Increase In Strength Research Articles

Oxidation behavior and subsequent mechanical properties of SiC/BN/SiBCN composite after exposure to steam at high temperature

Despite its importance when considering jet engine environments, the behavior of ceramic matrix composites following high temperature exposure in steam has received much less attention than in air. The present study investigates the oxidation behavior and the corresponding mechanical properties of a SiC/BN/SiBCN composite after exposure to steam at 950°C, 1050°C, 1200°C and 1350°C for 30 h. The SiBCN matrix shows crack-filling behavior, whereby microcracks are filled with oxide hindering internal oxidation of the composite. The oxide layers formed on both the SiC fiber and the SiBCN matrix exhibit a double layer structure, with the outer layer being more porous. With increasing temperature, the BN interphase is consumed and replaced by borosilicate glass that bonds the fiber and matrix. This alters the debonding location from the fiber/BN interface to the BN/SiBCN matrix interface. Three-point bending test shows the composite retains good flexural strength and a tough failure response even after exposure to steam at 1350°C. Single fibre push-out test shows a slight increase in interfacial shear strength with increasing thermal exposure.

Investigation of mechanical and electrical properties of photopolymer nanocomposites reinforced with carbon‐based nanoparticles produced by digital light processing 3D printing technique

AbstractDigital Light Processing (DLP) techniques are being increasingly investigated to create advanced composite materials with improved properties by incorporating a variety of nanoparticles. In this study, the mechanical and electrical properties of photopolymer nanocomposite materials reinforced with carbon‐based nanoparticles produced by DLP were investigated. The nanocomposites were produced by incorporating varying proportions of Multi‐Walled Carbon Nanotubes (MWCNT), reduced Graphene Oxide (rGO), and combinations of Carbon Black and Carbon Nanotubes (CB/CNT) into the photopolymer matrix. The mechanical properties of the nanocomposites were assessed by tensile testing, while their electrical conductivity was determined using the four‐point probe technique. This study was the first to investigate the most effective concentrations of three distinct carbon‐based nanoparticles and the impact of their homogeneous distribution on the performance of composites with a holistic approach. The morphological analysis of the composites, conducted using optical microscopy and Scanning Electron Microscopy (SEM), revealed the critical role of nanoparticle distribution in determining composite properties. The findings indicate that the incorporation of nanoparticles at low proportions (up to 0.5 wt%) resulted in a significant improvement, with up to an 82% increase in the ultimate tensile strength of the photopolymer. Nevertheless, as the nanoparticle ratio increased, a rise in material brittleness and a decrease in mechanical strength were observed. On the other hand, electrical conductivity showed a significant increase when the percolation threshold was exceeded in the composites reinforced with MWCNT (0.5%wt) and CB/CNT (0.75%wt).Highlights The properties of DLP composites with carbon nanoparticles are investigated. SEM analysis shows nanoparticle dispersion's key role in composite performance. 0.5% rGO reinforcement boosts tensile strength by up to 82%. Conductivity surges at 0.5% MWCNT, surpassing the percolation threshold. High nanoparticle ratios increase composite brittleness.

Increasing set volume relative to baseline does not augment skeletal muscle adaptations when compared to maintenance of baseline training volume in recreationally trained individuals.

This study compared the effects of prescribing an increased number of sets relative to baseline (ITV) to a maintenance of baseline training volume (BTV), in previously trained individuals. Forty-two adults with more than 6months of elbow flexion resistance training experience had each arm randomized to either the ITV or BTV condition. Participants performed 2-weekly sessions of unilateral standing dumbbell elbow flexion exercise for 12weeks, 8 of which were supervised. Muscle thickness of the elbow flexors at 50, 60, and 70% the distance of the upper arm and one repetition-maximum (1RM) strength for the unilateral standing dumbbell elbow flexion exercise were assessed pre- and post-intervention. For the 50% site, there was no evidence that the changes were different between BTV and ITV [∆BTV vs ∆ITV (cm) = 0.022 (95% CI - 0.096, 0.140)]. However, there was evidence that both conditions observed a greater change compared to the control. For the 60% site, there was no evidence that the changes were different between BTV and ITV [∆BTV vs ∆ITV (cm) = - 0.010 (95% CI - 0.155, 0.96)]. However, there was evidence that both conditions observed a greater change compared to the control. For the 70% site, there was no evidence that the changes were different between BTV and ITV [∆BTV vs ∆ITV (cm) = 0.004 (95% CI - 0.092, 0.101)]. However, there was evidence that both conditions observed a greater change compared to the control. For changes in 1RM, there was evidence that the change was greater in the BTV [∆BTV vs ∆Control (kg) = 1.915 (95% CI 1.219, 2.611)] and ITV [∆ITV vs ∆Control (kg) = 1.780 (95% CI 1.084, 2.475)] conditions compared to control. Prescribing an increased dose of sets relative to baseline did not augment muscular adaptations when compared to a maintenance of BTV, in recreationally trained individuals. Both training conditions were similarly effective in promoting significant increases in muscle thickness and 1RM strength of the elbow flexors.

Strengthening of RC beams defected in shear using external bonded ribs made of aluminum tube sandwich filled with strain hardening cementitious composites

Installing Aluminum Tubes (ATs) filled with Strain Hardening Cementitious Composite (SHCC) on the sides of Reinforced Concrete (RC) beams for shear strengthening has not been studied before. These tests combine the advantages of aluminum material as a new construction material with the superiority of SHCC for shear treatment of RC beams. Additionally, this study is interesting because it provides a thorough assessment of the special composite system's ability to strengthen RC beams—a capability that hasn't been thoroughly investigated in the literature. With a particular emphasis on comprehending how various aluminum tube rib configurations—such as their orientation, length, and number—can affect the efficacy of the strengthening strategy, this investigation aims to evaluate the improvements in shear capacity, failure modes, and deformation behaviors. Conducted under a one-point loading scheme, the research analyzed eight strengthened RC beams alongside a reference beam to determine the impact of AT rib number and configuration on beam behavior under shear stress. Key findings indicate that diagonal AT ribs, optimally aligned with shear forces, significantly enhance shear strength by 19 %-48 %. This configuration effectively controls and limits the spread of shear cracks, with extended rib lengths halting crack propagation at varying extents—up to two-thirds of the shear span. Notably, vertical ribs demonstrated progressive increases in shear strength as the number of ribs increased, with enhancements of 18 %, 35 %, and 52 % for one, two, and three ribs, respectively. Furthermore, SHCC as a filler material played a pivotal role in these enhancements, leading to a 27 % increase in peak load capacity and a 54 % rise in deflection, compared to those without. One, two, and three vertical ribs showed increases in the ductility by 46 %, 143 %, and 222 %, respectively, while diagonal ribs exhibited the most substantial improvements, with one and two ribs increasing ductility by 158 % and 215 %, respectively.

Seismic Performance of Concrete Columns Reinforced with Hot-Rolled Thermo-mechanically Treated Steel Bars

ABSTRACT The details of experimental testing of full-scale reinforced concrete columns are presented in this paper. The columns were reinforced with hot-rolled thermo-mechanically treated bars with uncertain yield strength which influences (particularly) the splice length demand and column response to seismic loads. The testing was carried out using quasi-static cyclic or monotonic loading under a constant axial load to study the seismic behaviour of the columns. The parameters of the study included lap splices, cold joints and lateral load scenarios. The damage concentration was higher close to the end of the dowel bar (as opposed to the column base) for the lap-spliced columns subjected to cyclic loading due to larger slippage in the dowel bars. Conversely, the damage was the least in a similar column subjected to monotonic loading which also exhibited the largest lateral load capacity and highest ductility. The influence of shear distortion was insignificant on the column free-end deflection. The pre-peak stiffness and lateral load capacity were less for the lap spliced columns tested under cyclic loading as a result of deficient development length due to unintended increase in the rebar yield strength. The lateral load capacity of the column was uninfluenced by the cold joint at the column base although it reduced the column ductility by nearly 25% compared to a similar column without a cold joint.

Three-dimensional simulation of film boiling on a horizontal surface with magnetic field

This study conducts a numerical investigation into the three-dimensional film boiling of liquid under the influence of external magnetic fields. The numerical method incorporates a sharp phase-change model based on the volume-of-fluid approach to track the liquid–vapour interface. Additionally, a consistent and conservative scheme is employed to calculate the induced current densities and electromagnetic forces. We investigate the magnetohydrodynamic effects on film boiling, particularly examining the pattern transition of the vapour bubble and the evolution of heat transfer characteristics, exposed to either a vertical or horizontal magnetic field. In single-mode scenarios, film boiling under a vertical magnetic field displays an isotropic flow structure, forming a columnar vapour jet at higher magnetic field intensities. In contrast, horizontal magnetic fields result in anisotropic flow, creating a two-dimensional vapour sheet as the magnetic strength increases. In multi-mode scenarios, the patterns observed in single-mode film boiling persist, with the interaction of vapour bubbles introducing additional complexity to the magnetohydrodynamic flow. More importantly, our comprehensive analysis reveals how and why distinct boiling effects are generated by various orientations of magnetic fields, which induce directional electromagnetic forces to suppress flow vortices within the cross-sectional plane.

The dose–response of the Copenhagen adduction exercise on adductor strength in high-level youth hockey players: A three-arm randomised controlled trial

ABSTRACT The aim of this cluster-randomised controlled trial was to investigate the training and detraining effects of two different-volume Copenhagen Adduction Exercise (CAE) protocols on adductor squeeze strength. Thirty high-level rink hockey players (14 y.o.) were allocated to a warm-up low-volume (LVG), high-volume (HVG) protocol, or a control group. Adductor strength change was evaluated over a period of 11 weeks (eight of intervention + three of detraining). Adherence to the intervention and reporting of delayed onset muscle soreness (DOMS) were also collected. Adductor strength increase was significantly higher in HVG compared to LVG (+24%, mean difference 0.68 Nm/kg, p = 0.03) or controls (+34%, mean difference 0.9 Nm/kg, p = 0.009) at the end of the intervention. No significant strength drop was observed after three weeks of detraining in any group (−2.7% − 6%, p = 0.16 - 0.66), while HVG values were still significantly higher compared to controls (+27%, mean difference 0.71 Nm/kg, p = 0.027) at week 11. Compliance was identical in both intervention groups (LVG: 92.3%, HVG: 93.3%) and one case of DOMS was reported across 208 individual sessions (0.48%). The CAE protocol performed twice a week enhances squeeze strength to a further extent compared to one weekly session.

Immediate effect of ischemic loading on quadriceps muscle output by using a pneumatic cuff

IntroductionTransient ischemic conditioning (TIC) is a technique that involves short periods of ischemia followed by reperfusion, which may enhance muscle strength by increasing blood flow and improving energy supply to muscle fibers. This study aims to investigate the effect of TIC on quadriceps strength and examine its potential as a warm-up exercise in rehabilitation. MethodsFifteen healthy male participants underwent TIC on the quadriceps. Ischemia was induced for 5 min, followed by reperfusion. Muscle strength was assessed at baseline, 10 min post-intervention, and 20 min post-intervention. ResultsTIC applied to the quadriceps resulted in a significant increase in muscle strength compared to baseline (p ≤ 0.05). This increase in strength was observed at both 10 min and 20 min after the intervention. DiscussionThe results suggest that TIC can passively enhance muscle strength without inducing muscle fatigue. Therefore, TIC could be a valuable tool in rehabilitation where maintaining or improving muscle strength is essential. ConclusionTIC has shown potential as an effective method for improving muscle strength without causing fatigue. As such, it may be beneficial as a warm-up modality during rehabilitation, contributing to the recovery of motor function and muscle performance.

Mechanical behaviour and subsurface characteristics of Ti-6Al-4V subjected to electropulsing-assisted multiple laser shock processing impacts

Electropulsing (EP)-assisted laser shock peening (LSP), involving the synchronous application of EP and LSP to Ti-6Al-4V samples, represents an innovative surface strengthening technology. A comprehensive series of evaluations and examinations were conducted to thoroughly investigate the effects of EP-assisted multiple laser shock processing impacts on the mechanical behaviour and subsurface characteristics of the Ti-6Al-4V sample. The strength and ductility properties, fatigue performance, microstructure features in subsurface regions and deformation characteristics at various depths of the treated Ti-6Al-4V samples were investigated. The results revealed that as the number of impacts increased, a prominent multilayered structure, including a remelting layer, a severe plastic deformation region, and a plastic deformation-affected zone in the subsurface developed. The observed increase in strength can be attributed to grain refinement, an increase in dislocation density and the presence of high-density nanotwins within the subsurface layer. A high fatigue life was achieved by EP-assisted multiple LSP, with a ∼328.1 % increase compared with that of the as-received sample.The improvement in durability is mainly related to the enhanced subsurface structure acted as a barrier to crack propagation.

Effect of the Infill Density on 3D-Printed Geometrically Graded Impact Attenuators.

Three-dimensional printing is widely becoming prevalent in various industries, including the automotive sector. As this technology advances, critical structures subjected to impact loads may also be produced using additive manufacturing. A key parameter in this technique is the infill density of the printed geometry, which directly affects mechanical properties such as strength, stiffness, and ductility. Functionally graded layouts present themselves as one of the best techniques to design effective impact attenuators. The present work combines these techniques and parameters to evaluate the behaviour of geometrically graded impact attenuators produced through additive manufacturing, with different infill densities for polylactic acid (PLA) and polycarbonate (PC) materials. The results obtained show an increase in the mechanical strength for both materials and all the infill densities when compared to reference quasi-static results.

Research on the mechanical and thermal properties of potting adhesive with different fillers of h-BN and MPCM

Using packaging materials to reduce contact thermal resistance has become a promising method to solve the problem of insufficient heat dissipation capacity of electronic components. The purpose of this work is to optimize the mechanical and thermodynamic performance of potting adhesive using phase change microcapsules (MPCM) and hexagonal boron nitride nano-powder (h-BN) as thermal conductive fillers. The experimental results indicated that h-BN has a positive effect on the tensile strength of the potting adhesive, with a 7.1 % increase in tensile strength at a mass fraction of 30 %. However, the addition of MPCM will weaken the tensile strength of the potting adhesive. Adding MPCM and h-BN can both effectively improve the thermal conductivity of the potting adhesive: when the filler mass fraction is lower than 20 %, the potting adhesive with MPCM filler exhibits more strengthening capability than h-BN type; while with the continuous increase of filler mass fraction, the thermal conductivity of the potting adhesive with h-BN filler is better. The thermal buffering capacity of the potting adhesive significantly increases with the mass fraction of MPCM, while the effect of h-BN on thermal buffering capacity is not significant. In addition, the addition of h-BN and MPCM significantly improves the temperature uniformity of the potting adhesive.

Enhancing durability and strength of concrete through an innovative abrasion and cement slurry treatment of recycled concrete aggregates

The increasing demand for sustainable construction materials has driven significant interest in utilizing recycled concrete aggregates (RCA). However, the mechanical performance and durability of RCA are often compromised due to the presence of residual mortar. This study explores an innovative surface treatment approach combining abrasion and cement slurry coating to improve the properties of RCA and enhance the performance of recycled aggregate concrete (RAC). Recycled concrete aggregates were subjected to mechanical abrasion, followed by a cement slurry coating, resulting in the production of Surface-Treated Recycled Concrete Aggregates (STRCA). The study evaluates the impact of STRCA on the compressive strength, drying shrinkage, electrical resistivity, and chloride ion penetration resistance of concrete mixes with varying replacement ratios (25 %, 50 %, 75 %, and 100 %). Results revealed that the water absorption of RCA was significantly reduced from 5.35 % to 2.61 % following the treatment. STRCA 25 and STRCA 50 mixtures exhibited compressive strength increases of 30.16 % and 18.99 % at 7 days, and 29.37 % and 17.13 % at 28 days, respectively. Higher replacement levels (STRCA 75 and STRCA 100) resulted in strength reductions, with 3.91 % and 16.64 % decreases at 7 days. Drying shrinkage increased progressively with higher RCA content, showing 1.72 %, 10.91 %, 25.86 %, and 38.79 % increases at 28 days for STRCA 25, STRCA 50, STRCA 75, and STRCA 100, respectively. Electrical resistivity improved for lower replacement levels, with STRCA 25 showing a 3.41 % increase at 28 days, while STRCA 100 exhibited a 26.25 % reduction. The rapid chloride penetration test results showed that STRCA 100 had the highest resistance to chloride ion penetration, with a 22.72 % and 28.69 % increase in passed charge at 28 and 56 days, respectively, compared to the reference concrete. The findings indicate that surface-treated RCA can enhance the mechanical and durability properties of concrete, especially at lower replacement levels, making it a viable option for sustainable construction.

Mechanical properties and micro-mechanisms of geopolymer solidified salinized loess

Salinized loess exhibits poor engineering properties, including low strength, salt migration, and instability, due to the combined characteristics of loess and saline soil. This poses serious threats to the safety and stability of buildings, roads, and other infrastructure. To address this issue, this study aims to solidify salinized loess using geopolymer produced through alkali activation of industrial waste, including slag powder and fly ash. An orthogonal experimental design was used to systematically investigate the mechanical properties, microstructural characteristics, and solidification mechanism of geopolymer solidified salinized loess. The tests included unconfined compressive strength (UCS), direct shear, pH, scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD) to evaluate the influences of different factors on the solidification effect. The results showed that the sodium silicate solution modulus was the primary factor affecting the strength of solidified salinized loess, followed by the amounts of fly ash and slag powder. The Baumé degree (°Bé) had the least impact. Under the optimal conditions (1 modulus, 35 °Bé, slag powder and fly ash ratio of 1:0), the UCS of the sample at 28 days reached 3204.06 kPa, which increased by 16.32 times compared with the unsolidified sample. Lowering the modulus and increasing the proportion of slag powder and the Baumé degree increased the sample pH. Micro-analysis revealed that the strength increase was mainly due to the bonding of soil particles by gel substances (C-S-H, N-A-S-H, and C-A-S-H) formed during alkali activation, as well as the filling effect of unreacted slag powder and fly ash. The findings of this study provide valuable theoretical and practical insights for treating salinized loess in engineering, offering essential references for optimizing geopolymer solidifier ratios.

Increasing the Donor Strength of Alkenylphosphines by Twisting the C=C Double Bond

AbstractElectron‐rich phosphines play a crucial role in transition metal‐based homogeneous catalysis. While alkyl groups have traditionally been employed to increase the phosphine donor strength, recent studies have shown that zwitterionic functional groups such as phosphorus ylides can result in a further enhancement. Herein we report the concept of twisting a C=C double bond to introduce a zwitterionic substituent by the synthesis and application of N‐heterocyclic olefin phosphines with a sulfonyl substituent (sNHOP). This sulfonyl group enables the twisting of the olefin moiety due to steric and electronic stabilization of the carbanionic center. The resulting zwitterionic structure leads to a significant increase of the donor strength of the sNHOP ligands compared to conventional NHOP systems with a planar N‐heterocyclic olefin moiety. The potential of this new ligand platform for catalysis is demonstrated by its application in the gold‐catalyzed hydroamination and cyclo‐isomerization of alkynes. Here, the ligands outperform the original NHOP ligands suggesting favorable properties for future catalysis applications.

Increasing the Donor Strength of Alkenylphosphines by Twisting the C=C Double Bond.

Electron-rich phosphines play a crucial role in transition metal-based homogeneous catalysis. While alkyl groups have traditionally been employed to increase the phosphine donor strength, recent studies have shown that zwitterionic functional groups such as phosphorus ylides can result in a further enhancement. Herein we report the concept of twisting a C=C double bond to introduce a zwitterionic substituent by the synthesis and application of N-heterocyclic olefin phosphines with a sulfonyl substituent (sNHOP). This sulfonyl group enables the twisting of the olefin moiety due to steric and electronic stabilization of the carbanionic center. The resulting zwitterionic structure leads to a significant increase of the donor strength of the sNHOP ligands compared to conventional NHOP systems with a planar N-heterocyclic olefin moiety. The potential of this new ligand platform for catalysis is demonstrated by its application in the gold-catalyzed hydroamination and cyclo-isomerization of alkynes. Here, the ligands outperform the original NHOP ligands suggesting favorable properties for future catalysis applications.

Investigation of Impact Behaviour of Sisal Fiber Reinforced Phenol Formaldehyde Composites

Short Sisal fiber reinforced Phenol Formaldehyde resin composites are prepared with varied fiber lengths (5 mm and 10 mm) and for varied weight fraction (20%, 25% and 30%) of the fibers. Here in this work, Sisal fiber is used as reinforcement. Since it is abundantly available in nature and majority of it is getting wasted without being used as reinforcement in engineering applications. Over the last thirty years composite materials, plastics and ceramics have been the dominant emerging materials. The 10 mm fiber length reinforced composite shown improved mechanical properties than 5 mm fiber length reinforced composite. Increase in impact strength is seen when the fiber content in the composite is increased from 20% to 25% and 25% to 30%. The fiber strength, for different fiber lengths and fiber volume fraction, the work of fracture is proportional to the fiber length and fiber volume fraction. Although results show increment in impact strength with fiber volume fraction, proportionality is not demonstrated. This suggests that there are other mechanisms that affect the impact strength of the composites. Crack propagation is the predominant toughening mechanism in notched impact test. Improvement in impact strength characterizes that fibers as stress transferring medium are able to absorb impact energy effectively. Good interaction with crack increases the energy needed for further crack formation and propagation. The exceptional case could be due to low fiber content and relatively short fiber length so that the energy is not dissipated effectively. Weak interfacial bonding of natural fibers is mainly due to incompatibility of hydrophobic matrix and hydrophilic fiber. High moisture absorption causes dimensional changes of natural fibers as well.

Experimental research on mechanically and thermally activation of nano-kaolin to improve the properties of ultra-high-performance fiber-reinforced concrete

Abstract The rising demand for ultra-high-performance concrete (UHPC) necessitates innovations in sustainable materials. This study explores the substitution of ordinary Portland cement (OPC) with thermally and mechanically activated nano-kaolin in varying proportions from 0.5 to 0.25%. A uniform quantity of double-hooked end steel fibers was added to all the mixes. Activated nano-kaolin variants showed significant enhancement in UHPC properties. Specifically, UHPC with 0.20% thermally activated kaolin (B3-TAK-20) exhibited a 21.6% increase in compressive strength and a 25.5% increase in modulus of elasticity at 90 days, with the modulus of rupture doubling compared to the reference mix. These improvements are attributed to the amorphous nature of thermally activated nano-kaolin, resulting in a denser concrete matrix and reduced porosity. Beyond the optimal 0.20% kaolin replacement, an increase to 0.25% diminished compressive strength. Durability tests showed enhanced acid resistance, with only a 6.7% mass loss for the thermally activated nano-kaolin mix and a consistent reduction in water absorption by 14.4% as kaolin proportions increased from 0.5 to 0.25%. The study also noted a decrease in water absorption by 22.9 and 12.3% at 56 and 90 days, respectively, indicating the thermally activated nano-kaolin’s enhanced performance. This research underscores the potential of activated kaolin as a viable alternative to OPC, paving the way for more sustainable UHPC production.

HEAVY-DUTY CONCRETE WITH FROST RESISTANCE F400 WITH COMPLEX CHEMICAL ADDITIVES

The article presents the results of studies of the influence of complex chemical additives on the physical and mechanical properties of concrete, taking into account the curing conditions. It has been experimentally confirmed that the complex additive: the hyperplasticizer Hidetal GP-9-Alpha, 0,7% of the cement mass, and the air-entraining additive Hidetal P8, 0,05% of the cement mass, allows to obtain concrete with a denser structure, promotes equally active strength gain of con-crete in the early stages under air-dry curing conditions and under low-temperature heat and humidity treatment, at the age of 28 days under curing under heat and humidity treatment provides an increase in concrete strength by 15%. New experimental data are presented on the efficiency of the combined use of the hyperplasticizer Hidetal GP-9-Alpha and the air-entraining additive Hidetal P8 for obtaining concrete of class C32/40 with frost resistance grade F 400.

Optimization and sensitivity analysis of magnetic fields on nanofluid flow on a wedge with machine learning techniques with joule heating, radiation and viscous dissipation

PurposeIn this study, the flow of nanofluids (NFDs), consisting of water and copper nanoparticles over a wedge, is simulated. The analysis considers the effects of a magnetic field (MFD) and Joule heating (JOH). Variables such as nanoparticle volume fraction (NVF), Eckert number (EC), radiation, and wedge angle (BT) are also examined for their impacts on the Nu and Cf. Design/methodology/approachThe simulation utilizes the similarity method and the Keller box method, implemented through custom coding. Additionally, machine learning techniques are applied for sensitivity analysis and optimization of the results by varying the parameters. FindingsThe findings indicate that increasing the BT, NVF and MFD strength can elevate the average friction coefficient (Cf-m) by up to 42.8 %. Sensitivity analysis reveals that factors like BT and MFD significantly influence the Cf-m and Nu. An increase in MFD strength generally reduces the Nu-m. A larger BT substantially boosts the Nu-m; however, heightened JOH results in a sharp decline in the Nu. An increase in the EC leads to a decrease in the Nu-m. At low radiation parameter (RD) values, increasing this parameter reduces the Nu-m, whereas at higher values, it increases the Nu. Originality/valueThe key contribution of the article is the optimization and sensitivity analysis of NFD flow over a surface, considering the effects of a MFD, JOH, radiation, EC, and BT. This is done to achieve maximum heat transfer and minimum friction loss.

Modeling and analysis of heterogeneous traffic flow with mixed regular and connected human-driven vehicles considering driver stochasticity

This paper presents a novel microscopic modeling framework to explore the impact of driver stochasticity and other related factors on heterogeneous traffic flows, consisting of both regular human-driven vehicles (RHDVs) and connected human-driven vehicles (CHDVs). We apply the stochastic optimal velocity car-following model for RHDVs, while an extended version of the stochastic continuous car-following model, taking into account optimal velocity guidance and driver compliance, is devised for CHDVs. The stability of CHDV car-following model is examined theoretically and numerically. Simulation experiments are conducted to analyze the stochastic heterogeneous traffic flow properties (i.e. stability and safety) with the proposed microscopic modeling framework under diverse parameter settings including CHDV penetration rate, driver compliance, and driver stochasticity. Results show that traffic flow stability and safety improve with the increase in CHDV penetration rate and driver compliance but deteriorate as the driver’s stochasticity strength increases. CHDVs significantly enhance traffic stability when the CHDV penetration rate or driver compliance exceeds a certain threshold, typically ranging between 0.5 and 0.7. Additionally, there is an interaction between driver stochasticity and CHDV penetration rate in their effect on traffic flow stability, where the contribution of stochasticity to traffic oscillations first increases and then decreases as the penetration rate rises. When the penetration rate is between 0 and 0.4, the traffic risk in emergency situations can be significantly reduced as the penetration rate increases. These findings may guide the management and control strategies of heterogeneous traffic flow.