Shadow Effect Research Articles

Experimental design and analysis of advanced three phase converter for PV application with WCO-P&O MPPT controller

Photovoltaic (PV)-based power generation systems are becoming increasingly popular as a due to its high performance and cleanliness. Several factors influence the performance of a PV system, including shadowing effects. PV systems employ MPPT methodologies to obtain the power from PV array. Conventional MPPTs works well under normal conditions when there is no shadow effects or partial shading. The presence of partial shading affects the system performance and generates several power peaks. This complicates the process of finding out of the global peak (GMPP) with improved tracking efficiency and reduced settling time including conversion efficiency. This work proposes three hybrid MPPT techniques: Water Cycle Optimisation-Perturb and Observe (WCO-PO), Artificial Neural Network Supported Adaptable Stepped-Scaled Perturb and Observe (ANN-ASSPO), Grey Wolf Optimisation-Modified Fast Terminal Sliding Mode Controller (GWO-MFTSMC), and two conventional MPPT techniques WCO and P&O have been implemented. The proposed system utilizes interleaved boost converter with three phase. The performances of proposed hybrid MPPTs strategies were compared in terms of output voltage, output current and extracted power. The comparison also includes conversion efficiency and average settling time. To analyse the performances, four different cases have been used to test the efficacy of hybrid MPPTs under changing climatic conditions. The MATLAB/Simulink tool has been used to analyze the PV system performances. In the three hybrid MPPT techniques, WCO-PO has performed better when compared to other two hybrid MPPTs in terms of conversion efficiency (99.56%) and settling time (1.4 m).

A novel acceleration approach to shadow calculation based on sunlight channel for urban building energy modeling

Shadow effect among buildings has great impacts on the building energy consumption and the performance of building photovoltaic, and calculating shadows on building surfaces in urban building energy modeling (UBEM) faces challenges of inefficiency, especially for dense urban areas. In this study, a novel shadow calculation approach based on sunlight channel is proposed that can streamline the surrounding environment and accelerate the shadow calculation process. The sunlight-channel algorithm can further accelerate the shadow calculation process by dynamically predetermining the shading surfaces according to the actual solar position. In a real urban context, the proposed approach can accelerate the computation process by over 10 times over the baseline and over 34 times over the non-accelerated method, with a mean absolute percentage error (MAPE) of 1.13% for the total solar radiation. The proposed approach copes well with both large-scale urban models and the complexity of building structures, particularly for urban models with complex changes in building heights. This approach can significantly enhance the computational efficiency in complex urban environments, facilitating an accurate and rapid analysis of the energy consumption and solar potential of buildings in dense cities.

Influence Of Shadow And Shuttle Run Exercises On Badminton Sports Footwork Aged 13 - 15 Years At Pb Jaya Raya Jakarta

This study was conducted to determine the effect of shadow and shuttle run training on badminton footwork aged 13–15 years at PB Jaya Raya Jakarta. This study uses an experimental method that utilizes a two-group pretest-posttest design. The population studied in this study were PB athletes. Jaya Raya Jakarta has a population of 30 people. A purposive sampling method was used in the study, with the following criteria: At least 75% of players were on the attendance list during the last two months of training (actively involved in training); (2) Participants are PB athletes. (3) Age 13–15 years, (4) Male gender. The sampling test in the form of a foot movement agility instrument is a circuit-based leg exercise tester. The t-test was used in the analysis of the data. The results of the research are: (1) There is an effect of shadow training on the sports footwork of children aged 13–15 years in PB. Jaya Raya Jakarta, with t count 3,289 > t table 2.26 and a significance value of 0.009 0.05, resulting in an effect of 9.55%. (2) There is an effect of the shuttle run exercise on the badminton footwork of children aged 13–15 years in PB. Jaya Raya Jakarta, with a count of 4.155 > table 2.26 and a significance value of 0.002 0.05, resulting in an effect of 10.69%. (3) The shuttle run method is more effective for badminton footwork aged 13–15 years in PB Jaya Raya Jakarta than the shadow method.

Numerical Analysis of the Stress Shadow Effects in Multistage Hydrofracturing Considering Natural Fracture and Leak-Off Effect

As a critical technological approach, multistage fracturing is frequently used to boost gas recovery in compact hydrocarbon reservoirs. Determining an ideal cluster distance that effectively integrates pre-existing natural fractures in the deposit creates a fracture network conducive to gas movement. Fracturing fluid leak-off also impacts water resources. In our study, we use a versatile finite element–discrete element method that improves the auto-refinement of the grid and the detection of multiple fracture movements to model staged fracturing in naturally fractured reservoirs. This computational model illustrates the interaction between hydraulic fractures and pre-existing fractures and employs the nonlinear Carter leak-off criterion to portray fluid leakage and the impacts of hydromechanical coupling during multistage fracturing. Numerical results show that sequential fracturing exhibits the maximum length in unfractured and naturally fractured models, and the leak-off volume of parallel fracturing is the smallest. Our study proposes an innovative technique for identifying and optimizing the spacing of fracturing clusters in unconventional reservoirs.

Numerical analysis of hydraulic fracture propagation in deep shale reservoir with different injection strategies

Deep shale reservoirs are characterized by elevated breakdown pressures, diminished fracture complexity, and reduced modified volumes compared to medium and shallow reservoirs. Therefore, it is urgent to investigate particular injection strategies that can optimize breakdown pressure and fracturing efficiency to address the increasing demands for deep shale reservoir stimulation. In this study, the efficiency of various stimulation strategies, including multi-cluster simultaneous fracturing, modified alternating fracturing, alternating shut-in fracturing, and cyclic alternating fracturing, was evaluated. Subsequently, the sensitivity of factors such as the cycle index, shut-in time, cluster spacing, and horizontal permeability was investigated. Additionally, the flow distribution effect within the wellbore was discussed. The results indicate that relative to multi-cluster simultaneous fracturing, modified alternating fracturing exhibits reduced susceptibility to the stress shadow effect, which results in earlier breakdown, extended hydraulic fracture lengths, and more consistent propagation despite an increase in breakdown pressure. The alternating shut-in fracturing benefits the increase of fracture length, which is closely related to the shut-in time. Furthermore, cyclic alternating fracturing markedly lowers breakdown pressure and contributes to uniform fracture propagation, in which the cycle count plays an important role. Modified alternating fracturing demonstrates insensitivity to variations in cluster spacing, whereas horizontal permeability is a critical factor affecting fracture length. The wellbore effect restrains the accumulation of pressure and flow near the perforation, delaying the initiation of hydraulic fractures. The simulation results can provide valuable numerical insights for optimizing injection strategies for deep shale hydraulic fracturing.

Optimizing Solar Potential: Site Potential Selection for Floating Photovoltaics in the Sepaku Semoi Dam Reservoir

Green energy is considered an essential solution to address the world’s energy scarcity. However, there are several technologies available for producing green energy, including photovoltaics, with a specific focus on floating photovoltaics. The application of photovoltaics on water surfaces can enhance the cooling effect of solar modules, thereby achieving optimal temperatures. The implementation of floating photovoltaics should be approached with careful consideration, for instance, hydrodynamic aspects, reservoir water level fluctuations, forest shadow effects, and safety distance from Dam Facilities. Furthermore, in light of the relocation of the Indonesian National Capital City from Jakarta to Ibu Kota Nusantara (IKN), the city’s green energy options must be thoroughly studied and researched. The Sepaku Semoi Dam is located in Penajam Paser Utara, Kalimantan Timur, and is designated as a flood control and raw rater supplier for IKN. In this research, hydrodynamic simulations using MIKE 21 were conducted to determine water surface velocities. These results were then combined with reservoir depth and the location of areas unaffected by forest shadows. The outcome of this analysis revealed that 15.2% of the water surface area in the Sepaku Semoi Dam Reservoir has the potential for installing floating photovoltaics. With an energy density of floating photovoltaic around 100 MW/km2, Sepaku Semoi Dam Reservoir would produce 50.83 MW. As a result, this research has generated a Potential Location Map for Floating Photovoltaics in Sepaku Semoi Reservoir Dam Reservoir.

A Hybrid Index for Monitoring Burned Vegetation by Combining Image Texture Features with Vegetation Indices

The detection and monitoring of burned areas is crucial for vegetation recovery, loss assessment, and anomaly analysis. Although vegetation indices (VIs) have been widely used, accurate vegetation detection is challenging due to potential confusion in the spectra of different types of land cover and the interference of shadow effects caused by terrain. In this work, a novel Vegetation Anomaly Spectral Texture Index (VASTI) is proposed, which leverages the merits of both spectral and spatial texture features to identify abnormal pixels for extracting burned vegetation areas. The performance of the VASTI and its components, the Global Environmental Monitoring Index (GEMI), the Enhanced Vegetation Index (EVI), and the texture feature Autocorrelation (AC) were assessed based on a global dataset previously established, which contains 1774 pairs of samples from 10 different sites. The results illustrated that, compared with the GEMI and EVI, the VASTI improved the user’s accuracy (UA), producer’s accuracy (PA), and kappa coefficient across the ten study areas by approximately 5% to 10%. Compared to AC, the VASTI improved the accuracy of abnormal vegetation detection by 13% to 25%. The improvements were mainly caused by the fact that the incorporation of texture features can reduce spectral confusion between pixels. The innovation of the VASTI is that it considers the relationship between anomalous pixels and surrounding pixels by explicitly integrating spatial texture features with traditional spectral features.

Construction alignment and closure control of CFST truss arch bridges based on temperature effect

To reveal the temperature deformation laws and achieve the accurate alignment prediction during the installation process of long-span concrete-filled steel tubular arch bridge ribs in complex environments, this paper establishes a three-dimensional refined heat transfer model for temperature field and effect calculation of truss arch ribs. The model uses the Ray Tracing Technology to recognize the member-caused-shading area on arch ribs. And by comparing with the actual measurement results and shadow effects to achieve the accurate calculation of temperature field. Finally, the variation of ribs deformation during construction and the optimal closure time are detailed analyzed. Results show that the computational method used in this paper can achieve accurate recognition of shadows and precise calculation of the complex three-dimensional temperature field of truss arch ribs. After considering the shadows, the maximum temperature difference between the upper chord sunshine area and lower chord shadow areas can reach 25 °C, which is significantly greater than 8 ℃ in the "Specifications for design of highway concrete-filled steel tubular arch bridge" (JTG/T D65–06-2015). Due to the solar incidence variation along the longitudinal direction of the arch ribs, extreme temperature fluctuation of the chord tubes occurs, with a maximum temperature difference of 21 °C. When arch ribs reach the maximum cantilever, the daily vertical displacement variation can reach approximately 87 mm, and the maximum displacement difference between arch ribs of two canyon sides can reach 15.6 mm at the same time. The solar-caused maximum compressive stress is 34 MPa, which can exceed 100 MPa after superimposing the gravity and cable effects. Based on the analysis of the displacement of both sides of the closure joint under the influence of sunlight, this paper identifies the window period for the closure control of the long-span steel truss arch ribs, laying the foundation for the accurate control of the rib construction alignment and the closure internal force state.

Study of application of bioclimatic architecture strategy at Citraland Residential House in Palu City

Palu City has a fairly hot air temperature, very high intensity of solar radiation, quite high rainfall, and a fairly large wind speed. When reviewing the climatic conditions of Palu City above, the planners in this case the Citraland housing architect team should be able to apply a bioclimatic architecture strategy to be able to respond to the climatic conditions of the city of Palu. Based on this background, it is necessary to conduct a research study on the application of bioclimatic architecture strategies in Citraland's residences. This study uses a rationalistic approach with an exploratory method. Research shows that Citraland Residence has implemented a bioclimatic architectural strategy in several ways, namely the use of shading or shadow effects in the form of roof canopy, eaves, and lattice made of wood, and protective plants, as well as the use of insulating materials such as natural stone affixed to the outer walls. residential home. In addition, the layout of the residence also plays a role in the flow of air circulation to the maximum. Then the strategy of making wind-catching rooms and the use of glass materials on several sides of the building which acts as a place to enter sunlight into the house

Demi-decadal land use land cover change analysis of Mizoram, India, with topographic correction using machine learning algorithm.

Mizoram (India) is part of UNESCO's biodiversity hotspots in India that is primarily populated by tribes who engage in shifting agriculture. Hence, the land use land cover (LULC) pattern of the state is frequently changing. We have used Landsat 5 and 8 satellite images to prepare LULC maps from 2000 to 2020 in every 5years. The atmospherically corrected images were pre-processed for removal of cloud cover and then classified into six classes: waterbodies, farmland, settlement, open forest, dense forest, and bare land. We applied four machine learning (ML) algorithms for classification, namely, random forest (RF), classification and regression tree (CART), minimum distance (MD), and support vector machine (SVM) for the images from 2000 to 2020. With 80% training and 20% testing data, we found that the RF classifier works best with the most accuracy than other classifiers. The average overall accuracy (OA) and Kappa coefficient (KC) from 2000 to 2020 were 84.00% and 0.79 when the RF classifier was used. When using SVM, CART, and MD, the average OA and KC were 78.06%, 0.73;78.60%, 0.72;and73.32%, 0.65, respectively. We utilised three methods of topographic correction, namely, C-correction, SCS (sun canopy sensor) correction, and SCS + C correction to reduce the misclassification due to shadow effects. SCS + C correction worked best for this region; hence, we prepared LULC maps on SCS + C corrected satellite image. Hence, we have used RF classifier for LULC preparation demi-decadal from 2000 to 2020. The OA for 2000, 2005, 2010, 2015, and 2020 was found to be 84%, 81%, 81%, 85%, and 89%, respectively, using RF. The dense forest decreased from 2000 to 2020 with an increase in open forest, settlement, and agriculture; nevertheless, when Farmland was low, there was an increase in the barren land. The results were significantly improved with the topographic correction, and misclassification was quite less.

Characterization of the future northeast monsoon rainfall based on the clustered climate zone under CMIP6 in Peninsular Malaysia

The Northeast monsoon (NEM) exerts a significant influence on the climate system of Peninsular Malaysia (PM) and has profound implications for water resource management, flood control, and disaster preparedness in the region. This study employed CHIRPS rainfall data from 1981 to 2022 at a spatial resolution of 0.25° to generate climate zones. The performance of global climate models (GCMs) in replicating monthly rainfall was evaluated using multiple statistical metrics, with the top-ranked ones being used for the generation of future projection downscaled ensemble models. The NEM months (November, December, January, February, and March) were used as input parameters to form clustered homogeneous groups using the Ward hierarchical method. The optimal number of climate zones was determined using the elbow method, silhouette width values, and spatial evaluation. Ultimately, a 7-cluster solution was chosen due to its consistency and meaningful cluster formation. The zones were categorized into two regions: the West Coast and the East Coast, based on their geographical location and distinctive monthly NEM rainfall patterns. The analysis of the probability distribution function (PDF) showed that rainfall in the West Coast region had a more spread-out pattern with varying amounts, while rainfall in the East Coast region was more concentrated and consistent. The Northeast climate zone received the highest rainfall, attributed to its proximity to the South China Sea, mountainous areas, and the NEM convergence zone. In contrast, the Northwest and Lower Central-West climate zones received the lowest rainfall due to the rain shadow effect, limited moisture availability, and distance from major moisture sources. The CMCC-ESM2, CMCC-CM2-SR5, EC-Earth3, and CanESM5 consistently ranked among the highest performing models. After linear scaling bias correction, validated GCMs showed significant improvements, with improvements in MAE, NRMSE, PBIAS, RSR, NSE, MD, CP, R2, and KGE by 11–45%, 15–47%, 96–100%, 15–47%, 10–79%, 5–37%, 68–113%, 11–73%, and 9–51%, respectively. Analysis of NEM season rainfall patterns across climate zones indicated consistent mid-future increases for the Northwest and Lower Central-West zones (12.4–19.8%) and the Upper Central-West and Southwest zones (0.2–5.4%) across all scenarios. In the far-future, the Southeast zone saw an overall increase in rainfall (4.9–11.4%), while the Central-West zone exhibited mixed results (−4.0 to 5.6%). The results also highlighted spatial variability and the need to consider specific climate zones when assessing the impacts of climate change on the NEM, emphasizing the importance of incorporating these projections into long-term planning and decision-making processes.

Modeling of scale-dependent perforation geometrical fracture growth in naturally layered media

In this study, the discrete lattice simulation of multi-scale fracture growth in layered media is conducted and validated against fracturing laboratory observation and field micro-seismic monitoring. The results reveal that the perforation can substantially influence hydraulic fracture initiation and extension. The vertically-oriented-perforation induced fracture will effectively initiate with moderate near-wellbore complexity, promoting fracture crossing at bedding interfaces. The interlaced design of perforation cluster can alleviate the stress shadow effect and facilitate uniform fracture propagation. The far-field fracture complexity are related to the bedding interfacial properties: more tensile interfaces tend to arrest induced fractures and restrict their vertical growth, while more fracturing fluid will be diverted into the permeable interfaces of lower shear strength. The complex fracture networks has the potential to trigger fault reactivation or serve as conduits for underground water, thus causing induce seismicity or aquifer contamination. The findings can enrich the understanding of multi-scale fluid-solid coupling mechanisms and further help us prevent geological hazards.

Quantitative Evaluation of the Batwing Effect on Depth Measurement in Coherence Scanning Interferometry for Rectangular Gratings

Coherence scanning interferometry (CSI) is a widely used non-contact method for measuring areal surface topography. The calculation of groove depth typically employs the ‘W/3 rule’ specified in ISO 5436-1. However, the batwing effect causes overshoots near the groove edges, which can introduce noise singularities in the selected W/3 region for depth calculation, thereby affecting the measurement of rectangular grating depth. This paper introduces the definition of batwing height and width and proposes a simulation model that considers various factors, such as the center wavelength, spectrum of the illuminating light, shadow effect, and numerical aperture, to analyze their influence on depth measurement. The simulation results demonstrate that the batwing width is the primary factor influencing depth measurement for small grating periods. Specifically, a decrease in numerical aperture increases the batwing width, leading to larger depth measurement errors, while a decrease in the center wavelength reduces the batwing width, resulting in smaller depth measurement errors. The influence of the illumination spectrum and shadow effect on depth measurement is found to be minor. Experimental validation using a step standard consisting of rectangular gratings with different periods and depths confirms the agreement between the experimental and simulated results. The proposed method provides a quantitative evaluation of depth measurement accuracy in CSI.

A deep learning framework for 3D vegetation extraction in complex urban environments

Accurate extraction of three-dimensional (3D) vegetation is essential for monitoring urban ecological environments and carbon sinks. Two-dimensional vegetation data in cities has been widely researched. However, large-scale urban vegetation height inventories are lacking. This study proposes a novel framework for 3D extraction of urban vegetation, which can be widely applied based on remote sensing approaches. A multi-task convolutional neural network is established to extract the urban vegetation cover and estimate the vegetation height at the pixel level. The results indicate that this method can derive the complete urban vegetation cover and height from stereo satellite data. Compared with the traditional stereo-photogrammetry method, this method enables rapid inference of vegetation height in urban areas with a root mean square error (RMSE) of 3.16 m. This model is capable of accurately separating vegetation in complex urban environments and performs well despite shadow effects. Furthermore, in this study, the first vegetation height map with 1-m spatial resolution has been produced, covering six urban districts in Beijing (approximately 1,378 km2). It only takes 2–3 min to process the imagery of the whole study area. The high-resolution map can display more urban vegetation details over the existing 10 m/30 m resolution vegetation height maps. Furthermore, the established framework and benchmark for urban vegetation 3D information offer unique insights and provide a basis for further research.

A vat photopolymerization process for structures reinforced with spatially steered flexible fibers

We present a modified vat photopolymerization process for realizing novel fiber-reinforced composite parts wherein continuous fibers are selectively positioned and oriented across multiple layers along the build direction. This is in contrast to laminates and fiber-wound parts made by repeating fiber patterns; and additively manufactured parts with fibers inserted a posteriori or co-extruded selectively. Our process endows two benefits to the parts made with it: (i) spatially steered fibers embedded along specific paths inside to increase stiffness and strength; and (ii) in-situ fiber-matrix interface concurrently cured with matrix material as opposed to the matrix-matrix interface that exists in co-extruded fibers. The process is enabled by a robot manipulator that guides the fiber in each layer by incrementally orienting it along the tangential direction to the bespoke path. The robot arm and the end-effector do not obstruct the UV light source as they pull the fiber taut from afar in multiple directions to alleviate the undesirable effects of shadows. The robot arm is integrated with the build platform and the UV projector, and the entire process is automated. Examples that illustrate making parts with single and multiple fibers are presented to show the efficacy of the process and the machine. An example is shown with continuous fibers embedded along a few spatially varying principal-stress-flow paths inside a part to improve its stiffness and strength. An increase of 71 % in stiffness and 90 % in strength of the part is observed at fiber volume fraction as small as 0.39 %.

Binaural hearing in monaural conductive or mixed hearing loss fitted with unilateral Bonebridge.

To determine the benefits of binaural hearing rehabilitation in patients with monaural conductive or mixed hearing loss treated with a unilateral bone conduction implant (BCI). This monocentric study includes 7 patients with monaural conductive or mixed hearing loss who underwent surgical implantation of a unilateral BCI (Bonebridge, Med-El). An ITA Matrix test was performed by each patient included in the study - without and with the BCI and in three different settings - to determine the summation effect, squelch effect and head shadow effect. Subjective hearing benefits were assessed using the Abbreviated Profile of Hearing Aid Benefit (APHAB) questionnaire. The difference in signal to noise ratio of patients without and with BCI was 0.79 dB in the summation setting (p < 0.05), 4.62 dB in the head shadow setting (p < 0.05) and 1.53 dB (p = 0.063) in the squelch setting. The APHAB questionnaire revealed a subjective discomfort in the presence of unexpected sounds in patients using a unilateral BCI (aversiveness score) compared to the same environmental situations without BCI, with a mean discomfort score of 69.00% (SD ± 21.24%) with monaural BCI versus 25.67% (SD ± 16.70%) without BCI (difference: -43.33%, p < 0.05). In terms of global score, patients wearing a unilateral Bonebridge implant did not show any significant differences compared to those without hearing aid (difference: -4.00%, p = 0.310). Our study shows that the use of a unilateral BCI in patients affected by monaural conductive or mixed hearing loss can improve speech perception under noise conditions due to the summation effect and to the decrease of the head shadow effect. However, since monaural BCIs might lead to discomfort under noise conditions in some subjects, a pre-operative assessment of the possible individual benefit of a monaural BCI should be carried out in patients affected by unilateral conductive or mixed hearing loss in order to investigate the possible additional effect of the fitting of hearing aids.

Experimental study of hydraulic fracture propagation with multi-cluster in-plane perforations in a horizontal well

Tri-axial fracturing studies were carried out to understand the impact of lateral mechanical parameters on fracture propagation from multiple in-plane perforations in horizontal wells. Additionally, the discussion covered the effects of geology, treatment, and perforation characteristics on the non-planar propagation behavior. According to experimental findings, two parallel transverse fractures can be successfully initiated from in-plane perforation clusters in the horizontal well because of the in-plane perforation, the guide nonuniform fishbone structure fracture propagation still can be exhibited. The emergence of transverse fractures and axial fractures combined as complex fractures under low horizontal principal stress difference and large pump rate conditions. The injection pressure was also investigated, and the largest breakdown pressure can be also found for samples under these conditions. The increase in perforation number or decrease in the cluster spacing could provide more chances to increase the complexity of the target stimulated zone, thus affecting the pressure fluctuation. In a contrast, the increase in fracturing fluid viscosity can reduce the multiple fracture complexity. The fracture propagation is significantly affected by the change in the rock mechanical properties. The fracture geometry in the high brittle zone seems to be complicated and tends to induce fracture reorientation from the weak-brittle zone. The stress shadow effect can be used to explain the fracture attraction, branch, connection, and repulsion in the multiple perforation clusters for the horizontal well. The increase in the rock heterogeneity can enhance the stress shadow effect, resulting in more complex fracture geometry. In addition, the variable density perforation and temporary plugging fracturing were also conducted, demonstrating higher likelihood for non-uniform multiple fracture propagation. Thus, to increase the perforation efficiency along the horizontal well, it is necessary to consider the lateral fracability of the horizontal well on target formation.

Sulfonated Polystyrene/Polybenzimidazole Bilayer Membranes for Vanadium Redox Flow Batteries

AbstractPolybenzimidazole has been widely examined as a separator for vanadium redox flow batteries (VRFBs) due to its low vanadium permeability. Its low conductivity can be tackled by combining 1–4 µm thin dense PBI layers with highly conductive mechanically supporting layers, either by lamination or loose stacking. While gel‐PBI is very soft and conductive, the shadow effect of the non‐conductive pore walls of porous supports adds resistance. In this work, these issues are addressed by coating a 25 µm thick highly conductive sulfonated polystyrene layer (S) with a 1 µm thin selective PBI layer (P) to block vanadium crossover. To reduce the number of potential defects, two bilayer membranes can be stacked. A 52 µm thick stack of two membranes (PS–SP, PBI faces the electrodes) shows an area‐specific resistance of 144.8 mΩ cm2 in VO2+‐containing electrolyte and a permeability of 6.85 × 10−14 m2 s−1, both lower than the values for Nafion 212. A VRFB cell test over 3500 charging cycles (1660 h) with an energy efficiency of up to 88.5% at 100 mA cm−2 is shown. Performance losses are reversed by electrolyte rebalancing. With material costs of 1.84 USD m−2, the PSSP(1‐25‐25‐1) membrane promises high performance at low costs.

Numerical insight into hydraulic fracture propagation in hot dry rock with complex natural fracture networks via fluid-solid coupling grain-based modeling

Abundant natural fractures (NFs) in hot dry rock (HDR) reservoirs serve as a crucial element in hydraulic fracturing technology and reservoir production. Nevertheless, the interaction mechanism between hydraulic fractures (HFs) and natural fracture networks (NFNs) remains poorly understood. This study combines the novel hydro-grain-based model (hydro-GBM) and discrete fracture network (DFN) model to investigate the effects of in-situ stress, fracture number, and fracture length on hydraulic fracturing behaviors in mineral-scale granite with NFNs. Results indicate that as the complexity of NFs increases, the stress shadow effect is amplified during HF propagation, while the spatial arrangement of NFs governs the propagation of secondary paths. Additionally, a downward trend is observed in average activity levels of acoustic emission (AE) events and proportions of large events within NFs and matrix. Damage and activation degrees in both NFs and matrix decrease with an increase in the number of NFs. The inability of main hydraulic paths to propagate over long distances can be attributed to the dispersion of fracturing fluid and the rapid decay of pressure within densely distributed, short NFs. These numerical findings shed light on the process of HFs activating NFNs and provide valuable insights for enhancing heat extraction efficiency in HDR reservoirs.

Microstructure and wear resistance of tungsten carbide particle reinforced titanium alloy coating by WAAM

A tungsten carbide particle reinforced Ti-6Al-3Nb-2Zr-1Mo alloy coating was prepared by wire arc additive manufacturing (WAAM) with wire-powder feeding simultaneously. The study shows that the titanium alloy matrix exists in the form of a metastable phase β-Ti, and the addition of tungsten carbide particles significantly refines its grains. Tungsten carbide particles retain a spherical shape, with only the surface undergoing dissolution and releasing W and C atoms. The results of the dry sliding friction test reveal the superior wear resistance of the composite coating, primarily attributed to the shadow effect of the tungsten carbide particles, the enhanced hardness, and the formation of a self-lubricating oxide layer.