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We propose a novel framework to reconstruct accurate appearance and geometry with neural radiance fields (NeRF) for interacting hands, enabling the rendering of photo-realistic images and videos for gesture animation from arbitrary views. Given multi-view images of a single hand or interacting hands, an off-the-shelf skeleton estimator is first employed to parameterize the hand poses. Then we design a pose-driven deformation field to establish correspondence from those different poses to a shared canonical space, where a pose-disentangled NeRF for one hand is optimized. Such unified modeling efficiently complements the geometry and texture cues in rarely-observed areas for both hands. Meanwhile, we further leverage the pose priors to generate pseudo depth maps as guidance for occlusion-aware density learning. Moreover, a neural feature distillation method is proposed to achieve cross-domain alignment for color optimization. We conduct extensive experiments to verify the merits of our proposed HandNeRF and report a series of state-of-the-art results both qualitatively and quantitatively on the large-scale InterHand2.6M dataset., CVPR 2023

The layer flatness and interfacial strength for the direct ink writing (DIW)-fabricated multilayer sensors are two significant factors in dominating the printing precision and the structural integrity of the sensors, respectively. However, it is still a challenge to control the interfacial strength and layer flatness of the multilayer sensors due to the multiplicity of materials and inherent lines-to-plane forming process of DIW technology. Here we probe a set of DIW fabrication parameters to optimize the layer flatness and design the interfacial strength of the multilayer sensors. The nonlinear thickness-dependent interfacial strength is then measured by single-lap joints experiments, which can be further predicted by an analytical model and finite element simulations. Finally, the high precision and stability of the printed strain sensors with considerably flat layers and high interfacial strength are further tested under static and cyclic tensile loadings. This study provides a feasible approach for parametrically designing and precisely manufacturing multilayer sensors based on the widely used DIW technology.

This work was devoted to investigating the long-term cumulative effect of municipal sewage treatment plant (STP) effluents on the sediments, near the plant outlet, in Yunliang River in Nanjing, China. Laboratory experiments were performed to assess the effect of different aeration modes on the migration and distribution of phosphorus (P) in the sediments. The field investigation showed that the concentrations of organic matter, different P fractions, dehydrogenase activity and alkaline phosphatase activity in sediments near the STP outlet were higher than those in the upstream site. The results of laboratory studies documented that the retention of P in sediments mainly depended on the characteristics of sediments. Collectively, long-term intermittent aeration accelerated the conversion of parts of organic phosphorus to occluded Fe–P due to that Fe2+ were oxidized to Fe3+ gradually, inactivating the sediments P, which preventing P release completely even in the case of anoxic conditions. Compared ...

Gas foil bearings have bright application prospects in oil-free turbomachinery such as aircraft air cycle machines, compressors, and gas turbines. To extend the applicability of foil bearings to high-speed and heavy-load systems, the axial force produced primarily by the pressure difference between the turbine and compressor sides must be taken into consideration. The thrust disc of the rotor is typically used to sustain the axial force and maintain the attitude of the rotor in a rotor-bearing system. In an analytical model used to predict the performance of gas foil thrust bearings, fluid–structure interaction must be considered because of the coupling effects of hydrodynamic lubrication and the compliance of bearing surface. In this study, a link-spring structural model was employed to calculate the equivalent vertical stiffness of the bump foil. This model exhaustively considered the effect of three factors: flexibility of the bump foil, interactions between bumps and frictional forces at the contact surfaces. In addition, top foil deflection that directly affects film thickness is calculated using a finite-element shell model. The static and dynamic characteristics of gas foil thrust bearings were predicted after solving the steady-state Reynolds equation and two linearized dynamic coefficient equations which were obtained with perturbation method by using finite-difference method. The structural deformation equation was substituted into the Reynolds equations in the calculation process. The calculated static load was compared with the published experimental data, and the results validated the theoretical analysis. Thereafter, the static and dynamic characteristics including impact of rotational speed, initial minimum film thickness and the ratio of the inlet to outlet film thicknesses were analyzed. Parametric studies were also conducted to evaluate the effect of different structural parameters of the bump foil and journal tilting on the static characteristics of gas foil thrust bearings. Because the proposed analytical model is completely algebraic, it can be easily programmed for accurately and effectively investigating the performance of gas foil thrust bearings.

With increasing need for high-speed, high-temperature, and oil-free turbomachinery, gas foil bearings (GFBs) have been considered to be the best substitutes for traditional oil-lubricated bearings. A multi-cantilever foil bearing (MCFB), a novel GFB with multi-cantilever foil strips serving as the compliant underlying structure, was designed, fabricated, and tested. A series of static and dynamic load tests were conducted to measure the structural stiffness and equivalent viscous damping of the prototype MCFB. Experiments of static load versus deflection showed that the proposed bearing has a large mechanical energy dissipation capability and a pronounced nonlinear static stiffness that can prevents overly large motion amplitude of journal. Dynamic load tests evaluated the influence of motion amplitude, loading orientation and misalignment on the dynamic stiffness and equivalent viscous damping with respect to excitation frequency. The test results demonstrated that the dynamic stiffness and damping are strongly dependent on the excitation frequency. Three motion amplitudes were applied to the bearing housing to investigate the effects of motion amplitude on the dynamic characteristics. It is noted that the bearing dynamic stiffness and damping decreases with incrementally increasing motion amplitudes. A high level of misalignment can lead to larger static and dynamic bearing stiffness as well as to larger equivalent viscous damping. With dynamic loads applied to two orientations in the bearing midplane separately, the dynamic stiffness increases rapidly and the equivalent viscous damping declines slightly. These results indicate that the loading orientation is a non-negligible factor on the dynamic characteristics of MCFBs.

The main advantages of the direct ink write (DIW) printed strain gauge are capable of achieving both the high sensitivity and the large stretchability. The performance of the DIW-printed strain gauge is mainly determined by the design parameters and fabrication process . However, it is still a big challenge for parametric design and precision manufacturing of the DIW-printed strain gauge due to the lack of universal analytical model and optimized process parameters. Here we propose an analytical model for designing widely used sandwich-structure strain gauges with coating-filament-base layers on substrates. The resistive strain gauges with a commercial carbon paste are fabricated by the DIW technology on polyimide and aluminium alloy substrates, respectively. Both its high sensitivity and large stretchability are designed from the present analytical model and reproduced well by the DIW-based fabrication. Our analytical model and DIW-based fabrication will be of great help for designing and fabricating other sandwich-structure gauges.