Felt Layer Research Articles

Sustainable conversion of carbon dioxide to high-value antioxidant astaxanthin through microbial electrosynthesis-assisted microalgae cultivation

Microbial electrosynthesis (MES) effectively converts carbon dioxide (CO2) to short carboxylic acids but has lower efficiency for higher molecular value-added products. This study used a two-stage process integrating MES with microalgae cultivation to convert CO2 into a value-added chemical—astaxanthin, a xanthophyll carotenoid with strong antioxidant activity. In the first stage, MESs featuring platinum-coated anodes and carbonaceous cathodes were employed to bioelectrochemically convert CO2 to volatile fatty acids (VFAs). In the second stage, microalgal cultivation for sustainable astaxanthin production was conducted using a VFA-containing MES effluent. In the MES operation, a newly designed cathode with alternating layers of carbon felt (CF) and reticulated vitreous carbon (RVC) significantly improved hydrodynamics and bacterial attachment. Consequently, the CF/RVC composite cathode produced 7.68 g/L VFAs from CO2, with the highest production rate of 1225.72 mg/L/day and the highest coulombic efficiency of 94.15 % at 2.8 V. Feeding acetate-containing catholyte effluent demonstrated faster growth of microalgae and astaxanthin accumulation compared to autotrophic culture, indicating synergistic integration of MES and microalgae for capturing value from CO2. Among tested microalgae strains, Haematococcus pluvialis most efficiently accumulated astaxanthin up to 12.95 mg/L as cultured with MES effluent. Successful CO2-to-astaxanthin conversion using MES and microalgae can contribute to resolving unprecedented environmental challenges attributed to the excess emission of CO2.

Risk Analysis of Wellbore Instability of “Felt Layer” in Qiudong Sag Based on Monte Carlo Method

Both domestic and international scholars have conducted in-depth research on wellbore stability issues. They have established various empirical models, analytical models, and numerical simulation methods. However, there is relatively little research on the impact of the uncertainty of input parameters on wellbore stability, and the understanding of this aspect remains unclear. To address this, this paper introduces a probability distribution method. It is based on a wellbore stability mechanical analytical model and, using reliability theory, establishes a method for evaluating wellbore instability risks. By employing the Monte Carlo random simulation method, this study investigates the sensitivity of input parameters to wellbore stability, clarifying that ground stress is the main controlling factor affecting wellbore stability. Combining the analysis of the “felt layer” ground stress profile, this study utilizes two-dimensional simulation experiments to validate the accurate determination of ground stress magnitude in wellbore stability analysis. It also examines the impact of reducing its uncertainty. The results show that this approach significantly reduces the risk of wellbore instability, addressing the challenging issue of identifying wellbore instability in the Qiu Dong Depression’s “felt layer” within the TH Basin.

Carbon felt (CF) acted as an “ionic capacitor” to enhance flow electrode capacitive deionization (FCDI) desalination performance

Flow electrode capacitive deionization (FCDI) is a new ion removal technology with sustainable deionization performance. However, the interface resistance has a significant impact on ions migration in FCDI. We therefore introduced a novel FCDI device that incorporated a layer of carbon felt as an “ionic capacitor” between the flow electrode and the ion exchange membrane, termed CF-FCDI. Mechanism exploration results revealed that the addition of carbon felt reduced device resistance, shorten electron transfer pathways, improved charge efficiency, and increased ion migration rate. Experimental results demonstrated that the improved CF-FCDI device achieved 44 % higher desalination rate compared to traditional device. In addition, long term operation experiments confirmed the stability of CF-FCDI device, highlighting its potential as a viable desalination solution. The findings of this study provided valuable insights for further development of FCDI and offered a promising solution for its applications such as seawater desalination.

Neutron Imaging Experiments to Study Mass Transport in Commercial Titanium Felt Porous Transport Layers

In this work, neutron imaging was used to visualize and study invasion phenomena in fibrous porous transport layers (PTLs) of titanium felt under different flow conditions of gas and liquid phase. The experiments were realized with flow cells that contained a gas and a liquid flow channel separated by PTLs with different thicknesses and pore size distributions. The invasion can be characterized by counter-current flow of water and air with joint imbibition and drainage processes. The dynamics were visualized with neutron radiography with a local resolution of 6.5 μm and a temporal resolution of 0.1 s. Individual static gas-liquid distributions were additionally studied by neutron tomography, with a local resolution of 22 μm and an exposure time of 1.5 s per image (projections: 800/360°). It is shown and discussed that the invasion occurred in continuously repeated imbibition/drainage cycles with frequencies depending on the flow conditions and the PTL structure as well. The change of the PTL saturation with air or water appeared almost independent from the specific PTL structure and the breakthrough of the gas phase occurred at almost constant positions.

Manufacturing and experimental analysis of a dew-point indirect evaporative cooler using fused deposition modelling 3D printing and polymeric materials

Evaporative cooling (EC) is an interesting alternative for reducing energy consumption and CO2 emission associated with the cooling of building. In the present work, a prototype of an innovative dew-point indirect evaporative cooler (DIEC) was manufactured by additive manufacturing technology. This prototype was made up of two types of materials: (a) one porous, with high water absorption capacity, polyvinyl alcohol (PVA) with felt, and therefore, high capacity of generate EC; and (b) another with high hydrophobic properties, polylactic acid (PLA) with bronze. The materials were characterised in terms of thermal, water absorption properties and morphological properties. Prior to manufacturing, a design of experiments was conducted in order to find the optimal manufacturing parameters. The prototype was produced through an innovative process, based on the simultaneous use of two extruders, and the manufacture of a porous layer of felt by dissolving the PVA matrix where the felt was initially embedded. Finally, the energy performance of the prototype was experimentally analysed, reaching values of dew-point effectiveness up to 0.9 and energy efficiency ratio up to 22.74 at 45 °C outside dry bulb temperature. These results show that additive manufacturing is promising for developing competitive compact and highly energy efficient DIEC systems.

A composite electrode with gradient pores for high-performance aqueous redox flow batteries

Large surface areas while maintaining a low mass transport resistance is a critical criterion for the optimal design of electrode structures for aqueous redox flow batteries. However, for conventional micro-scale electrode structures, increasing surface areas will lead to an increase in the mass transfer resistance. In this work, a composite electrode with a gradient porosity distribution is fabricated through combining two different carbon felt layers of different porosities. The smaller-porosity layer, offering a larger surface area, is placed adjacent to the membrane, while the larger-porosity layer, providing a smaller mass transfer resistance is placed on the flow field side. The thickness ratio of the two layers is adjusted in terms of the battery performance while applied in the vanadium redox flow battery. It is demonstrated that the battery with the structure-optimized composite electrode achieves a high energy efficiency of 82.7 % at 200 mA·cm−2 at an electrolyte flow rate of 30 mL·min−1, and delivers a discharge capacity of 240 mAh at 400 mA·cm−2, which is 2.18 times that of the conventional graphite felt electrode. This work offers an idea for the structural design of high-performance aqueous redox flow batteries.

Effect of Low-Temperature Plasma Treatment on The Properties of a Complex Wool-Containing Material

The article investigates a layer of felt in a complex material, which we intend as rehabilitation footwear element. The complex material consists of layers of rubber and felt, connected with polyurethane adhesive, and we design it for the manufacture of shoe-product sole. The layer of felt inside is in contact with the foot and serves as an insole. The felt was treated with low-temperature plasma (LTP) from the inside of the complex material. It was experimentally obtained the wettability index: for the complex material, containing a treated layer of felt, and a control untreated felt. The research obtained an increase in the hydrophilicity of the LTP-treated felt, which is explained by degreasing the surface, an increase in the porosity of the non-woven material «felt», as well as structural changes in the wool fiber due to plasma treatment. Plasma treatment of woolen felt layer can be recommended to increase the hydrophilicity of the surface and impart antibacterial properties to the inner («insole») surface of the complex material by applying infusions of medicinal plants, etc.

High gain couple feed multiband wearable antenna for 5G and sub‐6 GHz communications

A multi-band, small, high gain, low specific absorption rate (SAR), and circularly polarized (CP) textile wearable antenna fed using aperture coupled technique is designed on two layers of denim ( ε r = 1.2 , h = 0.787 mm as feeding layer) and felt ( ε r = 1.3 , h = 1.5 mm as a resonating layer) textile substrates. The antenna is designed on two layers with two relative permittivities to enhance the BW and reduce the negative mutual coupling. Afterward, another layer of denim with the complete ground of ShieldIt conductor is added to decrease the SAR value along with the directive gain. The antenna works for Industrial, Scientific, and Medical (ISM), 5G, and sub-6 GHz communication systems as it operates at 2.45–2.55 GHz and 3.8 GHz (3.6–4.15 GHz), and 5.6 GHz (5.55–5.65 GHz), respectively. The proposed antenna has the maximum directive gain of 8.35 dBi, acceptable SAR values at a 10 mm distance from the human body for both standards. In addition, the antenna's CP is examined, showing AR values of <2.5 dB at the working BW. Finally, the proposed antenna is measured and compared with the simulation results. A good agreement exists between simulation and measurement results.

LBM studies at pore scale for graded anodic porous transport layer (PTL) of PEM water electrolyzer

Oxygen invasion inside graded porous transport layer (PTL) of titanium felt is investigated based on Shan-Chen Lattice Boltzmann Model. The computation domain is obtained from X-ray computed tomography. The pore-scale study aims to investigate the counter-current transport of fluids within the spatially distributed structure with application to polymer electrolyte membrane water electrolysis (PEMWE). The results indicate that the transport mechanism is gas fingering for a current density of 1.356 A cm−2. The observed gas fingering is independent of the domain size, structure and boundary conditions in the studied ranges. But, the computed final local distribution of oxygen strongly depends on spatial porosity and pore size distributions. Furthermore, with different locations of the oxygen injection points along the invasion interface, different final saturation profiles are computed. The latter suggests the importance of oxygen entrance conditions, especially when the computational domain shall be realistically coupled with the catalyst layer along the oxygen invasion interface.

A New Modification for Anastomosing HeartMate 3 Apical Cuff for a Small Left Ventricle

<h3>Introduction</h3> A preoperative small left ventricular size has been associated with higher mortality and complications after left ventricular assist device (LVAD) implantation. The small left ventricle (LV) may result in repeated suction events and inflow obstruction, possibly leading to pump thrombosis and malfunction and thromboembolism. The inflow cannula length of HeartMate 3 is 22 mm, and the CT-measured protrusion depth of inflow cannula into the LV was 13.5 ± 1.0 mm in our previous HeartMate 3 series (16 patients). Based on the concept that making the protrusion depth shallow should decrease the risk for suction event, we adopted a hand-made apical cuff, whose actual thickness was 6mm, modified by stacking three layers of felt on the original PTFE felt during HeartMate 3 implantation for a small LV patient. Here, we report two cases in which this modified apical cuff was used. <h3>Case Report</h3> One patient is a 47-year-old woman with idiopathic dilated cardiomyopathy who underwent implantation of a HeartMate 3. Preoperative echocardiography showed a small left ventricular end-diastolic dimension (LVDd) of 49 mm. We anastomosed the described-above modified apical cuff in a core then sew technique. Postoperative LVDd was 30 mm and cardiac index was 2.7 L/min/m² under optimized pump setting. Another is a 58-year-old woman with dilated phase of hypertrophic cardiomyopathy who underwent implantation of a HeartMate 3. The preoperative LVDd of this patient was 48 mm. The same modified apical cuff was secured in a core then sew technique after resection of the intraventricular muscle through the apical coring hole. Postoperative LVDd was 37 mm and cardiac index was 2.2 L/min/m² under optimized pump setting. Both patients experienced no significant suction event or adverse events and are still waiting for heart transplantation as an outpatient. <h3>Summary</h3> This modified apical cuff is promising for achieving adequate pump performance of HeartMate 3 and possibly improving the outcomes of LVAD therapy in patients with the small LV.

Zoysia Soil-Less Green Roof’s Performance: A Life Cycle Assessment

Abstract The use of green roofs is demonstrated to improve the energy performance of buildings, increase biodiversity, reduce environmental impacts of urban areas, and mitigate climate change phenomena. Their use on a large scale is desirable in the coming years. Still, the choice of the most suitable green roof design solution should also consider the impacts of their production. Within this study, the Life Cycle Assessment methodology was used to evaluate the environmental impact of a particular typology of soil-less green roofs ideated by an Italian company. In this lightweight green roof, the growing medium is replaced by recycled felt layers, filtration is guaranteed by geotextile, and a closed-loop sub-irrigation system fertilises the pre-growth lawn placed on the top. The extremely low weight of this system suggests an optimal use in building retrofitting scenarios, but its environmental implication was not known. The environmental impact of this product has been assessed with an attributional cradle-to-gate approach through four different methodologies (ReCiPe midpoint and endpoint H V1.1, Ecological footprint V1.01, and IPCC 2013 GWP 100y V1.0) using the ecoinvent v3, Agri-footprint 1.0, and ELCD database on the SimaPro 8.4.4.0 software. The IPCC method has shown a Global Warming Potential of 7.66 kg of CO2 eq. for 1 m2 of Pratotetto® green roof; however, the reuse of waste materials from the textile industry must be considered.

Experimental evaluations of acoustic properties and long-term analysis of a novel indoor living wall

Indoor living walls are important decorative elements that can recreate a natural garden in enclosed spaces. Several aspects are addressed by the scientific literature such as, for instance, classification, the effects on air quality and indoor temperature, greater aesthetic and psychological impact, and improved acoustic treatment of indoor spaces. The main objective of this study is to analyse the acoustic performances of a novel indoor living wall (LW) where plants are rooted in felt layers and grown in hydroponics with no growing medium. The sound absorption of different LW solutions was measured in laboratory (reverberation room). One of them was installed in a Test Building, where sound absorption and sound insulation were measured. The LW has been installed for about two years in the Test Building under controlled conditions of temperature and relative humidity. This gave the unique opportunity to test the sound absorption of the same living wall in the same reverberation room after about two years. The results obtained indicate that the sound absorption performance of the LW is stable, as long as the plants remain in good health. Moreover, an estimation was performed with a calculation model of the reverberation time of the room containing the living wall. Evaluation in real working conditions confirms that indoor living walls can improve the acoustic comfort of indoor spaces by increasing both the sound insulation and the sound absorption area, allowing to reach the optimal reverberation time values provided for by Italian regulations.

Investigating environmental life cycle impacts of active living wall for improved indoor air quality

Life-Cycle Assessment (LCA) is the systematic analysis of the potential environmental impacts of any product or process throughout the life cycle. This work presents the LCA of Active Living Wall System (ALW), an advanced form of living wall, which is a vertical greening system designed to reduce the indoor air pollutants along with several other benefits for occupants and building environment. Although this system is considered as having high potential to improve indoor air quality, ALW has not yet been assessed thoroughly from environmental perspective. Hence, the environmental impacts of production, operation, maintenance, and finally disposal phases of ALW systems have been investigated through LCA in this paper. Built as an experimental set-up, two different ALW systems have been investigated extensively for this study including ALW system based on felt layers, and planter box ALW. Life-cycle environmental impacts have been analyzed using ReCiPe environmental impact methodology. Comprehensive study results showed similar environmental burden for both ALW systems for a life span of 10 years, indicating stainless steel and PVC as the most impacting construction materials. Operational energy was responsible for major impacts in climate change and terrestrial acidification category where incorporation of solar energy showed possible reduction of burden. Although having few limitations, this LCA study has the potential to help both the manufacturers and built environment experts to improve the balance between benefits and environmental impacts for a more sustainable ALW system that can ultimately lead us to an improved indoor environment.

Sound absorption performance of flexible polyurethane/silicon dioxide perforated coating composites

Perforated materials in the traditional sense are rigid, usually dense, costly and inflexible. For this study, polyester/cotton blended woven fabric as the base fabric, nano-SiO2 (silicon dioxide) as the functional particles and PU (polyurethane) as the matrix were selected. Accordingly, flexible PU/SiO2 perforated coating composites with different process parameters were developed. The influence of the nano-SiO2 content, perforation diameter, perforation rate, number of fiber felt layers and cavity depth on the sound absorption coefficient were investigated. The resonant frequencies of materials with different cavity depths were evaluated by both theoretical calculation and experimental method. It was found that the flexible perforated composite has good sound absorption and mechanical properties, and has great potential for applications requiring soft and lightweight sound absorption materials.

Study of Thermal Insulation Performance of Layered Jute Nonwoven: A Sustainable Material

ABSTRACT An eco-friendly sustainable thermal insulator has been developed as a replacement of some commercially available manmade materials to control heat transfer in case of buildings, and semi-permanent/temporary structures. Jute felts were prepared by needle pinching of fiber fleece. It is a self-sustained semi-rigid structure and could be placed on various surface profiles of the building/structure due to its balanced flexural rigidity and surface property of fiber. Effect of areal density, thickness, and number of layers of jute felt on its major thermal insulation property parameters were studied. Some major structural parameters of felts viz., pore size, bulk density, and air fraction as gas pockets in fibrous structure were analyzed and correlated with the insulation property. Felt having 500 g/m2 areal density showed best specific thermal insulation performance. When it was used in four layers, its thermal insulation value reached up to 341 m2K/kW, which is much comparable to those of glass wool (320 m2K/kW), nitrile rubber (320 m2K/kW), and polystyrene (381 m2K/kW) insulators. The cost of jute felts ($ 2.81 for four layers of 500 g/m2) was much comparable to synthetics ($2.9 for glass wool and $ 2.7 for nitrile rubber) of similar thermal insulation value. It also facilitates remarkable saving of costly floor space to the extent of 28% as compared to synthetics. The ease of tailorability of jute felt was also studied by measuring drapability, tensile strength, tear strength, and energy required to cut the felt. Inherent multiple lumens within fiber structure, partial anisotropy of polymer chains, and innumerable tiny gas pockets within the felt structure are the major reasons for the high thermal insulation of jute felt.

Metamaterial-based wearable flexible elliptical UWB antenna for WBAN and breast imaging applications

This paper presents a metamaterial-based flexible wearable ultra-wideband (UWB) antenna for breast imaging and wireless body area network (WBAN) applications. The wearable antenna is required to be a planar and low-profile structure using flexible materials. The proposed antenna comprises two layers of denim (10 × 10 mm2) and felt (10 × 15 mm2). The antenna was integrated with six metamaterial unit cells using a modified grain rice shape within a split ring resonator to enhance the bandwidth, gain, and directivity and reduce the specific absorption rate value to less than 2 W/kg. The proposed antenna operates within a broad bandwidth range (6.5 GHz–35 GHz) with the maximum gain and directivity of 8.85 dBi and 10 dBi, respectively, and a radiation efficiency of more than 70% over its operating frequency band. The results verified good agreement between the simulation and measurement of the proposed technique in detecting an existing tumor with a diameter of 4 mm from any location inside the breast. The results convincingly proved the capability of the proposed wearable UWB antenna system for both WBAN and breast imaging applications.

Facile segmented graphite felt electrode for iron-vanadium redox flow batteries with deep eutectic solvent (DES) electrolyte

In this work, the graphite felt electrode for an iron-vanadium redox flow battery (RFB) with deep eutectic solvent (DES) electrolyte is modified by the method of electrolysis in ammonium sulfate, and a segmented electrode is prepared by combining the pristine graphite felt part and the modified part. The electrolysis process not only makes the outermost layer of graphite felt partially fall off which enlarges the specific surface area, but also increases the number of oxygen-containing functional groups on the surface of the graphite felt. To uniform the electrochemical reaction along the electrolyte flow direction and reduce the over-potential, the pristine graphite felt part of the segmented electrode is placed in the electrolyte inlet region, and the modified graphite felt part is put in the outlet region. With the segmented electrode, the single cell test shows the maximum power density is 10.63% higher than that of the pristine electrode under the same operating condition, and the energy efficiency is also higher for charge-discharge cycles. Therefore, the accessibly prepared segmented electrode is promising for improving the performance of the DES electrolyte redox flow battery.

Measurement of the Acoustic Absorption Coefficient by Impedance Tube

Abstract The contribution deals with measurement of acoustic absorption coefficient for different single or double-layer materials: cork, two layers of polyethylene, polyethylene and felt. The measurement was performed on an impedance tube of our own construction, using the two-microphone method transfer function (ISO 10534-2: 1998) and the PULSE measuring system. Values of the acoustic absorption coefficient for the frequencies from 100 Hz to 1600 Hz were determined experimentally. Subsequently, those values were processed graphically.

Experimental comparison of green facades with outdoor test cells during a hot humid season

We used outdoor test cells during a hot humid period to analyse the surface temperatures behind the following four types of green walls: a felt layer wall; a planter boxes wall; a direct climbing plants wall, and; an indirect climbing plants wall. We compared these temperatures with temperatures of a bare wall and we found that all four types of green facades were able to maintain lower temperatures than the bare wall, and that the felt layer and planter boxes wall had lower temperatures than the other walls for the majority of the study period. In particular, the daily average and peak surface temperatures behind the felt layer wall were by 1.9 °C–4.8 °C and by 7.1 °C–13.4 °C respectively lower than the bare wall. We undertook a significance analysis and produced Pearson coefficients to better understand the relationship between average daily weather conditions and the surface temperatures on all five test cells. We noted that the average daily solar radiation flux did not affect the surface temperatures behind the planter boxes and felt layer walls, but the daily average ambient air temperature was significantly correlated with the average and peak surface temperatures behind all four green facades. Finally, we concluded that the cooling potential of the felt layer and the planter boxes walls increases with higher amounts of solar radiation and higher ambient temperatures. In addition, from the analysis of the diurnal temperature variations and the time series trends we illustrated that the temperatures behind the felt layer and planter boxes walls fluctuated less than the other walls, which lead to a slower rate of surface temperature reductions during a cooler day than the other wall types of the study.

Contaminants removal and bacterial activity enhancement along the flow path of constructed wetland microbial fuel cells

Microbial fuel cells implemented in constructed wetlands (CW-MFCs), albeit a relatively new technology still under study, have shown to improve treatment efficiency of urban wastewater. So far the vast majority of CW-MFC systems investigated were designed as lab-scale systems working under rather unrealistic hydraulic conditions using synthetic wastewater. The main objective of this work was to quantify CW-MFCs performance operated under different conditions in a more realistic setup using meso-scale systems with horizontal flow fed with real urban wastewater. Operational conditions tested were organic loading rate (4.9 ± 1.6, 6.7 ± 1.4 and 13.6 ± 3.2 g COD/m2·day) and hydraulic regime (continuous vs. intermittent feeding) as well as different electrical connections: CW control (conventional CW without electrodes), open-circuit CW-MFC (external circuit between anode and cathode not connected) and closed-circuit CW-MFC (external circuit connected).Eight horizontal subsurface flow CWs were operated for about four months. Each wetland consisted of a PVC reservoir of 0.193 m2 filled with 4/8 mm granitic riverine gravel (wetted depth 25 cm). All wetlands had intermediate sampling points for gravel and interstitial liquid sampling. The CW-MFCs were designed as three MFCs incorporated one after the other along the flow path of the CWs. Anodes consisted of gravel with an incorporated current collector (stainless steel mesh) and the cathode consisted of a graphite felt layer. Electrodes of closed-circuit CW-MFC systems were connected externally over a 220 Ω resistance.Results showed no significant differences between tested organic loading rates, hydraulic regimes or electrical connections, however, on average, systems operated in closed-circuit CW-MFC mode under continuous flow outperformed the other experimental conditions. Closed-circuit CW-MFC compared to conventional CW control systems showed around 5% and 22% higher COD and ammonium removal, respectively. Correspondingly, overall bacteria activity, as measured by the fluorescein diacetate technique, was higher (4% to 34%) in closed-circuit systems when compared to CW control systems.