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• A novel chain-shaped flow field (CSFF) is studied numerically and experimentally. • A modified agglomerate model is proposed. • The CSFF enhances under-rib convection and oxygen mass transfer. • A more uniform current density distribution is obtained in the CSFF. The flow field is crucial for the performance and efficiency of proton exchange membrane fuel cells (PEMFCs). In this research, an innovative chain-shaped flow field (CSFF) configuration is proposed and investigated, focusing on cell performance, oxygen mass transfer, and current density distribution. For this purpose, a three-dimensional multiphase PEMFC model that is based on a modified agglomerate model has been established. Simulation results demonstrate that the CSFF facilitates the under-rib convection between neighboring flow channels and boosts mass transfer from the flow channels to the catalyst layer, consequently increasing both the oxygen concentration and its uniformity within the catalyst layer. An increase of 18.9 % in the net power density of the optimized CSFF has been achieved compared to the parallel flow field (PFF). Experimental results corroborate the simulation, demonstrating that the CSFF achieves an output voltage that is 52 mV greater than the PFF at a current density of 2.9 A cm−2. Further evidence from electrochemical impedance confirms that the CSFF shows a reduced oxygen mass transfer resistance. Additionally, measurements of local current density suggest that the CSFF design enhances the uniformity of current distribution. The findings imply that the proposed CSFF shows great potential for practical application. [ABSTRACT FROM AUTHOR]

In this paper, we propose a novel time-domain end-to-end network (LaSNet) for solving the problem of multiple sound sources localization (SSL) and separation based on microphone array. The traditional time-frequency (T-F) signal representation is subject to various prior conditions and fails to separate the different sound signal components. Even the data-driven neural network does not develop an effectively integrated approach where localization and separation interplay to serve both challenge. To address the aforementioned issue, we propose a novel approach that involves the implementation of a Separation Driving Localization Network (SDLNet). This framework operates by extracting latent features from a separation network and subsequently employing them in the context of a localization network. Then we propose a simple multi-task network for both SSL and separation. Through the analysis of steering vector filter, we find that the localization and separation problems can be linked by the operation of pseudo-inverse (pinv). To facilitate a synergistic relationship between SSL and sound separation, while also enabling end-to-end network training, we develop a Pinv Module (PM). Fianlly, the Localization and Separation Network (LaSNet) structure of this paper is proposed. Inspired by the overlay mechanism of network, LasNet is extended to a multi-task and multi-layer network, in which separation task is divided into multiple subtasks. A fuzzy separation loss function is introduced for training multi-layer network. Numerical experiments demonstrate that the proposed method has a clearly better advantageous improvement than several well known models. LaSNet has greatly performance improvement in both separation and localization, and achieves at least 32% relative reduction in model size, compared with the baseline models. • The conventional multi-task network-based speech separation and source localization does not address dependency between multiple tasks. • Localization and SeparationNetwork (LaSNet) (MMNet) can be able to alleviate dependency using steering vector. • A selectable channel with residual connection can reduce computational complexity of LaSNet. • At least 32% relative reduction in model size are achieved. [ABSTRACT FROM AUTHOR]

To reveal homologous substitution and refined mechanisms, and improve mechanical properties, Ti42Al6Nb 2.5 C x Ta alloys were prepared by arc melting. Element distribution, lamellar colony size, length-diameter radio of Ti 2 AlC phase, tensile properties, and the corresponding influence mechanism were studied. Results show that the relative contents of γ and Ti 2 AlC phase increase, the content of α 2 phase decreases, when Ta content increases from 0 to 2.0 at%. The relative content of B2 phase increases among the lamellar colonies and the length-diameter ratio of Ti 2 AlC particle decreases. Lamellar colony size decreases from 24.9 to 10.6 µm. With the increase of Ta content, the supercooling at the front of the solid-liquid interface increases and the β phase is refined. The increase of the precipitated phase content leads to the increase of the number of α phase heterogeneous nucleation particles, which will refine the lamellar colony. Tensile results show that the strength increases from 238 to 513 MPa and strain increases from 2.7 % to 11.1 % of Ti42Al6Nb 2.5 C1.6Ta alloy when the tested temperature increases from 750 to 950 ℃. The high temperature tensile properties of the alloy with more Ta content are relatively higher. Ta forms large lattice distortion after solid solution into the matrix due to its large atomic size, and Ta makes more Nb dissolve into the collective to increase the effect of solid solution strengthening. Another reason is the refinement of microstructure. • Alloys with finer microstructure and better high temperature tensile properties were prepared by adding different contents of Ta. • The lamellar colony and the Ti2AlC precipitates are refined, the size of lamellar colony decreases from 24.9 to 10.6 µm. • The tensile strength and elongation of alloy increase with the increase of Ta content. • Tensile results show that the strength increases from 238 to 513 MPa and strain increase from 2.7 % to 11.1 % of Ti42Al6Nb2.5C1.6Ta alloy when the tested temperature increase from 750 to 950 ℃. [ABSTRACT FROM AUTHOR]

Recently, vision-based methods have exhibited promising prospects in assigning autonomous robots more capabilities for better environment perception. Since visual sensors are easily affected under extreme conditions, current image inpainting methods based on CNNs jointly with generative adversarial networks (GANs) usually generate patches quite different from the ground truth (GT), which is harmful to autonomous robots. In this paper, we propose a novel multiscale feature alignment module with an early fusion strategy to align the left and right feature maps to better capture the motion cues between them. Then, the aligned features are fused to fill holes in the left image. To aggregate the multiscale feature maps dynamically, we propose a multiscale feature aggregation module based on an attention mechanism, of which the fusion module is designed as a symmetrical architecture to adaptively incorporate the complementary contextual correlations from different feature branches. In addition, a spatial attention module able to capture the correlations among pixels is introduced into our network to enhance the inpainting capacity and generate more refined details. To evaluate the effectiveness of our proposed method, many experiments are conducted on a stereo image dataset. The quantitative and qualitative results show that our method significantly outperforms the recent state-of-the-art image inpainting methods while running over 22 fps on a single NVIDIA RTX2080Ti GPU. • A new image inpainting method which utilizes additional image as constraints to assist the inpainting process is proposed. • The multi-scale feature alignment module based on deformable convolution can realize the feature alignment of different images. • Implicitly detect and restore damaged regions by exploiting attention maps. • Image textures and features are refined through a long-range spatial attention mechanism. [ABSTRACT FROM AUTHOR]

A rapid and safe cold start is essential for the commercialisation of proton exchange membrane fuel cell (PEMFC) vehicles, and self-start is considered as the optimal way to fulfil this expectation. In this study, the self-start of large-area PEMFCs is investigated. It is found that there exists a severe temperature distribution nonuniformity along the flow direction during one-way air-supply self-start, and the cold-start capability is limited by the fact that most of the heat is concentrated in the inlet area, while less heat is in the outlet area, which makes it difficult to start at −15 °C. To solve this issue, an alternating air-supply strategy is suggested. By applying this strategy, temperature distribution uniformity and cold-start performance are significantly improved. Self-start from −15 °C and −20 °C can be achieved in 165 s and 142 s with starting voltages of 0.8 V and 0.6 V, respectively. The alternating interval has a negligible impact on start-up time but will affect the temperature distribution and fluctuation. The advantages of alternate air supply are analyzed based on the calculation of heat generation and water production. A performance degradation test indicates that cell performance is well preserved after 20 cold starts [Display omitted] [ABSTRACT FROM AUTHOR]

Mechanical stretching can accelerate Form II to Form I phase transitions in isotatic polybutene-1 (iPB-1). This study in-situ investigated the effect of pre-stretching on further phase transitions. Three tensile modes were considered. In mode A, the samples were stretched to their breaking point, and the phase transition was wholly completed. In mode B, the samples were pre-stretched to specific strains and annealed under quiescent conditions at room temperature. Mode C was studied under the same conditions as Mode B, but the samples were allowed free shrinkage during the phase transition. The phase transition process were investigated by mechanical testing and in situ wide-angle X-ray diffraction. The phase transition kinetics were obviously faster in the pre-stretched samples (even when stretched in the elastic zone) than in the un-stretched samples. The pre-stretching may affect the conformation or the lattice arrangement of the segments in Form II, thereby accelerating the subsequent phase transition. In the samples with pre-strain beyond the yield strain, the accelerated transition rate increased with the increased pre-strain, meanwhile, the growth dimension of Form I reduced, owing to the confinement effect of stretch-induced Form I. The residual stress in the mode-B stretched samples did not significantly affect the phase transition, because the residual stress was lower than the critical stress that triggers Form I nucleation. In summary, a small pre-strain accelerated the phase transition and affected the growth dimension of Form I. Image 1 • The phase transition from form II to form I in iPB-1 under three tensile modes was studied by wide angle X-ray diffraction technique. • The phase transition kinetics of the pre-stretched samples was obviously accelerated, even at very small strain in the elastic zone. • In samples with pre-strain beyond the yield strain, the growth dimension of Form I decreased due to the confinement effect. [ABSTRACT FROM AUTHOR]

Spontaneously phase transition from form II to I in isotactic polybutene-1 (iPB-1) products during storage at room temperature after processing limited their application. Investigations on phase transition in iPB-1 have practical importance, especially on oriented iPB-1 as oriented form II generated during processing where intense flow field is always imposed. The effects of flow on phase transition were studied with synchrotron radiation scanning X-ray microdiffraction (SR- μ SXRD) technique with beam size of 4.5 × 5.2 μm2 in the present work. Localized flow-field was imposed by pulling glass fiber through undercooled melt. Benefiting from the high resolution of SR- μ SXRD technique, the formation of fibrillar and oriented form II ( c I I f and c I I o ) were identified. The transformation from c I I f to fibrillar form I ( c I f ) completed in about 40 min, while c I I o transformed into oriented form I ( c I o ) partially in about 186 min. Quantitative analysis on SR- μ SXRD result showed that crystallographic lattice dimension of c I I f changed comparing with that of c I I o , where a and b increased while c decreased in c I I f . An obvious correlation between crystallographic lattice deformation and phase transition kinetics was is identified. Local internal stress plays an important role in promoting the phase transition kinetics, as the stress transmission efficiency in c I I f with rod-like morphology would be higher than that in c I I o with lamellar morphology. Image 1 • With in-situ SR- μ SXRD measurement, it's found that fibrillar and oriented form II were induced at high and low shear rate, respectively. • Fibrillar form II transformed into form I completely in about 40 min, which is much faster than that of oriented form II. • Deformation in lattice dimension of fibrillar form II is observed which may be due to partially conformation transition before lattice rearrangement. [ABSTRACT FROM AUTHOR]

To form in situ nano-borides in the solid-liquid two-phase region, Ti46 A l8Nb2·6C0.8Ta x B alloys were prepared under ultrasound to improve the microstructural and mechanical properties. The morphology and distribution of borides and the characteristics of lamellar colonies were observed with scanning and transmission electron microscopy and X-ray diffraction; these analyses revealed the influence of borides on microstructural evolution and improved strength and plasticity. The borides that form are elongated and spherical. As the B content increases, the borides gradually spheroidise, and nano-borides precipitate on the lamellar phase. There are a large number of dislocations around the borides to form stacking faults and dislocation walls. The average size of the lamellar colonies decreases from 26.9 to 19.3 μm. The increase in boride nucleation sites as the B content increases and ultrasound-mediate breaking of primary borides are the reasons for forming B27-type borides. The increase in nucleation particles refines the lamellar colony. The compressive strength increases from 2058 to 2299 MPa, and the strain increases from 25.2% to 32.3% when the addition of B increases from 0% to 1.2%. The significantly improved mechanical properties are due to uniformly distributed nano-borides that hinder the movement of dislocations to form stacking faults and dislocation walls and refinement of the lamellar colonies. [ABSTRACT FROM AUTHOR]