41 results on '"Zhiwei Shi"'
Search Results
2. Characteristics of the shedding vortex around the Coanda surface and its impact on circulation control airfoil performance
- Author
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Quanbing Sun, Zhiwei Shi, Zhikun Sun, Sinuo Chen, and Yongliang Chen
- Subjects
Fluid Flow and Transfer Processes ,Mechanics of Materials ,Mechanical Engineering ,Computational Mechanics ,Condensed Matter Physics - Abstract
This study investigates the characteristics of a shedding vortex around the Coanda surface and its impact on circulation control (CC) performance. Delay detach-eddy simulation based on the two-equation [Formula: see text] shear stress transport (SST) turbulence model is performed to solve the flow field. The simulation results show that near the Coanda trailing edge, large vortices periodically shed from the lip above the jet slot, and the shedding vortex is surrounded by a series of strip vortices during its downstream movement. The shedding vortex transfers the disturbance to the jet boundary layer and affects the near-wall velocity. Dynamic mode decomposition shows that the shedding vortex and its high-order harmonic flow structures attenuate very slowly and dominate the flow field. The mode with sub-harmonic frequency of the shedding vortex displays the strip vortices dragged out by the shedding vortex. A larger shedding vortex can intensify the mixing of the jet shear and boundary layers, making the jet velocity decay faster. The size of the shedding vortex can be reduced by decreasing the lip height, thus slowing down the attenuation of the jet velocity and improving the CC performance.
- Published
- 2023
3. Nonlinear wave interactions in a transitional hypersonic boundary layer
- Author
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Chuanhong Zhang and Zhiwei Shi
- Subjects
Fluid Flow and Transfer Processes ,Mechanics of Materials ,Mechanical Engineering ,Computational Mechanics ,Condensed Matter Physics - Abstract
The linear and nonlinear evolutions and breakdown of the second modes in hypersonic boundary layers (HBLs) on a flared cone are investigated using Rayleigh-scattering flow visualization and fast-response pressure sensors. Based on two spatially separated pressure signals, cross-bicoherence analysis that permits the distinction of sum- and difference-interactions is utilized to identify the nonlinear interactions. In addition, the visualization temporal and spatial resolution allows fine flow features to be captured to provide additional flow information. Amplitude correlation technique is used to estimate the nonlinear energy transfer between the modes. Our results show that nonlinear interactions between the second mode and the low-frequency wave contribute to the growth of the low-frequency wave, and the difference interactions between the second mode and its first harmonic play a dominant role in modulating the waves in the overall transition process. Amplitude correlation analysis reveals that the spectral energy is nonlinearly transferred from the second mode into its first harmonic and into low-frequency wave, in agreement with the cross-bicoherence analysis. The amplitude modulation of the second mode caused by the difference interaction between the second mode and its first harmonic will reduce the propagation speed of the second mode. However, at the final breakdown stage, this difference interaction vanishes, and the second-mode propagation velocity recovers quickly. Since the frequency of the second mode keeps almost unchanged over the entire transition process, a higher propagation velocity will result in a larger wavelength, indicating an elongation and deformation of the second mode. Eventually, the difference interaction between the second mode and the low-frequency wave accompanying the energy transfer from the second mode to low-frequency waves leads to the final breakdown of the HBLs into a turbulent state.
- Published
- 2022
4. Study of the transient flow structures generated by a pulsed nanosecond plasma actuator on a delta wing
- Author
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Sinuo Chen, Zhiwei Shi, Xi Geng, Zijie Zhao, Zhen Chen, and Quanbing Sun
- Subjects
Fluid Flow and Transfer Processes ,Mechanics of Materials ,Mechanical Engineering ,Computational Mechanics ,Condensed Matter Physics - Abstract
The transient flow structures produced by a pulsed nanosecond plasma actuator and the mechanism by which they are generated are investigated experimentally and through simulations for the case of flow control on a non-slender delta wing. Phase-averaged particle image velocimetry reveals a phenomenon in which, after each discharge pulse, two sub-vortices are generated in sequence and move along the shear layer regardless of the angle of attack, and this is confirmed by hot-wire anemometry. However, at high actuation frequencies ( F+ = fc/ U∞ ≥ 6.435), this phenomenon of double sub-vortices is not observed, and only one sub-vortex is generated per period. The results of pressure measurements indicate that each sub-vortex gives rise to a distinct pressure fluctuation on the wing surface. Numerical simulations reveal a number of residual heats resulting from plasma thermal effects in the shear layer, each of which turns out to induce a corresponding sub-vortex. At low actuation frequencies ( F+ ≤ 4.29), there is a division of the initial residual heat into two independent residual heats and, hence, double sub-vortices per period, whereas at high actuation frequencies ( F+ ≥ 6.435), residual heats from two consecutive periods merge into one, resulting in just one sub-vortex per period, which provides an explanation for the experimentally observed flow behavior.
- Published
- 2022
5. A study on flow control in a hypersonic inlet using a plasma synthetic jet actuator
- Author
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Weilin Zhang, Zhiwei Shi, Chuanhong Zhang, Xi Geng, Kangli Li, and Zhen Chen
- Subjects
Fluid Flow and Transfer Processes ,Mechanics of Materials ,Mechanical Engineering ,Computational Mechanics ,Condensed Matter Physics - Abstract
The plasma synthetic jet actuator (PSJA) has been proven to have potential for shock wave control in the supersonic/hypersonic flow. To evaluate the possibility for the PSJA applied in the hypersonic inlet under a Mach number greater than the design value and provide a deeper understanding of its control mechanism, the relevant two-dimensional numerical simulations are carried out. Based on the discussions about the numerical results, the effects are clear of the actuations generated by the PSJAs, including diffracted waves, synthetic jets, and discharged heat, on the oblique shock waves induced by the compression ramps and the aerodynamic performance of the hypersonic inlet. Concretely, the shapes of the oblique waves are changed by propagations of the diffracted waves, whose starting point moved due to the synthetic jets. A deceleration occurs near the surface of the hypersonic inlet caused by the movement of the discharged heat, leading to a thickener boundary layer. Furthermore, the incremental analysis about the total pressure recovery coefficient at the throat shows that the diffracted waves can increase the static pressure at the throat achieving a higher total pressure recovery coefficient, while the discharged heat makes the total pressure recovery coefficient drop due to a lower local Mach number at the throat. The effect of the discharged heat is more obvious than that of the diffracted waves.
- Published
- 2022
6. Effect of electrode geometry on the flow structure induced by plasma actuators
- Author
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Zhikun Sun, Zhiwei Shi, Zheng Li, Xi Geng, and Zhenquan Yin
- Subjects
Fluid Flow and Transfer Processes ,Mechanics of Materials ,Mechanical Engineering ,Computational Mechanics ,Condensed Matter Physics - Abstract
Pulsed surface arc discharge (PSAD) is one of the essential techniques in flow control. In this paper, the effects of electrode configuration on heat transfer characteristics of PSAD and disturbance characteristics of PSAD on the flow field were investigated by thermal imaging technology and high-speed photography technology. By defining the curvature of curve (COC) of the electrode, we investigated the physical mechanism of the electrode configuration, affecting the PSAD disturbed flow field. The results show that the COC has the optimal solution COC opt. When COC ≤ COC opt, the smaller the COC, the more concentrated the PSAD disturbances to the flow field. When COC > COC opt, the electrode configuration will have an end point effect, resulting in a deviation between the theoretical COC and the real COC. The larger the COC, the stronger the end point effect, and the more concentrated the PSAD disturbances to the flow field. The COC affects the disturbance degree of PSAD to the flow field by distorting the electric field intensity distribution. The change in the electric field intensity causes the fluctuation frequency of the flow field to be inconsistent with the discharge frequency of the PSAD. The stronger the distortion degree of the electric field intensity, the stronger the high-frequency characteristics of the fluctuating frequency of the flow field, and the stronger the high-frequency characteristics of the flow mode of the flow field. In addition, we obtained the value range of COC opt within 0.5–0.7 through theoretical derivation and established a mathematical model of electrode structure's effect on the flow field's flow structure.
- Published
- 2022
7. Evolution and composition of flow structures generated by nanosecond pulsed surface arc discharge in a magnetic field
- Author
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Zhikun Sun, Zhiwei Shi, Zheng Li, Xi Geng, and Zongsheng Ren
- Subjects
Fluid Flow and Transfer Processes ,Mechanics of Materials ,Mechanical Engineering ,Computational Mechanics ,Condensed Matter Physics - Abstract
The complete flow structure and the composition of the flow structure generated by Pulsed Surface Arc Discharge in a Magnetic Field (M-PSAD) are the keys to explaining the plasma application mechanism. The experimental results show that the M-PSAD can produce plasma clusters and detonation waves. The thermal motion of charged particles in the plasma cluster is the main reason for the thermal effect of arc discharge. The detonation wave consists of the shock wave, Taylor expansion wave, and two different thickness zones of charged particles. The experimental results provide a profound physical mechanism for applying plasma.
- Published
- 2022
8. Effect of flow structure frequency on flow separation control using dielectric barrier discharge actuator
- Author
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Xi Geng, Zhikun Sun, Zheng Li, Zhiwei Shi, Keming Cheng, and B. C. Khoo
- Subjects
Fluid Flow and Transfer Processes ,Mechanics of Materials ,Mechanical Engineering ,Computational Mechanics ,Condensed Matter Physics - Abstract
A better understanding of the mechanism of flow separation suppression by a dielectric barrier discharge is essential for flow control. This paper investigates the mechanism of improving the aerodynamic performance of the airfoil by dielectric barrier discharge when the Reynolds number is in the range of 6 × 104–4 × 105. The results show that the disturbance of the gas discharge to the flow field will form a new flow structure. The fluctuating frequency of the new flow structure determines the ability of the plasma actuator to suppress flow separation. This investigation improves and develops the mechanism of plasma flow control.
- Published
- 2022
9. Edge states supported by different boundaries of two helical lattices with opposite helicity
- Author
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Maowu Zuo, Huagang Li, and Zhiwei Shi
- Subjects
010302 applied physics ,Physics ,Condensed matter physics ,Edge states ,QC1-999 ,Different boundaries ,General Physics and Astronomy ,02 engineering and technology ,Radius ,Edge (geometry) ,021001 nanoscience & nanotechnology ,01 natural sciences ,Helicity ,Nonlinear system ,Amplitude ,Helical lattice ,Lattice (order) ,0103 physical sciences ,Helix ,Waveguide (acoustics) ,0210 nano-technology - Abstract
We discuss linear and nonlinear topological edge states on the bearded-bearded edge (BBE) and armchair-armchair edge (AAE) of two helical waveguide arrays with opposite helicity. The robustness of the linear topological edge state can be controlled by the helix radius, the angle of the incidence, and the amplitude of lattice potentials. In the nonlinear regime, multipole-like lattice quasisolitons may be found with a certain saturable nonlinear factor for AAE. The long-distance propagation dynamics of such quasisolitons are numerically studied from the evolution of their intensity patterns and the “center of mass”. On the contrary, no quasisoltion exists for BBE under the same conditions.
- Published
- 2021
10. Automated Measurement of Spatially Resolved Hair–Hair Single Fiber Adhesion
- Author
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Peter H. Koenig, Zhiwei Shi, Zhanping Zhang, Jeffrey Scott, Nicholas Cadirov, Kai Kristiansen, Roberto C. Andresen Eguiluz, Knut Meinert, Thomas R. Cristiani, Andrei Sergeevich Bureiko, and Jacob N. Israelachvili
- Subjects
Materials science ,Mean curvature ,integumentary system ,Confocal ,Video microscopy ,Surfaces and Interfaces ,Adhesion ,Bending ,Condensed Matter Physics ,Microstructure ,otorhinolaryngologic diseases ,Electrochemistry ,General Materials Science ,Millimeter ,sense organs ,Adhesive ,Composite material ,Spectroscopy - Abstract
The adhesion force between individual human hair fibers in a crosshair geometry was measured by observing their natural bending and adhesive jumps out of contact, using optical video microscopy. The hair fibers' natural elastic responses, calibrated by measuring their natural resonant frequencies, were used to measure the forces. Using a custom-designed, automated apparatus to measure thousands of individual hair-hair contacts along millimeter length scales of hair, it was found that a broad, yet characteristic, spatially variant distribution in adhesion force is measured on the 1 to 1000 nN scale for both clean and conditioner-treated hair fibers. Comparison between the measured adhesion forces and adhesion forces modeled from the hairs' surface topography (measured using confocal laser profilometry) shows they have a good order-of-magnitude agreement and have similar breadth and shape. The agreement between the measurements and the model suggests, perhaps unsurprisingly, that hair-hair adhesion is governed, to a first approximation, by the unique surface structure of the hairs' cuticles and, therefore, the large distribution in local mean curvature at the various individual contact points along the hairs' lengths. We posit that haircare products could best control the surface properties (or at least the adhesive properties) between hairs by directly modifying the hair surface microstructure.
- Published
- 2019
11. Experimental investigation of flow control of a curved-surface jet at Mach 5 hypersonic flow
- Author
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Zhikun Sun, Zhiwei Shi, Zheng Li, Xi Geng, Qijie Sun, Sinuo Chen, and Quanbing Sun
- Subjects
Fluid Flow and Transfer Processes ,Mechanics of Materials ,Mechanical Engineering ,Computational Mechanics ,Condensed Matter Physics - Abstract
Jet flow-control technology is a promising area of fluid research. In this work, the flow-control effect of a curved-surface jet in an incoming flow of Mach = 5 and its underlying control mechanism are experimentally studied using high-speed photography and dynamic force measurement. From the establishment of complete stability of the flow field, the evolutionary process can be roughly divided into five stages: two equilibrium stages (short and long term), jet acceleration stage, bow shock formation stage, interference removal stage, and stable state. By defining the pressure ratio (PR) as an independent variable, it is found that the flow control of the jet occurs through different wave-system structures. The interaction between the jet and the incoming flow produces an oblique shockwave and expansion waves. The shockwave generates thrust and forms a virtual rudder surface; the expansion waves interact with the backflow region and the separated shear layer to generate lift. Moreover, PR has an optimal solution of PR opt. When PR opt, the effect of flow control is related to α, Ve, and ρe, and the greater the PR, the stronger the flow-control effect. When PR > PR opt, the flow-control effect is related to α and ρe, and the larger the PR, the weaker the effect of the shockwave and the stronger the effect of the expansion waves but the slower the growth. In experiments, the thrust, pitching moment, and lift increased by 17.43%, 17.75%, and 9.45%, respectively, because of the appearance of wave-system structure when PR opt = 201.32.
- Published
- 2022
12. Vortex breakdown characteristics of flying wing aircraft based on jet flow control
- Author
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Jiachen Zhu, Zhiwei Shi, Xi Geng, Junquan Fu, Sinuo Chen, and Yongliang Chen
- Subjects
Fluid Flow and Transfer Processes ,Mechanics of Materials ,Mechanical Engineering ,Computational Mechanics ,Condensed Matter Physics - Published
- 2022
13. Theoretical study on regular reflection of shock wave–boundary layer interactions
- Author
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Zhiwei Shi, Bas van Oudheusden, Chengpeng Wang, Longsheng Xue, Keming Cheng, and Ferry Schrijer
- Subjects
Physics ,Shock wave ,boundary layer separation ,Mechanical Engineering ,Regular polygon ,Shock strength ,Ranging ,shock waves ,Mechanics ,Condensed Matter Physics ,01 natural sciences ,Wedge (geometry) ,010305 fluids & plasmas ,Flow separation ,Boundary layer ,symbols.namesake ,Mach number ,Mechanics of Materials ,0103 physical sciences ,symbols ,high-speed flow ,010306 general physics - Abstract
In this paper the configurations of shock wave-boundary layer interactions (SWBLI) are studied theoretically and experimentally in Mach number 2 and 2.5 flows on test models with various wedge angles ranging from to. The proposed theoretical method couples the free interaction theory (FIT) with the minimum entropy production (MEP) principle to predict the appearance of separation shock, resulting in convex, straight and concave separation shock waves according to different solution combinations, which agree well with current experiments. Additionally, several influences on SWBLI are studied experimentally, in which the parameters related to theoretical solutions are found mostly determining the flow configuration, and SWBLI is much more sensitive to incident shock strength than incoming flow properties. Separation could be suppressed by incident shock when the MEP solution is smaller than the FIT, while it could be intensified when the MEP solution is larger than FIT; by contrast, the effects of separation position and model mounting height could be very weak.
- Published
- 2020
14. Investigation of vertical tail buffeting alleviation controlled by nanosecond plasma actuators
- Author
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Sinuo Chen, Zhiwei Shi, Zhen Chen, Xi Geng, and Zijie Zhao
- Subjects
Fluid Flow and Transfer Processes ,Physics ,Mechanics of Materials ,business.industry ,Mechanical Engineering ,Computational Mechanics ,Optoelectronics ,Nanosecond ,Condensed Matter Physics ,business ,Aeroelasticity ,Plasma actuator - Published
- 2021
15. Experimental study on frequency characteristics of the actuations produced by plasma synthetic jet actuator and its geometric effects
- Author
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Zhikun Sun, Zhiwei Shi, Zheng Li, Xi Geng, Weilin Zhang, and Qijie Sun
- Subjects
Fluid Flow and Transfer Processes ,Physics ,Mechanics of Materials ,Mechanical Engineering ,Computational Mechanics ,Mechanics ,Plasma ,Condensed Matter Physics ,Synthetic jet actuator - Published
- 2021
16. Propagation of an Airy-Gaussian vortex beam in defected photonic lattices
- Author
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Zhiwei Shi, Yongtao Xu, Huagang Li, Xing Zhu, and Yang Li
- Subjects
Physics ,Condensed matter physics ,Self-focusing ,Soliton (optics) ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,Electronic, Optical and Magnetic Materials ,Vortex ,Intensity (physics) ,010309 optics ,Amplitude modulation ,Nonlinear system ,Lattice (module) ,0103 physical sciences ,Physics::Accelerator Physics ,Electrical and Electronic Engineering ,010306 general physics ,Beam (structure) - Abstract
We investigate numerically the propagation of an Airy-Gaussian vortex (AiGV) beam in the defected photonic lattices. The propagation properties of the AiGV beam are affected by positive and negative defects. Interestingly, we find that the intensity distribution of the AiGV beam focuses on the position of the defect and then forms a lattice soliton for the positive defect. On the contrary, the AiGV beam is diffused for the negative defect. The higher value the defected depth is, the more energy can be constrained by the positive defect and the shorter transmission distance for the beam forming a lattice soliton is. And the effect of nonlinear is smaller than the effect of defects. Moreover, by changing the effects of nonlinearity, the lattice modulation depth, the defect depth and the distribution factor, we can control the propagation distance for the AiGV beam focusing for the positive defect.
- Published
- 2017
17. Gap solitons in parity-time-symmetric mixed linear-nonlinear optical lattices with fourth-order diffraction
- Author
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Xing Zhu, Zhiwei Shi, and Huagang Li
- Subjects
Diffraction ,Physics ,Coupling constant ,Condensed matter physics ,business.industry ,Parity (physics) ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,Electronic, Optical and Magnetic Materials ,010309 optics ,Nonlinear optical ,Dipole ,Nonlinear Sciences::Exactly Solvable and Integrable Systems ,Fourth order ,Optics ,Quantum mechanics ,0103 physical sciences ,Electrical and Electronic Engineering ,Physical and Theoretical Chemistry ,010306 general physics ,business ,Nonlinear Sciences::Pattern Formation and Solitons - Abstract
We report on the existence and stability of fundamental and out-of-phase dipole gap solitons in parity-time (PT)-symmetric mixed linear-nonlinear optical lattices with a fourth-order diffraction. These solitons exist in the semi-infinite gap. For fundamental gap solitons, they can bifurcate from the higher edge of the first Bloch band, solitons are stable in the low power region. For dipole gap solitons, they cannot bifurcate from the higher edge of the first Bloch band, they can stably exist in the moderate power region. The coupling constant of the fourth-order diffraction can influence the stability of these gap solitons.
- Published
- 2017
18. Defect matter-wave gap solitons in spin–orbit-coupled Bose–Einstein condensates in Zeeman lattices
- Author
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Zhiwei Shi, Xing Zhu, and Huagang Li
- Subjects
Physics ,Zeeman effect ,Condensed matter physics ,General Physics and Astronomy ,01 natural sciences ,law.invention ,010309 optics ,Coupling (physics) ,Nonlinear system ,symbols.namesake ,law ,Quantum mechanics ,0103 physical sciences ,symbols ,Even and odd functions ,Matter wave ,Orbit (control theory) ,010306 general physics ,Nonlinear Sciences::Pattern Formation and Solitons ,Bose–Einstein condensate ,Spin-½ - Abstract
We report on the properties of fundamental defect matter-wave gap solitons in spin–orbit-coupled Bose–Einstein condensates in one-dimensional Zeeman lattices with attractive nonlinearity. One component of these solitons is a real even function, and the other is an imaginary odd function. When the defect is repulsive, these solitons can be stable in the semi-infinite, first, and second gaps. Increasing the strength of spin–orbit coupling, stable defect gap-stripe solitons in the semi-infinite and first gaps are found. However, for an attractive defect, the solitons only stably exist in the semi-infinite gap and cannot be close to the lower edge of the first Bloch band.
- Published
- 2016
19. Interaction of Airy-Gaussian beams in photonic lattices with defects
- Author
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Zhiwei Shi, Huagang Li, Ying Xiang, Xing Zhu, and Jing Xue
- Subjects
Physics ,Diffraction ,Condensed matter physics ,Breather ,Gaussian ,Interference (wave propagation) ,01 natural sciences ,010309 optics ,Nonlinear system ,symbols.namesake ,Amplitude ,Lattice (order) ,0103 physical sciences ,symbols ,Physics::Accelerator Physics ,010306 general physics ,Beam (structure) - Abstract
We investigate numerically the interaction between two finite Airy-Gaussian (AiG) beams in different media with the defected photonic lattices in one transverse dimension. We discuss that the beams with different intensities and phases launch into the different lattice structures but accelerate in opposite directions. During interactions, the interference fringe, breathers, and soliton pairs are observed. In the linear media, the initial deflection direction of the accelerated beams is changed by adjusting the phase shift and the beam interval. For a certain lattice period, the periodic interference fringe can form. A constructive or destructive interference can vary with the defect depth and phase shift. While the nonlinearity is introduced, the breathers is generated. Especially in the self-defocusing media, the appropriate AiG beam amplitude and lattice depth may lead to the formation of soliton pairs, On the contrary, the interaction of two Gaussian beams is diffraction.
- Published
- 2016
20. Study of the airflow induced by a sliding discharge plasma actuator
- Author
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Li Zheng, Qijie Sun, Zhiwei Shi, Hao Dong, and Xi Geng
- Subjects
Materials science ,Airflow ,Statistical and Nonlinear Physics ,Plasma ,Active flow control ,Mechanics ,Condensed Matter Physics ,01 natural sciences ,Deflection angle ,Particle image velocimetry ,0103 physical sciences ,Electric discharge ,010306 general physics ,Plasma actuator - Abstract
Sliding discharge, as a new type of electrical discharge, is being gradually applied in plasma active flow control in recent years. In this work, the particle image velocimetry (PIV) experiments were conducted to investigate the airflow characteristics induced by the sliding discharge plasma actuator at varied voltage signals. The results show that the integral thrust produced by the negative alternating current (AC) power is stronger than normal AC power under the same voltage magnitude. The induced airflow direction changes along with the changing of two power voltage signals. Furthermore, the angle of the induced airflow is mainly linear with the loading voltage.
- Published
- 2019
21. UV Photoactivated Room Temperature CVD of Aluminum on Functionalized Self-Assembled Monolayers Adsorbed on Au
- Author
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Amy V. Walker, Peng Lu, and Zhiwei Shi
- Subjects
Reaction mechanism ,Materials science ,Dimer ,Photodissociation ,Inorganic chemistry ,Self-assembled monolayer ,Surfaces and Interfaces ,Chemical vapor deposition ,Condensed Matter Physics ,Photochemistry ,Dissociation (chemistry) ,chemistry.chemical_compound ,Monomer ,chemistry ,Monolayer ,Electrochemistry ,General Materials Science ,Spectroscopy - Abstract
We have investigated the selective photoactivated room temperature chemical vapor deposition (CVD) of aluminum (Al) on functionalized self-assembled monolayers adsorbed on Au. The CVD precursor employed is trimethyl aluminum (TMA). Using a deuterium arc lamp we demonstrate that the rate of the Al film growth is approximately twice that observed for nonphotoactivated Al chemical vapor deposition (CVD) using TMA. At the wavelengths employed, the photolysis of TMA leads to the dissociation of the TMA dimer to its monomer followed by successive release of methyl groups to form (CH(3))(3-x)Al. The photogenerated (CH(3))(3-x)Al species react with -OH- and -COOH-terminated SAMs but not -CH(3)-terminated SAMs. Using these reactions we demonstrate that aluminum can be selectively deposited on -CH(3)/-COOH-patterned SAMs. The possible reaction mechanisms involved in the Al film growth are discussed. These results indicate that photoactivated CVD (laser CVD) processes are suitable for the deposition of stable films of metals and other materials on organic films.
- Published
- 2012
22. Selective Electroless Deposition of Copper on Organic Thin Films with Improved Morphology
- Author
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Zhiwei Shi, Amy V. Walker, and Peng Lu
- Subjects
Materials science ,chemistry.chemical_element ,Organic layer ,Electroless deposition ,Nanotechnology ,Surfaces and Interfaces ,Condensed Matter Physics ,Copper ,chemistry ,Chemical engineering ,Monolayer ,Electrochemistry ,General Materials Science ,Crystallite ,Thin film ,Spectroscopy - Abstract
We have investigated the selective electroless deposition (ELD) of Cu on functionalized self-assembled monolayers (SAMs). Previous studies have demonstrated that Cu deposits on -COOH and -CH(3) terminated SAMs using ELD. However, the deposited films were rough and contained irregular crystallites. Further, the copper penetrated through the film. In this Article, we demonstrate that copper can be selectively deposited on -COOH terminated SAMs with improved morphology and without penetration of copper through the organic layer. The method employs a Cu(II) seed layer and an additive, adenine or guanine. We demonstrate the efficacy of the technique on photopatterned -CH(3)/-COOH SAMs. Copper is observed to deposit only atop the -COOH terminated SAM area and not on the -CH(3) terminated SAM. The use of a Cu(II) seed layer increased the Cu ELD rate on both -COOH and -CH(3) terminated SAMs. The deposited copper layer strongly adheres to the -COOH terminated SAMs because the copper layer nucleates at Cu(2+)-carboxylate complexes. In contrast, the deposited copper layer can easily be removed from the -CH(3) terminated SAM surface because there is no specific copper-surface interaction. The additives adenine and guanine mediate the interaction of Cu(2+) and the deprotonated -COOH terminated SAMs via the formation of additive-carboxylate complexes. These complexes lead to significantly reduced copper penetration through the SAM. In the case of adenine, the diffusion of copper through the organic film was eliminated. This new technique for copper deposition will facilitate the development of inexpensive molecular electronics, sensors, and other nanotechological devices.
- Published
- 2011
23. Analysis of flow separation control using nanosecond-pulse discharge plasma actuators on a flying wing
- Author
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Hai Du, Geng Xi, Zhiwei Shi, Qijie Sun, Chenyao Wei, and Zheng Li
- Subjects
010302 applied physics ,Wing ,Materials science ,Fluid mechanics ,Dielectric ,Mechanics ,Aerodynamics ,Plasma ,Condensed Matter Physics ,01 natural sciences ,010305 fluids & plasmas ,Flow separation ,0103 physical sciences ,Actuator ,Plasma actuator - Published
- 2018
24. Experimental investigations on characteristics of boundary layer and control of transition on an airfoil by AC-DBD
- Author
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Zhiwei Shi, Keming Cheng, Qun Zhao, Xi Geng, Hao Dong, and Sinuo Chen
- Subjects
Airfoil ,020301 aerospace & aeronautics ,Materials science ,Statistical and Nonlinear Physics ,02 engineering and technology ,Aerodynamics ,Mechanics ,Plasma ,Condensed Matter Physics ,01 natural sciences ,010305 fluids & plasmas ,Physics::Fluid Dynamics ,Flow control (fluid) ,Boundary layer ,0203 mechanical engineering ,0103 physical sciences - Abstract
Plasma-based flow control is one of the most promising techniques for aerodynamic problems, such as delaying the boundary layer transition. The boundary layer’s characteristics induced by AC-DBD plasma actuators and applied by the actuators to delay the boundary layer transition on airfoil at Ma = 0.3 were experimentally investigated. The PIV measurement was used to study the boundary layer’s characteristics induced by the plasma actuators. The measurement plane, which was parallel to the surface of the actuators and 1 mm above the surface, was involved in the test, including the perpendicular plane. The instantaneous results showed that the induced flow field consisted of many small size unsteady vortices which were eliminated by the time average. The subsequent oil-film interferometry skin friction measurement was conducted on a NASA SC(2)-0712 airfoil at Ma = 0.3. The coefficient of skin friction demonstrates that the plasma actuators successfully delay the boundary layer transition and the efficiency is better at higher driven voltage.
- Published
- 2018
25. Modal Fields in a Symmetric Metal-Clad Planar Uniaxial Crystal Waveguide
- Author
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Zhiwei Shi and Qi Guo
- Subjects
Physics ,Waveguide (electromagnetism) ,Guided wave testing ,Condensed matter physics ,Uniaxial crystal ,business.industry ,Physics::Optics ,Atomic and Molecular Physics, and Optics ,Optics ,Electromagnetism ,Electric field ,Dispersion relation ,Dispersion (optics) ,Classical electromagnetism ,business - Abstract
Classical electromagnetic theory is applied to determine the eigenvalue equation and the fields of the allowed guided modes in a symmetric metal-clad planar uniaxial crystal waveguide for an arbitrary orientation of the optical axes. There are different hybrid guided modes in the different uniaxial crystals. For each mode, the conditions for their existence, the dispersion equation, and the accuracy of the solutions of the modal fields are analytically discussed. We report the propagation conditions and the asymmetry of various electric field distributions of the single modes.
- Published
- 2009
26. EXPERIMENTAL INVESTIGATION ON A PITCHING MOTION DELTA WING IN UNSTEADY FREE STREAM
- Author
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Zhiwei Shi and Xiao Ming
- Subjects
Flow visualization ,Washout (aeronautics) ,Delta wing ,Angle of attack ,Flow (psychology) ,Statistical and Nonlinear Physics ,Aerodynamics ,Mechanics ,Condensed Matter Physics ,Geology ,Vortex ,Wind tunnel - Abstract
As combat aircraft becomes more and more maneuverable, the need to understand the unsteady behavior of aircraft in dynamic flow fields becomes more important. Usually researchers pay more attention to the effects on the changes of AOA, but ignore the effects of velocity variations. It is known that the velocity of aircraft changes greatly when the aircraft undergoes a high angle of attack maneuver, like "cobra" maneuver. To completely simulate and study the effect of rapid changes in both free stream velocity and angle of attack, a pitching motion setup is developed in the unsteady wind tunnel of NUAA. By measuring unsteady loads, unsteady pressure distribution and flow visualization, the unsteady aerodynamic behavior of a pitching isolated delta wing and the pitching delta wing coupled with unsteady free stream are investigated. It is found that the oscillating free stream velocity affects the hysteresis characteristics of the pitching delta wing further. The pressure distribution and flow visualization measurements show that the changes in the structure of the leading-edge vortices are the main reason. These studies conclude that a good understanding of the unsteady aerodynamics is vitally important in the design of super-maneuverable aircraft.
- Published
- 2009
27. Chemical bath deposition of ZnO on functionalized self-assembled monolayers: selective deposition and control of deposit morphology
- Author
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Zhiwei Shi and Amy V. Walker
- Subjects
Materials science ,Inorganic chemistry ,Nucleation ,chemistry.chemical_element ,Ethylenediamine ,Self-assembled monolayer ,Surfaces and Interfaces ,Zinc ,Condensed Matter Physics ,Nanocrystalline material ,chemistry.chemical_compound ,chemistry ,Chemical engineering ,Monolayer ,Electrochemistry ,General Materials Science ,Crystallite ,Spectroscopy ,Chemical bath deposition - Abstract
We have developed a method by which to selectively and reproducibly deposit ZnO films on functionalized self-assembled monolayers (SAMs) using chemical bath deposition (CBD). The deposition bath is composed of zinc acetate and ethylenediamine. The deposition reaction pathways are shown to be similar to those observed for sulfides and selenides, even though ethylenediamine acts as both an oxygen source and a complexing agent. On -COOH terminated SAMs, Zn-carboxylate surface complexes act as nucleation sites for ion-by-ion growth, leading to the formation of adherent ZnO nanocrystallites. Cluster-by-cluster growth is also observed, which produces weakly adherent micrometer-sized ZnO crystallites. On -CH3 and -OH terminated SAMs, only micrometer-sized ZnO crystallites are observed because Zn(2+) does not complex with the SAM terminal group, preventing nucleation of the nanocrystalline phase. The application of either ultrasound ("sonication-assisted CBD") or stirring promotes ion-by-ion ZnO growth on -COOH terminated SAMs. Stirring produces smoother but less reproducible ZnO films than sonication-assisted CBD.
- Published
- 2015
28. Gap solitons in spin–orbit-coupled Bose–Einstein condensates in mixed linear–nonlinear optical lattices
- Author
-
Huagang Li, Xing Zhu, Zhiwei Shi, Ying Xiang, and Yingji He
- Subjects
Physics ,Angular momentum ,Condensed matter physics ,Condensed Matter Physics ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,Symmetry (physics) ,010305 fluids & plasmas ,law.invention ,Coupling (physics) ,symbols.namesake ,Nonlinear Sciences::Exactly Solvable and Integrable Systems ,Amplitude ,Stark effect ,law ,0103 physical sciences ,symbols ,Soliton ,010306 general physics ,Nonlinear Sciences::Pattern Formation and Solitons ,Bose–Einstein condensate ,Spin-½ - Abstract
We investigate the properties of gap solitons in spin–orbit-coupled Bose–Einstein condensates in mixed linear–nonlinear optical lattices. The mixed linear–nonlinear optical lattices can support parity-time (PT)-symmetric soliton solutions, and these PT-symmetric solitons can stably exist in the semi-infinite gap of linear optical lattices. The PT-symmetric gap-stripe solitons are found by increasing the strength of the spin–orbit coupling. It is found that the amplitude of the nonlinear optical lattices can significantly affect the stability of these gap and gap-stripe solitons. With an increase of the amplitude of the nonlinear optical lattices, the stable domains of the gap and gap-stripe solitons are shrunk. The unstable solitons can show unique evolution characteristics and the stability analyses are also confirmed by the evolution simulations.
- Published
- 2017
29. Experimental investigation of lift enhancement for flying wing aircraft using nanosecond DBD plasma actuators
- Author
-
Du Hai, Chengjun He, Haibo He, Zhiwei Shi, Danjie Zhou, and Junkai Yao
- Subjects
020301 aerospace & aeronautics ,Leading edge ,Lift coefficient ,Wing ,Materials science ,Angle of attack ,Stall (fluid mechanics) ,02 engineering and technology ,Mechanics ,Condensed Matter Physics ,01 natural sciences ,010305 fluids & plasmas ,0203 mechanical engineering ,Drag ,0103 physical sciences ,Pitching moment ,Plasma actuator - Abstract
The effects of the arrangement position and control parameters of nanosecond dielectric barrier discharge (NS-DBD) plasma actuators on lift enhancement for flying wing aircraft were investigated through wind tunnel experiments at a flow speed of 25 m s−1. The aerodynamic forces and moments were obtained by a six-component balance at angles of attack ranging from −4° to 28°. The lift, drag and pitching moment coefficients were compared for the cases with and without plasma control. The results revealed that the maximum control effect was achieved by placing the actuator at the leading edge of the inner and middle wing, for which the maximum lift coefficient increased by 37.8% and the stall angle of attack was postponed by 8° compared with the plasma-off case. The effects of modulation frequency and discharge voltage were also investigated. The results revealed that the lift enhancement effect of the NS-DBD plasma actuators was strongly influenced by the modulation frequency. Significant control effects were obtained at f = 70 Hz, corresponding to F + ≈ 1. The result for the pitching moment coefficient demonstrated that the plasma actuator can induce the reattachment of the separation flows when it is actuated. However, the results indicated that the discharge voltage had a negligible influence on the lift enhancement effect.
- Published
- 2017
30. Nonlocal defect solitons in parity-time-symmetric superlattices with defocusing nonlinearity
- Author
-
Limin Fang, Xing Zhu, Huagang Li, Zhiwei Shi, and Jie Gao
- Subjects
Physics ,Nonlinear system ,Transverse plane ,Quantum nonlocality ,Condensed matter physics ,Superlattice ,Quantum mechanics ,Parity (physics) ,Soliton ,Nonlinear Sciences::Pattern Formation and Solitons ,Atomic and Molecular Physics, and Optics - Abstract
We report on the nonlocal fundamental defect soliton in parity-time (PT)-symmetric superlattices with defocusing nonlinearity. For positive defect, soliton exist in the second gap, the first gap and the semi-infinite gap. They can be stable in the low power region in the first gap and semi-infinite gap. For negative defect, defect solitons only exist in the second gap, and can also be stable in the low power region. The degree of nonlocality can significantly affect the stability of these defect solitons. We also study the transverse power-flow of these defect solitons in the PT-symmetric superlattices.
- Published
- 2014
31. Efficient p-type dye-sensitized solar cells with all-nano-electrodes: NiCo2S4 mesoporous nanosheet counter electrodes directly converted from NiCo2O4 photocathodes
- Author
-
Hao Lu, Fengren Cao, Jun Guo, Zhiwei Shi, Kaimo Deng, Qiong Liu, and Liang Li
- Subjects
Photocurrent ,Materials science ,Nano Express ,Non-blocking I/O ,p-type ,Nanotechnology ,Ternary sulfides ,Electrolyte ,Tin oxide ,Condensed Matter Physics ,Dye-sensitized solar cells ,Dye-sensitized solar cell ,Chemical engineering ,Materials Science(all) ,Nanosheets ,Electrode ,General Materials Science ,Counter electrodes ,Mesoporous material ,Nanosheet - Abstract
We report the successful growth of NiCo2S4 nanosheet films converted from NiCo2O4 nanosheet films on fluorine-doped tin oxide substrates by a low-temperature solution process. Low-cost NiCo2S4 and NiCo2O4 nanosheet films were directly used for replacing conventional Pt and NiO as counter electrodes and photocathodes, respectively, to construct all-nano p-type dye-sensitized solar cells (p-DSSCs) with high performance. Compared to Pt, NiCo2S4 showed higher catalytic activity towards the I-/I3 - redox in electrolyte, resulting in an improved photocurrent density up to 2.989 mA/cm2, which is the highest value in reported p-DSSCs. Present p-DSSCs demonstrated a cell efficiency of 0.248 % that is also comparable with typical NiO-based p-DSSCs.
- Published
- 2014
32. Novel ZnO microflowers on nanorod arrays: local dissolution-driven growth and enhanced light harvesting in dye-sensitized solar cells
- Author
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Kaimo Deng, Hongtao Fan, Liang Li, Qiong Liu, Hao Lu, Zhiwei Shi, and Guobin Zhu
- Subjects
Nanostructure ,Materials science ,Nano Express ,Energy conversion efficiency ,Nanochemistry ,Nanotechnology ,Dye-sensitized solar cells ,Condensed Matter Physics ,Light scattering ,Light harvesting ,Microflowers ,Dye-sensitized solar cell ,Materials Science(all) ,ZnO ,Nanorod arrays ,General Materials Science ,Nanorod ,Dissolution ,Solution process - Abstract
ZnO nanostructures were manipulated, via a low-temperature solution process, from pure nanorod arrays to complex nanostructures of microflowers on nanorod arrays with adjusted quantities of flowers. We proposed the mechanism of local dissolution-driven growth to rationally discuss the novel growth process. These nanostructures were used as photoanodes in dye-sensitized solar cells. Compared to pure nanorod arrays, the nanorod array-microflower hierarchical structures improved the power conversion efficiency from 0.41% to 0.92%, corresponding to a 124% efficiency increase. The enhancement of the efficiency was mainly ascribed to the synergistic effect of the enhanced surface area for higher dye loading and the improved light harvesting from efficient light scattering. Present results provide a promising route to improve the capability of light-harvesting for ZnO nanorod array-based DSSCs.
- Published
- 2014
33. Bulk vortices and half-vortex surface modes in parity-time-symmetric media
- Author
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Chaohong Lee, Boris A. Malomed, Xing Zhu, Zhiwei Shi, Huagang Li, and Tianshu Lai
- Subjects
Physics ,Condensed matter physics ,FOS: Physical sciences ,Parity (physics) ,Pattern Formation and Solitons (nlin.PS) ,Parameter space ,Nonlinear Sciences - Pattern Formation and Solitons ,Atomic and Molecular Physics, and Optics ,Vortex ,Nonlinear optical ,Nonlinear system ,Photonic lattices ,Bloch wave ,Physics - Optics ,Optics (physics.optics) - Abstract
We demonstrate that in-bulk vortex localized modes, and their surface half-vortex ("horseshoe") counterparts self-trap in two-dimensional (2D) nonlinear optical systems with $\mathcal{PT}$-symmetric photonic lattices (PLs). The respective stability regions are identified in the underlying parameter space. The in-bulk states are related to truncated nonlinear Bloch waves in gaps of the PL-induced spectrum. The basic vortex and horseshoe modes are built, severally, of four and three beams with appropriate phase shifts between them. Their stable complex counterparts, built of up to 12 beams, are reported too., Comment: 5 pages, 4 figures
- Published
- 2014
- Full Text
- View/download PDF
34. Nonlocal solitons in dual-periodicPT-symmetric optical lattices
- Author
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Zhiwei Shi, Huagang Li, Xing Zhu, and Xiujuan Jiang
- Subjects
Physics ,Quantum nonlocality ,Nonlinear Sciences::Exactly Solvable and Integrable Systems ,Condensed matter physics ,Degree (graph theory) ,Quantum mechanics ,Energy flow ,State (functional analysis) ,Propagation constant ,Nonlinear Sciences::Pattern Formation and Solitons ,Stability (probability) ,Atomic and Molecular Physics, and Optics - Abstract
We numerically study the nonlocal solitons in dual-periodic parity-time ($\mathcal{PT}$) symmetric optical lattices built into a nonlocal self-focusing medium. We state the existence, stability, and propagation dynamics of such $\mathcal{PT}$-gap solitons in detail. Simulated results show that there exist stable gap solitons. The energy flow density and the stable region of the $\mathcal{PT}$-gap solitons in both the propagation constant and the degree of nonlocality are also examined.
- Published
- 2012
35. Synthesis of nickel nanowires via electroless nanowire deposition on micropatterned substrates
- Author
-
Zhiwei Shi and Amy V. Walker
- Subjects
Materials science ,Nanowire ,chemistry.chemical_element ,Nanotechnology ,Surfaces and Interfaces ,Condensed Matter Physics ,Metal ,Nickel ,chemistry ,visual_art ,Electrochemistry ,visual_art.visual_art_medium ,Deposition (phase transition) ,General Materials Science ,Vapor–liquid–solid method ,Spectroscopy - Abstract
Electroless nanowire deposition on micropatterned substrates (ENDOM) is a promising new technique by which to direct the synthesis and precise placement of metallic nanowires. ENDOM is generally applicable to the preparation of metallic, semiconducting, and even insulating nanowires on technologically relevant substrates, is inexpensive, and can achieve high growth rates. The deposited nanowires are ultralong (centimeters) and can be patterned in arbitrary shapes. We demonstrate ENDOM using the growth of nickel nanowires. By controlling the deposition time, the width of the nanowires can be varied from 200 to 1000 nm and the height can be varied from 7 to 20 nm.
- Published
- 2011
36. Investigation of the mechanism of nickel electroless deposition on functionalized self-assembled monolayers
- Author
-
Amy V. Walker and Zhiwei Shi
- Subjects
Chemistry ,Analytical chemistry ,Self-assembled monolayer ,Surfaces and Interfaces ,Condensed Matter Physics ,Secondary ion mass spectrometry ,X-ray photoelectron spectroscopy ,Chemical engineering ,Physical vapor deposition ,Monolayer ,Electrochemistry ,General Materials Science ,Self-assembly ,Thin film ,Spectroscopy ,Deposition (law) - Abstract
We have investigated the seedless electroless deposition (ELD) of Ni on functionalized self-assembled monolayers (SAMs) using scanning electron and optical microscopies, X-ray photoelectron spectroscopy, and time-of-flight secondary ion mass spectrometry. For all SAMs studied, the Ni deposition rate is dependent on the bath pH, deposition temperature, and complexing agent. In contrast to the physical vapor deposition of Ni on SAMs, electrolessly deposited Ni does not penetrate through the SAM. This behavior indicates that ELD is a suitable technique for the deposition of low-to-moderate reactivity on organic thin films. We demonstrate that Ni can be selectively deposited on SAMs using two different methods. First, selectivity can be imparted by the formation of Ni(II)-surface complexes. As a demonstration, we selectively deposited Ni on the -COOH terminated SAM areas of patterned -COOH/-CH(3) or -COOH/-OH terminated SAMs. Here, Ni(2+) ions form Ni(2+)-carboxylate complexes with the -COOH terminal group, which comprise the nucleation sites for subsequent metal deposition. Second, we demonstrate that nickel is selectively deposited on the -CH(3) terminated SAM areas of a patterned -OH/-CH(3) terminated SAM. In this case, the Ni(2+) ion does not specifically interact with the -CH(3) terminal group. Rather, selectivity is imparted by the interaction of the reductant, dimethylamine borane (DMAB), with the -OH and -CH(3) terminal groups.
- Published
- 2011
37. (2+1)D surface solitons at the interface between a linear medium and a nonlocal nonlinear medium
- Author
-
Qi Guo, Zhiwei Shi, and Huagang Li
- Subjects
Physics ,Condensed matter physics ,FOS: Physical sciences ,Statistical and Nonlinear Physics ,Pattern Formation and Solitons (nlin.PS) ,Nonlinear Sciences - Pattern Formation and Solitons ,Atomic and Molecular Physics, and Optics ,Linear medium ,Nonlinear system ,Dipole ,Surface wave ,Quantum mechanics ,Nonlinear medium ,Light beam ,Initial value problem ,Nonlinear Sciences::Pattern Formation and Solitons ,Beam (structure) - Abstract
We address (2+1)D surface solitons occurring at the interface between a linear medium and a nonlocal nonlinear medium whose nonlinear contribution to the refractive index has a initial value at the interface. We find that there exist stable single and dipole surface solitons which do not exhibit a power threshold. The properties of the surface solitons can be affected by the initial value and the degree of nonlocality. When a laser beam is launched away from the interface, the beam will be periodic oscillations., 16 pages, 6 figures
- Published
- 2011
38. Room temperature atomic layerlike deposition of ZnS on organic thin films: Role of substrate functional groups and precursors
- Author
-
Zhiwei Shi and Amy V. Walker
- Subjects
Chemistry ,Inorganic chemistry ,Substrate (chemistry) ,chemistry.chemical_element ,Self-assembled monolayer ,Surfaces and Interfaces ,Zinc ,Condensed Matter Physics ,Zinc sulfide ,Surfaces, Coatings and Films ,chemistry.chemical_compound ,Atomic layer deposition ,Monolayer ,Polymer chemistry ,Self-assembly ,Thin film - Abstract
The room temperature atomic layerlike deposition (ALLD) of ZnS on functionalized self-assembled monolayers (SAMs) was investigated, using diethyl zinc (DEZ) and in situ generated H2S as reactants. Depositions on SAMs with three different terminal groups, –CH3, –OH, and –COOH, were studied. It was found that the reaction of DEZ with the SAM terminal group is critical in determining the film growth rate. Little or no deposition is observed on –CH3 terminated SAMs because DEZ does not react with the methyl terminal group. ZnS does deposit on both –OH and –COOH terminated SAMs, but the grow rate on –COOH terminated SAMs is ∼10% lower per cycle than on –OH terminated SAMs. DEZ reacts with the hydroxyl group on –OH terminated SAMs, while on –COOH terminated SAMs it reacts with both the hydroxyl and carbonyl bonds of the terminal groups. The carbonyl reaction is found to lead to the formation of ketones rather than deposition of ZnS, lowering the growth rate on –COOH terminated SAMs. SIMS spectra show that both –OH and –COOH terminated SAMs are covered by the deposited ZnS layer after five ALLD cycles. In contrast to ZnO ALLD where the composition of the film differs for the first few layers on –COOH and –OH terminated SAMs, the deposited film composition is the same for both –COOH and –OH terminated SAMs. The deposited film is found to be Zn-rich, suggesting that the reaction of H2S with the Zn-surface adduct may be incomplete.
- Published
- 2015
39. Surface defect gap solitons in optical lattices with nonlocal nonlinearity
- Author
-
Jie Gao, Zhiwei Shi, Xing Zhu, Huagang Li, and Limin Fang
- Subjects
Physics ,Surface (mathematics) ,Nonlinear system ,Quantum nonlocality ,Optical lattice ,Nonlinear Sciences::Exactly Solvable and Integrable Systems ,Condensed matter physics ,Kerr nonlinearity ,Quantum mechanics ,Statistical and Nonlinear Physics ,Condensed Matter Physics ,Self-phase modulation ,Nonlinear Sciences::Pattern Formation and Solitons - Abstract
We show that stable surface fundamental defect solitons can exist in different gaps of an optical lattice with focusing nonlocal Kerr nonlinearity. For positive defect, solitons stably exist in the semi-infinite gap. For negative defect, solitons are stable in the semi-infinite gap and the first gap. Increasing the negative defect depth, the existent regions of defect solitons in the semi-infinite gap and in the first gap will be changed. The degree of the nonlocality will affect the profiles of these solitons.
- Published
- 2014
40. Transmission of nonparaxial nonlocal lattice solitons at nonlinear interfaces
- Author
-
Zhiwei Shi, Qi Guo, and Huagang Li
- Subjects
Physics ,Condensed matter physics ,Physics::Optics ,General Physics and Astronomy ,Nonlinear refractive index ,Trapping ,Nonlinear system ,Transverse plane ,Quantum nonlocality ,Lattice (order) ,Quantum mechanics ,Soliton propagation ,Nonlinear Sciences::Pattern Formation and Solitons ,Refractive index - Abstract
We report on transmission of nonparaxial nonlocal lattice solitons at an arbitrary angle of incidence to the interface separating two nonlinear media with transverse periodic modulation of the refractive index. The energy distribution of solitons in two media can be varied by the degree of nonlocality, the nonlinear refractive index mismatch parameter at the interface, the nonparaxial parameter, the angle of incidence and the lattice parameters. Importantly, the modulation period and depth can introduce different regimes of soliton propagation in the media including refraction and trapping.
- Published
- 2014
41. Nonlocal bright spatial solitons in defocusing Kerr media supported by \chem{\cal {PT}} symmetric potentials
- Author
-
Xing Zhu, Xiujuan Jiang, Zhiwei Shi, and Huagang Li
- Subjects
Physics ,Range (particle radiation) ,Transverse plane ,Quantum nonlocality ,Nonlinear Sciences::Exactly Solvable and Integrable Systems ,Condensed matter physics ,Energy flow ,General Physics and Astronomy ,Propagation constant ,Nonlinear Sciences::Pattern Formation and Solitons - Abstract
The bright spatial solitons in nonlocal defocusing Kerr media with parity-time () symmetric potentials are studied. The influence of the degree of nonlocality on the solitons and the transverse energy flow within the stable solitons are examined. We also find that these solitons can exist and be stable over a different range of the propagation constant and potential parameters. Interestingly, there exists a threshold value for the degree of nonlocality or potential parameters.
- Published
- 2012
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