploring fundamental physics. In this paper, we show how a Wiimote, which is a handheld remote controller for the Nintendo Wii video game system with an accelerometer, can be used to study the dynamics of circular motion with a very simple setup such as an old record player or a bicycle wheel.

Projectile and Circular Motion: A Model Four-Week Unit of Study for a High School Physics Class Using Physics Courseware.

ERIC Educational Resources Information Center

Geigel, Joan; And Others

A self-paced program designed to integrate the use of computers and physics courseware into the regular classroom environment is offered for physics high school teachers in this module on projectile and circular motion. A diversity of instructional strategies including lectures, demonstrations, videotapes, computer simulations, laboratories, and…

Janus Colloids Actively Rotating on the Surface of Water.

PubMed

Wang, Xiaolu; In, Martin; Blanc, Christophe; Würger, Alois; Nobili, Maurizio; Stocco, Antonio

2017-12-05

Biological or artificial microswimmers move performing trajectories of different kinds such as rectilinear, circular, or spiral ones. Here, we report on circular trajectories observed for active Janus colloids trapped at the air-water interface. Circular motion is due to asymmetric and nonuniform surface properties of the particles caused by fabrication. Motion persistence is enhanced by the partial wetted state of the Janus particles actively moving in two dimensions at the air-water interface. The slowing down of in-plane and out-of-plane rotational diffusions is described and discussed.

Rotary motion impairs attention to color change in 4-month-old infants.

PubMed

Kavšek, Michael

2013-06-01

Continuous color changes of an array of elements appear to stop changing if the array undergoes a coherent motion. This silencing illusion was demonstrated for adults by Suchow and Alvarez (Current Biology, 2011, vol. 21, pp. 140-143). The current forced-choice preferential looking study examined 4-month-old infants' sensitivity to the silencing illusion. Two experimental conditions were conducted. In the dynamic condition, infants were tested with two rotating rings of circular different-colored dots. In one of these rings the dots continuously changed color, whereas in the other ring the dots did not change color. In the static condition, the global rotary motion was eliminated from the targets. Infants preferred looking at the color-changing target in the static condition but not in the dynamic condition; they attended to the color changes in the static condition but failed to detect them in the dynamic condition. This differential looking pattern is consistent with the hypothesis that the silencing illusion can be established during early infancy. A control group of adults also responded to the silencing phenomenon. This substantiates that the stimuli generate a robust illusory effect. Copyright © 2013 Elsevier Inc. All rights reserved.

Using a Computer Microphone Port to Study Circular Motion: Proposal of a Secondary School Experiment

ERIC Educational Resources Information Center

Soares, A. A.; Borcsik, F. S.

2016-01-01

In this work we present an inexpensive experiment proposal to study the kinematics of uniform circular motion in a secondary school. We used a PC sound card to connect a homemade simple sensor to a computer and used the free sound analysis software "Audacity" to record experimental data. We obtained quite good results even in comparison…

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Jing; Hu, Jiawei; Yu, Hongwei, E-mail: hwyu@hunnu.edu.cn

We study the spontaneous excitation of a circularly accelerated atom coupled with vacuum Dirac field fluctuations by separately calculating the contribution to the excitation rate of vacuum fluctuations and a cross term which involves both vacuum fluctuations and radiation reaction, and demonstrate that although the spontaneous excitation for the atom in its ground state would occur in vacuum, such atoms in circular motion do not perceive a pure thermal radiation as their counterparts in linear acceleration do since the transition rates of the atom do not contain the Planckian factor characterizing a thermal bath. We also find that the contributionmore » of the cross term that plays the same role as that of radiation reaction in the scalar and electromagnetic fields cases differs for atoms in circular motion from those in linear acceleration. This suggests that the conclusion drawn for atoms coupled with the scalar and electromagnetic fields that the contribution of radiation reaction to the mean rate of change of atomic energy does not vary as the trajectory of the atom changes from linear acceleration to circular motion is not a general trait that applies to the Dirac field where the role of radiation reaction is played by the cross term. - Highlights: • Spontaneous excitation of a circularly accelerated atom is studied. • The atom interacts with the Dirac field through nonlinear coupling. • A cross term involving vacuum fluctuations and radiation reaction contributes. • The atom in circular motion does not perceive pure thermal radiation. • The contribution of the cross term changes as the atomic trajectory varies.« less

The effect of transponder motion on the accuracy of the Calypso Electromagnetic localization system.

PubMed

Murphy, Martin J; Eidens, Richard; Vertatschitsch, Edward; Wright, J Nelson

2008-09-01

To determine position and velocity-dependent effects in the overall accuracy of the Calypso Electromagnetic localization system, under conditions that emulate transponder motion during normal free breathing. Three localization transponders were mounted on a remote-controlled turntable that could move the transponders along a circular trajectory at speeds up to 3 cm/s. A stationary calibration established the coordinates of multiple points on each transponder's circular path. Position measurements taken while the transponders were in motion at a constant speed were then compared with the stationary coordinates. No statistically significant changes in the transponder positions in (x,y,z) were detected when the transponders were in motion. The accuracy of the localization system is unaffected by transponder motion.

Inertial migration of particles in Taylor-Couette flows

NASA Astrophysics Data System (ADS)

Majji, Madhu V.; Morris, Jeffrey F.

2018-03-01

An experimental study of inertial migration of neutrally buoyant particles in the circular Couette flow (CCF), Taylor vortex flow (TVF) and wavy vortex flow (WVF) is reported. This work considers a concentric cylinder Taylor-Couette device with a stationary outer cylinder and rotating inner cylinder. The device has a radius ratio of η = ri/ro = 0.877, where ri and ro are the inner and outer radii of the flow annulus. The ratio of the annular width between the cylinders (δ = ro - ri) and the particle diameter (dp) is α = δ/dp = 20. For η = 0.877, the flow of a Newtonian fluid undergoes transitions from CCF to TVF and TVF to WVF at Reynolds numbers Re = 120 and 151, respectively, and for the dilute suspensions studied here, these critical Reynolds numbers are almost unchanged. In CCF, particles were observed to migrate, due to the competition between the shear gradient of the flow and the wall interactions, to an equilibrium location near the middle of the annulus with an offset toward the inner cylinder. In TVF, the vortex motion causes the particles to be exposed to the shear gradient and wall interactions in a different manner, resulting in a circular equilibrium region in each vortex. The radius of this circular region grows with increase in Re. In WVF, the azimuthal waviness results in fairly well-distributed particles across the annulus.

On the local standard of rest

NASA Technical Reports Server (NTRS)

Yuan, C.

1982-01-01

Under the influence of a spiral gravitational field, there should be differences among the mean motions of different types of objects with different dispersion velocities in a sipral galaxy. The old stars with high dispersion velocity should have essentially no mean motion normal to the galactic rotation. On the other hand, young objects and interstellar gas may be moving relative to the old stars at a velocity of a few kilometer per second in both the radial (galacto-centric), and circular directions, depending on the spiral model adopted. Such a velocity is usually referred as the systematic motion or the streaming motion. The conventionally adopted local standard of rest is indeed co-moving with the young objects of the solar vicinity. Therefore, it has a net systematic motion with respect to the circular motion of an equilibrium galactic model, defined by the old stars.

Analytical treatment of particle motion in circularly polarized slab-mode wave fields

NASA Astrophysics Data System (ADS)

Schreiner, Cedric; Vainio, Rami; Spanier, Felix

2018-02-01

Wave-particle interaction is a key process in particle diffusion in collisionless plasmas. We look into the interaction of single plasma waves with individual particles and discuss under which circumstances this is a chaotic process, leading to diffusion. We derive the equations of motion for a particle in the fields of a magnetostatic, circularly polarized, monochromatic wave and show that no chaotic particle motion can arise under such circumstances. A novel and exact analytic solution for the equations is presented. Additional plasma waves lead to a breakdown of the analytic solution and chaotic particle trajectories become possible. We demonstrate this effect by considering a linearly polarized, monochromatic wave, which can be seen as the superposition of two circularly polarized waves. Test particle simulations are provided to illustrate and expand our analytical considerations.

Effect of rotation rate on the forces of a rotating cylinder: Simulation and control

NASA Technical Reports Server (NTRS)

Burns, John A.; Ou, Yuh-Roung

1993-01-01

In this paper we present numerical solutions to several optimal control problems for an unsteady viscous flow. The main thrust of this work is devoted to simulation and control of an unsteady flow generated by a circular cylinder undergoing rotary motion. By treating the rotation rate as a control variable, we can formulate two optimal control problems and use a central difference/pseudospectral transform method to numerically compute the optimal control rates. Several types of rotations are considered as potential controls, and we show that a proper synchronization of forcing frequency with the natural vortex shedding frequency can greatly influence the flow. The results here indicate that using moving boundary controls for such systems may provide a feasible mechanism for flow control.

Swimming trajectories of a three-sphere microswimmer near a wall

NASA Astrophysics Data System (ADS)

Daddi-Moussa-Ider, Abdallah; Lisicki, Maciej; Hoell, Christian; Löwen, Hartmut

2018-04-01

The hydrodynamic flow field generated by self-propelled active particles and swimming microorganisms is strongly altered by the presence of nearby boundaries in a viscous flow. Using a simple model three-linked sphere swimmer, we show that the swimming trajectories near a no-slip wall reveal various scenarios of motion depending on the initial orientation and the distance separating the swimmer from the wall. We find that the swimmer can either be trapped by the wall, completely escape, or perform an oscillatory gliding motion at a constant mean height above the wall. Using a far-field approximation, we find that, at leading order, the wall-induced correction has a source-dipolar or quadrupolar flow structure where the translational and angular velocities of the swimmer decay as inverse third and fourth powers with distance from the wall, respectively. The resulting equations of motion for the trajectories and the relevant order parameters fully characterize the transition between the states and allow for an accurate description of the swimming behavior near a wall. We demonstrate that the transition between the trapping and oscillatory gliding states is first order discontinuous, whereas the transition between the trapping and escaping states is continuous, characterized by non-trivial scaling exponents of the order parameters. In order to model the circular motion of flagellated bacteria near solid interfaces, we further assume that the spheres can undergo rotational motion around the swimming axis. We show that the general three-dimensional motion can be mapped onto a quasi-two-dimensional representational model by an appropriate redefinition of the order parameters governing the transition between the swimming states.

GENERAL: Application of Symplectic Algebraic Dynamics Algorithm to Circular Restricted Three-Body Problem

NASA Astrophysics Data System (ADS)

Lu, Wei-Tao; Zhang, Hua; Wang, Shun-Jin

2008-07-01

Symplectic algebraic dynamics algorithm (SADA) for ordinary differential equations is applied to solve numerically the circular restricted three-body problem (CR3BP) in dynamical astronomy for both stable motion and chaotic motion. The result is compared with those of Runge-Kutta algorithm and symplectic algorithm under the fourth order, which shows that SADA has higher accuracy than the others in the long-term calculations of the CR3BP.

Biomechanical analysis of the circular friction hand massage.

PubMed

Ryu, Jeseong; Son, Jongsang; Ahn, Soonjae; Shin, Isu; Kim, Youngho

2015-01-01

A massage can be beneficial to relieve muscle tension on the neck and shoulder area. Various massage systems have been developed, but their motions are not uniform throughout different body parts nor specifically targeted to the neck and shoulder areas. Pressure pattern and finger movement trajectories of the circular friction hand massage on trapezius, levator scapulae, and deltoid muscles were determined to develop a massage system that can mimic the motion and the pressure of the circular friction massage. During the massage, finger movement trajectories were measured using a 3D motion capture system, and finger pressures were simultaneously obtained using a grip pressure sensor. Results showed that each muscle had different finger movement trajectory and pressure pattern. The trapezius muscle experienced a higher pressure, longer massage time (duration of pressurization), and larger pressure-time integral than the other muscles. These results could be useful to design a better massage system simulating human finger movements.

Multiple Long-Time Solutions for Intermediate Reynolds Number Flow past a Circular Cylinder with a Nonlinear Inertial and Dissipative Attachment

NASA Astrophysics Data System (ADS)

Blanchard, Antoine B. E.; Bergman, Lawrence A.; Vakakis, Alexander F.; Pearlstein, Arne J.

2016-11-01

We consider two-dimensional flow past a linearly-sprung cylinder allowed to undergo rectilinear motion normal to the mean flow, with an attached "nonlinear energy sink" consisting of a mass allowed to rotate about the cylinder axis, and whose rotational motion is linearly damped by a viscous damper. For Re < 50, where the flow is expected to be two-dimensional, we use different inlet transients to identify multiple long-time solutions, and to study how they depend on Re and a dimensionless spring constant. For fixed values of the ratio of cylinder density to fluid density, dimensionless damping coefficient, and ratio of the rotating mass to the total mass, we find that different inlet transients lead to different long-time solutions, including solutions that are steady and symmetric (with a motionless cylinder), time-periodic, quasi-periodic, and chaotic. The results show that over a wide range of the parameters, the steady symmetric motionless-cylinder solution is locally, but not globally, stable. Supported by NSF Grant CMMI-1363231.

Stochastic particle instability for electron motion in combined helical wiggler, radiation, and longitudinal wave fields

NASA Astrophysics Data System (ADS)

Davidson, Ronald C.; McMullin, Wayne A.

1982-07-01

The relativistic motion of an electron is calculated in the combined fields of a transverse helical wiggler field (axial wavelength is λ0=2πk0) and the constant-amplitude, circularly polarized primary electromagnetic wave (δBT,ω,k) propagating in the z direction. For particle velocity near the beat-wave phase velocity ω(k+k0) of the primary wave, it is shown that the presence of a second, moderate-amplitude longitudinal wave (δÊL,ω,k) or transverse electromagnetic wave (δB2,ω2,k2) can lead to stochastic particle instability in which particles trapped near the separatrix of the primary wave undergo a systematic departure from the potential well. The condition for onset of instability is calculated, and the importance of these results for free-electron-laser (FEL) application is discussed. For development of long-pulse or steady-state free-electron lasers, the maintenance of beam integrity for an extended period of time will be of considerable practical importance. The fact that the presence of secondary, moderate-amplitude longitudinal or transverse electromagnetic waves can destroy coherent motion for certain classes of beam particles moving with velocity near ω(k+k0) may lead to a degradation of beam quality and concomitant modification of FEL emission properties.

Relationship between selected orientation rest frame, circular vection and space motion sickness

NASA Technical Reports Server (NTRS)

Harm, D. L.; Parker, D. E.; Reschke, M. F.; Skinner, N. C.

1998-01-01

Space motion sickness (SMS) and spatial orientation and motion perception disturbances occur in 70-80% of astronauts. People select "rest frames" to create the subjective sense of spatial orientation. In microgravity, the astronaut's rest frame may be based on visual scene polarity cues and on the internal head and body z axis (vertical body axis). The data reported here address the following question: Can an astronaut's orientation rest frame be related and described by other variables including circular vection response latencies and space motion sickness? The astronaut's microgravity spatial orientation rest frames were determined from inflight and postflight verbal reports. Circular vection responses were elicited by rotating a virtual room continuously at 35 degrees/s in pitch, roll and yaw with respect to the astronaut. Latency to the onset of vection was recorded from the time the crew member opened their eyes to the onset of vection. The astronauts who used visual cues exhibited significantly shorter vection latencies than those who used internal z axis cues. A negative binomial regression model was used to represent the observed total SMS symptom scores for each subject for each flight day. Orientation reference type had a significant effect, resulting in an estimated three-fold increase in the expected motion sickness score on flight day 1 for astronauts who used visual cues. The results demonstrate meaningful classification of astronauts' rest frames and their relationships to sensitivity to circular vection and SMS. Thus, it may be possible to use vection latencies to predict SMS severity and duration.

Wave drift damping acting on multiple circular cylinders (model tests)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kinoshita, Takeshi; Sunahara, Shunji; Bao, W.

1995-12-31

The wave drift damping for the slow drift motion of a four-column platform is experimentally investigated. The estimation of damping force of the slow drift motion of moored floating structures in ocean waves, is one of the most important topics. Bao et al. calculated an interaction of multiple circular cylinders based on the potential flow theory, and showed that the wave drift damping is significantly influenced by the interaction between cylinders. This calculation method assumes that the slow drift motion is approximately replaced by steady current, that is, structures on slow drift motion are supposed to be equivalent to onesmore » in both regular waves and slow current. To validate semi-analytical solutions of Bao et al., experiments were carried out. At first, added resistance due to waves acting on a structure composed of multiple (four) vertical circular cylinders fixed to a slowly moving carriage, was measured in regular waves. Next, the added resistance of the structure moored by linear spring to the slowly moving carriage were measured in regular waves. Furthermore, to validate the assumption that the slow drift motion is replaced by steady current, free decay tests in still water and in regular waves were compared with the simulation of the slow drift motion using the wave drift damping coefficient obtained by the added resistance tests.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Jing; Key Laboratory of Low Dimensional Quantum Structures and Quantum Control of Ministry of Education, Hunan Normal University, Changsha, Hunan 410081; Yu, Hongwei, E-mail: hwyu@hunnu.edu.cn

We study the spontaneous excitation of a detector (modeled by a two-level atom) in circular motion coupled nonlinearly to vacuum massless Rarita–Schwinger fields in the ultrarelativistic limit and demonstrate that the spontaneous excitation occurs for ground-state atoms in circular motion in vacuum but the excitation rate is not of a pure thermal form as that of the atoms in linear uniform acceleration. An interesting feature is that terms of odd powers in acceleration appear in the excitation rate whereas in the linear acceleration case there are only terms of even powers present. On the other hand, what makes the presentmore » case unique in comparison to the atom’s coupling to other fields that are previously studied is the appearance of the terms proportional to the seventh and ninth powers of acceleration in the mean rate of change of atomic energy which are absent in the scalar, electromagnetic and Dirac field cases. -- Highlights: •Circular Unruh effect for detector coupled to Rarita–Schwinger field. •Nonlinear coupling between the detector and the fields. •Detector in circular motion does not feel pure thermal bath. •Excitation rate contains terms of odd powers in acceleration.« less

Size-dependent quantum diffusion of Gd atoms within Fe nano-corrals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hu, J.; Cao, R. X.; Miao, B. F.

2013-12-01

We systematically studied the size-dependent quantum diffusion of Gd atoms within Fe circular quantum corrals on Ag(111). By varying the size of the quantum corrals, different types of patterns are observed inside the corrals, including a single dot and circular orbits for the diffusion of Gd adatoms. In addition, the motion of the adatoms also forms circular-like orbits outside the corral. Via quantitative analysis, we confirm that the regions with adatoms' high visiting probability are consistent with the positions of the local electronic density-of-states maxima, both inside and outside the corrals within a < 0.2 nm offset. The results agreemore » well with kinetic Monte Carlo simulations that utilize the experimentally determined interaction between Gd and Fe circular corrals. These findings demonstrate that one can engineer adatom motion by controlling the size of the quantum corrals.« less

Inquiry style interactive virtual experiments: a case on circular motion

NASA Astrophysics Data System (ADS)

Zhou, Shaona; Han, Jing; Pelz, Nathaniel; Wang, Xiaojun; Peng, Liangyu; Xiao, Hua; Bao, Lei

2011-11-01

Interest in computer-based learning, especially in the use of virtual reality simulations is increasing rapidly. While there are good reasons to believe that technologies have the potential to improve teaching and learning, how to utilize the technology effectively in teaching specific content difficulties is challenging. To help students develop robust understandings of correct physics concepts, we have developed interactive virtual experiment simulations that have the unique feature of enabling students to experience force and motion via an analogue joystick, allowing them to feel the applied force and simultaneously see its effects. The simulations provide students learning experiences that integrate both scientific representations and low-level sensory cues such as haptic cues under a single setting. In this paper, we introduce a virtual experiment module on circular motion. A controlled study has been conducted to evaluate the impact of using this virtual experiment on students' learning of force and motion in the context of circular motion. The results show that the interactive virtual experiment method is preferred by students and is more effective in helping students grasp the physics concepts than the traditional education method such as problem-solving practices. Our research suggests that well-developed interactive virtual experiments can be useful tools in teaching difficult concepts in science.

On the local standard of rest. [comoving with young objects in gravitational field of spiral galaxies

NASA Technical Reports Server (NTRS)

Yuan, C.

1983-01-01

Under the influence of a spiral gravitational field, there should be differences among the mean motions of different types of objects with different dispersion velocities in a spiral galaxy. The old stars with high dispersion velocity should have essentially no mean motion normal to the galactic rotation. On the other hand, young objects and interstellar gas may be moving relative to the old stars at a velocity of a few kilometer per second in both the radial (galacto-centric), and circular directions, depending on the spiral model adopted. Such a velocity is usually referred as the systematic motion or the streaming motion. The conventionally adopted local standard of rest is indeed co-moving with the young objects of the solar vicinity. Therefore, it has a net systematic motion with respect to the circular motion of an equilibrium galactic model, defined by the old stars. Previously announced in STAR as N83-24443

Nonlinear gyrotropic motion of skyrmion in a magnetic nanodisk

NASA Astrophysics Data System (ADS)

Chen, Yi-fu; Li, Zhi-xiong; Zhou, Zhen-wei; Xia, Qing-lin; Nie, Yao-zhuang; Guo, Guang-hua

2018-07-01

We study the nonlinear gyrotropic motion of a magnetic skyrmion in a nanodisk by means of micromagnetic simulations. The skyrmion is driven by a linearly polarized harmonic field with the frequency of counterclockwise gyrotropic mode. It is found that the motion of the skyrmion displays different patterns with increasing field amplitude. In the linear regime of weak driving field, the skyrmion performs a single counterclockwise gyrotropic motion. The guiding center of the skyrmion moves along a helical line from the centre of the nanodisk to a stable circular orbit. The stable orbital radius increases linearly with the field amplitude. When the driving field is larger than a critical value, the skyrmion exhibits complex nonlinear motion. With the advance of time, the motion trajectory of the skyrmion goes through a series of evolution process, from a single circular motion to a bird nest-like and a flower-like trajectory and finally, to a gear-like steady-state motion. The frequency spectra show that except the counterclockwise gyrotropic mode, the clockwise gyrotropic mode is also nonlinearly excited and its amplitude increases with time. The complex motion trajectory of the skyrmion is the result of superposition of the two gyrotropic motions with changing amplitude. Both the linear and nonlinear gyrotropic motions of the skyrmion can be well described by a generalized Thiele's equation of motion.

Modification of equation of motion of fluid-conveying pipe for laminar and turbulent flow profiles

NASA Astrophysics Data System (ADS)

Guo, C. Q.; Zhang, C. H.; Païdoussis, M. P.

2010-07-01

Considering the non-uniformity of the flow velocity distribution in fluid-conveying pipes caused by the viscosity of real fluids, the centrifugal force term in the equation of motion of the pipe is modified for laminar and turbulent flow profiles. The flow-profile-modification factors are found to be 1.333, 1.015-1.040 and 1.035-1.055 for laminar flow in circular pipes, turbulent flow in smooth-wall circular pipes and turbulent flow in rough-wall circular pipes, respectively. The critical flow velocities for divergence in the above-mentioned three cases are found to be 13.4%, 0.74-1.9% and 1.7-2.6%, respectively, lower than that with plug flow, while those for flutter are even lower, which could reach 36% for the laminar flow profile. By introducing two new concepts of equivalent flow velocity and equivalent mass, fluid-conveying pipe problems with different flow profiles can be solved with the equation of motion for plug flow.

Stop Faking It! Finally Understanding Science So You Can Teach It. Force and Motion.

ERIC Educational Resources Information Center

Robertson, William C.

This book aims to develop an understanding of basic physics concepts among school teachers in grades 3-8. The concepts covered in this book include force, motion, gravity, and circular motion without intimidating detailed units and formulas. Chapters include: (1) "Newton's First One"; (2) "In Which We Describe Motion and Then Change…

Self-Paced Physics, Segment 18.

ERIC Educational Resources Information Center

New York Inst. of Tech., Old Westbury.

Eighty-seven problems are included in this volume which is arranged to match study segments 2 through 14. The subject matter is related to projectiles, simple harmonic motion, kinetic friction, multiple pulley arrangements, motion on inclined planes, circular motion, potential energy, kinetic energy, center of mass, Newton's laws, elastic and…

Project Physics Tests 1, Concepts of Motion.

ERIC Educational Resources Information Center

Harvard Univ., Cambridge, MA. Harvard Project Physics.

Test items relating to Project Physics Unit 1 are presented in this booklet, consisting of 70 multiple-choice and 20 problem-and-essay questions. Concepts of motion are examined with respect to velocities, acceleration, forces, vectors, Newton's laws, and circular motion. Suggestions are made for time consumption in answering some items. Besides…

Circular stapler introducer: a novel device to facilitate stapled colorectal anastomosis.

PubMed

Guweidhi, Ahmed; Steffen, Rudolf; Metzger, Alejandro; Teuscher, Jürg; Flückiger, Petra; Z'graggen, Kaspar

2009-04-01

A circular stapler introducer was developed to protect the head of the circular stapler and enable atraumatic introduction and advancement of the circular stapler without interfering with the application and safety of an anastomosis. In a Phase I prospective study, we tested the feasibility and safety of the novel circular stapler introducer device in 60 consecutive patients undergoing left-sided colorectal resections. The median distance of the anastomoses from the anal verge was 12 cm (7-20, n = 60). Total morbidity was 15 percent. No mortality was observed. Handling of the circular stapler introducer was considered nonproblematic by all surgeons who participated in the study. No interference of the circular stapler introducer with the circular stapling devices used was encountered. The advancement of the stapler into the end of the colorectal stump was always possible with the aid of the circular stapler introducer. Use of the circular stapler introducer facilitates the double-stapling technique of colorectal anastomosis. The circular stapler introducer has great potential and should be tested in larger studies.

Loading system mechanism for dielectric elastomer generators with equi-biaxial state of deformation

NASA Astrophysics Data System (ADS)

Fontana, M.; Moretti, G.; Lenzo, B.; Vertechy, R.

2014-03-01

Dielectric Elastomer Generators (DEGs) are devices that employ a cyclically variable membrane capacitor to produce electricity from oscillating sources of mechanical energy. Capacitance variation is obtained thanks to the use of dielectric and conductive layers that can undergo different states of deformation including: uniform or non-uniform and uni- or multi-axial stretching. Among them, uniform equi-biaxial stretching is reputed as being the most effective state of deformation that maximizes the amount of energy that can be extracted in a cycle by a unit volume of Dielectric Elastomer (DE) material. This paper presents a DEG concept, with linear input motion and tunable impedance, that is based on a mechanical loading system for inducing uniform equi-biaxial states of deformation. The presented system employs two circular DE membrane capacitors that are arranged in an agonist-antagonist configuration. An analytical model of the overall system is developed and used to find the optimal design parameters that make it possible to tune the elastic response of the generator over the range of motion of interest. An apparatus is developed for the equi-biaxial testing of DE membranes and used for the experimental verification of the employed numerical models.

Collective circular motion in synchronized and balanced formations with second-order rotational dynamics

NASA Astrophysics Data System (ADS)

Jain, Anoop; Ghose, Debasish

2018-01-01

This paper considers collective circular motion of multi-agent systems in which all the agents are required to traverse different circles or a common circle at a prescribed angular velocity. It is required to achieve these collective motions with the heading angles of the agents synchronized or balanced. In synchronization, the agents and their centroid have a common velocity direction, while in balancing, the movement of agents causes the location of the centroid to become stationary. The agents are initially considered to move at unit speed around individual circles at different angular velocities. It is assumed that the agents are subjected to limited communication constraints, and exchange relative information according to a time-invariant undirected graph. We present suitable feedback control laws for each of these motion coordination tasks by considering a second-order rotational dynamics of the agent. Simulations are given to illustrate the theoretical findings.

Polynomial expansions of single-mode motions around equilibrium points in the circular restricted three-body problem

NASA Astrophysics Data System (ADS)

Lei, Hanlun; Xu, Bo; Circi, Christian

2018-05-01

In this work, the single-mode motions around the collinear and triangular libration points in the circular restricted three-body problem are studied. To describe these motions, we adopt an invariant manifold approach, which states that a suitable pair of independent variables are taken as modal coordinates and the remaining state variables are expressed as polynomial series of them. Based on the invariant manifold approach, the general procedure on constructing polynomial expansions up to a certain order is outlined. Taking the Earth-Moon system as the example dynamical model, we construct the polynomial expansions up to the tenth order for the single-mode motions around collinear libration points, and up to order eight and six for the planar and vertical-periodic motions around triangular libration point, respectively. The application of the polynomial expansions constructed lies in that they can be used to determine the initial states for the single-mode motions around equilibrium points. To check the validity, the accuracy of initial states determined by the polynomial expansions is evaluated.

Nonlinear Drift-Kinetic Equation in the Presence of a Circularly Polarized Wave

NASA Technical Reports Server (NTRS)

Khazanov, G. V.; Krivorutsky, E. N.; Whitaker, Ann F. (Technical Monitor)

2001-01-01

Equations of the single particle motion and nonlinear kinetic equation for plasma in the presence of a circularly polarized wave of arbitrary frequency in the drift approximation are presented. The nonstationarity and inhomogeneity of the plasma-wave system are taken into account.

EFFECTS OF NON-CIRCULAR MOTIONS ON AZIMUTHAL COLOR GRADIENTS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Martinez-Garcia, Eric E.; Gonzalez-Lopezlira, Rosa A.; Gomez, Gilberto C., E-mail: emartinez@cida.v, E-mail: r.gonzalez@crya.unam.m, E-mail: g.gomez@crya.unam.m

2009-12-20

Assuming that density waves trigger star formation, and that young stars preserve the velocity components of the molecular gas where they are born, we analyze the effects that non-circular gas orbits have on color gradients across spiral arms. We try two approaches, one involving semianalytical solutions for spiral shocks, and another with magnetohydrodynamic (MHD) numerical simulation data. We find that, if non-circular motions are ignored, the comparison between observed color gradients and stellar population synthesis models would in principle yield pattern speed values that are systematically too high for regions inside corotation, with the difference between the real and themore » measured pattern speeds increasing with decreasing radius. On the other hand, image processing and pixel averaging result in systematically lower measured spiral pattern speed values, regardless of the kinematics of stellar orbits. The net effect is that roughly the correct pattern speeds are recovered, although the trend of higher measured OMEGA{sub p} at lower radii (as expected when non-circular motions exist but are neglected) should still be observed. We examine the MartInez-GarcIa et al. photometric data and confirm that this is indeed the case. The comparison of the size of the systematic pattern speed offset in the data with the predictions of the semianalytical and MHD models corroborates that spirals are more likely to end at outer Lindblad resonance, as these authors had already found.« less

Possible microplate generation at RRR triple junctions due to the non-circular finite motion of plates relative to each other

NASA Astrophysics Data System (ADS)

Cronin, V. S.

2012-12-01

First generation ideas of the kinematic stability of triple junctions lead to the common belief that the geometry of ridge-ridge-ridge (RRR) triple junctions remains constant over time under conditions of symmetric spreading. Given constant relative motion between each plate pair -- that is, the pole of plate relative motion is fixed to both plates in each pair during finite motion, as assumed in many accounts of plate kinematics -- there would be no boundary mismatch at the triple junction and no apparent kinematic reason why a microplate might develop there. But if, in a given RRR triple junction, the finite motion of one plate as observed from the other plate is not circular (as is generally the case, given the three-plate problem of plate kinematics), the geometry of the ridges and the triple junction will vary with time (Cronin, 1992, Tectonophys 207, 287-301). To explore the possible consequences of non-circular finite motion between plates at an RRR triple junction, a simple model was coded based on the cycloid finite-motion model (e.g., Cronin, 1987, Geology 15, 1006-1009) using NNR-MORVEL56 velocities for individual plates (Argus et al., 2011, G3 12, doi: 10.1029/2011GC003751). Initial assumptions include a spherical Earth, symmetric spreading, and constant angular velocities during the modeled finite time interval. The assumed-constant angular velocity vectors constitute a reference frame for observing finite plate motion. Typical results are [1] that the triple junction migrates relative to a coordinate system fixed to the angular-velocity vectors, [2] ridge axes rotates relative to each other, and [3] a boundary mismatch develops at the synthetic triple junction that might result in microplate nucleation. In a model simulating the Galapagos triple junction between the Cocos, Nazca and Pacific plates whose initial state did not include the Galapagos microplate, the mismatch gap was as much as ~3.4 km during 3 Myr of model displacement (see figure). The centroid of the synthetic triple junction translates ~81 km toward azimuth ~352° in 3 Myr. Of course, the details will vary as different angular velocity vectors are used; however, modeling indicates that non-circular finite relative motion between adjacent plates generally results in boundary mismatches and rotation of ridge segments relative to each other at RRR triple junctions. Left: synthetic Galapagos triple junction at initial model time, without a microplate. Right: synthetic triple junction after 3 Myr displacement, illustrating the resulting boundary mismatch (gap) and rotated ridge axes.

Vibration of Shells

NASA Technical Reports Server (NTRS)

Leissa, A. W.

1973-01-01

The vibrational characteristics and mechanical properties of shell structures are discussed. The subjects presented are: (1) fundamental equations of thin shell theory, (2) characteristics of thin circular cylindrical shells, (3) complicating effects in circular cylindrical shells, (4) noncircular cylindrical shell properties, (5) characteristics of spherical shells, and (6) solution of three-dimensional equations of motion for cylinders.

Transmission of wave energy in curved ducts. [acoustic propagation within rigid walls

NASA Technical Reports Server (NTRS)

Rostafinski, W.

1974-01-01

Investigation of the ability of circular bends to transmit acoustic energy flux. A formulation of wave-energy flow is developed for motion in curved ducts. A parametric study over a range of frequencies shows the ability of circular bends to transmit energy in the case of perfectly rigid walls.

Numerical analysis of two and three dimensional buoyancy driven water-exit of a circular cylinder

NASA Astrophysics Data System (ADS)

Moshari, Shahab; Nikseresht, Amir Hossein; Mehryar, Reza

2014-06-01

With the development of the technology of underwater moving bodies, the need for developing the knowledge of surface effect interaction of free surface and underwater moving bodies is increased. Hence, the two-phase flow is a subject which is interesting for many researchers all around the world. In this paper, the non-linear free surface deformations which occur during the water-exit of a circular cylinder due to its buoyancy are solved using finite volume discretization based code, and using Volume of Fluid (VOF) scheme for solving two phase flow. Dynamic mesh model is used to simulate dynamic motion of the cylinder. In addition, the effect of cylinder mass in presence of an external force is studied. Moreover, the oblique exit and entry of a circular cylinder with two exit angles is simulated. At last, water-exit of a circular cylinder in six degrees of freedom is simulated in 3D using parallel processing. The simulation errors of present work (using VOF method) for maximum velocity and height of a circular cylinder are less than the corresponding errors of level set method reported by previous researchers. Oblique exit shows interesting results; formation of waves caused by exit of the cylinder, wave motion in horizontal direction and the air trapped between the waves are observable. In 3D simulation the visualization of water motion on the top surface of the cylinder and the free surface breaking on the front and back faces of the 3D cylinder at the exit phase are observed which cannot be seen in 2D simulation. Comparing the results, 3D simulation shows better agreement with experimental data, specially in the maximum height position of the cylinder.

Evolving geometrical heterogeneities of fault trace data

NASA Astrophysics Data System (ADS)

Wechsler, Neta; Ben-Zion, Yehuda; Christofferson, Shari

2010-08-01

We perform a systematic comparative analysis of geometrical fault zone heterogeneities using derived measures from digitized fault maps that are not very sensitive to mapping resolution. We employ the digital GIS map of California faults (version 2.0) and analyse the surface traces of active strike-slip fault zones with evidence of Quaternary and historic movements. Each fault zone is broken into segments that are defined as a continuous length of fault bounded by changes of angle larger than 1°. Measurements of the orientations and lengths of fault zone segments are used to calculate the mean direction and misalignment of each fault zone from the local plate motion direction, and to define several quantities that represent the fault zone disorder. These include circular standard deviation and circular standard error of segments, orientation of long and short segments with respect to the mean direction, and normal separation distances of fault segments. We examine the correlations between various calculated parameters of fault zone disorder and the following three potential controlling variables: cumulative slip, slip rate and fault zone misalignment from the plate motion direction. The analysis indicates that the circular standard deviation and circular standard error of segments decrease overall with increasing cumulative slip and increasing slip rate of the fault zones. The results imply that the circular standard deviation and error, quantifying the range or dispersion in the data, provide effective measures of the fault zone disorder, and that the cumulative slip and slip rate (or more generally slip rate normalized by healing rate) represent the fault zone maturity. The fault zone misalignment from plate motion direction does not seem to play a major role in controlling the fault trace heterogeneities. The frequency-size statistics of fault segment lengths can be fitted well by an exponential function over the entire range of observations.

Reynolds numbers influence the directionality of self-propelled microjet engines in the 10(-4) regime.

PubMed

Zhao, Guanjia; Nguyen, Nam-Trung; Pumera, Martin

2013-08-21

The motion directionality of self-propelled bubble-jet microengines is influenced by their velocities and/or viscosity of the media in which they move. The influence of the fuel concentration from 1 to 3 wt% of H2O2 in 0.5% steps and of the glycerol fraction from 0 to 64% in aqueous solution on the directionality of the microjets motions is examined systematically. We show that with decreasing Reynolds numbers of the system (that is, with increasing viscosity or decreasing velocity of the microjets), the directionality of the motion shifts from circular to linear motion. This translates to a shorter travel time towards a designated target for the microjets despite moving at a slower speed, since the movements are linear instead of circular. We show that such dependence of trajectories of microjets on Re is a general issue. This observation has a strong implication for the real-world applications of microjets.

Jogging on a Carousel

NASA Astrophysics Data System (ADS)

Wilson, Alpha E.

2011-12-01

To jog around the periphery of a carousel at rest requires that the jogger experience a constant state of acceleration perpendicular to the direction of motion and directed toward the axis of rotation (centripetal). The jogger could achieve this centripetal acceleration by leaning inward, thereby using a horizontal weight component to provide the necessary centripetal force. There are two ordinary cases of circular motion involving the carousel that can be handled by the simple centripetal acceleration formula, where the joggers speed v is squared and then divided by the radius r of the path being followed (a = v2/r). One case would be as above, with the carousel at rest and the jogger moving on a circular path around it. The other case would be the jogger at rest on the carousel at a radial point r while it is moving with linear speed v. The situation can be made significantly more interesting and informative by letting the jogger be in motion while the carousel is in motion.

A Circularly Arranged Sextuple Triptycene Gear Molecule.

PubMed

Ube, Hitoshi; Yamada, Ryo; Ishida, Jun-Ichi; Sato, Hiroyasu; Shiro, Motoo; Shionoya, Mitsuhiko

2017-11-22

Herein we report the synthesis of a circularly arranged sextuple triptycene gear molecule, hexakis(10-dodecyloxy-9-triptycyl)ethynylbenzene, via the trimerization of the corresponding triyne with a cobalt catalyst. The six triptycene gears are closely engaged with each other as confirmed by single crystal X-ray structure analysis, and their motion in solution was established by NMR spectroscopy. Notably, when one bulky RuCp* complex was attached to one triptycene gear, the whole movement of the six gears was highly restricted via their mechanical engagement. Development of such a multigear molecule would provide a structural basis for molecular motion transmission systems with a switching function.

19. Detail of base of revolving lens assembly, showing bottom ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

19. Detail of base of revolving lens assembly, showing bottom of lamp at center and brass tens framework at edges of circular platform. Mercury float bearing lies in circular well just beneath lens platform. (Blurred due to lens motion.) - Block Island Southeast Light, Spring Street & Mohegan Trail at Mohegan Bluffs, New Shoreham, Washington County, RI

Nonlinear Drift-Kinetic Equation in the Presence of a Circularly Polarized Wave

NASA Technical Reports Server (NTRS)

Khazanov, G. V.; Krivorutsky, E. N.; Six, N. Frank (Technical Monitor)

2002-01-01

Equations of the single particle motion and nonlinear kinetic equation for plasma in the presence of a circularly polarized wave of arbitrary frequency in the drift approximation are presented. The nonstationarity and inhomogeneity of the plasma-wave system are taken into account. The time dependent part of the ponderomotive force is discussed.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dubey, P., E-mail: purushd@barc.gov.in; Sharma, V. K.; Mitra, S.

Synthetic hydroxyapatite (HAp) is an important material in biomedical engineering due to its excellent biocompatibility and bioactivity. Here we report dynamics of cetyltrimethylammonium bromide (CTAB) in HAp composite, prepared by co-precipitation method, as studied by quasielastic neutron scattering (QENS) technique. It is found that the observed dynamics involved two time scales associated with fast torsional motion and segmental motion of the CTAB monomers. In addition to segmental motion of the hydrogen atoms, few undergo torsional motion as well. Torsional dynamics was described by a 2-fold jump diffusion model. The segmental dynamics of CTAB has been described assumimg the hydrogen atomsmore » undergoing diffusion inside a sphere of confined volume. While the diffusivity is found to increase with temperature, the spherical volumes within which the hydrogen atoms are undergoing diffusion remain almost unchanged.« less

Demonstrating the Direction of Angular Velocity in Circular Motion

ERIC Educational Resources Information Center

Demircioglu, Salih; Yurumezoglu, Kemal; Isik, Hakan

2015-01-01

Rotational motion is ubiquitous in nature, from astronomical systems to household devices in everyday life to elementary models of atoms. Unlike the tangential velocity vector that represents the instantaneous linear velocity (magnitude and direction), an angular velocity vector is conceptually more challenging for students to grasp. In physics…

Maximum Range of a Projectile Thrown from Constant-Speed Circular Motion

NASA Astrophysics Data System (ADS)

Poljak, Nikola

2016-11-01

The problem of determining the angle θ at which a point mass launched from ground level with a given speed v0 will reach a maximum distance is a standard exercise in mechanics. There are many possible ways of solving this problem, leading to the well-known answer of θ = π/4, producing a maximum range of D max = v0 2 / g , with g being the free-fall acceleration. Conceptually and calculationally more difficult problems have been suggested to improve student proficiency in projectile motion, with the most famous example being the Tarzan swing problem. The problem of determining the maximum distance of a point mass thrown from constant-speed circular motion is presented and analyzed in detail in this text. The calculational results confirm several conceptually derived conclusions regarding the initial throw position and provide some details on the angles and the way of throwing (underhand or overhand) that produce the maximum throw distance.

Self-Organized Dynamic Flocking Behavior from a Simple Deterministic Map

NASA Astrophysics Data System (ADS)

Krueger, Wesley

2007-10-01

Coherent motion exhibiting large-scale order, such as flocking, swarming, and schooling behavior in animals, can arise from simple rules applied to an initial random array of self-driven particles. We present a completely deterministic dynamic map that exhibits emergent, collective, complex motion for a group of particles. Each individual particle is driven with a constant speed in two dimensions adopting the average direction of a fixed set of non-spatially related partners. In addition, the particle changes direction by π as it reaches a circular boundary. The dynamical patterns arising from these rules range from simple circular-type convective motion to highly sophisticated, complex, collective behavior which can be easily interpreted as flocking, schooling, or swarming depending on the chosen parameters. We present the results as a series of short movies and we also explore possible order parameters and correlation functions capable of quantifying the resulting coherence.

Particle motion around magnetized black holes: Preston-Poisson space-time

DOE Office of Scientific and Technical Information (OSTI.GOV)

Konoplya, R. A.

We analyze the motion of massless and massive particles around black holes immersed in an asymptotically uniform magnetic field and surrounded by some mechanical structure, which provides the magnetic field. The space-time is described by the Preston-Poisson metric, which is the generalization of the well-known Ernst metric with a new parameter, tidal force, characterizing the surrounding structure. The Hamilton-Jacobi equations allow the separation of variables in the equatorial plane. The presence of a tidal force from the surroundings considerably changes the parameters of the test particle motion: it increases the radius of circular orbits of particles and increases the bindingmore » energy of massive particles going from a given circular orbit to the innermost stable orbit near the black hole. In addition, it increases the distance of the minimal approach, time delay, and bending angle for a ray of light propagating near the black hole.« less

Relationships of a Circular Singer Arm Gesture to Acoustical and Perceptual Measures of Singing: A Motion Capture Study

ERIC Educational Resources Information Center

Brunkan, Melissa C.

2016-01-01

The purpose of this study was to validate previous research that suggests using movement in conjunction with singing tasks can affect intonation and perception of the task. Singers (N = 49) were video and audio recorded, using a motion capture system, while singing a phrase from a familiar song, first with no motion, and then while doing a low,…

Spectral analysis of point-vortex dynamics: first application to vortex polygons in a circular domain

NASA Astrophysics Data System (ADS)

Speetjens, M. F. M.; Meleshko, V. V.; van Heijst, G. J. F.

2014-06-01

The present study addresses the classical problem of the dynamics and stability of a cluster of N-point vortices of equal strength arranged in a polygonal configuration (‘N-vortex polygons’). In unbounded domains, such N-vortex polygons are unconditionally stable for N\\leqslant 7. Confinement in a circular domain tightens the stability conditions to N\\leqslant 6 and a maximum polygon size relative to the domain radius. This work expands on existing studies on stability and integrability by a first giving an exploratory spectral analysis of the dynamics of N vortex polygons in circular domains. Key to this is that the spectral signature of the time evolution of vortex positions reflects their qualitative behaviour. Expressing vortex motion by a generic evolution operator (the so-called Koopman operator) provides a rigorous framework for such spectral analyses. This paves the way to further differentiation and classification of point-vortex behaviour beyond stability and integrability. The concept of Koopman-based spectral analysis is demonstrated for N-vortex polygons. This reveals that conditional stability can be seen as a local form of integrability and confirms an important generic link between spectrum and dynamics: discrete spectra imply regular (quasi-periodic) motion; continuous (sub-)spectra imply chaotic motion. Moreover, this exposes rich nonlinear dynamics as intermittency between regular and chaotic motion and quasi-coherent structures formed by chaotic vortices. Dedicated to the memory of Slava Meleshko, a dear friend and inspiring colleague.

The Milky Way's Circular Velocity Curve and Its Constraint on the Galactic Mass with RR Lyrae Stars

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ablimit, Iminhaji; Zhao, Gang, E-mail: iminhaji@nao.cas.cn, E-mail: gzhao@nao.cas.cn

We present a sample of 1148 ab-type RR Lyrae (RRLab) variables identified from Catalina Surveys Data Release 1, combined with SDSS DR8 and LAMOST DR4 spectral data. We first use a large sample of 860 Galactic halo RRLab stars and derive the circular velocity distributions for the stellar halo. With the precise distances and carefully determined radial velocities (the center-of-mass radial velocities) and by considering the pulsation of the RRLab stars in our sample, we can obtain a reliable and comparable stellar halo circular velocity curve. We follow two different prescriptions for the velocity anisotropy parameter β in the Jeansmore » equation to study the circular velocity curve and mass profile. Additionally, we test two different solar peculiar motions in our calculation. The best result we obtained with the adopted solar peculiar motion 1 of ( U , V , W ) = (11.1, 12, 7.2) km s{sup −1} is that the enclosed mass of the Milky Way within 50 kpc is (3.75 ± 1.33) × 10{sup 11} M {sub ⊙} based on β = 0 and the circular velocity 180 ± 31.92 (km s{sup −1}) at 50 kpc. This result is consistent with dynamical model results, and it is also comparable to the results of previous similar works.« less

The structure and stability of orbits in Hoag-like ring systems

NASA Astrophysics Data System (ADS)

Bannikova, Elena Yu

2018-05-01

Ring galaxies are amazing objects exemplified by the famous case of Hoag's Object. Here the mass of the central galaxy may be comparable to the mass of the ring, making it a difficult case to model mechanically. In a previous paper, it was shown that the outer potential of a torus (ring) can be represented with good accuracy by the potential of a massive circle with the same mass. This approach allows us to simplify the problem of the particle motion in the gravitational field of a torus associated with a central mass by replacing the torus with a massive circle. In such a system, there is a circle of unstable equilibrium that we call `Lagrangian circle' (LC). Stable circular orbits exist only in some region limited by the last possible circular orbit related to the disappearance of the extrema of the effective potential. We call this orbit `the outermost stable circular orbit' (OSCO) by analogy with the innermost stable circular orbit (ISCO) in the relativistic case of a black hole. Under these conditions, there is a region between OSCO and LC where the circular motion is not possible due to the competition between the gravitational forces by the central mass and the ring. As a result, a gap in the matter distribution can form in Hoag-like system with massive rings.

Twisting/Swirling Motions during a Prominence Eruption as Seen from SDO/AIA

NASA Astrophysics Data System (ADS)

Pant, V.; Datta, A.; Banerjee, D.; Chandrashekhar, K.; Ray, S.

2018-06-01

A quiescent prominence was observed at the northwest limb of the Sun using different channels of the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory. We report and analyze twisting/swirling motions during and after the prominence eruption. We segregate the observed rotational motions into small and large scales. Small-scale rotational motions manifest in the barbs of the prominence, while the large-scale rotation manifests as the roll motion during the prominence eruption. We noticed that both footpoints of the prominence rotate in the counterclockwise direction. We propose that a similar sense of rotation in both footpoints leads to a prominence eruption. The prominence erupted asymmetrically near the southern footpoint, which may be due to an uneven mass distribution and location of the cavity near the southern footpoint. Furthermore, we study the swirling motion of the plasma along different circular paths in the cavity of the prominence after the prominence eruption. The rotational velocities of the plasma moving along different circular paths are estimated to be ∼9–40 km s‑1. These swirling motions can be explained in terms of twisted magnetic field lines in the prominence cavity. Finally we observe the twist built up in the prominence, being carried away by the coronal mass ejection, as seen in the Large Angle Spectrometric Coronagraph on board the Solar and Heliospheric Observatory.

Rotating Magnetic Structures Associated with a Quasi-circular Ribbon Flare

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Haidong; Jiang, Yunchun; Yang, Jiayan

We present the detection of a small eruption and the associated quasi-circular ribbon flare during the emergence of a bipole occurring on 2015 February 3. Under a fan dome, a sigmoid was rooted in a single magnetic bipole, which was encircled by negative polarity. The nonlinear force-free field extrapolation shows the presence of twisted field lines, which can represent a sigmoid structure. The rotation of the magnetic bipole may cause the twisting of magnetic field lines. An initial brightening appeared at one of the footpoints of the sigmoid, where the positive polarity slides toward a nearby negative polarity field region.more » The sigmoid displayed an ascending motion and then interacted intensively with the spine-like field. This type of null point reconnection in corona led to a violent blowout jet, and a quasi-circular flare ribbon was also produced. The magnetic emergence and rotational motion are the main contributors to the energy buildup for the flare, while the cancellation and collision might act as a trigger.« less

Analysis of the Multiple-Solution Response of a Flexible Rotor Supported on Non-Linear Squeeze Film Dampers

NASA Astrophysics Data System (ADS)

ZHU, C. S.; ROBB, D. A.; EWINS, D. J.

2002-05-01

The multiple-solution response of rotors supported on squeeze film dampers is a typical non-linear phenomenon. The behaviour of the multiple-solution response in a flexible rotor supported on two identical squeeze film dampers with centralizing springs is studied by three methods: synchronous circular centred-orbit motion solution, numerical integration method and slow acceleration method using the assumption of a short bearing and cavitated oil film; the differences of computational results obtained by the three different methods are compared in this paper. It is shown that there are three basic forms for the multiple-solution response in the flexible rotor system supported on the squeeze film dampers, which are the resonant, isolated bifurcation and swallowtail bifurcation multiple solutions. In the multiple-solution speed regions, the rotor motion may be subsynchronous, super-subsynchronous, almost-periodic and even chaotic, besides synchronous circular centred, even if the gravity effect is not considered. The assumption of synchronous circular centred-orbit motion for the journal and rotor around the static deflection line can be used only in some special cases; the steady state numerical integration method is very useful, but time consuming. Using the slow acceleration method, not only can the multiple-solution speed regions be detected, but also the non-synchronous response regions.

Projectile Motion in the "Language" of Orbital Motion

ERIC Educational Resources Information Center

Zurcher, Ulrich

2011-01-01

We consider the orbit of projectiles launched with arbitrary speeds from the Earth's surface. This is a generalization of Newton's discussion about the transition from parabolic to circular orbits, when the launch speed approaches the value [image omitted]. We find the range for arbitrary launch speeds and angles, and calculate the eccentricity of…

Self-similar motion of a Nambu-Goto string

NASA Astrophysics Data System (ADS)

Igata, Takahisa; Houri, Tsuyoshi; Harada, Tomohiro

2016-09-01

We study the self-similar motion of a string in a self-similar spacetime by introducing the concept of a self-similar string, which is defined as the world sheet to which a homothetic vector field is tangent. It is shown that in Nambu-Goto theory, the equations of motion for a self-similar string reduce to those for a particle. Moreover, under certain conditions such as the hypersurface orthogonality of the homothetic vector field, the equations of motion for a self-similar string simplify to the geodesic equations on a (pseudo)Riemannian space. As a concrete example, we investigate a self-similar Nambu-Goto string in a spatially flat Friedmann-Lemaître-Robertson-Walker expanding universe with self-similarity and obtain solutions of open and closed strings, which have various nontrivial configurations depending on the rate of the cosmic expansion. For instance, we obtain a circular solution that evolves linearly in the cosmic time while keeping its configuration by the balance between the effects of the cosmic expansion and string tension. We also show the instability for linear radial perturbation of the circular solutions.

Two Episodes of Magnetic Reconnections during a Confined Circular-ribbon Flare

NASA Astrophysics Data System (ADS)

Li, Ting; Yang, Shuhong; Zhang, Qingmin; Hou, Yijun; Zhang, Jun

2018-06-01

We analyze a unique event with an M1.8 confined circular-ribbon flare on 2016 February 13, with successive formations of two circular ribbons at the same location. The flare had two distinct phases of UV and extreme ultraviolet emissions with an interval of about 270 s, of which the second peak was energetically more important. The first episode was accompanied by the eruption of a mini-filament and the fast elongation motion of a thin circular ribbon (CR1) along the counterclockwise direction at a speed of about 220 km s‑1. Two elongated spine-related ribbons were also observed, with the inner ribbon co-temporal with CR1 and the remote brightenings forming ∼20 s later. In the second episode, another mini-filament erupted and formed a blowout jet. The second circular ribbon and two spine-related ribbons showed similar elongation motions with that during the first episode. The extrapolated three-dimensional coronal magnetic fields reveal the existence of a fan-spine topology, together with a quasi-separatrix layer (QSL) halo surrounding the fan plane and another QSL structure outlining the inner spine. We suggest that continuous null-point reconnection between the filament and ambient open field occurs in each episode, leading to the sequential opening of the filament and significant shifts of the fan plane footprint. For the first time, we propose a compound eruption model of circular-ribbon flares consisting of two sets of successively formed ribbons and eruptions of multiple filaments in a fan-spine-type magnetic configuration.

Colonic smooth muscle responses in patients with diverticular disease of the colon: effect of the NK2 receptor antagonist SR48968.

PubMed

Maselli, M A; Piepoli, A L; Guerra, V; Caruso, M L; Pezzolla, F; Lorusso, D; Demma, I; De Ponti, F

2004-05-01

Little is known about the pathophysiology of diverticular disease. To compare passive and active stress and the response to carbachol of colonic smooth muscle specimens from patients with diverticular disease and patients with colon cancer. The effect of the NK2 receptor antagonist, SR48968, on electrically evoked contractions of circular muscle was also investigated. Sigmoid colon segments were obtained from 16 patients (51-83 years) undergoing elective sigmoid resection for diverticular disease and 39 patients (50-88 years) undergoing left hemicolectomy for non-obstructive sigmoid colon cancer. Isometric tension was measured on circular or longitudinal taenial muscle. Strips were stretched gradually to Lo (length allowing the development of optimal active tension with carbachol) and were also exposed to increasing carbachol concentrations. The effects of atropine, tetrodotoxin and SR48968 on electrically evoked (supramaximal strength, 0.3 ms, 0.1-10 Hz) contractions of circular strips from 8 patients with diverticular disease and 19 patients with colon cancer were also studied. Both passive and active stress in circular muscle strips obtained from patients with diverticular disease was higher than in patients with colon cancer (P < 0.05). Electrically evoked contractions were significantly reduced by atropine in all preparations and were virtually suppressed by combined SR48968 and atropine. Tetrodotoxin suppressed electrically evoked contractions only in patients with colon cancer, whereas a tetrodotoxin-resistant component was identified in patients with diverticular disease. The changes in both passive and active stress in specimens from patients with diverticular disease may reflect circular smooth muscle dysfunction. Acetylcholine and tachykinins are the main excitatory neurotransmitters mediating electrically evoked contractions in human sigmoid colon circular muscle.

Mechanism test bed. Flexible body model report

NASA Technical Reports Server (NTRS)

Compton, Jimmy

1991-01-01

The Space Station Mechanism Test Bed is a six degree-of-freedom motion simulation facility used to evaluate docking and berthing hardware mechanisms. A generalized rigid body math model was developed which allowed the computation of vehicle relative motion in six DOF due to forces and moments from mechanism contact, attitude control systems, and gravity. No vehicle size limitations were imposed in the model. The equations of motion were based on Hill's equations for translational motion with respect to a nominal circular earth orbit and Newton-Euler equations for rotational motion. This rigid body model and supporting software were being refined.

On the theory of the relativistic motion of a charged particle in the field of intense electromagnetic radiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Milant'ev, V. P., E-mail: vmilantiev@sci.pfu.edu.ru; Castillo, A. J., E-mail: vmilant@mail.ru

2013-04-15

Averaged relativistic equations of motion of a charged particle in the field of intense electromagnetic radiation have been obtained in the geometrical optics approximation using the Bogoliubov method. Constraints are determined under which these equations are valid. Oscillating additions to the smoothed dynamical variables of the particle have been found; they are reduced to known expressions in the case of the circularly and linearly polarized plane waves. It has been shown that the expressions for the averaged relativistic force in both cases contain new additional small terms weakening its action. The known difference between the expressions for the ponderomotive forcemore » in the cases of circularly and linearly polarized waves has been confirmed.« less

Oscillations of a Simple Pendulum with Extremely Large Amplitudes

ERIC Educational Resources Information Center

Butikov, Eugene I.

2012-01-01

Large oscillations of a simple rigid pendulum with amplitudes close to 180[degrees] are treated on the basis of a physically justified approach in which the cycle of oscillation is divided into several stages. The major part of the almost closed circular path of the pendulum is approximated by the limiting motion, while the motion in the vicinity…

Precise Measurement of Velocity Dependent Friction in Rotational Motion

ERIC Educational Resources Information Center

Alam, Junaid; Hassan, Hafsa; Shamim, Sohaib; Mahmood, Waqas; Anwar, Muhammad Sabieh

2011-01-01

Frictional losses are experimentally determined for a uniform circular disc exhibiting rotational motion. The clockwise and anticlockwise rotations of the disc, that result when a hanger tied to a thread is released from a certain height, give rise to vertical oscillations of the hanger as the thread winds and unwinds over a pulley attached to the…

Cinematique et dynamique des galaxies spirales barrees

NASA Astrophysics Data System (ADS)

Hernandez, Olivier

The total mass (luminous and dark) of galaxies is derived from their circular velocities. Spectroscopic Fabry-Perot observations of the ionized gas component of spiral galaxies allow one to derive their kinematics. In the case of purely axisymmetric velocity fields--as in non-active and unbarred spirals galaxies-- the circular velocities can be derived directly. However, the velocity fields of barred galaxies (which constitute two thirds of the spirals) exhibit strong non-circular motions and need a careful analysis to retrieve the circular component. This thesis proposes the necessary steps to recover the axisymmetric component of barred spiral galaxies. The first step was to develop the best instrumentation possible for this work. [Special characters omitted.] , which is the most sensitive photon counting camera ever developed, was coupled to a Fabry-Perot interferometer. The observations of a sample of barred spiral galaxies--the BH a BAR sample--was assembled in order to obtain the most rigourous velocity fields. Then, the Tremaine-Weinberg method, which can determine the bar pattern speed and is usually used with the observations of stellar component, has been tested on the ionised gas and gave satisfactory results. Finally, all the above techniques have been applied to the BH a BAR sample in order to study the key parameters of the galaxies' evolution--bar pattern speeds, multiple stationary waves, resonances etc.--which will allow one to use N-body+SPH simulations to model properly the non-circular motions and determine the true total mass of barred spiral galaxies.

Linear and angular control of circular walking in healthy older adults and subjects with cerebellar ataxia.

PubMed

Goodworth, Adam D; Paquette, Caroline; Jones, Geoffrey Melvill; Block, Edward W; Fletcher, William A; Hu, Bin; Horak, Fay B

2012-05-01

Linear and angular control of trunk and leg motion during curvilinear navigation was investigated in subjects with cerebellar ataxia and age-matched control subjects. Subjects walked with eyes open around a 1.2-m circle. The relationship of linear to angular motion was quantified by determining the ratios of trunk linear velocity to trunk angular velocity and foot linear position to foot angular position. Errors in walking radius (the ratio of linear to angular motion) also were quantified continuously during the circular walk. Relative variability of linear and angular measures was compared using coefficients of variation (CoV). Patterns of variability were compared using power spectral analysis for the trunk and auto-covariance analysis for the feet. Errors in radius were significantly increased in patients with cerebellar damage as compared to controls. Cerebellar subjects had significantly larger CoV of feet and trunk in angular, but not linear, motion. Control subjects also showed larger CoV in angular compared to linear motion of the feet and trunk. Angular and linear components of stepping differed in that angular, but not linear, foot placement had a negative correlation from one stride to the next. Thus, walking in a circle was associated with more, and a different type of, variability in angular compared to linear motion. Results are consistent with increased difficulty of, and role of the cerebellum in, control of angular trunk and foot motion for curvilinear locomotion.

Loop-the-Loop: An Easy Experiment, A Challenging Explanation

NASA Astrophysics Data System (ADS)

Asavapibhop, B.; Suwonjandee, N.

2010-07-01

A loop-the-loop built by the Institute for the Promotion of Teaching Science and Technology (IPST) was used in Thai high school teachers training program to demonstrate a circular motion and investigate the concept of the conservation of mechanical energy. We took videos using high speed camera to record the motions of a spherical steel ball moving down the aluminum inclined track at different released positions. The ball then moved into the circular loop and underwent a projectile motion upon leaving the track. We then asked the teachers to predict the landing position of the ball if we changed the height of the whole loop-the-loop system. We also analyzed the videos using Tracker, a video analysis software. It turned out that most teachers did not realize the effect of the friction between the ball and the track and could not obtain the correct relationship hence their predictions were inconsistent with the actual landing positions of the ball.

Dynamics of Space Particles and Spacecrafts Passing by the Atmosphere of the Earth

PubMed Central

Prado, Antonio Fernando Bertachini de Almeida; Golebiewska, Justyna

2013-01-01

The present research studies the motion of a particle or a spacecraft that comes from an orbit around the Sun, which can be elliptic or hyperbolic, and that makes a passage close enough to the Earth such that it crosses its atmosphere. The idea is to measure the Sun-particle two-body energy before and after this passage in order to verify its variation as a function of the periapsis distance, angle of approach, and velocity at the periapsis of the particle. The full system is formed by the Sun, the Earth, and the particle or the spacecraft. The Sun and the Earth are in circular orbits around their center of mass and the motion is planar for all the bodies involved. The equations of motion consider the restricted circular planar three-body problem with the addition of the atmospheric drag. The initial conditions of the particle or spacecraft (position and velocity) are given at the periapsis of its trajectory around the Earth. PMID:24396298

Post-Newtonian Circular Restricted 3-Body Problem: Schwarzschild primaries

NASA Astrophysics Data System (ADS)

Dubeibe, F. L.; Lora-Clavijo, F. D.; González, G. A.

2017-07-01

The restricted three-body problem (RTBP) has been extensively studied to investigate the stability of the solar system, extra-solar subsystems, asteroid capture, and the dynamics of two massive black holes orbited by a sun. In the present work, we study the stability of the planar circular restricted three-body problem in the context of post-Newtonian approximations. First of all, we review the results obtained from the post-Newtonian equations of motion calculated in the framework of the Einstein-Infeld-Hoffmann formalism (EIH). Therefore, using the Fodor-Hoenselers-Perjes formalism (FHP), we have performed an expansion of the gravitational potential for two primaries, deriving a new system of equations of motion, which unlike the EIH-approach, preserves the Jacobian integral of motion. Additionally, we have obtained approximate expressions for the Lagrange points in terms of a mass parameter μ, where it is found that the deviations from the classical regime are larger for the FHP than for the EIH equations.

Dynamics of space particles and spacecrafts passing by the atmosphere of the Earth.

PubMed

Gomes, Vivian Martins; Prado, Antonio Fernando Bertachini de Almeida; Golebiewska, Justyna

2013-01-01

The present research studies the motion of a particle or a spacecraft that comes from an orbit around the Sun, which can be elliptic or hyperbolic, and that makes a passage close enough to the Earth such that it crosses its atmosphere. The idea is to measure the Sun-particle two-body energy before and after this passage in order to verify its variation as a function of the periapsis distance, angle of approach, and velocity at the periapsis of the particle. The full system is formed by the Sun, the Earth, and the particle or the spacecraft. The Sun and the Earth are in circular orbits around their center of mass and the motion is planar for all the bodies involved. The equations of motion consider the restricted circular planar three-body problem with the addition of the atmospheric drag. The initial conditions of the particle or spacecraft (position and velocity) are given at the periapsis of its trajectory around the Earth.

Inclusion of heat transfer computations for particle laden flows

NASA Astrophysics Data System (ADS)

Feng, Zhi-Gang; Michaelides, Efstathios E.

2008-04-01

A newly developed direct numerical simulation method has been used to study the dynamics of nonisothermal cylindrical particles in particulate flows. The momentum and energy transfer equations are solved to compute the effects of heat transfer in the sedimentation of particles. Among the effects examined is the drag force on nonisothermal particles, which we found strongly depends on the Reynolds and Grashof numbers. It was observed that heat advection between hotter particles and fluid causes the drag coefficient of particles to significantly increase at relatively low Reynolds numbers. For Grashof number of 100, the drag enhancement effect diminishes when the Reynolds number exceeds 50. On the contrary, heat advection with colder particles reduces the drag coefficient for low and medium Reynolds number (Re<50) for Grashof number of -100. We used this numerical method to study the problem of a pair of hot particles settling in a container at different Grashof numbers. In isothermal cases, such a pair of particles would undergo the well-known drafting-kissing-tumbling (DKT) motion. However, it was observed that the buoyancy currents induced by the hotter particles reverse the DKT motion of the particles or suppress it altogether. Finally, the sedimentation of a circular cluster of 172 particles in an enclosure at two different Grashof numbers was studied and the main features of the results are presented.

Investigating Plasma Motion of Magnetic Clouds at 1 AU through a Velocity-modified Cylindrical Force-free Flux Rope Model

NASA Astrophysics Data System (ADS)

Wang, Y.; Shen, C.; Liu, R.; Zhou, Z.

2014-12-01

Magnetic clouds (MCs) are the interplanetary counterparts of coronal mass ejections (CMEs). Due to the very low value of Can't connect to bucket.int.confex.com:4201 (Connection refused) LWP::Protocol::http::Socket: connect: Connection refused at /usr/local/lib/perl5/site_perl/5.8.8/LWP/Protocol/http.pm line 51. in MCs, they are believed to be in a nearly force-free state and therefore are able to be modeled by a cylindrical force-free flux rope. However, the force-free state only describes the magnetic field topology but not the plasma motion of a MC. For a MC propagating in interplanetary space, the global plasma motion has three possible components: linear propagating motion of a MC away from the Sun, expanding motion and circular motion with respect to the axis of the MC. By assuming the quasi-steady evolution and self-similar expansion, we introduced the three-component motion into the cylindrical force-free flux rope model, and developed a velocity-modified model. Then we applied the model to 73 MCs observed by Wind spacecraft to investigate the properties of the plasma motion of MCs. It is found that (1) some MCs did not propagate along the Sun-Earth line, suggesting the direct evidence of the CME's deflected propagation and/or rotation in interplanetary space, (2) the expansion speed is correlated with the radial propagation speed and 62%/17% of MCs underwent a under/over-expansion at 1 AU, and (3) the circular motion does exists though it is only on the order of 10 km s-1. These findings advance our understanding of the MC's properties at 1 AU as well as the dynamic evolution of CMEs from the Sun to interplanetary space.

Space-time VMS computation of wind-turbine rotor and tower aerodynamics

NASA Astrophysics Data System (ADS)

Takizawa, Kenji; Tezduyar, Tayfun E.; McIntyre, Spenser; Kostov, Nikolay; Kolesar, Ryan; Habluetzel, Casey

2014-01-01

We present the space-time variational multiscale (ST-VMS) computation of wind-turbine rotor and tower aerodynamics. The rotor geometry is that of the NREL 5MW offshore baseline wind turbine. We compute with a given wind speed and a specified rotor speed. The computation is challenging because of the large Reynolds numbers and rotating turbulent flows, and computing the correct torque requires an accurate and meticulous numerical approach. The presence of the tower increases the computational challenge because of the fast, rotational relative motion between the rotor and tower. The ST-VMS method is the residual-based VMS version of the Deforming-Spatial-Domain/Stabilized ST (DSD/SST) method, and is also called "DSD/SST-VMST" method (i.e., the version with the VMS turbulence model). In calculating the stabilization parameters embedded in the method, we are using a new element length definition for the diffusion-dominated limit. The DSD/SST method, which was introduced as a general-purpose moving-mesh method for computation of flows with moving interfaces, requires a mesh update method. Mesh update typically consists of moving the mesh for as long as possible and remeshing as needed. In the computations reported here, NURBS basis functions are used for the temporal representation of the rotor motion, enabling us to represent the circular paths associated with that motion exactly and specify a constant angular velocity corresponding to the invariant speeds along those paths. In addition, temporal NURBS basis functions are used in representation of the motion and deformation of the volume meshes computed and also in remeshing. We name this "ST/NURBS Mesh Update Method (STNMUM)." The STNMUM increases computational efficiency in terms of computer time and storage, and computational flexibility in terms of being able to change the time-step size of the computation. We use layers of thin elements near the blade surfaces, which undergo rigid-body motion with the rotor. We compare the results from computations with and without tower, and we also compare using NURBS and linear finite element basis functions in temporal representation of the mesh motion.

Space-Time VMS Computation of Wind-Turbine Rotor and Tower Aerodynamics

NASA Astrophysics Data System (ADS)

McIntyre, Spenser W.

This thesis is on the space{time variational multiscale (ST-VMS) computation of wind-turbine rotor and tower aerodynamics. The rotor geometry is that of the NREL 5MW offshore baseline wind turbine. We compute with a given wind speed and a specified rotor speed. The computation is challenging because of the large Reynolds numbers and rotating turbulent ows, and computing the correct torque requires an accurate and meticulous numerical approach. The presence of the tower increases the computational challenge because of the fast, rotational relative motion between the rotor and tower. The ST-VMS method is the residual-based VMS version of the Deforming-Spatial-Domain/Stabilized ST (DSD/SST) method, and is also called "DSD/SST-VMST" method (i.e., the version with the VMS turbulence model). In calculating the stabilization parameters embedded in the method, we are using a new element length definition for the diffusion-dominated limit. The DSD/SST method, which was introduced as a general-purpose moving-mesh method for computation of ows with moving interfaces, requires a mesh update method. Mesh update typically consists of moving the mesh for as long as possible and remeshing as needed. In the computations reported here, NURBS basis functions are used for the temporal representation of the rotor motion, enabling us to represent the circular paths associated with that motion exactly and specify a constant angular velocity corresponding to the invariant speeds along those paths. In addition, temporal NURBS basis functions are used in representation of the motion and deformation of the volume meshes computed and also in remeshing. We name this "ST/NURBS Mesh Update Method (STNMUM)." The STNMUM increases computational efficiency in terms of computer time and storage, and computational exibility in terms of being able to change the time-step size of the computation. We use layers of thin elements near the blade surfaces, which undergo rigid-body motion with the rotor. We compare the results from computations with and without tower, and we also compare using NURBS and linear finite element basis functions in temporal representation of the mesh motion.

Origin and continuation of 3/2, 5/2, 3/1, 4/1 and 5/1 resonant periodic orbits in the circular and elliptic restricted three-body problem

NASA Astrophysics Data System (ADS)

Antoniadou, Kyriaki I.; Libert, Anne-Sophie

2018-06-01

We consider a planetary system consisting of two primaries, namely a star and a giant planet, and a massless secondary, say a terrestrial planet or an asteroid, which moves under their gravitational attraction. We study the dynamics of this system in the framework of the circular and elliptic restricted three-body problem, when the motion of the giant planet describes circular and elliptic orbits, respectively. Originating from the circular family, families of symmetric periodic orbits in the 3/2, 5/2, 3/1, 4/1 and 5/1 mean-motion resonances are continued in the circular and the elliptic problems. New bifurcation points from the circular to the elliptic problem are found for each of the above resonances, and thus, new families continued from these points are herein presented. Stable segments of periodic orbits were found at high eccentricity values of the already known families considered as whole unstable previously. Moreover, new isolated (not continued from bifurcation points) families are computed in the elliptic restricted problem. The majority of the new families mainly consists of stable periodic orbits at high eccentricities. The families of the 5/1 resonance are investigated for the first time in the restricted three-body problems. We highlight the effect of stable periodic orbits on the formation of stable regions in their vicinity and unveil the boundaries of such domains in phase space by computing maps of dynamical stability. The long-term stable evolution of the terrestrial planets or asteroids is dependent on the existence of regular domains in their dynamical neighbourhood in phase space, which could host them for long-time spans. This study, besides other celestial architectures that can be efficiently modelled by the circular and elliptic restricted problems, is particularly appropriate for the discovery of terrestrial companions among the single-giant planet systems discovered so far.

Antares alignment gimbal positioner linear bearing tests

DOE Office of Scientific and Technical Information (OSTI.GOV)

Day, R.D.; McKay, M.D.; Pierce, D.D.

1981-01-01

The data indicate that of the six configurations tested, the solid circular rails with either the wet or dry lubricant are superior to the other configurations. Therefore, these two will undergo additional tests. These tests will consist of (1) modifying the testing procedure to obtain a better estimation of the limits of precision; and (2) subjecting the bearings to moments more closely approximating the actual conditions they will undergo on the AGP.

Identification, Characterization, and Three-Dimensional Structure of the Novel Circular Bacteriocin, Enterocin NKR-5-3B, from Enterococcus faecium.

PubMed

Himeno, Kohei; Rosengren, K Johan; Inoue, Tomoko; Perez, Rodney H; Colgrave, Michelle L; Lee, Han Siean; Chan, Lai Y; Henriques, Sónia Troeira; Fujita, Koji; Ishibashi, Naoki; Zendo, Takeshi; Wilaipun, Pongtep; Nakayama, Jiro; Leelawatcharamas, Vichien; Jikuya, Hiroyuki; Craik, David J; Sonomoto, Kenji

2015-08-11

Enterocin NKR-5-3B, one of the multiple bacteriocins produced by Enterococcus faecium NKR-5-3, is a 64-amino acid novel circular bacteriocin that displays broad-spectrum antimicrobial activity. Here we report the identification, characterization, and three-dimensional nuclear magnetic resonance solution structure determination of enterocin NKR-5-3B. Enterocin NKR-5-3B is characterized by four helical segments that enclose a compact hydrophobic core, which together with its circular backbone impart high stability and structural integrity. We also report the corresponding structural gene, enkB, that encodes an 87-amino acid precursor peptide that undergoes a yet to be described enzymatic processing that involves adjacent cleavage and ligation of Leu(24) and Trp(87) to yield the mature (circular) enterocin NKR-5-3B.

Illusory object motion in the centre of a radial pattern: The Pursuit-Pursuing illusion.

PubMed

Ito, Hiroyuki

2012-01-01

A circular object placed in the centre of a radial pattern consisting of thin sectors was found to cause a robust motion illusion. During eye-movement pursuit of a moving target, the presently described stimulus produced illusory background-object motion in the same direction as that of the eye movement. In addition, the display induced illusory stationary perception of a moving object against the whole display motion. In seven experiments, the characteristics of the illusion were examined in terms of luminance relationships and figural characteristics of the radial pattern. Some potential explanations for these findings are discussed.

On orbital stability of planar oscillations of a satellite in a circular orbit on the boundary of the parametric resonance

NASA Astrophysics Data System (ADS)

Bardin, B. S.; Chekina, E. A.

2018-05-01

We consider the motion of a satellite about its center of mass in a circular orbit. We study the problem of orbital stability for planar pendulum-like oscillations of the satellite. It is supposed that the satellite is a rigid body whose mass geometry is that of a plate. For the unperturbed motion the plane of the satellite-plate is perpendicular to the plane of the orbit. We perform a nonlinear analysis of the orbital stability of planar pendulum-like oscillations for previously unexplored parameter values corresponding to the combination resonance. It appears that in this case both formal orbital stability and instability can take place. The results of stability study are shown in stability diagrams.

Effect of out-of-roundness on the performance of a diesel engine connecting-rod bearing

NASA Technical Reports Server (NTRS)

Vijayaraghavan, D.; Brewe, D. E.; Keith, T. G., Jr.

1993-01-01

In this paper, the dynamic performance of the Ruston and Hornsby VEB diesel engine connecting-rod bearing with circular and out-of-round profiles is analyzed. The effect of cavitation is considered by using a cavitation algorithm, which mimics JFO boundary conditions. The effect of mass inertia is accounted for by solving coupled nonlinear equations of motion. The journal profiles considered are circular, elliptical, semi-elliptical, and three lobe epicycloid. The predicted journal trajectory and other performance parameters for one complete load cycle are presented for all of the out-of-round profiles and are also compared with the predictions for the circular bearing.

Effect of out-of-roundness on the performance of a diesel engine connecting-rod bearing

NASA Technical Reports Server (NTRS)

Vijayaraghavan, D.; Brewe, D. E.; Keith, T. G., Jr.

1991-01-01

In this paper, the dynamic performance of the Ruston and Hornsby VEB diesel engine connecting-rod bearing with circular and out-of-round profiles is analyzed. The effect of cavitation is considered by using a cavitation algorithm, which mimics JFO boundary conditions. The effect of mass inertia is accounted for by solving coupled nonlinear equations of motion. The journal profiles considered are circular, elliptical, semi-elliptical, and three lobe epicycloid. The predicted journal trajectory and other performance parameters for one complete load cycle are presented for all of the out-of-round profiles and are also compared with the predictions for the circular bearing.

Accelerated and Airy-Bloch oscillations

NASA Astrophysics Data System (ADS)

Longhi, Stefano

2016-09-01

A quantum particle subjected to a constant force undergoes an accelerated motion following a parabolic path, which differs from the classical motion just because of wave packet spreading (quantum diffusion). However, when a periodic potential is added (such as in a crystal) the particle undergoes Bragg scattering and an oscillatory (rather than accelerated) motion is found, corresponding to the famous Bloch oscillations (BOs). Here, we introduce an exactly-solvable quantum Hamiltonian model, corresponding to a generalized Wannier-Stark Hamiltonian Ĥ, in which a quantum particle shows an intermediate dynamical behavior, namely an oscillatory motion superimposed to an accelerated one. Such a novel dynamical behavior is referred to as accelerated BOs. Analytical expressions of the spectrum, improper eigenfunctions and propagator of the generalized Wannier-Stark Hamiltonian Ĥ are derived. Finally, it is shown that acceleration and quantum diffusion in the generalized Wannier-Stark Hamiltonian are prevented for Airy wave packets, which undergo a periodic breathing dynamics that can be referred to as Airy-Bloch oscillations.

Anakinra

MedlinePlus

... administer the injection, follow these steps: Clean the injection site with an alcohol wipe using a circular motion, ... to pinch a fold of skin at the injection site. Do not lay the syringe down or allow ...

Motion sickness and gastric myoelectric activity as a function of speed of rotation of a circular vection drum

NASA Technical Reports Server (NTRS)

Hu, Senqi; Stern, Robert M.; Vasey, Michael W.; Koch, Kenneth L.

1989-01-01

Motion sickness symptoms and electrogastrograms (EGGs) were obtained from 60 healthy subjects while they viewed an optokinetic drum rotated at one of four speeds: 15, 30, 60 or 90 deg/s. All subjects experienced vection, illusory self-motion. Motion sickness symptoms increased as drums speed increased up to 60 deg/s. Power, spectral intensity, of the EGG at the tachygastria frequencies (4-9 cpm) was calculated at each drum rotation speed. The correlation between the motion sickness symptoms and the power at 4-9 cpm was significant. Thus, drum rotation speed influenced the spectral power of the EGG at 4-9 cpm, tachygastria, and the intensity of motion sickness symptoms.

Flow regimes of adiabatic gas-liquid two-phase under rolling conditions

NASA Astrophysics Data System (ADS)

Yan, Chaoxing; Yan, Changqi; Sun, Licheng; Xing, Dianchuan; Wang, Yang; Tian, Daogui

2013-07-01

Characteristics of adiabatic air/water two-phase flow regimes under vertical and rolling motion conditions were investigated experimentally. Test sections are two rectangular ducts with the gaps of 1.41 and 10 mm, respectively, and a circular tube with 25 mm diameter. Flow regimes were recorded by a high speed CCD-camera and were identified by examining the video images. The experimental results indicate that the characteristics of flow patterns in 10 mm wide rectangular duct under vertical condition are very similar to those in circular tube, but different from the 1.41 mm wide rectangular duct. Channel size has a significant influence on flow pattern transition, boundary of which in rectangular channels tends asymptotically towards that in the circular tube with increasing the width of narrow side. Flow patterns in rolling channels are similar to each other, nevertheless, the effect of rolling motion on flow pattern transition are significantly various. Due to the remarkable influences of the friction shear stress and surface tension in the narrow gap duct, detailed flow pattern maps of which under vertical and rolling conditions are indistinguishable. While for the circular tube with 25 mm diameter, the transition from bubbly to slug flow occurs at a higher superficial liquid velocity and the churn flow covers more area on the flow regime map as the rolling period decreases.

Astronaut John Glenn tests balance mechanism performance

NASA Image and Video Library

1962-02-01

S64-14849 (1962) --- Astronaut John H. Glenn Jr.'s balance mechanism (semi-circular-canals) is tested by running cool water into his ear and measuring effect on eye motions (nystagmus). Photo credit: NASA

Physics and Skiing.

ERIC Educational Resources Information Center

Swinson, Derek B.

1992-01-01

Presents examples of physics as applied to the sport of skiing. Examples examine the physics of sliding, unweighting, ski turning, wind resistance, the parabolic and circular motion of aerial skiers, and the aerial maneuvers of ski jumpers. (MDH)

Illusory object motion in the centre of a radial pattern: The Pursuit–Pursuing illusion

PubMed Central

Ito, Hiroyuki

2012-01-01

A circular object placed in the centre of a radial pattern consisting of thin sectors was found to cause a robust motion illusion. During eye-movement pursuit of a moving target, the presently described stimulus produced illusory background-object motion in the same direction as that of the eye movement. In addition, the display induced illusory stationary perception of a moving object against the whole display motion. In seven experiments, the characteristics of the illusion were examined in terms of luminance relationships and figural characteristics of the radial pattern. Some potential explanations for these findings are discussed. PMID:23145267

Beating motion of a circular cylinder in vortex-induced vibrations

NASA Astrophysics Data System (ADS)

Shen, Linwei; Chan, Eng-Soon; Wei, Yan

2018-04-01

In this paper, beating phenomenon of a circular cylinder in vortex-induced vibration is studied by numerical simulations in a systematic manner. The cylinder mass coefficients of 2 and 10 are considered, and the Reynolds number is 150. Two distinctive frequencies, namely cylinder oscillation and vortex shedding frequencies, are obtained from the harmonic analysis of the cylinder displacement. The result is consistent with that observed in laboratory experiments. It is found that the cylinder oscillation frequency changes with the natural frequency of the cylinder while the reduced velocity is varied. The added-mass coefficient of the cylinder in beating motion is therefore estimated. Meanwhile, the vortex shedding frequency does not change dramatically in the beating situations. In fact, it is very close to 0.2. Accordingly, the lift force coefficient has two main components associated with these two frequencies. Besides, higher harmonics of the cylinder oscillation frequency appear in the spectrum of the lift coefficient. Moreover, the vortex shedding timing is studied in the beating motion by examining the instantaneous flow fields in the wake, and two scenarios of the vortex formation are observed.

Vection: the contributions of absolute and relative visual motion.

PubMed

Howard, I P; Howard, A

1994-01-01

Inspection of a visual scene rotating about the vertical body axis induces a compelling sense of self rotation, or circular vection. Circular vection is suppressed by stationary objects seen beyond the moving display but not by stationary objects in the foreground. We hypothesised that stationary objects in the foreground facilitate vection because they introduce a relative-motion signal into what would otherwise be an absolute-motion signal. Vection latency and magnitude were measured with a full-field moving display and with stationary objects of various sizes and at various positions in the visual field. The results confirmed the hypothesis. Vection latency was longer when there were no stationary objects in view than when stationary objects were in view. The effect of stationary objects was particularly evident at low stimulus velocities. At low velocities a small stationary point significantly increased vection magnitude in spite of the fact that, at higher stimulus velocities and with other stationary objects in view, fixation on a stationary point, if anything, reduced vection. Changing the position of the stationary objects in the field of view did not affect vection latencies or magnitudes.

Effect of stationary objects on illusory forward self-motion induced by a looming display.

PubMed

Ohmi, M; Howard, I P

1988-01-01

It has previously been shown that when a moving and a stationary display are superimposed, illusory self-rotation (circular vection) is induced only when the moving display appears as the background. Three experiments are reported on the extent to which illusory forward self-motion (forward vection) induced by a looming display is inhibited by a superimposed stationary display as a function of the size and location of the stationary display and of the depth between the stationary and looming displays. Results showed that forward vection was controlled by the display that was perceived as the background, and background stationary displays suppressed forward vection by about the same amount whatever their size and eccentricity. Also, the perception of foreground-background properties of competing displays determined which controlled forward vection, and this control was not tied to specific depth cues. The inhibitory effect of a stationary background on forward vection was, however, weaker than that found with circular vection. This difference makes sense because, for forward body motion, the image of a distant scene is virtually stationary whereas, when the body rotates, it is not.

Single-particle tracking: applications to membrane dynamics.

PubMed

Saxton, M J; Jacobson, K

1997-01-01

Measurements of trajectories of individual proteins or lipids in the plasma membrane of cells show a variety of types of motion. Brownian motion is observed, but many of the particles undergo non-Brownian motion, including directed motion, confined motion, and anomalous diffusion. The variety of motion leads to significant effects on the kinetics of reactions among membrane-bound species and requires a revision of existing views of membrane structure and dynamics.

Optimum stacking sequence design of laminated composite circular plates with curvilinear fibres by a layer-wise optimization method

NASA Astrophysics Data System (ADS)

Guenanou, A.; Houmat, A.

2018-05-01

The optimum stacking sequence design for the maximum fundamental frequency of symmetrically laminated composite circular plates with curvilinear fibres is investigated for the first time using a layer-wise optimization method. The design variables are two fibre orientation angles per layer. The fibre paths are constructed using the method of shifted paths. The first-order shear deformation plate theory and a curved square p-element are used to calculate the objective function. The blending function method is used to model accurately the geometry of the circular plate. The equations of motion are derived using Lagrange's method. The numerical results are validated by means of a convergence test and comparison with published values for symmetrically laminated composite circular plates with rectilinear fibres. The material parameters, boundary conditions, number of layers and thickness are shown to influence the optimum solutions to different extents. The results should serve as a benchmark for optimum stacking sequences of symmetrically laminated composite circular plates with curvilinear fibres.

Geometric effects resulting from square and circular confinements for a particle constrained to a space curve

NASA Astrophysics Data System (ADS)

Wang, Yong-Long; Lai, Meng-Yun; Wang, Fan; Zong, Hong-Shi; Chen, Yan-Feng

2018-04-01

Investigating the geometric effects resulting from the detailed behaviors of the confining potential, we consider square and circular confinements to constrain a particle to a space curve. We find a torsion-induced geometric potential and a curvature-induced geometric momentum just in the square case, while a geometric gauge potential solely in the circular case. In the presence of electromagnetic field, a geometrically induced magnetic moment couples with magnetic field as an induced Zeeman coupling only for the circular confinement also. As spin-orbit interaction is considered, we find some additional terms for the spin-orbit coupling, which are induced not only by torsion, but also curvature. Moreover, in the circular case, the spin also couples with an intrinsic angular momentum, which describes the azimuthal motions mapped on the space curve. As an important conclusion for the thin-layer quantization approach, some substantial geometric effects result from the confinement boundaries. Finally, these results are proved on a helical wire.

A Galerkin method for linear PDE systems in circular geometries with structural acoustic applications

NASA Technical Reports Server (NTRS)

Smith, Ralph C.

1994-01-01

A Galerkin method for systems of PDE's in circular geometries is presented with motivating problems being drawn from structural, acoustic, and structural acoustic applications. Depending upon the application under consideration, piecewise splines or Legendre polynomials are used when approximating the system dynamics with modifications included to incorporate the analytic solution decay near the coordinate singularity. This provides an efficient method which retains its accuracy throughout the circular domain without degradation at singularity. Because the problems under consideration are linear or weakly nonlinear with constant or piecewise constant coefficients, transform methods for the problems are not investigated. While the specific method is developed for the two dimensional wave equations on a circular domain and the equation of transverse motion for a thin circular plate, examples demonstrating the extension of the techniques to a fully coupled structural acoustic system are used to illustrate the flexibility of the method when approximating the dynamics of more complex systems.

Photoexcitation circular dichroism in chiral molecules

NASA Astrophysics Data System (ADS)

Beaulieu, S.; Comby, A.; Descamps, D.; Fabre, B.; Garcia, G. A.; Géneaux, R.; Harvey, A. G.; Légaré, F.; Mašín, Z.; Nahon, L.; Ordonez, A. F.; Petit, S.; Pons, B.; Mairesse, Y.; Smirnova, O.; Blanchet, V.

2018-05-01

Chiral effects appear in a wide variety of natural phenomena and are of fundamental importance in science, from particle physics to metamaterials. The standard technique of chiral discrimination—photoabsorption circular dichroism—relies on the magnetic properties of a chiral medium and yields an extremely weak chiral response. Here, we propose and demonstrate an orders of magnitude more sensitive type of circular dichroism in neutral molecules: photoexcitation circular dichroism. This technique does not rely on weak magnetic effects, but takes advantage of the coherent helical motion of bound electrons excited by ultrashort circularly polarized light. It results in an ultrafast chiral response and the efficient excitation of a macroscopic chiral density in an initially isotropic ensemble of randomly oriented chiral molecules. We probe this excitation using linearly polarized laser pulses, without the aid of further chiral interactions. Our time-resolved study of vibronic chiral dynamics opens a way to the efficient initiation, control and monitoring of chiral chemical change in neutral molecules at the level of electrons.

Optimal rendezvous in the neighborhood of a circular orbit

NASA Technical Reports Server (NTRS)

Jones, J. B.

1975-01-01

The minimum velocity change rendezvous solutions, when the motion may be linearized about a circular orbit, fall into two separate regions; the phase-for-free region and the general region. Phase-for-free solutions are derived from the optimum transfer solutions, require the same velocity change expenditure, but may not be unique. Analytic solutions are presented in two of the three subregions. An algorithm is presented for determining the unique solutions in the general region. Various sources of initial conditions are discussed and three examples presented.

Velocity Memory Effect for polarized gravitational waves

NASA Astrophysics Data System (ADS)

Zhang, P.-M.; Duval, C.; Gibbons, G. W.; Horvathy, P. A.

2018-05-01

Circularly polarized gravitational sandwich waves exhibit, as do their linearly polarized counterparts, the Velocity Memory Effect: freely falling test particles in the flat after-zone fly apart along straight lines with constant velocity. In the inside zone their trajectories combine oscillatory and rotational motions in a complicated way. For circularly polarized periodic gravitational waves some trajectories remain bounded, while others spiral outward. These waves admit an additional "screw" isometry beyond the usual five. The consequences of this extra symmetry are explored.

The strange case of the missing apocentric librators in the 3:2 resonance. [in asteroidal belt

NASA Technical Reports Server (NTRS)

Ip, W.-H.

1976-01-01

From a comparison of the 2:1 and 3:2 resonances (in the asteroidal belt) two possible explanations to the absence of 3:2 apocentric librators are suggested. The first one is that such 3:2 resonant motion is dynamically unstable. The second interpretation requires the absence of near-circular orbits originally at 4 AU. The latter view, if correct, is inconsistent with cosmogonic models which predict the original orbits of the asteroids to be nearly circular.

Spacetime symmetries and Kepler's third law

NASA Astrophysics Data System (ADS)

Le Tiec, Alexandre

2012-11-01

The curved spacetime geometry of a system of two point masses moving on a circular orbit has a helical symmetry. We show how Kepler’s third law for circular motion, and its generalization in post-Newtonian theory, can be recovered from a simple, covariant condition on the norm of the associated helical Killing vector field. This unusual derivation can be used to illustrate some concepts of prime importance in a general relativity course, including those of Killing field, covariance, coordinate dependence and gravitational redshift.

About the possibility of magnetic and gravitational capture of the technogenic nanoparticles injected in the near-Earth space in high circular orbits

NASA Astrophysics Data System (ADS)

Kolesnikov, E. K.; Chernov, S. V.

2018-05-01

A detailed study of the conditions for the realization of the phenomena of magnetic and gravity capture (MGC) of nanoparticles (NP) injected into the near-Earth space in circular orbits with altitudes and inclinations characteristic for orbits of satellites of navigation systems (GLONASS, GPS, etc.) is carried out. Spherical aluminum oxide particles with radii from 4 to 100 nm were considered as injected particles. It was assumed that injection of NP is performed at various points of circular orbits with a height of 19130 km, an inclination angle to the equatorial plane equal to 64.8 degrees and a longitude of the ascending node of 0, 120 and 240 degrees. Calculations of the motion of nanoparticles in near-Earth space were performed for conditions of low level solar and geomagnetic activity. The results of numerical experiments show that for all the considered spatial orientations of the orbit of the parent body (PB) of the NP motion in the magnetic and gravitational capture mode with extremely long orbital existence times (more than two years) can be realized only for nanoparticles with radii in the narrow gap from 8.6 to 10.2 nm.

Motion fading is driven by perceived, not actual angular velocity.

PubMed

Kohler, P J; Caplovitz, G P; Hsieh, P-J; Sun, J; Tse, P U

2010-06-01

After prolonged viewing of a slowly drifting or rotating pattern under strict fixation, the pattern appears to slow down and then momentarily stop. Here we examine the relationship between such 'motion fading' and perceived angular velocity. Using several different dot patterns that generate emergent virtual contours, we demonstrate that whenever there is a difference in the perceived angular velocity of two patterns of dots that are in fact rotating at the same angular velocity, there is also a difference in the time to undergo motion fading for those two patterns. Conversely, whenever two patterns show no difference in perceived angular velocity, even if in fact rotating at different angular velocities, we find no difference in the time to undergo motion fading. Thus, motion fading is driven by the perceived rather than actual angular velocity of a rotating stimulus. Copyright (c) 2010 Elsevier Ltd. All rights reserved.

Transmission of wave energy in curved ducts

NASA Technical Reports Server (NTRS)

Rostafinski, W.

1973-01-01

A formation of wave energy flow was developed for motion in curved ducts. A parametric study over a range of frequencies determined the ability of circular bends to transmit energy for the case of perfectly rigid walls.

29 CFR 779.107 - Goods defined.

Code of Federal Regulations, 2010 CFR

2010-07-01

...; advertising, motion pictures, newspaper and radio copy; art work and manuscripts for publication; sample books, letterheads, envelopes, shipping tags, labels, checkbooks, blankbooks, book covers, advertising circulars, and... written materials such as newspapers, magazines, brochures, pamphlets, bulletins, and announcements...

Unusual structural transition of antimicrobial VP1 peptide.

PubMed

Shanmugam, Ganesh; Phambu, Nsoki; Polavarapu, Prasad L

2011-05-01

VP1 peptide, an active domain of m-calpain enzyme with antimicrobial activity is found to undergo an unusual conformational transition in trifluoroethanol (TFE) solvent. The nature of, and time dependent variations in, circular dichroism associated with the amide I vibrations, suggest that VP1 undergoes self-aggregation forming anti-parallel β-sheet structure in TFE. Transmission electron micrograph (TEM) images revealed that β-sheet aggregates formed by VP1 possess fibril-like assemblies. Copyright © 2011 Elsevier B.V. All rights reserved.

Circular Polarizations of Gravitational Waves from Core-Collapse Supernovae: A Clear Indication of Rapid Rotation.

PubMed

Hayama, Kazuhiro; Kuroda, Takami; Nakamura, Ko; Yamada, Shoichi

2016-04-15

We propose to employ the circular polarization of gravitational waves emitted by core-collapse supernovae as an unequivocal indication of rapid rotation deep in their cores just prior to collapse. It has been demonstrated by three dimensional simulations that nonaxisymmetric accretion flows may develop spontaneously via hydrodynamical instabilities in the postbounce cores. It is not surprising, then, that the gravitational waves emitted by such fluid motions are circularly polarized. We show, in this Letter, that a network of the second generation detectors of gravitational waves worldwide may be able to detect such polarizations up to the opposite side of the Galaxy as long as the rotation period of the core is shorter than a few seconds prior to collapse.

The Role of Visual Cues in Microgravity Spatial Orientation

NASA Technical Reports Server (NTRS)

Oman, Charles M.; Howard, Ian P.; Smith, Theodore; Beall, Andrew C.; Natapoff, Alan; Zacher, James E.; Jenkin, Heather L.

2003-01-01

In weightlessness, astronauts must rely on vision to remain spatially oriented. Although gravitational down cues are missing, most astronauts maintain a subjective vertical -a subjective sense of which way is up. This is evidenced by anecdotal reports of crewmembers feeling upside down (inversion illusions) or feeling that a floor has become a ceiling and vice versa (visual reorientation illusions). Instability in the subjective vertical direction can trigger disorientation and space motion sickness. On Neurolab, a virtual environment display system was used to conduct five interrelated experiments, which quantified: (a) how the direction of each person's subjective vertical depends on the orientation of the surrounding visual environment, (b) whether rolling the virtual visual environment produces stronger illusions of circular self-motion (circular vection) and more visual reorientation illusions than on Earth, (c) whether a virtual scene moving past the subject produces a stronger linear self-motion illusion (linear vection), and (d) whether deliberate manipulation of the subjective vertical changes a crewmember's interpretation of shading or the ability to recognize objects. None of the crew's subjective vertical indications became more independent of environmental cues in weightlessness. Three who were either strongly dependent on or independent of stationary visual cues in preflight tests remained so inflight. One other became more visually dependent inflight, but recovered postflight. Susceptibility to illusions of circular self-motion increased in flight. The time to the onset of linear self-motion illusions decreased and the illusion magnitude significantly increased for most subjects while free floating in weightlessness. These decreased toward one-G levels when the subject 'stood up' in weightlessness by wearing constant force springs. For several subjects, changing the relative direction of the subjective vertical in weightlessness-either by body rotation or by simply cognitively initiating a visual reorientation-altered the illusion of convexity produced when viewing a flat, shaded disc. It changed at least one person's ability to recognize previously presented two-dimensional shapes. Overall, results show that most astronauts become more dependent on dynamic visual motion cues and some become responsive to stationary orientation cues. The direction of the subjective vertical is labile in the absence of gravity. This can interfere with the ability to properly interpret shading, or to recognize complex objects in different orientations.

Illusory bending of a rigidly moving line segment: effects of image motion and smooth pursuit eye movements.

PubMed

Thaler, Lore; Todd, James T; Spering, Miriam; Gegenfurtner, Karl R

2007-04-20

Four experiments in which observers judged the apparent "rubberiness" of a line segment undergoing different types of rigid motion are reported. The results reveal that observers perceive illusory bending when the motion involves certain combinations of translational and rotational components and that the illusion is maximized when these components are presented at a frequency of approximately 3 Hz with a relative phase angle of approximately 120 degrees . Smooth pursuit eye movements can amplify or attenuate the illusion, which is consistent with other results reported in the literature that show effects of eye movements on perceived image motion. The illusion is unaffected by background motion that is in counterphase with the motion of the line segment but is significantly attenuated by background motion that is in-phase. This is consistent with the idea that human observers integrate motion signals within a local frame of reference, and it provides strong evidence that visual persistency cannot be the sole cause of the illusion as was suggested by J. R. Pomerantz (1983). An analysis of the motion patterns suggests that the illusory bending motion may be due to an inability of observers to accurately track the motions of features whose image displacements undergo rapid simultaneous changes in both space and time. A measure of these changes is presented, which is highly correlated with observers' numerical ratings of rubberiness.

Time-Varying Expression of the Formation Flying along Circular Trajectories

NASA Technical Reports Server (NTRS)

Kawaguchi, Jun'ichiro

2007-01-01

Usually, the formation flying associated with circular orbits is discussed through the well-known Hill s or C-W equations of motion. This paper dares to present and discuss the coordinates that may contain time-varying coefficients. The discussion presents how the controller s performance is affected by the selection of coordinates, and also looks at the special coordinate suitable for designating a target bin to which each spacecraft in the formation has only to be guided. It is revealed that the latter strategy may incorporate the J2 disturbance automatically.

Realization of localized Bohr-like wave packets.

PubMed

Mestayer, J J; Wyker, B; Lancaster, J C; Dunning, F B; Reinhold, C O; Yoshida, S; Burgdörfer, J

2008-06-20

We demonstrate a protocol to create localized wave packets in very-high-n Rydberg states which travel in nearly circular orbits around the nucleus. Although these wave packets slowly dephase and eventually lose their localization, their motion can be monitored over several orbital periods. These wave packets represent the closest analog yet achieved to the original Bohr model of the hydrogen atom, i.e., an electron in a circular classical orbit around the nucleus. The possible extension of the approach to create "planetary atoms" in highly correlated stable multiply excited states is discussed.

Optimal rendezvous in the neighborhood of a circular orbit

NASA Technical Reports Server (NTRS)

Jones, J. B.

1976-01-01

The minimum velocity-change rendezvous solutions, when the motion may be linearized about a circular orbit, fall into two separate regions; the phase-for-free region and the general region. Phase-for-free solutions are derived from the optimum transfer solutions, require the same velocity-change expenditure, but may not be unique. Analytic solutions are presented in two of the three subregions. An algorithm is presented for determining the unique solutions in the general region. Various sources of initial conditions are discussed and three examples are presented.

Derivation of Nonlinear Wave Equation for Flexural Motions of AN Elastic Beam Travelling in AN Air-Filled Tube

NASA Astrophysics Data System (ADS)

Sugimoto, N.; Kugo, K.; Watanabe, Y.

2002-07-01

Asymptotic analysis is carried out to derive a nonlinear wave equation for flexural motions of an elastic beam of circular cross-section travelling along the centre-axis of an air-filled, circular tube placed coaxially. Both the beam and tube are assumed to be long enough for end-effects to be ignored and the aerodynamic loading on the lateral surface of the beam is considered. Assuming a compressible inviscid fluid, the velocity potential of the air is sought systematically in the form of power series in terms of the ratios of the tube radius to a wavelength and of a typical deflection to the radius. Evaluating the pressure force acting on the lateral surface of the beam, the aerodynamic loading including the effects of finite deflection as well as of air's compressibility and axial curvature of the beam are obtained. Although the nonlinearity arises from the kinematical condition on the beam surface, it may be attributed to the presence of the tube wall. With the aerodynamic loading thus obtained, a nonlinear wave equation is derived, whereas linear theory is assumed for the flexural motions of the beam. Some discussions are given on the results.

Quantum motion of a point particle in the presence of the Aharonov–Bohm potential in curved space

DOE Office of Scientific and Technical Information (OSTI.GOV)

Silva, Edilberto O., E-mail: edilbertoo@gmail.com; Ulhoa, Sérgio C., E-mail: sc.ulhoa@gmail.com; Andrade, Fabiano M., E-mail: f.andrade@ucl.ac.uk

The nonrelativistic quantum dynamics of a spinless charged particle in the presence of the Aharonov–Bohm potential in curved space is considered. We chose the surface as being a cone defined by a line element in polar coordinates. The geometry of this line element establishes that the motion of the particle can occur on the surface of a cone or an anti-cone. As a consequence of the nontrivial topology of the cone and also because of two-dimensional confinement, the geometric potential should be taken into account. At first, we establish the conditions for the particle describing a circular path in suchmore » a context. Because of the presence of the geometric potential, which contains a singular term, we use the self-adjoint extension method in order to describe the dynamics in all space including the singularity. Expressions are obtained for the bound state energies and wave functions. -- Highlights: •Motion of particle under the influence of magnetic field in curved space. •Bound state for Aharonov–Bohm problem. •Particle describing a circular path. •Determination of the self-adjoint extension parameter.« less

Fast, Safe, Propellant-Efficient Spacecraft Motion Planning Under Clohessy-Wiltshire-Hill Dynamics

NASA Technical Reports Server (NTRS)

Starek, Joseph A.; Schmerling, Edward; Maher, Gabriel D.; Barbee, Brent W.; Pavone, Marco

2016-01-01

This paper presents a sampling-based motion planning algorithm for real-time and propellant-optimized autonomous spacecraft trajectory generation in near-circular orbits. Specifically, this paper leverages recent algorithmic advances in the field of robot motion planning to the problem of impulsively actuated, propellant- optimized rendezvous and proximity operations under the Clohessy-Wiltshire-Hill dynamics model. The approach calls upon a modified version of the FMT* algorithm to grow a set of feasible trajectories over a deterministic, low-dispersion set of sample points covering the free state space. To enforce safety, the tree is only grown over the subset of actively safe samples, from which there exists a feasible one-burn collision-avoidance maneuver that can safely circularize the spacecraft orbit along its coasting arc under a given set of potential thruster failures. Key features of the proposed algorithm include 1) theoretical guarantees in terms of trajectory safety and performance, 2) amenability to real-time implementation, and 3) generality, in the sense that a large class of constraints can be handled directly. As a result, the proposed algorithm offers the potential for widespread application, ranging from on-orbit satellite servicing to orbital debris removal and autonomous inspection missions.

Scale-by-scale energy budgets which account for the coherent motion

NASA Astrophysics Data System (ADS)

F, Thiesset; L, Danaila; A, Antonia R.; T, Zhou

2011-12-01

Scale-by-scale energy budget equations are written for flows where coherent structures may be prominent. Both general and locally isotropic formulations are provided. In particular, the contribution to the production, diffusion and energy transfer terms associated with the coherent motion is highlighted. Preliminary results are presented in the intermediate wake of a circular cylinder for phase-averaged second-and third-order structure functions. The experimental data provide adequate support for the scale-by-scale budgets.

Locomotion of bacteria in liquid flow and the boundary layer effect on bacterial attachment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Chao, E-mail: zhangchao@cqu.edu.cn; Institute of Engineering Thermophysics, Chongqing University, Chongqing 400030; Liao, Qiang, E-mail: lqzx@cqu.edu.cn

The formation of biofilm greatly affects the performance of biological reactors, which highly depends on bacterial swimming and attachment that usually takes place in liquid flow. Therefore, bacterial swimming and attachment on flat and circular surfaces with the consideration of flow was studied experimentally. Besides, a mathematical model comprehensively combining bacterial swimming and motion with flow is proposed for the simulation of bacterial locomotion and attachment in flow. Both experimental and theoretical results revealed that attached bacteria density increases with decreasing boundary layer thickness on both flat and circular surfaces, the consequence of which is inherently related to the competitionmore » between bacterial swimming and the non-slip motion with flow evaluated by the Péclet number. In the boundary layer, where the Péclet number is relatively higher, bacterial locomotion mainly depends on bacterial swimming. Thinner boundary layer promotes bacterial swimming towards the surface, leading to higher attachment density. To enhance the performance of biofilm reactors, it is effective to reduce the boundary layer thickness on desired surfaces. - Highlights: • Study of bacterial locomotion in flow as an early stage in biofilm formation. • Mathematical model combining bacterial swimming and the motion with flow. • Boundary layer plays a key role in bacterial attachment under flow condition. • The competition between bacterial swimming and the motion with flow is evaluated.« less

Rocking and rolling: A can that appears to rock might actually roll

NASA Astrophysics Data System (ADS)

Srinivasan, Manoj; Ruina, Andy

2008-12-01

A beer bottle or soda can on a table, when slightly tipped and released, falls to an upright position and then rocks up to a somewhat opposite tilt. Superficially this rocking motion involves a collision when the flat circular base of the container slaps the table before rocking up to the opposite tilt. A keen eye notices that the after-slap rising tilt is not generally just diametrically opposite the initial tilt but is veered to one side or the other. Cushman and Duistermaat [Regular Chaotic Dyn. 11, 31 (2006)] recently noticed such veering when a flat disk with rolling boundary conditions is dropped nearly flat. Here, we generalize these rolling disk results to arbitrary axi-symmetric bodies and to frictionless sliding. More specifically, we study motions that almost but do not quite involve a face-down collision of the round container’s bottom with the tabletop. These motions involve a sudden rapid motion of the contact point around the circular base. Surprisingly, similar to the rolling disk, the net angle of motion of this contact point is nearly independent of initial conditions. This angle of turn depends simply on the geometry and mass distribution but not on the moment of inertia about the symmetry axis. We derive simple asymptotic formulas for this “angle of turn” of the contact point and check the result with numerics and with simple experiments. For tall containers (height much bigger than radius) the angle of turn is just over π and the sudden rolling motion superficially appears as a nearly symmetric collision leading to leaning on an almost diametrically opposite point on the bottom rim.

Psychophysical scaling of circular vection (CV) produced by optokinetic (OKN) motion: individual differences and effects of practice.

PubMed

Kennedy, R S; Hettinger, L J; Harm, D L; Ordy, J M; Dunlap, W P

1996-01-01

Vection (V) refers to the compelling visual illusion of self-motion experienced by stationary individuals when viewing moving visual surrounds. The phenomenon is of theoretical interest because of its relevance for understanding the neural basis of ordinary self-motion perception, and of practical importance because it is the experience that makes simulation, virtual reality displays, and entertainment devices more vicarious. This experiment was performed to address whether an optokinetically induced vection illusion exhibits monotonic and stable psychometric properties and whether individuals differ reliably in these (V) perceptions. Subjects were exposed to varying velocities of the circular vection (CV) display in an optokinetic (OKN) drum 2 meters in diameter in 5 one-hour daily sessions extending over a 1 week period. For grouped data, psychophysical scalings of velocity estimates showed that exponents in a Stevens' type power function were essentially linear (slope = 0.95) and largely stable over sessions. Latencies were slightly longer for the slowest and fastest induction stimuli, and the trend over sessions for average latency was longer as a function of practice implying time course adaptation effects. Test-retest reliabilities for individual slope and intercept measures were moderately strong (r = 0.45) and showed no evidence of superdiagonal form. This implies stability of the individual circularvection (CV) sensitivities. Because the individual CV scores were stable, reliabilities were improved by averaging 4 sessions in order to provide a stronger retest reliability (r = 0.80). Individual latency responses were highly reliable (r = 0.80). Mean CV latency and motion sickness symptoms were greater in males than in females. These individual differences in CV could be predictive of other outcomes, such as susceptibility to disorientation or motion sickness, and for CNS localization of visual-vestibular interactions in the experience of self-motion.

Potential generated inner and outside a circular wire in its plane. Application to Saturn's ring

NASA Astrophysics Data System (ADS)

Najid, N.-E.; Zegoumou, M.; El Ourabi, E. H.

2012-12-01

In this article we derive the development of the potential generated by a homogeneous wire bent into a circular shape (Najid, Jammari & Zegoumou, 2005). We develop the potential as a power series of the distance from an appropriate origin to the test particle. The potential is expressed as a function of Legendre polynomials. We study both, the case where the test particle is inside or outside the circular wire. By Lagrangian formulation, we establish the differential equation of motion. The numerical resolution leads us to different orbits. Outside the wire we get a case where the test particle is confined between a maxima and minima of the radial position; while inner the wire the test particle is subjected to an escape case depending on the time of integration.

Unusual Circularly Polarized and Aggregation-Induced Near-Infrared Phosphorescence of Helical Platinum(II) Complexes with Tetradentate Salen Ligands.

PubMed

Song, Jintong; Wang, Man; Zhou, Xiangge; Xiang, Haifeng

2018-05-17

A series of chiral and helical Pt II -Salen complexes with 1,1'-binaphthyl linkers were synthesized and characterized. Owing to the restriction of intramolecular motions of central 1,1'-binaphthyls, the complexes exhibit unusual near-infrared aggregation-induced phosphorescence (AIP). The (R)/(S) enantiopure complexes were characterized by X-ray diffraction, circular dichroism spectra, time-dependent density functional theory calculations, and circularly polarized luminescence (CPL). The present work explores the use of tetradentate ligands that can be easily prepared from commercially available enantiopure compounds, and the subsequent preparation of stable CPL-active square planar Pt II complexes with AIP effect that may have interest in many applications. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Strain-controlled fatigue behaviors of porous PLA-based scaffolds by 3D-printing technology.

PubMed

Gong, Baoming; Cui, Shaohua; Zhao, Yun; Sun, Yongtao; Ding, Qian

2017-12-01

In the study, the low-cycle fatigue behaviors of 3D-printed poly lactic acid (PLA) scaffolds with 60% porosity and two kinds of geometrical pores were investigated under strain-controlled loading. The obtained Δε a -N f curves were fitted by Coffin-Manson relation. The mechanical stability of the porous structure under cyclic loading was studied. Both kinds of specimens undergo the strain softening after the initial cyclic hardening. The scaffold with circular pore exhibits stable resistance to the fatigue damage which is desirable for bone repairing. Regarding to the accumulation of inelastic deformation, the triangular-scaffold is more sensitive to the cyclic load. The superior fatigue behaviors of the scaffold with circular pore is attributed to homogeneous distribution of the applied mechanical stress and diminishing stress concentration by the introduction of circular pore.

Water entry and exit of horizontal circular cylinders

NASA Astrophysics Data System (ADS)

Greenhow, M.; Moyo, S.

This paper describes fully nonlinear two-dimensional numerical calculations of the free-surface deformations of initially calm water caused by the forced motion of totally or partially submerged horizontal circular cylinders. The paper considers the following. (i) Totally submerged cylinders moving with constant velocity in vertical, horizontal or combined motions. Results are compared with the small-time asymptotic solution obtained by Tyvand and Milohin 1995. Their results, which are taken to third-order (which is when gravity terms first appear in the expansions), are in excellent agreement with the numerical calculations for small times; beyond this only the numerical method gives accurate results until the free surface breaks or the cylinder emerges from the free surface. Breaking can occur during exit due to strongly negative pressures arising on the cylinder surface, or during the downwards motion causing a free-surface depression which closes up rapidly, forming splashes. Downwards motion is also shown to give rise to high-frequency waves in some cases. (ii) The free-surface deformations, pressures and forces acting on a cylinder in vertical or oblique forced motion during engulfment when it submerges from being initially half-submerged. The initial stages, when the cylinder still pierces the free surface, specify the initial conditions for a separate program for a completely submerged body, thereby allowing complete engulfment to be studied. The free surface closes up violently over the top of the cylinder resulting in jet flow, which, while difficult to handle numerically, has been shown to be insignificant for the bulk flow and the cylinder pressures and forces.

Time-Lapse Video Microscopy of Gliding Motility in Toxoplasma gondii Reveals a Novel, Biphasic Mechanism of Cell LocomotionV⃞

PubMed Central

Håkansson, Sebastian; Morisaki, Hiroshi; Heuser, John; Sibley, L. David

1999-01-01

Toxoplasma gondii is a member of the phylum Apicomplexa, a diverse group of intracellular parasites that share a unique form of gliding motility. Gliding is substrate dependent and occurs without apparent changes in cell shape and in the absence of traditional locomotory organelles. Here, we demonstrate that gliding is characterized by three distinct forms of motility: circular gliding, upright twirling, and helical rotation. Circular gliding commences while the crescent-shaped parasite lies on its right side, from where it moves in a counterclockwise manner at a rate of ∼1.5 μm/s. Twirling occurs when the parasite rights itself vertically, remaining attached to the substrate by its posterior end and spinning clockwise. Helical gliding is similar to twirling except that it occurs while the parasite is positioned horizontally, resulting in forward movement that follows the path of a corkscrew. The parasite begins lying on its left side (where the convex side is defined as dorsal) and initiates a clockwise revolution along the long axis of the crescent-shaped body. Time-lapse video analyses indicated that helical gliding is a biphasic process. During the first 180o of the turn, the parasite moves forward one body length at a rate of ∼1–3 μm/s. In the second phase, the parasite flips onto its left side, in the process undergoing little net forward motion. All three forms of motility were disrupted by inhibitors of actin filaments (cytochalasin D) and myosin ATPase (butanedione monoxime), indicating that they rely on an actinomyosin motor in the parasite. Gliding motility likely provides the force for active penetration of the host cell and may participate in dissemination within the host and thus is of both fundamental and practical interest. PMID:10564254

Extrasolar binary planets. I. Formation by tidal capture during planet-planet scattering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ochiai, H.; Nagasawa, M.; Ida, S., E-mail: nagasawa.m.ad@m.titech.ac.jp

2014-08-01

We have investigated (1) the formation of gravitationally bounded pairs of gas-giant planets (which we call 'binary planets') from capturing each other through planet-planet dynamical tide during their close encounters and (2) the subsequent long-term orbital evolution due to planet-planet and planet-star quasi-static tides. For the initial evolution in phase 1, we carried out N-body simulations of the systems consisting of three Jupiter-mass planets taking into account the dynamical tide. The formation rate of the binary planets is as much as 10% of the systems that undergo orbital crossing, and this fraction is almost independent of the initial stellarcentric semimajormore » axes of the planets, while ejection and merging rates sensitively depend on the semimajor axes. As a result of circularization by the planet-planet dynamical tide, typical binary separations are a few times the sum of the physical radii of the planets. After the orbital circularization, the evolution of the binary system is governed by long-term quasi-static tide. We analytically calculated the quasi-static tidal evolution in phase 2. The binary planets first enter the spin-orbit synchronous state by the planet-planet tide. The planet-star tide removes angular momentum of the binary motion, eventually resulting in a collision between the planets. However, we found that the binary planets survive the tidal decay for the main-sequence lifetime of solar-type stars (∼10 Gyr), if the binary planets are beyond ∼0.3 AU from the central stars. These results suggest that the binary planets can be detected by transit observations at ≳ 0.3 AU.« less

Numerical Simulation of Particle Motion in a Curved Channel

NASA Astrophysics Data System (ADS)

Liu, Yi; Nie, Deming

2018-01-01

In this work the lattice Boltzmann method (LBM) is used to numerically study the motion of a circular particle in a curved channel at intermediate Reynolds numbers (Re). The effects of the Reynolds number and the initial particle position are taken into account. Numerical results include the streamlines, particle trajectories and final equilibrium positions. It has been found that the particle is likely to migrate to a similar equilibrium position irrespective of its initial position when Re is large.

Mechanics, Waves and Thermodynamics

NASA Astrophysics Data System (ADS)

Ranjan Jain, Sudhir

2016-05-01

Figures; Preface; Acknowledgement; 1. Energy, mass, momentum; 2. Kinematics, Newton's laws of motion; 3. Circular motion; 4. The principle of least action; 5. Work and energy; 6. Mechanics of a system of particles; 7. Friction; 8. Impulse and collisions; 9. Central forces; 10. Dimensional analysis; 11. Oscillations; 12. Waves; 13. Sound of music; 14. Fluid mechanics; 15. Water waves; 16. The kinetic theory of gases; 17. Concepts and laws of thermodynamics; 18. Some applications of thermodynamics; 19. Basic ideas of statistical mechanics; Bibliography; Index.

Improved moving source photometry with TRIPPy

NASA Astrophysics Data System (ADS)

Alexandersen, Mike; Fraser, Wesley Cristopher

2017-10-01

Photometry of moving sources is more complicated than for stationary sources, because the sources trail their signal out over more pixels than a point source of the same magnitude. Using a circular aperture of same size as would be appropriate for point sources can cut out a large amount of flux if a moving source moves substantially relative to the size of the aperture during the exposure, resulting in underestimated fluxes. Using a large circular aperture can mitigate this issue at the cost of a significantly reduced signal to noise compared to a point source, as a result of the inclusion of a larger background region within the aperture.Trailed Image Photometry in Python (TRIPPy) solves this problem by using a pill-shaped aperture: the traditional circular aperture is sliced in half perpendicular to the direction of motion and separated by a rectangle as long as the total motion of the source during the exposure. TRIPPy can also calculate the appropriate aperture correction (which will depend both on the radius and trail length of the pill-shaped aperture), and has features for selecting good PSF stars, creating a PSF model (convolved moffat profile + lookup table) and selecting a custom sky-background area in order to ensure no other sources contribute to the background estimate.In this poster, we present an overview of the TRIPPy features and demonstrate the improvements resulting from using TRIPPy compared to photometry obtained by other methods with examples from real projects where TRIPPy has been implemented in order to obtain the best-possible photometric measurements of Solar System objects. While TRIPPy has currently mainly been used for Trans-Neptunian Objects, the improvement from using the pill-shaped aperture increases with source motion, making TRIPPy highly relevant for asteroid and centaur photometry as well.

High frequency circular translation pin-on-disk method for accelerated wear testing of ultrahigh molecular weight polyethylene as a bearing material in total hip arthroplasty.

PubMed

Saikko, Vesa

2015-01-21

The temporal change of the direction of sliding relative to the ultrahigh molecular weight polyethylene (UHMWPE) component of prosthetic joints is known to be of crucial importance with respect to wear. One complete revolution of the resultant friction vector is commonly called a wear cycle. It was hypothesized that in order to accelerate the wear test, the cycle frequency may be substantially increased if the circumference of the slide track is reduced in proportion, and still the wear mechanisms remain realistic and no overheating takes place. This requires an additional slow motion mechanism with which the lubrication of the contact is maintained and wear particles are conveyed away from the contact. A three-station, dual motion high frequency circular translation pin-on-disk (HF-CTPOD) device with a relative cycle frequency of 25.3 Hz and an average sliding velocity of 27.4 mm/s was designed. The pins circularly translated at high frequency (1.0 mm per cycle, 24.8 Hz, clockwise), and the disks at low frequency (31.4mm per cycle, 0.5 Hz, counter-clockwise). In a 22 million cycle (10 day) test, the wear rate of conventional gamma-sterilized UHMWPE pins against polished CoCr disks in diluted serum was 1.8 mg per 24 h, which was six times higher than that in the established 1 Hz CTPOD device. The wear mechanisms were similar. Burnishing of the pin was the predominant feature. No overheating took place. With the dual motion HF-CTPOD method, the wear testing of UHMWPE as a bearing material in total hip arthroplasty can be substantially accelerated without concerns of the validity of the wear simulation. Copyright © 2014 Elsevier Ltd. All rights reserved.

Deformation and Flexibility Equations for ARIS Umbilicals Idealized as Planar Elastica

NASA Technical Reports Server (NTRS)

Hampton, R. David; Leamy, Michael J.; Bryant, Paul J.; Quraishi, Naveed

2005-01-01

The International Space Station relies on the active rack isolation system (ARIS) as the central component of an integrated, stationwide strategy to isolate microgravity space-science experiments. ARIS uses electromechanical actuators to isolate an international standard payload rack from disturbances due to the motion of the Space Station. Disturbances to microgravity experiments on ARIS isolated racks are transmitted primarily via the ARIS power and vacuum umbilicals. Experimental tests indicate that these umbilicals resonate at frequencies outside the ARIS controller s bandwidth at levels of potential concern for certain microgravity experiments. Reduction in the umbilical resonant frequencies could help to address this issue. This work documents the development and verification of equations for the in-plane deflections and flexibilities of an idealized umbilical (thin, flexible, inextensible, cantilever beam) under end-point, in-plane loading (inclined-force and moment). The effect of gravity is neglected due to the on-orbit application. The analysis assumes an initially curved (not necessarily circular), cantilevered umbilical with uniform cross-section, which undergoes large deflections with no plastic deformation, such that the umbilical slope changes monotonically. The treatment is applicable to the ARIS power and vacuum umbilicals under the indicated assumptions.

The research of the coupled orbital-attitude controlled motion of celestial body in the neighborhood of the collinear libration point L1

NASA Astrophysics Data System (ADS)

Shmyrov, A.; Shmyrov, V.; Shymanchuk, D.

2017-10-01

This article considers the motion of a celestial body within the restricted three-body problem of the Sun-Earth system. The equations of controlled coupled attitude-orbit motion in the neighborhood of collinear libration point L1 are investigated. The translational orbital motion of a celestial body is described using Hill's equations of circular restricted three-body problem of the Sun-Earth system. Rotational orbital motion is described using Euler's dynamic equations and quaternion kinematic equation. We investigate the problem of stability of celestial body rotational orbital motion in relative equilibrium positions and stabilization of celestial body rotational orbital motion with proposed control laws in the neighborhood of collinear libration point L1. To study stabilization problem, Lyapunov function is constructed in the form of the sum of the kinetic energy and special "kinematic function" of the Rodriguez-Hamiltonian parameters. Numerical modeling of the controlled rotational motion of a celestial body at libration point L1 is carried out. The numerical characteristics of the control parameters and rotational motion are given.

Accurate orbit propagation in the presence of planetary close encounters

NASA Astrophysics Data System (ADS)

Amato, Davide; Baù, Giulio; Bombardelli, Claudio

2017-09-01

We present an efficient strategy for the numerical propagation of small Solar system objects undergoing close encounters with massive bodies. The trajectory is split into several phases, each of them being the solution of a perturbed two-body problem. Formulations regularized with respect to different primaries are employed in two subsequent phases. In particular, we consider the Kustaanheimo-Stiefel regularization and a novel set of non-singular orbital elements pertaining to the Dromo family. In order to test the proposed strategy, we perform ensemble propagations in the Earth-Sun Circular Restricted 3-Body Problem (CR3BP) using a variable step size and order multistep integrator and an improved version of Everhart's radau solver of 15th order. By combining the trajectory splitting with regularized equations of motion in short-term propagations (1 year), we gain up to six orders of magnitude in accuracy with respect to the classical Cowell's method for the same computational cost. Moreover, in the propagation of asteroid (99942) Apophis through its 2029 Earth encounter, the position error stays within 100 metres after 100 years. In general, as to improve the performance of regularized formulations, the trajectory must be split between 1.2 and 3 Hill radii from the Earth. We also devise a robust iterative algorithm to stop the integration of regularized equations of motion at a prescribed physical time. The results rigorously hold in the CR3BP, and similar considerations may apply when considering more complex models. The methods and algorithms are implemented in the naples fortran 2003 code, which is available online as a GitHub repository.

Preliminary study of the three-dimensional deformation of the vortex in Karman vortex street

NASA Astrophysics Data System (ADS)

Ling, Guocan; Guo, Liang; Wu, Zuobin; Ma, Huiyang

1992-03-01

The mechanism for 3D evolution of the isolated Karman vortex and the thin-vortex filament in a circular cylinder wake is studied numerically using the LIA method. The results show that the vortex motion is unstable for small 3D disturbances in the separated wake of a circular cylinder. Karman vortex in the time-averaged wake flowfield wolves into a horseshoe-spoon-like 3D structure. The thin vortex filament deforms three-dimensionally in the braid and generates streamwise vortex structures which incline to the region maximum-deformation direction of the flowfield.

Dispersion relation and electron acceleration in the combined circular and elliptical metallic-dielectric waveguide filled by plasma

NASA Astrophysics Data System (ADS)

Abdoli-Arani, A.; Montazeri, M. M.

2018-04-01

Two special types of metallic waveguide having dielectric cladding and plasma core including the combined circular and elliptical structure are studied. Longitudinal and transverse field components in the different regions are obtained. Applying the boundary conditions, dispersion relations of the electromagnetic waves in the structures are obtained and then plotted. The acceleration of an injected external relativistic electron in the considered waveguides is studied. The obtained differential equations related to electron motion are solved by the fourth-order Runge-Kutta method. Numerical computations are made, and the results are graphically presented.

Control of reversible magnetization switching by pulsed circular magnetic field in glass-coated amorphous microwires

NASA Astrophysics Data System (ADS)

Chizhik, Alexander; Zhukov, Arkady; Gonzalez, Julian; Stupakiewicz, Andrzej

2018-02-01

Magnetization reversal in magnetic microwires was studied in the presence of external mechanical stress and helical magnetic fields using the magneto-optical Kerr effect. It was found that a combination of tuned magnetic anisotropy and a direct current or pulsed circular magnetic field activated different types of magnetization reversal scenarios. The application of the pulsed magnetic field of 10 ns time duration induced a transient controlling action to switch the magnetic states without activating a domain wall motion. This created a promising method for tuning the giant magneto-impedance effect.

Electromagnetic tornado in the vacuum gap of a pulsar

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kontorovich, V. M., E-mail: vkont1001@yahoo.co

The solution for an electromagnetic tornado that describes the motion in the discharge filament of breakdown in the vacuum gap of a pulsar has been obtained. This solution can serve as an explanation of the observed circular polarization of giant radiation pulses from pulsars.

A Comparison of Averaged and Full Models to Study the Third-Body Perturbation

PubMed Central

Solórzano, Carlos Renato Huaura; Prado, Antonio Fernando Bertachini de Almeida

2013-01-01

The effects of a third-body travelling in a circular orbit around a main body on a massless satellite that is orbiting the same main body are studied under two averaged models, single and double, where expansions of the disturbing function are made, and the full restricted circular three-body problem. The goal is to compare the behavior of these two averaged models against the full problem for long-term effects, in order to have some knowledge of their differences. The single averaged model eliminates the terms due to the short period of the spacecraft. The double average is taken over the mean motion of the satellite and the mean motion of the disturbing body, so removing both short period terms. As an example of the methods, an artificial satellite around the Earth perturbed by the Moon is used. A detailed study of the effects of different initial conditions in the orbit of the spacecraft is made. PMID:24319348

Spontaneous symmetry breaking for geometrical trajectories of actin-based motility in three dimensions

NASA Astrophysics Data System (ADS)

Wen, Fu-Lai; Leung, Kwan-tai; Chen, Hsuan-Yi

2016-07-01

Actin-based motility is important for many cellular processes. In this article we extend our previous studies of an actin-propelled circular disk in two dimensions to an actin-propelled spherical bead in three dimensions. We find that for an achiral load the couplings between the motion of the load and the actin network induce a series of bifurcations, starting with a transition from rest to moving state, followed by a transition from straight to planar curves, and finally a further transition from motion in a plane to one with torsion. To address the intriguing, experimentally observed chiral motility of the bacterium Listeria monocytogenes, we also study the motility of a spherical load with a built-in chirality. For such a chiral load, stable circular trajectories are no longer found in numerical simulations. Instead, helical trajectories with handedness that depends on the chirality of the load are found. Our results reveal the relation between the symmetry of actin network and the trajectories of actin-propelled loads.

Laser Spot Tracking Based on Modified Circular Hough Transform and Motion Pattern Analysis

PubMed Central

Krstinić, Damir; Skelin, Ana Kuzmanić; Milatić, Ivan

2014-01-01

Laser pointers are one of the most widely used interactive and pointing devices in different human-computer interaction systems. Existing approaches to vision-based laser spot tracking are designed for controlled indoor environments with the main assumption that the laser spot is very bright, if not the brightest, spot in images. In this work, we are interested in developing a method for an outdoor, open-space environment, which could be implemented on embedded devices with limited computational resources. Under these circumstances, none of the assumptions of existing methods for laser spot tracking can be applied, yet a novel and fast method with robust performance is required. Throughout the paper, we will propose and evaluate an efficient method based on modified circular Hough transform and Lucas–Kanade motion analysis. Encouraging results on a representative dataset demonstrate the potential of our method in an uncontrolled outdoor environment, while achieving maximal accuracy indoors. Our dataset and ground truth data are made publicly available for further development. PMID:25350502

Wave Propagation Analysis of Edge Cracked Circular Beams under Impact Force

PubMed Central

Akbaş, Şeref Doğuşcan

2014-01-01

This paper presents responses of an edge circular cantilever beam under the effect of an impact force. The beam is excited by a transverse triangular force impulse modulated by a harmonic motion. The Kelvin–Voigt model for the material of the beam is used. The cracked beam is modelled as an assembly of two sub-beams connected through a massless elastic rotational spring. The considered problem is investigated within the Bernoulli-Euler beam theory by using energy based finite element method. The system of equations of motion is derived by using Lagrange's equations. The obtained system of linear differential equations is reduced to a linear algebraic equation system and solved in the time domain by using Newmark average acceleration method. In the study, the effects of the location of crack, the depth of the crack, on the characteristics of the reflected waves are investigated in detail. Also, the positions of the cracks are calculated by using reflected waves. PMID:24972050

A comparison of averaged and full models to study the third-body perturbation.

PubMed

Solórzano, Carlos Renato Huaura; Prado, Antonio Fernando Bertachini de Almeida

2013-01-01

The effects of a third-body travelling in a circular orbit around a main body on a massless satellite that is orbiting the same main body are studied under two averaged models, single and double, where expansions of the disturbing function are made, and the full restricted circular three-body problem. The goal is to compare the behavior of these two averaged models against the full problem for long-term effects, in order to have some knowledge of their differences. The single averaged model eliminates the terms due to the short period of the spacecraft. The double average is taken over the mean motion of the satellite and the mean motion of the disturbing body, so removing both short period terms. As an example of the methods, an artificial satellite around the Earth perturbed by the Moon is used. A detailed study of the effects of different initial conditions in the orbit of the spacecraft is made.

Innovative Interactive Lecture Demonstrations Using Wireless Force Sensors and Accelerometers for Introductory Physics Courses

NASA Astrophysics Data System (ADS)

Yoder, G.; Cook, J.

2010-12-01

Interactive lecture demonstrations1-6 (ILDs) are a powerful tool designed to help instructors bring state-of-the-art teaching pedagogies into the college-level introductory physics classroom. ILDs have been shown to improve students' conceptual understanding, and many examples have been created and published by Sokoloff and Thornton.6 We have used the new technology of Vernier's Wireless Dynamics Sensor System (WDSS)7 to develop three new ILDs for the first-semester introductory physics (calculus-based or algebra-based) classroom. These three are the Force Board, to demonstrate the vector nature of forces, addition of vectors, and the first condition of equilibrium; the Torque Board, to demonstrate torque and the second condition for equilibrium; and the Circular Motion Board, to discover the nature of the acceleration an object exhibiting uniform circular motion. With the WDSS, all three of these ILDs are easy to set up and use in any classroom or laboratory situation, and allow more instructors to utilize the technique of interactive lecture demonstrations.

MHD Effect on Unsteady Mixed Convection Boundary Layer Flow past a Circular Cylinder with Constant Wall Temperature

NASA Astrophysics Data System (ADS)

Ismail, M. A.; Mohamad, N. F.; Ilias, M. R.; Shafie, S.

2017-09-01

Magnetohydrodynamic (MHD) effect is a study on motion of electrical-conducting fluid under magnetic fields. This effect has great intention due to its applications such as design of heat exchanger and nuclear reactor. In the problem in fluid motion, flow of separation can reduced the effectiveness of the system as well as can increased the energy lost. This study will present the results on reducing the flow separation by considering magnetic effect. In this study, unsteady mixed convection boundary layer flow past a circular cylinder is given attention. Focus of study is on the separation times that affected by the magnetic fields. The mathematical models in the form of partial differential equations are transformed into nonlinear coupled ordinary differential equations and solved numerically using an implicit finite-difference scheme known as Keller-box method. The effect of magnetic parameter on velocity and temperature profiles as well as skin friction and Nusselt number are studied.

Laser spot tracking based on modified circular Hough transform and motion pattern analysis.

PubMed

Krstinić, Damir; Skelin, Ana Kuzmanić; Milatić, Ivan

2014-10-27

Laser pointers are one of the most widely used interactive and pointing devices in different human-computer interaction systems. Existing approaches to vision-based laser spot tracking are designed for controlled indoor environments with the main assumption that the laser spot is very bright, if not the brightest, spot in images. In this work, we are interested in developing a method for an outdoor, open-space environment, which could be implemented on embedded devices with limited computational resources. Under these circumstances, none of the assumptions of existing methods for laser spot tracking can be applied, yet a novel and fast method with robust performance is required. Throughout the paper, we will propose and evaluate an efficient method based on modified circular Hough transform and Lucas-Kanade motion analysis. Encouraging results on a representative dataset demonstrate the potential of our method in an uncontrolled outdoor environment, while achieving maximal accuracy indoors. Our dataset and ground truth data are made publicly available for further development.

Controlling motion sickness and spatial disorientation and enhancing vestibular rehabilitation with a user-worn see-through display.

PubMed

Krueger, Wesley W O

2011-01-01

An eyewear mounted visual display ("User-worn see-through display") projecting an artificial horizon aligned with the user's head and body position in space can prevent or lessen motion sickness in susceptible individuals when in a motion provocative environment as well as aid patients undergoing vestibular rehabilitation. In this project, a wearable display device, including software technology and hardware, was developed and a phase I feasibility study and phase II clinical trial for safety and efficacy were performed. Both phase I and phase II were prospective studies funded by the NIH. The phase II study used repeated measures for motion intolerant subjects and a randomized control group (display device/no display device) pre-posttest design for patients in vestibular rehabilitation. Following technology and display device development, 75 patients were evaluated by test and rating scales in the phase II study; 25 subjects with motion intolerance used the technology in the display device in provocative environments and completed subjective rating scales, whereas 50 patients were evaluated before and after vestibular rehabilitation (25 using the display device and 25 in a control group) using established test measures. All patients with motion intolerance rated the technology as helpful for nine symptoms assessed, and 96% rated the display device as simple and easy to use. Duration of symptoms significantly decreased with use of the technology displayed. In patients undergoing vestibular rehabilitation, there were no significant differences in amount of change from pre- to posttherapy on objective balance tests between display device users and controls. However, those using the technology required significantly fewer rehabilitation sessions to achieve those outcomes than the control group. A user-worn see-through display, utilizing a visual fixation target coupled with a stable artificial horizon and aligned with user movement, has demonstrated substantial benefit for individuals susceptible to motion intolerance and spatial disorientation and those undergoing vestibular rehabilitation. The technology developed has applications in any environment where motion sensitivity affects human performance.

Combined effect of oblateness, radiation and a circular cluster of material points on the stability of triangular liberation points in the R3BP

NASA Astrophysics Data System (ADS)

Singh, Jagadish; Taura, Joel John

2014-06-01

This paper studies the motion of an infinitesimal mass in the framework of the restricted three-body problem (R3BP) under the assumption that the primaries of the system are radiating-oblate spheroids, enclosed by a circular cluster of material points. It examines the effects of radiation and oblateness up to J 4 of the primaries and the potential created by the circular cluster, on the linear stability of the liberation locations of the infinitesimal mass. The liberation points are found to be stable for 0< μ< μ c and unstable for , where μ c is the critical mass value depending on terms which involve parameters that characterize the oblateness, radiation forces and the circular cluster of material points. The oblateness up to J 4 of the primaries and the gravitational potential from the circular cluster of material points have stabilizing propensities, while the radiation of the primaries and the oblateness up to J 2 of the primaries have destabilizing tendencies. The combined effect of these perturbations on the stability of the triangular liberation points is that, it has stabilizing propensity.

The dynamics and control of large flexible space structures. Part B: Development of continuum model and computer simulation

NASA Technical Reports Server (NTRS)

Bainum, P. M.; Kumar, V. K.; James, P. K.

1978-01-01

The equations of motion of an arbitrary flexible body in orbit were derived. The model includes the effects of gravity with all its higher harmonics. As a specific example, the motion of a long, slender, uniform beam in circular orbit was modelled. The example considers both the inplane and three dimensional motion of the beam in orbit. In the case of planar motion with only flexible vibrations, the pitch motion is not influenced by the elastic motion of the beam. For large values of the square of the ratio of the structural modal frequency to the orbital angular rate the elastic motion was decoupled from the pitch motion. However, for small values of the ratio and small amplitude pitch motion, the elastic motion was governed by a Hill's 3 term equation. Numerical simulation of the equation indicates the possibilities of instability for very low values of the square of the ratio of the modal frequency to the orbit angular rate. Also numerical simulations of the first order nonlinear equations of motion for a long flexible beam in orbit were performed. The effect of varying the initial conditions and the number of modes was demonstrated.

A Third Type of Defensive Behavior in the Tenebrionid Beetle Zophobas atratus Pupae

PubMed Central

Ichikawa, Toshio; Sakamoto, Hirofumi

2013-01-01

Pupae of the tenebrionid beetle Zophobas atratus Fabricius (Coleoptera: Tenebrionidae) exhibit two types of reflex abdominal motions in response to tactile stimulation: circular rotation and lateral bending to close pinching devices (gin-traps). In the present study, the pupa exhibited novel, sequential abdominal movements at 0.3–2.2 sec after the onset of mechanical stimulation. The most effective stimulation was gentle, double brushing on the ventral surface of an abdominal segment (sternite). The sequential abdominal movements consisted of the following three types of discrete elementary motions (100–350 ms in duration): rapid vibration of 30–40 Hz, circular rotation (or swing), and small wiggling movements. A sequence of abdominal movements generally started with a few bouts of vibration, but the number and order of subsequent motions varied considerably among different sessions and conditions. A restrained pupa often showed a prolonged sequence of many motions, including several rotations, whereas an unrestrained pupa often shortened the sequence by skipping a few rotations after the displacement of its whole body induced by the first abdominal rotation. Stimulation of two types of mechanosensitive sensilla, the hair sensilla (touch sensors) and campaniform sensilla (strain sensors), seemed to be necessary to initiate the defensive response. In natural environments, crawling of a small predator (or parasitoid) on the surface of the abdomen or repeated attacks of a large predator may induce this defensive response in the pupae. PMID:23895506

Study of periodic motions of a satellite with a magnetic damper

NASA Technical Reports Server (NTRS)

Sadov, Y. A.; Teterin, A. D.

1979-01-01

The motion of a satellite with a magnetic damper in the plane of a circular polar orbit is studied. The asymptotics of periodic solutions are constructed for a satellite close to axisymmetric and the radius of convergence is evaluated for the power series obtained. In a broad range of values of parameters, a periodic solution is obtained by numerical integration of equations of motion of the satellite. The asymptotics of a bifurcated curve obtained (the curve on which origin of a pair of periodic solutions occurs) in the space of the parameters agrees well with the results of numerical computation with all physical values of these parameters. A breakdown is made of the space of the initial data of phase variables in the field of effect of different types of periodic motion.

Betatron motion with coupling of horizontal and vertical degrees of freedom

DOE Office of Scientific and Technical Information (OSTI.GOV)

S. A. Bogacz; V. A. Lebedev

2002-11-21

The Courant-Snyder parameterization of one-dimensional linear betatron motion is generalized to two-dimensional coupled linear motion. To represent the 4 x 4 symplectic transfer matrix the following ten parameters were chosen: four beta-functions, four alpha-functions and two betatron phase advances which have a meaning similar to the Courant-Snyder parameterization. Such a parameterization works equally well for weak and strong coupling and can be useful for analysis of coupled betatron motion in circular accelerators as well as in transfer lines. Similarly, the transfer matrix, the bilinear form describing the phase space ellipsoid and the second order moments are related to the eigen-vectors.more » Corresponding equations can be useful in interpreting tracking results and experimental data.« less

Hinged Capsulotomy – Does it Decrease Floaters After Yttrium Aluminum Garnet Laser Capsulotomy?

PubMed Central

Alipour, Fatemeh; Jabbarvand, Mahmoud; Hashemian, Hesam; Hosseini, Simindokht; Khodaparast, Mehdi

2015-01-01

Objectives: The objective was to compare conventional circular yttrium aluminum garnet (YAG) laser capsulotomy with hinged capsulotomy to manage posterior capsular opacification (PCO). Materials and Methods: This prospective, randomized clinical trial enrolled pseudophakic patients with visually significant posterior capsule opacification. Patients were randomized to undergo posterior YAG laser capsulotomy with either conventional circular technique or a new technique with an inferior hinge. At 1-month postoperatively, patients were asked if they had any annoying floaters and the responses were compared between groups. P < 0.05 was considered statistically significant. Results: A total of 83 patients were enrolled. Forty-three patients underwent hinged posterior YAG capsulotomy and 40 patients underwent routine circular capsulotomy. At 1-month postoperatively, there was a statistically significant decrease in annoying floaters in the group that underwent circular capsulotomy (P = 0.02). There was no statistically significant association in the total energy delivered (P = 0.4) or the number of spots (P = 0.2) and patient perception of annoying floaters. Conclusion: Hinged YAG capsulotomy was effective at decreasing the rate of floaters in patients with PCO. PMID:26180476

Hinged Capsulotomy--Does it Decrease Floaters After Yttrium Aluminum Garnet Laser Capsulotomy?

PubMed

Alipour, Fatemeh; Jabbarvand, Mahmoud; Hashemian, Hesam; Hosseini, Simindokht; Khodaparast, Mehdi

2015-01-01

The objective was to compare conventional circular yttrium aluminum garnet (YAG) laser capsulotomy with hinged capsulotomy to manage posterior capsular opacification (PCO). This prospective, randomized clinical trial enrolled pseudophakic patients with visually significant posterior capsule opacification. Patients were randomized to undergo posterior YAG laser capsulotomy with either conventional circular technique or a new technique with an inferior hinge. At 1-month postoperatively, patients were asked if they had any annoying floaters and the responses were compared between groups. P < 0.05 was considered statistically significant. A total of 83 patients were enrolled. Forty-three patients underwent hinged posterior YAG capsulotomy and 40 patients underwent routine circular capsulotomy. At 1-month postoperatively, there was a statistically significant decrease in annoying floaters in the group that underwent circular capsulotomy (P = 0.02). There was no statistically significant association in the total energy delivered (P = 0.4) or the number of spots (P = 0.2) and patient perception of annoying floaters. Hinged YAG capsulotomy was effective at decreasing the rate of floaters in patients with PCO.

Three-dimensional plasmonic chiral tetramers assembled by DNA origami.

PubMed

Shen, Xibo; Asenjo-Garcia, Ana; Liu, Qing; Jiang, Qiao; García de Abajo, F Javier; Liu, Na; Ding, Baoquan

2013-05-08

Molecular chemistry offers a unique toolkit to draw inspiration for the design of artificial metamolecules. For a long time, optical circular dichroism has been exclusively the terrain of natural chiral molecules, which exhibit optical activity mainly in the UV spectral range, thus greatly hindering their significance for a broad range of applications. Here we demonstrate that circular dichroism can be generated with artificial plasmonic chiral nanostructures composed of the minimum number of spherical gold nanoparticles required for three-dimensional (3D) chirality. We utilize a rigid addressable DNA origami template to precisely organize four nominally identical gold nanoparticles into a three-dimensional asymmetric tetramer. Because of the chiral structural symmetry and the strong plasmonic resonant coupling between the gold nanoparticles, the 3D plasmonic assemblies undergo different interactions with left and right circularly polarized light, leading to pronounced circular dichroism. Our experimental results agree well with theoretical predictions. The simplicity of our structure geometry and, most importantly, the concept of resorting on biology to produce artificial photonic functionalities open a new pathway to designing smart artificial plasmonic nanostructures for large-scale production of optically active metamaterials.

AMD-stability in the presence of first-order mean motion resonances

NASA Astrophysics Data System (ADS)

Petit, A. C.; Laskar, J.; Boué, G.

2017-11-01

The angular momentum deficit (AMD)-stability criterion allows to discriminate between a priori stable planetary systems and systems for which the stability is not granted and needs further investigations. AMD-stability is based on the conservation of the AMD in the averaged system at all orders of averaging. While the AMD criterion is rigorous, the conservation of the AMD is only granted in absence of mean-motion resonances (MMR). Here we extend the AMD-stability criterion to take into account mean-motion resonances, and more specifically the overlap of first-order MMR. If the MMR islands overlap, the system will experience generalized chaos leading to instability. The Hamiltonian of two massive planets on coplanar quasi-circular orbits can be reduced to an integrable one degree of freedom problem for period ratios close to a first-order MMR. We use the reduced Hamiltonian to derive a new overlap criterion for first-order MMR. This stability criterion unifies the previous criteria proposed in the literature and admits the criteria obtained for initially circular and eccentric orbits as limit cases. We then improve the definition of AMD-stability to take into account the short term chaos generated by MMR overlap. We analyze the outcome of this improved definition of AMD-stability on selected multi-planet systems from the Extrasolar Planets Encyclopædia.

Ultraprecision XY stage using a hybrid bolt-clamped Langevin-type ultrasonic linear motor for continuous motion.

PubMed

Lee, Dong-Jin; Lee, Sun-Kyu

2015-01-01

This paper presents a design and control system for an XY stage driven by an ultrasonic linear motor. In this study, a hybrid bolt-clamped Langevin-type ultrasonic linear motor was manufactured and then operated at the resonance frequency of the third longitudinal and the sixth lateral modes. These two modes were matched through the preload adjustment and precisely tuned by the frequency matching method based on the impedance matching method with consideration of the different moving weights. The XY stage was evaluated in terms of position and circular motion. To achieve both fine and stable motion, the controller consisted of a nominal characteristics trajectory following (NCTF) control for continuous motion, dead zone compensation, and a switching controller based on the different NCTFs for the macro- and micro-dynamics regimes. The experimental results showed that the developed stage enables positioning and continuous motion with nanometer-level accuracy.

Targeted energy transfer in laminar vortex-induced vibration of a sprung cylinder with a nonlinear dissipative rotator

NASA Astrophysics Data System (ADS)

Blanchard, Antoine; Bergman, Lawrence A.; Vakakis, Alexander F.

2017-07-01

We computationally investigate the dynamics of a linearly-sprung circular cylinder immersed in an incompressible flow and undergoing transverse vortex-induced vibration (VIV), to which is attached a rotational nonlinear energy sink (NES) consisting of a mass that freely rotates at constant radius about the cylinder axis, and whose motion is restrained by a rotational linear viscous damper. The inertial coupling between the rotational motion of the attached mass and the rectilinear motion of the cylinder is ;essentially nonlinear;, which, in conjunction with dissipation, allows for one-way, nearly irreversible targeted energy transfer (TET) from the oscillating cylinder to the nonlinear dissipative attachment. At the intermediate Reynolds number Re = 100, the NES-equipped sprung cylinder undergoes repetitive cycles of slowly decaying oscillations punctuated by intervals of chaotic instabilities. During the slowly decaying portion of each cycle, the dynamics of the cylinder is regular and, for large enough values of the ratio ε of the NES mass to the total mass (i.e., NES mass plus cylinder mass), can lead to significant vortex street elongation with partial stabilization of the wake. As ε approaches zero, no such vortex elongation is observed and the wake patterns appear similar to that for a sprung cylinder with no NES. We apply proper orthogonal decomposition (POD) to the velocity flow field during a slowly decaying portion of the solution and show that, in situations where vortex elongation occurs, the NES, though not in direct contact with the surrounding fluid, has a drastic effect on the underlying flow structures, imparting significant and continuous passive redistribution of energy among POD modes. We construct a POD-based reduced-order model for the lift coefficient to characterize energy transactions between the fluid and the cylinder throughout the slowly decaying cycle. We introduce a quantitative signed measure of the work done by the fluid on the cylinder over one quasi-period of the slowly decaying response and find that vortex elongation is associated with a sign change of that measure, indicating that a reversal of the direction of energy transfer, with the cylinder ;leaking energy back; to the flow, is responsible for partial stabilization and elongation of the wake. We interpret these findings in terms of the spatial structure and energy distribution of the POD modes, and relate them to the mechanism of transient resonance capture into a slow invariant manifold of the fluid-structure interaction dynamics.

Evaluation of motion artifact metrics for coronary CT angiography.

PubMed

Ma, Hongfeng; Gros, Eric; Szabo, Aniko; Baginski, Scott G; Laste, Zachary R; Kulkarni, Naveen M; Okerlund, Darin; Schmidt, Taly G

2018-02-01

This study quantified the performance of coronary artery motion artifact metrics relative to human observer ratings. Motion artifact metrics have been used as part of motion correction and best-phase selection algorithms for Coronary Computed Tomography Angiography (CCTA). However, the lack of ground truth makes it difficult to validate how well the metrics quantify the level of motion artifact. This study investigated five motion artifact metrics, including two novel metrics, using a dynamic phantom, clinical CCTA images, and an observer study that provided ground-truth motion artifact scores from a series of pairwise comparisons. Five motion artifact metrics were calculated for the coronary artery regions on both phantom and clinical CCTA images: positivity, entropy, normalized circularity, Fold Overlap Ratio (FOR), and Low-Intensity Region Score (LIRS). CT images were acquired of a dynamic cardiac phantom that simulated cardiac motion and contained six iodine-filled vessels of varying diameter and with regions of soft plaque and calcifications. Scans were repeated with different gantry start angles. Images were reconstructed at five phases of the motion cycle. Clinical images were acquired from 14 CCTA exams with patient heart rates ranging from 52 to 82 bpm. The vessel and shading artifacts were manually segmented by three readers and combined to create ground-truth artifact regions. Motion artifact levels were also assessed by readers using a pairwise comparison method to establish a ground-truth reader score. The Kendall's Tau coefficients were calculated to evaluate the statistical agreement in ranking between the motion artifacts metrics and reader scores. Linear regression between the reader scores and the metrics was also performed. On phantom images, the Kendall's Tau coefficients of the five motion artifact metrics were 0.50 (normalized circularity), 0.35 (entropy), 0.82 (positivity), 0.77 (FOR), 0.77(LIRS), where higher Kendall's Tau signifies higher agreement. The FOR, LIRS, and transformed positivity (the fourth root of the positivity) were further evaluated in the study of clinical images. The Kendall's Tau coefficients of the selected metrics were 0.59 (FOR), 0.53 (LIRS), and 0.21 (Transformed positivity). In the study of clinical data, a Motion Artifact Score, defined as the product of FOR and LIRS metrics, further improved agreement with reader scores, with a Kendall's Tau coefficient of 0.65. The metrics of FOR, LIRS, and the product of the two metrics provided the highest agreement in motion artifact ranking when compared to the readers, and the highest linear correlation to the reader scores. The validated motion artifact metrics may be useful for developing and evaluating methods to reduce motion in Coronary Computed Tomography Angiography (CCTA) images. © 2017 American Association of Physicists in Medicine.

Joint correction of respiratory motion artifact and partial volume effect in lung/thoracic PET/CT imaging.

PubMed

Chang, Guoping; Chang, Tingting; Pan, Tinsu; Clark, John W; Mawlawi, Osama R

2010-12-01

Respiratory motion artifacts and partial volume effects (PVEs) are two degrading factors that affect the accuracy of image quantification in PET/CT imaging. In this article, the authors propose a joint motion and PVE correction approach (JMPC) to improve PET quantification by simultaneously correcting for respiratory motion artifacts and PVE in patients with lung/thoracic cancer. The objective of this article is to describe this approach and evaluate its performance using phantom and patient studies. The proposed joint correction approach incorporates a model of motion blurring, PVE, and object size/shape. A motion blurring kernel (MBK) is then estimated from the deconvolution of the joint model, while the activity concentration (AC) of the tumor is estimated from the normalization of the derived MBK. To evaluate the performance of this approach, two phantom studies and eight patient studies were performed. In the phantom studies, two motion waveforms-a linear sinusoidal and a circular motion-were used to control the motion of a sphere, while in the patient studies, all participants were instructed to breathe regularly. For the phantom studies, the resultant MBK was compared to the true MBK by measuring a correlation coefficient between the two kernels. The measured sphere AC derived from the proposed method was compared to the true AC as well as the ACs in images exhibiting PVE only and images exhibiting both PVE and motion blurring. For the patient studies, the resultant MBK was compared to the motion extent derived from a 4D-CT study, while the measured tumor AC was compared to the AC in images exhibiting both PVE and motion blurring. For the phantom studies, the estimated MBK approximated the true MBK with an average correlation coefficient of 0.91. The tumor ACs following the joint correction technique were similar to the true AC with an average difference of 2%. Furthermore, the tumor ACs on the PVE only images and images with both motion blur and PVE effects were, on average, 75% and 47.5% (10%) of the true AC, respectively, for the linear (circular) motion phantom study. For the patient studies, the maximum and mean AC/SUV on the PET images following the joint correction are, on average, increased by 125.9% and 371.6%, respectively, when compared to the PET images with both PVE and motion. The motion extents measured from the derived MBK and 4D-CT exhibited an average difference of 1.9 mm. The proposed joint correction approach can improve the accuracy of PET quantification by simultaneously compensating for the respiratory motion artifacts and PVE in lung/thoracic PET/CT imaging.

Temporal change of photophobic step-up responses of Euglena gracilis investigated through motion analysis

PubMed Central

Ozasa, Kazunari; Won, June; Song, Simon; Tamaki, Shun; Ishikawa, Takahiro; Maeda, Mizuo

2017-01-01

The adaptation to a strong light is one of the essential characteristics of green algae, yet lacking relatively the information about the photophobic responses of Eukaryotic microalgae. We investigated the photophobic step-up responses of Euglena gracilis over a time course of several hours with alternated repetition of blue-light pulse illumination and spatially patterned blue-light illumination. Four distinctive photophobic motions in response to strong blue light were identified in a trace image analysis, namely on-site rotation, running and tumbling, continuous circular swimming, and unaffected straightforward swimming. The cells cultured in autotrophic conditions under weak light showed mainly the on-site rotation response at the beginning of blue-light illumination, but they acquired more blue-light tolerant responses of running and tumbling, circular swimming, or straightforward swimming. The efficiency of escaping from a blue-light illuminated area improved markedly with the development of these photophobic motions. Time constant of 3.0 h was deduced for the evolution of photophobic responses of E. gracilis. The nutrient-rich metabolic status of the cells resulting from photosynthesis during the experiments, i.e., the accumulation of photosynthesized nutrient products in balance between formation and consumption, was the main factor responsible for the development of photophobic responses. The reduction-oxidation status in and around E. gracilis cells did not affect their photophobic responses significantly, unlike the case of photophobic responses and phototaxis of Chlamydomonas reinhardtii cells. This study shows that the evolution of photophobic motion type of E. gracilis is dominated mainly by the nutrient metabolic status of the cells. The fact suggests that the nutrient-rich cells have a higher threshold for switching the flagellar motion from straightforward swimming to rotation under a strong light. PMID:28234984

Demonstrating the Direction of Angular Velocity in Circular Motion

NASA Astrophysics Data System (ADS)

Demircioglu, Salih; Yurumezoglu, Kemal; Isik, Hakan

2015-09-01

Rotational motion is ubiquitous in nature, from astronomical systems to household devices in everyday life to elementary models of atoms. Unlike the tangential velocity vector that represents the instantaneous linear velocity (magnitude and direction), an angular velocity vector is conceptually more challenging for students to grasp. In physics classrooms, the direction of an angular velocity vector is taught by the right-hand rule, a mnemonic tool intended to aid memory. A setup constructed for instructional purposes may provide students with a more easily understood and concrete method to observe the direction of the angular velocity. This article attempts to demonstrate the angular velocity vector using the observable motion of a screw mounted to a remotely operated toy car.

Diffusion of isolated DNA molecules: dependence on length and topology.

PubMed

Robertson, Rae M; Laib, Stephan; Smith, Douglas E

2006-05-09

The conformation and dynamics of circular polymers is a subject of considerable theoretical and experimental interest. DNA is an important example because it occurs naturally in different topological states, including linear, relaxed circular, and supercoiled circular forms. A fundamental question is how the diffusion coefficients of isolated polymers scale with molecular length and how they vary for different topologies. Here, diffusion coefficients D for relaxed circular, supercoiled, and linear DNA molecules of length L ranging from approximately 6 to 290 kbp were measured by tracking the Brownian motion of single molecules. A topology-independent scaling law D approximately L(-nu) was observed with nu(L) = 0.571 +/- 0.014, nu(C) = 0.589 +/- 0.018, and nu(S) = 0.571 +/- 0.057 for linear, relaxed circular, and supercoiled DNA, respectively, in good agreement with the scaling exponent of nu congruent with 0.588 predicted by renormalization group theory for polymers with significant excluded volume interactions. Our findings thus provide evidence in support of several theories that predict an effective diameter of DNA much greater than the Debye screening length. In addition, the measured ratio D(Circular)/D(Linear) = 1.32 +/- 0.014 was closer to the value of 1.45 predicted by using renormalization group theory than the value of 1.18 predicted by classical Kirkwood hydrodynamic theory and agreed well with a value of 1.31 predicted when incorporating a recently proposed expression for the radius of gyration of circular polymers into the Zimm model.

Conjecture: imines as unidirectional photodriven molecular motors-motional and constitutional dynamic devices.

PubMed

Lehn, Jean-Marie

2006-08-07

Compounds containing the C==N group, such as imines and their derivatives, may undergo syn-anti isomerization by two different routes: 1) photochemically, by out-of-plane rotation around the carbon-nitrogen double bond through a "perpendicular" form, and 2) thermally, by in-plane nitrogen inversion through a "linear" transition state. When the two interconversions occur in sequence, a full, closed process is accomplished, restoring the initial state of the system along two different steps. In a chiral imine-type compound, for example, with an asymmetric center next to the C==N function, photoinduced rotation may be expected to occur in one sense in preference to the opposite one. Thus, photoisomerization followed by thermal isomerization in a chiral imine compound generates unidirectional molecular motion. Generally, imine-type compounds represent unidirectional molecular photomotors converting light energy into mechanical motion. As they are also able to undergo exchange of the carbonyl and amine partners, they present constitutional dynamics. Thus, imine-type compounds are double dynamic, motional, and constitutional devices.

Self-Paced Physics, Segments 6-10.

ERIC Educational Resources Information Center

New York Inst. of Tech., Old Westbury.

Five segments of the Self-Paced Physics Course materials are presented in this problems and solutions book for use as the second part of student course work. The subject-matter topics are related to circular motion, work, power, kinetic energy, potential energy, conservative forces, conservation of energy, spring problems, center of mass, and…

Pendulum Rides, Rotations and the Coriolis Effect

ERIC Educational Resources Information Center

Pendrill, Ann-Marie; Modig, Conny

2018-01-01

An amusement park is full of examples that can be made into challenging problems for students, combining mathematical modelling with video analysis, as well as measurements in the rides. Traditional amusement ride related textbook problems include free-fall, circular motion, pendula and energy conservation in roller coasters, where the moving…

From Concept to Reality in Implementing the Knowledge Triangle

ERIC Educational Resources Information Center

Sjoer, Ellen; Nørgaard, Bente; Goossens, Marc

2016-01-01

The concept of Knowledge Triangle (KT) links together research, education and innovation and replaces the traditional "one way" flow of knowledge, essentially from research to education, by a "both ways" circular motion between all the corners of a triangle that, besides research and education, also includes innovation, the…

Perceived Shrinkage of Motion Paths

ERIC Educational Resources Information Center

Sinico, Michele; Parovel, Giulia; Casco, Clara; Anstis, Stuart

2009-01-01

We show that human observers strongly underestimate a linear or circular trajectory that a luminous spot follows in the dark. At slow speeds, observers are relatively accurate, but, as the speed increases, the size of the path is progressively underestimated, by up to 35%. The underestimation imposes little memory load and does not require…

Teacher's Guide for Spinning Tables. Elementary Science Study.

ERIC Educational Resources Information Center

Hein, George E.; And Others

This teacher's guide suggests a number of ways to use a spinning table to explore circular motion. Activities are described which are appropriate for children in kindergarten through third grade. Suggestions are made for exploratory activities using the equipment rather than supplying detailed instructions for formal activities. Equipment and…

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schäfer, Gerhard

The current knowledge in the post-Newtonian (PN) dynamics and motion of non-spinning and spinning compact binaries will be presented based on the Arnowitt-Deser-Misner Hamiltonian approach to general relativity. The presentation will cover the binary dynamics with non-spinning components up to the 4PN order and for spinning binaries up to the next-to-next-to-leading order in the spin-orbit and spin-spin couplings. Radiation reaction will be treated for both non-spinning and spinning binaries. Explicit analytic expressions for the motion will be given, innermost stable circular orbits will be discussed.

Time variation in the reaction-zone structure of two-phase spray detonations.

NASA Technical Reports Server (NTRS)

Pierce, T. H.; Nicholls, J. A.

1973-01-01

A detailed theoretical analysis of the time-varying detonation structure in a monodisperse spray is presented. The theory identifies experimentally observed reaction-zone overpressures as deriving from blast waves formed therein by the explosive ignition of the spray droplets, and follows in time the motion, change in strength, and interactions of these blast waves with one another, and with the leading shock. The results are compared with experimental data by modeling the motion of a finite-size circular pressure transducer through the theoretical data field in an x-t space.

Investigation of the Observability of a Satellite Cluster in a Near Circular Orbit

DTIC Science & Technology

1989-12-01

investigation involved the use of dynamics based on the Clohessy - Wiltshire equa- tions and an on-board estimator based on the U-D covariance factorization...vectors were determined from the Clohessy - Wiltshire equations (10:80). These equations have the following * form: I I4 I I I sat i , ref pointI S iA lll ri... Clohessy - Wiltshire equations of motion, with 77 representing the mean motion (10:80). These equations are: 1 11I ;i - 2 )- 3 T12 X = 0 (27) +21 =0 (28

Media additives to promote spheroid circularity and compactness in hanging drop platform.

PubMed

Leung, Brendan M; Lesher-Perez, Sasha Cai; Matsuoka, Toshiki; Moraes, Christopher; Takayama, Shuichi

2015-02-01

Three-dimensional spheroid cultures have become increasingly popular as drug screening platforms, especially with the advent of different high throughput spheroid forming technologies. However, comparing drug efficacy across different cell types in spheroid culture can be difficult due to variations in spheroid morphologies and transport characteristics. Improving the reproducibility of compact, circular spheroids contributes to standardizing and increasing the fidelity of the desired gradient profiles in these drug screening three-dimensional tissue cultures. In this study we discuss the role that circularity and compaction has on spheroids, and demonstrate the impact methylcellulose (MethoCel) and collagen additives in the culture media can contribute to more compact and circular spheroid morphology. We demonstrate that improved spheroid formation is not a simple function of increased viscosity of the different macromolecule additives, suggesting that other macromolecular characteristics contribute to improved spheroid formation. Of the various macromolecular additives tested for hanging drop culture, MethoCel provided the most desirable spheroid formation. Additionally, the higher viscosity of MethoCel-containing media improved the ease of imaging of cellular spheroids within hanging drop cultures by reducing motion-induced image blur.

Gravitational self-force correction to the innermost stable circular equatorial orbit of a Kerr black hole.

PubMed

Isoyama, Soichiro; Barack, Leor; Dolan, Sam R; Le Tiec, Alexandre; Nakano, Hiroyuki; Shah, Abhay G; Tanaka, Takahiro; Warburton, Niels

2014-10-17

For a self-gravitating particle of mass μ in orbit around a Kerr black hole of mass M ≫ μ, we compute the O(μ/M) shift in the frequency of the innermost stable circular equatorial orbit due to the conservative piece of the gravitational self-force acting on the particle. Our treatment is based on a Hamiltonian formulation of the dynamics in terms of geodesic motion in a certain locally defined effective smooth spacetime. We recover the same result using the so-called first law of binary black-hole mechanics. We give numerical results for the innermost stable circular equatorial orbit frequency shift as a function of the black hole's spin amplitude, and compare with predictions based on the post-Newtonian approximation and the effective one-body model. Our results provide an accurate strong-field benchmark for spin effects in the general-relativistic two-body problem.

Transonic shock-induced dynamics of a flexible wing with a thick circular-arc airfoil

NASA Technical Reports Server (NTRS)

Bennett, Robert M.; Dansberry, Bryan E.; Farmer, Moses G.; Eckstrom, Clinton V.; Seidel, David A.; Rivera, Jose A., Jr.

1991-01-01

Transonic shock boundary layer oscillations occur on rigid models over a small range of Mach numbers on thick circular-arc airfoils. Extensive tests and analyses of this phenomena have been made in the past but essentially all of them were for rigid models. A simple flexible wing model with an 18 pct. circular arc airfoil was constructed and tested in the Langley Transonic Dynamics Tunnel to study the dynamic characteristics that a wing might have under these circumstances. In the region of shock boundary layer oscillations, buffeting of the first bending mode was obtained. This mode was well separated in frequency from the shock boundary layer oscillations. A limit cycle oscillation was also measured in a third bending like mode, involving wind vertical bending and splitter plate motion, which was in the frequency range of the shock boundary layer oscillations. Several model configurations were tested, and a few potential fixes were investigated.

Swarms with canonical active Brownian motion.

PubMed

Glück, Alexander; Hüffel, Helmuth; Ilijić, Saša

2011-05-01

We present a swarm model of Brownian particles with harmonic interactions, where the individuals undergo canonical active Brownian motion, i.e., each Brownian particle can convert internal energy to mechanical energy of motion. We assume the existence of a single global internal energy of the system. Numerical simulations show amorphous swarming behavior as well as static configurations. Analytic understanding of the system is provided by studying stability properties of equilibria.

Computational simulations of hydrogen circular migration in protonated acetylene induced by circularly polarized light

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shi, Xuetao; Li, Wen; Schlegel, H. Bernhard, E-mail: hbs@chem.wayne.edu

2016-08-28

The hydrogens in protonated acetylene are very mobile and can easily migrate around the C{sub 2} core by moving between classical and non-classical structures of the cation. The lowest energy structure is the T-shaped, non-classical cation with a hydrogen bridging the two carbons. Conversion to the classical H{sub 2}CCH{sup +} ion requires only 4 kcal/mol. The effect of circularly polarized light on the migration of hydrogens in oriented C{sub 2}H{sub 3}{sup +} has been simulated by Born-Oppenheimer molecular dynamics. Classical trajectory calculations were carried out with the M062X/6-311+G(3df,2pd) level of theory using linearly and circularly polarized 32 cycle 7 μmmore » cosine squared pulses with peak intensity of 5.6 × 10{sup 13} W/cm{sup 2} and 3.15 × 10{sup 13} W/cm{sup 2}, respectively. These linearly and circularly polarized pulses transfer similar amounts of energy and total angular momentum to C{sub 2}H{sub 3}{sup +}. The average angular momentum vectors of the three hydrogens show opposite directions of rotation for right and left circularly polarized light, but no directional preference for linearly polarized light. This difference results in an appreciable amount of angular displacement of the three hydrogens relative to the C{sub 2} core for circularly polarized light, but only an insignificant amount for linearly polarized light. Over the course of the simulation with circularly polarized light, this corresponds to a propeller-like motion of the three hydrogens around the C{sub 2} core of protonated acetylene.« less

The Ribosome Shape Directs mRNA Translocation through Entrance and Exit Dynamics

USDA-ARS?s Scientific Manuscript database

The protein-synthesizing ribosome undergoes large motions to effect the translocation of tRNAs (transfer ribonucleic acids) and mRNA (messenger ribonucleic acid); here the domain motions of this system are explored with a coarse-grained elastic network model using normal mode analysis. Crystal struc...

Exploration of bounded motion near binary systems comprised of small irregular bodies

NASA Astrophysics Data System (ADS)

Chappaz, Loic; Howell, Kathleen C.

2015-10-01

To investigate the behavior of a spacecraft near a pair of irregular bodies, consider a three-body configuration (one massless). Two massive bodies, P_1 and P_2, form the primary system; each primary is modeled as a sphere or an ellipsoid. Two primary configurations are addressed: `synchronous' and `non-synchronous'. Concepts and tools similar to those applied in the circular restricted three-body problem are exploited to construct periodic trajectories for a third body in synchronous systems. In non-synchronous systems, however, the search for third body periodic orbits is complicated by several factors. The mathematical model for the third-body motion is now time-variant and the motion of P_2 is not trivial.

Controlling Motion Sickness and Spatial Disorientation and Enhancing Vestibular Rehabilitation with a User-Worn See-Through Display

PubMed Central

Krueger, Wesley W.O.

2010-01-01

Objectives/Hypotheses An eyewear mounted visual display (“User-worn see-through display”) projecting an artificial horizon aligned with the user's head and body position in space can prevent or lessen motion sickness in susceptible individuals when in a motion provocative environment as well as aid patients undergoing vestibular rehabilitation. In this project, a wearable display device, including software technology and hardware, was developed and a phase I feasibility study and phase II clinical trial for safety and efficacy were performed. Study Design Both phase I and phase II were prospective studies funded by the NIH. The phase II study used repeated measures for motion intolerant subjects and a randomized control group (display device/no display device) pre-post test design for patients in vestibular rehabilitation. Methods Following technology and display device development, 75 patients were evaluated by test and rating scales in the phase II study; 25 subjects with motion intolerance used the technology in the display device in provocative environments and completed subjective rating scales while 50 patients were evaluated before and after vestibular rehabilitation (25 using the display device and 25 in a control group) using established test measures. Results All patients with motion intolerance rated the technology as helpful for nine symptoms assessed, and 96% rated the display device as simple and easy to use. Duration of symptoms significantly decreased with use of the technology displayed. In patients undergoing vestibular rehabilitation, there were no significant differences in amount of change from pre- to post-therapy on objective balance tests between display device users and controls. However, those using the technology required significantly fewer rehabilitation sessions to achieve those outcomes than the control group. Conclusions A user-worn see-through display, utilizing a visual fixation target coupled with a stable artificial horizon and aligned with user movement, has demonstrated substantial benefit for individuals susceptible to motion intolerance and spatial disorientation and those undergoing vestibular rehabilitation. The technology developed has applications in any environment where motion sensitivity affects human performance. PMID:21181963

Forced Convection Heat Transfer in Circular Pipes

ERIC Educational Resources Information Center

Tosun, Ismail

2007-01-01

One of the pitfalls of engineering education is to lose the physical insight of the problem while tackling the mathematical part. Forced convection heat transfer (the Graetz-Nusselt problem) certainly falls into this category. The equation of energy together with the equation of motion leads to a partial differential equation subject to various…

Inquiry Style Interactive Virtual Experiments: A Case on Circular Motion

ERIC Educational Resources Information Center

Zhou, Shaona; Han, Jing; Pelz, Nathaniel; Wang, Xiaojun; Peng, Liangyu; Xiao, Hua; Bao, Lei

2011-01-01

Interest in computer-based learning, especially in the use of virtual reality simulations is increasing rapidly. While there are good reasons to believe that technologies have the potential to improve teaching and learning, how to utilize the technology effectively in teaching specific content difficulties is challenging. To help students develop…

Loop-the-Loop: Bringing Theory into Practice

ERIC Educational Resources Information Center

Suwonjandee, N.; Asavapibhop, B.

2012-01-01

During the Thai high-school physics teacher training programme, we used an aluminum loop-the-loop system built by the Institute for the Promotion of Teaching Science and Technology (IPST) to demonstrate a circular motion and investigate the concept of the conservation of mechanical energy. There were 27 high-school teachers from three provinces,…

The conical pendulum: the tethered aeroplane

NASA Astrophysics Data System (ADS)

Mazza, Anthony P.; Metcalf, William E.; Cinson, Anthony D.; Lynch, John J.

2007-01-01

The introductory physics lab curriculum usually has one experiment on uniform circular motion (UCM). Physics departments typically have several variable-speed rotators in storage that, if they work, no longer work well. Replacing these rotators with new ones is costly, especially when they are only used once a year. This article describes how an inexpensive (ap10) tethered aeroplane, powered by a small electric motor, can be used to study UCM. The aeroplane is easy to see and entertaining to watch. For a given string length and air speed, a tethered aeroplane quickly finds a stable, horizontal, circular orbit. Using a digital video (DV) camcorder, VideoPoint Capture, QuickTime player, metre sticks and a stopwatch, data on the aeroplane's motion were obtained. The length of the string was varied from 120 to 340 cm while the air speed ranged from 200 to 480 cm s-1. For each string length and air speed, the period of the orbit and the diameter of the path were carefully measured. Theoretical values of path radii were then calculated using Newton's second law. The agreement between experiment and theory was usually better than 2%.

Electric and magnetic polarization singularities of first-order Laguerre-Gaussian beams diffracted at a half-plane screen.

PubMed

Luo, Yamei; Gao, Zenghui; Tang, Bihua; Lü, Baida

2013-08-01

Based on the vector Fresnel diffraction integrals, analytical expressions for the electric and magnetic components of first-order Laguerre-Gaussian beams diffracted at a half-plane screen are derived and used to study the electric and magnetic polarization singularities in the diffraction field for both two- and three-dimensional (2D and 3D) cases. It is shown that there exist 2D and 3D electric and magnetic polarization singularities in the diffraction field, which do not coincide each other in general. By suitably varying the waist width ratio, off-axis displacement parameter, amplitude ratio, or propagation distance, the motion, pair-creation, and annihilation of circular polarization singularities, and the motion of linear polarization singularities take place in 2D and 3D electric and magnetic fields. The V point, at which two circular polarization singularities with the same topological charge but opposite handedness collide, appears in the 2D electric field under certain conditions in the diffraction field and free-space propagation. A comparison with the free-space propagation is also made.

Locomotion of bacteria in liquid flow and the boundary layer effect on bacterial attachment.

PubMed

Zhang, Chao; Liao, Qiang; Chen, Rong; Zhu, Xun

2015-06-12

The formation of biofilm greatly affects the performance of biological reactors, which highly depends on bacterial swimming and attachment that usually takes place in liquid flow. Therefore, bacterial swimming and attachment on flat and circular surfaces with the consideration of flow was studied experimentally. Besides, a mathematical model comprehensively combining bacterial swimming and motion with flow is proposed for the simulation of bacterial locomotion and attachment in flow. Both experimental and theoretical results revealed that attached bacteria density increases with decreasing boundary layer thickness on both flat and circular surfaces, the consequence of which is inherently related to the competition between bacterial swimming and the non-slip motion with flow evaluated by the Péclet number. In the boundary layer, where the Péclet number is relatively higher, bacterial locomotion mainly depends on bacterial swimming. Thinner boundary layer promotes bacterial swimming towards the surface, leading to higher attachment density. To enhance the performance of biofilm reactors, it is effective to reduce the boundary layer thickness on desired surfaces. Copyright © 2015 Elsevier Inc. All rights reserved.

Image registration and analysis for quantitative myocardial perfusion: application to dynamic circular cardiac CT.

PubMed

Isola, A A; Schmitt, H; van Stevendaal, U; Begemann, P G; Coulon, P; Boussel, L; Grass, M

2011-09-21

Large area detector computed tomography systems with fast rotating gantries enable volumetric dynamic cardiac perfusion studies. Prospectively, ECG-triggered acquisitions limit the data acquisition to a predefined cardiac phase and thereby reduce x-ray dose and limit motion artefacts. Even in the case of highly accurate prospective triggering and stable heart rate, spatial misalignment of the cardiac volumes acquired and reconstructed per cardiac cycle may occur due to small motion pattern variations from cycle to cycle. These misalignments reduce the accuracy of the quantitative analysis of myocardial perfusion parameters on a per voxel basis. An image-based solution to this problem is elastic 3D image registration of dynamic volume sequences with variable contrast, as it is introduced in this contribution. After circular cone-beam CT reconstruction of cardiac volumes covering large areas of the myocardial tissue, the complete series is aligned with respect to a chosen reference volume. The results of the registration process and the perfusion analysis with and without registration are evaluated quantitatively in this paper. The spatial alignment leads to improved quantification of myocardial perfusion for three different pig data sets.

Annular dynamics after mitral valve repair with different prosthetic rings: A real-time three-dimensional transesophageal echocardiography study.

PubMed

Nishi, Hiroyuki; Toda, Koichi; Miyagawa, Shigeru; Yoshikawa, Yasushi; Fukushima, Satsuki; Kawamura, Masashi; Yoshioka, Daisuke; Saito, Tetsuya; Ueno, Takayoshi; Kuratani, Toru; Sawa, Yoshiki

2016-09-01

We assessed the effects of different types of prosthetic rings on mitral annular dynamics using real-time three-dimensional echocardiography (RT3DE). RT3DE was performed in 44 patients, including patients undergoing mitral annuloplasty using the Cosgrove-Edwards flexible band (Group A, n = 10), the semi-rigid Sorin Memo 3D ring (Group B, n = 17), the semi-rigid Edwards Physio II ring (Group C, n = 7) and ten control subjects. Various annular diameters were measured throughout the cardiac cycle. We observed flexible anterior annulus motion in all of the groups except Group C. A flexible posterior annulus was only observed in Group B and the Control group. The mitral annular area changed during the cardiac cycle by 8.4 ± 3.2, 6.3 ± 2.0, 3.2 ± 1.3, and 11.6 ± 5.0 % in Group A, Group B, Group C, and the Control group, respectively. The dynamic diastolic to systolic change in mitral annular diameters was lost in Group C, while it was maintained in Group A, and to a good degree in Group B. In comparison to the Control group, the mitral annulus shape was more ellipsoid in Group B and Group C, and more circular in Group A. Although mitral regurgitation was well controlled by all of the types of rings that were utilized in the present study, we demonstrated that the annulus motion and annulus shape differed according to the type of prosthetic ring that was used, which might provide important information for the selection of an appropriate prosthetic ring.

Energy harvesting from arterial blood pressure for powering embedded micro sensors in human brain

NASA Astrophysics Data System (ADS)

Nanda, Aditya; Karami, M. Amin

2017-03-01

This manuscript investigates energy harvesting from arterial blood pressure via the piezoelectric effect for the purpose of powering embedded micro-sensors in the human brain. One of the major hurdles in recording and measuring electrical data in the human nervous system is the lack of implantable and long term interfaces that record neural activity for extended periods of time. Recently, some authors have proposed micro sensors implanted deep in the brain that measure local electrical and physiological data which are then communicated to an external interrogator. This paper proposes a way of powering such interfaces. The geometry of the proposed harvester consists of a piezoelectric, circular, curved bimorph that fits into the blood vessel (specifically, the Carotid artery) and undergoes bending motion because of blood pressure variation. In addition, the harvester thickness is constrained such that it does not modify arterial wall dynamics. This transforms the problem into a known strain problem and the integral form of Gauss's law is used to obtain an equation relating arterial wall motion to the induced voltage. The theoretical model is validated by means of a Multiphysics 3D-FEA simulation comparing the harvested power at different load resistances. The peak harvested power achieved for the Carotid artery (proximal to Brain), with PZT-5H, was 11.7 μW. The peak power for the Aorta was 203.4 μW. Further, the variation of harvested power with variation in the harvester width and thickness, arterial contractility, and pulse rate is investigated. Moreover, potential application of the harvester as a chronic, implantable and real-time Blood pressure sensor is considered. Energy harvested via this mechanism will also have applications in long-term, implantable Brain Micro-stimulation.

Particle Diffusion in Chaotic Magnetic Fields Generated by Asymmetric Current Configurations

NASA Astrophysics Data System (ADS)

Ram, A. K.; Dasgupta, B.

2008-12-01

The observed cross-field diffusion of charged particles in cosmic rays is assumed to be due to the chaotic nature of the interplanetary/intergalactic magnetic fields. Among the classic works on this subject have been those of Parker [1] and Jokipii [2]. Parker considered the passage of cosmic ray particles and energetic solar particles in a large scale magnetic field containing small scale irregularities. In the context of cosmic ray propagation, Jokipii considered a small fluctuating component, added on to a uniform magnetic field, to study the spatial transport of particles. In these studies the irregular component of the magnetic field is prescribed in an ad hoc fashion. In contrast, we consider asymmetric, nonlinear, steady-state magnetic fields, in three spatial dimensions, generated by currents flowing in circular loops and straight lines [3]. These magnetic fields are completely deterministic and, for certain range of parameters, chaotic. We will present analytical and numerical studies on the spatial characteristics of these fields. The motion of charged particles in the nonlinear and chaotic magnetic fields is determined using the Lorentz equation. A particle moving in a deterministic chaotic magnetic field superposed on a uniform background magnetic field is found to undergo spatial transport. This shows that chaotic magnetic fields generated by simple current configurations can produce cross-field diffusion. A detailed analysis of particle motion and diffusion along with application to space plasmas will be presented. [1] E.N. Parker, Planet. Space Sci. 13, 9 (1965). [2] J.R. Jokipii, Astrophys. J. 146, 480 (1966), and J.R. Jokipii, Astrophys. J. 149, 405 (1967). [3] A.K. Ram and B. Dasgupta, Eos Trans. AGU 87 (52), Fall Meet. Suppl. Abstract NG31B-1593 (2006); and Eos Trans. AGU 88 (52), Fall Meet. Suppl. Abstract NG21B-0522 (2007).

HelioTrope: An innovative and efficient prototype for solar power production

NASA Astrophysics Data System (ADS)

Papageorgiou, George; Maimaris, Athanasios; Hadjixenophontos, Savvas; Ioannou, Petros

2014-12-01

The solar energy alternative could provide us with all the energy we need as it exist in vast quantities all around us. We only should be innovative enough in order to improve the efficiency of our systems in capturing and converting solar energy in usable forms of power. By making a case for the solar energy alternative, we identify areas where efficiency can be improved and thereby Solar Energy can become a competitive energy source. This paper suggests an innovative approach to solar energy power production, which is manifested in a prototype given the name HelioTrope. The Heliotrope Solar Energy Production prototype is tested on its' capabilities to efficiently covert solar energy to generation of electricity and other forms of energy for storage or direct use. HelioTrope involves an innovative Stirling engine design and a parabolic concentrating dish with a sun tracking system implementing a control algorithm to maximize the capturing of solar energy. Further, it utilizes a patent developed by the authors where a mechanism is designed for the transmission of reciprocating motion of variable amplitude into unidirectional circular motion. This is employed in our prototype for converting linear reciprocating motion into circular for electricity production, which gives a significant increase in efficiency and reduces maintenance costs. Preliminary calculations indicate that the Heliotrope approach constitutes a competitive solution to solar power production.

Analytical and numerical construction of vertical periodic orbits about triangular libration points based on polynomial expansion relations among directions

NASA Astrophysics Data System (ADS)

Qian, Ying-Jing; Yang, Xiao-Dong; Zhai, Guan-Qiao; Zhang, Wei

2017-08-01

Innovated by the nonlinear modes concept in the vibrational dynamics, the vertical periodic orbits around the triangular libration points are revisited for the Circular Restricted Three-body Problem. The ζ -component motion is treated as the dominant motion and the ξ and η -component motions are treated as the slave motions. The slave motions are in nature related to the dominant motion through the approximate nonlinear polynomial expansions with respect to the ζ -position and ζ -velocity during the one of the periodic orbital motions. By employing the relations among the three directions, the three-dimensional system can be transferred into one-dimensional problem. Then the approximate three-dimensional vertical periodic solution can be analytically obtained by solving the dominant motion only on ζ -direction. To demonstrate the effectiveness of the proposed method, an accuracy study was carried out to validate the polynomial expansion (PE) method. As one of the applications, the invariant nonlinear relations in polynomial expansion form are used as constraints to obtain numerical solutions by differential correction. The nonlinear relations among the directions provide an alternative point of view to explore the overall dynamics of periodic orbits around libration points with general rules.

Model of DNA topology simplification has come full (supercoiled) circle after two decades of research. Comment on "Disentangling DNA molecules" by Alexander Vologodskii

NASA Astrophysics Data System (ADS)

Stasiak, Andrzej

2016-09-01

Being a geek of DNA topology, I remember very well the stir caused by 1997 Science paper showing that DNA topoisomerases have the ability to simplify DNA topology below the topological equilibrium values [1]. In their seminal experiments Rybenkov et al. [1] started with linear double-stranded DNA molecules with cohesive ends. The mutual cohesiveness of DNA ends was due to mutual complementarity of single-stranded extensions at both ends of linear double-stranded DNA molecules. When such DNA molecules were heated up and then slowly cooled down the single-stranded ends eventually annealed with each other causing DNA circularization. This experimental protocol permitted the authors to establish topological/thermodynamic equilibrium within samples of circularized DNA molecules. Among simple unknotted circles one also observed knotted and catenated DNA molecules. The fraction of knotted molecules in DNA samples at topological equilibrium was increasing with the length of DNA molecules undergoing slow circularization. The fraction of catenated molecules was increasing with the length and the concentration of the molecules undergoing slow circularization. Rybenkov et al. incubated then such equilibrated DNA samples with type II DNA topoisomerases, which pass DNA duplex regions through each other, and observed that as the result of it the fraction of knotted and catenated DNA molecules was dramatically decreased (up to 80-fold). This elegant experiment indicated for the first time that type II DNA topoisomerases acting on knotted or catenated DNA molecules have the ability to select among many potential sites of DNA-DNA passages these that result in DNA unknotting or decatenation. Without such a selection topoisomerases could only maintain the original topological equilibrium obtained during the slow cyclization. The big question was how DNA topoisomerases can be directed to do DNA-DNA passages that preferentially result in DNA unknotting and decatenation.

Repeating firing fields of CA1 neurons shift forward in response to increasing angular velocity.

PubMed

Cowen, Stephen L; Nitz, Douglas A

2014-01-01

Self-motion information influences spatially-specific firing patterns exhibited by hippocampal neurons. Moreover, these firing patterns can repeat across similar subsegments of an environment, provided that there is similarity of path shape and head orientations across subsegments. The influence of self-motion variables on repeating fields remains to be determined. To investigate the role of path shape and angular rotation on hippocampal activity, we recorded the activity of CA1 neurons from rats trained to run on spiral-shaped tracks. During inbound traversals of circular-spiral tracks, angular velocity increases continuously. Under this condition, most neurons (74%) exhibited repeating fields across at least three adjacent loops. Of these neurons, 86% exhibited forward shifts in the angles of field centers relative to centers on preceding loops. Shifts were absent on squared-spiral tracks, minimal and less reliable on concentric-circle tracks, and absent on outward-bound runs on circular-spiral tracks. However, outward-bound runs on the circular-spiral track in the dark were associated with backward shifts. Together, the most parsimonious interpretation of the results is that continuous increases or decreases in angular velocity are particularly effective at shifting the center of mass of repeating fields, although it is also possible that a nonlinear integration of step counts contributes to the shift. Furthermore, the unexpected absence of field shifts during outward journeys in light (but not darkness) suggests visual cues around the goal location anchored the map of space to an allocentric reference frame.

The coherent states of the two-dimensional isotropic harmonic oscillator and the classical limit of the Landau theory of a charged particle in a uniform magnetic field

NASA Astrophysics Data System (ADS)

Li, Wangyao; Sebastian, Kunnat

2018-07-01

In this paper we show how the classical result of a charged particle moving in a circle in the xy plane, when a uniform magnetic field is directed along the z-axis, can be derived from the Landau quantum theory using the coherent states of the two-dimensional isotropic harmonic oscillator in the xy plane. The coherent states in this case are the simultaneous eigen vectors of the annihilation operators a + and a ‑. We prove that the time-dependent coordinate space wave packets representing the time-dependent coherent states move in a circle with the cyclotron frequency {ω }c=\\tfrac{| q| B}{m} and with a radius given by the classical expression, but given in terms of the quantum mechanical expectation values. The expectation value of the energy of the particle and of the square of the radius of its circular are proportional to the square of the magnitude of the eigen value of a + in the coherent state, where as the x and y coordinates of the centre of the circle are proportional to the real and the imaginary parts of the eigen value of a ‑. The phase of the circular motion is the same as the phase of the complex eigen value of a +. So for a given energy of the particle or for a given radius of the circular orbit, there are an infinite number of circles which differ from each other by the x and y coordinates of the centre as well as the phase of the circular motion. The infinite degeneracy of the Landau levels is due to the invariance of the energy eigen values under spatial translations in the xy plane and rotations about the z-axis. We also show that as the magnitude of the eigen value of a + becomes much larger than one, the relative uncertainty or fluctuation in the energy and in the radius of the circular orbit becomes negligibly small as we expect for a classical state.

Exact Fan-Beam Reconstruction With Arbitrary Object Translations and Truncated Projections

NASA Astrophysics Data System (ADS)

Hoskovec, Jan; Clackdoyle, Rolf; Desbat, Laurent; Rit, Simon

2016-06-01

This article proposes a new method for reconstructing two-dimensional (2D) computed tomography (CT) images from truncated and motion contaminated sinograms. The type of motion considered here is a sequence of rigid translations which are assumed to be known. The algorithm first identifies the sufficiency of angular coverage in each 2D point of the CT image to calculate the Hilbert transform from the local “virtual” trajectory which accounts for the motion and the truncation. By taking advantage of data redundancy in the full circular scan, our method expands the reconstructible region beyond the one obtained with chord-based methods. The proposed direct reconstruction algorithm is based on the Differentiated Back-Projection with Hilbert filtering (DBP-H). The motion is taken into account during backprojection which is the first step of our direct reconstruction, before taking the derivatives and inverting the finite Hilbert transform. The algorithm has been tested in a proof-of-concept study on Shepp-Logan phantom simulations with several motion cases and detector sizes.

Ultraprecision XY stage using a hybrid bolt-clamped Langevin-type ultrasonic linear motor for continuous motion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Dong-Jin; Lee, Sun-Kyu, E-mail: skyee@gist.ac.kr

2015-01-15

This paper presents a design and control system for an XY stage driven by an ultrasonic linear motor. In this study, a hybrid bolt-clamped Langevin-type ultrasonic linear motor was manufactured and then operated at the resonance frequency of the third longitudinal and the sixth lateral modes. These two modes were matched through the preload adjustment and precisely tuned by the frequency matching method based on the impedance matching method with consideration of the different moving weights. The XY stage was evaluated in terms of position and circular motion. To achieve both fine and stable motion, the controller consisted of amore » nominal characteristics trajectory following (NCTF) control for continuous motion, dead zone compensation, and a switching controller based on the different NCTFs for the macro- and micro-dynamics regimes. The experimental results showed that the developed stage enables positioning and continuous motion with nanometer-level accuracy.« less

Brownian motion in non-equilibrium systems and the Ornstein-Uhlenbeck stochastic process.

PubMed

Donado, F; Moctezuma, R E; López-Flores, L; Medina-Noyola, M; Arauz-Lara, J L

2017-10-03

The Ornstein-Uhlenbeck stochastic process is an exact mathematical model providing accurate representations of many real dynamic processes in systems in a stationary state. When applied to the description of random motion of particles such as that of Brownian particles, it provides exact predictions coinciding with those of the Langevin equation but not restricted to systems in thermal equilibrium but only conditioned to be stationary. Here, we investigate experimentally single particle motion in a two-dimensional granular system in a stationary state, consisting of 1 mm stainless balls on a plane circular surface. The motion of the particles is produced by an alternating magnetic field applied perpendicular to the surface of the container. The mean square displacement of the particles is measured for a range of low concentrations and it is found that following an appropriate scaling of length and time, the short-time experimental curves conform a master curve covering the range of particle motion from ballistic to diffusive in accordance with the description of the Ornstein-Uhlenbeck model.

Perturbed Equations of Motion for Formation Flight Near the Sun-Earth L2 Point

NASA Technical Reports Server (NTRS)

Segerman, Alan M.; Zedd, Michael F.

2005-01-01

This Memorandum Report consists of a compilation of three individual reports, of increasing complexity, describing investigations of formation flight of spacecraft in the vicinity of the L2 Sun-Earth 1ibration point. The individual reports form the following parts of this compilation: - Introduction to the relative motion of spacecraft about the Sun-Earth L2 Point - Linear and quadratic modelling and solution of the relative motion - Modelling the Perturbations - Elliptical Earth Orbit, Lunar Gravity, Solar Radiation Pressure, Thrusters. The three parts are self-contained, with somewhat, varying notation and terminology. After fair1y significant literature searches: this new work (of Parts 2 and 3) is deemed to be unique because it describes the primary perturbations to the description of relative motion between nearby spacecraft. The effect of the elliptical motion of the Earth about the Sun was verified to be the dominant perturbation to the circular restricted three body problem. Contributions due to lunar gravity and solar radiation pressure are seen to have much smaller effect.

Acoustic resonances in cylinder bundles oscillating in a compressibile fluid

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lin, W.H.; Raptis, A.C.

1984-12-01

This paper deals with an analytical study on acoustic resonances of elastic oscillations of a group of parallel, circular, thin cylinders in an unbounded volume of barotropic, compressible, inviscid fluid. The perturbed motion of the fluid is assumed due entirely to the flexural oscillations of the cylinders. The motion of the fluid disturbances is first formulated in a three-dimensional wave form and then casted into a two-dimensional Helmholtz equation for the harmonic motion in time and in axial space. The acoustic motion in the fluid and the elastic motion in the cylinders are solved simultaneously. Acoustic resonances were approximately determinedmore » from the secular (eigenvalue) equation by the method of successive iteration with the use of digital computers for a given set of the fluid properties and the cylinders' geometry and properties. Effects of the flexural wavenumber and the configuration of and the spacing between the cylinders on the acoustic resonances were thoroughly investigated.« less

Motions of Kepler circumbinary planets in restricted three-body problem under radiating primaries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dermawan, B., E-mail: budider@as.itb.ac.id; Hidayat, T., E-mail: taufiq@as.itb.ac.id; Huda, I. N., E-mail: ibnu.nurul@students.itb.ac.id

2015-09-30

By observing continuously a single field of view in the sky, Kepler mission reveals outstanding results on discoveries of exoplanets. One of its recent progress is the discoveries of circumbinary planets. A circumbinary planet is an exoplanet that moves around a binary system. In this study we investigate motions of Kepler circumbinary planets belong to six binary systems, namely Kepler-16, -34, -35, -38, -47, and -413. The motions are considered to follow the Restricted Three-Body Problem (RTBP). Because the primaries (central massive objects) are stars, they are both radiatives, while the planet is an infinitesimal object. The primaries move inmore » nearly circular and elliptic orbits with respect to their center of masses. We describe, in general, motions of the circumbinary planets in RTBP under radiating primaries. With respect to the averaged zero velocity curves, we show that motions of the exoplanets are stable, in accordance with their Hill stabilities.« less

Influence of Eccentricity and Angular Velocity on Force Effects on Rotor of Magnetorheological Damper

NASA Astrophysics Data System (ADS)

Šedivý, Dominik; Ferfecki, Petr; Fialová, Simona

2018-06-01

This article presents the evaluation of force effects on squeeze film damper rotor. The rotor is placed eccentrically and its motion is translate-circular. The amplitude of rotor motion is smaller than its initial eccentricity. The force effects are calculated from pressure and viscous forces which were measured by using computational modeling. Damper was filled with magnetorheological fluid. Viscosity of this non-Newtonian fluid is given using Bingham rheology model. Yield stress is not constant and it is a function of magnetic induction which is described by many variables. The most important variables of magnetic induction are electric current and gap width between rotor and stator. The simulations were made in finite volume method based solver. The motion of the inner ring of squeeze film damper was carried out by dynamic mesh. Numerical solution was solved for five different initial eccentricities and angular velocities of rotor motion.

Experimentally Building a Qualitative Understanding of Newton's Second Law

NASA Astrophysics Data System (ADS)

Gates, Joshua

2014-12-01

Newton's second law is one of the cornerstones of the introductory physics curriculum, but it can still trouble a large number of students well after its introduction, hobbling their ability to apply the concept to problem solving1 and to related concepts, such as momentum, circular motion, and orbits. While there are several possibilities for lab activities addressing the functional relationship among net force, mass, and acceleration, the qualitative understanding of the connection between forces and acceleration can still be lacking,2 leading to poor performance in problem solving and in assessments such as the Force Concept Inventory3 and Force and Motion Conceptual Evaluation.4 There is a need for strong conceptual understanding of the relationships between net force and acceleration and between acceleration and velocity in order to effectively address common force-motion misconceptions;5 there is a large literature concerning student understanding of force and motion.6

One- and Two-dimensional Solitary Wave States in the Nonlinear Kramers Equation with Movement Direction as a Variable

NASA Astrophysics Data System (ADS)

Sakaguchi, Hidetsugu; Ishibashi, Kazuya

2018-06-01

We study self-propelled particles by direct numerical simulation of the nonlinear Kramers equation for self-propelled particles. In our previous paper, we studied self-propelled particles with velocity variables in one dimension. In this paper, we consider another model in which each particle exhibits directional motion. The movement direction is expressed with a variable ϕ. We show that one-dimensional solitary wave states appear in direct numerical simulations of the nonlinear Kramers equation in one- and two-dimensional systems, which is a generalization of our previous result. Furthermore, we find two-dimensionally localized states in the case that each self-propelled particle exhibits rotational motion. The center of mass of the two-dimensionally localized state exhibits circular motion, which implies collective rotating motion. Finally, we consider a simple one-dimensional model equation to qualitatively understand the formation of the solitary wave state.

A molecular propeller effect for chiral separation and analysis

PubMed Central

Clemens, Jonathon B.; Kibar, Osman; Chachisvilis, Mirianas

2015-01-01

Enantiomers share nearly identical physical properties but have different chiral geometries, making their identification and separation difficult. Here we show that when exposed to a rotating electric field, the left- and right-handed chiral molecules rotate with the field and act as microscopic propellers; moreover, owing to their opposite handedness, they propel along the axis of field rotation in opposite directions. We introduce a new molecular parameter called hydrodynamic chirality to characterize the coupling of rotational motion of a chiral molecule into its translational motion and quantify the direction and velocity of such motion. We demonstrate >80% enrichment level of counterpart enantiomers in solution without using chiral selectors or circularly polarized light. We expect our results to have an impact on multiple applications in drug discovery, analytical and chiral chemistry, including determination of absolute configuration, as well as in influencing the understanding of artificial and natural molecular systems where rotational motion of the molecules is involved. PMID:26216219

Parametric control of maneuver of a space tether system

NASA Astrophysics Data System (ADS)

Bezglasnyi, S. P.; Piyakina, E. E.

2015-07-01

Planar motion of a space tether system (STS) simulated by a massless rod with two masses fixed on its edges and a third mass moving along the rod is considered. An equation of the pendulum-controlled motion of the system in an elliptical orbit is obtained. Problems of parametric control that takes the STS from one stable radial equilibrium state to another and stabilizes it with respect to planar excitations of two diametrically opposite positions of the relative equilibrium of the STS in a circular orbit are investigated. The control is a continuous law of motion for a moving mass along the tether on the swing principle. The solution is obtained in a closed form based on the second method of the classical stability theory by the construction of the corresponding Lyapunov functions. Asymptotic convergence of solutions is confirmed by the results of numerical modeling of the system motion.

Manufacturing in space: Fluid dynamics numerical analysis

NASA Technical Reports Server (NTRS)

Robertson, S. J.; Nicholson, L. A.; Spradley, L. W.

1982-01-01

Numerical computations were performed for natural convection in circular enclosures under various conditions of acceleration. It was found that subcritical acceleration vectors applied in the direction of the temperature gradient will lead to an eventual state of rest regardless of the initial state of motion. Supercritical acceleration vectors will lead to the same steady state condition of motion regardless of the initial state of motion. Convection velocities were computed for acceleration vectors at various angles of the initial temperature gradient. The results for Rayleigh numbers of 1000 or less were found to closely follow Weinbaum's first order theory. Higher Rayleigh number results were shown to depart significantly from the first order theory. Supercritical behavior was confirmed for Rayleigh numbers greater than the known supercritical value of 9216. Response times were determined to provide an indication of the time required to change states of motion for the various cases considered.

A molecular propeller effect for chiral separation and analysis

NASA Astrophysics Data System (ADS)

Clemens, Jonathon B.; Kibar, Osman; Chachisvilis, Mirianas

2015-07-01

Enantiomers share nearly identical physical properties but have different chiral geometries, making their identification and separation difficult. Here we show that when exposed to a rotating electric field, the left- and right-handed chiral molecules rotate with the field and act as microscopic propellers; moreover, owing to their opposite handedness, they propel along the axis of field rotation in opposite directions. We introduce a new molecular parameter called hydrodynamic chirality to characterize the coupling of rotational motion of a chiral molecule into its translational motion and quantify the direction and velocity of such motion. We demonstrate >80% enrichment level of counterpart enantiomers in solution without using chiral selectors or circularly polarized light. We expect our results to have an impact on multiple applications in drug discovery, analytical and chiral chemistry, including determination of absolute configuration, as well as in influencing the understanding of artificial and natural molecular systems where rotational motion of the molecules is involved.

Vanadium dioxide as a material to control light polarization in the visible and near infrared

NASA Astrophysics Data System (ADS)

Cormier, Patrick; Son, Tran Vinh; Thibodeau, Jacques; Doucet, Alexandre; Truong, Vo-Van; Haché, Alain

2017-01-01

We report on the possible use of vanadium dioxide to produce ultrathin (<100 nm) adjustable phase retarders working over a wide spectral range. The refractive index of vanadium dioxide undergoes large changes when the material undergoes a phase transition from semiconductor to metal at a temperature of 68 °C. In a thin film, the resulting optical phase shift is different for s- and p-polarizations in both reflection and transmission, and under certain conditions the polarization state changes between linear or circular or between linear polarizations oriented differently when the material phase transitions. Specific ultrathin modulators are proposed based on the results.

Colliding Stellar Wind Models with Orbital Motion

NASA Astrophysics Data System (ADS)

Wilkin, Francis P.; O'Connor, Brendan

2018-01-01

We present thin-shell models for the collision between two ballistic stellar winds, including orbital motion.The stellar orbits are assumed circular, so that steady-state solutions exist in the rotating frame, where we include centrifugal and Coriolis forces. Exact solutions for the pre-shock winds are incorporated. Here we discuss 2-D model results for equal wind momentum-loss rates, although we allow for the winds to have distinct speeds and mass loss rates. For these unequal wind conditions, we obtain a clear violation of skew-symmetry, despite equal momentum loss rates, due to the Coriolis force.

Plasmonic rack-and-pinion gear with chiral metasurface

NASA Astrophysics Data System (ADS)

Gorodetski, Yuri; Karabchevsky, Alina

2016-04-01

The effect of circularly polarized beaming excited by traveling surface plasmons, via chiral metasurface is experimentally studied. Here we show that the propagation direction of the plasmonic wave, evanescently excited on the thin gold film affects the handedness of the scattered beam polarization. Nanostructured metasurface leads to excitation of localized plasmonic modes whose relative spatial orientation induces overall spin-orbit interaction. This effect is analogical to the rack-and-pinion gear: the rotational motion into the linear motion converter. From the practical point of view, the observed effect can be utilized in integrated optical circuits for communication systems, cyber security and sensing.

Dihedral angle principal component analysis of molecular dynamics simulations.

PubMed

Altis, Alexandros; Nguyen, Phuong H; Hegger, Rainer; Stock, Gerhard

2007-06-28

It has recently been suggested by Mu et al. [Proteins 58, 45 (2005)] to use backbone dihedral angles instead of Cartesian coordinates in a principal component analysis of molecular dynamics simulations. Dihedral angles may be advantageous because internal coordinates naturally provide a correct separation of internal and overall motion, which was found to be essential for the construction and interpretation of the free energy landscape of a biomolecule undergoing large structural rearrangements. To account for the circular statistics of angular variables, a transformation from the space of dihedral angles {phi(n)} to the metric coordinate space {x(n)=cos phi(n),y(n)=sin phi(n)} was employed. To study the validity and the applicability of the approach, in this work the theoretical foundations underlying the dihedral angle principal component analysis (dPCA) are discussed. It is shown that the dPCA amounts to a one-to-one representation of the original angle distribution and that its principal components can readily be characterized by the corresponding conformational changes of the peptide. Furthermore, a complex version of the dPCA is introduced, in which N angular variables naturally lead to N eigenvalues and eigenvectors. Applying the methodology to the construction of the free energy landscape of decaalanine from a 300 ns molecular dynamics simulation, a critical comparison of the various methods is given.

Dihedral angle principal component analysis of molecular dynamics simulations

NASA Astrophysics Data System (ADS)

Altis, Alexandros; Nguyen, Phuong H.; Hegger, Rainer; Stock, Gerhard

2007-06-01

It has recently been suggested by Mu et al. [Proteins 58, 45 (2005)] to use backbone dihedral angles instead of Cartesian coordinates in a principal component analysis of molecular dynamics simulations. Dihedral angles may be advantageous because internal coordinates naturally provide a correct separation of internal and overall motion, which was found to be essential for the construction and interpretation of the free energy landscape of a biomolecule undergoing large structural rearrangements. To account for the circular statistics of angular variables, a transformation from the space of dihedral angles {φn} to the metric coordinate space {xn=cosφn,yn=sinφn} was employed. To study the validity and the applicability of the approach, in this work the theoretical foundations underlying the dihedral angle principal component analysis (dPCA) are discussed. It is shown that the dPCA amounts to a one-to-one representation of the original angle distribution and that its principal components can readily be characterized by the corresponding conformational changes of the peptide. Furthermore, a complex version of the dPCA is introduced, in which N angular variables naturally lead to N eigenvalues and eigenvectors. Applying the methodology to the construction of the free energy landscape of decaalanine from a 300ns molecular dynamics simulation, a critical comparison of the various methods is given.

Relativistic effects in local inertial frames including parametrized-post-Newtonian effects

NASA Astrophysics Data System (ADS)

Shahid-Saless, Bahman; Ashby, Neil

1988-09-01

We use the concept of a generalized Fermi frame to describe relativistic effects, due to local and distant sources of gravitation, on a body placed in a local inertial frame of reference. In particular we have considered a model of two spherically symmetric gravitating point sources, moving in circular orbits around a common barycenter where one of the bodies is chosen to be the local and the other the distant one. This has been done using the slow-motion, weak-field approximation and including four of the parametrized-post-Newtonian (PPN) parameters. The position of the classical center of mass must be modified when the PPN parameter ζ2 is included. We show that the main relativistic effect on a local satellite is described by the Schwarzschild field of the local body and the nonlinear term corresponding to the self-interaction of the local source with itself. There are also much smaller terms that are proportional, respectively, to the product of the potentials of local and distant bodies and to the distant body's self-interactions. The spatial axes of the local frame undergo geodetic precession. In addition we have an acceleration of the order of 10-11 cm sec-2 that vanish in the case of general relativity, which is discussed in detail.

Advanced Respiratory Motion Compensation for Coronary MR Angiography

PubMed Central

Henningsson, Markus; Botnar, Rene M.

2013-01-01

Despite technical advances, respiratory motion remains a major impediment in a substantial amount of patients undergoing coronary magnetic resonance angiography (CMRA). Traditionally, respiratory motion compensation has been performed with a one-dimensional respiratory navigator positioned on the right hemi-diaphragm, using a motion model to estimate and correct for the bulk respiratory motion of the heart. Recent technical advancements has allowed for direct respiratory motion estimation of the heart, with improved motion compensation performance. Some of these new methods, particularly using image-based navigators or respiratory binning, allow for more advanced motion correction which enables CMRA data acquisition throughout most or all of the respiratory cycle, thereby significantly reducing scan time. This review describes the three components typically involved in most motion compensation strategies for CMRA, including respiratory motion estimation, gating and correction, and how these processes can be utilized to perform advanced respiratory motion compensation. PMID:23708271

A passerine spreads its tail to facilitate a rapid recovery of its body posture during hovering

PubMed Central

Su, Jian-Yuan; Ting, Shang-Chieh; Chang, Yu-Hung; Yang, Jing-Tang

2012-01-01

We demonstrate experimentally that a passerine exploits tail spreading to intercept the downward flow induced by its wings to facilitate the recovery of its posture. The periodic spreading of its tail by the White-eye bird exhibits a phase correlation with both wingstroke motion and body oscillation during hovering flight. During a downstroke, a White-eye's body undergoes a remarkable pitch-down motion, with the tail undergoing an upward swing. This pitch-down motion becomes appropriately suppressed at the end of the downstroke; the bird's body posture then recovers gradually to its original status. Employing digital particle-image velocimetry, we show that the strong downward flow induced by downstroking the wings serves as an external jet flow impinging upon the tail, providing a depressing force on the tail to counteract the pitch-down motion of the bird's body. Spreading of the tail enhances a rapid recovery of the body posture because increased forces are experienced. The maximum force experienced by a spread tail is approximately 2.6 times that of a non-spread tail. PMID:22258552

A passerine spreads its tail to facilitate a rapid recovery of its body posture during hovering.

PubMed

Su, Jian-Yuan; Ting, Shang-Chieh; Chang, Yu-Hung; Yang, Jing-Tang

2012-07-07

We demonstrate experimentally that a passerine exploits tail spreading to intercept the downward flow induced by its wings to facilitate the recovery of its posture. The periodic spreading of its tail by the White-eye bird exhibits a phase correlation with both wingstroke motion and body oscillation during hovering flight. During a downstroke, a White-eye's body undergoes a remarkable pitch-down motion, with the tail undergoing an upward swing. This pitch-down motion becomes appropriately suppressed at the end of the downstroke; the bird's body posture then recovers gradually to its original status. Employing digital particle-image velocimetry, we show that the strong downward flow induced by downstroking the wings serves as an external jet flow impinging upon the tail, providing a depressing force on the tail to counteract the pitch-down motion of the bird's body. Spreading of the tail enhances a rapid recovery of the body posture because increased forces are experienced. The maximum force experienced by a spread tail is approximately 2.6 times that of a non-spread tail.

Preliminary Planar Formation: Flight Dynamics Near Sun-Earth L2 Point

NASA Technical Reports Server (NTRS)

Segerman, Alan M.; Zedd, Michael F.

2003-01-01

NASA's Goddard Space Flight Center is planning a series of missions in the vicinity of the Sun-Earth L2 libration point. Some of these projects will involve a distributed space system of telescope spacecraft acting together as a single telescope for high-resolution. The individual telescopes will be configured in a plane, surrounding a hub, where the telescope plane can be aimed toward various astronomical targets of interest. In preparation for these missions, it is necessary to develop an improved understanding of the dynamical behavior of objects in a planar configuration near L2. The classical circular restricted three body problem is taken as the basis for the analysis. At first order, the motion of such a telescope relative to the hub is described by a system of linear second order differential equations. These equations are identical to the circular restricted problem's linear equations describing the hub motion about L2. Therefore, the fundamental frequencies, both parallel to and normal to the ecliptic plane, are the same for the relative telescope motion as for the hub motion. To maintain the telescope plane for the duration necessary for the planned observations, a halo-type orbit of the telescopes about the hub is investigated. By using a halo orbit, the individual telescopes remain in approximately the same plane over the observation duration. For such an orbit, the fundamental periods parallel to and normal to the ecliptic plane are forced to be the same by careful selection of the initial conditions in order to adjust the higher order forces. The relative amplitudes of the resulting oscillations are associated with the orientation of the telescope plane relative to the ecliptic. As in the circular restricted problem, initial conditions for the linearized equations must be selected so as not to excite the convergent or divergent linear modes. In a higher order analysis, the telescope relative motion equations include the effects of the position of the hub relative to L2. In this paper, the differential equations are developed through second order in the distance of the hub from the libration point. A modified Lindstedt-Poincad perturbation method is employed to construct the solution of these differential equations through that same order of magnitude. In the course of the solution process, relationships are determined between the initial conditions of the telescopes, selected in order to avoid resonance excitation. As the differential equations include the hub position, it is necessary to simultaneously develop the solution for the hub. As has been done in past analyses of the circular restricted problem, the hub position is written in a power series formulation in terms of its distance from L2. Then, in order to be included in the telescope equations, the hub solution is cast in terms of the nonlinear frequency of the relative telescope motion. In the course of the analysis, it is determined that the hub should also maintain a halo orbit - about L2. Additionally, relationships are formed between the initial conditions of the telescopes and the hub. These relationships may be used to associate sets of initial conditions with particular orientations of the telescope plane. The accuracy of the analytical solution is verified through various simulations and comparison to numerical integration of the differential equations. The results of the simulations are presented, along with a graphical representation of the relationships between the initial conditions of the telescopes and hub.

Second-order motions contribute to vection.

PubMed

Gurnsey, R; Fleet, D; Potechin, C

1998-09-01

First- and second-order motions differ in their ability to induce motion aftereffects (MAEs) and the kinetic depth effect (KDE). To test whether second-order stimuli support computations relating to motion-in-depth we examined the vection illusion (illusory self motion induced by image flow) using a vection stimulus (V, expanding concentric rings) that depicted a linear path through a circular tunnel. The set of vection stimuli contained differing amounts of first- and second-order motion energy (ME). Subjects reported the duration of the perceived MAEs and the duration of their vection percept. In Experiment 1 both MAEs and vection durations were longest when the first-order (Fourier) components of V were present in the stimulus. In Experiment 2, V was multiplicatively combined with static noise carriers having different check sizes. The amount of first-order ME associated with V increases with check size. MAEs were found to increase with check size but vection durations were unaffected. In general MAEs depend on the amount of first-order ME present in the signal. Vection, on the other hand, appears to depend on a representation of image flow that combines first- and second-order ME.

Experimental and Analytic Evaluation of the Effects of Visual and Motion Simulation in SH-3 Helicopter Training. Technical Report 85-002.

ERIC Educational Resources Information Center

Pfeiffer, Mark G.; Scott, Paul G.

A fly-only group (N=16) of Navy replacement pilots undergoing fleet readiness training in the SH-3 helicopter was compared with groups pre-trained on Device 2F64C with: (1) visual only (N=13); (2) no visual/no motion (N=14); and (3) one visual plus motion group (N=19). Groups were compared for their SH-3 helicopter performance in the transition…

Mechanical Circle-Squaring

ERIC Educational Resources Information Center

Wagon, Stan; Cox, Barry

2009-01-01

A technique discovered in 1939 can be used to build a device that is driven by standard circular motion (as in a drill press) and drills exact square holes. This device is quite different from the classic design by Watts, which uses a Reuleaux triangle and drills a hole that is almost, but not exactly, square. We describe the device in detail,…

Experimentally Building a Qualitative Understanding of Newton's Second Law

ERIC Educational Resources Information Center

Gates, Joshua

2014-01-01

Newton's second law is one of the cornerstones of the introductory physics curriculum, but it can still trouble a large number of students well after its introduction, hobbling their ability to apply the concept to problem solving and to related concepts, such as momentum, circular motion, and orbits. While there are several possibilities for…

TEACHING PHYSICS: Biking around a hollow sphere

NASA Astrophysics Data System (ADS)

Mak, Se-yuen; Yip, Din-yan

1999-11-01

The conditions required for a cyclist riding a motorbike in a horizontal circle on or above the equator of a hollow sphere are derived using concepts of equilibrium and the condition for uniform circular motion. The result is compared with an empirical analysis based on a video show. Some special cases of interest derived from the general solution are elaborated.

Satellite Gravity and the Geosphere: Contributions to the Study of the Solid Earth and Its Fluid Earth

NASA Technical Reports Server (NTRS)

Dickey, J. O.; Bentley, C. R.; Bilham, R.; Carton, J. A.; Eanes, R. J.; Herring, T. A.; Kaula, W. M.; Lagerloef, G. S. E.; Rojstaczer, S.; Smith, W. H. F.;

Knee arthrodesis with circular external fixation.

PubMed

Garberina, M J; Fitch, R D; Hoffmann, E D; Hardaker, W T; Vail, T P; Scully, S P

2001-01-01

Knee arthrodesis can enable limb salvage in patients with disability secondary to trauma, infected total knee arthroplasty, pyarthrosis, and other complications. Historically, intramedullary nailing has resulted in the highest overall knee fusion rates. However, intramedullary nailing is relatively contraindicated in the presence of active infection. Nineteen patients who underwent knee arthrodesis with circular external fixation were studied retrospectively. Postoperative radiographs were evaluated for evidence of bony fusion, which was defined as trabecular bridging between the femur and tibia. Patients were interviewed and graded using the functional assessment portion of the Knee Society clinical rating system. Fusion was successful in 13 of 19 (68%) patients. Overall, patients spent an average of 4 months 8 days wearing the circular external fixator. Average time to radiographic and clinical evidence of arthrodesis (defined as lack of motion across the fusion site) was 4 months 18 days. No patient with successful fusion considered himself or herself housebound. All but one of these patients require some form of assistive device for ambulation. Complications occurred in 16 of 19 (84%) patients overall. Superficial pin tract infection (55%) and nonunion (32%) were the most common. Circular external fixation is an effective method for obtaining knee arthrodesis in patients who are not good candidates for intramedullary nailing.

Calculation of precision satellite orbits with nonsingular elements /VOP formulation/

NASA Technical Reports Server (NTRS)

Velez, C. E.; Cefola, P. J.; Long, A. C.; Nimitz, K. S.

1974-01-01

Review of some results obtained in an effort to develop efficient, high-precision trajectory computation processes for artificial satellites by optimum selection of the form of the equations of motion of the satellite and the numerical integration method. In particular, the matching of a Gaussian variation-of-parameter (VOP) formulation is considered which is expressed in terms of equinoctial orbital elements and partially decouples the motion of the orbital frame from motion within the orbital frame. The performance of the resulting orbit generators is then compared with the popular classical Cowell/Gauss-Jackson formulation/integrator pair for two distinctly different orbit types - namely, the orbit of the ATS satellite at near-geosynchronous conditions and the near-circular orbit of the GEOS-C satellite at 1000 km.

The planetary increase of brightness during retrograde motion: An explanandum constructed ad explanantem.

PubMed

Carman, Christián Carlos

2015-12-01

In Ancient Greek two models were proposed for explaining the planetary motion: the homocentric spheres of Eudoxus and the Epicycle and Deferent System. At least in a qualitative way, both models could explain the retrograde motion, the most challenging phenomenon to be explained using circular motions. Nevertheless, there is another explanandum: during retrograde motion the planets increase their brightness. It is natural to interpret a change of brightness, i.e., of apparent size, as a change in distance. Now, while according to the Eudoxian model the planet is always equidistant from the earth, according to the epicycle and deferent system, the planet changes its distance from the earth, approaching to it during retrograde motion, just as observed. So, it is usually affirmed that the main reason for the rejection of Eudoxus' homocentric spheres in favor of the epicycle and deferent system was that the first cannot explain the manifest planetary increase of brightness during retrograde motion, while the second can. In this paper I will show that this historical hypothesis is not as firmly founded as it is usually believed to be. Copyright © 2015 Elsevier Ltd. All rights reserved.

Global Motions of the Nuclear Pore Complex: Insights from Elastic Network Models

PubMed Central

Lezon, Timothy R.; Sali, Andrej; Bahar, Ivet

2009-01-01

The nuclear pore complex (NPC) is the gate to the nucleus. Recent determination of the configuration of proteins in the yeast NPC at ∼5 nm resolution permits us to study the NPC global dynamics using coarse-grained structural models. We investigate these large-scale motions by using an extended elastic network model (ENM) formalism applied to several coarse-grained representations of the NPC. Two types of collective motions (global modes) are predicted by the ENMs to be intrinsically favored by the NPC architecture: global bending and extension/contraction from circular to elliptical shapes. These motions are shown to be robust against tested variations in the representation of the NPC, and are largely captured by a simple model of a toroid with axially varying mass density. We demonstrate that spoke multiplicity significantly affects the accessible number of symmetric low-energy modes of motion; the NPC-like toroidal structures composed of 8 spokes have access to highly cooperative symmetric motions that are inaccessible to toroids composed of 7 or 9 spokes. The analysis reveals modes of motion that may facilitate macromolecular transport through the NPC, consistent with previous experimental observations. PMID:19730674

Global motions of the nuclear pore complex: insights from elastic network models.

PubMed

Lezon, Timothy R; Sali, Andrej; Bahar, Ivet

2009-09-01

The nuclear pore complex (NPC) is the gate to the nucleus. Recent determination of the configuration of proteins in the yeast NPC at approximately 5 nm resolution permits us to study the NPC global dynamics using coarse-grained structural models. We investigate these large-scale motions by using an extended elastic network model (ENM) formalism applied to several coarse-grained representations of the NPC. Two types of collective motions (global modes) are predicted by the ENMs to be intrinsically favored by the NPC architecture: global bending and extension/contraction from circular to elliptical shapes. These motions are shown to be robust against tested variations in the representation of the NPC, and are largely captured by a simple model of a toroid with axially varying mass density. We demonstrate that spoke multiplicity significantly affects the accessible number of symmetric low-energy modes of motion; the NPC-like toroidal structures composed of 8 spokes have access to highly cooperative symmetric motions that are inaccessible to toroids composed of 7 or 9 spokes. The analysis reveals modes of motion that may facilitate macromolecular transport through the NPC, consistent with previous experimental observations.

Evidence of 3-D Reconnection at Null Point from the Observations of Circular Flares and Homologous Jets

NASA Astrophysics Data System (ADS)

Wang, Haimin; Liu, C.

2012-05-01

In recent studies by Pariat, Antiochos and DeVore (2009, 2010), fan-separatrix topology and magnetic reconnection at the null-point were simulated and found to produce homologous jets. This motivates us to search for axisymmetric magnetic structure and associated flaring/jetting activity. Using high-resolution ( 0.15" per pixel) and high-cadence ( 15 s) H-alpha center/offband observations obtained from the recently digitized films of Big Bear Solar Observatory, we were able to identify five large circular flares with associated surges. All the events exhibit a central parasite magnetic field surrounded by opposite polarity, forming a circular polarity inversion line (PIL). Consequently, a compact flare kernel at the center is surrounded by a circular ribbon, and together with the upward ejecting dark surge, these seem to depict a dome-like magnetic structure. Very interestingly, (1) the circular ribbon brightens sequentially rather than simultaneously, (2) the central compact flare kernel shows obvious motion, and (3) a remote elongated, co-temporal flare ribbon at a region with the same polarity as the central parasite site is seen in the series of four homologous events on 1991 March 17 and 18. The remote ribbon is 120" away from the jet location. Moreover, magnetic reconnection across the circular PIL is evident from the magnetic flux cancellation. These rarely observed homologous surges with circular as well as central and remote flare ribbons provide valuable evidence concerning the dynamics of magnetic reconnection in a null-point topology. This study is dedicated to Professor Hal Zirin, the founder of Big Bear Solar Observatory, who passed away on January 3, 2012.

Rotary Motion Impairs Attention to Color Change in 4-Month-Old Infants

ERIC Educational Resources Information Center

Kavsek, Michael

2013-01-01

Continuous color changes of an array of elements appear to stop changing if the array undergoes a coherent motion. This "silencing" illusion was demonstrated for adults by Suchow and Alvarez ("Current Biology", 2011, vol. 21, pp. 140-143). The current forced-choice preferential looking study examined 4-month-old infants' sensitivity to the…

Effectiveness of standardized approach versus usual care on physiotherapy treatment for patients submitted to alveolar bone graft: a pilot study.

PubMed

Vidotto, Laís Silva; Bigliassi, Marcelo; Alencar, Tatiane Romanini Rodrigues; Silva, Thaísa Maria Santos; Probst, Vanessa Suziane

2015-07-01

To compare the acute effects of a standardized physiotherapy protocol versus a typical non-standardized physiotherapy protocol on pain and performance of patients undergoing alveolar bone graft (ABG). Sixteen patients (9 males; 12 [11-13] years) with cleft lip and palate undergoing ABG were allocated into two groups: (1) experimental group--EG (standardized physiotherapy protocol); and (2) control group--CG (typical, non-standardized physiotherapy treatment). Range of motion, muscle strength, gait speed, and pain level were assessed prior to surgical intervention (PRE), as well as on the first, second, and third post-operative days (1st, 2nd, and 3rd PO, respectively). Recovery with respect to range of motion of hip flexion was more pronounced in the EG (64.6 ± 11.0°) in comparison to the CG (48.5 ± 17.7° on the 3rd PO; p < 0.05). In addition, less pain was observed in the EG (0 [0-0.2] versus 2 [0.7-3] in the CG on the 3rd PO; p < 0.05). A standardized physiotherapy protocol appears to be better than a non-standardized physiotherapy protocol for acute improvement of range of motion of hip flexion and for reducing pain in patients undergoing ABG.

Casimir energy in Kerr space-time

NASA Astrophysics Data System (ADS)

Sorge, F.

2014-10-01

We investigate the vacuum energy of a scalar massless field confined in a Casimir cavity moving in a circular equatorial orbit in the exact Kerr space-time geometry. We find that both the orbital motion of the cavity and the underlying space-time geometry conspire in lowering the absolute value of the (renormalized) Casimir energy ⟨ɛvac⟩ren , as measured by a comoving observer, with respect to whom the cavity is at rest. This, in turn, causes a weakening in the attractive force between the Casimir plates. In particular, we show that the vacuum energy density ⟨ɛvac⟩ren→0 when the orbital path of the Casimir cavity comes close to the corotating or counter-rotating circular null orbits (possibly geodesic) allowed by the Kerr geometry. Such an effect could be of some astrophysical interest on relevant orbits, such as the Kerr innermost stable circular orbits, being potentially related to particle confinement (as in some interquark models). The present work generalizes previous results obtained by several authors in the weak field approximation.

Consequences of tidal interaction between disks and orbiting protoplanets for the evolution of multi-planet systems with architecture resembling that of Kepler 444

NASA Astrophysics Data System (ADS)

Papaloizou, J. C. B.

2016-11-01

We study orbital evolution of multi-planet systems with masses in the terrestrial planet regime induced through tidal interaction with a protoplanetary disk assuming that this is the dominant mechanism for producing orbital migration and circularization. We develop a simple analytic model for a system that maintains consecutive pairs in resonance while undergoing orbital circularization and migration. This model enables migration times for each planet to be estimated once planet masses, circularization times and the migration time for the innermost planet are specified. We applied it to a system with the current architecture of Kepler 444 adopting a simple protoplanetary disk model and planet masses that yield migration times inversely proportional to the planet mass, as expected if they result from torques due to tidal interaction with the protoplanetary disk. Furthermore the evolution time for the system as a whole is comparable to current protoplanetary disk lifetimes. In addition we have performed a number of numerical simulations with input data obtained from this model. These indicate that although the analytic model is inexact, relatively small corrections to the estimated migration rates yield systems for which period ratios vary by a minimal extent. Because of relatively large deviations from exact resonance in the observed system of up to 2 %, the migration times obtained in this way indicate only weak convergent migration such that a system for which the planets did not interact would contract by only {˜ }1 % although undergoing significant inward migration as a whole. We have also performed additional simulations to investigate conditions under which the system could undergo significant convergent migration before reaching its final state. These indicate that migration times have to be significantly shorter and resonances between planet pairs significantly closer during such an evolutionary phase. Relative migration rates would then have to decrease allowing period ratios to increase to become more distant from resonances as the system approached its final state in the inner regions of the protoplanetary disk.

Real-time prediction of respiratory motion based on a local dynamic model in an augmented space

NASA Astrophysics Data System (ADS)

Hong, S.-M.; Jung, B.-H.; Ruan, D.

2011-03-01

Motion-adaptive radiotherapy aims to deliver ablative radiation dose to the tumor target with minimal normal tissue exposure, by accounting for real-time target movement. In practice, prediction is usually necessary to compensate for system latency induced by measurement, communication and control. This work focuses on predicting respiratory motion, which is most dominant for thoracic and abdominal tumors. We develop and investigate the use of a local dynamic model in an augmented space, motivated by the observation that respiratory movement exhibits a locally circular pattern in a plane augmented with a delayed axis. By including the angular velocity as part of the system state, the proposed dynamic model effectively captures the natural evolution of respiratory motion. The first-order extended Kalman filter is used to propagate and update the state estimate. The target location is predicted by evaluating the local dynamic model equations at the required prediction length. This method is complementary to existing work in that (1) the local circular motion model characterizes 'turning', overcoming the limitation of linear motion models; (2) it uses a natural state representation including the local angular velocity and updates the state estimate systematically, offering explicit physical interpretations; (3) it relies on a parametric model and is much less data-satiate than the typical adaptive semiparametric or nonparametric method. We tested the performance of the proposed method with ten RPM traces, using the normalized root mean squared difference between the predicted value and the retrospective observation as the error metric. Its performance was compared with predictors based on the linear model, the interacting multiple linear models and the kernel density estimator for various combinations of prediction lengths and observation rates. The local dynamic model based approach provides the best performance for short to medium prediction lengths under relatively low observation rate. Sensitivity analysis indicates its robustness toward the choice of parameters. Its simplicity, robustness and low computation cost makes the proposed local dynamic model an attractive tool for real-time prediction with system latencies below 0.4 s.

Real-time prediction of respiratory motion based on a local dynamic model in an augmented space.

PubMed

Hong, S-M; Jung, B-H; Ruan, D

2011-03-21

Motion-adaptive radiotherapy aims to deliver ablative radiation dose to the tumor target with minimal normal tissue exposure, by accounting for real-time target movement. In practice, prediction is usually necessary to compensate for system latency induced by measurement, communication and control. This work focuses on predicting respiratory motion, which is most dominant for thoracic and abdominal tumors. We develop and investigate the use of a local dynamic model in an augmented space, motivated by the observation that respiratory movement exhibits a locally circular pattern in a plane augmented with a delayed axis. By including the angular velocity as part of the system state, the proposed dynamic model effectively captures the natural evolution of respiratory motion. The first-order extended Kalman filter is used to propagate and update the state estimate. The target location is predicted by evaluating the local dynamic model equations at the required prediction length. This method is complementary to existing work in that (1) the local circular motion model characterizes 'turning', overcoming the limitation of linear motion models; (2) it uses a natural state representation including the local angular velocity and updates the state estimate systematically, offering explicit physical interpretations; (3) it relies on a parametric model and is much less data-satiate than the typical adaptive semiparametric or nonparametric method. We tested the performance of the proposed method with ten RPM traces, using the normalized root mean squared difference between the predicted value and the retrospective observation as the error metric. Its performance was compared with predictors based on the linear model, the interacting multiple linear models and the kernel density estimator for various combinations of prediction lengths and observation rates. The local dynamic model based approach provides the best performance for short to medium prediction lengths under relatively low observation rate. Sensitivity analysis indicates its robustness toward the choice of parameters. Its simplicity, robustness and low computation cost makes the proposed local dynamic model an attractive tool for real-time prediction with system latencies below 0.4 s.

Inclined asymmetric librations in exterior resonances

NASA Astrophysics Data System (ADS)

Voyatzis, G.; Tsiganis, K.; Antoniadou, K. I.

2018-04-01

Librational motion in Celestial Mechanics is generally associated with the existence of stable resonant configurations and signified by the existence of stable periodic solutions and oscillation of critical (resonant) angles. When such an oscillation takes place around a value different than 0 or π , the libration is called asymmetric. In the context of the planar circular restricted three-body problem, asymmetric librations have been identified for the exterior mean motion resonances (MMRs) 1:2, 1:3, etc., as well as for co-orbital motion (1:1). In exterior MMRs the massless body is the outer one. In this paper, we study asymmetric librations in the three-dimensional space. We employ the computational approach of Markellos (Mon Not R Astron Soc 184:273-281, https://doi.org/10.1093/mnras/184.2.273, 1978) and compute families of asymmetric periodic orbits and their stability. Stable asymmetric periodic orbits are surrounded in phase space by domains of initial conditions which correspond to stable evolution and librating resonant angles. Our computations were focused on the spatial circular restricted three-body model of the Sun-Neptune-TNO system (TNO = trans-Neptunian object). We compare our results with numerical integrations of observed TNOs, which reveal that some of them perform 1:2 resonant, inclined asymmetric librations. For the stable 1:2 TNO librators, we find that their libration seems to be related to the vertically stable planar asymmetric orbits of our model, rather than the three-dimensional ones found in the present study.

Uncertainty propagation in q and current profiles derived from motional Stark effect polarimetry on TFTR (abstract)a)

NASA Astrophysics Data System (ADS)

Batha, S. H.; Levinton, F. M.; Bell, M. G.; Wieland, R. M.; Hirschman, S. P.

1995-01-01

The magnetic-field pitch-angle profile, γp(R)≡arctan(Bpol/Btor), is measured on the TFTR tokamak using a motional Stark effect (MSE) polarimeter. Measured profiles are converted to q profiles with the equilibrium code vmec. Uncertainties in the q profile due to uncertainties in the γp(R), magnetics, and kinetic measurements are quantified. Subsequent uncertainties in the vmec-calculated profiles of current density and shear, both of which are important for stability and transport analyses, are also quantified. Examples of circular plasmas under various confinement modes, including the supershot and L mode, will be given.

Effects of solar radiation pressure torque on the rotational motion of an artificial satellite

NASA Technical Reports Server (NTRS)

Zanardi, Maria Cecilia F. P. S.; Vilhenademoraes, Rodolpho

1992-01-01

The motion of an artificial satellite about its center of mass is studied considering torques due to the gravity gradient and direct solar radiation pressure. A model for direct solar radiation torque is derived for a circular cylindrical satellite. An analytical solution is obtained by the method of variation of the parameters. This solution shows that the angular variables have secular variation but that the modulus of the rotational angular momentum, the projection of rotational angular momentum on the z axis of the moment of inertia and inertial axis z, suffer only periodic variations. Considering a hypothetical artificial satellite, a numerical application is demonstrated.

Development of a robotic evaluation system for the ability of proprioceptive sensation in slow hand motion.

PubMed

Tanaka, Yoshiyuki; Mizoe, Genki; Kawaguchi, Tomohiro

2015-01-01

This paper proposes a simple diagnostic methodology for checking the ability of proprioceptive/kinesthetic sensation by using a robotic device. The perception ability of virtual frictional forces is examined in operations of the robotic device by the hand at a uniform slow velocity along the virtual straight/circular path. Experimental results by healthy subjects demonstrate that percentage of correct answers for the designed perceptual tests changes in the motion direction as well as the arm configuration and the HFM (human force manipulability) measure. It can be supposed that the proposed methodology can be applied into the early detection of neuromuscular/neurological disorders.

Perturbed Equations of Motion for Formation Flight Near the Sun-Earth L2 Point

NASA Technical Reports Server (NTRS)

Luquette, Richard; Segerman, A. M.; Zedd, M. F.

2005-01-01

NASA is planning missions to the vicinity of the Sun-Earth L(sub 2) point, some involving a distributed system of telescope spacecraft, configured in a plane about a hub. Several sets of differential equations are written for the formation flight of such telescopes relative to the hub, with varying levels of fidelity. Effects are cast as additive perturbations to the circular restricted three-body problem, expanded in terms of the system distanced, to an accuracy of 10-20 m. These include Earth's orbital eccentricity, lunar motion, solar radiation pressure, and small thrusting forces. Simulations validating the expanded differential equations are presented.

Projection-based circular constrained state estimation and fusion over long-haul links

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Qiang; Rao, Nageswara S.

In this paper, we consider a scenario where sensors are deployed over a large geographical area for tracking a target with circular nonlinear constraints on its motion dynamics. The sensor state estimates are sent over long-haul networks to a remote fusion center for fusion. We are interested in different ways to incorporate the constraints into the estimation and fusion process in the presence of communication loss. In particular, we consider closed-form projection-based solutions, including rules for fusing the estimates and for incorporating the constraints, which jointly can guarantee timely fusion often required in realtime systems. We test the performance ofmore » these methods in the long-haul tracking environment using a simple example.« less

Surface coil proton MR imaging at 2 T.

PubMed

Röschmann, P; Tischler, R

1986-10-01

We describe the design and application of surface coils for magnetic resonance (MR) imaging at high resonance frequencies (85 MHz). Circular, rectangular-frame, and reflector-type surface coils were used in the transmit-and-receive mode. With these coils, the required radio frequency power is reduced by factors of two up to 100 with respect to head and body coils. With the small, circular coils, high-resolution images of a small region of interest can be obtained that are free of foldback and motion artifacts originating outside the field of interest. With the rectangular-frame and reflector coils, large fields of view are also accessible. As examples of applications, single- and multiple-section images of the eye, knee, head and shoulder, and spinal cord are provided.

Strong-field gravitational-wave emission in Schwarzschild and Kerr geometries: some general considerations

NASA Astrophysics Data System (ADS)

Rodríguez, J. F.; Rueda, J. A.; Ruffini, R.

2018-01-01

We have used the perturbations of the exact solutions of the Einstein equations to estimate the relativistic wave emission of a test particle orbiting around a black hole. We show how the hamiltonian equations of motion of a test particle augmented with the radiation-reaction force can establish a priori constraints on the possible phenomena occurring in the merger of compact objects. The dynamical evolution consists of a helicoidal sequence of quasi-circular orbits, induced by the radiation-reaction and the background spacetime. Near the innermost stable circular orbit the evolution is followed by a smooth transition and finally plunges geodesically into the black hole horizon. This analysis gives physical insight of the merger of two equal masses objects.

Centripetal force draws the eyes, not memory of the target, toward the center.

PubMed

Kerzel, Dirk

2003-05-01

Many observers believe that a target will continue on a curved trajectory after exiting a spiral tube. Similarly, when observers were asked to localize the final position of a target moving on a circular orbit, displacement of the judged position in the direction of forward motion ("representational momentum") and toward the center of the orbit was observed (cf. T. L. Hubbard, 1996). The present study shows that memory displacement of targets on a circular orbit is affected by eye movements. Forward displacement was larger with ocular pursuit of the target, whereas inward displacement was larger with motionless eyes. The results challenge an account attributing forward and inward displacement to mental analogues of momentum and centripetal force, respectively.

Spacecraft Constrained Maneuver Planning for Moving Debris Avoidance Using Positively Invariant Constraint Admissible Sets (Postprint)

DTIC Science & Technology

2013-08-14

Time-Varying (LTV); Clohessy - Wiltshire -Hill (CWH) 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT 18. NUMBER OF PAGES 19a. NAME OF...linearized Hill- Clohessy - Wiltshire (HCW) equations [15] approximate the relative motion of the spacecraft on a circular orbit as ẍ− 3n2x− 2nẏ = Fx mc

Modelling low Reynolds number vortex-induced vibration problems with a fixed mesh fluid-solid interaction formulation

NASA Astrophysics Data System (ADS)

González Cornejo, Felipe A.; Cruchaga, Marcela A.; Celentano, Diego J.

2017-11-01

The present work reports a fluid-rigid solid interaction formulation described within the framework of a fixed-mesh technique. The numerical analysis is focussed on the study of a vortex-induced vibration (VIV) of a circular cylinder at low Reynolds number. The proposed numerical scheme encompasses the fluid dynamics computation in an Eulerian domain where the body is embedded using a collection of markers to describe its shape, and the rigid solid's motion is obtained with the well-known Newton's law. The body's velocity is imposed on the fluid domain through a penalty technique on the embedded fluid-solid interface. The fluid tractions acting on the solid are computed from the fluid dynamic solution of the flow around the body. The resulting forces are considered to solve the solid motion. The numerical code is validated by contrasting the obtained results with those reported in the literature using different approaches for simulating the flow past a fixed circular cylinder as a benchmark problem. Moreover, a mesh convergence analysis is also done providing a satisfactory response. In particular, a VIV problem is analyzed, emphasizing the description of the synchronization phenomenon.

Anisotropic interaction rules in circular motions of pigeon flocks: An empirical study based on sparse Bayesian learning

NASA Astrophysics Data System (ADS)

Chen, Duxin; Xu, Bowen; Zhu, Tao; Zhou, Tao; Zhang, Hai-Tao

2017-08-01

Coordination shall be deemed to the result of interindividual interaction among natural gregarious animal groups. However, revealing the underlying interaction rules and decision-making strategies governing highly coordinated motion in bird flocks is still a long-standing challenge. Based on analysis of high spatial-temporal resolution GPS data of three pigeon flocks, we extract the hidden interaction principle by using a newly emerging machine learning method, namely the sparse Bayesian learning. It is observed that the interaction probability has an inflection point at pairwise distance of 3-4 m closer than the average maximum interindividual distance, after which it decays strictly with rising pairwise metric distances. Significantly, the density of spatial neighbor distribution is strongly anisotropic, with an evident lack of interactions along individual velocity. Thus, it is found that in small-sized bird flocks, individuals reciprocally cooperate with a variational number of neighbors in metric space and tend to interact with closer time-varying neighbors, rather than interacting with a fixed number of topological ones. Finally, extensive numerical investigation is conducted to verify both the revealed interaction and decision-making principle during circular flights of pigeon flocks.

Elasticity of the living abdominal wall in laparoscopic surgery.

PubMed

Song, Chengli; Alijani, Afshin; Frank, Tim; Hanna, George; Cuschieri, Alfred

2006-01-01

Laparoscopic surgery requires inflation of the abdominal cavity and this offers a unique opportunity to measure the mechanical properties of the living abdominal wall. We used a motion analysis system to study the abdominal wall motion of 18 patients undergoing laparoscopic surgery, and found that the mean Young's modulus was 27.7+/-4.5 and 21.0+/-3.7 kPa for male and female, respectively. During inflation, the abdominal wall changed from a cylinder to a dome shape. The average expansion in the abdominal wall surface was 20%, and a working space of 1.27 x 10(-3)m(3) was created by expansion, reshaping of the abdominal wall and diaphragmatic movement. For the first time, the elasticity of human abdominal wall was obtained from the patients undergoing laparoscopic surgery, and a 3D simulation model of human abdominal wall has been developed to analyse the motion pattern in laparoscopic surgery. Based on this study, a mechanical abdominal wall lift and a surgical simulator for safe/ergonomic port placements are under development.

Pattern formation and three-dimensional instability in rotating flows

NASA Astrophysics Data System (ADS)

Christensen, Erik A.; Aubry, Nadine; Sorensen, Jens N.

1997-03-01

A fluid flow enclosed in a cylindrical container where fluid motion is created by the rotation of one end wall as a centrifugal fan is studied. Direct numerical simulations and spatio-temporal analysis have been performed in the early transition scenario, which includes a steady-unsteady transition and a breakdown of axisymmetric to three-dimensional flow behavior. In the early unsteady regime of the flow, the central vortex undergoes a vertical beating motion, accompanied by axisymmetric spikes formation on the edge of the breakdown bubble. As traveling waves, the spikes move along the central vortex core toward the rotating end-wall. As the Reynolds number is increased further, the flow undergoes a three-dimensional instability. The influence of the latter on the previous patterns is studied.

Quantum Brownian motion under generalized position measurements: a converse Zeno scenario

NASA Astrophysics Data System (ADS)

Magazzù, Luca; Talkner, Peter; Hänggi, Peter

2018-03-01

We study the quantum Brownian motion of a harmonic oscillator undergoing a sequence of generalized position measurements. Our exact analytical results capture the interplay of the measurement backaction and dissipation. Here we demonstrate that no freeze-in Zeno effect occurs upon increasing the monitoring frequency. A similar behavior is also found in the presence of generalized momentum measurements.

Passive swimming in viscous oscillatory flows

NASA Astrophysics Data System (ADS)

Jo, Ikhee; Huang, Yangyang; Zimmermann, Walter; Kanso, Eva

2016-12-01

Fluid-based locomotion at low Reynolds number is subject to the constraints of Purcell's scallop theorem: reciprocal shape kinematics identical under a time-reversal symmetry cannot cause locomotion. In particular, a single degree-of-freedom scallop undergoing opening and closing motions cannot swim. Most strategies for symmetry breaking and locomotion rely on direct control of the swimmer's shape kinematics. Less is known about indirect control via actuation of the fluid medium. To address how such indirect actuation strategies can lead to locomotion, we analyze a Λ -shaped model system analogous to Purcell's scallop but able to deform passively in oscillatory flows. Neutrally buoyant scallops undergo no net locomotion. We show that dense, elastic scallops can exhibit passive locomotion in zero-mean oscillatory flows. We examine the efficiency of swimming parallel to the background flow and analyze the stability of these motions. We observe transitions from stable to unstable swimming, including ordered transitions from fluttering to chaoticlike motions and tumbling. Our results demonstrate that flow oscillations can be used to passively actuate and control the motion of microswimmers, which may be relevant to applications such as surgical robots and cell sorting and manipulation in microfluidic devices.

Tidal regime of intact planetoid capture model for the Earth-Moon system: Does it relate to the archean sedimentary rock record?

NASA Technical Reports Server (NTRS)

Malcuit, Robert J.; Winters, Ronald R.

1993-01-01

Regardless of one's favorite model for the origin of the Earth-Moon system (fission, coformation, tidal capture, giant-impact) the early history of lunar orbital evolution would produce significant thermal and earth and ocean tidal effects on the primitive earth. Three of the above lunar origin models (fission, coformation, giant-impact) feature a circular orbit which undergoes a progressive increase in orbital radius from the time of origin to the present time. In contrast, a tidal capture model places the moon in an elliptical orbit undergoing progressive circularization from the time of capture (for model purposes about 3.9 billion years ago) for at least a few 10(exp 8) years following the capture event. Once the orbit is circularized, the subsequent tidal history for a tidal capture scenario is similar to that for other models of lunar origin and features a progressive increase in orbital radius to the current state of the lunar orbit. This elliptical orbit phase, if it occurred, should have left a distinctive signature in the terrestrial and lunar rock records. Depositional events would be associated terrestrial shorelines characterized by abnormally high, but progressively decreasing, ocean tidal amplitudes and ranges associated with such an orbital evolution. Several rock units in the age range 3.6-2.5 billion years before present are reported to have a major tidal component. Examples are the Warrawoona, Fortescue, and Hamersley Groups of Western Australia and the Pangola and Witwatersand Supergroups of South Africa. Detailed study of the features of these tidal sequences may be helpful in deciphering the style of lunar orbital evolution during the Archean Eon.

Motion and collision of particles in a rotating linear dilaton black hole

NASA Astrophysics Data System (ADS)

González, P. A.; Olivares, Marco; Papantonopoulos, Eleftherios; Vásquez, Yerko

2018-03-01

We study the motion of particles in the background of a four-dimensional linear dilaton black hole. We solve analytically the equations of motion of the test particles, and we describe their motion. We show that the dilaton black hole acts as a particle accelerator by analyzing the energy in the center of mass frame of two colliding particles in the vicinity of its horizon. In particular, we find that there is a critical value of the angular momentum, which depends on the string coupling, and a particle with this critical angular momentum can reach the inner horizon with an arbitrarily high c.m. energy. This is known as the Bañados, Silk, and West process. We also show that the motion and collisions of particles have behavior similar to the three-dimensional Bañados-Teitelboim-Zanelli black hole. In fact, the photons can plunge into the horizon or escape to infinity, and they cannot be deflected, while for massive particles there are no confined orbits of the first kind, like planetary or circular orbits.

Spontaneous emergence of milling (vortex state) in a Vicsek-like model

NASA Astrophysics Data System (ADS)

Costanzo, A.; Hemelrijk, C. K.

2018-04-01

Collective motion is of interest to laymen and scientists in different fields. In groups of animals, many patterns of collective motion arise such as polarized schools and mills (i.e. circular motion). Collective motion can be generated in computational models of different degrees of complexity. In these models, moving individuals coordinate with others nearby. In the more complex models, individuals attract each other, aligning their headings, and avoiding collisions. Simpler models may include only one or two of these types of interactions. The collective pattern that interests us here is milling, which is observed in many animal species. It has been reproduced in the more complex models, but not in simpler models that are based only on alignment, such as the well-known Vicsek model. Our aim is to provide insight in the minimal conditions required for milling by making minimal modifications to the Vicsek model. Our results show that milling occurs when both the field of view and the maximal angular velocity are decreased. Remarkably, apart from milling, our minimal model also exhibits many of the other patterns of collective motion observed in animal groups.

Hydrodynamic interaction of two deformable drops in confined shear flow.

PubMed

Chen, Yongping; Wang, Chengyao

2014-09-01

We investigate hydrodynamic interaction between two neutrally buoyant circular drops in a confined shear flow based on a computational fluid dynamics simulation using the volume-of-fluid method. The rheological behaviors of interactive drops and the flow regimes are explored with a focus on elucidation of underlying physical mechanisms. We find that two types of drop behaviors during interaction occur, including passing-over motion and reversing motion, which are governed by the competition between the drag of passing flow and the entrainment of reversing flow in matrix fluid. With the increasing confinement, the drop behavior transits from the passing-over motion to reversing motion, because the entrainment of the reversing-flow matrix fluid turns to play the dominant role. The drag of the ambient passing flow is increased by enlarging the initial lateral separation due to the departure of the drop from the reversing flow in matrix fluid, resulting in the emergence of passing-over motion. In particular, a corresponding phase diagram is plotted to quantitatively illustrate the dependence of drop morphologies during interaction on confinement and initial lateral separation.

Activity-Dependence of Synaptic Vesicle Dynamics

PubMed Central

Forte, Luca A.

2017-01-01

The proper function of synapses relies on efficient recycling of synaptic vesicles. The small size of synaptic boutons has hampered efforts to define the dynamical states of vesicles during recycling. Moreover, whether vesicle motion during recycling is regulated by neural activity remains largely unknown. We combined nanoscale-resolution tracking of individual synaptic vesicles in cultured hippocampal neurons from rats of both sexes with advanced motion analyses to demonstrate that the majority of recently endocytosed vesicles undergo sequences of transient dynamical states including epochs of directed, diffusional, and stalled motion. We observed that vesicle motion is modulated in an activity-dependent manner, with dynamical changes apparent in ∼20% of observed boutons. Within this subpopulation of boutons, 35% of observed vesicles exhibited acceleration and 65% exhibited deceleration, accompanied by corresponding changes in directed motion. Individual vesicles observed in the remaining ∼80% of boutons did not exhibit apparent dynamical changes in response to stimulation. More quantitative transient motion analyses revealed that the overall reduction of vesicle mobility, and specifically of the directed motion component, is the predominant activity-evoked change across the entire bouton population. Activity-dependent modulation of vesicle mobility may represent an important mechanism controlling vesicle availability and neurotransmitter release. SIGNIFICANCE STATEMENT Mechanisms governing synaptic vesicle dynamics during recycling remain poorly understood. Using nanoscale resolution tracking of individual synaptic vesicles in hippocampal synapses and advanced motion analysis tools we demonstrate that synaptic vesicles undergo complex sets of dynamical states that include epochs of directed, diffusive, and stalled motion. Most importantly, our analyses revealed that vesicle motion is modulated in an activity-dependent manner apparent as the reduction in overall vesicle mobility in response to stimulation. These results define the vesicle dynamical states during recycling and reveal their activity-dependent modulation. Our study thus provides fundamental new insights into the principles governing synaptic function. PMID:28954868

The effectiveness of a pneumatic compression belt in reducing respiratory motion of abdominal tumors in patients undergoing stereotactic body radiotherapy.

PubMed

Lovelock, D Michael; Zatcky, Joan; Goodman, Karyn; Yamada, Yoshiya

2014-06-01

Abdominal compression using a pneumatic abdominal compression belt developed in-house has been used to reduce respiratory motion of patients undergoing hypo-fractionated or single fraction stereotactic radio-ablative therapy for abdominal cancers. The clinical objective of belt usage was to reduce the cranial-caudal (CC) respiratory motion of the tumor to 5 mm or less during both CT simulation and treatment. A retrospective analysis was done to determine the effectiveness of the device and associated clinical procedures to reduce the CC respiratory motion of the tumor. 42 patients treated for tumors in the liver (30), adrenal glands (6), pancreas (3) and lymph nodes (3) using high dose hypofractionated radiotherapy between 2004 and the present were eligible for analysis. All patients had 2-3 radiopaque fiducial markers implanted near the tumor prior to simulation, or had clips from prior surgery. Integral to the belt is an inflatable air bladder that is positioned over the abdomen. The pneumatic pressure was set to a level in consultation with the patient. The CC motion was measured fluoroscopically with and without pneumatic pressure. Pneumatic pressure was used at all treatments to reduce to CC motion to that achieved at simulation. The mean CC motion with the belt in place, but no additional air pressure was 11.4 mm with a range of 5-20 mm. With the pressure applied, the mean CC motion was reduced to 4.4 mm with a range of 1-8 mm (P-value < 0.001). The clinical objective of reducing the CC motion of the tumor to a maximum excursion of 5 mm or less was achieved in 93% of cases. The use of a pneumatic compression belt and associated clinical procedures was found to result in a significant and frequently substantial reduction in the CC motion of the tumor.

Physics Teacher Demonstrations for the Classroom

NASA Astrophysics Data System (ADS)

Murfee, Lee

2005-04-01

A sharing of physics and physics teaching demonstrations by Lee Murfee, a teacher of students learning physics and mathematics at Berkeley Preparatory School and the United States Military Academy for 21 years, and active member of the Florida Section of American Association of Physics Teachers (AAPT). Presentation is a fast paced array of physics and physics teaching demonstrations. Topics include who and what we teach, a successful science department philosophy, forces, acceleration, impulse, momentum, observations, pendulums, springs, friction, inclined plane, rotational motion, moment of inertia, teaching description of motion with data, equations and graphing, slope, uniform circular motion, derivatives, integrals, PASCO Data Studio sensor applications, students presenting to students, flashboards, sound, pressure, and sensitivity analysis in determining specific heat. Demonstrations apply to high school and college introductory physics teaching; handouts and some door prizes/gifts will be provided.

Vortex-induced vibration (VIV) effects of a drilling riser due to vessel motion

NASA Astrophysics Data System (ADS)

Joseph, R. S.; Wang, J.; Ong, M. C.; Jakobsen, J. B.

2017-12-01

A marine riser undergoes oscillatory motion in water due to the vessel motions, known as global dynamic response. This to-and-fro motion of the riser will generate an equivalent flow that can cause Vortex-Induced Vibrations (VIVs), even in the absence of the ocean current. In the present work, full-scale measurement data of a drilling riser operating in the Gulf of Mexico are analysed. The VIV occurrences for the riser are identified from the data and the possible excitation sources are discussed. The oscillatory flow due to vessel motion is compared with the ocean current and its possibility to excite VIV is analysed. The full-scale data analysis provides an insight into the vessel motion-induced VIV of marine risers in the actual field environment.

Robust, Flexible Motion Control for the Mars Explorer Rovers

NASA Technical Reports Server (NTRS)

Maimone, Mark; Biesiadecki, Jeffrey

2007-01-01

The Mobility Flight Software, running on computers aboard the Mars Explorer Rover (MER) robotic vehicles Spirit and Opportunity, affords the robustness and flexibility of control to enable safe and effective operation of these vehicles in traversing natural terrain. It can make the vehicles perform specific maneuvers commanded from Earth, and/or can autonomously administer multiple aspects of mobility, including choice of motion, measurement of actual motion, and even selection of targets to be approached. Motion of a vehicle can be commanded by use of multiple layers of control, ranging from motor control at a low level, direct drive operations (e.g., motion along a circular arc, motion along a straight line, or turn in place) at an intermediate level to goal-position driving (that is, driving to a specified location) at a high level. The software can also perform high-level assessment of terrain and selection of safe paths across the terrain: this involves processing of the digital equivalent of a local traversability map generated from images acquired by stereoscopic pairs of cameras aboard the vehicles. Other functions of the software include interacting with the rest of the MER flight software and performing safety checks.

The dynamics and control of large flexible space structures. Volume 3, part B: The modelling, dynamics, and stability of large Earth pointing orbiting structures

NASA Technical Reports Server (NTRS)

Bainum, P. M.; Kumar, V. K.

1980-01-01

The dynamics and stability of large orbiting flexible beams, and platforms and dish type structures oriented along the local horizontal are treated both analytically and numerically. It is assumed that such structures could be gravitationally stabilized by attaching a rigid light-weight dumbbell at the center of mass by a spring loaded hinge which also could provide viscous damping. For the beam, the small amplitude inplane pitch motion, dumbbell librational motion, and the anti-symmetric elastic modes are all coupled. The three dimensional equations of motion for a circular flat plate and shallow spherical shell in orbit with a two-degree-of freedom gimballed dumbbell are also developed and show that only those elastic modes described by a single nodal diameter line are influenced by the dumbbell motion. Stability criteria are developed for all the examples and a sensitivity study of the system response characteristics to the key system parameters is carried out.

Motion-based nearest vector metric for reference frame selection in the perception of motion.

PubMed

Agaoglu, Mehmet N; Clarke, Aaron M; Herzog, Michael H; Ögmen, Haluk

2016-05-01

We investigated how the visual system selects a reference frame for the perception of motion. Two concentric arcs underwent circular motion around the center of the display, where observers fixated. The outer (target) arc's angular velocity profile was modulated by a sine wave midflight whereas the inner (reference) arc moved at a constant angular speed. The task was to report whether the target reversed its direction of motion at any point during its motion. We investigated the effects of spatial and figural factors by systematically varying the radial and angular distances between the arcs, and their relative sizes. We found that the effectiveness of the reference frame decreases with increasing radial- and angular-distance measures. Drastic changes in the relative sizes of the arcs did not influence motion reversal thresholds, suggesting no influence of stimulus form on perceived motion. We also investigated the effect of common velocity by introducing velocity fluctuations to the reference arc as well. We found no effect of whether or not a reference frame has a constant motion. We examined several form- and motion-based metrics, which could potentially unify our findings. We found that a motion-based nearest vector metric can fully account for all the data reported here. These findings suggest that the selection of reference frames for motion processing does not result from a winner-take-all process, but instead, can be explained by a field whose strength decreases with the distance between the nearest motion vectors regardless of the form of the moving objects.

Motion of the angular momentum vector in body coordinates for torque-free dual-spin spacecraft

NASA Technical Reports Server (NTRS)

Fedor, J. V.

1981-01-01

The motion of the angular momentum vector in body coordinates for torque free, asymmetric dual spin spacecraft without and, for a special case, with energy dissipation on the main spacecraft is investigated. Without energy dissipation, two integrals can be obtained from the Euler equations of motion. Using the classical method of elimination of variable, the motion about the equilibrium points (six for the general case) are derived with these integrals. For small nutation angle, theta, the trajectories about the theta = 0 deg and theta = 180 deg points readily show the requirements for stable motion about these points. Also the conditions needed to eliminate stable motion about the theta = 180 deg point as well as the other undesireable equilibrium points follow directly from these equations. For the special case where the angular momentum vector moves about the principal axis which contains the momentum wheel, the notion of 'free variable' azimuth angle is used. Physically this angle must vary from 0 to 2 pi in a circular periodic fashion. Expressions are thus obtained for the nutation angle in terms of the free variable and other spacecraft parameters. Results show that in general there are two separate trajectory expressions that govern the motion of the angular momentum vector in body coordinates.

Steering microtubule shuttle transport with dynamically controlled magnetic fields

DOE PAGES

Mahajan, K. D.; Ruan, G.; Dorcéna, C. J.; ...

2016-03-23

Nanoscale control of matter is critical to the design of integrated nanosystems. Here, we describe a method to dynamically control directionality of microtubule (MT) motion using programmable magnetic fields. MTs are combined with magnetic quantum dots (i.e., MagDots) that are manipulated by external magnetic fields provided by magnetic nanowires. MT shuttles thus undergo both ATP-driven and externally-directed motion with a fluorescence component that permits simultaneous visualization of shuttle motion. This technology is used to alter the trajectory of MTs in motion and to pin MT motion. Ultimately, such an approach could be used to evaluate the MT-kinesin transport system andmore » could serve as the basis for improved lab-on-a-chip technologies based on MT transport.« less

Quantitative analysis of random ameboid motion

NASA Astrophysics Data System (ADS)

Bödeker, H. U.; Beta, C.; Frank, T. D.; Bodenschatz, E.

2010-04-01

We quantify random migration of the social ameba Dictyostelium discoideum. We demonstrate that the statistics of cell motion can be described by an underlying Langevin-type stochastic differential equation. An analytic expression for the velocity distribution function is derived. The separation into deterministic and stochastic parts of the movement shows that the cells undergo a damped motion with multiplicative noise. Both contributions to the dynamics display a distinct response to external physiological stimuli. The deterministic component depends on the developmental state and ambient levels of signaling substances, while the stochastic part does not.

Powder Handling Device for Analytical Instruments

NASA Technical Reports Server (NTRS)

Sarrazin, Philippe C. (Inventor); Blake, David F. (Inventor)

2006-01-01

Method and system for causing a powder sample in a sample holder to undergo at least one of three motions (vibration, rotation and translation) at a selected motion frequency in order to present several views of an individual grain of the sample. One or more measurements of diffraction, fluorescence, spectroscopic interaction, transmission, absorption and/or reflection can be made on the sample, using light in a selected wavelength region.

The Effect of Using Concept Mapping on Student's Attitude and Achievement When Learning the Physics Topic of Circular and Rotational Motion

ERIC Educational Resources Information Center

Luchembe, Dennis; Chinyama, Kaumba; Jumbe, Jack

2014-01-01

The study was conducted to show the effectiveness of concept mapping as a teaching strategy to undergraduate students taking introductory physics course. A number of researchers have investigated the effectiveness of concept mapping on student academic achievement. The main focus of these studies have been on comparing the effectiveness of concept…

Electronic Warfare and Radar Systems Engineering Handbook. 4th Edition

DTIC Science & Technology

2013-10-01

and Maintainability R&M Reliability and Maintainability RAT Ram Air Turbine RBOC Rapid Blooming Offboard Chaff RCP or RHCP Right-hand Circular...Doppler shifted return (see Figure 10). Reflections off rotating jet engine compressor blades, aircraft propellers, ram air turbine (RAT...Doppler techniques, in order to precisely predict aircraft ground speed and direction of motion. Wind influences are taken into account, such that

Apollonius [Apollonios] of Perga (200-100 BC)

NASA Astrophysics Data System (ADS)

Murdin, P.

2000-11-01

Greek geometer from Perga, now in Turkey, who proposed that the planets revolved around the Sun, and the Sun revolves around the Earth. Apollonius left no astronomical works but is believed to be the inventor of the geometric system of epicycles and eccentric circles, by which perfect circular motions were combined into the actual elliptical orbits of the planets. His work was developed by HIPPAR...

Explicit Low-Thrust Guidance for Reference Orbit Targeting

NASA Technical Reports Server (NTRS)

Lam, Try; Udwadia, Firdaus E.

2013-01-01

The problem of a low-thrust spacecraft controlled to a reference orbit is addressed in this paper. A simple and explicit low-thrust guidance scheme with constrained thrust magnitude is developed by combining the fundamental equations of motion for constrained systems from analytical dynamics with a Lyapunov-based method. Examples are given for a spacecraft controlled to a reference trajectory in the circular restricted three body problem.

Maximum Range of a Projectile Thrown from Constant-Speed Circular Motion

ERIC Educational Resources Information Center

Poljak, Nikola

2016-01-01

The problem of determining the angle ? at which a point mass launched from ground level with a given speed v[subscript 0] will reach a maximum distance is a standard exercise in mechanics. There are many possible ways of solving this problem, leading to the well-known answer of ? = p/4, producing a maximum range of D[subscript max] = v[superscript…

The effectiveness of interactive computer simulations on college engineering student conceptual understanding and problem-solving ability related to circular motion

NASA Astrophysics Data System (ADS)

Chien, Cheng-Chih

In the past thirty years, the effectiveness of computer assisted learning was found varied by individual studies. Today, with drastic technical improvement, computers have been widely spread in schools and used in a variety of ways. In this study, a design model involving educational technology, pedagogy, and content domain is proposed for effective use of computers in learning. Computer simulation, constructivist and Vygotskian perspectives, and circular motion are the three elements of the specific Chain Model for instructional design. The goal of the physics course is to help students remove the ideas which are not consistent with the physics community and rebuild new knowledge. To achieve the learning goal, the strategies of using conceptual conflicts and using language to internalize specific tasks into mental functions were included. Computer simulations and accompanying worksheets were used to help students explore their own ideas and to generate questions for discussions. Using animated images to describe the dynamic processes involved in the circular motion may reduce the complexity and possible miscommunications resulting from verbal explanations. The effectiveness of the instructional material on student learning is evaluated. The results of problem solving activities show that students using computer simulations had significantly higher scores than students not using computer simulations. For conceptual understanding, on the pretest students in the non-simulation group had significantly higher score than students in the simulation group. There was no significant difference observed between the two groups in the posttest. The relations of gender, prior physics experience, and frequency of computer uses outside the course to student achievement were also studied. There were fewer female students than male students and fewer students using computer simulations than students not using computer simulations. These characteristics affect the statistical power for detecting differences. For the future research, more intervention of simulations may be introduced to explore the potential of computer simulation in helping students learning. A test for conceptual understanding with more problems and appropriate difficulty level may be needed.

[Origin of motion in the human ureter: mechanics, energetics and kinetics of the myosin molecular motors].

PubMed

Vargiu, Romina; Perinu, Anna; De Lisa, Antonello; Tintrup, Frank; Manca, Francesco; Mancinelli, Rino

2012-01-01

Ureteral peristalsis is the result of coordinated mechanical motor performance of longitudinal and circular smooth muscle layer of the ureter wall. The main aim of this study was to characterize in smooth muscle of proximal segments of human ureter, the mechanical properties at level of muscle tissue and at level of myosin molecular motors. Ureteral samples were collected from 15 patients, who underwent nephrectomy for renal cancer. Smooth muscle strips longitudinally and circularly oriented from proximal segments of human ureter were used for the in vitro experiments. Mechanical indices including the maximum unloaded shortening velocity (Vmax), and the maximum isometric tension (P0) normalized per cross-sectional area, were determined in vitro determined in electrically evoked contractions of longitudinal and circular smooth muscle strips. Myosin cross-bridge (CB) number per mm2 (Ψ) the elementary force per single CB (Ψ) and kinetic parameters were calculated in muscle strips, using Huxley's equations adapted to nonsarcomeric muscles. Longitudinal smooth muscle strips exhibited a significantly (p<0.05) faster Vmax (63%) and a higher P0 (40%), if compared to circular strips. Moreover, longitudinal muscle strips showed a significantly higher unitary force (Ψ) per CB. However, no significant differences were observed in CB number, the attachment (f1) and the detachment (g2) rate constants between longitudinal and circular muscle strips. The main result obtained in the present work documents that the mechanical, energetic and unitary forces per CB of longitudinal layer of proximal ureter are better compared to the circular one; these preliminary findings suggested, unlike intestinal smooth muscle, a major role of longitudinal smooth muscle layer in the ureter peristalsis.

Nanoscopic dynamics in hybrid hydroxyapatite-CTAB composite

NASA Astrophysics Data System (ADS)

Dubey, P. S.; Sharma, V. K.; Mitra, S.; Verma, G.; Hassan, P. A.; Dutta, B.; Johnson, M.; Mukhopadhyay, R.

2017-06-01

Synthetic hydroxyapatite (HAp) is an important material in biomedical engineering due to its excellent biocompatibility and bioactivity. HAp nanoparticles were synthesized by the co-precipitation method using cetyltrimethylammonium bromide (CTAB) micelles as a template and are characterized using x-ray diffraction, electron microscopy, and thermal gravimetric measurements. Transmission electron microscope (TEM) demonstrates the formation of rod-shaped HAp. Dynamics of CTAB in HAp-CTAB composite as studied by using quasielastic neutron scattering (QENS) technique is reported here. HAp-CTAB composite provides an ideal system for studying the dynamics of CTAB micelles without any aqueous media. QENS data indicate that the observed dynamics are reminiscent of localized motions in ionic micellar systems, consisting of segmental and fast torsional motions. Segmental dynamics has been described with a model, in which hydrogen atoms in the alkyl chain undergoes localized translation diffusion and the CH3 unit associated with the head group undergo 3-fold jump rotation. Within this model, the hydrogen atoms in the alkyl chain undergo diffusion within spherical domains having different radii and diffusivities. A simple linear distribution of the radius and diffusivity has been assumed, in which the CH2 unit nearest to the head group has the least value and the ones furthest from the head group, that is, at the end of the alkyl chain has the largest value. The fast torsional motion is described by a 2-fold jump rotation model. Quantitative estimate of the different parameters characterizing various dynamical motions active within the time scale of the instrument is also presented. We have provided a detailed description of the observed dynamical features in hybrid HAp-CTAB composite, a potential candidate for biomedical applications.

Branching instability in expanding bacterial colonies.

PubMed

Giverso, Chiara; Verani, Marco; Ciarletta, Pasquale

2015-03-06

Self-organization in developing living organisms relies on the capability of cells to duplicate and perform a collective motion inside the surrounding environment. Chemical and mechanical interactions coordinate such a cooperative behaviour, driving the dynamical evolution of the macroscopic system. In this work, we perform an analytical and computational analysis to study pattern formation during the spreading of an initially circular bacterial colony on a Petri dish. The continuous mathematical model addresses the growth and the chemotactic migration of the living monolayer, together with the diffusion and consumption of nutrients in the agar. The governing equations contain four dimensionless parameters, accounting for the interplay among the chemotactic response, the bacteria-substrate interaction and the experimental geometry. The spreading colony is found to be always linearly unstable to perturbations of the interface, whereas branching instability arises in finite-element numerical simulations. The typical length scales of such fingers, which align in the radial direction and later undergo further branching, are controlled by the size parameters of the problem, whereas the emergence of branching is favoured if the diffusion is dominant on the chemotaxis. The model is able to predict the experimental morphologies, confirming that compact (resp. branched) patterns arise for fast (resp. slow) expanding colonies. Such results, while providing new insights into pattern selection in bacterial colonies, may finally have important applications for designing controlled patterns. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

Classical-trajectory simulation of accelerating neutral atoms with polarized intense laser pulses

NASA Astrophysics Data System (ADS)

Xia, Q. Z.; Fu, L. B.; Liu, J.

2013-03-01

In the present paper, we perform the classical trajectory Monte Carlo simulation of the complex dynamics of accelerating neutral atoms with linearly or circularly polarized intense laser pulses. Our simulations involve the ion motion as well as the tunneling ionization and the scattering dynamics of valence electron in the combined Coulomb and electromagnetic fields, for both helium (He) and magnesium (Mg). We show that for He atoms, only linearly polarized lasers can effectively accelerate the atoms, while for Mg atoms, we find that both linearly and circularly polarized lasers can successively accelerate the atoms. The underlying mechanism is discussed and the subcycle dynamics of accelerating trajectories is investigated. We have compared our theoretical results with a recent experiment [Eichmann Nature (London)NATUAS0028-083610.1038/nature08481 461, 1261 (2009)].

DROMO formulation for planar motions: solution to the Tsien problem

NASA Astrophysics Data System (ADS)

Urrutxua, Hodei; Morante, David; Sanjurjo-Rivo, Manuel; Peláez, Jesús

2015-06-01

The two-body problem subject to a constant radial thrust is analyzed as a planar motion. The description of the problem is performed in terms of three perturbation methods: DROMO and two others due to Deprit. All of them rely on Hansen's ideal frame concept. An explicit, analytic, closed-form solution is obtained for this problem when the initial orbit is circular (Tsien problem), based on the DROMO special perturbation method, and expressed in terms of elliptic integral functions. The analytical solution to the Tsien problem is later used as a reference to test the numerical performance of various orbit propagation methods, including DROMO and Deprit methods, as well as Cowell and Kustaanheimo-Stiefel methods.

A static air flow visualization method to obtain a time history of the lift-induced vortex and circulation

NASA Technical Reports Server (NTRS)

Patterson, J. C., Jr.; Jordan, F. L., Jr.

1975-01-01

A recently proposed method of flow visualization was investigated at the National Aeronautics and Space Administration's Langley Research Center. This method of flow visualization is particularly applicable to the study of lift-induced wing tip vortices through which it is possible to record the entire life span of the vortex. To accomplish this, a vertical screen of smoke was produced perpendicular to the flight path and allowed to become stationary. A model was then driven through the screen of smoke producing the circular vortex motion made visible as the smoke was induced along the path taken by the flow and was recorded by highspeed motion pictures.

Radiation Pressure, Poynting-Robertson Drag, and Solar Wind Drag in the Restricted Three-Body Problem

NASA Technical Reports Server (NTRS)

Liou, Jer-Chyi; Zook, Herbert A.; Jackson, A. A.

1995-01-01

In this paper, we examine the effects of radiation pressure, Poynting-Robertson (PR) drag, and solar wind drag on dust grains trapped in mean motion resonances with the Sun and Jupiter in the restricted (negligible dust mass) three-body Problem. We especially examine the evolution of dust grains in the 1:1 resonance. As a first step, the Sun and Jupiter are idealized to both be in circular orbit about a common center of mass (circular restricted three-body problem). From the equation of motion of the dust particle in the rotating reference frame, the drag-induced time rate of change of its Jacobi "constant," C, is then derived and expressed in spherical coordinates. This new mathematical expression in spherical coordinates shows that C, in the 1:1 resonance, both oscillates and secularly increases with increasing time. The new expression gives rise to an easy understanding of how an orbit evolves when the radiation force and solar wind drag are included. All dust grain orbits are unstable in time when PR and solar wind drag are included in the Sun-Jupiter-dust system. Tadpole orbits evolve into horseshoe orbits; and these orbits continuously expand in size to lead to close encounters with Jupiter. Permanent trapping is impossible. Orbital evolutions of a dust grain trapped in the 1:1 resonance in the planar circular, an inclined case, an eccentric case, and the actual Sun-Jupiter case are numerically simulated and compared with each other and show grossly similar time behavior. Resonances other than 1:1 are also explored with the new expression. Stable exterior resonance trapping may be possible under certain conditions. One necessary condition for such a trap is derived. Trapping in interior resonances is shown to be always unstable.

The SAMI Galaxy Survey: gas streaming and dynamical M/L in rotationally supported systems

NASA Astrophysics Data System (ADS)

Cecil, G.; Fogarty, L. M. R.; Richards, S.; Bland-Hawthorn, J.; Lange, R.; Moffett, A.; Catinella, B.; Cortese, L.; Ho, I.-T.; Taylor, E. N.; Bryant, J. J.; Allen, J. T.; Sweet, S. M.; Croom, S. M.; Driver, S. P.; Goodwin, M.; Kelvin, L.; Green, A. W.; Konstantopoulos, I. S.; Owers, M. S.; Lawrence, J. S.; Lorente, N. P. F.

2016-02-01

Line-of-sight velocities of gas and stars can constrain dark matter (DM) within rotationally supported galaxies if they trace circular orbits extensively. Photometric asymmetries may signify non-circular motions, requiring spectra with dense spatial coverage. Our integral-field spectroscopy of 178 galaxies spanned the mass range of the Sydney-AAO Multi-object integral field spectrograph (SAMI) Galaxy Survey. We derived circular speed curves (CSCs) of gas and stars from non-parametric fits out to r ˜ 2re. For 12/14 with measured H I profiles, ionized gas and H I maximum velocities agreed. We fitted mass-follows-light models to 163 galaxies by approximating the radial light profile as nested, very flattened mass homeoids viewed as a Sérsic form. Fitting broad-band spectral energy distributions to Sloan Digital Sky Survey images gave median stellar mass/light 1.7 assuming a Kroupa initial mass function (IMF) versus 2.6 dynamically. Two-thirds of the dynamical mass/light measures were consistent with star+remnant IMFs. One-fifth required upscaled starlight to fit, hence comparable mass of unobserved baryons and/or DM distributed like starlight across the SAMI aperture that came to dominate motions as the starlight CSCs declined rapidly. The rest had mass distributed differently from light. Subtracting fits of Sérsic radial profiles to 13 VIKING Z-band images revealed residual weak bars. Near the bar major axis, we assessed m = 2 streaming velocities, and found deviations usually <30 km s-1 from the CSC; three showed no deviation. Thus, asymmetries rarely influenced the CSC despite colocated shock-indicating, emission-line flux ratios in more than 2/3 of our sample.

Corrections to the Thomson cross section caused by relativistic effects and by the presence of the drift velocity of a classical charged particle in the field of a monochromatic plane wave

NASA Astrophysics Data System (ADS)

Perestoronin, A. V.

2017-03-01

An approach to the solution of the relativistic problem of the motion of a classical charged particle in the field of a monochromatic plane wave with an arbitrary polarization (linear, circular, or elliptic) is proposed. It is based on the analysis of the 4-vector equation of motion of the charged particle together with the 4-vector and tensor equations for the components of the electromagnetic field tensor of a monochromatic plane wave. This approach provides analytical expressions for the time-averaged square of the 4-acceleration of the charge, as well as for the averaged values of any quantities periodic in the time of the reference frame. Expressions for the integral power of scattered radiation, which is proportional to the time-averaged square of the 4-acceleration of the charge, and for the integral scattering cross section, which is the ratio of the power of scattered radiation to the intensity of incident radiation, are obtained for an arbitrary inertial reference frame. An expression for the scattering cross section, which coincides with the known results at the circular and linear polarizations of the incident waves and describes the case of elliptic polarization of the incident wave, is obtained for the reference frame where the charged particle is on average at rest. An expression for the scattering cross section including relativistic effects and the nonzero drift velocity of a particle in this system is obtained for the laboratory reference frame, where the initial velocity of the charged particle is zero. In the case of the circular polarization of the incident wave, the scattering cross section in the laboratory frame is equal to the Thompson cross section.

The influence of imagery vividness on cognitive and perceptual cues in circular auditorily-induced vection.

PubMed

Väljamäe, Aleksander; Sell, Sara

2014-01-01

In the absence of other congruent multisensory motion cues, sound contribution to illusions of self-motion (vection) is relatively weak and often attributed to purely cognitive, top-down processes. The present study addressed the influence of cognitive and perceptual factors in the experience of circular, yaw auditorily-induced vection (AIV), focusing on participants imagery vividness scores. We used different rotating sound sources (acoustic landmark vs. movable types) and their filtered versions that provided different binaural cues (interaural time or level differences, ITD vs. ILD) when delivering via loudspeaker array. The significant differences in circular vection intensity showed that (1) AIV was stronger for rotating sound fields containing auditory landmarks as compared to movable sound objects; (2) ITD based acoustic cues were more instrumental than ILD based ones for horizontal AIV; and (3) individual differences in imagery vividness significantly influenced the effects of contextual and perceptual cues. While participants with high scores of kinesthetic and visual imagery were helped by vection "rich" cues, i.e., acoustic landmarks and ITD cues, the participants from the low-vivid imagery group did not benefit from these cues automatically. Only when specifically asked to use their imagination intentionally did these external cues start influencing vection sensation in a similar way to high-vivid imagers. These findings are in line with the recent fMRI work which suggested that high-vivid imagers employ automatic, almost unconscious mechanisms in imagery generation, while low-vivid imagers rely on more schematic and conscious framework. Consequently, our results provide an additional insight into the interaction between perceptual and contextual cues when experiencing purely auditorily or multisensory induced vection.

The influence of imagery vividness on cognitive and perceptual cues in circular auditorily-induced vection

PubMed Central

Väljamäe, Aleksander; Sell, Sara

2014-01-01

In the absence of other congruent multisensory motion cues, sound contribution to illusions of self-motion (vection) is relatively weak and often attributed to purely cognitive, top-down processes. The present study addressed the influence of cognitive and perceptual factors in the experience of circular, yaw auditorily-induced vection (AIV), focusing on participants imagery vividness scores. We used different rotating sound sources (acoustic landmark vs. movable types) and their filtered versions that provided different binaural cues (interaural time or level differences, ITD vs. ILD) when delivering via loudspeaker array. The significant differences in circular vection intensity showed that (1) AIV was stronger for rotating sound fields containing auditory landmarks as compared to movable sound objects; (2) ITD based acoustic cues were more instrumental than ILD based ones for horizontal AIV; and (3) individual differences in imagery vividness significantly influenced the effects of contextual and perceptual cues. While participants with high scores of kinesthetic and visual imagery were helped by vection “rich” cues, i.e., acoustic landmarks and ITD cues, the participants from the low-vivid imagery group did not benefit from these cues automatically. Only when specifically asked to use their imagination intentionally did these external cues start influencing vection sensation in a similar way to high-vivid imagers. These findings are in line with the recent fMRI work which suggested that high-vivid imagers employ automatic, almost unconscious mechanisms in imagery generation, while low-vivid imagers rely on more schematic and conscious framework. Consequently, our results provide an additional insight into the interaction between perceptual and contextual cues when experiencing purely auditorily or multisensory induced vection. PMID:25520683

Wave friction factor rediscovered

NASA Astrophysics Data System (ADS)

Le Roux, J. P.

2012-02-01

The wave friction factor is commonly expressed as a function of the horizontal water particle semi-excursion ( A wb) at the top of the boundary layer. A wb, in turn, is normally derived from linear wave theory by {{U_{{wb}}/T_{{w}}}}{{2π }} , where U wb is the maximum water particle velocity measured at the top of the boundary layer and T w is the wave period. However, it is shown here that A wb determined in this way deviates drastically from its real value under both linear and non-linear waves. Three equations for smooth, transitional and rough boundary conditions, respectively, are proposed to solve this problem, all three being a function of U wb, T w, and δ, the thickness of the boundary layer. Because these variables can be determined theoretically for any bottom slope and water depth using the deepwater wave conditions, there is no need to physically measure them. Although differing substantially from many modern attempts to define the wave friction factor, the results coincide with equations proposed in the 1960s for either smooth or rough boundary conditions. The findings also confirm that the long-held notion of circular water particle motion down to the bottom in deepwater conditions is erroneous, the motion in fact being circular at the surface and elliptical at depth in both deep and shallow water conditions, with only horizontal motion at the top of the boundary layer. The new equations are incorporated in an updated version (WAVECALC II) of the Excel program published earlier in this journal by Le Roux et al. Geo-Mar Lett 30(5): 549-560, (2010).

Study of Running Stability in Side-Suspended HTS-PMG Maglev Circular Line System

NASA Astrophysics Data System (ADS)

Zhou, Dajin; Zhao, Lifeng; Li, Linbo; Cui, Chenyu; Hsieh, Chang-Chun; Zhang, Yong; Guo, Jianqiang; Zhao, Yong

2017-07-01

A research on stability of the side-suspended HTS-PMG maglev circular line system is carried out through simulation experiment. The results show that the maglev vehicle will gradually get close to the track surface during acceleration under the action of centrifugal force, leading to decay of guidance force and occurrence of vertical eccentric motion. In case of linear array of YBa2Cu3O7-x (YBCO) bulks, the guidance force will be changed with the decreasing of the levitation gap. It can be suppressed through the complex arrangement of YBCO bulks. Fortunately, triangle array of YBCO bulks can effectively keep the guidance force constant and realize stable running during accelerating process of the prototype vehicle. Based on the research on stability of side-suspended maglev vehicle, a side-suspended PMG circular test track with diameter of 6.5 m and circumference of 20.4 m is successfully designed and established, enabling the prototype vehicle to run stably at up to 82.5 km/h under open atmosphere (9.6 × 104 Pa).

From Dust Devil to Sustainable Swirling Wind Energy

NASA Astrophysics Data System (ADS)

Zhang, Mingxu; Luo, Xilian; Li, Tianyu; Zhang, Liyuan; Meng, Xiangzhao; Kase, Kiwamu; Wada, Satoshi; Yu, Chuck Wah; Gu, Zhaolin

2015-02-01

Dust devils are common but meteorologically unique phenomena on Earth and on Mars. The phenomenon produces a vertical vortex motion in the atmosphere boundary layer and often occurs in hot desert regions, especially in the afternoons from late spring to early summer. Dust devils usually contain abundant wind energy, for example, a maximum swirling wind velocity of up to 25 m/s, with a 15 m/s maximum vertical velocity and 5 m/s maximum near-surface horizontal velocity can be formed. The occurrences of dust devils cannot be used for energy generation because these are generally random and short-lived. Here, a concept of sustained dust-devil-like whirlwind is proposed for the energy generation. A prototype of a circular shed with pre-rotation vanes has been devised to generate the whirlwind flow by heating the air inflow into the circular shed. The pre-rotation vanes can provide the air inflow with angular momentum. The results of numerical simulations and experiment illustrate a promising potential of the circular shed for generating swirling wind energy via the collection of low-temperature solar energy.

Analysis of Formation Flying in Eccentric Orbits Using Linearized Equations of Relative Motion

NASA Technical Reports Server (NTRS)

Lane, Christopher; Axelrad, Penina

2004-01-01

Geometrical methods for formation flying design based on the analytical solution to Hill's equations have been previously developed and used to specify desired relative motions in near circular orbits. By generating relationships between the vehicles that are intuitive, these approaches offer valuable insight into the relative motion and allow for the rapid design of satellite configurations to achieve mission specific requirements, such as vehicle separation at perigee or apogee, minimum separation, or a specific geometrical shape. Furthermore, the results obtained using geometrical approaches can be used to better constrain numerical optimization methods; allowing those methods to converge to optimal satellite configurations faster. This paper presents a set of geometrical relationships for formations in eccentric orbits, where Hill.s equations are not valid, and shows how these relationships can be used to investigate formation designs and how they evolve with time.

Driving mechanism of unsteady separation shock motion in hypersonic interactive flow

NASA Technical Reports Server (NTRS)

Dolling, D. S.; Narlo, J. C., II

1987-01-01

Wall pressure fluctuations were measured under the steady separation shock waves in Mach 5 turbulent interactions induced by unswept circular cylinders on a flat plate. The wall temperature was adiabatic. A conditional sampling algorithm was developed to examine the statistics of the shock wave motion. The same algorithm was used to examine data taken in earlier studies in the Princeton University Mach 3 blowdown tunnel. In these earlier studies, hemicylindrically blunted fins of different leading-edge diameters were tested in boundary layers which developed on the tunnel floor and on a flat plate. A description of the algorithm, the reasons why it was developed and the sensitivity of the results to the threshold settings, are discussed. The results from the algorithm, together with cross correlations and power spectral density estimates suggests that the shock motion is driven by the low-frequency unsteadiness of the downstream separated, vortical flow.

Skyrmion-based high-frequency signal generator

NASA Astrophysics Data System (ADS)

Luo, Shijiang; Zhang, Yue; Shen, Maokang; Ou-Yang, Jun; Yan, Baiqian; Yang, Xiaofei; Chen, Shi; Zhu, Benpeng; You, Long

2017-03-01

Many concepts for skyrmion-based devices have been proposed, and most of their possible applications are based on the motion of skyrmions driven by a dc current in an area with a constricted geometry. However, skyrmion motion driven by a pulsed current has not been investigated so far. In this work, we propose a skyrmion-based high-frequency signal generator based on the pulsed-current-driven circular motion of skyrmions in a square-shaped film by micromagnetic simulation. The results indicate that skyrmions can move in a closed curve with central symmetry. The trajectory and cycle period can be adjusted by tuning the size of the film, the current density, the Dzyaloshinskii-Moriya interaction constant, and the local in-plane magnetic anisotropy. The period can be tuned from several nanoseconds to tens of nanoseconds, which offers the possibility to prepare high-frequency signal generator based on skyrmions.

Stochastic analysis of pitch angle scattering of charged particles by transverse magnetic waves

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lemons, Don S.; Liu Kaijun; Winske, Dan

2009-11-15

This paper describes a theory of the velocity space scattering of charged particles in a static magnetic field composed of a uniform background field and a sum of transverse, circularly polarized, magnetic waves. When that sum has many terms the autocorrelation time required for particle orbits to become effectively randomized is small compared with the time required for the particle velocity distribution to change significantly. In this regime the deterministic equations of motion can be transformed into stochastic differential equations of motion. The resulting stochastic velocity space scattering is described, in part, by a pitch angle diffusion rate that ismore » a function of initial pitch angle and properties of the wave spectrum. Numerical solutions of the deterministic equations of motion agree with the theory at all pitch angles, for wave energy densities up to and above the energy density of the uniform field, and for different wave spectral shapes.« less

Figure ground segregation modulates perceived direction of ambiguous moving gratings and plaids.

PubMed

Tommasi, L; Vallortigara, G

1999-02-01

A translating oriented grating viewed through a circular aperture with an occluding area in the middle appeared to move alternately in an oblique or in a vertical direction depending on the foreground/background assignment on the central occluding area. The effect occurred even when the central area was simply removed from the display, thus giving rise to a 'subjective' occluder. Parametric studies revealed that the probability of seeing oblique or vertical motion was affected by the size of the central area but not by its contrast relationships with the grating. Similar phenomena of ambiguous motion direction were observed using changes in colour along a translating grating that produced neon colour spreading effects, or using oriented edge discontinuities that collapsed into subjective plaids composed of two one-dimensional gratings. These results are discussed with respect to the hypothesis that surface segmentation mechanisms play a crucial part in the interpretation of motion signals.

Introductory Physics Experiments Using the Wiimote

NASA Astrophysics Data System (ADS)

Somers, William; Rooney, Frank; Ochoa, Romulo

2009-03-01

The Wii, a video game console, is a very popular device with millions of units sold worldwide over the past two years. Although computationally it is not a powerful machine, to a physics educator its most important components can be its controllers. The Wiimote (or remote) controller contains three accelerometers, an infrared detector, and Bluetooth connectivity at a relatively low price. Thanks to available open source code, any PC with Bluetooth capability can detect the information sent out by the Wiimote. We have designed several experiments for introductory physics courses that make use of the accelerometers and Bluetooth connectivity. We have adapted the Wiimote to measure the: variable acceleration in simple harmonic motion, centripetal and tangential accelerations in circular motion, and the accelerations generated when students lift weights. We present the results of our experiments and compare them with those obtained when using motion and/or force sensors.

Dynamic deformation analysis of light-weight mirror

NASA Astrophysics Data System (ADS)

Zhang, Yingtao; Cao, Xuedong; Kuang, Long; Yang, Wei

2012-10-01

In the process of optical dynamic target work, under the effort of the arm of dynamic target, the mirror needs to do circular motion, additional accelerated motion and uniform motion. The maximum acceleration is 10°/s2 and the maximum velocity is 30°/s. In this paper, we mostly analyze the dynamic deformation of a 600 mm honeycomb light-weight mirror of a certain dynamic target. Using the FEA (finite element analysis) method, first of all, we analyze the deformation of the light-weight mirror induced in gravity at different position; later, the dynamic deformation of light-weight mirror is analyzed in detailed. The analysis results indicate that, when the maximum acceleration is 10°/s2 and the maximum velocity is 30°/s, the centripetal force is 5% of the gravity at the equal mass, and the dynamic deformation of the mirror is 6.1% of the deformation induced by gravity.

The Exact Solution for Linear Thermoelastic Axisymmetric Deformations of Generally Laminated Circular Cylindrical Shells

NASA Technical Reports Server (NTRS)

Nemeth, Michael P.; Schultz, Marc R.

2012-01-01

A detailed exact solution is presented for laminated-composite circular cylinders with general wall construction and that undergo axisymmetric deformations. The overall solution is formulated in a general, systematic way and is based on the solution of a single fourth-order, nonhomogeneous ordinary differential equation with constant coefficients in which the radial displacement is the dependent variable. Moreover, the effects of general anisotropy are included and positive-definiteness of the strain energy is used to define uniquely the form of the basis functions spanning the solution space of the ordinary differential equation. Loading conditions are considered that include axisymmetric edge loads, surface tractions, and temperature fields. Likewise, all possible axisymmetric boundary conditions are considered. Results are presented for five examples that demonstrate a wide range of behavior for specially orthotropic and fully anisotropic cylinders.

Active Control of Solar Array Dynamics During Spacecraft Maneuvers

NASA Technical Reports Server (NTRS)

Ross, Brant A.; Woo, Nelson; Kraft, Thomas G.; Blandino, Joseph R.

2016-01-01

Recent NASA mission plans require spacecraft to undergo potentially significant maneuvers (or dynamic loading events) with large solar arrays deployed. Therefore there is an increased need to understand and possibly control the nonlinear dynamics in the spacecraft system during such maneuvers. The development of a nonlinear controller is described. The utility of using a nonlinear controller to reduce forces and motion in a solar array wing during a loading event is demonstrated. The result is dramatic reductions in system forces and motion during a 10 second loading event. A motion curve derived from the simulation with the closed loop controller is used to obtain similar benefits with a simpler motion control approach.

Stepping-Motion Motor-Control Subsystem For Testing Bearings

NASA Technical Reports Server (NTRS)

Powers, Charles E.

1992-01-01

Control subsystem closed-loop angular-position-control system causing motor and bearing under test to undergo any of variety of continuous or stepping motions. Also used to test bearing-and-motor assemblies, motors, angular-position sensors including rotating shafts, and like. Monitoring subsystem gathers data used to evaluate performance of bearing or other article under test. Monitoring subsystem described in article, "Monitoring Subsystem For Testing Bearings" (GSC-13432).

Convective Self-Sustained Motion in Mixtures of Chemically Active and Passive Particles.

PubMed

Shklyaev, Oleg E; Shum, Henry; Yashin, Victor V; Balazs, Anna C

2017-08-15

We develop a model to describe the behavior of a system of active and passive particles in solution that can undergo spontaneous self-organization and self-sustained motion. The active particles are uniformly coated with a catalyst that decomposes the reagent in the surrounding fluid. The resulting variations in the fluid density give rise to a convective flow around the active particles. The generated fluid flow, in turn, drives the self-organization of both the active and passive particles into clusters that undergo self-sustained propulsion along the bottom wall of a microchamber. This propulsion continues until the reagents in the solution are consumed. Depending on the number of active and passive particles and the structure of the self-organized cluster, these assemblies can translate, spin, or remain stationary. We also illustrate a scenario in which the geometry of the container is harnessed to direct the motion of a self-organized, self-propelled cluster. The findings provide guidelines for creating autonomously moving active particles, or chemical "motors" that can transport passive cargo in microfluidic devices.

Unsteady surface pressure measurements on a slender delta wing undergoing limit cycle wing rock

NASA Technical Reports Server (NTRS)

Arena, Andrew S., Jr.; Nelson, Robert C.

1991-01-01

An experimental investigation of slender wing limit cycle motion known as wing rock was investigated using two unique experimental systems. Dynamic roll moment measurements and visualization data on the leading edge vortices were obtained using a free to roll apparatus that incorporates an airbearing spindle. In addition, both static and unsteady surface pressure data was measured on the top and bottom surfaces of the model. To obtain the unsteady surface pressure data a new computer controller drive system was developed to accurately reproduce the free to roll time history motions. The data from these experiments include, roll angle time histories, vortex trajectory data on the position of the vortices relative to the model's surface, and surface pressure measurements as a function of roll angle when the model is stationary or undergoing a wing rock motion. The roll time history data was numerically differentiated to determine the dynamic roll moment coefficient. An analysis of these data revealed that the primary mechanism for the limit cycle behavior was a time lag in the position of the vortices normal to the wing surface.

Sm@C2v(3)-C80: site-hopping motion of endohedral Sm atom and metal-induced effect on redox profile

NASA Astrophysics Data System (ADS)

Xu, Wei; Niu, Ben; Shi, Zujin; Lian, Yongfu; Feng, Lai

2012-10-01

A new metallofullerene Sm@C2v(3)-C80 was synthesized and characterized. X-Ray analysis showed that the endohedral Sm atom undergoes a hopping motion between several off-center sites, even at low temperature. In addition, a comparative electrochemical study between Sm@C2v(3)-C80 and Yb@C2v(3)-C80 revealed their different redox potentials, suggesting a metal-induced effect on their redox profiles.A new metallofullerene Sm@C2v(3)-C80 was synthesized and characterized. X-Ray analysis showed that the endohedral Sm atom undergoes a hopping motion between several off-center sites, even at low temperature. In addition, a comparative electrochemical study between Sm@C2v(3)-C80 and Yb@C2v(3)-C80 revealed their different redox potentials, suggesting a metal-induced effect on their redox profiles. CCDC reference number 894168. For crystallographic data in CIF or other electronic format see DOI: 10.1039/c2nr32193a

Nonlinear stability and control of gliding vehicles

NASA Astrophysics Data System (ADS)

Bhatta, Pradeep

In this thesis we use nonlinear systems analysis to study dynamics and design control solutions for vehicles subject to hydrodynamic or aerodynamic forcing. Application of energy-based methods for such vehicles is challenging due to the presence of energy-conserving lift and side forces. We study how the lift force determines the geometric structure of vehicle dynamics. A Hamiltonian formulation of the integrable phugoid-mode equations provides a Lyapunov function candidate, which is used throughout the thesis for deriving equilibrium stability results and designing stabilizing control laws. A strong motivation for our work is the emergence of underwater gliders as an important observation platform for oceanography. Underwater gliders rely on buoyancy regulation and internal mass redistribution for motion control. These vehicles are attractive because they are designed to operate autonomously and continuously for several weeks. The results presented in this thesis contribute toward the development of systematic control design procedures for extending the range of provably stable maneuvers of the underwater glider. As the first major contribution we derive conditions for nonlinear stability of longitudinal steady gliding motions using singular perturbation theory. Stability is proved using a composite Lyapunov function, composed of individual Lyapunov functions that prove stability of rotational and translational subsystem equilibria. We use the composite Lyapunov function to design control laws for stabilizing desired relative equilibria in different actuation configurations for the underwater glider. We propose an approximate trajectory tracking method for an aircraft model. Our method uses exponential stability results of controllable steady gliding motions, derived by interpreting the aircraft dynamics as an interconnected system of rotational and translational subsystems. We prove bounded position error for tracking prescribed, straight-line trajectories, and demonstrate good performance in tracking unsteady trajectories in the longitudinal plane. We present all possible relative equilibrium motions for a rigid body moving in a fluid. Motion along a circular helix is a practical relative equilibrium for an underwater glider. We present a study of how internal mass distribution and buoyancy of the underwater glider influence the size of the steady circular helix, and the effect of a vehicle bottom-heaviness parameter on its stability.

Dynamics of a flexible splitter plate in the wake of a circular cylinder

NASA Astrophysics Data System (ADS)

Shukla, S.; Govardhan, R. N.; Arakeri, J. H.

2013-08-01

Rigid splitter plates in the wake of bluff bodies are known to suppress the primary vortex shedding. In the present work, we experimentally study the problem of a flexible splitter plate in the wake of a circular cylinder. In this case, the splitter plate is free to continuously deform along its length due to the fluid forces acting on it; the flexural rigidity (EI) of the plate being an important parameter. Direct visualizations of the splitter plate motions, for very low values of flexural rigidity (EI), indicate periodic traveling wave type deformations of the splitter plate with maximum tip amplitudes of the order of 1 cylinder diameter. As the Reynolds number based on cylinder diameter is varied, two regimes of periodic splitter plate motions are found that are referred to as mode I and mode II, with a regime of aperiodic motions between them. The frequency of plate motions in both periodic modes is found to be close to the plane cylinder Strouhal number of about 0.2, while the average frequencies in the non-periodic regime are substantially lower. The measured normalized phase speed of the traveling wave for both periodic modes is also close to the convection speed of vortices in the plane cylinder wake. As the flexural rigidity of the plate (EI) is increased, the response of the plate was found to shift to the right when plotted with flow speed or Re. To better capture the effect of varying EI, we define and use a non-dimensional bending stiffness, K*, similar to the ones used in the flag flutter problem, K=EI/(0.5ρUL), where U is the free-stream velocity and L is the splitter plate length. Amplitude data for different EI cases when plotted against this parameter appear to collapse on to a single curve for a given splitter plate length. Measurements of the splitter plate motions for varying splitter plate lengths indicate that plates that are substantially larger than the formation length of the plane cylinder wake have similar responses, while shorter plates show significant differences.

An alternative model of free fall

NASA Astrophysics Data System (ADS)

Lattery, Mark

2018-03-01

In Two World Systems (Galileo 1632/1661 Dialogues Concerning Two New Sciences (New York: Prometheus)), Galileo attempted to unify terrestrial and celestial motions using the Aristotelian principle of circularity. The result was a model of free fall that correctly predicts the linear increase of the velocity of an object released from rest near the surface of the Earth. This historical episode provides an opportunity to communicate the nature of science to students.

Two Activities with a Simple Model of the Solar System: Discovering Kepler's 3rd Law and Investigating Apparent Motion of Venus

ERIC Educational Resources Information Center

Rovšek, Barbara; Guštin, Andrej

2018-01-01

An astronomy "experiment" composed of three parts is described in the article. Being given necessary data a simple model of inner planets of the solar system is made in the first part with planets' circular orbits using appropriate scale. In the second part revolution of the figurines used as model representations of the planets along…

Articulated distraction.

PubMed

Hosny, Gamal Ahmed

2011-07-01

Articular hip distraction can be applied either by using a monolateral articulated distractor or a circular fixator. The fixator should be aligned such that its axis is aligned with the transverse axis of the hip joint. Following distraction, the range of motion is maintained with regular physiotherapy. It is a useful salvage procedure in older children with hip stiffness, when other methods of containment are not applicable. Copyright © 2011 Elsevier Inc. All rights reserved.

Space Instrument Optimization by Implementing of Generic Three Bodies Circular Restricted Problem

NASA Astrophysics Data System (ADS)

Nejat, Cyrus

2011-01-01

In this study, the main discussion emphasizes on the spacecraft operation with a concentration on stationary points in space. To achieve these objectives, the circular restricted problem was solved for selected approaches. The equations of motion of three body restricted problem was demonstrated to apply in cases other than Lagrange's (1736-1813 A.D.) achievements, by means of the purposed CN (Cyrus Nejat) theorem along with appropriate comments. In addition to five Lagrange, two other points, CN1 and CN2 were found to be in unstable equilibrium points in a very large distance respect to Lagrange points, but stable at infinity. A very interesting simulation of Milky Way Galaxy and Andromeda Galaxy were created to find the Lagrange points, CN points (Cyrus Nejat Points), and CN lines (Cyrus Nejat Lines). The equations of motion were rearranged such a way that the transfer trajectory would be conical, by means of decoupling concept. The main objective was to make a halo orbit transfer about CN lines. The author purposes therefore that all of the corresponding sizing design that they must be developed by optimization techniques would be considered in future approaches. The optimization techniques are sufficient procedures to search for the most ideal response of a system.

Visualization of the contact line during the water exit of flat plates

NASA Astrophysics Data System (ADS)

Tassin, A.; Breton, T.; Forest, B.; Ohana, J.; Chalony, S.; Le Roux, D.; Tancray, A.

2017-08-01

We investigate experimentally the time evolution of the wetted surface during the lifting of a body initially floating at the water surface. This phenomenon is referred to as the water exit problem. The water exit experiments were conducted with transparent (PMMA) mock-ups of two different shapes: a circular disc and a square flat plate. Two different lighting systems were used to diffuse light in the mock-up material: a central high-power LED light normal to the surface and an edge-lighting system featuring an array of LED lights. These setups make it possible to illuminate the contact line, which delimits the surface of contact between the mock-up and the water. The characteristic size of the mock-ups is about 20 cm and the acceleration of the mock-up oscillates between 0 and 25 m/s^2. We show that the central light setup gives satisfactory results for the circular disc and that the edge lighting technique makes it possible to follow a contact line with a time-evolving complex shape (strong changes of convexity) up to 1000 fps. The observations presented in the paper support the possibility of extending this promising technique to more general three-dimensional bodies with arbitrary motion (e.g., including pitch motion).

Development of the wake behind a circular cylinder impulsively started into rotatory and rectilinear motion

NASA Technical Reports Server (NTRS)

Chen, Yen-Ming; Ou, Yuh-Roung; Pearlstein, Arne J.

1993-01-01

The temporal development of a 2D viscous incompressible flow generated by a circular cylinder started impulsively into steady rotatory and rectilinear motion is studied by integration of a velocity/vorticity formulation of the governing equations, using an explicit finite-difference/pseudo-spectral technique and an implementation of the Biot-Savart law. Results are presented for a Reynolds number of 200 (based on the cylinder diameter 2a and the magnitude U of the rectilinear velocity) for several values of the angular/rectilinear speed ratio alpha = omega(a)/U (where omega is the angular speed) up to 3.25. Several aspects of the kinematics and dynamics of the flow not considered earlier are discussed. For higher values of alpha, the results indicate that for Re = 200, vortex shedding does indeed occur for alpha = 3.25. However, consecutive vortices shed by the body can be shed from the same side and be of the same sense, in contrast to the nonrotating case, in which mirror-image vortices of opposite sense are shed alternately on opposite sides of the body. The implications of the results are discussed in relation to the possibility of suppressing vortex shedding by open or closed-loop control of the rotation rate.

Pilates and Dance to Breast Cancer Patients Undergoing Treatment

ClinicalTrials.gov

2017-08-12

Breast Cancer; Quality of Life; Lymphedema; Fatigue; Depressive Symptoms; Body Image; Self Esteem; Optimism; Sexual Function Disturbances; Stress; Sleep Disturbance; Pain; Muscular Weakness; Postural Balance; Range of Motion; Cardiorespiratory Fitness

Three dimensional dynamics of a flexible Motorised Momentum Exchange Tether

NASA Astrophysics Data System (ADS)

Ismail, N. A.; Cartmell, M. P.

2016-03-01

This paper presents a new flexural model for the three dimensional dynamics of the Motorised Momentum Exchange Tether (MMET) concept. This study has uncovered the relationships between planar and nonplanar motions, and the effect of the coupling between these two parameters on pragmatic circular and elliptical orbits. The tether sub-spans are modelled as stiffened strings governed by partial differential equations of motion, with specific boundary conditions. The tether sub-spans are flexible and elastic, thereby allowing three dimensional displacements. The boundary conditions lead to a specific frequency equation and the eigenvalues from this provide the natural frequencies of the orbiting flexible motorised tether when static, accelerating in monotonic spin, and at terminal angular velocity. A rotation transformation matrix has been utilised to get the position vectors of the system's components in an assumed inertial frame. Spatio-temporal coordinates are transformed to modal coordinates before applying Lagrange's equations, and pre-selected linear modes are included to generate the equations of motion. The equations of motion contain inertial nonlinearities which are essentially of cubic order, and these show the potential for intricate intermodal coupling effects. A simulation of planar and non-planar motions has been undertaken and the differences in the modal responses, for both motions, and between the rigid body and flexible models are highlighted and discussed.

Intermittently-visual Tracking Experiments Reveal the Roles of Error-correction and Predictive Mechanisms in the Human Visual-motor Control System

NASA Astrophysics Data System (ADS)

Hayashi, Yoshikatsu; Tamura, Yurie; Sase, Kazuya; Sugawara, Ken; Sawada, Yasuji

Prediction mechanism is necessary for human visual motion to compensate a delay of sensory-motor system. In a previous study, “proactive control” was discussed as one example of predictive function of human beings, in which motion of hands preceded the virtual moving target in visual tracking experiments. To study the roles of the positional-error correction mechanism and the prediction mechanism, we carried out an intermittently-visual tracking experiment where a circular orbit is segmented into the target-visible regions and the target-invisible regions. Main results found in this research were following. A rhythmic component appeared in the tracer velocity when the target velocity was relatively high. The period of the rhythm in the brain obtained from environmental stimuli is shortened more than 10%. The shortening of the period of rhythm in the brain accelerates the hand motion as soon as the visual information is cut-off, and causes the precedence of hand motion to the target motion. Although the precedence of the hand in the blind region is reset by the environmental information when the target enters the visible region, the hand motion precedes the target in average when the predictive mechanism dominates the error-corrective mechanism.

Simulation of the Beating Heart Based on Physically Modeling aDeformable Balloon

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rohmer, Damien; Sitek, Arkadiusz; Gullberg, Grant T.

2006-07-18

The motion of the beating heart is complex and createsartifacts in SPECT and x-ray CT images. Phantoms such as the JaszczakDynamic Cardiac Phantom are used to simulate cardiac motion forevaluationof acquisition and data processing protocols used for cardiacimaging. Two concentric elastic membranes filled with water are connectedto tubing and pump apparatus for creating fluid flow in and out of theinner volume to simulate motion of the heart. In the present report, themovement of two concentric balloons is solved numerically in order tocreate a computer simulation of the motion of the moving membranes in theJaszczak Dynamic Cardiac Phantom. A system ofmore » differential equations,based on the physical properties, determine the motion. Two methods aretested for solving the system of differential equations. The results ofboth methods are similar providing a final shape that does not convergeto a trivial circular profile. Finally,a tomographic imaging simulationis performed by acquiring static projections of the moving shape andreconstructing the result to observe motion artifacts. Two cases aretaken into account: in one case each projection angle is sampled for ashort time interval and the other case is sampled for a longer timeinterval. The longer sampling acquisition shows a clear improvement indecreasing the tomographic streaking artifacts.« less

Anisotropic field-of-view shapes for improved PROPELLER imaging☆

PubMed Central

Larson, Peder E.Z.; Lustig, Michael S.; Nishimura, Dwight G.

2010-01-01

The Periodically Rotated Overlapping ParallEL Lines with Enhanced Reconstruction (PROPELLER) method for magnetic resonance imaging data acquisition and reconstruction has the highly desirable property of being able to correct for motion during the scan, making it especially useful for imaging pediatric or uncooperative patients and diffusion imaging. This method nominally supports a circular field of view (FOV), but tailoring the FOV for noncircular shapes results in more efficient, shorter scans. This article presents new algorithms for tailoring PROPELLER acquisitions to the desired FOV shape and size that are flexible and precise. The FOV design also allows for rotational motion which provides better motion correction and reduced aliasing artifacts. Some possible FOV shapes demonstrated are ellipses, ovals and rectangles, and any convex, pi-symmetric shape can be designed. Standard PROPELLER reconstruction is used with minor modifications, and results with simulated motion presented confirm the effectiveness of the motion correction with these modified FOV shapes. These new acquisition design algorithms are simple and fast enough to be computed for each individual scan. Also presented are algorithms for further scan time reductions in PROPELLER echo-planar imaging (EPI) acquisitions by varying the sample spacing in two directions within each blade. PMID:18818039

Detecting apoptosis using dynamic light scattering with optical coherence tomography

NASA Astrophysics Data System (ADS)

Farhat, Golnaz; Mariampillai, Adrian; Yang, Victor X. D.; Czarnota, Gregory J.; Kolios, Michael C.

2011-07-01

A dynamic light scattering technique is implemented using optical coherence tomography (OCT) to measure the change in intracellular motion as cells undergo apoptosis. Acute myeloid leukemia cells were treated with cisplatin and imaged at a frame rate of 166 Hz using a 1300 nm swept-source OCT system at various times over a period of 48 h. Time correlation analysis of the speckle intensities indicated a significant increase in intracellular motion 24 h after treatment. This rise in intracellular motion correlated with histological findings of irregularly shaped and fragmented cells indicative of cell membrane blebbing and fragmentation.

Navier-Stokes predictions of pitch damping for axisymmetric shell using steady coning motion

NASA Technical Reports Server (NTRS)

Weinacht, Paul; Sturek, Walter B.; Schiff, Lewis B.

1991-01-01

Previous theoretical investigations have proposed that the side force and moment acting on a body of revolution in steady coning motion could be related to the pitch-damping force and moment. In the current research effort, this approach is applied to produce predictions of the pitch damping for axisymmetric shell. The flow fields about these projectiles undergoing steady coning motion are successfully computed using a parabolized Navier-Stokes computational approach which makes use of a rotating coordinate frame. The governing equations are modified to include the centrifugal and Coriolis force terms due to the rotating coordinate frame. From the computed flow field, the side moments due to coning motion, spinning motion, and combined spinning and coning motion are used to determine the pitch-damping coefficients. Computations are performed for two generic shell configurations, a secant-ogive-cylinder and a secant-ogive-cylinder-boattail.

An ice-motion tracking system at the Alaska SAR facility

NASA Technical Reports Server (NTRS)

Kwok, Ronald; Curlander, John C.; Pang, Shirley S.; Mcconnell, Ross

1990-01-01

An operational system for extracting ice-motion information from synthetic aperture radar (SAR) imagery is being developed as part of the Alaska SAR Facility. This geophysical processing system (GPS) will derive ice-motion information by automated analysis of image sequences acquired by radars on the European ERS-1, Japanese ERS-1, and Canadian RADARSAT remote sensing satellites. The algorithm consists of a novel combination of feature-based and area-based techniques for the tracking of ice floes that undergo translation and rotation between imaging passes. The system performs automatic selection of the image pairs for input to the matching routines using an ice-motion estimator. It is designed to have a daily throughput of ten image pairs. A description is given of the GPS system, including an overview of the ice-motion-tracking algorithm, the system architecture, and the ice-motion products that will be available for distribution to geophysical data users.

Contrast effects on speed perception for linear and radial motion.

PubMed

Champion, Rebecca A; Warren, Paul A

2017-11-01

Speed perception is vital for safe activity in the environment. However, considerable evidence suggests that perceived speed changes as a function of stimulus contrast, with some investigators suggesting that this might have meaningful real-world consequences (e.g. driving in fog). In the present study we investigate whether the neural effects of contrast on speed perception occur at the level of local or global motion processing. To do this we examine both speed discrimination thresholds and contrast-dependent speed perception for two global motion configurations that have matched local spatio-temporal structure. Specifically we compare linear and radial configurations, the latter of which arises very commonly due to self-movement. In experiment 1 the stimuli comprised circular grating patches. In experiment 2, to match stimuli even more closely, motion was presented in multiple local Gabor patches equidistant from central fixation. Each patch contained identical linear motion but the global configuration was either consistent with linear or radial motion. In both experiments 1 and 2, discrimination thresholds and contrast-induced speed biases were similar in linear and radial conditions. These results suggest that contrast-based speed effects occur only at the level of local motion processing, irrespective of global structure. This result is interpreted in the context of previous models of speed perception and evidence suggesting differences in perceived speed of locally matched linear and radial stimuli. Copyright © 2017 Elsevier Ltd. All rights reserved.

Brownian motion of arbitrarily shaped particles in two dimensions.

PubMed

Chakrabarty, Ayan; Konya, Andrew; Wang, Feng; Selinger, Jonathan V; Sun, Kai; Wei, Qi-Huo

2014-11-25

We implement microfabricated boomerang particles with unequal arm lengths as a model for nonsymmetric particles and study their Brownian motion in a quasi-two-dimensional geometry by using high-precision single-particle motion tracking. We show that because of the coupling between translation and rotation, the mean squared displacements of a single asymmetric boomerang particle exhibit a nonlinear crossover from short-time faster to long-time slower diffusion, and the mean displacements for fixed initial orientation are nonzero and saturate out at long times. The measured anisotropic diffusion coefficients versus the tracking point position indicate that there exists one unique point, i.e., the center of hydrodynamic stress (CoH), at which all coupled diffusion coefficients vanish. This implies that in contrast to motion in three dimensions where the CoH exists only for high-symmetry particles, the CoH always exists for Brownian motion in two dimensions. We develop an analytical model based on Langevin theory to explain the experimental results and show that among the six anisotropic diffusion coefficients only five are independent because the translation-translation coupling originates from the translation-rotation coupling. Finally, we classify the behavior of two-dimensional Brownian motion of arbitrarily shaped particles into four groups based on the particle shape symmetry group and discussed potential applications of the CoH in simplifying understanding of the circular motions of microswimmers.

Implied dynamics biases the visual perception of velocity.

PubMed

La Scaleia, Barbara; Zago, Myrka; Moscatelli, Alessandro; Lacquaniti, Francesco; Viviani, Paolo

2014-01-01

We expand the anecdotic report by Johansson that back-and-forth linear harmonic motions appear uniform. Six experiments explore the role of shape and spatial orientation of the trajectory of a point-light target in the perceptual judgment of uniform motion. In Experiment 1, the target oscillated back-and-forth along a circular arc around an invisible pivot. The imaginary segment from the pivot to the midpoint of the trajectory could be oriented vertically downward (consistent with an upright pendulum), horizontally leftward, or vertically upward (upside-down). In Experiments 2 to 5, the target moved uni-directionally. The effect of suppressing the alternation of movement directions was tested with curvilinear (Experiment 2 and 3) or rectilinear (Experiment 4 and 5) paths. Experiment 6 replicated the upright condition of Experiment 1, but participants were asked to hold the gaze on a fixation point. When some features of the trajectory evoked the motion of either a simple pendulum or a mass-spring system, observers identified as uniform the kinematic profiles close to harmonic motion. The bias towards harmonic motion was most consistent in the upright orientation of Experiment 1 and 6. The bias disappeared when the stimuli were incompatible with both pendulum and mass-spring models (Experiments 3 to 5). The results are compatible with the hypothesis that the perception of dynamic stimuli is biased by the laws of motion obeyed by natural events, so that only natural motions appear uniform.

The effect of asymmetric vortex wake characteristics on a slender delta wing undergoing wing rock motion

NASA Technical Reports Server (NTRS)

Arena, A. S., Jr.; Nelson, R. C.

1989-01-01

An experimental investigation into the fluid mechanisms responsible for wing rock on a slender delta wing with 80 deg leading edge sweep has been conducted. Time history and flow visualization data are presented for a wide angle-of-attack range. The use of an air bearing spindle has allowed the motion of the wing to be free from bearing friction or mechanical hysteresis. A bistable static condition has been found in vortex breakdown at an angle of attack of 40 deg which causes an overshoot of the steady state rocking amplitude. Flow visualization experiments also reveal a difference in static and dynamic breakdown locations on the wing. A hysteresis loop in dynamic breakdown location similar to that seen on pitching delta wings was observed as the wing was undergoing the limit cycle oscillation.

Size-dependent axisymmetric vibration of functionally graded circular plates in bifurcation/limit point instability

NASA Astrophysics Data System (ADS)

Ashoori, A. R.; Vanini, S. A. Sadough; Salari, E.

2017-04-01

In the present paper, vibration behavior of size-dependent functionally graded (FG) circular microplates subjected to thermal loading are carried out in pre/post-buckling of bifurcation/limit-load instability for the first time. Two kinds of frequently used thermal loading, i.e., uniform temperature rise and heat conduction across the thickness direction are considered. Thermo-mechanical material properties of FG plate are supposed to vary smoothly and continuously throughout the thickness based on power law model. Modified couple stress theory is exploited to describe the size dependency of microplate. The nonlinear governing equations of motion and associated boundary conditions are extracted through generalized form of Hamilton's principle and von-Karman geometric nonlinearity for the vibration analysis of circular FG plates including size effects. Ritz finite element method is then employed to construct the matrix representation of governing equations which are solved by two different strategies including Newton-Raphson scheme and cylindrical arc-length method. Moreover, in the following a parametric study is accompanied to examine the effects of the several parameters such as material length scale parameter, temperature distributions, type of buckling, thickness to radius ratio, boundary conditions and power law index on the dimensionless frequency of post-buckled/snapped size-dependent FG plates in detail. It is found that the material length scale parameter and thermal loading have a significant effect on vibration characteristics of size-dependent circular FG plates.

Bandgap modulation in photoexcited topological insulator Bi{sub 2}Te{sub 3} via atomic displacements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hada, Masaki, E-mail: hadamasaki@okayama-u.ac.jp; Materials and Structures Laboratory, Tokyo Institute of Technology, Yokohama 226-8503; PRESTO, Japan Science and Technology Agency, Kawaguchi 332-0012

2016-07-14

The atomic and electronic dynamics in the topological insulator (TI) Bi{sub 2}Te{sub 3} under strong photoexcitation were characterized with time-resolved electron diffraction and time-resolved mid-infrared spectroscopy. Three-dimensional TIs characterized as bulk insulators with an electronic conduction surface band have shown a variety of exotic responses in terms of electronic transport when observed under conditions of applied pressure, magnetic field, or circularly polarized light. However, the atomic motions and their correlation between electronic systems in TIs under strong photoexcitation have not been explored. The artificial and transient modification of the electronic structures in TIs via photoinduced atomic motions represents a novelmore » mechanism for providing a comparable level of bandgap control. The results of time-domain crystallography indicate that photoexcitation induces two-step atomic motions: first bismuth and then tellurium center-symmetric displacements. These atomic motions in Bi{sub 2}Te{sub 3} trigger 10% bulk bandgap narrowing, which is consistent with the time-resolved mid-infrared spectroscopy results.« less

Directed collective motion of bacteria under channel confinement

NASA Astrophysics Data System (ADS)

Wioland, H.; Lushi, E.; Goldstein, R. E.

2016-07-01

Dense suspensions of swimming bacteria are known to exhibit collective behaviour arising from the interplay of steric and hydrodynamic interactions. Unconfined suspensions exhibit transient, recurring vortices and jets, whereas those confined in circular domains may exhibit order in the form of a spiral vortex. Here we show that confinement into a long and narrow macroscopic ‘racetrack’ geometry stabilises bacterial motion to form a steady unidirectional circulation. This motion is reproduced in simulations of discrete swimmers that reveal the crucial role that bacteria-driven fluid flows play in the dynamics. In particular, cells close to the channel wall produce strong flows which advect cells in the bulk against their swimming direction. We examine in detail the transition from a disordered state to persistent directed motion as a function of the channel width, and show that the width at the crossover point is comparable to the typical correlation length of swirls seen in the unbounded system. Our results shed light on the mechanisms driving the collective behaviour of bacteria and other active matter systems, and stress the importance of the ubiquitous boundaries found in natural habitats.

Streaming motions and kinematic distances to molecular clouds

NASA Astrophysics Data System (ADS)

Ramón-Fox, F. G.; Bonnell, Ian A.

2018-02-01

We present high-resolution smoothed particle hydrodynamics simulations of a region of gas flowing in a spiral arm and identify dense gas clouds to investigate their kinematics with respect to a Milky Way model. We find that, on average, the gas in the arms can have a net radial streaming motion of vR ≈ -9 km s-1 and rotate ≈ 6 km s-1 slower than the circular velocity. This translates to average peculiar motions towards the Galaxy centre and opposite to Galactic rotation. These results may be sensitive to the assumed spiral arm perturbation, which is ≈ 3 per cent of the disc potential in our model. We compare the actual distance and the kinematic estimate and we find that streaming motions introduce systematic offsets of ≈1 kpc. We find that the distance error can be as large as ±2 kpc, and the recovered cloud positions have distributions that can extend significantly into the inter-arm regions. We conclude that this poses a difficulty in tracing spiral arm structure in molecular cloud surveys.

Betatron motion with coupling of horizontal and vertical degrees of freedom

DOE PAGES

Lebedev, V. A.; Bogacz, S. A.

2010-10-21

Presently, there are two most frequently used parameterezations of linear x-y coupled motion used in the accelerator physics. They are the Edwards-Teng and Mais-Ripken parameterizations. The article is devoted to an analysis of close relationship between the two representations, thus adding a clarity to their physical meaning. It also discusses the relationship between the eigen-vectors, the beta-functions, second order moments and the bilinear form representing the particle ellipsoid in the 4D phase space. Then, it consideres a further development of Mais-Ripken parameteresation where the particle motion is descrabed by 10 parameters: four beta-functions, four alpha-functions and two betatron phase advances.more » In comparison with Edwards-Teng parameterization the chosen parametrization has an advantage that it works equally well for analysis of coupled betatron motion in circular accelerators and in transfer lines. In addition, considered relationship between second order moments, eigen-vectors and beta-functions can be useful in interpreting tracking results and experimental data. As an example, the developed formalizm is applied to the FNAL electron cooler and Derbenev’s vertex-to-plane adapter.« less

Betatron motion with coupling of horizontal and vertical degrees of freedom

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lebedev, V. A.; Bogacz, S. A.

Presently, there are two most frequently used parameterezations of linear x-y coupled motion used in the accelerator physics. They are the Edwards-Teng and Mais-Ripken parameterizations. The article is devoted to an analysis of close relationship between the two representations, thus adding a clarity to their physical meaning. It also discusses the relationship between the eigen-vectors, the beta-functions, second order moments and the bilinear form representing the particle ellipsoid in the 4D phase space. Then, it consideres a further development of Mais-Ripken parameteresation where the particle motion is descrabed by 10 parameters: four beta-functions, four alpha-functions and two betatron phase advances.more » In comparison with Edwards-Teng parameterization the chosen parametrization has an advantage that it works equally well for analysis of coupled betatron motion in circular accelerators and in transfer lines. In addition, considered relationship between second order moments, eigen-vectors and beta-functions can be useful in interpreting tracking results and experimental data. As an example, the developed formalizm is applied to the FNAL electron cooler and Derbenev’s vertex-to-plane adapter.« less

Betatron motion with coupling of horizontal and vertical degrees of freedom

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lebedev, V.A.; /Fermilab; Bogacz, S.A.

Presently, there are two most frequently used parameterizations of linear x-y coupled motion used in the accelerator physics. They are the Edwards-Teng and Mais-Ripken parameterizations. The article is devoted to an analysis of close relationship between the two representations, thus adding a clarity to their physical meaning. It also discusses the relationship between the eigen-vectors, the beta-functions, second order moments and the bilinear form representing the particle ellipsoid in the 4D phase space. Then, it consideres a further development of Mais-Ripken parameteresation where the particle motion is described by 10 parameters: four beta-functions, four alpha-functions and two betatron phase advances.more » In comparison with Edwards-Teng parameterization the chosen parametrization has an advantage that it works equally well for analysis of coupled betatron motion in circular accelerators and in transfer lines. Considered relationship between second order moments, eigen-vectors and beta-functions can be useful in interpreting tracking results and experimental data. As an example, the developed formalizm is applied to the FNAL electron cooler and Derbenev's vertex-to-plane adapter.« less

Optical sideband spectroscopy of a single ion in a Penning trap

NASA Astrophysics Data System (ADS)

Mavadia, S.; Stutter, G.; Goodwin, J. F.; Crick, D. R.; Thompson, R. C.; Segal, D. M.

2014-03-01

We perform resolved optical sideband spectroscopy on a single 40Ca+ ion in a Penning trap. We probe the electric quadrupole allowed S1/2↔D5/2 transition at 729 nm and observe equally spaced sidebands for the three motional modes. The axial mode, parallel to the trap axis, is a one-dimensional harmonic oscillator, whereas the radial cyclotron and magnetron modes are circular motions perpendicular to the magnetic field. The total energy associated with the magnetron motion is negative, but here we probe only the (positive) kinetic energy. From the equivalent Doppler widths of the sideband spectra corresponding to the three motions we find effective temperatures of 1.1±0.2 mK, 7±3 mK, and 42±8 μK for the axial, modified cyclotron, and magnetron modes, respectively. These should be compared to the cooling limits, estimated using optimal laser parameters, of 0.38 mK, 0.8 mK, and ˜10 μK. In future work we aim to perform resolved-sideband cooling of the ion on the 729-nm transition.

Orbital revolution of a pair of bubbles in an acoustic field

NASA Astrophysics Data System (ADS)

Shirota, Minori; Yamashita, Kou; Inamura, Takao

2011-11-01

This experimental study aims to clarify the mechanism of orbital motion of two oscillating bubbles in an acoustic field. Trajectory of the orbital motion was observed using a high-speed video camera. Because of a good repeatability in volume oscillation of bubbles, we were also able to observe the radial motion driven at 24 kHz by stroboscopic like imaging; the cyclic bubble oscillation was appeared to slow down by capturing images at the framing rate close to the forcing frequency. The orbital motions of bubbles raging from 0.13 to 0.18 mm were examined with different forcing amplitude and in different viscous oils. As a result, we found that pairs of bubbles revolve along a circular orbit around the center of mass of the orbiting two bubbles. We also found that the two bubbles perform anti-phase radial oscillation. Although this radial oscillation should result in a repulsive secondary Bjerknes force, the bubbles kept a constant separate distance of about 1 mm, which indicates the existence of centripetal primary Bjerknes force. The angular velocity of orbital revolution increases linearly with the increase in Bjerknes force.

Combined Effect of Surface Roughness and Wake Splitter Plate on the Aerodynamic Characteristics of a Circular Cylinder

NASA Astrophysics Data System (ADS)

Saisanthosh, Iyer; Arunkumar, K.; Ajithkumar, R.; Srikrishnan, A. R.

2017-09-01

This paper is focussed on numerical investigation of flow around a stationary circular cylinder (diameter, D) with selectively applied surface roughness (roughness strips with thickness ‘k’) in the presence of a wake splitter plate (length, L). The plate leading edge is at a distance of ‘G’ from the cylinder base. For this study, the commercial software ANSYS Fluent is used. Fluid considered is water. Study was conducted the following cases (a) plain cylinder (b) cylinder with surface roughness (without splitter plate) (c) Cylinder with splitter plate (without surface roughness) and (d) cylinder with both roughness and splitter plate employed. The study Reynolds number (based on D) is 17,000 and k/δ = 1.25 (in all cases). Results indicate that, for cylinder with splitter plate (no roughness), lift coefficient gradually drops till G/D=1.5 further to which it sharply increases. Whereas, drag coefficient and Strouhal number undergoes slight reduction till G/D=1.0 and thereafter, gradually increase. Circumferential location of strip (α) does not influence the aerodynamic parameters significantly. With roughness alone, drag is magnified by about 1.5 times and lift, by about 2.7 times that of the respective values of the smooth cylinder. With splitter plate, for roughness applied at all ‘α’ values, drag and lift undergoes substantial reduction with the lowest value attained at G/D=1.0.

Monitoring Mars LOD Variations from a High Altitude Circular Equatorial Orbit: Theory and Simulation

NASA Astrophysics Data System (ADS)

Barriot, J.; Dehant, V.; Duron, J.

2003-12-01

We compute the perturbations of a high altitude circular equatorial orbit of a martian probe under the influence of an annual variation of the martian lenght of day. For this purpose, we use the first order perturbations of the newtonian equations of motion, where the small parameter is given from the hourglass model of Chao and Rubincam, which allow a simple computation of CO2 exchanges during the martian year. We are able to demonstrate that the perturbations contains two components: the first one is a sine/cosine modulation at the orbit frequency, the second one is composed of terms of the form exp(t)*sin(t), so the orbit may not stable in the long term (several martian years), with perturbations growing exponentially. We give the full theory and numbers.

Strength and reversibility of stereotypes for a rotary control with linear scales.

PubMed

Chan, Alan H S; Chan, W H

2008-02-01

Using real mechanical controls, this experiment studied strength and reversibility of direction-of-motion stereotypes and response times for a rotary control with horizontal and vertical scales. Thirty-eight engineering undergraduates (34 men and 4 women) ages 23 to 47 years (M=29.8, SD=7.7) took part in the experiment voluntarily. The effects of instruction of change of pointer position and control plane on movement compatibility were analyzed with precise quantitative measures of strength and a reversibility index of stereotype. Comparisons of the strength and reversibility values of these two configurations with those of rotary control-circular display, rotary control-digital counter, four-way lever-circular display, and four-way lever-digital counter were made. The results of this study provided significant implications for the industrial design of control panels for improved human performance.

Construction of a cost effective optical tweezers for manipulation of birefringent materials using circularly polarized light

NASA Astrophysics Data System (ADS)

McMahon, Allison; Sauncy, Toni

2008-10-01

Light manipulation is a very powerful tool in physics, biology, and chemistry. There are several physical principles underlying the apparatus known as the ``optical tweezers,'' the term given to using focused light to manipulate and control small objects. By carefully controlling the orientation and position of a focused laser beam, dielectric particles can be effectively trapped and manipulated. We have designed a cost efficient and effective undergraduate optical tweezers apparatus by using standard ``off the shelf'' components and starting with a standard undergraduate laboratory microscope. Images are recorded using a small CCD camera interfaced to a computer and controlled by LabVIEW^TM software. By using wave plates to produce circular polarized light, rotational motion can be induced in small particles of birefringent materials such as calcite and mica.

A Regulatory Switch Alters Chromosome Motions at the Metaphase to Anaphase Transition

PubMed Central

Su, Kuan-Chung; Barry, Zachary; Schweizer, Nina; Maiato, Helder; Bathe, Mark; Cheeseman, Iain McPherson

2016-01-01

Summary To achieve chromosome segregation during mitosis, sister chromatids must undergo a dramatic change in their behavior to switch from balanced oscillations at the metaphase plate to directed poleward motion during anaphase. However, the factors that alter chromosome behavior at the metaphase-to-anaphase transition remain incompletely understood. Here, we perform time-lapse imaging to analyze anaphase chromosome dynamics in human cells. Using multiple directed biochemical, genetic, and physical perturbations, our results demonstrate that differences in the global phosphorylation states between metaphase and anaphase are the major determinant of chromosome motion dynamics. Indeed, causing a mitotic phosphorylation state to persist into anaphase produces dramatic metaphase-like oscillations. These induced oscillations depend on both kinetochore-derived and polar ejection forces that oppose poleward motion. Thus, our analysis of anaphase chromosome motion reveals that dephosphorylation of multiple mitotic substrates is required to suppress metaphase chromosome oscillatory motions and achieve directed poleward motion for successful chromosome segregation. PMID:27829144

User's Guide for ECAP2D: an Euler Unsteady Aerodynamic and Aeroelastic Analysis Program for Two Dimensional Oscillating Cascades, Version 1.0

NASA Technical Reports Server (NTRS)

Reddy, T. S. R.

1995-01-01

This guide describes the input data required for using ECAP2D (Euler Cascade Aeroelastic Program-Two Dimensional). ECAP2D can be used for steady or unsteady aerodynamic and aeroelastic analysis of two dimensional cascades. Euler equations are used to obtain aerodynamic forces. The structural dynamic equations are written for a rigid typical section undergoing pitching (torsion) and plunging (bending) motion. The solution methods include harmonic oscillation method, influence coefficient method, pulse response method, and time integration method. For harmonic oscillation method, example inputs and outputs are provided for pitching motion and plunging motion. For the rest of the methods, input and output for pitching motion only are given.

Computation of supersonic laminar viscous flow past a pointed cone at angle of attack in spinning and coning motion

NASA Technical Reports Server (NTRS)

Agarwal, R.; Rakich, J. V.

1978-01-01

Computational results obtained with a parabolic Navier-Stokes marching code are presented for supersonic viscous flow past a pointed cone at angle of attack undergoing a combined spinning and coning motion. The code takes into account the asymmetries in the flow field resulting from the motion and computes the asymmetric shock shape, crossflow and streamwise shear, heat transfer, crossflow separation and vortex structure. The side force and moment are also computed. Reasonably good agreement is obtained with the side force measurements of Schiff and Tobak. Comparison is also made with the only available numerical inviscid analysis. It is found that the asymmetric pressure loads due to coning motion are much larger than all other viscous forces due to spin and coning, making viscous forces negligible in the combined motion.

Free Swimming in Ground Effect

NASA Astrophysics Data System (ADS)

Cochran-Carney, Jackson; Wagenhoffer, Nathan; Zeyghami, Samane; Moored, Keith

2017-11-01

A free-swimming potential flow analysis of unsteady ground effect is conducted for two-dimensional airfoils via a method of images. The foils undergo a pure pitching motion about their leading edge, and the positions of the body in the streamwise and cross-stream directions are determined by the equations of motion of the body. It is shown that the unconstrained swimmer is attracted to a time-averaged position that is mediated by the flow interaction with the ground. The robustness of this fluid-mediated equilibrium position is probed by varying the non-dimensional mass, initial conditions and kinematic parameters of motion. Comparisons to the foil's fixed-motion counterpart are also made to pinpoint the effect that free swimming near the ground has on wake structures and the fluid-mediated forces over time. Optimal swimming regimes for near-boundary swimming are determined by examining asymmetric motions.

Simulation of Molecular Transport in Systems Containing Mobile Obstacles.

PubMed

Polanowski, Piotr; Sikorski, Andrzej

2016-08-04

In this paper, we investigate the movement of molecules in crowded environments with obstacles undergoing Brownian motion by means of extensive Monte Carlo simulations. Our investigations were performed using the dynamic lattice liquid model, which was based on the cooperative movement concept and allowed to mimic systems at high densities where the motion of all elements (obstacles as well as moving particles) were highly correlated. The crowded environments are modeled on a two-dimensional triangular lattice containing obstacles (particles whose mobility was significantly reduced) moving by a Brownian motion. The subdiffusive motion of both elements in the system was analyzed. It was shown that the percolation transition does not exist in such systems in spite of the cooperative character of the particles' motion. The reduction of the obstacle mobility leads to the longer caging of liquid particles by mobile obstacles.

An inventory on rotational kinematics of a particle: unravelling misconceptions and pitfalls in reasoning

NASA Astrophysics Data System (ADS)

Mashood, K. K.; Singh, Vijay A.

2012-09-01

Student difficulties regarding the angular velocity (\\vec{\\omega }) and angular acceleration (\\vec{\\alpha }) of a particle have remained relatively unexplored in contrast to their linear counterparts. We present an inventory comprising multiple choice questions aimed at probing misconceptions and eliciting ill-suited reasoning patterns. The development of the inventory was based on interactions with students, teachers and experts. We report misconceptions, some of which are parallel to those found earlier in linear kinematics. Fixations with inappropriate prototypes were uncovered. Many students and even teachers mistakenly assume that all rotational motion is necessarily circular. A persistent notion that the direction of \\vec{\\omega } and \\vec{\\alpha } should be ‘along’ the motion exists. Instances of indiscriminate usage of equations were identified.

Aerodynamics in the amusement park: interpreting sensor data for acceleration and rotation

NASA Astrophysics Data System (ADS)

Löfstrand, Marcus; Pendrill, Ann-Marie

2016-09-01

The sky roller ride depends on interaction with the air to create a rolling motion. In this paper, we analyse forces, torque and angular velocities during different parts of the ride, combining a theoretical analysis, with photos, videos as well as with accelerometer and gyroscopic data, that may be collected e.g. with a smartphone. For interpreting the result, it must be taken into account that the sensors and their coordinate system rotate together with the rider. The sky roller offers many examples for physics education, from simple circular motion, to acceleration and rotation involving several axes, as well as the relation between wing orientation, torque and angular velocities and using barometer pressure to determine the elevation gain.

Effect of shaft frequency on cavitation in a journal bearing for noncentered circular whirl

NASA Technical Reports Server (NTRS)

Brewe, David E.; Khonsari, M. M.

1987-01-01

The effect of shaft frequency on the performance of a submerged journal undergoing noncentered circular whirl is examined. The main emphasis of the paper is on the behavior of the vapor cavitation bubble and its effect on the bearing performance as a function of frequency. A cavitation algorithm due to Elrod was implemented in a computer program which solves a time-dependent Reynolds equation. This algorithm automatically handles the boundary conditions by using a switch function and a control volume approach which conserves mass throughout the entire flow. The shaft frequencies in this investigation ranged from 0 rad/s (squeeze-film damper) to -104 rad/s (a case in which oil-whip condition was produced momentarily). For the particular vibration amplitude chosen in this investigation it was observed that vapor cavitation had an effect on the load components for the full range of shaft frequencies investigated.

On the Aerodynamics of Windblast.

DTIC Science & Technology

1981-11-13

streamline pattern that characterizes the cross-flow over two circular-cylindrical body segments in line contact with one another at time t = 0. That is, at...over the limbs of the ejection seat occupant. Note that MC may vary over different portions of the body that intercept the flow at different angles a...dimensional, rectilinear situation, one may estimate the kinematics of the ensuing motion of a body segment of mass Ms, subjected to the force

Bioengineered Skin From Stem Cells for Treatment of Cutaneous Vesicant Injury

DTIC Science & Technology

2006-11-01

sterile gauze; the gauze was dipped into the decontamination solution using forceps and gently applied to the injury site using circular motions...weight ratio of the skin biopsy of the animals exposed to CEES and treated with either bioengineered skin or saline. Briefly, at different time...The CEES + saline or CEES + bioengineered skin treated areas were excised using a sterile blade, scissors, and forceps . Half of the skin sample

Coulomb Thrusting Application Study

DTIC Science & Technology

2006-01-20

Acceleration Magnitudes To study the relative motion of spacecraft in nearly circular orbits, the Clohessy - Wiltshire - Hill equations are commonly...Modeling The Clohessy - Wiltshire -Hill’s equations12–14 for one of the spacecraft in the 2-craft Coulomb tether formation is given by ẍ1 − 2nẏ1...equa- tion was obtained using the Clohessy - Wiltshire - Hill equations, while the linearized differential equations of ψ and θ were derived from the full

Selectivity to Translational Egomotion in Human Brain Motion Areas

PubMed Central

Pitzalis, Sabrina; Sdoia, Stefano; Bultrini, Alessandro; Committeri, Giorgia; Di Russo, Francesco; Fattori, Patrizia; Galletti, Claudio; Galati, Gaspare

2013-01-01

The optic flow generated when a person moves through the environment can be locally decomposed into several basic components, including radial, circular, translational and spiral motion. Since their analysis plays an important part in the visual perception and control of locomotion and posture it is likely that some brain regions in the primate dorsal visual pathway are specialized to distinguish among them. The aim of this study is to explore the sensitivity to different types of egomotion-compatible visual stimulations in the human motion-sensitive regions of the brain. Event-related fMRI experiments, 3D motion and wide-field stimulation, functional localizers and brain mapping methods were used to study the sensitivity of six distinct motion areas (V6, MT, MST+, V3A, CSv and an Intra-Parietal Sulcus motion [IPSmot] region) to different types of optic flow stimuli. Results show that only areas V6, MST+ and IPSmot are specialized in distinguishing among the various types of flow patterns, with a high response for the translational flow which was maximum in V6 and IPSmot and less marked in MST+. Given that during egomotion the translational optic flow conveys differential information about the near and far external objects, areas V6 and IPSmot likely process visual egomotion signals to extract information about the relative distance of objects with respect to the observer. Since area V6 is also involved in distinguishing object-motion from self-motion, it could provide information about location in space of moving and static objects during self-motion, particularly in a dynamically unstable environment. PMID:23577096

Parametric study on the vortex-induced motions of semi-submersibles: Effect of rounded ratios of the column and pontoon

NASA Astrophysics Data System (ADS)

Liu, Mingyue; Xiao, Longfei; Yang, Jianmin; Tian, Xinliang

2017-05-01

The vortex-induced motions (VIMs) of semi-submersibles have emerged as an important issue in offshore engineering, as they pose a threat to safe and reliable operations and severely affect the fatigue lives of risers and mooring systems. The VIM response depends on the shape of the submerged structure and thus is significantly influenced by the design parameters related to the columns and pontoons. Numerical simulations by the detached Eddy simulation method are validated by experimental data and then used for parametric analysis of the VIM performance of various semi-submersibles with different column rounded ratios (Rc/L ) and pontoon rounded ratios (Rp/Lp ). The results show that the transverse amplitudes of a semi-submersible with circular columns at a 0° current heading are twice as large as those at a 45° current heading. However, the semi-submersible with rounded square columns shows more significant transverse motions at a 45° current heading than at a 0° current heading. Furthermore, at the 45° current heading, the transverse amplitudes of the semi-submersibles show a rapid increase as the column radius increases in the range of Rc/L <0.1 . The peak values remain roughly the same for 0.1 ≤Rc/L ≤0.2 and then decrease as the column radius increases (Rc/L ≥0.3 ). In addition, the effect of the pontoon shape on the transverse response is negligible for semi-submersibles with sharp square columns, while for semi-submersibles with rounded square columns or circular columns, the sharp rectangular pontoons greatly mitigate the VIM response.

Elimination of secular terms from the differential equations for the elements of perturbed two-body motion

NASA Technical Reports Server (NTRS)

Bond, Victor R.; Fraietta, Michael F.

1991-01-01

In 1961, Sperling linearized and regularized the differential equations of motion of the two-body problem by changing the independent variable from time to fictitious time by Sundman's transformation (r = dt/ds) and by embedding the two-body energy integral and the Laplace vector. In 1968, Burdet developed a perturbation theory which was uniformly valid for all types of orbits using a variation of parameters approach on the elements which appeared in Sperling's equations for the two-body solution. In 1973, Bond and Hanssen improved Burdet's set of differential equations by embedding the total energy (which is a constant when the potential function is explicitly dependent upon time.) The Jacobian constant was used as an element to replace the total energy in a reformulation of the differential equations of motion. In the process, another element which is proportional to a component of the angular momentum was introduced. Recently trajectories computed during numerical studies of atmospheric entry from circular orbits and low thrust beginning in near-circular orbits exhibited numerical instability when solved by the method of Bond and Gottlieb (1989) for long time intervals. It was found that this instability was due to secular terms which appear on the righthand sides of the differential equations of some of the elements. In this paper, this instability is removed by the introduction of another vector integral called the delta integral (which replaces the Laplace Vector) and another scalar integral which removes the secular terms. The introduction of these integrals requires a new derivation of the differential equations for most of the elements. For this rederivation, the Lagrange method of variation of parameters is used, making the development more concise. Numerical examples of this improvement are presented.

Induced rotational motion with nonabutting inducing and induced stimuli: implications regarding two forms of induced motion.

PubMed

Reinhardt-Rutland, A H

2003-07-01

Induced motion is the illusory motion of a static stimulus in the opposite direction to a moving stimulus. Two types of induced motion have been distinguished: (a) when the moving stimulus is distant from the static stimulus and undergoes overall displacement, and (b) when the moving stimulus is pattern viewed within fixed boundaries that abut the static stimulus. Explanations of the 1st type of induced motion refer to mediating phenomena, such as vection, whereas the 2nd type is attributed to local processing by motion-sensitive neurons. The present research was directed to a display that elicited induced rotational motion with the characteristics of both types of induced motion: the moving stimulus lay within fixed boundaries, but the inducing and induced stimuli were distant from each other. The author investigated the properties that distinguished the two types of induced motion. In 3 experiments, induced motion persisted indefinitely, interocular transfer of the aftereffect of induced motion was limited to about 20%, and the time-course of the aftereffect of induced motion could not be attributed to vection. Those results were consistent with fixed-boundary induced motion. However, they could not be explained by local processing. Instead, the results might reflect the detection of object motion within a complex flow-field that resulted from the observer's motion.

Wind-tunnel investigation of the aerodynamic characteristics of the Standard Dynamics Model in coning motion at Mach 0.6

NASA Technical Reports Server (NTRS)

Jermey, C.; Schiff, L. B.

1985-01-01

A series of wind-tunnel tests have been conducted on the Standard Dynamics Model (a simplified generic fighter-aircraft shape) undergoing coning motion at Mach 0.6. Six-component force and moment data are presented for a range of angles of attack, sideslip and coning rates. At the relatively low nondimensional coning rates employed, the lateral aerodynamic charactersitics generally show a linear variation with coning rate.

Path probability of stochastic motion: A functional approach

NASA Astrophysics Data System (ADS)

Hattori, Masayuki; Abe, Sumiyoshi

2016-06-01

The path probability of a particle undergoing stochastic motion is studied by the use of functional technique, and the general formula is derived for the path probability distribution functional. The probability of finding paths inside a tube/band, the center of which is stipulated by a given path, is analytically evaluated in a way analogous to continuous measurements in quantum mechanics. Then, the formalism developed here is applied to the stochastic dynamics of stock price in finance.

Complications encountered with circular ring fixation in persons with diabetes mellitus.

PubMed

Wukich, Dane K; Belczyk, Ronald J; Burns, Patrick R; Frykberg, Robert G

2008-10-01

The purpose of this study was to identify and report the complications associated with the use of circular ring fixation in diabetic patients, and to compare the frequency of complications in patients without diabetes. We hypothesized that complications with circular ring fixation occurred more frequently in patients with diabetes than patients without diabetes. Institutional Review Board approval was obtained and patient charts were retrospectively reviewed from June 2004 and February 2007. Fifty six consecutive patients undergoing midfoot, hindfoot and/or ankle surgery were treated with circular ring fixation which included 33 diabetic patients in the study group and 23 non-diabetic patients in the control group. Patient demographics, the duration of treatment with the external fixator, and complications were recorded. Males had a greater number of complications compared to females (p = 0.0014). The total number of complications was statistically greater in diabetic patients (study group) versus non-diabetic patients (control group) (p = 0.003). In multivariate logistic regression, diabetes and male sex were the only significant variables associated with wire complications (OR 7.35, 95% CI 1.93-28.04 and OR 0.22, 95% CI 0.05-8584111, respectively). Women are protected from wire complications with a risk reduction of 78% compared to males. Diabetics have a 7-fold risk for any wire complication compared to patients without diabetes. We found no adverse effects of BMI, obesity, age, smoking, neuropathy, or Charcot neuroarthropathy on a satisfactory recovery.

Supraperitoneal colorectal anastomosis: hand-sewn versus circular staples--a controlled clinical trial. French Associations for Surgical Research.

PubMed

Fingerhut, A; Hay, J M; Elhadad, A; Lacaine, F; Flamant, Y

1995-09-01

Although used widely for supraperitoneal anastomoses, circular stapled anastomoses have never been proved better than hand-sewn anastomoses. In the one prospective controlled trial that studied these anastomoses specifically, the only significant difference found was that there were more clinically obvious leakages with the circular stapled variety, but not in the overall clinical and roentgenologic leakage rates. One hundred fifty-nine consecutive patients (88 men and 71 women, mean age 65.8 +/- 12.1 years) were randomized to undergo hand-sewn (n = 74) or circular stapled (n = 85) supraperitoneal colorectal anastomosis after left colectomy. Patient demographics were similar in both groups. Overall mortality was 1.3% (2 of 159; one in each group). No statistically significant difference (NS) was found in the rate of early complications, including anastomotic leakage (4 of 74 versus 6 of 85) in the hand-sewn and stapled anastomoses, respectively). Mishaps (n = 10) and hemorrhage (n = 5) occurred in the stapled group only. Stapled anastomoses took an average of 8 minutes less to perform (p < 0.001), but this time gain did not significantly influence the overall duration of operation (identical median times). The median duration of hospitalization was 13 and 14 days, respectively (NS). At 8 months there were 2 of 74 strictures in the hand-sewn group and 4 of 85 strictures in the stapled group (NS). According to these results, there seems to be no advantage of routine or regular use of stapling instruments for supraperitoneal colorectal anastomosis.

Use of inpatient continuous passive motion versus no CPM in computer-assisted total knee arthroplasty.

PubMed

Alkire, Martha R; Swank, Michael L

2010-01-01

Continuous passive motion (CPM) has shown positive effects on tissue healing, edema, hemarthrosis, and joint function (L. Brosseau et al., 2004). CPM has also been shown to increase short-term early flexion and decrease length of stay (LOS) ( L. Brosseau et al., 2004; C. M. Chiarello, C. M. S. Gundersen, & T. O'Halloran, 2004). The benefits of CPM for the population of patients undergoing computer-assisted total knee arthroplasty (TKA) have not been examined. The primary objective of this study was to determine whether the use of CPM following computer-assisted TKA resulted in differences in range of motion, edema/drainage, functional ability, and pain. This was an experimental, prospective, randomized study of patients undergoing unilateral, computer-assisted TKA. The experimental group received CPM thrice daily and physical therapy (PT) twice daily during their hospitalization. The control group received PT twice daily and no CPM during the hospital stay. Both groups received PT after discharge. Measurement included Knee Society scores, Western Ontario McMaster Osteoarthritis Index values, range of motion, knee circumference, and HemoVac drainage. Data were collected at various intervals from preoperatively through 3 months. Although the control group was found to be higher functioning preoperatively, there was no statistically significant difference in flexion, edema or drainage, function, or pain between groups through the 3-month study period.

Inferring the direction of implied motion depends on visual awareness

PubMed Central

Faivre, Nathan; Koch, Christof

2014-01-01

Visual awareness of an event, object, or scene is, by essence, an integrated experience, whereby different visual features composing an object (e.g., orientation, color, shape) appear as an unified percept and are processed as a whole. Here, we tested in human observers whether perceptual integration of static motion cues depends on awareness by measuring the capacity to infer the direction of motion implied by a static visible or invisible image under continuous flash suppression. Using measures of directional adaptation, we found that visible but not invisible implied motion adaptors biased the perception of real motion probes. In a control experiment, we found that invisible adaptors implying motion primed the perception of subsequent probes when they were identical (i.e., repetition priming), but not when they only shared the same direction (i.e., direction priming). Furthermore, using a model of visual processing, we argue that repetition priming effects are likely to arise as early as in the primary visual cortex. We conclude that although invisible images implying motion undergo some form of nonconscious processing, visual awareness is necessary to make inferences about motion direction. PMID:24706951

Robotized High Intensity Focused Ultrasound (HIFU) system for treatment of mobile organs using motion tracking by ultrasound imaging: An in vitro study.

PubMed

Chanel, Laure-Anais; Nageotte, Florent; Vappou, Jonathan; Luo, Jianwen; Cuvillon, Loic; de Mathelin, Michel

2015-01-01

High Intensity Focused Ultrasound (HIFU) therapy is a very promising method for ablation of solid tumors. However, intra-abdominal organ motion, principally due to breathing, is a substantial limitation that results in incorrect tumor targeting. The objective of this work is to develop an all-in-one robotized HIFU system that can compensate motion in real-time during HIFU treatment. To this end, an ultrasound visual servoing scheme working at 20 Hz was designed. It relies on the motion estimation by using a fast ultrasonic speckle tracking algorithm and on the use of an interleaved imaging/HIFU sonication sequence for avoiding ultrasonic wave interferences. The robotized HIFU system was tested on a sample of chicken breast undergoing a vertical sinusoidal motion at 0.25 Hz. Sonications with and without motion compensation were performed in order to assess the effect of motion compensation on thermal lesions induced by HIFU. Motion was reduced by more than 80% thanks to this ultrasonic visual servoing system.

TH-AB-202-07: Radar Tracking of Respiratory Motion in Real Time

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fung, A; Li, C; Torres, C

Purpose: To propose a method of real time tracking of respiratory motion in patients undergoing radiation therapy. Radar technology can be employed to detection the movement of diaphragm and thoracic anatomy. Methods: A radar transceiver was specially designed. During experiment, the radar device was securely attached to a fixed frame. Respiratory motion was simulated with: 1) Varian RPM phantom, 2) Standard Imaging Respiratory Gating Platform. Signals recorded with radar equipment were compared with those measured with Varian RPM system as a reference. Results: Motion generated by Varian RPM phantom was recorded by the radar device, and compared to the signalsmore » recorded by RPM camera. The results showed exact agreement between the two monitoring equipments. Motion was also generated by Standard Imaging Respiratory Motion Platform. The results showed the radar device was capable of measuring motion of various amplitudes and periods. Conclusion: The proposed radar device is able to measure movements such as respiratory motion. Compared to state-of-the-art respiratory detection instrument, the radar device is shown to be equally precise and effective for monitoring respiration in radiation oncology patients.« less

Inferring the direction of implied motion depends on visual awareness.

PubMed

Faivre, Nathan; Koch, Christof

2014-04-04

Visual awareness of an event, object, or scene is, by essence, an integrated experience, whereby different visual features composing an object (e.g., orientation, color, shape) appear as an unified percept and are processed as a whole. Here, we tested in human observers whether perceptual integration of static motion cues depends on awareness by measuring the capacity to infer the direction of motion implied by a static visible or invisible image under continuous flash suppression. Using measures of directional adaptation, we found that visible but not invisible implied motion adaptors biased the perception of real motion probes. In a control experiment, we found that invisible adaptors implying motion primed the perception of subsequent probes when they were identical (i.e., repetition priming), but not when they only shared the same direction (i.e., direction priming). Furthermore, using a model of visual processing, we argue that repetition priming effects are likely to arise as early as in the primary visual cortex. We conclude that although invisible images implying motion undergo some form of nonconscious processing, visual awareness is necessary to make inferences about motion direction.

A real-time dynamic-MLC control algorithm for delivering IMRT to targets undergoing 2D rigid motion in the beam's eye view.

PubMed

McMahon, Ryan; Berbeco, Ross; Nishioka, Seiko; Ishikawa, Masayori; Papiez, Lech

2008-09-01

An MLC control algorithm for delivering intensity modulated radiation therapy (IMRT) to targets that are undergoing two-dimensional (2D) rigid motion in the beam's eye view (BEV) is presented. The goal of this method is to deliver 3D-derived fluence maps over a moving patient anatomy. Target motion measured prior to delivery is first used to design a set of planned dynamic-MLC (DMLC) sliding-window leaf trajectories. During actual delivery, the algorithm relies on real-time feedback to compensate for target motion that does not agree with the motion measured during planning. The methodology is based on an existing one-dimensional (ID) algorithm that uses on-the-fly intensity calculations to appropriately adjust the DMLC leaf trajectories in real-time during exposure delivery [McMahon et al., Med. Phys. 34, 3211-3223 (2007)]. To extend the 1D algorithm's application to 2D target motion, a real-time leaf-pair shifting mechanism has been developed. Target motion that is orthogonal to leaf travel is tracked by appropriately shifting the positions of all MLC leaves. The performance of the tracking algorithm was tested for a single beam of a fractionated IMRT treatment, using a clinically derived intensity profile and a 2D target trajectory based on measured patient data. Comparisons were made between 2D tracking, 1D tracking, and no tracking. The impact of the tracking lag time and the frequency of real-time imaging were investigated. A study of the dependence of the algorithm's performance on the level of agreement between the motion measured during planning and delivery was also included. Results demonstrated that tracking both components of the 2D motion (i.e., parallel and orthogonal to leaf travel) results in delivered fluence profiles that are superior to those that track the component of motion that is parallel to leaf travel alone. Tracking lag time effects may lead to relatively large intensity delivery errors compared to the other sources of error investigated. However, the algorithm presented is robust in the sense that it does not rely on a high level of agreement between the target motion measured during treatment planning and delivery.

Entropic Approach to Brownian Movement.

ERIC Educational Resources Information Center

Neumann, Richard M.

1980-01-01

A diffusional driving force, called the radial force, which is responsible for the increase with time of the scalar separation between a fixed point and a particle undergoing three-dimensional Brownian motion, is derived using Boltzmann's equation. (Author/HM)

Dark energy from the motions of neutrinos

NASA Astrophysics Data System (ADS)

Simpson, Fergus; Jimenez, Raul; Pena-Garay, Carlos; Verde, Licia

2018-06-01

Ordinarily, a scalar field may only play the role of dark energy if it possesses a potential that is either extraordinarily flat or extremely fine-tuned. Here we demonstrate that these restrictions are lifted when the scalar field undergoes persistent energy exchange with another fluid. In this scenario, the field is prevented from reversing its direction of motion, and instead may come to rest while displaced from the local minimum of its potential. Therefore almost any scalar potential is capable of initiating a prolonged phase of cosmic acceleration. If the rate of energy transfer is modulated via a derivative coupling, the field undergoes a rapid process of freezing, after which the field's equation of state mimicks that of a cosmological constant. We present a physically motivated realisation in the form of a neutrino-majoron coupling, which avoids the dynamical instabilities associated with mass-varying neutrino models. Finally we discuss possible means by which this model could be experimentally verified.

Reliable low-power control of ultrafast vortex-core switching with the selectivity in an array of vortex states by in-plane circular-rotational magnetic fields and spin-polarized currents

NASA Astrophysics Data System (ADS)

Kim, Sang-Koog; Lee, Ki-Suk; Yu, Young-Sang; Choi, Youn-Seok

2008-01-01

The authors investigated the technological utility of counterclockwise (CCW) and clockwise (CW) circular-rotating fields (HCCW and HCW) and spin-polarized currents with an angular frequency ωH close to the vortex eigenfrequency ωD, for the reliable, low-power, and selective switching of the bistate magnetization (M) orientations of a vortex core (VC) in an array of soft magnetic nanoelements. CCW and CW circular gyrotropic motions in response to HCCW and HCW, respectively, show remarkably contrasting resonant behaviors, (i.e., extremely large-amplitude resonance versus small-amplitude nonresonance), depending on the M orientation of a given VC. Owing to this asymmetric resonance characteristics, the HCCW(HCW) with ωH˜ωD can be used to effectively switch only the up (down) core to its downward (upward) M orientation, selectively, by sufficiently low field (˜10Oe) and current density (˜107A/cm2). This work provides a reliable, low power, effective means of information storage, information recording, and information readout in vortex-based random access memory, simply called VRAM.

Modal radiation patterns of baffled circular plates and membranes.

PubMed

Christiansen, Thomas Lehrmann; Hansen, Ole; Thomsen, Erik Vilain; Jensen, Jørgen Arendt

2014-05-01

The far field velocity potential and radiation pattern of baffled circular plates and membranes are found analytically using the full set of modal velocity profiles derived from the corresponding equation of motion. The derivation is valid for a plate or membrane subjected to an external excitation force, which is used as a sound receiver in any medium or as a sound transmitter in a gaseous medium. A general, concise expression is given for the radiation pattern of any mode of the membrane and the plate with arbitrary boundary conditions. Specific solutions are given for the four special cases of a plate with clamped, simply supported, and free edge boundary conditions as well as for the membrane. For all non-axisymmetric modes, the velocity potential along the axis of the radiator is found to be strictly zero. In the long wavelength limit, the radiation pattern of all axisymmetric modes approaches that of a monopole, while the non-axisymmetric modes exhibit multipole behavior. Numerical results are also given, demonstrating the implications of having non-axisymmetric excitation using both a point excitation with varying eccentricity and a homogeneous excitation acting on half of the circular radiator.

Adjacent-Level Hypermobility and Instrumented-Level Fatigue Loosening With Titanium and PEEK Rods for a Pedicle Screw System: An In Vitro Study.

PubMed

Agarwal, Aakas; Ingels, Marcel; Kodigudla, Manoj; Momeni, Narjes; Goel, Vijay; Agarwal, Anand K

2016-05-01

Adjacent-level disease is a common iatrogenic complication seen among patients undergoing spinal fusion for low back pain. This is attributed to the postsurgical differences in stiffness between the spinal levels, which result in abnormal forces, stress shielding, and hypermobility at the adjacent levels. In addition, as most patients undergoing these surgeries are osteoporotic, screw loosening at the index level is a complication that commonly accompanies adjacent-level disease. Recent studies indicate that a rod with lower rigidity than that of titanium may help to overcome these detrimental effects at the adjacent level. The present study was conducted in vitro using 12 L1-S1 specimens divided into groups of six, with each group instrumented with either titanium rods or PEEK (polyetheretherketone) rods. The test protocol included subjecting intact specimens to pure moments of 10 Nm in extension and flexion using an FS20 Biomechanical Spine Test System (Applied Test Systems) followed by hybrid moments on the instrumented specimens to achieve the same L1-S1 motion as that of the intact specimens. During the protocol's later phase, the L4-L5 units from each specimen were segmented for cyclic loading followed by postfatigue kinematic analysis to highlight the differences in motion pre- and postfatigue. The objectives included the in vitro comparison of (1) the adjacent-level motion before and after instrumentation with PEEK and titanium rods and (2) the pre- and postfatigue motion at the instrumented level with PEEK and titanium rods. The results showed that the adjacent levels above the instrumentation caused increased flexion and extension with both PEEK and titanium rods. The postfatigue kinematic data showed that the motion at the instrumented level (L4-L5) increased significantly in both flexion and extension compared to prefatigue motion in titanium groups. However, there was no significant difference in motion between the pre- and postfatigue data in the PEEK group.

Shaping liquid drops by vibration

NASA Astrophysics Data System (ADS)

Pototsky, Andrey; Bestehorn, Michael

2018-02-01

We present and analyze a minimal hydrodynamic model of a vertically vibrated liquid drop that undergoes dynamic shape transformations. In agreement with experiments, a circular lens-shaped drop is unstable above a critical vibration amplitude, spontaneously elongating in the horizontal direction. Smaller drops elongate into localized states that oscillate with half of the vibration frequency. Larger drops evolve by transforming into a snake-like structure with gradually increasing length. The worm state is long-lasting with a potential to fragment into smaller drops.

Conformal Surface Coatings to Enable High Volume Expansion Li-Ion Anode Materials

DTIC Science & Technology

2010-07-12

the formation of a metastable amor - phous alloy, sustaining up to 4.4 Li+ per Si.[2] Transition metal oxides undergo a conversion reaction at lower...in Figure 1a. The ele - mental composition of the circular area labeled P1 was exam- ined using energy dispersive X-ray spectroscopy (EDS) to verify...electrodes were of a 70:10:20 composition active material (AM): acetylene black ( AB ): binder (PVDF) and subjected to 250 8C heat treatment. For

Four-corner fusion of the wrist: clinical and radiographic outcome of 31 patients.

PubMed

Mavrogenis, Andreas F; Flevas, Dimitrios A; Raptis, Konstantinos; Megaloikonomos, Panayiotis D; Igoumenou, Vasilios G; Antoniadou, Thekla; Dimopoulos, Leonidas; Antonopoulos, Dimitrios; Spyridonos, Sarantis G

2016-12-01

Four-corner fusion is a rational surgical option for the management of degenerative conditions of the wrist. Most related studies have compared four-corner fusion with scaphoid excision or proximal row carpectomy, with a variety of reported results. To enhance the literature, we performed this study to evaluate a series of patients with degenerative conditions of the wrist treated with four-corner fusion using 3 surgical techniques and to discuss the clinical and radiographic outcome of the patients. We retrospectively studied 31 patients (24 men, 7 women; mean age, 43 years; 9 heavy manual laborers) who underwent four-corner fusion of their wrists for degenerative conditions from 2005 to 2015. Internal fixation was done using multiple Kirschner wires (14 patients), headless compressive screws (8 patients), or a circular plate (9 patients). Mean follow-up was 4 years (1-11 years). We evaluated the clinical outcome with the Patient-Rated Wrist Evaluation (PRWE) score and fusion with radiographs. All patients experienced improvement of their pain, function, range of motion and grip strength (p < 0.05). Twenty-three patients (74 %) reported no pain, and eight patients reported mild, occasional pain. Twenty-one patients (68 %) were able to do usual and specific activities. Mean wrist motion improved to 70 % and mean grip strength improved to 85 % of opposite wrist. Two heavy manual labor patients requested a job modification because of wrist impairment. Radiographs of the wrist showed fusion of all fused joints in 28 (90.3 %) patients and partial fusion in three patients (9.7 %). No patient with partial fusion required a reoperation for symptomatic nonunion until the period of this study. Three patients experienced complications (10 %). Two patients treated with a circular plate experienced complex regional pain syndrome and painful implant impingement; another patient treated with Kirschner wires and headless compression screws experienced radiolunate arthritis from impingement of the lunate screw to the radius. Four-corner fusion is a reliable limited wrist fusion technique that provides pain relief, grip strength and satisfactory range of motion in patients with degenerative conditions of the wrist. Partial union is more common with Kirschner wire fixation and complications are more common with circular plate fixation.

Breaking Symmetry in Time-Dependent Electronic Structure Theory to Describe Spectroscopic Properties of Non-Collinear and Chiral Molecules

NASA Astrophysics Data System (ADS)

Goings, Joshua James

Time-dependent electronic structure theory has the power to predict and probe the ways electron dynamics leads to useful phenomena and spectroscopic data. Here we report several advances and extensions of broken-symmetry time-dependent electronic structure theory in order to capture the flexibility required to describe non-equilibrium spin dynamics, as well as electron dynamics for chiroptical properties and vibrational effects. In the first half, we begin by discussing the generalization of self-consistent field methods to the so-called two-component structure in order to capture non-collinear spin states. This means that individual electrons are allowed to take a superposition of spin-1/2 projection states, instead of being constrained to either spin-up or spin-down. The system is no longer a spin eigenfunction, and is known a a spin-symmetry broken wave function. This flexibility to break spin symmetry may lead to variational instabilities in the approximate wave function, and we discuss how these may be overcome. With a stable non-collinear wave function in hand, we then discuss how to obtain electronic excited states from the non-collinear reference, along with associated challenges in their physical interpretation. Finally, we extend the two-component methods to relativistic Hamiltonians, which is the proper setting for describing spin-orbit driven phenomena. We describe the first implementation of the explicit time propagation of relativistic two-component methods and how this may be used to capture spin-forbidden states in electronic absorption spectra. In the second half, we describe the extension of explicitly time-propagated wave functions to the simulation of chiroptical properties, namely circular dichroism (CD) spectra of chiral molecules. Natural circular dichroism, that is, CD in the absence of magnetic fields, originates in the broken parity symmetry of chiral molecules. This proves to be an efficient method for computing circular dichroism spectra for high density-of-states chiral molecules. Next, we explore the impact of allowing nuclear motion on electronic absorption spectra within the context of mixed quantum-classical dynamics. We show that nuclear motion modulates the electronic response, and this gives rise to infrared absorption as well as Raman scattering phenomena in the computed dynamic polarizability. Finally, we explore the accuracy of several perturbative approximations to the equation-of-motion coupled-cluster methods for the efficient and accurate prediction of electronic absorption spectra.

Cross-stream distribution of red blood cells in sickle-cell disease

NASA Astrophysics Data System (ADS)

Zhang, Xiao; Lam, Wilbur; Graham, Michael

2017-11-01

Experiments revealed that in blood flow, red blood cells (RBCs) tend to migrate away from the vessel walls, leaving a cell-free layer near the walls, while leukocytes and platelets tend to marginate towards the vessel walls. This segregation behavior of different cellular components in blood flow can be driven by their differences in stiffness and shape. An alteration of this segregation behavior may explain endothelial dysfunction and pain crisis associated with sickle-cell disease (SCD). It is hypothesized that the sickle RBCs, which are considerably stiffer than the healthy RBCs, may marginate towards the vessel walls and exert repeated damage to the endothelial cells. Direct simulations are performed to study the flowing suspensions of deformable biconcave discoids and stiff sickles representing healthy and sickle cells, respectively. It is observed that the sickles exhibit a strong margination towards the walls. The biconcave discoids in flowing suspensions undergo a so-called tank-treading motion, while the sickles behave as rigid bodies and undergo a tumbling motion. The margination behavior and tumbling motion of the sickles may help substantiate the aforementioned hypothesis of the mechanism for the SCD complications and shed some light on the design of novel therapies.

First implementation of burrowing motions in dual-reciprocating drilling using an integrated actuation mechanism

NASA Astrophysics Data System (ADS)

Pitcher, Craig; Gao, Yang

2017-03-01

The dual-reciprocating drill (DRD) is a biologically-inspired low-mass alternative to traditional drilling techniques, using backwards-facing teethed halves to grip the surrounding substrate, generating a traction force that reduces the required overhead penetration force. Previous experiments using a proof-of-concept test bench have provided evidence as to the significant role of sideways movements and lateral forces in improving drilling performance. The system is also progressing to a first system prototype concept, in which an actuation mechanism is integrated within the drill heads. To experimentally determine the effect of lateral motions, a new internal actuation mechanism was developed to allow the inclusion of controlled sideways movements, resulting in the creation of the circular and diagonal burrowing motions. This paper presents an investigation into the performance of the reciprocation and burrowing motions by testing them in a planetary regolith simulant. Analysis of force sensor measurements has shown a relationship between the penetration and traction forces and the internal friction of the mechanism and depth achieved. These tests have also experimentally demonstrated the benefit of lateral motions in drilling performance, with both the burrowing mechanisms and drilling tests performed at an angle able to penetrate further than traditional vertical reciprocation, leading to the proposition of new burrowing and diagonal drilling mechanics. From this, a new fully integrated system prototype can be developed which incorporates lateral motions that can optimise the drilling performance.

3D Asymmetrical motions of the Galactic outer disc with LAMOST K giant stars

NASA Astrophysics Data System (ADS)

Wang, Haifeng; López-Corredoira, Martín; Carlin, Jeffrey L.; Deng, Licai

2018-07-01

We present a three dimensional velocity analysis of Milky Way disc kinematics using LAMOST K giant stars and the GPS1 proper motion catalogue. We find that Galactic disc stars near the anticentre direction (in the range of Galactocentric distance between R = 8 and 13 kpc and vertical position between Z = -2 and 2 kpc) exhibit asymmetrical motions in the Galactocentric radial, azimuthal, and vertical components. Radial motions are not zero, thus departing from circularity in the orbits; they increase outwards within R ≲ 12 kpc, show some oscillation in the northern (0 < Z < 2 kpc) stars, and have north-south asymmetry in the region corresponding to a well-known nearby northern structure in the velocity field. There is a clear vertical gradient in azimuthal velocity, and also an asymmetry that shifts from a larger azimuthal velocity above the plane near the solar radius to faster rotation below the plane at radii of 11-12 kpc. Stars both above and below the plane at R ≳ 9 kpc exhibit net upward vertical motions. We discuss some possible mechanisms that might create the asymmetrical motions, such as external perturbations due to dwarf galaxy minor mergers or dark matter sub-haloes, warp dynamics, internal processes due to spiral arms or the Galactic bar, and (most likely) a combination of some or all of these components.

Complex Ion Dynamics in Carbonate Lithium-Ion Battery Electrolytes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ong, Mitchell T.; Bhatia, Harsh; Gyulassy, Attila G.

Li-ion battery performance is strongly influenced by ionic conductivity, which depends on the mobility of the Li ions in solution, and is related to their solvation structure. In this work, we have performed first-principles molecular dynamics (FPMD) simulations of a LiPF6 salt solvated in different Li-ion battery organic electrolytes. We employ an analytical method using relative angles from successive time intervals to characterize complex ionic motion in multiple dimensions from our FPMD simulations. We find different characteristics of ionic motion on different time scales. We find that the Li ion exhibits a strong caging effect due to its strong solvationmore » structure, while the counterion, PF6– undergoes more Brownian-like motion. Lastly, our results show that ionic motion can be far from purely diffusive and provide a quantitative characterization of the microscopic motion of ions over different time scales.« less

Complex Ion Dynamics in Carbonate Lithium-Ion Battery Electrolytes

DOE PAGES

Ong, Mitchell T.; Bhatia, Harsh; Gyulassy, Attila G.; ...

2017-03-06

Li-ion battery performance is strongly influenced by ionic conductivity, which depends on the mobility of the Li ions in solution, and is related to their solvation structure. In this work, we have performed first-principles molecular dynamics (FPMD) simulations of a LiPF6 salt solvated in different Li-ion battery organic electrolytes. We employ an analytical method using relative angles from successive time intervals to characterize complex ionic motion in multiple dimensions from our FPMD simulations. We find different characteristics of ionic motion on different time scales. We find that the Li ion exhibits a strong caging effect due to its strong solvationmore » structure, while the counterion, PF6– undergoes more Brownian-like motion. Lastly, our results show that ionic motion can be far from purely diffusive and provide a quantitative characterization of the microscopic motion of ions over different time scales.« less

Implied Dynamics Biases the Visual Perception of Velocity

PubMed Central

La Scaleia, Barbara; Zago, Myrka; Moscatelli, Alessandro; Lacquaniti, Francesco; Viviani, Paolo

2014-01-01

We expand the anecdotic report by Johansson that back-and-forth linear harmonic motions appear uniform. Six experiments explore the role of shape and spatial orientation of the trajectory of a point-light target in the perceptual judgment of uniform motion. In Experiment 1, the target oscillated back-and-forth along a circular arc around an invisible pivot. The imaginary segment from the pivot to the midpoint of the trajectory could be oriented vertically downward (consistent with an upright pendulum), horizontally leftward, or vertically upward (upside-down). In Experiments 2 to 5, the target moved uni-directionally. The effect of suppressing the alternation of movement directions was tested with curvilinear (Experiment 2 and 3) or rectilinear (Experiment 4 and 5) paths. Experiment 6 replicated the upright condition of Experiment 1, but participants were asked to hold the gaze on a fixation point. When some features of the trajectory evoked the motion of either a simple pendulum or a mass-spring system, observers identified as uniform the kinematic profiles close to harmonic motion. The bias towards harmonic motion was most consistent in the upright orientation of Experiment 1 and 6. The bias disappeared when the stimuli were incompatible with both pendulum and mass-spring models (Experiments 3 to 5). The results are compatible with the hypothesis that the perception of dynamic stimuli is biased by the laws of motion obeyed by natural events, so that only natural motions appear uniform. PMID:24667578

Design, analysis and testing of a new piezoelectric tool actuator for elliptical vibration turning

NASA Astrophysics Data System (ADS)

Lin, Jieqiong; Han, Jinguo; Lu, Mingming; Yu, Baojun; Gu, Yan

2017-08-01

A new piezoelectric tool actuator (PETA) for elliptical vibration turning has been developed based on a hybrid flexure hinge connection. Two double parallel four-bar linkage mechanisms and two right circular flexure hinges were chosen to guide the motion. The two input displacement directional stiffness were modeled according to the principle of virtual work modeling method and the kinematic analysis was conducted theoretically. Finite element analysis was used to carry out static and dynamic analyses. To evaluate the performance of the developed PETA, off-line experimental tests were carried out to investigate the step responses, motion strokes, resolutions, parasitic motions, and natural frequencies of the PETA along the two input directions. The relationship between input displacement and output displacement, as well as the tool tip’s elliptical trajectory in different phase shifts was analyzed. By using the developed PETA mechanism, micro-dimple patterns were generated as the preliminary application to demonstrate the feasibility and efficiency of PETA for elliptical vibration turning.

The Motion of a Satellite of the Moon

NASA Technical Reports Server (NTRS)

Lass, Harry

1960-01-01

The motion of a satellite of the Moon depends on the potential field due to the Moon as well as the gravitational effects of the Earth and Sun. If one chooses a frame of reference attached to the Moon, it can be shown that the force field resulting from the Sun can be neglected when compared with the perturbing field of the Moon resulting from its oblateness. The effect of the Earth's field on the satellite is of the some order of magnitude as the Moon's perturbing field and must be included in an analysis of the motion of a satellite of the Moon. We will assume that the distance between Earth and Moon remains constant, and we will consider satellite orbits of small eccentricity. It will be shown that a nearly circular polar orbit will digress less than 1 deg from a polar orbit and that the change in eccentricity is less than a factor of e in one year.

Swarming Patterns in a Two-Dimensional Kinematic Model for Biological Groups

NASA Astrophysics Data System (ADS)

Topaz, Chad

2004-03-01

We construct a continuum model for the motion of biological organisms experiencing social interactions and study its pattern-forming behavior. The model takes the form of a conservation law in two spatial dimensions. Social interactions are modeled in the velocity term, which is nonlocal in the population density. The dynamics of the model may be uniquely decomposed into incompressible motion and potential motion. For the purely incompressible case, the model resembles that for fluid dynamical vortex patches. There exist solutions that have constant population density and compact support for all time. Numerical simulations produce rotating structures with circular cores and spiral arms, reminiscent of naturally observed swarms such as ant mills. For the purely potential case, the model resembles a nonlocal (forwards or backwards) porous media equation, describing aggregation or dispersion of the population. For the aggregative case, the population clumps into regions of high and low density with a predictable characteristic length scale that is confirmed by numerical simulations.

Nanoprobe diffusion in entangled polymer solutions: Linear vs. unconcatenated ring chains

NASA Astrophysics Data System (ADS)

Nahali, Negar; Rosa, Angelo

2018-05-01

We employ large-scale molecular dynamics computer simulations to study the problem of nanoprobe diffusion in entangled solutions of linear polymers and unknotted and unconcatenated circular (ring) polymers. By tuning both the diameter of the nanoprobe and the density of the solution, we show that nanoprobes of diameter smaller than the entanglement distance (tube diameter) of the solution display the same (Rouse-like) behavior in solutions of both polymer architectures. Instead, nanoprobes with larger diameters appear to diffuse markedly faster in solutions of rings than in solutions of linear chains. Finally, by analysing the distribution functions of spatial displacements, we find that nanoprobe motion in rings' solutions shows both Gaussian and ergodic behaviors, in all regimes considered, while, in solutions of linear chains, nanoprobes exceeding the size of the tube diameter show a transition to non-Gaussian and non-ergodic motion. Our results emphasize the role of chain architecture in the motion of nanoprobes dispersed in polymer solutions.

Pure rotation of a prism on a ramp

PubMed Central

Zhao, Zhen; Liu, Caishan; Ma, Daolin

2014-01-01

In this work, we study a prism with a cross section in polygon rolling on a ramp inclined at a small angle. The prism under gravity rolls purely around each individual edge, intermittently interrupted by a sequence of face collisions between the side face of the prism and the ramp. By limiting the prism in a planar motion, we propose a mathematical model to deal with the events of the impacts. With a pair of laser-Doppler vibrometers, experiments are also conducted to measure the motions of various prisms made of different materials and with different edge number. Not only are good agreements achieved between our numerical and experimental results, but also an intriguing physical phenomenon is discovered: the purely rolling motion is nearly independent of the prism's materials, yet it is closely related to the prism's geometry. Imagine that an ideal circular section can be approximately equivalent to a polygon with a large enough edge number N, the finding presented in this paper may help discover the physical mechanism of rolling friction. PMID:25197242

Development of a Wearable Assist Robot for Walk Rehabilitation After Knee Arthroplasty Surgery

NASA Astrophysics Data System (ADS)

Terada, H.; Zhu, Y.; Horiguchi, K.; Nakamura, M.; Takahashi, R.

In Japan, it is popular that the disease knee joints will be replaced to artificial joints by surgery. And we have to assist so many patients for walk rehabilitation. So, the wearable assist robot has been developed. This robot includes the knee motion assist mechanism and the hip joint support mechanism. Especially, the knee motion assist mechanism consists of a non-circular gear and grooved cams. This mechanism rotates and slides simultaneously, which has two degree-of-freedom. Also, the hip joint support mechanism consists of a hip brace and a ball-joint. This mechanism can avoid motion constraints which are the internal or external rotation and the adduction or abduction. Then, the control algorithm, which considers an assisting timing for the walk rehabilitation, has been proposed. A sensing system of a walk state for this control system uses a heel contacts sensor and knee and hip joint rotation angle sensors. Also, the prototype robot has been tested. And it is confirmed that the assisting system is useful.

Space time neural networks for tether operations in space

NASA Technical Reports Server (NTRS)

Lea, Robert N.; Villarreal, James A.; Jani, Yashvant; Copeland, Charles

1993-01-01

A space shuttle flight scheduled for 1992 will attempt to prove the feasibility of operating tethered payloads in earth orbit. due to the interaction between the Earth's magnetic field and current pulsing through the tether, the tethered system may exhibit a circular transverse oscillation referred to as the 'skiprope' phenomenon. Effective damping of skiprope motion depends on rapid and accurate detection of skiprope magnitude and phase. Because of non-linear dynamic coupling, the satellite attitude behavior has characteristic oscillations during the skiprope motion. Since the satellite attitude motion has many other perturbations, the relationship between the skiprope parameters and attitude time history is very involved and non-linear. We propose a Space-Time Neural Network implementation for filtering satellite rate gyro data to rapidly detect and predict skiprope magnitude and phase. Training and testing of the skiprope detection system will be performed using a validated Orbital Operations Simulator and Space-Time Neural Network software developed in the Software Technology Branch at NASA's Lyndon B. Johnson Space Center.

Pure rotation of a prism on a ramp.

PubMed

Zhao, Zhen; Liu, Caishan; Ma, Daolin

2014-09-08

In this work, we study a prism with a cross section in polygon rolling on a ramp inclined at a small angle. The prism under gravity rolls purely around each individual edge, intermittently interrupted by a sequence of face collisions between the side face of the prism and the ramp. By limiting the prism in a planar motion, we propose a mathematical model to deal with the events of the impacts. With a pair of laser-Doppler vibrometers, experiments are also conducted to measure the motions of various prisms made of different materials and with different edge number. Not only are good agreements achieved between our numerical and experimental results, but also an intriguing physical phenomenon is discovered: the purely rolling motion is nearly independent of the prism's materials, yet it is closely related to the prism's geometry. Imagine that an ideal circular section can be approximately equivalent to a polygon with a large enough edge number N , the finding presented in this paper may help discover the physical mechanism of rolling friction.

Computational design of microscopic swimmers and capsules: From directed motion to collective behavior

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nikolov, Svetoslav V.; Shum, Henry; Balazs, Anna C.

Systems of motile microscopic particles can exhibit behaviors that resemble those of living microorganisms, including cooperative motion, self-organization, and adaptability to changing environments. Using mesoscale computational modeling, we design synthetic microswimmers and microcapsules that undergo controllable, self-propelled motion in solution. Stimuli-responsive hydrogels are used to actuate the microswimmers and to enable their navigation and chemotaxing behavior. The self-propelled motion of microcapsules on solid surfaces is achieved by the release of encapsulated solutes that alter the surface adhesiveness. These signaling solutes also enable interactions among multiple microcapsules that lead to complex, cooperative behavior. Our findings provide guidelines for creating microscopic devicesmore » and machines able to autonomously move and mimic the communication and chemotaxis of biological microorganisms.« less

Human pelvis motions when walking and when riding a therapeutic horse.

PubMed

Garner, Brian A; Rigby, B Rhett

2015-02-01

A prevailing rationale for equine assisted therapies is that the motion of a horse can provide sensory stimulus and movement patterns that mimic those of natural human activities such as walking. The purpose of this study was to quantitatively measure and compare human pelvis motions when walking to those when riding a horse. Six able-bodied children (inexperienced riders, 8-12years old) participated in over-ground trials of self-paced walking and leader-paced riding on four different horses. Five kinematic measures were extracted from three-dimensional pelvis motion data: anteroposterior, superoinferior, and mediolateral translations, list angle about the anteroposterior axis, and twist angle about the superoinferior axis. There was generally as much or more variability in motion range observed between riding on the different horses as between riding and walking. Pelvis trajectories exhibited many similar features between walking and riding, including distorted lemniscate patterns in the transverse and frontal planes. In the sagittal plane the pelvis trajectory during walking exhibited a somewhat circular pattern whereas during riding it exhibited a more diagonal pattern. This study shows that riding on a horse can generate movement patterns in the human pelvis that emulate many, but not all, characteristics of those during natural walking. Copyright © 2014 Elsevier B.V. All rights reserved.

Innermost stable circular orbit of spinning particle in charged spinning black hole background

NASA Astrophysics Data System (ADS)

Zhang, Yu-Peng; Wei, Shao-Wen; Guo, Wen-Di; Sui, Tao-Tao; Liu, Yu-Xiao

2018-04-01

In this paper we investigate the innermost stable circular orbit (ISCO) (spin-aligned or anti-aligned orbit) for a classical spinning test particle with the pole-dipole approximation in the background of Kerr-Newman black hole in the equatorial plane. It is shown that the orbit of the spinning particle is related to the spin of the test particle. The motion of the spinning test particle will be superluminal if its spin is too large. We give an additional condition by considering the superluminal constraint for the ISCO in the black hole backgrounds. We obtain numerically the relations between the ISCO and the properties of the black holes and the test particle. It is found that the radius of the ISCO for a spinning test particle is smaller than that of a nonspinning test particle in the black hole backgrounds.

Influence of obstacles on bubbles rising in water-saturated sand

NASA Astrophysics Data System (ADS)

Poryles, Raphaël; Varas, Germán; Vidal, Valérie

2017-06-01

This work investigates the dynamics of air rising through a water-saturated sand confined in a Hele- Shaw cell in which a circular obstacle is trapped. The air is injected at constant flow rate through a single nozzle at the bottom center of the cell. Without obstacle, in a similar configuration, previous studies pointed out the existence of a fluidized zone generated by the central upward gas motion which entrains two granular convection rolls on its sides. Here, a circular obstacle which diameter is of the order of the central air channel width is trapped at the vertical of the injection nozzle. We analyze the influence of the obstacle location on the size of the fluidized zone and its impact on the morphology of the central air channel. Finally, we quantify the variations of the granular free surface. Two configurations with multiple obstacles are also considered.

Viscous near-wall flow in a wake of circular cylinder at moderate Reynolds numbers

NASA Astrophysics Data System (ADS)

Okhotnikov, D. I.; Molochnikov, V. M.; Mazo, A. B.; Malyukov, A. V.; Goltsman, A. E.; Saushin, I. I.

2017-11-01

Here we present the results of experimental investigation of a cross flow around a circular cylinder mounted near the wall of a channel with rectangular cross section. The experiments were carried out in the range of Reynolds numbers corresponding to the transition to turbulence in a wake of the cylinder. Flow visualization and SIV-measurements of instantaneous velocity fields were carried out. Evolution of the flow pattern behind the cylinder and formation of the regular vortex structures were analyzed. It is shown that in the case of flow around the cylinder, there is no spiral motion of fluid from the side walls of the channel towards its symmetry plane, typical of the flow around a spanwise rib located on the channel wall. The laminar-turbulent transition in the wake of the cylinder is caused by the shear layer instability.

On the horizontal wobbling of an object levitated by near-field acoustic levitation.

PubMed

Kim, Cheol-Ho; Ih, Jeong-Guon

2007-11-01

A circular planar object can be levitated with several hundreds of microns by ultrasonic near-field acoustic levitation (NFAL). However, when both the sound source and the levitated object are circularly shaped and the center of the levitated object does not coincide with the source center, instability problem often occurs. When this happens, it becomes difficult to pick up or transport the object for the next process. In this study, when the center of the levitated object was offset from the source center, the moving direction of the levitated object was predicted by using the time averaged potential around the levitated object. The wobbling frequency of the levitated object was calculated by analyzing the nonlinear wobbling motion of the object. It was shown that the predicted wobbling frequencies agreed with measured ones well. Finally, a safe zone was suggested to avoid the unstable movement of an object.

A visual investigation of turbulence in stagnation flow about a circular cylinder

NASA Technical Reports Server (NTRS)

Sadeh, W. Z.; Brauer, H. J.

1978-01-01

A visual investigation of turbulence in stagnation flow around a circular cylinder was carried out in order to gain a physical insight into the model advocated by the corticity-amplification theory. Motion pictures were taken from three different viewpoints, and a frame by frame examination of selected movie strips was conducted. Qualitative and quantitative analyses of the flow events focused on tracing the temporal and spatial evolution of a cross-vortex tube outlined by the entrained smoke filaments. The visualization supplied evidence verifying: (1) the selective stretching of cross-vortex tubes which is responsible for the amplification of cross vorticity and, hence, of streamwise turbulence; (2) the streamwise tilting of stretched cross-vortex tubes; (3) the existence of a coherent array of vortices near the stagnation zone; (4) the interaction of the amplified vorticity with the body laminar boundary layer; and, (5) the growth of a turbulent boundary layer.

Influence of mass moment of inertia on normal modes of preloaded solar array mast

NASA Technical Reports Server (NTRS)

Armand, Sasan C.; Lin, Paul

1992-01-01

Earth-orbiting spacecraft often contain solar arrays or antennas supported by a preloaded mast. Because of weight and cost considerations, the structures supporting the spacecraft appendages are extremely light and flexible; therefore, it is vital to investigate the influence of all physical and structural parameters that may influence the dynamic behavior of the overall structure. The study primarily focuses on the mast for the space station solar arrays, but the formulations and the techniques developed in this study apply to any large and flexible mast in zero gravity. Furthermore, to determine the influence on the circular frequencies, the mass moment of inertia of the mast was incorporated into the governing equation of motion for bending. A finite element technique (MSC/NASTRAN) was used to verify the formulation. Results indicate that when the mast is relatively flexible and long, the mass moment inertia influences the circular frequencies.

Observational signature of high spin at the Event Horizon Telescope

NASA Astrophysics Data System (ADS)

Gralla, Samuel E.; Lupsasca, Alexandru; Strominger, Andrew

2018-04-01

We analytically compute the observational appearance of an isotropically emitting point source on a circular, equatorial orbit near the horizon of a rapidly spinning black hole. The primary image moves on a vertical line segment, in contrast to the primarily horizontal motion of the spinless case. Secondary images, also on the vertical line, display a rich caustic structure. If detected, this unique signature could serve as a `smoking gun' for a high spin black hole in nature.

Cubic nonlinearity in shear wave beams with different polarizations

PubMed Central

Wochner, Mark S.; Hamilton, Mark F.; Ilinskii, Yurii A.; Zabolotskaya, Evgenia A.

2008-01-01

A coupled pair of nonlinear parabolic equations is derived for the two components of the particle motion perpendicular to the axis of a shear wave beam in an isotropic elastic medium. The equations account for both quadratic and cubic nonlinearity. The present paper investigates, analytically and numerically, effects of cubic nonlinearity in shear wave beams for several polarizations: linear, elliptical, circular, and azimuthal. Comparisons are made with effects of quadratic nonlinearity in compressional wave beams. PMID:18529167

Distributed Arrays and Signal Processing for the TechSat21 Space-Based Radar

DTIC Science & Technology

2009-04-01

lIlustrating the derivation of minimum aperture size and coherent integration time ............. 25 B 4. Global coordinate system and satellite-based...work of Dr. Robert Mailloux. Dr. Peter Franchi . and Dr. Scott Santarelli. VII Summary The TechSat2l space-based radar concept, suggested by AFRUVS...Linearization for small motions around a reference point in a global circular orbit leads to the Hill equations, derived in 1878, and alternatively named

Estimated Satellite Cluster Elements in Near Circular Orbit

DTIC Science & Technology

1988-12-01

cluster is investigated. TheAon-board estimator is the U-D covariance factor’xzatiion’filter with dynamics based on the Clohessy - Wiltshire equations...Appropriate values for the velocity vector vi can be found irom the Clohessy - Wiltshire equations [9] (these equations will be explained in detail in the...explained in this text is the f matrix. The state transition matrix was developed from the Clohessy - Wiltshire equations of motion [9:page 3] as i - 2qý

Bifilm Defect Formation in Hydraulic Jump of Liquid Aluminum

NASA Astrophysics Data System (ADS)

Hsu, Fu-Yuan

2016-06-01

In aluminum gravity casting, as liquid aluminum fell through a vertical sprue and impacted on the horizontal flat surface, a phenomenon known as hydraulic jump ( i.e., flow transition from super-critical to sub-critical flows) was observed. As the jump was transformed, a reverse eddy motion on the surface of the jump was created. This motion entrained aluminum oxide film from the surface into aluminum melt. This folded film (so-called "bifilm" defect) was engulfed by the melt and caused its quality to deteriorate. To understand this phenomenon, aluminum casting experiments and computational modeling were conducted. In the casting experiment, a radius ( R j) to the point where the circular hydraulic jump occurred was measured. This is the circular region of `irregular surface feature', a rough oxidized surface texture near the center area of the castings. To quantify contents of the bifilm defects in the outer region of the jump, the samples in this region were sectioned and re-melted for doing re-melted reduced pressure test (re-melt RPT). An "area-normalized" bifilm index map was plotted to analyze bifilms' population in the samples. The flow transition in the hydraulic jump of liquid aluminum depended on three pressure heads: inertial, gravitational, and surface-tension pressures. A new theoretical equation containing surface tension for describing the flow transition of liquid metal was proposed.

Development of the wake behind a circular cylinder impulsively started into rotatory and rectilinear motion: Intermediate rotation rates

NASA Technical Reports Server (NTRS)

Chen, Yen-Ming; Ou, Yuh-Roung; Pearlstein, Arne J.

1991-01-01

The temporal development of two-dimensional viscous incompressible flow generated by a circular cylinder started impulsively into steady rotatory and rectilinear motion is studied by integration of a velocity/vorticity formulation of the governing equations, using an explicit finite-difference/pseudo-spectral technique and an implementation of the Biot-Savart law. Results are presented for a Reynolds number of 200 (based on the cylinder diameter 2a and the magnitude U of the rectilinear velocity) for several values of the angular/rectilinear speed ratio alpha = (omega x a)/U (where omega is the angular speed) up to 3.25. Several aspects of the kinematics and dynamics of the flow not considered earlier are discussed. For higher values of alpha, the results indicate that for Re = 200, vortex shedding does indeed occur for alpha = 3.25. The shedding process is; however, very different from that which gives rise to the usual Karman vortex street for alpha = 0. In particular, consecutive vortices shed by the body can be shed from the same side and be of the same sense, in contrast to the nonrotating case, in which mirror-image vortices of opposite sense are shed alternately on opposite sides of the body. The implications of the results are discussed in relation to the possibility of suppressing vortex shedding by open or closed-loop control of the rotation rate.

Numerical investigation of the vibration effect of a flexible membrane on the flow behaviour around a circular cylinder

NASA Astrophysics Data System (ADS)

Maktouf, Nabaouia; Moussa, Ali Ben; Turki, Saïd

2018-06-01

Active control of the flow behind a bluff body is obtained by integrating a vibrating membrane. A numerical study has been conducted to investigate the effect of the vibration of a flexible membrane, stuck to the rear side of a circular cylinder, on the global flow parameters such as the Strouhal number, the drag and lift coefficients. The shape of the membrane is evolving as a vibrating chord using a dynamic mesh. The governing equations of 2D and laminar flow have been solved using ANSYS Fluent 16.0 as a solver and the Gambit as a modeler. The motion of the membrane is managed by two parameters: frequency f and amplitude A. The effect of the flexible membrane motion is studied for the range of conditions as 0.1 Hz ≤ f ≤ 6 Hz and 5 × 10-4 m ≤ A ≤ 10-3 m at a fixed Reynolds number, Re = 150. Three different sizes of the flexible membrane have been studied. Results show that a beat phenomenon affects the drag coefficient. The amplitude does not affect significantly the Strouhal number as well as drag and lift coefficients. By increasing the size of the flexible membrane, we show a lift enhancement by a growth rate equal to 39.15% comparing to the uncontrolled case.

On stimulated resonance radiation by channeled particles

NASA Astrophysics Data System (ADS)

Dabagov, S. B.; Kalashnikov, N. P.

2017-07-01

The channeled particles undergo quasiperiodic transverse bound motion along main crystallographic directions at either 1D planar or 2D axial channeling. This motion is accompanied by spontaneous radiation known as channeling radiation due to projectile's transmission between discrete quantum states. In this work we have presented preliminary evaluation of the processes of resonance scattering of external electromagnetic field when the external frequency becomes close to the channeled particle transition energies that might be of the source for induced radiation at channeling.

Unlikely Fluctuations and Non-Equilibrium Work Theorems-A Simple Example.

PubMed

Muzikar, Paul

2016-06-30

An exciting development in statistical mechanics has been the elucidation of a series of surprising equalities involving the work done during a nonequilibrium process. Astumian has presented an elegant example of such an equality, involving a colloidal particle undergoing Brownian motion in the presence of gravity. We analyze this example; its simplicity, and its link to geometric Brownian motion, allows us to clarify the inner workings of the equality. Our analysis explicitly shows the important role played by large, unlikely fluctuations.

Aerodynamic characteristics of the standard dynamics model in coning motion at Mach 0.6

NASA Technical Reports Server (NTRS)

Jermey, C.; Schiff, L. B.

1985-01-01

A wind tunnel test was conducted on the Standard Dynamics Model (a simplified generic fighter aircraft shape) undergoing coning motion at Mach 0.6. Six component force and moment data are presented for a range of angle of attack, sideslip, and coning rates. At the relatively low non-dimensional coning rate employed (omega b/2V less than or equal to 0.04), the lateral aerodynamic characteristics generally show a linear variation with coning rate.

Hamilton-Jacobi modelling of relative motion for formation flying.

PubMed

Kolemen, Egemen; Kasdin, N Jeremy; Gurfil, Pini

2005-12-01

A precise analytic model for the relative motion of a group of satellites in slightly elliptic orbits is introduced. With this aim, we describe the relative motion of an object relative to a circular or slightly elliptic reference orbit in the rotating Hill frame via a low-order Hamiltonian, and solve the Hamilton-Jacobi equation. This results in a first-order solution to the relative motion identical to the Clohessy-Wiltshire approach; here, however, rather than using initial conditions as our constants of the motion, we utilize the canonical momenta and coordinates. This allows us to treat perturbations in an identical manner, as in the classical Delaunay formulation of the two-body problem. A precise analytical model for the base orbit is chosen with the included effect of zonal harmonics (J(2), J(3), J(4)). A Hamiltonian describing the real relative motion is formed and by differing this from the nominal Hamiltonian, the perturbing Hamiltonian is obtained. Using the Hamilton equations, the variational equations for the new constants are found. In a manner analogous to the center manifold reduction procedure, the non-periodic part of the motion is canceled through a magnitude analysis leading to simple boundedness conditions that cancel the drift terms due to the higher order perturbations. Using this condition, the variational equations are integrated to give periodic solutions that closely approximate the results from numerical integration (1 mm/per orbit for higher order and eccentricity perturbations and 30 cm/per orbit for zonal perturbations). This procedure provides a compact and insightful analytic description of the resulting relative motion.

Horizon-absorbed energy flux in circularized, nonspinning black-hole binaries, and its effective-one-body representation

NASA Astrophysics Data System (ADS)

Nagar, Alessandro; Akcay, Sarp

2012-02-01

We propose, within the effective-one-body approach, a new, resummed analytical representation of the gravitational-wave energy flux absorbed by a system of two circularized (nonspinning) black holes. This expression is such that it is well-behaved in the strong-field, fast-motion regime, notably up to the effective-one-body-defined last unstable orbit. Building conceptually upon the procedure adopted to resum the multipolar asymptotic energy flux, we introduce a multiplicative decomposition of the multipolar absorbed flux made by three factors: (i) the leading-order contribution, (ii) an “effective source” and (iii) a new residual amplitude correction (ρ˜ℓmH)2ℓ. In the test-mass limit, we use a frequency-domain perturbative approach to accurately compute numerically the horizon-absorbed fluxes along a sequence of stable and unstable circular orbits, and we extract from them the functions ρ˜ℓmH. These quantities are then fitted via rational functions. The resulting analytically represented test-mass knowledge is then suitably hybridized with lower-order analytical information that is valid for any mass ratio. This yields a resummed representation of the absorbed flux for a generic, circularized, nonspinning black-hole binary. Our result adds new information to the state-of-the-art calculation of the absorbed flux at fractional 5 post-Newtonian order [S. Taylor and E. Poisson, Phys. Rev. D 78, 084016 (2008)], which is recovered in the weak-field limit approximation by construction.

Energy buildup in coronal magnetic flux tubes

NASA Technical Reports Server (NTRS)

Steinolfson, R. S.; Tajima, T.

1987-01-01

A time-dependent two-dimensional MHD simulation is used to study the response of the magnetic field in coronal loops to photospheric motion. From an initially uniform field, circular sections of the ends of the loop are slowly rotated to represent the photospheric motion. The evolution of the field and flow is characterized by three phases: (1) a phase of negligible kinetic energy where the current and field are predominantly parallel; (2) a phase where the field twist increases, the axial field at and near the axis increases, and the axial field decreases in two cylindrical regions away from the axis; and (3) a phase in which a significant portion of the field makes several rotations at large radii, with a corresponding reducton in the axial field to a few percent of the initial value.

A high efficiency stirrer for suspension cell culture with or without microcarriers.

PubMed

de Bruyne, N A

1984-01-01

The stirrer described in this paper employs "Teaspoon stirring" in which a secondary motion is superimposed on the rotation of the liquid. This secondary motion arises from the viscous drag from the wall and bottom of the flask. The culture medium is rotated by a bulb-ended rod suspended from inside the flask cap: the bulb orbits around in a circular trough formed between a central indent in the base and the rounded periphery of the base. There are no bearings and no stagnant areas. The power used to stir 4 flasks each holding 500 ml of medium is less than 2 watts. The speed is electronically controlled by a tachometer and automatically gives a smooth start and stop as well as "Interval stirring" to assist initial attachment of cells.

Helical vortices generated by flapping wings of bumblebees

NASA Astrophysics Data System (ADS)

Engels, Thomas; Kolomenskiy, Dmitry; Schneider, Kai; Farge, Marie; Lehmann, Fritz-Olaf; Sesterhenn, Jörn

2018-02-01

High resolution direct numerical simulations of rotating and flapping bumblebee wings are presented and their aerodynamics is studied focusing on the role of leading edge vortices and the associated helicity production. We first study the flow generated by only one rotating bumblebee wing in circular motion with 45◦ angle of attack. We then consider a model bumblebee flying in a numerical wind tunnel, which is tethered and has rigid wings flapping with a prescribed generic motion. The inflow condition of the wind varies from laminar to strongly turbulent regimes. Massively parallel simulations show that inflow turbulence does not significantly alter the wings’ leading edge vortex, which enhances lift production. Finally, we focus on studying the helicity of the generated vortices and analyze their contribution at different scales using orthogonal wavelets.

Null geodesics and red-blue shifts of photons emitted from geodesic particles around a noncommutative black hole space-time

NASA Astrophysics Data System (ADS)

Kuniyal, Ravi Shankar; Uniyal, Rashmi; Biswas, Anindya; Nandan, Hemwati; Purohit, K. D.

2018-06-01

We investigate the geodesic motion of massless test particles in the background of a noncommutative geometry-inspired Schwarzschild black hole. The behavior of effective potential is analyzed in the equatorial plane and the possible motions of massless particles (i.e. photons) for different values of impact parameter are discussed accordingly. We have also calculated the frequency shift of photons in this space-time. Further, the mass parameter of a noncommutative inspired Schwarzschild black hole is computed in terms of the measurable redshift of photons emitted by massive particles moving along circular geodesics in equatorial plane. The strength of gravitational fields of noncommutative geometry-inspired Schwarzschild black hole and usual Schwarzschild black hole in General Relativity is also compared.

Hydrodynamic impeller stiffness, damping, and inertia in the rotordynamics of centrifugal flow pumps

NASA Technical Reports Server (NTRS)

Jery, S.; Acosta, A. J.; Brennen, C. E.; Caughey, T. K.

1984-01-01

The lateral hydrodynamic forces experienced by a centrifugal pump impeller performing circular whirl motions within several volute geometries were measured. The lateral forces were decomposed into: (1) time averaged lateral forces and (2) hydrodynamic force matrices representing the variation of the lateral forces with position of the impeller center. It is found that these force matrices essentially consist of equal diagonal terms and skew symmetric off diagonal terms. One consequence of this is that during its whirl motion the impeller experiences forces acting normal and tangential to the locus of whirl. Data on these normal and tangential forces are presented; it is shown that there exists a region of positive reduced whirl frequencies, within which the hydrodynamic forces can be destablizing with respect to whirl.

Ensemble framework based real-time respiratory motion prediction for adaptive radiotherapy applications.

PubMed

Tatinati, Sivanagaraja; Nazarpour, Kianoush; Tech Ang, Wei; Veluvolu, Kalyana C

2016-08-01

Successful treatment of tumors with motion-adaptive radiotherapy requires accurate prediction of respiratory motion, ideally with a prediction horizon larger than the latency in radiotherapy system. Accurate prediction of respiratory motion is however a non-trivial task due to the presence of irregularities and intra-trace variabilities, such as baseline drift and temporal changes in fundamental frequency pattern. In this paper, to enhance the accuracy of the respiratory motion prediction, we propose a stacked regression ensemble framework that integrates heterogeneous respiratory motion prediction algorithms. We further address two crucial issues for developing a successful ensemble framework: (1) selection of appropriate prediction methods to ensemble (level-0 methods) among the best existing prediction methods; and (2) finding a suitable generalization approach that can successfully exploit the relative advantages of the chosen level-0 methods. The efficacy of the developed ensemble framework is assessed with real respiratory motion traces acquired from 31 patients undergoing treatment. Results show that the developed ensemble framework improves the prediction performance significantly compared to the best existing methods. Copyright © 2016 IPEM. Published by Elsevier Ltd. All rights reserved.

A recursive approach to the equations of motion for the maneuvering and control of flexible multi-body systems

NASA Technical Reports Server (NTRS)

Kwak, Moon K.; Meirovitch, Leonard

1991-01-01

Interest lies in a mathematical formulation capable of accommodating the problem of maneuvering a space structure consisting of a chain of articulated flexible substructures. Simultaneously, any perturbations from the 'rigid body' maneuvering and any elastic vibration must be suppressed. The equations of motion for flexible bodies undergoing rigid body motions and elastic vibrations can be obtained conveniently by means of Lagrange's equations in terms of quasi-coordinates. The advantage of this approach is that it yields equations in terms of body axes, which are the same axes that are used to express the control forces and torques. The equations of motion are nonlinear hybrid differential quations. The partial differential equations can be discretized (in space) by means of the finite element method or the classical Rayleigh-Ritz method. The result is a set of nonlinear ordinary differential equations of high order. The nonlinearity can be traced to the rigid body motions and the high order to the elastic vibration. Elastic motions tend to be small when compared with rigid body motions.

Tapered structure construction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smith, Eric D.; Takata, Rosalind K.; Slocum, Alexander H.

Feeding stock used to form a tapered structure into a curving device such that each point on the stock undergoes rotational motion about a peak location of the tapered structure; and the stock meets a predecessor portion of stock along one or more adjacent edges.

The Barberplaid Illusion

NASA Technical Reports Server (NTRS)

Beutter, B. R.; Mulligan, J. B.; Stone, L. S.; Statler, Irving C. (Technical Monitor)

1994-01-01

Mulligan showed that the perceived direction of a moving grating can be biased by the shape of the Gaussian window in which it is viewed. We sought to determine if a 2-D pattern with an unambiguous velocity would also show such biases. Observers viewed a drifting plaid (sum of two orthogonal 2.5 c/d sinusoidal gratings of 12% contrast, each with a TF of 4 Hz.) whose contrast was modulated spatially by a stationary, asymmetric 2-D Gaussian window (i.e. unequal standard deviations in the principal directions). The direction of plaid motion with respect to the orientation of the window's major axis (Delta Theta) was varied while all other motion parameters were held fixed. Observers reported the perceived plaid direction of motion by adjusting the orientation of a pointer. All five observers showed systematic biases in perceived plaid direction that depended on Delta Theta and the aspect ratio of the Gaussian window (lambda). For circular Gaussian windows Lambda = 1), plaid direction was veridically perceived. However, biases of up to 10 deg. were found for lambda = 2 and Delta Theta = 30 deg. These data present a challenge to models of motion perception which do not explicitly consider the integration of information across the visual field.

Let's Get Physical: Teaching Physics Through Gymnastics

NASA Astrophysics Data System (ADS)

Sojourner, Elena J.; Burgasser, Adam J.; Weise, Eric D.

2018-01-01

The concept of embodied learning—that we can learn with our bodies and with our minds—is a well-established concept in physics and math education research, and includes symbolic understanding (e.g., gestures that track how students think or facilitate learning to model complex systems of energy flow) as well as the literal experience of exploring physical phenomena through body movements. Sport has long served as a guide for both illustrating and experiencing physical concepts and phenomena, with a particularly relevant example being the sport of gymnastics. Here, the practitioner is subjected to a wide range of forces and torques, and experiences translational and rotational motions, all guided by control of body positioning, shape, strength, and leverage. Smith provides a comprehensive study of the mechanics used to analyze gymnastic movements, which includes core concepts such as force balance, leverage and torque, center of mass and stability, moment of inertia, ballistic motion, pendulum motion, and circular motion. For life science majors, gymnastics also provides relevant physical examples of biomechanics and the physical limits of biological materials (skin, bones, ligaments). The popularity of gymnastics—consider the phenomenon of Simone Biles—makes it broadly accessible and engaging, particularly across genders.

A Probabilistic Model of Spin and Spin Measurements

NASA Astrophysics Data System (ADS)

Niehaus, Arend

2016-01-01

Several theoretical publications on the Dirac equation published during the last decades have shown that, an interpretation is possible, which ascribes the origin of electron spin and magnetic moment to an autonomous circular motion of the point-like charged particle around a fixed centre. In more recent publications an extension of the original so called "Zitterbewegung Interpretation" of quantum mechanics was suggested, in which the spin results from an average of instantaneous spin vectors over a Zitterbewegung period. We argue that, the corresponding autonomous motion of the electron should, if it is real, determine non-relativistic spin measurements. Such a direct connection with the established formal quantum mechanical description of spin measurements, into which spin is introduced as a "non-classical" quantity has, to our knowledge, not been reported. In the present work we show that, under certain "model assumptions" concerning the proposed autonomous motion, results of spin measurements, including measurements of angular correlations in singlet systems, can indeed be correctly described using classical probabilities. The success of the model is evidence for the "reality" of the assumed autonomous motion. The resulting model violates the Bell—inequalities to the same extent as quantum mechanics.

Impact of Eccentricity on East-west Stationkeeping for GPS Class of Orbits

NASA Technical Reports Server (NTRS)

Ely, Todd A.

1999-01-01

There exists a strong relationship between eccentricity and the potential for a repeating groundtrack orbit to exhibit chaotic motion. This is true at all values of eccentricity, but, perhaps most dramatic, is that it is true even for orbits that are nearly circular. These complex motions can have a significant impact on the east-west stationkeeping process for maintaining the repeating groundtrack property of a commensurate orbit. Ely and Howell have shown that traditional stationkeeping (SK) methods are unable to maintain a repeating groundtrack in the presence of complex dynamics, such as with chaotic motion. They developed an alternate SK method that is able to maintain a repeating groundtrack for eccentric, commensurate orbits. The focus of the current study is to investigate orbits with characteristics that are similar to GPS satellites except with modestly larger eccentricities. It will be shown that at eccentricities larger than approx. .01 the chaotic regions become significant, and the need arises for a robust stationkeeping approach, such as developed in. FurtheRmore, the investigation will reveal that the influence of luni-solar perturbations contributes to the growth of eccentricity, thus increasing the probability of encountering chaotic motion during a typical satellite lifetime.

Altered perception of apparent motion in schizophrenia spectrum disorder.

PubMed

Tschacher, Wolfgang; Dubouloz, Priscilla; Meier, Rahel; Junghan, Uli

2008-06-30

Apparent motion (AM), the Gestalt perception of motion in the absence of physical motion, was used to study perceptual organization and neurocognitive binding in schizophrenia. Associations between AM perception and psychopathology as well as meaningful subgroups were sought. Circular and stroboscopic AM stimuli were presented to 68 schizophrenia spectrum patients and healthy participants. Psychopathology was measured using the Positive and Negative Syndrome Scale (PANSS). Psychopathology was related to AM perception differentially: Positive and disorganization symptoms were linked to reduced gestalt stability; negative symptoms, excitement and depression had opposite regression weights. Dimensions of psychopathology thus have opposing effects on gestalt perception. It was generally found that AM perception was closely associated with psychopathology. No difference existed between patients and controls, but two latent classes were found. Class A members who had low levels of AM stability made up the majority of inpatients and control subjects; such participants were generally young and male, with short reaction times. Class B typically contained outpatients and some control subjects; participants in class B were older and showed longer reaction times. Hence AM perceptual dysfunctions are not specific for schizophrenia, yet AM may be a promising stage marker.

Dynamic Portrait of the Retrograde 1:1 Mean Motion Resonance

NASA Astrophysics Data System (ADS)

Huang, Yukun; Li, Miao; Li, Junfeng; Gong, Shengping

2018-06-01

Asteroids in mean motion resonances with giant planets are common in the solar system, but it was not until recently that several asteroids in retrograde mean motion resonances with Jupiter and Saturn were discovered. A retrograde co-orbital asteroid of Jupiter, 2015 BZ509 is confirmed to be in a long-term stable retrograde 1:1 mean motion resonance with Jupiter, which gives rise to our interests in its unique resonant dynamics. In this paper, we investigate the phase-space structure of the retrograde 1:1 resonance in detail within the framework of the circular restricted three-body problem. We construct a simple integrable approximation for the planar retrograde resonance using canonical contact transformation and numerically employ the averaging procedure in closed form. The phase portrait of the retrograde 1:1 resonance is depicted with the level curves of the averaged Hamiltonian. We thoroughly analyze all possible librations in the co-orbital region and uncover a new apocentric libration for the retrograde 1:1 resonance inside the planet’s orbit. We also observe the significant jumps in orbital elements for outer and inner apocentric librations, which are caused by close encounters with the perturber.

Computational model for amoeboid motion: Coupling membrane and cytosol dynamics

NASA Astrophysics Data System (ADS)

Moure, Adrian; Gomez, Hector

2016-10-01

A distinguishing feature of amoeboid motion is that the migrating cell undergoes large deformations, caused by the emergence and retraction of actin-rich protrusions, called pseudopods. Here, we propose a cell motility model that represents pseudopod dynamics, as well as its interaction with membrane signaling molecules. The model accounts for internal and external forces, such as protrusion, contraction, adhesion, surface tension, or those arising from cell-obstacle contacts. By coupling the membrane and cytosol interactions we are able to reproduce a realistic picture of amoeboid motion. The model results are in quantitative agreement with experiments and show how cells may take advantage of the geometry of their microenvironment to migrate more efficiently.

Optical head tracking for functional magnetic resonance imaging using structured light.

PubMed

Zaremba, Andrei A; MacFarlane, Duncan L; Tseng, Wei-Che; Stark, Andrew J; Briggs, Richard W; Gopinath, Kaundinya S; Cheshkov, Sergey; White, Keith D

2008-07-01

An accurate motion-tracking technique is needed to compensate for subject motion during functional magnetic resonance imaging (fMRI) procedures. Here, a novel approach to motion metrology is discussed. A structured light pattern specifically coded for digital signal processing is positioned onto a fiduciary of the patient. As the patient undergoes spatial transformations in 6 DoF (degrees of freedom), a high-resolution CCD camera captures successive images for analysis on a computing platform. A high-speed image processing algorithm is used to calculate spatial transformations in a time frame commensurate with patient movements (10-100 ms) and with a precision of at least 0.5 microm for translations and 0.1 deg for rotations.

Modeling repetitive motions using structured light.

PubMed

Xu, Yi; Aliaga, Daniel G

2010-01-01

Obtaining models of dynamic 3D objects is an important part of content generation for computer graphics. Numerous methods have been extended from static scenarios to model dynamic scenes. If the states or poses of the dynamic object repeat often during a sequence (but not necessarily periodically), we call such a repetitive motion. There are many objects, such as toys, machines, and humans, undergoing repetitive motions. Our key observation is that when a motion-state repeats, we can sample the scene under the same motion state again but using a different set of parameters; thus, providing more information of each motion state. This enables robustly acquiring dense 3D information difficult for objects with repetitive motions using only simple hardware. After the motion sequence, we group temporally disjoint observations of the same motion state together and produce a smooth space-time reconstruction of the scene. Effectively, the dynamic scene modeling problem is converted to a series of static scene reconstructions, which are easier to tackle. The varying sampling parameters can be, for example, structured-light patterns, illumination directions, and viewpoints resulting in different modeling techniques. Based on this observation, we present an image-based motion-state framework and demonstrate our paradigm using either a synchronized or an unsynchronized structured-light acquisition method.

Identifying intrinsically disordered protein regions likely to undergo binding-induced helical transitions.

PubMed

Glover, Karen; Mei, Yang; Sinha, Sangita C

2016-10-01

Many proteins contain intrinsically disordered regions (IDRs) lacking stable secondary and ordered tertiary structure. IDRs are often implicated in macromolecular interactions, and may undergo structural transitions upon binding to interaction partners. However, as binding partners of many protein IDRs are unknown, these structural transitions are difficult to verify and often are poorly understood. In this study we describe a method to identify IDRs that are likely to undergo helical transitions upon binding. This method combines bioinformatics analyses followed by circular dichroism spectroscopy to monitor 2,2,2-trifluoroethanol (TFE)-induced changes in secondary structure content of these IDRs. Our results demonstrate that there is no significant change in the helicity of IDRs that are not predicted to fold upon binding. IDRs that are predicted to fold fall into two groups: one group does not become helical in the presence of TFE and includes examples of IDRs that form β-strands upon binding, while the other group becomes more helical and includes examples that are known to fold into helices upon binding. Therefore, we propose that bioinformatics analyses combined with experimental evaluation using TFE may provide a general method to identify IDRs that undergo binding-induced disorder-to-helix transitions. Copyright © 2016 Elsevier B.V. All rights reserved.

The transition zone above a lumbosacral fusion.

PubMed

Hambly, M F; Wiltse, L L; Raghavan, N; Schneiderman, G; Koenig, C

1998-08-15

The clinical and radiographic effect of a lumbar or lumbosacral fusion was studied in 42 patients who had undergone a posterolateral fusion with an average follow-up of 22.6 years. To examine the long-term effects of posterolateral lumbar or lumbosacral fusion on the cephalad two motion segments (transition zone). It is commonly held that accelerated degeneration occurs in the motion segments adjacent to a fusion. Most studies are of short-term, anecdotal, uncontrolled reports that pay particular attention only to the first motion segment immediately cephalad to the fusion. Forty-two patients who had previously undergone a posterolateral lumbar or lumbosacral fusion underwent radiographic and clinical evaluation. Rate of fusion, range of motion, osteophytes, degenerative spondylolisthesis, retrolisthesis, facet arthrosis, disc ossification, dynamic instability, and disc space height were all studied and statistically compared with an age- and gender-matched control group. The patient's self-reported clinical outcome was also recorded. Degenerative changes occurred at the second level above the fused levels with a frequency equal to those occurring in the first level. There was no statistical difference between the study group and the cohort group in the presence of radiographic changes within the transition zone. In those patients undergoing fusion for degenerative processes, 75% reported a good to excellent outcome, whereas 84% of those undergoing fusion for spondylolysis or spondylolisthesis reported a good to excellent outcome. Radiographic changes occur within the transition zone cephalad to a lumbar or lumbosacral fusion. However, these changes are also seen in control subjects who have had no surgery.

Mass Spectrometer Containing Multiple Fixed Collectors

NASA Technical Reports Server (NTRS)

Moskala, Robert; Celo, Alan; Voss, Guenter; Shaffer, Tom

2008-01-01

A miniature mass spectrometer that incorporates features not typically found in prior mass spectrometers is undergoing development. This mass spectrometer is designed to simultaneously measure the relative concentrations of five gases (H2, He, N2, O2, and Ar) in air, over the relative-concentration range from 10(exp -6) to 1, during a sampling time as short as 1 second. It is intended to serve as a prototype of a product line of easy-to-use, portable, lightweight, highspeed, relatively inexpensive instruments for measuring concentrations of multiple chemical species in such diverse applications as detecting explosive or toxic chemicals in air, monitoring and controlling industrial processes, measuring concentrations of deliberately introduced isotopes in medical and biological investigations, and general environmental monitoring. The heart of this mass spectrometer is an integral combination of a circular cycloidal mass analyzer, multiple fixed ion collectors, and two mass-selective ion sources. By circular cycloidal mass analyzer is meant an analyzer that includes (1) two concentric circular cylindrical electrodes for applying a radial electric field and (2) a magnet arranged to impose a magnetic flux aligned predominantly along the cylindrical axis, so that ions, once accelerated into the annulus between the electrodes, move along circular cycloidal trajectories. As in other mass analyzers, trajectory of each ion is determined by its mass-to-charge ratio, and so ions of different species can be collected simultaneously by collectors (Faraday cups) at different locations intersected by the corresponding trajectories (see figure). Unlike in other mass analyzers, the installation of additional collectors to detect additional species does not necessitate increasing the overall size of the analyzer assembly.

Theory of unfolded cyclotron accelerator

NASA Astrophysics Data System (ADS)

Rax, J.-M.; Robiche, J.

2010-10-01

An acceleration process based on the interaction between an ion, a tapered periodic magnetic structure, and a circularly polarized oscillating electric field is identified and analyzed, and its potential is evaluated. A Hamiltonian analysis is developed in order to describe the interplay between the cyclotron motion, the electric acceleration, and the magnetic modulation. The parameters of this universal class of magnetic modulation leading to continuous acceleration without Larmor radius increase are expressed analytically. Thus, this study provides the basic scaling of what appears as a compact unfolded cyclotron accelerator.

Burgers approximation for two-dimensional flow past an ellipse

NASA Technical Reports Server (NTRS)

Dorrepaal, J. M.

1982-01-01

A motivation is given for studying Burgers flow and a solution technique is outlined which works equally well for Oseen or Burgers flow past a circular cylinder. The separation behind the cylinder, the drag experienced by the cylinder, and asymptotic behavior far from the cylinder are described. It is shown that the predictions of Burgers flow near the cylinder provide a substantial improvement over those of Oseen flow. Finally, the equations of motion for Burgers flow past an ellipse are formulated and solved.

Development of the Wake Behind a Circular Cylinder Impulsively Started into Rotatory and Rectilinear Motion: Intermediate Rotation Rates

DTIC Science & Technology

1991-01-01

cylindre fixe ou en rotation. Effet Magnus . J. Mec. 14, 109-134. Taneda, S. 1977 Visual study of unsteady separated flows around bodies. Prog. Aero...enhancement schemes employing the Magnus effect (Swanson 1961). Rotating all or part of a body may also have applications in active or feedback control of...and yt into the governing equations in the generalized coordinate system. In this study, the body-fitted grid is simply one of cylindrical polar

Fluid-loop reaction system

NASA Technical Reports Server (NTRS)

Lurie, Boris J. (Inventor); Schier, J. Alan (Inventor); Iskenderian, Theodore C. (Inventor)

1991-01-01

An improved fluid actuating system for imparting motion to a body such as a spacecraft is disclosed. The fluid actuating system consists of a fluid mass that may be controllably accelerated through at least one fluid path whereby an opposite acceleration is experienced by the spacecraft. For full control of the spacecraft's orientation, the system would include a plurality of fluid paths. The fluid paths may be circular or irregular, and the fluid paths may be located on the interior or exterior of the spacecraft.

Single-Molecule Visualization of Living Polymerization

DTIC Science & Technology

2014-02-18

Brownian motion, and its horizontal mean square displacement 〈∆x2〉 or 〈∆y2〉 is directly related to the length of the polymer1 and can thus be used... movements of the particles around their respective vertical axes. Fig 6B shows the x and y positions of the two polynorbornene-tethered particles from...Fig 6A. The shorter-polynorbornene-tethered particle shows free precession movement with its x, y positions following a circular pattern with a

Novel Expressions of Equations of Relative Motion and Control in Keplerian Orbits

DTIC Science & Technology

2009-04-01

Control, and Dynamics, Vol. 29, No. 2, March– April 2006, pp. 495–499. doi:10.2514/1.19148 [12] Singla, P., Subbarao , K ., and Junkins, J. L...negative orbit normal, and thex axis is defined as i j k , where i; j and k are the basis vector of the LVLH frame. Thus, in a circular orbit, the x...a. REPORT unclassified b . ABSTRACT unclassified c. THIS PAGE unclassified Standard Form 298 (Rev. 8-98) Prescribed by ANSI Std Z39-18

Spacecraft Orbit Design in the Circular Restricted Three-Body Problem Using Higher-Dimensional Poincare Maps

DTIC Science & Technology

2013-12-01

the plane of the primary bodies. That is, motion is possible only in the x and y directions. For example, in the ...Earth-Moon planar CR3BP, the S/C path remains in the same plane as the Moon’s orbit about the Earth—more precisely, the orbit of both the Earth and...travels out of the plane of the massive primaries, in the z direction as well. Importantly, there is added complexity in the spatial

Electron kinematics in a plasma focus

NASA Technical Reports Server (NTRS)

Hohl, F.; Gary, S. P.

1977-01-01

The results of numerical integrations of the three-dimensional relativistic equations of motion of electrons subject to given electric and magnetic fields are presented. Fields due to two different models are studied: (1) a circular distribution of current filaments, and (2) a uniform current distribution; both the collapse and the current reduction phases are studied in each model. Decreasing current in the uniform current model yields 100 keV electrons accelerated toward the anode and, as for earlier ion computations, provides general agreement with experimental results.

Microwave transmission efficiency and simulations of electron plasma in ELTRAP device

NASA Astrophysics Data System (ADS)

Ikram, M.; Mushtaq, A.; Ali, S.

2017-11-01

A Thomson backscattering experiment has been performed in a Penning-Malmberg device ELTRAP. To estimate the minimum sensitivity of diagnostics, we have computed the signal to noise ratio and found that the present bunch has a number density of 4.3 × 108 cm-3, which is three orders of magnitude less than the desired density of 1011 cm-3. To increase the signal level from the RF studies to the GHz range, the transmission efficiency from the rectangular waveguide orthogonally coupled to a prototype circular waveguide was experimentally analyzed on a test-bench. It is observed that the lengths of waveguides play an important role in the transmission efficiency and return loss. When the length of the optimum rectangular waveguide (>2 λg = 31 cm) is reduced to 7 cm, due to geometrical constraints of the ELTRAP device, consequently, the transmission efficiency is also reduced and shifts away from the maximum 3 GHz operating frequency. The useful frequency band is then reduced with the increasing length of the prototype circular waveguide (102 cm). Using the electromagnetic Particle-In-Cell simulations involving the electron cyclotron resonance heating (ECRH), we have utilized a magnetic field of 0.1 T resonating with 2.8 GHz RF drive during each time step (1 ps) having the power level of 0.04 V to the middle and to the end of the trap. A more efficient increase in the radial and azimuthal temperature profiles is observed as compared to the axial temperature profile. The reason is the use of ECRH to heat electrons in cyclotron motion, which is completely kinetic and magnetron motion which is almost entirely potential based. The axial motion interchanges in between the kinetic and potential with a slight enhancement in axial motion to maintain the total canonical angular momentum conserved. The temperature profile of the confined electron plasma increases with the variation of densities from 5 × 107 m-3 to 1012 m-3. The major heating effect occurs when the RF power is injected from the position close to one end with respect to the middle position of the trap.

Automatically tracking neurons in a moving and deforming brain

PubMed Central

Nguyen, Jeffrey P.; Linder, Ashley N.; Plummer, George S.; Shaevitz, Joshua W.

2017-01-01

Advances in optical neuroimaging techniques now allow neural activity to be recorded with cellular resolution in awake and behaving animals. Brain motion in these recordings pose a unique challenge. The location of individual neurons must be tracked in 3D over time to accurately extract single neuron activity traces. Recordings from small invertebrates like C. elegans are especially challenging because they undergo very large brain motion and deformation during animal movement. Here we present an automated computer vision pipeline to reliably track populations of neurons with single neuron resolution in the brain of a freely moving C. elegans undergoing large motion and deformation. 3D volumetric fluorescent images of the animal’s brain are straightened, aligned and registered, and the locations of neurons in the images are found via segmentation. Each neuron is then assigned an identity using a new time-independent machine-learning approach we call Neuron Registration Vector Encoding. In this approach, non-rigid point-set registration is used to match each segmented neuron in each volume with a set of reference volumes taken from throughout the recording. The way each neuron matches with the references defines a feature vector which is clustered to assign an identity to each neuron in each volume. Finally, thin-plate spline interpolation is used to correct errors in segmentation and check consistency of assigned identities. The Neuron Registration Vector Encoding approach proposed here is uniquely well suited for tracking neurons in brains undergoing large deformations. When applied to whole-brain calcium imaging recordings in freely moving C. elegans, this analysis pipeline located 156 neurons for the duration of an 8 minute recording and consistently found more neurons more quickly than manual or semi-automated approaches. PMID:28545068

Automatically tracking neurons in a moving and deforming brain.

PubMed

Nguyen, Jeffrey P; Linder, Ashley N; Plummer, George S; Shaevitz, Joshua W; Leifer, Andrew M

2017-05-01

Advances in optical neuroimaging techniques now allow neural activity to be recorded with cellular resolution in awake and behaving animals. Brain motion in these recordings pose a unique challenge. The location of individual neurons must be tracked in 3D over time to accurately extract single neuron activity traces. Recordings from small invertebrates like C. elegans are especially challenging because they undergo very large brain motion and deformation during animal movement. Here we present an automated computer vision pipeline to reliably track populations of neurons with single neuron resolution in the brain of a freely moving C. elegans undergoing large motion and deformation. 3D volumetric fluorescent images of the animal's brain are straightened, aligned and registered, and the locations of neurons in the images are found via segmentation. Each neuron is then assigned an identity using a new time-independent machine-learning approach we call Neuron Registration Vector Encoding. In this approach, non-rigid point-set registration is used to match each segmented neuron in each volume with a set of reference volumes taken from throughout the recording. The way each neuron matches with the references defines a feature vector which is clustered to assign an identity to each neuron in each volume. Finally, thin-plate spline interpolation is used to correct errors in segmentation and check consistency of assigned identities. The Neuron Registration Vector Encoding approach proposed here is uniquely well suited for tracking neurons in brains undergoing large deformations. When applied to whole-brain calcium imaging recordings in freely moving C. elegans, this analysis pipeline located 156 neurons for the duration of an 8 minute recording and consistently found more neurons more quickly than manual or semi-automated approaches.

Manual calf massage and passive ankle motion reduce the incidence of deep vein thromboembolism after total hip arthroplasty.

PubMed

Imai, Norio; Ito, Tomoyuki; Suda, Ken; Miyasaka, Dai; Endo, Naoto

2017-07-01

Venous thromboembolism is one of the general complications following total hip arthroplasty, wherein various preventive treatments have been recommended. Several studies reported that venous thromboembolism incidence after total hip arthroplasty was similar in patients who were administered prophylaxis with a conventional mechanical procedure alone, and those who were administered pharmacological anticoagulation therapy. Therefore, the optimum methods of prophylaxis are still controversial. The purpose of this study was to investigate whether manual calf massage and passive ankle motion could lower the risk for venous thromboembolism after total hip arthroplasty. We retrospectively reviewed the data of 126 consecutive patients undergoing elective primary unilateral total hip arthroplasty wherein manual calf massage and passive ankle motion were performed after the surgery at our hospitals between January and October 2014. The 138 patients of the control group underwent total hip arthroplasty using the same surgical approach and pre- and postoperative protocols without this mechanical prophylaxis between January and December 2013. This mechanical prophylaxis was performed simultaneously 30 times during approximately 10 s; these procedures were repeated thrice immediately after total hip arthroplasty. Duplex ultrasonography was performed to observe the veins of both legs in all the patients on postoperative day 7. The incidence of deep vein thrombosis was 6.52% and 0.79% in the control and manual calf massage and passive ankle motion groups, respectively. The odds ratio for the manual calf massage and passive ankle motion groups was 8.72. Performing this mechanical prophylaxis reduced the incidence of venous thromboembolism after total hip arthroplasty. This mechanical prophylaxis is not only simple and easy, but is also safe and inexpensive. We therefore recommend that manual calf massage and passive ankle motion be performed in patients who will undergo total hip arthroplasty, if deep vein thrombosis does not exist before the surgery. Copyright © 2017 The Japanese Orthopaedic Association. Published by Elsevier B.V. All rights reserved.

Forward and backward motion of artificial helical swimmers in cylindrical channels

NASA Astrophysics Data System (ADS)

Acemoglu, Alperen; Temel, Fatma Zeynep; Yesilyurt, Serhat

2013-11-01

Motion of micro swimmers in confined geometries such as channels is important due to its relevance in in vivo medical applications such as minimally invasive surgery and drug delivery. Here, swimmers with diameters 0.8 mm and lengths 2 to 3 mm are produced with a 3D printer and cylindrical Nd2Fe14B magnets are placed inside the bodies. Rotating external magnetic field is used for the actuation of artificial swimmers. Different body and tail geometries are produced and experiments are conducted with a glycerol filled circular channel. Result demonstrate that decreasing channel diameter directly affects the forward motion of the swimmer due to the increasing drag. It is observed that step-out frequency, which defines maximum frequency at which the swimmer can establish a synchronous rotation with the external magnetic field, depends on the geometry of the swimmer and the channel diameter. There are significant differences between low and high frequency motion and forward and backward swimming. Longer tails enable higher forward velocities in high frequencies than backward ones, whereas forward and backward velocities are approximately the same at low frequencies. Furthermore backward motion is more stable than the forward one; at high frequencies, swimmers travel almost at the center of the channel for backward motion, and follow a helical trajectory near the wall during the forward motion. According to simulation results there is a flow which is induced by the rotation of the swimmer rotation that affects the swimmer's trajectory. We acknowledge the support from TUBITAK (Techonological & Research Council of Turkey) under the grant no: 111M376.

Motion in a central field in the presence of a constant perturbing acceleration in a co-moving coordinate system

NASA Astrophysics Data System (ADS)

Sannikova, T. N.; Kholshevnikov, K. V.

2015-08-01

The motion of a point mass under the action of a gravitational force toward a central body and a perturbing acceleration P is considered. The magnitude of P is taken to be small compared to the main gravitational acceleration due to the central body, and the direction of P to be constant in a standard astronomical coordinate system with its origin at the central body and axes directed along the radius vector, the transversal, and the binormal. Consideration of a constant vector perturbing acceleration simplifies averaging of the Euler equations for the motion in osculating elements, making it straightforward to obtain evolutionary differential equations of motion in the mean elements, as was done earlier in a first small-parameter approximation. This paper is devoted to integration of the mean equations. The system is integratable by quadratures if at least one component of the perturbing acceleration is zero, and also if the orbit is initially circular. Moreover, all the quadratures can be expressed in terms of elementary functions and elliptical integrals of the first kind in Jacobi form. If all three components of P are non-zero, this problem reduces to a system of two first-order differential equations, which are apparently not integrable. Possible applications include the motion of natural and artificial satellites taking into account light pressure, the motion of a spacecraft with low thrust, and the motion of an asteroid subject to a thrust from an engine mounted on it or to a gravitational tractor designed, for example, to avoid a collision with Earth.

Ponderomotive ion acceleration in dense magnetized laser-irradiated thick target plasmas

NASA Astrophysics Data System (ADS)

Sinha, Ujjwal; Kaw, Predhiman

2012-03-01

When a circularly polarized laser pulse falls on an overdense plasma, it displaces the electrons via ponderomotive force creating a double layer. The double layer constitutes of an ion and electron sheath with in which the electrostatic field present is responsible for ion acceleration. In this paper, we have analyzed the effect a static longitudinal magnetic field has over the ion acceleration mechanism. The longitudinal magnetic field changes the plasma dielectric constant due to cyclotron effects which in turn enhances or reduces the ponderomotive force exerted by the laser depending on whether the laser is left or right circularly polarized. Also, the analysis of the ion space charge region present behind the ion sheath of the laser piston that undergoes coulomb explosion has been explored for the first time. We have studied the interaction of an incoming ion beam with the laser piston and the ion space charge. It has been found that the exploding ion space charge has the ability to act as an energy amplifier for incoming ion beams.

Development and clinical evaluation of a simple optical method to detect and measure patient external motion.

PubMed

Barbés, Benigno; Azcona, Juan Diego; Prieto, Elena; de Foronda, José Manuel; García, Marina; Burguete, Javier

2015-09-08

A simple and independent system to detect and measure the position of a number of points in space was devised and implemented. Its application aimed to detect patient motion during radiotherapy treatments, alert of out-of-tolerances motion, and record the trajectories for subsequent studies. The system obtains the 3D position of points in space, through its projections in 2D images recorded by two cameras. It tracks black dots on a white sticker placed on the surface of the moving object. The system was tested with linear displacements of a phantom, circular trajectories of a rotating disk, oscillations of an in-house phantom, and oscillations of a 4D phantom. It was also used to track 461 trajectories of points on the surface of patients during their radiotherapy treatments. Trajectories of several points were reproduced with accuracy better than 0.3 mm in the three spatial directions. The system was able to follow periodic motion with amplitudes lower than 0.5 mm, to follow trajectories of rotating points at speeds up to 11.5 cm/s, and to track accurately the motion of a respiratory phantom. The technique has been used to track the motion of patients during radiotherapy and to analyze that motion. The method is flexible. Its installation and calibration are simple and quick. It is easy to use and can be implemented at a very affordable price. Data collection does not involve any discomfort to the patient and does not delay the treatment, so the system can be used routinely in all treatments. It has an accuracy similar to that of other, more sophisticated, commercially available systems. It is suitable to implement a gating system or any other application requiring motion detection, such as 4D CT, MRI or PET.

Chirality sensing with stereodynamic biphenolate zinc complexes.

PubMed

Bentley, Keith W; de Los Santos, Zeus A; Weiss, Mary J; Wolf, Christian

2015-10-01

Two bidentate ligands consisting of a fluxional polyarylacetylene framework with terminal phenol groups were synthesized. Reaction with diethylzinc gives stereodynamic complexes that undergo distinct asymmetric transformation of the first kind upon binding of chiral amines and amino alcohols. The substrate-to-ligand chirality imprinting at the zinc coordination sphere results in characteristic circular dichroism signals that can be used for direct enantiomeric excess (ee) analysis. This chemosensing approach bears potential for high-throughput ee screening with small sample amounts and reduced solvent waste compared to traditional high-performance liquid chromatography methods. © 2015 Wiley Periodicals, Inc.

System Architectures Near the 2:1 Resonance

NASA Astrophysics Data System (ADS)

Boisvert, John; Steffen, Jason H.; Nelson, Benjamin E.

2018-01-01

Uncovering the architectures of planetary systems give insight into their formation and evolution. For example, the protoplanetary disk in multi-planet systems can drive adjacent planets into mean-motion resonances (such as the 2:1), while simultaneously damping their eccentricities. On the other hand, planet-planet scattering will produce single planets with eccentric orbits.In the RV signal, there is a degeneracy between models with two planets on circular orbits near the 2:1 period ratio and single planets on eccentric orbits. Historically, single planet models have been favored on simplicity grounds. However, the prominence of the 2:1 period ratio for systems observed by Kepler motivates additional scrutiny for single eccentric systems.We analyzed 95 planetary systems from the NASA Exoplanet Archive that are reported as single planet systems. We fit models of single eccentrics, circular doubles with a period ratio of 2:1, and circular doubles with a period ratio near 2.17:1 to the data. We computed the Bayes factors between each model in order to determine which is more likely given the current data. We find a significant fraction of these systems prefer double planet models. New observations are being planned to further break the degeneracy for these systems. This fraction suggests that disk-migration may be more important than the currently reported parameters propose.

Movement compatibility for frontal controls with displays located in four cardinal orientations.

PubMed

Chan, Alan H S; Hoffmann, Errol R

2010-12-01

Strength and reversibility of direction-of-motion stereotypes and response times are presented for different configurations of horizontal, vertical and rotary controls with horizontal, vertical and circular displays. Measures of the strength and reversibility of stereotypes were used to analyse the effects of direction of turn instruction (clockwise/anticlockwise; up/down; left/right), display orientation (North; East; South; West) and hand side (left/right) on movement compatibility. A number of acceptable display/control arrangements were identified for displays in each of the North, East, South and West orientations relative to the operator. For the horizontally moving control, the Worringham and Beringer principle was found to identify display/control arrangements having both high stereotype strength and high reversibility. Vertically moving controls are excellent with vertical displays but poor with horizontal and circular displays. Rotary controls have high stereotype strength and reversibility with both horizontal and circular displays (with the indicator at the 12 o'clock position). STATEMENT OF RELEVANCE: Design of display/control arrangements requires a strong relationship between operator's expectancies and the response of a device to control inputs. The present research fills in gaps for stereotypes where data are not available, in particular where the operator is not seated facing a display directly to the front.

A complete system for 3D reconstruction of roots for phenotypic analysis.

PubMed

Kumar, Pankaj; Cai, Jinhai; Miklavcic, Stanley J

2015-01-01

Here we present a complete system for 3D reconstruction of roots grown in a transparent gel medium or washed and suspended in water. The system is capable of being fully automated as it is self calibrating. The system starts with detection of root tips in root images from an image sequence generated by a turntable motion. Root tips are detected using the statistics of Zernike moments on image patches centred on high curvature points on root boundary and Bayes classification rule. The detected root tips are tracked in the image sequence using a multi-target tracking algorithm. Conics are fitted to the root tip trajectories using a novel ellipse fitting algorithm which weighs the data points by its eccentricity. The conics projected from the circular trajectory have a complex conjugate intersection which are image of the circular points. Circular points constraint the image of the absolute conics which are directly related to the internal parameters of the camera. The pose of the camera is computed from the image of the rotation axis and the horizon. The silhouettes of the roots and camera parameters are used to reconstruction the 3D voxel model of the roots. We show the results of real 3D reconstruction of roots which are detailed and realistic for phenotypic analysis.

Face-Sealing Butterfly Valve

NASA Technical Reports Server (NTRS)

Tervo, John N.

1992-01-01

Valve plate made to translate as well as rotate. Valve opened and closed by turning shaft and lever. Interactions among lever, spring, valve plate, and face seal cause plate to undergo combination of translation and rotation so valve plate clears seal during parts of opening and closing motions.

Ring-through-ring molecular shuttling in a saturated [3]rotaxane

NASA Astrophysics Data System (ADS)

Zhu, Kelong; Baggi, Giorgio; Loeb, Stephen J.

2018-06-01

Mechanically interlocked molecules such as rotaxanes and catenanes comprise two or more components whose motion relative to each other can be controlled. A [2]rotaxane molecular shuttle, for example, consists of an axle bearing two recognition sites and a single macrocyclic wheel that can undergo a to-and-fro motion along the axle—shuttling between the recognition sites. The ability of mechanically interlocked molecules to undergo this type of large-amplitude change is the core mechanism behind almost every interlocked molecular switch or machine, including sophisticated mechanical systems such as a molecular elevator and a peptide synthesizer. Here, as a way to expand the scope of dynamics possible at the molecular level, we have developed a molecular shuttling mechanism involving the exchange of rings between two recognition sites in a saturated [3]rotaxane (one with no empty recognition sites). This was accomplished by passing a smaller ring through a larger one, thus achieving ring-through-ring molecular shuttling.

Piecewise mass flows within a solar prominence observed by the New Vacuum Solar Telescope

NASA Astrophysics Data System (ADS)

Li, Hongbo; Liu, Yu; Tam, Kuan Vai; Zhao, Mingyu; Zhang, Xuefei

2018-06-01

The material of solar prominences is often observed in a state of flowing. These mass flows (MF) are important and useful for us to understand the internal structure and dynamics of prominences. In this paper, we present a high resolution Hα observation of MFs within a quiescent solar prominence. From the observation, we find that the plasma primarily has a circular motion and a downward motion separately in the middle section and legs of the prominence, which creates a piecewise mass flow along the observed prominence. Moreover, the observation also shows a clear displacement of MF's velocity peaks in the middle section of the prominence. All of these provide us with a detailed record of MFs within a solar prominence and show a new approach to detecting the physical properties of prominence.

The Inertia Coefficients of an Airship in a Frictionless Fluid

NASA Technical Reports Server (NTRS)

Bateman, H.

1979-01-01

The apparent inertia of an airship hull is examined. The exact solution of the aerodynamical problem is studied for hulls of various shapes with special attention given to the case of an ellipsoidal hull. So that the results for the ellipsoidal hull may be readily adapted to other cases, they are expressed in terms of the area and perimeter of the largest cross section perpendicular to the direction of motion by means of a formula involving a coefficient kappa which varies only slowly when the shape of the hull is changed, being 0.637 for a circular or elliptic disk, 0.5 for a sphere, and about 0.25 for a spheroid of fineness ratio. The case of rotation of an airship hull is investigated and a coefficient is defined with the same advantages as the corresponding coefficient for rectilinear motion.

Large Eddy Simulation of a Turbulent Jet

NASA Technical Reports Server (NTRS)

Webb, A. T.; Mansour, Nagi N.

2001-01-01

Here we present the results of a Large Eddy Simulation of a non-buoyant jet issuing from a circular orifice in a wall, and developing in neutral surroundings. The effects of the subgrid scales on the large eddies have been modeled with the dynamic large eddy simulation model applied to the fully 3D domain in spherical coordinates. The simulation captures the unsteady motions of the large-scales within the jet as well as the laminar motions in the entrainment region surrounding the jet. The computed time-averaged statistics (mean velocity, concentration, and turbulence parameters) compare well with laboratory data without invoking an empirical entrainment coefficient as employed by line integral models. The use of the large eddy simulation technique allows examination of unsteady and inhomogeneous features such as the evolution of eddies and the details of the entrainment process.

Black hole binary inspiral: Analysis of the plunge

NASA Astrophysics Data System (ADS)

Price, Richard H.; Nampalliwar, Sourabh; Khanna, Gaurav

2016-02-01

Binary black hole coalescence has its peak of gravitational-wave generation during the "plunge," the transition from quasicircular early motion to late quasinormal ringing (QNR). Although advances in numerical relativity have provided plunge waveforms, there is still no intuitive or phenomenological understanding of plunge comparable to that of the early and late stages. Here we make progress in developing such understanding by relying on insights of the linear mathematics of the particle perturbation model for the extreme mass limit. Our analysis, based on the Fourier-domain Green function, and a simple initial model, point to the crucial role played by the kinematics near the "light ring" (the circular photon orbit) in determining the plunge radiation and the excitation of QNR. That insight is then shown to successfully explain results obtained for particle motion in a Schwarzschild background.

Change of temporal-order judgment of sounds during long-lasting exposure to large-field visual motion.

PubMed

Teramoto, Wataru; Watanabe, Hiroshi; Umemura, Hiroyuki

2008-01-01

The perceived temporal order of external successive events does not always follow their physical temporal order. We examined the contribution of self-motion mechanisms in the perception of temporal order in the auditory modality. We measured perceptual biases in the judgment of the temporal order of two short sounds presented successively, while participants experienced visually induced self-motion (yaw-axis circular vection) elicited by viewing long-lasting large-field visual motion. In experiment 1, a pair of white-noise patterns was presented to participants at various stimulus-onset asynchronies through headphones, while they experienced visually induced self-motion. Perceived temporal order of auditory events was modulated by the direction of the visual motion (or self-motion). Specifically, the sound presented to the ear in the direction opposite to the visual motion (ie heading direction) was perceived prior to the sound presented to the ear in the same direction. Experiments 2A and 2B were designed to reduce the contributions of decisional and/or response processes. In experiment 2A, the directional cueing of the background (left or right) and the response dimension (high pitch or low pitch) were not spatially associated. In experiment 2B, participants were additionally asked to report which of the two sounds was perceived 'second'. Almost the same results as in experiment 1 were observed, suggesting that the change in temporal order of auditory events during large-field visual motion reflects a change in perceptual processing. Experiment 3 showed that the biases in the temporal-order judgments of auditory events were caused by concurrent actual self-motion with a rotatory chair. In experiment 4, using a small display, we showed that 'pure' long exposure to visual motion without the sensation of self-motion was not responsible for this phenomenon. These results are consistent with previous studies reporting a change in the perceived temporal order of visual or tactile events depending on the direction of self-motion. Hence, large-field induced (ie optic flow) self-motion can affect the temporal order of successive external events across various modalities.

Modeling microcapsules that communicate through nanoparticles to undergo self-propelled motion.

PubMed

Usta, O Berk; Alexeev, Alexander; Zhu, Guangdong; Balazs, Anna C

2008-03-01

Using simulation and theory, we demonstrate how nanoparticles can be harnessed to regulate the interaction between two initially stationary microcapsules on a surface and promote the self-propelled motion of these capsules along the substrate. The first microcapsule, the "signaling" capsule, encases nanoparticles, which diffuse from the interior of this carrier and into the surrounding solution; the second capsule is the "target" capsule, which is initially devoid of particles. Nanoparticles released from the signaling capsule modify the underlying substrate and thereby initiate the motion of the target capsule. The latter motion activates hydrodynamic interactions, which trigger the signaling capsule to follow the target. The continued release of the nanoparticles sustains the motion of both capsules. In effect, the system constitutes a synthetic analogue of biological cell signaling and our findings can shed light on fundamental physical forces that control interactions between cells. Our findings can also yield guidelines for manipulating the interactions of synthetic microcapsules in microfluidic devices.

Planned secondary wound closure at the circular stapler insertion site after laparoscopic gastric bypass reduces postoperative morbidity, costs, and hospital stay.

PubMed

Vetter, Diana; Raptis, Dimitri Aristotle; Giama, Mira; Hosa, Hanna; Muller, Markus K; Nocito, Antonio; Schiesser, Marc; Moos, Rudolf; Bueter, Marco

2017-12-01

The aims of the present study were to assess whether planned secondary wound closure at the insertion site of the circular stapler reduces wound infection rate and postoperative morbidity after laparoscopic Roux-en-Y gastric bypass (RYGB) and to identify independent predictive factors increasing the risk for wound infections after RYGB. This paper is a retrospective single-center analysis of a prospectively collected database of 1400 patients undergoing RYGB surgery in circular technique between June 2000 and June 2016. Planned secondary wound closure at the circular stapler introduction site was performed at postoperative day 3 in 291 (20.8%) consecutive patients and compared to a historical control of 1109 (79.2%) consecutive patients with primary wound closure. Independent predictive factors for wound infection were assessed by multivariable analysis. Secondary wound closure significantly decreased wound infection rate from 9.3% (103/1109) to 1% (3/291) (p < 0.001) leading to a shorter hospital stay (mean 9 (SD8) vs. 7 days (SD2), p < 0.001), lower costs (p = 0.039), and reduced postoperative morbidity (mean 90-day Comprehensive Complication Index (CCI) 7.4 (SD14.0) vs. 5.1 (SD11.1) p = 0.008) when compared to primary wound closure. Primary wound closure, dyslipidemia, and preoperative gastritis were independent predictive risk factors for developing wound infections both in the univariate (p < 0.001; p = 0.048; p = 0.003) and multivariable analysis (p < 0.001; p = 0.040; p = 0.012). Further, on multivariable analysis, the female gender was a predictive factor (p = 0.034) for wound infection development. Secondary wound closure at the circular stapler introduction site in laparoscopic RYGB significantly reduces the overall wound infection rate as well as postoperative morbidity, costs, and hospital stay when compared to primary wound closure.

Exact solutions to the Mo-Papas and Landau-Lifshitz equations

NASA Astrophysics Data System (ADS)

Rivera, R.; Villarroel, D.

2002-10-01

Two exact solutions of the Mo-Papas and Landau-Lifshitz equations for a point charge in classical electrodynamics are presented here. Both equations admit as an exact solution the motion of a charge rotating with constant speed in a circular orbit. These equations also admit as an exact solution the motion of two identical charges rotating with constant speed at the opposite ends of a diameter. These exact solutions allow one to obtain, starting from the equation of motion, a definite formula for the rate of radiation. In both cases the rate of radiation can also be obtained, with independence of the equation of motion, from the well known fields of a point charge, that is, from the Maxwell equations. The rate of radiation obtained from the Mo-Papas equation in the one-charge case coincides with the rate of radiation that comes from the Maxwell equations; but in the two-charge case the results do not coincide. On the other hand, the rate of radiation obtained from the Landau-Lifshitz equation differs from the one that follows from the Maxwell equations in both the one-charge and two-charge cases. This last result does not support a recent statement by Rohrlich in favor of considering the Landau-Lifshitz equation as the correct and exact equation of motion for a point charge in classical electrodynamics.

Angle-dependent rotation of calcite in elliptically polarized light

NASA Astrophysics Data System (ADS)

Herne, Catherine M.; Cartwright, Natalie A.; Cattani, Matthew T.; Tracy, Lucas A.

2017-08-01

Calcite crystals trapped in an elliptically polarized laser field exhibit intriguing rotational motion. In this paper, we show measurements of the angle-dependent motion, and discuss how the motion of birefringent calcite can be used to develop a reliable and efficient process for determining the polarization ellipticity and orientation of a laser mode. The crystals experience torque in two ways: from the transfer of spin angular momentum (SAM) from the circular polarization component of the light, and from a torque due to the linear polarization component of the light that acts to align the optic axis of the crystal with the polarization axis of the light. These torques alternatingly compete with and amplify each other, creating an oscillating rotational crystal velocity. We model the behavior as a rigid body in an angle-dependent torque. We experimentally demonstrate the dependence of the rotational velocity on the angular orientation of the crystal by placing the crystals in a sample solution in our trapping region, and observing their behavior under different polarization modes. Measurements are made by acquiring information simultaneously from a quadrant photodiode collecting the driving light after it passes through the sample region, and by imaging the crystal motion onto a camera. We finish by illustrating how to use this model to predict the ellipticity of a laser mode from rotational motion of birefringent crystals.

Wing Rock Motion and its Flow Mechanism over a Chined-Body Configuration

NASA Astrophysics Data System (ADS)

Wang, Yankui; Li, Qian; Shi, Wei

2015-11-01

Wing rock motion is one kind of uncommanded oscillation around the body axis over the most of the aircraft at enough high angle of attack and has a strong threat to the flight safety. The purpose of this paper is to investigate the wing rock motion over a typical body-wing configuration with a chined fuselage at fixed angle of attack firstly and four kinds of wing rock motion are revealed based on the flow phenomena, namely non-oscillation, lateral deflection, limit-cycle oscillation and irregular oscillation. Simultaneously, some special relationship between the wing rock motion and the flow over the chined body configuration are discussed. In addition, the evolution of wing rock motion and its corresponding flows when the model undergoes pitching up are also given out. All the experiments have been conducted in a low-speed wind tunnel at a Reynolds number of 1.87*10E5 and angle of attack from 0deg to 65deg. National Natural Science Foundation of China(11472028) and Open fund from State Key Laboratory of Aerodynamics.

Nanoscopic dynamics of bicontinous microemulsions: effect of membrane associated protein

DOE PAGES

Sharma, V. K.; Hayes, Douglas G.; Urban, Volker S.; ...

2017-06-12

Bicontinous microemulsions (BμE) generally consist of nanodomains formed by surfactant in a mixture of water and oil at nearly equal proportions and are potential candidates for the solubilization and purification of membrane proteins. In this paper, we present the first time report of nanoscopic dynamics of surfactant monolayers within BμEs formed by the anionic surfactant sodium dodecyl sulfate (SDS) measured on the nanosecond to picosecond time scale using quasielastic neutron scattering (QENS). BμEs investigated herein consisted of middle phases isolated from Winsor-III microemulsion systems that were formed by mixing aqueous and oil solutions under optimal conditions. QENS data indicates thatmore » surfactants undergo two distinct motions, namely (i) lateral motion along the surface of the oil nanodomains and (ii) localized internal motion. Lateral motion can be described using a continuous diffusion model, from which the lateral diffusion coefficient is obtained. Internal motion of surfactant is described using a model which assumes that a fraction of the surfactants’ hydrogens undergoes localized translational diffusion that could be considered confined within a spherical volume. The effect of cytochrome c, an archetypal membrane-associated protein known to strongly partition near the surfactant head groups in BμEs (a trend supported by small-angle X-ray scattering [SAXS] analysis), on the dynamics of BμE has also been investigated. QENS results demonstrated that cytochrome c significantly hindered both the lateral and the internal motions of surfactant. The lateral motion was more strongly affected: a reduction of the lateral diffusion coefficient by 33% was measured. This change is mainly attributable to the strong association of cytochrome c with oppositely charged SDS. In contrast, analysis of SAXS data suggested that thermal fluctuations (for a longer length and slower time scale compared to QENS) were increased upon incorporation of cytochrome c. Finally, this study demonstrates the utility of QENS for evaluating dynamics of BμEs in nanoscopic region, and that proteins directly affect the microscopic dynamics, which is of relevance for evaluating release kinetics of encapsulated drugs from BμE delivery systems and the use of BμEs as biomembrane mimetic systems for investigating membrane protein–biomembrane interactions.« less

Implementation of Free-Formulation-Based Flat Shell Elements into NASA Comet Code and Development of Nonlinear Shallow Shell Element

NASA Technical Reports Server (NTRS)

Barut, A.; Madenci, Erdogan; Tessler, A.

1997-01-01

This study presents a transient nonlinear finite element analysis within the realm of a multi-body dynamics formulation for determining the dynamic response of a moderately thick laminated shell undergoing a rapid and large rotational motion and nonlinear elastic deformations. Nonlinear strain measure and rotation, as well as 'the transverse shear deformation, are explicitly included in the formulation in order to capture the proper motion-induced stiffness of the laminate. The equations of motion are derived from the virtual work principle. The analysis utilizes a shear deformable shallow shell element along with the co-rotational form of the updated Lagrangian formulation. The shallow shell element formulation is based on the Reissner-Mindlin and Marguerre theory.

Feedback control of vibrations in a moving flexible robot arm with rotary and prismatic joints

NASA Technical Reports Server (NTRS)

Wang, P. K. C.; Wei, Jin-Duo

1987-01-01

A robot with a long extendible flexible arm which can also undergo both vertical translation and rotary motion is considered. First, A distributed-parameter model for the robot arm dynamics is developed. It is found that the extending motion could enhance the arm vibrations. Then, a Galerkin-type approximation based on an appropriate time-dependent basis for the solution space is used to obtain an approximate finite-dimensional model for simulation studies. A feedback control for damping the motion-induced vibrations is derived by considering the time rate-of-change of the total vibrational energy of the flexible arm. The authors conclude with some simulation results for a special case with the proposed control law.

Dynamics with a Nonstandard Inertia-Acceleration Relation: An Alternative to Dark Matter in Galactic Systems

NASA Astrophysics Data System (ADS)

Milgrom, M.

1994-02-01

We investigate particle dynamics that is governed by a nonstandard kinetic action of a special form. We are guided by a phenomenological scheme-the modified dynamics (MOND)-that imputes the mass discrepancy, observed in galactic systems, not to the presence of dark matter, but to a departure from Newtonian dynamics below a certain scale of accelerations, a0. The particle's equation of motion in a potential φ is derived from an action, S, of the form S ~ Sk[r(t), a0] - ∫ φ dt. The limit a0 --> 0 corresponds to Newtonian dynamics, and there the kinetic action Sk must take the standard form. In the opposite limit, a0 --> ∞ we require Sk --> 0-and more specifically, for circular orbits Sk ~ a-10-in order to attain the phenomenological success of MOND. Galilei-invariant such theories must be strongly nonlocal. This is a blessing, as such theories need not suffer from the illnesses that are endemic to higher-derivative theories. We comment on the possibility that such a modified law of motion is an effective theory resulting from the elimination of degrees of freedom pertaining to the universe at large (the near equality a0 ≍ cH0 being a trace of that connection). We derive a general virial relation for bounded trajectories. Exact solutions are obtained for circular orbits, which pertain to rotation curves of disk galaxies. We also explore, in passing, theories that depart from the conventional Newtonian dynamics for very low frequencies.

L^1 -optimality conditions for the circular restricted three-body problem

NASA Astrophysics Data System (ADS)

Chen, Zheng

2016-11-01

In this paper, the L^1 -minimization for the translational motion of a spacecraft in the circular restricted three-body problem (CRTBP) is considered. Necessary conditions are derived by using the Pontryagin Maximum Principle (PMP), revealing the existence of bang-bang and singular controls. Singular extremals are analyzed, recalling the existence of the Fuller phenomenon according to the theories developed in (Marchal in J Optim Theory Appl 11(5):441-486, 1973; Zelikin and Borisov in Theory of Chattering Control with Applications to Astronautics, Robotics, Economics, and Engineering. Birkhäuser, Basal 1994; in J Math Sci 114(3):1227-1344, 2003). The sufficient optimality conditions for the L^1 -minimization problem with fixed endpoints have been developed in (Chen et al. in SIAM J Control Optim 54(3):1245-1265, 2016). In the current paper, we establish second-order conditions for optimal control problems with more general final conditions defined by a smooth submanifold target. In addition, the numerical implementation to check these optimality conditions is given. Finally, approximating the Earth-Moon-Spacecraft system by the CRTBP, an L^1 -minimization trajectory for the translational motion of a spacecraft is computed by combining a shooting method with a continuation method in (Caillau et al. in Celest Mech Dyn Astron 114:137-150, 2012; Caillau and Daoud in SIAM J Control Optim 50(6):3178-3202, 2012). The local optimality of the computed trajectory is asserted thanks to the second-order optimality conditions developed.

Tracking and characterizing the head motion of unanaesthetized rats in positron emission tomography

PubMed Central

Kyme, Andre; Meikle, Steven; Baldock, Clive; Fulton, Roger

2012-01-01

Positron emission tomography (PET) is an important in vivo molecular imaging technique for translational research. Imaging unanaesthetized rats using motion-compensated PET avoids the confounding impact of anaesthetic drugs and enables animals to be imaged during normal or evoked behaviour. However, there is little published data on the nature of rat head motion to inform the design of suitable marker-based motion-tracking set-ups for brain imaging—specifically, set-ups that afford close to uninterrupted tracking. We performed a systematic study of rat head motion parameters for unanaesthetized tube-bound and freely moving rats with a view to designing suitable motion-tracking set-ups in each case. For tube-bound rats, using a single appropriately placed binocular tracker, uninterrupted tracking was possible greater than 95 per cent of the time. For freely moving rats, simulations and measurements of a live subject indicated that two opposed binocular trackers are sufficient (less than 10% interruption to tracking) for a wide variety of behaviour types. We conclude that reliable tracking of head pose can be achieved with marker-based optical-motion-tracking systems for both tube-bound and freely moving rats undergoing PET studies without sedation. PMID:22718992

Measurement of the passive stiffness of ankle joint in 3 DOF using stewart platform type ankle foot device.

PubMed

Nomura, Kenta; Yonezawa, Teru; Mizoguchi, Hiroshi; Takemura, Hiroshi

2016-08-01

This paper presents a method to measure the passive stiffness of an ankle joint in three degrees of freedom (DOF) under two motion speeds (1 Hz and 5 degree/s) using a developed Stewart platform-type device. The developed device can reproduce input motions of the foot in 6 DOF by controlling six pneumatic linear motion actuators. We used the device to measure the passive stiffness of an ankle joint undergoing three kinds of motion, namely dorsi-plantar flexion, inversion-eversion, and adduction-abduction. The measured values of the passive stiffness of the ankle joint in dorsiflexion that we obtained agreed well with that obtained in a previous study, indicating that the developed device is useful for measuring the passive stiffness of ankle joint. In addition, the developed device can be used to measure the stiffness in inversion-eversion and adduction-abduction motions as well, parameters that have never been measured. The results we obtained demonstrated certain interesting features as we varied both the direction and pace of motion (e.g., there were significant differences in the stiffness not only between adduction and abduction during the faster pace, but also between these and the other motions).

Slewing maneuvers and vibration control of space structures by feedforward/feedback moment-gyro controls

NASA Technical Reports Server (NTRS)

Yang, Li-Farn; Mikulas, Martin M., Jr.; Park, K. C.; Su, Renjeng

1993-01-01

This paper presents a moment-gyro control approach to the maneuver and vibration suppression of a flexible truss arm undergoing a constant slewing motion. The overall slewing motion is triggered by a feedforward input, and a companion feedback controller is employed to augment the feedforward input and subsequently to control vibrations. The feedforward input for the given motion requirement is determined from the combined CMG (Control Momentum Gyro) devices and the desired rigid-body motion. The rigid-body dynamic model has enabled us to identify the attendant CMG momentum saturation constraints. The task for vibration control is carried out in two stages; first in the search of a suitable CMG placement along the beam span for various slewing maneuvers, and subsequently in the development of Liapunov-based control algorithms for CMG spin-stabilization. Both analytical and numerical results are presented to show the effectiveness of the present approach.

Can the self-propulsion of anisotropic microswimmers be described by using forces and torques?

NASA Astrophysics Data System (ADS)

ten Hagen, Borge; Wittkowski, Raphael; Takagi, Daisuke; Kümmel, Felix; Bechinger, Clemens; Löwen, Hartmut

2015-05-01

The self-propulsion of artificial and biological microswimmers (or active colloidal particles) has often been modelled by using a force and a torque entering into the overdamped equations for the Brownian motion of passive particles. This seemingly contradicts the fact that a swimmer is force-free and torque-free, i.e. that the net force and torque on the particle vanish. Using different models for mechanical and diffusiophoretic self-propulsion, we demonstrate here that the equations of motion of microswimmers can be mapped onto those of passive particles with the shape-dependent grand resistance matrix and formally external effective forces and torques. This is consistent with experimental findings on the circular motion of artificial asymmetric microswimmers driven by self-diffusiophoresis. The concept of effective self-propulsion forces and torques significantly facilitates the understanding of the swimming paths, e.g. for a microswimmer under gravity. However, this concept has its limitations when the self-propulsion mechanism of a swimmer is disturbed either by another particle in its close vicinity or by interactions with obstacles, such as a wall.

Motion of the moonlet in the binary system 243 Ida

NASA Astrophysics Data System (ADS)

Lan, L.; Ni, Y.; Jiang, Y.; Li, J.

2018-02-01

The motion of the moonlet Dactyl in the binary system 243 Ida is investigated in this paper. First, periodic orbits in the vicinity of the primary are calculated, including the orbits around the equilibrium points and large-scale orbits. The Floquet multipliers' topological cases of periodic orbits are calculated to study the orbits' stabilities. During the continuation of the retrograde near-circular orbits near the equatorial plane, two period-doubling bifurcations and one Neimark-Sacker bifurcation occur one by one, leading to two stable regions and two unstable regions. Bifurcations occur at the boundaries of these regions. Periodic orbits in the stable regions are all stable, but in the unstable regions are all unstable. Moreover, many quasi-periodic orbits exist near the equatorial plane. Long-term integration indicates that a particle in a quasi-periodic orbit runs in a space like a tire. Quasi-periodic orbits in different regions have different styles of motion indicated by the Poincare sections. There is the possibility that moonlet Dactyl is in a quasi-periodic orbit near the stable region I, which is enlightening for the stability of the binary system.

Autoregressive harmonic analysis of the earth's polar motion using homogeneous International Latitude Service data

NASA Technical Reports Server (NTRS)

Chao, B. F.

1983-01-01

The homogeneous set of 80-year-long (1900-1979) International Latitude Service (ILS) polar motion data is analyzed using the autoregressive method (Chao and Gilbert, 1980), which resolves and produces estimates for the complex frequency (or frequency and Q) and complex amplitude (or amplitude and phase) of each harmonic component in the data. The ILS data support the multiple-component hypothesis of the Chandler wobble. It is found that the Chandler wobble can be adequately modeled as a linear combination of four (coherent) harmonic components, each of which represents a steady, nearly circular, prograde motion. The four-component Chandler wobble model 'explains' the apparent phase reversal during 1920-1940 and the pre-1950 empirical period-amplitude relation. The annual wobble is shown to be rather stationary over the years both in amplitude and in phase, and no evidence is found to support the large variations reported by earlier investigations. The Markowitz wobble is found to be marginally retrograde and appears to have a complicated behavior which cannot be resolved because of the shortness of the data set.

Artificial neural network EMG classifier for functional hand grasp movements prediction.

PubMed

Gandolla, Marta; Ferrante, Simona; Ferrigno, Giancarlo; Baldassini, Davide; Molteni, Franco; Guanziroli, Eleonora; Cotti Cottini, Michele; Seneci, Carlo; Pedrocchi, Alessandra

2017-12-01

Objective To design and implement an electromyography (EMG)-based controller for a hand robotic assistive device, which is able to classify the user's motion intention before the effective kinematic movement execution. Methods Multiple degrees-of-freedom hand grasp movements (i.e. pinching, grasp an object, grasping) were predicted by means of surface EMG signals, recorded from 10 bipolar EMG electrodes arranged in a circular configuration around the forearm 2-3 cm from the elbow. Two cascaded artificial neural networks were then exploited to detect the patient's motion intention from the EMG signal window starting from the electrical activity onset to movement onset (i.e. electromechanical delay). Results The proposed approach was tested on eight healthy control subjects (4 females; age range 25-26 years) and it demonstrated a mean ± SD testing performance of 76% ± 14% for correctly predicting healthy users' motion intention. Two post-stroke patients tested the controller and obtained 79% and 100% of correctly classified movements under testing conditions. Conclusion A task-selection controller was developed to estimate the intended movement from the EMG measured during the electromechanical delay.

Ideas for Use of an IPad in Introductory Physics Education

NASA Astrophysics Data System (ADS)

Aurora, Tarlok S.

2014-03-01

Mobile devices such as an IPad, tablet computers and smartphones offer an opportunity to collect information to facilitate physics teaching and learning. The data collected with built-in sensors, such as a video camera, may be analyzed on the mobile device itself or on a desktop computer. In this work, first, the circular motion of a steel ball rolling in a cereal bowl was analyzed to show that it consisted of two simple harmonic motions, in perpendicular directions. Secondly, motion of two balls-one dropped vertically down, and the other one launched as a projectile - was analyzed. Data was analyzed with Logger Pro software, and value of g was determined graphically. Details of the work, its limitations and additional examples will be described. The material so obtained may be used as a demonstration, in a classroom, to clarify physics concepts. In a school, where students are required to have such portable devices, one may assign such activities as homework, to enhance student engagement in learning physics. The author is thankful to USciences for the IPad; and Rich Cosgriff, Phyllis Blumberg and Elia Eschenazi for useful discussions.

Neural dynamics for landmark orientation and angular path integration

PubMed Central

Seelig, Johannes D.; Jayaraman, Vivek

2015-01-01

Summary Many animals navigate using a combination of visual landmarks and path integration. In mammalian brains, head direction cells integrate these two streams of information by representing an animal's heading relative to landmarks, yet maintaining their directional tuning in darkness based on self-motion cues. Here we use two-photon calcium imaging in head-fixed flies walking on a ball in a virtual reality arena to demonstrate that landmark-based orientation and angular path integration are combined in the population responses of neurons whose dendrites tile the ellipsoid body — a toroidal structure in the center of the fly brain. The population encodes the fly's azimuth relative to its environment, tracking visual landmarks when available and relying on self-motion cues in darkness. When both visual and self-motion cues are absent, a representation of the animal's orientation is maintained in this network through persistent activity — a potential substrate for short-term memory. Several features of the population dynamics of these neurons and their circular anatomical arrangement are suggestive of ring attractors — network structures proposed to support the function of navigational brain circuits. PMID:25971509

Moving target feature phenomenology data collection at China Lake

NASA Astrophysics Data System (ADS)

Gross, David C.; Hill, Jeff; Schmitz, James L.

2002-08-01

This paper describes the DARPA Moving Target Feature Phenomenology (MTFP) data collection conducted at the China Lake Naval Weapons Center's Junction Ranch in July 2001. The collection featured both X-band and Ku-band radars positioned on top of Junction Ranch's Parrot Peak. The test included seven targets used in eleven configurations with vehicle motion consisting of circular, straight-line, and 90-degree turning motion. Data was collected at 10-degree and 17-degree depression angles. Key parameters in the collection were polarization, vehicle speed, and road roughness. The collection also included a canonical target positioned at Junction Ranch's tilt-deck turntable. The canonical target included rotating wheels (military truck tire and civilian pick-up truck tire) and a flat plate with variable positioned corner reflectors. The canonical target was also used to simulate a rotating antenna and a vibrating plate. The target vehicles were instrumented with ARDS pods for differential GPS and roll, pitch and yaw measurements. Target motion was also documented using a video camera slaved to the X-band radar antenna and by a video camera operated near the target site.