Self-similarity of spanwise rotational motions’population trends in decelerating open-channel flow

Decelerating open-channel flow is a type of flow that gradually moves forward with decreasing velocity and increasing water depth.Although all flow parameters change along the streamwise direction,previous studies have revealed that these parameters’vertical distributions at different sections can be universally described with a single profile when being nondimensionalised by appropriate scales.This study focuses on the population trends of spanwise rotational motions at various sections along the main flow direction by particle imaging velocimetry(PIV)measurement.The wall-normal population distributions of density,radius,swirling strength,and convection velocity of the prograde and retrograde motions show similar trends in uniform open-channel flows.The dimensionless representation is invariant along the main flow direction.This study’s results indicate the self-similar characteristic of population trends of spanwise rotational motions prevails in decelerating open-channel flow.

Calculation of Ground Rotational Motions Using Seismic Array Data

This article gives a description of our first study on ground rotational motion and its pre-liminary results. The ground rotational motions around vertical axis were obtained using near-field translational records of a temporal seismic array with observational distances of 1.8 to 2.7 km. The sources used are explosions with explosive of 500 kg for each. Ground rotational velocities were calcu-lated using the space derivatives of the horizontal components of translational velocities from the array. The peak ground rotational velocities （PGRV） are approximately 30 to 57 ？rad/s. Our results are very close to those from Wassermann et al. （2009）, who used both a seismic array and a rotational sensor to record an explosion in Germany and obtained PGRV values of about 50 ？rad/s. Their explosives are 150 kg, only one third of ours, but their observational distance is 250 m, much less than ours.

Numerical Analysis of the Rotational Magnetic Springs for EDS Maglev Train

Different from the traditional railway trains,the combined levitation and guidance EDS maglev train is more likely to rotate after being disturbed.Therefore,the rotational electromagnetic stiffnesses are significant operating parameters for the train.In this paper,the different effects of each translational offset generated in the rotational motion on the corresponding rotational electromagnetic stiffnesses in the EDS maglev train are analyzed and calculated.Firstly,a three-dimensional model of the maglev train is established.Then,based on the space harmonic method and the equivalent circuit of the levitation and guidance circuits,the formulas of rolling,pitching and yawing stiffness are presented.Finally,by comparing with the three-dimensional finite element simulation results,the key translational displacements in the rotational motion which has a great impact on the stiffness are obtained.Hence,the three-dimensional analytical formula can be simplified and the computation can be reduced.In addition,the accuracy of the calculation results is verified by comparing with the experimental data of Yamanashi test line.

Effect of Rotational and Sliding Motions on Friction and Degeneration of Articular Cartilage under Dry and Wet Friction

Understanding the tribological properties of articular cartilage allows scientists to evaluate degenerative joint diseases and develop new treatment techniques. The objectives of this study are to demonstrate the detrimental effect of rotational motion under both dry and wet friction and to evaluate the friction and wear behavior of bovine articular cartilage with sliding and rotational testing configurations that represent fluid film and boundary lubrication mechanisms, respectively. The articular cartilage pin and plate samples were harvested from healthy adult bovine and then tested on a self-made friction and wear simulator. Cartilage samples were subjected to sliding and rotational motions under constant load. Friction coefficients and wear factors were calculated under three conditions： using bovine serum, phosphate buffered saline and with no lubricant present. The friction coefficient and wear factor of the articular cartilage were significantly increased with rotational motion under both dry and wet friction. Using bovine serum as lubricant in the sliding testing configuration the friction coefficient and wear factor of articular cartilage were both decreased. A similar decrease in the tribological properties of cartilage was initially observed for the rotational testing configuration with bovine serum; however, the friction coefficient and wear factor were increased after 150,000 cycles. In the absence of lubricant, the articular cartilage was entirely worn on contact area in both sliding and rotational testing configurations. Bovine serum proved an effective fluid film lubricant for articular cartilage surfaces.

MEASUREMENT OF ANGULAR VIBRATION AMPLITUDE BY ACTIVELY BLURRED IMAGES

A novel motion-blur-based method for measuring the angular amplitude of a high-frequency rotational vibration is schemed. The proposed approach combines the active vision concept and the mechanism of motion-from-blur, generates motion blur on the image plane actively by extending exposure time, and utilizes the motion blur information in polar images to estimate the angular amplitude of a high-frequency rotational vibration. This method obtains the analytical results of the angular vibration amplitude from the geometric moments of a motion blurred polar image and an unblurred image for reference. Experimental results are provided to validate the presented scheme.

Baseline correction for near-fault ground motion recordings of the 2008 Wenchuan Ms8.0 earthquake

In this study, both records of a digital accelerometer and a seismograph at a far-field station for the 2008 Ms8.0 Wenchuan earthquake were analyzed, and a pulsive noise model for acceleration record was found. By comparing with the result of a rotary-table tilt test, we concluded that the noises in the acceleration records were caused by ground tilt as a result of rotational ground motion. We analyzed the key noises that may cause baseline offset, and proposed a baseline-correction scheme for preserving the long-period ground motion in accordance with specific pulse positions. We then applied this correction method to some near-field strongmotion acceleration records. The result shows that this method can obtain near-field ground displacements, including permanent displacements, in agreement with GPS data, and that this method is more stable than other methods.

Apparent velocity estimation with P-SV ratio method

The apparent velocity of the incident wave is an important parameter for simulating rotational ground motion with theoretical methods, but it is difficult to estimate effectively when there is only a single record. This paper discusses a P-SV ratio method based on elastodynamic theory in a multi-layer isotropic elastic half space. The apparent velocities of four earthquakes in the SMART1 array are calculated with this method. The result is close to a method that uses travel time analysis. Furthermore, the factors that impact the apparent velocity and equivalent incident angle are considered according to records from the Chi-Chi earthquake. There is no obvious relationship between the equivalent incident angle and epicenter distance. However, the equivalent incident angle is obviously dependent on the site conditions.

High Resolution Clinometers for Measurement of Roll Error Motion of a Precision Linear Slide

This paper proposes a new method for measurement of the roll error motion of a slide table in a precision linear slide. The proposed method utilizes a pair of clinometers in the production process of a precision linear slide, where the roll error motion measurement will be carried out repeatedly to confirm whether the surface form errors of slide guideways in the linear slide are su ciently corrected by hand scraping process. In the proposed method, one of the clinometers is mounted on the slide table, while the other is placed on a vibration isolation table, on which the precision linear slide is mounted, so that influences of external disturbances can be cancelled. An experimental setup is built on a vibration isolation table, and some experiments are carried out to verify the feasibility of the proposed method.

Decomposition of Molecular Motions into Translational, Rotational, and Intramolecular Parts by a Projection Operator Technique

The motion of the atoms in a molecule may be described as a superposition of translational motion of the molecular center-of-mass,rotational motion about the principal molecular axes,and an intramolecular motion that may be associated with vibrations and librations as well as molecular conformational changes.We have constructed projection operators that use the atomic coordinates and velocities at any two times,t=0 and a later time t,to determine the molecular center-of-mass,rotational,and intramolecular motions in a molecular dynamics simulation.This model-independent technique facilitates characterization of the atomic motions within a system of complex molecules and is important for the interpretation of experiments that rely on time correlation functions of atomic and molecular positions and velocities.The application of the projection operator technique is illustrated for the inelastic neutron scattering functions and for the translational and rotational velocity autocorrelation functions.

The limit properties of spatial coherence of seismic ground motion

The limit properties of spatial coherence of seismic ground motion are studied based on the differential relation between rotation and translation in elastic theory, the results show that the empirical mathematical model of spatial coherence must satisfy some functional characteristics. It is also indicated that the key problem to estimate rotational power spectrum densities is to obtain precisely the two order derivative of spatial coherence.

Rotational motion of polyanion versus volume effect associated with ionic conductivity of several solid electrolytes

Volume effect has been extensively investigated in several families of solid electrolytes, i.e., expanding the skeleton lattice by bigger-size substitution favors the ionic conduction. However, this effect is not applicable in α-Li2SO4 and α-Na3PO4 based inorganic ionic plastic crystal electrolytes, a unique family of solid electrolytes. Here, it is proposed that the underlying rotational motion effect of polyanion, which is actually inhibited by the substitution of bigger-size polyanion in single-phase solid solution region and causes the unexpected lowering of the ionic conductivity instead, should need the more consideration. Furthermore, through utilizing the rotational motion effect of polyanion, it is given that a new explanation of the ionic conductivities of Li10MP2S12 （M = Si, Ge, Se） electrolytes deviating from the volume effect. These results inspire new vision of rationalization of the high-performance solid electrolytes by tuning the rotational motion effect of polyanion.

Rigid-Liquid-Flexible Dynamic Formulation for a Two-Dimensional Tank Undergoing Translational and Rotational Motion

Considering rigid-liquid-flexible coupling effect, dynamic formulation for a two-dimensional rectangular tank with liquid sloshing connected to a flexible beam is proposed. Differing from the traditional formulation which considered either the rotational motion or the translational motion of the tank, this formulation can be applied for rigid-liquid-flexible coupling dynamic analysis of tank undergoing translational and rotational motion based on the theorem of momentum and the theorem of moment of momentum. Furthermore, stiffening terms are included in the dynamics equations of the flexible beam. Firstly, the dynamic equations of the rigid-liquid coupling system and the flexible beam are derived, respectively, and then by introducing the Lagrange-multipliers,the rigid-liquid-flexible coupling equations can be combined with acceleration constraint equations. Finally, the mix differential-algebraic equations are solved to investigate the rigid-liquid-flexible coupling dynamic performance of the system.

Interaction between Neighboring Supercritical Water Molecules and Density Fluctuation by Molecular Dynamics Simulations

Supercritical water(scW)is important for various engineering applications.The structure and distribution of sc W is key to dominate the related processes and phenomena.Here,scW is investigated using molecular dynamics(MD)simulation with controlled pressure and temperature.Density oscillation is observed to occur in a 1 nm thickness bin,indicating mass exchange of particles across the bin interface.We show that the low density scW behaves strong heterogeneity.Quantitative analysis of system density fluctuations is performed by square root error and maximum structure factor,demonstrating the agreement between the two methods.The scW molecules are tightly gathered to form“liquid island”locally,but are very sparse in other regions,which are similar to the gas-liquid mixture in subcritical pressure.A target molecule is tracked to plot 3D displacements and rotating angles,with the former indicating large amplitude ballistic(diffusing)motion and small amplitude oscillation,and the latter displaying two scales of angle jumping.Both translation and rotating motion are related to hydrogen bond break up and reorganization.The low density scW behaves isolated molecules with few combinations of hydrogen bonds between molecules,while the high density scW behaves more combinations of molecules via hydrogen bonds.The two scales motion is expected to influence thermal/chemical process in supercritical state,deepening the fundamental understanding of scW structure.