Narrow Results

A criterion was proposed for the prediction of the multiaxial fatigue strength of specimens containing small holes. The criterion was applied to nodular cast irons containing graphite nodules and small casting defects such as microshrinkage cavities. Combined axial and torsional fatigue tests were carried out to examine the influences of torsional shear stress amplitude, axial normal stress amplitude, the ratio of these stress amplitudes, phase difference, and mean stress. The materials investigated were nodular cast irons with a ferrite matrix, JIS FCD400, and a pearlite matrix, JIS FCD700. A method for the prediction of the lower bound of fatigue strength was presented. Reasonable agreement between predictions and experimental results was obtained.

This paper investigates the resilience of oscillatory power networks with Kuramoto-type nodal dynamics via phase difference. Here, we propose a general framework to measure the resilience of power network in response to perturbations affecting nodes and transmission lines during operation. Moreover, the assessing resilience approaches provide an estimation of the phase difference and power difference. To identify the resilience of power network that makes stable operation possible, several small-size oscillatory networks are selected to validate the effectiveness and feasibility of the proposed schemes. Simulation results show that the resilience plays a crucial role in the synchronous performance.

The complex interactions of two and three spark-generated bubbles are studied using high speed photography. The corresponding simulations are performed using a 3D Boundary Element Method (BEM) code. The bubbles generated are between 3 to 5 mm in radius, and they are either in-phase or out-of-phase with one another. The possible interaction phenomena between two identically sized bubbles are summarized. Depending on their relative distances and phase differences, they can coalesce, jet towards or away from one another, split into smaller bubbles, or 'catapult' away from one another. The 'catapult' effect can be utilized to generated high speed jet in the absence of a solid boundary or shockwave. Also three bubble interactions are highlighted. Complicated phenomena such as bubble forming an elliptical shape and bubble splitting are observed. The BEM simulations provide insight into the physics of the phenomena by providing details such as detailed bubble shape changes (experimental observations are limited by the temporal and spatial resolution), and jet velocity. It is noted that the well-tested BEM code [1,2] utilized here is computationally very efficient as compared to other full-domain methods since only the bubble surface is meshed.

We show how the quantum hydrodynamical formulation of quantum mechanics converts the nonlocality in the standard wave-like description of quantum systems by an instability of the quantum system, which opens the door to a new way for studying quantum systems based on known methodologies for studying the stability of fluids. As a second result, we show how the Madelung equations describe quantized energies without any external quantization conditions.

The signal phase differences of Coriolis sensor and the mass flow are proportional. To improve the measurement accuracy of flow signal processing for Coriolis mass flowmeter, a novel method based on Hilbert Transform algorithm was proposed. The main method is as follows, two signals enhanced by LZ-filter with noise-canceling were considered as Hilbert Transform, then, the phase difference of the two filtered signals was calculated by a triangle characteristic of sin function. Synchronously, the instantaneous frequency was estimated by the structure of the analytical signal. Finally, the mass flow value was obtained by calculating the phase difference. The simulation experiments and Digital Signal Processing system (DSP) verification testing demonstrate that the new signal processing method, which is the LZ algorithm, has better characteristics of real-time and high-precision than the others. The experimental results show that the accuracy of phase difference measurement is 0.02% and the tracking accuracy of frequency is better than 0.07%.

Aiming at the characteristics of the fault spectrum of industrial robots, a new phase difference correction method is proposed on the basis of Fourier transform, which combines autocorrelation technology and windowing technology to convert the original signal into a discrete spectrum with fault characteristics, which effectively improves the accuracy of fault spectrum correction and provides important help for robot fault diagnosis. Simulation analysis and example verification show that the new algorithm is quite effective in the extraction of industrial robot fault features, and the algorithm still has a smaller relative error than the traditional algorithm under noise conditions, with high estimation accuracy and strong compatibility and robustness. The algorithm not only has high theoretical value in pattern recognition, but also has great practical significance in engineering fields such as robot diagnosis.

The modified hybrid Van der Pol/Rayleigh (MHVR) oscillator was originally proposed by the authors to model the lateral oscillations of a pedestrian walking on a rigid floor and it was shown that for the autonomous case, the MHVR oscillator can correctly fit the experimental data. The case of a pedestrian walking on a laterally moving floor is modeled by a nonautonomous oscillator. The case of a floor subjected to a harmonic lateral motion has been then studied by the authors, with focus on the amplitude and stability of the entrained response, i.e. the response having the same frequency as that of the given periodic excitation. For the nonautonomous (moving floor) case, the main focus of this paper is on the analysis of the phase difference between the oscillator entrained response and the external excitation. Both analytical and numerical calculations have been performed. The approximate analytical method is the harmonic balance method. Then, the model is used to represent the experimental results for the pedestrian lateral oscillations during walking. Comparison is made for the examples along with discussions.

Shocks, jumps, booms and busts are typical large fluctuation markers which appear in crisis. Models and leading indicators vary according to crisis type in spite of the fact that there are a lot of different models and leading indicators in literature to determine structure of crisis. In this paper, we investigate structure of dynamic correlation of stock return, interest rate, exchange rate and trade balance differences in crisis periods in Turkey over the period between October 1990 and March 2015 by applying wavelet coherency methodologies to determine nature of crises. The time period includes the Turkeys currency and banking crises; US sub-prime mortgage crisis and the European sovereign debt crisis occurred in 1994, 2001, 2008 and 2009, respectively. Empirical results showed that stock return, interest rate, exchange rate and trade balance differences are significantly linked during the financial crises in Turkey. The cross wavelet power, the wavelet coherency, the multiple wavelet coherency and the quadruple wavelet coherency methodologies have been used to examine structure of dynamic correlation. Moreover, in consequence of quadruple and multiple wavelet coherence, strongly correlated large scales indicate linear behavior and, hence VARMA (vector autoregressive moving average) gives better fitting and forecasting performance. In addition, increasing the dimensions of the model for strongly correlated scales leads to more accurate results compared to scalar counterparts.

This paper develops an uncertainty propagation analysis method to analyze transmit/receive (T/R) modules with uncertain parameters, such as variability and tolerances in the physical parameters and geometry produced in the manufacturing processes. The method is a combination of the variance decomposition-based sensitivity analysis and the moment-based arbitrary polynomial chaos (MBaPC). First, the electromagnetic simulation model of a practical T/R module is created. Secondly, based on the model, the sensitivity analysis is carried out to determine the sensitive parameters to the amplitude difference and the phase difference between the input and output electromagnetic signal. Thirdly, their four order statistical moments are calculated using the MBaPC. At last, according to the maximum entropy principle, the statistical moments are used to fit the probability distribution functions of the amplitude difference and the phase difference of the T/R module. The results computed by MBaPC have been validated accurate and efficient compared with Monte Carlo simulation approach.

To improve the calculation accuracy of the horizontal-to-vertical spectral ratio (HVSR) method, this study theoretically analyzed the influencing factors of Rayleigh wave polarizability. The phase difference of the horizontal component and the phase difference of the vertical component are found to play a key role in calculating the polarizability. The influence mechanism of the superposition of body waves and different Rayleigh waves on the polarizability of the Rayleigh wave is derived. The effects of the body wave, amplitude, frequency and Rayleigh wave superposition of different sources on the polarizability are verified by numerical simulation. The results show that the body wave significantly interferes with the polarizability of the Rayleigh wave. When a signal contains more than one set of Rayleigh waves, the superposition of the same-source Rayleigh waves does not affect the ratio. However, the superposition of Rayleigh waves from different sources significantly interferes with the calculation of the polarizability. This provides a technical method and a theoretical basis for accurately extracting the Rayleigh wave polarizability dispersion curve from a seismic record signal. This would help improve the detection accuracy of the HVSR method for ground pulse signals.

Antenna phase center offsets (PCO) and phase center variations (PCV) play an important role in high-precision GNSS applications. For the fixed pattern antenna array, the amplitude and phase difference between antennas may cause phase center degrading. In this paper, the effect of amplitude and phase difference on the phase center is studied. The method of computing the PCO and PCV for a given antenna pattern is first described, followed by the calculation of the far-field phase pattern including the amplitude and phase difference for the antenna array. Lastly, the phase center character of a two-element patch antenna array is presented and analyzed as a practical example.

This paper proposes a new direction finding system consisting of a transmitter and two receivers. The phase differences of different frequency signals received by the two receivers are used to resolve interferometer phase ambiguity in this method and the direction is obtained through the phase differences obtained. The simulation results demonstrate the effectiveness of this method.