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121.
Xing Fan Shou‐Ze Wang Ai‐Li Zheng Xian‐Yong Wei Yun‐Peng Zhao Zhi‐Min Zong Wei Zhao 《Microscopy research and technique》2013,76(7):744-750
Infrared light from a pulsed optical parametric oscillator laser system was used to irradiate succinic acid (SA), a usual solid matrix used in matrix‐assisted laser desorption ionization, under vacuum. Ablated SA particles were trapped using a silica plate mounted 3.0 mm above and parallel to the sample surface. The morphology and particle size of ablated particles at different laser fluences were investigated using a scanning electron microscope (SEM). The dynamics of plume propagation for SA desorption process was studied with fast photography at atmospheric pressure. Plume expanding at 1.12 J/cm2 laser fluence was recorded using a high‐speed CMOS camera and corresponding propagation distance was measured. The solid matrix desorption was driven by phase explosion according to plume model fitting, which was consistent with the results of SEM. Microsc. Res. Tech. 76:744–750, 2013. © 2013 Wiley Periodicals, Inc. 相似文献
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123.
微弱信号的幅值通常很小,且常被噪声淹没,难以检测。文中提出基于互相关和李雅普诺夫指数的微弱正弦信号混沌检测方法。该方法利用互相关方法对微弱正弦信号进行初步去噪,再利用混沌检测方法提取有效信号,以充分发挥互相关及混沌检测在噪声抑制及信号提取方面的优势;将最大李雅普诺夫指数作为判断混沌系统相变的量化依据,自动识别混沌系统的临界状态,从而准确给出用于确定微弱正弦信号幅值的策动力临界阈值。仿真实例分析表明,该方法能有效地检测出深埋于强噪声中的微弱正弦信号,且其检测精度较单独的互相关方法和混沌检测方法更优。 相似文献
124.
论述了基于DSP技术的声表面波射频射别(SAWRFID)阅读器的设计方法。在描述SAWRFID系统的基础上,给出了阅读器的硬件设计和与系统软件流程。最后对标签的反碰撞问题进行了研究。 相似文献
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126.
Milinda Pattanayak Md Nadim F Hoque Zhaoyang Fan Ayrton A. Bernussi 《Science and Technology of Advanced Materials》2018,19(1):693-701
We report large amplitude modulation waveforms as large as ~ 10 V using vanadium dioxide micro-channel devices operating under current-controlled conditions. The self-sustained electrical oscillations were generated by controlling the applied current in the negative differential resistance region of the investigated devices. An appropriate value of internal capacitance was achieved as parasitic capacitance in the device structure to stabilize the electrical oscillations. This eliminates the need of an external pulsed source or any external passive component connected to the micro-channel devices. Amplitude and frequency of the oscillation were tuned by illuminating the device micro-channel with an external laser. An equivalent circuit model was developed to simulate the waveforms. A good agreement between experiment and simulation was verified. 相似文献
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128.
Yu Liu Xing Zou Xiaowei Niu Zhengquan Hu 《International Journal of Circuit Theory and Applications》2020,48(12):2056-2064
According to the characteristics of the chaotic oscillator in detecting weak signals, an algorithm based on Duffing chaotic oscillator array was proposed for acquisition of weak GLONASS signals. By means of GLONASS intermediate frequency and Duffing chaotic oscillator models, Lyapunov exponent is adopted to judge the critical condition of phase track and decide whether GLONASS signals exist or not by the change of the critical condition, and numeric iteration procedure is used to calculate the exponent. Finally, the performance of algorithm is simulated using GLONASS intermediate frequency data. The results indicate that acquisition algorithm can satisfy the need of object positioning in low signal-to-noise ratio environment. 相似文献
129.
Gurumurthy Komanapalli Rajeshwari Pandey Neeta Pandey 《International Journal of Circuit Theory and Applications》2019,47(5):666-685
The objective of this brief is to introduce four new structures of electronically tunable sinusoidal oscillators (SOs) designed using operational transresistance amplifier (OTRA). Each of the proposed SO consists of forward path derived from a generic structure along with one/two OTRA-based resistive gain stages or differentiator in its feedback path. All the proposed SOs enjoy independent tuning of the frequency of oscillation (FO) through resistors without affecting the condition of oscillation (CO). Further, all topologies are found to exhibit low fo sensitivities at all frequencies with respect to circuit parameters, and the second topology is capable of achieving very low frequencies (VLFs) using less RC component spread and provides linear tuning too. The fourth circuit provides quadrature output. The proposed SOs have been successfully implemented and verified in 180-nm CMOS technology node using ADE (analog design environment) tool Cadence Virtuoso. Both prelayout and postlayout simulation results have been included. To assess the oscillator prefabrication performances, Monte Carlo and process-voltage-temperature (PVT) analyses have been performed. The total harmonic distortion (THD) is observed to be less than 3.5%. 相似文献
130.
This paper deals with propagation of Love type waves in a Piezomagnetic layer with corrugated boundaries overlying an inhomogeneous half-space. Inhomogeneity of elastic half-space is caused due to exponential variations in elastic parameters. Dispersion relations are obtained for magnetically open and short cases. Prominent effects of inhomogeneity, layer's width and corrugation on the phase velocity of considered wave are illustrated through graphs. Some particular cases are derived and exhibited through graphs. Also the influence of undulation parameter, elastic parameter, and piezomagnetic coefficient on phase velocity of considered wave has been marked separately. The present study finds its applications in designing and optimization of Love wave sensors and Seismic Acoustic Wave (SAW) devices. Findings may also be used for analytical study of wave propagation in piezomagnetic coupled structures. 相似文献