Break junctions are important in generating nanosensors and single molecular devices. The mechanically con- trollable break junction is the most widely used method for a break junction due to its simplicity and stabil...Break junctions are important in generating nanosensors and single molecular devices. The mechanically con- trollable break junction is the most widely used method for a break junction due to its simplicity and stability. However, the bandwidths of traditional devices are limited to about a few hertz. Moreover, when using traditional methods it is hard to allow independent control of more than one junction. Here we propose on-chip thermally controllable break junctions to overcome these challenges. This is verified by using finite element analysis. Adopting microelectromechanical systems produces features of high bandwidth and independent controllability to this new break junction system. The proposed method will have a wide range of applications on on-chip high speed independent controllable and highly integrated single molecule devices.展开更多
Background Fourth-generation photon sources like Free Electron Lasers(FEL)and Diffraction-Limited Storage Rings(DLSR)have high requirements for beam emittance.In the case of DLSR sources,a set of high-performance fast...Background Fourth-generation photon sources like Free Electron Lasers(FEL)and Diffraction-Limited Storage Rings(DLSR)have high requirements for beam emittance.In the case of DLSR sources,a set of high-performance fast orbit feedback system(FOFB)is needed to correct the beam orbit quickly and accurately.Purpose FOFB system has four key components,which is BPM,orbit feedback calculation,fast correction magnet and fast corrector power supply.The FOFB gives the correction command and controls the fast corrector power supply to drive the fast correction magnet to correct the beam quickly and accurately.The corrector power supply has an important impact on the performance of FOFB.The corrector power supply needs to have high bandwidth and low output current ripple.Methods The new GaN power device is used to solve the restriction of the high-speed switching.The switching frequency of the power supply is increased to 300 kHz.The control system is designed to improve the bandwidth and optimize the output current ripple.The modeling analysis of the key parts of the system is given and the simulation experiments are carried out with MATLAB.Results and conclusion The test results showed that bandwidth of the designed power supply is 20 kHz.The step response time is 18us and output current ripple is lower than 1 mA.展开更多
A backside illuminated mesa-structure In Ga As/In P modified uni-traveling-carrier photodiode（MUTC-PD） with wide bandwidth and high saturation power is fabricated and investigated. The device structure is optimized ...A backside illuminated mesa-structure In Ga As/In P modified uni-traveling-carrier photodiode（MUTC-PD） with wide bandwidth and high saturation power is fabricated and investigated. The device structure is optimized to reduce the capacitance and resistance. For the 22-μm-diameter device, the maximum responsivity at 1.55 μm is 0.5 A/W, and the 3-d B cutoff frequency reaches up to 28 GHz. The output photocurrent at the 1-d B compression point is measured to be 54 m A at 25 GHz, with a corresponding output radio frequency（RF） power of up to 15.5 d Bm. The saturation characteristics of the MUTC-PD are also verified by the electric field simulation, and electric field collapse is found to be the cause of the saturation phenomenon.展开更多
目的探讨压缩感知结合层面编码金属伪影校正(compressed sensing-slice-encoding metal artifact correction,CS-SEMAC)技术用于脊柱金属植入物术后MRI的应用价值。材料与方法比较招募的35例脊柱金属植入物术后患者3.0 T MRI矢状位CS-SE...目的探讨压缩感知结合层面编码金属伪影校正(compressed sensing-slice-encoding metal artifact correction,CS-SEMAC)技术用于脊柱金属植入物术后MRI的应用价值。材料与方法比较招募的35例脊柱金属植入物术后患者3.0 T MRI矢状位CS-SEMAC序列、高带宽(high bandwidth,HBW)序列和水脂分离(Dixon)三种序列在金属植入物伪影面积、椎体信噪比(signal-to-noise ratio,SNR)、图像质量、图像清晰度、脂肪抑制效果以及植入物周围解剖结构的可见性方面的差异。结果CS-SEMAC在T1、T2矢状位图像上金属伪影面积分别为(15.45±6.84)、(22.23±9.76)cm^(2),显著低于其他两种序列,差异具有统计学意义(P<0.001);三种序列在T2抑脂矢状面图像上的SNR两两比较显示:HBW序列椎体SNR显著高于其他两种序列,Dixon序列椎体SNR显著低于其他两种序列,CS-SEMAC序列椎体SNR低于HBW序列,高于Dixon序列,差异均有统计学意义(P<0.001);在图像清晰度上,T2WI-tirm-CS-SEMAC序列评分低于其他两种序列,差异具有统计学意义(P<0.001);T2WI-tirm-CS-SEMAC序列在图像质量和脂肪抑制效果方面评分显著优于其他两种序列,差异具有统计学意义(P<0.001);并且CS-SEMAC序列相较于其他两种序列更能清晰显示植入物周围椎体、椎弓根、椎间孔及神经根,差异具有统计学意义(P<0.001)。结论CS-SEMAC序列相比于HBW、Dixon序列能够有效减少植入物周围的金属伪影,并且能显著提高T2抑脂序列的图像质量和脂肪抑制效果,虽然在T2抑脂上金属植入物邻近椎体SNR相比HBW序列有所下降,图像比HBW和Dixon图像略模糊,但是椎体周围关键解剖结构的可见度明显提升,对脊柱术后解剖结构的显示有一定优势。展开更多
随着高带宽需求的不断增长,软件定义网络(Software Defined Networking,SDN)领域内的切片分组网(Slicing Packet Network,SPN)网络架构应运而生。这一架构通过独到的设计,为高速数据传输应用提供了所需的弹性与伸缩能力。然而,针对高带...随着高带宽需求的不断增长,软件定义网络(Software Defined Networking,SDN)领域内的切片分组网(Slicing Packet Network,SPN)网络架构应运而生。这一架构通过独到的设计,为高速数据传输应用提供了所需的弹性与伸缩能力。然而,针对高带宽应用的SPN网络却面临着带宽攻击、数据隐私泄露以及认证与授权管理等问题。文章深入分析这些问题,并提出针对性的解决策略与技术手段。这些解决方案涵盖流量监管、加密防护、隐私保密、身份验证及权力控制等关键领域,并提供一整套安全准则与流量管控技术。展开更多
基金Supported by the National Key Basic Research Program of China under Grant No 2013CB921800the National Natural Science Foundation of China under Grant Nos 11227901,91021005,11274299,11104262 and 10834005the Strategic Priority Research Program(B)of the Chinese Academy of Sciences under Grant No XDB01030400
文摘Break junctions are important in generating nanosensors and single molecular devices. The mechanically con- trollable break junction is the most widely used method for a break junction due to its simplicity and stability. However, the bandwidths of traditional devices are limited to about a few hertz. Moreover, when using traditional methods it is hard to allow independent control of more than one junction. Here we propose on-chip thermally controllable break junctions to overcome these challenges. This is verified by using finite element analysis. Adopting microelectromechanical systems produces features of high bandwidth and independent controllability to this new break junction system. The proposed method will have a wide range of applications on on-chip high speed independent controllable and highly integrated single molecule devices.
文摘Background Fourth-generation photon sources like Free Electron Lasers(FEL)and Diffraction-Limited Storage Rings(DLSR)have high requirements for beam emittance.In the case of DLSR sources,a set of high-performance fast orbit feedback system(FOFB)is needed to correct the beam orbit quickly and accurately.Purpose FOFB system has four key components,which is BPM,orbit feedback calculation,fast correction magnet and fast corrector power supply.The FOFB gives the correction command and controls the fast corrector power supply to drive the fast correction magnet to correct the beam quickly and accurately.The corrector power supply has an important impact on the performance of FOFB.The corrector power supply needs to have high bandwidth and low output current ripple.Methods The new GaN power device is used to solve the restriction of the high-speed switching.The switching frequency of the power supply is increased to 300 kHz.The control system is designed to improve the bandwidth and optimize the output current ripple.The modeling analysis of the key parts of the system is given and the simulation experiments are carried out with MATLAB.Results and conclusion The test results showed that bandwidth of the designed power supply is 20 kHz.The step response time is 18us and output current ripple is lower than 1 mA.
基金Project supported by the National Basic Research Program of China(Grant Nos.2012CB315605 and 2014CB340002)the National Natural Science Foundation of China(Grant Nos.61176015,61176059,61210014,61321004,and 61307024)the Open Fund of State Key Laboratory on Integrated Optoelectronics,China(Grant Nos.IOSKL2012KF08 and IOSKL2014KF09)
文摘A backside illuminated mesa-structure In Ga As/In P modified uni-traveling-carrier photodiode（MUTC-PD） with wide bandwidth and high saturation power is fabricated and investigated. The device structure is optimized to reduce the capacitance and resistance. For the 22-μm-diameter device, the maximum responsivity at 1.55 μm is 0.5 A/W, and the 3-d B cutoff frequency reaches up to 28 GHz. The output photocurrent at the 1-d B compression point is measured to be 54 m A at 25 GHz, with a corresponding output radio frequency（RF） power of up to 15.5 d Bm. The saturation characteristics of the MUTC-PD are also verified by the electric field simulation, and electric field collapse is found to be the cause of the saturation phenomenon.
文摘目的探讨压缩感知结合层面编码金属伪影校正(compressed sensing-slice-encoding metal artifact correction,CS-SEMAC)技术用于脊柱金属植入物术后MRI的应用价值。材料与方法比较招募的35例脊柱金属植入物术后患者3.0 T MRI矢状位CS-SEMAC序列、高带宽(high bandwidth,HBW)序列和水脂分离(Dixon)三种序列在金属植入物伪影面积、椎体信噪比(signal-to-noise ratio,SNR)、图像质量、图像清晰度、脂肪抑制效果以及植入物周围解剖结构的可见性方面的差异。结果CS-SEMAC在T1、T2矢状位图像上金属伪影面积分别为(15.45±6.84)、(22.23±9.76)cm^(2),显著低于其他两种序列,差异具有统计学意义(P<0.001);三种序列在T2抑脂矢状面图像上的SNR两两比较显示:HBW序列椎体SNR显著高于其他两种序列,Dixon序列椎体SNR显著低于其他两种序列,CS-SEMAC序列椎体SNR低于HBW序列,高于Dixon序列,差异均有统计学意义(P<0.001);在图像清晰度上,T2WI-tirm-CS-SEMAC序列评分低于其他两种序列,差异具有统计学意义(P<0.001);T2WI-tirm-CS-SEMAC序列在图像质量和脂肪抑制效果方面评分显著优于其他两种序列,差异具有统计学意义(P<0.001);并且CS-SEMAC序列相较于其他两种序列更能清晰显示植入物周围椎体、椎弓根、椎间孔及神经根,差异具有统计学意义(P<0.001)。结论CS-SEMAC序列相比于HBW、Dixon序列能够有效减少植入物周围的金属伪影,并且能显著提高T2抑脂序列的图像质量和脂肪抑制效果,虽然在T2抑脂上金属植入物邻近椎体SNR相比HBW序列有所下降,图像比HBW和Dixon图像略模糊,但是椎体周围关键解剖结构的可见度明显提升,对脊柱术后解剖结构的显示有一定优势。
文摘随着高带宽需求的不断增长,软件定义网络(Software Defined Networking,SDN)领域内的切片分组网(Slicing Packet Network,SPN)网络架构应运而生。这一架构通过独到的设计,为高速数据传输应用提供了所需的弹性与伸缩能力。然而,针对高带宽应用的SPN网络却面临着带宽攻击、数据隐私泄露以及认证与授权管理等问题。文章深入分析这些问题,并提出针对性的解决策略与技术手段。这些解决方案涵盖流量监管、加密防护、隐私保密、身份验证及权力控制等关键领域,并提供一整套安全准则与流量管控技术。
