Antireflection self-reference method based on ultrathin metallic nanofilms for improving terahertz reflection spectroscopy

We present the potential of an antireflection self-reference method based on ultrathin tantalum nitride (TaN) nanofilms for improving terahertz (THz) reflection spectroscopy. The antireflection self-reference method is proposed to eliminate mutual interference caused by unwanted reflections, which significantly interferes with the important reflection from the actual sample in THz reflection measurement. The antireflection self-reference model was investigated using a wave-impedance matching approach, and the theoretical model was verified in experimental studies. We experimentally demonstrated this antireflection selfreference method can completely eliminate the effect of mutual interference, accurately recover the actual sample’s reflection and improve THz reflection spectroscopy. Our method paves the way to implement a straightforward, accurate and efficient approach to investigate THz properties of the liquids and biological samplesThe Fund from Hefei University of Technology (407-0371000019); Sichuan Province Science and Technology Support Program (No. 2016GZ0250); the Fundamental Research Funds for the Central Universities (Grant No. JD2017JGPY0006); National Natural Science Foundation of China (Grant No.51607050); MINECO (MAT2015–74381-JIN to B.P., RYC2014–16962 and CTQ2017-89588-R to P.dP.); Xunta de Galicia (Centro singular de investigación de Galicia accreditation 2016–2019, ED431G/09); European Union (European Regional Development Fund – ERDF)S

Contact Resistance Parallel Model for Edge-Contacted 2D Material Back-Gate FET

Because 2D materials have adjust band gap, high mobility ratio, bipolar, anisotropy and flexibility characters, they have become the new direction for FET’s channel materials. According to the characteristics of the layers of 2D materials, the current transport characteristics can be improved by using the edge-contacted electrode. Moreover, the research on the current transfer mechanism between channel layers is the basis of the practical application of 2D transistors. In the research, the 2D material-MoS2 is used as the channel material, the back-gate transistors with different layers are prepared by dry etching and edge-contacted electrode structure. We also discuss the current transport mechanism of channel and established the channel resistance parallel transport model. The parallel model and TLM are used to analyze the contact resistance of the edge-contacted structure, and the total resistance, total contact resistance, and single-layer contact resistance of different layers are calculated. The parallel model is verified by dc test data. The number of channel layers is closely related to contact resistance, total resistance, and mobility. In addition, the of single MoS2 is about 7.27 kΩ·um. This contact resistance parallel model can also be applied to other 2D materials edge-contacted FET

A Polarization-Dependent Frequency-Selective Metamaterial Absorber with Multiple Absorption Peaks

A polarization-dependent, frequency-selective metamaterial (MM) absorber based on a single-layer patterned resonant structure intended for F frequency band is proposed. The design, fabrication, and measurement for the proposed absorber are presented. The absorber’s absorption properties at resonant frequencies have unique characteristics of a single-band, dual-band, or triple-band absorption for different polarization of the incident wave. The calculated surface current distributions and power loss distribution provide further understanding of physical mechanism of resonance absorption. Moreover, a high absorption for a wide range of TE-polarized oblique incidence was achieved. Hence, the MM structure realized on a highly flexible polyimide film, makingthe absorber suitable for conformal geometry applications. The proposed absorber has great potential in the development of polarization detectors and polarizers

High temperature deformation behavior and constitutive model of Zirlo zirconium alloy

In order to study the thermal deformation behavior of Zirlo alloy at ranges of 550-700 ℃ deformation temperature and 0.01-10 s-1 strain rate, the Zirlo alloy was subjected to compression under condition of isothermal and constant strain rate by using the Gleeble-3800 thermal simulated test machine. Through introducing strains on the basis of the Arrhenius type hyperbolic sine function equation, an Arrhenius constitutive model was developed based on strain compensation, and founded on a combination of dislocation density evolution causing work hardening model and phenomenological softening model, a segmented phenomenological constitutive model was constructed. The results show that the flow stress of Zirlo zirconium alloy increases with the decrease of temperature and the increase of strain rate, the flow stress exhibits higher temperature sensitivity at low strain rate, and flow stress curves separately exhibit characteristics as work hardening, dynamic recovery and dynamic recrystallization under different deformation conditions. Through error analysis, it was revealed that errors of the most stresses predicted by the Arrhenius constitutive model based on strain compensation are within 15%, which exhibits high accuracy. The maximum relative average absolute errors of the segmented phenomenological constitutive model are less than 3%, exhibiting an accuracy of over 97%. The segmented phenomenological constitutive model can accurately predict the stress-strain curve of the Zirlo alloy and has good expansibility; moreover, it can preliminarily predict the type of the stress-strain curve and has good practicability

Nationalism and multilateralism in Chinese foreign policy: implications for Southeast Asia

One of Michael Leifer's main fears for the future role of ASEAN arose from the spectre of a rising nationalistic China. This article assesses whether recent developments have borne out those fears by looking at the nature of Beijing's evolving multilateral approach towards the region. Agreeing with Leifer that nationalism is an important influence on Chinese foreign policy, the article explores the complex relationship between domestic politics and the discourse of multipolarity in China to propose that multilateralism is an effective way for Beijing to increase its regional power while avoiding confrontation with the United States or regional powers like India and Japan. However, Beijing's multilateralism is still premised on hard conceptions of state sovereignty and has to be developed in the context of a nationalistic political culture that prevents the achievement of regional stability through compromise on issues such as the South China Sea disputes and the Taiwan question. China's continuing economic growth also means that its multilateralism in Southeast Asia will unavoidably be shaped by issues such as the role of the ethnic Chinese as economic bridgeheads and the realities of an increasingly asymmetrical balance of power. Meanwhile, the relative economic weakness of the Southeast Asian states also means that nature of ASEAN-style regionalism will continue to be determined by the extra-mural balance of power, with China as one of the major actors, as Michael Leifer predicted