Microwave absorption in radar stealth technology is faced with challenges in terms of its effectiveness in low-frequency regions.Herein,we report a new laser-based method for producing an ultrawideband metamaterial-ba...Microwave absorption in radar stealth technology is faced with challenges in terms of its effectiveness in low-frequency regions.Herein,we report a new laser-based method for producing an ultrawideband metamaterial-based microwave absorber with a highly uniform sheet resistance and negative magnetic permeability at resonant frequencies,which results in a wide bandwidth in the L-to S-band.Control of the electrical sheet resistance uniformity has been achieved with less than 5%deviation at 400Ωsq^(-1)and 6%deviation at 120Ωsq^(-1),resulting in a microwave absorption coefficient between 97.2%and 97.7%within a1.56–18.3 GHz bandwidth for incident angles of 0°–40°,and there is no need for providing energy or an electrical power source during the operation.Porous N-and S-doped turbostratic graphene 2D patterns with embedded magnetic nanoparticles were produced simultaneously on a polyethylene terephthalate substrate via laser direct writing.The proposed low-frequency,wideband,wide-incident-angle,and high-electromagnetic-absorption microwave absorber can potentially be used in aviation,electromagnetic interference(EMI)suppression,and 5G applications.展开更多
This article discusses the impact of central bank digital currency(CBDC)from the perspective of monetary and fiscal policy.We mainly discuss how retail CBDC can improve traditional policy performance.We argue that A C...This article discusses the impact of central bank digital currency(CBDC)from the perspective of monetary and fiscal policy.We mainly discuss how retail CBDC can improve traditional policy performance.We argue that A CBDC helps existing monetary policies to break through the zero lower bound,shorten the policy time lag,realize selective policy interventions,and make possible the price level target policy system.Similarly,the combination of CBDC and smart contracts can directly affect the performance of the fiscal policy.Compared with the convenience and impact of CDBC as a medium of exchange,its impact as a policy tool is more profound.The current monetary policy is facing a zero lower bound.The fiscal policy is facing a huge sovereign debt crisis and the impact of other private digital currencies on fiat money,which makes the importance of CBDC as a new policy tool more prominent.However,the research on CBDC as a policy tool has many fundamental questions that remain to be answered.This paper contextualizes CBDC with global challenges in policies and new technology advances,and the authors rethink CBDC from a policy perspective,which may provide many new thoughts and have implications for the rise of global CBDC.展开更多
文摘Microwave absorption in radar stealth technology is faced with challenges in terms of its effectiveness in low-frequency regions.Herein,we report a new laser-based method for producing an ultrawideband metamaterial-based microwave absorber with a highly uniform sheet resistance and negative magnetic permeability at resonant frequencies,which results in a wide bandwidth in the L-to S-band.Control of the electrical sheet resistance uniformity has been achieved with less than 5%deviation at 400Ωsq^(-1)and 6%deviation at 120Ωsq^(-1),resulting in a microwave absorption coefficient between 97.2%and 97.7%within a1.56–18.3 GHz bandwidth for incident angles of 0°–40°,and there is no need for providing energy or an electrical power source during the operation.Porous N-and S-doped turbostratic graphene 2D patterns with embedded magnetic nanoparticles were produced simultaneously on a polyethylene terephthalate substrate via laser direct writing.The proposed low-frequency,wideband,wide-incident-angle,and high-electromagnetic-absorption microwave absorber can potentially be used in aviation,electromagnetic interference(EMI)suppression,and 5G applications.
文摘This article discusses the impact of central bank digital currency(CBDC)from the perspective of monetary and fiscal policy.We mainly discuss how retail CBDC can improve traditional policy performance.We argue that A CBDC helps existing monetary policies to break through the zero lower bound,shorten the policy time lag,realize selective policy interventions,and make possible the price level target policy system.Similarly,the combination of CBDC and smart contracts can directly affect the performance of the fiscal policy.Compared with the convenience and impact of CDBC as a medium of exchange,its impact as a policy tool is more profound.The current monetary policy is facing a zero lower bound.The fiscal policy is facing a huge sovereign debt crisis and the impact of other private digital currencies on fiat money,which makes the importance of CBDC as a new policy tool more prominent.However,the research on CBDC as a policy tool has many fundamental questions that remain to be answered.This paper contextualizes CBDC with global challenges in policies and new technology advances,and the authors rethink CBDC from a policy perspective,which may provide many new thoughts and have implications for the rise of global CBDC.
