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981.
微波溶样ICP-AES法测定甘肃东紫苏中的无机元素 总被引:9,自引:3,他引:6
将正交试验和方差分析应用于微波溶样ICP-AES法测定东紫苏地上部分K, Na, Ca, Ba, Pb, Zn, Mn, Cu, Mg, Fe和Al等无机元素的分析中,此方法简单、快速、灵敏度高、准确性好,且多种元素可同时测定,该方法的加标回收率为93.2%~104.1%, RSD(n=5)<3.20%。结果表明: 东紫苏中含有丰富的对人体有益的微量元素,此结果可为探讨东紫苏中元素含量与其药效的相关性提供理论依据。 相似文献
982.
In recent years, a practice of tidal prediction based on a deterministic model or by a time series forecasting model has been established. A deterministic model can predict tidal movement and capture the dynamics of the flow pattern over the entire domain. However, due to the simplification of model settings and near shore effects, the accuracy of the numerical model can diminish. Time series forecasting is capable of capturing the underlying mechanism that may not be revealed in the deterministic model simulation. However, such data‐driven forecast fails to maintain accuracy with the progress of forecast horizon. In this paper, a scheme that combines the advantages of these two methods is introduced. The model errors are forecasted to different time horizons using a data‐driven approach, and are then superimposed on the simulation results in order to correct the model output. Based on the proposed method, it is found that the accuracy is significantly improved with more than 50% of the errors removed on the average. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
983.
Noise reduction in Raman spectra: Finite impulse response filtration versus Savitzky–Golay smoothing
Application of the finite impulse response (FIR) filtration technique for the removal of spectral noise and background broadband deformations from the Raman spectra is tested. Optimal parameters of FIR filters are found and their effectiveness is compared with the Savitzky–Golay (SG) smoothing procedure. The FIR filtration is found to be an effective procedure to treat the whole Raman spectra, but high computing power is needed. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
984.
985.
Measurements of Forces and Temperature Fields in High-Speed Machining of 6061-T6 Aluminum Alloy 总被引:1,自引:0,他引:1
This study focuses on experimental modeling of dry high-speed machining at 30 m/s cutting velocity using 6061-T6 aluminum
alloy. A modified Hopkinson bar apparatus is employed to simulate orthogonal machining, a focused array of mercury–cadmium–tellurium
infrared detectors is used to measure the temperature distribution around the tool tip, and a three-component quartz force
transducer is utilized in measuring the cutting and feed forces. The resulting measurements confirm the assumption of steady-state
cutting and allow for estimation of the partition of cutting work into heating, shear, and momentum changes in the chip. In
an earlier study, measurements of temperature distributions showed little heating of the finished surface. Therefore, a study
of the temperature fields generated during machining with a cutting tool that has a wear-land was performed. The wear-land
contributes significantly to the heating of the workpiece and, at this speed, is the most likely mechanism for the generation
of residual stresses and a temperature rise on the finished surface. 相似文献
986.
Foucault Pendulum-like problems: A tensorial approach 总被引:1,自引:1,他引:0
The paper offers a comprehensive study of the motion in a central force field with respect to a rotating non-inertial reference frame. It is called Foucault Pendulum-like motion and it is a generalization of a classic Theoretical Mechanics problem. A closed form vectorial solution to this famous problem is presented. The vectorial time-explicit solution for the classic Foucault Pendulum problem is obtained as a particular case of the considerations made in the present approach. New interesting conservation laws for the Foucault Pendulum-like motion are deduced by using simple differential and vectorial computations. They help to visualize the shape of the trajectories. Exact vectorial expressions for the law of motion and the velocity are also offered. The case of the driven Foucault Pendulum is also analyzed, and a closed form solution is deduced based on the general considerations. In the end, an new tensorial prime integral for the Foucault Pendulum problem is offered. It helps to reveal in a concise form, within a single entity, all the scalar and vectorial conservation laws for the Foucault Pendulum motion.Two important engineering applications to this approach are presented: the motion of a satellite with respect to a rotating reference frame and the Keplerian relative orbital motion. The latter has a great importance in modeling the problems concerning satellite formation flying, satellite constellations and space terminal rendezvous. The classic problem of the harmonic oscillator in an electromagnetic field is also solved by using the instruments presented in this paper. 相似文献
987.
Yangyang Dai Feng Duan Fan Feng Zhe Sun Yu Zhang Cesar F. Caiafa Pere Marti-Puig Jordi Sol-Casals 《Entropy (Basel, Switzerland)》2021,23(9)
An electroencephalogram (EEG) is an electrophysiological signal reflecting the functional state of the brain. As the control signal of the brain–computer interface (BCI), EEG may build a bridge between humans and computers to improve the life quality for patients with movement disorders. The collected EEG signals are extremely susceptible to the contamination of electromyography (EMG) artifacts, affecting their original characteristics. Therefore, EEG denoising is an essential preprocessing step in any BCI system. Previous studies have confirmed that the combination of ensemble empirical mode decomposition (EEMD) and canonical correlation analysis (CCA) can effectively suppress EMG artifacts. However, the time-consuming iterative process of EEMD may limit the application of the EEMD-CCA method in real-time monitoring of BCI. Compared with the existing EEMD, the recently proposed signal serialization based EEMD (sEEMD) is a good choice to provide effective signal analysis and fast mode decomposition. In this study, an EMG denoising method based on sEEMD and CCA is discussed. All of the analyses are carried out on semi-simulated data. The results show that, in terms of frequency and amplitude, the intrinsic mode functions (IMFs) decomposed by sEEMD are consistent with the IMFs obtained by EEMD. There is no significant difference in the ability to separate EMG artifacts from EEG signals between the sEEMD-CCA method and the EEMD-CCA method (p > 0.05). Even in the case of heavy contamination (signal-to-noise ratio is less than 2 dB), the relative root mean squared error is about 0.3, and the average correlation coefficient remains above 0.9. The running speed of the sEEMD-CCA method to remove EMG artifacts is significantly improved in comparison with that of EEMD-CCA method (p < 0.05). The running time of the sEEMD-CCA method for three lengths of semi-simulated data is shortened by more than 50%. This indicates that sEEMD-CCA is a promising tool for EMG artifact removal in real-time BCI systems. 相似文献
988.
CHEN Li-Mei CAO Li WU Da-Jin GE Guo-Qin 《理论物理通讯》2005,44(4):638-642
The effect on intensity correlation time T by input signal is studied for gain-noise model of a single-mode laser driven by colored pump noise and colored quantum noise with colored cross-correlation with a bias signal modulation in this paper. By using the linear approximation method, we detect that there exists maximum (i.e., resonance) in the curve of the intensity correlation time T upon bias current io when the noise correlation coefficient λ is positive; and there exists minimum (i.e., suppression) in the T-io curve when λ is negative. And whenλ is zero, T increases monotonously with increasing io. Furthermore, the curve of T upon the signal frequency Ω is also studied. Our study shows that no matter what the value of λ is, there exists minimum (i.e., suppression) in the T-Ω curve. 相似文献
989.
基于周期调节的随机共振算法对化学弱信号的检测研究 总被引:3,自引:0,他引:3
提出了一种新的随机共振算法,通过对系统的周期进行调节以实现系统的共振.讨论了实现共振的系统参数,并对模拟信号和拉曼光谱实验信号进行了处理.结果表明,该方法不仅可方便地用于弱化学信号的处理,克服检出信号的滞后现象,而且对不同噪声水平的信号均有良好的适用性. 相似文献
990.
适用于高维数据的正交信号校正预处理方法 总被引:4,自引:0,他引:4
建立了一种高维正交信号校正方法,基于二维PLS到高维PLS的发展思想,把适用于二维数据预处理的正交信号校正方法发展成适用于高维数据预处理的方法.不仅在理论上扩展了正交信号校正方法,而且在实际应用中也能通过与高维PLS的联用产生更有效的高维数据校正方法. 相似文献