Search Results (2,717)

This paper presents the design, fabrication, and characterization of a sub-milliwatt graphene-based micro thermal conductivity detector (µTCD) that utilizes a suspended multilayer graphene (MLG) bridge to sense volatile organic compounds (VOCs) in the gas phase based on their thermal transport properties. The graphene bridge is transferred onto a silicon chip with integrated microchannels using a photolithography-free process. By incorporating microchannel designs, this approach enables precise transfer of suspended MLG dimensions without conventional patterning steps. A key innovation of this work lies in the use of an ultra-low thermal mass suspended graphene architecture, which significantly increases temperature rise per unit input power, thereby enhancing sensitivity per unit power compared to conventional metal-based TCDs. The fabricated µTCD successfully produces chromatograms of multiple VOC species, closely matching those obtained using a standard flame ionization detector (FID). The device demonstrates an estimated limit of detection (LOD) of 190 ppm while consuming an average power of 151 µW under DC operation. Full article

This paper presents a numerical comparative study on the ignition characteristics of straight-channel and U-bend micro catalytic combustors, with particular focus on the role of inlet velocity. A two-dimensional computational fluid dynamics model with coupled gas-phase and surface catalytic reaction kinetics for propane combustion is developed using a fluid simulation program ANSYS Fluent. The catalyst coating (Pt/Al₂O₃) is modeled as a zero-thickness reaction surface, and the U-bend design features an uncoated recirculating channel to ensure identical catalyst loading between the two configurations. Simulations are conducted over an inlet velocity range of 0.25–8 m/s. Key ignition and combustion metrics including ignition temperature, ignition time, maximum combustion temperature, heterogeneous reaction contribution, and thermal/species field distributions are systematically compared. Results reveal a crossover in relative performance depending on flow regime. At low velocities (≤2 m/s), the straight-channel combustor exhibits lower ignition temperatures; at high velocities (≥4 m/s), the U-bend design achieves superior ignition performance with lower ignition temperatures (e.g., 526 K vs. 555 K at 8 m/s) and higher combustion temperatures (1726 K vs. 1474 K at 8 m/s). However, the straight-channel combustor consistently yields shorter ignition times across all velocities (25.9–108.6 s) compared to the U-bend (52.6–145.2 s). The heterogeneous reaction contribution decreases with increasing inlet velocity for both designs, with the straight-channel maintaining higher values than the U-bend. The U-bend achieves higher maximum temperatures due to enhanced heat recirculation, particularly at high flow rates. The findings suggest that the U-bend configuration is advantageous for high-flow-rate applications requiring low ignition temperatures and high combustion temperatures, whereas the straight-channel design is preferable for rapid cold-start scenarios. Full article

Z- and U-type parallel pipe network configurations are widely used in engineering applications such as solar collectors, fuel cells, microchannels, spargers, and irrigation systems. Although the Z configuration is more commonly employed, the U configuration may provide advantages under specific operating conditions. This study presents a comparative analysis of the two configurations in terms of flowdistribution uniformity and pressure drop. A three-dimensional computational fluid dynamics (CFD) model was developed to simulate realistic solar collector conditions, including both fluid and solid domains together with detailed inlet and outlet junctions. The system consists of manifolds and headers with a diameter of 20 mm and a length of 1150 mm, connected to ten parallel tubes of 7 mm diameter and 1780 mm length. The analysis was conducted over a wide range of inlet Reynolds numbers (Re_D = 100–5000) to represent diverse practical operating conditions. The CFD model was validated against experimental data from the literature and showed good agreement. Flowdistribution uniformity was evaluated using two quantitative indicators. The results show that flow maldistribution increases with Reynolds number in both configurations; however, the U configuration exhibits significantly improved flow uniformity at higher Reynolds numbers. In addition, both configurations exhibited comparable pressure drop characteristics over the investigated operating range. The findings suggest that the U configuration is better suited to high-flow-rate applications that require improved hydraulic and thermal uniformity, while the Z configuration remains effective at lower Reynolds numbers. Full article

Microfluidic devices are widely used for cell manipulation, but the effects of physical contact between cells and microchannel walls are not well understood. This study examines how such contact influences the behaviour of red blood cells (RBCs) during controlled manipulation. RBCs were driven through a narrow microchannel constriction (3.6 × 3.0 µm in cross-section and 2500 µm in length), enabling precise application of mechanical load. A pump system allowed accurate control of flow conditions, ranging from complete immobilisation to defined shear stress by adjusting flow rates. Under immobilised conditions, the recovery time constant of RBCs increased with longer loading durations, consistent with previous studies. However, when shear stress was introduced, recovery dynamics changed significantly. Notably, a 30-fold difference in recovery time constant was observed between a 5 s immobilisation and a 5 s load applied at a flow speed of 0.5 mm/s. Furthermore, the rapid elastic recovery typically occurring within approximately 0.1 s after unloading was suppressed under flow conditions. These results demonstrate that viscous interactions between channel walls and surrounding fluid play a critical role in determining cellular responses during microfluidic manipulation. Full article

The presence of a gas film at the solid–liquid interface can effectively reduce fluid flow resistance. This study utilizes numerical simulations to explore how groove microstructures on the lower wall of microchannels affect the evolution of trapped bubbles into gas films, as well as the resultant fluid flow behaviors inside microchannels. The influences of groove number, groove shape and double-layer microstructures on gas film formation and fluid boundary slip length are analyzed in detail. The results show that increasing the groove number can significantly improve the continuity and stability of the gas film. Groove shape also has a prominent effect on the evolution of bubbles and gas films. With the longest spreading length of gas film, rectangular grooves present a slip length about 23.9% higher than that of triangular grooves. Simultaneously, it was discovered that bilayer microstructures, especially in cases with smaller periods, can notably enhance the spreading speed, length and thickness of gas film. This improvement, in turn, further increases the slip length and boosts the drag reduction effect. This work highlights that rational optimization of wall microstructures in superhydrophobic microchannels facilitates the generation of stable, continuous gas films, yields a prominent enhancement in slip length, and consequently achieves efficient drag reduction in microfluidic systems. The present findings offer valuable fundamental understanding and technical guidance for the structural design of advanced microfluidic devices. Full article

To mitigate 3D spatial blockages and channel uncertainty in VHF/low-UHF UAV emergency networks, this paper presents a multimodal environment-aware framework for 3D virtual fluid antenna port scheduling within an Integrated Sensing, Computing, and Communication (ISCCC) architecture. Under rigorously verified spatial resolution and channel stationarity conditions, UAV micro-mobility is mapped onto a discrete 3D virtual port array, transforming continuous flight space into a controllable fluid antenna system (FAS). We define a spatial efficiency metric that quantifies the Pareto trade-off between spatial degrees of freedom and estimation error, parameterized by an error-sensitivity index, and prove the existence of a unique optimal flight scale. Utilizing a joint spatio-temporal channel model, we derive the irreducible entropy lower bound of channel uncertainty, demonstrating that intrinsic environmental randomness constitutes a fundamental predictability limit regardless of port density—a benchmark independent of any specific scheduling strategy. To ensure real-time viability, we introduce an ISCCC-inspired computation-and-caching strategy that leverages pre-calculated stationary probabilities to drive a multidimensional scoring mechanism incorporating channel entropy-based stability, predictive SNR, and load balancing. The suboptimality gap relative to a perfect-CSI oracle is analytically bounded, and proven to narrow significantly under the high temporal correlation inherent in VHF bands. Numerical results confirm that the proposed strategy attains 10.36 bps/Hz effective throughput and 10.5% outage probability, consistently outperforming rule-based, learning-based, and 2D spatial baselines, particularly under prolonged structural obstructions. Full article

Ventilation air methane (VAM) discharged from coal mines is considerable in volume, causing serious environmental pollution and energy resource waste. The methane concentration of raw VAM is generally lower than 0.3%, which greatly limits its efficient utilization. Blending low-cost solid fuels with VAM for regenerative oxidation is a practical and promising strategy to overcome the technical bottlenecks of VAM resource recovery. Clarifying the gas–solid two-phase flow behaviors inside millimeter-scale regenerative microchannels is critical for optimizing the process parameters and structural design of regenerative oxidation devices. In this work, numerical simulations are conducted using ANSYS Fluent 2022 R2 software to systematically explore the flow evolution characteristics and corresponding influencing factors of gas–solid two-phase flow in millimeter-scale microchannels to investigate three key objectives: (1) reveal the flow evolution characteristics of gas–solid two-phase flow in millimeter-scale microchannels along the flow direction; (2) quantify the effects of particle size and inlet velocity on particle deposition rate and deposition velocity; and (3) propose optimal operational parameter ranges to avoid microchannel blockage and improve particle transport performance. Along the flow direction, the near-wall velocity gradient gradually declines with the flow distance, while the thickness of the boundary layer grows continuously. Both particle deposition rate and deposition velocity are positively correlated with particle size. At an inlet velocity of 2 m/s, once the particle size exceeds 60 μm, the deposition rate and velocity rise markedly, and the particle outflow probability decreases significantly. For a fixed particle size, increasing flow velocity reduces both deposition rate and deposition velocity, which enhances the transport ability of pulverized coal particles and weakens wall adhesion. When the flow velocity is lower than 2.5 m/s, the outlet deposition rate exceeds 60%, and the particle deposition velocity rises sharply. Accordingly, maintaining flow velocity above 2.5 m/s and controlling particle size below 60 μm can effectively inhibit rapid particle deposition, improve particle transport performance, and avoid microchannel blockage. This study provides a theoretical basis and parameter reference for the structural and operational optimization of horizontal microchannels in pulverized coal-blended VAM regenerative oxidation systems. Full article

In the context of extreme climate events and increasingly stringent environmental regulation, insufficient corporate green resilience has become a micro-level bottleneck to achieving China’s “dual-carbon” targets. Using panel data on Chinese A-share listed firms from 2015 to 2023, this study treats the approval of the National Pilot Zone for Artificial Intelligence Innovation Applications as a quasi-natural experiment and employs a double machine learning (DML)–augmented difference-in-differences framework to estimate the causal impact of the policy on firms’ green resilience. We find that the pilot-zone policy significantly increases corporate green resilience by about 32%, with stronger effects among high-tech firms, non-heavily polluting industries, regulated sectors, and large enterprises. Mechanism analyses show that the policy improves green resilience through four channels—accelerating green innovation, enhancing supply-chain efficiency, alleviating financing constraints, and reducing operating costs—with innovation and supply-chain efficiency playing dominant roles. These findings provide firm-level causal evidence that AI-oriented place-based policies can strengthen firms’ capability to sustain green development under disturbances and inform the coordination of the “Digital China” and “Dual Carbon” agendas. Full article

Marine invertebrates exhibit diverse thermoregulatory capabilities enabled by hierarchical architectures, porous skeletal frameworks, and adaptive interfaces. These biological features provide engineering cues for controlling heat conduction, convection, and radiation, particularly when lightweight and multifunctional thermal designs are required. This review surveys marine-invertebrate-inspired thermal management from an engineering perspective and synthesizes biological structure–function relationships into transferable design concepts. Literature was collected from Scopus, Web of Science, and Google Scholar. Studies were included if they (i) explicitly referenced marine invertebrate morphology, structural organization, interfacial behavior, or adaptive mechanisms and (ii) quantitatively reported thermal metrics such as thermal conductivity, heat capacity/latent heat, heat dissipation performance, or temperature modulation. To maintain biological scope while enabling cross-comparison, the review is organized across major marine invertebrate phyla frequently used in bioinspired engineering—Mollusca, Porifera, Cnidaria, Echinodermata, and Arthropoda—and the engineering literature is classified into three categories: (A) bio-inspired functional materials for thermal transport or optical–thermal control; (B) bio-inspired structural architectures that guide heat flow via hierarchical or porous geometries; and (C) integrated thermal management systems that couple multiple mechanisms at the device or system scale. Across these categories, the reviewed studies demonstrate promising routes toward electronics cooling and aerospace thermal protection. Remaining challenges include scalable fabrication over large areas, flow uniformity in microchannel-based platforms, and long-term reliability under combined pressure, salinity, and thermal cycling. Full article

In oil-rich countries, petroleum contamination of soils frequently occurs during refining, transportation, and exploitation. Such contamination significantly alters soil behavior and properties from a geotechnical perspective. Given that some fine-grained soils exhibit insufficient bearing capacity or excessive settlement, soil improvement is often necessary. The selective use of nanoparticles offers a promising novel approach in this regard. This study investigates the effects of diesel contamination and nanosilica modification on the physical and mechanical properties of clayey sand and aims to interpret the variations in the mechanical properties and the permeability of the treated soil based on microstructural observations. Diesel (0–10% in 2% increments) and nanosilica (0%, 1%, 2%) were added to the soil, preparing a total of 18 mixtures for testing. The microstructural changes directly alter the physical parameters such as specific gravity, optimum moisture content (OMC), and maximum dry unit weight, consequently affecting the permeability and the mechanical behavior. The microstructural analysis via scanning electron microscopy revealed diesel-induced clay flocculation and increasing macroporosity, while the nanosilica at 1% improved the soil fabric through pore filling and interparticle bonding, whereas 2% nanosilica led to partial dispersion and agglomeration. The findings demonstrate that soil behavior is controlled by the interplay between diesel (lubrication, pore blocking, hydrophobicity) and nanosilica (surface activation, micro-bonding, agglomeration). Increasing the diesel content consistently reduces the specific gravity across all the mixtures, due to the replacement of heavier mineral particles by lighter hydrocarbon, diesel adsorption onto the soil grains, the formation of low-density organic films, and increased micro-voids. Diesel addition reduces the OMC but increases the maximum dry unit weight due to its lubrication effect. Mechanically, the unconfined compressive strength (UCS) peaked at approximately 4% diesel contamination, with the addition of 1% nanosilica yielding the highest strength overall. Conversely, the California Bearing Ratio (CBR) increased continuously with diesel due to improved packing and frictional resistance and was further improved by nanosilica. The results show that permeability decreases with increasing diesel content due to hydrophobic diesel molecules coating soil particles, filling micro-voids, and blocking pore channels, while the consolidation parameters exhibit non-monotonic trends, peaking at moderate contamination levels. An optimal nanosilica content effectively mitigated some of the adverse effects of diesel and enhanced the mechanical performance, providing valuable insights for managing hydrocarbon-contaminated soils. Full article

Urban streams typically exhibit altered hydromorphology and large fluctuations in water quality variables, creating stressful conditions for biota. In this study, we investigated periphyton along two urban streams (Bliznec, B, and Veliki Potok, VP) in Zagreb (the Croatian capital) over one year. Both streams were sampled in an upstream pristine reach within Medvednica Nature Park, a middle reach influenced by either agriculture or low-density residential areas (houses with gardens) and affected by channelization, and a lower reach, also channelized, impacted by a mix of agricultural influence and more intensive residential development with higher population density. Nutrient concentration, conductivity, COD, and chlorophyll a showed an increasing trend from upper to lower sites, reflecting the influence of urbanization. The number of periphytic taxa and their abundance correlated positively with the increasing urbanization, probably due to increased food sources. Periphyton consisted mainly of ubiquitous taxa, with 55 phagotrophic protist and 10 micro-metazoan taxa. Ciliates dominated both in diversity (44 taxa) and abundance (over 90% of mean abundance), mainly comprising bacterivorous taxa. Periphyton exhibited pronounced seasonal dynamics, with occasional high similarity between the two urban streams studied and high turnover rates of assemblages between samplings. This pattern indicates that urban streams support highly dynamic periphytic communities, strongly shaped by environmental disturbance and that these assemblages have the capacity to withstand frequent environmental variability in urbanization-influenced reaches. Full article

Traumatic injuries often result in nerve tissue damage and functional deficits due to limited regeneration. Silk fibroin, a biopolymer with inherent biocompatibility and tunable properties, is a promising material for 3D-bioprinted neural tissue scaffolds. This review highlights recent advancements in silk-derived composite scaffolds, often incorporating additional materials like collagen or conductive polymers to enhance their performance. This review examines how material composition, scaffold architecture, and fabrication strategy influence biological response and functional recovery. This comprehensive review follows PRISMA guidelines and uses comprehensive searches of PubMed, MEDLINE, Embase, Web of Science, Cochrane Central, and ClinicalTrials.gov for studies published through 2025. Studies were screened for eligibility based on substance type, mechanical properties, production methods, and outcomes. Findings were synthesized qualitatively. Twelve studies were included, comprising rat (50%), canine (8.3%), and in vitro (41.7%) models. Analysis reveals that silk fibroin acts as a highly adaptable mechanical backbone. It can consistently integrate with bioactive additives (collagen, dECM) or conductive polymers (Polypyrrole, MXene) to meet specific therapeutic demands. For spinal cord injuries, composites reached a compressive modulus capable of resisting physiological pressures and preventing scaffold collapse. In soft tissue applications, silk–hydrogel blends provided localized release of exosomes and small molecules during the acute injury phase, reducing neuroinflammatory markers. Additionally, adding conductive materials allowed the scaffolds to bridge electrical gaps and promote Schwann cell proliferation and neuronal differentiation. Furthermore, 3D bioprinting enabled the creation of defined microchannels that replicate native fascicular architecture. In vivo outcomes consistently showed superior axonal regeneration, myelination, and synaptic reconnection compared to controls, correlating with significant improvements in electrophysiological and motor function. This review highlights the clinical potential of silk fibroin-based 3D-printed biomaterials for nerve regeneration, including neural repair and neural tissue engineering. More recent studies place greater emphasis on integrating mechanical, architectural, and biological considerations into scaffold design, resulting in increasingly multifunctional scaffold systems. Despite promising efficacy, the heterogeneity of fabrication methods and the predominance of rodent models highlight the need for standardized protocols and evaluations in relevant models to facilitate clinical translation. Full article

Producing hydrogen from ethanol steam reforming (ESR) is a carbon-neutral and environment-friendly method, which has been expected to reduce the excessive emission of environmental pollution and over-exploitation of fossil resources. Currently, great advances have been made on heterogeneous catalysts, but an in-depth and more comprehensive understanding to further promote this reaction process is still required. Herein, the thermodynamic and kinetic analyses of ESR are firstly highlighted. Then, various reaction pathways of ESR are discussed in detail, respectively combined with experimental studies and density functional theory calculations. On this basis, the key factors affecting the catalytic performance over non-noble and noble metal catalysts are summarized, such as alloying, optimization of the preparation methods, promoter addition and support modification. In addition, the process intensification technologies, including catalytic membrane reactors, adsorption-enhanced reforming and microchannel reactors, are analyzed regarding breaking the thermodynamic limitations and improving the heat and mass transfer efficiency. Finally, the challenges and potential strategies of ESR in the research of dynamic reaction mechanisms, regulation of catalyst stability and integration of intensification technologies are summarized. Full article

In the context of revitalizing rural development, farmer entrepreneurship has emerged as a significant driver of rural economic growth. However, existing research has not sufficiently examined the specific mechanisms or heterogeneous effects through which digital skills influence farm household entrepreneurial behavior. This gap is the focus of the present study. Utilizing micro-level survey data collected from 936 farm households across Shandong, Shaanxi, and Henan provinces in 2021, we construct a digital skills index using factor analysis. We then employ a Probit model and an Interaction term model to examine the impact of digital skills on entrepreneurial behavior among Chinese rural households and its underlying mechanisms. Additionally, we explore heterogeneity across different household types. The results show that digital skills are positively associated with entrepreneurial decision-making. Further analysis provides suggestive evidence that this relationship may operate through three channels: shaping risk preferences, expanding relational networks, and improving access to credit. Heterogeneity tests reveal that the promoting effect of digital skills is stronger among disadvantaged households, households with a head younger than 45, and those engaged in opportunity-driven or online entrepreneurship. Theoretically, this study contributes by empirically validating a multi-pathway mechanism framework and identifying relevant boundary conditions. Practically, it offers targeted insights for policymakers to design skill-based interventions and foster inclusive entrepreneurial ecosystems in rural areas. Full article

In this work, a partitioned coupling algorithm is developed by integrating the improved discrete velocity method (IDVM) with the lattice Boltzmann flux solver (LBFS) to address conjugate heat transfer (CHT) in microscale systems across all flow regimes. Specifically, the flow field is solved by the IDVM, generating a heat flux that acts as a Neumann boundary condition at the interface for the solid domain. Subsequently, the LBFS calculates the thermal distribution inside the solid, and the updated temperature at the interface is then applied to the fluid computations as a Dirichlet condition. The proposed framework effectively combines the strengths of the IDVM in modeling rarefied gas flows with the advantages of the LBFS in handling heat conduction in complex geometries. Crucially, the current approach implicitly captures temperature jump discontinuities at the conjugate boundary, bypassing the requirement for supplementary jump conditions. To evaluate its performance, several CHT test cases involving rarefied gas in microchannels were conducted. Computational evidence suggests that the scheme is robust across diverse flow regimes. Full article