To simulate the price fluctuation dynamics of financial markets, a novel financial price model is developed by the voter dynamic system on the Watts-Strogtz small-world network and the random jump ...process. The voter system is a classical statistical physics system, which describes the dynamics of voters’ attitudes towards a certain topic in the mutual influence. The Watts-Strogtz small-world network is a special kind of complex networks, which can be used to study the transmission dynamics of different things in complex and real-world systems. The paper first attempts to use the voter dynamic system on the small-world network to reproduce the micro-mechanism of price fluctuations caused by the interaction among different investors in financial markets, where investors can potentially disseminate information and interact via additional long-distance contacts. Moreover, considering that external macro environments have the impact on price fluctuations in financial markets, this paper introduces the random jump process in the price model. The effectiveness of the proposed model can be verified by comparing price returns generated by the model with returns of several important stock indexes in terms of nonlinear fluctuation behaviors. First, some statistical behaviors of the fluctuation dynamics are explored, including distribution characteristics and autocorrelation. Moreover, based on the ensemble empirical mode decomposition method, multifractal behaviors and complexity behaviors of returns and the first three intrinsic mode functions are investigated. The empirical results show that the dynamical model can well simulate these nonlinear fluctuation behaviors of real markets.
This paper presents a Doppler radar vital sign detection system with random body movement cancellation (RBMC) technique based on adaptive phase compensation. An ordinary camera was integrated with ...the system to measure the subject's random body movement (RBM) that is fed back as phase information to the radar system for RBMC. The linearity of the radar system, which is strictly related to the circuit saturation problem in noncontact vital sign detection, has been thoroughly analyzed and discussed. It shows that larger body movement does not necessarily mean larger radar baseband output. High gain configuration at baseband is required for acceptable SNR in noncontact vital sign detection. The phase compensation at radar RF front-end helps to relieve the high-gain baseband from potential saturation in the presence of large body movement. A simple video processing algorithm was presented to extract the RBM without using any marker. Both theoretical analysis and simulation have been carried out to validate the linearity analysis and the proposed RBMC technique. Two experiments were carried out in the lab environment. One is the phase compensation at RF front end to extract a phantom motion in the presence of another large shaker motion, and the other one is to measure the subject person breathing normally but randomly moving his body back and forth. The experimental results show that the proposed radar system is effective to relieve the linearity burden of the baseband circuit and help compensate the RBM.
This paper focuses on the exploitation of linear-frequency-modulated continuous-wave (LFMCW) radars for noncontact range tracking of vital signs, e.g., respiration. Such short-range system combines ...hardware simplicity and tracking precision, thus outperforming other remote-sensing approaches in the addressed biomedical scenario. A rigorous mathematical analysis of the operating principle of the LFMCW radar in the context of vital-sign monitoring, which includes the explanation of key aspects for the maintenance of coherence, is detailed. A precise phase-based range-tracking algorithm is also presented. Exhaustive simulations are carried out to confirm the suitability and robustness against clutter, noise, and multiple scatterers of the proposed radar architecture, which is subsequently implemented at the prototype level. Moreover, live data from real experiments associated to a metal plate and breathing subjects are obtained and studied.
The strength–ductility trade-off has been a long-standing challenge when designing and fabricating a novel metal matrix composite. In this study, graphene-nanosheets (GNSs)-reinforced copper ...(Cu)-matrix-laminated composites were fabricated through two methods, i.e., the alternating electrodeposition technique followed by spark plasma sintering (SPS) and direct electrodeposition followed by hot-press sintering. As a result, a Cu-GNS-Cu layered structure formed in the composites with various Cu layer thicknesses. Compared with the pure Cu, the yield strength of the GNS/Cu composites increased. However, the mechanical performance of the GNS/Cu composites was strongly Cu-layer-thickness-dependent, and the GNS/Cu composite possessed a brittle fracture mode when the Cu layer was thin (≤10 μm). The fracture mechanism of the GNS/Cu composites was thoroughly investigated and the results showed that the premature failure of the GNS/Cu composites with a thin Cu layer may be due to the lack of Cu matrix, which can relax the excessive stress intensity triggered by GNSs and delay the crack connection between neighboring GNS layers. This study highlights the soft Cu matrix in balancing the strength and ductility of the GNS/Cu-laminated composites and provides new technical and theoretical support for the preparation and optimization of other laminated metal matrix composites.
We report on a frequency-comb-referenced absolute interferometer which instantly measures long distance by integrating multi-wavelength interferometry with direct synthetic wavelength interferometry. ...The reported interferometer utilizes four different wavelengths, simultaneously calibrated to the frequency comb of a femtosecond laser, to implement subwavelength distance measurement, while direct synthetic wavelength interferometry is elaborately introduced by launching a fifth wavelength to extend a non-ambiguous range for meter-scale measurement. A linearity test performed comparatively with a He-Ne laser interferometer shows a residual error of less than 70.8 nm in peak-to-valley over a 3 m distance, and a 10 h distance comparison is demonstrated to gain fractional deviations of ~3 × 10
versus 3 m distance. Test results reveal that the presented absolute interferometer enables precise, stable, and long-term distance measurements and facilitates absolute positioning applications such as large-scale manufacturing and space missions.
The present work introduced first-principles calculation to explore the substitution behavior of Ag atoms for Al or Ti atoms in the Ti2AlC MAX phase ceramic. The effect of Ag substitution on ...supercell parameter, bonding characteristic, and stability of the Ti2AlC was investigated. The results show that for the substitution of Ag for Al, the Al-Ti bond was replaced by a weaker Ti-Ag bond, decreasing the stability of the Ti2AlC. However, the electrical conductivity of the Ti2AlC was enhanced after the substitution because of the contribution of Ag 4d orbital electrons toward the density of states (DOS) at the Fermi level coupled with the filling of Ti d orbital electrons. For the substitution of Ag for Ti, new bonds, such as Ag-Al bond, Ag-C bond, Al-Al bond, Ti-Ti anti-bond, and C-C anti-bond were generated in the Ti2AlC. The Ti-Ti anti-bond was strengthened as well as the number of C-C anti-bond was increased with increasing the substitution ratio of Ag for Ti. Similar to the substitution of Ag for Al, the stability of the Ti2AlC also decreased because the original Al-Ti bond became weaker as well as the Ti-Ti and C-C anti-bonds were generated during the substitution of Ag for Ti. Comparing with the loss of Ti d orbital electrons, Ag 4d orbits contributed more electrons to the DOS at the Fermi level, improving the electrical conductivity of the Ti2AlC after substitution. Based on the calculation, the substitution limit of Ag for Al or Ti was determined. At last, the substitution behavior of Ag for Al or Ti was compared to discriminate that Ag atoms would tend to preferentially substitute for Ti atoms in Ti2AlC. The current work provides a new perspective to understand intrinsic structural characteristic and lattice stability of the Ti2AlC MAX phase ceramic.
A multi-wavelength interferometer utilizing the frequency comb of a femtosecond laser as the wavelength ruler is tested for its capability of ultra-precision positioning for machine axis control. The ...interferometer uses four different wavelengths phase-locked to the frequency comb and then determines the absolute position through a multi-channel scheme of detecting interference phases in parallel so as to enable fast, precise and stable measurements continuously over a few meters of axis-travel. Test results show that the proposed interferometer proves itself as a potential candidate of absolute-type position transducer needed for next-generation ultra-precision machine axis control, demonstrating linear errors of less than 61.9 nm in peak-to-valley over a 1-meter travel with an update rate of 100 Hz when compared to an incremental-type He-Ne laser interferometer.
The void fraction of composite tape winding products is one of the key characteristic parameters affecting the quality and mechanical properties of composite products. In this paper, the leading ...cause of void formation in the winding process is analyzed, and the critical winding process variables, including winding velocity, consolidation force, and roller temperature, which influence the void content of the products are proposed. Then, the thermal model, inter-laminar, and intra-laminar void content model for prepreg tape winding process are developed aim at control products void content. The effect rule of multi-parameter on void content is discussed. The accuracy of the theoretical model is also validated by comparing predicted results with experimental data. Moreover, based on the predicted model, the multidimensional mapping relationships and three-dimension (3D) process window for tape winding is obtained in order to provide the theoretical basis for control the void content of tape winding products. The model predictions and experimental results show that a combination of high winding temperature, strong pressure and low winding velocity can help to reduce the final void content of winding products. Using the combination of process parameters in this 3D process window for tape winding, the void content of the product can be controlled within 1%.
A prototype laser distance interferometer is demonstrated by incorporating the frequency comb of a femtosecond laser for mass-production of optoelectronic devices such as flat panel displays and ...solar cell devices. This comb-referenced interferometer uses four different wavelengths simultaneously to enable absolute distance measurement with the capability of comprehensive evaluation of the measurement stability and uncertainty. The measurement result reveals that the stability reaches 3.4 nm for a 3.8 m distance at 1.0 s averaging, which further reduces to 0.57 nm at 100 s averaging with a fractional stability of 1.5 × 10(-10). The uncertainty is estimated to be in a 10(-8) level when distance is measured in air due to the inevitable ambiguity in estimating the refractive index, but it can be enhanced to a 10(-10) level in vacuum.
The laser frequency stabilization technology is very important in the development of laser applications, and the improvement of this technology has tend to further expectations for portability and ...low cost, in addition to the realization of strict frequency control. In this context, we construct a dual-cavity laser frequency stabilization system based on an intracavity dual-mode self-reference mechanism. With this approach, we achieve remarkable results with a laser frequency drift of about 6.6 kHz and an Allen deviation (ADEV) of 10 −13 levels over an integration time scale from 0.01 s to 1000 s. Notably, the solution achieves one of the best results without the need for an external reference structure. This work provides a way to realize wavelength-stabilized laser sources by interlocking two DFB lasers. This approach is distinguished by its simplicity and cost-effectiveness, making it a promising option for a variety of applications outside of the laboratory environment.
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