Mat Thickness Research Articles

Hot-Pressing Process of Flat-Pressed Wood-Polymer Composites: Theory and Experiment.

The objective of this research was to develop a mathematical model of the hot-pressing process for making flat-pressed wood-polymer composites (FPWPCs). This model was used to calculate and predict the temperature and time required for FPWPC pressing. The model's performance was analysed using the experimental results of hot pressing FPWPCs. It was found that an increase in the content of wood particles led to a rapid increase in the pressing time. The model and experiment showed that the core temperature of the wood-polymer mat remained nearly constant for the first 20-30 s of the hot-pressing process. After this period, this temperature increased rapidly until it reached 100 °C, after which the rate of increase began to decelerate sharply. This transition was more distinct in FPWPCs with a high wood-particle content, while in those with a high thermoplastic-polymer content, it was smoother. Increasing the pressing temperature contributed to a reduction in the time required to heat the FPWPC, as confirmed by both experimental data and the modelling of the hot-pressing process. A decrease in the predicted density of the FPWPC resulted in a directly proportional increase in the time required to heat the mat. Validation of the mathematical model revealed a mean absolute percentage error (MAPE) of only 2.5%, confirming its high precision and reliability. The developed mathematical model exhibited a high degree of accuracy and can be used for further calculations of the time required for FPWPC pressing, considering variable parameters such as pressing temperature, wood-polymer ratio, mat thickness, and density.

Preliminary investigation of nanofibrous membranes for sound absorption

Nanofibrous membranes show interesting mechanical properties, low thickness and lightness, besides the possibility of using a great variety of polymers. The electrospinning technique makes possible the production of polymeric random nanofibres to form nonwoven membranes, which are currently used in several application fields, such as filtration, biomedicine, biomechanics, electronics, and composite materials. Their application in the automotive and aerospace engineering field could bring significant benefits to the acoustic comfort design. However, their acoustics properties still need to be further assessed. This study investigates the acoustic absorption of electrospinning-made nanofibrous membranes in Nylon 66 with different fibre diameters and mat thicknesses. Morphological and thermal characterisation of the electrospun membranes have been assessed via Scanning Electron Microscope (SEM) and Differential Scanning Calorimetry (DSC), respectively. The acoustic absorption characteristics of various samples changing fibre diameter, membrane thickness and mounting conditions were tested in the impedance tube. The results showed more relevant acoustic absorption properties in the nanofibrous membrane coupled with a polyester fibre. Further studies will clarify if filament direction and constituent material can be improved for a more durable and resistant membrane application.

The Effect of Protective Mat Thickness on the Upper Limb Strike Force Simulation in Combat Sports and Self Defense

The Effect of Protective Mat Thickness on the Upper Limb Strike Force Simulation in Combat Sports and Self Defense

Heat transport during drop impact onto a heated wall covered with an electrospun nanofiber mat: The influence of wall superheat, impact velocity, and mat thickness

Nanofiber surface coating is a promising method for the enhancement of heat transfer during spray cooling. In the present work, the drop dynamics as well as local and overall heat transfer during single drop impact onto a heated wall covered with a polyacrylonitrile (PAN) nanofiber mat are investigated to obtain insight into the mechanisms governing the heat transport enhancement. The influence of wall superheat, drop impact velocity, and mat thickness on the hydrodynamics and heat transfer from the heated wall to the fluid is studied. The experiments were conducted inside a temperature-controlled test cell with a pure vapor atmosphere maintained with refrigerant FC−72 (perfluorohexane). The temperature field at the solid–fluid interface was observed with a high-speed infrared camera, and the heat flux field was derived by solving a three-dimensional transient heat conduction equation within the substrate. The presence of the nanofiber mat on the heater surface suppresses the drop receding phase due to the pinning of the contact line at the end of the spreading phase. Two different heat transfer scenarios are observed depending on the wall superheat and drop impact velocity: scenario (I), in which the liquid drop completely penetrated through the porous nanofiber mat and made contact with the heater surface; and scenario (II) in which the vapor produced inside the pores of the nanofiber mat prevented the liquid drop from touching the heater surface. In scenario (I), an up 450% heat flow enhancement during the sessile drop evaporation stage has been observed. In scenario (II), a 80% heat flow enhancement at this stage has been registered.

Effect of different organic nutrient solutions and day of harvest on growth, biomass yield and chemical composition of hydroponically grown sorghum

An experiment was carried out to investigate the effect of different organic nutrient solutions and day of harvest on growth parameters, biomass and chemical composition of hydroponically grown sorghum red fodder. The experiment was a 3 × 2 factorial design comprising of 3 nutrient solutions (cattle, poultry and rabbit) and 2 harvesting regimes (8th and 10th day). Cattle, poultry and rabbit dungs were collected fresh and processed into nutrient solutions. Sorghum red seeds were treated, planted on trays, and irrigated twice per day with organic nutrient solution according to the treatments. Growth parameters which were investigated included fodder mat thickness, seedling height, leaf length and width, number of leaves, fresh and dry matter yield; and proximate composition. The results showed that sorghum red fodder irrigated with cattle manure nutrient solution (NS) harvested at 10 days was higher in all, except one (fodder mat thickness) of the growth parameters considered. The crude protein (CP) was highest and similar (P > 0.05) for Poultry NS harvested at 8 and 10 days, and Cattle NS at 10 days (13.13%, 12.67%, and 12.69% respectively). The ash content also favored Cattle NS at 10 days. Cattle NS at 10 days harvest was significantly (P < 0.05) the highest (7.00%), but comparable (P > 0.05) with Rabbit NS at 10 days for NDF. Fresh and DM yields were highest for Cattle harvested at 10 and 8 days respectively. The study recommends Cattle NS as hydroponic organic NS for sorghum red as it enhances fresh and dry matter yields, and nutritive values.

Predicting lateral displacement of sand for mat foundation under simplified seismic loading

This research presents the settlement factor of sand for the lateral seismic excitation considering various peak ground accelerations. For this reason, analytical formulations are proposed to calculate the settlement factor. A one-dimensional model is considered to derive these formulations, which is the simplified form of the three-dimensional model. The seismic excitation is simplified by considering only peak ground acceleration (PGA) for the development of formulations. The proposed formulations are verified by the previous numerical studies. Also, a parametric study is conducted to consider the variable parameters such as super-structure loads, mat thickness, PGA factors, and depths of sand. According to the verification results, the observed and calculated sand settlement factor variation rates are slightly higher because of the considerations for the development of the proposed model. The maximum value of the sand settlement factor is found to be 434 for the PGA factor of 0.36 at the highest depth of the sand layer. Also, the sand settlement factor is gradually increased with the increment of the depth for all cases due to the increment of the stiffness. The lateral sand settlement factor is varied within a range of (60 ~ 434) considering all PGAs of the lateral seismic excitation.

Utilization of response surface methodology to optimize the mechanical behaviour of flax/nano TiO2/Epoxy based hybrid composites under liquid nitrogen environment

Linum usitatissimum commonly known as flax fibers, emerges as a promising reinforcement phase for artificial polymer resins, boasting ecological benefits, low density, and easy accessibility. However, the mechanical behavior of such composites hinges crucially on factors such as fiber mat thickness, nanoTiO2 filler content, and the application of cryogenic treatment. Addressing this complex interplay, this study employs a hand lay-up technique for composite construction, subjecting nanocomposite plates to the challenging liquid nitrogen conditions at 77 K post-manufacture. Recognizing the need for an optimized approach, Response Surface Methodology (RSM) based on Box-Benhken designs is employed to enhance the mixing features of linum usitatissimum polymer composites. The study calculates anticipated mechanical strength values through rigorous ANOVA inferential analysis, uncovering the pivotal roles played by fiber mat thickness, nanofiller content, and cryogenic treatment in the two feature interactions (2FI) model components. The methodology proves robust with high R2 values (0.9670 for tensile, 0.9845 for flexural, and 0.9670 for interlaminar shear strength) consistently aligning with experimental findings. The study culminates in identifying optimized parameters for maximal mechanical properties—300 gsm flax fiber thickness, 5 wt.% nano TiO2 concentration, and a 15-min cryogenic treatment—a result that advances our understanding of fundamental factors influencing composite performance and provides practical guidelines for applications in fields requiring superior mechanical strength in challenging environments.

Mats Made from Recycled Tyre Rubber and Polyurethane for Improving Growth Performance in Buffalo Farms

This study focuses on anti-trauma mats designed for buffaloes’ comfort, using as raw materials rubber powder from end-of-life tyres (ELTs) and an isocyanate-based polyurethane resin binder. The first part of the study focused on mat formulation. Whilst it was possible to select a unique combination of raw materials and design features, it was necessary to investigate the relationship between three critical parameters affecting mat consistency and therefore buffalo comfort: binder quantity, mat thickness, and desired final mat density (bulk). In order to quantitatively assess the variation in hardness, various combinations were investigated within well-defined ranges based on the relevant literature. The results obtained from nine selected combinations indicate that increases in the three critical parameters do not induce a real phase transition in the final product consistency, although the hardness suggests an increasing trend. The mats consistently exhibited a moderately soft/hard consistency, offering environmental benefits in terms of increased rubber usage and potentially reduced chemical binder, depending on the desired thickness. The selected mixture showed excellent resistance to heavy chemical loads, suggesting reliability for frequent cleaning operations. The second part of the study involved field trials of the mats with calves. This involved monitoring their weight gain and appetite levels over a 90-day period. The results showed excellent growth performance compared to uncoated grids (i.e., weight gain was approximately 20% higher at the end of the observation period); this was similar to that achieved with the use of straw bedding. However, compared to straw bedding, the mats (i) exhibit long-term durability, with no signs of wear from washing or trampling over the months of the trial, (ii) allow for quick and efficient cleaning, and (iii) enable companies to save on labour, material (straw), and waste disposal costs, while maintaining (or even improving) the same welfare levels associated with the use of straw.

Measuring the Thickness of Fiber Mats Using Light Transmittance via Image Processing

Fiber materials possess unique properties, including a large active surface area, high surface-to-volume ratio, high porosity, high mechanical performance, and low density. Consequently, they serve as key components in various applications such as energy production and storage cells, batteries, wastewater treatment membranes, sensors, drug-releasing band-aids, and protective clothing. Electrospinning is a simple and versatile method for producing fiber materials. Despite its simplicity in terms of working principles, it faces challenges in achieving homogeneous thickness (evenly on the entire surface) throughout fiber mats due to inherent bending instability during the process. Non-uniform thickness not only diminishes the efficiency of these mats in applications but also adversely impacts their mechanical functionality. In this study, the aim is to develop a thickness measurement system based on image processing and the principle of light transmittance as a solution to the issues encountered in achieving uniform thickness and thickness control of fiber mats produced by electrospinning devices. To accomplish this, a closed mechanism with a light-impermeable encapsulation method was established. Various fiber mats, produced at different times were placed on the acetate floor built on LED lighting on the base of the mechanism. Using a camera with the adjusted settings positioned at the focal point on top of the mechanism, images of the fiber mats were captured, and image processing techniques were employed to determine threshold value ranges for the mat thicknesses. The actual thicknesses of the fiber mats were verified using an optical microscope, revealing that regions defined with the same color in different samples exhibited similar thicknesses.

Optimizing mat quality and transplanter performance using soil mix with vermicompost and farmyard manure in paddy tray nursery: A sustainable smart farming approach in India

In order to improve transplanter performance and mat characteristics in mat-type paddy tray nurseries in paddy cultivation and to increase the paddy seedling quality and yield, a soil mix fertilizer with vermicompost and farmyard manure was optimized in different proportions. The investigation provides valuable insights for optimizing paddy cultivation practices, with emphasis on the potential of a specific treatment TC7, composed of 50% vermicompost, 30% farmyard manure, and 20% soil, to contribute to more robust and productive paddy cultivation systems. The TC7 treatment showed notable results, including highest average paddy seed germination (93.00 ​± ​2.24%), significant paddy seedling height (16.85 ​± ​1.72 ​cm), balanced root-to-shoot ratio (0.72 ​± ​0.013), robust seedling vigour index (1567.05 ​± ​121.45), substantial biomass production (0.481 ​± ​0.0010 ​g), and significant dry matter production (0.0422 ​± ​0.0029 ​g). The highest mat thickness of 28.10 ​± ​0.05 ​mm and the lowest mat weight per m2 area of 22.30 ​± ​1.56 ​kg/m2 was recorded in TC4 treatment containing 44% vermicompost, 44% farmyard manure, and 12% soil. The highest rolling quality of the mat with a rolling score of 10.00 ​± ​0.027 in TC8 treatment containing 30% vermicompost, 50% farmyard manure, and 20% soil, and the maximum mat strength of 54.90 ​± ​3.82 ​kg/m2 in TC10 treatment (soil alone). Mechanical transplanter performance exhibited superiority maximum planted hills per meter run (7 ​± ​1), optimum seedlings per hill (3), minimum occurrences of missing hills (1), and a maximum plant population per m2 (116 ​± ​5) utilizing seedling mats prepared with TC7 treatment. The highest grain yield of 4180 ​± ​449 ​kg/ha and grain straw ratio of 0.88 ​± ​0.0317 was recorded in the TC7 treatment. Thus, this study recommends fine-tuning and adopting the TC7 treatment combination to facilitate sustainable smart farming practices in India. Farmers are encouraged to consider implementing TC7 treatment combinations to elevate the quality and productivity of paddy cultivation.

Homogeneity of Needleless Electrospun Nanofiber Mats.

Nanofiber mats can be electrospun by different techniques, usually subdivided into needle-based and needleless. The latter allow for producing large-area nanofiber mats, e.g., with a width of 50 cm and lengths of several meters, if electrospinning proceeds for several hours, depending on the required thickness. Even spinning smaller samples, however, raises the question of homogeneity, especially if defined mechanical properties or a defined thickness is required, e.g., for filtration purposes. Very often, only the inner parts of such electrospun nanofiber mats are used to avoid too high variation of the nanofiber mat thickness. For this study, we used wire-based electrospinning to prepare nanofiber mats with slightly varying spinning parameters. We report investigations of the thickness and mass per unit area, measured on different positions of needleless electrospun nanofiber mats. Martindale abrasion tests on different positions are added as a measure of the mechanical properties. All nanofiber mats show unexpectedly strong variations of thickness, mass per unit area, and porosity, as calculated from the apparent density of the membranes. The thickness especially varied by nearly one order of magnitude within one sample, while the apparent density, as the most uniform parameter, still showed variations by more than a factor of two within one sample. This shows that even for apparently highly homogeneous areas of such nanofiber mats, variations cannot be neglected for all potential applications.

On investigation of flexural, morphological, and shape memory properties for 3D printed PLA-PVDF NFs-PLA interleave composite structures for smart gripper applications

In the present study, the flexural, morphological, and shape memory properties of polylactic acid (PLA) matrix sandwiched with polyvinylidene difluoride (PVDF) Nanofibers (NFs) interleave composite structures have been investigated for applications of 4D printing such as smart grippers, and smart actuators. Firstly, an electrospinning process was carried out to form a PVDF NFs mat (thickness: 0.10–0.20 mm) under a flow rate of 3 µL/sec, an applied voltage of 12 kV, and a TCD of 100 mm. Further, the PVDF NFs mat was deposited in between the PLA layers, primed through fused filament fabrication (FFF) based 3D printing to manufacture the PLA-PVDF NFs-PLA based structures. In the next stage, the flexural properties were investigated for manufactured composite structures. The results highlight that the flexural strength of the composites was enhanced by 6.47% as compared to PLA. Results of the study are supported by a scanning electron microscope (SEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR), V-I, V-R, and shape memory analysis. The finding of the study suggests that composite structures primed by higher mat thickness and zig-zag infill pattern have resulted in higher electrical resistance and better shape memory effect. However, increasing the voltage in the composite structure having higher mat thickness with a zig-zag fill pattern has resulted in a higher resistance drop.

Topography and canopy cover influence soil organic carbon composition and distribution across a forested hillslope in the discontinuous permafrost zone

AbstractTopography and canopy cover influence ground temperature in warming permafrost landscapes, yet soil temperature heterogeneity introduced by mesotopographic slope positions, microtopographic differences in vegetation cover, and the subsequent impact of contrasting temperature conditions on soil organic carbon (SOC) dynamics are understudied. Buffering of permafrost‐affected soils against warming air temperatures in boreal forests can reflect surface soil characteristics (e.g., thickness of organic material) as well as the degree and type of canopy cover (e.g., open cover vs. closed cover). Both landscape and soil properties interact to determine meso‐ and microscale heterogeneity of ground warming. We sampled a hillslope catena transect in a discontinuous permafrost zone near Fairbanks, Alaska, to test the small‐scale (1 to 3 m) impacts of slope position and cover type on soil organic matter composition. Mineral active layer samples were collected from backslope, low backslope, and footslope positions at depths spanning 19 to 60 cm. We examined soil mineralogical composition, soil moisture, total carbon and nitrogen content, and organic mat thickness in conjunction with an assessment of SOC composition using Fourier‐transform ion cyclotron resonance mass spectrometry (FT‐ICR‐MS). Soils in the footslope position had a higher relative contribution of lignin‐like compounds, whereas backslope soils had more aliphatic and condensed aromatic compounds as determined using FT‐ICR‐MS. The effect of open versus closed tree canopy cover varied with the slope position. On the backslope, we found higher oxidation of molecules under open cover than closed cover, indicating an effect of warmer soil temperature on decomposition. Little to no effect of the canopy was observed in soils at the footslope position, which we attributed, in part, to the strong impact of soil moisture content in SOC dynamics in the water‐gathering footslope position. The thin organic mat under open cover on the backslope position may have contributed to differences in soil temperature and thus SOC oxidation under open and closed canopies. Here, the thinner organic mat did not appear to buffer the underlying soil against warm season air temperatures and thus increased SOC decomposition as indicated by the higher oxidation of SOC molecules and a lower contribution of simple molecules under open cover than the closed canopy sites. Our findings suggest that the role of canopy cover in SOC dynamics varies as a function of landscape position and soil properties, namely, organic mat thickness and soil moisture. Condition‐specific heterogeneity of SOC composition under open and closed canopy cover highlights the protective effect of canopy cover for soils on backslope positions.

Tropical Red Fruit Blend Foam Mat Drying: Effect of Combination of Additives and Drying Temperatures

Foam mat drying is a widely used technique for liquid products because it has a number of advantages; however, for an efficient process, the choice of additives and temperatures is extremely important. The objective of this study was to evaluate the effect of additives and drying temperatures on the powders obtained from the blend of tropical red fruits, such as acerola, guava, and pitanga. The foam formulations were prepared by mixing the pulps of the three fruits in equal proportions (1:1:1), all added with 6% albumin and 1% stabilizing agent: E1, gum Arabic; E2, guar gum; E3, gelatin. The combinations were subjected to beating, and subsequently, they were dried in an oven with forced air circulation at four temperatures (50 to 80 °C), with a mat thickness of 0.5 cm. The obtained powders showed low levels of water and water activity and high levels of bioactive compounds, colors with a predominance of yellow, intermediate cohesiveness, poor fluidity, and solubility above 50%. The best temperature for obtaining the powders was 60 °C. The formulation that produced the best results for the production of the tropical red fruit blend powder was the combination of albumin and gelatin.

Optimizing Numerous Influencing Parameters of Nano-SiO2/Banana Fiber-Reinforced Hybrid Composites using Taguchi and ANN Approach

High specific strength, strength-to-weight ratio, cheap cost, and other advantages, nanofillers are now the subject of most research on natural fibers. The current research’s main goal is to combine the Taguchi and artificial neural networks (ANN) approaches to maximize the mechanical characteristics of nanocomposites. The parameters: (i) nano-SiO2 wt%, (ii) banana fiber wt%, (iii) compression pressure in MPa, and (iv) compression molding temperature in °C were selected to achieve the objectives above. An L16 orthogonal array was used to optimize the process parameters based on the Taguchi technique. According to the intended experiment, mechanical characteristics, such as tension, bending, and impact strength, were assessed. The ANN was used to forecast outcomes that were optimized. The fiber mat thickness of banana fiber and the weight ratio of nano-SiO2 showed a considerable improvement in the mechanical characteristics of hybrid composites. According to the Taguchi technique, the most significant mechanical characteristics were 47.36 MPa tensile, 64.48 MPa flexural, and 35.33 kJ of impact under circumstances of 5% SiO2, 19 MPa pressure, and 110 °C. With 95% accuracy, ANN-predicted mechanical strength. The ANN forecast was more accurate than the regression model and experimental data. The above nanobased hybrid composites are mainly employed to satisfy the needs of the contemporary vehicle sector.

Biomass production and biochemical composition of Chlorella vulgaris grown in Net-House Photobioreactor (NHPBR) using sugarcane press mud waste

The present Net-House Photobioreactor (NHPBR), which has a final capacity of 500 liters, was developed for the purpose of cultivating the Chlorella vulgaris by employing vinasse waste as a source of organic carbon and certain minerals in an effort to lower the cost of production. The growth unit consisted of one reservoir tank carrying 4 Plexi-glass ponds. For each plate, growth and biochemical composition were routinely evaluated to assess the precipitation and growth. Our data revealed no differences in the biomass and chemical constituents in the running algal slurry. However, differences were observed in the precipitated algal biomass for each plate, with the reservoir (CR) and the lower plate (P1) forming the greatest precipitation in terms of dry weight and mat thickness, respectively. The biochemical composition of the harvested biomass was 51.0% crude protein, 13.4% total carbohydrates, 12.1% lipids, and 7.2% ash.

A Numerical Study on the Application of Geocell Mat System for Buried Flexible Pipes

Mitigating surface settlement due to the applied pressure caused by loaded footings, construction activities, and traffic loads is of particular concern for designers. For sites with buried conduits at shallow depth, this problem becomes even more challenging as a result of transferred pressure to the pipe and subsequent pipe overstressing and deforming concerns. Several solutions have been introduced by many researchers to tackle this problem and yet new approaches are welcomed by engineering parties. The presented study aims to investigate the effect of Geocell Mat System (GMS) as soil reinforcement to control the footing and pipe performance. As the three-dimensional geocell structure has a significant effect on the soil-geocell interaction, several 3D models employing ABAQUS finite-element program were developed to examine the efficiency of mat systems. The focus was on the geometrical characteristics of GMS including the width of the mat (Bg), mat anchors distance (s), and mat thickness (h). The results of conducted analyses show that by including a mat system beneath the loaded area, the maximum ground surface is noticeably reduced. The role of Bg, however, should be considered with particular attention. It was concluded that by using mats with small widths, the buried pipe experiences radial strains more than values in unreinforced cases. Moreover, it has been shown that the upper half of buried pipe is subjected to the more variation in all studied cases compared to the lower half part. As Well, the effect of anchors distance on the performance of pipe and footing could be regarded as an insignificant factor.

Acceleration of Electrospun PLA Degradation by Addition of Gelatin.

Biocompatible polyesters are widely used in biomedical applications, including sutures, orthopedic devices, drug delivery systems, and tissue engineering scaffolds. Blending polyesters with proteins is a common method of tuning biomaterial properties. Usually, it improves hydrophilicity, enhances cell adhesion, and accelerates biodegradation. However, inclusion of proteins to a polyester-based material typically reduces its mechanical properties. Here, we describe the physicochemical properties of an electrospun polylactic acid (PLA)-gelatin blend with a 9:1 PLA:gelatin ratio. We found that a small content (10 wt%) of gelatin does not affect the extensibility and strength of wet electrospun PLA mats but significantly accelerates their in vitro and in vivo decomposition. After a month, the thickness of PLA-gelatin mats subcutaneously implanted in C57black mice decreased by 30%, while the thickness of the pure PLA mats remained almost unchanged. Thus, we suggest the inclusion of a small amount of gelatin as a simple tool to tune the biodegradation behavior of PLA mats.

The influence of the taphonomically active zone on peat formation: Establishing modern peat analogs to decipher mangrove sub-habitats from historical peats

Mangroves create unique and highly productive wetland communities in intertidal zones of tropical and subtropical coastlines. Despite their many ecosystem services, such as carbon sequestration, mangroves remain threatened by climate change, sea-level rise, and human development. The inclusion of conservation paleobiology and long-term perspectives on how these ecosystems have responded to past environmental change can inform current policy and lead to more effective conservation and restoration management strategies for modern mangrove communities. In South Florida, humified plant debris, or peat, in mangroves provides this historical record. Our research takes a novel paleobiological approach by using plant organ- and taxon-based measures to describe the influence of the taphonomically active zone (TAZ: the zone near the surface of the substrate where taphonomic processes actively formation and degrade accumulated detritus) on the decomposition of mangrove peat with depth. This allows us to understand the taphonomic biases imposed on mangrove peat as it is sequestered into the sedimentological record and provides us with the paleoecological context to better interpret preserved peats and reconstruct past mangrove sub-habitats from peat cores. Accordingly, we collected modern surficial peat cores from two contrasting mangrove sub-habitats in Barnes Sound, FL. These surficial cores were characterized and compared to historical, deep cores from other South Florida mangrove peat deposits. By comparing the proportional abundance of mangrove peat constituents in these samples, we established modern analogs needed to interpret changes in the depositional environment of historical mangrove peats found in sediment cores, which is critical for understanding shoreline responses of mangroves to sea-level rise and anthropogenic change. We demonstrate that (1) leaf mat thickness may be a relative indicator of surficial peat decomposition rates because it correlates with the degree of tidal activity and detritivore access to the leaf litter layer; (2) root percentages are valid tools to differentiate between peats at depth, and can be used as relative indicators for the distance of in situ peat from shorelines; and (3) organismal signals, such as foraminifera and insect parts, provide a means for deciphering precursor mangrove sub-habitats from sequestered peats.

Experimental and numerical testing of prototypical under ballast mats (UBMs) produced from deconstructed tires – The effect of mat thickness

In this study, the authors analyse performance of prototypical under ballast mats (UBMs) made of recycled rubber granulate and fibres, produced from end-of-life tires. First, a series of experimental tests is performed, in order to identify static and dynamic elastic characteristics (static bedding modulus, low- and high-frequency dynamic bedding modulus) of four UBMs with the same density and different thicknesses. Additionally, fatigue strength of the mat with a thickness of 20 mm is analysed. Then, the values of static and dynamic bedding moduli are used as an input in the finite element model of the ballasted track structure with UBM. The main aim of the numerical simulations is to compare mechanical behaviour of the reference system and systems with four different mats. It is proved that the thickness of UBMs has a significant effect on the values of static and dynamic bedding moduli, and on the effectiveness of vibration isolation. The insertion loss values vary between 62 % for the thickness 15 mm and 75 % for the thickness 30 mm (at the frequency 31.5 Hz, that is vibration), and between 37 % for the thickness 15 mm and 54 % for the thickness 30 mm (at the frequency 125 Hz, that is structure-borne noise).