| 1. |
- Liu, Wei, et al.
(författare)
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Microencapsulated phase change material through cellulose nanofibrils stabilized Pickering emulsion templating
- 2023
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Ingår i: advanced composites and hybrid materials. - 2522-0128. ; 6:4
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Tidskriftsartikel (refereegranskat)abstract
- Phase change materials (PCMs) possess remarkable capability to store and release substantial amounts of energy during the processes of melting and crystallization across a wide temperature range, thus holding great promise in applications related to temperature regulation and thermal energy storage. Herein, to effectively address PCM leakage and enhance thermal conduction, PCM microcapsules with melamine-formaldehyde resin (MF) shell were prepared using in situ polymerization of Pickering emulsions stabilized by cellulose nanofibrils (CNFs). CNFs were selected as the stabilizers for the Pickering emulsions and as reinforcing nanofillers for the MF shell, owing to their excellent emulsifying capability, high mechanical strength, and sustainable nature. Paraffin wax (PW) was utilized as the PCM material. The resulting PCM microcapsules with MF resin shells and PW core had a diameter ranging from 2 to 4 & mu;m. Results showed that microcapsule with the core-shell ratio of 2 (Micro-2.0) exhibited the highest latent heat of crystallization and latent heat of fusion, measuring approximately 128.40 J/g and 120.23 J/g, respectively. The encapsulation efficiency of Micro-2.0 was determined to be approximately 79.84%.
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| 2. |
- Du, Kun, et al.
(författare)
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Numerical Investigation on Flow and Cooling Characteristics of a Micro-Ribbed Vane Endwall
- 2023
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Ingår i: Journal of Thermal Science. - : Springer Science and Business Media LLC. - 1003-2169 .- 1993-033X. ; 32:2, s. 786-799
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Tidskriftsartikel (refereegranskat)abstract
- The secondary flow originated from the inherent pressure gradient inside the vane cascade has a strong impact on the endwall cooling performance as the crossflow sweeps the upstream coolant jet towards the suction side, resulting in intensifying thermal load near the pressure side endwall. Hence a novel ribbed-endwall is introduced to suppress passage crossflow. The effects of the mass flow ratio and the rib layout were examined using numerical simulations by solving the three-dimensional Reynolds-averaged Navier-Stokes (RANS) equations with the shear stress transport (SST) k-ω turbulence model. The results indicate that the ribs effectively prevent the coolant migrating from the pressure side to the suction side, helping the coolant jet to spread along the lateral orientation. Therefore, the endwall adiabatic film cooling effectiveness is substantially improved. The maximum cooling effectiveness is achieved for the case with three-ribs when the height of the rib equals one hole diameter among all cases. The area-averaged adiabatic cooling effectiveness is enhanced by 31.6% relative to the flat endwall when the mass flow ratio of coolant to mainstream equals to 0.52%. More importantly, the ribbed-endwall obtains a relatively lower level of aerodynamic loss owing to the reduced lateral migration inside the vane cascade.
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| 3. |
- Lewin, Harris A., et al.
(författare)
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The Earth BioGenome Project 2020 : Starting the clock
- 2022
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences (PNAS). - 0027-8424 .- 1091-6490. ; 119:4
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 4. |
- Li, Yuling, et al.
(författare)
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Bilateral Teleoperation of Multiple Robots under Scheduling Communication
- 2020
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Ingår i: IEEE Transactions on Control Systems Technology. - 1063-6536. ; 28:5, s. 1770-1784
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, bilateral teleoperation of multiple slaves coupled to a single master under scheduling communication is investigated. The sampled-data transmission between the master and the multiple slaves is fulfilled over a delayed communication network, and at each sampling instant, only one slave is allowed to transmit its current information to the master side according to some scheduling protocols. To achieve the master-slave synchronization, round-robin (RR) scheduling protocol and try-once-discard (TOD) scheduling protocol are employed, respectively. By designing a scheduling-communication-based controller, some sufficient stability criteria related to the controller gain matrices, sampling intervals, and communication delays are obtained for the closed-loop teleoperation system under the RR and TOD scheduling protocols, respectively. Finally, simulation studies are given to validate the effectiveness of the proposed results.
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| 5. |
- Li, Yuling, et al.
(författare)
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Distributed Neural-Network-Based Cooperation Control for Teleoperation of Multiple Mobile Manipulators Under Round-Robin Protocol
- 2021
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Ingår i: IEEE Transactions on Neural Networks and Learning Systems. - 2162-237X.
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Tidskriftsartikel (refereegranskat)abstract
- This article addresses the distributed cooperative control design for a class of sampled-data teleoperation systems with multiple slave mobile manipulators grasping an object in the presence of communication bandwidth limitation and time delays. Discrete-time information transmission with time-varying delays is assumed, and the Round-Robin (RR) scheduling protocol is used to regulate the data transmission from the multiple slaves to the master. The control task is to guarantee the task-space position synchronization between the master and the grasped object with the mobile bases in a fixed formation. A fully distributed control strategy including neural-network-based task-space synchronization controllers and neural-network-based null-space formation controllers is proposed, where the radial basis function (RBF) neural networks with adaptive estimation of approximation errors are used to compensate the dynamical uncertainties. The stability and the synchronization/formation features of the single-master-multiple-slaves (SMMS) teleoperation system are analyzed, and the relationship among the control parameters, the upper bound of the time delays, and the maximum allowable sampling interval is established. Experiments are implemented to validate the effectiveness of the proposed control algorithm.
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| 6. |
- Pan, Junxiu, et al.
(författare)
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pi-Extended Nonfullerene Acceptors for Efficient Organic Solar Cells with a High Open-Circuit Voltage of 0.94 V and a Low Energy Loss of 0.49 eV
- 2021
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Ingår i: ACS Applied Materials and Interfaces. - : AMER CHEMICAL SOC. - 1944-8244 .- 1944-8252. ; 13:19, s. 22531-22539
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Tidskriftsartikel (refereegranskat)abstract
- A combination of high open-circuit voltage (V-oc) and short-circuit current density (J(sc)) typically creates effective organic solar cells (OSCs). Y5, a member of the Y-series acceptors, can achieve high V-oc of 0.94 V with PM6 but low J(sc) of 12.8 mA cm(-2). To maintain the high V-oc while increasing the J(sc) of devices, we developed a new nonfullerene acceptor, namely, BTP-C2C4-N, by extending the conjugation of a Y5 molecule with a naphthalenebased end acceptor. In comparison with Y5-based devices, PM6:BTP-C2C4-N-based devices exhibited significantly higher J(sc) of 18.2 mA cm(-2) followed by a high V-oc. To further increase the photovoltaic properties of BTP-C2C4-N analogues, BTP-C4C6-N and BTP-C6C8-N molecules with better processability and film morphology are obtained by adjusting the alkyl branched chain length. The optimized OSCs based on BTP-C4C6-N with a moderate alkyl branched chain length exhibited the best PCE of 12.4% with a high V-oc of 0.94 V and J(sc) of 20.7 mA cm(-2). Notably, the devices achieved a low energy loss of 0.49 eV (0.51 eV for Y5 system) accompanied by a small nonradiative energy loss. The results indicate that nonfullerene acceptors with extended terminal motifs and optimized branched chain lengths can effectively enhance the performance of OSCs and reduce energy loss.
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| 7. |
- Sun, Huiliang, et al.
(författare)
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Reducing energy loss via tuning energy levels of polymer acceptors for efficient all-polymer solar cells
- 2020
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Ingår i: Science China Chemistry. - : Springer Science and Business Media LLC. - 1869-1870 .- 1674-7291. ; 63:12, s. 1785-1792
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Tidskriftsartikel (refereegranskat)abstract
- The open-circuit voltage (Voc) of all-polymer solar cells (all-PSCs) is typically lower than 0.9 V even for the most efficient ones. Large energy loss is the main reason for limiting Voc and efficiency of all-PSCs. Herein, through materials design using electron deficient building blocks based on bithiophene imides, the lowest unoccupied molecular orbital (LUMO) energy levels of polymer acceptors can be effectively tuned, which resulted in a reduced energy loss induced by charge generation and recombination loss due to the suppressed charge-transfer (CT) state absorption. Despite a negligible driving force, all-PSC based on the polymer donor and acceptor combination with well-aligned energy levels exhibited efficient charge transfer and achieved an external quantum efficiency over 10% while maintaining a large Voc of 1.02 V, leading to a 9.21% efficiency. Through various spectroscopy approaches, this work sheds light on the mechanism of energy loss in all-PSCs, which paves an avenue to achieving efficient all-PSCs with large Voc and drives the further development of all-PSCs.
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| 8. |
- Sun, Huiliang, et al.
(författare)
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Reducing energy lossviatuning energy levels of polymer acceptors for efficient all-polymer solar cells
- 2020
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Ingår i: Science China Chemistry. - : Science China Press and Springer-Verlag GmbH Germany. - 1674-7291 .- 1869-1870. ; 63, s. 1785-1792
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Tidskriftsartikel (refereegranskat)abstract
- The open-circuit voltage (V-oc) of all-polymer solar cells (all-PSCs) is typically lower than 0.9 V even for the most efficient ones. Large energy loss is the main reason for limitingV(oc)and efficiency of all-PSCs. Herein, through materials design using electron deficient building blocks based on bithiophene imides, the lowest unoccupied molecular orbital (LUMO) energy levels of polymer acceptors can be effectively tuned, which resulted in a reduced energy loss induced by charge generation and recombination loss due to the suppressed charge-transfer (CT) state absorption. Despite a negligible driving force, all-PSC based on the polymer donor and acceptor combination with well-aligned energy levels exhibited efficient charge transfer and achieved an external quantum efficiency over 10% while maintaining a largeV(oc)of 1.02 V, leading to a 9.21% efficiency. Through various spectroscopy approaches, this work sheds light on the mechanism of energy loss in all-PSCs, which paves an avenue to achieving efficient all-PSCs with largeV(oc)and drives the further development of all-PSCs.
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