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Abstract The demand for sustainable energy has motivated the development of artificial photosynthesis. Yet the catalyst and reaction interface designs for directly fixing permanent gases (e.g. CO 2 , ... O 2 , N 2 ) into liquid fuels are still challenged by slow mass transfer and sluggish catalytic kinetics at the gas-liquid-solid boundary. Here, we report that gas-permeable metal-organic framework (MOF) membranes can modify the electronic structures and catalytic properties of metal single-atoms (SAs) to promote the diffusion, activation, and reduction of gas molecules (e.g. CO 2, O 2 ) and produce liquid fuels under visible light and mild conditions. With Ir SAs as active centers, the defect-engineered MOF (e.g. activated NH 2 -UiO-66) particles can reduce CO 2 to HCOOH with an apparent quantum efficiency (AQE) of 2.51% at 420 nm on the gas-liquid-solid reaction interface. With promoted gas diffusion at the porous gas-solid interfaces, the gas-permeable SA/MOF membranes can directly convert humid CO 2 gas into HCOOH with a near-unity selectivity and a significantly increased AQE of 15.76% at 420 nm. A similar strategy can be applied to the photocatalytic O 2 -to-H 2 O 2 conversions, suggesting the wide applicability of our catalyst and reaction interface designs. more

In this paper, we train turbulence models based on convolutional neural networks. These learned turbulence models improve under-resolved low-resolution solutions to the incompressible Navier–Stokes ... equations at simulation time. Our study involves the development of a differentiable numerical solver that supports the propagation of optimisation gradients through multiple solver steps. The significance of this property is demonstrated by the superior stability and accuracy of those models that unroll more solver steps during training. Furthermore, we introduce loss terms based on turbulence physics that further improve the model accuracy. This approach is applied to three two-dimensional turbulence flow scenarios, a homogeneous decaying turbulence case, a temporally evolving mixing layer and a spatially evolving mixing layer. Our models achieve significant improvements of long-term a posteriori statistics when compared with no-model simulations, without requiring these statistics to be directly included in the learning targets. At inference time, our proposed method also gains substantial performance improvements over similarly accurate, purely numerical methods. more

The influence of pH on the degradation of refractory organics (benzoic acid, BA) in UV(254 nm)/Peroxymonosulfate (UV/PMS) system was investigated. The degradation of BA was significantly enhanced at ... the pH range of 8–11, which could not be explained only by the generally accepted theory that SO4 •‑ was converted to HO• at higher pH. A hypothesis was proposed that the rate of PMS photolysis into HO• and SO4 •‑ increased with pH. The hypothesis was evidenced by the measured increase of apparent-molar absorption coefficient of PMS (εPMS, 13.8–149.5 M–1·cm–1) and photolysis rate of PMS with pH, and further proved by the increased quasi-stationary concentrations of both HO• and SO4 •‑ at the pH range of 8–10. The formation of HO• and SO4 •‑ in the UV/PMS system was confirmed mainly from the cooperation of the photolysis of PMS, the decay of peroxomonosulfate radical (SO5 •‑) and the conversion of SO4 •‑ to HO• by simulation and experimental results. Additionally, the apparent quantum yield for SO4 •‑ in the UV/PMS system was calculated as 0.52 ± 0.01 at pH 7. The conclusions above as well as the general kinetic expressions given might provide some references for the UV/PMS applications. more

Efficiently predicting the flow field and load in aerodynamic shape optimisation remains a highly challenging and relevant task. Deep learning methods have been of particular interest for such ... problems, due to their success in solving inverse problems in other fields. In the present study, U-net-based deep neural network (DNN) models are trained with high-fidelity datasets to infer flow fields, and then employed as surrogate models to carry out the shape optimisation problem, i.e. to find a minimal drag profile with a fixed cross-sectional area subjected to a two-dimensional steady laminar flow. A level-set method as well as Bézier curve method are used to parameterise the shape, while trained neural networks in conjunction with automatic differentiation are utilised to calculate the gradient flow in the optimisation framework. The optimised shapes and drag force values calculated from the flow fields predicted by the DNN models agree well with reference data obtained via a Navier–Stokes solver and from the literature, which demonstrates that the DNN models are capable not only of predicting flow field but also yielding satisfactory aerodynamic forces. This is particularly promising as the DNNs were not specifically trained to infer aerodynamic forces. In conjunction with a fast runtime, the DNN-based optimisation framework shows promise for general aerodynamic design problems. more

本文以成書、出版於1943年的《皇民奉公經附孝經》為探討對象，討論該經典之內容、背景、流通模式及相關人士。並且以這些人為切入點，透過鸞堂資料及日記等材料理解其宗教網絡以及鸞堂系統，梳理出經書誕生的時代意義。本研究發現，《皇民奉公經附孝經》內容雖符合戰時國家意識形態，但其內容仍有傳統漢文化的道德觀念及宗教思維，保持透過善書進行社會教化的功能。並且《皇民奉公經附孝經》的成書帶有漢文化保存、維繫鸞務的目的，可視為民間社會透過宗教文本自行配合當局政策的一種方式。《皇民奉公經附孝經》中的相關人士身分多為地方菁英與鸞堂成員，其身分包含實業家、農主、公學校教師等職務。並且這些人多受過漢文教育薰陶。此外，《皇民奉公經附孝經》一書背後的宗教網絡及相關鸞堂為彰化三興堂系統下醒化堂體系，這些人多為醒化堂體系下鸞堂之成員，或相關鸞務參與者，其分布均集中在臺中、彰化、南投一帶。因此該經書背後所構成的人際網絡可視為中部地區鸞堂活動的縮影。本文認為，《皇民奉公經附孝經》的誕生可能是中部地區鸞堂成員、地方菁英在時局的壓力下，為了其宗教經營、事業維護及社會教化及漢文化保存等目標，透過合作及編纂，促成該書的誕生。

Photocatalytic nitrogen fixation reaction can harvest the solar energy to convert the abundant but inert N2 into NH3. Here, utilizing metal–organic framework (MOF) membranes as the ideal assembly of ... nanoreactors to disperse and confine gold nanoparticles (AuNPs), we realize the direct plasmonic photocatalytic nitrogen fixation under ambient conditions. Upon visible irradiation, the hot electrons generated on the AuNPs can be directly injected into the N2 molecules adsorbed on Au surfaces. Such N2 molecules can be additionally activated by the strong but evanescently localized surface plasmon resonance field, resulting in a supralinear intensity dependence of the ammonia evolution rate with much higher apparent quantum efficiency and lower apparent activation energy under stronger irradiation. Moreover, the gas-permeable Au@MOF membranes, consisting of numerous interconnected nanoreactors, can ensure the dispersity and stability of AuNPs, further facilitate the mass transfer of N2 molecules and (hydrated) protons, and boost the plasmonic photocatalytic reactions at the designed gas–membrane–solution interface. As a result, an ammonia evolution rate of 18.9 mmol gAu –1 h–1 was achieved under visible light (>400 nm, 100 mW cm–2) with an apparent quantum efficiency of 1.54% at 520 nm. more

This article presents a study on the influence of selective laser melting (SLM) process on microstructure and property of a cemented carbide system containing high entropy alloy. Analysis along the ... building direction indicated variation of chemical composition and microstructure, and this was influenced by two effects, firstly the dilution effect due to elemental diffusion from the baseplate and secondly the elements evaporation caused by high-power laser. At the lower half of the specimen, high fraction of η-carbide formed near the level of baseplate, and there were chemical gradients of major binder elements along the building direction. At the upper half of the specimen, there were relatively less variation in chemical composition and more homogeneously distributed phases including WC, W2C, η-carbide and FCC metal binder. The hardness of the lower half specimen varied from 711.7 HV1 (bottom of the specimen) to 1178.6 HV1 at 1 mm height. For the upper half of the specimen, hardness values could range from 1306.8 HV1 to 1413.4 HV1 and fracture toughness varied from 9.74 MPa m1/2 to 13.29 MPa m1/2. •A complex cemented carbide system was subjected to selective laser melting process.•The cemented carbide system contains a high entropy alloy.•Composition and microstructure of the cemented carbide were heterogeneous.•Dilution effect, evaporation, and laser scanning tracks could affect the built.•Hardness and toughness varied due to variation in composition and microstructure. more

This study presents a novel eddy current sensing method for imaging defect distribution in multilayered nonferrous metal plates using an array of magnetic sensors. This method involves dividing the ... metal plate into small voxels to facilitate reconstruction and uses multifrequency to excite the coil. For each frequency, reconstructing defects from magnetic flux density (MFD) measurements is formulated as a linear inverse problem. The absence or presence of a defect strongly suggests that the solution to the linear inverse problem is binary. This study develops an algorithm under a statistical framework to solve the linear inverse problem with binary constraints. The algorithm introduces a Bernoulli prior over the hidden variables and uses a variational Bayesian inference (VBI) to analytically approximate the posterior probability of the hidden variables conditioned on the observed data. The effectiveness of the proposed method is demonstrated using numerically simulated data and a prototype consisting of a coil and an <inline-formula> <tex-math notation="LaTeX">8\times8 </tex-math></inline-formula> array of magnetic sensors with 4 mm intervals. The results demonstrate that the method is feasible for imaging defects of 2 mm with a depth resolution of 0.5 mm. more

Photodetectors based on reduced graphene oxide (rGO) have attracted much attention owing to their simple and low‐cost fabrication process. However, the aggregation and defects of rGO flakes still ... limit the performance of rGO photodetectors. Controlling the composition of rGO has become a vital factor for its prospective applications. For example, the interconnection between rGO and polymers for modified morphologies of rGO films leads to an enhanced performance of devices. In this work, a practical approach to engineer surface uniformity and enhance the performance of a photodetector by modifying the rGO film with hydrophilic polymers poly(vinyl alcohol) (PVA) is reported. Compared with the rGO photodetector, the on/off ratio for the PVA/rGO photodetector shows 3.5 times improvement, and the detectivity shows 53% enhancement even when the photodetector is operated at a low bias of 0.3 V. This study provides an effective route to realize PVA/rGO photodetectors with a low‐power operation which shows promising opportunities for the future development of green systems. A practical approach to enhance the performance of a reduced graphene oxide (rGO) photodetector by modifying the rGO film with poly(vinyl alcohol) (PVA) is reported. Compared with the rGO photodetector, the on/off ratio for the PVA/rGO photodetector shows 3.5 times improvement, and the detectivity shows 53% enhancement at a low operating bias of 0.3 V. more

Despite its activity, monometallic Ni-catalyst is highly susceptible to coke deposition and sintering in catalyzing dry reforming of methane (DRM). To counter these, a novel tremella-like ... monometallic Ni/SiO2 catalyst was hydrothermally synthesized herein, realizing excellent activity, outstanding coke inhibition and robust structural stability for a durable DRM reaction. Functionality-speaking, the tapered ends of Ni-petals, sized at 8–15 nm, permit high DRM activity with suppressed coke formation while its thicker base spatially prevents Ni-sintering during high temperature reaction. Meanwhile, the open structure of catalyst resulting from such tremella-like structure also enhances the diffusion of reactants/products gas to/from catalytic surface, thus augmenting its activity for DRM. With merely 5 wt% Ni incorporated, CO2 and CH4 conversions of ∼90% could be attained with only ∼15% activity drop after 75 h of DRM. Full-restoration of activity could facilely be attained using 90 min in-situ oxidative regeneration. Mechanistic study coupling sorptive investigation, ex-situ XRD, and SEM reveals the pronounced adsorption tendency of CH4 over those of CO2, H2 and CO, confirming the adherence of DRM to Eley-Rideal reaction model in current study. Significantly, this study provides a new morphological-controlled strategy to conveniently impart excellent coke-inhibiting and sintering-resisting capability to monometallic Ni-catalyst. Display omitted •Tremella-like Ni/SiO2 is highly active toward dry reforming of methane (DRM).•Tapered end of Ni-petal suppresses coke formation during DRM reaction.•Thick Ni base permits robust metal-support interaction for improved stability.•Open structure of Ni/SiO2 improves the accessibility of reactants and products. more