Vertical Channel Research Articles

Recording the tactile P300 with the cEEGrid for potential use in a brain-computer interface.

Brain-computer interfaces (BCIs) are scientifically well established, but they rarely arrive in the daily lives of potential end-users. This could be in part because electroencephalography (EEG), a prevalent method to acquire brain activity for BCI operation, is considered too impractical to be applied in daily life of end-users with physical impairment as an assistive device. Hence, miniaturized EEG systems such as the cEEGrid have been developed. While they promise to be a step toward bridging the gap between BCI development, lab demonstrations, and home use, they still require further validation. Encouragingly, the cEEGrid has already demonstrated its ability to record visually and auditorily evoked event-related potentials (ERP), which are important as input signal for many BCIs. With this study, we aimed at evaluating the cEEGrid in the context of a BCI based on tactually evoked ERPs. To compare the cEEGrid with a conventional scalp EEG, we recorded brain activity with both systems simultaneously. Forty healthy participants were recruited to perform a P300 oddball task based on vibrotactile stimulation at four different positions. This tactile paradigm has been shown to be feasible for BCI repeatedly but has never been tested with the cEEGrid. We found distinct P300 deflections in the cEEGrid data, particularly at vertical bipolar channels. With an average of 63%, the cEEGrid classification accuracy was significantly above the chance level (25%) but significantly lower than the 81% reached with the EEG cap. Likewise, the P300 amplitude was significantly lower (cEEGrid R2-R7: 1.87 μV, Cap Cz: 3.53 μV). These results indicate that a tactile BCI using the cEEGrid could potentially be operated, albeit with lower efficiency. Additionally, participants' somatosensory sensitivity was assessed, but no correlation to the accuracy of either EEG system was shown. Our research contributes to the growing amount of literature comparing the cEEGrid to conventional EEG systems and provides first evidence that the tactile P300 can be recorded behind the ear. A BCI based on a thus simplified EEG system might be more readily accepted by potential end-users, provided the accuracy can be substantially increased, e.g., by training and improved classification.

HYDROLOGICAL REGIME OF THE IKVA RIVER (SOUTHERN BUG BASIN)

This article reveals the issue of a detailed study of the hydrological regime of small plain rivers in the presence of data from regular observations. The Ikva River, the object of our study, belongs to the Southern Bug basin and is its small tributary, on which a hydrological indicators monitoring station has been operating since 1939. Since 1955, a continuous series of observations has been available, which allowed us to carry out a detailed analysis and description of the main hydrological characteristics – levels (H, cm) and water flows (Q, m3/s), to evaluate their fluctuations in time, cyclicity and the relationship Q= f(H). The construction of the corresponding graphs confirmed that the Ikva River is characterized by cyclic flow fluctuations, and since 1965 we have already observed two complete cycles of fluctuations in water level lasting about 30 years. At the moment (2022), the flow indicators record the minimum of the low-water phase of the second cycle, so we can expect an increase in the flow in the near future and the transition to a new cycle. We have also determined that the amplitude of water level fluctuations of the Ikva River at the post in the village of Stara Sinyava over many years is 60 cm, and varies from a minimum of 75 cm (1957) to 135 cm (1981), that is, a little more than 0.5 meters in total. This agrees quite well with the literature data and estimates of other authors, considering the plain nature and small size of this object. The long-term course of the water levels of the Ikva River is characterized by a slight increase, while the long-term fluctuations of the average water flow at this station also do not have a large amplitude: from 0.66 m3/s (2020) to 3.64 m3/s (1979) i.e. 2.98 m3/s. At the same time, the general trend line for multi-year cost fluctuations shows, on the contrary, a tendency to decrease them. Therefore, we can state that the graphs of multi-year costs and levels are not synchronous, which is evidence of the manifestation of vertical channel deformations in the area of the post. As the water level increases, the decrease in water consumption is a direct sign of siltation of the riverbed in this area and the raising of the bottom level due to accumulative processes over a long period. The largest amplitudes are characterized by the parameters of the maximum runoff, that is, the amplitudes of the maximum levels (∆Нmax = 168 cm) and maximum flows (∆Qmax = 92.9 m3/s), which is not surprising, because we are talking about the characteristics of the period of floods and inundations, which are always marked by significant fluctuations in time. An interesting fact, identified for us for the first time, is that the characteristics of the minimum flow of the closed period of the channel are characterized by higher amplitudes than the characteristics of the open period. Therefore, the summer low water is more pronounced than the winter low water, which means that in the warm period (summer), the lack of precipitation more clearly provokes a decrease in water levels and flows in the channel system than during the winter period. The reason can be both winter thaws and the specifics of the groundwater regime. Key words: hydrological regime; water level; water flows; hydrological cycle; low water phase; high water phase; relationship Q=f(H).

GaSb/Si Heterojunction Based Pocket Engineered Vertical Non-Uniform Channel Double Gate TFETs for Low Power Applications

This article compares the performance of two Vertical Non-Uniform Channel Double Gate Tunnel Field Effect Transistors (VNUCDGTFETs), a normal all-Silicon Tunnel Field-Effect Transistor (TFET) having a pocket and another one a Gallium Antimonide/Silicon heterojunction TFET with pocket. GaSb is a III-V narrow energy band gap material, employed in the source area of the TFET structure to decrease the tunneling width and thus to make more number of carriers capable enough to tunnel through the heterojunction. The proposed source pocket heterojunction non uniform channel TFET presents superior performance as compared to the conventional non uniform channel vertical TFET with a pocket, regarding a larger ION/IOFF ratio, a reduced sub-threshold swing, and a smaller threshold voltage at VDS = 0.5 V. Furthermore, the proposed TFET device undergoes a comprehensive analysis of both DC parameters and various analog/RF parameters.

Convection instability of linear Oldroyd-B fluids in a vertical channel with non-Fourier heat flux model

Owing to the importance of non-Fourier heat flux model in several natural and engineering processes, the convection of binary viscoelastic fluid in a vertical channel with non-Fourier heat flux model is investigated. The linear Oldroyd-B constitutive equation is used to model viscoelasticity. The presence of the basic flow in the vertical y-direction makes the problem challenging compared with the case in Rayleigh–Bénard convection. We use the Chebyshev collocation method to explore the instability characteristics of the linear Oldroyd-B fluid under a wide variety of physical parameters. Results show that the non-Fourier effect and relaxation time contribute to destabilize the system for oscillatory convection. The retardation time can inhibit the instability of the convective system. In the absence of the non-Fourier effect, the vertical fluid layer cannot support oscillatory motions. Oscillatory motion is possible, and the neutral stability curve branches when the non-Fourier effect is taken into account in the fluid. In addition, a new interesting phenomenon can be found: under the coupling action of viscoelastic fluids and the non-Fourier effect, the neutral stability curve would change from single to two branches and then to a single branch with the increase in relaxation time.

22‐1: Invited Paper: About a Trench Oxide TFT

We introduce new structure of oxide TFT, providing high current in a small footprint and suitable Von. The trench TFT consisted of lateral region of high current path and thin two vertical channels. This can suppress not only channel shortening, also negative Von shift of high current driving oxide TFT.

P‐17: Development of Vertical Oxide Channel Thin Film Transistor Based on Hard‐Mask Etching

Avertical oxide semiconductor thin film transistor (VTFT) with channel lengthof 0.4 μm wasdeveloped in our work. This VTFT has a small footprint, which isconducive to achieving higher resolutiom. In this work, we produced a VTFT by usinga hardmask etching process and designed different vertical structures, such asslope, hole, etc. The device achieved an on‐state current of 20.6 μA (normalized with width) and an off‐state current below 1 pA.

Investigation of Prandtl-Eyring fluid flow under the influence of peristalsis through an inclined elliptic channel

This work considers the peristaltic flow of non-Newtonian Prandtl-Eyring fluid via a duct having an elliptical cross-section. The elliptic conduit is taken inclined with horizontal. The mathematical model of the problem is converted into non-dimensional form using dimensionless variables with the assumptions of long wavelength approach. The perturbation approach and polynomial solutions are incorporated to solve the mathematical model analytically. The analytically achieved results are analyzed and presented using graphical representation of several physical parameters. The impact of different physical parameters on velocity, temperature, pressure gradient, and pressure rise is studied graphically. The Grashof number is found to have a significant impact on the pressure gradient and velocity profile. The flow characteristics (velocity and pressure gradient) are observed to be more prominent for the vertical channel than the horizontal and inclined conduit. The velocity profile showed a parabolic nature and achieved high values at the center of the conduit and progressively lowered near the wall of the conduit.

Study on the Pumping Performance and Structure Parameters Optimization of High-Speed Small Compound Molecular Pump.

A molecular pump is the core component of vacuum systems in portable mass spectrometers and other analytical instruments. The forms of the existing molecular pumps mainly are the combinations of vertical bleed and compression channel, which have the shortcomings of heavy mass and large volume, which seriously restricts the application and development of portable mass spectrometers. Aiming at the problems of low strength and insufficient pumping performance under the miniaturization constraints (mass of 1.8 kg; exhaust diameter of 25 mm) of molecular pumps, a compound pump consisting of a horizontal bleed channel and multi-stage spiral compression channel is proposed. The pumping principle of the compound molecular pump is analyzed to obtain its preliminary structural size parameters. The test particle Monte Carlo method is presented for establishing an aerodynamic model for a high-speed small compound molecular pump, which can be used to investigate the pumping performance of bleed blades and compression channels in a thin air environment. On the basis of the aerodynamic model, the NNIA multi-objective optimization algorithm is presented to optimize the structural parameters of the compound molecular pump. After structural parameter optimization, the maximum flow rate and compression ratio of the compound molecular pump are increased by 13.6% and 41.6%, respectively. The experimental results of the pumping performance show that the predicted data of the aerodynamic model are in good agreement with the experimental data, with an error of 12-27%. Namely, the established aerodynamic model has high accuracy and the optimized structural parameters of the compound molecular pump can provide basic conditions for the large-scale application and promotion of portable mass spectrometers.

Influence of variable gravity on the phase change material for enclosed vertical channels with helical fins

This study numerically investigates the influence of variable gravity on the melting behaviour of a phase change material (PCM- paraffin wax RT27) contained within an enclosed vertical channel under different gravity conditions, specifically those found on the Earth, the Moon, and under the microgravity environments. Furthermore, the impacts of incorporating various number of helical fins within the PCM unit under different gravitational conditions are assessed for the first time. The findings indicate that the melting efficiency of PCM is considerably affected by the reduced gravity conditions, due to changes in the natural convection, velocity, and temperature; the melting time is twice as long under the moon-gravity conditions and sixfold longer under the microgravity conditions compared to the earth-gravity. It is also observed that reduced efficiency can be remedied by the insertion of fins into the PCM unit. The breakdown of the natural convection vortices with different number and orientation of fins expedites the melting process for all gravity conditions thus leading to improved performance in melting and energy storage.

Numerical simulation of wave-number effects on the performance of traveling wave pump-turbine in turbine mode

Pumped storage represents an economically viable, highly efficient, and extensive energy storage solution, receiving substantial research attention worldwide. This study utilized the energy dissipation of fish swimming in the water, and the traveling wave plate was arranged in a vertical rectangular flow channel to obtain energy through reverse thinking. Numerical simulation was employed to investigate the performance characteristics of the traveling wave turbine under varying wave number across high and low water head. The results reveal that the efficiency at low water head starts to increase and then decreases with the increase of wave number. There is an optimal wave number N = 4 to maximize turbine efficiency, and the maximum efficiency under low water head condition is 89.35 %. The efficiency of the high head condition shows a continuous upward trend, with a maximum value of 92.27 % in the range of wave number studied. With the increase of wave number, the instantaneous mass flow coefficient and power coefficient become more stable. The advantage of increasing the wave number is that more traveling wave plates can participate in energy capture, which is conducive to reducing the force required by each traveling wave plate and making the pressure distribution in each working cavity more regular.

Phase transition of multiple encapsulated PCMs in a U-shaped channel under MHD with ternary nanofluid

Purpose Multiple encapsulated phase change materials (PCMs) are used in a wide range of applications, including convective drying, electronic cooling, waste heat recovery and air conditioning. Therefore, it is important to understand the performance of multiple PCMs in channels with flow separation and develop methods to increase their effectiveness. The aim of the study is to analyze the phase transition dynamics of multiple encapsulated PCMs mounted in a U-shaped tube under inclined magnetic field by using ternary nanofluid. Design/methodology/approach The PCMs used in the upper horizontal channel, vertical channel and lower horizontal channel are denoted by M1, M2 and M3. Magnetic field is uniform and inclined while finite element method is used as the solution technique. Triple encapsulated-PCM system study is carried out taking into account different values of Reynolds number (Re, ranges from 300 to 1,000), Hartmann number (Ha ranges from 0 and 60), magnetic field inclination (between 0 and 90) and solid volume fraction of ternary nanofluid (between 0 and 0.03). The dynamic response of the liquid fraction is estimated for each PCM with varying Re, Ha and t using an artificial neural network. Findings It is observed that for PCMs M2 and M3, the influence of Re on the phase transition is more effective. For M2 and M3, entire transition time (t-F) lowers by approximately 47% and 47.5% when Re is increased to its maximum value, whereas it only falls by 10% for M1. The dynamic characteristics of the phase transition are impacted by imposing MGF and varying its strength and inclination. When Ha is raised from Ha = 0 to Ha = 50, the t-F for PCM-M2 (PCM-M3) falls (increases) by around 30% (29%). For PCMs M1, M2 and M3, the phase transition process accelerates by around 20%, 30% and 28% when the solid volume fraction is increased to its maximum value. Originality/value Outcomes of this research is useful for understanding the phase change behavior of multiple PCMs in separated flow and using various methods such as nano-enhanced magnetic field to improve their effectiveness. Research outputs are beneficial for initial design and optimization of using multiple PCMs in diverse energy system technologies, including solar power, waste heat recovery, air conditioning, thermal management and drying.

Comprehensive study of tri-hybrid nanofluid flow in a vertical channel with Cu, Al2O3, and TiO2 nanoparticles via fractional dynamics and non-local kernel approach

Nanofluids and hybrid nanofluids enhance the transfer of heat with low nanoparticle concentration. Tri-hybrid nanofluids combine different nanoparticles (NPs) to further increase the performance of base fluids. Tri-hybrid nanofluids have significant uses in several industries, including electronic cooling, heat transport, biomedical engineering as well as energy storage systems. This study investigates the thermal performance of tri-hybrid nanofluid in the existence of a magnetic field and porous saturated space along with copper (Cu), aluminium oxide (Al2O3), and titanium dioxide (TiO2) NPs dispersed in base fluid, i.e. water (H2O) flowing through a vertical channel by convection. The resultant partial differential equations based on Atangana–Baleanu time-fractional derivative (having non-singular and non-local kernel) are solved using the Laplace transform along with the appropriate physical conditions. The Stehfest as well as Tzou’s numerical approaches are then utilized to compute the Laplace inverse, to check the validity of obtained solutions and to get the graphical representations of, concentration, energy, and velocity fields. The results show that tri-hybrid nanofluids have advanced thermal as well as momentum characteristics compared to nanofluids and hybrid nanofluids.

Improving the capacitive performance of wood-derived carbon monolith by anchoring heteroatom-doped carbon nanotubes in the vessels via in situ chemical vapor deposition

Wood, with high carbon contents and abundant vertically oriented channels, has unique advantages in preparing high mass-loading carbon-based freestanding supercapacitor electrodes. However, there is considerable room for enhancing the capacitive performance of wood-derived carbon electrodes. A one-step chemical vapor deposition (CVD) method mediated by dicyandiamide using iron-based nanoparticles as catalysts was proposed to enhance the utilization of vertical channels in wood-based carbon electrodes and improve their pore structure and chemical composition. This approach aimed to fabricate composite electrodes with enhanced mass loading, interwoven conductive carbon nanotube networks, well-developed hierarchical porous structure, and abundant nitrogen/oxygen-containing functional groups. The effect of CVD temperature on the physical/chemical properties and capacitance performance of the composite material was investigated. Consequently, the optimal electrode (CW/NCNTs-800) attained a competitive initial specific capacitance of 5762 mF cm−2 at 5 mA cm−2 and demonstrated a satisfactory rate performance with the specific capacitance of 3520 mF cm−2 at 300 mA cm−2. In addition, the durable electrode demonstrated commendable cycle stability, maintaining a capacitance retention of 93 % through 30,000 cycles at 30 mA cm−2. This study on wood-derived high mass-loading supercapacitor electrodes can provide a novel perspective on the application of high-performance energy storage devices.

Double-layered cellulosic interfacial evaporator via upcycling of waste cotton fabrics for efficient solar desalination

Constructing efficient solar-driven interfacial evaporators (SDIEs) derived from biomass or waste stream materials (e.g., cellulose) is still challenging due to their less elaborate porous structure. Herein, we showed waste cotton fabrics could be dissolved and regenerated into aerogels with tunable channels suitable for constructing a double-layered SDIE. The evaporator consists of a polypyrrol-coated top layer featuring vertical channels with larger pores and a hydrophilic bottom layer featuring smaller pores. With such design, the photothermal and pro-evaporative capabilities of the top layer was coupled with the strong capillary effect of the bottom layer to drive effective evaporation. A desirable evaporation rate of 3.20 kg m−2h−1, 80.0% solar-to-vapor conversion efficiency under 1 sun irradiation, and a reduced evaporation enthalpy of 962 J g−1 was achieved. The SDIE also exhibits high purification efficiency (exceeding 99%) during long-term operation of seawater desalination and shows great potential in treatment of waste streams of high salinity dyeing effluent. In summary, this work demonstrates a case of upcycling waste cotton fabrics for water desalination.

A Technique for SAR Significant Wave Height Retrieval Using Azimuthal Cut-Off Wavelength Based on Machine Learning

A Technique for SAR Significant Wave Height Retrieval Using Azimuthal Cut-Off Wavelength Based on Machine Learning

Influences of Variable Viscosity and Variable Thermal Conductivity on a Mixed Convective Hydromagnetic Flow in a Vertical Channel with Thermophoretic Deposition

Influences of Variable Viscosity and Variable Thermal Conductivity on a Mixed Convective Hydromagnetic Flow in a Vertical Channel with Thermophoretic Deposition

Advancements in laser-based spatiotemporal measurements of flow boiling

Recent advancements in laser and imaging systems, as well as in computational processing capabilities, have made quantitative optical imaging, which is often combined with laser illumination, highly adaptable, robust and reliable. Laser-based diagnostic techniques, such as planar laser-induced fluorescence (PLIF), offer the possibility of simultaneous spatiotemporally resolved measurements of temperature fields in the liquid phase at boiling conditions. In this paper, we examine the applicability of two-colour PLIF (2cPLIF), where the ratio between individual fluorescent emissions from uniformly dispersed dyes is used to take temperature measurements in the liquid phase in the presence of moving vapour-liquid interfaces typical of boiling flow. The implementation of 2cPLIF necessitates uniformity in the concentration of different dyes across the flow field. However, in the case of a multiphase flow such as boiling, thermophoresis can lead to inhomogeneous dye distributions. To overcome this challenge, a single-dye multispectral planar laser-induced fluorescence (SDMS-PLIF) method has been developed, which employs fluorescent emissions in different spectral bands of the same dye (Nile Red). The spectral characteristics of Nile Red were measured using a spectrometer to identify its temperature-sensitive bands over a wide range of dye concentrations, from 0.3 to 30 mg/L. Following this, we demonstrate the measurement capabilities of SDMS-PLIF thermography as applied to a boiling flow in a miniaturised vertical square channel, gaining insight into the thermohydrodynamic interactions between vapour bubbles and a heated wall.

Study on the difference in subcooling flow boiling of materials in a vertical rectangular channel at a low flow rate

Alloy materials with excellent properties are widely used in different industrial fields. Conducting flow boiling studies on alloy surfaces will help explore their applications in flow boiling, especially in heat exchange equipment. Five alloys were selected, including 304SS, Inconel600, Monel400, Zr4 and FeCrAl. Bubble dynamics in a vertically upward-flowing rectangular channel were observed using a high-speed camera under the condition of atmospheric pressure, 400 kg·m^-2·s^-1 mass flowrate and 5 K inlet subcooling. Results show that roughness and wettability cannot individually define material-sensitive heat transfer coefficient (HTC) and critical heat flux (CHF). Thermal effusivity shows a linear relationship to HTC. Material-sensitive CHF seems to be a power-law function of the nondimensional parameter of the product of the maximum nucleation site density and the minimum bubble nucleation area.

Measuring liquid film thickness during downflow condensation in a minichannel

The availability of experimental liquid film thickness data during in-tube condensation heat transfer is fundamental for the development of reliable correlations for the design of condensers. During annular flow condensation, the heat transfer is directly linked to the liquid film thickness, as the main thermal resistance is due to thermal conduction through the film of condensate. Therefore, understanding the liquid film characteristics is paramount for modelling two-phase annular flows. Although several prediction methods for liquid film thickness are available in the literature, they are mainly related to air-water adiabatic experiments. More liquid film thickness data are required for a better understanding of the condensation phenomena and for the development of more accurate models. In this work, the liquid film thickness characteristics of R245fa, R134a and HFE-7000 have been investigated during condensation inside a vertical channel with 3.38 mm inner diameter. Shadowgraphy and chromatic confocal imaging were used to detect the evolution of the liquid film thickness with high temporal resolution. The experimental data were useful to address the existence of a dependence of the liquid film thickness on dimensionless numbers. The combination of two dimensionless numbers, specifically the vapor Weber number and the Reynolds number of the liquid phase, allows to better catch the liquid film thickness trends with the varying operating conditions.

Study of turbulent wavy annular flow inside a 3.4 mm diameter vertical channel by using the Volume of Fluid method in OpenFOAM

In annular downward flow, an annular liquid film flows at the perimeter of the channel pushed down by the gravity force and by the shear stress that the vapor core exerts on it. Depending on the working conditions, the vapor-liquid interface can be flat or rippled by waves. The knowledge of the liquid film thickness is very important for the study of annular flow condensation because the thermal resistance of the liquid is often the most important parameter controlling the heat transfer. A new approach for the simulation of annular flow is here proposed using an in-house developed transient solver based on the Volume of Fluid (VOF) adiabatic solver interIsoFoam available in OpenFOAM. With the VOF method, in addition to the standard set of equations (continuity and momentum), a transport equation related to the advection of the volume fraction scalar field has to be solved. The numerical setup consists of 2D axisymmetric domain. An adaptive mesh refinement (AMR) method is added to the solver to better capture the interface position. The k-ω SST model is used for turbulence modelling in both the liquid and vapor phases and a source term (whose magnitude is controlled by a model parameter named B) is included in the ω equation to damp the turbulence at the interface.