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  • AIP Publishing  (232)
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  • AIP Publishing  (232)
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  • 1
    Online Resource
    Online Resource
    On the mechanisms of sheet-like extension structures formation and self-sustaining process in elasto-inertial turbulence
    AIP Publishing ; 2021
    In:  Physics of Fluids Vol. 33, No. 8 ( 2021-08-01)
    Details
    In: Physics of Fluids, AIP Publishing, Vol. 33, No. 8 ( 2021-08-01)
    Abstract: The elasto-inertial turbulence (EIT) of viscoelastic fluid is induced by the interaction between elastic instability and flow inertia. The recent discovery of the EIT regime enables new insights into the maximum drag reduction phenomenon of viscoelastic fluid flows and verifies the role of elastic instability in drag-reducing turbulence. In this study, the direct numerical simulation (DNS) of EIT is carried out by using the Oldroyd-B model for the first time. EIT simulations are conducted at a fixed Weissenberg number of 60 with a Reynolds number ranging from 1000 to 6000. Based on the DNS results, the Reynolds stress and elastic stress budgets are analyzed, and the formation of sheet-like structures of polymer extension is confirmed. It indicates that EIT has a complex energy picture. The self-sustaining nature of EIT not only involves the energy transformation from streamwise elastic energy (EE) into turbulent kinetic energy (TKE), but also relies on the energy transformation of wall-normal TKE into EE, which further induces energy absorption of elastic shear stress from the mean motion and the transformation of this energy into streamwise EE. Sheet-like structures reflect the polymer extension characteristics in the streamwise direction. Their formation comes from the wall-normal extension induced by turbulence perturbations, which further generates extra nonlinear elastic shear stress that absorbs energy from the mean motion and eventually forms sheet-like structures. In the self-sustaining cycle, fluid inertia lifts the sheet-like structures of polymer extension, further inducing flow instability.
    Type of Medium: Online Resource
    ISSN: 1070-6631 , 1089-7666
    URL: Article
    DOI: 10.1063/5.0057181
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2021
    detail.hit.zdb_id: 1472743-2
    detail.hit.zdb_id: 241528-8
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  • 2
    Online Resource
    Online Resource
    Robust frame-reduced structured illumination microscopy with accelerated correlation-enabled parameter estimation
    AIP Publishing ; 2022
    In:  Applied Physics Letters Vol. 121, No. 15 ( 2022-10-10)
    Details
    In: Applied Physics Letters, AIP Publishing, Vol. 121, No. 15 ( 2022-10-10)
    Abstract: Structured illumination microscopy (SIM), with the advantages of full-field imaging and low photo-damage, is one of the most well-established fluorescence super-resolution microscopy techniques that raised great interest in biological sciences. However, conventional SIM techniques generally require at least nine images for image reconstruction, and the quality of super-resolution significantly depends on high-accuracy illumination parameter estimation, which is usually computationally intense and time-consuming. To address these issues, we propose a robust seven-frame SIM reconstruction algorithm with accelerated correlation-enabled parameter estimation. First, a modulation-assigned spatial filter is employed to remove unreliable backgrounds associated with low signal-to-noise ratios. Then, we propose a coarse-to-fine accelerated correlation algorithm to eliminate the redundant iterations of the traditional correlation-based scheme. The frame reduction is achieved by a specially designed phase-shifting strategy combined with pixel-wise fluorescence pre-calibration. We experimentally demonstrate that, compared with conventional iterative correlation-based methods, the proposed algorithm improves the computational efficiency by a factor of 4.5 while maintaining high accuracy illumination parameter estimation. Meanwhile, our method achieves high-quality super-resolution reconstruction even with a reduction in two raw images, which improves the efficiency of image acquisition and ensures the robustness toward complex experimental environments.
    Type of Medium: Online Resource
    ISSN: 0003-6951 , 1077-3118
    URL: Article
    DOI: 10.1063/5.0107510
    RVK:
    UA 1000
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2022
    detail.hit.zdb_id: 211245-0
    detail.hit.zdb_id: 1469436-0
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  • 3
    Online Resource
    Online Resource
    A joint experimental and theoretical study on structural, electronic, and magnetic properties of MnGen− (n = 3–14) clusters
    AIP Publishing ; 2021
    In:  The Journal of Chemical Physics Vol. 154, No. 20 ( 2021-05-28)
    Details
    In: The Journal of Chemical Physics, AIP Publishing, Vol. 154, No. 20 ( 2021-05-28)
    Abstract: A systematic structure and property investigation of MnGen− (n = 3–14) was conducted by means of density functional theory coupled with mass-selected anion photoelectron spectroscopy. This combined theoretical and experimental study allows global minimum and coexistence structures to be identified. It is found that the pentagonal bipyramid shape is the basic framework for the nascent growth process of MnGen− (n = 3–10), and from n = 10, the endohedral structures can be found. For n = 12, the anion MnGe12− cluster probably includes two isomers: a major isomer with a puckered hexagonal prism geometry and a minor isomer with a distorted icosahedron geometry. Specifically, the puckered hexagonal prism isomer follows the Wade–Mingos rules and can be suggested as a new kind of superatom with the magnetic property. Furthermore, the results of adaptive natural density partitioning and deformation density analyses suggest a polar covalent interaction between Ge and Mn for endohedral clusters of MnGe12−. The spin density and natural population analysis indicate that MnGen− clusters have high magnetic moments localized on Mn. The density of states diagram visually shows the significant spin polarization for endohedral structures and reveals the weak interaction between the Ge 4p orbital and the 4s, 3d orbitals of Mn.
    Type of Medium: Online Resource
    ISSN: 0021-9606 , 1089-7690
    URL: Article
    DOI: 10.1063/5.0053414
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2021
    detail.hit.zdb_id: 3113-6
    detail.hit.zdb_id: 1473050-9
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  • 4
    Online Resource
    Online Resource
    Selective area epitaxy of degenerate n-GaN for HEMT ohmic contact by MOCVD
    AIP Publishing ; 2022
    In:  Applied Physics Letters Vol. 121, No. 21 ( 2022-11-21)
    Details
    In: Applied Physics Letters, AIP Publishing, Vol. 121, No. 21 ( 2022-11-21)
    Abstract: This Letter reports low-temperature (700 °C) growth of heavily Si-doped GaN (n++GaN) by metal-organic chemical vapor deposition with a resistivity as low as 1.9 × 10−4 Ω·cm and an atomically smooth surface. Indium adatoms added during the growth of n++GaN play an important role in improving both the surface morphology and free electron concentration. On the one hand, acting as surfactant, they greatly boost the adatoms surface mobility at low growth temperature and mitigate Si-induced anti-surfactant effect. On the other hand, they can effectively suppress the formation of compensating defects, thus contributing to an extremely high electron concentration of 2.8 × 1020 cm−3. This high-quality n++GaN was further applied to the realization of Ohmic contacts with an ultra-low contact resistance for AlGaN/GaN high electron mobility transistors. The carrier gas was carefully modulated for the selective area epitaxy (SAE) of n++GaN to facilitate the nucleation of GaN on the dielectric mask, which effectively suppressed the undesired mass transport and resulted in a uniform SAE of n++GaN in the recessed source/drain regions. A nearly defect-free interface between the n++GaN and two-dimensional electron gas channel has been also realized, and the resistance induced by the interface was only 0.03 Ω·mm. As a result, an ultra-low contact resistance of 0.07 Ω·mm has been realized. This work lays a solid foundation for further improving the performance of GaN-based RF and power devices.
    Type of Medium: Online Resource
    ISSN: 0003-6951 , 1077-3118
    URL: Article
    DOI: 10.1063/5.0129997
    RVK:
    UA 1000
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2022
    detail.hit.zdb_id: 211245-0
    detail.hit.zdb_id: 1469436-0
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  • 5
    Online Resource
    Online Resource
    Construction and Evaluation of Merged Pharmacophore Based on Peroxisome Proliferator Receptor-Alpha Agonists
    AIP Publishing ; 2016
    In:  Chinese Journal of Chemical Physics Vol. 29, No. 4 ( 2016-08-27), p. 508-516
    Details
    In: Chinese Journal of Chemical Physics, AIP Publishing, Vol. 29, No. 4 ( 2016-08-27), p. 508-516
    Abstract: Pharmacophore is a commonly used method for molecular simulation, including ligand-based pharmacophore (LBP) and structure-based pharmacophore (SBP). LBP can be utilized to identify active compounds usual with lower accuracy, and SBP is able to use for distinguishing active compounds from inactive compounds with frequently higher missing rates. Merged pharmacophore (MP) is presented to integrate advantages and avoid shortcomings of LBP and SBP. In this work, LBP and SBP models were constructed for the study of peroxisome proliferator receptor-alpha (PPARα) agonists. According to the comparison of the two types of pharmacophore models, mainly and secondarily pharmacological features were identified. The weight and tolerance values of these pharmacological features were adjusted to construct MP models by single-factor explorations and orthogonal experimental design based on SBP model. Then, the reliability and screening efficiency of the best MP model were validated by three databases. The best MP model was utilized to compute PPARα activity of compounds from traditional Chinese medicine. The screening efficiency of MP model outperformed individual LBP or SBP model for PPARα agonists, and was similar to combinatorial screening of LBP and SBP. However, MP model might have an advantage over the combination of LBP and SBP in evaluating the activity of compounds and avoiding the inconsistent prediction of LBP and SBP, which would be beneficial to guide drug design and optimization.
    Type of Medium: Online Resource
    ISSN: 1674-0068 , 2327-2244
    URL: Article
    DOI: 10.1063/1674-0068/29/cjcp1602025
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2016
    detail.hit.zdb_id: 2381472-X
    SSG: 6,25
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  • 6
    Online Resource
    Online Resource
    Spectral features of the geodesic acoustic mode and its interaction with turbulence in a tokamak plasma
    AIP Publishing ; 2008
    In:  Physics of Plasmas Vol. 15, No. 5 ( 2008-05-01)
    Details
    In: Physics of Plasmas, AIP Publishing, Vol. 15, No. 5 ( 2008-05-01)
    Abstract: The three-dimensional wavenumber and frequency spectrum for the geodesic acoustic mode (GAM) has been measured in the HuanLiuqi-2A tokamak for the first time. The spectrum provides definite evidence for the GAM, which is characterized by kθ=kϕ=0 and krρi≈0.04−0.09 with the full width at half-maximum Δkrρi≈0.03−0.07. The localized GAM packet is observed to propagate outward in the radial direction with nearly the same phase and group velocity. The envelopes of the radial electric field and density fluctuations are observed to be modulated by the GAM. By comparing the experimental result with that of the envelope analysis using model signals, the mechanism of the envelope modulation has been identified. The results strongly suggest that the envelope modulation of the Ẽr fluctuations is dominantly caused by the direct regulation of the GAM during the GAM generation in the energy-conserving triad interaction, and the envelope modulation of the density fluctuations is induced by the GAM shearing effect, which transfers the fluctuation energy from low to high frequencies. In addition, the cross- and auto-bicoherences for interactions between the GAM and turbulent fluctuations show a similar peaked feature that may reflect the resonant property in the nonlinear coupling between the GAM and turbulent fluctuations.
    Type of Medium: Online Resource
    ISSN: 1070-664X , 1089-7674
    URL: Article
    DOI: 10.1063/1.2838242
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2008
    detail.hit.zdb_id: 1472746-8
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  • 7
    Online Resource
    Online Resource
    A progressively reduced pretension method to fabricate Bradbury-Nielsen gates with uniform tension
    AIP Publishing ; 2015
    In:  Review of Scientific Instruments Vol. 86, No. 11 ( 2015-11-01)
    Details
    In: Review of Scientific Instruments, AIP Publishing, Vol. 86, No. 11 ( 2015-11-01)
    Abstract: A Bradbury-Nielsen gate (BNG) is often used to modulate ion beams. It consists of two interleaved and electrically isolated sets of wires with uniform tension, which ideally keep parallel, equidistant, and coplanar over a wide temperature range, making the BNG reliable and robust. We have previously analyzed the non-uniformity problem of wire tensions with sequentially winding method and developed a template-based transfer method to solve this problem. In this paper, we introduced a progressively reduced pretension method, which allows directly and sequentially fixing wires onto the substrate without using a template. Theoretical analysis shows that by applying proper pretension to each wire when fixing it, the final wire tensions of all wires can be uniform. The algorithm and flowchart to calculate the pretension sequence are given, and the fabrication process is introduced in detail. Pretensions are generated by weight combination with a weaving device. A BNG with stainless steel wire and a printed circuit board substrate is constructed with this method. The non-uniformity of the final wire tensions is less than 2.5% in theory. The BNG is successfully employed in our ion mobility spectrometer, and the measured resolution is 33.5 at a gate opening time of 350 μs. Compared to the template-based method, this method is simpler, faster, and more flexible with comparable production quality when manufacturing BNGs with different configurations.
    Type of Medium: Online Resource
    ISSN: 0034-6748 , 1089-7623
    URL: Article
    DOI: 10.1063/1.4934930
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2015
    detail.hit.zdb_id: 209865-9
    detail.hit.zdb_id: 1472905-2
    SSG: 11
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  • 8
    Online Resource
    Online Resource
    Oscillations of interlayer coupling and magneto-optics in sputtered Co–Al/Cu multilayers
    AIP Publishing ; 1996
    In:  Applied Physics Letters Vol. 69, No. 1 ( 1996-07-01), p. 127-129
    Details
    In: Applied Physics Letters, AIP Publishing, Vol. 69, No. 1 ( 1996-07-01), p. 127-129
    Abstract: We have prepared [Co90Al10/Cu]30 multilayers by ion beam sputtering and studied the behavior of interlayer coupling, magnetoresistance, and the magneto-optical Kerr effect. For Co–Al/Cu multilayers, the in-plane saturation field, coercive force HC and magnetoresistance ratio ΔR/R have been observed to oscillate with a period of about 0.9 nm, as a function of Cu spacer layer thickness. Furthermore, polar Kerr rotation θk in visible wavelength range also oscillates with the same period. The magneto-optical activities may be attributed to changes in the optical constants with the magnetic state.
    Type of Medium: Online Resource
    ISSN: 0003-6951 , 1077-3118
    URL: Article
    DOI: 10.1063/1.118097
    RVK:
    UA 1000
    Language: English
    Publisher: AIP Publishing
    Publication Date: 1996
    detail.hit.zdb_id: 211245-0
    detail.hit.zdb_id: 1469436-0
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  • 9
    Online Resource
    Online Resource
    Determination of Mn composition in Zn1− x Mn x Se from Faraday rotation analysis
    AIP Publishing ; 1996
    In:  Journal of Applied Physics Vol. 79, No. 8 ( 1996-04-15), p. 5193-5194
    Details
    In: Journal of Applied Physics, AIP Publishing, Vol. 79, No. 8 ( 1996-04-15), p. 5193-5194
    Abstract: In Zn1−xMnxSe, Mn2+ d→d* transitions were found to induce giant Faraday rotation, and peaks of the Faraday rotation spectra were red-shifted linearly with increasing Mn composition. Through studying the magneto-optical transition variation with Mn composition, the Mn composition can be determined. Results from the Faraday rotation analysis were compared with the x-ray diffraction data and were found in good agreement with each other.
    Type of Medium: Online Resource
    ISSN: 0021-8979 , 1089-7550
    URL: Article
    DOI: 10.1063/1.361336
    Language: English
    Publisher: AIP Publishing
    Publication Date: 1996
    detail.hit.zdb_id: 220641-9
    detail.hit.zdb_id: 3112-4
    detail.hit.zdb_id: 1476463-5
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  • 10
    Online Resource
    Online Resource
    Effect of surface hydrophilicity on the nanofretting behavior of Si(100) in atmosphere and vacuum
    AIP Publishing ; 2010
    In:  Journal of Applied Physics Vol. 108, No. 3 ( 2010-08-01)
    Details
    In: Journal of Applied Physics, AIP Publishing, Vol. 108, No. 3 ( 2010-08-01)
    Abstract: With an atomic force microscopy, the effect of surface hydrophilicity on the nanofretting behavior of Si(100) against SiO2 microsphere was investigated under vacuum and atmosphere conditions, respectively. The surface hydrophilicity revealed a strong effect on the motion behavior, adhesion force, friction force, and nanofretting damage of Si(100)/SiO2 pairs. The increase in the hydrophilicity of Si(100) surface could expand the stick regime of Si(100)/SiO2 pairs into a higher value of displacement amplitude. While the nanofretting ran in atmosphere, both adhesion and friction forces in the initial cycle would be larger when the Si(100) surface was more hydrophilic. However, because of the in situ chemical modification of SiO2 tip in nanofretting, they might reveal a decrease with increasing nanofretting cycles. Either in vacuum or in atmosphere, the nanofretting damage was weaker when the Si(100) surface was more hydrophobic. Because of the lack of oxygen and vapor in vacuum, the nanofretting damage on the Si(100) surface was dominated by mechanical interaction. The damage was characterized as the depression of 0.1–0.2 nm in depth on hydrophilic Si and the hillocks of 0.8–0.9 nm in height on hydrophobic Si and original Si. However, the nanofretting damage in atmosphere was much more serious, which was identified as the grooves of 8–11 nm in depth on Si(100) surfaces. Analysis indicated that even if the nanofretting damage in atmosphere was the coupled results of mechanical interaction and tribochemical reaction, the tribochemical reaction played a dominated role. These results will help us to understand the effect of surface properties on nanofretting of silicon and optimize the surface treatment technology to minimize the potential nanofretting failure of microdevices in microelectromechanical system (MEMS).
    Type of Medium: Online Resource
    ISSN: 0021-8979 , 1089-7550
    URL: Article
    DOI: 10.1063/1.3463306
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2010
    detail.hit.zdb_id: 220641-9
    detail.hit.zdb_id: 3112-4
    detail.hit.zdb_id: 1476463-5
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