Longitudinal Velocity Changes Research Articles

Review of the Low-Temperature Acoustic Properties of Water, Aqueous Solutions, Lipids, and Soft Biological Tissues.

Existing data on the acoustic properties of low-temperature biological materials is limited and widely dispersed across fields. This makes it difficult to employ this information in the development of ultrasound applications in the medical field, such as cryosurgery and rewarming of cryopreserved tissues. In this review, the low-temperature acoustic properties of biological materials, and the measurement methods used to acquire them were collected from a range of scientific fields. The measurements were reviewed from the acoustic setup to thermal methodologies for samples preparation, temperature monitoring, and system insulation. The collected data contain the longitudinal and shear velocity, and attenuation coefficient of biological soft tissues and biologically relevant substances-water, aqueous solutions, and lipids-in the temperature range down to -50 °C and in the frequency range from 108 kHz to 25 MHz. The multiple reflection method (MRM) was found to be the preferred method for low-temperature samples, with a buffer rod inserted between the transducer and sample to avoid direct contact. Longitudinal velocity changes are observed through the phase transition zone, which is sharp in pure water, and occurs more slowly and at lower temperatures with added solutes. Lipids show longer transition zones with smaller sound velocity changes; with the longitudinal velocity changes observed during phase transition in tissues lying between these two extremes. More general conclusions on the shear velocity and attenuation coefficient at low-temperatures are restricted by the limited data. This review enhance knowledge guiding for further development of ultrasound applications in low-temperature biomedical fields, and may help to increase the precision and standardization of low-temperature acoustic property measurements.

Vehicle Sideslip Angle and Road Friction Estimation Using Online Gradient Descent Algorithm

Estimating vehicle sideslip angle and road friction in real time is of great significance for vehicle stability control and intelligent vehicle lateral control. These parameters are often difficult to obtain directly and the high cost of measuring instruments restricts their application in general vehicle control. Therefore, an estimation method based on online gradient descent (OGD) algorithm for vehicle sideslip angle and road friction is proposed. For the front-wheel-steer and front-wheel-drive vehicle, the vehicle's lateral dynamics model is established with smaller assumptions. And an unknown input observer is designed to estimate the tire's lateral force of the rear wheel. On the basis of this, the parameter estimation is transformed into the parameter optimization problem and the cost function is designed by using the nonlinear tire model, i.e., magic formula, and its gradient formula. Then, the OGD algorithm is used to estimate the sideslip angle and road friction, respectively. The effectiveness of the proposed method is evaluated via numerical simulation based on MATLAB/Simulink and CarSim software platform. The results show that the method can reliably and accurately estimate the vehicle sideslip angle and the road friction under a variety of test conditions. The proposed algorithm can effectively suppress the influences of sensor noise, longitudinal velocity change, and tire force nonlinearity on the estimation results.

Ultrasonic study on the change in elastic properties of cementite with temperature and Mn content using nearly full density polycrystalline bulk samples

The elastic properties of cementite were studied using a laser-ultrasonic technique. The temperature dependence and effect of Mn alloying were investigated using nearly full density polycrystalline bulk cementite samples. The Young’s modulus (E), shear modulus (G), bulk modulus (B), and Poisson’s ratio (ν) were obtained from the measured longitudinal and shear velocities (VL and VS, respectively). The elastic properties of cementite changed substantially with the temperature, especially around its Curie temperature (TC). The change in longitudinal velocity around Curie temperature was larger than the change in shear velocity. Around Curie temperature, a small decrease was observed in Young’s modulus and shear modulus and sharp minima were observed in bulk modulus and Poisson’s ratio. Mn addition to cementite increased the sound velocity and elastic stiffness and decreased Curie temperature. The present study revealed the temperature dependence of the elastic constants of cementite across Curie temperature for the first time.

Sideslip angle estimation considering short-duration longitudinal velocity variation

The accurate estimation of sideslip angle is necessary for many vehicle control systems. The detection of sliding and skidding is especially critical in emergency situations. In this paper, a sideslip angle estimation method is proposed that considers severe longitudinal velocity variation over the short period of time during which a vehicle may lose stability due to sliding or spinning. An extended Kalman filter (EKF) based on a kinematic model of a vehicle is used without initialization of the inertial measurement unit to estimate vehicle longitudinal velocity. A dynamic compensation method that compensates for the difference in the locations of the vehicle velocity sensor and the IMU in on-road vehicle tests is proposed. Evaluations with a CarSim™ 27-degree-of-freedom (DOF) model for various vehicle test scenarios and with on-road tests using a real vehicle show that the proposed sideslip angle estimation method can accurately predict sideslip angle, even when vehicle longitudinal velocity changes significantly.

Change of Longitudinal Velocity in Rock around the Hydraulic Fracture Area

Change of Longitudinal Velocity in Rock around the Hydraulic Fracture Area

Pure Aluminum Single Crystal Study on Point Defect Dependence of Ultrasonic Longitudinal Wave Velocity

In the authors' previous study, velocity changes of ultrasonic waves under simple and pure shear states were studied both theoretically and experimentally. The research work revealed the quite different longitudinal wave velocity changes between under the simple and pure shear states and also distinguished longitudinal velocity change under the pure shear state, on the other hand transverse wave velocity changes under simple and pure shear states showed almost the same change tendencies similar to the texture development under both shear states. Therefore, to clear the different effects due to plastic deformation on transverse and longitudinal waves velocity changes under simple and pure shear states the microstructural changes of polycrystal solids were investigated via finite element polycrystal model (FEPM). The analyzed results suggested that the transverse wave velocity depends upon texture developments mainly, whereas the longitudinal wave velocity depends heavily upon point defects induced by intersected cross slips among dislocations. The principal object of this paper is experimental verification of point defects dependence of the longitudinal wave velocity using a pure Aluminum single crystal. As a result, no point defects occurring under single slip stage was simulated by FEM analysis for crystal plasticity and experimental evidence of no longitudinal wave velocity changes under same stage was shown. It was confirmed that the longitudinal waves velocity depends under the point defects.

Feasibility of a storage ring for polar molecules in strong-field-seeking states

We show, through modeling and simulation, that it is feasible to construct a storage ring that will store dense bunches of strong-field-seeking polar molecules at 30 m/s (kinetic energy of 2 K) and hold them, for several minutes, against losses due to defocusing, oscillations, and diffusion. The ring, 3 m in diameter, has straight sections that afford access to the stored molecules and a lattice structure that may be adapted for evaporative cooling. Simulation is done using a newly-developed code that tracks the particles, in time, through 400 turns; it accounts for longitudinal velocity changes as a function of external electric field, focusing and deflection nonlinearities, and the effects of gravity. An injector, decelerator, and source are included and intensities are calculated.

Velocity scheduled driver assisted control

This paper investigates the effectiveness of velocity-scheduled Driver Assisted Control (DAC) to control the yaw rate of a front wheel drive, four-wheel steer passenger vehicle. The goal of this research is to be able to impart new handling characteristics to a vehicle through the entire range of operational longitudinal velocities. The DAC uses vehicle yaw rate as input and the rear steering angle as output, thus allowing the driver to maintain a direct line of vehicle control via the front wheels for safety reasons. Multiple DAC controllers are designed for discrete longitudinal velocities within the vehicle's operating range. A transition methodology was then implemented to switch between DAC controllers as the longitudinal velocity changes. Finally, the controller was tested experimentally on a scaled vehicle testbed.

Long-wavelength end-effect undulator radiation (Transition Undulator Radiation)

As first pointed out by K.-J. Kim (KIM K.-J.,Phys. Rev. Lett.,76 (1996) 1244) undulator radiation contains a broad-band component in the long-wavelength region. This radiation is due to the change in longitudinal velocity of an electron upon entering and leaving an undulator. The radiation pattern is a hollow cone, peaked in the forward direction, with an opening angle of approximately 1γ, with a spectrum covering a wide range, including the infra-red and the visible. The radiation is radially polarized, analogous to transition radiation, and exhibits interference effects between the entrance and exit ends of the undulator, similar to the interference effects observed for transition radiation from a thin slab of material. A straightforward application of formulas from Jackson (JACKSON J. D.,Classical Electrodynamics, 2nd edition (J.Wiley & Sons, N.Y.) 1975) results in a closed-form exact expression for the low-frequency limit of this novel radiation effect, Transition Undulator Radiation or TUR.

A study of the water sorption kinetic of Poly(HEMA) hydrogels by SLAM and FT-IR measurements

The relative changes in the ultrasonic attenuation measured by scanning laser acoustic microscopy (SLAM) during water sorption in poly-hydroxy-ethil-methacrilate[Poly(HEMA)] are analyzed. Acoustical images performed at 10 and 30 MHz of Poly(HEMA) during water absorption show an ultrasonic attenuation increase followed by a decrease. This phenomenon is analyzed in terms of reflections, scattering, and absorption of the acoustic waves. However, the contribution of scattering and reflection may be neglected and the time dependence of acoustic attenuation is attributed to absorption of the acoustic waves occuring in accordance with the glass transition, although induced by a solvent and not by temperature. Fourier transform infrared spectrometry (FT-IR) measurements indicate that bound water is responsible for the glass-rubber transition. On the other hand, the longitudinal velocity changes are only affected by the variations of density and mechanical properties of the polymer during water sorption. The traditional weight gain data are compared with the attenuation changes observed by ultrasonic measurements.

Laser cooling of stored high-velocity ions by means of the spontaneous force.

A longitudinal laser cooling of ion beams at about 5% of the velocity of light has been performed at the Heidelberg Test Storage Ring with various cooling schemes employing the spontaneous force. For a 7.29-MeV $^{9}\mathrm{Be}^{+}$ beam with an initial longitudinal temperature of 2700 K, the main characteristics of laser cooling in a storage ring are discussed. When undamped, the transverse betatron oscillations of the coasting ions limit the longitudinal temperature after laser cooling to typically 1 K. After damping the transverse motion by precooling the ions with an electron cooler, longitudinal temperatures of below 30 mK have been obtained in the subsequent laser cooling. In this case, the longitudinal ion-beam temperature can be understood as an equilibrium of the laser cooling rate with the heating rate due to intrabeam scattering. Moreover, single binary Coulomb collisions between the (still transversely hot) ions can cause such longitudinal velocity changes that ions are lost out of the critical capture range of the laser cooling force. In these two ways, intrabeam scattering imposes a substantial limit on the temperature or number of laser cooled ions in a storage ring. In our experiments, this process presently limits the ratio between the density-dependent Coulomb energy and the longitudinal thermal energy spread to a value on the order of 1, where liquid rather than gaseous behavior of the ion beam is expected to set in.

Acoustic measurements of stress fields and microstructure

A very precise system for measuring two-dimensional velocity fields in solid samples has been used for nondestructive measurements of both externally applied and residual inhomogeneous stresses in solids,J integrals, stress intensity factors of cracks, and hardness of quenched steel. The longitudinal velocity measurement is based on precise determination of the propagation transit time through the stressed solid specimen using a small diameter, water-coupled acoutic transducer, which is scanned mechanically over the sample. Changes in velocity are then related to changes of stress in the sample by the theory of acoustoelasticity. Similar measurements show a high degree of correlation between longitudinal velocity changes and changes in microstructure in steel samples. Applications to problems of solid mechanics and material science illustrate the utility of this nondestructive measuring technique.

Thermoelastic properties of Zerodur® glass-ceramic

The elastic moduli and their temperature and pressure derivatives for Zerodur glass-ceramic have been measured at room temperature. The material is characterized by a high bulk modulus, positive temperature derivatives and negative pressure derivatives, and the longitudinal velocity changes appreciably under pressure. From the measured data, the elastic Grüneisen constant as a function of temperature has been evaluated, and compared with values of the thermal Grüneisen constant. The correlation between the pressure derivatives of Zerodur and other silica-rich glasses is discussed.

Measurements on Athabasca Glacier relating to the flow law of ice

The relation between the second invariants of the strain rate and stress deviator tensors is compared with the simple power law determined by laboratory experiments with ice. Comparison is made for change of longitudinal velocity with depth in boreholes and change of longitudinal surface velocity across the glacier. Agreement is satisfactory for the borehole data, with the upper third of the glacier thickness excluded, and for some of the surface data. This is interpreted as evidence that the underlying theory of Nye is substantially correct. However, allowance must be made for the finite width of the glacier by including a ‘shape factor’ in the formula for the shear stress. A variation of longitudinal strain rate with depth is also introduced. Of three laboratory flow laws, that of Glen for quasi-viscous creep best fits the data. The fit would be improved if the mean temperature of the glacier were slightly below pressure melting point. Results appear to show that the index in the power law is reduced at stresses below about 0.6 bar, but the result is not considered to be established definitely.