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Xie C.,Huazhong University of Science and Technology | Chen B.,Huazhong University of Science and Technology | Wu J.,Wenhua College
Micromachines | Year: 2017

The interaction of dielectrophoresis (DEP) particles in an electric field has been observed in many experiments, known as the "particle chains phenomenon". However, the study in 3D models (spherical particles) is rarely reported due to its complexity and significant computational cost. In this paper, we employed the iterative dipole moment (IDM) method to study the 3D interaction of a large number of dense DEP particles randomly distributed on a plane perpendicular to a uniform alternating current (AC) electric field in a bounded or unbounded space. The numerical results indicated that the particles cannot move out of the initial plane. The similar particles (either all positive or all negative DEP particles) always repelled each other, and did not form a chain. The dissimilar particles (a mixture of positive and negative DEP particles) always attracted each other, and formed particle chains consisting of alternately arranged positive and negative DEP particles. The particle chain patterns can be randomly multitudinous depending on the initial particle distribution, the electric properties of particles/fluid, the particle sizes and the number of particles. It is also found that the particle chain patterns can be effectively manipulated via tuning the frequency of the AC field and an almost uniform distribution of particles in a bounded plane chip can be achieved when all of the particles are similar, which may have potential applications in the particle manipulation of microfluidics. © 2017 by the authors.

PubMed | Xiamen University, Wenhua College, Peking University and Huazhong University of Science and Technology
Type: | Journal: Scientific reports | Year: 2016

Surface plasmonic systems provide extremely efficient ways to modulate light-matter interaction in photon emission, light harvesting, energy conversion and transferring, etc. Various surface plasmon enhanced luminescent behaviors have been observed and investigated in these systems. But the origin of an avalanche-like photoluminescence, which was firstly reported in 2007 from Au and subsequently from Ag nanowire arrays/monomers, is still not clear. Here we show, based on systematic investigations including the excitation power/time related photoluminescent measurements as well as calculations, that this avalanche-like photoluminescence is in fact a result of surface plasmon assisted thermal radiation. Nearly all of the related observations could be perfectly interpreted with this concept. Our finding is crucial for understanding the surface plasmon mediated thermal and photoemission behaviors in plasmonic structures, which is of great importance in designing functional plasmonic devices.

Xu X.Y.,Wenhua College | Wang K.,China Classification Society Wuhan Branch
Advanced Materials Research | Year: 2014

A design layout optimization for deformable trimaran with the basis of DTMB5415 based on BP neural network is presented. With taking CFD software calculated results for its sample values, BP neural network can predict resistances of the unit displacement under different layout and speed through trained. From above, the best layout of the ship adjusted with the speed can be drawn on the basis of ensuring the calculation accuracy. Compared to traditional CFD method, BP neural network can not only greatly reduce the computational time but also search for the optimal layout corresponding to any speed quickly and reliably. CFD method limited the layout and speed to obtain the minimum resistance value, and BP neural network method broke this inherent mode above and it really play the “deformable” advantage. It can be better applied to engineering practice and provides a new idea for computer-aided layout optimization of triamran. © (2014) Trans Tech Publications, Switzerland.

Yu Y.,Huazhong University of Science and Technology | Fan S.-S.,Huazhong University of Science and Technology | Dai H.-W.,Huazhong University of Science and Technology | Ma Z.-W.,Huazhong University of Science and Technology | And 3 more authors.
Applied Physics Letters | Year: 2014

The third-order optical nonlinearity and response time of Au nanobipyramids have been investigated by using optical Kerr effect technique. Large third-order nonlinear optical susceptibility (χ(3)) and ultrafast optical response time have been obtained at the longitudinal surface plasmon resonance (LSPR) wavelength. As the excitation laser wavelength varies from non-resonance wavelength of 780 nm to the LSPR wavelength of 825 nm, χ(3) increases from 7.4 × 10-14 to 3.9 × 10-13 esu, the fast component of the response time decreases from 141 ± 23 to 83 ± 8 fs and the ratio of the fast component remains around 48%, while the slow response time decreases from 3200 ± 200 to 2310 ± 158 fs. The large enhancement of χ(3) is due to the large local field enhancement caused by the surface plasmon resonance, and the shortening of the response times are induced by the increased probability of the electron-electron and electron-phonon scatterings in the nanosystem. This significant ultrafast optical property in Au nanobipyramids has great application in future ultrafast information processors. © 2014 AIP Publishing LLC.

Zhu H.,Wenhua College | Hu L.,Huazhong University of Science and Technology
Measurement: Journal of the International Measurement Confederation | Year: 2016

In the displacement measurement using digital speckle correlation method, significant measuring error due to the multi-peak nature of the correlation coefficient function is a critical issue as sometimes the secondary peak can be wrongly determined as the maximum instead of the highest peak. In the multi-frequency harmonic wave correlation method (MHCM) as proposed in this work, for speckle patterns before and after the displacement, correlation calculations were performed on corresponding sets of data matrices assembled by amplitudes/intensities obtained from harmonic waves with different frequencies. The calculated maximum correlation coefficients were compared with each other to locate the maximum in order to measure the displacement. Both ultrasonic speckle MHCM and laser speckle MHCM were applied to the displacement measurement respectively. Measured results indicated that MHCM effectively helps to ensure the correct determination of the maximum correlation coefficient, to avoid random errors caused by other factors and improves the measurement accuracy in the meanwhile. © 2016 Elsevier Ltd. All rights reserved.

Wang L.-J.,Wenhua College | Han T.,Huazhong University of Science and Technology
Proceedings - 2014 International Conference on Wireless Communication and Sensor Network, WCSN 2014 | Year: 2014

Based on the quadratic function relation between terminal battery energy consumption and transmission power, this paper introduces the relaying scheme of combining cellular networks and Ad Hoc user terminals to establish the single node model of relay selection mechanism, then an optimal relay selection scheme can be proposed constraint to the specific interrupt probability and power allocation. When part of the base stations are in sleep mode to contribute to save costs and energy consumption, the multi-hop nodes as cooperation relays can ensure the normal communication and realize the optimization of energy efficiency, thus saving the costs caused by a large number of fixed relays. © 2014 IEEE.

Liu L.,Huazhong University of Science and Technology | Xie C.,Huazhong University of Science and Technology | Chen B.,Huazhong University of Science and Technology | Wu J.,Wenhua College
Journal of Chemical Technology and Biotechnology | Year: 2016

BACKGROUND: Dielectrophoresis (DEP) has widely been used to manipulate bio-particles in microfluidic system. The calculation of DEP interaction of a large number of dense particles has been a challenging issue. The Maxwell stress tensor (MST) method is strictly accurate in theory for DEP forces, but the complicated numerical computation is very difficult to implement. An iterative dipole moment method (IDM) is proposed in this paper to study the interaction forces and particle chains of a large number of dense particles in a uniform electrical field. RESULTS: The numerical example of ten particles interaction confirms that the IDM is able to calculate particle interaction forces in good agreement with the MST method. Particle chains of fifty randomly distributed dense particles in a uniform electrical field were simulated using the IDM method and were well consistent with experimental observations. Particle chains of different particle sizes are also investigated. CONCLUSION: The interaction forces of DEP particles calculated by the IDM method are found to be in good agreement with those obtained using the Maxwell stress tensor (MST) method and easy to implement. The simulated particle chains show essential characteristics well consistent with experimental observations. © 2015 Society of Chemical Industry © 2016 Society of Chemical Industry.

Zhu S.,Huazhong University of Science and Technology | Liu J.,Huazhong University of Science and Technology | Ni Y.,Wenhua College | Yao K.,Huazhong University of Science and Technology | Yao K.,CAS International Center for Materials Physics
Journal of Alloys and Compounds | Year: 2016

We report the electronic transport properties of the MnAs(001)/InP(001) magnetic tunnel junctions by first principles calculations. The half-metallic MnAs was predicted as a result of 100% spin polarization and then minority spin current is absolutely inhibited when the bias voltage is applied to terminals of both MnAs and InP. Majority spin current is inhibited when 0.8 V and "relaxed" when the bias voltage increases. Spin-up and spin-down currents flowing in opposite directions are proved to be induced by temperature difference between left and right electrodes called Seebeck Effect rather than external electrical bias. Thermal current was demonstrated perfect spin filtering effects to indicating possible use for fabrication of highly-efficient spin filter devices in this study. © 2015 Elsevier B.V.

Zhu H.,Wenhua College | Wu Y.,Wuhan Institute of Technology
Applied Acoustics | Year: 2016

The digital ultrasonic speckle phase-shifting method (USPM), which is introduced in this paper, can be applied to the measurement of small displacement that is smaller than speckle size at the test point compared to traditional ultrasonic speckle correlation method (USCM). Using USPM, a digital ultrasonic reference signal is introduced to interfere with the ultrasonic speckle signal, which is picked up at the test point on an object surface and is referred to as the object signal. As the phase of the reference signal is shifted several times using the software and then they superimpose with the object signal respectively, the phase of the object signal can be calculated according to the intensities of the superimposed signals. If the object surface moves a small distance, the phase variation of the object speckle can be detected by the same process. As a result, the displacement of the object surface can be measured. Based on the feature of ultrasonic speckles, inner surface displacement of an object can be measured using this proposed method. In this case, the effect of outer surface roughness to the measurement accuracy of USPM is examined experimentally. The experimental results show that the measurement is successful when the displacement is smaller than half of the speckle size at the test point and the roughness parameter Ra of the outer surface of the specimen is less than about 5.47 μm. © 2015 Elsevier Ltd. All rights reserved.

Yu K.,Wenhua College | Bao J.-Q.,Wenhua College
Guangxue Jingmi Gongcheng/Optics and Precision Engineering | Year: 2016

When a thin-film filter is used in oblique incidence, the central wavelengths of the polarization light will be separated obviously, and it will cause serious polarization dependent loss. Therefore, this paper designs a 100 GHz channel spacing stack to depolarize in the central wavelength based on the equivalent layer theory and to realize the angle and wavelength tunes of the thin film filter. Firstly, the depolarization equivalent refractive index in the space layer of the filter was calculated by a phase analysis and to complement the alignment of the different polarization lights. Based on the equivalent layer theory, a symmetric three layer stack was designed to replace the depolarization equivalent refractive index of the spacer. As comparing with the original five layer low polarization thin film filter, the three layer spacer stack is simpler, and it is more accurate to replace the depolarization equivalent refractive index. The simulation and experimental results indicate that the stack can align the polarization light central wavelength from 0° to 20°, in which the polarization light separation is less than 0.03 nm and the wavelength tuning range reaches 35 nm. © 2016, Science Press. All right reserved.

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