Air Resistance Research Articles

A junction temperature model based on heat flow distribution in an IGBT module with solder layer voids

The presence of voids in a solder layer affects the thermal reliability of an insulated-gate bipolar transistor (IGBT). In this work, the effects of the size and fraction of solder layer voids and the power losses of chips on heat flow distribution, junction temperature and thermal resistance were investigated. It was found that it was difficult for the heat to flow through the voids due to the high thermal resistance of air. Therefore, the heat above the voids could only flow horizontally, and then avoid the voids and move downward in the solder layer and the following layers, leading to a temperature difference in the surface chip layer. An improved junction temperature model based on the heat flow distribution (HD) considering the solder layer voids was established, the horizontal thermal resistance and horizontal heat capacity are introduced to characterize the effect of the solder layer voids, and the parameter extraction method was proposed. The temperature difference on the surface of the module increased with the increase of the void fraction, and when the void fraction increased from 0 % to 40 %, the surface temperature difference increased from 9.591 °C to 109.86 °C. The results showed that the proposed model not only had a higher accuracy in the estimation of the junction temperature compared with the traditional Cauer model and the improved Cauer model, but also monitored the horizontal temperature differences in the chip layer precisely.

Two-Dimensional Piezoelectric Nanofibrous Webs by Self-Polarized Assembly for High-Performance PM0.3 Filtration.

Particulate matter (PM) pollution has posed a serious threat to public health, especially the global spread of infectious diseases. Most existing air filtration materials are still subjected to a compromise between removal efficiency and air permeability on account of their stacking bulk structures. Here, we proposed a self-polarized assembly technique to create two-dimensional piezoelectric nanofibrous webs (PNWs) directly from polymer solutions. The strategy involves droplets deforming into ultrathin liquid films by inertial flow, liquid films evolving into web-like architectures by instantaneous phase inversion, and enhanced dipole alignment by cluster electrostatics. The assembled continuous webs exhibit integrated structural superiorities of nanoscale diameters (∼20 nm) of the internal fibers and through pores (∼100 nm). Combined with the wind-driven electrostatic property derived from the enhanced piezoelectricity, the PNW filter shows high efficiency (99.48%) and low air resistance (34 Pa) against PM0.3 as well as high transparency (84%), superlight weight (0.7 g m-2), and long-term stable service life. This creation of such versatile nanomaterials may offer insight into the design and upgrading of high-performance filters.

A porous Janus nanofiber membrane with unidirectional water vapor transport for efficient dust personal protection

The generation of coal dust affects all aspects of coal mining, posing a serious threat to miner’s health. However, developing a novel respirator material with high respiratory efficiency and low resistance poses a significant challenge. Additionally, traditional masks can cause water vapor from exhaled breath to condense into minuscule droplets that adhere to the inside of the mask, reducing comfort. In this study, a porous Janus nanofiber membrane was successfully prepared using sequential electrospinning technology combined with post-treatment techniques. Due to its unique porous structure and double-sided anisotropy, the Janus nanofiber membrane achieves high filtration efficiency and low air resistance simultaneously. Under a high-intensity respiration rate of 85 L/min, the Janus nanofiber membrane maintains a filtration efficiency of 99.98 % and a pressure drop of 134.7 Pa. Moreover, the Janus nanofiber membrane can effectively transport water vapor from exhaled breath to the external environment. The external hydrophobic membrane effectively intercepts water mist from the air. The Janus nanofiber membrane water vapor transmittance can reach 2633.863 cm3/m2·d·Pa. The contact angle of the hydrophobic side of the nanofiber membrane reached 145°, while the contact angle of the hydrophilic side reached 0° after 3 s of water droplet exposure. These features greatly improve user comfort. Taken together, our findings demonstrate the promising potential of the newly developed Janus nanofiber membrane for individual protection.

Aircraft Wake Evolution Prediction Based on Parallel Hybrid Neural Network Model

To overcome the time-consuming drawbacks of Computational Fluid Dynamics (CFD) numerical simulations, this paper proposes a hybrid model named PA-TLA (parallel architecture combining a TCN, LSTM, and an attention mechanism) based on the concept of intelligent aerodynamics and a parallel architecture. This model utilizes CFD data to drive efficient predictions of aircraft wake evolution at different initial altitudes during the approach phase. Initially, CFD simulations of continuous initial altitudes during the approach phase are used to generate aircraft wake evolution data, which are then validated against real-world LIDAR data to verify their reliability. The PA-TLA model is designed based on a parallel architecture, combining Long Short-Term Memory (LSTM) networks, Temporal Convolutional Networks (TCNs), and a tensor concatenation module based on the attention mechanism, which ensures computational efficiency while fully leveraging the advantages of each component in a parallel processing framework. The study results show that the PA-TLA model outperforms both the LSTM and TCN models in predicting the three characteristic parameters of aircraft wake: vorticity, circulation, and Q-criterion. Compared to the serially structured TCN-LSTM, PA-TLA achieves an average reduction in mean squared error (MSE) of 6.80%, in mean absolute error (MAE) of 7.70%, and in root mean square error (RMSE) of 4.47%, with an average increase in the coefficient of determination (R2) of 0.36% and a 35% improvement in prediction efficiency. Lastly, this study combines numerical simulations and the PA-TLA deep learning architecture to analyze the near-ground wake vortex evolution. The results indicate that the ground effect increases air resistance and turbulence as vortices approach the ground, thereby slowing the decay rate of the wake vortex strength at lower altitudes. The ground effect also accelerates the dissipation and movement of vortex centers, causing more pronounced changes in vortex spacing at lower altitudes. Additionally, the vortex center height at lower altitudes initially decreases and then increases, unlike the continuous decrease observed at higher altitudes.

Research on Design and Optimization of Micro-Hole Aerostatic Bearing in Vacuum Environment

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.

Studying the rotational dynamics of a meter stick using the Arduino board and 3D printed parts

We present a low-cost experimental apparatus designed for studying the rotational dynamics of a meter stick. This apparatus uses everyday laboratory supplies, 3D printed parts, and an Arduino board for data acquisition. It consists of a common bearing fixed to a vertical axle, connected to the meter stick through a 3D printed spindle adapter. A thread attached to a hanging weight and winded around the spindle applies a constant external torque to the stick. The moment of inertia of the apparatus may be changed by incorporating weights into the apparatus through 3D printed adapters. An Arduino board records the time interval between consecutive half turns of the stick, allowing the calculation of the angular displacement over time. The data collected from experiments is compared with theoretical models. Among others, the effect of the applied torque, air resistance and moment of inertia of the stick is studied. This experimental apparatus is particularly suitable for undergraduate students enrolled in a classical mechanics course, offering them a practical, hand-on experience while remaining cost-effective.

Air speed and direction affect metabolic and thermoregulatory responses during walking and running in a temperate environment.

Revisiting classical experiments on the impact of air resistance on metabolic rate, we aimed to overcome limitations of previous research, notably: low participant numbers (n = 1-3), highly turbulent wind, and confounding effects of rising body temperature. In a custom-built wind tunnel with reduced turbulence, 14 participants (8 males, 6 females) walked (5 km·h-1) and ran on a treadmill (70%V̇o2max) at 0, 2, 4, and 6 m·s-1 headwind or tailwind in a counterbalanced design, with rest breaks between each exposure to avoid rises in body core temperature. Oxygen consumption (V̇o2) exhibited strong linear relationships versus wind direction, dynamic pressure, and air speed squared (Vwr2), lower in magnitude for headwind than tailwind. A moderate linear relationship was observed between heart rate, wind direction, dynamic pressure, and Vwr2. Below 4 m·s-1, the effect of wind was well within inter- and intraindividual variation and equipment uncertainty, and only at wind speeds ≥4 m·s-1 did the differences in physiological responses reach statistical significance. Our data indicate that at running speeds below 4 m·s-1 (14.4 km/h), indoor treadmills and outdoor running are comparable in terms of the metabolic impact of air movement relative to the person. However, this does not extend to the thermoregulatory effect of wind, with outdoor running providing a higher cooling rate due to the self-generated wind created during running. By removing the confounding impact of core temperature rises, the observed effects of headwind were lower and those of tailwind larger than observed previously. In the context of middle-distance running, the headwind created by running at 21.5 km·h-1 would result in a 2.2% increase of V̇o2. A relative tailwind of the same speed would lead to a 3.1% reduction.NEW & NOTEWORTHY Revisiting classical work by Pugh and Davies on the metabolic effects of air speed and direction, shortcomings in the original studies were addressed. Using more participants, less turbulent wind, and avoiding confounding effects of work-induced core temperature increases, new equations describing the impact of air speed/direction were developed. This study observed a lower impact of headwind and a larger impact of tailwind in the absence of an exercise-induced core temperature increase.

Low-vacuum SEM imaging and viability test of L929 cells exposed to a Euro 6 diesel exhaust gas mixture in a BAT-CELL chamber in comparison with hydrocarbons emission

Exhaust emissions, which count among the most common causes of premature death worldwide, can cause irreversible changes in cells, leading to their damage or degeneration. In this research, L929 line cells were observed after exposure in the BAT-CELL chamber to exhaust gases emitted from a Euro 6 compression-ignition engine. Real road traffic conditions were simulated, taking into account air resistance while driving at speeds of 50 km/h, 120 km/h and idling engine. Morphological analysis of the cells was performed using an environmental scanning electron microscope. It has been observed that diesel exhaust fumes can cause inflammation, which can induce apoptosis or leads to necrotic cell death. The impact of the vehicle exhaust gases can inhibit cell proliferation by almost three times. Moreover, a correlation has been observed between the speed of the inflammatory reaction in cells and the presence of specific hydrocarbon compounds that determine the toxicity of exhaust gases. Research has shown that the toxicity of the emitted exhaust gases has been the highest at the driving speed of 120 km/h. In order to reduce the harmful effects of exhaust emissions, ecological alternatives and the supplementation of legal provisions regarding the compounds subject to limitation are necessary.

Dependencies for determining heat transfer coefficients and air resistance for heat exchangers with tubular-plate heat exchange surface

Problem. The article analyzes existing generalized dependencies for determining convective heat transfer coefficients and air resistance coefficients for tubular-plate surfaces widely used in the production of modern charge air coolers and radiators. It is established that practical application of such dependencies, in some cases, is associated with significant errors revealed during experimental checks. Consequently, there is a need to adjust such dependencies for corridor bundles of flat-oval tubes with transverse grouped finning by flat fins. Goal. The aim of this study is to correct experimental dependencies for heat exchange and resistance. Numerical coefficients are adjusted on this basis, while the structure of dimensional dependencies remains unchanged. Simultaneously, the study is conducted for further improvement of the methodology for obtaining similar dependencies. Methodology. Adjustment of generalized dependencies for determining convective heat transfer coefficients and air resistance coefficients for tubular-plate heat exchange surfaces is carried out experimentally. Results. New dependencies are proposed for determining heat transfer coefficients and air resistance coefficients for tubular-plate heat exchange surfaces. Their accuracy and efficiency are investigated over a wide range of regimes. Originality and practical value. Unlike known dependencies of a similar nature, the proposed dependencies are provided in a single complex that should be used in modern heat exchanger calculation methods. It is established that the maximum error in determining air temperature according to the proposed dependence does not exceed 0.3 °C for the entire investigated range, and the error in determining aerodynamic resistance does not exceed 8 %, indicating high accuracy of modeling. Such accuracy ensures the possibility of applying the proposed dependencies for engineering calculations.

Bio-inspired gradient poly(lactic acid) nanofibers for active capturing of PM0.3 and real-time respiratory monitoring

The concept of bio-inspired gradient hierarchies, in which the well-defined MOF nanocrystals serve as active nanodielectrics to create electroactive shell at poly(lactic acid) (PLA) nanofibers, is introduced to promote the surface activity and electroactivity of PLA nanofibrous membranes (NFMs). The strategy enabled significant refinement of PLA nanofibers during coaxial electrospinning (∼40 % decline of fiber diameter), accompanied by remarkable increase of specific surface area (nearly 1.5 m2/g), porosity (approximately 85 %) and dielectric constants for the bio-inspired gradient PLA (BG-PLA) NFMs. It largely boosted initial electret properties and electrostatic adsorption capability of BG-PLA NFMs, as well as charge regeneration by TENG mechanisms even under high-humidity environment. The BG-PLA NFMs thus featured exceptionally high PM0.3 filtration efficiencies with well-controlled air resistance (94.3 %, 163.4 Pa, 85 L/min), in contrast to the relatively low efficiency of only 80.0 % for normal PLA. During the application evaluation of outdoor air purification, excellent long-term filtering performance was demonstrated for the BG-PLA for up to 4 h (nearly 98.0 %, 53 Pa), whereas normal PLA exhibited a gradually declined filtration efficiency and an increased pressure drop. Moreover, the BG-PLA NFMs of increased electroactivity were ready to generate tribo-output currents as driven by respiratory vibrations, which enabled real-time monitoring of electrophysiological signals. This bio-inspired gradient strategy opens up promising pathways to engender biodegradable nanofibers of high surface activity and electroactivity, which has significant implications for intelligent protective membranes.

Bioinspired green fabricating design of ultra-breathable and moisture wicking fabric via a sustainable route

Functional textiles with breathability, thermal conductivity and moisture wicking performance are critical to achieving human comfort and reducing energy consumption. However, conventional finishing processes used for fabricating moisture wicking fabrics are usually highly polluting and exhibit poor durability as well as low recyclability, which may be detrimental to environmental sustainability. Inspired by the shorebird's beak with a conical-shaped liquid pathway for transporting liquid drops, a novel biomimetic porous fabric is proposed by using natural cotton fibers through industrial and eco-friendly knitting technology, featuring ultra-breathability, thermal conductivity and moisture wicking properties. Moreover, the effects of the pore size and arrangement on the thermal conductivity and air resistance are investigated. Obvious linearities can be obtained (R2 = 0.99). In addition, the synergistic effects of basic pore and biomimetic pore can create surface energy gradients, which result in the asymmetric pressure and water transport. As a result, when the biomimetic pore distances are 3 mm and 5 mm, respectively, high linearities of 0.99 between biomimetic pore diameter and the wicking height can be found. More importantly, the resultant biomimetic pore fabric exhibits good water absorption rate of 350%, an outstanding water vapor transmission (>10000 g/m2/24 h) and high recyclability. The green fabricating design of biomimetic porous fabric opens up a pathway to develop air, thermal, moisture regulating fabric through a sustainable route for more diverse applications, e.g., athletic apparel, industrial workwear and medical garments.

Aluminum Carboxylate Modification Enabled Efficient and Stable Perovskite-Polystyrene Thin Films for Light-Emitting Applications.

Lead halide perovskite nanocrystals (PNCs) have demonstrated great potential in emerging display technologies. However, the practical application of PNCs is hindered by the inherent instability of their ionic surface. Here, we proposed a surface modification approach to enhance the stability of CsPbBr3 PNCs by postsynthetic treatment with aluminum phenylbutyrate (Al(PA)3). Our study reveals that Al(PA)3 displaces ammonium ligands and binds tightly on surface halide, providing excellent air and moisture resistance while preserving a high quantum efficiency of 81.6%. The modified PNCs maintain a constant photoluminescence intensity under continuous UV light illumination for 500 h. Additionally, the Al(PA)3 ligand is compatible with styrene, enabling homogeneous dispersion of PNCs in polystyrene matrices to form bright and uniform PNC-PS thin films. We demonstrated the application of the composite films for display backlighting, which exhibits a wide color gamut of 125% NTSC. The result highlights the potential of AlPA-modified PNCs in light-emitting and other optoelectronic devices.

Comparison of Tire Rolling Resistance Measuring Methods for Different Surfaces

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.

Improving carrier transport and catalytic oxidation of Bi2O3/Co3O4 hybrid structures to enhance gas sensing selectivity and response toward n-butanol gas

N-butanol is a widely used and multifunctional raw material, but is harmful to the environment and human health. Developing gas sensing materials with high selectivity toward n-butanol is the foundation and crux to achieve n-butanol precise detection. Herein, Bi2O3/Co3O4 hybrid structures have been constructed by a feasible two-step strategy and employed as gas sensing materials. The gas sensor based on Bi2O3/Co3O4 composites treated at 400 °C (BCO-400) presents a high selectivity, a superior stability/reliability, a well humidity resistance and a low detection limit of 1 ppm toward n-butanol at a relatively low operating temperature of 130 °C. The response and response/recovery time of BCO-400 to 1 ppm n-butanol is 14.9 % and 51 s/53 s, respectively. In the hybrid structures, p-type Bi2O3 semiconductor as a catalyst promotes the catalytic selectivity of Bi2O3/Co3O4 toward n-butanol gas while the semiconductor Co3O4 significantly improves carrier transport and further decreases baseline resistance in air of hybrid structures, which collaboratively brings about the improved gas sensing performance to n-butanol. This work provides a preferable strategy for bismuth based semiconductor materials in the field of the low temperature volatile organic gas detection.

A Short Paper about Fundamental Pedagogical Concepts of Constructivism Theory in Relation to TPACK Framework

The influence of constructivism as a pedagogical theory is mainly concentrated on adult education. Its main concepts stem from significant conclusions coming from other theories related to pedagogical and philosophical school practice. The key point is that knowledge is the desired learning outcome that can be accomplished through active learning participation which is closely related to construct. Also, some basic ideas of constructivism rely on idea-based interactions and ideas produced by learners. Certain aspects of the above-mentioned theory in learning and teaching seem to be very helpful for learners to develop their ideas and achieve learning outcomes. The basic aim of this paper is to examine the influence of Constructivism on adult education by utilising Technological Pedagogical Content Knowledge Framework’s (TPACK) dimensions in learning and teaching everyday practice. A mixed method analysis was conducted which contains a theoretical analysis, and experimentation through a quiz game. Our experimental approach through the quiz game was to study Newtonian physics and specifically the Law of Gravitation and the 2nd Law of Motion, finding that the mass terms cancel, and ending up making a prediction that all objects fall at the same rate. The experiment would then involve verifying the prediction and explaining any deviations from the prediction in terms of the intuitive idea of air resistance. The findings showed that students after answering the quizzes of the quiz game, were able to discuss their results using logical argument as opposed to when they did the experiment before the theory and their discussion was little more than guesswork. Thus, we could see how students performed on each question and use that information to figure out what needs to be readdressed or retaught.

Computational Analysis of Aerodynamic Drafting Effects in Lemans Racing Cars

Le Mans racing is a comprehensive motorsport event that tests not only the long-distance stability of race cars but also considers fuel economy and speed, where aerodynamics plays a crucial role. Many manufacturers place great emphasis on the aerodynamic design of race cars. However, in-depth research on the application of drafting effects in Le Mans racing and studies on team formations are somewhat lacking. Through Ansys simulations, this study deeply explores the impact of drafting on race cars and, by varying the distances between cars, identifies differences in air resistance encountered by different formations. The findings reveal that drafting can substantially decrease the aerodynamic drag experienced by race cars when they are positioned at relatively close proximities to each other. As this distance increases, a "drag bubble" phenomenon occurs within a certain range, where the trailing cars begin to experience increased resistance. On the other hand, the study of car formations under race-regulated conditions has identified optimal vehicle spacing that minimizes the average aerodynamic drag faced by the team, providing strategic insights into the arrangement of team formations for improved race performance.

Computations on fall of the leaning tower with considering air resistance

The free fall of a sphere was studied by considering air buoyancy and resistance. After selecting the reasonable drag coefficient formula recommended by the literature, partial differential formulas on the motion of balls falling in the Leaning Tower of Pisa are solved. The variation process of acceleration, velocity and displacement over time during the falling process of two spheres is obtained. The research results indicate that the kinematics of free fall considering air resistance is different from that neglecting air resistance. Air Resistance must be considered in the free fall of the solid ball after 0.3005 seconds. In the free fall of the leaning tower, air resistance makes the solid ball land at 0.4418 seconds which is earlier than the hollow. The variation of the acceleration of a solid ball with time can be described by a second-order function a=-0.115t2 -0.022t+9.801. Velocity does not satisfy the product of acceleration and time but can be described as a polynomial function of the velocity variation with time v = c1t2 + c2t + c3 . About the relationship between displacement and time, for a solid sphere, displacement is proportional to 1.9526 power of time h=5.4945t1.9526 , while for a hollow sphere, it cannot be expressed by a function. The relationship between air resistance and velocity during the falling process of an iron ball satisfies a polynomial function Fd =c1v2 -c2v+c3 rather than a simple relationship where air resistance is directly proportional to the first or second power of speed, which was used in many papers as a reasonable assumption.

Karakteristik Arang Kulit Buah Kakao dan Arang Batang Bambu Terhadap Mutu Briket

The purpose of this research is to determine the optimum properties of biodegradable plastic made from banana weevil starch with the addition of straw cellulose as reinforcement. This research was conducted using Completely Randomized Method (CRD) with four treatments and four replications. In this study were the addition of straw cellulose with a ratio of starch and cellulose 1:0; 1:0,5 ; 1:1 and 1:1,5. Tests were carried out on strong tensile strength, elongation at break, biodegradation, swelling and water vapor transmission rate. The data obtained were analyzed statistically using analysis of variance (ANOVA). The addition of straw cellulose had a significant effect on the manufacture of biodegradable plastics. The result were biodegradable plastic increase tensile strength, decreases elongation at break, increase biodegradation and air resistance, reduces the rate of water vapor transmission. Biodegradable plastic with the best treatment is the ratio of starch starch ratio of 1 : 1.5 cellulose. The best result biodegrabable plastic has for tensile strength value of 9.56 MPa, elongation 6.8%, complete biodegradation on day 6, swelling 41.51% and WVTR 0.0156%.

A Method for the Rapid Propagation of Emergency Event Notifications in a Long Vehicle Convoy

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.

A High Efficiency, Low Resistance Antibacterial Filter Formed by Dopamine-Mediated In Situ Deposition of Silver onto Glass Fibers.

The coating of filter media with silver is typically achieved by chemical deposition and aerosol processes. Whilst useful, such approaches struggle to provide uniform coating and are prone to blockage. To address these issues, an in situ method for coating glass fibers is presented via the dopamine-mediated electroless metallization method, yielding filters with low air resistance and excellent antibacterial performance. It is found that the filtration efficiency of the filters is between 94 and 97% and much higher than that of silver-coated filters produced using conventional dipping methods (85%). Additionally, measured pressure drops ranged between 100 and 150Pa, which are lower than those associated with dipped filters (171.1Pa). Survival rates of Escherichia coli and Bacillus subtilis bacteria exposed to the filters decreased to 0 and 15.7%±1.49, respectively after 2h, with no bacteria surviving after 6 h. In contrast, survival rates of E. coli and B. subtilis bacteria on the uncoated filters are 92.5% and 89.5% after 6 h. Taken together, these results confirm that the in situ deposition of silver onto fiber surfaces effectively reduces pore clogging, yielding low air resistance filters that can be applied for microbial filtration and inhibition in a range of environments.