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  • AIP Publishing  (16)
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  • AIP Publishing  (16)
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  • 1
    Online Resource
    Online Resource
    A novel large-orbit electron beam generated by a Cuccia coupler for a Ka-band third-harmonic slotted peniotron
    AIP Publishing ; 2010
    In:  Physics of Plasmas Vol. 17, No. 12 ( 2010-12-01)
    Details
    In: Physics of Plasmas, AIP Publishing, Vol. 17, No. 12 ( 2010-12-01)
    Abstract: In this work, a novel large-orbit electron beam generated by a Cuccia coupler for a Ka-band third-harmonic slotted is proposed. The Cuccia coupler was originally used in the electron coupler for amplitude modulation and power control at ultrahigh frequencies. It is demonstrated by the 3D-PIC simulation that a 6 kV, 0.5 A beam will be gyroresonantly accelerated when a microwave power of 16 kW at 10 GHz is injected into the coupler, from which a 37 kV, 0.5 A large-orbit electron beam will be obtained; it is characterized by a relative velocity spread lower than 1% and a velocity ratio α (υ⊥/υz) up to 2.3. Moreover, other electron beam parameters including transverse velocity (υ⊥), longitudinal velocity (υz) and deviation of guiding center could be adjusted independently, whereas these are rather difficult for the cusp gun. Finally, the Ka-band third-harmonic slotted peniotron in 2π mode driven by such a beam is verified by 3D-PIC simulation, which is predicted to yield an output power of 8 kW at 30 GHz, with a microwave power conversion efficiency up to 50% and a device efficiency up to 43%, respectively.
    Type of Medium: Online Resource
    ISSN: 1070-664X , 1089-7674
    URL: Article
    DOI: 10.1063/1.3520074
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2010
    detail.hit.zdb_id: 1472746-8
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  • 2
    Online Resource
    Online Resource
    A W-band sixth-harmonic magnetron-type slotted peniotron
    AIP Publishing ; 2013
    In:  Physics of Plasmas Vol. 20, No. 4 ( 2013-04-01)
    Details
    In: Physics of Plasmas, AIP Publishing, Vol. 20, No. 4 ( 2013-04-01)
    Abstract: This paper has numerically investigated operating characteristics of a w-band six-harmonic magnetron-type slotted peniotron with 7 vanes. With the new structure design, a high efficiency of 40% w-band 30 kW medium power microwave source has been achieved and the mode competition can be somewhat suppressed. The main advantage of such a peniotron, based on a permanent magnet, is that it can have much more compact size and lower cost, and its operation gap can be greatly reduced.
    Type of Medium: Online Resource
    ISSN: 1070-664X , 1089-7674
    URL: Article
    DOI: 10.1063/1.4799553
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2013
    detail.hit.zdb_id: 1472746-8
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  • 3
    Online Resource
    Online Resource
    Exciton valley dynamics in monolayer Mo1-xWxSe2 (x = 0, 0.5, 1)
    AIP Publishing ; 2017
    In:  Applied Physics Letters Vol. 111, No. 15 ( 2017-10-09)
    Details
    In: Applied Physics Letters, AIP Publishing, Vol. 111, No. 15 ( 2017-10-09)
    Abstract: We study the exciton valley dynamics in monolayers MoSe2, Mo0.5W0.5Se2, and WSe2 by employing helicity-resolved two-color transient reflection spectroscopy. The valley depolarization dynamics as a function of the excitation laser energy is studied systematically at above-resonant excitation of excitons at 10 K. A longer intervalley scattering time is obtained as the excitation energy approaches the A exciton resonance for the three studied materials. The excitation energy dependence of exciton valley relaxation proves that the long-range electron-hole exchange interaction dominates the intervalley scattering in transition metal dichalcogenide monolayers. The longer valley scattering time and higher valley polarization degree commonly observed for WSe2 than for MoSe2 is discussed to result from the interplay between the intervalley electron-hole exchange interaction and dark-bright exciton scattering, where the existence of energetically lower lying dark excitonic states in monolayer WSe2 favors the suppression of the intervalley electron-hole exchange interaction.
    Type of Medium: Online Resource
    ISSN: 0003-6951 , 1077-3118
    URL: Article
    DOI: 10.1063/1.4995517
    RVK:
    UA 1000
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2017
    detail.hit.zdb_id: 211245-0
    detail.hit.zdb_id: 1469436-0
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  • 4
    Online Resource
    Online Resource
    Numerical study of an 8 mm third-harmonic peniotron with a gradual reversal of the magnetic field
    AIP Publishing ; 2012
    In:  Physics of Plasmas Vol. 19, No. 2 ( 2012-02-01)
    Details
    In: Physics of Plasmas, AIP Publishing, Vol. 19, No. 2 ( 2012-02-01)
    Abstract: A novel large-orbit electron gun with a gradual reversal of the magnetic field for the 8 mm third-harmonic peniotron is numerically studied in this paper. In the permanent magnetic condition, an electron beam with axial velocity spread of 4.78%, guiding center deviation of 7.18%, and velocity ratio of 2.2 is generated in the gun, satisfying the special requirements of beam-wave interaction in the third-harmonic peniotron. Compared with the traditional three stage method, it is unnecessary here to generate a thin tubular electron beam before the reversal point and the mutational distribution of reversal magnetic field. In addition, the emission band can be placed in the area of axial magnetic field where its magnitude decreases gradually, which reduces the structure complexity and the difficulties in tube-making process greatly. Finally, the peniotron is predicted to yield an output power of 31.9 kW at 30 GHz, with its microwave conversion efficiency of up to 49.4%, which shows the perfect matching between its high frequency system and its electron-optical system. According to the numerical calculations, the device performance is very sensitive to the relative axial position between the magnetic system and the electrode system. If the magnetic system shifts 0.8 mm to the right, the device efficiency would decrease from 49.4% to 31.7%. This phenomenon provides meaningful information in the device hot-test.
    Type of Medium: Online Resource
    ISSN: 1070-664X , 1089-7674
    URL: Article
    DOI: 10.1063/1.3677825
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2012
    detail.hit.zdb_id: 1472746-8
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  • 5
    Online Resource
    Online Resource
    Electro-osmotic flow of generalized Maxwell fluids in triangular microchannels based on distributed order time fractional constitutive model
    AIP Publishing ; 2023
    In:  AIP Advances Vol. 13, No. 2 ( 2023-02-01)
    Details
    In: AIP Advances, AIP Publishing, Vol. 13, No. 2 ( 2023-02-01)
    Abstract: Based on the linearized Poisson–Boltzmann equation, the electro-osmotic flow of a generalized Maxwell fluid under an alternating field in an isosceles right triangle microchannel is studied. The finite volume method and L2 interpolation method are used to obtain the numerical solution. An analytical solution is constructed to verify the accuracy of the numerical solution. Under the alternating current, the velocity will oscillate periodically. The velocity amplitude of the Maxwell fluid with the distributed order time fractional derivative is larger than that of Newtonian fluids and fractional Maxwell fluids, which indicates that its elastic characteristics further promote fluid flow. However, oscillation of the velocity does not achieve synchronization with the oscillation of the electric fields. Furthermore, due to the existence of the angle effect, the velocity will develop at acute angles and form a larger value of velocity first. The numerical results show that the relaxation time, electrokinetic width, zeta potential, and angular Reynolds number play important roles in determining the velocity and amplitude of electro-osmosis.
    Type of Medium: Online Resource
    ISSN: 2158-3226
    URL: Article
    DOI: 10.1063/5.0138004
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2023
    detail.hit.zdb_id: 2583909-3
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  • 6
    Online Resource
    Online Resource
    Gate-controlled spin relaxation in bulk WSe2 flakes
    AIP Publishing ; 2020
    In:  AIP Advances Vol. 10, No. 4 ( 2020-04-01)
    Details
    In: AIP Advances, AIP Publishing, Vol. 10, No. 4 ( 2020-04-01)
    Abstract: We have studied the spin relaxation dynamics in both n- and p-type layered bulk WSe2 under a perpendicular electric field by employing time-resolved Kerr rotation and helicity-resolved transient reflection measurements. The experimental results reveal the efficient tuning of spin relaxation time from 3 ps to 46 ps by the external electric field at 10 K. The dependence of spin relaxation time on the external electric field is understood based on active interlayer hopping. These studies demonstrate the gate-tunable spin polarization and relaxation in bulk transition metal dichalcogenides (TMDCs), which are fundamentally important for understanding spin dynamics and the practical design of spintronic devices based on bulk TMDCs.
    Type of Medium: Online Resource
    ISSN: 2158-3226
    URL: Article
    DOI: 10.1063/1.5144070
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2020
    detail.hit.zdb_id: 2583909-3
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  • 7
    Online Resource
    Online Resource
    Ultrafast dynamics of four-state magnetization reversal in (Ga,Mn)As
    AIP Publishing ; 2009
    In:  Applied Physics Letters Vol. 95, No. 5 ( 2009-08-03)
    Details
    In: Applied Physics Letters, AIP Publishing, Vol. 95, No. 5 ( 2009-08-03)
    Abstract: The ultrafast dynamics of in-plane four-state magnetization reversal from compressively strained (Ga,Mn)As film was investigated by magneto-optical Kerr rotation measurement. The magnetization reversal signal was dramatically suppressed upon pumping, and recovered slowly with time evolution. The low switching field Hc1 increased abruptly from 30 to 108 G on the first several picoseconds and recovered back to the value before optical pumping within about 500 ps, whereas the high switching field Hc2 did not change obviously upon pumping, implying a domain-wall nucleation/propagation at low fields and coherent magnetization rotation at high fields in the magnetization reversal process.
    Type of Medium: Online Resource
    ISSN: 0003-6951 , 1077-3118
    URL: Article
    DOI: 10.1063/1.3202395
    RVK:
    UA 1000
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2009
    detail.hit.zdb_id: 211245-0
    detail.hit.zdb_id: 1469436-0
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  • 8
    Online Resource
    Online Resource
    Characterization of background carriers in InAs/GaSb quantum well
    AIP Publishing ; 2016
    In:  Journal of Applied Physics Vol. 119, No. 9 ( 2016-03-07)
    Details
    In: Journal of Applied Physics, AIP Publishing, Vol. 119, No. 9 ( 2016-03-07)
    Abstract: The origin of the background carriers in an undoped InAs/GaSb quantum well (QW) at temperatures between 40 K and 300 K has been investigated using conventional Hall measurements. It is found that the Hall coefficient changes its sign at around 200 K, indicating that both electrons and holes exist in the quantum well. The two-carrier Hall model is thus adopted to analyze the Hall data, which enables the temperature dependence of the carrier density to be obtained. It is found that considerable numbers of holes exist under low temperature conditions ( & lt;40 K) in the InAs/GaSb QW, and the hole density is one to two orders higher than that of the electrons within the experimental temperature range. The origin of these low temperature holes and the temperature-dependent behavior of the carrier density over the entire experimental temperature range are then discussed.
    Type of Medium: Online Resource
    ISSN: 0021-8979 , 1089-7550
    URL: Article
    DOI: 10.1063/1.4943188
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2016
    detail.hit.zdb_id: 220641-9
    detail.hit.zdb_id: 3112-4
    detail.hit.zdb_id: 1476463-5
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  • 9
    Online Resource
    Online Resource
    The electro-osmotic flow and heat transfer of generalized Maxwell fluids with distributed-order time-fractional characteristics in microtubules under an alternating field
    AIP Publishing ; 2021
    In:  Physics of Fluids Vol. 33, No. 11 ( 2021-11-01)
    Details
    In: Physics of Fluids, AIP Publishing, Vol. 33, No. 11 ( 2021-11-01)
    Abstract: The electro-osmotic flow and heat transfer of a Maxwell fluid with distributed-order time-fractional characteristics in a microchannel under an alternating field is investigated, while considering viscous dissipation and Joule heating. The unsteady momentum and energy equations are computed numerically directly using the finite volume method. The accuracy of the numerical method is validated by comparison the constructed velocity distribution with the velocity distribution in previous references. With the time going on, oscillation of alternating current with a constant amplitude will afford periodic velocity distribution. The temperature will periodically increase. Furthermore, the velocity and temperature distributions characteristics of a Newtonian fluid, fractional Maxwell fluid, and generalized Maxwell fluid with time distribution are compared. Finally, the effects of different physical parameters K, S, Br, Ha, λ, Ω, ψ1, ψ2, Pr, and δ on the velocity and heat distributions under an alternating field are discussed.
    Type of Medium: Online Resource
    ISSN: 1070-6631 , 1089-7666
    URL: Article
    DOI: 10.1063/5.0073752
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2021
    detail.hit.zdb_id: 1472743-2
    detail.hit.zdb_id: 241528-8
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  • 10
    Online Resource
    Online Resource
    On fluid flow and heat transfer of turbulent boundary layer of pseudoplastic fluids on a semi-infinite plate
    AIP Publishing ; 2020
    In:  Physics of Fluids Vol. 32, No. 7 ( 2020-07-01)
    Details
    In: Physics of Fluids, AIP Publishing, Vol. 32, No. 7 ( 2020-07-01)
    Abstract: The boundary layer of a pseudoplastic fluid on a semi-infinite plate for a high generalized Reynolds number is analyzed. Based on the Prandtl mixing length theory, the turbulent region is divided into two regions. The coupled momentum and temperature equations, with a generalized thermal conductivity model, have made the process of finding the analytical solutions much difficult. By using the similarity transformation, the equations are converted to four ordinary differential equations constrained by ten boundary conditions. An interesting technique of scaling and translation of the calculation domain of one region into another is used to make the system of equations easier to solve. It is found that the fluid with a smaller power-law index, associated with a thinner velocity boundary layer thickness, processes a lower friction coefficient. Furthermore, the increase in the Reynolds number causes a thinner velocity boundary layer and a decreasing friction coefficient on the wall. Changes in temperature occur more slowly near the plate surface with a rise in the power-law index and a decrease in the Reynolds number.
    Type of Medium: Online Resource
    ISSN: 1070-6631 , 1089-7666
    URL: Article
    DOI: 10.1063/5.0011292
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2020
    detail.hit.zdb_id: 1472743-2
    detail.hit.zdb_id: 241528-8
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