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
目的探讨借鉴乳腺影像报告和数据系统(breast imaging reporting and data system,BI-RADS)分类方式对胸腺肿瘤MRI表现进行分类诊断的可行性。材料与方法纳入2014年5月至2018年8月MRI检查发现85例经病理证实的胸腺肿瘤,结合MRI信号和形...目的探讨借鉴乳腺影像报告和数据系统(breast imaging reporting and data system,BI-RADS)分类方式对胸腺肿瘤MRI表现进行分类诊断的可行性。材料与方法纳入2014年5月至2018年8月MRI检查发现85例经病理证实的胸腺肿瘤,结合MRI信号和形态学特征,借鉴乳腺BI-RADS分级模式,对病灶进行Ⅰ~Ⅴ类的分类诊断,并与WHO的组织细胞分类和Masaoka-Koga分期进行匹配对照。结果MRI分期与WHO分类和Masaoka-Koga分期可以形成较好的对应关系。根据病灶的信号和形态特征,85例胸腺肿瘤中,15/16例胸腺囊性病变被划分为Ⅱ类,对应良性病变;2/3例良性胸腺增生、4例A型、15/17例AB型、14/17例B1胸腺瘤被划分为Ⅲ类,对应低危病变;5/6例B2型和6例B3型胸腺瘤被划分为Ⅳ类,对应高危病变;9/11例胸腺癌被划分为Ⅴ类,对应侵袭性恶性病变。Spearmen相关系数为0.808,t=12.499,P<0.01。结论利用多模态MRI信息将胸腺肿瘤划分为Ⅰ~Ⅴ类,在一定程度上体现了WHO的组织学分型和Masaoka-Koga分期特征,有利于胸腺瘤的诊断治疗计划。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.
文摘目的探讨借鉴乳腺影像报告和数据系统(breast imaging reporting and data system,BI-RADS)分类方式对胸腺肿瘤MRI表现进行分类诊断的可行性。材料与方法纳入2014年5月至2018年8月MRI检查发现85例经病理证实的胸腺肿瘤,结合MRI信号和形态学特征,借鉴乳腺BI-RADS分级模式,对病灶进行Ⅰ~Ⅴ类的分类诊断,并与WHO的组织细胞分类和Masaoka-Koga分期进行匹配对照。结果MRI分期与WHO分类和Masaoka-Koga分期可以形成较好的对应关系。根据病灶的信号和形态特征,85例胸腺肿瘤中,15/16例胸腺囊性病变被划分为Ⅱ类,对应良性病变;2/3例良性胸腺增生、4例A型、15/17例AB型、14/17例B1胸腺瘤被划分为Ⅲ类,对应低危病变;5/6例B2型和6例B3型胸腺瘤被划分为Ⅳ类,对应高危病变;9/11例胸腺癌被划分为Ⅴ类,对应侵袭性恶性病变。Spearmen相关系数为0.808,t=12.499,P<0.01。结论利用多模态MRI信息将胸腺肿瘤划分为Ⅰ~Ⅴ类,在一定程度上体现了WHO的组织学分型和Masaoka-Koga分期特征,有利于胸腺瘤的诊断治疗计划。
