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J P R Wells - One of the best experts on this subject based on the ideXlab platform.

  • absorption spectra defect site distribution and upconversion excitation spectra of caf2 srf2 baf2 yb3 er3 nanoparticles
    Journal of Alloys and Compounds, 2020
    Co-Authors: Sangeetha Balabhadra, Michael F Reid, Vladimir B Golovko, J P R Wells
    Abstract:

    Abstract We report studies of the Yb3+ site distribution in Er3+ co-doped upconverting alkaline earth fluoride nanoparticles using high-resolution absorption measurements. It is found that Yb3+ single ion cubic (Oh) sites and preferentially formed Clusters are the dominant centres for moderate dopant concentrations. At higher concentrations, and for larger particle sizes, a minority C4v(F−) centre is also observed. Furthermore, the behaviour of Yb3+ Cluster centres, whose primary absorption band is centred at 10205 cm−1 (in near resonance with 980 nm laser diodes) was studied by tuning the metal cation in the host lattice from Ca2+→Sr2+→Ba2+. For co-doped materials, with Heterogeneous Cluster centres, Er3+ upconversion fluorescence was observed upon selective excitation of Yb3+, resulting in a strong visible emission from 2H11/2, 4S3/2 and 4F9/2 multiplets. By monitoring the Er3+ fluorescence, whilst scanning a laser through the wavelength dependent Yb3+ absorption, we obtain an excitation spectrum for these Heterogeneous Cluster centres. Spectral features associated with excited state absorption as well as significant deviation from the linear absorption spectra are observed.

Sangeetha Balabhadra - One of the best experts on this subject based on the ideXlab platform.

  • absorption spectra defect site distribution and upconversion excitation spectra of caf2 srf2 baf2 yb3 er3 nanoparticles
    Journal of Alloys and Compounds, 2020
    Co-Authors: Sangeetha Balabhadra, Michael F Reid, Vladimir B Golovko, J P R Wells
    Abstract:

    Abstract We report studies of the Yb3+ site distribution in Er3+ co-doped upconverting alkaline earth fluoride nanoparticles using high-resolution absorption measurements. It is found that Yb3+ single ion cubic (Oh) sites and preferentially formed Clusters are the dominant centres for moderate dopant concentrations. At higher concentrations, and for larger particle sizes, a minority C4v(F−) centre is also observed. Furthermore, the behaviour of Yb3+ Cluster centres, whose primary absorption band is centred at 10205 cm−1 (in near resonance with 980 nm laser diodes) was studied by tuning the metal cation in the host lattice from Ca2+→Sr2+→Ba2+. For co-doped materials, with Heterogeneous Cluster centres, Er3+ upconversion fluorescence was observed upon selective excitation of Yb3+, resulting in a strong visible emission from 2H11/2, 4S3/2 and 4F9/2 multiplets. By monitoring the Er3+ fluorescence, whilst scanning a laser through the wavelength dependent Yb3+ absorption, we obtain an excitation spectrum for these Heterogeneous Cluster centres. Spectral features associated with excited state absorption as well as significant deviation from the linear absorption spectra are observed.

Michael F Reid - One of the best experts on this subject based on the ideXlab platform.

  • absorption spectra defect site distribution and upconversion excitation spectra of caf2 srf2 baf2 yb3 er3 nanoparticles
    Journal of Alloys and Compounds, 2020
    Co-Authors: Sangeetha Balabhadra, Michael F Reid, Vladimir B Golovko, J P R Wells
    Abstract:

    Abstract We report studies of the Yb3+ site distribution in Er3+ co-doped upconverting alkaline earth fluoride nanoparticles using high-resolution absorption measurements. It is found that Yb3+ single ion cubic (Oh) sites and preferentially formed Clusters are the dominant centres for moderate dopant concentrations. At higher concentrations, and for larger particle sizes, a minority C4v(F−) centre is also observed. Furthermore, the behaviour of Yb3+ Cluster centres, whose primary absorption band is centred at 10205 cm−1 (in near resonance with 980 nm laser diodes) was studied by tuning the metal cation in the host lattice from Ca2+→Sr2+→Ba2+. For co-doped materials, with Heterogeneous Cluster centres, Er3+ upconversion fluorescence was observed upon selective excitation of Yb3+, resulting in a strong visible emission from 2H11/2, 4S3/2 and 4F9/2 multiplets. By monitoring the Er3+ fluorescence, whilst scanning a laser through the wavelength dependent Yb3+ absorption, we obtain an excitation spectrum for these Heterogeneous Cluster centres. Spectral features associated with excited state absorption as well as significant deviation from the linear absorption spectra are observed.

Vladimir B Golovko - One of the best experts on this subject based on the ideXlab platform.

  • absorption spectra defect site distribution and upconversion excitation spectra of caf2 srf2 baf2 yb3 er3 nanoparticles
    Journal of Alloys and Compounds, 2020
    Co-Authors: Sangeetha Balabhadra, Michael F Reid, Vladimir B Golovko, J P R Wells
    Abstract:

    Abstract We report studies of the Yb3+ site distribution in Er3+ co-doped upconverting alkaline earth fluoride nanoparticles using high-resolution absorption measurements. It is found that Yb3+ single ion cubic (Oh) sites and preferentially formed Clusters are the dominant centres for moderate dopant concentrations. At higher concentrations, and for larger particle sizes, a minority C4v(F−) centre is also observed. Furthermore, the behaviour of Yb3+ Cluster centres, whose primary absorption band is centred at 10205 cm−1 (in near resonance with 980 nm laser diodes) was studied by tuning the metal cation in the host lattice from Ca2+→Sr2+→Ba2+. For co-doped materials, with Heterogeneous Cluster centres, Er3+ upconversion fluorescence was observed upon selective excitation of Yb3+, resulting in a strong visible emission from 2H11/2, 4S3/2 and 4F9/2 multiplets. By monitoring the Er3+ fluorescence, whilst scanning a laser through the wavelength dependent Yb3+ absorption, we obtain an excitation spectrum for these Heterogeneous Cluster centres. Spectral features associated with excited state absorption as well as significant deviation from the linear absorption spectra are observed.

Haitao Zhang - One of the best experts on this subject based on the ideXlab platform.

  • CloudCom - Proactive Data Placement for Surveillance Video Processing in Heterogeneous Cluster
    2016 IEEE International Conference on Cloud Computing Technology and Science (CloudCom), 2016
    Co-Authors: Haitao Zhang, Bin Xu, Huadong Ma
    Abstract:

    Large-scale surveillance video analytic is a kind of typical big data application. The Spark framework combined with Hadoop Distributed File System (HDFS) is a promising solution for the efficient surveillance video processing. However, the current HDFS distributes data to multiple nodes according to the disk space availability, and this data placement mode will lead to the serious skew of the video task completion time and the performance degradation of the distributed video processing in the Heterogeneous Spark Cluster. In this paper, we firstly design a distributed surveillance video processing platform architecture which supports the seamless integration with the standard video surveillance system. Our platform uses the Spark computing framework over the data stored in HDFS. Then, we propose a novel proactive video data placement strategy to schedule the input video data into the appropriate Cluster node adaptively. Our strategy adopts a novel Computing Time Prediction Model (CTPM) which can accurately estimate the execution time of the video processing task by incorporating the several important video task features. In our strategy, an Initial Data Placement Algorithm (IDPA) is used to place the data needed by the video processing jobs on the appropriate Cluster node in the process of the initial data loading, and then a Data Rebalance Algorithm (DRA) is further used to schedule the data for the workload balancing during the process of the job execution. Finally, we build a distributed surveillance video processing system according to the proposed platform architecture and conduct the extensive experiments. The experimental results verify the accuracy of CTPM and show that our system can reduce the overhead of the data transferring and improve the job execution efficiency compared with the current widely used methods.

  • proactive data placement for surveillance video processing in Heterogeneous Cluster
    IEEE International Conference on Cloud Computing Technology and Science, 2016
    Co-Authors: Haitao Zhang, Jin Yan, Lujie Liu
    Abstract:

    Large-scale surveillance video analytic is a kind of typical big data application. The Spark framework combined with Hadoop Distributed File System (HDFS) is a promising solution for the efficient surveillance video processing. However, the current HDFS distributes data to multiple nodes according to the disk space availability, and this data placement mode will lead to the serious skew of the video task completion time and the performance degradation of the distributed video processing in the Heterogeneous Spark Cluster. In this paper, we firstly design a distributed surveillance video processing platform architecture which supports the seamless integration with the standard video surveillance system. Our platform uses the Spark computing framework over the data stored in HDFS. Then, we propose a novel proactive video data placement strategy to schedule the input video data into the appropriate Cluster node adaptively. Our strategy adopts a novel Computing Time Prediction Model (CTPM) which can accurately estimate the execution time of the video processing task by incorporating the several important video task features. In our strategy, an Initial Data Placement Algorithm (IDPA) is used to place the data needed by the video processing jobs on the appropriate Cluster node in the process of the initial data loading, and then a Data Rebalance Algorithm (DRA) is further used to schedule the data for the workload balancing during the process of the job execution. Finally, we build a distributed surveillance video processing system according to the proposed platform architecture and conduct the extensive experiments. The experimental results verify the accuracy of CTPM and show that our system can reduce the overhead of the data transferring and improve the job execution efficiency compared with the current widely used methods.