Small Mesh Research Articles

Application of a finite element method variant in nonconvex domains to parabolic problems

In this paper we address one of the major difficulties which is the nonconvex behavior of the domains while finding the solution of the problems. The part of the domain where the nonsmoothness appears is where the challenge arises and the way that area is handled using different numerical methods reveals the effectiveness of these techniques. Here in this article, we study the semilinear parabolic problem in nonconvex polygonal domain. For the approximation of the solution we use the Composite Finite Element (CFE) method, which is a classification of the Finite Element Method. CFE discusses the two-scale discretization — the larger mesh also known as the coarse mesh with the size H and the smaller mesh, also known as the fine mesh with the size h. It helps in reducing the dimension of the domain space of consideration. The fine scale grid is used to resolve the nonconvexity of the boundary whereas the coarse scale grid is comprised of larger grids at an appropriate distance from the boundary. The degrees of freedom depends on the coarse grid. This is the precedence of CFE over other methods, i.e., it eases the task of reducing the domain complexity. In this article, we consider two approaches — the semi discrete analysis where only space discretization is carried out, and the fully discrete analysis where both the time and space discretization is done using both backward Euler and Crank–Nicolson method. We study the error analysis in the L∞(L2)-norm and in the L∞(H1)-norm for the semidiscrete case whereas for the fully discrete case, we study the error analysis in the L∞(L2)-norm. Also, we check for the optimal results. For the CFE technique in the L∞(L2)-norm, we derive the convergence having optimal order in time and almost optimal order in space even if the domain is nonconvex. We consider a T-shaped domain and another star shaped domain to carry out the theoretical findings. Thereafter, numerical computations are implemented to validate the theoretical results.

Coupling algorithm of cavity expansion theory and finite element for penetrating reinforced concrete

Aiming at the dynamic problem of projectile penetrating reinforced concrete, this paper creatively proposes a coupling algorithm combining cavity expansion theory and the finite element method. This approach effectively resolves the problem of low efficiency in finite element simulations while ensuring computational accuracy. In this study, based on the cavity expansion theory, we have redeveloped the display dynamics software. Radial stress in the concrete is applied to the warhead surface in the normal direction, and the interaction between the projectile and the steel bar is simulated using the finite element contact algorithm. A coupling algorithm has been developed that can stably and quickly simulate the penetration of reinforced concrete by a projectile. The study indicates that the implementation of the coupling algorithm primarily includes four steps: model establishment and meshing, stress load program design, load application, and initial condition setting. Through verification and analysis, the coupling algorithm presented in this paper is demonstrated to effectively compute the dynamic response of a projectile during penetration. It exhibits superior computational stability and speed compared to the finite element method, and shows minimal sensitivity to grid size. When applied to numerical models with small meshes, it achieves both high precision and rapid computation. The coupling algorithm program design proposed in this paper can be implemented in any display dynamics software, offering a robust approach for engineers and researchers to predict projectile penetration effects. Furthermore, it provides a rapid assessment method for the anti-penetration performance of reinforced concrete structures.

Biocompatibility and Haemocompatibility Assessments of RBC with Polymeric Coated Cardiac Stent.

The current investigation was conducted to evaluate the biocompatibility and hemocompatibility of polymeric-coated cardiac stents. Coronary stents are typically small wire mesh tubes that are used to open arteries that are obstructed over time as a result of the buildup of fat, cholesterol, or other materials. A 10 milliliter isolated blood red blood cell was obtained using the Prozeta cobalt chromium coronary stent, which had the following specifications: stent length = 18 mm, strut thickness = 0.065 mm, expansion range = 2.25 mm to 4.00 mm, and burst pressure = 6ATM. Using an R&D coating equipment, polyethylene glycol (PEG) polymers were applied to the coronary stent. Assessments of the polymeric-coated cardiac stent’s biocompatibility and hemocompatibility were conducted using various evaluation criteria. CAD software has been used to help with the stent’s modeling. According to the supplied catalog, the strut’s thickness and width are calculated to be 0.065 mm and its length is 18 mm. The histology of RBC in an isolated sample (polymer coated on stent) found at 2000 Rx was examined using a motic microscope. Using a UV-visible spectrophotometer set to 414 wave length, a 10µg/ml solution of RBC in distilled water was scanned at 200–500 nm to measure the UV absorption maximum. The absorbance was found to be 0.8312 nm. An FTIR analysis of RBC reveals absorptions that include bending and stretching vibrations. Peak Position was discovered at wave numbers 3661.76, 1684.62, 1547.98, 1472.07, 1278.06, and 841.98. Using SEM the surface morphology of RBC was study and it was found the measurements 6.1, 4.2, 3.3, 3.2, 3.1, and 2.2 µm in diameter with standard error 0.548584. It has been determined that PEG-coated material demonstrated significant outcomes that resulted in coronary stent that was both biocompatible and hemocompatible of polymeric-coated cardiac stent, which is a step towards altering the treatment regimen.

An actinomycosis infection resembling peritoneal dissemination of rectal cancer: a case report

BackgroundActinomycosis is a suppurative and granulomatous inflammation commonly caused by Actinomyces israelii. Due to its rarity and the paucity of characteristic clinical features, diagnosis of intra-abdominal actinomycosis is challenging, especially when the patient has a treatment history of abdominal cancer.Case presentationThe patient is a 72-year-old man who has a history of multiple abdominal surgeries for rectal cancer, including low anterior resection for primary rectal cancer, partial hepatic resection for metachronous liver metastasis, and Hartmann surgery for local recurrence. The patient has also undergone parastomal hernia repair using the Sugarbaker method. One year after hernia repair, computed tomography (CT) identified a mass lesion between the abdominal wall and the mesh, suggesting the possibility of peritoneal recurrence of rectal cancer. The accumulation of fluorodeoxyglucose (FDG) was evident via positron emission tomography-CT (PET-CT), while tumor marker levels were within the normal range. On laparotomy, the small intestine, abdominal wall, mesh, colon, and stoma were observed to be associated with the mass lesion, and en bloc resection was carried out. However, postoperative histopathological examination revealed an actinomyces infection without any cancerous cells.ConclusionsThis case highlights the challenges faced by surgeons regarding preoperative diagnosis of actinomycosis, especially when it occurs after the resection of abdominal cancer. Also, this case reminds us of the importance of a histopathological examination for abdominal masses or nodules before starting chemotherapy.

Source identification and human exposure assessment of organophosphate flame retardants and plasticisers in soil and outdoor dust from Nigerian e-waste dismantling and dumpsites

Electronic waste (e-waste) dismantling and dumpsite processes are major sources of organophosphate flame retardant and plasticiser emissions and may pose potentially adverse effects on environment and human health. In 20 outdoor dust and 49 soil samples collected from four e-waste dismantling and three e-waste dumpsites in two States of Nigeria (Lagos and Ogun), we identified 13 alternative plasticisers (APs), 7 legacy phthalate plasticisers (LPs), and 17 organophosphorus flame retardants (OPFRs) for the first time in African e-waste streams. In the samples from dismantling sites, the range (median) concentrations of ∑13APs, ∑7LPs, and ∑17OPFRs were 11 to 2747 μg/g (144 μg/g), 11 to 396 μg/g (125 μg/g), and 0.2 to 68 μg/g (5.5 μg), in dust respectively and 1.8 to 297 μg/g (55 μg/g), 1.3 to 274 μg/g (48.5 μg/g), and 1.6 to 62 μg/g (1.6 μg/g), in soil respectively. Results for soil samples from e-waste dumpsites were (6.6 to 195 μg/g (23.7 μg/g), 6.0 to 295 μg/g (54.8), and 0.4 to 42.3 μg/g (9.0 μg/g) for ∑13APs, ∑7LPs, and ∑17OPFRs respectively. Overall, concentrations of APs were significantly higher at the dismantling sites (p = 0.005) compared to dumpsites, levels of LPs were higher at dismantling sites but not significant, while OPFR concentrations were significantly higher in dumpsite samples (p = 0.005). Plasticisers were found to be major contributors to pollution at e-waste dismantling sites, while OPFRs were associated with both automobile dismantling and e-waste dumpsite processes. Following particle size fractionation of selected soil samples, higher concentrations of targeted compounds were observed in the smaller mesh (180 μm) soil sieve fraction. For dust, the total median estimated daily intake via ingestion and dermal adsorption (EDIing and EDIderm) ranged from 43 to 74 ng/kg bw/day and 0.4 to 0.7 ng/kg bw/day, respectively. Correspondingly, 4.6 to 45 ng/kg bw/day and 0.015 to 0.57 ng/kg bw/day were the values found for soil, respectively. According to these results, the targeted chemicals do not appear to pose a non-carcinogenic risk to e-waste workers through ingestion or dermal contact of bio-accessible fractions of the chemicals. Human biomonitoring campaigns are recommended in the Nigerian e-waste environment considering the elevated concentration levels found for the majority of targeted compounds and that risk parameters required for exposure assessment were only available for a limited number of compounds.

Treg-enhancing and immunomodulating microgel scaffold promotes cell ingrowth and heart function recovery post-acute myocardial infarction in vivo

The ingrowth of endogenous cells into tissue scaffolds and modulation of Treg population take a pivotal function in restoring the structure and function of heart post-acute myocardial infarction (MI). However, the traditional hydrogels are failed to achieve such functions due to their critically small mesh size and inherent bioinertness. In this study, a Treg-regulated microgel scaffold (GTK-TK-drug) was prepared by inter-microgels assembly of microgels having cyclodextrin (CD) or adamantane (Ad) with a particle size of about 220 μm. The raw materials to obtain the microgels included gelatin methacryloyl (GelMA), reactive oxygen species (ROS)-responsive crosslinking agent poly(ethylene glycol)-thioketal-poly(ethylene glycol) (PEG-TK-PEG), ROS-responsive release prodrug aminooxyacetic acid (PEG-TK-AOA), PEG-CD or PEG-Ad, and photoinitiator lithium phenyl-2,4,6-trimethylbenzoylphosphinate (LAP). Quantitative real-time PCR (qPCR), cell counting kit-8, and immunofluorescence staining revealed the effectiveness of AOA for the differentiation of T cells into Treg and the ingrowth of cells in vitro and in vivo. During the short treatment of MI in vivo, the levels of plasma inflammatory factors, cardiomyocyte apoptosis and inflammatory cells were reduced significantly. In the long-term animal experiments, the recovery of cardiac function was significantly enhanced as characterized by echocardiography and the degree of myocardial fibrosis compared to the unassembled microgels control.

Effect on catch efficiency and bycatch by introducing an Excluder device in the trawl fishery for lesser sandeel (Ammodytes marinus).

Sampling of the North Sea trawl fishery for lesser sandeel (Ammodytes marinus) showed that 96% of the catch weight consisted of the target species, and experimental sea trials demonstrated that the observed small bycatch percentages of haddock (Melanogrammus aeglefinus), mackerel (Scomber scombrus) and grey gurnard (Eutrigla gurnardus) could be significantly lowered by inserting a netting-based sorting device, an Excluder, in front of the codend. The sandeel fishery is conducted with small meshes in the codend, due to the small size and elongated body shape of this species. It is not mandatory for sandeel trawls to have any other selection devices than the small-meshed codend, and this can potentially cause problems with bycatch of unwanted species, if these are abundant on the fishing grounds. Therefore, we sampled the catch composition in this fishery and further, we compared the capture efficiency and species composition of a standard trawl, and one fitted with an additional sorting device called the Excluder. Overall, results showed small percentages of bycatch in the trips sampled and during the trials, the excluder significantly reduced the bycatches of mackerel, grey gurnard, and haddock above certain sizes. For other bycatch species results were inconclusive due to wide confidence limits affected by low bycatch numbers during the trials. The overall capture efficiency for the target species was not affected by adding the excluder in the trawl except for a significant reduction for a few semi-centimetre groups of the largest sizes of the species. These results highlight the potential of the Excluder as a bycatch reduction tool in the sandeel fishery for situations where bycatch can constitute a problem.

Investigation of ultrasonic welding of CF/PA66 using nylon mesh energy directors

AbstractCarbon fiber reinforced polyamide 66 (CF/PA66) sheets are ultrasonically welded by applying nylon meshes as energy directors (EDs) in this paper. The influence of mesh dimensions is revealed by observing the joint formation process, joint mechanical performance, joint cross‐sectional morphology and joint failure mode. Results show that the joint formation process can be divided into wire flattening stage, ED spread stage, tight bonding stage, and mixing stage. The nylon mesh ED with moderate wire spacing, small wire diameter and small mesh area promotes better weld quality. Welding energy will be dispersed rather than concentrated if the mesh area is too large, resulting in reduced failure load. The joints exhibit two fracture modes: interfacial fracture (IF) and workpiece fracture (WF), and the fracture mode of the joints with nylon mesh EDs transits from IF to WF as the welding energy increases.Highlights Five types of nylon mesh are used as energy directors to join CF/PA66 sheets by ultrasonic welding. The influence of nylon mesh dimensions on the mechanical property and fracture mode of joints is investigated. The formation process of ultrasonically welded joints can be separated into wires flattening stage, ED spread stage, tight bonding stage, and mixing stage.

The performance of anchovy purse seine in the North Coastal Java Sea, Indonesia

Small pelagic fishes including anchovies in Indonesia are caught by using different types of fishing gears. However, the anchovy purse seine commonly used polyethylene (PE) as material webbing which is less effective in the North Coastal Java Sea. This study aims to describe the design and construction of the anchovy purse seine and the characteristics of this gear construction. The research was carried out in the North Coastal Java Sea of Indonesia between May and June 2021. The main data from the nine anchovy purse seine units were collected using purposive sampling. The sampling method was performed by identifying and measuring the components of the number of anchovy purse seiners. The ratio of the length of the head rope to the length of the ground rope is between 0.926 and 0.991, so the net is not exactly rectangular, but almost trapezium in shape. The anchovy purse seine was constructed using webbing polyamide (PA) with 8 mm–9 mm in mesh size, which is considered a small mesh size. It is assembled with some ropes, floats, and sinkers. The anchovy purse seine is characterized by the dominant buoyancy value, 48 % larger than the sinking force. The sinking speed is 0.15 m/s, and the sinking time is 164 s. The anchovy purse seine's design and construction are suitable for operating in the waters of North Coast of Java.

Chewing analysis of horses consuming bermudagrass hay in different styles of slow feeders as compared to loose hay

Mastication is the initial phase of digestion and is crucial to equine health due to its role in saliva production and food particle reduction. Hay nets have been promoted to slow the rate of hay consumption, with many styles of slow feeders available. Limited research has shown that nets may slow consumption, but no research has examined their effect on the horse's chewing frequency and patterns. The objective of this study was to compare chew frequency (CF, total number of chews/kg consumed) and chew duration (CD, total minutes chewed/kg consumed), as well as distribution of chews over a feeding period, of horses eating bermudagrass hay in three styles of hay nets [large mesh (LM), small mesh (SM), bottom hole (BH)] as compared to a control of loose hay (CTL). Treatments were assigned in a replicated Latin square 4 × 4 using eight horses. Horses were given a 24-hr acclimation period prior to recording their chewing patterns over a 24-hr period using an automated halter fit with a pressure-sensor noseband. Results indicate that CF was not influenced by treatment. However, SM resulted in longer CD as compared to CTL (P = 0.007). Additionally, BH resulted in a higher percentage of chews completed in the first 240 min compared to SM (P = 0.039), indicating more rapid consumption. Results of this study indicate hay nets may not influence the number of chews a horse performs while masticating hay, but small mesh feeders may increase the CD and reduce early consumption rate.

Investigating the structure and properties of polyurethane hydrogels with varying soft and hard segments

AbstractIn this study, polyurethane (PU) hydrogels were synthesized via mercapto curing reaction to elucidate the effect of molecular interactions between isocyanate and soft segments on the properties of hydrogels. Further, the mesh size, mechanical properties, hydrophilicity, and biological properties of the PU hydrogels were determined. In the isocyanate series, the structural regularity and rigidity of 4,4′‐dicyclohexylmethane diisocyanate (HMDI) favored the formation of hydrogel materials with small mesh size, high modulus, and low water absorption. In contrast, l‐lysine diisocyanate (LDI) favored the materials with large mesh size, low modulus, and good hydrophilicity. In the soft‐segment series, the strong hydrogen bonds of polycarbonate diol (PCDL) favored the formation of materials with small mesh size, dense cross‐link points, and high modulus, whereas weak hydrogen bonds of polytetrahydrofuran ether glycol (PTMG) favored the hydrogel materials with small mesh size, few crosslink points, and low modulus. PU hydrogels exhibit excellent cytocompatibility, anti‐cell adhesion, and anti‐inflammatory properties. Therefore, this study offers valuable insights into understanding the chain structure and macroscopic properties, thus contributing to preparing PU hydrogels with varying performances, as desired.

Application of Delaunay adaptive mesh refinement in flood risk assessment of multi-bridge system with short distance

To ensure bridge safety, the flood risk analysis is significant important. However, due to the small size and large number of piers in the short-distance multi-bridge system, the extremely long calculation time and low efficiency of the numerical model are induced by the small mesh size and large mesh number. In this paper, a flood risk assessment model of the multi-bridge system with short distance was established to improve the calculation efficiency based on the finite volume method combined with the Delaunay mesh adaptive refinement method. The calculated water level with refined and non-refined mesh was compared with the experimental data of a partial failure dam break test case and Shukry experiment of open channel bend flow. The calculated water level results are in good agreement with the experimental data. In addition, the mesh refinement model improved the calculation efficiency by more than 73% with ensuring the calculation accuracy. Finally, the flood risk of a real multi-bridge system with short distance was evaluated by using the numerical model. The calculated results shown that, different from the general flow law, the water level in the upstream and downstream channel of Bridge 2 rose with a maximum difference value of 0.326 m while the water level in the far downstream channel of Bridge 2 dropped result from the construction of Bridge 2 on the basis of the Bridges 1, 3 and 4. The construction of Bridge 2 also increased the flow velocity around Bridge 3 with maximum 0.013 m/s. This study provides a new tool and technical reference for flood risk analyses of similar multi-bridge system with short distance.

Elastic reverse time migration based on nested triangular mesh in 2D isotropic media

Abstract Reverse time migration (RTM) based on two-way wave equation is an important imaging tool, which has been widely used in exploration geophysics. It offers distinct advantages in handling complex geological structures. Moreover, elastic reverse time migration (ERTM) can produce more physically meaningful images for subsurface and has received increasing attention in recent years. However, rugged topography presents challenges in the reconstruction of subsurface structures for ERTM. To overcome this problem, we introduce the grid method for topography ERTM, which is an unstructured mesh based algorithm. However, the conventional gird method for RTM is implementing by discretizing model into small meshes, leading to high computational cost. To address this problem, we introduce the grid method based on nested unstructured meshes to implement ERTM with complex surface topography. Low-order small meshes, due to their fine scale, can accurately depict complex surface topography. However, their generation process is relatively time-consuming. In contrast, high-order large meshes contain many similar small meshes internally, which can be processed in parallel, resulting in higher computational efficiency. Therefore, we propose the following strategy: for the receiver wavefield, several layers on surface discreted by the small meshes are used to place receivers and remaining layers discreted by the large meshes to improve computational efficiency. For the source wavefield, only the large meshes are used because the spacing of shot is relatively large. In this way, we ensure the accurate description of complex surface topography for the implementation of ERTM with high computational efficiency. Finally, the effectiveness of our method is validated through experiments on three models with complex topography.

Unraveling the ecological impacts of alewife in a large Midwest reservoir decades after introduction

Alewives Alosa pseudoharengus are native to the Atlantic Coast but have been introduced to inland waters as forage for sportfish populations. Alewife introductions have benefitted sportfish growth and body condition but have also negatively influenced larval fish survival through predation or competition for zooplankton. In 1986, alewives were stocked into Lake McConaughy, Nebraska, and became abundant and self-sustaining shortly thereafter. It has since been hypothesized that the alewife introduction altered zooplankton size and species composition and potentially negatively influenced Walleye recruitment. However, no studies on alewife distribution or food habits have been conducted on Lake McConaughy to date to investigate the potential influences of alewife on the fish and zooplankton communities. We collected alewives in the nearshore areas of Lake McConaughy during May–July 2022 and 2023 using short-term (about 1 h) small mesh horizontal gill net sets. We spatially assessed alewives by sampling the north and side south sides in addition to four classified quadrants of the reservoir. Total lengths (mm) were recorded, and stomachs were collected from up to 20 alewife per net. Prey were identified and food habits were summarized as percent composition by number. Zooplankton consumption was also paired with vertical Wisconsin zooplankton net tows taken at each site to assess prey selectivity. There was no evidence of piscivory suggesting that alewife predation is not influencing fish recruitment in Lake McConaughy. Alewives almost exclusively consumed zooplankton throughout the study period, suggesting the potential for interspecific competition with young-of-year fish. Our research provides a greater understanding of how introducing a non-native prey species to benefit sport fishes may have unintended negative consequences.

Use of Figueiredo’s technique for treating extensive infected skin lesions – a case report

Demonstrate that a low-complexity surgical technique can effectively solve problems of extensive skin lesions in cities where microsurgical techniques are not available. We present a 59-year-old male patient with diabetes mellitus and an extensive and infected lesion in his right ankle region, suggestive of a diabetic foot. Urgent surgical treatment was performed with debridement of the devitalized tissues, drainage of a large amount of purulent secretion, and exhaustive washing with 0.9% saline solution. After a new debridement, abundant washing with 0.9% saline solution and coverage of the extensive bloody area with a polypropylene prosthesis were performed. He remained under outpatient follow-up, and subsequently, twice, new cleanings were performed, and a small diameter mesh was applied due to the good evolution of healing. A good range of motion was maintained in the right ankle and foot, with the medial wound completely healed, leaving only a small area of the lateral wound to complete the healing process. Figueiredo’s technique, described in 2017 for fingertip lesions, uses a flexible thermoplastic polymer, which can be obtained from a small portion of silicone from a saline bag, to form a semi-occlusive dressing that allows the drainage of secretions and provides a favorable environment and temperature for healing. The exact limits of this technique are not yet well established, but the practice has shown excellent results in larger lesions. Figueiredo’s technique is a simple, low-cost, and effective option for treating extensive infected skin lesions. Level of Evidence IV; Therapeutic studies; Case Report.

A stream-aligned mixed polyhedral meshing strategy for integrated surface-subsurface hydrological models

Mesh refinement near river corridors is commonly deployed to resolve topographic details important for accurately representing riverine flow dynamics in watershed-scale spatially distributed integrated hydrology models. However, this increased accuracy comes with higher computational costs due to larger mesh and smaller time steps resulting from small mesh cells. We present a novel stream-aligned mixed-polygonal meshing approach that resolves river-corridor topography efficiently by placing long quadrilateral cells along the mapped center lines of the rivers and standard Triangulated Irregular Network (TIN) mesh in the rest of the domain. Our integrated hydrology simulations using mixed-polyhedral mesh generated from the mixed-polygonal approach closely match those using a highly refined extruded-TIN mesh but with a 96.43% reduction in the number of mesh cells and a 99.75% reduction in CPU hours. Conversely, coarser extruded-TIN meshes, due to poor water conveyance relative to the refined mesh simulations, yielded lower peak flows, longer recession curves, and higher inundation fractions.The creation of this mixed-polyhedral mesh is implemented within the Watershed Workflow tool, a Python-based workflow library for watershed simulation. We also implemented a layered process of hydrologic conditioning specific to the cells in the river corridor, which are explicitly meshed within the mixed-polyhedral mesh. The hydrologic conditioning enforces monotonic topographic gradients, removes spurious obstructions, and allows for burning-in depths of the river cells based on ancillary information. This approach paves the way for efficiently modeling narrow engineered channels and specifying river-specific hydrodynamic details and biogeochemical processes.

Punching of Concrete Slabs Reinforced by Recycling Waste

Abstract This study aims to experimentally evaluate the mechanical properties of concrete slabs reinforced with two types of fibers: metallic fibers (MF) and grids based on polypropylene fibers (PPG). The metallic fibers, sourced from machining waste of steel parts, are randomly distributed in the concrete, while the polypropylene fibers are arranged in grids. The investigation includes punching tests conducted on slabs measuring [25x50x7] cm³, as well as compression tests on cylinders with a diameter of Ø16 cm and a height of H32 cm. Mechanical resistance and tearing characteristics of the fibers were also assessed. The concrete’s composition was determined using the experimental “Dreux-Gorisse” method. Five different metal fiber contents (MF) were studied (W=0.2%, W=0.4%, W=0.6%, W=0.8%, and W=1%), alongside a control concrete sample (BT) with no fibers (W=0%) having the same composition as the matrix. Two variants of grids based on small-mesh polypropylene fibers (PPG/SM) and large-mesh (PPG/LM) configurations were considered. The comparative analysis of the results highlights that, at a fiber content of W=0.8%, metallic fibers (MF) enhance both resistance and rigidity more effectively than polypropylene fibers in small meshes (PPG/SM) and large meshes (PPG/LM), thereby limiting the formation of puncturing cracks.

Catch composition, catch per unit effort (CPUE) and species selectivity of fishing gears on multi-species Kaptai Lake in Bangladesh

Kaptai Lake, the largest artificial reservoir in Southeast Asia, is home to a diverse fish fauna that supports thousands of livelihoods and is distinguished by multi-species and multi-gear fisheries. In Kaptai Lake, the gear-based catch composition, catch rate and distribution pattern are little known. From August 2020 to April 2021, a nine-month study was conducted in five upazilas using direct catch assessment surveys and fishing effort surveys from four fishing gears, namely seine nets, gill nets, lift nets, and push nets. A total of 49 morpho-species from 22 families were found, with three species from the Clupeidae accounting for 93.63 % of the catch in all gear combined. The total catch composition and CPUE were higher in seine nets (75.07 %, 13.86 ± 1.8 kg/gear/trip respectively) and lower in lift nets (4.97 %, 1.01 ± 0.21 kg/gear/trip) and showed significant differences among gears, except sampling sites whereas CPUE was higher in Naniarchar for seine nets (17.29 ± 8.89 kg/gear/trip) and lower in Langadu for lift nets (0.62 ± 0.25 kg/gear/trip). Seine nets captured more species, and the number of species increased significantly as CPUE increased. Our study assessed four gears that targeted different fish species with little overlap in leading species; seine nets and gill nets primarily targeted Clupeidae (96.53 % and 41.69 %, respectively), whereas lift nets and push nets primarily targeted Cyprinidae and Palaemonidae (38.93 % and 99.37 % respectively). The observed abundance and variety of fish species captured in gill nets suggest a significant overlap in the selectivity of this fishing method with that of lift nets. Due to the varying contributions of sites and gears, the nMDS ordination pattern reveals a weak spatial variation in catch composition. According to the SIMPER results, Bagridae, Gobiidae, and Ambassidae were the most significant contributors to site grouping patterns across all gears. Furthermore, the findings indicate that the catch composition does not follow the typical pattern of spatial variation. By implementing measures to eliminate or decrease the usage of small mesh nets, there is expected to be a corresponding decrease in the capture of small fish. Additionally, this action will help mitigate the issue of overlapping selectivity among the current fishing gears. Our findings provide baseline data on the potential efficacy of gear limitation and suggest a gear-based management strategy.

Structural behavior of RC one-way slabs strengthened with ferrocement and FRP composites

Existing research lacks focus on the structural behavior of reinforced concrete (RC) one-way slabs reinforced with ferrocement, and there's a notable absence of comparative studies between fiber-reinforced polymers (FRPs) and ferrocement strengthening methods for these slabs. Given the cost-effectiveness and widespread use of ferrocement in structural reinforcement, this study aimed to address these gaps through an experimental program. Three sizes of wire mesh, categorized as Type-I (small), Type-II (medium), and Type-III (large), were employed in this study. Chemical or mechanical anchors were used to attach ferrocement jackets. Moreover, 6, 12, or 18 anchors were used to assess the effect of anchor configuration. The goal was to enhance the structural performance of slabs and compare them with slabs reinforced using FRP jackets. The study focused on preventing debonding of the strengthening layers, employing either mechanical or chemical anchors. All slabs exhibited ductile failure with flexural cracks. The peak load and ultimate deflection were enhanced by up to 49.00% and 109.07%, respectively, by the application of ferrocement jackets, whereas the dissipated energy was increased by up to 174.00 %. Notably, the use of chemical anchors demonstrated a superior ability to delay debonding and enhance ductility compared to mechanical anchors. Slabs reinforced with glass FRP (GFRP) showed delayed debonding relative to carbon FRP (CFRP) reinforced slabs, indicating the superior performance of chemical anchors with GFRP layers. Moreover, the type and size of wire mesh significantly influenced performance, with small and medium-sized mesh configurations enhancing ductility, while large-sized mesh exhibited relatively earlier debonding. The orientation of the wire mesh also played a crucial role, with parallel orientation to the longitudinal axis of slabs yielding better performance.

Dynamic behaviors of concrete gravity dam against combined blast wave and bubble pulsation of underwater explosion

Underwater explosion process mainly includes the preceding blast wave and the succeeding bubble pulsation, while the effect of bubble pulsation on hydraulic structures is always neglected. This paper aims to numerically study the dynamic behaviors of prototype concrete gravity dam against underwater explosion, considering the combined effects of blast wave and bubble pulsation. Firstly, a finite element analysis (FEA) approach for predicting the underwater explosion loadings, as well as the damage evolution and dynamic responses of dam against underwater explosions was proposed, in which the hydrostatic pressure of reservoir and the dead load of dam were considered. Based on Cole's formula and the existing underwater explosion tests, the reliability of FEA approach, including the mesh sizes, material models and the corresponding parameters, as well as the mapping, Fluid-Structure Interaction and contact algorithms, was comprehensively validated. Secondly, to realize the simulation of the prototype gravity dam impeded by the validated small Lagrange mesh size, a mesh transition strategy was proposed based on the equivalence of dam damage modes and total eroded element mass. Finally, the dynamic behaviors of a typical 120 m-height concrete gravity dam against underwater explosion, i.e., 1 t of TNT equivalence detonated at a depth of 35 m and standoff distances of 4–16 m, were examined. The dimensionless distance λR, i.e., the ratio of the standoff distance to the maximum bubble radius, was introduced to quantitatively evaluate the underwater explosion loadings and dynamic behaviors of the dam. It indicates that, the blast wave firstly leads to the local compressive damage on the upstream surface, as well as the tensile damage on the downstream folded slope and dam heel. The succeeding free vibration and bubble pulsation will further aggravate the damage degree, resulting in the cracking of dam neck and heel. Especially for the scenarios when λR ≤ 1.22, the overall sliding of dam is highly prone to occur.