介绍了基于砷化镓(GaAs)伪形态高电子迁移率晶体管(pseudo-morphology High Electron Mobility Transistor,pHEMT)工艺,输出信号为W波段的八倍频放大芯片的设计方法。通过合理划分电路方案,将倍频器方案设计为输入频率经过四倍频器在Q...介绍了基于砷化镓(GaAs)伪形态高电子迁移率晶体管(pseudo-morphology High Electron Mobility Transistor,pHEMT)工艺,输出信号为W波段的八倍频放大芯片的设计方法。通过合理划分电路方案,将倍频器方案设计为输入频率经过四倍频器在Q波段进行放大,最后通过二倍频输出W波段信号。基于上述方案,设计了一款输入频率为10.8~11.5 GHz、输出频率为86.4~92 GHz的八倍频多功能芯片。芯片通过探针台在片测试,在工作频带内七次谐波抑制均优于15 dBc,九次谐波抑制均优于20 dBc,输出功率大于0 dBm。展开更多
基于砷化镓赝配高电子迁移率晶体管(pseudomorphic High Electron Mobility Transistor,pHEMT)工艺,进行了覆盖10~20 GHz宽带二倍频放大芯片的设计,着重分析了在本振链路中基波和三次谐波产生的原因和抑制方法。基于差分电路,设计了一...基于砷化镓赝配高电子迁移率晶体管(pseudomorphic High Electron Mobility Transistor,pHEMT)工艺,进行了覆盖10~20 GHz宽带二倍频放大芯片的设计,着重分析了在本振链路中基波和三次谐波产生的原因和抑制方法。基于差分电路,设计了一款不含滤波器且基波频率为10~20 GHz宽带二倍频放大芯片。该芯片通过探针台在片测试,证实在工作频带内,基波和三次谐波抑制均优于35 dBc,倍频损耗优于-0.5 dB。展开更多
基于GaAs PHEMT ED25B与薄膜工艺设计了基于倒装应用的DC^26 GHz的单刀双掷(SPDT)开关。首先对倒装芯片与传统的正装芯片进行比较,倒装芯片MMIC技术具有明显的优势;然后对比了不同倒装情况对芯片性能的影响进而提出对倒装无源元器件和Ga...基于GaAs PHEMT ED25B与薄膜工艺设计了基于倒装应用的DC^26 GHz的单刀双掷(SPDT)开关。首先对倒装芯片与传统的正装芯片进行比较,倒装芯片MMIC技术具有明显的优势;然后对比了不同倒装情况对芯片性能的影响进而提出对倒装无源元器件和GaAs PHEMT开关建模的概念,利用建模软件提取了相应的模型;对倒装单刀双掷开关MMIC的设计进行了详细阐述;对制备的倒装单刀双掷开关MMIC进行测试。测试结果表明,回波损耗大于15 d B,插损小于2.8 d B,隔离度大于28 d B。最后对芯片进行温度循环试验和恒定加速度试验,验证了这款基于倒装应用的单刀双掷开关MMIC的可靠性。展开更多
The aim of ＂green chemistry＂ and ＂atom economy＂ is to utilize carbon dioxide and replace harmful reactants such as CO and phosgene for the production of cyclic carbonates. In this paper, metal-free catalysts inclu...The aim of ＂green chemistry＂ and ＂atom economy＂ is to utilize carbon dioxide and replace harmful reactants such as CO and phosgene for the production of cyclic carbonates. In this paper, metal-free catalysts including organic bases, ionic liquids, supported catalysts, organic copolymers and carbon materials for the synthesis of cyclic carbonates by the cycloaddition of carbon dioxide to epoxides are reviewed. Recent advances in the design of the catalysts and the understanding of the reaction mechanism are summarized and discussed. The synergistic effects of organic bases and hydrogen bond donors, organic bases and nucleophilic anions, hydrogen bond donors and nucleophilic anions and active components and supports are highlighted. The challenge is to develop metal-free catalysts suitable for carbon dioxide capture and fixation. The ultimate goal is to synthesize cyclic carbonates in a flow reactor directly using carbon dioxide from industrial flue gas at ambient temperature and atmospheric pressure. By using synergetic effects, a multi-functional approach can meet the design strategy of metal-free catalysts for carbon dioxide adsorption and activation as well as epoxide ring opening.展开更多
We investigate a class of gravity theories respecting only spatial covariance,termed spatially covariant gravity,in the presence of an auxiliary scalar field.We examine the conditions on the Lagrangian required to eli...We investigate a class of gravity theories respecting only spatial covariance,termed spatially covariant gravity,in the presence of an auxiliary scalar field.We examine the conditions on the Lagrangian required to eliminate scalar degrees of freedom,allowing only two tensorial degrees of freedom to propagate.Instead of strict constraint analysis,in this paper,we employ the perturbation method and focus on the necessary conditions to evade the scalar mode at the linear order in perturbations around a cosmological background.Beginning with a general action and solving the auxiliary perturbation variables in terms of a would-be dynamical scalar mode,we derive the condition to remove its kinetic term,thus ensuring that no scalar mode propagates.As an application of the general condition,we study a polynomial-type Lagrangian as a concrete example,in which all monomials are spatially covariant scalars containing two derivatives.We find that the auxiliary scalar field is essential,and new terms in the Lagrangian are allowed.Our analysis provides insights into constructing gravity theories with two degrees of freedom in the extended framework of spatially covariant gravity.展开更多
In the context of massive （bi-）gravity, non-minimal matter couplings have been proposed. These couplings are special in the sense that they are free of the Boulware-Deser ghost below the strong coupling scale and ca...In the context of massive （bi-）gravity, non-minimal matter couplings have been proposed. These couplings are special in the sense that they are free of the Boulware-Deser ghost below the strong coupling scale and can be used consistently as an effective field theory. Furthermore, they enrich the phenomenology of massive gravity. We consider these couplings in the framework of bimetric gravity and study the cosmological implications for background and linear tensor, vector, and scalar Previous works have investigated special branches of solutions. Here we perform a complete perturbation analysis for the general background equations of motion, completing previous analyses.展开更多
MoO_2@N-doped C nanofibers（MoO_2@NC NFs）were synthesized by electrospinning with polyacrylonitrile as carbon source.The in situ formed MoO_2nanocrystals are completely embedded in the carbon nanofibers,which can not...MoO_2@N-doped C nanofibers（MoO_2@NC NFs）were synthesized by electrospinning with polyacrylonitrile as carbon source.The in situ formed MoO_2nanocrystals are completely embedded in the carbon nanofibers,which can not only accelerate ion transition,but also act as a buffer to avoid the mechanical degradation of active material due to the volume changes during charge/discharge cycling.When used as the anode material for both Li/Na-ion batteries,the as-synthesized MoO_2@NC NFs displayed excellent Li~＋/Na~＋storage properties.As the anode for Li-ion battery,the MoO_2@NC NFs display a high discharge capacity of 930 mA h g^（-1）at a current density of 200 mA g^（-1）for 100 cycles,and 720 mA h g^（-1）at a current density of 1 A g^（-1）for 600 cycles.Moreover,the discharge capacity of 350 mA h g^（-1）could be realized at a current density of 100 mA g^（-1）for 200 cycles for Na-ion battery.展开更多
文摘介绍了基于砷化镓(GaAs)伪形态高电子迁移率晶体管(pseudo-morphology High Electron Mobility Transistor,pHEMT)工艺,输出信号为W波段的八倍频放大芯片的设计方法。通过合理划分电路方案,将倍频器方案设计为输入频率经过四倍频器在Q波段进行放大,最后通过二倍频输出W波段信号。基于上述方案,设计了一款输入频率为10.8~11.5 GHz、输出频率为86.4~92 GHz的八倍频多功能芯片。芯片通过探针台在片测试,在工作频带内七次谐波抑制均优于15 dBc,九次谐波抑制均优于20 dBc,输出功率大于0 dBm。
文摘基于砷化镓赝配高电子迁移率晶体管(pseudomorphic High Electron Mobility Transistor,pHEMT)工艺,进行了覆盖10~20 GHz宽带二倍频放大芯片的设计,着重分析了在本振链路中基波和三次谐波产生的原因和抑制方法。基于差分电路,设计了一款不含滤波器且基波频率为10~20 GHz宽带二倍频放大芯片。该芯片通过探针台在片测试,证实在工作频带内,基波和三次谐波抑制均优于35 dBc,倍频损耗优于-0.5 dB。
文摘基于GaAs PHEMT ED25B与薄膜工艺设计了基于倒装应用的DC^26 GHz的单刀双掷(SPDT)开关。首先对倒装芯片与传统的正装芯片进行比较,倒装芯片MMIC技术具有明显的优势;然后对比了不同倒装情况对芯片性能的影响进而提出对倒装无源元器件和GaAs PHEMT开关建模的概念,利用建模软件提取了相应的模型;对倒装单刀双掷开关MMIC的设计进行了详细阐述;对制备的倒装单刀双掷开关MMIC进行测试。测试结果表明,回波损耗大于15 d B,插损小于2.8 d B,隔离度大于28 d B。最后对芯片进行温度循环试验和恒定加速度试验,验证了这款基于倒装应用的单刀双掷开关MMIC的可靠性。
基金supported by the National Science and Technology Support Project of China(2013BAC11B03)the National Natural Science Foundation of China(21401054,21476065,21273067)the Graduate Student Scientific Research Innovation Fund Project of Hunan Province(CX2015B082)~~
文摘The aim of ＂green chemistry＂ and ＂atom economy＂ is to utilize carbon dioxide and replace harmful reactants such as CO and phosgene for the production of cyclic carbonates. In this paper, metal-free catalysts including organic bases, ionic liquids, supported catalysts, organic copolymers and carbon materials for the synthesis of cyclic carbonates by the cycloaddition of carbon dioxide to epoxides are reviewed. Recent advances in the design of the catalysts and the understanding of the reaction mechanism are summarized and discussed. The synergistic effects of organic bases and hydrogen bond donors, organic bases and nucleophilic anions, hydrogen bond donors and nucleophilic anions and active components and supports are highlighted. The challenge is to develop metal-free catalysts suitable for carbon dioxide capture and fixation. The ultimate goal is to synthesize cyclic carbonates in a flow reactor directly using carbon dioxide from industrial flue gas at ambient temperature and atmospheric pressure. By using synergetic effects, a multi-functional approach can meet the design strategy of metal-free catalysts for carbon dioxide adsorption and activation as well as epoxide ring opening.
基金Supported by theNatural Science Foundation of China(11975020)。
文摘We investigate a class of gravity theories respecting only spatial covariance,termed spatially covariant gravity,in the presence of an auxiliary scalar field.We examine the conditions on the Lagrangian required to eliminate scalar degrees of freedom,allowing only two tensorial degrees of freedom to propagate.Instead of strict constraint analysis,in this paper,we employ the perturbation method and focus on the necessary conditions to evade the scalar mode at the linear order in perturbations around a cosmological background.Beginning with a general action and solving the auxiliary perturbation variables in terms of a would-be dynamical scalar mode,we derive the condition to remove its kinetic term,thus ensuring that no scalar mode propagates.As an application of the general condition,we study a polynomial-type Lagrangian as a concrete example,in which all monomials are spatially covariant scalars containing two derivatives.We find that the auxiliary scalar field is essential,and new terms in the Lagrangian are allowed.Our analysis provides insights into constructing gravity theories with two degrees of freedom in the extended framework of spatially covariant gravity.
基金Supported by the Chinese National Youth Thousand Talents Program(71000-41180003)JSPS Grant-in-Aid for Scientific Research(15H02082,25287054,26610062)Financial Support from Dr.Max Rssler,the Walter Haefner Foundation and the ETH Zurich Foundation
文摘In the context of massive （bi-）gravity, non-minimal matter couplings have been proposed. These couplings are special in the sense that they are free of the Boulware-Deser ghost below the strong coupling scale and can be used consistently as an effective field theory. Furthermore, they enrich the phenomenology of massive gravity. We consider these couplings in the framework of bimetric gravity and study the cosmological implications for background and linear tensor, vector, and scalar Previous works have investigated special branches of solutions. Here we perform a complete perturbation analysis for the general background equations of motion, completing previous analyses.
基金supported by the National Natural Science Foundation of China (51302079)
文摘MoO_2@N-doped C nanofibers（MoO_2@NC NFs）were synthesized by electrospinning with polyacrylonitrile as carbon source.The in situ formed MoO_2nanocrystals are completely embedded in the carbon nanofibers,which can not only accelerate ion transition,but also act as a buffer to avoid the mechanical degradation of active material due to the volume changes during charge/discharge cycling.When used as the anode material for both Li/Na-ion batteries,the as-synthesized MoO_2@NC NFs displayed excellent Li~＋/Na~＋storage properties.As the anode for Li-ion battery,the MoO_2@NC NFs display a high discharge capacity of 930 mA h g^（-1）at a current density of 200 mA g^（-1）for 100 cycles,and 720 mA h g^（-1）at a current density of 1 A g^（-1）for 600 cycles.Moreover,the discharge capacity of 350 mA h g^（-1）could be realized at a current density of 100 mA g^（-1）for 200 cycles for Na-ion battery.
