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Objective: The current systematic review and meta-analysis assessed the prevalence of central precocious puberty (CPP) throughout the novel coronavirus disease 2019 (COVID-19) pandemic. Design: A systematic review and meta-analysis were carried out following the principles outlined by the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA, 2020). Data sources: PubMed, Embase, Web of Science, and WANFANG databases were searched from January 1, 2019, to March 30, 2023. Eligibility criteria for selecting studies: (1) children and adolescents ≤ 15 years; (2) studies with the outcome of frequency of central precocious puberty, measured prior to and throughout the COVID-19 pandemic; (3) a novel CPP diagnosis was created depending on all of the following criteria: girls with a chronological age < 8 years and boys with a chronological age < 9 years at the onset of symptoms, basal luteinizing hormone (LH) levels > 0.3 UI/L, and/or GnRH-stimulated peak LH levels > 5 IU/L. Data extraction and synthesis: The process of extracting data and evaluating the likelihood of bias was carried out by two independent reviewers. The data were pooled employing the generic inverse-variance method and presented as mean differences (MDs) with 95% CIs. The evaluation of heterogeneity was conducted employing the Cochran Q statistic, and the degree of heterogeneity was measured employing the I2 statistic. Results: This meta-analysis included 17 studies. In contrast to the same period prior to the COVID-19 pandemic, the occurrence of CPP elevated (OR = 2.57; 95% CI, 1.85–3.56). Moreover, body mass index standard deviation score (BMI SDS) differences between CPP patients prior to COVID-19 and throughout the pandemic follow-up was 0.12 (95% CI − 0.01 to 0.25 P = 0.06). Conclusion: Overall, CPP frequency significantly elevated throughout the COVID-19 pandemic. Given the restricted number of cohort investigations in this meta-analysis, additional research may be conducted on larger groups of children in order to establish a correlation between the observed rise in precocious puberty and specific pathogenic factors. [ABSTRACT FROM AUTHOR]

The basal texture of traditional magnesium alloy AZ31 is easy to form and exhibits poor plasticity at room temperature. To address these problems, a multi-micro-alloyed high-plasticity Mg–1.8Zn–0.8Gd–0.1Ca–0.2Mn (wt%) alloy was developed using the unique role of rare earth and Ca solute atoms. In addition, the influence of the annealing process on the grain size, second phase, texture, and mechanical properties of the warm-rolled sheet at room temperature was analyzed with the goal of developing high-plasticity magnesium alloy sheets and obtaining optimal thermal-mechanical treatment parameters. The results show that the annealing temperature has a significant effect on the microstructure and properties due to the low alloying content: there are small amounts of larger-sized block and long string phases along the rolling direction (RD), as well as several spherical and rodlike particle phases inside the grains. With increasing annealing temperature, the grain size decreases and then increases, and the morphology, number, and size of the second phase also change correspondingly. The particle phase within the grains vanishes at 450°C, and the grain size increases sharply. In the full recrystallization stage at 300–350°C, the optimum strength-plasticity comprehensive mechanical properties are presented, with yield strengths of 182.1 and 176.9 MPa, tensile strengths of 271.1 and 275.8 MPa in the RD and transverse direction (TD), and elongation values of 27.4% and 32.3%, respectively. Moreover, there are still some larger-sized phases in the alloy that influence its mechanical properties, which offers room for improvement. [ABSTRACT FROM AUTHOR]

The carbon emitted by vehicles traveling on curved roads is greatly affected by the alignment of the route, yet the mechanism behind this is not yet clear, leading to current horizontal alignment designs being unable to avoid this problem. To clarify the principles and indicator thresholds of low-carbon design for planar geometry, this study takes the carbon emission of traveling on curved routes as the research object, and establishes a relationship model between carbon emissions and design indicators based on the principles of vehicle dynamics and kinematics. Field tests were conducted to validate the quantitative relationship model. The model shows that both radius and superelevation are negatively correlated with carbon emissions, while the lateral force coefficient is positively correlated with carbon emissions. The contribution of radius to carbon emissions is greater than that of superelevation. This study clarifies the recommended values of low-carbon design indicators by assessing carbon emissions according to the current route design specification, outlines the principles of superelevation settings, and proposes a methodology to deal with the relationship between superelevation and the lateral friction coefficient. The research findings promote the quantification and standardization of low-carbon highway design, contributing to the early mitigation of high-carbon emissions from curved traffic during the design phase. [ABSTRACT FROM AUTHOR]

Tunnel–interchange connecting sections pose significant safety challenges on mountainous expressways due to their high incidence of accidents. Improving road safety necessitates a comprehensive understanding of driver behavior in such areas. This study explores the influences of road characteristics, signage information volume, and traffic conditions on drivers' car-following and lane-changing behavior in tunnel–interchange diverging areas. Utilizing driving data from 25 subjects of 72 simulated road models, driving performance is assessed using the Friedman rank test and multivariate variance analysis. The results highlight the significant influence of both connection distance and signage information load on driving behavior. In tunnel–interchange scenarios, the reduction in velocity increased by 62.61%, and speed variability surged by 61.11%, indicating potential adverse effects on driving stability due to the environmental transitions. Decreased connection distances are associated with reduced lane-changing durations, larger steering angles, and increased failure rates. Furthermore, every two units of increase in signage information leads to a 13.16% rise in maximum deceleration and a 5% increase in time headway. Notably, the signage information volume shows a significant interaction with connection distance (F > 1.60, p < 0.045) for most car-following indicators. Hence, the study recommends a maximum connection distance of 700 m and signage information not exceeding nine units for optimal safety and stability. [ABSTRACT FROM AUTHOR]

Piezoelectric (PE) fan is a novel type of active cooling device which enhance heat transfer with less power consumption. In order to achieve the theoretical limit of heat transfer performance of multiple PE fans system in confined volume, the blade location effects on that were investigated in detail by conducting three-dimensional simulations. Here, the blade pitch ranges from 1.6 to 4.2 times the fan width, and the optimal values of blade pitch with respect to four typical vibration phase angles (0°, 60°, 120°, 180°) were obtained, respectively. For all vibration modes, the air volume variation curve follows a parabola trend with blade pitch. The largest air volume is obtained when fans operating in-phase mode (φ = 0°), a conclusion that differs from that in infinite space. We attribute this to the vortex action, and its formation is determined by two effects. The positive one is the attenuation of counteracting effect from normal forces with the increasing blade pitch, where the force was exerted by two blades onto their inner fluid. The negative one is weakening of the coupling effect of two jets formed by the blade tips when spacing of dual fans is gradually increased. In addition, the local hot spot phenomenon was observed in both in-phase and counter-phase mode. It was observed that the distance between local hot spots broadens with the increasing blade pitch for in-phase mode while remains substantially constant for counter-phase mode. Our work provides a design principle for heat transfer optimization of dual PE fans in confined volume and will benefit both theoretical understanding and application in thermal management of PE fan system. [ABSTRACT FROM AUTHOR]

Supercritical CO2 heat transfer in vertical tubes has been widely studied, but limited work exists for that in horizontal tubes. In this work, experiments were conducted for CO2 in a horizontal tube with inner diameter of 8 mm under wide range of pressures (5.51–20.41 MPa), covering both subcritical and supercritical conditions. The ranges of heat flux and mass flux were 97.5–404.0 kW/m2 and 510.2–1314.2 kg/m2s, respectively. The heat transfer for subcritical pressure far below critical pressure showed typical flow boiling characteristics, with a wall temperature peak along the tube corresponding to departure from nucleate boiling. For near-critical pressure, it showed characteristics similar to supercritical heat transfer, with continuous increase of wall temperature along the tube. The effects of different parameters including pressure, mass flux, and heat flux on the heat transfer behavior were analyzed and discussed. Moreover, using the pseudo-vapor quality concept of the supercritical three-regime-model introduced in a previous work, the heat transfer coefficient was found to behave very similarly between subcritical and supercritical conditions. The experimental results showed significant deviation from single-phase convection within the two-phase/two-phase-like region compared with the single-phase regions, and which validates the similarity between subcritical boiling and supercritical pseudo-boiling. [ABSTRACT FROM AUTHOR]

Droplet evaporation is a complex and fundamental topic that holds great scientific interest due to its relevance in numerous physical and biological processes. We systematically study laser-induced nanofluid droplet evaporation under varying light frequencies. Our findings indicate the existence of two spectral regimes where droplet evaporation is either enhanced or inhibited, which is in stark contrast to the constant regime observed under fixed laser power. The enhanced regime is attributed to the rapid heat transfer initiated by the formation of vapor microbubbles inside the droplet, causing an increase in the overall temperature of the droplet. Conversely, the inhibited regime is associated with reduced heat conduction inside the droplet resulting from localized cooling effects brought about by droplet evaporation. Correlations between heat transfer mechanisms and thermal responses at the droplet surface further support these observations. We also demonstrate that both convective and conductive heat transfers determine the critical light frequency to enhance droplet evaporation. Three light-driven flow patterns are additionally identified inside the droplet. These are photophobic, phototropic, and rolling flows, which are driven by the explosive bubble growth, surface tension gradients, and mass shifts in the droplet center, respectively. Understanding these properties is important for developing miniature evaporators, nanoparticle self-assembly, and various biomedicine applications requiring precise temperature and kinetic control. [ABSTRACT FROM AUTHOR]

The high carbon emissions of vehicles traveling on horizontal curve road sections cannot be ignored. Facing the difficulty of accurately quantifying the carbon emission of driving on horizontal curves and the unknown causes of high carbon emission, this study proposes to construct a carbon emission prediction model applicable to road sections with different planar geometries. The direct and indirect effects of horizontal curve alignment on vehicle carbon emissions are represented in the model interms of travel stabilization and speed changes, respectively. A lateral force coefficient parameter was introduced into the model to integrate the carbon emission quantification problem for different planar geometry sections. Meanwhile, field tests were conducted to assess the reliability of the model and the research findings. The model reveals that the geometric parameters of horizontal curves that affect carbon emissions are the radius of the circular curve, the superelevation, and the length of the gentle curve. The root causes of high carbon emissions on horizontal curve road sections are curve driving resistance and speed fluctuations. Under the free-flow driving condition of the highway, the maximum curve radius affecting the carbon emissions of passenger cars and trucks is 400 m and 550 m, respectively. The research results can realize the carbon emission quantification of vehicles on the road sections with different plane geometries. Also, it is helpful to control the high carbon emission of vehicles traveling on horizontal curve road sections. [ABSTRACT FROM AUTHOR]

This paper explores the supercritical heat transfer mechanism by characterizing the boiling contribution ratio qb/q, where qb is the boiling heat flux and q is the applied heat flux. Experiments are performed using nickel–chromium wire in 15 °C liquid carbon dioxide at 5.2, 7.6, 9.0, and 11.0 MPa. The evaporation heat flux qe is the amount of heat used for vapor generation, while qb is the heat transfer in the bulk liquid due to the disturbance of the flow/temperature field by vapor–liquid interface motion. A data processing procedure is developed to measure qb/q from the captured images. Similar trends appear for both supercritical pseudo-boiling and subcritical boiling. The evaporation-like regime at supercritical pressures reaches qb/q = 0.21–0.43, while the film boiling (evaporation) regime achieves qb/q = 0.08. In the supercritical-boiling-like regime, qb/q increases sharply from 0.19 to 0.65, whereas in the subcritical-nucleate-boiling regime, qb/q maintains a value of 0.30 followed by a rapid rise to 0.68 under a vigorous bubble merging and departing mechanism. At both subcritical and supercritical pressures, the heat transfer deteriorates in the evaporation regime, but is significantly enhanced by phase-change-induced flow/temperature field perturbations. The boiling curves differ in the two pressure domains. At supercritical pressures, natural convection transitions smoothly to the evaporation-like regime, then to the boiling-like regime. At subcritical pressures, a steep transition from natural convection to nucleate boiling occurs, and then, film boiling is induced through the action of surface tension. The above findings complete the inverse boiling curves in the two pressure domains. [ABSTRACT FROM AUTHOR]

Although road horizontal curves are high-risk sections for accidents, current road safety assessments often neglect the dynamic evolution of superelevation and the friction factor. The connotation for road safety level was clarified by examining the significance of road factors in traffic safety through the systemic characteristics of roads. Among these characteristics, curve safety level is determined by the ratio of the supply and demand of the lateral friction factor. On the basis of international standards and specifications, this study clarified the design supply and demand of friction factors for curve by considering the distribution of tangential and lateral friction factors. Expanding on the steady-state bicycle model while accounting for road geometric parameters and vehicle operation characteristics, the lateral friction factor demanded for vehicles was quantified. Meanwhile, the characteristics of the friction factor supplied and the superelevation variation were analyzed by using the road service life as a variable, along with their influence on the actual supply of the friction factor and the curve safety level. The results of the analysis indicate a rapid decrease in curve safety level during the first two years of road utilization, followed by a slower declining trend, with a significant 27% reduction in curve safety level by the end of the second year. Furthermore, the decline in the curve safety level is mainly attributed to variations in the road surface friction factor, whereas the influence of superelevation variation on the curve safety level is restricted. In the absence of maintenance interventions, the curve safety level will decrease by over 30% after three years of operation. Controlling operational speed is one of the effective measures for ensuring traffic safety. Meanwhile, the impact of the friction factor and the superelevation variation on the curve safety level accumulates over time, thus causing drivers to have difficulty perceiving these alterations. Therefore, dynamic safety evaluations that account for the fluctuation in the friction factor and superelevation induced by repetitive vehicle loading must be undertaken. [ABSTRACT FROM AUTHOR]

Background: Psoriasis is a common chronic, recurrent, and inflammatory skin disease. Identifying novel and potential biomarkers is valuable in the treatment and diagnosis of psoriasis. The goal of this study was to identify novel key biomarkers of psoriasis and analyze the potential underlying mechanisms.Methods: Psoriasis-related datasets were downloaded from the Gene Expression Omnibus database to screen differential genes in the datasets. Functional and pathway enrichment analyses were performed on the differentially expressed genes (DEGs). Candidate biomarkers for psoriasis were identified from the GSE30999 and GSE6710 datasets using four machine learning algorithms, namely, random forest (RF), least absolute shrinkage and selection operator (LASSO) logistic regression, weighted gene co-expression network analysis (WGCNA), and support vector machine recursive feature elimination (SVM-RFE), and were validated using the GSE41662 dataset. Next, we used CIBERSORT and single-cell RNA analysis to explore the relationship between ADAM23 and immune cells. Finally, we validated the expression of the identified biomarkers expressions in human and mouse experiments.Results: A total of 709 overlapping DEGs were identified, including 426 upregulated and 283 downregulated genes. Enhanced by enrichment analysis, the differentially expressed genes (DEGs) were spatially arranged in relation to immune cell involvement, immune-activating processes, and inflammatory signals. Based on the enrichment analysis, the DEGs were mapped to immune cell involvement, immune-activating processes, and inflammatory signals. Four machine learning strategies and single-cell RNA sequencing analysis showed that ADAM23, a disintegrin and metalloprotease, may be a unique, critical biomarker with high diagnostic accuracy for psoriasis. Based on CIBERSORT analysis, ADAM23 was found to be associated with a variety of immune cells, such as macrophages and mast cells, and it was upregulated in the macrophages of psoriatic lesions in patients and mice.Conclusion: ADAM23 may be a potential biomarker in the diagnosis of psoriasis and may contribute to the pathogenesis by regulating immunological activity in psoriatic lesions. [ABSTRACT FROM AUTHOR]

Supercritical fluids have been widely used in a variety of applications, in which heat transfer under supercritical pressure is of great importance. This paper presents a critical review on supercritical heat transfer, including a summary on the past work focusing on in-tube heat transfer and the pseudo-boiling concept, the understanding of the mechanisms of supercritical heat transfer, and suggestions for future work. For supercritical fluids heated in tubes, the typical characteristics, the effects of various parameters, the buoyancy and flow acceleration effects, and the heat transfer deterioration phenomenon are all discussed, and the heat transfer correlations and numerical methodologies are summarized. For supercritical fluids cooled in tubes, the experimental observations and explanations, the proposed heat transfer correlations, and the numerical results are summarized and discussed. More importantly, this review provides a comprehensive review of the supercritical pseudo-boiling concept, including the experimentally observed pseudo-boiling phenomenon, the theoretical studies for supercritical fluids to reveal their heterogenous two-phase features, and the progress in the application of the pseudo-boiling concept on supercritical heat transfer. Finally, suggestions for future research are provided to further advance the understanding and enable accurate prediction of supercritical heat transfer. [ABSTRACT FROM AUTHOR]

Flow transport of supercritical fluids (SFs) in nanopores widely occurs in shale and deep geothermal systems. Pressure is an important parameter for describing SFs, but the effect of pressure on the flow and slip behaviors of SFs in nanochannels is unknown. In this study, molecular dynamics simulations of the Poiseuille flow of supercritical water (SCW) in graphene nanochannels are performed by applying a driving force to water molecules between two walls. Fluid pressure is realized by varying water density. The effect of pressure on the slip length under different surface wettability is investigated. The results show that the slip length nonmonotonically varies with the pressure, which is divided into three regions according to the three-regime-model of SFs. For the gas phase and gas-like SCW, the slip length gradually decreases with increasing pressure. For two-phase-like SCW, the slip length increases with pressure. For liquid-like (LL) SCW, the slip length decreases with increasing pressure. The slip length nonmonotonically varies due to the nonlinear variation of the fluid viscosity and interfacial friction with pressure. For LL SCW, the slip length is linearly related to the inverse of the density ratio, and the effect of pressure and wettability on the slip length is evaluated using the density ratio and energy barrier. Furthermore, the relationship between the slip length and pressure is verified for application to a wide range of wettability, different channel heights, and different fluid types and solid wall types. This study deepens the understanding of the microscale flow theory under supercritical conditions. [ABSTRACT FROM AUTHOR]

Low-speed driving is an underestimated dangerous behavior that may cause safety issues, such as speed dispersion and traffic flow bottlenecks. To investigate the influence mechanism of low-speed driving behavior, this study constructed the low-speed specific model (LSSM) by extending theory of planned behavior (TPB). The LSSM incorporated two factors, namely, risk perception and behavior habit, into the standard TPB components (attitude, subjective norm, perceived behavioral control, and behavior intention). Web-based questionnaires were used to collect data from a valid sample of 374, of which males accounted for 50%. The participants were aged from 18 to 65 years (M = 35.40, SD = 0.88). The structural equation model was applied to calculate and validate the interrelationships among the components of LSSM. Results showed that the LSSM could explain the variance in low-speed driving behavior and behavior intention by 46% and 76%, respectively. Meanwhile, attitude (β = 0.52, p < 0.001) and behavior habit (β = 0.48, p < 0.001) had the strongest positive influence and prediction power over low-speed driving behavior, respectively, whereas subjective norm (β = 0.05, p > 0.01) and perceived behavioral control (β = -0.12, p > 0.01) showed few significant in influencing the intention. LSSM also showed that people who were sensitive to driving risk perception would avoid low-speed driving behaviors and attitudes. Our findings may provide theoretical support for interventions on low-speed driving behavior. [ABSTRACT FROM AUTHOR]

In emergency scenarios, lane changing can provide a considerable advantage over braking by aiding in the prevention of rear-end collisions. However, executing lane changes on horizontal curves might lead to rollover collisions. This study proposes a systematic methodology for quantifying the rollover safety margin during lane-changing maneuvers by encompassing the complex characteristics of vehicle-road interactions. Specifically, an enhanced six-degree-of-freedom vehicle dynamics model was developed for a tractor-semitrailer and integrates road superelevation. Using this model, the rollover safety margin reduction rate (fS) was calculated. The fS represents the ratio of the difference between the lateral load transfer ratio margins under both reference state and emergency lane change conditions to the lateral load transfer ratio margin in the reference state. The reference state corresponds to vehicles maintaining 80 km·h-1 on a 270 m radius curve, while the emergency condition is defined as lane change durations of less than 4 seconds. The results reveal that emergency lane change maneuvers and roadway alignment significantly affect rollover safety margin. Shorter lane change duration, higher speed, and smaller radius worsen the rollover safety margin; these effects are further amplified when the lane change direction is opposite to the curve's bending direction. When the tractor-semitrailer performs a lane change at 60 km·h-1 within a 4-second duration on a 600 m radius curve, the fS exceeds 100%, indicating an imminent rollover. Consequently, this study contributes valuable evidence to the development of more reliable and secure lane-change strategies. [ABSTRACT FROM AUTHOR]

Due to the dynamic nature of work conditions in the manufacturing plant, it is difficult to obtain accurate information on process processing time and energy consumption, affecting the implementation of scheduling solutions. The fuzzy flexible job shop scheduling problem with uncertain production parameters has not yet been well studied. In this paper, a scheduling optimization model with the objectives of maximum completion time, production cost and delivery satisfaction loss is developed using fuzzy triangular numbers to characterize the time parameters, and an improved quantum particle swarm algorithm is proposed to solve it. The innovations of this paper lie in designing a neighborhood search strategy based on machine code variation for deep search; using cross-maintaining the diversity of elite individuals, and combining it with a simulated annealing strategy for local search. Based on giving full play to the global search capability of the quantum particle swarm algorithm, the comprehensive search capability of the algorithm is enhanced by improving the average optimal position of particles. In addition, a gray target decision model is introduced to make the optimal decision on the scheduling scheme by comprehensively considering the fuzzy production cost. Finally, simulation experiments are conducted for test and engineering cases and compared with various advanced algorithms. The experimental results show that the proposed algorithm significantly outperforms the compared ones regarding convergence speed and precision in optimal-searching. The method provides a more reliable solution to the problem and has some application value. [ABSTRACT FROM AUTHOR]

To improve the critical heat flux (CHF) in boiling heat transfer, an idea of triggering three-dimensional mixed boiling was proposed, and the corresponding surface with an extended thin film (ETFS) was designed by adding a film structure on the plain surface (PS). With ethanol as working fluid, experiments were conducted to explore mixed boiling heat transfer and CHF enhancement mechanisms on ETFS. The results demonstrate that ETFS induces spatially uneven temperatures on the boiling surface, which triggered mixing boiling in the spatial dimension—the coexistence of nucleate and film boiling—leading to a significant CHF enhancement. Nucleate boiling in the falling liquid along the extended surface is the key to stabilizing the surface temperature during the formation of dry spots on the base surface. Compared with PS and the traditional pin–fin surface, ETFS increased CHF by approximately 110% and 45%, respectively. Analysis indicated that mutual interference between nucleate boiling and film boiling effectively inhibits heat transfer deterioration caused by the deactivation of nucleating points. Through decoupling analysis of the mutual interference process in mixed boiling, it is shown that at heights of 2.0, 4.0, 6.0, and 8.0 mm, the contributions of extended film to total heat transfer are 12%, 64%, 37%, and 24%, respectively, indicating an optimal extended film height of 4.0 mm for maximum boiling heat transfer performance. This novel boiling surface with extended film structure not only improves CHF, but also reduces design costs, offering valuable guidance for radiator design purposes. [ABSTRACT FROM AUTHOR]

Pre-crash injury risk (IR) assessment is essential for guiding efforts toward active vehicle safety. This work aims to conduct crash severity assessment using pre-crash information and establish the intrinsic mechanism of IR with proper interpretation methods. The impulse–momentum theory is used to propose novel a priori formulations of several severity indicators, including velocity change (ΔV), energy equivalent speed (EES), crash momentum index (CMI), and crash severity index (CSI). Six IR models based on different machine learning methods were applied to a fusion dataset containing 24,082 vehicle-level samples. Prediction results indicate that the pre-crash indicators (PCIs) are more influential than the commonly used basic crash information because the average accuracy of six models can be improved by 14.35% after utilizing PCIs. Furthermore, the features' importance and their marginal effects are interpreted based on parameter estimation, Shapley additive explanation value, and partial dependence. The ΔV, EES, and CMI are identified as the determinant indicators of the potential IR, and their partial distributions are significantly influenced by the crash type and impact position. Based on partial dependence probabilities, the study establishes decision thresholds for PCIs for each severity category for different impact positions, which can serve as a useful reference for developing targeted safety strategies. These results suggest that the proposed method can effectively improve pre-crash IR assessment, which can be readily transferred to safety-related modeling in an active traffic management system. [ABSTRACT FROM AUTHOR]

Supercritical fluids (SFs) are classically regarded as single-phase fluids without bubbles or interfaces, but a recent study shows nanobubbles in SFs under unconfined conditions. The objective of this paper is to explore the phase distribution under confined conditions. Molecular dynamics simulations are performed for supercritical argon. Two walls containing the SF have equal fluid–wall interactions with equal and unequal wall temperatures. An external force is applied on the top wall to control the pressure at 1.5Pc, in which Pc is the critical pressure. Periodic boundary conditions are applied on the four side surfaces of the simulation box. The study indicates that the bulk fluid density is not only dependent on pressure and temperature, but also on fluid–wall interactions, this result deviates from the classical theory, where density depends on only pressure and temperature. For strong fluid–wall interactions, three- or five-layer structures are found, including liquid-like (LL) layers on the walls and two-phase-like (TPL) and gas-like (GL) layers (depending on bulk density) in the channel core. For weak fluid–wall interactions, the phase distribution becomes GL on the wall, and TPL and LL (depending on bulk density) in the channel core, which is inverse to those of strong fluid–wall interactions. Correspondingly, the phase distributions for strong and weak fluid–wall interactions can be analogous to annular or Leidenfrost patterns at subcritical pressures, respectively. The density profile is symmetric against the channel centerline at equal wall temperatures, but symmetry-breaking may exist when applying different wall temperatures. This work provides a phase-distribution link between subcritical and supercritical pressures, which is useful for the design and analysis of SF systems. [ABSTRACT FROM AUTHOR]

While the progress made in vitro culture of Chinese fir has produced satisfactory results, further improvements are warranted. To understand the mechanism of somatic embryogenesis (SE) in Chinese fir, we conducted phenotypic observations, physiological and biochemical measurements, and transcriptome analysis of embryonic (EC) and non-embryogenic callus (NEC) to provide a scientific basis for SE in this species. We found that EC and NEC showed significant morphological and physiological-biochemical indicators differences. Compared with NEC, EC had higher levels of soluble protein and proline and lower levels of malondialdehyde (MDA), peroxidase (POD), superoxide dismutase (SOD), and catalase (CAT). Callus transcriptome sequencing assembled 152,229 unigenes, and 438 differentially expressed genes (DEGs) were screened, including transcription factor-related (TFs), DNA methylation-related, cell wall component protein, signal transduction-related, and stress response-related. GO and KEGG enrichment analyses of DEGs identified starch and sucrose, glutathione, and cysteine and methionine metabolism as the most representative pathways significantly enriched in EC and NEC genes and were associated with cell proliferation and embryogenesis. For the first time, the specific patterns of gene expression in Chinese fir callus were found through transcriptome comparison between callus, 16-year-old Chinese fir cambium, and drought-stressed tissue culture seedlings. In Chinese fir callus, 75.1% of genes were co-expressed in 16-year-old Chinese fir cambium and drought-stressed tissue culture seedlings, and 24.9% were only specifically expressed in callus. DEGs from EC and NEC indicated that 68.2 and 31.8% were co-expressed and specifically expressed, respectively. These results provided a basis for Chinese fir rapid propagation, which is expected to have theoretical and practical significance. [ABSTRACT FROM AUTHOR]

Inspired by the light-diverging effect induced by convex mirrors, we propose a novel droplet actuator for potential application in mixing/reaction. We use a rectangle formed by an open tunnel and two convex surfaces. When a droplet contacts a convex surface, a sufficiently large thrust force is generated due to contact-induced explosive boiling, generating self-sustained droplet oscillation. The convex surface enhances the droplet motion in the width direction. A thermal insulation technique is applied to reach hotter hydrophilic convex surfaces but a colder superhydrophobic tunnel. The former generates thrust and scatters the droplet trajectories, but the latter is used for rapid droplet transportation. The collision frequency with the tunnel surface when using the convex side surface (CSS) with θ = 15.0° is three times that obtained from the flat side surface (FSS), where θ is the half-curvature angle of CSS. Holding CSS constant, the enhanced collision with the tunnel surface creates fold line trajectories for the droplet. Meanwhile, the statistical droplet velocity in the y-component when using the CSS is two times that obtained using the FSS. Incident angles and reflection angles are analyzed for collisions with the contact boiling surfaces. We conclude that the range of reflection angles becomes larger when using the CSS. Droplet rotation further increases the reflection angle. The enlarged reflection angle is the key mechanism for forming the fold line trajectory and enhancing the motion in the width direction. This work provides a new principle for creating perturbations to enhance mixing/reaction for chemical and biological applications. [ABSTRACT FROM AUTHOR]

In terms of developing supercritical CO2 (sCO2) coal-fired power plants, enhancing cooling wall performance is one of significant factors to improve system performance. In this paper, a new cooling wall tube structure is proposed to match the non-uniform heat flux (NUH) with the thermal resistance by changing the cooling wall tube eccentricity. A three-dimensional multi-physical coupling model of cooling wall is constructed to compare the novel structure to the conventional structures. The properties of fluid dynamics, thermal stress, coupled heat transfer and cooling wall deformation are analyzed. In contrast to the traditional structure, the maximum temperature and circumferential temperature difference (CTD) of the proposed structure can be reduced by 2% and 27.4%, respectively. The essential working parameters related to the performances of the cooling wall tube are discussed. The maximum temperature of the new structure is reduced by 8–13 K and the maximum thermal stress is reduced by about 10%–15% under all the simulated working conditions when the eccentricity changes from 0 to 0.2. The proposed structure can effectively reduce the maximum temperature and circumferential temperature gradient under NUH. Consequently, a novel insight is put out for the design and optimization of the cooling wall tube in coal-fired power plants. [ABSTRACT FROM AUTHOR]

This study investigates whether serum prolactin (PRL) is a key factor for nonalcoholic fatty liver disease (NAFLD) in children. A total of 691 obese childred participated in this study and were divided into a NAFLD group (n=366) and simple obesity (SOB) group (n=325) according to the hepatic ultrasound results. The two groups were matched for gender, age, pubertal development, and body mass index (BMI). All patients underwent an OGTT test, and fasting blood samples were collected to measure prolactin. Stepwise logistic regression was performed to identify significant predictors of NAFLD. Serum prolactin levels were significantly lower in NAFLD subjects than in the SOB subjects [82.4 (56.36, 118.70) vs. 99.78 (63.89, 153.82), p<0.001] (mIU/l). NAFLD was strongly associated with insulin resistance (HOMA-IR) and prolactin, with lower levels of prolactin increasing the risk of NAFLD (adjusted ORs=1.741; 95% CI: 1.059–2.860) across the prolactin concentration tertiles after adjustment for confounders. Low serum prolactin levels are associated with the presence of NAFLD; thus, increased circulating prolactin might be a compensatory response for obesity in children. [ABSTRACT FROM AUTHOR]

The jet always sweeps to the leftmost and rightmost points in the sweeping jet and film composite cooling (SJF) process, resulting in a different coolant flow in each film hole. The film can not easily cover the outer surface evenly under the scouring of the mainstream. This work presents a case study to analyze the effects of two mainstream variables on the film areodynamic and cooling performance of the SJF. Three different mainstream velocities (Vm= 10 m/s, 50 m/s, 90 m/s) and three different mainstream turbulence intensities (Tu = 1%, 10%, 20%) are discussed. Results indicate that the increase of mainstream velocity yields to better film attachment. When the mainstream velocity increases from 10 m/s to 50 m/s, the overall cooling effectiveness and total pressure loss coefficient are reduced by 17.68% and 98.60%, respectively. When the mainstream velocity increases from 50 m/s to 90 m/s, the overall cooling effectiveness and total pressure loss coefficient are almost unchanged. The effect of turbulence intensity on the overall cooling effectiveness and total pressure loss coefficient are relatively small. The increase of mainstream turbulence intensity enhances the disturbance of the mainstream to the coolant from the middle film holes, and the distribution of adiabatic film cooling effectiveness is more uneven when the mainstream turbulence intensity is raised to 10% and 20%. In the research scope of present work, the flow structure, total pressure loss coefficient and overall cooling effectiveness are the most expected under the conditions of lower turbulence intensity and higher mainstream velocity (Tu = 1%, Vm= 90 m/s). [ABSTRACT FROM AUTHOR]

The low-altitude technology of unmanned airborne infrared detection system is used to effectively monitor the temperature segregation in the paving stage and realize the temperature uniformity control of asphalt pavement construction. The image mosaic method can splice two images with overlapping areas together to form a panoramic image. In order to solve the problems of long time-consuming and low accuracy of aerial image mosaic algorithm, the low-temperature area of the whole pavement can be obtained quickly and accurately. In this paper, threshold segmentation technology is introduced to convert the image captured by the unmanned aerial vehicle (UAV) into a binary greyscale image so as to compensate for the mosaic error caused by temperature difference. In order to improve the efficiency and accuracy of splicing, a reference plate is used, which can provide enough feature points for splicing. Finally, the image mosaic method proposed in this paper can quickly obtain the image of the whole low-temperature area of the newly paved asphalt pavement, which has practical value and positive significance for the quality control of asphalt pavement. [ABSTRACT FROM AUTHOR]

Carbon emission changes significantly when the vehicle is driving at a variable speed. Given that the rule of vehicle carbon emissions under different driving behaviors is underexplored, this study filled this research gap by establishing a theoretical carbon emission model when vehicles are driving at fluctuating speed. The model was established based on the law of conservation of mechanical energy, the first law of thermodynamics, the theory of vehicle dynamics. Two passenger cars and three trucks were selected as typical vehicles. A field test was carried out under different driving behaviors with uniform acceleration. The proposed model can forecast the carbon emissions of vehicles that fluctuate in speed during travel and showed strong accuracy in model validation. As the speed fluctuation increased, the influence of acceleration on carbon emissions became more apparent. Gradient has a more significant influence on vehicle carbon emissions, followed by acceleration. By controlling the driving behavior of the vehicle on the round trip, the same carbon emissions as driving on a flat route at a constant speed can be achieved. The findings of this study will provide a theoretical basis for low-carbon transportation. [ABSTRACT FROM AUTHOR]

The variation in road cross slope with service life affects the pavement drainage and has an adverse effect on vehicle operation safety. This paper describes a cross-slope variation prediction method influenced by the coupling effect of traffic load and soil consolidation, considering characteristics of embankment to cover the shortage for insufficient consideration of compacted embankment. First, the traffic load-induced settlement equation of a highway on soft soil foundation was introduced, which considers the effects of traffic load stress, confining pressure, soil structure, strength weakening and cyclic loading times on different positions along the cross-section. Then, the finite element model of a highway on soft soil foundations under soil consolidation is established, considering the influence of soil seepage. Finally, predictions of long-term settlement and cross-slope variation generated by coupling action of traffic load and soil consolidation were carried out with contrastive analysis with measured data. We find the following: (1) the long-term settlement was mostly from the consolidation of natural soft subsoil, while the cross-slope variation was mainly affected by traffic load; (2) variation in the cross slope of highway in soft soil areas mainly occurs within 1 year of operation. The effect of passenger cars and trucks on cross-slope variation shows diametrically opposite results, as the passenger car lane decreases while the truck lane increases; (3) the relative error of the cross-slope variation prediction results with the measured data are 2.86% and 2.5% for the left and right lane cross slopes, respectively. [ABSTRACT FROM AUTHOR]

Flooding may take place for in-tube condensation, causing unstable flow and deteriorated heat transfer. Here, the phase separation principle is proposed to eliminate flooding. Comparative experiments of condensation were performed in both bare tube (BT) and modulated heat transfer tube (MHTT) with a mesh membrane tube (MMT) insert. The working fluid is water-steam under a sub-atmospheric pressure. It was observed that slug flow exists at small mass fluxes and vapor mass qualities in BT. Due to the periodic formation of liquid column over the tube cross section, flooding indeed takes place, causing unstable flow, deteriorated heat transfer, and large pressure drop. The MHTT completely eliminated flooding, converting the unstable flow into a stable flow. Heat transfer coefficients are 7.47 times of those in BT, maximally, accompanying reduced pressure drops. High-speed visualization and theoretical analysis indicated that smaller pore size provides larger capability to prevent the vapor phase penetrating the mesh screen, resulting in larger driving force for liquid suction toward the MMT inside. The MMT provided a tunnel for liquid transportation in the upward direction, which is the mechanism to eliminate flooding. The modulation of the annular flow pattern was also performed and analyzed by using the phase separation principle, and the results indicated the effectiveness of MMT in the annular flow regime. This work is benefit for applications, such as air-cooled condenser, whose performance is important to influence the whole system performance for power generation. [ABSTRACT FROM AUTHOR]

During the operation of supercritical CO 2 (sCO 2 ) radial inflow turbines (RITs), sonic conditions may happen, which will decrease their efficiency. Non-standard design geometries are needed to reduce the losses. However, modifying the turbine geometry is a challenge, especially as the optimum shape may be non-intuitive; commercial computational fluid dynamics (CFD) software is not friendly towards automation by surrogate scripts, and the traditional design method for blade passage shape is not suited to the optimisation of aerodynamic turbine design. Hence, in this study, a stator nozzle for a 120 kW sCO 2 RIT, whose geometries are obtained from in-house preliminary design code TOPGEN t m , has been optimised with a modularised geometry optimiser. To parametrise the geometry, a parametrised stator mesh generator based on a meridional streamline is developed. Bulk CFD simulations are carried out with OpenFOAM ® , to form a Pareto front with a vector of 14 variables. Three final stators have been selected: they are the optimised Mach number distribution ( σ M ), the optimised outlet flow angle distribution ( σ α ) and a compromise case. The the outlet boundary properties of these stators are extracted and discussed. The optimised σ M case has the shortest divergent nozzle, returns the best σ M and the least loss; the optimised σ α case has the longest divergent nozzle and returns a better-uniformed outlet flow; the compromise case has the medium length of the divergent case. All these stators have fixed mass flow rates to allow de-coupling of the upstream system from the rotor. This study will ultimately benefit the development of the sCO 2 power cycle. [ABSTRACT FROM AUTHOR]

During the operation of supercritical CO 2 (sCO 2 ) turbomachineries, large pressure ratios, supersonic conditions and non-ideal gas fluid dynamic phenomenon may happen, which will decrease the whole cycle efficiencies. Hence non-standard designs for the turbomachineries geometry are needed. Successfully simulations in capturing non-ideal gas fluid dynamics and coupled with optimization algorithm are hard and currently not available in any commercial CFD software. Therefore, the problem of optimizing sCO 2 turbomachinery is difficult to solve, which has become a major obstacle to obtain compact and high-efficiency sCO 2 turbomachineries. In this study, a modularized geometry optimizer is developed to obtain the non-standard geometric designs for sCO 2 turbomachineries. Multiple techniques are applied to this optimizer, include the Nelder–Mead algorithm, Mahalanobis distance and stochastic algorithm. The newly developed optimizer can successfully find the optimum satisfying the objective function under given weighting factors. The computational cost can be reduced through a stochastic algorithm. To validate the optimizer, a convergent–divergent nozzle for air with a target Mach number equal to 2.4 is optimized. Different starting points and combinations of weighting factors are used to create a Pareto front. Adjust the weighting factors for different terms of the objective function leading the optimizer to go to different directions in n-dimensional spaces. Three optimized cases, one is Mach number optimized, one is outlet flow uniformity optimized and the other is compromised case, are picked out and analyzed. The results show that the optimizer can successfully find optimized geometry than the reference case and potentially save computational cost. Due to the modularized characteristics, the components of this optimizer can be replaced with any available techniques, which mean the optimizer can be applied to solve different types of optimization problems. [ABSTRACT FROM AUTHOR]

Recently, there is an increased interest in supercritical CO2 and organic Rankine cycles (ORC) for their ability to achieve higher thermodynamic efficiency. However, the non-ideal gas thermodynamic in these cycles may affect the flow properties critically, necessitating the research of non-ideal compressible fluid dynamics (NICFD). Thus, simulation tools that can accurately predict fluid flows with NICFD are significant. This study presents a new approximation Riemann solver in OpenFOAM for NICFD. The new solver uses a real-gas (look-up table based) approximate Riemann flux calculator (modified from HLLC ALE flux calculator) through adding a new thermodynamic library tightly coupled with the OpenFOAM®. To validate the solver, three cases are presented, including a NASA transonic nozzle operating with air, to confirm the ability to correctly simulate the transonic flow phenomena and the shock waves; the VKI 2D cascade operated with MDM to assess the ability in simulating non-ideal gas flows typically to industrial applications; and the dense gas flow (MD4M) passing a backward ramp to illustrate the ability of the flux calculator and look-up table mechanism that can work well in the non-ideal region of fluid properties. This study can benefit future engineering applications of computational fluid mechanics of NICFD and the OpenFOAM community. [ABSTRACT FROM AUTHOR]

Using supercritical CO2 (S-CO2) instead of water steam as heat transfer fluid for coal-fired power plants is another way to further improve the power generation efficiency. In this paper, a multi-field coupling model that integrates fluid flow, heat transfer and thermal stress is proposed to solve the complex problem. The effects of the key operating parameters on the performances of the cooling wall are numerically investigated. More details of the characteristics of fluid dynamics, thermal stress, pressure drop, coupled heat transfer and the whole flow and temperature fields in the S-CO2 cooling wall are revealed and discussed. A comparison study is made between the cooling wall tube and waterwall tube. Both temperature and thermal deformations of cooling wall tube are much higher than that of water. Numerical simulation results indicate that inclination angle has little effects on the temperature distribution, while increase of pressure drop is obvious as the inclination angle increases. Increasing tube diameter can effectively reduce both the pressure drop and the temperature of the cooling wall tube. As a result, a new insight is introduced for the design of S-CO2 power cycle. [ABSTRACT FROM AUTHOR]

Roadway multi-fatality crashes have always been a vital issue for traffic safety. This study aims to explore the contributory factors and interdependent characteristics of multi-fatality crashes using a novel framework combining association rules mining and rules graph structures. A case study is conducted using data from 1068 severe fatal crashes in China from 2015 to 2020, and 1452 interesting rules are generated using an association rule mining approach. Several modular rules graph structures are constructed based on graph theory to reflect the interactions and patterns between different variables. The results indicate that multi-fatality crashes are highly associated with improper operations, passenger overload, fewer lanes, mountainous terrain, and run-off-the-road crashes, representing the key variables of factors concerning driver, vehicle, road, environment, and accident, respectively. Furthermore, crashes involving different severity levels, road categories, and terrain are verified to possess unique association rules and independent crash patterns. Moreover, the proportion of severe crashes caused by a combination of human-vehicle-road-environment factors (43%) is much higher than that of normal crashes (3%). This study reveals that the hidden associations between various factors contribute to the overrepresentation and severity of multi-fatality crashes. It also demonstrates that the crash mechanisms involving multi-fatality crashes and their interactions are more complex at the system level than those for normal crashes. The proposed framework can effectively map the intrinsic link between multiple crash factors and potential risks, providing transportation agencies with helpful insights for targeted safety measures and preventive strategies. [ABSTRACT FROM AUTHOR]

Leidenfrost droplet evaporation on a liquid bath exhibits unique features such as ultra-low resistance to sample transition and low-temperature operation; however, the physical mechanisms responsible for these phenomena are incompletely understood. Droplet size and temperature are two key parameters influencing Leidenfrost droplet evaporation. We report herein the thermal non-equilibrium process of an FC-72 droplet over a thin oil layer. We show that the Leidenfrost droplet radius follows the power law R(t) ∼ (1 − t/τ)n, where τ is the characteristic droplet lifetime and n ranges from 0.63 to 0.91. Based on experimental results and theoretical predictions, the remarkable nonmonotonic variation of droplet temperature departs from the saturation-temperature assumption. For lower oil superheating, a cold (subcooled) droplet can sustain evaporation until it disappears. For higher oil superheating, the droplet goes through both subcooled and superheating stages. This phenomenon is well described by sensible heat absorption and release throughout droplet evaporation. These results are helpful for applications such as drug delivery, wherein a cold droplet can float on a liquid bath, thereby extending the lifetime of the biological sample in a high-temperature environment via a localized, low-temperature system. [ABSTRACT FROM AUTHOR]

Recent research indicates that the coronavirus disease 2019 (COVID-19) pandemic has impacted road traffic operation quality. From the perspective of service level, safety level, and operation orderliness, this study attempts to analyze the limited responses of the operation quality of the provincial expressway network (PEN) to the impact of COVID-19. The traffic operation data of the PEN in Shaanxi Province were collected for three consecutive years (from 2019 to 2021) before and after the COVID-19 outbreak, including weekly average daily traffic, weekly traffic interruption times, weekly traffic control time, weekly traffic accidents, weekly traffic injuries, and weekly traffic deaths. Through descriptive statistics and dynamic analysis, we studied the limited responses of the safety and service levels of the PEN to the impact of COVID-19. An evaluation model of operation orderliness of the PEN was established by using dissipative structure theory and entropy theory. Results show that in 2020, the service level, safety level, and operation orderliness of the PEN dropped to their lowest. With the gradual control of pandemic, its negative impacts on the service level and operation orderliness of the PEN gradually decreased but did not recover to the pre-pandemic level. In terms of the safety level, the number of traffic accidents, traffic injuries, and traffic deaths decreased, whereas the traffic accident rate and accident casualty rate remained high. In summary, the operation quality of the PEN in Shaanxi Province has had a limited response to the impact of COVID-19. [ABSTRACT FROM AUTHOR]

An unreasonable design hourly volume (DHV) greatly impacts road facility construction costs and traffic efficiency. With the rapid rise in the tourism economy and widespread emergence of holiday travel characteristics in China, DHV applicability for suburban expressways requires verification. This study collected annual traffic volume data over 8760 h along Xi'an Ring Expressway from 2017 to 2019. Traffic demand distribution patterns throughout the year and peak hours were analyzed on the basis of the descending order of the obtained hourly traffic volume (HV) and factor data. HV distribution characteristics, 30th highest hourly volume (30 HV) typicality, and DHV factor applicability were investigated. Due to travel characteristics under the background of the tourism economy, the peak HV distribution exhibits polarization characteristics. The recommended value of the design hour traffic factor in the specification corresponded to a number of hours greater than 200, with the 30 HV factor under the background of the tourism economy being 25% higher than the recommended value. Considering the tourism economy, the high level of traffic operation time increased significantly, and the characteristics of a sharp decline in the peak HV disappeared. The 30 HV factor no longer exhibited traditional characteristics. The design causes of traffic congestion are identified herein. [ABSTRACT FROM AUTHOR]

The friction coefficient is one of the dominant parameters affecting vehicle driving stability on horizontal curves. However, there is no comprehensive framework to assess the traffic safety on the horizontal curve with the evolution of the friction coefficient caused by the traffic flow. In light of this, this paper developed an integrated risk-assessment framework to evaluate the safety on the horizontal curve with the friction coefficient evolving under different traffic characteristics. The speed distribution on the horizontal curve of the freeway is obtained through field experiments that serve as the basic parameters of the model. A new multi-vehicle risk index (MRI) is introduced to assess the traffic safety risk for the horizontal curve by coupling the reliability theory and negative binomial. Three traffic characteristics are considered in the analysis: cumulative traffic volume (CTV), annual average daily traffic (AADT), and average daily traffic of heavy goods vehicles (AADTHGV). The results show that the AADT and AADTHGV have a considerable impact on the road risk level. When the truck traffic volume is less than 1000 veh/d, the risk of horizontal curves changes less as road operational time goes. The research results can provide a reference for the road maintenance department to determine the timing of road maintenance. [ABSTRACT FROM AUTHOR]

The friction coefficient between the tire and the road is one of the key parameters affecting road traffic safety. The purpose of this paper is to quantify the risk of skidding for the vehicles due to the friction evolution caused by the traffic polishing in the horizontal curve. Based on the reliability theory, an innovative dynamic risk assessment model is developed in the present study for passenger cars and trucks. The influence of two traffic characteristics for pavement friction is quantified: cumulative traffic volume (CTV) and annual average daily traffic of trucks (AADTT). The speed distribution on the horizontal curve of the motorway is obtained through field experiments as the basic parameter of the model. The Hasofer-Lind Method is adopted to solve the reliability and the risk probability of vehicle skidding. The results show that in the traffic characteristics, the AADTT has a significant impact on the pavement friction; When the AADTT on the road exceeds 2000 veh/d, the increasing CTV leads to friction decrease rapidly and therefore has a significant impact on the risk of horizontal curve. Especially for roads with more than 50 million vehicles of the CTV, the risk of the horizontal curve shows a sharp increase with CTV rising. The research results can provide reference for the road maintenance department to determine the timing of road maintenance. [ABSTRACT FROM AUTHOR]

In order to explore the directional support method of jointed rock mass and ensure the stable operation of roadway, the support effect of jointed rock mass was analyzed by numerical simulation and on-site monitoring. The results showed that directional support could effectively reduce the deformation and ensured the stability of surrounding rock. In the process of directional reinforcement support construction, the plane formed by multiple bolts was guaranteed to be perpendicular to the structural plane, and the bolt hole extended along the normal plane of roadway, the control effect of this support mode was the best. The stress change law of surrounding rock of roadway was monitored by using borehole force meter. The results showed that the stress released occurs in surrounding rock of roadway after excavation, and the cumulative stress change value did not increase 5 to 7 days after excavation. The jointed rock mass remained in a stable state under the action of directional reinforcement support. The directional reinforcement of roadway surrounding rock had a good control effect on roadway stability. [ABSTRACT FROM AUTHOR]

The internal heat transfer performance and flow structures of a sweeping jet and film composite cooling on a flat plate were numerically studied. Sweeping jet and film composite cooling consists of a fluidic oscillator and 20 cylindrical film holes; the direct jet is formed by removing the feedback from the fluidic oscillator, which is different from the traditional cylindrical nozzle. Four different mass flow rates of coolant were considered, and the inclination angle of the film hole was 30°. The Conjugate Heat Transfer method (CHT) and Unsteady Reynolds Averaged Navier Stokes equation (URANS) were employed. The results indicated that the flow resistance coefficients of the sweeping jet were larger than those of the direct jet, and the Nusselt number monotonously increased with the increase in the mass flow rate. Compared to the direct jet, the sweeping jet had a more spatially uniform heat removal rate, and the area-averaged Nusselt number was slightly lower. Therefore, the sweeping jet and film composite cooling caused the distribution of the flat plate heat transfer to be more uniform. It is worth noting that the novel direct jet nozzle in the present work had considerable area-averaged impingement cooling effectiveness. [ABSTRACT FROM AUTHOR]

Owing to the complicated geometric conditions and increasingly diversified driving environment, freeway curves have become a road section with frequent serious accidents. To ensure safe driving on curves, drivers must first perceive the movement condition and the vehicle's position, and accurately evaluate the characteristics of the road to make the right speed choice. In this process, the perception of speed plays a crucial role. The present study aims to investigate the driver's speed perception characteristics with respect to freeway curves to better understand the driver speed selection mechanism. We first construct six three-dimensional (3D) virtual highway models, which are consistent with the geometric lines and traffic engineering instruments of real freeways. A virtual simulation test is then conducted in a highly immersive environment. After the completion of the simulation experiment, we conduct a field verification experiment, test the actual driving speed and perceived speed of drivers in the same place as the simulation experiment, and verify the effectiveness of the simulation method. Finally, 25 3D curve models of four different types are constructed, and the influence of curve characteristics (e.g., curve radius, curve combination, tangent length between curves) on drivers' speed perception accuracy are tested on the simulation platform. The results show that the driver's perceived speed is lower than the real speed when driving on curves, and the tangent-to-spiral (TS) point is the section where the driver's speed is most underestimated. Radius was the most important factor affecting driver's speed perception, but the tangent length between curves also had a lesser influence. However, the curve combination had no effect on it. Our findings can help researchers and road designers understand the reasons for drivers' speed choice, thus promoting drivers' safety on freeway curves. [ABSTRACT FROM AUTHOR]

Leidenfrost droplet possesses ultra-low flow resistance, but it is challenging to obtain large thrust force for fast transportation and regulate the direction of droplet motion. Here, for the first time, we demonstrate a novel mechanism for the control of droplet dynamics by explosive boiling. Our system consists of two surfaces that have different functions: a smooth surface running in the Leidenfrost state for droplet levitation and a skirt ring edge surface (SRES) as an explosive boiling trigger. For droplet-wall collision with SRES, micro/nanoscale roughness not only enhances energy harvesting from the skirt ring to the droplet due to increased radiation heat transfer but also provides nucleation sites to trigger explosive boiling. The symmetry breaking of explosive boiling creates a thrust force that is sufficient to propel the droplet. The suppression of the thrust force relative to the inertia force regulates the droplet trajectory as it passes through a target location. We show orbit lines passing through a focusing spot that is ∼1% of the Leidenfrost surface area around its center with a maximum traveling speed of ∼85 cm/s, which is ∼2 times of that reported in the literature. The scale law analysis explains the droplet size effect on the self-propelling droplet dynamics. Our work is attractive for applications under the conditions of the required traveling speed and direction of the droplet. [ABSTRACT FROM AUTHOR]

Supercritical water (scW) is important for various engineering applications. The structure and distribution of scW is key to dominate the related processes and phenomena. Here, scW is investigated using molecular dynamics (MD) simulation with controlled pressure and temperature. Density oscillation is observed to occur in a 1 nm thickness bin, indicating mass exchange of particles across the bin interface. We show that the low density scW behaves strong heterogeneity. Quantitative analysis of system density fluctuations is performed by square root error and maximum structure factor, demonstrating the agreement between the two methods. The scW molecules are tightly gathered to form "liquid island" locally, but are very sparse in other regions, which are similar to the gas-liquid mixture in subcritical pressure. A target molecule is tracked to plot 3D displacements and rotating angles, with the former indicating large amplitude ballistic (diffusing) motion and small amplitude oscillation, and the latter displaying two scales of angle jumping. Both translation and rotating motion are related to hydrogen bond break up and reorganization. The low density scW behaves isolated molecules with few combinations of hydrogen bonds between molecules, while the high density scW behaves more combinations of molecules via hydrogen bonds. The two scales motion is expected to influence thermal/chemical process in supercritical state, deepening the fundamental understanding of scW structure. [ABSTRACT FROM AUTHOR]

On fully enclosed freeways, the service area is the only key node for certain crowd activities such as resting, toileting, and dining. In these activities, using the toilet is the most important purpose for people to enter the service area. A reasonable toilet location and size in the service area is the basis for its efficient operation. This study conducts field surveys on several service areas, including Meicun, Tai'an, and Qianxian, through video recording and crowd tracking questionnaires. We summarize and analyze the characteristics of population flow in Chinese freeway service areas. The key data obtained through field surveys are reported, such as the priority and length of stay of customers in the facilities during peak hours at weekends, to analyze the characteristics of pedestrian traffic in the service areas. Finally, based on a large number of pedestrian simulation methods used in studies on the layout of subways and airport facilities, the AnyLogic simulation software is applied to establish a crowd movement model for these areas. The study not only obtained the pedestrian characteristics of the service area but also showed that only changing the location of toilets has no effect on the efficiency of toilet use without changing the level of service, whereas changing the number of toilets has a significant impact on the efficiency. Most importantly, this paper establishes a relationship model between the toilet size of the service area and the service area pedestrians flow; when the toilet seats 266/158/148 people, the maximum flow of people in the service area is about 3,115/2200/2000 p/h, which can provide help for the scale design of the service area. [ABSTRACT FROM AUTHOR]