The problem of two-dimensional direction of arrival(2D-DOA)estimation for uniform planar arrays(UPAs)is investigated by employing the reduced-dimensional(RD)polynomial root finding technique and 2D multiple signal cla...The problem of two-dimensional direction of arrival(2D-DOA)estimation for uniform planar arrays(UPAs)is investigated by employing the reduced-dimensional(RD)polynomial root finding technique and 2D multiple signal classification(2D-MUSIC)algorithm.Specifically,based on the relationship between the noise subspace and steering vectors,we first construct 2D root polynomial for 2D-DOA estimates and then prove that the 2D polynomial function has infinitely many solutions.In particular,we propose a computationally efficient algorithm,termed RD-ROOT-MUSIC algorithm,to obtain the true solutions corresponding to targets by RD technique,where the 2D root-finding problem is substituted by two one-dimensional(1D)root-finding operations.Finally,accurate 2DDOA estimates can be obtained by a sample pairing approach.In addition,numerical simulation results are given to corroborate the advantages of the proposed algorithm.展开更多
Sparse arrays of telescopes have a limited (u, v)-plane coverage. In this paper, an optimization method for designing planar arrays of an aperture synthesis telescope is proposed that is based on distributed genetic a...Sparse arrays of telescopes have a limited (u, v)-plane coverage. In this paper, an optimization method for designing planar arrays of an aperture synthesis telescope is proposed that is based on distributed genetic algorithm. This distributed genetic algorithm is implemented on a network of workstations using community communication model. Such an aperture synthesis system performs with imperfection of (u, v) components caused by deviations and(or) some missing baselines. With the maximum (u, v)-plane coverage of this rotation-optimized array, the image of the source reconstructed by inverse Fourier transform is satisfactory.展开更多
A novel low-cost 4-element planar array antenna directly fed by a coaxial cable for Ultra-WideBand(UWB) application is presented. The proposed antenna consists of 2×2 bowtie elements and a simple 1:4 power divide...A novel low-cost 4-element planar array antenna directly fed by a coaxial cable for Ultra-WideBand(UWB) application is presented. The proposed antenna consists of 2×2 bowtie elements and a simple 1:4 power divider feeding network. Compared to the basic bowtie element, the impedance bandwidth of the array antenna has a significant improvement that the low cut-off frequency is extended from 6 GHz of the bowtie element to 2 GHz. The measured results show that the proposed antenna has a large bandwidth of 2 GHz to 11 GHz for Voltage Standing Wave Ratio(VSWR)<2, and exhibits a bidirectional radiation pattern and a modest gain across the operating band and a peak gain of about 9 dBi at 11 GHz.展开更多
In this paper,a 4×4 wideband linearly po-larization(LP)antenna array is proposed by using pla-nar dual-arm spiral structures.Wideband balun struc-tures,composed of microstrip line-fed coupling slots,are adopted t...In this paper,a 4×4 wideband linearly po-larization(LP)antenna array is proposed by using pla-nar dual-arm spiral structures.Wideband balun struc-tures,composed of microstrip line-fed coupling slots,are adopted to feed two dual-arms spiral structures with opposite phases.Then,by combining the left-and right-hand circular polarizations,a linearly polar-ization is achieved.The proposed antenna has a wide operating bandwidth due to the wideband nature of the spiral structure.Simulated results show that the an-tenna element can achieve a 68.73%impedance band-width and a maximum gain of 6.64 dBi within 19.44–38.83 GHz.A 4×4 array prototype is designed to verify the concept.Measured results show that an impedance bandwidth of 63.73%is obtained.The pro-posed array has the merits of a wide bandwidth,a low profile,a low cost,and a small size,which is promis-ing for the application in millimeter wave wireless sys-tems.展开更多
Millimeter-wave(mmWave) and massive multiple-input multiple-output(MIMO) are broadly recognized as key enabling technologies for the fifth generation(5G) communication systems. In this paper, a low-complexity angle-de...Millimeter-wave(mmWave) and massive multiple-input multiple-output(MIMO) are broadly recognized as key enabling technologies for the fifth generation(5G) communication systems. In this paper, a low-complexity angle-delay parameters estimation(ADPE) algorithm was put forward for wideband mmWave systems with uniform planar arrays(UPAs). In particular, the ADPE algorithm effectively decouples the angle-delay parameters and converts the angle-delay estimation problem into three independent subproblems. Accordingly, the ability to devise an off-grid method based on discrete Fourier transform(DFT) with a closed-form solution for angle-delay estimation and potential path number acquisition can be realized. In actuality, only a limited number of potential paths are close to the true paths influenced by noise. Consequently, the removal of noise paths to acquire the corresponding true path gains through a sparsity adaptive path gains estimation(APGE) algorithm is postulated. Finally, the simulation results substantiate the effectiveness of ADPE and APGE algorithms.展开更多
Radio antenna arrays have many advantages for astronomical observations,such as high resolution,high sensitivity,multi-target simultaneous observation,and flexible beam formation.Problems surrounding key indices,such ...Radio antenna arrays have many advantages for astronomical observations,such as high resolution,high sensitivity,multi-target simultaneous observation,and flexible beam formation.Problems surrounding key indices,such as sensitivity enhancement,scanning range extension,and sidelobe level suppression,need to be solved urgently.Here,we propose a sparse optimization scheme based on a genetic algorithm for a 64-array element planar radio antenna array.As optimization targets for the iterative process of the genetic algorithm,we use the maximum sidelobe levels and beamwidth of multiple cross-section patterns that pass through the main beam in three-dimensions,with the maximum sidelobe levels of the patterns at several different scanning angles.Element positions are adjusted for iterations,to select the optimal array configuration.Following sparse layout optimization,the simulated 64-element planar radio antenna array shows that the maximum sidelobe level decreases by 1.79 dB,and the beamwidth narrows by 3°.Within the scan range of±30°,after sparse array optimization,all sidelobe levels decrease,and all beamwidths narrow.This performance improvement can potentially enhance the sensitivity and spatial resolution of radio telescope systems.展开更多
The resistance and inductance of a wire array during an implosion are very important parameters of interest to：researchers. A variety of inductances and resistances directly affect the kinetic energy and resistance h...The resistance and inductance of a wire array during an implosion are very important parameters of interest to：researchers. A variety of inductances and resistances directly affect the kinetic energy and resistance heat energy coupled from a pulsed-power generator. In this paper, the inductance and resistance of a planar wire array during the Z-pinch process are analyzed. The inductance is calculated from the data obtained by a time-resolved soft X-ray framed camera, while the resistance is calculated through the voltage and the current of the wire array load combined with the variety of the inductance. The results show that the resistance of the load increases with the development of the implosion, and reaches its maximum at 0.29 ± 0.16Ω near the pinched time.展开更多
Two dynamics modes, named short ablation mode and long ablation mode, are observed in implosion experiments of planar wire array Z pinch on ＇QiangGuang-I＇ facility utilizing an optical streak camera. The long ablati...Two dynamics modes, named short ablation mode and long ablation mode, are observed in implosion experiments of planar wire array Z pinch on ＇QiangGuang-I＇ facility utilizing an optical streak camera. The long ablation mode has a lagged trajectory compared with the short ablation mode. For shot 10035 in a short ablation mode, the initial time of K-shell radiation is consistent with the interaction time for ablation plasma arriving at the centre of wire array, while for shot 10038 in long ablation mode, the initial time of K-shell radiation is about 10 ns earlier. In the two modes, the partial ablation plasma could traverse the wire array plane and then collide in the centre to form a dense plasma column with a diameter of 2.2 mm for shot 10035 and 1.5 mm for shot 10038.展开更多
The concept of difference and sum co-array(DSCA)has become a new design idea for planar sparse arrays.Inspired by the shifting invariance property of DSCA,a specific configuration named here as the improved L-shaped a...The concept of difference and sum co-array(DSCA)has become a new design idea for planar sparse arrays.Inspired by the shifting invariance property of DSCA,a specific configuration named here as the improved L-shaped array is proposed.Compared to other traditional 2D sparse array configurations such as 2D nested arrays and hourglass arrays,the proposed configuration has larger central consecutive ranges in its DSCA,thus increasing the DOF.At the same time,the mutual coupling effect is also reduced due to the enlarged spacing between the adjacent sensors.Simulations further demonstrate the superiority of the proposed arrays in terms of detection performance and estimation accuracy.展开更多
The concept of difference and sum(diff-sum)coarray has attracted a lot of attentions in the estimation of direction-of-arrival(DOA)for the past few years,due to its high degrees-of-freedom(DOFs).A vectorized conjugate...The concept of difference and sum(diff-sum)coarray has attracted a lot of attentions in the estimation of direction-of-arrival(DOA)for the past few years,due to its high degrees-of-freedom(DOFs).A vectorized conjugate augmented MUSIC(VCA-MUSIC)algorithm is applied to generate an equivalent signal model which contains the virtual sensor positions of both the difference and sum of the physical sensors in the two-dimensional(2D)arrays,by utilizing both the spatial and temporal information.Besides,an augmented 2D coprime array configuration is presented with the basis on the concept of difference and sum coarray.By compressing the inter-element spacing of one subarray and introducing the proper separation between the two subarrays of 2D coprime array,the redundancy between the difference coarray and the sum one can be reduced so that more virtual sensors in both coarrays can make contributions to the DOFs.As a result,a much larger consecutive area in the diff-sum coarray can be achieved,which can significantly increase the DOFs.Numerical simulations verify the superiority of the proposed array configuration.展开更多
Naturally suited array geometry for 360° coverage is the uniform circular array (UCA). A comparison of two types of uniform circular array configurations is presented in this paper. Due to its symmetrical...Naturally suited array geometry for 360° coverage is the uniform circular array (UCA). A comparison of two types of uniform circular array configurations is presented in this paper. Due to its symmetrical geometry UCA is always targeted which results in minimal change inside lobe levels and beam width when scanned by a phased array antenna. Particle Swarm Optimization and Cuckoo algorithm are used for the calculation of complex weights of the array elements. Comparisons are drawn in the context of adaptive beam forming capabilities. Obtained results suggest that planar uniform circular array (9:10) using Cuckoo algorithm, has better beam forming properties with also reduced side lobe levels when compared to other geometry.展开更多
The performance of space antennas is significantly affected by thermal deformation owing to the harsh thermal environment in space.This results in potential degradation in pointing accuracy and overall functionality.T...The performance of space antennas is significantly affected by thermal deformation owing to the harsh thermal environment in space.This results in potential degradation in pointing accuracy and overall functionality.This study focused on the analysis and control of thermal deformation in large-scale two-dimensional planar phased array antennas.Employing the finite element method,we developed a comprehensive thermal and structural model of the antenna.This enabled us to simulate the steady-state temperature field and the associated thermal deformation at various orbital positions.To address this deformation issue,we propose an innovative shape-control approach that utilizes distributed cable actuators.The shape control challenge was reformulated into a layered optimization problem concerning actuator placement and force application.In the outer optimization layer,a discrete particle swarm optimization algorithm was used to determine the optimal locations for the actuators.In the inner optimization layer,quadratic programming was subsequently applied to calculate the optimal control forces for each actuator.We validated the proposed method by numerically simulating a novel large-scale two-dimensional planar phased array antenna.The results demonstrated the effectiveness of our method in mitigating thermal deformation and maintaining the structural integrity and shape accuracy of the antennas.展开更多
In this paper,we investigate the end-to-end performance of intelligent reflecting surface(IRS)-assisted wireless communication systems.We consider a system in which an IRS is deployed on a uniform planar array(UPA)con...In this paper,we investigate the end-to-end performance of intelligent reflecting surface(IRS)-assisted wireless communication systems.We consider a system in which an IRS is deployed on a uniform planar array(UPA)configuration,including a large number of reflecting elements,where the transmitters and receivers are only equipped with a single antenna.Our objective is to analytically obtain the achievable ergodic rate,outage probability,and bit error rate(BER)of the system.Furthermore,to maximize the system’s signal-to-noise ratio(SNR),we design the phase shift of each reflecting element and derive the optimal reflection phase of the IRS based on the channel state information(CSI).We also derive the exact expression of the SNR probability density function(p.d.f.)and show that it follows a non-central Chi-square distribution.Using the p.d.f.,we then derive the theoretical results of the achievable rate,outage probability,and BER.The accuracy of the obtained theoretical results is also verified through numerical simulation.Itwas shown that the achievable rate,outage probability,and BER could be improved by increasing the number of reflecting elements and choosing an appropriate SNR regime.Furthermore,we also find that the IRS-assisted communication system achieves better performance than the existing end-to-end wireless communication.展开更多
A large planar microphone array, which consists of 111 microphones, was successfully developed. The positions of 111 microphones in the array were determined by a random optimization procedure for the largest possible...A large planar microphone array, which consists of 111 microphones, was successfully developed. The positions of 111 microphones in the array were determined by a random optimization procedure for the largest possible amplification and dynamic range. The beam pattern of planar array was obtained by numerical calculation. This planar array was applied to measure a two-dimensional mapping of the sound sources on landing aircraft. It is shown that important airframe noise sources can be identified. The spectra and directivity of any interested noise source can also be obtained by this measurement.展开更多
To achieve a dopamine （DA） response with high sensitivity and high signal-to-noise ratio （S/N） with a patch-clamp system, polypyrrole/graphene （PPy/GR） nanocomposites were steadily electrodeposited by an electro...To achieve a dopamine （DA） response with high sensitivity and high signal-to-noise ratio （S/N） with a patch-clamp system, polypyrrole/graphene （PPy/GR） nanocomposites were steadily electrodeposited by an electrochemical method on a planar mi- croelectrode array （pMEA） fabricated by a standard micromachining process. The electrodeposition process was carried out by chronopotentimetry measurement scanning from 0.1 to 0.8 C/cm2 at the current of 2 mA; 0.5 C/cm2 was found to be optimal. The pMEA modified by PPy/GR at the 0.5 C/cm2 exhibits remarkable properties; for instance, the standard deviation （SD） de- creases from 8.4614×10-al to 5.62×10 11 A, reduced by 33.52%, and the sensitivity increases from 2566.88 to 76114.65 gAmMcm2 , 29.65 times higher than the bare Pt （platinum）. A good linear relationship between the current and DA concentra- tion in the range of 0.30 to 61.71 grn was obtained, with a correlation coefficient of 0.997. The sensor is meaningful for neuro- science research and the treatment of neurological diseases.展开更多
Purpose-The purpose of this paper is to propose radiating system by avoiding electromagnetic interference in unwanted directions and to radiate the energy in the required direction with an optimization technique.Desig...Purpose-The purpose of this paper is to propose radiating system by avoiding electromagnetic interference in unwanted directions and to radiate the energy in the required direction with an optimization technique.Design/methodology/approach-Practically,multiple,incompatible variables require concurrent boost on a synthesis of systematic antenna assemblage.The authors have worked out the main statistic penalty function to ensure all the restrictions.Here,MBPSO(Modified Binary Particle Swarm Optimization)is developed and introduced thin planar synthesis restriction.The sigmoid function is used to update the particle position.Different analytical demonstrations have been carried out,and the exhibited methods are predominant than the algorithms.Findings-A 20310 planar antenna array is synthesized using modified BPSO.The authors have suppressed the PSLL in two principal planes and as well as in the entire f plane.Numerical results state that MBPSO outperforms the other binary BPSO,BCSO,ACO,RGA,GAoptimization techniques.MBPSO achieved a51.84 dB PSLL level,whereas BPSO achieved48.57 dB with the same 50%thinning.Originality/value-Planar array antenna formation is one of the most complex syntheses because the array gets filled with more antenna elements.The machine-like complication and implementation of such an antenna arrangement with a broad opening would be expensive.It is not easy to control the required radiation patterns shape by using a uniform feeding network.To get better flexibility for sustaining the sidelobe levelheaded along with consistent amplitude distribution.So as far as prominence has been given to the evolutionary algorithm,find an ideal solution for objective array combinational problems.展开更多
Controlling the vapor-deposited nanoribbons to grow along a consistent orientation will enable the desired in situ integration of functional devices,representing a major technological advance compared to post-growth p...Controlling the vapor-deposited nanoribbons to grow along a consistent orientation will enable the desired in situ integration of functional devices,representing a major technological advance compared to post-growth processing strategies.In this work,ntype F_(16)CuPc molecules are self-assembled into horizontally-oriented nanoribbons with a consistent growth axis after creating periodic hydrophobic nanogrooves on a sapphire surface.Consequently,electrodes are deposited directly on the growth substrate to enable in situ fabrication of photodetectors.Depending on the deposited electrodes,these horizontally-oriented nanoribbons are connected to form a monolithic photodetector with a large sensing area or an on-chip array of photodetectors with multiple detector units.This in situ integration strategy avoids potential structural damage and contamination from impurities associated with post-growth processing steps.Therefore,the vapor-deposited nanoribbons can retain their high quality during the device manufacturing process,which contributes to performance improvement.As a result,the in-situ integrated F_(16)CuPc photodetectors exhibit a sensitive response in the ultraviolet-visible-near-infrared(UV-vis-NIR)region.The response time is on the order of tens of milliseconds,the fastest record ever for the F_(16)CuPc-based photodetectors.Furthermore,statistics from an array of 6×6 photodetectors show little variation in their sensitivity and response time,and hence this in situ fabrication scheme will contribute to the implementation of on-chip integrated photodetectors with consistent performance based on bottom-up nanoribbons.Overall,this self-oriented growth provides a versatile option to achieve desired in-situ integrated functional devices based on bottom-up nanoribbons.展开更多
基金supported by the National Natural Science Foundation of China(Nos.61631020,61971218,61601167,61371169)。
文摘The problem of two-dimensional direction of arrival(2D-DOA)estimation for uniform planar arrays(UPAs)is investigated by employing the reduced-dimensional(RD)polynomial root finding technique and 2D multiple signal classification(2D-MUSIC)algorithm.Specifically,based on the relationship between the noise subspace and steering vectors,we first construct 2D root polynomial for 2D-DOA estimates and then prove that the 2D polynomial function has infinitely many solutions.In particular,we propose a computationally efficient algorithm,termed RD-ROOT-MUSIC algorithm,to obtain the true solutions corresponding to targets by RD technique,where the 2D root-finding problem is substituted by two one-dimensional(1D)root-finding operations.Finally,accurate 2DDOA estimates can be obtained by a sample pairing approach.In addition,numerical simulation results are given to corroborate the advantages of the proposed algorithm.
基金This project was supported by the High Technology Research and Development Programme of China (2002AA111040).
文摘Sparse arrays of telescopes have a limited (u, v)-plane coverage. In this paper, an optimization method for designing planar arrays of an aperture synthesis telescope is proposed that is based on distributed genetic algorithm. This distributed genetic algorithm is implemented on a network of workstations using community communication model. Such an aperture synthesis system performs with imperfection of (u, v) components caused by deviations and(or) some missing baselines. With the maximum (u, v)-plane coverage of this rotation-optimized array, the image of the source reconstructed by inverse Fourier transform is satisfactory.
基金Supported by the National High Technology Research and Development Program(No.2012AA121901)
文摘A novel low-cost 4-element planar array antenna directly fed by a coaxial cable for Ultra-WideBand(UWB) application is presented. The proposed antenna consists of 2×2 bowtie elements and a simple 1:4 power divider feeding network. Compared to the basic bowtie element, the impedance bandwidth of the array antenna has a significant improvement that the low cut-off frequency is extended from 6 GHz of the bowtie element to 2 GHz. The measured results show that the proposed antenna has a large bandwidth of 2 GHz to 11 GHz for Voltage Standing Wave Ratio(VSWR)<2, and exhibits a bidirectional radiation pattern and a modest gain across the operating band and a peak gain of about 9 dBi at 11 GHz.
基金supported in part by the National Natural Science Foundation of China under Grant 62131008the Fundamental Research Funds for the Central Universities 2242022k60003.
文摘In this paper,a 4×4 wideband linearly po-larization(LP)antenna array is proposed by using pla-nar dual-arm spiral structures.Wideband balun struc-tures,composed of microstrip line-fed coupling slots,are adopted to feed two dual-arms spiral structures with opposite phases.Then,by combining the left-and right-hand circular polarizations,a linearly polar-ization is achieved.The proposed antenna has a wide operating bandwidth due to the wideband nature of the spiral structure.Simulated results show that the an-tenna element can achieve a 68.73%impedance band-width and a maximum gain of 6.64 dBi within 19.44–38.83 GHz.A 4×4 array prototype is designed to verify the concept.Measured results show that an impedance bandwidth of 63.73%is obtained.The pro-posed array has the merits of a wide bandwidth,a low profile,a low cost,and a small size,which is promis-ing for the application in millimeter wave wireless sys-tems.
基金supported by the National Key Technology R&D Program of China (2022YFB2902302)。
文摘Millimeter-wave(mmWave) and massive multiple-input multiple-output(MIMO) are broadly recognized as key enabling technologies for the fifth generation(5G) communication systems. In this paper, a low-complexity angle-delay parameters estimation(ADPE) algorithm was put forward for wideband mmWave systems with uniform planar arrays(UPAs). In particular, the ADPE algorithm effectively decouples the angle-delay parameters and converts the angle-delay estimation problem into three independent subproblems. Accordingly, the ability to devise an off-grid method based on discrete Fourier transform(DFT) with a closed-form solution for angle-delay estimation and potential path number acquisition can be realized. In actuality, only a limited number of potential paths are close to the true paths influenced by noise. Consequently, the removal of noise paths to acquire the corresponding true path gains through a sparsity adaptive path gains estimation(APGE) algorithm is postulated. Finally, the simulation results substantiate the effectiveness of ADPE and APGE algorithms.
基金supported by the Ministry of Science and Technology SKA Special Project(2020SKA0110202)the Special Project on Building a Science and Technology Innovation Center for South and Southeast Asia–International Joint Innovation Platform in Yunnan Province:"Yunnan Sino-Malaysian International Joint Laboratory of HF-VHF Advanced Radio Astronomy Technology"(202303AP140003)+4 种基金the National Natural Science Foundation of China (NSFC) Joint Fund for Astronomy (JFA) incubator program (U2031133)the International Partnership Program Project of the International Cooperation Bureau of the Chinese Academy of Sciences:"Belt and Road"Cooperation (114A11KYSB20200001)the Kunming Foreign (International) Cooperation Base Program:"Yunnan Observatory of the Chinese Academy of Sciences-University of Malaya Joint R&D Cooperation Base for Advanced Radio Astronomy Technology"(GHJD-2021022)the China-Malaysia Collaborative Research on Space Remote Sensing and Radio Astronomy Observation of Space Weather at Low and Middle Latitudes under the Key Special Project of the State Key R&D Program of the Ministry of Science and Technology for International Cooperation in Science,Technology and Innovation among Governments (2022YFE0140000)the High-precision calibration method for low-frequency radio interferometric arrays for the SKA project of the Ministry of Science and Technology(2020SKA0110300).
文摘Radio antenna arrays have many advantages for astronomical observations,such as high resolution,high sensitivity,multi-target simultaneous observation,and flexible beam formation.Problems surrounding key indices,such as sensitivity enhancement,scanning range extension,and sidelobe level suppression,need to be solved urgently.Here,we propose a sparse optimization scheme based on a genetic algorithm for a 64-array element planar radio antenna array.As optimization targets for the iterative process of the genetic algorithm,we use the maximum sidelobe levels and beamwidth of multiple cross-section patterns that pass through the main beam in three-dimensions,with the maximum sidelobe levels of the patterns at several different scanning angles.Element positions are adjusted for iterations,to select the optimal array configuration.Following sparse layout optimization,the simulated 64-element planar radio antenna array shows that the maximum sidelobe level decreases by 1.79 dB,and the beamwidth narrows by 3°.Within the scan range of±30°,after sparse array optimization,all sidelobe levels decrease,and all beamwidths narrow.This performance improvement can potentially enhance the sensitivity and spatial resolution of radio telescope systems.
基金supported by National Natural Science Fundation of China(No.10905047)
文摘The resistance and inductance of a wire array during an implosion are very important parameters of interest to：researchers. A variety of inductances and resistances directly affect the kinetic energy and resistance heat energy coupled from a pulsed-power generator. In this paper, the inductance and resistance of a planar wire array during the Z-pinch process are analyzed. The inductance is calculated from the data obtained by a time-resolved soft X-ray framed camera, while the resistance is calculated through the voltage and the current of the wire array load combined with the variety of the inductance. The results show that the resistance of the load increases with the development of the implosion, and reaches its maximum at 0.29 ± 0.16Ω near the pinched time.
文摘Two dynamics modes, named short ablation mode and long ablation mode, are observed in implosion experiments of planar wire array Z pinch on ＇QiangGuang-I＇ facility utilizing an optical streak camera. The long ablation mode has a lagged trajectory compared with the short ablation mode. For shot 10035 in a short ablation mode, the initial time of K-shell radiation is consistent with the interaction time for ablation plasma arriving at the centre of wire array, while for shot 10038 in long ablation mode, the initial time of K-shell radiation is about 10 ns earlier. In the two modes, the partial ablation plasma could traverse the wire array plane and then collide in the centre to form a dense plasma column with a diameter of 2.2 mm for shot 10035 and 1.5 mm for shot 10038.
基金Supported by the National Natural Science Foundation of China(61801024)。
文摘The concept of difference and sum co-array(DSCA)has become a new design idea for planar sparse arrays.Inspired by the shifting invariance property of DSCA,a specific configuration named here as the improved L-shaped array is proposed.Compared to other traditional 2D sparse array configurations such as 2D nested arrays and hourglass arrays,the proposed configuration has larger central consecutive ranges in its DSCA,thus increasing the DOF.At the same time,the mutual coupling effect is also reduced due to the enlarged spacing between the adjacent sensors.Simulations further demonstrate the superiority of the proposed arrays in terms of detection performance and estimation accuracy.
基金Supported by the National Natural Science Foundation of China(61801024)。
文摘The concept of difference and sum(diff-sum)coarray has attracted a lot of attentions in the estimation of direction-of-arrival(DOA)for the past few years,due to its high degrees-of-freedom(DOFs).A vectorized conjugate augmented MUSIC(VCA-MUSIC)algorithm is applied to generate an equivalent signal model which contains the virtual sensor positions of both the difference and sum of the physical sensors in the two-dimensional(2D)arrays,by utilizing both the spatial and temporal information.Besides,an augmented 2D coprime array configuration is presented with the basis on the concept of difference and sum coarray.By compressing the inter-element spacing of one subarray and introducing the proper separation between the two subarrays of 2D coprime array,the redundancy between the difference coarray and the sum one can be reduced so that more virtual sensors in both coarrays can make contributions to the DOFs.As a result,a much larger consecutive area in the diff-sum coarray can be achieved,which can significantly increase the DOFs.Numerical simulations verify the superiority of the proposed array configuration.
文摘Naturally suited array geometry for 360° coverage is the uniform circular array (UCA). A comparison of two types of uniform circular array configurations is presented in this paper. Due to its symmetrical geometry UCA is always targeted which results in minimal change inside lobe levels and beam width when scanned by a phased array antenna. Particle Swarm Optimization and Cuckoo algorithm are used for the calculation of complex weights of the array elements. Comparisons are drawn in the context of adaptive beam forming capabilities. Obtained results suggest that planar uniform circular array (9:10) using Cuckoo algorithm, has better beam forming properties with also reduced side lobe levels when compared to other geometry.
基金the National Natural Science Foundation of China(grant numbers 12172214 and 12102252)Fundamental Research Funds for the Central Universities(grant number USCAST2023-25).
文摘The performance of space antennas is significantly affected by thermal deformation owing to the harsh thermal environment in space.This results in potential degradation in pointing accuracy and overall functionality.This study focused on the analysis and control of thermal deformation in large-scale two-dimensional planar phased array antennas.Employing the finite element method,we developed a comprehensive thermal and structural model of the antenna.This enabled us to simulate the steady-state temperature field and the associated thermal deformation at various orbital positions.To address this deformation issue,we propose an innovative shape-control approach that utilizes distributed cable actuators.The shape control challenge was reformulated into a layered optimization problem concerning actuator placement and force application.In the outer optimization layer,a discrete particle swarm optimization algorithm was used to determine the optimal locations for the actuators.In the inner optimization layer,quadratic programming was subsequently applied to calculate the optimal control forces for each actuator.We validated the proposed method by numerically simulating a novel large-scale two-dimensional planar phased array antenna.The results demonstrated the effectiveness of our method in mitigating thermal deformation and maintaining the structural integrity and shape accuracy of the antennas.
基金supported in part by the Joint Research Fund for Guangzhou University and Hong Kong University of Science and Technology under Grant No.YH202203the Guangzhou Basic Research Program Municipal School(College)Joint Funding Project,the Research Project of Guizhou University for Talent Introduction under Grant No.[2020]61+7 种基金the Cultivation Project of Guizhou University under Grant No.[2019]56the Open Fund of Key Laboratory of Advanced Manufacturing Technology,Ministry of Education under Grant No.GZUAMT2021KF[01]the National Natural Science Foundation of China under Grant Nos.51978089 and 62171119the Key R&D Plan of Sichuan Science and Technology Department under Grant No.22ZDYF2726the Chengdu Normal University Scientific Research and Innovation Team under Grant Nos.CSCXTD2020B09,ZZBS201907,CS21ZC01the Open Project of Intelligent Manufacturing Industry Technology Research Institute under Grant No.ZNZZ2208the National Key Research and Development Program of China under Grant No.2020YFB1807201Key research and development plan of Jiangsu Province under Grant No.BE2021013-3.
文摘In this paper,we investigate the end-to-end performance of intelligent reflecting surface(IRS)-assisted wireless communication systems.We consider a system in which an IRS is deployed on a uniform planar array(UPA)configuration,including a large number of reflecting elements,where the transmitters and receivers are only equipped with a single antenna.Our objective is to analytically obtain the achievable ergodic rate,outage probability,and bit error rate(BER)of the system.Furthermore,to maximize the system’s signal-to-noise ratio(SNR),we design the phase shift of each reflecting element and derive the optimal reflection phase of the IRS based on the channel state information(CSI).We also derive the exact expression of the SNR probability density function(p.d.f.)and show that it follows a non-central Chi-square distribution.Using the p.d.f.,we then derive the theoretical results of the achievable rate,outage probability,and BER.The accuracy of the obtained theoretical results is also verified through numerical simulation.Itwas shown that the achievable rate,outage probability,and BER could be improved by increasing the number of reflecting elements and choosing an appropriate SNR regime.Furthermore,we also find that the IRS-assisted communication system achieves better performance than the existing end-to-end wireless communication.
基金the Bundesministerium fur Bildung und Forschung (BMBF) of Germany.
文摘A large planar microphone array, which consists of 111 microphones, was successfully developed. The positions of 111 microphones in the array were determined by a random optimization procedure for the largest possible amplification and dynamic range. The beam pattern of planar array was obtained by numerical calculation. This planar array was applied to measure a two-dimensional mapping of the sound sources on landing aircraft. It is shown that important airframe noise sources can be identified. The spectra and directivity of any interested noise source can also be obtained by this measurement.
基金supported by the National Natural Science Foundation of China(Grant Nos.61125105,61101048,61271147,and 61002037)National Basic Research Program of China("973" Program)(Grant Nos.2011CB933202,2014CB744605)
文摘To achieve a dopamine （DA） response with high sensitivity and high signal-to-noise ratio （S/N） with a patch-clamp system, polypyrrole/graphene （PPy/GR） nanocomposites were steadily electrodeposited by an electrochemical method on a planar mi- croelectrode array （pMEA） fabricated by a standard micromachining process. The electrodeposition process was carried out by chronopotentimetry measurement scanning from 0.1 to 0.8 C/cm2 at the current of 2 mA; 0.5 C/cm2 was found to be optimal. The pMEA modified by PPy/GR at the 0.5 C/cm2 exhibits remarkable properties; for instance, the standard deviation （SD） de- creases from 8.4614×10-al to 5.62×10 11 A, reduced by 33.52%, and the sensitivity increases from 2566.88 to 76114.65 gAmMcm2 , 29.65 times higher than the bare Pt （platinum）. A good linear relationship between the current and DA concentra- tion in the range of 0.30 to 61.71 grn was obtained, with a correlation coefficient of 0.997. The sensor is meaningful for neuro- science research and the treatment of neurological diseases.
文摘Purpose-The purpose of this paper is to propose radiating system by avoiding electromagnetic interference in unwanted directions and to radiate the energy in the required direction with an optimization technique.Design/methodology/approach-Practically,multiple,incompatible variables require concurrent boost on a synthesis of systematic antenna assemblage.The authors have worked out the main statistic penalty function to ensure all the restrictions.Here,MBPSO(Modified Binary Particle Swarm Optimization)is developed and introduced thin planar synthesis restriction.The sigmoid function is used to update the particle position.Different analytical demonstrations have been carried out,and the exhibited methods are predominant than the algorithms.Findings-A 20310 planar antenna array is synthesized using modified BPSO.The authors have suppressed the PSLL in two principal planes and as well as in the entire f plane.Numerical results state that MBPSO outperforms the other binary BPSO,BCSO,ACO,RGA,GAoptimization techniques.MBPSO achieved a51.84 dB PSLL level,whereas BPSO achieved48.57 dB with the same 50%thinning.Originality/value-Planar array antenna formation is one of the most complex syntheses because the array gets filled with more antenna elements.The machine-like complication and implementation of such an antenna arrangement with a broad opening would be expensive.It is not easy to control the required radiation patterns shape by using a uniform feeding network.To get better flexibility for sustaining the sidelobe levelheaded along with consistent amplitude distribution.So as far as prominence has been given to the evolutionary algorithm,find an ideal solution for objective array combinational problems.
基金The authors acknowledge the financial support by the 2019QN01C290Guangdong Basic and Applied Basic Research Foundation(No.2021A1515012235)+1 种基金the Outstanding Young Scholar at South China Normal University,Science and Technology Program of Guangzhou(No.2019050001)Guangdong Provincial Key Laboratory of Optical Information Materials and Technology(No.2017B030301007).
文摘Controlling the vapor-deposited nanoribbons to grow along a consistent orientation will enable the desired in situ integration of functional devices,representing a major technological advance compared to post-growth processing strategies.In this work,ntype F_(16)CuPc molecules are self-assembled into horizontally-oriented nanoribbons with a consistent growth axis after creating periodic hydrophobic nanogrooves on a sapphire surface.Consequently,electrodes are deposited directly on the growth substrate to enable in situ fabrication of photodetectors.Depending on the deposited electrodes,these horizontally-oriented nanoribbons are connected to form a monolithic photodetector with a large sensing area or an on-chip array of photodetectors with multiple detector units.This in situ integration strategy avoids potential structural damage and contamination from impurities associated with post-growth processing steps.Therefore,the vapor-deposited nanoribbons can retain their high quality during the device manufacturing process,which contributes to performance improvement.As a result,the in-situ integrated F_(16)CuPc photodetectors exhibit a sensitive response in the ultraviolet-visible-near-infrared(UV-vis-NIR)region.The response time is on the order of tens of milliseconds,the fastest record ever for the F_(16)CuPc-based photodetectors.Furthermore,statistics from an array of 6×6 photodetectors show little variation in their sensitivity and response time,and hence this in situ fabrication scheme will contribute to the implementation of on-chip integrated photodetectors with consistent performance based on bottom-up nanoribbons.Overall,this self-oriented growth provides a versatile option to achieve desired in-situ integrated functional devices based on bottom-up nanoribbons.
