The Experts below are selected from a list of 324 Experts worldwide ranked by ideXlab platform
Tabassam Yasmeen - One of the best experts on this subject based on the ideXlab platform.
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impact of cattaneo christov heat flux model in flow of variable thermal conductivity fluid over a variable thicked surface
International Journal of Heat and Mass Transfer, 2016Co-Authors: Tasawar Hayat, Ijaz M Khan, M Farooq, A Alsaedi, M Waqas, Tabassam YasmeenAbstract:Abstract Here temperature dependent thermal conductivity in stagnation point flow toward a nonlinear stretched surface with variable thickness is considered. Heat flux in formulation is based upon Cattaneo–Christov theory. Double stratification and chemical reaction effects are further retained. Convergent series solution for flow of Jeffrey fluid and heat and mass transfer are developed. Residual errors are calculated for the velocity, temperature and concentration equations and results are discussed through graphs. Influences of skin friction coefficient is also studied. It is observed that temperature profile decreases for higher thermal Relaxation Parameter.
Herbert Köstler - One of the best experts on this subject based on the ideXlab platform.
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consideration of slice profiles in inversion recovery look locker Relaxation Parameter mapping
Magnetic Resonance Imaging, 2014Co-Authors: Johannes Trangia, Tobias Wech, Dietbert Hahn, Thorsten Alexander Bley, Herbert KöstlerAbstract:Abstract Purpose To include the flip angle distribution caused by the slice profile into the model used for describing the Relaxation curves observed in inversion recovery Look–Locker FLASH T 1 mapping for a more accurate determination of the Relaxation Parameters. Materials and methods For each inversion time, the flip angle dependent signal of the mono-exponential Relaxation model is integrated across the slice profile. The resulting Consideration of Slice Profiles (CSP) Relaxation curves are compared to the mono-exponential signal model in numerical simulations as well as in phantom and in-vivo experiments. Results All measured Relaxation curves showed systematic deviations from a mono-exponential curve increasing with flip angle and T 1 but decreasing with repetition time. Additionally, the accuracy of T 1 was found to be largely dependent on the temporal coverage of the Relaxation curve. All these systematic errors were largely reduced by the CSP model. Conclusion The proposed CSP model represents a useful extension of the conventionally used mono-exponential Relaxation model. Despite inherent model inaccuracies, the mono-exponential model was found to be sufficient for many T 1 mapping situations. However, if only a poor temporal coverage of the Relaxation process is achievable or a very precise modeling of the Relaxation course is needed as in model-based techniques, the mono-exponential model leads to systematic errors and the CSP model should be used instead.
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Consideration of slice profiles in inversion recovery Look–Locker Relaxation Parameter mapping
Magnetic Resonance Imaging, 2014Co-Authors: Johannes Tran-gia, Tobias Wech, Dietbert Hahn, Thorsten Alexander Bley, Herbert KöstlerAbstract:Abstract Purpose To include the flip angle distribution caused by the slice profile into the model used for describing the Relaxation curves observed in inversion recovery Look–Locker FLASH T 1 mapping for a more accurate determination of the Relaxation Parameters. Materials and methods For each inversion time, the flip angle dependent signal of the mono-exponential Relaxation model is integrated across the slice profile. The resulting Consideration of Slice Profiles (CSP) Relaxation curves are compared to the mono-exponential signal model in numerical simulations as well as in phantom and in-vivo experiments. Results All measured Relaxation curves showed systematic deviations from a mono-exponential curve increasing with flip angle and T 1 but decreasing with repetition time. Additionally, the accuracy of T 1 was found to be largely dependent on the temporal coverage of the Relaxation curve. All these systematic errors were largely reduced by the CSP model. Conclusion The proposed CSP model represents a useful extension of the conventionally used mono-exponential Relaxation model. Despite inherent model inaccuracies, the mono-exponential model was found to be sufficient for many T 1 mapping situations. However, if only a poor temporal coverage of the Relaxation process is achievable or a very precise modeling of the Relaxation course is needed as in model-based techniques, the mono-exponential model leads to systematic errors and the CSP model should be used instead.
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Consideration of slice profiles in inversion recovery Look-Locker Relaxation Parameter mapping
Magnetic Resonance Imaging, 2014Co-Authors: Johannes Tran-gia, Tobias Wech, Dietbert Hahn, Thorsten Alexander Bley, Herbert KöstlerAbstract:Purpose: To include the flip angle distribution caused by the slice profile into the model used for describing the Relaxation curves observed in inversion recovery Look-Locker FLASH T1 mapping for a more accurate determination of the Relaxation Parameters. Materials and methods: For each inversion time, the flip angle dependent signal of the mono-exponential Relaxation model is integrated across the slice profile. The resulting Consideration of Slice Profiles (CSP) Relaxation curves are compared to the mono-exponential signal model in numerical simulations as well as in phantom and in-vivo experiments. Results: All measured Relaxation curves showed systematic deviations from a mono-exponential curve increasing with flip angle and T1 but decreasing with repetition time. Additionally, the accuracy of T1 was found to be largely dependent on the temporal coverage of the Relaxation curve. All these systematic errors were largely reduced by the CSP model. ?? 2014 Elsevier Inc.
Tasawar Hayat - One of the best experts on this subject based on the ideXlab platform.
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impact of cattaneo christov heat flux model in flow of variable thermal conductivity fluid over a variable thicked surface
International Journal of Heat and Mass Transfer, 2016Co-Authors: Tasawar Hayat, Ijaz M Khan, M Farooq, A Alsaedi, M Waqas, Tabassam YasmeenAbstract:Abstract Here temperature dependent thermal conductivity in stagnation point flow toward a nonlinear stretched surface with variable thickness is considered. Heat flux in formulation is based upon Cattaneo–Christov theory. Double stratification and chemical reaction effects are further retained. Convergent series solution for flow of Jeffrey fluid and heat and mass transfer are developed. Residual errors are calculated for the velocity, temperature and concentration equations and results are discussed through graphs. Influences of skin friction coefficient is also studied. It is observed that temperature profile decreases for higher thermal Relaxation Parameter.
Jingqi Huang - One of the best experts on this subject based on the ideXlab platform.
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modeling the phase change process for a two phase closed thermosyphon by considering transient mass transfer time Relaxation Parameter
International Journal of Heat and Mass Transfer, 2016Co-Authors: Zhi Xu, Yaning Zhang, Bingxi Li, Jingqi HuangAbstract:Abstract The method with minimal errors considering transient mass transfer time Relaxation Parameter for the phase change process is proposed in this study. A model coupled Volume of Fluid (VOF) model, phase change model and continuum surface force model is developed to simulate heat transfer characteristics and phase change process for a two-phase closed thermosyphon. The mass transfer process is implemented by adding User Define Function (UDF) to FLUENT code. The results obtained from this study show that the model with transient mass transfer time Relaxation Parameter has smaller relative errors (0.27–0.73%) for absolute temperature distributions along the wall of a two-phase closed thermosyphon than the model without transient mass transfer time Relaxation Parameter (2.01–2.97%). The model with transient mass transfer time Relaxation Parameter has smaller relative errors for the thermal resistances at evaporation and condensation sections (3.21–4.23% and 2.45–6.78%) than the model without transient mass transfer time Relaxation Parameter (18.31–21.74% and 15.34–28.25%), respectively. The model developed in this study can also detail the phase change process and therefore can be used to predict heat performance better for different types of heat pipes.
Zhi Xu - One of the best experts on this subject based on the ideXlab platform.
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modeling the phase change process for a two phase closed thermosyphon by considering transient mass transfer time Relaxation Parameter
International Journal of Heat and Mass Transfer, 2016Co-Authors: Zhi Xu, Yaning Zhang, Bingxi Li, Jingqi HuangAbstract:Abstract The method with minimal errors considering transient mass transfer time Relaxation Parameter for the phase change process is proposed in this study. A model coupled Volume of Fluid (VOF) model, phase change model and continuum surface force model is developed to simulate heat transfer characteristics and phase change process for a two-phase closed thermosyphon. The mass transfer process is implemented by adding User Define Function (UDF) to FLUENT code. The results obtained from this study show that the model with transient mass transfer time Relaxation Parameter has smaller relative errors (0.27–0.73%) for absolute temperature distributions along the wall of a two-phase closed thermosyphon than the model without transient mass transfer time Relaxation Parameter (2.01–2.97%). The model with transient mass transfer time Relaxation Parameter has smaller relative errors for the thermal resistances at evaporation and condensation sections (3.21–4.23% and 2.45–6.78%) than the model without transient mass transfer time Relaxation Parameter (18.31–21.74% and 15.34–28.25%), respectively. The model developed in this study can also detail the phase change process and therefore can be used to predict heat performance better for different types of heat pipes.
