Center Of Motion Research Articles

Effect of Moving Mass Center on Atomic Transition Probability in a Single-Mode Cavity

By considering a two-level atom coupling with a single-mode cavity field which is prepared in three different initial states respectively, the influence of spatial motion of the atomic centre of mass on the atomic transition probability is studied. It is shown that the oscillation with collapse and revival in atomic transition probability may be suppressed due to Doppler effect.

Assessment of elliptic flame front propagation characteristics of hydrogen in an optically accessible spark ignition engine

The absence of carbon content of hydrogen fuel makes it an attractive candidates for future energy carriers. Hydrogen or dual fuelled engines are a practical alternative to pure hydrocarbon fuelling modes. However, fine tuning of current engines is necessary. In this study premixed hydrogen flame propagation is investigated in a single-cylinder, spark-ignited, four-stroke optically accessible spark ignition test engine using high-speed imaging. Ellipses were fitted on the flame contours during the analysis to obtain flame speeds and flame centre motion. The test conditions covered a range of engine speeds from 1000 rpm to 2000 rpm with 100 rpm increments using a lean mixture, ϕ = 0.67. The fine temporal resolution allowed the time, at which spark governed kernel formation becomes a function of engine parameters to be determined. The few data that have been published in the literature regarding hydrogen flame speeds were compared with the finding of this study.

Nonlinear transient stability study of two lobe symmetric hole entry worn hybrid journal bearing operating with non-Newtonian lubricant

The present paper, deals with a theoretical study concerning the effect of non-Newtonian lubricant on the stability of a two lobe symmetric hole entry worn hybrid journal bearing, compensated with constant flow valve restrictor. Trajectories of journal center motion have been obtained by solving the nonlinear equation of motion for the journal center with the Runge–Kutta method. The numerically simulated results indicate that the non-Newtonian behavior of the lubricant has a profound influence on the journal trajectories and stability of a worn hybrid journal bearing. A proper selection of parameters such as offset factor, wear depth parameter and the non-linearity factor may provide better bearing stability.

Self-similar evolution of theA-particle island–semi-infiniteB-particle sea reaction-diffusion system

We consider diffusion-controlled evolution of the A-particle island-semi-infinite B-particle sea system at propagation of the sharp annihilation front A+B→0. We show that at a large initial number of island particles the system evolution is described by the universal scaling laws with nonmonotonous front trajectory and a constant velocity of the island center motion. We demonstrate that asymptotically the island moves self-similarly retaining its velocity, shape and width.

Experimental evidence for mobile luminescence center mobility on partial dislocations in 4H-SiC using hyperspectral electroluminescence imaging

We report on the formation, motion, and concentration of localized green emission centers along partial dislocations (PDs) bounding recombination-induced stacking faults (RISFs) in 4H-SiC pin diodes. Electroluminescence imaging depicted the motion of these green emitting point defects during forward bias operation along carbon-core PDs that bound the RISFs. Following high temperature annealing, these green emitting point defects did not contract with the PDs, but remained in the final location during the expansion. This implies that the motion of these green emitting point dislocations is enabled through a recombination-enhanced motion, similar to the process for RISF expansion and contraction within SiC.

AB0756 Application of plantoconturographic examination to the assessment of foot statics disturbances in patients with rheumatoid arthritis

BackgroundRheumatoid arthritis (RA) is a chronic, inflammatory and multiple-system disorder of connective tissue leading to damage, deformation and functional impairment of joints. It frequently affects joints and periarticular structures of...

Biomechanical behavior of two different cervical total disc replacement designs in relation of concavity of articular surfaces: ProDisc-C® vs. Prestige-LP®

Recently, many cervical total disc replacement (TDR) devices have been introduced in a variety of designs in an attempt to recreate motion behavior of the normal cervical spine thereby to limit the progression of adjacent degeneration. The purposes of this study were to evaluate and compare the range of motion (ROM) and location of instant center of rotation (COR), and load sharing characteristics of two major products with different design concepts in cervical TAR-Prodisc-C® and Prestige-LP®. A 3-D finite element (FE) model of intact cervical spine (C3-6) was made from CT scans of a normal person and validated. Based on this model, postoperative FE models simulating TDR implantation at the C4-5 disc space were made for Prodisc-C® (Synthes Spine, Paoli, PA) and Prestige-LP® (Medtronic Sofamor Danek, Memphis, TN), respectively. These two TDR devices feature different design concepts that affect kinematics: Rotations and some translations were allowed at the articulating surface of Prestige LP® as the ‘concave down’ articulating surface is less constrained whereas only rotations were allowed with Prodisc-C® that features ball & socket articulating surface in ‘concave up’ orientation. Hybrid protocol (intact: 1Nm) with a compressive follower load of 73.6N were applied at the superior endplate of the C3 vertebral body. The inferior endplate of C6 vertebral body was constrained in all directions. At the index level, Prestige-LP® showed 15% less motion than Prodisc-C® in extension and about the same in flexion. Differences in ROM were negligible at the adjacent level. Here, the COR of Prestige-LP® was located more postero-inferiorly than that of Prodisc-C® by about 1-mm during extension at the index level. Facet load was less with Prestige-LP® by about 10% at the index level but 14% more at the adjacent level. The results of this study indicated that the biomechanical behavior of the postoperative cervical spine can be indeed influenced by the design features such as concavity orientation and extent of constraint of the articulating surfaces. Particularly, ROM and COR location as well as the facet loads at the index level and adjacent levels were more sensitive during extension. It would be interesting to note that resulting differences in facet load at the index and adjacent levels between the two designs will manifest to different clinical results in terms of postoperative facet degeneration.

The effect of the Earth’s oblateness on the Moon’s physical libration in latitude

The Moon’s physical libration in latitude generated by gravitational forces caused by the Earth’s oblateness has been examined by a vector analytical method. Libration oscillations are described by a close set of five linear inhomogeneous differential equations, the dispersion equation has five roots, one of which is zero. A complete solution is obtained. It is revealed that the Earth’s oblateness: a) has little effect on the instantaneous axis of Moon’s rotation, but causes an oscillatory rotation of the body of the Moon with an amplitude of 0.072″ and pulsation period of 16.88 Julian years; b) causes small nutations of poles of the orbit and of the ecliptic along tight spirals, which occupy a disk with a cut in a center and with radius of 0.072″. Perturbations caused by the spherical Earth generate: a) physical librations in latitude with an amplitude of 34.275″; b) nutational motion for centers of small spiral nutations of orbit (ecliptic) pole over ellipses with semi-major axes of 113.850″ (85.158″) and the first pole rotates round the second one along a circle with radius of 28.691″; c) nutation of the Moon’s celestial pole over an ellipse with a semi-major axis of 45.04″ and with an axes ratio of about 0.004 with a period of T = 27.212 days. The principal ellipse’s axis is directed tangentially with respect to the precession circumference, along which the celestial pole moves nonuniformly nearly in one dimension. In contrast to the accepted concept, the latitude does not change while the Moon’s poles of rotation move. The dynamical reason for the inclination of the Moon’s mean equator with respect to the ecliptic is oblateness of the body of the Moon.

Multiple Frequencies Elliptical Whirling Orbit Model and Transient RANS Solution Approach to Rotordynamic Coefficients of Annual Gas Seals Prediction

Abstract A numerical method using the multiple frequencies elliptical whirling orbit model and transient Reynolds-averaged Navier–Stokes (RANS) solution was proposed for prediction of the frequency dependent rotordynamic coefficients of annular gas seals. The excitation signal was the multiple frequencies waveform that acts as the whirling motion of the rotor center. The transient RANS solution combined with mesh deformation method was utilized to solve the leakage flow field in the annular gas seal and obtain the transient response forces on the rotor surface. Frequency dependent rotordynamic coefficients were determined by transforming the dynamic monitoring data of response forces and rotor motions to the frequency domain using the fast fourier transform. The frequency dependent rotordynamic coefficients of three types of annular gas seals, including a labyrinth seal, a fully partitioned pocket damper seal and a hole-pattern seal, were computed using the presented numerical method at thirteen or fourteen frequencies of 20–300 Hz. The obtained rotordynamic coefficients of three types of annular gas seals were all well agreement with the experimental data. The accuracy and availability of the proposed numerical method was demonstrated. The static pressure distributions and leakage flow rate of three types of annular gas seals were also illustrated.

Effects of electrohydrodynamic instability in smectic C liquid crystals

The effects of electrohydrodynamic instability (EHDI) in smectic C liquid crystals in an electric field are studied. The objects of study are oriented layers of para-hydroxybenzoic acid possessing a smectic phase. The observed effects are divided into three groups according to the character of the motion of molecular centers of mass and the orientation of the director and the smectic C liquid crystal layers. The instabilities of the azimuthal and Kapustin-Williams domains are experimentally found. The experimental cell consists of two glass plates with tin dioxide electrodes separated by Mylar spacers of a specified thickness. Various schemes of domain rotation are considered. The EHDI is found to depend on the layer geometry.

Rigid-Flexible Hybrid MBD Based Modeling and Simulation Method for Coupler Mechanism

The coupler mechanism is a key component of vehicle connection. The geometric shape of parts are very complex. Between the working parts there is a certain clearance, and mechanism function is implementated by the collision contact of these parts. So, it is very difficult to analyze how coupler works exactly. The RecurDyn software, the latest research results of multi-body dynamics (MBD), is used for modeling and simulation. The working state of the coupler device was reproduced in the software. The modeling and simulation of coupler irregular mechanism was created by using the rigid-flexible hybrid MBD system. Through the simulation results, including main parts parameter curves about mass centre motion, force curves on the joints, contact force between parts, and key components stress concentration area as well, the functional reliability and the structural reliability of coupler were analyzed in operating environment. Applying the MBD theory and technology above, the structural and functional reliability can be predicted for coupler liked complex mechanism.

Control of the motion of the body's center of mass in relation to the center of pressure during high-heeled gait

High-heeled shoes are associated with instability and falling, leading to injuries such as fracture and ankle sprain. Knowledge of the motion of the body's center of mass (COM) with respect to the center of pressure (COP) during high-heeled gait may offer insights into the balance control strategies and provide a basis for approaches that minimize the risk of falling and associated adverse effects. The study aimed to investigate the influence of the base and height of the heels on the COM motion in terms of COM–COP inclination angles (IA) and the rate of change of IA (RCIA). Fifteen females who regularly wear high heels walked barefoot and with narrow-heeled shoes with three heel heights (3.9cm, 6.3cm and 7.3cm) while kinematic and ground reaction force data were measured and used to calculate the COM and COP, as well as the temporal-distance parameters. The reduced base of the heels was found to be the primary factor for the reduced normalized walking speed and the reduced frontal IA throughout the gait cycle. This was achieved mainly through the control of the RCIA during double-leg stance (DLS). The heel heights affected mainly the peak RCIA during DLS, which were not big enough to affect the IA. These results suggest young adults adopt a conservative strategy for balance control during narrow-heeled gait. The results will serve as baseline data for future evaluation of patients and/or older adults during narrow-heeled gait with the aim of reducing the risk of falling.

A web-based virtual system for turn-milling center

This paper presents a three-dimensional, web-based, interactive simulation system for turn-milling center. To overcome the disadvantages of transferring files over the Internet and depending on expensive computer-aided design (CAD)/computer-aided manufacturing (CAM) softwares, the system is developed by virtual reality modeling language (VRML)/JavaScript interaction. The system files produced by machining simulation have small size, and could be transmitted on the web easily. Firstly, a dynamic interactive technology based on VRML and JavaScript, which is essential to a web-based simulation system, has been presented in this paper. Secondly, the geometric and kinematic model is created for representing the turn-milling center motion. Then, the key technologies for machining simulation including material removal, NC codes compiling and collision detection are studied. Finally, to validate feasibility of the proposed system, the virtual machining process for a stepped shaft in the machine tool is carried out. Since the system realizes multiple dynamic demonstrations of virtual machine tool, users can comprehensively understand the product performance. The research for the web-based virtual system of turn-milling center has important research value and application prospect.

11207 衝突系に発生する低周波振動(OS8-1【振動騒音および制御(1)】))

There are some systems that involve impacts, e.g. vibrating screens. Sometimes unwanted low frequency vibration occurs in such vibroimpact systems. This report examines effects of a bouncing mass on the low frequency vibration using an experimental apparatus. Results show that the variation of bouncing height has exciting or damping effect depending on its phase related to the motion of the gravity center.

Speed Testing of the Graviton and the Movement Track of Graviton in the Spiral Galaxy

According to a series of hypothesis, for the spiral galaxy, a mathematical equation of the graviton movement track is built, it is also the central curve of the nebulae density distribution, which offers the method to measure the moving speed of the graviton. Using the observed images of the M51 galaxy, it confirms that the graviton movement curve in the spiral galaxy conforms to the image, QUOTE QUOTEis a constant. It points out that by measuring the rate of angular motion of the equivalent center in the galaxy, the real speed of the graviton can be estimated. Under the measuring condition of the M51,. The theory presented in this article also helps to calculate the rotation speed of a galaxy, provided the graviton speed is known for certain. With the model in this article and fitting data from the observation images of M51 galaxy, the guess which says “the moving speed of graviton is a constant” is supported unprecedentedly by observation data. It is for the first time that the upper limit of graviton speed, i.e. no more than times of light speed, is obtained from observation data. At the same time, the paper puts forward one possible way that the lower limit of graviton speed may be measured. And a new idea also brought forward in the paper is that the rotational angular velocity w of the equivalent center which plays an important role in a spiral galaxy may be measured according to the observed data of the thickness of galactic center of the spiral galaxy.

A Robot with a Suspended Load: The Statistical Relationship Between Energy Cost and Mass Center Motion

A Robot with a Suspended Load: The Statistical Relationship Between Energy Cost and Mass Center Motion

Size-scaling effect on the velocity field of an internal combustion engine, part I: Bulk motion

In-cylinder velocity measurements were acquired to study the bulk fluid motion in two geometrically scaled, two-valve, optically accessible, and single-cylinder research engines. Different port geometries (two), different port orientations (two), and both shrouded and nonshrouded intake valves were tested to vary the intake-generated flow. The engines were motored at speeds ranging from 300 to 1200 r/min for the larger engine and from 600 to 1800 r/min for the smaller engine. Prior to testing on the engines, the different head configurations were tested on a steady flow bench. Particle image velocimetry data were taken on a single plane, parallel to the piston surface, in the engines to characterize the large-scale flow phenomena. The mean location of the swirl center and the mean angular velocity were determined by fitting a solid-body profile to the flow. The results showed that the swirl center location was relatively insensitive to engine speed for both engines, but did change position throughout the cycle. The swirl center locations, scaled by the cylinder radii, were found to be in nearly the same location for the two-scaled engines in the same nominal configuration, indicating that the swirl center motion was deterministic in nature. Normalizing the best-fit solid-body angular velocity by the engine rotation rate was found to collapse the data from the multiple engine speeds nearly onto a single curve for a given engine configuration. The angular velocity was found to decrease with crank angle due to wall friction, which was higher for the small engine because of the higher surface-to-volume ratio.

The Energy Consumption Analysis of Four-Legged Walking Robot by Using Different Motion Laws

In this paper, controlling the motion of mass center of robot by different motion laws is discussed to reduce motor’s drive power of robot joint. Firstly, correlation theory is described; obtain that if the (AV) value of motion parameter of robot’ mass center is smaller; the torque of drive motor which needs to drive robot is smaller under the same conditions. Then, in the process of robot ZQROT-I running the straight gait, two typical motion laws are used to control mass motion of robot; motion performance of the robot is analyzed with Adams. Analysis result indicates that control mass motion of robot by the use of motion laws with small (AV) value has certain effect in saving working energy of robot.

Body dynamics and hydrodynamics of swimming fish larvae: a computational study

To understand the mechanics of fish swimming, we need to know the forces exerted by the fluid and how these forces affect the motion of the fish. To this end, we developed a 3-D computational approach that integrates hydrodynamics and body dynamics. This study quantifies the flow around a swimming zebrafish (Danio rerio) larva. We used morphological and kinematics data from actual fish larvae aged 3 and 5 days post fertilization as input for a computational model that predicted free-swimming dynamics from prescribed changes in body shape. We simulated cyclic swimming and a spontaneous C-start. A rigorous comparison with 2-D particle image velocimetry and kinematics data revealed that the computational model accurately predicted the motion of the fish's centre of mass as well as the spatial and temporal characteristics of the flow. The distribution of pressure and shear forces along the body showed that thrust is mainly produced in the posterior half of the body. We also explored the effect of the body wave amplitude on swimming performance by considering wave amplitudes that were up to 40% larger or smaller than the experimentally observed value. Increasing the body wave amplitude increased forward swimming speed from 7 to 21 body lengths per second, which is consistent with experimental observations. The model also predicted a non-linear increase in propulsive efficiency from 0.22 to 0.32 while the required mechanical power quadrupled. The efficiency increase was only minor for wave amplitudes above the experimental reference value, whereas the cost of transport rose significantly.

Macro-quantization of the guiding centre motion of charged particles in a magnetic field

AbstractThis review describes the results of investigations on charged particle dynamics in a magnetic field carried out over a number of years. The studies have unravelled the existence of some very surprising and unusual phenomena. Though existing on the macro-scale, they are found to be of quantum origin, and are thereby not covered by the Lorentz equation, which has been regarded conventionally as the descriptor of electrodynamic phenomena on the macro-scale. These novel phenomena have been found to be attributed to the ‘quantum modulation’ of the de Broglie wave along the magnetic field. This is brought about through the scattering-induced transition across Landau levels, leading to the modulation of the plane wave state along the field as a result of the entanglement between the parallel and perpendicular degrees of freedom. These findings were motivated by the predictions of a formalism developed by the author and include such unusual phenomena as (i) macro-scale matter wave interference effects and (ii) the detection of curl-free vector potential also on the macro-scale, both attributed to quantum modulation which is a matter wave on the macro-scale. The formalism is thus described as ‘macro-quantization of guiding centre motion’.