The Underwater Communication Link(UCL)is a crucial component of Underwater Wireless Optical Communication(UWOC)systems,requiring optimised design to mitigate the high power attenuation inherent in seawater.To ensure t...The Underwater Communication Link(UCL)is a crucial component of Underwater Wireless Optical Communication(UWOC)systems,requiring optimised design to mitigate the high power attenuation inherent in seawater.To ensure the reliability of an optimal UCL design,it is essential to account for the three primary scattering regimes:forward scattering(FSC),backward scattering(BSC),and isotropic scattering(ISC)in seawater channels.This study introduces a new photon-tracking model based on a discrete equation,facilitating Monte Carlo Simulation(MCS)to evaluate how different scattering regimes influence received photon distribution.Three distinct Scattering Regime Contribution Weight(SRCW)probability sets were employed,each representing different UCL operational configurations dominated by specific scattering regimes.The proposed modeling approach enables a comprehensive assessment of the temporal characteristics of received optical pulses,channel loss,and time spread-ultimately defining the optimal UCL design parameters.The key findings of this study include:(1)Enhancing the FSC regime dominance leads to a quasi-light waveguide effect over link spans and small Fields of View(FOV)<25°,significantly improving channel performance in Harbor seawater compared to Coastal seawater.(2)A well-designed UCL with a small FOV(<25°)can minimise channel loss and time spread,ensuring high capacity and efficient performance in both Coastal and Harbor seawaters.(3)When BSC and ISC contributions exceed FSC dominance,the received optical pulse undergoes significant temporal broadening,particularly for larger FOV angles(>25°)and extended link spans.(4)The developed novel MCS-based discrete equation provides a simple yet robust model for simulating photon propagation in both homogeneous and inhomogeneous underwater channels.These insights contribute to developing more efficient and reliable UCL designs with military standards by enhancing UWOC system performance over a longer linkspan for a given limited optical power across various underwater environments.展开更多
The space time spreading, superimposed training sequences, and space-time coding are used to present a multiple input and multiple output （MIMO） systems model, and a closed-form of average error probability upper bo...The space time spreading, superimposed training sequences, and space-time coding are used to present a multiple input and multiple output （MIMO） systems model, and a closed-form of average error probability upper bound expression for MIMO correlated frequency-selective channel in the presence of interference （co-channel interference and jamming signals） is derived. Moreover, the correlation at both ends of the wireless link that can be incorporated equivalently into correlation at the transmit end is also derived, which is significant to analyze space-time link algorithm of MIMO systems.展开更多
Ultrawide bandwidth (UWB) radio, a very promising technique carrying information in very short basic pulses, has properties that make it a viable candidate for short-range wireless communications. In this paper, sever...Ultrawide bandwidth (UWB) radio, a very promising technique carrying information in very short basic pulses, has properties that make it a viable candidate for short-range wireless communications. In this paper, several short-pulse waveforms based on Gaussian genetic monocycle as well as Gaussian pulse waveform, as candidates of basic UWB pulse waveforms, are firstly proposed and investigated. Their spectrum characteristics, bit transmission rate (BTR), and bit error rate (BER) performance in AWGN channel using time hopping spread spectrum (THSS) and pulse position modulation (PPM) are simulated and evaluated. The numerical results are compared and show that the basic pulse waveforms determine the spectrum characteristics of UWB signals and have much effect on the performance of UWB radio system. The performance of UWB radio system achieved by the proposed basic pulse waveforms is much better than that of UWB radio system realized by other used basic pulse waveforms under the uniform conditions. Also, the polarity of these short basic pulses does not affect the performance of UWB radio system.展开更多
An analysis process is described for adaptive quadrature amplitude modulation(AQAM)of constant-power constant-symbol-rate over frequency-selective Rayleigh fading channels with inter symbol interference(ISI)and Gaussi...An analysis process is described for adaptive quadrature amplitude modulation(AQAM)of constant-power constant-symbol-rate over frequency-selective Rayleigh fading channels with inter symbol interference(ISI)and Gaussian noise.The delay spread resistance of the AQAM scheme is put forward by studying its average throughput and average bit-error-rate(BER),both of which can be expressed as functions of two variables,the ratio of root mean square(RMS)delay spread to symbol period and the ratio of average symbol energy to noise.Average throughput reacts regularly to the latter,whereas it does not react to the former.The AQAM scheme is highly superior in the delay spread resistance in comparison with the fixed modulation modes.Gains of the AQAM scheme over the fixed modes become more significant as the delay spread becomes severer or the average throughput decreases.展开更多
This electronic factory building project is located in the 78M2 plot of Beijing Economic and Technological Development Zone, with a construction area of 21000 m2. It has two floors above the ground and one floor parti...This electronic factory building project is located in the 78M2 plot of Beijing Economic and Technological Development Zone, with a construction area of 21000 m2. It has two floors above the ground and one floor partially, without basement. The north-south span is 132.8m, the east-west span is 81m, the structural form is frame structure, the foundation is independent column foundation, and the column spacing is 6000×9000. After completion, it will become the largest production base of the electronic products company in Beijing. The first floor is a wear-resistant concrete floor, which is compacted by plain soil with a 300mm thick graded sand cushion layer and a compaction coefficient of not less than 0.95;200mm thick C20 concrete with Φ 6 @ 200 double-layer bidirectional reinforcement;80mm thick C25 fine stone concrete (internally equipped with φ6@200 single-layer bidirectional reinforcing steel bar), the design requires that 2mm thick wear-resistant material should be evenly spread on the surface of concrete before initial setting (refer to the design requirements for details of wear-resistant material). After the spreading is completed, mechanical trowel should be used for slurry lifting, troweling and calendering, so that the wear-resistant material can be embedded into the concrete surface layer and react with certain components in the concrete to finally form a hard wear-resistant surface layer so as to improve the wear resistance and impact resistance of the concrete surface. A series of technical measures, such as throwing the wear-resistant material twice, controlling the timing of throwing the wear-resistant material and the uniformity of throwing the material, curing the film and mechanically cutting the gap, etc., were adopted to form the ground with a smooth and smooth surface, uniform color, clear and straight grid seams, good appearance, strength and quality meeting the specification requirements, which were well received.展开更多
Background Jiangmen Underground Neutrino Observation(JUNO)is one of the largest experimental facilities for neutrino detecting.As its main structure,the central detector contains 20 kiloton liquid scintillator filled ...Background Jiangmen Underground Neutrino Observation(JUNO)is one of the largest experimental facilities for neutrino detecting.As its main structure,the central detector contains 20 kiloton liquid scintillator filled in an acrylic shell,and there are 18,00020-inch photomultiplier tubes(PMTs)and 25,0003-inch PMTs covering the shell.Purpose As an independent photon detection system,3-inch PMTs have been required to have excellent resolution for the single photoelectron detection,high quantum efficiency,small transit time spread and low dark noise rate.Methods Two kinds of 3-inch PMTs from HZC Photonics and Hamamatsu have been investigated as candidates.A dedicated test system for 3-inch PMTs has been designed,and various characterization parameters have been studied.Conclusion The preliminary results show these PMTs can meet the requirements of JUNO.展开更多
基金The Deanship of Scientific Research(DSR)at King Abdulaziz University(KAU),Jeddah,Saudi Arabia,has funded this project under Grant No.(KEP-PhD:72-130-1443).
文摘The Underwater Communication Link(UCL)is a crucial component of Underwater Wireless Optical Communication(UWOC)systems,requiring optimised design to mitigate the high power attenuation inherent in seawater.To ensure the reliability of an optimal UCL design,it is essential to account for the three primary scattering regimes:forward scattering(FSC),backward scattering(BSC),and isotropic scattering(ISC)in seawater channels.This study introduces a new photon-tracking model based on a discrete equation,facilitating Monte Carlo Simulation(MCS)to evaluate how different scattering regimes influence received photon distribution.Three distinct Scattering Regime Contribution Weight(SRCW)probability sets were employed,each representing different UCL operational configurations dominated by specific scattering regimes.The proposed modeling approach enables a comprehensive assessment of the temporal characteristics of received optical pulses,channel loss,and time spread-ultimately defining the optimal UCL design parameters.The key findings of this study include:(1)Enhancing the FSC regime dominance leads to a quasi-light waveguide effect over link spans and small Fields of View(FOV)<25°,significantly improving channel performance in Harbor seawater compared to Coastal seawater.(2)A well-designed UCL with a small FOV(<25°)can minimise channel loss and time spread,ensuring high capacity and efficient performance in both Coastal and Harbor seawaters.(3)When BSC and ISC contributions exceed FSC dominance,the received optical pulse undergoes significant temporal broadening,particularly for larger FOV angles(>25°)and extended link spans.(4)The developed novel MCS-based discrete equation provides a simple yet robust model for simulating photon propagation in both homogeneous and inhomogeneous underwater channels.These insights contribute to developing more efficient and reliable UCL designs with military standards by enhancing UWOC system performance over a longer linkspan for a given limited optical power across various underwater environments.
基金the National Basic Research Program of China "973"(2008CB317109)the National "863" High-Tech Research and Development Program (2002AA123032)+2 种基金the National Natural Science Foundation of China (60572054)the Innovative Research Team Program of University of Electronic and Technology of Chinathe Doctor Foundation of Guilin University of Electronic Technology.
文摘The space time spreading, superimposed training sequences, and space-time coding are used to present a multiple input and multiple output （MIMO） systems model, and a closed-form of average error probability upper bound expression for MIMO correlated frequency-selective channel in the presence of interference （co-channel interference and jamming signals） is derived. Moreover, the correlation at both ends of the wireless link that can be incorporated equivalently into correlation at the transmit end is also derived, which is significant to analyze space-time link algorithm of MIMO systems.
文摘Ultrawide bandwidth (UWB) radio, a very promising technique carrying information in very short basic pulses, has properties that make it a viable candidate for short-range wireless communications. In this paper, several short-pulse waveforms based on Gaussian genetic monocycle as well as Gaussian pulse waveform, as candidates of basic UWB pulse waveforms, are firstly proposed and investigated. Their spectrum characteristics, bit transmission rate (BTR), and bit error rate (BER) performance in AWGN channel using time hopping spread spectrum (THSS) and pulse position modulation (PPM) are simulated and evaluated. The numerical results are compared and show that the basic pulse waveforms determine the spectrum characteristics of UWB signals and have much effect on the performance of UWB radio system. The performance of UWB radio system achieved by the proposed basic pulse waveforms is much better than that of UWB radio system realized by other used basic pulse waveforms under the uniform conditions. Also, the polarity of these short basic pulses does not affect the performance of UWB radio system.
基金National Natural Science Foundation of China(No.61071087)Research contract from Shandong University of Scienceand Technology(Chun Lei2009BWZ037)
文摘An analysis process is described for adaptive quadrature amplitude modulation(AQAM)of constant-power constant-symbol-rate over frequency-selective Rayleigh fading channels with inter symbol interference(ISI)and Gaussian noise.The delay spread resistance of the AQAM scheme is put forward by studying its average throughput and average bit-error-rate(BER),both of which can be expressed as functions of two variables,the ratio of root mean square(RMS)delay spread to symbol period and the ratio of average symbol energy to noise.Average throughput reacts regularly to the latter,whereas it does not react to the former.The AQAM scheme is highly superior in the delay spread resistance in comparison with the fixed modulation modes.Gains of the AQAM scheme over the fixed modes become more significant as the delay spread becomes severer or the average throughput decreases.
文摘This electronic factory building project is located in the 78M2 plot of Beijing Economic and Technological Development Zone, with a construction area of 21000 m2. It has two floors above the ground and one floor partially, without basement. The north-south span is 132.8m, the east-west span is 81m, the structural form is frame structure, the foundation is independent column foundation, and the column spacing is 6000×9000. After completion, it will become the largest production base of the electronic products company in Beijing. The first floor is a wear-resistant concrete floor, which is compacted by plain soil with a 300mm thick graded sand cushion layer and a compaction coefficient of not less than 0.95;200mm thick C20 concrete with Φ 6 @ 200 double-layer bidirectional reinforcement;80mm thick C25 fine stone concrete (internally equipped with φ6@200 single-layer bidirectional reinforcing steel bar), the design requires that 2mm thick wear-resistant material should be evenly spread on the surface of concrete before initial setting (refer to the design requirements for details of wear-resistant material). After the spreading is completed, mechanical trowel should be used for slurry lifting, troweling and calendering, so that the wear-resistant material can be embedded into the concrete surface layer and react with certain components in the concrete to finally form a hard wear-resistant surface layer so as to improve the wear resistance and impact resistance of the concrete surface. A series of technical measures, such as throwing the wear-resistant material twice, controlling the timing of throwing the wear-resistant material and the uniformity of throwing the material, curing the film and mechanically cutting the gap, etc., were adopted to form the ground with a smooth and smooth surface, uniform color, clear and straight grid seams, good appearance, strength and quality meeting the specification requirements, which were well received.
基金the Strategic Priority Research Program of the Chinese Academy of Sciences,Grant No.XDA10011200.
文摘Background Jiangmen Underground Neutrino Observation(JUNO)is one of the largest experimental facilities for neutrino detecting.As its main structure,the central detector contains 20 kiloton liquid scintillator filled in an acrylic shell,and there are 18,00020-inch photomultiplier tubes(PMTs)and 25,0003-inch PMTs covering the shell.Purpose As an independent photon detection system,3-inch PMTs have been required to have excellent resolution for the single photoelectron detection,high quantum efficiency,small transit time spread and low dark noise rate.Methods Two kinds of 3-inch PMTs from HZC Photonics and Hamamatsu have been investigated as candidates.A dedicated test system for 3-inch PMTs has been designed,and various characterization parameters have been studied.Conclusion The preliminary results show these PMTs can meet the requirements of JUNO.
