The rapid progress of proton exchange membrane fuel cells (PEMFCs) and alkaline exchange membrane fuel cells (AMFCs) has boosted the hydrogen economy concept via diverse energy applications in the ...past decades. For a holistic understanding of the development status of PEMFCs and AMFCs, recent advancements in electrocatalyst design and catalyst layer optimization, along with cell performance in terms of activity and durability in PEMFCs and AMFCs, are summarized here. The activity, stability, and fuel cell performance of different types of electrocatalysts for both oxygen reduction reaction and hydrogen oxidation reaction are discussed and compared. Research directions on the further development of active, stable, and low‐cost electrocatalysts to meet the ultimate commercialization of PEMFCs and AMFCs are also discussed.
The development of fuel cells is of great significance for achieving a sustainable society. Recent progress in cathodic electrocatalysts for proton exchange membrane fuel cells and anodic and cathodic electrocatalysts for alkaline exchange membrane fuel cells is summarized. The rational design strategies, structure evolution, activities, fuel cell performance, and durability of noble‐metal‐ and non‐noble‐metal‐based electrocatalysts are discussed.
In the aircraft industry, three-dimensional (3D) printing can confer several benefits, such as shortened cycle times, reduced production costs, and lighter part weights. However, some concerns must ...be addressed for 3D-printing applications to be viable. This paper investigated these concerns by reviewing the current 3D printing practices in the aircraft industry. The literature review identified five factors critical to the applicability of advanced 3D printing technologies to the aircraft industry, and a fuzzy systematic approach was applied to assess the applicability and relative importance of the identified factors, combining fuzzy geometric mean and fuzzy analytical hierarchy process. The findings provide valuable input for countries or regions considering expanding 3D printing applications to their aircraft industries.
A high‐performance nonprecious‐metal oxygen‐reduction electrocatalyst is prepared via in situ growth of bimetallic zeolitic imidazolate frameworks on multiwalled carbon nanotubes (CNTs) followed by ...adsorption of furfuryl alcohol and pyrolysis. The networking boosts the conductivity and performance in a polymer electrolyte membrane fuel cell, yielding a maximal power density of 820 mW cm−2.
Fe/N/C is a promising non‐Pt electrocatalyst for the oxygen reduction reaction (ORR), but its catalytic activity is considerably inferior to that of Pt in acidic medium, the environment of polymer ...electrolyte membrane fuel cells (PEMFCs). An improved Fe/N/C catalyst (denoted as Fe/N/C‐SCN) derived from Fe(SCN)3, poly‐m‐phenylenediamine, and carbon black is presented. The advantage of using Fe(SCN)3 as iron source is that the obtained catalyst has a high level of S doping and high surface area, and thus exhibits excellent ORR activity (23 A g−1 at 0.80 V) in 0.1 M H2SO4 solution. When the Fe/N/C‐SCN was applied in a PEMFC as cathode catalyst, the maximal power density could exceed 1 W cm−2.
A non‐precious Fe/N/C electrocatalyst was prepared through pyrolysis of Fe(SCN)3, poly‐m‐phenylenediamine, and carbon black. The obtained Fe/N/C catalyst has high level of S doping and high surface area, and thus exhibits excellent catalytic activity for the oxygen reduction reaction in acidic solution. A polymer electrolyte membrane fuel cell using this catalyst as the cathode can yield a maximal power density as high as 1.03 W cm−2.
Interstitial fibrosis is an important contributor to graft loss in chronic renal allograft injury. Inflammatory macrophages are associated with fibrosis in renal allografts, but how these cells ...contribute to this damaging response is not clearly understood. Here, we investigated the role of macrophage-to-myofibroblast transition in interstitial fibrosis in human and experimental chronic renal allograft injury. In biopsy specimens from patients with active chronic allograft rejection, we identified cells undergoing macrophage-to-myofibroblast transition by the coexpression of macrophage (CD68) and myofibroblast (
-smooth muscle actin
-SMA) markers. CD68
/
-SMA
cells accounted for approximately 50% of the myofibroblast population, and the number of these cells correlated with allograft function and the severity of interstitial fibrosis. Similarly, in C57BL/6J mice with a BALB/c renal allograft, cells coexpressing macrophage markers (CD68 or F4/80) and
-SMA composed a significant population in the interstitium of allografts undergoing chronic rejection. Fate-mapping in Lyz2-Cre/Rosa26-Tomato mice showed that approximately half of
-SMA
myofibroblasts in renal allografts originated from recipient bone marrow-derived macrophages. Knockout of
protected against interstitial fibrosis in renal allografts and substantially reduced the number of macrophage-to-myofibroblast transition cells. Furthermore, the majority of macrophage-to-myofibroblast transition cells in human and experimental renal allograft rejection coexpressed the M2-type macrophage marker CD206, and this expression was considerably reduced in
-knockout recipients. In conclusion, our studies indicate that macrophage-to-myofibroblast transition contributes to interstitial fibrosis in chronic renal allograft injury. Moreover, the transition of bone marrow-derived M2-type macrophages to myofibroblasts in the renal allograft is regulated
a Smad3-dependent mechanism.
In this work we investigate the effects of two distinct actuation methods on the hydrodynamics of elastic rectangular plates oscillating at resonance. Plates are driven by plunging motion at the root ...or actuated by a distributed internal bending moment at Reynolds numbers between 500 and 4000. The latter actuation method represents internally actuated smart materials and emulates the natural ability of swimming animals to continuously change their shapes with muscles. We conduct experiments with plunging elastic plates and piezoelectric plate actuators that are simulated using a fully coupled three-dimensional computational model based on the lattice Boltzmann method. After experimental validation the computational model is employed to probe plate hydrodynamics for a wide range of parameters, including large oscillation amplitudes which prompts nonlinear effects. The comparison between the two actuation methods reveals that, for the same level of tip deflection, externally actuated plates significantly outperform internally actuated plates in terms of thrust production and hydrodynamic efficiency. The reduced performance of internally actuated plates is associated with their suboptimal bending shapes which leads to a trailing edge geometry with enhanced vorticity generation and viscous dissipation. Furthermore, the difference in actuation methods impacts the inertia coefficient characterizing the plate oscillations, especially for large amplitudes. It is found that the inertia coefficient strongly depends on the tip deflection amplitude and the Reynolds number, and actuation method, especially for larger amplitudes.
Preparation of reliable, stable, and highly responsive gas-sensing devices for the detection of acetone has been considered to be a key issue for the development of accurate disease diagnosis systems ...via exhaled breath. In this paper, novel CeO2 nanodot-decorated WO3 nanowires are successfully synthesized through a sequential hydrothermal and thermolysis process. Such CeO2 nanodot-decorated WO3 nanowires exhibited a remarkable enhancement in acetone-sensing performance based on a miniaturized micro-electromechanical system device, which affords high response (S = 1.30–500 ppb, 1.62–2.5 ppm), low detection limit (500 ppb), and superior selectivity toward acetone. The improved performance of the acetone sensor is likely to be originated from the fast carrier transportation of WO3 nanowires, the formation of WO3–CeO2 heterojunctions, and the existence of large amounts of oxygen vacancies in CeO2. The improved reaction thermodynamics and sensing mechanisms have also been revealed by the specific band alignment and X-ray photoelectron spectroscopy analysis.
The bistable fluttering response of heavy inverted flags with different aspect ratios ($AR$) is investigated to determine how the vortical structures affect the intermittent vibration response of the ...flag. A heavy inverted flag in a uniform flow may exhibit several response modes; amongst them are three major modes that occur over an extended velocity range: stationary, large-scale periodic oscillation and one-sided deflected modes. Significant hysteretic bistability is observed at the transition between these modes for all $AR$, which is notably different from the conventional flag vibration with a fixed leading edge and free trailing edge where no hysteresis is observed at the lower $AR$ limit ($AR<1$). The difference is associated with the distinct roles of vortices around the flag. Experiments with flags made of spring steel are conducted in a wind tunnel, where the flow speed is steadily increased and later decreased to obtain different oscillatory modes of the heavy inverted flags. The experimental results are used to validate the numerical model of the same problem. It is found that different critical velocities exist for increasing and decreasing flow velocities, and there is a sustained hysteresis for all $AR$ controlled by the initiation threshold and growth of the leading-edge and side-edge vortices. The effect of the vortices in the bistable oscillation regime is quantified by formulating a modal force partitioning approach. It is shown that $AR$ can significantly alter the static and dynamic vortex interaction with the flexible plate, thereby changing the flag's hysteresis behaviour and bistable response.
Purpose
To understand which environmental factors influence the distribution and ecological functions of bacteria in agricultural soil.
Method
A broad range of farmland soils was sampled from 206 ...locations in Jilin province, China. We used 16S rRNA gene-based Illumina HiSeq sequencing to estimated soil bacterial community structure and functions.
Result
The dominant taxa in terms of abundance were found to be, Actinobacteria, Acidobacteria, Gemmatimonadetes, Chloroflexi, and Proteobacteria. Bacterial communities were dominantly affected by soil pH, whereas soil organic carbon did not have a significant influence on bacterial communities. Soil pH was significantly positively correlated with bacterial operational taxonomic unit abundance and soil bacterial α-diversity (P<0.05) spatially rather than with soil nutrients. Bacterial functions were estimated using FAPROTAX, and the relative abundance of anaerobic and aerobic chemoheterotrophs, and nitrifying bacteria was 27.66%, 26.14%, and 6.87%, respectively, of the total bacterial community. Generally, the results indicate that soil pH is more important than nutrients in shaping bacterial communities in agricultural soils, including their ecological functions and biogeographic distribution.
This study proposes a hybrid big data analytics and Industry 4.0 (BD-I4) approach to enhancing the effectiveness of cycle time range projections for factory jobs. As a joint application of big data ...analytics and Industry 4.0, the BD-I4 approach is distinct from existing methods in this field. In this approach, each expert first constructs a fuzzy deep neural network to project the cycle time range of a job, an application of big data analytics (i.e., deep learning). Subsequently, the fuzzy weighted intersection operator is applied to aggregate the projected cycle times such that unequal authority levels can be considered, an application of Industry 4.0 (i.e., artificial intelligence). Applying the BD-I4 approach to a real case that the proposed methodology improved the projection precision by up to 72%, suggesting that instead of relying on a single expert, collaboration among multiple experts may be more effective and efficient.
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