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This study introduces a multi-scale convolutional neural network (MCNN) for diagnosing various faults in proton exchange membrane fuel cell (PEMFC) systems. Using simulated fault data from a 240 kW PEMFC stack, the MCNN method is validated. Compared to traditional methods like backpropagation neural network (BP), support vector machine (SVM), and temporal convolutional neural network (TCNN), MCNN achieves an average accuracy of 96.31%, outperforming BP (88.88%), SVM (90.67%), and TCNN (93.80%). The study demonstrates MCNN's effectiveness in diagnosing recoverable faults, fatal faults, and multiple faults in PEMFC systems, achieving fault diagnosis accuracies of over 97%. By leveraging its inherent advantages such as multi-channel processing, automatic feature learning, and parameter sharing, MCNN provides an effective solution for accurately diagnosing faults in PEMFC. The utilization of these advantages has enabled MCNN to perform efficient and accurate fault diagnosis in PEMFC systems. • MCNN achieves 96.31% accuracy, surpassing BP, SVM, and TCNN in diagnosing faults. • MCNN achieves over 97% accuracy in categorizing recoverable, fatal, and multiple faults. • MCNN provides swift and accurate fault diagnosis in PEMFC systems. [ABSTRACT FROM AUTHOR]

On nanopillar-arrayed superhydrophobic surfaces, the contact time of oblique nanodroplet impacts is for the first time investigated via molecular dynamics simulations. Here, oblique nanodroplet impacts are triggered by nanodroplets impacting superhydrophobic surfaces under various impact angles, α. The simulation results show that owing to the non-axisymmetry of spreading factors on nanopillar-arrayed superhydrophobic surfaces, the contact time of oblique nanodroplet impacts is always less on nanopillar-arrayed rather than smooth superhydrophobic surfaces under same impact angles. As the impact angle is increased from 5° to 65°, that is, under different impact conditions, the non-axisymmetry is more remarkable as α > 35° instead of α < 35° at the low, medium, and high normal Weber numbers, Wen. Hence, the contact time is sharp as α > 35° and then slowly reduced as α < 35° at the low, medium, and high Wen, at which the drastically increased sliding length as α > 35° further promotes the rapid reduction in contact time. As the impact angle is constant at 35°, the non-axisymmetry is more remarkable as h/w < 1 instead of h/w > 1 as the aspect ratio of nanopillars, h/w, is increased, that is, under different surface conditions. Hence, the contact time is sharp as h/w < 1 and then slowly reduced as h/w > 1 at the low, medium, and high Wen, at which the drastically reduced sliding length as h/w > 1 further hinders the rapid reduction in contact time. [ABSTRACT FROM AUTHOR]

Under parallel electric fields and free evaporation conditions, the statics and dynamics of spreading–evaporating nanodroplets are investigated on an isothermally heated surface via molecular dynamics (MD) simulations. The simulation results show that at the substrate temperature of Ts = 320 K, the static and dynamic contact angles on the left and right edges are initially asymmetric and then symmetric with increasing field strengths of E = 0.00–0.06 V Å−1, resulting in the asymmetric-to-symmetric spreading transition of spreading–evaporating nanodroplets. Under weak evaporation condition, that is, at Ts = 320 K, the asymmetric-to-symmetric spreading transition is triggered by enhancing the intrinsic surface wettability θ0 = 49°–80° at a constant field strength of E = 0.03 V Å−1. However, at the substrate temperature of Ts = 350 K, the symmetric-to-asymmetric spreading transition first appears for the static and dynamic contact angles on the left and right edges, and then the asymmetric-to-symmetric spreading transition appears with increasing field strength. Under strong evaporation condition, that is, at Ts = 350 K, as the field strength is constant at E = 0.03 V Å−1, the asymmetric-to-symmetric spreading transition also appears with increasing surface wettability. [ABSTRACT FROM AUTHOR]

Working temperature is a critical parameter that influences the performance of proton exchange membrane fuel cells (PEMFCs). Appropriate thermal management can improve the efficiency of PEMFCs and prevent irreversible internal damage such as membrane degradation. To solve the slow response and poor dynamic performance of traditional temperature control strategies, the dynamic temperature mode of PEMFCs is established and a temperature control strategy based on the sparrow search algorithm-proportional integral differential (SSA-PID) is proposed in this study. The performance of the SSA-PID temperature control is verified by the simulations of current step change, vehicle dynamic load, and working parameter variation. The results show that the proposed method has the advantages of fast convergence, better dynamic performance, and anti-disturbance ability. The maximum power density of the SSA-PID temperature controller is 6.58% and 12.94% higher than GA (genetic algorithm)-PID and traditional PID controllers, respectively. Moreover, the proposed method can ensure temperature fluctuations within 0.5 K under dynamic disturbance. • The PEMFC temperature control strategy based on sparrow search algorithm is proposed. • The performance of the temperature control strategy under external disturbance is discussed. • The proposed control method is compared with the GA-PID and traditional PID controllers. • The proposed method can ensure temperature fluctuations within 0.5 K. [ABSTRACT FROM AUTHOR]

This study presents a hybrid power generation system that combines a proton exchange membrane fuel cell (PEMFC) and an internal combustion engine (ICE), utilizing ammonia decomposition as the primary fuel source. The system comprises various components, including an ammonia decomposition subsystem, PEMFC, ICE, heat exchanger, solenoid valve, and power electronic converter. The research focuses on evaluating the system's performance by analyzing the impact of key thermodynamic parameters, such as decomposition temperature and separation ratio, as well as economic factors like ammonia and hydrogen prices, and service life. The findings reveal that the hybrid power generation system achieves a maximum output power of 16.23 kW and an efficiency of 50.28 %. Furthermore, it is observed that when the power ratio (α) between PEMFC and ICE is set to 1.2, the system achieves optimal electric power output. The levelized cost of energy (LCOE) for the system is calculated to be 0.0774 $ kWh−1 when the ammonia price is 0.35 $ kg−1. Additionally, the system exhibits a significant reduction in greenhouse gas (GHG) emissions, with an estimated decrease of 4.39 × 107 g. The hybrid power generation system has excellent thermodynamic, economic, and environmental performance, which lays a foundation for promoting the spread of high efficiency and zero pollution distributed hybrid power generation system. • A novel hybrid power system of PEMFC and ICE based on ammonia decomposition is presented. • The effects of thermodynamic and economic factors on the system performance are investigated. • The maximum power and efficiency of the system are 16.23 kW and 50.28 % respectively. [ABSTRACT FROM AUTHOR]

On a rectangular-ridged superhydrophobic surface, the contact time of the rebounding-coalescing droplet is for the first time investigated via lattice Boltzmann method simulations, where the rebounding-coalescing droplet is caused by an impinging droplet coalescing with an adhesive droplet. The simulation results show that at constant initial radii of impinging droplets, R0, and various initial radii of adhesive droplets, R1, the contact time of rebounding–coalescing droplets depends not only on the impact condition but also on the surface condition. Under various impact conditions, that is, with increased Weber numbers of We = 1–30, the contact time is gradually reduced, and then nearly constant, and eventually constant after slightly reduced at R0 = 35 and R1 = 25. However, at R0 = 35 and R1 = 10, it is gradually reduced, then increased, and eventually constant. It indicates that the contact time of rebounding-coalescing droplets is affected by the initial radii of adhesive droplets. Under different surface conditions, that is, with increased spacing distances between adhesive droplets and ridges of L = 3–17, the contact time is reduced at the low Weber number of We = 3, constant at the moderate Weber number of We = 12, and increased at the high Weber number of We = 28 at R0 = 35 and R1 = 25. However, at R0 = 35 and R1 = 10, it is reduced at both low and moderate Weber numbers of We = 3 and 12, and constant at the high Weber number of We = 28. It indicates that under different surface conditions, the contact time of rebounding-coalescing droplets is also affected by the initial radii of adhesive droplets. [ABSTRACT FROM AUTHOR]

Two geometrical parameters, amplitude and wavelength, of the structure of the wavy-flow field in a proton exchange membrane fuel cell (PEMFC) were investigated on their impacts on cell performances via a three-dimensional, multiphase, and non-isothermal model. Amplitude and wavelength significantly influence oxygen transport, friction resistance, and current densities in PEMFC operations. The enhancement of current density peaks at an amplitude of 0.4 mm and a wavelength of 2 mm, increased by 10.40% compared to the non-wavy design. The wavy channels would increase the oxygen concentration gradient and the viscous friction, increasing entropy generation. The entropy generation rates increase more significantly at small wavelengths and large amplitudes. The entropy generation ratio (EGR) evaluates the performances of different wavy channels based on the accurate description of oxygen transport in PEMFC without calculating the associated pumping power consumption rates. The EGR decreases with decreasing wavelength or increasing amplitude. • Entropy generation by mass transport and friction is greatly influenced by flow field types. • The entropy generation analysis is introduced to verify the superiority of flow fields. • EGR is proposed for the evaluation of oxygen transport under unequal pumping power consumptions. [ABSTRACT FROM AUTHOR]

In this study, a kW-grade air-cooled proton exchange membrane fuel cell (PEMFC) stack with a dead-end anode (DEA) operation is designed and manufactured. The gravity-assisted drainage principle is applied for the stack to design the wettability of gas diffusion layers (GDLs) and the anode channel geometry, which can help the liquid water that diffuses to the anode to drain out of the anode porous electrode and move down the anode channel outlets. As a result, the stack can stably operate in a long purge interval of 268 s and in a short purge time of 2 s. In addition, using this design, only four small-power fans are employed to pump air to the cathode to provide oxygen for the electrochemical reaction and cool the stack. With a constant load current of 30, 45, or 60 A, the stack output voltage is experimentally tested at various cathode air flow rates (CAFRs). The local temperatures (60 measurement points) inside the stack and the pressure differences across anode channels are also monitored to understand heat dissipation and the back diffusion of liquid water. In a wide range of operating conditions, the designed stack possesses superior and stable voltage output characteristics with relatively uniform temperature distributions. The measured maximum output power is 3.83 kW, and the parasitic powers of fans are only 80∼112 W. • A kW-grade air-cooled PEMFC system under dead-ended anode operation is designed. • The effect of cathode air flow rate on dynamic temperature evolution is studied. • Modified anode channels based on gravity drainage are applied to the cell system. • A stringing fan arrangement is used to improve cooling efficiency. [ABSTRACT FROM AUTHOR]

For turbine blade internal cooling, the performance of turbulent flow and convective heat transfer in the cooling channel is numerically investigated via the computational fluid dynamics method, where the cooling channel adopts the combination of transverse rib arrangements and round-edged rib configurations or the combination of oblique rib arrangements and round-edged rib configurations. Under these two combination conditions, the simulation result shows that in the wide Reynolds number range of Re = 20 000–80 000, the heat transfer enhancement and the flow loss reduction, such as the larger normalized Nusselt number of Nu/Nu0 and smaller normalized friction factor of f/f0, are simultaneously realized by the oblique rather than transverse rib arrangement. In the oblique rib channel, the relationship between turbulent flow and convective heat transfer is for the first time revealed by the relationship between secondary vortices and turbulent kinetic energies. Based on the relation between secondary vortices and turbulent kinetic energies, the overall performance of turbulent flow and convective heat transfer for the oblique rib channel is first optimized by various normalized rib height, e/Dh, and rib spacing, p/e, and then evaluated by both overall performance factors of OPT1 and OPT2. Both OPT1 and OPT2 are larger at e/Dh = 0.062 and p/e = 15.00 in the wide range of e/Dh = 0.047–0.101 and p/e = 10.00–15.00. As a result of the comprehensive evaluation of OPT1 and OPT2, the combination of e/Dh = 0.062 and p/e = 15.00 is eventually employed by the oblique rib channel. [ABSTRACT FROM AUTHOR]

On a single-ridge superhydrophobic surface, the rebound dynamics of double droplet impacts is investigated via lattice Boltzmann method (LBM) simulations, where one droplet is on the left of macro-ridges, whereas the other droplet being on the top of macro-ridges, leading to the asymmetrical impact of double droplets. The simulation results show that under different impact conditions of various Weber numbers, that is, at low, moderate and high Weber numbers, the rebound regime of double droplet impacts always consists of the complete-coalescence-rebound (CCR), partial-coalescence-rebound (PCR) and coalescence-split-rebound (CSR) regimes. Under these three rebound regimes, the contact time of double droplet impacts is always reduced by the increased We , as the center-to-center distances in the horizontal and vertical directions, L x and L z , are constant. At constant L x and We , the contact time of double droplet impacts on single-ridge superhydrophobic surfaces is increased by the increased L z because of the earlier formation of liquid bridges at larger L z. But under different impact conditions of various center-to-center distances in the horizontal direction, that is, at the increased L x , the rebound regime of double droplet impacts is not always composed of the CCR, PCR and CSR regimes at low, moderate and high Weber numbers. At constant We and L z , both coalescence strength and rebound regime are significantly affected by the increased L x for double droplet impacts. So that the contact time of double droplet impacts on singe-ridge superhydrophobic surfaces depends on the center-to-center distance in the horizontal direction, that is, in the x - direction. [Display omitted] • The coupling effect of droplet coalescences and droplet impacts is studied. • The influence of coupling effects on the bouncing dynamics of double droplet impacts is focused. • The influence of Weber numbers and center-center distances on the coupling effect is analyzed. • The correlations between rebound regimes and contact time is revealed. [ABSTRACT FROM AUTHOR]

• The performances of parallel and interdigitated flow field PEMFCs with wavelike GCs are discussed. • The effect of curved MEAs on output current densities is investigated. • The oxygen transport and liquid water removal are greatly influenced by curved MEAs. • The normalized oxygen distribution uniformity and oxygen transport resistance are analyzed. The effect of curved membrane electrode assemblies (MEAs) on performances of parallel and interdigitated flow field PEMFCs with wavelike gas channels (GCs) are for the first time investigated at various curved MEA deformation levels, where the curved MEA is triggered by the pressure difference between anodes and cathodes. The results show that on the cathode side of parallel flow field PEMFCs with wavelike GCs, the oxygen consumption and liquid water generation are small with the increased MEA deformation level at the high operation voltage being larger than 0.8 V, leading to the constant cell performance, that is, leading to the constant output current density. However, the current density is first increased and then decreased with the increased MEA deformation level at the low operation voltage being less than 0.8 V. Because at the low operation voltage, the oxygen consumption and liquid water generation are significantly increased and affected by the increased MEA deformation level. When the MEA deformation level is increased at the high operation voltage being larger than 0.8 V, the current density of interdigitated flow PEMFCs with wavelike GCs is also constant because of small oxygen consumptions and liquid water generations. However the oxygen consumption and liquid water generation are large enough and depend on the oxygen transport and liquid water removal at the low operation voltage being less than 0.8 V. At the low voltage, the oxygen transport and liquid water removal are modified by the increased MEA deformation level. Consequently the current density is first decreased and then increased at the low operation voltage. [ABSTRACT FROM AUTHOR]

• The effects of cathode GDL thickness on cell performances are studied numerically. • The steady-state and load-varying conditions are both considered. • A principle of selecting the optimal GDL thickness is proposed. This work proposes a design principle of the optimal thickness for cathode gas diffusion layers (GDLs) of proton exchange membrane fuel cells (PEMFCs) based on a balance of cell performances under both steady-state and load-varying conditions. Using a three-dimensional and two-phase model, the effects of cathode GDL thickness (50, 100, 200, and 400 μm) on steady-state performances and transient response characteristics are studied. The results show that under steady-state conditions, an extremely thin cathode GDL would lead to non-uniform oxygen and liquid water distributions, whereas an especially thick cathode GDL would increase oxygen transport resistance. Thus, there is an optimal cathode GDL thickness, yielding the best steady-state performance. A current overshoot phenomenon, arising from high local oxygen concentrations at cathode catalyst layers (CLs), is observed when the load voltage decreases abruptly. Thinner cathode GDLs would weaken the overshoot and shorten the recovery time of current density. Conversely, low local oxygen concentrations at cathode CLs caused by high liquid water saturation levels lead to a current undershoot phenomenon when the load voltage increases abruptly. Thinner cathode GDLs would strengthen the undershoot but shorten the recovery time of current density. The optimal choice of cathode GDL thickness should weigh up the steady-state and the transient performance. Based on this principle, the optimal cathode GDL thickness is selected as 100 µm. [ABSTRACT FROM AUTHOR]

Background Few safety and effectiveness results have been published regarding the administration of tenofovir alafenamide fumarate (TAF) during pregnancy for the prevention of mother-to-child transmission (MTCT) of hepatitis B virus (HBV). Methods In this multicenter prospective observational study, pregnant women with HBV DNA levels higher than 200 000 IU/mL who received TAF or tenofovir disoproxil fumarate (TDF) from gestational weeks 24–35 to delivery were 1:1 enrolled and followed until postpartum month 6. Infants received immunoprophylaxis. The primary endpoint was the safety of mothers and infants. The secondary endpoint was the hepatitis B surface antigen (HBsAg)-positive rate at 7 months for infants. Results In total, 116 and 116 mothers were enrolled, and 117 and 116 infants were born, in the TAF and TDF groups, respectively. TAF was well tolerated during a mean treatment duration of 11.0 weeks. The most common maternal adverse event was nausea (19.0%). One (0.9%), 3 (2.6%), and 9 (7.8%) mothers had abnormal alanine aminotransferase levels at delivery and at postpartum months 3 and 6, respectively. The TDF group had safety profiles that were comparable to those of the TAF group. No infants had birth defects in either group. The infants' physical and neurological development at birth and at 7 months in the TAF group were comparable with those in the TDF group. The HBsAg positive rate was 0% at 7 months in all 233 infants. Conclusions Antiviral prophylaxis with TAF was determined to be generally safe for both mothers and infants and reduced the MTCT rate to 0%. [ABSTRACT FROM AUTHOR]

Background: Liver injuries have been reported in patients with coronavirus disease 2019 (COVID-19). This study aimed to investigate the clinical role played by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).Methods: In this multicentre, retrospective study, the parameters of liver function tests in COVID-19 inpatients were compared between various time-points in reference to SARS-CoV-2 shedding, and 3 to 7 days before the first detection of viral shedding was regarded as the reference baseline.Results: In total, 70 COVID-19 inpatients were enrolled. Twenty-two (31.4%) patients had a self-medication history after illness. At baseline, 10 (14.3%), 7 (10%), 9 (12.9%), 2 (2.9%), 15 (21.4%), and 4 (5.7%) patients already had abnormal alanine aminotransferase (ALT), aspartate aminotransferase (AST), gamma-glutamyl transferase (GGT), alkaline phosphatase (ALP), albumin, and total bilirubin (TBIL) values, respectively. ALT and AST abnormal rates and levels did not show any significant dynamic changes during the full period of viral shedding (all p > 0.05). The GGT abnormal rate (p = 0.008) and level (p = 0.033) significantly increased on day 10 of viral shedding. Meanwhile, no simultaneous significant increases in abnormal ALP rates and levels were observed. TBIL abnormal rates and levels significantly increased on days 1 and 5 of viral shedding (all p < 0.05). Albumin abnormal decrease rates increased, and levels decreased consistently from baseline to SARS-CoV-2 clearance day (all p < 0.05). Thirteen (18.6%) patients had chronic liver disease, two of whom died. The ALT and AST abnormal rates and levels did not increase in patients with chronic liver disease during SARS-CoV-2 shedding.Conclusions: SARS-CoV-2 does not directly lead to elevations in ALT and AST but may result in elevations in GGT and TBIL; albumin decreased extraordinarily even when SARS-CoV-2 shedding ended. [ABSTRACT FROM AUTHOR]

In this study, a novel cathode flow field plate with additional tapered oblique fin (OF) channels is proposed for air-cooled proton exchange membrane fuel cells (PEMFCs) to promote their heat dissipation and output power. Air-cooled PEMFC stacks with conventional (parallel configuration) and novel flow fields are respectively manufactured and experimentally tested under various load currents. The performance and temperature distributions of the stacks are comparatively studied in detail. Besides, a three-dimensional and two-phase numerical model is established and validated by the experiment data to further comparative investigate the heat and mass transport mechanism of the two studied flow field designs. The results show that the stack with the novel flow field has higher output power, which is 4.87% higher than that with a conventional design at a load current density of 0.55 A cm−2. Due to the forced convection and secondary vortex phenomena in the OF channels, the local overheating in the porous electrode is relieved. Moreover, the entropy generations due to heat transfer of the cathode CL and cooling channels are significantly increased. The oxygen transport under cathode ribs is also noteworthily enhanced when the OF channels are adopted. • An air-cooled PEMFC stack with tapered oblique fin channels is designed and fabricated. • Tapered oblique fin channel design enhances stack performance and heat dissipation. • Local multi-physics fields inside the PEMFC are studied by numerical methods. • Mass transport and thermal behaviors inside the air-cooled PEMFC are optimized. • Entropy generation due to mass transport and heat transfer is studied for the PEMFC. [ABSTRACT FROM AUTHOR]

Currently, COVID‐19 has been reported in nearly all countries globally. To date, little is known about the viral shedding duration, clinical course and treatment efficacy of COVID‐19 near Hubei Province, China. This multicentre, retrospective study was performed in 12 hospitals in Henan and Shaanxi Provinces from 20 January to 8 February 2020. Clinical outcomes were followed up until 26 March 2020. The viral shedding duration, full clinical course and treatment efficacy were analysed in different subgroups of patients. A total of 149 COVID‐19 patients were enrolled. The median age was 42 years, and 61.1% (91) were males. Of them, 133 (89.3%) had fever, 131 of 144 (91%) had pneumonia, 27 (18.1%) required intensive care unit (ICU) management, 3 (2%) were pregnant, and 3 (2%) died. Two premature newborns were negative for SARS‐CoV‐2. In total, the median SARS‐CoV‐2 shedding period and clinical course were 12 (IQR: 9–17; mean: 13.4, 95% CI: 12.5, 14.2) and 20 (IQR: 16–24; mean: 21.2, 95% CI: 20.1, 22.3) days, respectively, and ICU patients had longer median viral shedding periods (21 [17–24] versus 11 [9–15]) and clinical courses (30 [22–33] vs. 19 [15.8–22]) than non‐ICU patients (both p <.0001). SARS‐CoV‐2 clearances occurred at least 2 days before fatality in 3 non‐survivors. Current treatment with any anti‐viral agent or combination did not present the benefit of shortening viral shedding period and clinical course (all p >.05) in real‐life settings. In conclusion, the viral shedding duration and clinical course in Henan and Shaanxi Provinces were shorter than those in Hubei Province, and current anti‐viral therapies were ineffective for shortening viral shedding duration and clinical course in real‐world settings. These findings expand our knowledge of the SARS‐CoV‐2 infection and may be helpful for management of the epidemic outbreak of COVID‐19 worldwide. Further studies concerning effective anti‐viral agents and vaccines are urgently needed. [ABSTRACT FROM AUTHOR]

Currently, coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has been reported in almost all countries globally. No effective therapy has been documented for COVID-19, and the role of convalescent plasma therapy is unknown. In the current study, 6 patients with COVID-19 and respiratory failure received convalescent plasma a median of 21.5 days after viral shedding was first detected, all tested negative for SARS-CoV-2 RNA within 3 days after infusion, and 5 eventually died. In conclusion, convalescent plasma treatment can end SARS-CoV-2 shedding but cannot reduce the mortality rate in critically ill patients with end-stage COVID-19, and treatment should be initiated earlier. [ABSTRACT FROM AUTHOR]

Currently, coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has been reported in almost all countries globally. No effective therapy has been documented for COVID-19, and the role of convalescent plasma therapy is unknown. In the current study, 6 patients with COVID-19 and respiratory failure received convalescent plasma a median of 21.5 days after viral shedding was first detected, all tested negative for SARS-CoV-2 RNA within 3 days after infusion, and 5 eventually died. In conclusion, convalescent plasma treatment can end SARS-CoV-2 shedding but cannot reduce the mortality rate in critically ill patients with end-stage COVID-19, and treatment should be initiated earlier. [ABSTRACT FROM AUTHOR]