| 1. |
- Kristan, Matej, et al.
(författare)
-
The first visual object tracking segmentation VOTS2023 challenge results
- 2023
-
Ingår i: 2023 IEEE/CVF International conference on computer vision workshops (ICCVW). - : Institute of Electrical and Electronics Engineers Inc.. - 9798350307443 - 9798350307450 ; , s. 1788-1810
-
Konferensbidrag (refereegranskat)abstract
- The Visual Object Tracking Segmentation VOTS2023 challenge is the eleventh annual tracker benchmarking activity of the VOT initiative. This challenge is the first to merge short-term and long-term as well as single-target and multiple-target tracking with segmentation masks as the only target location specification. A new dataset was created; the ground truth has been withheld to prevent overfitting. New performance measures and evaluation protocols have been created along with a new toolkit and an evaluation server. Results of the presented 47 trackers indicate that modern tracking frameworks are well-suited to deal with convergence of short-term and long-term tracking and that multiple and single target tracking can be considered a single problem. A leaderboard, with participating trackers details, the source code, the datasets, and the evaluation kit are publicly available at the challenge website1
|
|
| 2. |
- Watts, Anna L., et al.
(författare)
-
Dense matter with eXTP
- 2019
-
Ingår i: Science China Physics, Mechanics & Astronomy. - : Science Press. - 1674-7348 .- 1869-1927. ; 62:2
-
Forskningsöversikt (refereegranskat)abstract
- In this White Paper we present the potential of the Enhanced X-ray Timing and Polarimetry (eXTP) mission for determining the nature of dense matter; neutron star cores host an extreme density regime which cannot be replicated in a terrestrial laboratory. The tightest statistical constraints on the dense matter equation of state will come from pulse profile modelling of accretion-powered pulsars, burst oscillation sources, and rotation-powered pulsars. Additional constraints will derive from spin measurements, burst spectra, and properties of the accretion flows in the vicinity of the neutron star. Under development by an international Consortium led by the Institute of High Energy Physics of the Chinese Academy of Sciences, the eXTP mission is expected to be launched in the mid 2020s.
|
|
| 3. |
- Huang, Jianqing, et al.
(författare)
-
A detailed study on the micro-explosion of burning iron particles in hot oxidizing environments
- 2022
-
Ingår i: Combustion and Flame. - : Elsevier BV. - 0010-2180. ; 238
-
Tidskriftsartikel (refereegranskat)abstract
- As a promising carbon-free fuel, iron powder can directly combust with air and has great potential to provide clean and high-grad heat for various applications. The combustion characteristics of iron particles are of great significance for developing iron combustion model, designing efficient combustor, and optimizing combustion technologies. In this work, the micro-explosion behavior of burning iron particles was experimentally investigated based on optical diagnostics. With two high-speed cameras operating at 10,000 frames per second, the three-dimensional (3D) motion and mean surface temperature of burning iron particles during the micro-explosion process were measured using the stereo imaging technique and two-color pyrometry, respectively. The probability of micro-explosions in different oxidizing environments were statistically studied. Three distinct micro-explosion modes have been observed. The results showed that the micro-explosion of burning iron particles heavily depended on oxygen concentration. The micro-explosion would slightly reduce the particle surface temperature by 30–70 K within 0.5 ms, since a lot of smaller fragments were produced. In addition, the 3D velocity of most fragments would sharply increase to 2–6 times within 0.2 ms after the micro-explosion occurred. Regarding the mechanism of the micro-explosion, three types of potential gas sources inside the particle were discussed. The sharp gradients of gas temperature and oxygen concentration may facilitate the rapid increase of the internal pressure in the particle, which eventually causes the micro-explosion.
|
|
| 4. |
- Pucilowski, Mateusz, et al.
(författare)
-
Comparison of kinetic mechanisms for numerical simulation of methanol combustion in dici heavy-duty engine
- 2019
-
Ingår i: Technical Paper - WCX SAE World Congress Experience. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191. ; 2019
-
Konferensbidrag (refereegranskat)abstract
- The combustion process in a homogeneous charge compression ignition (HCCI) engine is mainly governed by ignition wave propagation. The in-cylinder pressure, heat release rate, and the emission characteristics are thus largely driven by the chemical kinetics of the fuel. As a result, CFD simulation of such combustion process is very sensitive to the employed reaction mechanism, which model the real chemical kinetics of the fuel. In order to perform engine simulation with a range of operating conditions and cylinder-piston geometry for the design and optimization purpose, it is essential to have a chemical kinetic mechanism that is both accurate and computational inexpensive. In this paper, we report on the evaluation of several chemical kinetic mechanisms for methanol combustion, including large mechanisms and skeletal/reduced mechanisms. These mechanisms are evaluated in terms of homogeneous ignition delay time, laminar flame speed, and multi-phase simulations of HCCI heavy-duty engine. The results are compared with experimental data and evaluated in terms of the accuracy and computational cost. It was found that scattering of ignition delay time predicted from different chemical kinetic mechanisms reported in the literature under homogeneous mixture ignition conditions give rise to a high sensitivity of the engine in-cylinder pressure prediction to the selected mechanism.
|
|
| 5. |
- Xu, Shijie, et al.
(författare)
-
Phase change and combustion of iron particles in premixed CH4/O2/N2 flames
- 2024
-
Ingår i: Combustion and Flame. - 0010-2180. ; 259
-
Tidskriftsartikel (refereegranskat)abstract
- Metal powder is a promising carbon-free and recyclable energy carrier. Direct combustion of the micron-sized iron particles involves complex physical and chemical processes, such as heat transfer, surface reaction, and phase change. In this work, computational modelling of these processes is investigated and validated against experiments. A single iron particle combustion and phase change model is proposed in an Eulerian–Lagrangian framework. The new phenomenological model considers five stages, i.e., solid phase oxidation, melting of iron oxides and raw iron, liquid phase oxidation, cooling of liquid iron oxides, and solidification of super-cooled liquid iron oxides. The proposed model is first validated and then adopted in simulations of micron-sized iron particle combustion in premixed CH4/O2/N2 flames to study the effects of ambient temperature and oxygen concentration on single iron combustion. Results show that the new model is capable of replicating the melting, heterogeneous surface reaction, cooling, and solidification processes. Two-stage solidification is observed in experiments and modelled in simulations. This two-stage solidification includes a fast solidification with a significant temperature rise (∼150–200 K) and a thermal equilibrium solidification featuring a constant temperature and a slight particle radiant intensity decrease. In addition, a diffusion-controlled mechanism is identified during the melting process, in which the oxygen concentration dominates the melting time and the subsequent burning time. Furthermore, it is found that the reaction between iron and CH4/O2/N2 flame products, such as CO2 and H2O, plays a non-negligible role in the iron combustion process.
|
|
| 6. |
- Zhou, Guoyi, et al.
(författare)
-
Climate and litter C/N ratio constrain soil organic carbon accumulation
- 2019
-
Ingår i: National Science Review. - : Oxford University Press (OUP). - 2095-5138 .- 2053-714X. ; 6:4, s. 746-757
-
Tidskriftsartikel (refereegranskat)abstract
- Soil organic carbon (SOC) plays critical roles in stabilizing atmospheric CO2 concentration, but the mechanistic controls on the amount and distribution of SOC on global scales are not well understood. In turn, this has hampered the ability to model global C budgets and to find measures to mitigate climate change. Here, based on the data from a large field survey campaign with 2600 plots across China's forest ecosystems and a global collection of published data from forested land, we find that a low litter carbon-to-nitrogen ratio (C/N) and high wetness index (P/PET, precipitation-to-potential-evapotranspiration ratio) are the two factors that promote SOC accumulation, with only minor contributions of litter quantity and soil texture. The field survey data demonstrated that high plant diversity decreased litter C/N and thus indirectly promoted SOC accumulation by increasing the litter quality. We conclude that any changes in plant-community composition, plant-species richness and environmental factors that can reduce the litter C/N ratio, or climatic changes that increase wetness index, may promote SOC accumulation. The study provides a guideline for modeling the carbon cycle of various ecosystem scales and formulates the principle for land-based actions for mitigating the rising atmospheric CO2 concentration.
|
|
| 7. |
- Guo, Li, et al.
(författare)
-
Flame characteristics of methane/air with hydrogen addition in the micro confined combustion space
- 2022
-
Ingår i: International Journal of Hydrogen Energy. - : Elsevier BV. - 0360-3199. ; 47:44, s. 19319-19337
-
Tidskriftsartikel (refereegranskat)abstract
- This paper investigated methane/air flame characteristics with hydrogen addition in micro confined combustion space experimentally and computationally. The focus is on the effect of hydrogen addition on the methane/air flame stabilization, the onset of flame with repetitive extinction and ignition (FREI), and the global flame quenching in decreasing continuously combustion space. Furthermore, the effects of hydrogen addition on the flame temperature and the local equivalence ratio distribution were analyzed systematically using numerical simulations. In addition, the effects of hydrogen addition on the concentrations of OH and H radicals, and the critical scalar dissipation rate of local flame extinction were discussed. With a higher hydrogen ratio, the mixing is faster, and the flame is smaller. When the micro confined space is narrower, the heat loss to the combustor walls has a higher impact on the flames. The flames with higher hydrogen ratios have therefore lower peak flame temperatures and lower concentrations of H and OH radicals. The results show that hydrogen addition can effectively widen the stable combustion range of methane/air flames in the micro confined space by about 20% when the hydrogen addition ratio reaches 50%. The frequency and the maximum propagation velocity of FREI flames can be increased as well. The quenching distance of methane/hydrogen/air flames decreases nearly linearly with the increase of hydrogen ratio. This is attributed to the higher critical scalar dissipation rate of local flame extinction in flames with a higher hydrogen ratio.
|
|
| 8. |
|
|
| 9. |
- Li, Kuijie, et al.
(författare)
-
Investigating the effect of packing format on LiNixCoyMnzO2 lithium-ion battery failure behavior based on multidimensional signals
- 2024
-
Ingår i: Journal of Power Sources. - : Elsevier. - 0378-7753 .- 1873-2755. ; 614
-
Tidskriftsartikel (refereegranskat)abstract
- Prismatic and pouch packaging formats are commonly used in LiNi x Co y Mn z O 2 (NCM) batteries for electric vehicles, each showing distinct failure dynamics. However, a comprehensive study is lacking on how these packaging types affect thermal runaway (TR) at the cell level and its propagation at the module level, with a particular gap in understanding the dynamics of multidimensional signals. In this study, we experimentally explore the effect of cell format on 40 Ah NCM523 prismatic and pouch battery failure behaviors under overcharging and overheating conditions, by applying multidimensional signals, including the swelling force, gas, voltage, and temperature of the batteries. Results indicate that both types of batteries exhibit similar time scales for the failure modes when overcharged. In contrast, under overheating conditions, the pouch batteries fail significantly earlier than the prismatic batteries, including abnormal swelling, venting, gas emission, internal short circuit, and TR. Additionally, the prismatic batteries can withstand a swelling force of 5000 N at venting, while it is 2000 N for the pouch batteries. During TR, the prismatic batteries present a maximum temperature increase rate below 100 K/s, while the pouch batteries exhibit one over 200 K/s. Furthermore, the pouch batteries generally display more severe TR hazards and faster TR propagation than the prismatic cells. This study enhances the comprehension of TR and TR propagation mechanisms across different cell formats, providing crucial insights for the safety design and early warning strategies of battery modules.
|
|
| 10. |
- Song, Jiali, et al.
(författare)
-
Solid additive engineering enables high-efficiency and eco-friendly all-polymer solar cells
- 2022
-
Ingår i: Matter. - : ELSEVIER. - 2590-2393 .- 2590-2385. ; 5:11, s. 4047-4059
-
Tidskriftsartikel (refereegranskat)abstract
- Currently, morphology optimization of all-polymer solar cells (all-PSCs) strongly depends on the use of solvent additives, which are usually highly toxic and harmful to the environment and human health. Here, we report a green and volatile solid additive, 2-methoxynaphthalene (2-MN). It was found that the incorporation of 2-MN into a PM6:PY-DT blend can effectively manipulate the aggregations of PM6 and PY-DT during film depositing and thermal annealing processes and results in highly ordered molecular packing and favorable phase-separated morphology. Consequently, a re-cord-high efficiency of 17.32% is achieved for the PM6:PY-DT de-vice. Moreover, 2-MN-processed all-PSCs were fabricated by using non-halogenated solvent. High efficiencies of 17.03% and 16.67% are obtained for all-PSCs fabricated under nitrogen atmosphere and ambient conditions, respectively. Our work shows that the utili-zation of 2-MN as a green and solid additive is a simple and feasible strategy to optimize the morphology and sheds new light on eco-friendly fabrication and application of all-PSCs.
|
|
