This paper considers a multi-antenna ac-cess point(AP)transmitting secrecy message to a single-antenna user in the presence of a single-antenna illegal eavesdropper(Eve)and proposes a double ac-tive reconfigurable int...This paper considers a multi-antenna ac-cess point(AP)transmitting secrecy message to a single-antenna user in the presence of a single-antenna illegal eavesdropper(Eve)and proposes a double ac-tive reconfigurable intelligent surfaces(DARISs)as-sisted physical layer security(PLS)scheme denoted by DARISs-PLS to protect the secrecy message trans-mission.We formulate a secrecy rate maximization problem for the proposed DARISs-PLS scheme by considering a power budget constraint for the two ac-tive reconfigurable intelligent surfaces(ARISs)and AP.To address the formulated optimization problem,we jointly optimize the reflecting coefficients for the two ARISs and the beamforming at the AP in an it-erative manner by applying Dinkelbach based alter-nating optimization(AO)algorithm and a customized iterative algorithm together with the semidefinite re-laxation(SDR).Numerical results reveal that the pro-posed DARISs-PLS scheme outperforms the dou-ble passive reconfigurable intelligent surfaces-assisted PLS method(DPRISs-PLS)and single ARIS-assisted PLS method(SARIS-PLS)in terms of the secrecy rate.展开更多
In this paper,we examine an illegal wireless communication network consisting of an illegal user receiving illegal signals from an illegal station and propose an active reconfigurable intelligent surface(ARIS)-assiste...In this paper,we examine an illegal wireless communication network consisting of an illegal user receiving illegal signals from an illegal station and propose an active reconfigurable intelligent surface(ARIS)-assisted multi-antenna jamming(MAJ)scheme denoted by ARIS-MAJ to interfere with the illegal signal transmission.In order to strike a balance between the jamming performance and the energy consumption,we consider a so-called jamming energy efficiency(JEE)which is defined as the ratio of achievable rate reduced by the jamming system to the corresponding power consumption.We formulate an optimization problem to maximize the JEE for the proposed ARIS-MAJ scheme by jointly optimizing the jammer’s beamforming vector and ARIS’s reflecting coefficients under the constraint that the jamming power received at the illegal user is lower than the illegal user’s detection threshold.To address the non-convex optimization problem,we propose the Dinkelbach-based alternating optimization(AO)algorithm by applying the semidefinite relaxation(SDR)algorithm with Gaussian randomization method.Numerical results validate that the proposed ARIS-MAJ scheme outperforms the passive reconfigurable intelligent surface(PRIS)-assisted multi-antenna jamming(PRIS-MAJ)scheme and the conventional multiantenna jamming scheme without RIS(NRIS-MAJ)in terms of the JEE.展开更多
随着城市化交通的发展,感知计算在智慧城市起着重要的作用。针对传统密度聚类算法无法适配海量出租车GPS轨迹数据及可视化的问题,提出了BCS-DBSCAN(Big-Data Cluster Center Statistics Density-Based Spatial Clustering of Applicatio...随着城市化交通的发展,感知计算在智慧城市起着重要的作用。针对传统密度聚类算法无法适配海量出租车GPS轨迹数据及可视化的问题,提出了BCS-DBSCAN(Big-Data Cluster Center Statistics Density-Based Spatial Clustering of Applications with Noise)聚类算法。该算法可以对轨迹数据切分及并行化聚类且能够提取最大密度簇心,并将结果适配可视化模型。实验结果表明,与其它流行的方法相比,在海量数据下提取城市载客热点区域的聚类速度、精确化及可视化方面具有十分显著的优势,对进一步提升城市规划、提高交通效率提供了重要的决策信息。展开更多
High quality gallium oxide(Ga_2O_3) thin films are deposited by remote plasma-enhanced atomic layer deposition(RPEALD) with trimethylgallium(TMG) and oxygen plasma as precursors. By introducing in-situ NH3 plasma pret...High quality gallium oxide(Ga_2O_3) thin films are deposited by remote plasma-enhanced atomic layer deposition(RPEALD) with trimethylgallium(TMG) and oxygen plasma as precursors. By introducing in-situ NH3 plasma pretreatment on the substrates, the deposition rate of Ga_2O_3 films on Si and GaN are remarkably enhanced, reached to 0.53 and 0.46 ?/cycle at 250 °C,respectively. The increasing of deposition rate is attributed to more hydroxyls(–OH) generated on the substrate surfaces after NH3 pretreatment, which has no effect on the stoichiometry and surface morphology of the oxide films, but only modifies the surface states of substrates by enhancing reactive site density. Ga_2O_3 film deposited on GaN wafer is crystallized at 250 °C, with an epitaxial interface between Ga_2O_3 and GaN clearly observed. This is potentially very important for reducing the interface state density through high quality passivation.展开更多
A random simulation method was used for treatment of systems of Volterra integral equations of the second kind. Firstly, a linear algebra system was obtained by discretization using quadrature formula. Secondly, this ...A random simulation method was used for treatment of systems of Volterra integral equations of the second kind. Firstly, a linear algebra system was obtained by discretization using quadrature formula. Secondly, this algebra system was solved by using relaxed Monte Carlo method with importance sampling and numerical approximation solutions of the integral equations system were achieved. It is theoretically proved that the validity of relaxed Monte Carlo method is based on importance sampling to solve the integral equations system. Finally, some numerical examples from literatures are given to show the efficiency of the method.展开更多
In this study,we propose and demonstrate an all-fiber orbital-angular-momentum(OAM)mode encoding system,where through helical fiber gratings(HFGs),binary symbols are encoded to or decoded from two OAM modes with topol...In this study,we propose and demonstrate an all-fiber orbital-angular-momentum(OAM)mode encoding system,where through helical fiber gratings(HFGs),binary symbols are encoded to or decoded from two OAM modes with topological charges(TCs)of-1 and+1,respectively.We experimentally validate that the OAM mode generated by a clockwise-helix HFG(cHFG)can be converted back into fundamental mode by using an HFG with a helix orientation opposite to that of the cHFG,i.e.,ccHFG.Benefited from utilization of the HFGs,the proposed OAM mode encoding system has a low cost,low insertion loss,high mode conversion efficiency,and polarization independence.To the best of our knowledge,this is the first demonstration of the HFGs-based all-fiber OAM mode encoding/decoding scheme,which may find potential applications in optical communication and quantum communication as well.展开更多
Solar-driven interfacial evaporation holds great potential for seawater desalination,yet its efficiency and long-term viability are critically hindered by salt crystallization.Herein,we develop a spiral-layered hydrog...Solar-driven interfacial evaporation holds great potential for seawater desalination,yet its efficiency and long-term viability are critically hindered by salt crystallization.Herein,we develop a spiral-layered hydrogel(SLH)solar evaporator to overcome these persistent challenges.The SLH features a layered architecture with nonuniform pore sizes across its upper and lower layers,ensuring adequate water supply to the evaporation interface while minimizing heat loss to the bulk water.Coupled with high light absorption and reduced evaporation enthalpy,the SLH achieves an impressive evaporation rate of 4.7 kg·m^(-2)·h^(-1).The Janus structure of the SLH suppresses salt crystallization on the surface,while the omnidirectional groove configuration and spiral flow dynamics synergistically prevent salt ion accumulation within the pores.Furthermore,the electronegativity of graphdiyne(GDY)surface together with conjugate two-dimensional plane,act as a barrier to chloride ion infiltration.In a 20 wt.%NaCl solution,the cost-effective SLH maintains a robust evaporation rate of 4.23 kg·m^(-2)·h^(-1)over an extended period of 20 days.Outdoor validation with a cylindrical prototype demonstrated a maximum freshwater collection rate of 1.8 L·m^(-2)·h^(-1).Such functional design and salt management strategy may provide possible prescriptions to salt accumulation challenges,establishing a foundation for sustainable and high-efficiency water production systems.展开更多
Background：Differentiating benign from malignant sinonsal lesions is essential for treatment planning as well as determining the patient＇s prognosis,but the differentiation is often difficult in clinical practice.Th...Background：Differentiating benign from malignant sinonsal lesions is essential for treatment planning as well as determining the patient＇s prognosis,but the differentiation is often difficult in clinical practice.The study aimed to determine whether the combination of diffusion-weighted （DW） and dynamic contrast-enhanced magnetic resonance imaging （DCE-MRI） can improve the performance in differentiating benign from malignant sinonasal tumors.Methods：This retrospective study included 197 consecutive patients with sinonasal tumors （116 malignant tumors and 81 benign tumors）.All patients underwent both DW and DCE-MRI in a 3-T magnetic resonance scanner.Two different settings ofb values （0,700 and 0,1000 s/mm^2） and two different strategies of region of interest （ROI） including whole slice （WS） and partial slice （PS） were used to calculate apparent diffusion coefficients （ADCs）.A DW parameter with WS ADCsb0.1000 and two DCE-MRI parameters （time intensity curve [TIC] and time to peak enhancement [Tpeak]） were finally combined to use in differentiating the benign from the malignant tumors in this study.Results：The mean ADCs of malignant sinonasal tumors （WS ADCsb0,1000=1.084 × 10^-3 mm^2/s） were significantly lower than those of benign tumors （WS ADCsb0,1000=1.617 × 10^-3 mm^2/s,P 〈 0.001）.The accuracy using WS ADCsb0,1000 alone was 83.7% in differentiating the benign from the malignant tumors （85.3% sensitivity,81.2% specificity,86.4% positive predictive value [PPV],and 79.5% negative predictive value [NPV]）.The accuracy using DCE with Tpeak and TIC alone was 72.1% （69.1% sensitivity,74.1% specificity,77.5% PPV,and 65.1% NPV）.Using DW-MRI parameter was superior than using DCE parameters in differentiation between benign and malignant sinonasal tumors （P 〈 0.001）.The accuracy was 87.3% （90.5% sensitivity,82.7% specificity,88.2% PPV,and 85.9% NPV） using DW-MRI combined with DCE-MRI,which was superior than that using DCE-MRI alone or using DW-MRI alone （both P 〈 0.001） in differentiating the benign from the malignant tumors.Conclusions：Diffusion-weighted combined with DCE-MRI can improve imaging performance in differentiating benign from malignant sinonasal tumors,which has the potential to improve diagnostic accuracy and to provide added value in the management for these tumors.展开更多
基金supported in part by the National Natural Science Foundation of China under Grant 62071253,Grant 62371252 and Grant 62271268in part by the Jiangsu Provincial Key Research and Development Program under Grant BE2022800in part by the Jiangsu Provincial 333 Talent Project.
文摘This paper considers a multi-antenna ac-cess point(AP)transmitting secrecy message to a single-antenna user in the presence of a single-antenna illegal eavesdropper(Eve)and proposes a double ac-tive reconfigurable intelligent surfaces(DARISs)as-sisted physical layer security(PLS)scheme denoted by DARISs-PLS to protect the secrecy message trans-mission.We formulate a secrecy rate maximization problem for the proposed DARISs-PLS scheme by considering a power budget constraint for the two ac-tive reconfigurable intelligent surfaces(ARISs)and AP.To address the formulated optimization problem,we jointly optimize the reflecting coefficients for the two ARISs and the beamforming at the AP in an it-erative manner by applying Dinkelbach based alter-nating optimization(AO)algorithm and a customized iterative algorithm together with the semidefinite re-laxation(SDR).Numerical results reveal that the pro-posed DARISs-PLS scheme outperforms the dou-ble passive reconfigurable intelligent surfaces-assisted PLS method(DPRISs-PLS)and single ARIS-assisted PLS method(SARIS-PLS)in terms of the secrecy rate.
基金supported in part by the National Natural Science Foundation of China under Grant 62071253,Grant 62371252 and Grant 62271268in part by the Jiangsu Provincial Key Research and Development Program under Grant BE2022800in part by the Jiangsu Provincial 333 Talent Project.
文摘In this paper,we examine an illegal wireless communication network consisting of an illegal user receiving illegal signals from an illegal station and propose an active reconfigurable intelligent surface(ARIS)-assisted multi-antenna jamming(MAJ)scheme denoted by ARIS-MAJ to interfere with the illegal signal transmission.In order to strike a balance between the jamming performance and the energy consumption,we consider a so-called jamming energy efficiency(JEE)which is defined as the ratio of achievable rate reduced by the jamming system to the corresponding power consumption.We formulate an optimization problem to maximize the JEE for the proposed ARIS-MAJ scheme by jointly optimizing the jammer’s beamforming vector and ARIS’s reflecting coefficients under the constraint that the jamming power received at the illegal user is lower than the illegal user’s detection threshold.To address the non-convex optimization problem,we propose the Dinkelbach-based alternating optimization(AO)algorithm by applying the semidefinite relaxation(SDR)algorithm with Gaussian randomization method.Numerical results validate that the proposed ARIS-MAJ scheme outperforms the passive reconfigurable intelligent surface(PRIS)-assisted multi-antenna jamming(PRIS-MAJ)scheme and the conventional multiantenna jamming scheme without RIS(NRIS-MAJ)in terms of the JEE.
文摘随着城市化交通的发展,感知计算在智慧城市起着重要的作用。针对传统密度聚类算法无法适配海量出租车GPS轨迹数据及可视化的问题,提出了BCS-DBSCAN(Big-Data Cluster Center Statistics Density-Based Spatial Clustering of Applications with Noise)聚类算法。该算法可以对轨迹数据切分及并行化聚类且能够提取最大密度簇心,并将结果适配可视化模型。实验结果表明,与其它流行的方法相比,在海量数据下提取城市载客热点区域的聚类速度、精确化及可视化方面具有十分显著的优势,对进一步提升城市规划、提高交通效率提供了重要的决策信息。
基金supported jointly by the National Natural Science Foundation of China(Nos.61674165,61604167,61574160,61704183,61404159,11604366)the Natural Science Foundation of Jiangsu Province(Nos.BK20170432,BK20160397,BK20140394)+2 种基金the National Key R&D Program of China(No.2016YFB0401803)the Strategic Priority Re-search Program of the Chinese Academy of Science(No.XDA09020401)the support at the Platform for Characterization&Test,Suzhou Institute of Nano-Tech and Nano-Bionics(SINANO),Chinese Academy of Sciences
文摘High quality gallium oxide(Ga_2O_3) thin films are deposited by remote plasma-enhanced atomic layer deposition(RPEALD) with trimethylgallium(TMG) and oxygen plasma as precursors. By introducing in-situ NH3 plasma pretreatment on the substrates, the deposition rate of Ga_2O_3 films on Si and GaN are remarkably enhanced, reached to 0.53 and 0.46 ?/cycle at 250 °C,respectively. The increasing of deposition rate is attributed to more hydroxyls(–OH) generated on the substrate surfaces after NH3 pretreatment, which has no effect on the stoichiometry and surface morphology of the oxide films, but only modifies the surface states of substrates by enhancing reactive site density. Ga_2O_3 film deposited on GaN wafer is crystallized at 250 °C, with an epitaxial interface between Ga_2O_3 and GaN clearly observed. This is potentially very important for reducing the interface state density through high quality passivation.
文摘A random simulation method was used for treatment of systems of Volterra integral equations of the second kind. Firstly, a linear algebra system was obtained by discretization using quadrature formula. Secondly, this algebra system was solved by using relaxed Monte Carlo method with importance sampling and numerical approximation solutions of the integral equations system were achieved. It is theoretically proved that the validity of relaxed Monte Carlo method is based on importance sampling to solve the integral equations system. Finally, some numerical examples from literatures are given to show the efficiency of the method.
基金National Key Research and Development Program of China(2023YFB2804900)National Natural Science Foundation of China(62375134)+2 种基金Japan Society for the Promotion of Science(JP24K21609,JP23K22816)Amano Institute of TechnologyNatural Science Research of Jiangsu Higher Education Institutions of China(22KJB510030)。
文摘In this study,we propose and demonstrate an all-fiber orbital-angular-momentum(OAM)mode encoding system,where through helical fiber gratings(HFGs),binary symbols are encoded to or decoded from two OAM modes with topological charges(TCs)of-1 and+1,respectively.We experimentally validate that the OAM mode generated by a clockwise-helix HFG(cHFG)can be converted back into fundamental mode by using an HFG with a helix orientation opposite to that of the cHFG,i.e.,ccHFG.Benefited from utilization of the HFGs,the proposed OAM mode encoding system has a low cost,low insertion loss,high mode conversion efficiency,and polarization independence.To the best of our knowledge,this is the first demonstration of the HFGs-based all-fiber OAM mode encoding/decoding scheme,which may find potential applications in optical communication and quantum communication as well.
基金supported by the National Natural ScienceFoundation of China(Nos.52122208 and 52188101)the NationalKey Research and Development Program of China(Nos.2018YFA0703503,2021YFA1200196,2022YFA1204500,and2022YFA1204502)+3 种基金the National Natural Science Foundation ofChina(Nos.52072031,51991340,and 51991342)the OverseasExpertise Introduction Projects for Discipline Innovation(No.B14003)the State Key Laboratory for Advanced Metals andMaterials(Nos.2018Z-03 and 2019Z-04)the FundamentalResearch Funds for the Central Universities(Nos.ONXM20210013,FRF-TP-2021-03C1,and FRF-TP-20-008A3).
文摘Solar-driven interfacial evaporation holds great potential for seawater desalination,yet its efficiency and long-term viability are critically hindered by salt crystallization.Herein,we develop a spiral-layered hydrogel(SLH)solar evaporator to overcome these persistent challenges.The SLH features a layered architecture with nonuniform pore sizes across its upper and lower layers,ensuring adequate water supply to the evaporation interface while minimizing heat loss to the bulk water.Coupled with high light absorption and reduced evaporation enthalpy,the SLH achieves an impressive evaporation rate of 4.7 kg·m^(-2)·h^(-1).The Janus structure of the SLH suppresses salt crystallization on the surface,while the omnidirectional groove configuration and spiral flow dynamics synergistically prevent salt ion accumulation within the pores.Furthermore,the electronegativity of graphdiyne(GDY)surface together with conjugate two-dimensional plane,act as a barrier to chloride ion infiltration.In a 20 wt.%NaCl solution,the cost-effective SLH maintains a robust evaporation rate of 4.23 kg·m^(-2)·h^(-1)over an extended period of 20 days.Outdoor validation with a cylindrical prototype demonstrated a maximum freshwater collection rate of 1.8 L·m^(-2)·h^(-1).Such functional design and salt management strategy may provide possible prescriptions to salt accumulation challenges,establishing a foundation for sustainable and high-efficiency water production systems.
基金This work was supported by Beijing Excellent Talents Foundation （No. 2010D003034000033） Beijing Municipal Natural Science Foundation （No. 7112030）, and high levels of health technical personnel in Beijing city （No. 2011-3-047）.
文摘Background：Differentiating benign from malignant sinonsal lesions is essential for treatment planning as well as determining the patient＇s prognosis,but the differentiation is often difficult in clinical practice.The study aimed to determine whether the combination of diffusion-weighted （DW） and dynamic contrast-enhanced magnetic resonance imaging （DCE-MRI） can improve the performance in differentiating benign from malignant sinonasal tumors.Methods：This retrospective study included 197 consecutive patients with sinonasal tumors （116 malignant tumors and 81 benign tumors）.All patients underwent both DW and DCE-MRI in a 3-T magnetic resonance scanner.Two different settings ofb values （0,700 and 0,1000 s/mm^2） and two different strategies of region of interest （ROI） including whole slice （WS） and partial slice （PS） were used to calculate apparent diffusion coefficients （ADCs）.A DW parameter with WS ADCsb0.1000 and two DCE-MRI parameters （time intensity curve [TIC] and time to peak enhancement [Tpeak]） were finally combined to use in differentiating the benign from the malignant tumors in this study.Results：The mean ADCs of malignant sinonasal tumors （WS ADCsb0,1000=1.084 × 10^-3 mm^2/s） were significantly lower than those of benign tumors （WS ADCsb0,1000=1.617 × 10^-3 mm^2/s,P 〈 0.001）.The accuracy using WS ADCsb0,1000 alone was 83.7% in differentiating the benign from the malignant tumors （85.3% sensitivity,81.2% specificity,86.4% positive predictive value [PPV],and 79.5% negative predictive value [NPV]）.The accuracy using DCE with Tpeak and TIC alone was 72.1% （69.1% sensitivity,74.1% specificity,77.5% PPV,and 65.1% NPV）.Using DW-MRI parameter was superior than using DCE parameters in differentiation between benign and malignant sinonasal tumors （P 〈 0.001）.The accuracy was 87.3% （90.5% sensitivity,82.7% specificity,88.2% PPV,and 85.9% NPV） using DW-MRI combined with DCE-MRI,which was superior than that using DCE-MRI alone or using DW-MRI alone （both P 〈 0.001） in differentiating the benign from the malignant tumors.Conclusions：Diffusion-weighted combined with DCE-MRI can improve imaging performance in differentiating benign from malignant sinonasal tumors,which has the potential to improve diagnostic accuracy and to provide added value in the management for these tumors.
