Search

Phenomena-driven instruction is an effective method for addressing science misconceptions. Research has shown that simply teaching correct information does not automatically remove misconceptions, as students often revert back to their prior thinking. To create a permanent change in students' thinking, misconceptions must be directly addressed. Phenomena, which are real-world events or situations, can be used as teaching tools to engage students and help them develop a deeper understanding of concepts. By encountering phenomena that contradict their misconceptions, students can correct their thinking and gain a better understanding of scientific principles. [Extracted from the article]

In response to an investigation on the paths of changes in the crystallization and radial differences during the forming process of nascent fibers, in this study, we conducted numerical simulation and analyzed the changes in crystallization mechanical parameters and tensile properties through a fluid dynamics two-phase model. The model was based on the melt-spinning method focusing on melt spinning, the environment of POLYFLOW, and the method of joint simulation, coupled with Nakamura crystallization kinetics, including the development of process collaborative parameters, stretch-induced crystallization, viscoelasticity, filament cooling, gravity term, inertia, and air resistance. Finally, for nylon 6 BHS and CN9987 resin spinning, the model successfully predicted the distribution changes in temperature, velocity, strain rate tensor, birefringence, and stress tensor along the axial and radial fibers and obtained the variation pattern of fibers' crystallinity along the entire spinning process under different stretching rates. Furthermore, we also explored the effects of spinning conditions, including inlet flow rate, winding speeds, and the extrusion temperature, on the fibers' crystallization process and obtained the influence rules of different spinning conditions on fiber crystallization. Knowing the paths of changes in mechanical performance can provide important guidance and optimization strategies for the future industrial preparation of high-performance fibers. [ABSTRACT FROM AUTHOR]

The article explores the issue of projectile motion with atmospheric drag, specifically focusing on vertical launch. The authors present an analytical solution for the projectile's position and maximum height over time, assuming a constant drag coefficient. They compare this solution with a numerical one that allows for a varying drag coefficient. The article emphasizes the importance of intermediate-level solutions in physics education and the need to consider drag forces in projectile motion problems. The authors also discuss the application of the analytical solution in studying volcanic eruptions and highlight its potential use in analyzing volcanic bomb trajectories. The research was supported by the European Research Council. [Extracted from the article]

This article discusses the use of 3D camera systems and accompanying software in physics instruction. The authors describe a Python program that can track and analyze the momentum of a midair collision between two playground balls. The program is freely available for instructors and can be used in student lab settings or as an instructor-led exercise. The article provides detailed information on the camera system used, the data collection and analysis process, and the results obtained. The authors conclude that the use of 3D cameras and tracking software expands the possibilities for physics experiments and enhances students' understanding of complex systems. [Extracted from the article]

Students bring with them rich cultural and linguistic ways of knowing and communicating when engaged in figuring out explanations of phenomena. However, it is a challenge for teachers to support bi/multilingual learners in language-intensive science and engineering practices when they don't share a common language. When we position students' bi/multilingualism as an asset rather than an obstacle, we can support bi/multilingual students' equitable sensemaking. To support bi/multilingual learners' equitable sensemaking, we offer two tools: language surveys and the multiple ways of communicating strategies sheet. We describe how a teacher (second author) used these resources to adapt an investigation about air resistance and contact forces for his bi/multilingual students. The tools and examples provided can help educators better understand their students and make principled changes to science instruction, to expand how we use language in science. We hope the tools aid teachers in this challenging work but also reframe how educators see what students are saying and doing as assets for developing their ideas and learning. [ABSTRACT FROM AUTHOR]

This article introduces a rapid interception trajectory generation algorithm tailored for the mitigation of malicious drone activities and other high-speed airborne threats. The proposed method facilitates a high degree of flexibility in defining the terminal state parameters, including position, velocity, and acceleration, as well as the anticipated duration of drone maneuvers, thereby enabling the fulfillment of a variety of mission objectives. The approach employed in this study linearizes the aerodynamic resistance model and computes an efficient closed-form solution for the optimal trajectory motion primitive by applying Pontryagin's Maximum Principle. Concurrently, it minimizes the cost function associated with the aggression of control inputs. The motion primitive is defined by the combination of the initial and terminal states of the drone, as well as the expected movement time. An efficient input feasibility verification method has been designed for the optimal trajectory. This algorithm can serve as a low-level trajectory generator for advanced task planning methods. After compilation, it can evaluate and compare thousands of motion primitives per second on a personal portable computer, thereby achieving certain advanced goals. The reliability of the algorithm is verified by setting up a multi-objective approach task in a physical simulation environment. [ABSTRACT FROM AUTHOR]

As the velocity of a train increases, the corresponding air pumping power consumption of the brake discs increases proportionally. In the present experimental study, a standard axle-mounted brake disc with circumferential pillars was analyzed using a 1:1 scale model and a test rig in a wind tunnel. In particular, three upstream velocities were selected on the basis of earlier investigations of trains operating at 160, 250, and 400 km/h, respectively. Moreover, 3D steady computational fluid dynamics (CFD) simulations of the flow field were conducted to compare with the wind tunnel test outcomes. The results for a 3-car train at 180 km/h demonstrated: (1) good agreement between the air resistance torques obtained from the wind tunnel tests and the related numerical results, with differences ranging from 0.95% to 5.88%; (2) discrepancies ranging from 3.2 to 3.8 N · m; (3) cooling ribs contributing more than 60% of the air resistance torque; (4) the fast rotation of brake discs causing a significantly different flow field near the bogie area, resulting in 25 times more air pumping power loss than that obtained in the stationary brake-disc case. [ABSTRACT FROM AUTHOR]

The rolling resistance of car tires is one of the most important parameters characterizing tires today. This resistance has a very significant contribution to the energy consumption of wheeled vehicles. The climate crisis has forced tire and car manufacturers to place great emphasis on the environmental impact of their products. Paradoxically, the development of electric vehicles has led to an even greater importance of rolling resistance, because in electric vehicles, a large part of the influence of grade resistance and inertial resistance has been eliminated due to re-generative braking, which resulted in rolling resistance and air resistance remain as the most important factors. What is more, electric and hybrid vehicles are usually heavier, so the rolling resistance is increased accordingly. To optimize tires for rolling resistance, representative test methods must exist. Unfortunately, the current standards for measuring rolling resistance assume that tests are carried out in conditions that are far from real road conditions. This article compares the results of rolling resistance tests conducted in road conditions with the results of laboratory tests conducted on roadwheel facilities. The overview of results shows that the results of tests conducted in accordance with ISO and SAE standards on steel drums are very poorly correlated with more objective results of road tests. Significant differences occur both in the Coefficients of Rolling Resistance (CRR) and in the tire ranking. Only covering the drums with replicas of road surfaces leads to a significant improvement in the results obtained. For investigations of rolling resistance in non-steady-state conditions, the flat track testing machine (TTF), equipped with asphalt cassettes, is shown to provide measurement data in agreement with the road test data. [ABSTRACT FROM AUTHOR]

The changes in the life status of Larix gmelinii along the gradient of urbanized ecotypes were considered on the basis of the population analysis and morphometric approach. L. gmelinii growing under different conditions differed in a number of size and growth characteristics of the photosynthetic activity. The highest values were found in plants growing in public gardens and on city streets under conditions of high insolation. Population analysis of L. gmelinii in an urbanized environment was carried out on the basis of quantitative parameters that characterized the growth and morphogenesis of plants (annual growth, indicators of photosynthetic activity). The determining set of characters for the vitality analysis of L. gmelinii consisted of biologically significant characters with a high degree of variability: length of shoot growth (CV varied from 39.09 to 68.86%), weight of needles at annual growth (CV 51.81–120.52%), weight of annual shoot (CV 67.73–119.85). The vitality structure of the populations of the species in the vegetative ontogenetic state changed from depressive to equilibrium, with the population quality index changing from 0.2 to 0.333. The analysis of landscaping of the city transport highways demonstrated that local populations of L. gmelinii in the generative ontogenetic state were of a prosperous type, with the population quality index varying slightly from 0.47 to 0.49. The plasticity of the species and a high viability of L. gmelinii due to the resistance to air pollution and unpretentiousness to soil conditions support a broad application of the larch for landscaping of urban areas. [ABSTRACT FROM AUTHOR]

A simple method of demonstrating apparent weightlessness in free fall is described. The Apollo 15 hammer and feather drop experiment can be recreated in the classroom using a book to shield the feather from air resistance. Plastic toys and a feather thrown together in a plastic bottle can be used to recreate an apparent weightless environment close to the surface of the Earth. Since the bottle follows a parabolic trajectory, the objects within also follow a parabolic path and are seen to float as if in a space ship in orbit around the Earth. This demonstration is useful for demonstrating to students that apparent weightlessness is not confined to outer space. The use of toy fish in the experiments makes a connection with the neutral buoyancy training of astronauts. The experiments also exemplify Newton's second law that force is mass times acceleration. [ABSTRACT FROM AUTHOR]

Long-term exposure to high concentrations of fine particulate matter (PM2.5) in the atmosphere has negative impact on the long-term health effect of human beings. Traditional air filtration materials are difficult to take into account the high-efficiency and low-resistance protection, and are non-degradable, which not only aggravates global plastic pollution, but also tends to cause stronger microplastics hazards. To solve the problems above-mentioned, self-powered and biodegradable nanofibrous membranes with air slip effect are developed to achieve a long-term and low-resistance respiratory protection. A two-step hydrothermal method is proposed to prepare the easily dispersed BTO dielectric with an average particle size of 49.6 nm, then the BTO nanoparticles (BTO NPs) are embedded into the PLA nanofibrous membranes by a combined “electrospinning‒electrospray” strategy. The frictional electricity effect and size effect of BTO NPs are utilized to simultaneously regulate the filtration efficiency and resistance of nanofibrous membranes. By controlling the concentration of BTO NPs in spraying suspension, the relationship between it and electroactivity, filtration properties and mechanical properties of PLA/BTO nanofibrous membranes is investigated. Microstructure characterization and performance testing show that the PLA/BTO nanofibrous membranes have excellent electroactivity, filtration properties and mechanical properties. The surface potential of PLA/BTO nanofibrous membranes is up to 5.9 kV, the dielectric constant is up to 1.20 F/m, and the average output voltage is up to 12.4 V. Benefiting from the enhanced slip effect and increased electroactivity, the electrospun-electrosprayed PLA/BTO10 nanofibrous membrane could significantly reduce air resistance (as low as 20 Pa), while improving the filtration efficiency of PM0.3 by 7.78%−9.05% and the filtration efficiency of PM2.5 by 2.90%−13.19%. Even at the high airflow velocity of 85 L/min, the filtration efficiency of PM2.5 still achieves as high as 97.25%. At the same time, the increase of tensile strength of PLA/BTO nanofibrous membranes is up to 60% (22.5 MPa), the increase of elongation at break is up to 68% (25%), and the fracture toughness increases by 1.3 times (3.6 MJ/m3). Therefore, the proposed degradable PLA/BTO nanofibrous membrane filters with long-term and low-resistance filtration properties have some broad application prospects in the field of respiratory protection, and also provide a new approach to alleviate the plastic pollution exacerbated by discarded masks.

Micro-hole aerostatic bearings are important components in micro-low-gravity simulation of aerospace equipment, and the accuracy of micro-low-gravity simulation tests is affected by them. In order to eliminate the influence of air resistance on the attitude control accuracy of remote sensing satellites and achieve high fidelity of micro-low-gravity simulation tests, in this study, a design and parameter optimization method was proposed for micro-hole aerostatic bearings for a vacuum environment. Firstly, the theoretical analysis was conducted to investigate the impact of various bearing parameters and external conditions on the bearing load capacity and mass flow. Subsequently, a function model describing the variation in bearing load capacity and mass flow with bearing parameters was obtained utilizing a BP neural network. The parameters of aerostatic bearings in a vacuum environment were optimized using the non-dominated sorting genetic algorithm (NSGA-II) with the objectives of maximizing the load capacity and minimizing the mass flow. Subsequently, experimental tests were conducted on the optimized bearings in both atmospheric and vacuum conditions to evaluate their load capacity and mass flow. The results show that in a vacuum environment, the load capacity and mass flow of aerostatic bearings are increased compared to those in standard atmospheric conditions. Furthermore, it has been determined that the optimal solution for the bearing's load capacity and mass flow occurs when the bearing has an orifice aperture of 0.1 mm, 36 holes, and an orifice distribution diameter of 38.83 mm. The corresponding load capacity and mass flow are 460.644 N and 11.816 L/min, respectively. The experimental and simulated errors are within 10%; thus, the accuracy of the simulation is verified. [ABSTRACT FROM AUTHOR]

During engineering blasting operations, various man-made elements (particles) can be formed from the structure due to the impact of an explosion, which, as experimental data show, can have a completely arbitrary shape and a fairly large mass and speed. This article is devoted to consideration of the ballistics of elongated elements and the derivation of the calculated dependencies that allow one to estimate the trajectory of their movement. [ABSTRACT FROM AUTHOR]

The coexistence of PM2.5 pollution and the ongoing pandemic poses significant risks to human health. Protective masks incorporating high-efficiency particulate air filters offer adequate protection against PM2.5 particles. Micro/nanofibrous nonwovens, including melt-blown and electrospun nonwovens, are essential filter materials. This study focuses on the filtration mechanism and geometric structure design of multi-level structured micro/nanofibrous nonwovens. A comprehensive investigation was conducted on a filter core material composed of polyacrylonitrile, a polystyrene electrospun membrane, a polypropylene (PP) melt-blown membrane, and a supporting outer layer of a PP spun-bonded membrane. The resulting nonwovens exhibited exceptional filtration efficiency of 99.98% for PM0.3 particles, with a low pressure drop of 60 Pa at 32 L/min inlet air velocity. Filtration efficiencies of 99.99% and 100% were achieved for PM1.0 and PM2.5 particles, respectively. These characteristics make the designed composite nonwovens a very promising filter material for masks. The study contributes to understanding filtration mechanisms and developing advanced high-efficiency filter materials, enhancing protection against airborne pollutants. [ABSTRACT FROM AUTHOR]

Copyright of Düzce University Journal of Forestry / Düzce Üniversitesi Orman Fakültesi Ormancılık Dergisi is the property of Duzce University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Platooning is an effective way to reduce air resistance and fuel consumption in vehicular transportation. However, stochastically generated disturbances can significantly impact the string stability of platoons. This article proposes a novel control law, based on sliding mode control and leader‐predecessor communications, designed to improve the exponential mean‐square string stability of platoons with Ito‐type stochastic disturbances that consider friction force. Specifically, our approach employs a third‐order nonlinear dynamic model to capture the relevant spatiotemporal correlations present in vehicle platoons. The proposed longitudinal control strategy effectively stabilizes the platoons with time delay and was verified through simulation experimentation. In this study, the stability of sliding mode motion is thoroughly investigated by means of sub‐reachable and practical stability analysis with sliding mode control. The findings of this study provide a theoretical foundation for further research on vehicle platoons with increasingly complicated interference and time delays. Overall, our results demonstrate that our approach can achieve significant improvements in both fuel economy and exhaust emissions while maintaining high levels of string stability, further contributing to the development of efficient and sustainable transportation systems. [ABSTRACT FROM AUTHOR]

Gas embolism is a medical condition that occurs when gas bubbles are present in veins or arteries, decreasing blood flow and potentially reducing oxygen delivery to vital organs, such as the brain. Although usually reported as rare, gas embolism can lead to severe neurological damage or death. However, presently, only limited understanding exists regarding the microscale processes leading to the formation, persistence, movement, and resolution of gas emboli, as modulated by microvasculature geometrical features and blood properties. Because gas embolism is initially a physico-chemical-only process, with biological responses starting later, the opportunity exists to fully study the genesis and evolution of gas emboli using in vitro microfluidic networks mimicking small regions of microvasculature. The microfluidics networks used in this study, which aim to mimic microvasculature geometry, comprise linear channels with T-, or Y-junction air inlets, with 20, 40, and 60 μm widths (arterial or venous), and a 30 μm width honeycombed network (arterial) with three bifurcation angles (30°, 60°, and 90°). Synthetic blood, equivalent to 46% haematocrit concentrations, and water were used to study the modulation of gas embolism-like events by liquid viscosity. Our study shows that (i) longer bubbles with lower velocity occur in narrower channels, e.g., with 20 μm width; (ii) the resistance of air bubbles to the flow increases with the higher haematocrit concentration; and lastly (iii) the propensity of gas embolism-like events in honeycomb architectures increases for more acute, e.g., 30°, bifurcation angles. A dimensionless analysis using Euler, Weber, and capillary numbers demarcated the conditions conducive to gas embolism. This work suggests that in vitro experimentation using microfluidic devices with microvascular tissue-like structures could assist medical guidelines and management in preventing and mitigating the effects of gas embolism. [ABSTRACT FROM AUTHOR]

The extensive use of antibiotics in the medical and aquaculture industries has led to antibiotic resistance, be a global public health concern. Compared with soil and water, there are few reports on antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs) in the air. To provide theoretical support for scientific and effective response to the cross-media migration of microbial resistance, this paper comprehensively reviewed the occurrence status, influencing factors and transmission mechanism of ARB and ARGs in different types of ambient air at home and abroad. The results showed that the abundance of ARB and ARGs in the air was affected by environmental conditions and sampling factors. The pollution was more serious in typical polluted areas such as animal farms, sewage treatment plants and hospitals. The dominant types of ARGs in the above environment were tetracyclines, sulfonamides and β-lactams. Among them, the abundance of ARGs in the air of animal farms was about 2-3 orders of magnitude higher than that in other environments. The highest abundance was found in pig farm compared to other animal houses. At present, there was still no standard for the sampling requirements of ARB and ARGs in the air. The sampling season, duration, particle size and coexisting pollutants all affected their detection. Air pollution, soil water content, rainfall and air mass movement were proved to play a certain role in affecting the spread of ARB and ARGs in the air. Based on it, the research on the migration mechanism of ARB and ARGs at the soil-air interface needs to be further intensified. The review aimed to comprehensively reveal the occurrence characteristics of ARB and ARGs in the air, and provide theoretical support for the scientific and effective response to the cross-media migration of microbial resistance. [ABSTRACT FROM AUTHOR]

The cooling performance of a centrifuge was enhanced using a perforated windshield. The windshield spatially separates the rotor and the chamber, reducing turbulence and air resistance. On the other hand, during centrifuge rotation, heat is generated by friction between the internal structure and air. Optimizing the windshield shape and facilitating efficient heat exchange with the chamber wall are essential for cooling the sample container inside the windshield. This study examined the cooling performance of the perforated windshield through analysis and experiment. The effects of the presence, location, and diameter of the perforations were compared using computational fluid dynamics (CFD) simulations and considering temperature and flow characteristics. These results suggest that the perforated windshield enhances the cooling performance of the centrifuge. [ABSTRACT FROM AUTHOR]

The paper presents the results of creating protective coatings on niobium and tantalum samples. These coated samples are tested for heat resistance in air in the temperature range of 1700–1900°C. The coating is formed by the method of activated vacuum diffusion saturation at temperatures of 1150–1310°C. When forming a part of the protective coatings, a layer of slurry is applied to the surface of the samples, followed by chemical and thermal treatment in a vacuum in the presence of NaCl vapours. A thermodynamic analysis of possible chemical reactions taking place in the process of formation of protective coatings is carried out. The developed heat-resistant coatings provide protection of niobium samples from air oxidation at a temperature of 1700°C from 8 to 13.5 hours. Heat-resistant coatings created on samples with Nb and Ta protect them from exposure to an oxidizing environment from 3 to 6.3 hours at a temperature of 1800°C and for 0.5 hours at a temperature of 1900°C. [ABSTRACT FROM AUTHOR]

Convoys composed of autonomous vehicles could improve the transportation and freight industries in several ways. One of the avenues of improvement is in fuel efficiency, where the vehicles maintain a close following distance to each other in order to reduce air resistance by way of the draft effect. While close following distances improve fuel efficiency, they also reduce both the margin of safety and the system's tolerance to disturbances in relative position. The system's tolerance to disturbances is known as string stability, where the error magnitude either grows or decays as it propagates rearward through the convoy. One of the major factors in a system's string stability is its delay in sending state updates to other vehicles, the most pertinent being a hard braking maneuver. Both external sensors and vehicle-to-vehicle communication standards have relatively long delays between peer vehicle state changes and the information being actionable by the ego vehicle. The system presented here, called the Convoy Vehicular Ad Hoc Network (Convoy VANET), was designed to reliably propagate emergency event messages with low delay while maintaining reasonable channel efficiency. It accomplishes this using a combination of several techniques, notably relative position-based retransmission delays. Our results using Network Simulator 3 (ns3) show the system propagating messages down a 20-vehicle convoy in less than 100 ms even with more than a 35% message loss between vehicles that are not immediately adjacent. These simulation results show the potential for this kind of system in situations where emergency information must be disseminated quickly in low-reliability wireless environments. [ABSTRACT FROM AUTHOR]

Understanding both positive and negative impacts of climate change is essential for comprehensively assessing and well adapting to the impacts of changing climate. Conventionally, climate warming is revealed to negatively impact human activities. Here, we reveal that human beings' performance in anaerobic sports may benefit from climate warming. Using global weather observation and athletes' performance datasets, we show that world-top athletes' performances in nearly all athletics anaerobic events (i.e., sprints, jumps and throws) substantially improve as ambient temperature rises. For example, 100 m performance monotonically improves by 0.26 s as ambient temperature rises from 11.8° to 36.4 °C. Using Coupled Model Intercomparison Project Phase 6 datasets, we further show that global warming can substantially improve world-top athletes' performance in eleven of the thirteen Olympics athletics anaerobic events by 0.27%–0.88% and 0.14–0.48% under high-emission and medium-emission scenarios, respectively, during 1979–2100. Among them, the improvements for 100 m are 0.59% (0.063 s) and 0.32% (0.034 s), respectively. Mechanism analysis shows that the warmed ambient atmosphere can improve competitors' performance through expanding the air and thus reducing the air resistance to the competitors and throwing implements for hummer throw and all the sprints, hurdling and jumps. Quantitative analysis estimates that this thermodynamic process is essential for the impacts of warmed ambient atmosphere on the performances in these events as physiological processes are. [ABSTRACT FROM AUTHOR]

Accumulation landslides are prone to occur during the continuous infiltration of heavy rainfall, which seriously threatens the lives and property safety of local residents. In this paper, based on the Green-Ampt (GA) infiltration model, a new slope rainfall infiltration function is derived by combining the effect of air resistance and lateral seepage of saturated zone. Considering that when the soil layer continues to infiltrate after the saturation zone is formed, the air involvement cannot be discharged in time, which delays the infiltration process. Therefore, the influence of air resistance factor in soil pores is added. According to the infiltration characteristics of finite long slope, the lateral seepage of saturated zone is introduced, which makes up for the deficiency that GA model is only applicable to infinite long slope. Finally, based on the seepage characteristics of the previous analysis, the overall shear strength criterion is used to evaluate the stability of the slope. The results show that the safety factor decreases slowly with the increase of size and is inversely correlated with the slope angle and initial moisture content. The time of infiltration at the same depth increases with the increase of size and slope angle, and is inversely correlated with the initial moisture content, but is less affected by rainfall intensity. By comparing with the results of experimental data and other methods, the results of the proposed method are more consistent with the experimental results than other methods. [ABSTRACT FROM AUTHOR]

Ballistics is an area of flight, and fewer subjects were of greater importance to nation states in the eighteenth century. William Mountaine who published on the topic in 1747 and 1781, wrote: 'It is not possible in the nature of things for any one kingdom to continue long in a state of peace and tranquility', and 'the art of gunnery has from time to time engaged the attention of the most eminent mathematicians'. This paper describes the slow up-take of ideas, first put forward explicitly by Benjamin Robins in 1742, which challenged the belief that air resistance could be neglected in the flight of cannon balls, and asks why it could be, that for a topic so pressing, a clearly wrong mathematical theory was upheld for so long. While considering a number of factors, it argues the attraction of beautiful and simple geometry can be beguiling. [ABSTRACT FROM AUTHOR]

In high-speed motors, there is a huge amount of heat generation from core and winding losses, which may result in thermal failures or motor performance deterioration. In the prevention of heat accumulation, efficient cooling technology is critical for smooth and reliable motor movement. This paper summarizes the diverse application of high-speed motor and thermal requirements, such as in electrical devices, turbo-machinery, and high-precision machine tools. Three paths of case convection—cooling, internal ventilation cooling and spindle core cooling—are analyzed. Methods for configuring thermal resistance and improving cooling efficiency are summarized. Among them, coolant flow characteristics and flow channel shapes, gas supply ventilation systems, and methods to reduce air resistance, as well as axial cooling and integrated heat pipe structures, are extensively investigated. Finally, the development prospects of high-speed motor cooling are also forecasted. At present, the primary research directions are to reduce the heat generated by the heat source, utilize the latent heat of the coolant, optimize the cooling flow path of the shell, design an axial air-cooling circulation system, and enhance the heat dissipation of the spindle. [ABSTRACT FROM AUTHOR]

We formulate a phenomenological model to study the power applied by a cyclist on a velodrome—for individual timetrials—taking into account the straights, circular arcs, connecting transition curves, and banking. The dissipative forces we consider are air resistance, rolling resistance, lateral friction and drivetrain resistance. Also, in general, the power is used to increase the kinetic and potential energy. However, to model a steady ride—as expected for individual timetrials—we assume a constant centre-of-mass speed and allow the cadence and power to vary during a lap. Hence, the only mechanical energy to consider is the increase of potential energy due to raising the centre of mass upon exiting each curve. Following derivations and justifications of expressions that constitute this mathematical model, we present a numerical example. We show that, as expected, the cadence and power vary only slightly during a steady ride. In addition, we examine changes in the required average power per lap due to modifications of various quantities, such as air density at a velodrome, laptime and several others. Such an examination is of immediate use in strategizing the performance for individual pursuits and the Hour Record. [ABSTRACT FROM AUTHOR]

The loading and unloading elevators are the primary equipment in the refueling system, used for transferring fuel assemblies in the sodium-cooled fast reactors. The guideway friction pairs are the critical components of these elevators in the refueling system. With the excellent hardness and wear resistance in air, nitrided W18Cr4V steel is a promising material for the guideway friction pairs. In order to assess the feasibility of using nitrided W18Cr4V steel, it is essential to understand the aging behavior of nitrided W18Cr4V steel in high-temperature sodium. Aging tests were conducted on nitrided W18Cr4V steel in sodium and in argon environments at various temperatures for different exposure times. The results showed that the nitrogen atoms in the nitrided layer exhibited bidirectional diffusion behavior in the sodium or argon environment at 540 °C. Compared to the argon environment, cracks formed within the nitrided layer and the diffusion of nitrogen into the sodium was accelerated in the nitrided layer. As a significant number of nitrogen atoms had diffused into the sodium, there was little difference in the hardness between nitrided W18Cr4V steel and non-nitrided W18Cr4V steel after long-term exposure to 540 °C sodium. [ABSTRACT FROM AUTHOR]

The article discusses the development of an unmanned aerial-aquatic vehicle system called TJ-FlyingFish. The system is designed to maneuver effectively in both water and air, utilizing a dual-speed and tilting propulsion units for thrust and agility. A multi-sensor-based localization system supports seamless transitions between aerial and aquatic environments. The article presents the design, control scheme, and experimental results of the TJ-FlyingFish system. The text also discusses challenges in localization, dynamics modeling, and control design, as well as the performance of the propulsion units. Ongoing efforts are focused on improving algorithm and structure design for better performance. [Extracted from the article]

The study of insect flight is important for conservation and sustainability efforts, as predicting insect dispersal can aid management programmes in tackling economic and ecological harm from, for example, invasive species. Flight mills are invaluable tools for measuring the factors of insect flight under laboratory conditions, as they lower several technical and financial barriers to conduct experiments. It is especially difficult, however, to make assumptions about the energetic cost of tethered flights conducted using different tethers, or even on different flight mills, due to the mechanical variability of the bearing friction and air resistance of the rotating assembly. This additional uncertainty necessitates a larger number of replicates for any given standard of statistical confidence. By characterising flight mill friction, this uncertainty can both be reduced in magnitude and assigned a specific, well‐defined numerical value. We present a simple methodology to characterise this friction through dynamic calibration of the flight mill, at a high statistical confidence. This study uses videography of a flight mill undergoing free velocity decay due to friction, using an in‐house developed software to extract angular velocity from video data. However, the technique is readily adaptable to other measurement techniques. Using the velocity, alongside the mass moment of inertia of the flight mill, allows us to determine the rotational friction coefficient. This friction coefficient provides precise measurements of thrust production, and therefore the energy expenditure of flight, by the tethered insect. [ABSTRACT FROM AUTHOR]

Air salinity is one of the problems for horticulture production in coastal areas. Cabbage and Cauliflower are horticulture commodities that have the potential to develop in coastal areas. The present study aimed to examine the agro-physiological response of cabbage (Brassica oleracea var. capitata) and cauliflower (B. oleracea var. botrytis) to different concentrations of air salinity. This research was a factorial experiment on polybags arranged according to a completely randomized block design with two factors. The first factor was the crop type, namely cabbage (Grand 22) and cauliflower (Larissa F1). The second factor was the concentration of air salinity, namely 0 dS. m-1, 6 dS. m-1, 12 dS. m-1, and 18 dS. m-1. The agro-physiological changes studied were crop yield, leaf chlorophyll content, stomata density, and proline content. A stress tolerance index was measured to determine the level of crop resistance to air salinity stress. The results explained that air salinity was not able to affect crop growth and yield, but it enabled to affect crops physiologically. The highest decrease in leaf chlorophyll content was at 18 dS. m-1 of 29.16% in the vegetative stage and 37.88% in the generative stage. There was an increase in proline accumulation of leaf (1,320.63%) when the air salinity was increased (18 dS. m-1). However, the accumulation of cabbage proline was lower than that of cauliflower. Based on the stress tolerance index, cabbage is included in the category of tolerant, while cauliflower is in the category of moderate tolerance to air salinity. [ABSTRACT FROM AUTHOR]

This paper explains the detailed design and implementation process of a solar car. The design of the proposed solar car system represents a broader perspective than that of traditional solar or electric cars. It can be regarded as a hybrid vehicle that integrates solar power as a fundamental aspect of its performance, while also offering the option of direct plug-in charging. The proposed solar-powered four-wheeled car uses two motors to increase the efficiency of power consumption, as both motors generate a relatively high torque and power ratio. The design of the car considers aerodynamics. The solar panel placement has a unique geometric shape that reduces air resistance, thus increasing efficiency and stability on the road. To increase the total rated power to 810 W, six panels were installed on top of the car. Each panel is capable of producing 135 W with an efficiency of 23%. In addition, the car features two identical motor controllers paired with adjacent motors, which contributes to a rear-wheel-drive experience. To safeguard the motor controllers, the system includes protective elements such as an in-line fuse, which is directly connected to the battery. The conducted testing of the implemented car validates the successful and adaptable design, offering promising prospects for an efficient commercial prototype of a solar car. [ABSTRACT FROM AUTHOR]

Installing a precooler behind the intake is an effective approach for hypersonic air-breathing pre-cooled engine to cool the hot incoming air. Synergetic airbreathing rocket engine is a revolutionary hypersonic air-breathing pre-cooled engine with complex thermodynamic cycle i.e. air cycle, helium cycle. Air/helium precooler is a key component and its configuration and operating condition have great effect on the performance characteristics of air-breathing pre-cooled engine. Thus, the minimum periodic flow and heat transfer model of the precooler are established. The effects of key parameters on the heat transfer performance of precooler are numerically studied. The results indicate that: when the tube row number increases from 7 to 15, the average heat transfer coefficient of air side decreases by 57%, the heat exchange rate increases by 19%, and effectiveness increases by 18.4%. The tube transverse pitch can enhance the heat transfer coefficient of air and helium side, while the heat exchange rate decreases by 33 % when the tube transverse pitch increases from 1.5 to 3.5. The helium inlet velocity can improve the heat transfer performance of precooler and reduce the flow resistance of air side. [ABSTRACT FROM AUTHOR]

Since the dead-zone fault in substations often has a relatively long removal time, it may damage the insulation of power equipment and even threaten the stability of the power system. In this paper, the movement of the dead-zone fault electric arc in a 220-kV substation is investigated. The arc chain model for the dead-zone fault electric arc is developed; the influences of electromagnetic force, thermal buoyancy, and the air resistance stressed on the electric arc are comprehensively considered. The electric arc velocity and displacement are computed. Then, the spreading characteristics of the dead-zone electric arc under various conditions are studied. The spreading trend of the dead-zone fault electric arc is summarized. Finally, measures to inhibit the spreading of the electric arc are suggested. The study indicates that the movement of the electric arc in the dead zone during the early stage is primarily influenced by the electromagnetic force resulting from the overpass and conductor, and the arc is concave and has an irregular trajectory. The inclination angle of the conductor significantly affects the direction of the electromagnetic force. If the conductor is laid horizontally, the electric arc is subjected to a smaller force. The electromagnetic force stressed on the electric arc is mainly attributed to the fault phase conductor and the electric arc body itself, whereas those from the other phase conductors are minor. The initial position of the arc root has a certain impact on the movement of the electric arc. The use of the insulating materials restricts the arc root movement. [ABSTRACT FROM AUTHOR]

Highly permeable particulate matter (PM) can carry various bacteria, viruses and toxics and pose a serious threat to public health. Nevertheless, current respirators typically sacrifice their thickness and base weight for high-performance filtration, which inevitably causes wearing discomfort and significant consumption of raw materials. Here, we show a facile yet massive splitting eletrospinning strategy to prepare an ultrathin, ultralight and radiative cooling dual-scale fiber membrane with about 80% infrared transmittance for high-protective, comfortable and sustainable air filter. By tailoring antibacterial surfactant-triggered splitting of charged jets, the dual-scale fibrous filter consisting of continuous nanofibers (44 ± 12 nm) and submicron-fibers (159 ± 32 nm) is formed. It presents ultralow thickness (1.49 μm) and base weight (0.57 g m−2) but superior protective performances (about 99.95% PM0.3 removal, durable antibacterial ability) and wearing comfort of low air resistance, high heat dissipation and moisture permeability. Moreover, the ultralight filter can save over 97% polymers than commercial N95 respirator, enabling itself to be sustainable and economical. This work paves the way for designing advanced and sustainable protective materials. Development of high-performance, comfortable and sustainable air filters is challenging. Here, authors design an ultrathin, ultralight dual scale fiber mat composed of true nanofibers and submicron-fibers to integrate the high protection, thermal wet comfort and save raw materials. [ABSTRACT FROM AUTHOR]

This study delves into the intricate dynamics of laser-induced damage in fused silica using a time-resolved pump-probe (TRPP) shadowgraph. Three typical ultra-fast processes, laser-induced plasma evolution, shockwave propagation and material fracture splashing, were quantitatively investigated. The results indicate that the diameter of plasma is proportional to the pulse laser energy and increases linearly during the pulse laser duration with an expansion rate of approximately 6 km/s. The maximum shockwave velocity on the air side is 9 km/s, occurring at the end of the pulse duration, and then rapidly decreases due to air resistance, reaching approximately 1 km/s around a 300 ns delay. After hundreds of nanoseconds, there is a distinct particle splashing phenomenon, with the splashing particle speed distribution ranging from 0.15 km/s to 2.0 km/s. The particle sizes of the splashing particles range from 4 μm to 15 μm. Additionally, the smaller the delay, the faster the speed of the splashing particles. Overall, TRPP technology provides crucial insights into the temporal evolution of laser-induced damage in fused silica, contributing to a comprehensive understanding essential for optimizing the performance and safety of laser systems. [ABSTRACT FROM AUTHOR]

The air pressure resistance experienced by an automotive door during its closing process significantly affects user experience. However, owing to the motion complexity of sliding doors, their aerodynamic behavior during closing has not been investigated. In this study, a fluid–solid coupled simulation approach is proposed, in which data exchange between multibody dynamics simulation and computational fluid dynamics simulation is achieved via the functional mockup interface protocol. Actual vehicle tests are conducted to validate the coupled simulation approach, and the results show an average error of 5.2% for the maximum air pressure in the cabin during door-closing. Investigations into the aerodynamic behavior show that the air pressure distribution inside the cabin remains highly uniform throughout the door-closing process and that a significant correlation exists between the air pressure variation and sliding door motion. The effects of the motion mechanism parameters of the sliding door on air pressure are analyzed. A positive correlation is indicated between the air pressure and middle rail radius. When the radius increases from 60 to 120 mm, the maximum air pressure increases by 13.6%. Positive correlations are indicated between the air pressure and the offsets of the hinge of the middle arm along the x- and y-directions. When the hinge's offset is changed from −10 to 10 mm along the x- and y-directions, the maximum air pressure increases by 5.5% and 8.9%, respectively. [ABSTRACT FROM AUTHOR]

This article presents the findings of two experiments that measured the acceleration of a ball rolling down a V-shaped channel. Despite using different release and timing methods, the experiments yielded similar results. The article also examines the disparities between Galileo's description of the experiment and the actual setup, particularly regarding the groove's depth. The results indicate that velocity changes in equal time intervals, and displacement increases as the square of the time taken. The article concludes by discussing the implications of rolling and rectilinear motion on the experiment and emphasizes the significance of precise measurement techniques and manual skills. In another experiment, the article compares manual and mechanical timing methods for measuring the descent of balls down an inclined plane. The results show that both methods produced similar outcomes, with a slight discrepancy between theoretical and experimental data. The article suggests that factors like surface roughness and ball imperfections may contribute to these discrepancies. Overall, the experiment underscores the importance of accurate measurement techniques and the complexities of real-world motion. [Extracted from the article]

This study details the development and validation of a graphene-based ice detection system, designed to enhance flight safety by monitoring ice accumulation on aircraft surfaces. The system employs a semiconductive polymer (PEDOT:PSS) with graphene electrodes, interpreting resistance changes to detect water impact and ice formation in real time. The sensor's performance was rigorously tested in a wind tunnel under various temperature and airflow conditions, focusing on resistance signal dependency on air temperature and phase change. The results demonstrate the sensor's ability to distinguish water droplet impacts from ice formation, with a notable correlation between resistance signal amplitude and water droplet impacts leading to ice accretion. Further analysis shows a significant relationship between air temperature and the resistance signal amplitude, particularly at lower temperatures beneficial to ice formation. This underlines the sensor's precision in varied atmospheric conditions. The system's compact design and accurate detection highlight its potential for improving aircraft ice monitoring, offering a path toward a robust and reliable ice detection system. [ABSTRACT FROM AUTHOR]

This study presents a specialized mixer design for gas burners aimed at improving the efficiency of phase mixing while minimizing system resistance and energy consumption. The proposed design utilizes a multi‐cavity mixer employing both radial and axial mixing techniques, eliminating the need for additional power supply. Full premixed combustion of small gas‐fired industrial boiler has the function of "inhibiting" NOx emission from the source, and good mixing of fuel and combustion supporting air in the early stage is the primary prerequisite for realizing full premixed combustion denitration. In this article, a radial multichamber static mixer is designed following the characteristics of full premixed mixing in gas‐fired industrial boilers. The results demonstrate that the maximum pressure drop of the static mixer is 806 Pa; for gas and air branch pipes, the resistance coefficient f decreases rapidly with the increase in Reynolds number; when Re ≥ 1.2 × 103, the resistance coefficient in the air branch pipe decreases slowly; when Re ≥ 4.5 × 103, the resistance coefficient of gas branch pipe decreases slowly. Additionally, the maximum calculation error of symmetrical gas branch pipe is 9.1%. The static mixer's inlet exhibits a converted velocity of 24 m/s, and the outlet demonstrates an airflow velocity of 23.2 m/s. As a result, a kinetic energy loss of 6.5% is observed. The static mixing chamber makes the airflow rotate and causes different gases to shear and mix. The mixing channel has the function of correcting the airflow deviation, especially for the sudden expansion section. Generally, the two gases can be mixed evenly at the outlet of the mixer. The standard k‐e model and realizable k‐e model are employed to simulate the sudden expansion channel, and indicate that the standard k‐e has a wider range of influence. Further investigation is recommended to better comprehend and optimize this particular area of influence. [ABSTRACT FROM AUTHOR]

Copyright of Gold (1001-1277) is the property of Gold Magazine Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Purpose: The purpose of this study is to investigate the mechanical properties of denim fabrics constructed from ring-spun and open-end rotor spun yarns. Design/methodology/approach: Yarns of 10s Ne count using cotton fibers were spun using the ring and open-end rotor spinning technologies. The yarns were used to produce a denim fabric on an air-jet loom with a 3/1 twill weave structure. Mechanical tests – tensile strength, tear strength, abrasion resistance and pilling resistance – of denim fabrics were evaluated. The test results were analyzed using analysis of variance with the help of Software Package for Social Sciences. Findings: Denim fabrics made by using ring-spun yarns exhibited better tensile and tear strength properties than denim fabrics made by using open-end rotor spun yarns. On the contrary, denim produced using open-end rotor yarns have better abrasion resistance, pilling resistance and air permeability than those produced using ring-spun yarns. Originality/value: Both spinning techniques have a significant influence on the properties of denim fabrics. Whenever better tensile and tear strength is required, it is better to use ring-spun yarns, while if the requirement is better abrasion resistance and pilling resistance with high air permeability, then open-end rotor spun yarns shall be used. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Ordnance Equipment Engineering is the property of Chongqing University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)