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151.
Yu Liu 《数学学报(英文版)》2019,35(8):1334-1356
In the previous article “Hearts of twin cotorsion pairs on exact categories. J. Algebra, 394, 245–284 (2013)”, we introduced the notion o 相似文献
152.
《Chinese Journal of Physics (Taipei)》2018,56(6):3033-3038
Structural and electronic properties of vacancy, water and ethylenediamine substitutions in nitromethane were calculated using the first-principles density-functional theory. The results indicate both vacancy and substitution decrease the band gaps, which suggests the sensitivity of nitromethane has been enhanced. Compared with vacancy and water substitution, ethylenediamine substitution even more distinctly decreases the band gap. It suggests that ethylenediamine substitution has a more remarkable effect on the sensitivity of nitromethane. The calculated formation energies show that the formations of these defects from pure crystals need extra energies. And the elastic constants of defective crystals imply a weak performance in elastic deformation. 相似文献
153.
Magnetic fluid is a kind of colloidal material with tunable microstructure and unique optical properties. The tunable magneto-optical modulation property of magnetic fluid under externally switchable magnetic field with various modulation periods is investigated theoretically and experimentally. The transitional modulation period (lower limit of the working frequency) between the square-like and oscillation-like modulation is achieved and found to be magnetic-field- and sample-concentration-dependent. The modulation mechanism is analyzed and ascribed to the dynamic microstructure of magnetic fluid under different modulation periods of external magnetic fields. The result of this work may be helpful for the pragmatic applications of magnetic fluid based on the square-like modulation. 相似文献
154.
The design of the mold and the choice of the injection parameters for metal injection molding (MIM) is required to maintain homogeneity of the filled mixture. However, powder segregation is unavoidable in MIM because of the significant difference in densities of the metallic powder and the polymer binder. To achieve an effective prediction of segregation effect, a biphasic model based on mixture theory is employed. The viscous behaviors of each phase and the interaction coefficient between the flows of the two phases should be determined. The solution of two coupled Navier–Stokes equations results in a tremendous computation effort. The previous development of an explicit algorithm makes the biphasic simulation much faster than that of the classic methods. However, it is strongly desired to reduce or even eliminate the numerous global solutions for pressure fields at each time step. Hence, a new vectorial algorithm is proposed and developed to perform the simulation only by vectorial operations. It provides the anticipated efficiency in the simulation of biphasic modeling, and the advantage to use the classic elements of equal‐order interpolations. Some results produced by the two algorithms are compared with the experimental values to validate the new vectorial algorithm. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
155.
C.J. Yang W.D. Zhu G.X. Ren 《Communications in Nonlinear Science & Numerical Simulation》2013,18(12):3271-3277
This short communication presents an efficient method for calculating dominant Lyapunov exponents (LEs) of high-dimensional nonlinear dynamic systems based on their reduced-order models obtained from the linear model reduction theory. Mathematical derivation shows that the LEs of the reduced-order models correspond to the dominant LEs of the original systems. Two numerical examples are provided to demonstrate the effectiveness of the method. 相似文献
156.
In this paper, a duopoly Stackelberg model of competition on output is formulated. The firms announce plan products sequentially in planning phase and act simultaneously in production phase. For the duopoly Stackelberg model, a nonlinear dynamical system which describes the time evolution with different strategies is analyzed. We present results on existence, stability and local bifurcations of the equilibrium points. Numerical simulations demonstrate that the system with varying model parameters may drive to chaos and the loss of stability may be caused by period doubling bifurcations. It is also shown that the state variables feedback and parameter variation method can be used to keep the system from instability and chaos. 相似文献
157.
A communication system is implemented on digital signal processors (DSPs) for the underwater acoustic environment. The implemented receiver uses time reversal multi-channel combining followed by a single-channel decision feedback equalizer. Periodic channel estimation is employed to track the channel fluctuations. These techniques are used to mitigate time-varying inter-symbol interference, which is the main challenge in the underwater acoustic channel at operating frequencies greater than 10 kHz. Various optimization tasks are performed to reduce the receiver computational complexity. A fast implementation of the matching pursuit algorithm is tested on the DSP platform. Its performance, in terms of accuracy and run-time, is compared with that of the basic matching pursuit algorithm. Experimental results of the transmission and demodulation of binary phase-shift keying signals at three different symbol rates were obtained in the local Delaware Bay. The low bit error rates demonstrate the effectiveness of our implementation. 相似文献
158.
为了对全国平均每百户居民私家车拥有量进行预测,建立了可分离变量微分方程的数学模型,采用最小二乘法,借助Excel作为计算工具,得到了微分方程近似解的参数值,并用微分方程的近似解估计了最大拥有量以及2010年以后某些年的拥有量. 相似文献
159.
Polyethylene glycol (PEG) as a phase change material possesses three obstacles, such as leakage, low thermal conductivity and low thermal stability. A novel solid-solid phase change material (PCM) based on functionalized graphene oxide (GO), Polyethylene glycol (PEG) was prepared, and the three obstacles of PEG as a PCM was solved in one and the same material. Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), Raman and Transmission electron microscope (TEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetric analysis (TG) and thermogravimetric analysis/infrared spectrometry (TG-IR) were used to study the properties of supporting material and composite PCM (CPCM). The results indicated that the PEG was grafted on the surface of the supporting material; Compared with pure PEG, the latent heat of CPCM with 9.6 wt% supporting material decreased only 5.3%, however, the thermal conductivity of CPCM increased 111% and the heat peak release rate of CPCM decreased 33.4%. 相似文献
160.