In order to improve the bandwidth of the conventional sub-harmonic mixer, a broad-band, high intermediate frequency（IF） sub-harmonic mixer for W-band applications is proposed. Replacing the open and short stubs that...In order to improve the bandwidth of the conventional sub-harmonic mixer, a broad-band, high intermediate frequency（IF） sub-harmonic mixer for W-band applications is proposed. Replacing the open and short stubs that are used in the convertional sub-harmonic mixer with a broad-band band-pass filter and a low-pass filter, respectively, a wide operating frequency band is achieved. Furthermore, without the use of the edge-coupled band-pass filter at radio frequency（RF） port, the proposed structure can be realized by common hybrid microwave integrated circuit technology at W- band. The measured results show that the proposed subharmonic mixer can operate from 80 to 107.5 GHz for RF frequency and support up to 18 GHz for the IF bandwidth. Also, the measured results show that the single-sideband conversion loss is less than 13. 7 dB over the available RF frequency band, while the minimum conversion loss is about 9 dB at an RF of 92. 5 GHz and an 1F of 3 GHz. Thus, a large operating bandwidth performance at W-band can be achieved by the orooosed mixer.展开更多
Gas hydrate drilling expeditions in the Pearl River Mouth Basin,South China Sea,have identified concentrated gas hydrates with variable thickness.Moreover,free gas and the coexistence of gas hydrate and free gas have ...Gas hydrate drilling expeditions in the Pearl River Mouth Basin,South China Sea,have identified concentrated gas hydrates with variable thickness.Moreover,free gas and the coexistence of gas hydrate and free gas have been confirmed by logging,coring,and production tests in the foraminifera-rich silty sediments with complex bottom-simulating reflectors(BSRs).The broad-band processing is conducted on conventional three-dimensional(3D)seismic data to improve the image and detection accuracy of gas hydratebearing layers and delineate the saturation and thickness of gas hydrate-and free gas-bearing sediments.Several geophysical attributes extracted along the base of the gas hydrate stability zone are used to demonstrate the variable distribution and the controlling factors for the differential enrichment of gas hydrate.The inverted gas hydrate saturation at the production zone is over 40% with a thickness of 90 m,showing the interbedded distribution with different boundaries between gas hydrate-and free gas-bearing layers.However,the gas hydrate saturation value at the adjacent canyon is 70%,with 30-m-thick patches and linear features.The lithological and fault controls on gas hydrate and free gas distributions are demonstrated by tracing each gas hydrate-bearing layer.Moreover,the BSR depths based on broad-band reprocessed 3D seismic data not only exhibit variations due to small-scale topographic changes caused by seafloor sedimentation and erosion but also show the upward shift of BSR and the blocky distribution of the coexistence of gas hydrate and free gas in the Pearl River Mouth Basin.展开更多
NaBaPO4:Eu^2+,Er^3+phosphors and Ag nano-particles(NPs)were prepared by the solid-state reaction and chemical reduction method,respectively.The fluorescence spectra and decay curves demonstrate the effective energy tr...NaBaPO4:Eu^2+,Er^3+phosphors and Ag nano-particles(NPs)were prepared by the solid-state reaction and chemical reduction method,respectively.The fluorescence spectra and decay curves demonstrate the effective energy transfer from Eu^2+to Er^3+and the existence of three-photon quantum-cutting through two-step cross-relaxation of Er^3+.The quantum-cutting emission is peaked at 1534 nm with a broad excitation band centered at 352 nm,Plasmon-enhanced quantum-cutting of NaBaPO4:Eu^2+,Er^3+phosphors was realized by decorating Ag NPs.The largest enhancement factor is 1.395.It is hopeful to improve the photovoltaic conversion efficiency of Ge solar cells by using this phosphor.展开更多
Broad-band all-optical wavelength conversion of differential phase-shift keyed （DPSK） signal is experimentally demonstrated. This scheme is composed of a one-bit delay interferometer demodulation stage followed by a...Broad-band all-optical wavelength conversion of differential phase-shift keyed （DPSK） signal is experimentally demonstrated. This scheme is composed of a one-bit delay interferometer demodulation stage followed by a semiconductor optical amplifier （SOA） based nonlinear polarization switch. A wavelength converter for the 10 G b/s DPSK signal is presented, which has a wide wavelength range of more than 30 nm. The converted signals experience small power penalties less than 1.4 dB compared with the original signal, at a bit error rate of 10-9. Additionally, the optical spectra, the measured waveforms and the open eye diagrams of the converted signals show a high quality wavelength conversion performance.展开更多
The low Gilbert damping factor, which is usually measured by ferromagnetic resonance, is crucial in spintronic applications. Two-magnon scattering occurs when the orthogonMity of the ferromagnetic resonance mode and o...The low Gilbert damping factor, which is usually measured by ferromagnetic resonance, is crucial in spintronic applications. Two-magnon scattering occurs when the orthogonMity of the ferromagnetic resonance mode and other degenerate spin wave modes was broken by magnetic anisotropy, voids, second phase, surface defects, etc., which is important in analysis of ferromagnetic resonance linewidth. Direct fitting to linewidth with Gilbert damping is advisable only when the measured linewidth is a linear function of measuring frequency in a broad band measurement. We observe the nonlinear ferromagnetic resonance linewidth of Co2MnSi thin films with respect to measuring frequency in broad band measurement. Experimental data could be well fitted with the model including two-magnon scattering with no fixed parameters. The fitting results show that two-magnon scattering results in the nonlinear linewidth behavior, and the Gilbert damping factor is much smaller than reported ones, indicating that our Co2MnSi films are more suitable for the applications of spin transfer torque.展开更多
Broad band and very broad band (BB and VBB) records of Chinese Digital Seismograph Network (CDSN) from 65 earthquakes are used to calculate the horizontal relative displacement, relative velocity and absolute accelera...Broad band and very broad band (BB and VBB) records of Chinese Digital Seismograph Network (CDSN) from 65 earthquakes are used to calculate the horizontal relative displacement, relative velocity and absolute acceleration response spectra with critical damping ratio ζ =0.005, 0.01, 0.02, 0.05 and 0.10, respectively. The results show that it is insufficient to obtain the credible characteristics of long-period ground motion response spectra only with the common ground acceleration records in engineering, while the broad band records of CDSN, as an important supplementary to ground acceleration records, can be used to study the characteristics of long-period ground motion response spectra.展开更多
This thesis is based on the design and development of ADSL access networks. We have completed the hardware and software functions in two main ADSL equipments: ATU C and ATU R. With the system design, we carry out re...This thesis is based on the design and development of ADSL access networks. We have completed the hardware and software functions in two main ADSL equipments: ATU C and ATU R. With the system design, we carry out researches to find out effective methods to improved performance in the following aspects: (a) how to allocate limited bandwith among services with different QoS requirements and (b) what is the effect of asymmetric links on TCP end to end flow control mechanism. We make detailed analyses and propose useful solutions to those problems we find. The main contents of this thesis are as follows: (1) the design and realization of ADSL access system. This part includes the principles of ADSL access technology, ADSL broadband access network architecture, and ATM over ADSL protocol models that we use in our system. We give detailed hardware and software design steps in this part, and list system testing results to show the system performance. In our hardware, the CPU is a RISC microprocessor. Combined with a high speed digital signal processor, the whole system can hold high reliability. Our software design platform is a pSOS multi task real time operation system. We have developed a series of hardware drivers besides other tasks for high level control and interruption processing. Currently, our system has reached the expected performance under test environment. Our next step is the development of DSLAM and in this part we give a feasible design scheme. (2) Packet scheduling policy in ADSL system. In order to optimize ATU R performance, we need a scheduling policy to regulate the order and number of packet output to the uplink. For this purpose, we study the scheduling algorithm design methods in a single network node and their performance. After studying the existing algorithms carefully, we first conclude certain important design principles and criterions for scheduling policy evaluation. And then by using service curve function, we make detailed performance analysis of a typical scheduling policy — the earliest deadline first. The advantage of characterizing service by using a function is that the service curve can provide a wide spectrum of service characterization. With this method, we first develop a generalized algorithm for calculating the deadlines used in the service curve based on the earliest deadline first policy, and then design a simplified computing program for an important curve. After that, holding fair bandwidth allocation and packet deadline guarantee as policy evaluation standards, we analyze this scheduling policy performance and propose solutions to those problems that we find. Finally, we, in theory, prove these improving algorithms. All these solutions and algorithms we design in this part are now under development in real systems and will enhance system performance. (3) Effects of asymmetric links on TCP performance and solutions. TCP is a widely used transmission control protocol. It regulates its forward data sending through reverse ACKs. What are the new problems to its flow control mechanism on asymmetric links and how to solve them are the two main points of this part. We first study the relationship between normalized bandwidth ratio, link buffer capacity and TCP link throughput under asymmetric link models. We find that TCP ack transportation on slow backward link is a key reason that causes the problems in TCP asymmetric links. Serving this as a start point, we present several improving solutions to TCP flow control algorithm and test them through simulation. Besides, TCP has been widely implemented in many networks. To give compatibility with current TCP end users, we use scheduling solutions to regulate data packet and ack packet transmission ratio onto uplinks. In the theoretical analysis of several typical scheduling policies, we find a feasible algorithm to control TCP data efficiency on asymmetric links. Finally, we prove those analyses and propose algorithm through simulation.展开更多
基金Research Foundation of China ( No.9140A01020209JW0601)
文摘In order to improve the bandwidth of the conventional sub-harmonic mixer, a broad-band, high intermediate frequency（IF） sub-harmonic mixer for W-band applications is proposed. Replacing the open and short stubs that are used in the convertional sub-harmonic mixer with a broad-band band-pass filter and a low-pass filter, respectively, a wide operating frequency band is achieved. Furthermore, without the use of the edge-coupled band-pass filter at radio frequency（RF） port, the proposed structure can be realized by common hybrid microwave integrated circuit technology at W- band. The measured results show that the proposed subharmonic mixer can operate from 80 to 107.5 GHz for RF frequency and support up to 18 GHz for the IF bandwidth. Also, the measured results show that the single-sideband conversion loss is less than 13. 7 dB over the available RF frequency band, while the minimum conversion loss is about 9 dB at an RF of 92. 5 GHz and an 1F of 3 GHz. Thus, a large operating bandwidth performance at W-band can be achieved by the orooosed mixer.
基金supported by the State Key Laboratory of Natural Gas Hydrate(No.2022-KFJJ-SHW)the National Natural Science Foundation of China(No.42376058)+2 种基金the International Science&Technology Cooperation Program of China(No.2023YFE0119900)the Hainan Province Key Research and Development Project(No.ZDYF2024GXJS002)the Research Start-Up Funds of Zhufeng Scholars Program.
文摘Gas hydrate drilling expeditions in the Pearl River Mouth Basin,South China Sea,have identified concentrated gas hydrates with variable thickness.Moreover,free gas and the coexistence of gas hydrate and free gas have been confirmed by logging,coring,and production tests in the foraminifera-rich silty sediments with complex bottom-simulating reflectors(BSRs).The broad-band processing is conducted on conventional three-dimensional(3D)seismic data to improve the image and detection accuracy of gas hydratebearing layers and delineate the saturation and thickness of gas hydrate-and free gas-bearing sediments.Several geophysical attributes extracted along the base of the gas hydrate stability zone are used to demonstrate the variable distribution and the controlling factors for the differential enrichment of gas hydrate.The inverted gas hydrate saturation at the production zone is over 40% with a thickness of 90 m,showing the interbedded distribution with different boundaries between gas hydrate-and free gas-bearing layers.However,the gas hydrate saturation value at the adjacent canyon is 70%,with 30-m-thick patches and linear features.The lithological and fault controls on gas hydrate and free gas distributions are demonstrated by tracing each gas hydrate-bearing layer.Moreover,the BSR depths based on broad-band reprocessed 3D seismic data not only exhibit variations due to small-scale topographic changes caused by seafloor sedimentation and erosion but also show the upward shift of BSR and the blocky distribution of the coexistence of gas hydrate and free gas in the Pearl River Mouth Basin.
基金Project supported by the National Natural Science Foundation of China(11204039,51202033)the Natural Science Foundation of Fujian Province of China(2017I01399,2017I01677,2019I01283)。
文摘NaBaPO4:Eu^2+,Er^3+phosphors and Ag nano-particles(NPs)were prepared by the solid-state reaction and chemical reduction method,respectively.The fluorescence spectra and decay curves demonstrate the effective energy transfer from Eu^2+to Er^3+and the existence of three-photon quantum-cutting through two-step cross-relaxation of Er^3+.The quantum-cutting emission is peaked at 1534 nm with a broad excitation band centered at 352 nm,Plasmon-enhanced quantum-cutting of NaBaPO4:Eu^2+,Er^3+phosphors was realized by decorating Ag NPs.The largest enhancement factor is 1.395.It is hopeful to improve the photovoltaic conversion efficiency of Ge solar cells by using this phosphor.
文摘Broad-band all-optical wavelength conversion of differential phase-shift keyed （DPSK） signal is experimentally demonstrated. This scheme is composed of a one-bit delay interferometer demodulation stage followed by a semiconductor optical amplifier （SOA） based nonlinear polarization switch. A wavelength converter for the 10 G b/s DPSK signal is presented, which has a wide wavelength range of more than 30 nm. The converted signals experience small power penalties less than 1.4 dB compared with the original signal, at a bit error rate of 10-9. Additionally, the optical spectra, the measured waveforms and the open eye diagrams of the converted signals show a high quality wavelength conversion performance.
基金Supported by the National Basic Research Program of China under Grant No 2015CB921502the National Natural Science Foundation of China under Grant Nos 11474184 and 11174183+4 种基金the Program for New Century Excellent Talents of China under Grant No NCET-10-0541the Scientific Research Foundation for Returned Overseas Chinese Scholars under Grant No B13029the Natural Science Foundation of Shandong Province under Grant No JQ201201the Doctorate Foundation of Shandong Province under Grant No BS2013CL042the Young Scientists Fund of the National Natural Science Foundation of China under Grant No 11204164
文摘The low Gilbert damping factor, which is usually measured by ferromagnetic resonance, is crucial in spintronic applications. Two-magnon scattering occurs when the orthogonMity of the ferromagnetic resonance mode and other degenerate spin wave modes was broken by magnetic anisotropy, voids, second phase, surface defects, etc., which is important in analysis of ferromagnetic resonance linewidth. Direct fitting to linewidth with Gilbert damping is advisable only when the measured linewidth is a linear function of measuring frequency in a broad band measurement. We observe the nonlinear ferromagnetic resonance linewidth of Co2MnSi thin films with respect to measuring frequency in broad band measurement. Experimental data could be well fitted with the model including two-magnon scattering with no fixed parameters. The fitting results show that two-magnon scattering results in the nonlinear linewidth behavior, and the Gilbert damping factor is much smaller than reported ones, indicating that our Co2MnSi films are more suitable for the applications of spin transfer torque.
文摘Broad band and very broad band (BB and VBB) records of Chinese Digital Seismograph Network (CDSN) from 65 earthquakes are used to calculate the horizontal relative displacement, relative velocity and absolute acceleration response spectra with critical damping ratio ζ =0.005, 0.01, 0.02, 0.05 and 0.10, respectively. The results show that it is insufficient to obtain the credible characteristics of long-period ground motion response spectra only with the common ground acceleration records in engineering, while the broad band records of CDSN, as an important supplementary to ground acceleration records, can be used to study the characteristics of long-period ground motion response spectra.
文摘This thesis is based on the design and development of ADSL access networks. We have completed the hardware and software functions in two main ADSL equipments: ATU C and ATU R. With the system design, we carry out researches to find out effective methods to improved performance in the following aspects: (a) how to allocate limited bandwith among services with different QoS requirements and (b) what is the effect of asymmetric links on TCP end to end flow control mechanism. We make detailed analyses and propose useful solutions to those problems we find. The main contents of this thesis are as follows: (1) the design and realization of ADSL access system. This part includes the principles of ADSL access technology, ADSL broadband access network architecture, and ATM over ADSL protocol models that we use in our system. We give detailed hardware and software design steps in this part, and list system testing results to show the system performance. In our hardware, the CPU is a RISC microprocessor. Combined with a high speed digital signal processor, the whole system can hold high reliability. Our software design platform is a pSOS multi task real time operation system. We have developed a series of hardware drivers besides other tasks for high level control and interruption processing. Currently, our system has reached the expected performance under test environment. Our next step is the development of DSLAM and in this part we give a feasible design scheme. (2) Packet scheduling policy in ADSL system. In order to optimize ATU R performance, we need a scheduling policy to regulate the order and number of packet output to the uplink. For this purpose, we study the scheduling algorithm design methods in a single network node and their performance. After studying the existing algorithms carefully, we first conclude certain important design principles and criterions for scheduling policy evaluation. And then by using service curve function, we make detailed performance analysis of a typical scheduling policy — the earliest deadline first. The advantage of characterizing service by using a function is that the service curve can provide a wide spectrum of service characterization. With this method, we first develop a generalized algorithm for calculating the deadlines used in the service curve based on the earliest deadline first policy, and then design a simplified computing program for an important curve. After that, holding fair bandwidth allocation and packet deadline guarantee as policy evaluation standards, we analyze this scheduling policy performance and propose solutions to those problems that we find. Finally, we, in theory, prove these improving algorithms. All these solutions and algorithms we design in this part are now under development in real systems and will enhance system performance. (3) Effects of asymmetric links on TCP performance and solutions. TCP is a widely used transmission control protocol. It regulates its forward data sending through reverse ACKs. What are the new problems to its flow control mechanism on asymmetric links and how to solve them are the two main points of this part. We first study the relationship between normalized bandwidth ratio, link buffer capacity and TCP link throughput under asymmetric link models. We find that TCP ack transportation on slow backward link is a key reason that causes the problems in TCP asymmetric links. Serving this as a start point, we present several improving solutions to TCP flow control algorithm and test them through simulation. Besides, TCP has been widely implemented in many networks. To give compatibility with current TCP end users, we use scheduling solutions to regulate data packet and ack packet transmission ratio onto uplinks. In the theoretical analysis of several typical scheduling policies, we find a feasible algorithm to control TCP data efficiency on asymmetric links. Finally, we prove those analyses and propose algorithm through simulation.
