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In this work, a systematic approach aimed at investigating and validating a novel way of realizing pyroelectric harvesting is presented. Generating a direct-current (dc) signal through a temperature gradient within a less than 7 nm-thick ferroelectric zirconium-doped hafnium oxide (HZO) nano-film, embedded in planar interdigitated capacitors on high-resistivity silicon, is a new, simple, effective, and reproducible solution. Temperature-related structural modifications in HZO are first simulated using advanced ab initio calculations. Then, rigorous multiphysics simulations of the final devices provide insight into the expected performance of the pyroelectric harvester, as a function of temperature, contact area, and crystal orientation, showing a maximum open-circuit voltage of up to 900 mV. The fabrication of the harvesters involves the area-selective wet etching of the HZO layer to retain it exclusively in between the fingers of each capacitor. This choice maximizes the pyroelectric effect (which strongly depends on the area) and represents a new paradigm in the development of HZO-based electronics, which are conventionally built on ferroelectric continuous films. Experimental validation at both low frequencies and microwaves confirms the pyroelectric effect, exhibiting a significant increase in the output current for higher temperature gradients, and a generated dc voltage of several hundred millivolts.

Changes in HeLa cell morphology, membrane permeability, and viability caused by the presence of Triton X-100 (TX100), a nonionic surfactant, were studied by scanning electrochemical microscopy (SECM). No change in membrane permeability was found at concentrations of 0.15 mM or lower during an experimental period of 30 to 60 min. Permeability of the cell membrane to the otherwise impermeable, highly charged hydrophilic molecule ferrocyanide was seen starting at concentrations of TX100 of about 0.17 mM. This concentration level of TX100 did not affect cell viability. Based on a simulation model, the membrane permeability for ferrocyanide molecules passing though the live cell membrane was 6.5± 2.0 × 10⁻⁶ m/s. Cells underwent irreversible permeabilization of the membrane and structural collapse when the TX100 concentration reached the critical micelle concentration (CMC), in the range of 0.19 to 0.20 mM. The impermeability of ferrocyanide molecules in the absence of surfactant was also used to determine the height and diameter of a single living cell with the aid of the approach curve and probe scan methods in SECM.

Vapor chambers (VCs) are efficient heat spreaders that rely on wicks to realize the circulation of a phase-changing working liquid and can be used to address heat dissipation problems in electronic devices, aerospace, and satellite equipment. In this study, we propose a novel vapor chamber with biomimetic wick structures and composite lattice supports to enhance the thermal management and load-bearing performance of vapor chambers. The experiments and COMSOL multiphysics 6.1 simulation results indicate that the biomimetic design can improve the startup performance, thermal management, and load-bearing performance of the VC. Compared to conventional VCs, at a filling ratio of 20% the biomimetic VC reduces the time to reach a steady state by 11.7% and improves the uniformity of temperature by 7.74%. This study provides a novel design concept for VCs and verifies the operating performance of vapor in high heat flux density cases, providing a reference for the innovative design and enhanced heat transfer of phase change-based thermal management equipment.

This paper presents an in-depth investigation of the biogeochemical modeling approaches applied to underground hydrogen storage. It delves into the intricate dynamics of hydrogen in the subsurface, focusing on small (pore-lab scale) and reservoir-scale models, highlighting the importance of capturing microbial, geochemical, and fluid flow dynamic interactions in porous media to simulate storage performance accurately. Small-scale models offer detailed insights into localized phenomena, such as microbial hydrogen consumption and mineral reactions, and can be verified and calibrated against laboratory data. Conversely, large-scale models are essential to assess the feasibility of a project and forecast the storage performance, but cannot be proven by real data yet. This work addresses the challenge of transitioning from fine-scale to reservoir models, integrating spatial heterogeneity and long-term dynamics while retaining biogeochemical complexity. Through the use of several simulation tools, like PHREEQC, Comsol, DuMuX, Eclipse, CMG-GEM, and others, this study explores how modeling approaches are evolving to incorporate multiphysics processes and biochemical feedback loops, which are essential for predicting hydrogen retention, flow, and potential risks. The findings highlight the strengths and limitations of current modeling techniques and suggest a workflow for exploiting at best existing modeling capabilities and developing reservoir models to support hydrogen storage appraisal and management.

The stability of flooded coal pillars has long been a challenging issue in coal pillar research, especially during the recovery of production after water inrush disasters. Due to the harsh on-site conditions, it is difficult to directly collect samples for analysis, which brings numerous challenges in both design and production. Based on the engineering background of the 1314 working face of Xiaoyun Coal Mine, this paper proposes a clustering optimization algorithm and successfully uses microseismic data collected on-site to identify the boundary of the flooded coal pillar, validating the results through simulation comparisons. The study found that the flooded state within the coal pillar can be classified into saturated flooded zones, unsaturated flooded zones, and dry zones. The characteristics of the flooded coal pillar during the early stage of mining are more complex, with irregular variations in the flood boundary and local phenomena of sudden changes. Through the analysis of stress and delamination data, the primary controlling factors of this phenomenon are identified and the causes are explained. The research not only demonstrates the feasibility of using microseismic data to identify the flooding status of coal pillars but also provides valuable insights for analyzing the flooded state of coal pillars during the recovery of production after water inrush incidents. This study, particularly regarding coal pillar monitoring and safety control, presents new challenges.

Residual stress plays a key role in the mechanical properties and geometry stability of the printing parts during Fused Deposition Modeling (FDM). Being the representative thermoplastic in this type of manufacturing process, the process parameters of polylactic acid (PLA) in FDM have a significant impact on the residual stress of PLA. According to the multiphysics model established, the residual stress decreases with increasing layer thickness, printing speed or platform temperature. Because such traditional finite element analysis takes a long time to calculate the stress, a back propagation (BP) neural network model is established for rapid stress prediction under different processing parameters during FDM. Only 0.56 s is required with such model during each run and the prediction error is controlled in 10%. A close loop system is simulated with temperature modification to mimic an ideal real-time feedback. Meanwhile, by off-line adjusting the FDM process parameters, the residual stress along X direction can be controlled to a certain range from experiments. An intelligent additive manufacturing system can be envisaged with the possibility of stress state modification at any time and any position in the future.

This work addresses the two great challenges of the spark plasma sintering (SPS) process: The sintering of complex shapes and the simultaneous production of multiple parts. A new controllable interface method is employed to concurrently consolidate two nickel gear shapes by SPS. A graphite deformable sub-mold is specifically designed for the mutual densification of both complex parts in a unique 40 mm powder deformation space. An energy efficient SPS configuration is developed to allow the sintering of a large-scale powder assembly under electric current lower than 900 A. The stability of the developed process is studied by electro-thermal-mechanical (ETM) simulation. The ETM simulation reveals that homogeneous densification conditions can be attained by inserting an alumina powder at the sample/punches interfaces, enabling the energy efficient heating and the thermal confinement of the nickel powder. Finally, the feasibility of the fabrication of the two near net shape gears with a very homogeneous microstructure is demonstrated.

A new molten salt reactor (MSR) design has been developed aiming for long‐term operation and high safety. In order to enhance the integrity and economy of the system during the long‐term operation, pumps were removed from the primary system, and the fuel salt flow was developed by natural circulation. In terms of thermal–fluidic, the natural circulation operation without a pump increases the reactor safety and resistance to accidents. The normal operation feasibility of the reactor was evaluated with the multiphysics analysis conducted with the Generalized Nuclear Foam (GeN‐Foam) code. It was shown that the reactor can maintain stable power under a fixed heat exchanger outlet temperature condition. To increase the natural circulation, the active core region was designed to have a simple cylindrical shape, which induced a stagnation zone with slow velocity near the side wall. Due to the slow velocity, the stagnation zone has a substantially high temperature, and a flow guide was introduced to mitigate the stagnation effect. The impact of the flow guide was evaluated, including the reactivity feedback and delayed neutron precursor drift effect. The results highlight the importance of analyzing the flow distribution within the core in an MSR and demonstrate the effectiveness of the guide structure in ensuring stable core flow.

Constant development of robotics forces scientists and engineers to work on robots that are more visually and rigidly compatible with the environment around us. To make this possible, new flexible structures are necessary that enable programmatic shape change. To meet this need, in this work we present the concept and modelling methodology of a new structure enabling shape change using electromagnetic forces produced in liquid metal conductor and its stiffening using a granular jamming mechanism. This work presents the structure concept, the description of modelling methodology and empirical validation including the magnetitic field, scanned by magnetic field camera, and displacement distribution.