Numerical Study Research Articles

Exploring the acoustic potential of 3D printed micro-perforated panels: A comparative analysis

In the present study, the sound absorption performance of inhomogeneous Micro-Perforated Panels (MPPs) with multiple cavities is investigated. Two models, a three-cavity system and a four-cavity system, are proposed and a numerical study is performed using MATLAB. The models are validated through experimental analysis in an impedance tube. The study meticulously varies the geometrical parameters, including pore diameter, thickness of the MPP, perforation ratio, and back-cavity length. It is found that MPPs with a greater number of sub-cavities have a better sound absorption coefficient than two-cavity systems. The results suggest that the back air cavity is predominantly responsible for multiple peaks, ensuring wideband sound absorption. It is also found that smaller perforation ratios for sub-cavities with larger pore diameters improve sound absorption performance in the lower frequency region. The study indicates that a pore diameter of less than 0.5 mm should be used for better sound absorption above the range of 800–850 Hz, and back cavity length has greater control than pore diameter between 850 Hz and 2000 Hz to make the curve smooth with less fluctuation. The findings have significant implications for the design of MPPs for real-world applications.

Evaluation of immunomodulatory potential of probiotic conditioned medium on murine macrophages

Probiotics are a mixture of beneficial live bacteria and/or yeasts that naturally exist in our bodies. Recently, numerous studies have focused on the immunostimulatory effects of single-species or killed multi-species probiotic conditioned mediums on macrophages. This study investigates the immunostimulatory effect of commercially available active, multi-species probiotic conditioned medium (CM) on RAW264.7 murine macrophages. The probiotic CM was prepared by culturing the commercially available probiotic in a cell-culture medium overnight at 37 °C, followed by centrifugation and filter-sterilization to be tested on macrophages. The immunostimulatory effect of different dilution percentages (50%, 75%, 100%) of CM was examined using the MTT assay, proinflammatory cytokine (tumor necrosis factor TNF-alpha) production in macrophages, migration, and phagocytosis assays. For all the examined CM ratios, the percentages of cell viability were > 80%. Regarding the migration scratch, TNF-alpha and phagocytosis assays, CM demonstrated a concentration-dependent immunostimulatory effect. However, the undiluted CM (100%) showed a significant (p-value < 0.05) stimulatory effect compared to the positive and negative controls. The findings suggest that the secretions and products of probiotics, as measured in the CM, may be closely associated with their immune-boosting effects. Understanding this relationship between probiotic secretions and immune function is crucial for further exploring the potential benefits of probiotics in enhancing overall health and well-being.

Experimental and Numerical Study on Flexural Behavior of Concrete Beams Using Notches and Repair Materials

In a concrete beam, cracking is generated on the tension side under the effect of flexure, shear, and torsional loadings. Accordingly, these weak concrete members require repair and/or strengthening to increase or restore their internal load capacity. In the current experimental and numerical investigations on concrete beams, the impact of using notches with different width to depth ratios on the ultimate flexural load under a three-point test was considered. Further, the flexural behavior performance of a notched concrete beam repaired using the three repair materials—cement mortar, bacterial mortar, and adhesive—was also examined. Consequently, a comparative study was implemented between the experimental and numerical results. A concrete damage plasticity (CDP) model was used for the finite element numerical analysis of the beams. The differences in numerical and experimental measured results ranged from 0.65 to 22.20% for the ultimate load carrying capacity. As the notch size increased, the ultimate load carrying capacity of the beam reduced. Additionally, a linear regression model was used to predict the ultimate load values at a notch width interval of 5 mm up to a maximum notch width of 100 mm. It was observed that the ultimate load capacity for a repaired beam increased as compared to the notched beam for all three repair materials under consideration. And the maximum ultimate load increased in the case of notched beams repaired using adhesive. Furthermore, in comparison to the cement mortar, the performance of the bacterial mortar in terms of the ultimate load was more. The bacterial mortar was found to be more sustainable and more durable as a repair material for concrete structures.

A Numerical Study of a Stabilized Hyperbolic Equation Inspired by Models for Bio-Polymerization

Abstract This report investigates a stabilization method for first order hyperbolic differential equations applied to DNA transcription modeling. It is known that the usual unstabilized finite element method contains spurious oscillations for nonsmooth solutions. To stabilize the finite element method the authors consider adding to the first order hyperbolic differential system a stabilization term in space and time filtering. Numerical analysis of the stabilized finite element algorithms and computations describing a few biological settings are studied herein.

En-route charge scheduling for an electric bus network: Stochasticity and real-world practice

Bus electrification, with its high energy conversion efficiency and zero tailpipe emissions, has a significant impact on addressing the petroleum crisis and lowering carbon emissions in urban transportation. However, long charging times and uncertain operational risks hinder their wider adoption. This paper explores the robust en-route charge scheduling problem for electric buses to overcome uncertain energy consumption while ensuring charging accessibility. The problem is first described as a deterministic mixed-integer linear programming model that employs a time-of-use electricity price to balance the charging demand. Additionally, a robust counterpart model is formulated to account for stochastic energy. Numerical studies are designed to evaluate the proposed model in a real network, followed by a sensitivity analysis to investigate the impact of battery type, fleet composition, and depth of discharge on the charging schedule. The results show that the robust optimization model provides system feasibility against uncertainty with a comparable price and emissions.

The effect of yoga practices on health parameters: A review

Yoga, a practice originating in India thousands of years ago, has gained immense popularity today and its effects are under scrutiny. Numerous studies demonstrate the positive impact of various types of yoga on human physiology. Specifically, research highlights the ability of yoga to mitigate stress and anxiety, as well as increase serotonin and dopamine hormones, facilitating healthy coping mechanisms in modern living. For a healthy lifestyle, yoga can be an important addition to a nutritious diet. While numerous studies have reported on the positive effects of yoga, its complete impact has yet to be fully understood. It may be recommended that the studies planned to be addressed in the future on the subject should be carried out for a specific health problem, should have a methodologically good and high quality structure and the sample size should be kept large. This review found that yoga has significant positive effects on anxiety and depression. It also increases hormones such as serotonin and dopamine in the body, which can lead to a more positive outlook. However, the review found statistically insignificant decreases in fasting blood glucose levels, postprandial blood glucose levels, and HbA1c. Additionally, yoga was found to significantly improve quality of life.

Multi-objective optimization of a sequentially inspected system prone to revealing and non-revealing failures via particle swarm optimization and a fuzzy method

ABSTRACT Maintenance models rely heavily on the failure characteristics and inspection or maintenance actions. This paper introduced a sequentially inspected system whose failure alternated between revealing and non-revealing failures. The distinctive characteristic of the proposed model is that inspections are imperfect, inspection and maintenance time are non-negligible, and corrective maintenance is perfect. The proposed study contributed on the multi-objective availability and cost optimization issue of the aforementioned system, which was lacking in the prior studies. This paper focused on evaluating the general expressions for limiting availability and long-run average cost of the sequentially inspected system and addressed the multi-objective optimization issue using particle swarm optimization to generate the Pareto optimal solutions followed by a fuzzy method to select the best compromise solution. Moreover, reasonable results were achieved using a numerical case study and the findings of the existing studies were found to be the special case of this model.

An LMI-based robust state-feedback controller design for the position control of a knee rehabilitation exoskeleton robot: Comparative analysis

Rehabilitation exoskeleton robots play a crucial role in restoring functional lower limb movements for individuals with locomotor disorders. Numerous research studies have concentrated on adapting the control of these rehabilitation robotic systems. In this study, we investigate an affine state-feedback control law for robust position control of a knee exoskeleton robot, taking into account its nonlinear dynamic model that includes solid and viscous frictions. To ensure robust stabilization, we employ the Lyapunov approach and propose three methods to establish stability conditions using the Schur complement, the Young inequality, the matrix inversion lemma, and the S-procedure lemma. These conditions are formulated as Linear Matrix Inequalities (LMIs). Furthermore, we conduct a comprehensive comparison among these methods to determine the most efficient approach. At the end of this work, we present simulation results to validate the developed LMI conditions and demonstrate the effectiveness of the adopted control law in achieving robust position control of the knee exoskeleton robot.

Photoinduced Generation of Active Intermediates from Unmodified 1,3‐Dicarbonyl Compounds for Organic Transformations

AbstractPhotocatalysis utilizes light as the initial driving force for chemical reactions, enabling reactions with high energy barriers in traditionally thermal chemistry to proceed under mild conditions. 1,3‐Dicarbonyl compounds occur as important active molecules in nature and are intermediates in pharmaceutical syntheses. In recent years, there have been numerous studies of these compounds, and it is common practice to pre‐modify them before the reaction, which is, however, unfavorable for the atom economy of the process. This paper provides a comprehensive review of the latest advancements in the site‐specific activation of unmodified 1,3‐dicarbonyl compounds by photoinduction. The focus is on elucidating the mechanisms of these reactions to provide insights and directions for future research in designing novel reactions.

Immunopathogenesis and detection methods of type 2 diabetes

Diabetes is a disease that is increasingly prevalent on a global scale. Type 2 diabetes (T2D) accounts for 90% of all diabetes cases and is a chronic condition primarily influenced by factors such as obesity and genetics. This condition often leads to the development of various cardiovascular diseases. A diverse of different detection methods for the T2D have been developed and achieved good detection and analysis results. In addition, numerous studies have indicated a close connection between T2D and immune inflammation. This research primarily introduces the current status of diabetes, provides a detailed summary of the connection betweenT2D and the immune system, and presents novel immune biomarkers related to T2D. Some new immunological testing methods will be analyzed in this research. In the future, there is hope that these new biomarkers can be used to design more advantageous therapeutic drugs for diabetes patients and more convenient, sensitive, and low-cost detection methods.

Synthesis and characterization of Al2O3-methanol nanofluid and its usage in bubble column for an improved mass transfer rate

Methanol-based physical absorption, known for its effective CO2 capture ability, has been employed in acid gas removal (AGR) unit. However, the high energy consumption associated cooling methanol and acid gas hampers its widespread adoption. To address this challenge, numerous studies have explored the use of nanoparticles to enhance the CO2 absorption at room temperature, thereby reducing the energy requirements. In this study, the objective is to synthesize and characterize the Al2O3-methanol nanofluid and investigate its application in a bubble column for improved mass transfer rates during CO2 absorption. The methanol based Al2O3 nanofluid was prepared using the two-step method with ultrasonication technology and CO2 absorption in the resultant product was investigated. Initially, 0.001 vol%, 0.01 vol % and 0.1 vol% Al2O3 nanoparticles was added to methanol solution and to mixture them well via ultrasonication technology. The static settlement method and zeta potential analysis were utilized to characterize the stability of the as-prepared nanofluid. Both impact of sonication power and time on the stability of nanofluid were discussed as well. Then, numerical simulations was employed to investigate the mass transfer coefficient for CO2 absorption and the numerical uncertainty was carefully analyzed to verify the reliability of the numerical method. It revealed a 7.3%, 29.2% and 60.7% enhancement in mass transfer coefficient during CO2 absorption for 0.001 vol%, 0.01 vol% and 0.1 vol% nanoparticles under room temperature, respectively. The visualized reason for this improvement was related to the enhanced bubble breakup and coalescence after adding nanoparticles to methanol. The expanded interfacial area between gas and liquid plays a vital role in the mechanism of this improvement.

Does hyperphenylalaninemia induce brain glucose hypometabolism? Cerebral spinal fluid findings in treated adult phenylketonuric patients

Despite numerous studies in human patients and animal models for phenylketonuria (PKU; OMIM#261600), the pathophysiology of PKU and the underlying causes of brain dysfunction and cognitive problems in PKU patients are not well understood. In this study, lumbar cerebral spinal fluid (CSF) was obtained immediately after blood sampling from early-treated adult PKU patients who had fasted overnight. Metabolite and amino acid concentrations in the CSF of PKU patients were compared with those of non-PKU controls. The CSF concentrations and CSF/plasma ratios for glucose and lactate were found to be below normal, similar to what has been reported for glucose transporter1 (GLUT1) deficiency patients who exhibit many of the same clinical symptoms as untreated PKU patients. CSF glucose and lactate levels were negatively correlated with CSF phenylalanine (Phe), while CSF glutamine and glutamate levels were positively correlated with CSF Phe levels. Plasma glucose levels were negatively correlated with plasma Phe concentrations in PKU subjects, which partly explains the reduced CSF glucose concentrations. Although brain glucose concentrations are unlikely to be low enough to impair brain glucose utilization, it is possible that the metabolism of Phe in the brain to produce phenyllactate, which can be transported across the blood-brain barrier to the blood, may consume glucose and/or lactate to generate the carbon backbone for glutamate. This glutamate is then converted to glutamine and carries the Phe-derived ammonia from the brain to the blood. While this mechanism remains to be tested, it may explain the correlations of CSF glutamine, glucose, and lactate concentrations with CSF Phe.

Experimental and numerical study of impact resistance and compression properties after impact of none-felt needled composites

In this paper, the impact and after-impact compression (CAI) properties of new none-felt needled composites were investigated by finite element and experimental methods. Micro-CT and digital image correlation (DIC) were used for structural characterization and recording surface strains in CAI specimens. The impact and CAI finite element models of needled composites were developed, and the damage mechanisms were analyzed. The results showed that the impact and CAI properties of none-felt needled composite were substantially improved. In the impact experiments, the failure firstly occurred in the interlayer and gradually extended to the fiber layer. In the CAI experiment, the damage gradually extended from the impact damage region to the specimen edges, and the specimen finally failed when the damage with the specimen edges extended together. The established finite element model agreed well with both the impact and CAI tests, and the errors were less than 5 % and 10 %.

Coupled DEM-FDM numerical model for EPB shield tunnelling simulation with foam conditioning

It is widely recognized that an appropriate application of soil conditioning significantly improves the tunnelling performance of earth pressure balance (EPB) shield tunnel boring machines (TBMs). This study presents a numerical approach that simulates an EPB shield tunnelling, considering the injection of foam into the soil. To enhance computational efficiency and reduce the number of particles simulated in the ground formation, the numerical study coupled the discrete element method (DEM) and the finite difference method (FDM). The properties of in-situ soil and foam-conditioned soil were incorporated into the DEM domain by determining the contact parameters of particles using two calibration models: the triaxial compression test and the pressurized vane shear test models. With the established model, tunnelling analyses were conducted under specific TBM operation conditions, such as the penetration rate, and rotational speed of the cutter head and the screw conveyor. The effect of foam injection on EPB shield TBM operation was evaluated by adjusting the contact parameters of DEM elements. The numerical simulations revealed that foam conditioning reduced the torque, thrust force, and forces on cutting tools. These simulations provided valuable insights into the applicability of the numerical approach in assessing foam conditioning for EPB shield TBMs.

Turbulent flow-thermal-thermodynamic characteristics of a solar air heater with spiral fins

This work proposes a strategy by employing multiple spiral fins (SFs) for enhancing the low heat transfer rate of traditional smooth solar air heaters (SAHs). A numerical study involving the effects of the pitch ratio (P/Dh), quantity (N), and arrangement of SFs on fluid flow, heat transfer, and thermodynamic characteristics of the SAHs was conducted. The research findings indicated that the flow field was homogenized and the thermal boundary layer was weakened by inserting multiple SFs into the smooth SAH. This could increase the heat transfer rate by 30.63–137.51 % and decrease the overall entropy generation by 9.64–57.05 %, causing a 25.01–99.18 % improvement in thermodynamic efficiency. Reducing P/Dh and increasing N could improve the heat transfer rate, increase flow viscous entropy generation, reduce thermal entropy generation, and augment thermodynamic efficiency (ηⅡ). In addition, changing the rotation arrangement of the SFs from the counterclockwise to the counter-swirl improved the thermal-hydraulic performance parameter (THPP). Within the scope of this study, the SAH with P/Dh = 1.5 and N = 5 in a counter-swirl layout achieved the highest THPP of 1.04, and the SAH with P/Dh = 0.6 and N = 5 in an anticlockwise arrangement yielded the lowest entropy generation ratio of 0.43 and the maximum ηⅡ of 18.16 %.

Identifying Immunological Markers for Bowel Cancer.

The role of immunological processes in the pathophysiology of colorectal cancer has received a lot of attention lately and has been extensively researched. Immune processes are significantly regulated by cytokines and antimicrobial peptides (AMP). Numerous studies have demonstrated the significance of cytokines in the prognosis and surveillance of malignant oncological illnesses. In group II, the blood serum concentration of Calprotectin was found to be greater in 13 patients (92.0 %) and lower in 1 patient (8.0 %) compared to control limits (χ = 24.27, p &lt; 0.001). The obtained results show that, in comparison to the control group, the concentration of Calprotectin rises statistically consistently by 3.5 times, with a coefficient of integrity of p &lt; 0.001. According to the data, there is a statistically significant rise in Calprotectin concentration (3.5 times higher than in the control group) with a p-value of less than 0.001. The average mathematical density of this indicator is 3.42 ± 0.48 pg/ml, the minimum density is 0.7 pg/ml, and the maximum thickness is 6.1 pg/ml.

Phantom validation of a novel RSA-based impingement metric to assess component-on-component impingement risk.

Component-on-component impingement in total hip arthroplasty may lead to post-operative complications including dislocation. Despite numerous clinical studies focusing on reducing this risk, assessment methods remain limited to qualitative radiography, finite element analysis, and cadaver studies. There is a need for more precise measurements of impingement in the research setting. We aimed to validate a novel RSA-based impingement metric to measure component-on-component impingement in vivo. A phantom experiment of a standard metal-on-polyethylene total hip system was performed. RSA examinations were performed as typical for a traditional weight-bearing RSA exam for large joints. The phantom was placed in 10 possible impinged positions and one neutral position. Double exposure radiographs were taken to measure repeatability. The closest distance between the skirt of the head and the inner circumference of the acetabular cup liner was measured to assess impingement risk. Distances between the closest point of the hood to the edge of the cup in 10 impinged positions ranged from 0.05 to 1.03 mm, with the average being 0.67 mm. In the neutral position, the distance measured is 11.02 mm. Excellent repeatability was observed, with a standard deviation of 0.03 mm with an r value of 0.09. A validated RSA-based risk metric was established to evaluate in vivo hip impingement. A 1 mm threshold may be proposed to define impingement where distances approaching 1.00 mm are at a greater risk of impingement. This simplified metric holds promise for upcoming clinical studies on component-on-component impingement.

Numerical study of heat transfer in circular pipe filled with porous medium

AbstractForced convection heat transfer was studied in a horizontally heated circular pipe with constant heat flux. Porous medium was created using 1 and 3 mm stainless-steel balls (porosity: 0.3690 and 0.3912). Reynolds numbers ranged from 3,200 to 6,500 based on pipe diameter, with heat flux rates of 6,250 and 12,500 W m−2. ANSYS Fluent simulated a 51.4 mm diameter, 5 mm thick, 304 mm long stainless-steel pipe. Results showed increased turbulence and eddy formation. Analysis revealed higher convective heat transfer coefficient, pressure drop, and Nusselt number with increasing Reynolds number. Nusselt number also increased with 1–3 mm ball diameter. 6% porosity increase reduced pressure drop by 84.4%. Nusselt number rose by 46.7% (Reynolds 3,200–6,500) and 4.36% (heat flux 6,250–12,500 W m−2).

Towards the use of natural thermal insulation on the exterior of vertical building walls in desert regions: A case study in the city of Bechar, Algeria

The use of natural-based exterior thermal insulation systems constitutes a significant challenge for achieving energy efficiency of construction. The purpose of this article is to propose new exterior thermal insulation solutions based on natural materials such as wood wool, cellulose wadding, expanded cork, hemp fiber, and sheep’s wool, in order to minimize energy consumption, address durability concerns, maintain thermal comfort, and promote the use of natural materials in thermal insulation system designs. The methodology followed consists of presenting a comparative numerical study of different exterior insulation techniques (ETI) using a dynamic thermal simulator for desert regions. The study evaluated ETI systems for vertical walls attached to a concrete block wall, including one EPS system with coating (wet process) and six systems with cladding (dry process). The results show that applying exterior insulation to walls using the two cladding systems based on hemp fiber and sheep wool resulted in a total reduction in building energy consumption of 42.21% and 42.81%, respectively. These results confirm the effectiveness of natural materials in improving the energy performance of buildings, particularly the system based on sheep wool.

Numerical study on the energy-harvesting performance of a semi-activated coupled-pitching hydrofoil in shear flows

A two-dimensional numerical model of a semi-activated coupled-pitching hydrofoil was established using the computational fluid dynamics software ANSYS Fluent. The kinematic response, hydrodynamic characteristics, and energy-harvesting performance of the hydrofoil in shear flow were investigated. The coupled-pitching hydrofoil achieved a stable limited-cycle passive-pitching motion and efficient energy harvesting in shear flows under various shear rates, pitching amplitudes, and reduced frequencies. The flow structures, pressure distributions, and hydrodynamic torque were analyzed to reveal the mechanism of the stable passive-pitching motion of the coupled-pitching hydrofoil in shear flow. The stable passive-pitching motion was dominated by the hydrodynamic torque, which was equivalent during the upward and downward strokes. Shear flow has a certain degree of influence on energy-harvesting efficiency. The energy-harvesting efficiency decreased with increasing shear rate. When the activated-pitching amplitude is small, the effect of shear rate on energy-harvesting performance was limited. The effect of shear rate was enhanced as the activated-pitching amplitude increased. The average relative difference in the energy-harvesting efficiency in the uniform and shear flows was 15 %, when the activated-pitching amplitude was 70° and the shear rate was 1.0. The peak value of the efficiency can reach 19.8 % when the shear rate was 1.0. The coupled-pitching hydrofoil is adaptable to shear flows. The results of this study provide valuable information for the application of coupled-pitching hydrofoils under real tidal flow conditions.