Filler Material Research Articles

Characteristics and control of impact vibration and noise in rail belt conveyor

The rail belt conveyor is an innovative energy-saving belt conveyor. Revolutionizing the traditional roller support, it utilizes interval-spaced carriages to support the conveyor belt. The study of impact vibrations in rail belt conveyors remains underexplored in current research. This paper investigates the impact vibration and noise characteristics of the wheel–rail-steel structure coupling system, as well as their control and optimization strategies. First, vibration and noise measurements were conducted along the track. Results indicate that impact vibrations and noise originating from expansion joints and inserted joints fall within the frequency range of 1.5 kHz–5 kHz. Particularly noteworthy is the pronounced impact noise near inserted joints, with dominant frequencies ranging from 1.5 kHz to 2.5 kHz. Further investigation has revealed that the impacts on inserted joints encompass interactions between the wheel and rail, as well as between different sections of the rail itself. Next, the characteristics of filler materials such as polyurethane rubber, silicone, polyurethane resin, and epoxy resin were analyzed and compared. The experimental results show that filling rubber in expansion joints can reduce lateral impact vibrations by 61% and vertical impact vibrations by 66%. Additionally, the sound pressure level was reduced by approximately 1.7 dBA. Finally, welding the guiding rail to its preceding rail and grinding the welded surface effectively eliminated the composite impact vibrations and sharp noise at the inserted joint, resulting in a decrease of approximately 3 dBA in the sound pressure level. This paper provides guidance on the structural improvement and acoustic optimization of rail belt conveyors.

Nonsurgical Rhinoplasty after Rhinoplasty: A Systematic Review of the Technique, Results, and Complications.

Introduction: Surgical rhinoplasty is a complex procedure with a high revision rate. Nonsurgical rhinoplasty (NSR) could avoid secondary rhinoplasty allowing the correction of postsurgical defects. A systematic review has been performed among adult patients who had previously undergone surgical rhinoplasty and now presenting for NSR with filler, demonstrated most common indications, fillers, and complications in this technique. Materials and Methods: A systematic review was performed according to the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) system guidelines. Primary outcomes included indications for NSR in patients with prior rhinoplasty and complication rate. Secondary outcomes included filler material and degree of patient satisfaction. Results: Twenty articles met the inclusion criteria, obtaining 2,048 patients analyzed in the review. Hyaluronic acid was the most used filler, found in 67% of patients. Indications were highly variable, considering deformities of the middle third of the nose the most remarkable. A high degree of satisfaction was found in the analyzed studies and the rate of major complications was low. Discussion and Conclusions: NSR in patients with prior rhinoplasty is a useful option for correcting a range from subtle aesthetic defects to severe nasal deformities. However, this technique is not exempt from complications, since an increased risk of skin necrosis has been observed.

Microstructure and dynamic behaviours of polyurethane-cured sea sand under traffic–load–induced stress path

Employing sea sand as fill material for roadbeds presents significant challenges due to its naturally high dispersibility and low bearing capacity, which contribute to substantial settlement deformations under traffic load impacts. In this investigation, a two-component polyurethane was applied to enhance mechanical properties of sea sand. Alterations in the microstructure and dynamic behaviours of the polyurethane-cured sea sand were observed via Scanning Electron Microscopy (SEM) and hollow cylindrical torsional shear testing. It was found that polyurethane is incorporated into the sea sand as adhesives between particles, attachments on the particles and floating adhesives. With an increase in polyurethane content, a transition from a granular to a solid state in the sand was noted, accompanied by a progressive improvement in structural integrity. This resulted in an enhanced bonding effect at interparticle contacts with diminishing relative particle movements during shearing, leading to an increase in the critical dynamic stress ratio and a decrease in the maximum damping ratio, with both ratios being higher in cured sea sand with lower polyurethane content compared to that with higher content. Additionally, high polyurethane content induced strain hardening in the cured sea sand, resulting in a higher maximum dynamic shear modulus in low-content cured sea sand compared to high-content. Furthermore, the dynamic shear modulus ratio in sea sand with high polyurethane content was found to increase with the number of vibrations.

Prediction of resilient modulus and critical dynamic stress of recycled aggregates: Experimental study and machine learning methods

This paper aimed to investigate the feasibility of partially or completely replacing natural aggregates with recycled aggregates from construction and demolition wastes for low-carbon-emission use as coarse-grained embankment fill materials. The laboratory specimens were prepared by blending natural and recycled aggregates at varying proportions, and a series of laboratory repeated load triaxial compression tests were carried out to study the effects of material index properties and dynamic stress states on the resilient modulus and permanent strain characteristics. Based on the experimental results and by considering the main influencing parameters of the resilient modulus and permanent deformation, an artificial neural network (ANN) prediction model with optimal architecture was developed and optimized by the particle swarm optimization (PSO) algorithm, and its performance and accuracy were verified by supplementary analyses. A shakedown state classification method was proposed based on the unsupervised clustering algorithm, and a prediction model of critical dynamic stress was established based on the machine learning (ML) method and the shakedown state classification results. The research results indicate that the stress state has a greater influence on the resilient modulus and permanent deformation characteristics than other factors, and the shear stress ratio has a significant effect on the shakedown state. The resilient modulus and critical dynamic stress of such specimens vary linearly with confining pressure. The improved PSO-ANN prediction model exhibits high prediction accuracy and robustness, superior to several other commonly used ML regression prediction algorithms. The resilient modulus and critical dynamic stress prediction methods based on ML algorithms can provide technical guidance and theoretical basis for the design and in-service maintenance of similar unbound granular materials.

Increased thermal stability by the addition of ZrO2 into a 0.48Ba(Zr0.2Ti0.8)O3-0.52(Ba0.7Ca0.3)TiO3 matrix material

Ferroelectric ceramics based on x(Ba0.7Ca0.3)TiO3–(1−x)Ba(Zr0.2Ti0.8)O3 (BCZT100x) are regarded as promising lead-free candidates for piezoelectric applications. Heightened piezoelectric properties are found around specific temperatures, i.e. polymorphic phase boundaries. As broader thermal stability is required for certain applications, this study aims to increase the diffusiveness of the phase transitions by introducing ZrO2 as a filler material into a BCZT52 matrix. The diffuseness factor of the Curie point was evaluated and increased from approximately 1.60 to 1.88 with the addition of 4 vol% ZrO2 to BCZT52. As a result, samples with an additional 2 vol% showed the highest thermal stability in the temperature range between 25 °C and 70 °C. Here, the large signal piezoelectric strain coefficient d33* degraded only by 18%, compared to 30% in BCZT52. This increase was caused by the inhomogeneous distribution of Zr within the sample.

Effects of spherical fillers reinforcement on the efficacy of thermal conductivity in epoxy and polyester matrices: Experimental validation and prediction using finite element method

AbstractThe creation of a theoretical heat conduction model for polymers embedded with spherical inclusions is described in this study. It also contains the experimental confirmation of the suggested correlation for utilizing the model to estimate the effective thermal conductivity (K) of such composites. According to ASTM‐E‐1530, composites are made with varying amounts of aluminium oxide and pine wood dust reinforced in polyester resin. The effective thermal conductivities (Keff) of the composites are then determined using the Unitherm TM model 2022. Ansys 19.R2 software is used to evaluate the effective thermal conductivity of these composites with a uniform filler distribution, while Digimat‐FE software is used determine the thermal conductivity values of such particle filled polymer composites with a random filler distribution. After comparison and validation with experimental data, these values are shown to be fairly good agreement with the theoretical values from the suggested correlation. The investigation is further expanded to determine the thermal conductivities for epoxy composites using wood apple shell dust and coir dust particle. Also epoxy and polyester composites reinforced with SiO2 and TiO2 have been investigated in the similar manner. The main thrust of this report to validate the numerical results of composites by varying numerous polymers. The thermal conductivity all the composites grow monotonically with increase in filler content. The thermal conductivity of silicon dioxide, titanium oxide, and aluminium oxide filled epoxy composites is measured as 1.5, 7, and 35 W/m‐K respectively.Highlights In this study spherical fillers are successfully used as a potential filler material in polyester composites The thermal conductivity predicted by proposed mathematical model of polyester is validated with measured value and found better agreement. The Ansys 19.R2 and digimat software are used to predict the thermal conductivity values of these composites. The mathematical model is further used to predict thermal conductivity of epoxy composites to check the accuracy of the model.

Unidirectional fibre reinforcement of syntactic metal foams

Abstract Metal matrix syntactic foams are porous structures where the porosity is formed by introducing a porous filler material into the metal matrix. They have low density and absorb significant energy during compression but cannot withstand tensile stress. The main goal of this study was to apply unidirectional fibre reinforcement to syntactic metal foams. Therefore, a lightweight double-composite structure that can be utilised against tensile load and has advantageous properties during compression was created. Copper-nickel coated carbon fibre bundles were used as unidirectional long fibre reinforcement, lightweight expanded clay aggregate particles as filler material and Al99.5 aluminium as matrix material. The samples were created with vacuum infiltration and formed into cylindrical tensile specimens. Quasi-static tensile tests were carried out on the specimens and fibre trusses, and quasi-static compression was applied on specimens in the parallel and perpendicular direction to the unidirectional fibre truss.

EXPRESS: A Machine Learning Approach to Solve the E-commerce Box-Sizing Problem

E-commerce packages are notorious for their inefficient usage of space. More than one-quarter volume of a typical e-commerce package comprises air and filler material. The inefficient usage of space significantly reduces the transportation and distribution capacity increasing the operational costs. Therefore, designing an optimal set of packaging box sizes is crucial for improving efficiency. We present the first learning-based framework to determine the optimal packaging box sizes. In particular, we propose a three-stage optimization framework that combines unsupervised learning, reinforcement learning, and tree search to design box sizes. The package optimization problem is formulated into a sequential decision-making task called the box-sizing game. A neural network agent is then designed to play the game and learn heuristic rules to solve the problem. In addition, a tree-search operator is developed to improve the performance of the learned networks. When benchmarked with company-based optimization formulation and two alternate optimization models, we find that our ML-based approach can effectively solve large-scale problems within a stipulated time. We evaluated our model on real-world datasets supplied by a large e-commerce platform. The framework is currently adopted by a large e-commerce company across its 28 fulfillment centers, which is estimated to save the company about 7.1 million USD annually. In addition, it is estimated that paper consumption will be reduced by 2080 metric tons and greenhouse gas emissions by 1960 metric tons annually. The presented optimization framework serves as a decision support tool for designing packaging boxes at large e-commerce warehouses.

Analysis of mechanical properties of basalt fabric reinforced fly ash filled vinyl ester composites using multi criteria decision making technique

The current research was to examine the mechanical properties of composite material made of vinyl ester filled with fly ash of various weight percentages. Before fabrication the amount of fly ash and resin were identified by using the Multi Criteria Decision Making technique (MCDM). The best filler weight percentage of 5 wt% is determined by using Weighted Aggregate Sum Product Assessment (WASPAS) which is one of the MCDM methods. The virgin samples of vinyl esters are mixed with weight of 5 wt%fly ash by incremental of 5 wt% up to 20 wt%. All the mechanical tests of the specimen were conducted as per ASTM standards. Subsequently based on the results from the WASPAS method of fly ash content, the basalt fabric was reinforced with fly ash filled vinyl ester to fabricate the hybrid composites. By the mixing of fly-ash with vinyl ester the strength of the fly ash filled composites has been found to be enhanced in the filler. The results from the mechanical testing signified that fly ash can be used as filler material in basalt fabric reinforced vinyl ester resin. The fly ash infused basalt fibre reinforced yields significant development in mechanical performance contrast to the other fabricated composites.

Effects of Three Retrograde Filling Materials on Production of Inflammatory Cytokines and Resorbing Mediators

: Root-end filling materials are typically used following endodontic surgeries, and due to their different chemical compositions, they have varying effects on the survival and differentiation of tissues around the root apex. The purpose of this in vitro study was to evaluate the effects of three retrograde filling materials—ProRoot MTA, Super ethoxy benzoic acid (EBA), and Geristore—on the production of pro-inflammatory and resorptive cytokines (RANK, RANK-L, OPG, IL-1β, and TNF-α). After mixing and setting, the experimental materials were exposed to UV rays and then applied to the prepared cells. This study used osteoblast (MG-63) and THP-1 monocyte cell lines, as well as peripheral blood monocytes (PBM). The evaluation times for RANK-L and OPG were 24 and 48 hours, while IL-1β and tumor necrosis factor (TNF-α) were evaluated at 24 hours. The RANK levels were measured using flow cytometry, and monocyte survival was assessed at different times using the MTT assay. The results were analyzed using Minitab statistical software, which indicated that the type of material significantly affected cytokine production. Exposure of monocytes to EBA resulted in a decrease in TNF-α and IL-1β secretion compared to the other groups. However, in the THP-1 cell line, there was no significant difference in the release of pro-inflammatory cytokines between the groups. Conversely, Geristore induced the highest level of RANK-L and the lowest level of OPG in cultures with the MG-63 cell line. According to the MTT assay, the viability order of the materials from early to late was Geristore < EBA < MTA.

Corrosion protection performance of stretched graphene-modified cold-sprayed zinc coating for steel rebar

The cold-sprayed zinc technology exhibits unique advantages in the field of metal corrosion prevention due to its environmental friendliness and convenient construction. However, compared to hot-dip galvanizing, there is still a necessity to improve its corrosion resistance. Graphene as a filler material, effectively strengthens the anticorrosive properties of the coating. Nevertheless, the resistance of graphene-modified cold-sprayed zinc coating to chloride ion induced metal corrosion remains unknown. In this study, cold-sprayed zinc coating and graphene-modified zinc coating were employed to steel rebar that was subjected to different levels of tensile stress. The passivation and de-passivation process of the stretched zinc-coated rebar in the simulated concrete pore solution were investigated with electrochemical tests and microscopic analyses. The research findings reveal that compared with ordinary cold-sprayed zinc coating, graphene-modified coating can significantly improve the coating resistance and reduce the corrosion rate of rebar under different levels of tensile stress attributed to the high surface area of graphene. However, due to the discontinuity between zinc powders induced by graphene, a complete passivation film cannot form on the surface of graphene-modified zinc coating, which resulted in a lower resistance against chloride ion induced de-passivation. This study indicates that graphene-modified cold-sprayed zinc-coating is not fit for marine environment.

CHARACTERISTICS OF YALIMO PAPUA KINANG JINGKION POWDER AS FILLER IN HRS-WC MIXTURE

<span lang="EN-US">Kinang Jingkion is the name of a region in Yalimo Regency, Papua, which has unique material deposits with specifications that make it suitable for use as aggregate in road pavement, including as filler in powder form. Jan Ukago, one of the first researchers on this aggregate, named the material after the region or location, so the material from the Kinang Jingkion region is now called Kinang Jingkion material. The high construction costs in the Yalimo region and generally in the Papua Mountains are caused by logistics, where materials such as cement and asphalt are mobilized using airplanes. With the alternative of using local filler material, it will eliminate long and expensive mobilization. The testing method was carried out according to the 2018 General Specifications Revision 2, Directorate General of Highways and Indonesian National Standard (SNI) for each test, including asphalt, coarse and fine aggregates, and Kinang Jingkion material. The Optimum Asphalt Content (OAC) obtained from Kinang Jingkion Filler was 6.85%. The Marshall characteristic test results for Kinang Jingkion Filler at OAC of 6.85% showed a stability value of 1194.40 Kg, MQ of 460.2 Kg/mm, VIM of 2.68%, and VFB of 80.16</span>

Comparison of the Ability to Mask the Color of Endodontic Filling Materials Using Several Types of Base Materials

In clinical pediatric dentistry, a base material with optical properties, including transparency, that can mask the color of the material used for root canal-filling is preferred. This study aimed to examine the optical properties of various base materials by thickness. The disk-shaped specimens were photopolymerized and fabricated using Ionosit (IN), TheraCal LC (TL), TheraCal PT (PT), and A2 shade of Filtek<sup>TM</sup> Supreme Flowable Restorative (FZ), Fuji II LC (FL), and Ketac<sup>TM</sup> Fil (KF) with 1 and 2 mm thickness. The color parameters of these specimens were measured using a spectrophotometer on a black and white background and were measured using the same method on a mold containing Vitapex® and gutta-percha. The translucency parameter (TP) and color difference were calculated for each group. The Kruskal-Wallis and Bonferroni tests were used in the statistical analyses. The TP decreased when the thickness was 2 mm compared with 1 mm. The TP values of TL and PT were the lowest at all thicknesses. The TP values of 2 mm thickness in all molds filled with Vitapex® and gutta-percha were the lowest for TL, PT, KF, and IN. In TL and PT, the color difference before and after the application of the canal-filling material was the smallest, regardless of material thickness. Within the limits of this in vitro study, TL, PT, KF, and IN demonstrated better masking of the color of canal-filling material.

Enhancing wear resistance, mechanical properties of composite materials through sisal and glass fiber reinforcement with epoxy resin and graphite filler

This study investigates the mechanical and wears properties of sisal and glass fiber-reinforced epoxy composites with graphite as filler material. We assessed the mechanical properties of the hand-layup-fabricated composite materials, including hardness, tensile strength, flexural strength, and impact strength, by ASTM standards. We also performed wear evaluations using a pin-on-disc apparatus. The results showed that the weight fractions of sisal fiber, glass fiber, graphite, and epoxy resin significantly affected the mechanical properties of the composites. In contrast to composites reinforced with individual fibers, hybrid composites exhibited enhanced mechanical properties. The optimized compositions showed improvements in tensile, flexural, impact, and hardness properties. The wear analysis revealed that a variety of factors, including the weight percentage of reinforcement, sliding velocity, load, and sliding distance, had an impact on the composites' wear resistance. The SEM images provided significant insights into the composite material's micro structural characteristics and failure mechanisms. In general, this research showcases the potential of graphite filler-reinforced sisal and glass fiber epoxy composites for use in applications that demand exceptional abrasion resistance and mechanical strength. Further refinement of the composition and processing methodologies could lead to the development of composites tailored to specific application demands.

Induction assisted autogenous plasma arc welding of HSLA steel

In this work, a high frequency induction heating (HFIH) assisted plasma arc welding (IPAW) technique is proposed to weld 6 mm thick S690QL high strength low alloy steel plates in square butt joint configuration and without using any filler material. A 3D finite element based coupled electromagnetic-thermal analysis is carried out to ascertain the weld's thermal characteristics. Microstructure evolution and mechanical performance are investigated using scanning electron microscopy, electron back scattered diffraction, transmission electron microscopy, tensile test, Charpy impact test and micro hardness test. The results demonstrate that 15 s initial static heating using a co-directional current coil with magnetic flux concentrator predominantly improves the weld penetration by 48 % and joint efficiency reaches 90 % to the base plate strength. Microstructural study shows that the addition of HFIH promotes low angle grain boundaries (LAGB) with bainite ferrite and granular bainite micro-constituents in the fusion zone, which causes localised yielding and failure in this zone during tensile test. Further investigation reveals that the HFIH encourages the formation of BI-type bainite ferrite laths of 1.3–2.2 μm width, combined with slender martensite-austenite (M-A) island at the bainite ferrite lath boundaries. The results also reveal that the induction heating promotes the formation of M23C6 precipitates and B2 structured Cu-enrich nano precipitates in the fusion zone (FZ). The microhardness distribution indicates that the FZ and coarse grain heat affected zone are significantly reduced due to the assistance of the HFIH. The impact test result shows a lower energy absorption by the IPAW weldments due to dominance of the LAGB with unfavourable strain distribution.

Delayed Hypersensitivity Reaction to Dermal Fillers Following mRNA COVID-19 Vaccination

Dear Editor, I wish to bring attention to a potential delayed immune reaction associated with dermal fillers in the context of mRNA COVID-19 vaccines. While severe vaccine reactions remain uncommon, the widespread administration of mRNA vaccines and the prevalent use of dermal fillers necessitate a closer examination of their possible interactions. We recently encountered a 59-year-old female patient who developed persistent facial swelling months after receiving the Pfizer-BioNTech SARS-CoV-2 mRNA vaccine. Notably, the patient had a history of dermal filler injections, predominantly hyaluronic acid, administered three to four years prior. Despite various therapeutic interventions, including antihistamines, corticosteroids, and ACE inhibitors, she experienced recurrent episodes of swelling. Ultrasound assessment revealed the absence of residual filler material, leading us to consider an immune-mediated response potentially triggered by the mRNA vaccine. This case highlights the importance of further research into the interaction between mRNA COVID-19 vaccines and dermal fillers. It suggests that individuals with a history of dermal fillers may be susceptible to delayed inflammatory reactions post-vaccination. Clinicians should be aware of this potential adverse event, particularly when evaluating patients with unexplained facial swelling following vaccination.

Effects of filler material on the characteristics of electrospun polyvinyl alcohol/Nafion nanofibrous membranes

AbstractIn this study, polyvinyl alcohol/Nafion nanofibrous composite membranes were produced to investigate their possible application as a polymer electrolyte membrane (PEM) in direct methanol fuel cells. Electrospinning method was used for nanofibrous membrane production, in which the mixture of polyvinyl alcohol (PVA) and Nafion solutions was directly electrospun. Produced nanofibers were subjected to physical stabilization, filler application, and sulfonating to produce composite nanofibrous membranes. PVA and Nafion polymers were used also as filler materials. The properties of resultant composite membranes were compared in terms of water swelling, weight loss in water and methanol solution, thermal stability, morphology, proton conductivity, and methanol permeability. Proton conductivity of the membranes depending on the humidity was also investigated. TGA analysis showed that the membranes had adequate thermal properties regardless of the filler material. The nanofibrous structure was shown to be preserved by scanning electron microscopy (SEM) after treatment with water and methanol solution. It was shown that PVA/Nafion nanofibers displayed proton conductivity after filling process. The use of PVA as a filler material led to higher proton conductivity at 100 RH%. It was reported that proton conductivity could only be obtained at higher relative humidity values (>80% RH). A lower methanol permeability of PVA‐filled membranes was reported.Highlights PVA/Nafion nanofibrous membranes were produced by electrospinning. PVA and Nafion were also used as pore filling materials. PVA‐filled membranes had higher proton conductivity and lower methanol permeability. Proton conductivity could only be obtained at higher RH% values.

Enhanced Mechanical and Thermal Properties in Epoxy-Based Glass Fabric Composites via Nano Silica Integration

ABSTRACT The objective of this study is to improve the mechanical, thermal, and microstructural characteristics of glass fabric composites made of epoxy by adding nano silica fillers. Composites were produced through compression molding, incorporating different concentrations of nano silica (0%, 2.5%, 5%, 7.5%, and 10%). The study encompassed testing the tensile and flexural strength, analyzing thermal properties through TGA and DTA, and characterizing the microstructure using FESEM and FTIR. The findings indicated that composites containing 5% nano silica exhibited the greatest tensile and flexural strengths, enhanced thermal stability, and superior heat dissipation in comparison to composites with different concentrations. The analysis of the microstructure revealed improved distribution of the filler material and decreased voids, resulting in a stronger bond between the matrix and the reinforcement. The findings emphasize the potential of nano silica-enhanced composites in aerospace, automotive, and other engineering sectors. This represents a notable advancement in composite technology for creating strong and efficient materials.

Analysis of the Suitability of Ultrasonic Testing for Verification of Nonuniform Welded Joints of Austenitic-Ferritic Sheets.

The purpose of the presented research was to determine the suitability of using ultrasonic testing (UT) to inspect heterogeneous, from a material point of view, welded joints on the example of the joints of a ferritic steel element with elements made of an austenitic steel. The echo technique with transverse (SEK) and longitudinal wave heads (SEL) addressed this issue. Due to the widespread use of 13CrMo4-5 and X2CrNiMo17-12-2 steel grades in the energy industry, they were selected as the test materials for the study. The objects of the presented research were welded joint specimens with thicknesses of 8, 12, and 16 mm and dimensions of 300 × 300 mm, made using the 135 metal active gas (MAG) process with the use of the Lincoln 309LSi wire-a ferritic-austenitic filler material. The stages of the research task were (1) making distance-amplitude curve (DAC) patterns from the test materials; (2) preparation of specimens of welded joints with artificial discontinuities in the form of through-holes; (3) performing UT tests on welded joints with artificial discontinuities using heads with 60° and 70° angles for the transverse wave and angle heads for longitudinal waves with similar beam insertion angles; (4) selection, by radiographic testing (RT), of welded joint specimens with natural discontinuities in the form of a lack of sidewall fusion; (5) performing UT tests on welded joints with natural discontinuities, using heads as welded joints with artificial discontinuities. It was found that (1) the highest sensitivity of discontinuity detection was obtained by performing tests on the ferritic steel side, which is due to the lower attenuation of the ultrasonic wave propagating in ferritic steel compared to austenitic steel; (2) the best detection of discontinuities could be obtained using a longitudinal ultrasonic wave; (3) there is a relationship between the thickness of the welded elements, the angle of the ultrasonic beam introduction, and the effectiveness of discontinuity detection.

Bioretention cells filled with epoxy resin-modified loess for stormwater purification

As a filler material in bioretention cells, loess has a good ability to remove nitrogen and phosphorus. However, its low permeability can easily trigger cell blockage. To improve permeability, the modification of loess has become important in the construction of bioretention cells. This study tested water-soluble epoxy resin-modified loess and investigated its feasibility as a filler for bioretention cells. Its purification performance under different rainfall conditions, including intensity and dry periods, was analyzed and compared with traditional sand bioretention cells both with and without a submerged zone. Epoxy-modified loess could be used as a bioretention cell filler, significantly increasing the permeability coefficient of the cell. Although modification with epoxy resin did not affect the crystal composition of the loess, the cross-linking reaction that occurred on its surface increased the C content, decreased the Si content, and made the texture rougher. When the amount of epoxy resin was 2.5 % (SZ25), the resulting loess met the permeability coefficient design requirements; its maximum adsorption capacity for ammonium-nitrogen was at least 1.92 times more than that of sand. For phosphate, the maximum adsorption capacity reached 5.17 mg/g. The average removal efficiencies of ammonium-nitrogen, nitrate-nitrogen, total nitrogen, and total phosphorus in the epoxy-modified loess bioretention cells were 91.67 %, −12.42 %, 39.91 %, and 91.97 %, respectively, 3.14 %, 28.91 %, 20.07 %, and 9.59 % higher than those in the sand bioretention cell. Microbiological analyses revealed that modified loess filler promoted the enrichment of denitrifying bacteria to a relative abundance 14.31 %–26.47 % higher than that in traditional sand filler. Based on the Functional Annotation of Prokaryotic Taxa analysis, the modified loess bioretention cell had stronger C and N cycling than that of the traditional sand bioretention cell, indicating that microbial metabolism and denitrification were stronger and nitrogen removal was improved.