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 paper,we study a diffusive predator-prey model with hyperbolic mortality and prey-taxis under homogeneous Neumann boundary condition.We first analyze the influence of prey-taxis on the local stability of const...In this paper,we study a diffusive predator-prey model with hyperbolic mortality and prey-taxis under homogeneous Neumann boundary condition.We first analyze the influence of prey-taxis on the local stability of constant equilibria.It turns out that prey-taxis has influence on the stability of the unique positive constant equilibrium,but has no influence on the stability of the trivial equilibrium and the semi-trivial equilibrium.We then derive Hopf bifurcation and steady state bifurcation related to prey-taxis,which imply that the prey-taxis plays an important role in the dynamics.展开更多
An acidic extracellular polysaccharide(EPS)was gained from Stropharia rugosoannulata fermentation broth by the alcohol precipitate method.Sulfated derivative of EPS(S-EPS)was gained by chlorosulfonic acid-pyridine met...An acidic extracellular polysaccharide(EPS)was gained from Stropharia rugosoannulata fermentation broth by the alcohol precipitate method.Sulfated derivative of EPS(S-EPS)was gained by chlorosulfonic acid-pyridine method and the conditions were as follows:pyridine as the reaction solvent,temperature 80°C,and reaction time 90 min.The chemical structure and chain conformation of EPS and S-EPS were characterized by FT-IR,NMR and size exclusion chromatography(SEC)coupled with multi-angle laser light scattering(MALLS)detection.FT-IR spectra indicated the sulfated group was linked to the polymer.The EPS mainly consists of mannose,glucose and glucuronic acid,and the glycosidic bond type is mainly(1→4)-linked and(1→6)-linked.C6 and C2 were substituted by sulfate groups.The EPS was degraded into smaller molecular weight(Mw)polysaccharides with the larger molecular size(Rg)after sulfation and S-EPS has better hydrophilicity.Moreover,the sulfated derivative S-EPS was found to have a better scavenging ability on hydroxyl radicals than EPS.It proved that the chemical modification of S.rugosoannulata polysaccharides by sulfation effectively enhanced their antioxidant activity.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
In this work,we have successfully grown high quality epitaxialβ-Ga_(2)O_(3)thin films onβ-Ga_(2)O_(3)(100)and Al_(2)O_(3)(0001)substrates using pulsed laser deposition(PLD).By optimizing temperature and oxygen press...In this work,we have successfully grown high quality epitaxialβ-Ga_(2)O_(3)thin films onβ-Ga_(2)O_(3)(100)and Al_(2)O_(3)(0001)substrates using pulsed laser deposition(PLD).By optimizing temperature and oxygen pressure,the best conditions were found to be 650-700℃and 0.5 Pa.To further improve the quality of hetero-epitaxialβ-Ga_(2)O_(3),the sapphire substrates were pretreated for atomic terraced surface by chemical cleaning and high temperature annealing.From the optical transmittance measurements,the films grown at 600-750℃exhibit a clear absorption edge at deep ultraviolet region around 250-275 nm wavelength.High resolution transmission electron microscope(HRTEM)images and X-ray diffraction(XRD)patterns demonstrate thatβ-Ga_(2)O_(3)(-201)//Al_(2)O_(3)(0001)epitaxial texture dominated the epitaxial oxide films on sapphire substrate,which opens up the possibilities of high power electric devices.展开更多
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supported by the Natural Science Foundation of Shandong Province,China(Nos.ZR2021MA028 and ZR2021MA025).
文摘In this paper,we study a diffusive predator-prey model with hyperbolic mortality and prey-taxis under homogeneous Neumann boundary condition.We first analyze the influence of prey-taxis on the local stability of constant equilibria.It turns out that prey-taxis has influence on the stability of the unique positive constant equilibrium,but has no influence on the stability of the trivial equilibrium and the semi-trivial equilibrium.We then derive Hopf bifurcation and steady state bifurcation related to prey-taxis,which imply that the prey-taxis plays an important role in the dynamics.
基金We gratefully acknowledge the financial supports from the Program for Innovative Research Team(in Science and Technology)at the University of Henan Province(20IRTSTHN022)Major Public Welfare Projects in Henan Province(201300110200).
文摘An acidic extracellular polysaccharide(EPS)was gained from Stropharia rugosoannulata fermentation broth by the alcohol precipitate method.Sulfated derivative of EPS(S-EPS)was gained by chlorosulfonic acid-pyridine method and the conditions were as follows:pyridine as the reaction solvent,temperature 80°C,and reaction time 90 min.The chemical structure and chain conformation of EPS and S-EPS were characterized by FT-IR,NMR and size exclusion chromatography(SEC)coupled with multi-angle laser light scattering(MALLS)detection.FT-IR spectra indicated the sulfated group was linked to the polymer.The EPS mainly consists of mannose,glucose and glucuronic acid,and the glycosidic bond type is mainly(1→4)-linked and(1→6)-linked.C6 and C2 were substituted by sulfate groups.The EPS was degraded into smaller molecular weight(Mw)polysaccharides with the larger molecular size(Rg)after sulfation and S-EPS has better hydrophilicity.Moreover,the sulfated derivative S-EPS was found to have a better scavenging ability on hydroxyl radicals than EPS.It proved that the chemical modification of S.rugosoannulata polysaccharides by sulfation effectively enhanced their antioxidant activity.
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.
基金the National Natural Science Foundation of China(61674165,61604167,61574160,61704183,61404159,11604366)the Natural Science Foundation of Jiangsu Province(BK20170432,BK20160397,BK20140394)+2 种基金the National Key R&D Program of China(2016YFB0401803)the Strategic Priority Research Program of the Chinese Academy of Science(XDA09020401)XRD,AFM and TEM experiments were performed at the Platform for Characterization&Test,Suzhou Institute of Nano-Tech and Nano-Bionics(SINANO),Chinese Academy of Sciences.
文摘In this work,we have successfully grown high quality epitaxialβ-Ga_(2)O_(3)thin films onβ-Ga_(2)O_(3)(100)and Al_(2)O_(3)(0001)substrates using pulsed laser deposition(PLD).By optimizing temperature and oxygen pressure,the best conditions were found to be 650-700℃and 0.5 Pa.To further improve the quality of hetero-epitaxialβ-Ga_(2)O_(3),the sapphire substrates were pretreated for atomic terraced surface by chemical cleaning and high temperature annealing.From the optical transmittance measurements,the films grown at 600-750℃exhibit a clear absorption edge at deep ultraviolet region around 250-275 nm wavelength.High resolution transmission electron microscope(HRTEM)images and X-ray diffraction(XRD)patterns demonstrate thatβ-Ga_(2)O_(3)(-201)//Al_(2)O_(3)(0001)epitaxial texture dominated the epitaxial oxide films on sapphire substrate,which opens up the possibilities of high power electric devices.
