Channel Depth Research Articles

Investigation of roll forming process and quality control factors for metal bipolar plates

Metal bipolar plates (BPPs) are crucial components of proton exchange membrane fuel cells (PEMFCs), with the quality of their formation affects the power generation efficiency and lifespan of the fuel cells. The predominant manufacturing method, stamping, often results in localized excessive stretching of metal BPPs, thereby limiting the depth of the flow channels. Roll forming, dominated by bending deformation, is a forming process that ensures uniform thinning and greater depth of BPPs. The multi-directional flow channel roll forming model for BPPs is constructed in this paper for the first time, the characteristics of the roll forming process is investigated. Effects of process parameters on the forming results are discussed. The investigation indicates that during the roll forming process, the channel ports and corners are critical areas where defects are most likely to occur. The average filling ratio of the longitudinal flow channels is 5.6% higher than that of the transverse flow channels. The plastic strain in the longitudinal flow channels is about 36% higher than in the transverse ones, which making the form is more difficult to form, but the thickness is more uniform. Increasing the diameter of the rollers can enhance the filling ratio and flatness, but it will exacerbate thinning at the corners of the flow channels. When the ratio of the flow channel width to the rib width is close to 1, the filling ratio of the BPP is higher, with less thinning, resulting in a better forming result. As the depth of the flow channel increases, resulting in a thinner BPP, when depth-to-width ratio exceeding 0.6 is more likely to lead to failure. Increasing the speed of roll forming can lead to a greater thinning of the BPP and may even cause it to crack. The thinner the sheet metal is, the higher the filling ratio of the BPP and the more uniform its thickness. Those results can provide technical references for the structural design and forming process optimization of BPPs.

The Channel Migration of Inland Waterway Channels in Ilaje, Ondo State, Nigeria

The channel migration or shifting of navigable river channels have been an issue of major concern, as their effects on the transport environment, channel corridors, the manoeuvrability of vessels transiting these channels and vessels navigation amongst other factors result to inefficiency in inland transport in the riverine region of Ilaje, Nigeria. Most navigational and operational challenges have been attributable to alterations in the waterway channel due to aggradation and degradation processes in the river regime. The study’s goal is to explore channel migration along the Igbokoda-Ayetoro waterway with a view to provide mitigation methods to address potential difficulties along the waterway channel and in the adjoining environment. The objectives of the study include gathering satellite imagery of the study area between 1972 and 2022; assessing the morphological planforms of the study river channel, and assessing the river channel’s effective width using the segment-transect method. The study considered channel width, depth and alignment as indicators to be carefully evaluated to ensure safe, sustainable and efficient inland navigation measures. To ascertain the shapes and forms of the channel during the study period, geospatial and computer-aided techniques were used. Channel widths were extracted using the Segment-Transect method at 100-meter intervals. 50 year and 100-year estimate of the extent of channel/banklines shifting were determined. According to the study, there are changes in the channel’s width, depth and planform (alignment) that make the waterway indeterminate and unsuitable for vessels transiting on two-way manoeuvrability lanes. Hence, the study recommended the sustainable mitigation strategies to tackle the potential challenges pose by channel migration and reduce its impact on the vessel manoeuvrability, navigation and the adjoining environment.

Enhanced Feature Refinement Network Based on Depthwise Separable Convolution for Lightweight Image Super-Resolution

Image super-resolution (SR) techniques aim to enhance the clarity and realism of images. Recently, a wide range of excellent SR algorithms with powerful characterization capabilities have emerged and are widely used. However, there are still challenges and room for improvement in designing a lighter and more edge-friendly SR networks for hardware devices. In this paper, we propose a lightweight enhanced feature refinement network (EFRN) based on depthwise separatable convolution for SR reconstruction. The core network components consist of multiple enhanced feature refinement blocks (EFRB), which fully fuse channel features to extract more accurate low-frequency information based on the attention of different channels. In addition, a lightweight residual block (LRB) and a lightweight dual attention block (LDAB) are designed to enhance network information extraction with minimal parameter cost. We improve the feature refinement by using 1 × 1 convolution instead of a channel selection operation to reduce the dimensionality of the features and extract the refined features more efficiently. Finally, to achieve better reconstruction performance, the depth and number of channels of the network are expanded while keeping the total number of parameters at a low level. Extensive experiments have been conducted to demonstrate the superiority of our EFRN over other mainstream SR algorithms in terms of reconstruction results and the number of parameters.

Guiding properties of Bessel–Gaussian and super-Gaussian pulses in inhomogeneous parabolic plasma channels

The guidance and stable propagation of laser pulses over many Rayleigh lengths are crucial for the plasma electron acceleration in the laser wakefield accelerators. Using plasma channels with specific characteristics can lead to the proper guidance of the laser pulse. Here, quasi-three-dimensional particle-in-cell (PIC) simulations are performed to investigate the guidance of Bessel–Gaussian pulse (BGP) of zeroth order and super-Gaussian pulse (SGP) of 3rd and 4th orders in an axially and radially inhomogeneous plasma channel. The effects of the channel radius and depth, the laser wavelength and initial spot size, and the plasma channel inhomogeneity on the guidance of the laser pulse are also examined. The results indicate that the guidance of a laser pulse in the plasma channel depends on the pulse profile, and under certain conditions, the pulses can be guided with the least variation of spot size in the inhomogeneous plasma channel. It is shown that the channel depth and the initial laser spot size are very effective in pulse guiding, as the values of these parameters increase, the pulse guidance is done better. In addition, the results show that the guidance of laser pulse is dependent on the type of plasma inhomogeneity represented by three different kinds of initial conditions, as considering the nonlinear-axial inhomogeneity in the parabolic plasma channel can lead to more convergence than the axially homogeneous and linear-axially plasma density profiles.

Flow regime discrimination and methodology for calculating discharge in trapezoidal sluice gates

This study introduces a novel trapezoidal sluice gate designed for water division and flow control within irrigation networks featuring canals with trapezoidal cross-sections. Experiments were conducted on trapezoidal channels with side slopes of m = 1.5, 1.75, and 2.0, using trapezoidal sluice gates at various gate openings, upstream water depths, and downstream depths. A total of 411 experimental sets were conducted to study methodologies for discerning between free flow and submerged flow conditions and for determining discharge rates. A method was proposed to distinguish flow patterns of trapezoidal sluice gates: submerged flow occurs when the downstream channel depth (ht) exceeds the submergence threshold (Ht'), while free flow is indicated when ht is less than Ht'. The formula for calculating Ht' was derived, along with formulas for computing discharge rates under free flow and submerged flow conditions for trapezoidal sluice gates. The results revealed that the average relative errors of the formulas obtained through the partition method and the submergence coefficient correction method were 2.24 % and 5.37 %, respectively, demonstrating high accuracy and reliability. The scale effects on the flow regimes and formulas of discharge rates are also discussed. Findings from this study enhance the understanding of the hydraulic characteristics of trapezoidal sluice gates, which hold significant implications for the adoption and intelligent management of such gates in irrigation areas, offering a viable solution for selecting appropriate water gate configurations in irrigation systems.

Numerical simulation of open channel basaltic lava flow through topographical bends

In this study, we utilised computational fluid dynamics to investigate the behaviour of open-channel basaltic lava flows navigating bends on shield volcanoes. Our focus was on understanding the relationship between flow velocity, rheology, and bend geometry. Employing a simple Force Balance Model (FBM), which considers the equilibrium between hydrostatic pressure and centrifugal force, we accurately approximated the changes in the height of the lava’s free surface through various bend geometries. Our analysis includes examining the influence of channel depth, width, and bend radius on the flow, revealing that variations in these parameters significantly affect the flow’s vertical displacement. Additionally, the bend sector angle emerged as a critical factor, indicating a minimum angle necessary for the flow to fully develop before exiting the bend.Further, we assessed the applicability of the Shallow Water Equations (SWE) for modelling the inertial displacement of the lava flow in bends, finding a good fit. The study extended to comparing the FBM’s predictions of the tilt angle of the flow’s free surface with the SWE results, showing notable agreement under specific conditions, particularly at a bend angle of 90 degrees. The impact of fluid density was also considered, revealing that density is a contributing factor to the development of the wetted line in the bend, a factor that is not captured by the simple FBM model. Finally, we explored different rheologies akin to natural lava flows, such as viscoplastic flow, and determined that factors like yield stress, consistency index, and power law index have a small impact on the flow behaviour in a steady-state condition within a bend.

Application of 3D Geological Modeling Technology for Single Sand Body in Block S

Abstract The P oil layer is generally in a medium to high water cut period, with scattered macroscopic residual oil distribution. The reserves are mainly distributed in the microfacies of river sand bodies, and the main layer is severely flooded with water, resulting in ineffective circulation in some areas. Therefore, it is necessary to tackle the modeling technology within the layer and describe the remaining oil within the layer to meet the needs of tapping the potential of remaining oil during the high water cut period. This article takes the establishment of a three-dimensional geological model of a single sand body within the S block layer as an example. Based on the establishment of a fine structural model, the “plane and vertical dual control” modeling method is used. The implementation method is: controlling the range of sedimentary facies maps → using the top surface of the sand body as the top depth of the river channel → controlling the vertical shape of the river channel through the facies controlled sandstone contour map, thereby achieving the vertical shape of the river channel through the facies controlled sandstone contour map, and establishing a three-dimensional sedimentary facies model of a single sand body. Optimize the method for characterizing interlayers, achieve modeling of single sand body interlayers, and perform random simulation interpolation in phases to obtain attribute models. The use of a single sand body model within a layer can visually display the three-dimensional channel morphology and classify the identified connected bodies within the study area. The upscaling method of sedimentary facies models with irregular boundaries greatly reduces the number of model grids and provides a relatively refined geological model for numerical simulation.

Three-dimensional numerical investigation on flow and heat transfer characteristics and multi-objective optimization of interconnected microchannels

The interconnected microchannel demonstrates excellent performance in enhancing flow heat transfer. However, the optimal width of the interconnecting slot has not been thoroughly investigated. To address this gap, this paper numerically simulates the three-dimensional flow and heat transfer of interconnected microchannels featuring varied slot widths and channel depths. The investigated slot widths range from 50 to 1000 μm and depths of 100, 200, and 300 μm. Evaluation of overall performance encompasses heat transfer and flow characteristics such as average wall temperature, heat transfer coefficient, thermal resistance as well as pressure drop. It is the interconnected slots that interrupt the velocity and thermal boundary layers, contributing to enhanced heat transfer. Furthermore, the back propagation neural network and non-dominated sorting genetic algorithm-II are utilized for multi-objective optimization of thermal resistance and pressure drop. The technique for order preference by similarity to an ideal solution (TOPSIS) method combined with the entropy weight method is employed to select the compromise optimal solution from the Pareto optimal solutions. The optimized slot widths are 369, 424, and 167 μm for channel depths of 100, 200, and 300 μm, respectively. This research provides data support for the optimization design and engineering manufacturing of interconnected microchannels.

Stable bubble formations in a depth-perturbed Hele-Shaw channel

The propagation of polydisperse bubbles inside a rectangular Hele-Shaw channel by the constant volumetric flux flow of an ambient viscous liquid is generally unsteady; pairs of neighboring bubbles will either separate or coalesce because their propagation speeds increase monotonically with their sizes. Thus, any group of bubbles will eventually rearrange itself in order of decreasing size, individual bubbles will separate, and, crucially, there are no stable multiple-bubble states. Remarkably, the introduction of a small axially uniform elevation to the channel's lower boundary (on the order of a percent of the channel's depth) leads to the creation of stable multiple-bubble states and, thus, disrupts the usual reordering by bubble sizes. The constituent bubbles of such states lie in alternation on opposite sides of the elevation. The elevation provides a mechanism for the trailing bubbles to reduce their propagation speeds when approaching their preceding nearest neighbors. The stable multiple-bubble states are always led by the smallest bubble while the trailing bubbles can be arranged in any order and, thus, their number grows factorially as the number of bubbles increases. Published by the American Physical Society 2024

Micro-Channel Cooling of Hot Spots Through Non-Uniform Aspect Ratio Designs

Abstract Electronic devices experience spatial variation in power dissipation, which results in high-temperature hot spots. These locations require aggressive thermal management, which can be complex and costly. Simple solutions such as single-phase micro-channels can provide adequate heat transfer, but they are not designed to control heat transfer locally. However, micro-channels can be tailored to control local flow rates and heat transfer, potentially mitigating hot spot temperatures. Using a conductive and convective resistance network for a micro-channel, an analytical model is generated for heat transfer within an individual passage. For a given channel width, this model relates the channel depth to its resistance through a power law. Over a wide range of heat fluxes, the optimal design balances local temperatures to within 3 K. The analytical model is validated using computational simulations of the optimized heat sink. For a randomly-generated, non-uniform power distribution, device temperatures are balanced with a sample standard deviation below 2.5%, which is significantly better than a baseline design. When heat spreading is incorporated, the temperature increase is smaller but remains uniform, indicating that the hot spots can be mitigated.

Exploring the influence of flexural rigidity variability of aquatic plants on stem deflection geometry and flow characteristics

The existing assumption of a constant flexural rigidity (EI) for the entire height of aquatic plants in the analysis of flow past flexible vegetation may not translate in to real scenario as EI of a flexible plant stem varies along the height due to variation in tissue structure and cross section. This variation is therefore needed to be effectively quantified for better analysis of flow-vegetation interaction. In this regard, the own-weight cantilever method was used to represent the variability of EI along the stem height of three plants: water lily, water chestnut, and lotus. Analytical models are proposed to predict stem deflection geometry and vertical velocity distribution across channel depth incorporating EI as a function of stem height. Analytical and experimental data, obtained from open-channel flume tests, significantly support the developed models and confirm the assumption of variable flexural rigidity. Further investigations show that the flexural rigidity, transcends being a mere constant numeric value; it profoundly influences various aspects of the fluid-vegetation interaction such as: the extent of deflection geometry, velocity reduction, Reynold stress variation, and penetration length. Therefore, this study is crucial for better understanding of the physics of sediment transport, pollutant mixing, and wetland management and restoration.

Environmental Impact of River Bank Erosion on Stream Morphology: A Study of the Mini Piti Stream, Obio-Akpor, Nigeria

This study was designed to assess the impact of river bank erosion on the environment and the channel morphology for the Mini-Piti stream in Obio-Akpor local government area of Rivers State, Nigeria. This study determined the depth variations from width measurements due to bank erosion activities and the impact of indiscriminate waste dumps on the river channel. Physical water quality parameters of temperature, turbidity, transparency and TSS were determined using standard methods. The stream was divided into three stations; upstream 2.5km, midstream 2.5km, and downstream with intervals of 1km measured to differentiate each station as 5 samples were obtained per station at intervals of 0.5km apart. The flow velocity and discharge were estimated as the average depth recorded upstream being DS 0.9m, WS 1.4m, Midstream DS 1.3m, WS 1.7m, and Downstream = DS 1.5m WS 1.7m. The maximum width of 11m and minimum of 0.1m were recorded though natives confirmed that the stream is closing up unless maintenance dredging to expand the depth and width, the loss of this channel cannot exceed 20 years. The field observation and the impacts of precipitation and storm water from the built area of midstream were very intensive whose action increased the water level above its channel capacity and eroded the bank. From t-test analysis, there were significant seasonal variations in the depth for the measured widths for the upstream T (8) =2.1, p= 0.036 and the midstream, T (8) =2.36, p=0.023. Similarly using the one-ANOVA, a significant variation in the depths of five locations during the dry season downstream F (4, 60) = 2.79, p= .03 was recorded. The Tukey’s HSD post hoc test showed the locations have no significantly high depths for the studied widths sizes (p<0.01 and p<0.05). A one-way ANOVA revealed a significant variation in the depths of five locations during the wet season upstream F (4, 60) = 5.966, p= .000. The Tukey’s HSD post hoc test showed the locations have significantly high depths for the studied widths sizes (p<0.01 and p<0.05) at locations L2:L4 at Q=5.53 (p=0.00216, L2:L5 at Q= 4.72 (p=0.1214), L3:L4 at Q=4.90 (p=0.00841) and L3:L5 at Q=4.10 (p=0.0403). The studied physical parameters were all above WHO permissible standards and there were no significant variations between dry and wet seasons (38% turbidity midstream, TSS-33%, 31% and 30.6% variation upstream, midstream and downstream respectively) as well as spatial changes. The collapsed sediments and waste dumped at the bank of the stream were transported downstream due to reduced velocity and coarser sediments trapped at the stream bed causing shallow depth while the suspended fine sediment on the water column reduced the clarity of the stream resulting in adverse flooding over 20 years now. The research revealed that bank erosion has significant impact on water quality due to poor transparency and geometry of stream by the alterations of the channel depth and width, flow rate, scouring and deposition of sediments in the stream. The need for regulatory agencies to control anthropogenic inputs and enhance bank erosion prevention programmes cannot be over-emphasized. The monitoring of indiscriminate urbanization programmes to limit excess scouring activities by National Inland Waterways Authority (NIWA) is very essential to reduce excessive sand mining.

Analytical modeling of STFET biosensor using modulated dielectric for ultrasensitive detection of biomolecules

AbstractThis paper proposed analytical modeling of a Schottky tunnel field‐effect transistor (STFET)—based biosensor with adjusted gate oxide. This model is developed by resolving the Poisson's equation and calculating the parabolic potential lateral to the channel depth. The special property of the bio‐transistor, which serves as a biosensor, is then included in the analytical modeling of drain current. After the biomolecule interacts with the bio‐transistor, a change in the drain current was employed as a metric to determine the sensitivity. The advanced analytical modeling explored several device restrictions. A device simulation is used to maintain and validate the established and planned characteristic trend. Consequently, the suggested model can be the right solution for the best design and fabrication of a biosensor.

Finite Element Analysis of Flow-Electrode Capacitive Deionization

As access to freshwater diminishes due to climate change and population growth, drought-stricken regions across the globe continue to turn to groundwater and desalination. A largely untapped water resource in many parts of the world is brackish water - defined as water with total dissolved solids (TDS) in the range of 500 ppm to 10,000 ppm. Flow Capacitive Deionization (FCDI) is an electrochemical ion removal technology that is well-suited for the continuous desalination of brackish waters. Traditional Capacitive Deionization (CDI) consists of two fixed capacitive electrodes which are charged and discharged cyclically to capture ions from the solution being treated, and then regenerated to create a waste brine stream. During FCDI operation however, an applied potential drives ions out of a center water channel, typically through a pair of cation and anion exchange membranes (CEM/AEM), and into two flowing capacitive slurry electrodes (Figure 1). Because the electrodes are mobile, they can be moved into an adjacent cell for regeneration, thus enabling continuous operation of the desalination system without cyclical charge/discharge. The cathode and anode slurries typically consist of activated carbon suspended in a salt solution.Because the electrodes are flowing in FCDI, models describing this system must translate the Eulerian derivative to describe transient capacitive charge/discharge to a Lagrangian material derivative following the electrode material flowing through space. A flowing capacitive electrode is a significantly more complex system than a stationary porous and capacitive electrode matrix, incorporating the fluid dynamics of the slurries, ion transport within the slurry’s electrolyte medium, etc. Despite nearly a decade of research into FCDI, few researchers have probed the transient and spatially dependent mechanisms of ion transport and electro-adsoprtion within flow electrodes. While the overall electrodialytic contributions to ion capture within FCDI systems have been studied (1,2), the mechanism of competition between the electrodialysis and capacitive ion capture within the flow electrodes remains somewhat elusive. Additional analysis of the ion transport phenomena within these flow electrodes could bring forth insights into optimal design of FCDI devices and/or electrode formulations.In this study, an existing 2-dimensional mathematical model (3,4) for electrochemical flow capacitors is adapted to FCDI and solved via finite element analysis in COMSOL Multiphysics. Transport equations describing the advection of overpotential along with the flowing electrode are coupled with the Nernst-Planck equations which govern ion transport within the CEM/AEM, center water channel, and slurry electrolyte medium. This study investigates the effect of slurry flow velocity and sodium chloride concentration in the influent water on electrical potential profiles within an FCDI cell, and illustrates the active regions of capacitive electro-adsorption through the depth of the flow channel. Models of electrodialysis and FCDI are compared to understand the fundamental differences in driving forces for ion removal between the two technologies. The model shows agreement with experimental data through prediction of salt adsorption rate trends (mmol NaCl m-2 s-1) vs. influent sodium chloride concentrations. Through this analysis, it is shown that this model may serve as a valuable groundwork for expansion of FCDI modeling capabilities to include three dimensional cell geometries and subsequent optimization of operational parameters and cell dimensions. P. Nativ, Y. Badash, and Y. Gendel, Electrochem. Commun., 76, 24–28 (2017). J. Ma, C. He, C. Zhang, and T. D. Waite, Water Res., 144, 296–303 (2018). N. C. Hoyt, J. S. Wainright, and R. F. Savinell, J. Electrochem. Soc., 152, A652–A657 (2015). N. C. Hoyt, R. F. Savinell, and J. S. Wainright, Chem. Eng. Sci., 144, 288–297(2016). Figure 1

Water Management in Hariwan Municipality of Nepal: Groundwater Harvesting from Riverbeds and Aquifers

Most of the regions of the Siwalik and Northern Terai (Bhabar) have a scarcity of water due to the water level beyond the suction limit of ordinary centrifugal pumping. In the present study, the Lakhandehi River section in the Sarlahi district is selected for shallow aquifer prospecting. The objective of this study was to assess potential zones of shallow aquifers including riverbeds. It was also aimed to assess the status of the existing subsurface water conditions, and distribution system, and find out suitable locations for groundwater harvesting and uses. The methodological part of the present study covers the field data collection and finding the appropriate shallow aquifer for groundwater extraction. In the field study, both the geological as well as hydrogeological maps were prepared on a 1:25,000 scale to assess the aquifer condition. A social survey was also carried out to find the most water scarcity areas and water availability conditions in the region. The main water scarcity area is found in the Hariwan Municipality, around the northern part of Bhabar and the southernmost region of the Chure region. The water insufficiency area for the present study was found in the places like Hariyon Khola section (Dumrighari), Sano Dume and Dume Khola sections (Samari Bhanjyang), Kothi Khola section (Kothikholagaun), and Attrauli Khola section (Atrauli village) of Hariwan Municipality due to the presence of impermeable layers in shallow depth. The concept of the development of swamp wells by retaining the groundwater flow from the shallow depth of the river channel is proposed in areas like the Samari Bhanjyang and Atrauli villages. Similarly, the development of shallow wells is proposed for the other two regions. To ensure a cost-effective water supply to the communities, it is advisable to implement a water lifting system to elevate the reservoir, followed by gravity-flow distribution.

Investigation of a microfluidic free-flow electrophoresis chip of glass substrate with integrated indium tin oxide electrodes

Free-flow electrophoresis (FFE) is a unique form of electrophoresis that allows continuous electrophoresis separation. Small scale FFE is very practical for processing of limited amounts of samples for analytical purposes. In this work, glass substrate was designed as a chip FFE and its performance was visually demonstrated and characterized using fluorescent probes. The chip consisted of two pieces of glass substrate. One of them was patterned with a planar indium tin oxide (ITO) electrodes, and the other glass was designed with inlets for sample infusion and electrolyte transfer. The depth of the separation channel (15 × 60 mm) is defined by a tape spacer of 85 μm. Since the integrated ITO electrodes in direct contact with the working solution in the separation channel, a voltage as high as 600 V can be applied without bubbling problems. The main operation factors such as buffer concentration, pH, voltage, and flow rate were optimized to separate the probes, and the results were compared with capillary electrophoresis. The role of EOF and electrolysis was also discussed. Compared to photolithographic wet etching, this design is easier to implement, and it enables effective FFE operation. This chip FFE system has potential application in processing and cell sorting.

Three-dimensional numerical simulation of two-phase flow in a proton exchange membrane electrolysis cell and study of the effect of flow channel depth

Abstract The flow channel play a critical role in water-gas transfer within an electrolysis cell, directly impacting its mass and heat transfer capacity. While most studies concentrate on the overall shape and structure of the flow channel, limited attention has been given to its dimensions. This paper investigates the influence of various operational conditions and changes in flow channel depth on the electrolytic cell using a three-dimensional numerical model of PEMEC. Results indicate that higher temperatures enhance electrolysis cell performance, whereas the impact of water inlet velocity on the polarization curve is insignificant. Under constant inlet velocity, increasing the depth of the flow channel improves mass and heat transfer as well as electrolysis performance, whereas, under constant water flow rate, changes in inlet velocity have a greater effect than alterations in flow channel depth.

Advancing Parsimonious Deep Learning Weather Prediction Using the HEALPix Mesh

AbstractWe present a parsimonious deep learning weather prediction model to forecast seven atmospheric variables with 3‐hr time resolution for up to 1‐year lead times on a 110‐km global mesh using the Hierarchical Equal Area isoLatitude Pixelization (HEALPix). In comparison to state‐of‐the‐art (SOTA) machine learning (ML) weather forecast models, such as Pangu‐Weather and GraphCast, our DLWP‐HPX model uses coarser resolution and far fewer prognostic variables. Yet, at 1‐week lead times, its skill is only about 1 day behind both SOTA ML forecast models and the SOTA numerical weather prediction model from the European Center for Medium‐Range Weather Forecasts. We report several improvements in model design, including switching from the cubed sphere to the HEALPix mesh, inverting the channel depth of the U‐Net, and introducing gated recurrent units (GRU) on each level of the U‐Net hierarchy. The consistent east‐west orientation of all cells on the HEALPix mesh facilitates the development of location‐invariant convolution kernels that successfully propagate weather patterns across the globe without requiring separate kernels for the polar and equatorial faces of the cube sphere. Without any loss of spectral power after the first 2 days, the model can be unrolled autoregressively for hundreds of steps into the future to generate realistic states of the atmosphere that respect seasonal trends, as showcased in 1‐year simulations.

Impact of flexible vegetation on hydraulic characteristics in compound channels with converging floodplains

ABSTRACT Floodplains in natural rivers are curved and narrow, rather than following a straight path and the presence of vegetation and varying depth of flow affects the flow parameters of the channels. The purpose of this study is to investigate the effects of the convergence of the channel and relative depth of flow on the depth-averaged velocity (DAV) and boundary shear stress (BSS) of a converging compound channel. The effect of vegetation on DAV and BSS was also deliberated. To examine the effect of vegetation, synthetic grass 8 cm in height was used as a flexible vegetation to depict the natural conditions of the rivers. The DAV was calculated using an acoustic Doppler velocimeter (ADV) and the measurement of BSS was done using the Preston tube technique. After analysing the data, it was revealed that as the convergence of floodplains increases, maximum DAV increases. The presence of vegetation reduces the velocity specifically at lower flow depths. BSS increases with the convergence as well as vegetation. This research provides valuable data and results which will be helpful in better flood management, river restoration, and designing effective hydraulic structures.

Fabrication of microneedles using wire electric discharge machining and improving surface quality by electrochemical polishing

Microneedle (MN) arrays have many applications in biomedical engineering to deliver drugs transdermally or extract biomarkers from the interstitial fluid from the human skin. Several methods have been developed to fabricate different sizes and shapes of MN using polymers, ceramics and metals. However, most of these methods require expensive sophisticated machines and clean room facilities. So, it is difficult to fabricate microneedle arrays in large quantities at a reasonable cost. This study reports the fabrication of a high-quality stainless steel master pattern for an MN array using a wire-cut electric discharge machining process followed by electrochemical polishing (ECP). Different densities of a 5 × 5 array of microneedles with pyramidal shapes were fabricated by machining channels onto the workpiece surface in a criss-cross pattern. A systematic experimental study was carried out with reference to the offset between the two consecutive channel faces and the depth of channels. The output parameters are MN height (MNH), MN base (MNBW) and tip width (MNTW). The average needle tip width, base width, and height of microneedles were found to be 55.3 ± 5 µm, 679.8 ± 10 µm, and 914.7 ± 19 µm. Finally, the sharpness of the MN tips and the overall surface finish of the MN array were improved with ECP. The reductions in MNH, MNBW, and MNTW were reported to be −18.3%, −9.7%, and −95.4%, respectively, with a final tip width of 2.55 ± 1.62 µm. The MNs’ tip angle was reported to be 32.52° ± 1.56.