Conduction Channel Research Articles

Research on flow field characteristics in the karst tunnel face drilling hole (conduit) under the coupling between turbulence and seepage

Tunnel water inrush is one of the most common engineering problems during tunnel construction and operation, especially in karst aquifers. Among them, tunnel face drilling holes and karst conduits are strong water conductivity channels (called the “conduit” here), while the porous rock matrix is a weak water conductivity area. A second-order accuracy tunnel face water inrush model is established to investigate the coupling between the turbulent flow in the conduit and the seepage in the porous rock matrix. In the model, the incompressible Reynolds average Navier–Stokes (RANS) equation and the Brinkman-extended Darcy equation are used to govern the turbulence in the conduit and seepage in the porous rock matrix, respectively. The expressions of velocity distribution and water inflow discharge are derived requiring the velocities and their gradients of the turbulent and seepage flow to be equaled at the flow-solid interface. The validity of the present model is verified by the existing analytical solutions and COMSOL numerical solutions. Furthermore, parameter sensitivity results show that the velocity has a positive relation with the Laplace parameter, Reynolds number, Darcy number, and conduit radius. Finally, the tunnel face water inrush in the new Zhongliangshan expansion tunnel is selected as a real field engineering case. The error of the water inflow discharge in the tunnel face drilling hole between the present predicted results and the field measured results is within 10%. After introducing cosine fluctuation with amplitude 0.15 and period 500 s to optimize the model, the error for the stable water gushing stage can be reduced to within 5%. This model can provide a reference for predicting the water inflow discharge in the drilling holes or karst conduits on tunnel faces.

Probing the photocurrent in two-dimensional titanium disulfide

Generating photocurrent in a condensed matter system involves the excitation, relaxation, and transportation of charge carriers. As such, it is viewed a potent method for probing the dynamics of non-equilibrium carriers and the electronic band structure of solid state materials. In this research, we analyze the photoresponse of the mechanically exfoliated titanium disulfide (TiS2), a transition metal dichalcogenide whose classification as either a semimetal or a semiconductor has been the subject of debate for years. The scanning photocurrent microscopy and the temperature-dependent photoresponse characterization expose the appearance of a photovoltaic current primarily from the metal/TiS2 junction in an unbiased sample, while negative photoconductivity due to the bolometric effect is observed in the conductive TiS2 channel. The optoelectronic experimental results, combined with electrical transport characterization and angle-resolved photoemission spectroscopy measurements, indicate that the TiS2 employed in this study is likely a heavily-doped semiconductor. Our findings unveil the photocurrent generation mechanism of two dimensional TiS2, highlighting its prospective optoelectronic applications in the future.

Highly sensitive and selective nanoengineered PtO2-BNNT heterostructures for ppb level ammonia gas sensing

Ammonia is a frequently used gas in many industrial sectors which is both poisonous and highly corrosive to our human environment. In this study, boron nitride nanotubes (BNNTs) decorated PtO2 nanoparticles (NPs) were used to form a heterojunction for enhancing the room temperature (RT, 28 °C) gas sensing towards dry NH3 gas varying from 0.05 to 10 ppm. The BNNT was synthesized by boron oxide-assisted chemical vapor deposition (BOCVD). The fabrication of PtO2-BNNT heterostructures was done by RF sputtering of Pt NPs and subsequent deposition of BNNTs using slurry casting and annealing. The existence of BNNT-PtO2 heterostructure was confirmed by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), transmission electron microscopy (TEM), and energy spectroscopy (EDS) compositional analysis. The integration of PtO2 NPs onto BNNTs provides a synergistic effect, enabling enhanced NH3 sensing capabilities. According to the results, the response time of the PtO2-BNNT sensor to -decorated BNNT sensor to 1 ppm NH3 is 19 s with a low detection limit of 5 ppb NH3 as compared to the pristine PtO2 sensor. Extended modulation of conduction channels by BNNTs functionalized with PtO2 facilitated the large sensor response and selectivity of PtO2–BNNTs sensor with high repeatability, excellent resistance against humidity, and long-term stability.

N-Doped Graphene Nanofibers with Porous Channel Comprising Fe x S y Nanocrystals and Intertwined N-Doped CNTs as Efficient Interlayers for Li-S Batteries

Hierarchically porous and conductive nanofibers (NFs) comprising nitrogen-doped reduced graphene oxide (N-rGO) and iron sulfide (Fe x S y ) nanocrystals along with highly intertwined nitrogen-doped carbon nanotubes (N-CNTs) abbreviated as “P-rGO@Fe x S y /N-CNT NFs” were synthesized via electrospinning technique as multifunctional interlayers via coating on the commercial separator for stable lithium-sulfur (Li-S) batteries. The porous N-rGO framework acts as a backbone to enhance the structural integrity of the nanostructure. The N-CNTs and N-rGO guarantee various conductive channels for quick electron transfer thus allowing fast redox reactions. The thermal breakdown of polystyrene (PS) resulted in the formation of continuous longitudinal channels. Correspondingly, the Li-S cell incorporating the P-rGO@Fe x S y /N-CNT NF-modified separator and S electrode (2.41 mg cm-2) exhibited boosted electrochemical properties such as justifiable rate capability and steady cycling performance (after 800 charge-discharge, cell exhibits a capacity of 464 mA h g-1 with 44% retention at 0.1 C). The novel synthesis strategy discussed herein will provide significant intuitions to the advancement of innovative nanostructures for different rechargeable purposes.

FeF3/(Acetylene Black and Multi-Walled Carbon Nanotube) Composite for Cathode Active Material of Thermal Battery through Formation of Conductive Network Channels.

Considerable research is being conducted on the use of FeF3 as a cathode replacement for FeS2 in thermal batteries. However, FeF3 alone is inefficient as a cathode active material because of its low electrical conductivity due to its wide bandgap (5.96 eV). Herein, acetylene black and multi-walled carbon nanotubes (MWCNTs) were combined with FeF3, and the ratio was optimized. When acetylene black and MWCNTs were added separately to FeF3, the electrical conductivity increased, but the mechanical strength decreased. When acetylene black and MWCNTs were both added to FeF3, the FeF3/M1AB4 sample (with 1 wt.% MWCNTs and 4% AB) afforded a discharge capacity of approximately 74% of the theoretical capacity (712 mAh/g) of FeF3. Considering the electrical conductivity and mechanical strength, this composition was confirmed to be the most suitable.

An enhanced proton conductivity of proton exchange membranes by constructing proton-conducting nanopores using PVP-UiO-66-NH-SO3H nanoparticles

The performance of proton exchange membranes (PEMs) can be enhanced by creating continuous proton conduction channels. In this work, PVP-UiO-66-NH-SO3H nanoparticles (PUNSNPs) were prepared and filled into sulfonated poly (ether ether ketone) (SPEEK) to fabricate PUNSNPs/SPEEK composite PEMs. To further improve the performance of the PEMs, phosphoric acid (PA) was doped and a continuous nanopore network was formed in PA/PUNSNPs/SPEEK porous PEMs due to the dissolution of PUNSNPs. The PA/PUNSNPs/SPEEK porous PEMs have high PA uptake ratio (96%–117 %) and dimensional stability thanks to the anchoring effect of the nitrogen-containing heterocyclic ring on the PVP chains. The acid-base pairing interaction between the chains (residual ligands from PUNSNPs) inside the unique continuous nanopore structure allows PA/PUNSNPs/SPEEK = 20 % porous PEMs to have the highest proton conductivity of 0.350 S cm−1 (80 °C/100 % RH). Furthermore, the PA/PUNSNPs/SPEEK porous PEMs retained PA up to more than 80 % (80 °C, 40 % RH, 7 days). Similarly, PA/PUNSNPs/SPEEK = 20 % porous PEMs immersed in deionized water for 45 days were able to maintain a proton conductivity of more than 83 %. Finally, PA/PUNSNPs/SPEEK porous PEMs have low methanol permeability. Thus, this study provides a new method for the preparation of porous PEMs with a continuous nanopore network structure and excellent performance.

Attaining the strength-plasticity-electricity balance of carbon nanotube/Cu composites through combining the intragranular carbonized polymer dots distribution

Insight into the well-balanced mechanical-electrical properties of copper composites is requisite to provide an understanding for the development of novel structure–function integrated materials. In this study, the multi-dimensional hybrid reinforcements, carbon nanotube and zero-dimensional carbonized polymer dots (abbreviated as: CNT + CPD), were incorporated within copper matrix via spraying pyrolysis dispersion and segmented ball milling routes. A novel strategy was developed to simultaneously introduce intragranular CPD and intergranular CNT by controlling the spatial configuration. Characterization results show that the dispersibility and interface wettability of CNT-Cu were improved by the spraying pyrolysis. Intragranular CPD facilitated the trapping and accumulation of dislocations inside grain interior, which enhanced the strain hardening capability. 3.0 vol% CNT-CPD/Cu composites achieved good strength-plasticity compatibility (410 MPa and 19.8 %, i.e., 146.6 % and 139.3 % of the CNT/Cu composites, respectively). Meanwhile, composites had also displayed good electrical conductivity (96.5% IACS), which was attributed to the creation of conductive graphitic channels locally around intragranular CPD and produced a potent electric field with little charge loss. This work presented an effective route for the design of advanced copper composites and demonstrated potential in applications as progressive multi-functional materials.

Fabrication of a disposable aptasensing chip for simultaneous label-free detection of four common coexisting mycotoxins

BackgroundCoexisting multiple mycotoxins in food poses severe health risks on humans due to the augmented toxicity. Current multiplex detection methods for mycotoxins have evolved from instrumental analyses to rapid methods based on the specific recognition of antibody/aptamer using different signal transducers. However, nearly all of the reported aptasensors for multiple mycotoxins detection require external labels and can only simultaneous detection of two mycotoxins due to the limitation of distinguishable labels. The tedious labeling process definitely increases the operation complexity and the detection cost. Therefore, rapid method for simultaneous label-free detection of multiple mycotoxins in cereals is urgently needed. ResultsA disposable aptasensing chip was designed for simultaneous label-free detection of fumonisin B1 (FB1), aflatoxin B1 (AFB1), zearalenone (ZEN), and ochratoxin A (OTA) in one sample. Specifically, ITO conductive glass was divided into a rectangle (35 × 25 mm) and then etched by laser to set aside the required four ITO working electrodes (6 mm in diameter) with respective conductive channels. Gold nanoparticles were electrodeposited on the working electrodes to provide abundant anchoring sites for thiolated aptamers immobilization. On this basis, a disposable aptasensing chip for simultaneous label-free detection of four common coexisting mycotoxins has been developed, which used electrochemical impedance spectroscopy as transducer to measure direct biorecognition of the aptamer and corresponding target. This aptasensing chip provided wide linear ranges of 5–1000, 10–250, 10–1250, 10–1500 ng/mL for FB1, AFB1, ZEN, OTA, respectively, with the respective detection limit of 2.47, 3.19, 5.38, 4.87 ng/mL (S/N = 3). Significance and noveltyThis aptasensing chip shows fantastic characteristics of great simplicity and portability, easy operation, and multiple mycotoxins recognition. They are easy to produce on a large scale at low cost and the design concept can be easily expanded to screen a large panel of coexisting targets. This work provides a new avenue for multi-target detection and represents a substantial advance toward food quality and safety monitoring or other fields.

Preparation of High Conductive Medium and Establishment of Laege Capacity Conductive Channel.

The preparation of highly conductive media and the construction of conducting channels play a crucial role in improving the electrical conductivity of electrically conductive adhesives. Therefore, a new MXene structure is reported in this paper, and the improved structure is rationally designed by computational modeling, which greatly prevents the buildup of MXene nanosheets, improves the stability of the structure, and creates a wide electron transfer channel, and the capacitance contribution of this structure is up to 86.3%. By mixing MXene modified with Ag-plated copper powder in a quantitative relationship to form high conductive media, the electrical conductivity is largely improved and the defect of low electron transfer rate of conventional conductive fillers is broken. The potential value of high conductive media is largely exploited using high throughput and machine learning methods, and here we show that the resistivity has reached 9.668 × 10-7 Ω m. The first principles investigate the conductive channels and electron transfer pathways of high-conductive media at the atomic level, further revealing the mechanism of action of high-conductive media. This study is also the first report on the application of MXene to high-conductive media.

Omega‐Gate Silicon Nanowire Geometric Diodes with Reconfigurable Self‐Switching Operation and THz Rectification

AbstractGeometric diodes (GDs) represent a relatively unconventional class of diode that produces an asymmetric current response through carrier transport in an asymmetric geometry. Synthesized from the bottom up, Si nanowire‐based GDs are three‐dimensional, cylindrically symmetric nanoscale versions capable of room‐temperature rectification at GHz‐THz frequencies with near zero‐bias turn‐on voltages. Here, by fabricating three‐terminal n‐type Si nanowire GDs with axial contacts and an omega‐gate electrode, a distinct class of reconfigurable self‐switching geometric diodes (SSGDs) is reported. Single‐nanowire SSGD device measurements demonstrate a significant dependence of diode current and polarity on gate potential, where the diode polarity reverses at a gate potential of ≈−1 V under specific grounding conditions. Finite‐element modeling reproduces the experimental results and reveals that the gate potential—in combination with the morphology and dopant profile—produces an asymmetric potential along the nanowire axis that changes asymmetrically with axial bias, altering the effective conductive channel within the nanowire to yield diode behavior. The self‐switching effect is retained in two‐terminal SSGD devices, and modeling demonstrates that both three‐terminal and two‐terminal devices support rectification through THz frequencies. The results reveal a new mechanism of operation for nanowire‐based GDs and characterize a new type of self‐switching diode with reconfigurable polarity.

Post-Ablation cardiac Magnetic resonance to assess Ventricular Tachycardia recurrence (PAM-VT study).

Conducting channels (CCs) detected by late gadolinium enhancement cardiac magnetic resonance (LGE-CMR) are related to ventricular tachycardia (VT). The aim of this work was to study the ability of post-ablation LGE-CMR to evaluate ablation lesions. This is a prospective study of consecutive patients referred for a scar-related VT ablation. LGE-CMR was performed 6-12 months prior to ablation and 3-6 months after ablation. Scar characteristics of pre- and post-ablation LGE-CMR were compared. During the study period (March 2019-April 2021), 61 consecutive patients underwent scar-related VT ablation after LGE-CMR. Overall, 12 patients were excluded (4 had poor-quality LGE-CMR, 2 died before post-ablation LGE-CMR, and 6 underwent post-ablation LGE-CMR 12 months after ablation). Finally, 49 patients (age: 65.5 ± 9.8 years, 97.9% male, left ventricular ejection fraction: 34.8 ± 10.4%, 87.7% ischaemic cardiomyopathy) were included. Post-ablation LGE-CMR showed a decrease in the number (3.34 ± 1.03 vs. 1.6 ± 0.2; P < 0.0001) and mass (8.45 ± 1.3 vs. 3.5 ± 0.6 g; P < 0.001) of CCs. Arrhythmogenic CCs disappeared in 74.4% of patients. Dark core was detected in 75.5% of patients, and its presence was not related to CC reduction (52.2 ± 7.4% vs. 40.8 ± 10.6%, P = 0.57). VT recurrence after one year follow-up was 16.3%. The presence of two or more channels in the post-ablation LGE-CMR was a predictor of VT recurrence (31.82% vs. 0%, P = 0.0038) with a sensibility of 100% and specificity of 61% (area under the curve 0.82). In the same line, a reduction of CCs < 55% had sensibility of 100% and specificity of 61% (area under the curve 0.83) to predict VT recurrence. Post-ablation LGE-CMR is feasible, and a reduction in the number of CCs is related with lower risk of VT recurrence. The dark core was not present in all patients. A decrease in VT substrate was also observed in patients without a dark core area in the post-ablation LGE-CMR.

Estimation of the activation energy in the Ag/SnSe/Ge2Se3/W self-directed channel memristor

In this study, we conducted an investigation into the Ag/SnSe/Ge2Se3/W ionic memristor, focusing on the determination of activation energies associated with its two primary operational processes: the formation of conductive filaments and memristor degradation. To ascertain the electrical conductivity of the memristor in both its basic electronic states, a low resistance state and a high resistance state, we constructed current-voltage characteristics. The estimation of activation energy values was carried out employing the Arrhenius law and the provisions of irreversible thermodynamics, with specific reference to Onsager's second postulate. This fundamental concept posits that the growth rate of irreversible component of entropy can be expressed as the summation of products involving fluxes and thermodynamic forces when a system tends towards its equilibrium state. In the context of this study, the equilibrium state of the memristor is defined as the condition at which the memristor can no longer function as a resistive memory cell. Our experimentation involved the application of a flux of Ag+ ions (electromigration). The calculated activation energy values were found to be 0.24 eV for the initial process and 1.16 eV for the latter. These divergent activation energy values indicate the differentiation between the agglomerative mechanism that governs the formation of conductive channels, prevalent in the Ag/SnSe/Ge2Se3/W memristor, and the "conventional" substance transfer mechanism based on a group of point defects that manifests itself during the memristor's degradation.

Homogenization of fluid saturated double porosity media with a new type of the contrast in the Biot mesoscopic model

This paper presents a mathematical model of a double poro-elastic medium derived by the homogenization of a two-component periodically heterogeneous Biot continuum characterized by strong heterogeneities in the permeability and poroelastic coefficients of mesoscopic structure. A new scaling of the mesoscopic material parameters with respect to the small parameter which is involved in the asymptotic analysis is introduced to capture this high contrast quality of the mesoscopic model. It is shown that such a scaling ansatz of the mesoscopic material parameters can be justified using different micromodels associated with the two mesoscopic components. While the “matrix” is a little permeable stiff phase, the “conductive channels” are made of a very soft fibrous structure equivalently represented by an network of helical springs. The unfolding method of the homogenization is employed to derive the macroscopic model involving the frequency-dependent effective parameters. Semipermeable interfaces between hard dual porosity and soft primary porosity are considered. The wave dispersion of two shear wave modes S1,S2, and two pressure wave modes P1,P2, is illustrated in an numerical example and validated, in a part, using the reference dispersion analysis based on the Bloch wave decomposition.

Low temperature spin relaxation length exceeding 3 μm in highly conductive copper channels

Despite extensive studies of spin transport in metallic structures, it remains a challenge to achieve spin relaxation length well above 1 μm in metals even at low temperatures. We explore nonlocal spin transport in Cu channels with a cross section of 0.5 × 0.5 μm2, which exhibit superior values of electrical conductivity and residual resistivity ratio (RRR). Based on structures fabricated in a single batch, we found an average spin relaxation length of λCu=3.2±0.7μm and an average spin relaxation time of τs = 120 ± 50 ps at 30 K. Substantial variations of λCu, RRR, and resistivity ρCu are found among the structures and the three quantities correlate well to one another. The most conductive Cu channel in the batch yields λCu=5.3±0.8μm and τs=250±80ps. These superior values exceed expectations for metals and can be attributed to reduced spin relaxation from grain boundaries and surfaces.

More than 60% RF loss reduction and improved crystal quality of GaN-on-Si achieved by in-situ doping tert-butylphosphorus

In this work, the parasitic conductive channel in a silicon substrate is compensated using in-situ doping for the first time. The experimental results show that in-situ doping of tert-butylphosphorus (TBP) has little adverse effect on the mobility and the density of two-dimensional electron gas but the compensation of the parasitic channel in the substrate is effective, and the aluminum nitride (AlN) / Si template based on the optimized conditions reduces the radio frequency loss by more than 60%. In addition, it was found that a suitable preflow of TBP can enhance the migration of Al atoms on the substrate surface and improve the crystal quality of gallium nitride (GaN), which reduces the dislocation density of GaN by 25% compared to the sample without TBP preflow. The hypothesis is that TBP preflow can affect the strain of the substrate, which makes the dislocations more likely to annihilate during the subsequent growth of AlN nucleation layer, resulting in the eventual improvement of GaN crystal quality.

Label-Free Chemiresistive Sensors Based on Self-Assembled Ti3C2Tx MXene Films for Monitoring of Microcystin-LR in Water Samples.

Herein, we propose a label-free chemiresistive sensor for the highly sensitive and selective detection of microcystin (MC)-LR in water samples. The sensor uses a layer-by-layer (LBL) assembled conductive film consisting of Ti3C2Tx nanosheets as the sensing channel. It is further modified by using an aptamer for the specific recognition of MC-LR. The response signal is based on the change in resistance of the conductive channel upon binding of MC-LR with the aptamer. Our novel strategy is the first concept proposed for immobilizing the aptamer containing -SH on the channel surface through a Ti-S bond under weakly alkaline condition. The resulting sensor is highly sensitive and stable for the detection of MC-LR, with a detection limit of 0.18 ng L-1 and a wide linear range from 1 to 104 ng L-1. We used the sensor to continuously monitor MC-LR released by cultivated Microcystis aeruginosa, showing a strong relationship between MC-LR and cell density. Furthermore, the sensor was successfully used to measure MC-LR in freshwater lakes with moderate algal blooms, and the results agreed well with those obtained by liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis. The present study provides a reliable method for highly sensitive and selective detection of MC-LR in environmental waters.

Origin, evolution and diversification of plant mechanosensitive channel of small conductance-like (MSL) proteins

Mechanosensitive (MS) ion channels provide efficient molecular mechanism for transducing mechanical forces into intracellular ion fluxes in all kingdoms of life. The mechanosensitive channel of small conductance (MscS) was one of the best-studied MS channels and its homologs (MSL, MscS-like) were widely distributed in cell-walled organisms. However, the origin, evolution and expansion of MSL proteins in plants are still not clear. Here, we identified more than 2100 MSL proteins from 176 plants and conducted a broad-scale phylogenetic analysis. The phylogenetic tree showed that plant MSL proteins were divided into three groups (I, II and III) prior to the emergence of chlorophytae algae, consistent with their specific subcellular localization. MSL proteins were distributed unevenly into each of plant species, and four parallel expansion was identified in angiosperms. In Brassicaceae, most MSL duplicates were derived by whole-genome duplication (WGD)/segmental duplications. Finally, a hypothetical evolutionary model of MSL proteins in plants was proposed based on phylogeny. Our studies illustrate the evolutionary history of the MSL proteins and provide a guide for future functional diversity analyses of these proteins in plants.

Significant Influence of Sand Production on the Well's Drainage Area

The exploration of unconventional oil and gas reservoirs is a prominent global trend today. Achieving cost-effective and efficient hydrocarbon production from these reservoirs necessitates advanced technologies. One such technology that has been employed in the oil and gas industry for many decades is hydraulic fracturing. It is used to create highly conductive channels within formations characterized by extremely low permeability values. The successful implementation of hydraulic fracturing hinges on the development of an effective fracturing design. This design is crucial to achieving the anticipated production outcomes from unconventional reservoirs, including tight gas, shale gas, coal bed methane, and reservoirs with very low permeability. Key parameters for the success of hydraulic fracturing operations include the determination of the optimal fracturing rate, fracture height, and the selection of propping agents. These factors collectively contribute to the efficiency and productivity of hydraulic fracturing activities in unconventional reservoirs.

Facilitating Li+ conduction channels and suppressing lithium dendrites by introducing Zn-based MOFs in composite electrolyte membrane with excellent thermal stability for solid-state lithium metal batteries

Facilitating Li+ conduction channels and suppressing lithium dendrites by introducing Zn-based MOFs in composite electrolyte membrane with excellent thermal stability for solid-state lithium metal batteries

Lithium mobility along conduction channels of ceramic LiTa2PO8

Lithium mobility along conduction channels of ceramic LiTa2PO8