| 1. |
- Mo, Lixin, et al.
(författare)
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Nano-Silver Ink of High Conductivity and Low Sintering Temperature for Paper Electronics
- 2019
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Ingår i: Nanoscale Research Letters. - : Springer New York LLC. - 1931-7573 .- 1556-276X. ; 14
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Tidskriftsartikel (refereegranskat)abstract
- Highly conductive ink with low sintering temperature is important for printed electronics on paper substrate. Silver nanoparticles (Ag NPs) of different average radii ranging from 48 to 176 nm were synthesized by adjusting the Ag+ concentration in the reaction process. The electric resistivity of the Ag NP-based ink film in relation to Ag NP size, sintering temperature, amount of PVP capping agent on Ag NP surface, and morphology evolution of the film during heating process was investigated. It was found that the resistivity of the films reduced very rapidly with increasing particle size due above all to reduced amount of protective agent capping on the Ag NPs. A semi-empirical relationship between the resistivity and the particle size was proposed. With the help of this mathematical expression, one gains both systematic and detailed insight to the resistivity evaluation with regard to the Ag particle size. The optimal electric resistivity of 4.6 μΩ cm was achieved at 140 °C for 10 min which was very close to the resistivity value of bulk Ag (1.58 μΩ cm). Mechanical flexibility of the printed electronics with the Ag NP-based ink on paper substrates was investigated. The prints on the art coated paper exhibited better flexibility compared to that on the photopaper. This might be attributed to the surface coating composition, surface morphology of the paper, and their corresponding ink absorption property. © 2019, The Author(s).
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| 2. |
- Mo, Lixin, et al.
(författare)
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Silver Nanoparticles Based Ink with Moderate Sintering in Flexible and Printed Electronics
- 2019
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Ingår i: International Journal of Molecular Sciences. - : MDPI AG. - 1661-6596 .- 1422-0067. ; 20:9
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Tidskriftsartikel (refereegranskat)abstract
- Printed electronics on flexible substrates has attracted tremendous research interest research thanks its low cost, large area production capability and environmentally friendly advantages. Optimal characteristics of silver nanoparticles (Ag NPs) based inks are crucial for ink rheology, printing, post-print treatment, and performance of the printed electronics devices. In this review, the methods and mechanisms for obtaining Ag NPs based inks that are highly conductive under moderate sintering conditions are summarized. These characteristics are particularly important when printed on temperature sensitive substrates that cannot withstand sintering of high temperature. Strategies to tailor the protective agents capping on the surface of Ag NPs, in order to optimize the sizes and shapes of Ag NPs as well as to modify the substrate surface, are presented. Different (emerging) sintering technologies are also discussed, including photonic sintering, electrical sintering, plasma sintering, microwave sintering, etc. Finally, applications of the Ag NPs based ink in transparent conductive film (TCF), thin film transistor (TFT), biosensor, radio frequency identification (RFID) antenna, stretchable electronics and their perspectives on flexible and printed electronics are presented.
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| 3. |
- Chen, T., et al.
(författare)
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An Improved Multimodal Trajectory Prediction Method Based on Deep Inverse Reinforcement Learning
- 2022
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Ingår i: Electronics. - : MDPI. - 2079-9292. ; 11:24
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Tidskriftsartikel (refereegranskat)abstract
- With the rapid development of artificial intelligence technology, the deep learning method has been introduced for vehicle trajectory prediction in the internet of vehicles, since it provides relative accurate prediction results, which is one of the critical links to guarantee security in the distributed mixed-driving scenario. In order to further enhance prediction accuracy by making full utilization of complex traffic scenes, an improved multimodal trajectory prediction method based on deep inverse reinforcement learning is proposed. Firstly, a fused dilated convolution module for better extracting raster features is introduced into the existing multimodal trajectory prediction network backbone. Then, a reward update policy with inferred goals is improved by learning the state rewards of goals and paths separately instead of original complex rewards, which can reduce the requirement for predefined goal states. Furthermore, a correction factor is introduced in the existing trajectory generator module, which can better generate diverse trajectories by penalizing trajectories with little difference. Abundant experiments on the current popular public dataset indicate that the prediction results of our proposed method are a better fit with the basic structure of the given traffic scenario in a long-term prediction range, which verifies the effectiveness of our proposed method. © 2022 by the authors.
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| 4. |
- Guo, Qinghua, et al.
(författare)
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Numerical study on thermally driven smoke flow characteristics in long tunnels under natural ventilation
- 2023
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Ingår i: International journal of thermal sciences. - : Elsevier Masson s.r.l.. - 1290-0729 .- 1778-4166. ; 192
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Tidskriftsartikel (refereegranskat)abstract
- The paper focuses on the flow structures and mass flow rates of thermally driven smoke flows induced by fires in long transportation tunnels under natural ventilation. The important influencing factors including heat release rate (HRR), tunnel width and height, are taken into consideration. The mechanism of the smoke flow movement is explored. The results show that for a fire in a long naturally ventilated transportation tunnel, there exists a critical point which is dependent on HRR and tunnel geometry. This critical point is defined as the location where the smoke layer thickness and the outgoing mass flow rate increase towards it and decrease after it. Further, it is found that the critical point moves farther away from the fire source in a wider or higher tunnel, while it lies closer to the fire source for a higher HRR. A correlation is proposed to estimate the location of the critical point. The outgoing mass flow rates along the tunnel are calculated using the two-layer flow model and well-mixed flow model of thermally driven flows, and the results indicate that these models produce satisfactory predictions of the mass flow rates if the vertical temperature profile is known. © 2023 The Authors
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| 5. |
- Guo, Qinghua, et al.
(författare)
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Study on spilled liquid from a continuous leakage in sloped tunnels
- 2022
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Ingår i: Tunnelling and Underground Space Technology. - : Elsevier Ltd. - 0886-7798 .- 1878-4364. ; 120
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Tidskriftsartikel (refereegranskat)abstract
- The study focuses on the behaviors of spilled liquid from a continuously leaked tank in sloped tunnels. Spillage width and area, which impact the potential heat release rates in case of fire, are investigated under different tunnel slopes and leakage flow rates by numerical simulations using interFoam based on the VOF method in the OpenFOAM toolbox following the validation. The simulation results show that the spillage width initially decreases rapidly and then slowly as the tunnel slope increases. Other parameters, including road surface roughness, physical properties of liquid and leakage source height, are also considered. Empirical models for predicting the spillage width and area are established considering both tunnel slope and leakage flow rate. The results may provide guidance for tunnel safety design and drainage system design affiliated with a tank leakage inside a tunnel. © 2021 The Author(s)
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| 6. |
- Guo, Qinghua, et al.
(författare)
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Theoretical and numerical study on mass flow rates of smoke exhausted from short vertical shafts in naturally ventilated urban road tunnel fires
- 2021
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Ingår i: Tunnelling and Underground Space Technology. - : Elsevier Ltd. - 0886-7798 .- 1878-4364.
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Tidskriftsartikel (refereegranskat)abstract
- The study focuses on the mass flow rate of the buoyancy-driven gases exhausted from the shaft in naturally ventilated urban road tunnel fires. Theoretical analyses and numerical simulations are performed. The model to predict the mass flow rate of the incoming smoke exhausted by the nearest shaft is developed by considering that the smoke is exhausted along the four sides of the shaft separately. Based on the heat balance between the incoming smoke exhausted and the total gas flow exhausted, the model to estimate the total mass flow rate exhausted from the shaft (both smoke and entrained air) is also established. Meanwhile, a series of numerical simulation in a naturally ventilated tunnel considering the heat release rate (HRR), the shaft height, shaft length and width, shaft location was carried out. The simulation results show that the shaft height has a limited contribution to the mass flow rate of the incoming smoke exhausted while a larger shaft cross-sectional area shows a favorable performance in exhausting the smoke. Further, the air entrainment into the shaft increases with both the shaft height and shaft cross-sectional area. Comparisons of the mass flow rates of the incoming smoke and the total mass flow rates exhausted between simple calculations and simulations are made, showing that the simple models perform well. Further, it is found that there exist two regimes for the total mass flow rate corresponding to different smoke modes in the shaft (complete plug-holing, plug-holing and without plug-holing), which is caused by the different driven forces in the shaft. The outcomes of this work could provide some guidance for the design of vertical shaft and smoke control in naturally ventilated tunnel in urban area.
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| 7. |
- Guo, Qinghua, et al.
(författare)
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Theoretical studies on buoyancy-driven ceiling jets of tunnel fires with natural ventilation
- 2020
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Ingår i: Fire safety journal. - : Elsevier Ltd. - 0379-7112 .- 1873-7226. ; 119
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Tidskriftsartikel (refereegranskat)abstract
- The paper presents a theoretical study on the ceiling jets induced by small fires in tunnels. The ceiling jet thickness, temperature rise and velocity are analyzed theoretically with Non-Boussinesq approximation. The study focuses on the radial and one-dimensional ceiling jets. Numerical solutions in the radial region and one-dimensional shooting region are obtained and new analytical solutions in the critical flow region are achieved. Analytical solutions indicate that the ceiling jet thickness increases with distance away from the fire source, which largely differs from the existing models implying that the ceiling jet thickness in the one-dimensional critical flow remains constant. Additionally, impacts of the air entrainment, friction and heat transfer on the ceiling jet are analyzed. It is found that in the radial and one-dimensional shooting flow regions, the air entrainment has a much more significant effect than the friction and heat transfer. However, in the one-dimensional critical flow region, the impact of air entrainment seems to be negligible and the flow is dominated by the friction and heat transfer. Further, validation of the present theory is made by comparing with previous theories, semi-empirical models, and experiments. The results show that the present theory provides a good prediction of the ceiling jet properties with natural ventilation for a small fire. © 2020 The Authors
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| 8. |
- Llamas, Ángel David García, et al.
(författare)
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Rapid change of particle velocity due to volatile gas release during biomass devolatilization
- 2022
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Ingår i: Combustion and Flame. - : Elsevier. - 0010-2180 .- 1556-2921. ; 238
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Tidskriftsartikel (refereegranskat)abstract
- Our earlier study showed significant differences in average particle velocity between simulation and experimental results for devolatilizing biomass particles in an idealised entrained flow reactor [N. Guo et al., Fuel, 2020]. This indicates that the simulations do not accurately describe the physicochemical transformations and fluid dynamic processes during devolatilization. This article investigates the reasons for these discrepancies using time-resolved analyses of the experimental data and complementary modelling work. The experiments were conducted in a downdraft drop-tube furnace with optical access, which uses a fuel-rich flat flame (CH4 O2 CO2) to heat the particles. Gas flow was characterized using particle image velocimetry, equilibrium calculations and thermocouple measurements. High-speed images of devolatilizing Norway spruce (Picea Abies) particles were captured and analysed using time-resolved particle tracking velocimetry methods. The data were used to estimate the balance of forces and fuel conversion. Thrust and “rocket-like” motions were frequently observed, followed by quick entrainment in the gas flow. Rocketing particles were, on average, smaller, more spherical and converted faster than their non-rocketing counterparts. These differences in conversion behaviour could be captured by a particle-size dependent, 0-D devolatilization model, corrected for non-isothermal effects. The results from this investigation can provide a basis for future modelling and simulation work relevant for pulverized firing technologies.
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