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Enhancing oxidation resistance of carbon fibre reinforced phenolic composites by ZrO2 nanoparticles through out-of-autoclave vacuum infusion
No full textThis study reports a vacuum-assisted resin infusion method for achieving low-porosity carbon fibre/phenolic resin composites utilizing a low-viscosity (∼281 cp) phenolic resin enhanced by ZrO2 nanoparticles. The experimental results reveal that this method can yield composites with a low porosity of 8.6 ± 2.5 % and average pore size of 3.8 ± 1.73 μm, demonstrating mechanical properties that show great potential for high-temperature structural applications, such as rocket motor nozzles. Moreover, the resultant composites exhibit distinct advantages over composites produced using other out-of-autoclave and autoclave methods investigated in this study in terms of flexural strength and modulus after oxidation treatment. The vacuum infusion approach retains higher resin content in composites than the autoclave method, leading to increased residual modulus post-oxidation. Furthermore, incorporating ZrO2 nanoparticles in the phenolic matrix has significantly enhanced the residual mass, flexural strength, and flexural modulus of the composites following exposure to oxidation at 1200 °C
A low-complexity DOA estimation algorithm using UAMP with Bernoulli-Gaussian prior
No full textIn this paper, we design a low-complexity direction-of-arrival (DOA) estimation algorithm based on the unitary approximate message passing (UAMP) and Bernoulli-Gaussian (BG) prior. We first show that the estimation of DOA can be transferred into a sparse signal recovery problem, where we turn to UAMP with damping technique to solve this problem. Furthermore, we assume the BG prior on the sparse vector to be estimated, resulting in the fast estimation of the positions of non-zero elements. Moreover, expectation maximum (EM) is leveraged to automatically learn the BG parameters. Compared to the state-of-the-art UAMP-based algorithm with sparse Bayesian learning (SBL), the proposed approach can achieve the same DOA mean square error (MSE) performance with a much faster convergence speed
Investigation of a semi-active suspension system for high-speed trains based on magnetorheological isolator with negative stiffness characteristics
No full textAs the operation speed of high-speed train increases, trains with fixed suspension stiffness will encounter dramatical vibrations, especially when its lateral resonance occurs. This greatly affects the ride comfort and safety of the trains. Based on this motivation, a novel stiffness variable suspension system using magnetorheological elastomer (MRE) isolator with negative stiffness is proposed. The controllable stiffness can make the train avoid lateral resonance while the negative stiffness characteristics can provide an actuating force similar to the active control, which further improve the vibration attenuation performance of the suspension. The new MRE isolator was firstly fabricated and tested to verify its stiffness variability, especially negative stiffness characteristics. Four different suspension systems were then tested on a 6-DOF vibration platform for the performance comparison. The experimental results show that this new semi-active lateral suspension system has improved vibration attenuation performance than the passive system and the traditional MRE isolation system without negative stiffness. The vibration attenuation performance of the new suspension system is even comparable to that of some of the existing active suspensions while avoiding the disadvantages of the active control
Recent advances and strategies of metal phosphides for accelerating polysulfide redox and regulating Li plating
No full textLithium-sulfur batteries (LSBs) are widely acknowledged as the most promising energy storage systems for the future, primarily due to their remarkably high theoretical energy density. Nonetheless, the advancement of LSBs encounters various hurdles, including the substantial expansion of the cathode material, inadequate conductivity of the active material S and discharge product Li2S, the evident shuttle effect of lithium polysulfide (LiPS), and the sluggish sulfur conversion kinetics. These challenges become particularly evident when handling high sulfur loading. The issue of uneven Li dendrite growth at the anode significantly affects the long-term functionality and safety of batteries. Consequently, there is a pressing requirement for battery designs that effectively tackle these challenges. Metal phosphide, owing to its remarkable catalytic activity and distinctive physicochemical properties, has been extensively investigated and is anticipated to serve as a bifunctional material in LSBs systems. By manipulating the composition of cations, it is possible to obtain monometallic phosphide, bimetallic phosphide, and trimetallic phosphide through tailored design approaches. It has been found that metal phosphide catalysts can effectively adsorb soluble LiPS and catalyze its rapid conversion. Moreover, the synthesis of composite materials by incorporating metal phosphides with other compounds results in a synergistic effect that significantly improves catalytic performance. This study offers a thorough overview of the diverse applications of metal phosphides in enhancing cathode sulfur support materials, modifying separators, and protecting lithium anodes. The significance of metal phosphides in facilitating the anchoring of lithium polysulfides, improving electrochemical reaction rates, facilitating the nucleation and dissolution of lithium sulfide, enhancing electron and ion transport, and promoting uniform lithium deposition was underscored. Additionally, the obstacles and potential opportunities for metal phosphides in future lithium-sulfur batteries are examined, along with their practical utility
Impact of the COVID-19 pandemic on daily travel: Findings from New South Wales, Australia
No full textThe COVID-19 pandemic has caused major disruptions to people's daily life and travel. This paper aims to reveal the impact of the COVID-19 pandemic on people's travel in New South Wales (NSW), Australia, and to explore potential measures to recover public transport patronage in the new normal. Research data is collected from a survey of 1,045 residents in NSW, Australia between October 2021 and May 2022. Results show that travel behaviors are significantly different during the pandemic compared to the pre-COVID and the new normal periods. Multiple key factors affecting travelers’ choices in terms of travel mode, travel purpose and their acceptance of emerging mobilities like on-demand transport, autonomous vehicles and drones are identified, including age group, residential area, household status (e.g., couple family with children), household income, need for travel assistance, and travel-related attitude towards health and safety. The research findings suggest that emerging mobilities could provide potential solutions to transport services in a pandemic scenario
Conversion mechanism of sulfur in room-temperature sodium-sulfur battery with carbonate-based electrolyte
No full textRoom temperature sodium-sulfur batteries have attracted considerable interest due to their remarkable cost-effectiveness and specific capacity. However, due to the limited comprehension of its conversion mechanism, the decrease in sulfur cathode capacity in carbonate electrolytes is usually loosely attributed to the shuttle effect, which is well known in lithium-sulfur batteries that work in ether-based electrolytes. This work proposes a complete sulfur reaction mechanism in which the confined space is very important by combining the results from the theoretical calculations and electrochemical characterization. Specifically, crystal sulfur outside the pores is reduced to polysulfides, leading to irreversible reactions with carbonate solvents. Meanwhile, amorphous sulfur within the narrow pores undergoes an activation process during the first discharge and experiences a reversible conversion in subsequent cycles through a two-step solid-state reaction. Furthermore, the discharge/charge processes unveil divergent dynamics that can be clarified through the lens of chemomechanical stress in a confined environment. The increased comprehension of the sulfur conversion process in electrolytes composed of carbonate highlights the importance of confined space and electrolytes. This newly acquired knowledge holds the potential to offer theoretical insights guiding the design of high-performance sulfur cathodes
In-Situ synthesis of NbC Nanoparticle-Decorated Polyimide-Derived graphene for enhanced thermal management
No full textThermal management and heat dissipation are universal challenges related to high-power systems. Graphene and its related composite materials exhibit the potential for widespread application as thermal management materials owing to their high thermal conductivity and emissivity. In this study, we synthesize polyimide (PI)-derived graphene (PDG) incorporated with NbC nanoparticles via CO2 laser scribing on Nb precursor-containing PI sheets. The resultant NbC-decorated PDG (NbC-PDG) shows improved thermal conductivity (0.70 W/m·K) compared with bare PDG (0.24 W/m·K). We use NbC-PDG as an efficient heat sink for industrial computers (ICs), light-emitting diode (LED) modules, and lithium-ion batteries (LIBs). The equilibrium temperature of the applications can be reduced significantly by the NbC-PDG layer owing to its excellent radiation heat transfer. After integration of the NbC-PDG heat sink, the equilibrium temperatures of the IC, LED module, and LIB decreased by 8.1, 9.9, and 7.3 °C, respectively. Accordingly, the performance, efficiency, and lifetime of optoelectronic and electrochemical systems can be enhanced considerably. The NbC-PDG composite with broadband absorption and excellent photothermal properties can be applied for efficient solar–thermal energy conversion. Additionally, we fabricate an NbC-PDG-deposited melamine sponge via spray coating and evaluate its performance in solar-driven desalination and water purification
Understanding the relationship between surfing performance and fin design
No full textThis research aimed to determine whether accomplished surfers could accurately perceive how changes to surfboard fin design affected their surfing performance. Four different surfboard fins, including conventional, single-grooved, and double-grooved fins, were developed using computer-aided design combined with additive manufacturing (3D printing). We systematically installed these 3D-printed fins into instrumented surfboards, which six accomplished surfers rode on waves in the ocean in a random order while blinded to the fin condition. We quantified the surfers’ wave-riding performance during each surfing bout using a sport-specific tracking device embedded in each instrumented surfboard. After each fin condition, the surfers rated their perceptions of the Drive, Feel, Hold, Speed, Stiffness, and Turnability they experienced while performing turns using a visual analogue scale. Relationships between the surfer’s perceptions of the fins and their surfing performance data collected from the tracking devices were then examined. The results revealed that participants preferred the single-grooved fins for Speed and Feel, followed by double-grooved fins, commercially available fins, and conventional fins without grooves. Crucially, the surfers’ perceptions of their performance matched the objective data from the embedded sensors. Our findings demonstrate that accomplished surfers can perceive how changes to surfboard fins influence their surfing performance
Preliminary Characterization of an Active CMOS Pad Detector for Tracking and Dosimetry in HDR Brachytherapy
No full textWe assessed the accuracy of a prototype radiation detector with a built in CMOS amplifier for use in dosimetry for high dose rate brachytherapy. The detectors were fabricated on two substrates of epitaxial high resistivity silicon. The radiation detection performance of prototypes has been tested by ion beam induced charge (IBIC) microscopy using a 5.5 MeV alpha particle microbeam. We also carried out the HDR Ir-192 radiation source tracking at different depths and angular dose dependence in a water equivalent phantom. The detectors show sensitivities spanning from (5.8 ± 0.021) × 10−8 to (3.6 ± 0.14) × 10−8 nC Gy−1 mCi−1 mm−2. The depth variation of the dose is within 5% with that calculated by TG-43. Higher discrepancies are recorded for 2 mm and 7 mm depths due to the scattering of secondary particles and the perturbation of the radiation field induced in the ceramic/golden package. Dwell positions and dwell time are reconstructed within ±1 mm and 20 ms, respectively. The prototype detectors provide an unprecedented sensitivity thanks to its monolithic amplification stage. Future investigation of this technology will include the optimisation of the packaging technique
Sleep apnea multi-level surgery trial: long-term observational outcomes
No full textStudy Objectives: The sleep apnea multi-level surgery (SAMS) randomized clinical trial showed surgery improved outcomes at 6 months compared to ongoing medical management in patients with moderate or severe obstructive sleep apnea (OSA) who failed continuous positive airway pressure therapy. This study reports the long-term outcomes of the multi-level surgery as a case series. Methods: Surgical participants were reassessed >2 years postoperatively with the same outcomes reported in the main SAMS trial. Primary outcomes were apnea-hypopnea index (AHI) and Epworth sleepiness scale (ESS), with secondary outcomes including other polysomnography measures, symptoms, quality of life, and adverse events. Long-term effectiveness (baseline to long-term follow-up [LTFU]) and interval changes (6 month to LTFU) were assessed using mixed effects regression models. Control participants were also reassessed for rate of subsequent surgery and outcomes. Results: 36/48 (75%) of surgical participants were reevaluated (mean (standard deviation)) 3.5 (1.0) years following surgery, with 29 undergoing polysomnography. AHI was 41/h (23) at preoperative baseline and 21/h (18) at follow-up, representing persistent improvement of −24/h (95% CI −32, −17; p < 0.001). ESS was 12.3 (3.5) at baseline and 5.5 (3.9) at follow-up, representing persistent improvement of −6.8 (95% CI −8.3, −5.4; p < 0.001). Secondary outcomes were improved long term, and adverse events were minor. Interval change analysis suggests stability of outcomes. 36/43 (84%) of the control participants were reevaluated, with 25 (69%) reporting subsequent surgery, with symptom and quality of life improvements. Conclusion: Multi-level upper airway surgery improves OSA burden with long-term maintenance of treatment effect in adults with moderate or severe OSA in whom conventional therapy failed. Clinical Trial: Multi-level airway surgery in patients with moderate-severe obstructive sleep apnea (OSA) who have failed medical management to assess change in OSA events and daytime sleepiness; https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=366019&isReview=true; ACTRN12614000338662