| 1. |
- Wang, Ji, et al.
(författare)
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Microstructural evolution of epitaxial Ti3AlC2 film on sapphire under ion irradiation and nanoindentation-induced deformation
- 2018
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Ingår i: Journal of Nuclear Materials. - : ELSEVIER SCIENCE BV. - 0022-3115 .- 1873-4820. ; 509, s. 181-187
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Tidskriftsartikel (refereegranskat)abstract
- Feasibility of Ti3AlC2 phase as the protective coatings of accident tolerant fuels (ATFs) was investigated by means of ions irradiation, nanoindentation and transmission electron microscopy. Au ions irradiation was carried out on thin Ti3AlC2 film to simulate the high displacement damage induced by the energetic particles in the nuclear reactors. Nanoindentation on the Ti3AlC2 film was followed subsequently as a source of external stress to simulate the high pressure applied on the cladding in nuclear reactor cores of pressurized water reactors (PWRs). TEM was used to characterize the microstructural evolution of Ti3AlC2 film after irradiation and nanoindentation. TEM analysis shows that Ti3AlC2 film remains pristine layered structure and no amorphization was detected after irradiation to similar to 14 dpa. The combined nanoindentation and TEM show that no rupture and exfoliation of the Au-irradiated Ti3AlC2 film occur even the extern stress and total elongation induced by nanoindentation reach to 16.6 GPa and similar to 5%, respectively. The above results show good irradiation resistance and good ductility as well as excellent adhesion of the Ti3AlC2 coating on the substrate after high dose irradiation and under high external stress. This indicates the good feasibility of Ti3AlC2 thin films as the coatings of ATF claddings. (C) 2018 Elsevier B.V. All rights reserved.
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| 2. |
- Zheng, Shao Fei, et al.
(författare)
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An inverse optimization of turbulent flow and heat transfer for a cooling passage with hierarchically arranged ribs in turbine blades
- 2024
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Ingår i: International Journal of Heat and Mass Transfer. - 0017-9310. ; 220
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Tidskriftsartikel (refereegranskat)abstract
- Owing to the limited cold-air amount and pressure in supply systems, high-efficient heat transfer with low-level friction loss is highly desired for cooling units of a turbine blade. To exploit the potential improvement of hierarchically arranged ribs in cooling passages proposed previously, multi-parameter optimizations for rib arrangements are implemented by integrating the simplified conjugate-gradient algorithm with the turbulent flow and heat transfer model. Rib heights as design variables are optimized with various performance indices as objective functions at a fixed Re. The optimizations confirm that using the wall temperature difference and Nu as the objective function, respectively, a limited heat transfer improvement is achieved with a greatly increased friction loss. Taking the overall performance factor as the objective function, different optimal designs at different constraint conditions possess hierarchical characteristics. A significant friction loss reduction of 52.1%, 54.7%, and 54.8%, is achieved with a moderate heat transfer loss of 10.9%, 7.0%, and 2.3%. Despite different thermal and friction performances, their overall performances are consistent with a remarkable increase of 13.9%, 21.2%, and 27.3%. Finally, the optimization strategy coupling the multi-parameter optimization and hierarchical scheme is confirmed as effective for enhancing the thermohydraulic performance of convective heat transfer systems with perturbation elements.
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| 3. |
- Zheng, Shao Fei, et al.
(författare)
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Performance evaluation with turbulent flow and heat transfer characteristics in rectangular cooling channels with various novel hierarchical rib schemes
- 2023
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Ingår i: International Journal of Heat and Mass Transfer. - 0017-9310. ; 214
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Tidskriftsartikel (refereegranskat)abstract
- Turbulators, such as ribs, dimples, and pin-fins, play a vital role in the internal cooling efficiency of turbine blades. As a typical turbulator, various rib configurations using a uniform arrangement scheme have indicated high heat transfer enhancement but the friction loss is simultaneously subject to a great increase. In this work, a novel hierarchical arrangement scheme of ribs is developed aiming to improve the cooling efficiency. Adopting the uniform scheme as a baseline, the hierarchical scheme is implemented for six representative rib configurations (including transverse ribs, angled ribs, V-shaped ribs, inverted V-shaped ribs, M-shaped ribs, and inverted M-shaped ribs) and evaluated for its feasibility and generality. For different cooling designs, turbulent flow and heat transfer of the ribbed cooling channel are studied by three-dimensional numerical simulations based on the finite volume method with a constructed turbulence model. It is found that for all rib configurations, the hierarchical scheme can remarkably reduce the friction loss as desired, especially for the inverted V-shaped rib with a reduction of up to 50%. Due to the occurrence of flow separation, secondary flows offered by transverse ribs are characterized by a two-dimensional recirculation vortex behind the rib. For other rib configurations, secondary flows present a typical three-dimensional characteristic including the downwash flows along the inclined rib leg and the longitudinal vortices. The usage of the hierarchical scheme with small ribs strongly suppresses these secondary flows, which contributes to the significant decrease in form drag loss. Meanwhile, using the hierarchical scheme produces a slight heat transfer deterioration commonly, which is because the constrained secondary vortices weaken the turbulent mixing and convection heat transfer. Significantly, for the two W-shaped ribs, the limited secondary vortices but fully developed under the hierarchical scheme achieve a higher heat transfer enhancement. Finally, for all considered ribs, the hierarchical scheme can improve the overall performance factor of (Nu/Nu0)/(f/f0)1/3 by more than 10%, and up to 21.15% for the V-shaped rib. Adjusting design variables, including the decreasing ratio of the rib size and the initial rib size, the hierarchical scheme still provides even higher performance enhancement.
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| 4. |
- Zheng, Pai, et al.
(författare)
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Augmented Reality-assisted Mutual Cognitive System for Human-Robot Interaction Safety Concerns
- 2023
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Ingår i: Jixie Gongcheng Xuebao/Journal of Mechanical Engineering. - : Chinese Mechanical Engineering Society. - 0577-6686. ; 59:6, s. 173-184
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Tidskriftsartikel (refereegranskat)abstract
- In modern manufacturing, the interaction and symbiosis between humans and the industrial robot are one of the foci of smart manufacturing. During human-robot interaction(HRI), the potential risk of any injury to workers caused by industrial robots is very critical and should be well-addressed to ensure manufacturing safety. However, in the dynamic and uncertain manufacturing environment, the current HRI safety is still based on the robot's perception of the environment to achieve collision avoidance, lacking adaptable decision-makings under mutual cognition. Therefore, to enhance the cognition of human operators in the working environment and improve the robot's collision avoidance and adaptive motion planning capabilities, this work designs and further implements a mutual cognitive HRI safety system based on augmented reality (AR) in a wearable manner. In the proposed system, the wearable AR device serves as the bridging interface to realize the virtual-real registration of the robot, the virtual-physical mapping of the working environment of the HRI process, and to collect the information of human, robot, and working space. In addition to these, a hierarchical HRI safety strategy is introduced for real-time mutual cognitive assistance to both humans and robots, namely: 1) robot motion speed control and safety area visualization based on human-robot distance, 2) virtual-physical mapping for robot motion preview and collision detection, and 3) deep reinforcement learning-driven motion planning for collision avoidance strategies generation. Lastly, a prototype system is further developed to validate the feasibility and effectiveness of the proposed strategies. By leveraging advanced artificial intelligence and human-robot interaction technologies, it is envisioned this work can bring insightful safety protection mechanisms to better achieve symbiotic human-robot collaboration.
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| 5. |
- Wang, Deyu, et al.
(författare)
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FPGA-Based HPC for Associative Memory System
- 2024
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Ingår i: 29TH ASIA AND SOUTH PACIFIC DESIGN AUTOMATION CONFERENCE, ASP-DAC 2024. - : Institute of Electrical and Electronics Engineers (IEEE). ; , s. 52-57
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Konferensbidrag (refereegranskat)abstract
- Associative memory plays a crucial role in the cognitive capabilities of the human brain. The Bayesian Confidence Propagation Neural Network (BCPNN) is a cortex model capable of emulating brain-like cognitive capabilities, particularly associative memory. However, the existing GPU-based approach for BCPNN simulations faces challenges in terms of time overhead and power efficiency. In this paper, we propose a novel FPGA-based high performance computing (HPC) design for the BCPNN-based associative memory system. Our design endeavors to maximize the spatial and timing utilization of FPGA while adhering to the constraints of the available hardware resources. By incorporating optimization techniques including shared parallel computing units, hybrid-precision computing for a hybrid update mechanism, and the globally asynchronous and locally synchronous (GALS) strategy, we achieve a maximum network size of 150x10 and a peak working frequency of 100 MHz for the BCPNN-based associative memory system on the Xilinx Alveo U200 Card. The tradeoff between performance and hardware overhead of the design is explored and evaluated. Compared with the GPU counterpart, the FPGA-based implementation demonstrates significant improvements in both performance and energy efficiency, achieving a maximum latency reduction of 33.25x, and a power reduction of over 6.9x, all while maintaining the same network configuration.
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| 6. |
- Weng, Zhenhua, et al.
(författare)
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Lead-Free Cs2BiAgBr6 Double Perovskite-Based Humidity Sensor with Superfast Recovery Time
- 2019
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Ingår i: Advanced Functional Materials. - : WILEY-V C H VERLAG GMBH. - 1616-301X .- 1616-3028. ; 29:24
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Tidskriftsartikel (refereegranskat)abstract
- Lead halide perovskites have demonstrated outstanding achievements in photoelectric applications owing to their unique properties. However, the moisture sensitivity of lead halide perovskite has rarely been developed into an applicable humidity sensor due to the intrinsic instability and toxicity issue. Herein, as a highly stable lead-free perovskite, a Cs2BiAgBr6 thin film is chosen to be the active material for humidity sensor due to its extraordinary humidity-dependent electrical properties and good stability. This Cs2BiAgBr6 thin film humidity sensor demonstrates a superfast response time (1.78 s) and recovery time (0.45 s). The superfast response and recovery properties can be attributed to the reversible physisorption of water molecules, which can be easily adsorbed onto or desorbed from the thin film surface. Moreover, the sensor also shows an excellent reliability and stability properties as well as logarithmic linearity in a relative humidity's range of 15% to 78%. The lead-free Cs2BiAgBr6 perovskite possesses great potential for application in real-time humidity sensing.
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| 7. |
- Tu, Li, et al.
(författare)
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A wide-range operating synaptic device based on organic ferroelectricity with low energy consumption
- 2018
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Ingår i: RSC Advances. - : Royal Society of Chemistry. - 2046-2069. ; 8:47, s. 26549-26553
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Tidskriftsartikel (refereegranskat)abstract
- In thiswork, a wide-range operating synaptic device based on organic ferroelectricity has been demonstrated. The device possesses a simple two-terminal structure by using a ferroelectric phase-separated polymer blend as the active layer and gold/indium tin oxide (ITO) as the top/bottom electrodes, and exhibits a distinctive history-dependent resistive switching behavior at room temperature. And the device with low energy consumption (similar to 50 fJ mu m(-2) per synaptic event) can provide a reliable synaptic function of potentiation, depression and the complex memory behavior simulation of differential responses to diverse stimulations. In addition, using simulations, the accuracy of 32 x 32 pixel image recognition is improved from 76.21% to 85.06% in the classical model Cifar-10 with 1024 levels of the device, which is an important step towards the higher performance goal in image recognition based on memristive neuromorphic networks.
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| 8. |
- Zheng, Shao Fei, et al.
(författare)
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Scale effect of micro ribs on the turbulent transport in an internal cooling channel
- 2024
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Ingår i: Physics of Fluids. - 1070-6631. ; 36:2
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Tidskriftsartikel (refereegranskat)abstract
- Owing to the limited supply and pressure margin in the air system, a cooling technique providing efficient heat transfer with lower flow loss is highly desirable for gas turbine blades. Microscale ribs have promised to be a potential cooling candidate. In this work, large eddy simulations are implemented to reveal the scale effect of micro ribs on the near-wall turbulent transport in a cooling channel. Considering a mechanistic study and practical applications, both single-rib and rib-array arrangements are studied with a wide range of dimensionless viscous-scaled rib heights involving the entire boundary layer. The results indicate that the rib-induced destruction and regeneration of coherent structures are, respectively, responsible for the weakened momentum transport and enhanced heat transport in the near-wall region. Using tiny ribs, regenerated quasi-streamwise vortices are mainly located in the buffer layer. The resulting turbulence burst greatly enhances wall heat transfer while keeping a lower flow loss due to the weak form drag. Regenerated hairpin vortices using tall ribs are activated in the log-law layer and intensively interact with mainstream. Along with improved wall heat transfer, the significant form drag results in a remarkably high flow loss. Accordingly, heat transfer and flow loss show different dependencies on the rib height, which contributes to an optimum height interval of ribs (e+ = 20-40) located in the high buffer and low log-law layer for maximizing the overall performance. Furthermore, for the rib-array scheme, adequate inter-rib spacing is essential to achieve turbulence regeneration for enhancing near-wall heat transport.
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| 9. |
- Sun, Huibin, et al.
(författare)
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Evaluation method of product-service performance
- 2012
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Ingår i: International journal of computer integrated manufacturing (Print). - : Taylor & Francis. - 0951-192X .- 1362-3052. ; 25:2, s. 150-157
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Tidskriftsartikel (refereegranskat)abstract
- In order to analyse product–service performance (PSP) during product–service systems’ (PSSs) running time, a PSP evaluation method is proposed. Interrelationship between a PSS’s provider and accepter is defined as product–service relationship (PSR). Concepts of product–service network and product–service chain are put forward to describe interrelationship among PSRs from different perspectives. The concept of PSP is proposed to evaluate interrelationship among PSR. Detailed evaluation indexes are designed to measure the five factors of PSP, including time, quality, cost, stability and reliability. A case study is provided to test the validity and efficiency of the evaluation model of PSP. The analysis results show that the evaluation model can make good efforts in benefiting product–service platform’s running, monitoring and optimising.
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| 10. |
- Jin, Junchen, et al.
(författare)
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PRECOM : A Parallel Recommendation Engine for Control, Operations, and Management on Congested Urban Traffic Networks
- 2021
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Ingår i: IEEE transactions on intelligent transportation systems (Print). - : Institute of Electrical and Electronics Engineers (IEEE). - 1524-9050 .- 1558-0016. ; , s. 1-11
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Tidskriftsartikel (refereegranskat)abstract
- This paper proposes a parallel recommendation engine, PRECOM, for traffic control operations to mitigate congestion of road traffic in the metropolitan area. The recommendation engine can provide, in real-time, effective and optimal control plans to traffic engineers, who are responsible for manually calibrating traffic signal plans especially when a road network suffers from heavy congestion due to disruptive events. With the idea of incorporating expert knowledge in the operation loop, the PRECOM system is designed to include three conceptual components: an artificial system model, a computational experiment module, and a parallel execution module. Meanwhile, three essential algorithmic steps are implemented in the recommendation engine: a candidate generator based on a graph model, a spatiotemporal ranker, and a context-aware re-ranker. The PRECOM system has been deployed in the city of Hangzhou, China, through both offline and online evaluation. The experimental results are promising, and prove that the recommendation system can provide effective support to the current human-in-the-loop control scheme in the practice of traffic control, operations, and management.
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