American Institute of Physics: AIP Advances: Table of Contents
Table of Contents for AIP Advances. List of articles from both the latest and ahead of print issues.
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American Institute of Physics: AIP Advances: Table of Contents
American Institute of Physics
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AIP Advances
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https://aip.scitation.org/loi/adv?af=R&feed=mostrecent

Natural frequencies of a bubble near a solid sphere
https://aip.scitation.org/doi/10.1063/5.0101841?af=R&feed=mostrecent
AIP Advances, <a href="https://aip.scitation.org/toc/adv/12/8">Volume 12, Issue 8</a>, August 2022. <br/>This paper presents an analytical and computational method to describe natural frequencies of a spherical bubble residing near a solid sphere of an arbitrary size in an otherwise unbounded fluid. Under low capillary and Reynolds number limits, the relevant hydrodynamic fields are converted into timeinvariant but frequencydependent quantities by temporal Fourier transform. Then, the spatial variations in the velocity and the pressure can be expressed in terms of two sets of harmonic basis functions involving spherical coordinates centered around the particle and the bubble. A subsequent derivation of transformation coefficients between the aforementioned two sets allows a matrix equation relating the unknown amplitudes to the boundary conditions at all interfaces. Finally, natural frequencies corresponding to different modes of pulsation are obtained from the eigenvalues of the constructed matrix. The results show fast convergence of the computed frequencies with the increasing number of basis functions. These values change significantly with the distance of the bubble from the particle and even decay to zero for some modes when their surfacetosurface separation vanishes. Furthermore, bubble oscillation near a solid plate is also discussed when the radius of the solid sphere is increased to an infinitely large dimension. Thus, this article renders a comprehensive study of naturally pulsating submerged bubbles in the presence of a nearby solid surface of various kinds.
AIP Advances, Volume 12, Issue 8, August 2022. <br/>This paper presents an analytical and computational method to describe natural frequencies of a spherical bubble residing near a solid sphere of an arbitrary size in an otherwise unbounded fluid. Under low capillary and Reynolds number limits, the relevant hydrodynamic fields are converted into timeinvariant but frequencydependent quantities by temporal Fourier transform. Then, the spatial variations in the velocity and the pressure can be expressed in terms of two sets of harmonic basis functions involving spherical coordinates centered around the particle and the bubble. A subsequent derivation of transformation coefficients between the aforementioned two sets allows a matrix equation relating the unknown amplitudes to the boundary conditions at all interfaces. Finally, natural frequencies corresponding to different modes of pulsation are obtained from the eigenvalues of the constructed matrix. The results show fast convergence of the computed frequencies with the increasing number of basis functions. These values change significantly with the distance of the bubble from the particle and even decay to zero for some modes when their surfacetosurface separation vanishes. Furthermore, bubble oscillation near a solid plate is also discussed when the radius of the solid sphere is increased to an infinitely large dimension. Thus, this article renders a comprehensive study of naturally pulsating submerged bubbles in the presence of a nearby solid surface of various kinds.
Natural frequencies of a bubble near a solid sphere
10.1063/5.0101841
AIP Advances
20220802T05:35:24Z
© 2022 Author(s).
Bo Liu
Sukalyan Bhattacharya

A modified Michelson interferometer to measure submilliradian changes in angle
https://aip.scitation.org/doi/10.1063/5.0100720?af=R&feed=mostrecent
AIP Advances, <a href="https://aip.scitation.org/toc/adv/12/8">Volume 12, Issue 8</a>, August 2022. <br/>Modern shortrange gravity experiments that seek to test the Newtonian inversesquare law or weak equivalence principle of general relativity typically involve measuring the minute variations in the twist angle of a torsion pendulum. Motivated by various theoretical arguments, recent efforts largely focus on measurements with test mass separations in the submillimeter regime. To measure the twist, many experiments employ an optical autocollimator with a noise performance of ∼300 nrad[math] in the 0.1–10 mHz band, enabling a measurement uncertainty of a few nanoradians in a typical integration time. We investigated an alternative method for measuring a small twist angle through the construction of a modified Michelson interferometer. The main modification is the introduction of two additional arms that allow for improved angular alignment. A series of detectors and LabView software routines were developed to determine the orientation of a mirror attached to a sinusoidally driven rotation stage that oscillated with an amplitude of 0.35 mrad and a period of 200 s. In these measurements, the resolution of the interferometer is 8.1 μrad per fringe, while its dynamic range spanned 0.962 mrad. We compare the performance of this interferometric optical system to existing autocollimatorbased methods, discussing its implementation, possible advantages, and future potential, as well as disadvantages and limitations.
AIP Advances, Volume 12, Issue 8, August 2022. <br/>Modern shortrange gravity experiments that seek to test the Newtonian inversesquare law or weak equivalence principle of general relativity typically involve measuring the minute variations in the twist angle of a torsion pendulum. Motivated by various theoretical arguments, recent efforts largely focus on measurements with test mass separations in the submillimeter regime. To measure the twist, many experiments employ an optical autocollimator with a noise performance of ∼300 nrad[math] in the 0.1–10 mHz band, enabling a measurement uncertainty of a few nanoradians in a typical integration time. We investigated an alternative method for measuring a small twist angle through the construction of a modified Michelson interferometer. The main modification is the introduction of two additional arms that allow for improved angular alignment. A series of detectors and LabView software routines were developed to determine the orientation of a mirror attached to a sinusoidally driven rotation stage that oscillated with an amplitude of 0.35 mrad and a period of 200 s. In these measurements, the resolution of the interferometer is 8.1 μrad per fringe, while its dynamic range spanned 0.962 mrad. We compare the performance of this interferometric optical system to existing autocollimatorbased methods, discussing its implementation, possible advantages, and future potential, as well as disadvantages and limitations.
A modified Michelson interferometer to measure submilliradian changes in angle
10.1063/5.0100720
AIP Advances
20220802T02:49:43Z
© 2022 Author(s).
C. K. LeDesma
M. P. Ross
B. E. Daly
C. D. Hoyle
M. M. Mola

Effects of wall temperature on separation structures in supersonic flow over a semicircular cavity
https://aip.scitation.org/doi/10.1063/5.0098438?af=R&feed=mostrecent
AIP Advances, <a href="https://aip.scitation.org/toc/adv/12/8">Volume 12, Issue 8</a>, August 2022. <br/>The influence of wall temperature on the vortex structure and flow characteristics of flow in semicircular cavities is numerically investigated in this paper. The results show that the separation and reattachment points move downstream, and the secondary vortex increases with increases in wall temperature. In the secondary vortex section, normalized wall shear stress in the polar map has good consistency at different wall temperatures, and the flow properties of the three extreme points on the map are similar to Couette flow. In addition, the secondary vortex region can be regarded as an isobaric highpressure region, while the pressure gradients slowly vary as the wall temperature increases. We confirm the independence of separation pressure for the wall temperature using pressure distribution and find that the peak and inflection points are at the reattachment points and separation points, respectively. Moreover, using a series of numerical calculations of the positions of the vortex center at different wall temperatures, explicit empirical formulas for estimating the positions of the primary vortex center are put forward. Using a topological mapping method, cavity flow is converted into quasionedimensional steadystate compressible viscous flow through a variable crosssection pipe, and the flow parameter distribution, including the Mach number and pressure, conforms to the rule of quasionedimensional flow.
AIP Advances, Volume 12, Issue 8, August 2022. <br/>The influence of wall temperature on the vortex structure and flow characteristics of flow in semicircular cavities is numerically investigated in this paper. The results show that the separation and reattachment points move downstream, and the secondary vortex increases with increases in wall temperature. In the secondary vortex section, normalized wall shear stress in the polar map has good consistency at different wall temperatures, and the flow properties of the three extreme points on the map are similar to Couette flow. In addition, the secondary vortex region can be regarded as an isobaric highpressure region, while the pressure gradients slowly vary as the wall temperature increases. We confirm the independence of separation pressure for the wall temperature using pressure distribution and find that the peak and inflection points are at the reattachment points and separation points, respectively. Moreover, using a series of numerical calculations of the positions of the vortex center at different wall temperatures, explicit empirical formulas for estimating the positions of the primary vortex center are put forward. Using a topological mapping method, cavity flow is converted into quasionedimensional steadystate compressible viscous flow through a variable crosssection pipe, and the flow parameter distribution, including the Mach number and pressure, conforms to the rule of quasionedimensional flow.
Effects of wall temperature on separation structures in supersonic flow over a semicircular cavity
10.1063/5.0098438
AIP Advances
20220803T02:43:24Z
© 2022 Author(s).

Direct barrier evaluation method for SiC devices with junction barrier Schottky structures demonstrated with quasicontinuous spacing variation
https://aip.scitation.org/doi/10.1063/5.0100828?af=R&feed=mostrecent
AIP Advances, <a href="https://aip.scitation.org/toc/adv/12/8">Volume 12, Issue 8</a>, August 2022. <br/>Junction barrier Schottky (JBS) structures are extensively used in silicon carbide devices; however, the complex surface composition makes the direct barrier evaluation difficult. To exclude the fielddependent distortion on a barrier for a direct unbiased evaluation in JBS structures, this work proposes a new evaluation method with a physicsbased derivation and experimental demonstration, where a batch of JBS diodes are fabricated with a quasicontinuous spacing variation distribution achieved by the spreading etching technique. In addition, a detailed analysis based on the fielddependent barrier is provided. The result illustrates the chainlike activation and its saturation limit with a quantitative estimate in the straggle region. With the capability of the high linearity to exploit the statistical information for analysis stability, the proposed indicator could be a quantitative and versatile reference for designers dealing with nonideal surfaces.
AIP Advances, Volume 12, Issue 8, August 2022. <br/>Junction barrier Schottky (JBS) structures are extensively used in silicon carbide devices; however, the complex surface composition makes the direct barrier evaluation difficult. To exclude the fielddependent distortion on a barrier for a direct unbiased evaluation in JBS structures, this work proposes a new evaluation method with a physicsbased derivation and experimental demonstration, where a batch of JBS diodes are fabricated with a quasicontinuous spacing variation distribution achieved by the spreading etching technique. In addition, a detailed analysis based on the fielddependent barrier is provided. The result illustrates the chainlike activation and its saturation limit with a quantitative estimate in the straggle region. With the capability of the high linearity to exploit the statistical information for analysis stability, the proposed indicator could be a quantitative and versatile reference for designers dealing with nonideal surfaces.
Direct barrier evaluation method for SiC devices with junction barrier Schottky structures demonstrated with quasicontinuous spacing variation
10.1063/5.0100828
AIP Advances
20220804T02:47:01Z
© 2022 Author(s).
Hu Long
Na Ren
Kuang Sheng

Perfect doublelayer terahertz absorber based on graphene metamaterial
https://aip.scitation.org/doi/10.1063/5.0099346?af=R&feed=mostrecent
AIP Advances, <a href="https://aip.scitation.org/toc/adv/12/8">Volume 12, Issue 8</a>, August 2022. <br/>Using bilayer graphene structures (Ltype and disktype structures), we numerically demonstrate a tunable singleband terahertz metamaterial absorber with nearly perfect (100%) absorption by continuously adjusting the graphene Fermi energy parameters to determine the maximum absorption rate, the corresponding center frequency, and bandwidth. Graphene distinct dielectric–metal transition properties make it possible to achieve tunable terahertz absorption. The maximum absorption rate increases from 18% to 100% when the Fermi energy is increased from 0.1 to 1 eV. At 1 eV, the absorption rate exceeds 90% in the range of 0.57–1.03 THz. The incident angle is also tested. When the angle is in the range of 60°, excellent adsorption performance is maintained.
AIP Advances, Volume 12, Issue 8, August 2022. <br/>Using bilayer graphene structures (Ltype and disktype structures), we numerically demonstrate a tunable singleband terahertz metamaterial absorber with nearly perfect (100%) absorption by continuously adjusting the graphene Fermi energy parameters to determine the maximum absorption rate, the corresponding center frequency, and bandwidth. Graphene distinct dielectric–metal transition properties make it possible to achieve tunable terahertz absorption. The maximum absorption rate increases from 18% to 100% when the Fermi energy is increased from 0.1 to 1 eV. At 1 eV, the absorption rate exceeds 90% in the range of 0.57–1.03 THz. The incident angle is also tested. When the angle is in the range of 60°, excellent adsorption performance is maintained.
Perfect doublelayer terahertz absorber based on graphene metamaterial
10.1063/5.0099346
AIP Advances
20220808T02:04:47Z
© 2022 Author(s).
Haoduo Jia
Xin Tang
Hui Li
Ziwen Qian
Ming Li
Dai Wu
Peng Li
Jianxin Wang
Xinghua Zhu
Dingyu Yang

Underactuated USV path following control under multiple constraints
https://aip.scitation.org/doi/10.1063/5.0094347?af=R&feed=mostrecent
AIP Advances, <a href="https://aip.scitation.org/toc/adv/12/8">Volume 12, Issue 8</a>, August 2022. <br/>The path following control of an underactuated unmanned surface vehicle (USV) under the constraints of rudder angle, rudder velocity, and rudder response time in the disturbing environment is studied, and a cascaded path following control system based on guidance law and heading control law is designed. First, the guidance law is designed on the basis of integral lineofsight, while the tracking error state is introduced to design a variable gain disturbance observer, which not only ensures the stability of the convergence section but also takes into account the tracking accuracy of the stable section. The stability of the system is analyzed. Subsequently, the rudder maneuverability constraint and rudder effect delay are further imposed after fully considering the limited range of rudder angle, rudder velocity, and rudder response time in the process of path following. In addition, the heading control law is, therefore, designed on the basis of the rolling optimization strategy, which effectively reduces the oscillation while ensuring the convergence speed. The stability of the control law is further proved. Thereafter, a simulation experiment proves the effectiveness and advancement of the algorithm designed in this paper. In the end, based on the software and hardware design of the control system, “Sea Sturgeon” USV is used for the lake test of the proposed control algorithm to verify its feasibility in practical engineering applications.
AIP Advances, Volume 12, Issue 8, August 2022. <br/>The path following control of an underactuated unmanned surface vehicle (USV) under the constraints of rudder angle, rudder velocity, and rudder response time in the disturbing environment is studied, and a cascaded path following control system based on guidance law and heading control law is designed. First, the guidance law is designed on the basis of integral lineofsight, while the tracking error state is introduced to design a variable gain disturbance observer, which not only ensures the stability of the convergence section but also takes into account the tracking accuracy of the stable section. The stability of the system is analyzed. Subsequently, the rudder maneuverability constraint and rudder effect delay are further imposed after fully considering the limited range of rudder angle, rudder velocity, and rudder response time in the process of path following. In addition, the heading control law is, therefore, designed on the basis of the rolling optimization strategy, which effectively reduces the oscillation while ensuring the convergence speed. The stability of the control law is further proved. Thereafter, a simulation experiment proves the effectiveness and advancement of the algorithm designed in this paper. In the end, based on the software and hardware design of the control system, “Sea Sturgeon” USV is used for the lake test of the proposed control algorithm to verify its feasibility in practical engineering applications.
Underactuated USV path following control under multiple constraints
10.1063/5.0094347
AIP Advances
20220810T02:14:34Z
© 2022 Author(s).
Hongbin Wang
Jiao Dong
Jianqiang Zhang
Yan Li
Shiqi Wang

Nanocarbon ohmic electrodes fabricated by coaxial arc plasma deposition for phosphorusdoped diamond electronics application
https://aip.scitation.org/doi/10.1063/5.0093470?af=R&feed=mostrecent
AIP Advances, <a href="https://aip.scitation.org/toc/adv/12/8">Volume 12, Issue 8</a>, August 2022. <br/>nType (phosphorusdoped) diamond is a promising material for diamondbased electronic devices. However, realizing good ohmic contacts for phosphorusdoped diamonds limits their applications. Thus, the search for nonconventional ohmic contacts has become a hot topic for many researchers. In this work, nanocarbon ohmic electrodes with enhanced carrier collection efficiency were deposited by coaxial arc plasma deposition. The fabricated nanocarbon ohmic electrodes were extensively examined in terms of specific contact resistance and corrosion resistance. The circular transmission line model theory was used to estimate the charge collection efficiency of the nanocarbon ohmic electrodes in terms of specific contact resistance at a specific voltage range (5–10 V); they exhibited a specific contact resistance of 1 × 10−3 Ωcm2. The result revealed one order reduction in the specific contact resistance and, consequently, a potential drop at the diamond/electrode interface compared to the conventional Ti electrodes. Moreover, the fabricated nanocarbon electrodes exhibited high mechanical adhesion and chemical inertness over repeated acid treatments. In device applications, the nanocarbon electrodes were evaluated for Ni/ntype diamond Schottky diodes, and they exhibited nearly one order enhancement in the rectification ratio and a fast charge collection at lower biasing voltages.
AIP Advances, Volume 12, Issue 8, August 2022. <br/>nType (phosphorusdoped) diamond is a promising material for diamondbased electronic devices. However, realizing good ohmic contacts for phosphorusdoped diamonds limits their applications. Thus, the search for nonconventional ohmic contacts has become a hot topic for many researchers. In this work, nanocarbon ohmic electrodes with enhanced carrier collection efficiency were deposited by coaxial arc plasma deposition. The fabricated nanocarbon ohmic electrodes were extensively examined in terms of specific contact resistance and corrosion resistance. The circular transmission line model theory was used to estimate the charge collection efficiency of the nanocarbon ohmic electrodes in terms of specific contact resistance at a specific voltage range (5–10 V); they exhibited a specific contact resistance of 1 × 10−3 Ωcm2. The result revealed one order reduction in the specific contact resistance and, consequently, a potential drop at the diamond/electrode interface compared to the conventional Ti electrodes. Moreover, the fabricated nanocarbon electrodes exhibited high mechanical adhesion and chemical inertness over repeated acid treatments. In device applications, the nanocarbon electrodes were evaluated for Ni/ntype diamond Schottky diodes, and they exhibited nearly one order enhancement in the rectification ratio and a fast charge collection at lower biasing voltages.
Nanocarbon ohmic electrodes fabricated by coaxial arc plasma deposition for phosphorusdoped diamond electronics application
10.1063/5.0093470
AIP Advances
20220810T02:16:52Z
© 2022 Author(s).
Sreenath Mylo Valappil
Shinya Ohmagari
Abdelrahman Zkria
Phongsaphak Sittimart
Eslam Abubakr
Hiromitsu Kato
Tsuyoshi Yoshitake

Investigation on the influence of gas temperature characteristics for engine combustion chamber on plasma jet deflection with MHD control
https://aip.scitation.org/doi/10.1063/5.0091932?af=R&feed=mostrecent
AIP Advances, <a href="https://aip.scitation.org/toc/adv/12/8">Volume 12, Issue 8</a>, August 2022. <br/>This paper is devoted to investigating the influence of gas temperature on plasma jet under magnetic control. The combustion temperature and the conductivity of the chemical equilibrium state were calculated by using a numerical method. K2CO3 was selected as the ionization seed. The characteristics of gas plasma in ionization were compared for methane/air/K2CO3 and acetylene/air/K2CO3 combustion schemes. The results showed that the acetylene/air/K2CO3 combustion scheme can obtain higher gas temperature and conductivity. The functional relationship between the conductivity and the gas temperature is fitted in polynomial form. The experiments on the deflection of plasma were carried out on the combustion and flow control test rig at temperatures of 1600–2500 K and in a magnetic field of intensity 0.6 T. The effect of jet deflection was analyzed from macroscopic and microscopic points of view. When the gas temperature increases, the ionization degree increases, the positive Lorentz force in ions increases, and plasma jet deflection becomes more obvious. The Lorentz force on the positive ion determines the effect of plume deflection. The calculated and experimental results indicated that the high temperature condition is very helpful to improve the characteristics of gas plasma in ionization. The results provide references for corresponding experimental research.
AIP Advances, Volume 12, Issue 8, August 2022. <br/>This paper is devoted to investigating the influence of gas temperature on plasma jet under magnetic control. The combustion temperature and the conductivity of the chemical equilibrium state were calculated by using a numerical method. K2CO3 was selected as the ionization seed. The characteristics of gas plasma in ionization were compared for methane/air/K2CO3 and acetylene/air/K2CO3 combustion schemes. The results showed that the acetylene/air/K2CO3 combustion scheme can obtain higher gas temperature and conductivity. The functional relationship between the conductivity and the gas temperature is fitted in polynomial form. The experiments on the deflection of plasma were carried out on the combustion and flow control test rig at temperatures of 1600–2500 K and in a magnetic field of intensity 0.6 T. The effect of jet deflection was analyzed from macroscopic and microscopic points of view. When the gas temperature increases, the ionization degree increases, the positive Lorentz force in ions increases, and plasma jet deflection becomes more obvious. The Lorentz force on the positive ion determines the effect of plume deflection. The calculated and experimental results indicated that the high temperature condition is very helpful to improve the characteristics of gas plasma in ionization. The results provide references for corresponding experimental research.
Investigation on the influence of gas temperature characteristics for engine combustion chamber on plasma jet deflection with MHD control
10.1063/5.0091932
AIP Advances
20220810T02:21:12Z
© 2022 Author(s).
Kai Zhao
Yongji Lu
Chunyu Wang
Feng Li

Research on flashover characteristics of typical interconnect structures on printed circuit board and influential factors under DC voltage
https://aip.scitation.org/doi/10.1063/5.0100668?af=R&feed=mostrecent
AIP Advances, <a href="https://aip.scitation.org/toc/adv/12/8">Volume 12, Issue 8</a>, August 2022. <br/>With the development of highdensity and highly integrated electronic devices, the insulation characteristics between the interconnects of printed circuit boards (PCBs) are the key issues to be considered in their design and production. Most of the existing studies on insulation characteristics are based on parallel interconnect structures; however, the possibility of flashover or breakdown on PCB at parallel interconnects is relatively low compared to other irregular structures. The flashover characteristics of PCB interconnects need to be more comprehensively presented. In this paper, the commonly used interconnects were divided into three typical structures. Under the same DC excitation, the “interconnect with pad” structure had the most severe electric field concentration, and the insulation characteristic of this structure was the worse of the three. Furthermore, the effects of the distance between the interconnect and pad size on the flashover voltages of the “interconnect with pad” structure were investigated and explained by the maximum electric field strength, which could be approximately calculated by the existing equation.
AIP Advances, Volume 12, Issue 8, August 2022. <br/>With the development of highdensity and highly integrated electronic devices, the insulation characteristics between the interconnects of printed circuit boards (PCBs) are the key issues to be considered in their design and production. Most of the existing studies on insulation characteristics are based on parallel interconnect structures; however, the possibility of flashover or breakdown on PCB at parallel interconnects is relatively low compared to other irregular structures. The flashover characteristics of PCB interconnects need to be more comprehensively presented. In this paper, the commonly used interconnects were divided into three typical structures. Under the same DC excitation, the “interconnect with pad” structure had the most severe electric field concentration, and the insulation characteristic of this structure was the worse of the three. Furthermore, the effects of the distance between the interconnect and pad size on the flashover voltages of the “interconnect with pad” structure were investigated and explained by the maximum electric field strength, which could be approximately calculated by the existing equation.
Research on flashover characteristics of typical interconnect structures on printed circuit board and influential factors under DC voltage
10.1063/5.0100668
AIP Advances
20220810T02:23:32Z
© 2022 Author(s).
Yuhui Lv
Xiong Yang
Xianjun Shao
Yitong Yao
Xiaoxin Chen
Haibao Mu

Ultraefficiency broadband terahertz polarization converter based on a crossshaped metamaterial
https://aip.scitation.org/doi/10.1063/5.0098815?af=R&feed=mostrecent
AIP Advances, <a href="https://aip.scitation.org/toc/adv/12/8">Volume 12, Issue 8</a>, August 2022. <br/>In this study, we describe the design, fabrication, and characterization of a crossshaped structure reflective broadband THz polarization converter. The operating bandwidth of the proposed polarization converter was in the range of 0.8–1.6 THz. The polarization conversion rate (PCR) exceeded 85% in the frequency range of 1.07–1.35 THz and was as high as 91% at 1.35 THz. The cross PCR value exceeded 85% in the frequency range of 1.05–1.35 THz and reached a maximum value of 91%. The performance characteristics (bandwidth and PCR) of the proposed polarization converter were compared with those of similar previously reported devices, and the results indicated that the proposed polarization converter exhibits better performance. The proposed THz polarization converter is suitable for a wide range of applications in communication and polarization manipulation devices.
AIP Advances, Volume 12, Issue 8, August 2022. <br/>In this study, we describe the design, fabrication, and characterization of a crossshaped structure reflective broadband THz polarization converter. The operating bandwidth of the proposed polarization converter was in the range of 0.8–1.6 THz. The polarization conversion rate (PCR) exceeded 85% in the frequency range of 1.07–1.35 THz and was as high as 91% at 1.35 THz. The cross PCR value exceeded 85% in the frequency range of 1.05–1.35 THz and reached a maximum value of 91%. The performance characteristics (bandwidth and PCR) of the proposed polarization converter were compared with those of similar previously reported devices, and the results indicated that the proposed polarization converter exhibits better performance. The proposed THz polarization converter is suitable for a wide range of applications in communication and polarization manipulation devices.
Ultraefficiency broadband terahertz polarization converter based on a crossshaped metamaterial
10.1063/5.0098815
AIP Advances
20220803T02:43:29Z
© 2022 Author(s).
Wenjia Liu
Yonggang Zhang
Lanju Liang
Haiyun Yao
Xin Yan
Fu Qiu
Chengcheng Huang
Weili Li
Yihui Tan
Weiran Li
Yuxuan Huang
Jingbo Wu
Caihong Zhang
Biaobing Jin

The effect of organic coatings in the magnetization of CoFe2O4 nanoparticles
https://aip.scitation.org/doi/10.1063/5.0078167?af=R&feed=mostrecent
AIP Advances, <a href="https://aip.scitation.org/toc/adv/12/8">Volume 12, Issue 8</a>, August 2022. <br/>Cobalt ferrite has attracted considerable attention in recent years due to its unique physical properties, such as high Curie temperature, large magnetocrystalline anisotropy, high coercivity, moderate saturation magnetization, large magnetostrictive coefficient, and excellent chemical stability and mechanical hardness. This work focuses on the neutron scattering results of the magnetic response characteristics of polysaccharide fucan coated cobalt ferrite nanoparticles for their application as a solid support for enzyme immobilization and other biotechnology applications. Here, we unambiguously show that surfactant coating of nanoparticles can significantly affect their magnetic response throughout the nanoparticle volume. While it has been recently suggested that oleic acid may preserve nanoscale magnetism in ferrites, we present evidence that the influence of oleic acid on the magnetic response of CoFe2O4 nanoparticles is more than a surface effect, instead pervading throughout the interior of the nanoparticle.
AIP Advances, Volume 12, Issue 8, August 2022. <br/>Cobalt ferrite has attracted considerable attention in recent years due to its unique physical properties, such as high Curie temperature, large magnetocrystalline anisotropy, high coercivity, moderate saturation magnetization, large magnetostrictive coefficient, and excellent chemical stability and mechanical hardness. This work focuses on the neutron scattering results of the magnetic response characteristics of polysaccharide fucan coated cobalt ferrite nanoparticles for their application as a solid support for enzyme immobilization and other biotechnology applications. Here, we unambiguously show that surfactant coating of nanoparticles can significantly affect their magnetic response throughout the nanoparticle volume. While it has been recently suggested that oleic acid may preserve nanoscale magnetism in ferrites, we present evidence that the influence of oleic acid on the magnetic response of CoFe2O4 nanoparticles is more than a surface effect, instead pervading throughout the interior of the nanoparticle.
The effect of organic coatings in the magnetization of CoFe2O4 nanoparticles
10.1063/5.0078167
AIP Advances
20220804T02:47:03Z
© 2022 Author(s).
Priscyla L. Andrade
Valdeene A. J. Silva
Kathryn L. Krycka
Juscelino B. Leão
ILin Liu
Maria P. C. Silva
J. Albino Aguiar

Study on transmission line icing prediction based on microtopographic correction
https://aip.scitation.org/doi/10.1063/5.0096989?af=R&feed=mostrecent
AIP Advances, <a href="https://aip.scitation.org/toc/adv/12/8">Volume 12, Issue 8</a>, August 2022. <br/>For the requirement of refinement prediction of transmission line icing thickness, this paper presents an icing thickness correction method which combines the prediction using low spatial resolution with the correction of microtopography features. By analyzing the regional characteristics of microtopography, the areas can be divided into three categories: plains, highaltitude mountains, and lowaltitude mountains. For each type of terrain, the quantitative correction model for the icing thickness is established, which is dependent on altitude, relief amplitude, slope angle, slope aspect, water system, valley line, ridge line, and saddle point. In this paper, according to the numerical prediction on the 3 [math] 3 km2 grids, the icing thickness of the transmission line on the 300 [math] 300 m2 grids with microtopography is obtained using the correction method in Hubei Power Grid. The results show that the correction method is efficient and convenient to improve the accuracy of icing thickness prediction of the transmission line.
AIP Advances, Volume 12, Issue 8, August 2022. <br/>For the requirement of refinement prediction of transmission line icing thickness, this paper presents an icing thickness correction method which combines the prediction using low spatial resolution with the correction of microtopography features. By analyzing the regional characteristics of microtopography, the areas can be divided into three categories: plains, highaltitude mountains, and lowaltitude mountains. For each type of terrain, the quantitative correction model for the icing thickness is established, which is dependent on altitude, relief amplitude, slope angle, slope aspect, water system, valley line, ridge line, and saddle point. In this paper, according to the numerical prediction on the 3 [math] 3 km2 grids, the icing thickness of the transmission line on the 300 [math] 300 m2 grids with microtopography is obtained using the correction method in Hubei Power Grid. The results show that the correction method is efficient and convenient to improve the accuracy of icing thickness prediction of the transmission line.
Study on transmission line icing prediction based on microtopographic correction
10.1063/5.0096989
AIP Advances
20220808T02:13:16Z
© 2022 Author(s).
Junjie Huang
Xueming Zhou

Polarization of Bi2Se3 thin film toward nonvolatile memory applications
https://aip.scitation.org/doi/10.1063/5.0093212?af=R&feed=mostrecent
AIP Advances, <a href="https://aip.scitation.org/toc/adv/12/8">Volume 12, Issue 8</a>, August 2022. <br/>In recent years, topological insulators have drawn growing interest as a unique electronic state of matter toward quantum information technology. Despite the logic devices with magnetization switching through spin–orbit torque or the topological magnetoelectric effect, realizing memory devices based on topological insulators has been urged in quantum computing applications. In this work, we report the design and fabrication of a nonvolatile memory device that employs polarization of Bi2Se3 thin films achieving fast memory speed, sufficient memory window, and good reliability. The Bi2Se3 film polarizes under an external electrical field with charges accumulated on the top and bottom surfaces separating the electrons and holes. Such polarization is much faster than the carrier tunneling in conventional floatinggate flash memory and ferroelectricbased memory devices. In addition, good memory retention and endurance properties have also been obtained, showing great potential in highperformance memory application in future topological insulatorinvolved information technology.
AIP Advances, Volume 12, Issue 8, August 2022. <br/>In recent years, topological insulators have drawn growing interest as a unique electronic state of matter toward quantum information technology. Despite the logic devices with magnetization switching through spin–orbit torque or the topological magnetoelectric effect, realizing memory devices based on topological insulators has been urged in quantum computing applications. In this work, we report the design and fabrication of a nonvolatile memory device that employs polarization of Bi2Se3 thin films achieving fast memory speed, sufficient memory window, and good reliability. The Bi2Se3 film polarizes under an external electrical field with charges accumulated on the top and bottom surfaces separating the electrons and holes. Such polarization is much faster than the carrier tunneling in conventional floatinggate flash memory and ferroelectricbased memory devices. In addition, good memory retention and endurance properties have also been obtained, showing great potential in highperformance memory application in future topological insulatorinvolved information technology.
Polarization of Bi2Se3 thin film toward nonvolatile memory applications
10.1063/5.0093212
AIP Advances
20220808T02:15:55Z
© 2022 Author(s).
Kai Zhang
Xinyi Zhu
Yafen Yang
Hao Zhu

Numerical simulation of an external cusp magnetic field on the welding arc
https://aip.scitation.org/doi/10.1063/5.0097534?af=R&feed=mostrecent
AIP Advances, <a href="https://aip.scitation.org/toc/adv/12/8">Volume 12, Issue 8</a>, August 2022. <br/>A controlled welding arc is an upandcoming research area for highefficiency and highprecision wire arc additive manufacturing. This numerical simulation demonstrates that an alternating external cusp magnetic field (ECMF) can compress the arc. This is the result of the reversal of the Lorentz force direction caused by the reversal of the magnetic poles. The simulation results show that the solenoid current directly affects the arc section ellipticity, and the alternating frequency affects the arc contraction. The highspeed photos demonstrate the feasibility of ECMF.
AIP Advances, Volume 12, Issue 8, August 2022. <br/>A controlled welding arc is an upandcoming research area for highefficiency and highprecision wire arc additive manufacturing. This numerical simulation demonstrates that an alternating external cusp magnetic field (ECMF) can compress the arc. This is the result of the reversal of the Lorentz force direction caused by the reversal of the magnetic poles. The simulation results show that the solenoid current directly affects the arc section ellipticity, and the alternating frequency affects the arc contraction. The highspeed photos demonstrate the feasibility of ECMF.
Numerical simulation of an external cusp magnetic field on the welding arc
10.1063/5.0097534
AIP Advances
20220803T02:43:31Z
© 2022 Author(s).
Dan Liu
Honglei Zhao
Lei Shi
Yunlong Chang

Influences of HMX contents on potential reaction violence and fragmentation degree of PBTpropellants after impact load
https://aip.scitation.org/doi/10.1063/5.0099253?af=R&feed=mostrecent
AIP Advances, <a href="https://aip.scitation.org/toc/adv/12/8">Volume 12, Issue 8</a>, August 2022. <br/>The extent of damage that is developed during the production, transportation, storage, and handling of propellants after a lowvelocity impact is an important factor in evaluating a dangerous threat such as deflagrationtodetonation transition. In this paper, a friability test was performed to evaluate the critical impact ignition velocity (CIIV), fragmentation degree, and potential reaction violence of four 3, 3Bis(azidomethyl)oxetane (BAMO) and tetrahydrofuran (THF) copolymerpropellants (PBTpropellants) with various 3,5,7tetranitro1,3,5,7tetrazocine (HMX) contents under impact at different velocities. The results showed that as the HMX contents increased, the CIIV decreased and changes of that also decreased. Simultaneously, the fragmentation degree increased with the increase in impact velocity, as it was judged by the initial dynamic activity ratio. Then, we calculated the maximum value of the initial dynamic activity ratio by fitting the data using Boltzmann, which were 27 (HMX = 0), 39 (HMX = 5%), 48 (HMX = 10%), and 56 (HMX = 15%). The ratios of the maximum value of the initial dynamic activity ratio between PBTpropellants containing HMX and those without HMX were 1.44, 1.78, and 2.07. The addition of HMX increased the maximum fragmentation degree of PBTpropellants under impact. The potential reaction violence increased as the impact velocity increased due to the increase in the fragmentation degree of PBTpropellants after impact. Similarly, we also obtained the maximum values of potential reaction violence, which were 62.39, 50.17, 41.89, and 34.65. The maximum value of potential reaction violence decreased with the increase in HMX contents, and the addition of HMX improved the safety of PBTpropellants burning after impact.
AIP Advances, Volume 12, Issue 8, August 2022. <br/>The extent of damage that is developed during the production, transportation, storage, and handling of propellants after a lowvelocity impact is an important factor in evaluating a dangerous threat such as deflagrationtodetonation transition. In this paper, a friability test was performed to evaluate the critical impact ignition velocity (CIIV), fragmentation degree, and potential reaction violence of four 3, 3Bis(azidomethyl)oxetane (BAMO) and tetrahydrofuran (THF) copolymerpropellants (PBTpropellants) with various 3,5,7tetranitro1,3,5,7tetrazocine (HMX) contents under impact at different velocities. The results showed that as the HMX contents increased, the CIIV decreased and changes of that also decreased. Simultaneously, the fragmentation degree increased with the increase in impact velocity, as it was judged by the initial dynamic activity ratio. Then, we calculated the maximum value of the initial dynamic activity ratio by fitting the data using Boltzmann, which were 27 (HMX = 0), 39 (HMX = 5%), 48 (HMX = 10%), and 56 (HMX = 15%). The ratios of the maximum value of the initial dynamic activity ratio between PBTpropellants containing HMX and those without HMX were 1.44, 1.78, and 2.07. The addition of HMX increased the maximum fragmentation degree of PBTpropellants under impact. The potential reaction violence increased as the impact velocity increased due to the increase in the fragmentation degree of PBTpropellants after impact. Similarly, we also obtained the maximum values of potential reaction violence, which were 62.39, 50.17, 41.89, and 34.65. The maximum value of potential reaction violence decreased with the increase in HMX contents, and the addition of HMX improved the safety of PBTpropellants burning after impact.
Influences of HMX contents on potential reaction violence and fragmentation degree of PBTpropellants after impact load
10.1063/5.0099253
AIP Advances
20220803T02:43:30Z
© 2022 Author(s).
Nian Yang
Teng Ma
Jingping Liu
Dayu Bai
Yang Li
Xu Wang
Yinsheng Huang
Dabin Liu
Sen Xu

Thermal conductivity tensor of γ and ɛhexanitrohexaazaisowurtzitane as a function of pressure and temperature
https://aip.scitation.org/doi/10.1063/5.0105161?af=R&feed=mostrecent
AIP Advances, <a href="https://aip.scitation.org/toc/adv/12/8">Volume 12, Issue 8</a>, August 2022. <br/>Using reverse nonequilibrium molecular dynamics simulations, we have determined the dependences on temperature and pressure of the thermal conductivity tensors for the monoclinic γ and ɛ polymorphs of hexanitrohexaazaisowurtzitane (HNIW or CL20). A recently developed nonreactive force field [X. Bidault and S. Chaudhuri, RSC Adv. 9, 39649–39661 (2019)], designed to study polymorphism and phase transitions in CL20, is employed. The effects of temperature and pressure are investigated between 200 and 500 K and up to 0.5 GPa for γCL20 and 2 GPa for ɛCL20. In order to obtain the full thermal conductivity tensor, κij, for the monoclinic crystals, four distinct heat propagation directions are used. We find that κij for both polymorphs is more isotropic than for other energetic molecular crystals, including α and γRDX, βHMX, and PETN, with a maximum difference of 9.8% between orientations observed at 300 K and 0 GPa for γCL20 and a maximum difference of 4.8% for ɛCL20. The average thermal conductivity, [math], of ɛCL20 is 6.4% larger than that of γCL20 at 300 K and 0 GPa. Analytic linear functions of the inverse temperature and the pressure are provided, which fit the data well and can be used to predict the thermal conductivity of both polymorphs for any orientation, pressure, and temperature in and around the fitting range. Our predictions agree reasonably well with the limited available experimental data, for which the polymorph type is unknown.
AIP Advances, Volume 12, Issue 8, August 2022. <br/>Using reverse nonequilibrium molecular dynamics simulations, we have determined the dependences on temperature and pressure of the thermal conductivity tensors for the monoclinic γ and ɛ polymorphs of hexanitrohexaazaisowurtzitane (HNIW or CL20). A recently developed nonreactive force field [X. Bidault and S. Chaudhuri, RSC Adv. 9, 39649–39661 (2019)], designed to study polymorphism and phase transitions in CL20, is employed. The effects of temperature and pressure are investigated between 200 and 500 K and up to 0.5 GPa for γCL20 and 2 GPa for ɛCL20. In order to obtain the full thermal conductivity tensor, κij, for the monoclinic crystals, four distinct heat propagation directions are used. We find that κij for both polymorphs is more isotropic than for other energetic molecular crystals, including α and γRDX, βHMX, and PETN, with a maximum difference of 9.8% between orientations observed at 300 K and 0 GPa for γCL20 and a maximum difference of 4.8% for ɛCL20. The average thermal conductivity, [math], of ɛCL20 is 6.4% larger than that of γCL20 at 300 K and 0 GPa. Analytic linear functions of the inverse temperature and the pressure are provided, which fit the data well and can be used to predict the thermal conductivity of both polymorphs for any orientation, pressure, and temperature in and around the fitting range. Our predictions agree reasonably well with the limited available experimental data, for which the polymorph type is unknown.
Thermal conductivity tensor of γ and ɛhexanitrohexaazaisowurtzitane as a function of pressure and temperature
10.1063/5.0105161
AIP Advances
20220803T03:43:44Z
© 2022 Author(s).
Romain Perriot
M. J. Cawkwell

Correct use of excess configurational entropies to study the ideal glass transition in hardsphere systems with continuous polydispersity
https://aip.scitation.org/doi/10.1063/5.0096421?af=R&feed=mostrecent
AIP Advances, <a href="https://aip.scitation.org/toc/adv/12/8">Volume 12, Issue 8</a>, August 2022. <br/>We systematically apply the resolution to the configurational entropy paradox from our previous paper [V. Baranau and U. Tallarek, J. Chem. Phys. 147, 224503 (2017)] to study configurational entropies and the glass transition in polydisperse hardsphere systems with lognormal particle radius distributions (r) over a wide range of polydispersities [math]. The resolution implies the careful use of excess quantities for vibrational and configurational entropies. We obtain the fluid entropy from the fluid equation of state and the vibrational entropy from the glass equation of state; thereby, the configurational entropy becomes their difference. We discovered that the Adam–Gibbs relation is able to fit the asymptotic alpharelaxation times τα of the hardsphere systems under study at high volume fractions φ when our excess configurational entropies are supplied. For polydispersity δ = 0.1, the Adam–Gibbs relation is able to fit the data over the entire range of φ studied. Ideal glass transition densities φg obtained in this way are below predictions from the Vogel–Fulcher–Tammann fits. Our results indicate by extrapolation that the glass close packing limit φGCP for monodisperse systems is [math], consistent with granular matter studies. Our configurational entropies extrapolated to the monodisperse case are found to match Edwards entropies from granular matter studies very well.
AIP Advances, Volume 12, Issue 8, August 2022. <br/>We systematically apply the resolution to the configurational entropy paradox from our previous paper [V. Baranau and U. Tallarek, J. Chem. Phys. 147, 224503 (2017)] to study configurational entropies and the glass transition in polydisperse hardsphere systems with lognormal particle radius distributions (r) over a wide range of polydispersities [math]. The resolution implies the careful use of excess quantities for vibrational and configurational entropies. We obtain the fluid entropy from the fluid equation of state and the vibrational entropy from the glass equation of state; thereby, the configurational entropy becomes their difference. We discovered that the Adam–Gibbs relation is able to fit the asymptotic alpharelaxation times τα of the hardsphere systems under study at high volume fractions φ when our excess configurational entropies are supplied. For polydispersity δ = 0.1, the Adam–Gibbs relation is able to fit the data over the entire range of φ studied. Ideal glass transition densities φg obtained in this way are below predictions from the Vogel–Fulcher–Tammann fits. Our results indicate by extrapolation that the glass close packing limit φGCP for monodisperse systems is [math], consistent with granular matter studies. Our configurational entropies extrapolated to the monodisperse case are found to match Edwards entropies from granular matter studies very well.
Correct use of excess configurational entropies to study the ideal glass transition in hardsphere systems with continuous polydispersity
10.1063/5.0096421
AIP Advances
20220804T02:47:03Z
© 2022 Author(s).
Vasili Baranau
Ulrich Tallarek

Dust charge fluctuation and ion acoustic wave propagation in dusty plasma with qnonextensive hot and Maxwellian cold electrons
https://aip.scitation.org/doi/10.1063/5.0100914?af=R&feed=mostrecent
AIP Advances, <a href="https://aip.scitation.org/toc/adv/12/8">Volume 12, Issue 8</a>, August 2022. <br/>We have employed the selfconsistent kinetic theory to study the linear dispersion relation of ion acoustic waves in a fourcomponent plasma consisting of nonextensive hot electrons, Maxwellian cold electrons, positive ions, and dust particles. The dust charging process with the modified ion acoustic wave damping, as well as its unstable mode, has been graphically illustrated. It is found that the dust charging mechanism depends on the density of hot electrons, the degree of nonextensive electron distribution, and the temperature ratio of hot to cold electrons. It is shown that the damping and instability rates of ion acoustic waves due to dust charge fluctuations explicitly depend on the choice of electron distribution and the magnitude of dusty plasma parameters. In addition, we have studied the ion acoustic Landau damping in the absence of dust particles. It is found that the weak damping region broadens, while the strong damping region shrinks and is shifted toward the short wavelength region for the increase in the temperature ratio of hot to cold electrons.
AIP Advances, Volume 12, Issue 8, August 2022. <br/>We have employed the selfconsistent kinetic theory to study the linear dispersion relation of ion acoustic waves in a fourcomponent plasma consisting of nonextensive hot electrons, Maxwellian cold electrons, positive ions, and dust particles. The dust charging process with the modified ion acoustic wave damping, as well as its unstable mode, has been graphically illustrated. It is found that the dust charging mechanism depends on the density of hot electrons, the degree of nonextensive electron distribution, and the temperature ratio of hot to cold electrons. It is shown that the damping and instability rates of ion acoustic waves due to dust charge fluctuations explicitly depend on the choice of electron distribution and the magnitude of dusty plasma parameters. In addition, we have studied the ion acoustic Landau damping in the absence of dust particles. It is found that the weak damping region broadens, while the strong damping region shrinks and is shifted toward the short wavelength region for the increase in the temperature ratio of hot to cold electrons.
Dust charge fluctuation and ion acoustic wave propagation in dusty plasma with qnonextensive hot and Maxwellian cold electrons
10.1063/5.0100914
AIP Advances
20220810T02:27:52Z
© 2022 Author(s).
Shiva Bikram Thapa
Suresh Basnet
Raju Khanal

Selfformation of InAs/InGaAsSb typeII superlattice structures on InP substrates by MBE and their application to midinfrared LEDs
https://aip.scitation.org/doi/10.1063/5.0100423?af=R&feed=mostrecent
AIP Advances, <a href="https://aip.scitation.org/toc/adv/12/8">Volume 12, Issue 8</a>, August 2022. <br/>InAs/InGaAsSb typeII superlattice structures (SLSs) were spontaneously formed by the molecular beam epitaxy of InAs/GaAs0.86Sb0.14 SLSs on InP substrates. The strain due to lattice mismatch between InAs and GaAs0.86Sb0.14 induced two exchange reactions of In–Ga and As–Sb at both InAs/GaAs0.86Sb0.14 heterointerfaces, resulting in the strain relaxation and the selfformation of InAs/InGaAsSb typeII SLS. By energy dispersive xray spectroscopy analysis, the mixed crystal composition of the InGaAsSb layer was determined to be approximately In0.8Ga0.2As0.9Sb0.1. Electroluminescence spectra of LEDs, including the selfformed InAs/In0.8Ga0.2As0.9Sb0.1 2.5periodic SLS, showed double peaks of 2.6 and 3.2 µm at 15 K. The luminescence spectrum was based on two transition mechanisms of typeI transition in InAs and typeII transition between InAs and InGaAsSb. The experimental results of luminescence spectra were supported by theoretical calculations. The 3.3 µm emission was maintained above 220 K.
AIP Advances, Volume 12, Issue 8, August 2022. <br/>InAs/InGaAsSb typeII superlattice structures (SLSs) were spontaneously formed by the molecular beam epitaxy of InAs/GaAs0.86Sb0.14 SLSs on InP substrates. The strain due to lattice mismatch between InAs and GaAs0.86Sb0.14 induced two exchange reactions of In–Ga and As–Sb at both InAs/GaAs0.86Sb0.14 heterointerfaces, resulting in the strain relaxation and the selfformation of InAs/InGaAsSb typeII SLS. By energy dispersive xray spectroscopy analysis, the mixed crystal composition of the InGaAsSb layer was determined to be approximately In0.8Ga0.2As0.9Sb0.1. Electroluminescence spectra of LEDs, including the selfformed InAs/In0.8Ga0.2As0.9Sb0.1 2.5periodic SLS, showed double peaks of 2.6 and 3.2 µm at 15 K. The luminescence spectrum was based on two transition mechanisms of typeI transition in InAs and typeII transition between InAs and InGaAsSb. The experimental results of luminescence spectra were supported by theoretical calculations. The 3.3 µm emission was maintained above 220 K.
Selfformation of InAs/InGaAsSb typeII superlattice structures on InP substrates by MBE and their application to midinfrared LEDs
10.1063/5.0100423
AIP Advances
20220803T02:43:28Z
© 2022 Author(s).
Kou Uno
Naoto Iijima
Naoya Miyashita
Koichi Yamaguchi

Low contact resistivity of metal/nGaN by the reduction of gap states with an epitaxially grown GaOx insulating layer
https://aip.scitation.org/doi/10.1063/5.0100250?af=R&feed=mostrecent
AIP Advances, <a href="https://aip.scitation.org/toc/adv/12/8">Volume 12, Issue 8</a>, August 2022. <br/>We investigated the contact properties of metal/nGaN and metal/GaOx/nGaN in terms of Fermi level pinning (FLP) by metalinduced and disorderinduced gap states (MIGS and DIGS). The work function of ten different metals spanned a wide range from 4.2 to 5.7 eV. The measured Schottky barrier height vs metal work function in metal/nGaN showed the linear relationship with the slope parameter of S = 0.26 ± 0.01 for the doped and the undoped GaN, indicating a strong FLP. The insertion of a GaOx layer increased S to 0.35 corresponding to the decrease of the gap state density by ∼1.1 × 1013 states/(cm2 eV). A contact resistivity of 1.3 × 10−5 [math] cm2 was obtained in Al/GaOx (2.3 nm)/nGaN (doped with 2 × 1018 cm−3 of Si), which was smaller by nearly three orders than that without the GaOx layer. The insulating property and partially epitaxial structure of GaOx were considered to be responsible for the reduction of the MIGS and DIGS densities, respectively, thereby relaxing FLP and leading to low contact resistivity. Optimization of the GaOx growth parameters may further improve the contact property.
AIP Advances, Volume 12, Issue 8, August 2022. <br/>We investigated the contact properties of metal/nGaN and metal/GaOx/nGaN in terms of Fermi level pinning (FLP) by metalinduced and disorderinduced gap states (MIGS and DIGS). The work function of ten different metals spanned a wide range from 4.2 to 5.7 eV. The measured Schottky barrier height vs metal work function in metal/nGaN showed the linear relationship with the slope parameter of S = 0.26 ± 0.01 for the doped and the undoped GaN, indicating a strong FLP. The insertion of a GaOx layer increased S to 0.35 corresponding to the decrease of the gap state density by ∼1.1 × 1013 states/(cm2 eV). A contact resistivity of 1.3 × 10−5 [math] cm2 was obtained in Al/GaOx (2.3 nm)/nGaN (doped with 2 × 1018 cm−3 of Si), which was smaller by nearly three orders than that without the GaOx layer. The insulating property and partially epitaxial structure of GaOx were considered to be responsible for the reduction of the MIGS and DIGS densities, respectively, thereby relaxing FLP and leading to low contact resistivity. Optimization of the GaOx growth parameters may further improve the contact property.
Low contact resistivity of metal/nGaN by the reduction of gap states with an epitaxially grown GaOx insulating layer
10.1063/5.0100250
AIP Advances
20220803T02:43:26Z
© 2022 Author(s).
Jiro Koba
Junichi Koike

Highquality resonances in quasiperiodic clusters of scatterers for flexural waves
https://aip.scitation.org/doi/10.1063/5.0098239?af=R&feed=mostrecent
AIP Advances, <a href="https://aip.scitation.org/toc/adv/12/8">Volume 12, Issue 8</a>, August 2022. <br/>Multiple scattering theory is applied to the study of clusters of pointlike scatterers attached to a thin elastic plate and arranged in quasiperiodic distributions. Two types of structures are specifically considered: the twisted bilayer and the quasiperiodic line. The former consists in a couple of twodimensional lattices rotated a relative angle, so that the cluster forms a moiré pattern. The latter can be seen as a periodic onedimensional lattice where an incommensurate modulation is superimposed. Multiple scattering theory allows for the fast and efficient calculation of the resonant modes of these structures as well as for their quality factor, which is thoroughly analyzed in this work. The results show that quasiperiodic structures present a large density of states with high quality factors, being therefore a promising way for the design of high quality wavelocalization devices.
AIP Advances, Volume 12, Issue 8, August 2022. <br/>Multiple scattering theory is applied to the study of clusters of pointlike scatterers attached to a thin elastic plate and arranged in quasiperiodic distributions. Two types of structures are specifically considered: the twisted bilayer and the quasiperiodic line. The former consists in a couple of twodimensional lattices rotated a relative angle, so that the cluster forms a moiré pattern. The latter can be seen as a periodic onedimensional lattice where an incommensurate modulation is superimposed. Multiple scattering theory allows for the fast and efficient calculation of the resonant modes of these structures as well as for their quality factor, which is thoroughly analyzed in this work. The results show that quasiperiodic structures present a large density of states with high quality factors, being therefore a promising way for the design of high quality wavelocalization devices.
Highquality resonances in quasiperiodic clusters of scatterers for flexural waves
10.1063/5.0098239
AIP Advances
20220804T02:47:02Z
© 2022 Author(s).
Marc MartíSabaté
Sébastien Guenneau
Dani Torrent

UAV formation control based on distributed Kalman model predictive control algorithm
https://aip.scitation.org/doi/10.1063/5.0102391?af=R&feed=mostrecent
AIP Advances, <a href="https://aip.scitation.org/toc/adv/12/8">Volume 12, Issue 8</a>, August 2022. <br/>To address the perturbation of formation of multiple unmanned aerial vehicles (UAVs) subject to external disturbances, an algorithm of distributed Kalman model predictive control is proposed in this paper to improve the accuracy of maintaining a formation in flight. A UAV twoorder discretetime system model was built before devising a Kalman prediction model based on the standard prediction model. The desired formation configuration and neighbor Kalman optimal state estimation were conducted to determine the reference state of UAVs. While taking into account the formation tracking error and input stability, a logarithmic barrier function was introduced in the design of the overall cost function to ensure flight safety. Meanwhile, information was exchanged with neighbors with the directed and timeinvariant communication topological structure. With the Lyapunov stability theorem, sufficient conditions were defined for the asymptotic stability of the formation system. Simulation results revealed that the algorithm could effectively suppress the perturbation in the formation of UAVs arising from external disturbances, allowing the formation to cope with the conflicts between individual UAVs.
AIP Advances, Volume 12, Issue 8, August 2022. <br/>To address the perturbation of formation of multiple unmanned aerial vehicles (UAVs) subject to external disturbances, an algorithm of distributed Kalman model predictive control is proposed in this paper to improve the accuracy of maintaining a formation in flight. A UAV twoorder discretetime system model was built before devising a Kalman prediction model based on the standard prediction model. The desired formation configuration and neighbor Kalman optimal state estimation were conducted to determine the reference state of UAVs. While taking into account the formation tracking error and input stability, a logarithmic barrier function was introduced in the design of the overall cost function to ensure flight safety. Meanwhile, information was exchanged with neighbors with the directed and timeinvariant communication topological structure. With the Lyapunov stability theorem, sufficient conditions were defined for the asymptotic stability of the formation system. Simulation results revealed that the algorithm could effectively suppress the perturbation in the formation of UAVs arising from external disturbances, allowing the formation to cope with the conflicts between individual UAVs.
UAV formation control based on distributed Kalman model predictive control algorithm
10.1063/5.0102391
AIP Advances
20220804T02:47:01Z
© 2022 Author(s).
Qiangwei Pang
Yongyong Zhu
Ye Chen
Deshi Wang
Wenkai Suo

Mainlobe maintenance for FDAMIMO radar
https://aip.scitation.org/doi/10.1063/5.0099177?af=R&feed=mostrecent
AIP Advances, <a href="https://aip.scitation.org/toc/adv/12/8">Volume 12, Issue 8</a>, August 2022. <br/>During radar detection, the adaptive beamforming technique needs to create nulls to resist the interference. When the interference appears within the mainlobe, the main detection beam will become distorted. To solve this problem, a new method for the covariance matrix reconstruction is proposed for the mainlobe maintenance problem, and a worstcase performance optimization (WCPO) algorithm with enhanced waveform robustness is obtained. Its integration is performed over a known region without the target information to obtain the improved covariance matrix, which is then brought into the convex optimization equation to solve for the weight vector. Simulation results show that the output signaltonoise ratio of this algorithm is higher than that of the conventional WCPO algorithm with a robust beam for the same signaltonoise ratio. It can also effectively eliminate the primary lobe offset and secondary lobe elevation problems.
AIP Advances, Volume 12, Issue 8, August 2022. <br/>During radar detection, the adaptive beamforming technique needs to create nulls to resist the interference. When the interference appears within the mainlobe, the main detection beam will become distorted. To solve this problem, a new method for the covariance matrix reconstruction is proposed for the mainlobe maintenance problem, and a worstcase performance optimization (WCPO) algorithm with enhanced waveform robustness is obtained. Its integration is performed over a known region without the target information to obtain the improved covariance matrix, which is then brought into the convex optimization equation to solve for the weight vector. Simulation results show that the output signaltonoise ratio of this algorithm is higher than that of the conventional WCPO algorithm with a robust beam for the same signaltonoise ratio. It can also effectively eliminate the primary lobe offset and secondary lobe elevation problems.
Mainlobe maintenance for FDAMIMO radar
10.1063/5.0099177
AIP Advances
20220805T12:38:38Z
© 2022 Author(s).
YanJie Xu
ChunYang Wang
Jian Gong
YingJian Zhao
ChangLin Zhou

Effect of multiwall carbon nanotubes on electrochemical performances of MnO2
https://aip.scitation.org/doi/10.1063/5.0102197?af=R&feed=mostrecent
AIP Advances, <a href="https://aip.scitation.org/toc/adv/12/8">Volume 12, Issue 8</a>, August 2022. <br/>Composites of MnO2/multiwall carbon nanotubes (MWCNTs) were prepared using different weight ratios of MWCNTs: KMnO4 (1:2, 1:5, 1:10, 1:15, 1:20, and 1:25) using a onepot hydrothermal method. The synthesized materials were physically characterized by xray diffraction, transmission electron microscopy (TEM), field emissionscanning electron microscopy (FESEM), (Brunauer–Emmett–Teller) BET, and thermogravimetric analysis. TEM and SEM studies indicate that MnO2 is homogeneously entangled with MWCNTs. The electrochemical performance evaluation was performed in a 3electrode system using MnO2/MWCNT electrodes coated onto a Ni mesh as the working electrode, a Pt foil as the counter electrode, and Ag/AgCl as the reference electrode. The specific capacitance was obtained from charge–discharge studies at varying current densities between 0.5 and 5 A/g. The specific capacitance of MWCNTKMnO4 (1:10, 1:15, and 1:25) samples was obtained as 114, 164, and 100 F/g, respectively, at a current density of 1 A/g.
AIP Advances, Volume 12, Issue 8, August 2022. <br/>Composites of MnO2/multiwall carbon nanotubes (MWCNTs) were prepared using different weight ratios of MWCNTs: KMnO4 (1:2, 1:5, 1:10, 1:15, 1:20, and 1:25) using a onepot hydrothermal method. The synthesized materials were physically characterized by xray diffraction, transmission electron microscopy (TEM), field emissionscanning electron microscopy (FESEM), (Brunauer–Emmett–Teller) BET, and thermogravimetric analysis. TEM and SEM studies indicate that MnO2 is homogeneously entangled with MWCNTs. The electrochemical performance evaluation was performed in a 3electrode system using MnO2/MWCNT electrodes coated onto a Ni mesh as the working electrode, a Pt foil as the counter electrode, and Ag/AgCl as the reference electrode. The specific capacitance was obtained from charge–discharge studies at varying current densities between 0.5 and 5 A/g. The specific capacitance of MWCNTKMnO4 (1:10, 1:15, and 1:25) samples was obtained as 114, 164, and 100 F/g, respectively, at a current density of 1 A/g.
Effect of multiwall carbon nanotubes on electrochemical performances of MnO2
10.1063/5.0102197
AIP Advances
20220808T02:17:25Z
© 2022 Author(s).
Rahul Singhal
Bhagirath Saini
Monica KiehnleBenitez
Thomas Sadowski
Christine Broadbridge
Jules Scanley
Peter K. LeMaire
Rakesh K. Sharma

Elastic interactions in physics are reflections in geometry
https://aip.scitation.org/doi/10.1063/5.0087903?af=R&feed=mostrecent
AIP Advances, <a href="https://aip.scitation.org/toc/adv/12/8">Volume 12, Issue 8</a>, August 2022. <br/>A simple standard problem in physics is the study of elastic collisions between elements of an ideal system, which consists of two point masses and a wall. Based on energy and momentum conservation laws, solving the problem consists in finding the intersection of a straight line with a conic. Relationships between the solutions are easily obtained if we consider the right (fundamental) basis to express the solutions. The geometric interpretation follows easily: moving from one point to another on a conic using directions given by this basis. With simple changes in variables, reflections and rotations appear clearly. Similarities with other phenomena such as Heron’s reflection principle in optics and Kepler’s second law of planetary motion are pointed out.
AIP Advances, Volume 12, Issue 8, August 2022. <br/>A simple standard problem in physics is the study of elastic collisions between elements of an ideal system, which consists of two point masses and a wall. Based on energy and momentum conservation laws, solving the problem consists in finding the intersection of a straight line with a conic. Relationships between the solutions are easily obtained if we consider the right (fundamental) basis to express the solutions. The geometric interpretation follows easily: moving from one point to another on a conic using directions given by this basis. With simple changes in variables, reflections and rotations appear clearly. Similarities with other phenomena such as Heron’s reflection principle in optics and Kepler’s second law of planetary motion are pointed out.
Elastic interactions in physics are reflections in geometry
10.1063/5.0087903
AIP Advances
20220810T02:30:13Z
© 2022 Author(s).
François Dubeau

An approximated volume of fluid method with the modified height function method in the simulation of surface tension driven flows
https://aip.scitation.org/doi/10.1063/5.0098717?af=R&feed=mostrecent
AIP Advances, <a href="https://aip.scitation.org/toc/adv/12/8">Volume 12, Issue 8</a>, August 2022. <br/>Surface tension in twophase flow problems plays a dominant role in many microflow phenomena and has an important influence on the development of flow instability phenomena that contain free surfaces. In this study, the multimoment finite volume method is extended for direct numerical simulation of twophase flow problems. A constraint interpolation profile–CSL (semiLagrangian) scheme is used for discretization of the advection part in the momentum equation. A compact volume of fluid method–approximated piecewise linear calculation method without flux limiter is proposed for capturing the moving interface. For modeling the surface tension accurately, the logic in curvature estimation is redesigned based on the height function (HF) method. The isolated volumetric fractions that may reduce accuracy in HF integration are excluded, and the numerical solution shows that the accuracy in the curvature estimation is improved for a coarse mesh. The present method is implemented with a parallel blockstructured adaptive mesh refinement (BAMR) strategy; thus, the computational cost can be reduced significantly. Numerical tests show that the present BAMR solver is capable of reproducing the theoretical predictions of capillary wave instability problems with high accuracy. The simulation of droplet collisions further demonstrates the accuracy of the surface tension model. Finally, we extend it to the liquid jet atomization. The wavy disturbance, film breakup, liquid filament pinchoff, and droplet generation are well reproduced. The droplet size distribution satisfies the experimental measurement and theoretical predictions powerlaw. BAMR shows a huge advantage in computational efficiency than the traditional Cartesian grid. The findings of this study can help for a better understanding of the micromechanism of surface tension driven flows.
AIP Advances, Volume 12, Issue 8, August 2022. <br/>Surface tension in twophase flow problems plays a dominant role in many microflow phenomena and has an important influence on the development of flow instability phenomena that contain free surfaces. In this study, the multimoment finite volume method is extended for direct numerical simulation of twophase flow problems. A constraint interpolation profile–CSL (semiLagrangian) scheme is used for discretization of the advection part in the momentum equation. A compact volume of fluid method–approximated piecewise linear calculation method without flux limiter is proposed for capturing the moving interface. For modeling the surface tension accurately, the logic in curvature estimation is redesigned based on the height function (HF) method. The isolated volumetric fractions that may reduce accuracy in HF integration are excluded, and the numerical solution shows that the accuracy in the curvature estimation is improved for a coarse mesh. The present method is implemented with a parallel blockstructured adaptive mesh refinement (BAMR) strategy; thus, the computational cost can be reduced significantly. Numerical tests show that the present BAMR solver is capable of reproducing the theoretical predictions of capillary wave instability problems with high accuracy. The simulation of droplet collisions further demonstrates the accuracy of the surface tension model. Finally, we extend it to the liquid jet atomization. The wavy disturbance, film breakup, liquid filament pinchoff, and droplet generation are well reproduced. The droplet size distribution satisfies the experimental measurement and theoretical predictions powerlaw. BAMR shows a huge advantage in computational efficiency than the traditional Cartesian grid. The findings of this study can help for a better understanding of the micromechanism of surface tension driven flows.
An approximated volume of fluid method with the modified height function method in the simulation of surface tension driven flows
10.1063/5.0098717
AIP Advances
20220810T02:31:45Z
© 2022 Author(s).
Cheng Liu
Ruoqing Gao
Changhong Hu

A model for the prediction of the shielding effectiveness of cylindrical enclosure
https://aip.scitation.org/doi/10.1063/5.0091183?af=R&feed=mostrecent
AIP Advances, <a href="https://aip.scitation.org/toc/adv/12/8">Volume 12, Issue 8</a>, August 2022. <br/>This paper presents a model to predict the shielding effectiveness (SE) and resonant modes of cylindrical enclosure with apertures or dielectric substrate. In this model, the Robinson equivalent circuit model (RECM) is introduced to deal with aperture impedance, and the extended form of the Baum–Liu–Tesche equation is deduced to calculate the induced voltage in the enclosure. The electromagnetic topology (EMT) model is established to analyze the process of energy transmission inside the enclosure. The energy propagation coefficient matrix and the scattering coefficient matrix are calculated to deal with the SE results of the observation point. To quantify the efficiency of the proposed model, the calculation results are compared with the fullwave transmission line matrix method (TLM) and RECM through the Fréchet distance. The comparison results show that the accuracy of the proposed model is better over a wide frequency range compared with RECM, and meanwhile, it consumes less run time and fewer CPU resources than traditional numerical methods. The validity of the presented model is verified by TLM.
AIP Advances, Volume 12, Issue 8, August 2022. <br/>This paper presents a model to predict the shielding effectiveness (SE) and resonant modes of cylindrical enclosure with apertures or dielectric substrate. In this model, the Robinson equivalent circuit model (RECM) is introduced to deal with aperture impedance, and the extended form of the Baum–Liu–Tesche equation is deduced to calculate the induced voltage in the enclosure. The electromagnetic topology (EMT) model is established to analyze the process of energy transmission inside the enclosure. The energy propagation coefficient matrix and the scattering coefficient matrix are calculated to deal with the SE results of the observation point. To quantify the efficiency of the proposed model, the calculation results are compared with the fullwave transmission line matrix method (TLM) and RECM through the Fréchet distance. The comparison results show that the accuracy of the proposed model is better over a wide frequency range compared with RECM, and meanwhile, it consumes less run time and fewer CPU resources than traditional numerical methods. The validity of the presented model is verified by TLM.
A model for the prediction of the shielding effectiveness of cylindrical enclosure
10.1063/5.0091183
AIP Advances
20220810T02:33:23Z
© 2022 Author(s).
Kaibai Chen
Min Gao
Xiaodong Zhou