Ra Values Research Articles

Comprehensive analysis of heat transfer and pressure drop in square multiple impingement jets employing innovative hybrid nanofluids

This study presents a comprehensive analysis of heat transfer and pressure drop characteristics in square multiple impingement jets utilising a novel class of hybrid nanofluids. This study goes beyond the usual vertical impingement method by looking at the use of oblique impingement in a multiple impinging jet configuration with a hybrid nanofluid. Al2O3–Cu/water with different volume fractions (φhnf) such as 0.1%, 0.33%, 0.75%, and 1.0% are employed as a working fluid. The purpose of the study is to clarify the impact of the jet angle (β), the jet Reynolds number (Re), extended jet height (Ej), and different volume fraction (φhnf) on the heat transfer behaviours of the curved target surface. The jet Reynolds number varies from 8000 to 24,000, and five different jet angles (β = 15 °, 30°, 45°, 60°, 90 °) and three extended jet heights (Ej = 0.2H, 0.4H, and 0.6H) are adopted. Outcomes disclosed that the highest values of Re and φhnf greatly led to an increase in heat transfer rate and pressure drop of the system. It is uncovered that the heat transfer rate of binary hybrid nanofluids enhances with increasing volume fraction from for all jet angles and Re. Results also exposed that the angle of jet, which is 45°, gives a higher Nusselt number compared to other angles proposed in this study, and the maximum boost reaches 35%. Besides, despite the fact that reducing the height of the extended jet yields enhanced heat transfer rates in comparison to other methods, it concurrently results in an elevation in pressure drop. Finally, this research yielding insights that can be applied to improve the efficiency of heat transfer systems in practical applications.

Thermo-entropy analysis of water-FMWCNT nano-fluid flow in a backward-facing channel with obstacle

Thermo hydraulic analysis of nano-fluid flow phenomena through backward-facing channel has currently gained attention of the researchers, and is applied in a variety of engineering applications. Hydro-thermal properties of water/FMWCNT nano-fluid flow in a backward-facing channel embedded with an obstacle under uniform heat flux have been studied numerically with the variations in the values of Reynolds numbers ( Re ) , weight percentage of carbon nano-particle ( wt . % ) , and differently shaped obstacles. The governing equations (continuity, x-momentum, y-momentum, and energy) have been solved using the finite volume approach, and fluent software has been used to visualize the simulation results. Impact of various forms of obstacle (plane, elliptical, and triangular), the ratio of obstacle height to width (A/B), the ratio of obstacle pitch to width ( B 1 / B ) , wt . % , and the values of Re on the different rheological behaviour of nano-fluid flow have been investigated. For all the forms of obstacle configuration, the distributions of velocity streamlines, temperature contours, absolute pressure drop ( Δ p ) , average friction factor ( F ) , local Nusselt number ( Nu ( x ) ) , skin friction coefficients ( c f ( x ) ) , average Nusselt number ( N u avg ), and pumping power ( P ) have been demonstrated for several values of Re ( 1 , 50 and 150 ) , and wt . % ( 0 , 0.12 and 0.25 ) . For several values of Re and wt . % , generations of frictional entropy ( N frictional ) , thermal entropy ( N thermal ) , and Bejan number ( Be ) have been explored. It seems that the presence of obstacle, and the increase in the values of Re , wt . % causes the rise of the values of Δ p , P , and N u avg than the case of smooth channel. Moreover, at wt . % = 0.25 and Re = 150 , it has been found that the % increase in N u avg becomes 47.37 in the case of backward-facing channel with plane obstacle (A/B = 1) as compared to the case of smooth channel. Furthermore, at a constant value of wt . % it has been found that the generation of N thermal decreases but the generation of N frictional entropy increases with the rise in the values of Re .

Machinability and Surface Properties of Cryogenic Poly(methyl methacrylate) Machined via Single-Point Diamond Turning.

Poly(methyl methacrylate) (PMMA), with a glass transition temperature (Tg) over 100 °C, shows good mechanical and optical properties and has broad applications after being machined with single-point diamond turning (SPDT) at room temperature. Because of the high Tg, current efforts mostly focus on optimizing machining parameters to improve workpiece precision without considering the modification of material properties. Cryogenic cooling has been proven to be an effective method in assisting ultra-precision machining for certain types of metals, alloys, and polymers, but has never been used for PMMA before. In this work, cryogenic cooling was attempted during the SPDT of PMMA workpieces to improve surface quality. The machinability and surface properties of cryogenically cooled PMMA were investigated based on the mechanical properties at corresponding temperatures. Nanoindentation tests show that, when temperature is changed from 25 °C to 0 °C, the hardness and Young's modulus are increased by 37% and 22%, respectively. At these two temperature points, optimal parameters including spindle speed, feed rate and cut depth were obtained using Taguchi methods to obtain workpieces with high surface quality. The surface quality was evaluated based on the total height of the profile (Pt) and the arithmetic mean deviation (Ra). The measurement results show that the values of Pt and Ra of the workpiece machined at 0 °C are 124 nm and 6 nm, respectively, while the corresponding values of that machined at 25 °C are 291 nm and 11 nm. The test data show that cryogenic machining is useful for improving the form accuracy and reducing the surface roughness of PMMA. Moreover, the relationship between temperature, material properties and machinability weas established with dynamic mechanical analysis (DMA) data and a theoretical model. This can explain the origin of the better surface quality of the cryogenic material. The basis of this is that temperature affects the viscoelasticity of the polymer and the corresponding mechanical properties due to relaxation. Then, the material property changes will affect surface profile formation during machining. The experimental results and theoretical analysis show that cryogenically cooled PMMA has good machinability and improved surface quality when using SPDT compared to that at ambient temperature.

Self-etching primer versus hydrofluoric acid and air-abrasion: effects on flexural and resin bond strengths of resin-based CAD/CAM material

This study aimed to evaluate the effect of self-etching primer (Monobond Etch & Prime; MEP), hydrofluoric acid (HF), and air-abrasion (A) protocols on shear bond strength (SBS) of resin cement and flexural strength (FS) of nanoparticle-filled resin-based CAD/CAM material. Bar- and rectangular-shaped specimens (n = 130 for each) were obtained from a resin-based material (Cerasmart 270). The specimens were divided into 13 subgroups according to surface treatments: Control (C); HF for 60, 90, and 120 s; MEP for 60, 90, and 120 s; air-abrasion for 10, 15, and 20 s; air-abrasion followed by HF; air-abrasion followed by MEP; HF followed by MEP. Surface roughness (Ra) values were measured using a profilometer (Surftest SJ-210) by applying 9 readings per specimen. One specimen per group was examined by atomic force microscopy (AFM; Multimode 8) in a 20 μm × 20 μm area, and scanning electron microscopy (SEM; EVO LS-10) under ×1000 magnification. FS and SBS data were obtained using a universal test device (Marestek) at a crosshead speed of 1 mm/min. Air-abraded groups showed the highest Ra (A10: 1.331 ± 0.213; A15: 1.409 ± 0.110; A20: 1.491 ± 0.111; A + HF: 1.415 ± 0.138; A + MEP: 1.309 ± 0.071 μm) and the lowest FS values (A10: 122.59 ± 16.80; A15: 118.94 ± 11.74; A20: 117.22 ± 11.18; A + HF: 114.42 ± 18.09; A + MEP: 128.98 ± 19.74 MPa). FS values of HF- and/or MEP-applied groups were statistically similar to the control group (C: 167.37 ± 27.02; HF60: 186.74 ± 30.66; HF90: 162.79 ± 29.31; HF120: 184.11 ± 17.18; MEP60: 171.98 ± 29.65; MEP90: 162.49 ± 20.38; MEP120: 173.55 ± 22.50; HF + MEP: 175.09 ± 21.64 MPa). SBS values of MEP-applied groups were higher than those of HF-etched groups with the same duration. Significant differences in SBS values were found after etching protocols with different durations (HF60: 4.14 ± 0.64; HF90: 4.48 ± 0.33; HF120: 6.76 ± 1.65; MEP60: 6.24 ± 1.23; MEP90: 9.92 ± 1.25; MEP120: 10.22 ± 1.27 MPa). Prolonged MEP application (90 s and 120 s) can be the preferred surface treatment for resin-based CAD/CAM materials. However, air-abrasion may adversely affect its mechanical properties.

Steady and Unsteady Dynamics of Magneto-Nanofluidic Flow in a Bottom-Heated Top-Cooled Recto-Triangular Thermal System

This work numerically explores the evolution flow features during the journey through unsteady to steady dynamics in a magneto-nanofluidic thermal system of recto-triangular shape. This system, which is partially heated using the triangular surface and employs a top-cooling configuration, features an upper rectangular and a lower triangular part. The study addresses laminar flow for various Rayleigh numbers (Ra) up to 105 considering uniform magnetic fields at different inclination angles and utilizing a 0.1% nanoparticle concentration (fixed) CuO-water nanofluid along with a finite element-based solver. The results reveal the formation of multi-vortical structures with varying numbers of circulation cells. The most important observation is the transformation of cells from a four-cell configuration to a one-cell configuration, and finally to a two-cell configuration as Ra changes from 103 to 104 to 105 without a magnetic field. The one-cell structure sustains over a narrow range of Ra and is sensitive to the Hartmann number (Ha). The inclined magnetic fields have a severe impact on the flow structure. Starting from a quiescent state and progressing through the unsteady flow stages, the system rapidly reaches a steady state under different temperature differences (simulated by Ra), except for a few exceptions of Ra and Ha values. The analysis of the unsteady stages of flow development provides deeper insights into the dynamics of multi-cellular flows.

Entropy generation for thermo-magnetic fractional order convective flow in complex porous enclosures: a numerical study

PurposeThis study aims to analyze the impact of fractional derivatives on heat transfer and entropy generation during transient free convection inside various complex porous enclosures, such as triangle, L-shape and square-containing wavy surfaces. These porous enclosures are saturated with Cu-water nanofluid and subjected to the influence of a uniform magnetic field.Design/methodology/approachIn the present study, Darcy’s model is used for the momentum transport equation in the porous matrix. Additionally, the Caputo time fractional derivative is introduced in the energy equation to assess the heat transfer phenomenon. Furthermore, the total entropy generation has been computed by combining the entropy generation due to fluid friction (Sff), heat transfer (Sht) and magnetic field (Smf). The complete mathematical model is further simulated using the penalty finite element method, and the Caputo time derivative term is approximated using the L1 scheme. The study is conducted for various ranges of the Rayleigh number (102≤Ra≤104), Hartmann number (0≤Ha≤20) and fractional order parameter (0<α<1) with respect to time.FindingsIt has been observed that the fractional order parameter α governs the characteristics of entropy generation and heat transfer within the selected range of parameters. The Bejan number associated with heat transfer (Beht), fluid friction (Beff) and magnetic field (Bemf) further demonstrate the dominance of flow irreversibilities. It becomes evident that the initial evolution state of streamlines, isotherms and local entropy varies according to the choice of α. Additionally, increasing Ra values from 102 to 104 shows that the heat transfer rate increases by 123.8% for a square wavy enclosure, 7.4% for a triangle enclosure and 69.6% for an L-shape enclosure. Moreover, an increase in the value of Ha leads to a reduction in heat transfer rates and entropy generation. In this case, Bemf→1 shows the dominance of the magnetic field irreversibility in the total entropy generation.Practical implicationsRecently, fractional-order models have been widely used to express numerous physical phenomena, such as anomalous diffusion and dispersion in complex viscoelastic porous media. These models offer a more accurate representation of physical reality that classical models fail to capture; this is why they find a broad range of applications in science and engineering.Originality/valueThe fractional derivative model is used to illustrate the flow pattern, heat transfer and entropy-generating characteristics under the influence of a magnetic field. Furthermore, to the best of the author’s knowledge, a fractional-derivative-based mathematical model for the entropy generation phenomenon in complex porous enclosures has not been previously developed or studied.

Evaluating the Efficacy of Continuous Water-Cooling 115-Watt 6.78-MHz Monopolar RF Therapy for Fine Wrinkle Reduction.

Cosmetic procedures using radiofrequency (RF) technology have garnered significant attention as noninvasive approaches to skin rejuvenation and wrinkle reduction. This study investigates the efficacy of RF therapy in enhancing skin texture, firmness, and appearance. By harnessing the 6.78-MHz "VolNewMer" RF device, skin aging concerns, particularly in terms of skin roughness, laxity, and wrinkles, can be treated. This study engaged a cohort of 50 participants seeking wrinkle reduction and skin-lifting treatments. Employing noninvasive methods, the efficacy of RF therapy was evaluated immediately posttreatment and 1-month posttreatment. Skin roughness was quantified using a computer-based analysis of standardized 3D scanner images, capturing uniform lighting and angles to ensure accurate measurements. Among the 45 participants who completed the study, significant improvements in skin roughness were observed. The average roughness (Ra) value decreased from 16.71 to 11.88 arbitrary units immediately posttreatment, signifying a 28.42% enhancement. At the 1-month follow-up, the Ra value further decreased to 12.33 arbitrary units, reflecting a sustained 26.23% improvement. However, 16 participants exhibited even greater improvements at 1 month than immediate. RF therapy's profound impact on skin tightening and rejuvenation is rooted in its ability to trigger immediate collagen contraction, bolstering skin elasticity. The dual-phase process of immediate and delayed skin improvement underscores the intricate interplay between thermal stimulation and collagen remodeling. Optimal energy levels and controlled endpoint monitoring ensure safe and effective RF treatments. The use of the VolNewMer device tips and sliding technique contributes to patient comfort and treatment precision.

Integrating response surface methodology and machine learning for analyzing the unconventional machining properties of hybrid fiber‐reinforced composites

AbstractThe aim of this investigation was to delve into the impact of abrasive water jet machining (AWJM) process variables on the surface roughness (Ra) and kerf angle (Ka) of hybrid fiber‐reinforced polyester composites. Utilizing both response surface methodology (RSM) and artificial neural network (ANN) prediction models, the study sought to optimize the input parameters for abrasive water jet machining, specifically in the context of paddy straw and PALF‐reinforced polyester hybrid composites. The process parameters targeted for optimization included the abrasive flow rate, traverse rate, and standoff distance during AWJM. The investigation identified an optimal combination of AWJM parameters that effectively meets the practical requirements for machining hybrid fiber‐reinforced polyester composites. According to the RSM, the suggested optimal values for the process parameters are an abrasive flow rate set at 300 g/min, traverse speed at 110 mm/min, and standoff distance at 1 mm. The ANN exhibited robust predictive capabilities, achieving high R2 scores of 0.932 and 0.962 for surface roughness and kerf angle, respectively. To enhance the performance of abrasive water jet machining and minimize surface roughness and kerf angle, the researchers conducted an optimization of the process parameters. Subsequently, confirmation experiments were executed to validate the predictive model and fine‐tune the set of process parameters for practical application.Highlights Investigated AWJM impact on Ra value and kerf angle of hybrid composites. Used RSM and ANN models for parameter optimization in biocomposite. Optimal AWJM parameters: AFR (300 g/min), TS (110 mm/min), and SOD (1 mm). ANN showed strong predictions: R2 scores 0.932 (Ra) and 0.962 (Ka). Confirmation experiments validated the predictive model for applications.

Uterine Arteriovenous Malformation, Grey- Scale and Colour Doppler findings: A Case Report and Review

Introduction: Uterine arteriovenous malformations can either be congenital or acquired and are rare vascular disorders seen in women of child bearing age, with varied presentation. The clinical features range from being asymptomatic to life threatening haemorrhage. Imaging, particularly grey scale and color Doppler ultrasonography play a major role in the prompt diagnosis of this condition as the findings are useful when differentiating between the types as well as in planning the management of these patients. Objectives: To make a report of a rare case of arteriovenous malformation of the uterus in a young female patient with a review of relevant literature as well as to highlight the importance of Colour Doppler ultrasonography in the evaluation of uterine lesions. Case Presentation: The case is of a 36year old female patient with a 2 years history of amenorrhoea following multiple sessions of dilatation and curettage. She also had chemotherapy due to choriocarcinoma. Pregnancy test was negative. Pelvic ultrasound scan done showed multiple cystic tubular spaces that were hypervascular on colour Doppler interrogation. High velocities and low RI values were recorded. Conclusion: Uterine arteriovenous malformations (AVMs) are important rare vascular disorders of the uterine vessels that need to be recognized early on imaging for appropriate management to be instituted.

Incompressible smoothed particle hydrodynamics solutions of double diffusion of nanoparticle-enhanced phase change materials in vertical mounted circular cylinders

The scheme of incompressible smoothed particle hydrodynamics (ISPH) method is developed to solve the time-conformable systems that control the double diffusion of nanoparticle-enhanced phase change materials (NEPCM) inside two circular cylinders saturated by a porous medium. The use of the time-conformable operator in the ISPH approach for addressing the double diffusion of NEPCM in a new domain is what distinguishes this work. This investigation revealed a comprehensive rate of change that impacts the quickening and slowdown of the monotonicity for the nonlinear systems. The physical parameters are time-conformable operator α , time parameter τ , nanoparticles parameter ϕ , Hartmann number Ha , thermal radiation parameter Rd , Darcy parameter Da , Rayleigh number Ra , and fusion temperature θ f . The principal outcomes of the numerical simulations revealed that the nanofluid flow is slowing down by an augmentation in ϕ , Ha , and Rd . The Rayleigh number is working well in enhancing the nanofluid flow and thermosolutal convection within the two circular cylinders. As a result, variable values of Ra are affecting the phase change material. The fusion temperature parameter controls the position/intensity of the phase change material within the two circular cylinders. Besides, the numerical results indicate the significance of α on the transition process of reaching the steady state. The thermosolutal convection and nanofluid speed are varied with the changes on the time-conformable derivative.

Heavy metals contamination and ecological risks in agricultural soils of Uşak, western Türkiye: a geostatistical and multivariate analysis.

This research aimed to determine and evaluate the concentrations ofAs, Cu, Hg, Ni, and Pb, and the physicochemical properties of 48 agricultural soil samples, to identify potential ecological risks and their sources associated with heavy metals contamination in Usak, western Türkiye. Various methods were used to assess ecological risks, including geoaccumulation index (Igeo), enrichment factor (EF), degree of contamination (Cdeg), potential ecological risk (RI), and pollution load index (PLI). The heavy metals concentrations ranged from 4 to 61mg/kg for As, 8-48mg/kg for Cu, 0.01-0.06mg/kg for Hg, 30-813mg/kg for Ni, and 4-30mg/kg for Pb. The mean As and Ni concentrations were much greater than Earth's crustal average, the world's mean values, and mean values from many other emerging countries. Igeo and EF values for As, Ni, and Pb indicate various degrees of contamination. Cdeg values show that 96% of the study area is affected to some degree by contamination. For RI values, 38% indicate ecological risks ranging from moderate to considerable degrees. PLI values show that 75% of the agricultural soils are moderately polluted. Spatial distribution maps of Cdeg, RI, and PLI show that the northeastern and southwestern parts of the study area have been polluted to different levels by As, Ni, and Pb. Industrial activities and excessive use of fertilizers, pesticides, fungicides, and herbicides were identified as major sources of heavy metals contamination in the agricultural soils of Uşak.

Parametric optimization to establish eco-friendly nanofluid minimum quantity lubrication (NMQL) practice for turning superalloy Inconel 718

Purpose The purpose of this paper, an experimental study, is to investigate the optimal machining parameters for turning of nickel-based superalloy Inconel 718 under eco-friendly nanofluid minimum quantity lubrication (NMQL) environment to minimize cutting tool flank wear (Vb) and machined surface roughness (Ra). Design/methodology/approach The central composite rotatable design approach under response surface methodology (RSM) is adopted to prepare a design of experiments plan for conducting turning experiments. Findings The optimum value of input turning parameters: cutting speed (A), feed rate (B) and depth of cut (C) is found as 79.88 m/min, 0.1 mm/rev and 0.2 mm, respectively, with optimal output response parameters: Vb = 138.633 µm and Ra = 0.462 µm at the desirability level of 0.766. Feed rate: B and cutting speed: A2 are the leading model variables affecting Vb, with a percentage contribution rate of 12.06% and 43.69%, respectively, while cutting speed: A and feed rate: B are the significant factors for Ra, having a percentage contribution of 38.25% and 18.03%, respectively. Results of validation experiments confirm that the error between RSM predicted and experimental observed values for Vb and Ra is 3.28% and 3.75%, respectively, which is less than 5%, thus validating that the formed RSM models have a high degree of conformity with the obtained experimental results. Practical implications The outcomes of this research can be used as a reference machining database for various metal cutting industries to establish eco-friendly NMQL practices during the turning of superalloy Inconel 718 to enhance cutting tool performance and machined surface integrity. Originality/value No study has been communicated till now on the turning of Inconel 718 under NMQL conditions using olive oil blended with multi-walled carbon nanotubes-based nanofluid. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-10-2023-0317/

Diagnostic performance of spectral Doppler in acute appendicitis with an equivocal Alvarado score.

This study aims to evaluate the added value of duplex Doppler examination to the routinely graded compression grayscale ultrasound (US) for patients with suspected acute appendicitis (AA) in correlation with surgical management outcomes. The study lasted from January 2020 to March 2021. Throughout that period, patients who had suspected appendicitis were included with a visible appendix in the grayscale US. These patients were categorized clinically based on Alvarado's score. They underwent graded compression grayscale US of the appendix and duplex Doppler study. Subsequently, they were assigned for non-contrast multislice computed tomography (MSCT) according to Alvarado's score and underwent either emergency appendicectomy or conservative clinical management afterward. A Student's t-test was used to determine if there were significant differences in the mean values between the groups. The diagnostic performance of spectral Doppler US for the diagnosis of AA was depicted. Eighty-four patients with visualized color flow in the appendicular Doppler US were enrolled, with 60 (71.4%) having AA, and 24 (28.6%) not having appendicitis. Spectral Doppler criterion of PSV greater than 8.6 cm/s demonstrated a high sensitivity of 91.67% and specificity of 77.78% for patients with Alvarado score ranging from 4 to 7, and appendiceal MOD ranging from 6 to 8 mm, while a discriminatory criterion of RI greater than 0.51 had a high sensitivity of 100% and a relatively lower specificity of 66.67%. The patients with AA have significantly higher point PSV and point RI values than those without AA and are especially useful in equivocal patients whose MODs and Alvarado scores are in the diagnostically equivocal ranges of 6-8 mm and 4-7, respectively, with the point PSV and RI demonstrating negative predictive value 87.5% and 100%.

Effect of C2H2 flow rate on microstructure, properties, and application in micro-drilling of a-C:H films deposited by PECVD

The drilling of printed circuit board (PCB) using micro-drills is an important processing method in modern industry. A protective film with good lubricating and anti-wear properties is generally applied to improve the processing problems of micro-drills during operation. In this study, the effects of C2H2 flow rate on the microstructure, mechanical, and tribological properties of a-C:H films deposited by plasma enhanced chemical vapor deposition (PECVD) technique were investigated. The results showed that when the C2H2 flow rate was low, varying the flow rate had little effect on the microstructure of the prepared a-C:H films. However, when the C2H2 flow rate was greater than 210 sccm, the increase in flow rate caused large particles of carbon clusters to aggregate on the surface of a-C:H films, which resulting in an increase Ra value. Not only did it reduce the adhesion between the film and the substrate, but it also deteriorated the mechanical and tribological properties of the a-C:H film produced. In addition, a-C:H films were also deposited on the micro-drill, and were used for drilling tests on the PCBs to evaluate its servce capability. The optimal parameters of a-C:H film deposited on the micro-drill surface were obtained by observing the morphology of the micro-drill surface after drilling and the hole accuracy statistics. The results showed that a-C:H film deposited on the surface of the micro-drill showed the best machining performance when the C2H2 flow rate was 180 sccm. The surface wear of micro-drill was minimal, the entanglement of tangled chips was minimal. The value of the process capability index (CPK) after 500, 1000, and 2000 drilling of PCB boards was 5.95, 4.33, and 3.15 respectively, which showed the highest drilling accuracy. This is mainly attributed to the better overall properties of the a-C:H films prepared at C2H2 flow rate of 180 sccm, such as lower surface roughness, lowest residual stress, higher hardness, better adhesion, and lower friction coefficient.

Impaired plasma glucose clearance is a key determinant of fasting hyperglycemia in people with obesity.

The objective of this study was to evaluate the relative importance of the basal rate of glucose appearance (Ra) in the circulation and the basal rate of plasma glucose clearance in determining fasting plasma glucose concentration in people with obesity and different fasting glycemic statuses. The authors evaluated basal glucose kinetics in 33 lean people with normal fasting glucose (<100 mg/dL; Lean < 100 group) and 206 people with obesity and normal fasting glucose (Ob < 100 group, n = 118), impaired fasting glucose (100-125 mg/dL; Ob 100-125 group, n = 66), or fasting glucose diagnostic of diabetes (≥126 mg/dL; Ob ≥ 126 group, n = 22). Although there was a large (up to three-fold) range in glucose Ra within each group, the ranges in glucose concentration in the Lean < 100, Ob < 100, and Ob 100-125 groups were small because of a close relationship between glucose Ra and clearance rate. However, the glucose clearance rate at any Ra value was lower in the hyperglycemic than the normoglycemic groups. In the Ob ≥ 126 group, plasma glucose concentration was primarily determined by glucose Ra, because glucose clearance was markedly attenuated. Fasting hyperglycemia in people with obesity represents a disruption of the precisely regulated integration of glucose production and clearance rates.

Magnetic field effect on mixed convection flow inside an oval-shaped annulus enclosure filled by a non-Newtonian nanofluid

The phenomenon of flow around a static or rotating circular cylinder has significant applications in various engineering fields, such as building, bridge, and structure engineering. It can be used to control flow-induced vibration, blowing or suction, moving surfaces, acoustic thriller, and synthetic jet. Additionally, there is a need to enhance heat transfer rates in many life and industrial applications, including cavity shape enhancement, heating or cooling spread inside a cavity, heat dissipation in electronic devices, thermal mixing in storage units, solar collectors, desalination, and journal bearing lubrication. This study explores the effect of a horizontal magnetic field and a rotating inner circular cylinder on mixed convection within a two-dimensional oval-shaped enclosure filled with a non-Newtonian nanofluid. The Galerkin Finite Element Method (GFEM) is utilized for analysis, with the enclosure undergoing differential heating and cooling on the inner cylinder wall and the enclosure wall, respectively. The nanofluid consists of water infused with copper nanoparticles. The study explores various simulation parameters, including the Richardson number (Ri), Hartmann number (Ha), the inclination angle of the enclosure (β), power-law index (n), circle center eccentricity (e), and nanoparticles volume fraction (φ). It has been observed that as the Ha and n index increase for different Ri values, a wavy trend in local Nusselt number (Nu) profiles along the heat source surface is observed. Additionally, the heat transfer rate decreases with increasing Ri for various combinations of Ha and n index. Under specific conditions, such as Ri = 0.001, Ha = 60, e = 0, φ = 0.09, and β = 90, the results show that, compared to a Newtonian fluid (n = 1), the heat transfer rate exhibits percentage gains of approximately 6.31% for a pseudo-plastic fluid (n = 0.6) and 8.47% for a Dilatant fluid (n = 1.4). The convective heat transfer was significantly enhanced when the eccentricity of the cylinder was positioned in the lower or upper regions of the oval-shaped enclosure, particularly at e = - 0.3. The highest heat transfer rates were observed at β = 60 and 240.

Facile synthesis of UV-curable fluorosilicone polymers and coatings with good corrosive resistance on account of the reaction of disulfide bonds with vinyl groups

A new UV curing strategy is introduced into the curing field of fluorosilicone polymers. This strategy is predicated on the reaction of sulfur radicals generated from disulfide bonds with vinyl groups under the presence of UV light. Here, we engineered and synthesized a kind of novel fluorosilicone polymers (FS-SS) with disulfide bonds and vinyl groups. The disulfide bonds contained in FS-SS undergo photocleavage under ultraviolet irradiation, generating sulfide radicals, which can interact with vinyl groups to complete the curing reaction. Subsequently, the UV curing behavior of coatings on the basis of the novel polymers and photo-initiator 1173 was investigated by FT-IR spectroscopy and a possible UV-curable reaction mechanism based on disulfide bonds and vinyl groups was proposed. The results showed that curing reactions based on disulfide bonds and vinyl groups can reach a relatively high degree of reaction in a short period of time in terms of reaction rate. However, the lower conversion rate of the reaction may be due to the fact that the sulfur radicals generated by disulfide bonds are more inclined to form disulfide bonds rather than undergo addition reactions with vinyl groups. Subsequently, a series of fluorosilicone coatings with good optical transparency (transmittance above 90 %), good hydrophobicity (the lowest value of surface energy is 21.54 mN/m), lower roughness value (Ra values was in the region of 2.24 nm– 12.2 nm) and high temperature resistance were prepared by utilizing this curing strategy. Furthermore, the applicable experiment of fluorosilicone coatings to protect tinplate as anti-corrosive coatings was also performed. The corrosive resistance results formalize its practical value for possible application as preventive coatings.

Evaluation of the machinability performance of PH 13-8 Mo maraging steel used in the aerospace industry

This study focused on investigating the impacts of machining parameters on cutting force (Fc), surface roughness (Ra), cutting power (Pc), and specific cutting energy (SCE) and determining optimum machining parameters in turning PH 13-8 Mo stainless steel. For this purpose, an experimental design was set with Taguchi's L32 orthogonal array by identifying cutting parameters such as cutting speed (Vc), feed rate (f), and depth of cut (ap) at different levels. The turning tests were carried out on the CNC lathe using a coated carbide cutting tool under dry-cutting conditions. Signal/Noise (S/N) ratio and analysis of variance (ANOVA) were used to determine the impacts of cutting parameters on Fc, Ra, Pc, and SCE values obtained after turning experiments. In addition, regression analysis was performed to identify the correlation between Fc, Ra, Pc, and SCE and cutting parameters through linear and quadratic regression models. The main findings of the study are that the lowest Fc (A1B1C3), Ra (A1B1C4), Pc (A1B1C1) and SCE (A2B4C3) values were measured at 287.8 N, 0.59 µm, 697.16 W and 1549.55 J/mm3 in turning PH 13-8 Mo martensitic stainless steel. ANOVA, the most important process parameter affecting Fc, Ra, Pc, and SCE was feed rate at the rate of 85.57%, 84.93%, 71.10% and 60%. It was observed that the mathematical model findings obtained with the test results are in good agreement. In general, wear mechanisms such as adhesion, BUE, chips, crater, notch, fracture, and chipping on the cutting tool were detected in the turning of PH 13-8 Mo stainless steel.

Assessment of metal pollution and effects of physicochemical factors on soil microbial communities around a landfill

The physicochemical properties, chemical fractions of six metals (Cu, Zn, Pb, Cd, Cr, and Mn), and microbial communities of soil around a typical sanitary landfill were analyzed. The results indicate that soils around the landfill were from neutral to weak alkalinity. The contents of organic matter (OM), total nitrogen (TN), total phosphorous (TP), and activities of catalase, cellulase, and urease were significantly higher in landfill soils than those in background soils. Negative correlations were found between pH and metals. Cr was the dominant metal. Cu, Pb, Cr, and Mn were accumulated in the nearby farmland soils. Cd had the highest percentage of exchangeable fraction (33.7%−51.8%) in landfill and farmland soils, suggesting a high bioavailability to the soil environment affected by the landfill. Pb, Cr, and Mn existed mostly in oxidable fraction, and Cu and Zn were dominant in residual fraction. There was a low risk of soil metals around the landfill based on the RI values, while according to RAC classification, Cd had high to very high environmental risk. The MisSeq sequencing results showed that Actinobacteria, Proteobacteria, Chloroflexi, and Acidobacteria were the dominant phyla of bacteria, and the most abundant phylum of fungi was Ascomycota. The NMDS analysis revealed that the landfill could influence soil fungal communities more intensely than bacterial communities. TN, cellulase, and bioavailable metals (Pb-Bio and Cr-Bio) were identified to have main influences on microbial communities. Pb-Bio was the most dominant driving factor for bacterial community structures. For fungi, Pb-Bio was significantly negatively related to Olpidiomycota and Cr-Bio had a significantly negative correlation with Ascomycota. It manifests that bioavailable metals play important roles in assessing environmental risks and microbial community structures of soil around landfill.

Fabrication of high aspect ratio grooves on aluminium nitride by laser and chemical milling enhanced micro milling

Aluminium nitride (AlN) ceramic is a typically difficult-to-machine material used in electronic packaging. Laser and chemical milling enhanced micro milling (LCMEM), a high-quality and efficient processing method for AlN, is proposed in this study. Rough machining is completed by repeated alternating laser ablation and chemical removal; the final finish is achieved by micro milling (MM). To achieve precise laser and chemical milling parameters based on the target structure, a laser and chemical milling (LCM) prediction model is established and verified; this can be used to predict the morphology of the grooves after LCM. The change trend of the grooves after LCM with the laser parameters is investigated. It was found that LCMEM can improve the surface quality by 60 %, and an optimal finishing surface with a surface roughness Ra value of 54 nm can be obtained when the feed per tooth is 0.4 µm/z. Lastly, this study uses LCMEM to produce a high aspect ratio groove with aspect ratio of 2.5 and depth of 1250 µm. Compared with conventional MM, LCMEM reduces the allowance of MM by 71.95 %, improves the groove accuracy, and reduces tool wear.