Membrane Elements Research Articles

Seismic Upgrade of an Existing Reinforced Concrete Building Using Steel Plate Shear Walls (SPSW)

Steel Plate Shear Walls (SPSW) provide significant lateral load capacity and can be utilized in the seismic retrofit and upgrade of existing reinforced concrete (r/c) buildings. In this study, the application of SPSW to retrofit a r/c building designed according to older seismic provisions is presented. Three different options to model SPSW are utilized, i.e., by equivalent braces, by finite elements, and by membrane elements, seeking not only to appropriately simulate the actual behavior of the SPSW but also to achieve the desired seismic behavior of the retrofitted building. Specific seismic response indices, including plastic hinge formations, are derived by non-linear time-history analyses in order to assess the seismic behavior of the retrofitted r/c building. Inspection of the results provided by non-linear analyses in conjunction with the different modeling options of the SPSW leads to the conclusion that the model with the membrane elements exhibits the best performance, implying that for the seismic retrofit and upgrade of existing r/c buildings, the use of membrane elements to model the SPSW is recommended.

Synthesis and Structural Characterization of Four Different Concentrations of Ant Nest (Myrmecodia pendens) Collagen Membranes with Potential for Medical Applications.

The purpose of this study was to synthesize and structurally characterize four ant nest membranes in four different concentrations and determine the best concentration that could potentially be used as an alternative material for the production of new collagen barrier membranes. Membranes were created by mixing ant nest extracts at various concentrations of 0.5%, 1%, 1.5%, and 2%, as well as collagen, chitosan, and Polyvinyl Alcohol (PVA) using a film casting. A Universal Testing Machine (UTM) was used to evaluate mechanical properties including elastic modulus, tensile strength, maximum elongation, elongation at break, and maximum force. Water absorption was performed, FTIR was used for functional group identification, and morphology was examined using SEM. Additionally, EDS was used to identify the composition and distribution of elements in membranes. Statistical analysis was conducted using ANOVA (analysis of variance) and post hoc testing with a significance level of p <0.01 for quantitative data. The results showed that the mechanical properties produced the following mean (standard deviation): elastic modulus 0.87 Mpa (0.11), tensile strength 16.32 N/mm2 (2.46), maximum elongation 4.96% (1.72), elongation at break 5.23% (1.87), and maximum force 22.50 N (5.06). The average water absorption capacity of all four membranes had a p-value <0.01. FTIR spectrum showed various peaks corresponding to functional groups, while SEM results indicated a homogeneous mixture. EDS analysis confirmed that the addition of ant plant extract at 0.5%, 1%, and 1.5% resulted in the presence of elements C, O, and Ca. Meanwhile, membranes prepared with 2% concentration had a different composition, namely C, O, Ca, and Na. Increasing the concentration of ant nest affects the values of the membrane's mechanical properties parameters, including the elastic modulus (0.87 Mpa), tensile strength (16.32 N/mm2), maximum elongation (4.96%), elongation at break (5.23%), and maximum force (22.50 N). The average membrane absorption of water (p value <0.01) was also affected. SEM images showed homogeneous mixing, and membrane EDS results consisted of C, O, and Ca composition. However, there was no effect on FTIR functional groups. The anthill membrane with a 1% concentration has the potential to serve as an alternative membrane in guided tissue regeneration.

Биохимические и гематологические характеристики крови коров красной степной породы Павлодарской области Казахстана

To predict the breeding and productive characteristics of cattle, along with molecular genetic markers, biochemical and hematological indicators are used. The purpose of the study is to conduct a hemato-biochemical analysis of the blood serum of red steppe cows in the Pavlodar region of Kazakhstan. Deviations of protein level from the norm indicates metabolic disorders in the body, ration of animals. The total protein in the blood serum of cows is in the upper limit of reference values and makes 81,07±4,28 g/L. Determination of bilirubin content in blood allows to find out the ability of the liver to secrete bile. Total bilirubin amounted to 1,58±0,26 umol/L, which does not exceed the specified values. Urea is the end product of protein metabolism. Its content in blood increases with delayed excretion by kidneys. In the blood serum of cows the concentration of urea is 4,91±0,22 mmol/L. In biochemical analysis, alanine aminotransferase and aspartate aminotransferase are an indicator of cell damage in internal organs. Aspartateaminotransferase was 105,9±8,46 U/L, is within the reference values, indicating the absence of disorders in nitrogen metabolism. The concentration of alanine aminotransferase enzyme was 47,3±4,07 U/L, also indicating the absence of damage in the liver. Cholesterol as an important structural element of cell membrane participates in the formation of complexes with proteins of the inner mitochondrial membrane. Total cholesterol content – 4,72±0,32 mmol/L. Decrease in blood sugar level is a symptom of serious disturbance of carbohydrate metabolism and lack of glycogen reserves in liver and muscles. Decrease of sugar content in blood of cows can be considered as a result of mismatch of energy intake with feed and its expenditure on metabolic processes and milk formation. Glucose concentration was 2,00±0,31 mmol/L. Insignificant deviation from the reference values of amylase enzyme, which hydrolyzes starch and glycogen, was detected. The level of these blood proteins is characterized by great stability and is subject to small fluctuations under normal conditions. The concentration of the enzyme totaled 73,7±6,37 U/L.

A multiphase membrane element with rotational DOFs for the elastic analysis of date palm fibre reinforced PVC composite

A multiphase membrane element with rotational DOFs for the elastic analysis of date palm fibre reinforced PVC composite

One-step rejuvenation for prolonging running lifespan of nanofiltration membranes

Commercial nanofiltration (NF) membranes based on polyamides may experience a decline in permeation performance after prolonged operation. The short lifespan of NF membranes will lead to waste and additional carbon emissions. Thus, rejuvenating membranes and extending their lifespan seem more meaningful than investigating new materials. In this paper, polyamide NF membranes were modified with various polyphenol monomers to improve their permeation performance. The effects of different polyphenols on pore size, surface morphology, and permeation performance of the NF membranes were thoroughly investigated. After modification with tannic acid, the NF membrane exhibits improved salt rejection while experiencing an acceptable decrease in water flux. It should be noted that the commercial NF membrane element fabricated by Koch can recover its Na2SO4 rejection from 83.0% to 94.2% and demonstrate long-term stability after rejuvenation with tannic acid. Combined with the environmental friendliness of polyphenols, this straightforward modification method has the potential for prolonging the operational lifespan of industrial NF membrane products.

Role of Ayurveda in Postponing Arthroplasty in Severe Degenerative Joint Diseases

Degenerative joint disease, also known as osteoarthritis (OA) is a common “wear and tear” disease. Typically, relentless repetitive motion deteriorates structural joints and causes inflammation is the underlying cause of this illness. Although it may affect any joint, it is usually seen in the hands, hips, knees, and spine. Bilateral hip osteoarthritis is described as a non-inflammatory degenerative condition of the hip joint that typically manifests in middle or late life. It is marked by acetabular dysplasia and growth or maturational abnormalities in the femoral neck and head. Pain experienced while moving or carrying weight is a prevalent symptom. As per Ayurvedic classics, the clinical presentation can be understood as Sandhigatavata in the initial stages and later as Asthigathavatha. Initial presentation includes difficulty in moving joints. Bony pain and joint discomfort are explained as Sakthi and Sandhi Shoolam and associated with Theevram balakshayam [severe weakness]. Internal and external applications of Sneha are the main therapeutic modalities explained in Asthi-majja gatha vatha chikitsa by Bruhathrayees. In Charaka samhitha, Ksheera, Basthi and Sarpi with Thiktha rasa Dravya are mentioned as the primary treatment along with Panchakarmas. Because it is the best of the four Snehas, cow's ghee was chosen for the study. According to Sanskaranuvartana, Ghrita has the ability to change in order to absorb the properties of things that are introduced while retaining its original attributes. Ghee's inherent property, oleate, settles Vata and Pitta while without raising Kapha. Phospholipid bilayers are the core elements of cell membranes. Molecules and ions are unable to directly get into or out of the cell via the lipid layer. We constantly need a lipid medium to go deeper. Asthi, Majja, and Sukra have been considered as deeper Dhatus in Ayurveda. The greatest administration for that is Samana accha snehapana. Degenerative joint condition can be effectively treated with traditional Asthigathavata Chikitsa.

Reverse osmosis desalination combining feed flow reversal with permeate flush for mitigation of mineral scaling

The performance of a spiral-wound reverse osmosis (RO) membrane system, operating in a cyclic mode of normal feed flow (NFF)-feed flow reversal (FFR), was evaluated for desalting feed water of high gypsum mineral scaling potential. The membrane system, with six membrane elements in series, was operated without antiscalant dosing at the condition of gypsum supersaturation at the membrane surface of the tail RO element. Automated NFF/FFR switching was triggered by an optical membrane monitoring system (MMS) installed at the last membrane element. This element alternated from being the tail to lead element at NFF and FFR modes, respectively. Multicycle NFF/FFR operation demonstrated partial cycle-to-cycle restoration of the permeate flux. However, progressive flux decline was noticeable with increased NFF/FFR cycles. Complete restoration of element productivity (in terms of permeate flux) was attained via permeate flushing (at the early membrane scaling stage) owing to gypsum scale dissolution. The study results suggest that NFF/FFR RO operation under conditions of high mineral scaling potential can be effectively combined with periodic permeate flushing. However, establishing the long-term approach feasibility will require a strategy for optimizing the frequency of NFF/FFR switching and permeate flushing in relation to the feed water quality and desalting operating conditions.

Finite Element Formulation and Computation of Superplastic Metal Forming Processes with Optimized Rate of Deformation Control

Superplastic forming (SPF) is a material forming technique that uses superplastic exceptional elongations and deformation characteristics to form superplastic materials into certain shapes. The combination of superplastic forming with diffusion bonding (SPF/DB) gives rise to an almost unlimited extension of superplastic forming since more integral lightweight cellular structural components can be manufactured. This paper discusses numerical modelling of the mechanism of superplasticity in metallic materials. The SPF computational method based on the finite element technique augmented with the controlling rate of deformations is developed to examine a range of design or operating conditions leading to more economical forming processes. The non-Newtonian ‘viscous flow’ material is used to model the constitutive of superplastic material during the forming period. The contact mechanics between the sheet material and the mold surface and the intersheet material contact mechanics are imposed using the penalty control method, in which the sticking contact boundary conditions are employed. The space discretization is carried out using the membrane element under plane strain and axisymmetric flow stress conditions, while the implicit time integration technique is utilized to follow the shape changes of the formed sheet material. The validation of the SPF finite element formulation was performed by comparing it with the available analytical solution of Hydraulic Free Bulging of Thin strips. The SPF of a hemispherical dome made of 7475 aluminum sheet alloy was performed to demonstrate the forming process as well as to validate the results obtained between the SPF finite element numerical simulation and the experimental results. The SPF/DB of the multicell component section is considered in the final part.

Carrier-Tumor Cell Membrane Interactions for Optimized Delivery of a Promising Drug, 4(RS)-4-F4t-Neuroprostane.

Nanomedicines engineered to deliver molecules with therapeutic potentials, overcoming drawbacks such as poor solubility, toxicity or a short half-life, are targeted towards their cellular destination either passively or through various elements of cell membranes. The differences in the physicochemical properties of the cell membrane between tumor and nontumor cells have been reported, but they are not systematically used for drug delivery purposes. Thus, in this study, a new approach based on a match between the liposome compositions, i.e., membrane fluidity, to selectively interact with the targeted cell membrane was used. Lipid-based carriers of two different fluidities were designed and used to deliver 4(RS)-4-F4t-Neuroprostane (F4t-NeuroP), a potential antitumor molecule derived from docosahexaenoic acid (DHA). Based on its hydrophobic character, F4t-NeuroP was added to the lipid mixture prior to liposome formation, a protocol that yielded over 80% encapsulation efficiency in both rigid and fluid liposomes. The presence of the active molecule did not modify the liposome size but increased the liposome negative charge and the liposome membrane fluidity, which suggested that the active molecule was accommodated in the lipid membrane. F4t-NeuroP integration in liposomes with a fluid character allowed for the selective targeting of the metastatic prostate cell line PC-3 vs. fibroblast controls. A significant decrease in viability (40%) was observed for the PC-3 cancer line in the presence of F4t-NeuroP fluid liposomes, whereas rigid F4t-NeuroP liposomes did not alter the PC-3 cell viability. These findings demonstrate that liposomes encapsulating F4t-NeuroP or other related molecules may be an interesting model of drug carriers based on membrane fluidity.

Fluid-structure interaction behaviors of tension membrane roofs by fully-coupled numerical simulation

This study aims to investigate fluid-structure interaction (FSI) behaviors of an enclosed-type tension membrane flat roof. The roof with rectangular shape is chosen as the object because of its relatively idealized geometry for FSI analysis, which is a simplified shape compared to typical membrane roofs. Fully-coupled numerical simulations are performed to obtain the wind induced vibration, aerodynamic forces and surrounding flow field of the tension membrane roof structure, where large-eddy simulation (LES) is used for solving of the flow field, non-linear membrane elements are adopted for the structure field and partitioned algorithm is applied for the coupling between the flow and membrane vibration. The numerical simulations are validated by the aero-elastic experimental results. The characteristics of the wind-induced displacements and aerodynamic forces of the tension membrane roof are investigated in both time and frequency domains. The energy transfer characteristics between wind and the vibrating roof are investigated based on the phase analysis between the generalized forces and displacements of the membrane roof. The underlying mechanism of the modal-jump phenomena that the vibration mode of the membrane jumps from the first mode to the second mode with increasing wind velocity, as well as the instability mechanism of the tension membrane roof, are revealed by flow visualizations and unsteady aerodynamic forces identifications. It is found that the aero-elastic instability of the flat membrane roof is a kind of vortex-induced vibration (VIV), where the modal-jump phenomena and unstable vibration of the membrane roof occur with the occurrence of negative aerodynamic damping, induced by the interaction between the vortex transporting and the roof motion.

Development of high-integrity reverse osmosis membranes for enhanced removal of microorganisms

Improved integrity of reverse osmosis (RO) membranes for pathogenic microorganisms can enhance the microbiological safety of potable water reuse. This study aimed to produce a high-integrity RO membrane that is less prone to defects or failures of the polyamide skin layer. The commercial track-etched (TE) microfiltration membranes with uniform pore sizes of 0.2 μm were adopted as a robust support layer. The polyamide skin layer was successfully formed by creating a thin m-phenylenediamine (MPD) layer using a spin coater before the interfacial polymerization. The best TE-based RO membranes had a pure water permeability of 1.1 L/m2hbar and a salt rejection of 97 %. The field emission scanning electron microscopy revealed that the skin layer thickness of the TE-based membrane (approx. 31 nm) was equivalent to a commercial RO membrane. The removal of bacteria-sized particles (0.5 μm fluorescent microspheres) by the fabricated TE-based membrane (8.6-log) was greater than that by the commercial RO membrane taken out from an RO membrane element (7.8-log). Although complete removal of bacteria-sized particles was not achieved with small TE-based RO membrane coupons, this study established a viable protocol for producing a high-integrity RO membrane by forming the polyamide skin layer on the TE support layer.

Antifouling treatment enables membranes to deal with oil and grease

PPG Industries Inc, which supplies paints, coatings and speciality materials, has developed and introduced a high-performance ultrafiltration (UF) membrane and filter elements that help to improve the reuse of industrial process water.

NF membranes enable lithium to be produced from more sustainable sources

DuPont has developed nanofiltration (NF) membrane elements to support direct lithium extraction operations. The company says that they will enable the metal – which is used to manufacture rechargeable batteries for electric vehicles – to be produced from more sustainable and accessible sources.

Membrane properties overview in integrated forward osmosis/osmotically assisted reverse osmosis systems

Integration of forward osmosis (FO) and osmotically assisted reverse osmosis (OARO) provides low energy consumption and controlled fouling for brine treatment. This study explains the membrane properties required for cost–optimal OARO-based systems. A detailed model accounting for the relationship between burst pressure, permeate spacer gap, and structural parameters of OARO membranes was implemented with woven and non-woven spacers. Results indicate that the tradeoff between internal concentration polarization (ICP) and permeate–side pressure drop in OARO stages is a crucial consideration for optimal membrane element design. Due to the lower ICP of no-woven spacers, a system using non-woven spacers yielded lower levelized cost of water (LCOW) and specific energy consumption (5.83 $/m3 and 11.65 kWh/m3, respectively) as compared to the system with woven spacers (7.31 $/m3 and 9.90 kWh/m3, respectively) for dewatering a stream of 75 g/L salinity with 70 % water recovery. Sensitivity analysis shows that increasing the maximum pressure in OARO membranes requires a higher membrane structural parameter, aggravating ICP; however, the elevated driving force mitigates adverse effects of ICP. Moreover, a 15 % reduction in LCOW can be achieved if the membrane replacement factor of RO and OARO is reduced from 15 % to 5 %, which accounts for mitigated fouling.

A finite element framework for fluid–membrane interactions involving fracture

We propose a novel framework for investigating fluid–membrane interactions involving fracture, and apply it to simulate initial stages during the bursting of a balloon. Fluid flow is computed using a stabilized space–time finite element method over a body-fitted mesh. The membrane is modelled as a hyperelastic material and the equations are solved using the standard Galerkin method. Structural failure is incorporated using the element deletion technique based on a simple strain based criterion. Change in topology of the fluid domain due to element deletion is handled without resorting to remeshing. The coincident fluid nodes on either side of the deleted membrane elements on the surface of the balloon are connected, thereby allowing the fluid to gush through the opening. First, fluid–membrane interaction, without failure, in a square sail with fixed edges is studied. The sail exhibits vibration owing to vortices shed from its edges. We then study the inflation and deflation of a spherical balloon equipped with an inlet pipe. A hydrostatic pressure gradient is applied to drive the flow into the balloon. Effect of different values of membrane density, stiffness and the hydrostatic pressure gradient on inflation rate and balloon shape is studied. The bursting of the inflated balloon is initiated by deleting one structural element on its surface. The proposed algorithm is then applied to simulate the subsequent dynamics of the fluid–membrane system.

Development of multi-fiber approach finite element model for reinforced concrete beam using frp reinforcements under pure torsion

A finite element model using a multi-fiber approach is proposed in this paper for the analysis of reinforced concrete (RC) members using fiber-reinforced polymer (FRP) reinforcements, with a specific focus on the effect of pure torsion. The proposed model is formulated using a displacement-based approach and a kinematic assumption involving a two-node Timoshenko beam. The compatibility and equilibrium between concrete and FRP materials in the membrane elements are formulated based on a discretization of the cross-section into several areas following its stress state and the principle of the Modified Compression Field Theory. The nonlinear responses of RC elements with FRP bars can be predicted using an appropriate constitutive material law with internal equilibrium of transverse reinforcement and concrete. The pure torsional response is implemented using an enhanced formulation of concrete's tensile behavior, which is based on experimental tests on torsion and the characteristics of FRP materials. The good agreement between the numerical results and experimental data confirms the validity of the proposed model

Bioactive decellularized adipose matrix prepared using a rapid, nonchemical/enzymatic method for adipogenesis.

Recent developments in the field of regenerative surgeries and medical applications have led to a renewed interest in adipose tissue-enriched mesenchymal stem cell scaffolds. Various advantages declared for the decellularized adipose matrix (DAM) have caused its extensive use in the transfer of stem cells or growth factors for soft tissue regeneration induction. Meanwhile, the long-term application of detergents toward DAM regeneration has been assumed as a risky obstacle in this era. Herein, a rapid, mechanical protocol was developed to prepare DAM (M-DAM) without chemicals/enzymes and was comprehensively compared with the ordinary DAM (traditional chemical method). Accordingly, this method could effectively hinder oils and cells, sustain the structural and biological elements, and contain a superior level of collagen content. In addition, more protein numbers, as well as higher basement membrane elements, glycoproteins, and extracellular matrix-related proteins were detected in the regenerated M-DAM. Also, superior adipogenesis and angiogenesis proteins were distinguished. The noncytotoxicity of the M-DAM was also approved, and a natural ecological niche was observed for the proliferation and differentiation of stem cells, confirming its great potential for vascularization and adipogenesis in vivo. The suggested technique could effectively prepare the modified DAM in variant constructions of tablets, powders, emulsions, hydrogels, and different three-dimensional-printed structures. Hence, this rapid, mechanical process can produce bioactive DAM, which has the potential to be widely used in various research fields of regenerative medicine.

A Numerical Analysis Model of Composite Pneumatic Formwork Considering the Stiffness Contribution of Polyurethane Layer

Pneumatic formwork is a kind of inflated fabric-polyurethane composite formwork formed by spraying polyurethane on the interior surface of the membrane. A numerical analysis model of composite pneumatic formwork considering the stiffness contribution of polyurethane is proposed to predict the structural response. The analysis model simulates the component of fabric and polyurethane with membrane elements and shell elements respectively, and Tie constraint of surface to surface is defined at the interface. A nonlinear material model for fabric is adopted considering the influence of stress ratio and loading history, and the constitutive relation of polyurethane is described in the foaming plane with different properties for tension and compression. Newton-Raphson incremental iterative method is used to solve the involved nonlinear problems. The simulation accuracy of the proposed analysis model is verified by comparing its predictions with test results about the loaddeformation response of an inflated membrane structure and the corresponding composite pneumatic formwork under horizontal loading. The numerical model is further used to investigate the influence of the thickness of polyurethane layer on the improvement of overall structural stiffness of a larger pneumatic formwork under horizontal fresh gale, and the polyurethane is proved to be beneficial for the shape-control of pneumatic formwork.

A model for the observed secondary-maximum in backwash-effluent-TDS-data obtained during backwash of spiral-wound RO membranes

Observation of a “secondary maximum” in the effluent Total Dissolved Solids (TDS) concentration data, during back-washing of micro-scale spiral-wound Reverse Osmosis (RO) membranes, has been reported (Varma and Chatterjee, 2023). This observation is of interest because a “wash-out” process for any system, may be expected to produce effluent water, which shows an exponential decline in the contaminant, from its initial peak concentration, to that of the water used for washing. Hence the observation of a “secondary maximum” in the back-wash effluent TDS data is interesting and has been examined experimentally in (Varma and Chatterjee, 2023). In this work, we present a mathematical model, which can explain the above observations. This model shows that high TDS water is trapped in the RO membrane element, when the RO system is shut-off. A complete wash-out of this high TDS water, which is held close to the membrane surface requires RO permeate osmotic backwash of a “critical” volume. This “critical” RO permeate volume, can be estimated from the method used in this study. The model is based on coupled-unsteady-state material balances for the salt held in different pseudo-compartments within the RO membrane module.

PH-responsive polyacrylic acid chemical cross-linking for end-of-life reverse osmosis membrane rejuvenation

An in-situ chemical cross-linking rejuvenation technique for reverse osmosis (RO) membranes was developed and investigated utilizing pH-responsive polymer with multiple carboxyl groups to improve the salt rejection and performance stability of end-of-life RO membranes. Polyacrylic acid (PAA) was used as a rejuvenating agent to cross-link with amino groups on the degraded RO membrane through EDC/NHS activated reaction. Indicated by ATR-FTIR, XPS, Zeta potential and SEM analyses, the covalent bonds between carboxyl groups and amino groups were generated on the PAA-rejuvenated membrane. The end-of-life RO membrane elements with an average NaCl rejection of 92.68 % could be recovered to 97.26 % by PAA rejuvenation. As a result of pH responsivity, PAA-rejuvenated membranes exhibit excellent rejection stability after continuous 12 cycles of alkali and acid alternate cleaning. The adjustable salt rejection and the durability of PAA-rejuvenated membrane elements were validated in real water tests for 185 days at a coal mine water treatment plant, indicating the practical application potentiality. The effects of initial end-of-life RO membrane condition on PAA rejuvenation are also provided.