The Experts below are selected from a list of 324 Experts worldwide ranked by ideXlab platform
Yu Fang - One of the best experts on this subject based on the ideXlab platform.
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ultrafast Bulk Carrier dynamics in various gan crystals at near infrared wavelengths under one and two photon absorption
Applied Physics Letters, 2019Co-Authors: Yu Fang, Junyi Yang, Yongqiang Chen, Zhengguo Xiao, Jidong Jia, Yinglin SongAbstract:Femtosecond transient absorption (TA) as a probe of ultrafast Carrier dynamics was conducted at near-infrared wavelengths in a series of GaN crystals. The TA kinetics in all the GaN crystals appeared to be single exponential under one-photon (1P) excitation but biexponential under two-photon (2P) excitation, which was inconsistent with previous experimental reports and model predictions. Surface recombination and Carrier diffusion could be eliminated and the TA responses were identified as phonon-assisted indirect free-Carrier absorption. Modelling the Bulk Carrier dynamics with a simplified model revealed that, at a 1P high Carrier injection level, the Carrier recombination was limited by the slow capture rate of electrons via deep defects, while at a 2P low Carrier injection level, the initial Carrier lifetime decreased remarkably due to fast hole capturing and could be further controlled by the inherent Carrier and/or dislocation concentrations.Femtosecond transient absorption (TA) as a probe of ultrafast Carrier dynamics was conducted at near-infrared wavelengths in a series of GaN crystals. The TA kinetics in all the GaN crystals appeared to be single exponential under one-photon (1P) excitation but biexponential under two-photon (2P) excitation, which was inconsistent with previous experimental reports and model predictions. Surface recombination and Carrier diffusion could be eliminated and the TA responses were identified as phonon-assisted indirect free-Carrier absorption. Modelling the Bulk Carrier dynamics with a simplified model revealed that, at a 1P high Carrier injection level, the Carrier recombination was limited by the slow capture rate of electrons via deep defects, while at a 2P low Carrier injection level, the initial Carrier lifetime decreased remarkably due to fast hole capturing and could be further controlled by the inherent Carrier and/or dislocation concentrations.
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ultrafast Bulk Carrier recombination transients in n type and semi insulating 4h sic crystals
Applied Physics Letters, 2018Co-Authors: Yu Fang, Junyi Yang, Gaoyuan Chen, Yongqiang Chen, Yinglin SongAbstract:Carrier recombination influences the performance of SiC-based optoelectronic devices, and Carrier recombination via traps is one of the limiting factors of Carrier lifetime. In this work, we utilized transient absorption spectroscopy with near-homogeneous Carrier distribution to evaluate ultrafast Bulk Carrier recombination in conductive (n-type) nitrogen-doped and semi-insulating (SI) vanadium-doped 4H-SiC wafers. Compared to n-type 4H-SiC, a pronounced modulation of transient absorption was observed in SI 4H-SiC, resulting from an additional decay process subsequent to intraband recombination (2–3 ps) caused by Carrier trapping of V3+/4+ deep acceptors. The Carrier-trapping lifetime (∼16 ps) was three orders of magnitude faster than that via N-doping and/or inherent defects. With a simplified model and global analysis, the Carrier recombination mechanisms and lifetimes in 4H-SiC were determined unambiguously.
Yinglin Song - One of the best experts on this subject based on the ideXlab platform.
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ultrafast Bulk Carrier dynamics in various gan crystals at near infrared wavelengths under one and two photon absorption
Applied Physics Letters, 2019Co-Authors: Yu Fang, Junyi Yang, Yongqiang Chen, Zhengguo Xiao, Jidong Jia, Yinglin SongAbstract:Femtosecond transient absorption (TA) as a probe of ultrafast Carrier dynamics was conducted at near-infrared wavelengths in a series of GaN crystals. The TA kinetics in all the GaN crystals appeared to be single exponential under one-photon (1P) excitation but biexponential under two-photon (2P) excitation, which was inconsistent with previous experimental reports and model predictions. Surface recombination and Carrier diffusion could be eliminated and the TA responses were identified as phonon-assisted indirect free-Carrier absorption. Modelling the Bulk Carrier dynamics with a simplified model revealed that, at a 1P high Carrier injection level, the Carrier recombination was limited by the slow capture rate of electrons via deep defects, while at a 2P low Carrier injection level, the initial Carrier lifetime decreased remarkably due to fast hole capturing and could be further controlled by the inherent Carrier and/or dislocation concentrations.Femtosecond transient absorption (TA) as a probe of ultrafast Carrier dynamics was conducted at near-infrared wavelengths in a series of GaN crystals. The TA kinetics in all the GaN crystals appeared to be single exponential under one-photon (1P) excitation but biexponential under two-photon (2P) excitation, which was inconsistent with previous experimental reports and model predictions. Surface recombination and Carrier diffusion could be eliminated and the TA responses were identified as phonon-assisted indirect free-Carrier absorption. Modelling the Bulk Carrier dynamics with a simplified model revealed that, at a 1P high Carrier injection level, the Carrier recombination was limited by the slow capture rate of electrons via deep defects, while at a 2P low Carrier injection level, the initial Carrier lifetime decreased remarkably due to fast hole capturing and could be further controlled by the inherent Carrier and/or dislocation concentrations.
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ultrafast Bulk Carrier recombination transients in n type and semi insulating 4h sic crystals
Applied Physics Letters, 2018Co-Authors: Yu Fang, Junyi Yang, Gaoyuan Chen, Yongqiang Chen, Yinglin SongAbstract:Carrier recombination influences the performance of SiC-based optoelectronic devices, and Carrier recombination via traps is one of the limiting factors of Carrier lifetime. In this work, we utilized transient absorption spectroscopy with near-homogeneous Carrier distribution to evaluate ultrafast Bulk Carrier recombination in conductive (n-type) nitrogen-doped and semi-insulating (SI) vanadium-doped 4H-SiC wafers. Compared to n-type 4H-SiC, a pronounced modulation of transient absorption was observed in SI 4H-SiC, resulting from an additional decay process subsequent to intraband recombination (2–3 ps) caused by Carrier trapping of V3+/4+ deep acceptors. The Carrier-trapping lifetime (∼16 ps) was three orders of magnitude faster than that via N-doping and/or inherent defects. With a simplified model and global analysis, the Carrier recombination mechanisms and lifetimes in 4H-SiC were determined unambiguously.
Junyi Yang - One of the best experts on this subject based on the ideXlab platform.
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ultrafast Bulk Carrier dynamics in various gan crystals at near infrared wavelengths under one and two photon absorption
Applied Physics Letters, 2019Co-Authors: Yu Fang, Junyi Yang, Yongqiang Chen, Zhengguo Xiao, Jidong Jia, Yinglin SongAbstract:Femtosecond transient absorption (TA) as a probe of ultrafast Carrier dynamics was conducted at near-infrared wavelengths in a series of GaN crystals. The TA kinetics in all the GaN crystals appeared to be single exponential under one-photon (1P) excitation but biexponential under two-photon (2P) excitation, which was inconsistent with previous experimental reports and model predictions. Surface recombination and Carrier diffusion could be eliminated and the TA responses were identified as phonon-assisted indirect free-Carrier absorption. Modelling the Bulk Carrier dynamics with a simplified model revealed that, at a 1P high Carrier injection level, the Carrier recombination was limited by the slow capture rate of electrons via deep defects, while at a 2P low Carrier injection level, the initial Carrier lifetime decreased remarkably due to fast hole capturing and could be further controlled by the inherent Carrier and/or dislocation concentrations.Femtosecond transient absorption (TA) as a probe of ultrafast Carrier dynamics was conducted at near-infrared wavelengths in a series of GaN crystals. The TA kinetics in all the GaN crystals appeared to be single exponential under one-photon (1P) excitation but biexponential under two-photon (2P) excitation, which was inconsistent with previous experimental reports and model predictions. Surface recombination and Carrier diffusion could be eliminated and the TA responses were identified as phonon-assisted indirect free-Carrier absorption. Modelling the Bulk Carrier dynamics with a simplified model revealed that, at a 1P high Carrier injection level, the Carrier recombination was limited by the slow capture rate of electrons via deep defects, while at a 2P low Carrier injection level, the initial Carrier lifetime decreased remarkably due to fast hole capturing and could be further controlled by the inherent Carrier and/or dislocation concentrations.
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ultrafast Bulk Carrier recombination transients in n type and semi insulating 4h sic crystals
Applied Physics Letters, 2018Co-Authors: Yu Fang, Junyi Yang, Gaoyuan Chen, Yongqiang Chen, Yinglin SongAbstract:Carrier recombination influences the performance of SiC-based optoelectronic devices, and Carrier recombination via traps is one of the limiting factors of Carrier lifetime. In this work, we utilized transient absorption spectroscopy with near-homogeneous Carrier distribution to evaluate ultrafast Bulk Carrier recombination in conductive (n-type) nitrogen-doped and semi-insulating (SI) vanadium-doped 4H-SiC wafers. Compared to n-type 4H-SiC, a pronounced modulation of transient absorption was observed in SI 4H-SiC, resulting from an additional decay process subsequent to intraband recombination (2–3 ps) caused by Carrier trapping of V3+/4+ deep acceptors. The Carrier-trapping lifetime (∼16 ps) was three orders of magnitude faster than that via N-doping and/or inherent defects. With a simplified model and global analysis, the Carrier recombination mechanisms and lifetimes in 4H-SiC were determined unambiguously.
Yongqiang Chen - One of the best experts on this subject based on the ideXlab platform.
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ultrafast Bulk Carrier dynamics in various gan crystals at near infrared wavelengths under one and two photon absorption
Applied Physics Letters, 2019Co-Authors: Yu Fang, Junyi Yang, Yongqiang Chen, Zhengguo Xiao, Jidong Jia, Yinglin SongAbstract:Femtosecond transient absorption (TA) as a probe of ultrafast Carrier dynamics was conducted at near-infrared wavelengths in a series of GaN crystals. The TA kinetics in all the GaN crystals appeared to be single exponential under one-photon (1P) excitation but biexponential under two-photon (2P) excitation, which was inconsistent with previous experimental reports and model predictions. Surface recombination and Carrier diffusion could be eliminated and the TA responses were identified as phonon-assisted indirect free-Carrier absorption. Modelling the Bulk Carrier dynamics with a simplified model revealed that, at a 1P high Carrier injection level, the Carrier recombination was limited by the slow capture rate of electrons via deep defects, while at a 2P low Carrier injection level, the initial Carrier lifetime decreased remarkably due to fast hole capturing and could be further controlled by the inherent Carrier and/or dislocation concentrations.Femtosecond transient absorption (TA) as a probe of ultrafast Carrier dynamics was conducted at near-infrared wavelengths in a series of GaN crystals. The TA kinetics in all the GaN crystals appeared to be single exponential under one-photon (1P) excitation but biexponential under two-photon (2P) excitation, which was inconsistent with previous experimental reports and model predictions. Surface recombination and Carrier diffusion could be eliminated and the TA responses were identified as phonon-assisted indirect free-Carrier absorption. Modelling the Bulk Carrier dynamics with a simplified model revealed that, at a 1P high Carrier injection level, the Carrier recombination was limited by the slow capture rate of electrons via deep defects, while at a 2P low Carrier injection level, the initial Carrier lifetime decreased remarkably due to fast hole capturing and could be further controlled by the inherent Carrier and/or dislocation concentrations.
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ultrafast Bulk Carrier recombination transients in n type and semi insulating 4h sic crystals
Applied Physics Letters, 2018Co-Authors: Yu Fang, Junyi Yang, Gaoyuan Chen, Yongqiang Chen, Yinglin SongAbstract:Carrier recombination influences the performance of SiC-based optoelectronic devices, and Carrier recombination via traps is one of the limiting factors of Carrier lifetime. In this work, we utilized transient absorption spectroscopy with near-homogeneous Carrier distribution to evaluate ultrafast Bulk Carrier recombination in conductive (n-type) nitrogen-doped and semi-insulating (SI) vanadium-doped 4H-SiC wafers. Compared to n-type 4H-SiC, a pronounced modulation of transient absorption was observed in SI 4H-SiC, resulting from an additional decay process subsequent to intraband recombination (2–3 ps) caused by Carrier trapping of V3+/4+ deep acceptors. The Carrier-trapping lifetime (∼16 ps) was three orders of magnitude faster than that via N-doping and/or inherent defects. With a simplified model and global analysis, the Carrier recombination mechanisms and lifetimes in 4H-SiC were determined unambiguously.
Torgeir Moan - One of the best experts on this subject based on the ideXlab platform.
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Ultimate hull girder strength of a Bulk Carrier under combined global and local loads in the hogging and alternate hold loading condition using nonlinear finite element analysis
Journal of Marine Science and Technology, 2012Co-Authors: Torgeir MoanAbstract:For Bulk Carriers in hogging, the most critical situation is the alternate hold loading (AHL) condition with odd numbered holds loaded with high density cargoes and even numbered holds empty. The effect of the local lateral pressure loads should be considered in the assessment of ultimate hull girder strength in the hogging and AHL conditions. In the present paper the ultimate strength of a Capesize Bulk Carrier hull girder under combined global and local loads in the hogging and AHL condition is extensively and systematically investigated using nonlinear finite element (FE) analysis with ABAQUS software. Since the Bulk Carrier used as a reference vessel in this study is an old design we also studied the effect of modified scantlings by multiplying the plate thickness in the bottom structure by a design modification factor (DMF). In particular, it should be noted that a DMF of 1.4 gives a design in accordance with the new CSR rules. Based on the results obtained by nonlinear FE analyses, a practical interaction equation is established between global hogging bending capacity and average external sea pressure over the bottom.
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Reliability Analysis of Ultimate Strength of a Capesize Bulk Carrier in Hogging and Alternate Hold Loading Condition
29th International Conference on Ocean Offshore and Arctic Engineering: Volume 2, 2010Co-Authors: Zhi Shu, Torgeir MoanAbstract:This paper deals with the structural reliability analysis (SRA) of ultimate strength of a Capesize Bulk Carrier in hogging and alternate hold loading condition (AHL). The ultimate strength in hogging and AHL condition is very important for the safety of Bulk Carriers since the local loads due to internal cargo loads and external sea pressure can reduce the ultimate bending capacity. In the present paper, the characteristic ultimate bending capacity of the subject Bulk Carrier is investigated by nonlinear finite element (FE) analysis and the characteristic value of the global and local loads are determined in accordance with the Common Structural Rules for Bulk Carriers (CSR-BC). The uncertainties associated with the loading capacity and load effects are appropriately modelled. The First Order Reliability Method (FORM) is adopted to calculate the annual probability of failure of this Bulk Carrier in hogging and AHL condition. The effect of heavy weather avoidance on the global and local loads is also evaluated in the SRA. The results show that the local loads have a significant impact on the failure probability of such vessels in the hogging and AHL condition.Copyright © 2010 by ASME
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ultimate strength analysis of a Bulk Carrier hull girder under alternate hold loading condition part 2 stress distribution in the double bottom and simplified approaches
Marine Structures, 2009Co-Authors: Hadi K K Amlashi, Torgeir MoanAbstract:This is the second of two companion papers dealing with nonlinear finite element modelling and ultimate strength analysis of the hull girder of a Bulk Carrier under Alternate Hold Loading (AHL) condition. The methodology for nonlinear finite element modelling as well as the ultimate strength results from the nonlinear FE analyses was discussed in the companion paper (Part 1). The purpose of the present paper is to use the FE results to contribute towards developing simplified methods applicable to practical design of ship hulls under combined global and local loads. An important issue is the significant double bottom bending in the empty hold in AHL due to combined global hull girder bending moment and local loads. Therefore, the stress distributions in the double bottom area at different load levels i.e. rule load level and ultimate failure load level are presented in detail. The implication of different design pressures obtained by different rules (CSR-BC rules and DNV rules) on the stress distribution is investigated. Both (partially) heavy cargo AHL and fully loaded cargo AHL are considered. Factors of influence of double bottom bending such as initial imperfections, local loads, stress distribution and failure modes on the hull girder strength are discussed. Simplified procedures for determination of the hull girder strength for Bulk Carriers under AHL conditions are also discussed in light of the FE analyses.
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ultimate strength analysis of a Bulk Carrier hull girder under alternate hold loading condition a case study part 1 nonlinear finite element modelling and ultimate hull girder capacity
Marine Structures, 2008Co-Authors: Hadi K K Amlashi, Torgeir MoanAbstract:This is the first of two companion papers dealing with nonlinear finite element modelling and analysis of the ultimate strength of a Bulk Carrier hull girder under alternate hold loading (AHL) condition. The purpose is to contribute to establishing rational ultimate longitudinal strength criteria for the hull girder under combined loading. The focus is on the hogging condition. An important issue is the significant double bottom bending in empty holds in AHL due to combined global hull girder bending moment and local loads. The local loads may substantially reduce the strength of the hull girder. Different AHL conditions, i.e. fully loaded cargo and (partially) heavy cargo are considered. A critical review of external and internal design pressures for different AHL conditions is accomplished using both CSR-BC rules and DNV rules. A methodology for nonlinear finite element modelling of hold tanks of a Bulk Carrier under AHL is presented by use of ABAQUS. A mesh convergence study is carried out in order to find the appropriate mesh for the model. The implication of using different design pressures on the hull girder strength is assessed. The FE results can be used as a basis for establishing simplified methods applicable to practical design of ship hulls under combined loadings. This issue is discussed in the companion paper.
