| 1. |
- Kristan, Matej, et al.
(författare)
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The Visual Object Tracking VOT2017 challenge results
- 2017
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Ingår i: 2017 IEEE INTERNATIONAL CONFERENCE ON COMPUTER VISION WORKSHOPS (ICCVW 2017). - : IEEE. - 9781538610343 ; , s. 1949-1972
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Konferensbidrag (refereegranskat)abstract
- The Visual Object Tracking challenge VOT2017 is the fifth annual tracker benchmarking activity organized by the VOT initiative. Results of 51 trackers are presented; many are state-of-the-art published at major computer vision conferences or journals in recent years. The evaluation included the standard VOT and other popular methodologies and a new "real-time" experiment simulating a situation where a tracker processes images as if provided by a continuously running sensor. Performance of the tested trackers typically by far exceeds standard baselines. The source code for most of the trackers is publicly available from the VOT page. The VOT2017 goes beyond its predecessors by (i) improving the VOT public dataset and introducing a separate VOT2017 sequestered dataset, (ii) introducing a realtime tracking experiment and (iii) releasing a redesigned toolkit that supports complex experiments. The dataset, the evaluation kit and the results are publicly available at the challenge website(1).
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| 2. |
- Kristan, Matej, et al.
(författare)
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The Visual Object Tracking VOT2016 Challenge Results
- 2016
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Ingår i: COMPUTER VISION - ECCV 2016 WORKSHOPS, PT II. - Cham : SPRINGER INT PUBLISHING AG. - 9783319488813 - 9783319488806 ; , s. 777-823
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Konferensbidrag (refereegranskat)abstract
- The Visual Object Tracking challenge VOT2016 aims at comparing short-term single-object visual trackers that do not apply pre-learned models of object appearance. Results of 70 trackers are presented, with a large number of trackers being published at major computer vision conferences and journals in the recent years. The number of tested state-of-the-art trackers makes the VOT 2016 the largest and most challenging benchmark on short-term tracking to date. For each participating tracker, a short description is provided in the Appendix. The VOT2016 goes beyond its predecessors by (i) introducing a new semi-automatic ground truth bounding box annotation methodology and (ii) extending the evaluation system with the no-reset experiment.
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| 3. |
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| 4. |
- Liu, Qingming, et al.
(författare)
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A numerical study of the transition from slug to annular flow in micro-channel convective boiling
- 2017
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Ingår i: Applied Thermal Engineering. - : Elsevier. - 1359-4311 .- 1873-5606. ; 112, s. 73-81
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Tidskriftsartikel (refereegranskat)abstract
- A numerical study on the transition from slug flow (or elongated flow) to annular flow of convective boiling under high heat flux in a micro-channel with diameter of 0.4 mm is conducted. A constant velocity inlet boundary with mass flux 400 kg/m2 s, and heated wall with a constant heat flux (160, 80 kW/m2) are applied. A novel initialization method is proposed. Growth rate of the bubble and transition of the flow regime are well predicted by comparing with an experimental visualization. Effects of the transition are studied and findings are that this process disturbs thermal boundary layer which further enhances bubble evaporation.
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| 5. |
- Liu, Qingming, et al.
(författare)
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Bubble interaction of annular flow in micro-channel boiling
- 2019
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Ingår i: International Communications in Heat and Mass Transfer. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0735-1933 .- 1879-0178. ; 101, s. 76-81
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Tidskriftsartikel (refereegranskat)abstract
- The development of heat transfer models of micro-channel boiling relies on understanding of all individual flow regimes as well as interactions and transitions between them. The presented paper performs a detailed study on the interactions between annular flow and its trailing bubbles in a cylindrical micro-channel with a diameter of 0.4 mm. Inlet mass flux is 400 kg/(m(2).s) and constant wall heat flux is 80 and 160 kW/m(2), respectively. The growth rate of the bubble and the flow regime transition are validated against published experimental data. Comparisons of the results between transition flow and single annular flow show that the transition processes enhance bubble evaporation. A new phenomenon is observed: extreme high local heat transfer rates are observed under certain conditions. A detailed investigation of the thin film region unveil that this enhancement is a consequence of the interface distortion caused by the presence of the trailing bubble. This bubble interface deformation depends primarily on a few factors including wall heat flux, surface tension, trailing bubble.
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| 6. |
- Liu, Qingming, et al.
(författare)
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Mathmatical Modeling of the Thermal Behavior of a Long Lithium-Ion Battery
- 2023
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Ingår i: 2023 3rd International Conference on Energy, Power and Electrical Engineering, EPEE 2023. - : Institute of Electrical and Electronics Engineers (IEEE). ; , s. 460-465
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Konferensbidrag (refereegranskat)abstract
- A two-dimensional mathematical model is proposed to study the thermal behavior of a long lithium-ion battery. Bernardi's electrochemical heat generation theory is adopted and a finite element method is used to discrete the coupled electrochemical thermal equations. The potential and current density distribution in the electrodes of the batteries are presented as function of depth of discharge. Modelling results shows that the battery temperature increases as increase of discharging time. The temperature distribution in the battery electrodes are calculated and compared to experiments. It is found that the simulation has good agreement with the experimental studies.
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| 7. |
- Liu, Qingming, et al.
(författare)
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Numerical study of bubbles rising and merging during convective boiling in micro-channels
- 2016
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Ingår i: Applied Thermal Engineering. - : Elsevier. - 1359-4311 .- 1873-5606. ; 99, s. 1141-1151
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Tidskriftsartikel (refereegranskat)abstract
- A three dimensional numerical study on bubble growth and merger in a micro-channel with diameter of 0.64 mm has been conducted. The working fluid is R134a and the wall material is steel. The inlet Reynolds number is set at 549 in order to keep the flow in laminar regime. Two different heat fluxes () are supplied to the wall to heat up the fluid. The coupled level set and volume of fluid (CLSVOF) method is used to capture the distorted two-phase interface. An evaporation model is also implemented through UDF (User defined function). The combination of these two methods has successfully eliminated spurious velocities which is a common problem in two phase flow simulation. The boiling and merger processes are well-predicted by the simulation. It is found that the whole process can be divided into three sub-stages: sliding, merger, and post-merger. The dynamics and heat transfer are found to be different in these stages. The evaporation rate is much higher in the first two stages due to the thermal boundary layer effects.
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| 8. |
- Liu, Qingming
(författare)
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Numerical study of flow boiling in micro/mini channels
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Boiling phenomena in micro scale has emerged as an interesting topic due to its complexity and increasing usage in micro electronic and mechanical systems (MEMS). Experimental visualization has discovered five main flow regimes: nucleate boiling, isolated bubbles, confine bubbly flow, elongated bubbly (or slug) flow, and annular flow. Two of these patterns (confine bubbles and slug flow) are rarely found in macro channels and are believed to have very different heat transfer mechanisms to that of nucleate boiling.The development of a phenomenological model demands a deep understanding of each flow regime as well as the transition process between them. While studies in every individual flow pattern are available in literature, the mechanisms of transition processes between them remain mysterious. More specifically, how the isolated bubbles evolve into a confined bubbly flow, and how this further evolves into elongated bubbles and finally an annular flow. The effects of boundary conditions such as wall heat flux, surface tension, and interfacial velocity are unclear, too.The aims of this thesis are to develop and validate a new numerical algorithm, perform a comprehensive numerical study on these transition processes, uncover the transition mechanisms and investigate effects of boundary and operating conditions.Firstly, a sophisticated and robust numerical model is developed by combining a coupled level set method (CLSVOF) and a non-equilibrium phase change model, which enables an accurate capture of the two-phase interface, as well as the interface temperature.Secondly, several flow regime transitions are studied in this thesis: nucleate bubbles to confined bubbly flow, multi confined bubbles moving consecutively in a micro channel, and slug to annular flow transition. Effects of surface tension, heat flux, mass flux, and fluid properties are examined. All these regimes are studied separately, which means an appropriate initial condition is needed for each regime. The author developed a simplified model based on energy balance to set the initial and boundary conditions.
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| 9. |
- Liu, Qingming, et al.
(författare)
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On the dynamics and heat transfer of bubble train in micro-channel flow boiling
- 2017
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Ingår i: International Communications in Heat and Mass Transfer. - : Elsevier. - 0735-1933 .- 1879-0178. ; 87, s. 198-203
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Tidskriftsartikel (refereegranskat)abstract
- The dynamics and heat transfer characteristics of flow boiling bubble train moving in a micro channel is studied numerically. The coupled level set and volume of fluid (CLSVOF) is utilized to track interface and a non-equilibrium phase change model is applied to calculate the interface temperature as well as heat flux jump. The working fluid is R134a and the wall material is aluminum. The fluid enters the channel with a constant mass flux (335 kg/m(2)*s), and the boundary wall is heated with constant heat flux (14 kW/m(2)). The growth of bubbles and the transition of flow regime are compared to an experimental visualization. Moreover, the bubble evaporation rate and wall heat transfer coefficient have been examined, respectively. Local heat transfer is significantly enhanced by evaporation occurring vicinity of interface of the bubbles. The local wall temperature is found to be dependent on the thickness of the liquid film between the bubble train and the wall.
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| 10. |
- Liu, Qingming, et al.
(författare)
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Simulation on the flow and heat transfer characteristics of confined bubbles in micro-channels
- 2012
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Ingår i: ASME 2012 10th Int. Conf. on Nanochannels, Microchannels, and Minichannels Collocated with the ASME 2012 Heat Transfer Summer Conf. and the ASME 2012 Fluids Engineering Division Sum, ICNMM 2012. - 9780791844793 ; , s. 63-70
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Konferensbidrag (refereegranskat)abstract
- 3D simulations on confined bubbles in micro-channels with diameter of 1.24 mm were conducted. The working fluid is R134a with a mass flux range from 125kg/m2s to 375kg/m2s. The VOF model is chosen to capture the 2 phase interface while the geo-construction method was used to re-construct the 2-phase interface. A heated boundary wall with heat flux varying from 15kW/m2 to 102kW/m2 is supplied. The wall temperature was calculated. The effects of mass flux and heat flux are studied. The shape of the bubble was predicted by the simulation successfully and the results show that they are independent of the initial shape. Both thin film evaporation and micro convection enhance the heat transfer. However, the micro convection which is caused by bubble motion has greater contribution to the total heat transfer at the stage of bubble growth studied.
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| 11. |
- Liu, Qingming, et al.
(författare)
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WITHDRAWN: Numerical study of the interactions and merge of multiple bubbles during convective boiling in micro channels
- 2017
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Ingår i: International Communications in Heat and Mass Transfer. - : Elsevier. - 0735-1933 .- 1879-0178. ; 80, s. 10-17
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Tidskriftsartikel (refereegranskat)abstract
- Multi bubbles interaction and merger in a micro-channel flow boiling has been numerically studied. Effects of mass flux (56, 112, 200, and 335 kg/m2 ∗ s), wall heat flux (5, 10, and 15 kW/m2) and saturated temperature (300.15 and 303.15 K) are investigated. The coupled level set and volume of fluid (CLSVOF) method and non-equilibrium phase model are implemented to capture the two-phase interface, and the lateral merger process. It is found that the whole transition process can be divided to three sub-stages: sliding, merger, and post-merger. The evaporation rate is much higher in the first two stages due to the boundary layer effects in. Both the mass flux and heat flux affect bubble growth. Specifically, the bubble growth rate increase with the increase of heat flux, or the decrease of mass flux.
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| 12. |
- Zheng, H., et al.
(författare)
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Thermal performance of copper foam/paraffin composite phase change material
- 2018
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Ingår i: Energy Conversion and Management. - : Elsevier. - 0196-8904 .- 1879-2227. ; 157, s. 372-381
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Tidskriftsartikel (refereegranskat)abstract
- Phase change materials are promising options for thermal energy storage and thermal energy devices. However, their low thermal conductivity lowers their charging and discharging rate. In this paper, copper foam was utilized to enhance the thermal performance of the paraffin. A visible experimental device was built to investigate the melting behavior of paraffin with and without copper foam. The effect of the heating position on the thermal performance of copper foam/paraffin composite phase change material (CPCM) was also discussed. The heat transfer characteristics including solid-liquid interface development, temperature distribution and wall temperature of the heater were tested and recorded. In addition, a numerical model was established using one-temperature volume averaging method to analyze the melting process of the CPCM. The experimental results showed that the total melting time of the CPCM was 20.5% shorter than that of pure paraffin, and the CPCM heated at the top melted slowest and reached the biggest temperature difference in the three heating conditions, so the effect of natural convection on the melting process of the CPCM could not be neglected. A two dimensional numerical simulation was also performed to analyze the melting behavior of CPCM, and the numerical results were well consistent with the experimental data.
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