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We consider a fast-fashion brand that cooperates with a luxury brand, jointly launching a co-branded product. The impacts of the co-branding on the two brands’ original product lines are uncertain, and each brand can be either risk averse or risk neutral. Consumers, driven by exclusivity or conformity, are classified as either snobs or conformists. The equilibrium retail price, quality investment, and investment support are derived. The optimal market-targeting strategy for the fast-fashion brand as marketer of the co-branded product, is identified. We show that the fast-fashion brand is willing to give up either the conformist or the snob market under certain conditions, even when it has sales in both markets. In addition, given a particular market-targeting strategy, the fast-fashion brand benefits from its own risk aversion if the cost of risk is low, but the luxury brand is always worse off; the luxury brand may benefit from the fast-fashion brand’s risk aversion, however, if the market-targeting strategy is changed. Both brands are worse off when the luxury brand is risk averse.

Direct ethanol fuel cell (DEFC) as a promising device for converting chemical energy to electricity has been paid ever-increasing attention. However, the slow kinetics of ethanol electrooxidation at an anode hinders the application of DEFCs. Although Pt is the best catalyst among all the pure metal catalysts, it still has a relatively poor ability to break the C C bond, is deactivated by the accumulated COad intermediates, and undergoes unwanted desired structure change over long-term operation. In recent years, the addition of other metals to form binary, ternary, and quaternary catalysts have significantly improved electroactivity and stability. Ternary catalysts can have numerous element combinations and complicated architectures and, therefore, have been the subject of considerable research. In this review, most of the reported ternary catalysts will be summarized and categorized according to their structure while discussing the essence of the role of each component.

Lead halide perovskite nanocrystals (CsPbX3 NCs) have been regarded as promising materials in photocatalysis. Combining metal single atoms with CsPbX3 NCs may be a practical way in exploring perovskite-based catalysts. However, such hybrids have not been achieved experimentally yet, mainly due to the weak interaction between the metal atom and the CsPbX3 surface. Here, we demonstrate that Pt single atoms can be deposited on CsPbBr3 NCs through a photoassisted approach, in which the surface was partially oxidized first, followed by the anchoring of Pt single atoms through the formation of Pt-O and Pt-Br bonds. The deposition of Pt single atoms can significantly change the photophysical properties of CsPbBr3 NCs by inducing the generation of deep trap states in the band gap. The as-prepared Pt-SA/CsPbBr3 can be used as efficient and durable catalysts for photocatalytic semi-hydrogenation of propyne. A CsPbBr3 nanocrystal might be a suitable substrate for anchoring other metal single atoms, such as Cu, Au, Ag, Pd, and so on.

This paper reports that the optical properties of anthraquinone (AQ) and its photo-catalytic performance in the visible light-driven p-xylene (PX) oxidation can be fine-tuned and improved through varying its skeleton substituents at the molecular level, and the electron-withdrawing substituent exhibits a better improvement effect than the electron-donating one. The best catalyst 2-carboxyanthraquinone (AQ-COOH) can achieve 70.9% PX conversion and 88.2% p-toluic acid selectivity under visible light illumination and 1 atm O2 pressure. The addition of benzenesulfonic acid in the above photocatalytic system can further increase PX conversion to 86.7%, along with a significant improvement in the selectivity of p-carboxybenzaldehyde and terephthalic acid, which likely originates from the unique recombination behavior of the photo-generated charge carriers of the catalyst and the additive driven by the strong interactions between their aromatic skeletons and acidic substituents. Furthermore, AQ-COOH can achieve almost quantitative yield of acetylacetone in ethylbenzene photooxidation and the regulating effect of toluene's para-position substituents on its reactivity is also reported in the AQ-COOH photocatalysis system. Based on quenching tests and EPR spectral characterizations, the oxygen vacancies (h+), superoxide free radicals (O2•-) and singlet oxygen (1O2) as the photo-generated active species are involved in the proposed photo-catalysis mechanism.

Controllable fabrication of Fe-N-C based single-atom catalysts (SACs) for enhanced electrocatalytic performance is highly desirable but still challenging. Here, an in situ surface-confined strategy was demonstrated for the synthesis of single atomic Fe-N4 on N-doped carbon nanoleaves (L-FeNC). The in situ generated Zn3[Fe(CN)6]2 could not only serve as a protection layer against collapse of nanoleaves but also provide abundant Fe source for the formation of Fe-N moieties during pyrolysis, leading to high surface area and high graphitization degree of L-FeNC simultaneously. Benefiting from abundant Fe-N4 active sites, enhanced mass and charge transfer, the as-prepared L-FeNC manifested a half-wave potential of 0.89 V for oxygen reduction reaction (ORR) in 0.1 M KOH. A maximum power density of 140 mW cm−2 and stable discharge voltage even after operation for 50,000 s have been demonstrated when the L-FeNC was used as air cathode for Zn-air battery. This work not only provided a unique surface-confined strategy for the synthesis of two-dimensional nanocarbons, but also demonstrated the significant benefit from rational design and engineering of Fe-N-C SACs, thus offering great opportunities for fabrication of efficient energy conversion and storage devices.

Novel cross-coupled dual-band bandpass filters (BPFs) with compact size are proposed based on dual-mode isosceles right-angled triangular (IRAT) resonators. The dominant mode in the IRAT resonator is the TM100Z mode. By introducing posts in the resonators, an LC resonant unit is formed, which resonates at a lower frequency than the TM100Z mode. In the design of novel dual-band filters, the LC mode constitutes the first passband while the TM100Z mode produces the second passband. As cross-coupling is applied, two and eight transmission zeros (TZs) are produced in the responses of third-order and fourth-order dual-band BPFs, respectively. Two third-order cross-coupled dual-band BPFs with altered passbands and one fourth-order cross-coupled dual-band BPF are fabricated and measured. The measured results agree very well with the simulated results, demonstrating attractive advantages of the proposed BPFs such as compact size and decent performance.

Coal is the primary source of energy in China’s energy structure system. With the large-scale mining of mineral resources, a large amount of mine water will be produced in the process of development, construction, and production, which will pollute and damage the ecological environment of mine water. At present, China vigorously advocates coal revolution, implements low-carbon economy, and carries out clean production of energy development and utilization. Green mining, precision mining, and other strategic ideas have been applied to mine development to guide production practice. This paper does an in-depth analysis of the physical, chemical, biological, and environmental characteristics of mine water, puts forward the basic classification of mine water, and points out the characteristics of environmental hazards of mine water. Aiming at different types of mine water, such as mine wastewater, drainage water, goaf water, mine water with suspended solids, high salinity mine water, acid mine water, and mine water with special pollution, the paper puts forward the mine water treatment and resource utilization technology with different characteristics and strong pertinence. On this basis, the comprehensive treatment and development direction of mine water in the future are prospected.

Hydrogen network integration is a crucial way to achieve resource conservation and cost reduction of refinery and it is performed on quantitative and thermodynamic properties of hydrogen streams su...

We consider the capacitated inverse optimal value problem on minimum spanning tree under Hamming distance. Given a connected undirected network $$G=(V,E)$$ and a spanning tree $$T^0$$ , we aim to modify the weights of the edges such that $$T^0$$ is not only the minimum spanning tree under the new weights but also the weight of $$T^0$$ is equal to a given value K. The objective is to minimize the modification cost under bottleneck Hamming distance. We add a lower bound l and an upper bound u on the modification of weights and consider three cases (uncapacitated, lower bounded, capacitated) of the problem based on the bound vectors. Suppose $$l=-\,\infty , u=+\,\infty $$ in the uncapacitated problem, $$l>-\,\infty , u=+\,\infty $$ in the lower bounded problem and $$l>-\,\infty , u

In this paper, the vibration response of the double-FG porous beam system (DFGPBS) acted by a moving load is investigated. The DFGPBS composed of two parallel FG porous beams with their material properties varying along both the axial and transverse directions, i.e., bi-directional FG material distribution, is taken into account. The porous imperfection is simulated by distributing the porosity along the beam thickness with even and uneven patterns. The governing equations of this bi-directional DFGPBS under a moving load are established with the aid of the Hamilton principle associated with the Timoshenko beam theory. The Ritz method is adopted to discrete the differential governing equations, which are solved by the Newmark-β approach. The validation of the present model is performed by comparing the numerical results with two previous works. Then, the parametric study is carried out to investigate the influences of bi-directional gradient indices, porosity volume fraction, boundary conditions, stiffness of elastic layer, and velocity of the moving load on the vibration response of bi-directional DFGPBSs excited by a moving load. It is demonstrated that the vibration response of the double-beam system subjected to moving loads can be governed by tailoring the distribution of the bi-directional FG materials. The present work can be used to guide the multi-functional design of a double-beam system under dynamic loadings.

This article reveals parasitics-induced current distortion (PCD) effect in discontinuous conduction mode boost power factor (PF) correction (PFC) converter. With consideration of parasitics, accurate inductor current is derived through total differential functions of line voltage, output voltage and duty cycle. Furthermore, the proposed current model is used to analyze PFC converter under conventional sensorless average current mode (SACM) control, which is achieved by a variable duty cycle. It is found that parasitics have considerable influence to the input current, and PCD leads to a degraded PF. In order to solve this issue, a current reshaping strategy is proposed to reduce the PCD phenomenon. Based on the damped current equations, a compensation gain is derived to reshape the input current, which reduces the current damping and distortion caused by parasitics. Both the PCD phenomenon and the current reshaping strategy are verified by simulations and experiments.

Laminated composites are extensively employed in many aerospace structures due to their excellent mechanical properties. In this paper, a size-dependent model on the basis of the nonlocal strain gradient theory is adopted to reveal the vibration behavior of laminated nanoplate with piezo-magnetic face sheets in its upper and lower surfaces. The governing equations are derived by employing the Hamilton’s principle and Mindlin plate theory. The validation of the present study is carried out by comparison with two previous works and good agreements are achieved. By comparing the vibrational frequencies of composite laminated core sandwich nanoplate with and without the piezo-magnetic face sheets, it is demonstrated that the upper and lower piezo-magnetic face sheets will extensively enhance the vibrational frequencies of laminated core sandwich nanoplates. Furthermore, a comprehensive numerical investigation is performed to examine the influence of the cross-ply laminated type, external electric and magnetic potentials, thickness ratio, size scale parameters, as well as aspect and width-to-thickness ratios on the vibration of the laminated core piezo-magnetic sandwich nanoplate. It is expected that the current work can provide some helpful guidelines for employing the piezo-magnetic surfaces as sensors and actuators to control their vibration behaviors of composite laminated nanostructures.

We consider the maximum shortest path interdiction problem by upgrading edges on trees under Hamming distance (denoted by (MSPITH)), which has wide applications in transportation network, network war and terrorist network. The problem (MSPITH) aims to maximize the length of the shortest path from the root of a tree to all its leaves by upgrading edge weights such that the upgrade cost under sum-Hamming distance is upper-bounded by a given value. We show that the problem (MSPITH) under weighted sum-Hamming distance is NP-hard. We consider two cases of the problem (MSPITH) under unit sum-Hamming distance based on the number K of critical edges. We propose a greedy algorithm within $$O(n+l\log l)$$ time when $$K=1$$ and a dynamic programming algorithm within $$O(n(\log n+K^3))$$ time when $$K>1$$ , where n and l are the numbers of nodes and leaves in a tree, respectively. Furthermore, we consider a minimum cost shortest path interdiction problem by upgrading edges on trees under unit Hamming distance, denoted by (MCSPITUH) and propose a binary search algorithm within $$O(n^4\log n)$$ time, where a dynamic programming algorithm is executed in each iteration to solve its corresponding problem (MSPITH). Finally, we design numerical experiments to show the effectiveness of the algorithms.

The slow kinetics at the cathode of oxygen reduction reaction (ORR) seriously limits the efficiencies of fuel cells and metal-air batteries. Pt, the state-of-the-art ORR electrocatalyst, suffers from high cost, low earth abundance, and poor stability. Here a self-templated strategy based on metal-organic frameworks (MOFs) is proposed for the fabrication of hollow nitrogen-doped carbon spheres that are embedded with cobalt nanoparticles (Co/HNC). The Co/HNC manifests better ORR activities, methanol tolerance, and stability than commercial Pt/C. The high ORR performance of Co/NHC can be attributed to the hollow structure which provides enlarged electrochemically active surface area, the formation of more Co-N species, and the introduction of defects. This work highlights the significance of rational engineering of MOFs for enhanced ORR activity and stability and offers new routes to the design and synthesis of high-performance electrocatalysts.

Reverse conduction loss of GaN high electron mobility transistors (HEMTs) in very high frequency (VHF) converters is non-neglectable due to the absence of body diode. To reduce the reverse conduction time, this paper proposes a linear equivalent model for class $\Phi _{2}$ inverter to derive optimal duty cycles for different working conditions. The proposed model is derived from frequency-domain perspective, which simplifies the derivation process and provides an intuitive physical insight for class $\Phi _{2}$ inverter. Firstly, the power switch is modeled as a current source according to time-domain expressions of inductor current, which simplifies the circuit to a linear network. Based on quantitative analysis of the current source spectrum characteristics, the linear network response to the current excitation is derived, which forms the linear equivalent model. Then, drain voltage of the main switch under different working conditions is obtained. With the zero-crossing point of the drain voltage, numerical solutions of the optimal duty cycles are calculated. Finally, the optimal duty cycles are implemented with a high-resolution duty cycle generation circuit in a 27.12MHz prototype, which achieves not only a peak efficiency of 93.6% at full load, but also higher efficiency over the whole load and input voltage range compared to conventional fixed duty cycle.

Hydrogen is the core source to both refinery and synthetic plant of chemicals. Refinery consumes high purity hydrogen while synthetic plant of chemicals needs syngas consists of hydrogen and carbon oxides. As main hydrogen production technologies, industrial coal gasification and steam methane reforming based pathways generate H2, CO and CO2, which is actually the mixture of hydrogen and carbon oxides. Hence, the gases demand of refinery and synthetic plant of chemicals and their supply from hydrogen production can form hybrid hydrogen networks. On the basis of complementary reuse, this paper firstly proposes integration of hybrid hydrogen network for refinery and synthetic plant of chemicals. Superstructures of individual and hybrid hydrogen networks are employed as problem illustration and corresponding linear programming (LP) mathematical models are formulated. Practical refinery and synthetic plant of chemicals cases are employed to demonstrate its application. Compared with individual networks, the natural gas conservation case can recover 8660.4 Nm3·h-1 hydrogen in purge gas, reduce 1386.6 Nm3·h-1 CO2 emission, equaling to reduction of 278.11 kmol·h-1 natural gas feedstock and 14.8% of total gas production load; the coal conservation case can even waive the total coal consumption and extra 104.1 kmol·h-1 natural gas, recover 8660.4 Nm3·h-1 hydrogen in purge gas, reduce 5255.8 Nm3·h-1 of CO2 emission and decrease 21.2% of the total gas production load. Furthermore, economic evaluation is also placed to account for the economic advantage of hybrid network.

Due to the multi-functional requirements, more and more multi-dimensional functionally graded structures are reported, while their thermo-mechanical performances are still unclear. This paper aims at theoretically examining the thermo-mechanical behaviors of two-dimensional functionally graded (2D-FG) microbeam excited by a moving load. The formulation is established in the framework of the modified couple stress theory in combination with Hamilton's principle, and this problem is numerically solved through the finite element method (FEM). The material properties of the 2D-FG microbeam are treated as temperature-dependent parameters that vary smoothly along with both the axial and thickness directions, and three different thermal loads including the uniform, linear, and nonlinear temperature rises are taken into account. Both the fundamental frequency and the dynamic transverse deflection are analyzed with consideration of different axial and thickness gradient indexes, thermal load types, temperature rise amplitudes, and small scale parameters. The conclusion obtained in this paper can serve as a guideline for assessing the thermal performance of microstructures subjected to a moving load.

The production of CO from the CO2 reduction reaction (CO2RR) is of great interest in the renewable energy storage and conversion, the neutral carbon emission, and carbon recycle utilization. Silver (Ag) is one of the catalytic metals that are active for electrochemical CO2 reduction into CO, but the catalysis requires a large overpotential to achieve higher selectivity. Constructing a metal-oxide interface could be an effective strategy to boost both activity and selectivity of the catalysis. Herein, density functional theory (DFT) calculations were first conducted to reveal the chemical insights of the catalytic performance on the interface between metal oxide and Ag(111) (MOx/Ag(111)). The results show that the *COOH intermediates can be more stabilized on the surfaces of MOx/Ag(111) than pure Ag(111). The hydrogen evolution reaction on MOx/Ag(111) can be suppressed due to the significantly higher Gibbs free energy for hydrogen adsorption (ΔGH*), thereby enhancing the selectivity toward CO2RR. A series of MOx/Ag composites with the unique interface based on the DFT results were then introduced though a two-step approach. The as-obtained MOx/Ag catalysts boosted both the CO activity and selectivity at a relatively positive potential range, especially in the case of MnO2/Ag. The reduction current density on the MnO2/Ag catalyst can reach 4.3 mA cm-2 at -0.7 V (vs RHE), which is 21.5 times higher than that on pure Ag, and the overpotential of CO2 to CO (390 mV) possesses is much lower than that on pure Ag NPs (690 mV). This study proposes an effective design strategy to construct a metal-oxide interface for CO2RR based on the synergistic effect between metals and MOx.

Although lead halide perovskites are demonstrated to be promising photocatalysts for hydrogen evolution from hydrogen halide splitting, it still remains challenging to fabricate efficient and stabl...

The scaffold structures formed by the incorporation of reduced graphene oxide (RGO) nanomaterials can be studied to improve the 3D matrix properties in the applications of bone regeneration. On the other hand, RGO has delayed the incorporation into the mixtures that were determined to generate scaffolds on using 3D printing because of its poor colloidal stability of particles and weak solubility in water. Moreover, to produce RGO, the graphene oxide (GO) was treated with hydrazine hydrate solution, which was well known as a reducing agent that is highly hazardous. To outcome these drawbacks, an unique eco-friendly method was established to gather scaffolds that were 3D printed by the incorporation of RGO. This was obtained using the Gallic acid induced in situ reduction of the GO already existing on the gelatin/chitosan/tricalcium phosphate scaffolds. Moreover, scaffolds also exhibited antibacterial activity without conceding osteoblasts’ cell proliferation and viability. Furthermore, the obtained scaffolds showed good osteoblasts proliferation and viability indicating their possibility for applications in bone fracture healing.

Network interdiction problems by deleting critical edges have wide applicatio ns. However, in some practical applications, the goal of deleting edges is difficult to achieve. We consider the maximum shortest path interdiction problem by upgrading edges on trees (MSPIT) under unit/weighted $$l_1$$ norm. We aim to maximize the the length of the shortest path from the root to all the leaves by increasing the weights of some edges such that the upgrade cost under unit/weighted $$l_1$$ norm is upper-bounded by a given value. We construct their mathematical models and prove some properties. We propose a revised algorithm for the problem (MSPIT) under unit $$l_1$$ norm with time complexity O(n), where n is the number of vertices in the tree. We put forward a primal dual algorithm in $$O(n^2)$$ time to solve the problem (MSPIT) under weighted $$l_1$$ norm, in which a minimum cost cut is found in each iteration. We also solve the problem to minimize the cost to upgrade edges such that the length of the shortest path is lower bounded by a value and present an $$O(n^2)$$ algorithm. Finally, we perform some numerical experiments to compare the results obtained by these algorithms.

A facile strategy for the preparation of a nanoconfined Ti3C2/Ru cocatalyst by direct reduction of Ru3+ ions without an additional reductant was developed. The in situ formation of TiO2 nanosheets on the Ti3C2/Ru surface ensures the separation of the semiconductor and cocatalyst (TiO2-Ti3C2/Ru), resulting in charge segregation and migration more effective than those achieved by traditionally prepared Ru-TiO2-Ti3C2. Owing to its low Fermi level, the self-assembled Ti3C2/Ru cocatalyst accepted the photogenerated electrons and promoted H2 evolution without an induction period, while exhibiting high surface structure stability. The changes in the work function and surface terminations of Ti3C2 during the photocatalysis were revealed by DFT calculations and in situ diffuse reflectance infrared Fourier transform spectroscopy. The efficient electron transfer enabled by the structurally separated Ti3C2/Ru-based photocatalyst significantly reduced the electron-hole recombination, increasing the photocatalytic H2 evolution activity. This work provides a guiding design approach for future solar energy conversion with the semiconductor-cocatalyst system.

We consider the lower bounded inverse optimal value problem on minimum spanning tree under unit $$l_{\infty }$$ norm. Given an edge weighted connected undirected network $$G=(V,E,\varvec{w})$$ , a spanning tree $$T^0$$ , a lower bound vector $$\varvec{l}$$ and a value K, we aim to find a new weight vector $$\bar{\varvec{w}}$$ respecting the lower bound such that $$T^0$$ is a minimum spanning tree under the vector $$\bar{\varvec{w}}$$ with weight K, and the objective is to minimize the modification cost under unit $$l_{\infty }$$ norm. We present a mathematical model of the problem. After analyzing optimality conditions of the problem, we develop a strongly polynomial time algorithm with running time O(|V||E|). Finally, we give an example to demonstrate the algorithm and present the numerical experiments.

Single atom catalysts (SACs) have recently attracted great attention in heterogeneous catalysis and have been regarded as ideal models for investigating the strong interaction between metal and support. Despite the huge progress over the past decade, the deep understanding on the structure-performance correlation of SACs at a single atom level still remains to be a great challenge. In this study, we demonstrate that the variation in the coordination number of the Pt single atom can significantly promote the propylene selectivity during propyne semihydrogenation (PSH) for the first time. Specifically, the propylene selectivity greatly increases from 65.4% to 94.1% as the coordination number of Pt-O increases from ∼3.4 to ∼5, whereas the variation in the coordination number of Pt-O slightly influences the turnover frequency values of SACs. We anticipate that the present work may deepen the understanding on the structure-performance of SACs and also promote the fundamental research in single atom catalysis.

The utilization of structural water in chemical self-assembly has not only effectively eliminated the negative influences of solvents from solutions or gels but has also provided new insight into the fabrication of new materials in bulk. However, up to now, supramolecular polymerization triggered by structural water has been dominated more by serendipity than rational design. After carefully analyzing the chemical structures of artificial monomers and gaining a deep understanding of the water-triggered assembly process, we report herein the bulk formation of polymeric materials from water and low-molecular weight monomers by rational design instead of serendipity.

Molecularly imprinting polymers (MIPs), as artificial antibodies with high recognition selectivity to template molecules, are widely used in various biosensors. To improve further the selectivity of MIPs-based photoelectrochemical (PEC) biosensors, we report a differential strategy using non-imprinted polymers (NIPs) as the reference. In a proof-to-concept example for the determination of dopamine (DA), MIPs and NIPs membranes were fabricated by electrochemical polymerization of polypyrrole membranes on the surface of graphene quantum dots (GQDs)/TiO2 nanotubes (NTs). The photocurrent difference between the two PEC cells, MIPs@GQDs/TiO2 NTs−Pt and NIPs@GQDs/TiO2 NTs−Pt, was measured as the signal. As the non-specific adsorption of non-template molecules on the outside surface of MIPs and NIPs membranes is similar, the anti-interference ability for the determination of DA is much improved by using differential strategy. In the normal and differential PEC measurement models, 10.0 μM ascorbic acid is equivalent to 3.12 and 0.40 μM DA, respectively. Further, the smaller specific surface area in NIPs membrane was compensated by using a weight factor to correct the residual interference in a modified differential model. By using 10.0 μM ascorbic acid as the balance point, the presence of 10.0 μM H2O2, glutathione, uric acid or glucose is equivalent only to 0.090, 0.061,0.11 or 0.041 μM of DA, respectively, which are about 3–7% of their interference levels in the normal photocurrent model. The differential PEC method was applied in the determination of DA in serum samples in the linear range of 0.05–12.5 μM, with the detection limit of 0.018 μM.

Solar-driven interfacial steam generation is a promising technique for clean water production because it can minimize thermal loss by localizing solar-to-heat conversion at the air/liquid interface. Here we report an integrated solar evaporator by partially growing 2D polypyrrole microsheets within a melamine foam through chemical vapor polymerization. These microsheets can induce multiple light reflections within the foam, enable omnidirectional light absorption, provide abundant surfaces to promote heat transfer, and achieve spatially defined hydrophobicity to facilitate vapor escape. Meanwhile, the inherent hydrophilicity of the bottom part of the foam promotes spontaneous upward water transport and suppresses heat loss. The composite foam exhibits an excellent apparent evaporation rate of ∼2 kg/(m

The electrochemical reduction of CO2 and H2O to syngas, a widely used precursor for chemical synthesis, has attracted increased attention. However, producing syngas over a wide range of CO:H2 ratios is important for its potential application. Herein, a facile method using an anodic oxidizing zinc plate has been developed to obtain lattice-dislocated ZnO, which exhibited higher faradaic efficiencies (above 90%) of syngas than that of ZnO without lattice dislocation. Moreover, the ratio of CO to H2 can be regulated in a wide range from 0.28 to 2.11 by applying different electrolyzing potentials, which is applicable to the synthesis of various chemicals. With density functional theory calculations, we conclude that the lattice dislocation defects in ZnO promote the electroreduction of CO2. In addition, stability and electrochemical noise tests show that lattice-dislocated ZnO can withstand long-term operation due to its effective corrosion resistance.

The widespread application of direct ethanol fuel cells is hampered due to the low activity, high cost and poor operation durability of electrocatalysts for ethanol oxidation reaction (EOR). Herein, we report a one-pot synthetic method to synthesize PdPb3 nanochains with well-defined shape, size and composition via a solution-phase reduction method. The morphology, composition distribution and structure characteristics of PdPb3 nanochains were investigated by transmission electron microscopy, X-ray photoelectron spectroscopy and X-ray diffraction. Thanks to the unique structure, the as-obtained PdPb3 nanochains can manifest much higher mass activity (2523 mA·mg−1) and higher operation durability than commercial Pd/C (1272 mA·mg−1) during the EOR measurements. More importantly, further CO-stripping measurements indicate that the incorporation of Pb species could favor the oxidative removal of CO intermediates on the Pd electrode at the negative potential and enhance the EOR activity and stability, making it possible to develop highly active and durable electrocatalysts.

Chemical design of multicomponent nanocrystals requires atomic-level understanding of reaction kinetics. Here, we apply single-particle imaging coupled with atomistic simulation to study reaction pathways and rates of Pd@Au and Cu@Au core-shell nanocubes undergoing oxidative dissolution. Quantitative analysis of etching kinetics using in situ transmission electron microscopy (TEM) imaging reveals that the dissolution mechanism changes from predominantly edge-selective to layer-by-layer removal of Au atoms as the reaction progresses. Dissolution of the Au shell slows down when both metals are exposed, which we attribute to galvanic corrosion protection. Morphological transformations are determined by intrinsic anisotropy due to coordination-number-dependent atom removal rates and extrinsic anisotropy induced by the graphene window. Our work demonstrates that bimetallic core-shell nanocrystals are excellent probes for the local physicochemical conditions inside TEM liquid cells. Furthermore, single-particle TEM imaging and atomistic simulation of reaction trajectories can inform future design strategies for compositionally and architecturally sophisticated nanocrystals., Rational design of multicomponent nanocrystals requires atomic-level understanding of reaction kinetics. Here, the authors apply single-particle liquid-cell electron microscopy imaging coupled with atomistic simulations to understand pathways and rates of bimetallic core-shell nanocubes undergoing oxidative dissolution.

Nowadays, hierarchically macro-/meso-/microporous 3D carbon materials have been paid more attention due to their imaginative application potential in specific electrochemistry. Here, we report a dual-template strategy using eutectic NaCl/ZnCl2 melt as airtight and swelling agent to obtain 3D mesoporous skeleton structured carbon from renewable lignin. The prepared lignin-derived biocarbon material (LN-3-1) has a high specific surface area (1289 m2 g−1), a large pore volume (2.80 cm3 g−1), and a well-connected and stable structure. LN-3-1 exhibits extremely high activity and stability in acidic medium for oxygen reduction reaction (ORR), superior to Pt/C catalyst and most non noble-metal catalysts reported in recent literatures. The prepared carbon material was used as a cathode catalyst to assemble a H2-O2 single fuel cell, and its excellent catalytic performance has been confirmed with the maximum power density of 779 mW cm−2, which is one of the highest power densities among non-metallic catalysts so far. Density functional theory (DFT) calculations indicate that the synergy of chlorine and nitrogen reconciles the intermediate adsorption energies, leading to an appropriate theoretical ORR onset potential. We develop a cost-effective and highly efficient method to prepare biocarbon catalyst for ORR in proton-exchange membrane fuel cells.

Lead-free perovskite ceramics with the formula of (1-x)BaTiO3-xBaCo0.5Nb0.5O3-δ ((1-x)BT-xBCN), exhibit structural phase transition, modified band-gap (Eg), ferromagnetic and ferroelectric orders at room-temperature (RT). All ceramics have no impurity phase but the structural transition from tetragonal to cubic phase is observed with the increase of x. A possible mechanism is proposed to explain the variation of crystal structure. Raman scattering analysis not only proves the existence of doping-induced phase transition but also indicates the changed bonding vibration modes between adjacent atoms. The appearance of two band-gaps in doping samples, the low Eg is about 1.3 eV, obviously smaller than that of 3.2 eV for pure BaTiO3 (BT), which is attributed to the electronic orbital of Co 3d within the gap of BT. Moreover, the RT ferromagnetic behavior is obtained at x = 0.05, which can be interpreted via the F center exchange model. These results show the potential applications for perovskite oxides on solar energy conversion apparatus and multiferroic devices.

Miniaturized stretchable strain sensors are key components in E-skins for applications such as personalized health-monitoring, body motion perception, and human-machine interfaces. However, it remains a big challenge to fabricate miniaturized stretchable strain sensors with high imperceptibility. Here, we reported for the first time novel ultraminiaturized stretchable strain sensors based on single centimeter-long silicon nanowires (cm-SiNWs). With the diameter of the active materials even smaller than that of spider silks, these sensors are highly imperceptible. They exhibit a large strain sensing range (45%) and a high durability (10 000 cycles). Their optimum strain sensing ranges could be modulated by controlling the prestrains of the stretchable cm-SiNWs. On the basis of this capability, sensors with appropriate sensing ranges were chosen to respectively monitor large and subtle human motions including joint motion, swallow, and touch. The strategy of applying single cm-SiNWs in stretchable sensors would open new doors to fabricate ultraminiaturized stretchable devices.

An incompletely covered CdS/ZnS core/shell is synthesized via a simple hydrothermal method. Due to the defect energy levels introduced by zinc vacancies, the typical type-I heterojunction of CdS/Zn...

An efficient Ni2P–CdS photocatalyst for photocatalytic hydrogen evolution was synthesized by phosphorizing β-Ni(OH)2 nanosheet with exposed (001) facets on CdS nanorods. The obtained Ni2P–CdS composite displays an outstanding and stable photocatalytic hydrogen generation rate of 68.47 mmol g−1 h−1 in 10 vol% lactic acid under visible light irradiation, more than 17 times higher than that for pure CdS nanorods. The transient photocurrent response, EIS measurement, Mott-Schottky plots, acidic LSV measurement, and PL spectra have proved that Ni2P loading can significantly improve the separation of photo-excited electron-hole pairs in CdS nanorods and enhance the hydrogen evolution capability for CdS. These improvements are achieved by features of Ni2P such as the high capability of trapping photo-generated electrons from CdS, lifting the total Fermi level and lowering the hydrogen evolution overpotential of the composite. The results show that β-Ni(OH)2 precursor with a high exposure degree of (001) facet is contributed to the epitaxial formation of (001)-facet-exposed Ni2P co-catalyst on CdS nanorods, resulting in that the Fermi level and the hydrogen evolution overpotential of the composite can be further lifted and lowered. This study has provided a novel precursor-derived route to fabricate high-performance co-catalysts with highly exposed active facets on CdS nanorods for effective photocatalytic hydrogen evolution.

We consider the inverse optimal value problem on minimum spanning tree under unit $$l_{\infty }$$ norm. Given an edge weighted connected undirected network $$G=(V, E, {\varvec{w}})$$ and a spanning trees $$T^0$$ , we aim to modify the weights of the edges such that $$T^0$$ is the minimum spanning tree under the new weight vector whose weight is equal to a given value K and the modification cost under unit $$l_{\infty }$$ norm is minimized. We present a mathematical model of the problem. After analyzing the properties, we propose a sufficient and necessary condition for optimal solutions of the problem. Then we develop a strongly polynomial time algorithm with running time O(|V||E|). Finally, we give an example to demonstrate the algorithm.

Direct methanol fuel cells (DMFCs) and direct ethanol fuel cells (DEFCs) have drawn great attention as promising power sources for mobile and portable devices. However, the anodic reactions in DMFCs and DEFCs, namely the methanol oxidation reaction (MOR) and ethanol oxidation reaction (EOR), suffer from notoriously sluggish kinetics which seriously limited their large-scale applications. In this review, we will present a brief review on the interfacial engineering of noble metals for the MOR and EOR. This review starts by introducing the fundamental electrochemistry of the MOR and EOR and the performance evaluation of MOR and EOR electrocatalysts. We then move to summarize recent advances in the design and synthesis of MOR and EOR electrocatalysts in acidic and alkaline electrolytes, in which we emphasize the importance of rational engineering of the interface in noble metals (such as Pt, Pd and Rh) for enhanced activity and improved stability toward the MOR and EOR. Finally, challenges and prospects will be concluded for designing better MOR and EOR electrocatalysts.

In motor drives, distortions of phase voltages and currents are often caused by nonlinear effects of inverters such as dead time, turn-on delay, turn-off delay and voltage drop of power devices. To eliminate these distortions, the dead-time compensation voltage is usually investigated. Furthermore, the relationship between the dead-time compensation voltage and phase currents is nonlinear, which is related to not only the parameters mentioned above, but also the snubber and parasitic capacitance of inverters. A nonlinear function is constructed to model the nonlinear relationship in this paper. To identify the nonlinear function, a method based on artificial neural networks is proposed without inverter parameters. According to the criterion that the trajectory of voltage vector in $\alpha - \beta $ coordinate system is a circle, an adaptive law is constructed to modify the parameters of the nonlinear function. Therefore, the nonlinear dead-time compensation voltage model is obtained accurately, where the distortions of voltages and currents are reduced without any additional hardware. Applying this method to the current predictive control, the bandwidth of a current loop is increased by 500Hz. Effectiveness of the method is verified by experiments.

In this work, we report a simple ratiometric electrochemiluminescence (ECL) method for ultra-sensitive immunoanalysis. A glassy carbon electrode (GCE) was modified by a mixture of porous g-C3N4 nanosheets and carbon nanotubes (CNTs). Secondary antibodies were labeled using CuS nanoparticles as the tags. After immune recognition, CuS nanoparticles in the immunocomplex were dissolved as Cu2+, which can quench the ECL of g-C3N4. The amount of Cu2+ was determined to quantify the concentration of the target antigen. To enhance the sensitivity, Cu2+ ions were firstly enriched and reduced to Cu on the surface of GCE/CNTs-g-C3N4, and the cathodic ECL of g-C3N4 was measured as the reference signal in the ratiometric ECL measurements. After applying a potential of 0.6 V (vs. Ag/AgCl) for 6 s, Cu was dissolved as Cu2+, which can quench the ECL of g-C3N4 with much higher efficiency because the freshly dissolved Cu2+ ions were distributed mainly within the Helmholtz layer of GCE/CNTs-g-C3N4. By using the ECL intensity ratio of GCE/CNTs-g-C3N4 (Cu2+) to GCE/CNTs-g-C3N4 (Cu) measured under the potentiostatic model as the signal indictor, the ratiometric ECL method was used to detect a biomarker of alpha fetoprotein with the limit of detection of 0.1 fg mL-1. It was shown that the influence of the difference in electrode modification and ECL measurement conditions on the determination of Cu2+ is suppressed greatly in the ratiometric ECL method. The combination of ratiometric ECL with electrochemical enrichment and biometallization is a useful strategy to enhance the sensitivity and reproducibility in immunoanalysis.

This paper presents an experimental study on a semi-active hybrid energy storage system consisting of a battery pack and a supercapacitor pack for electric vehicle application. First, a real-time energy management control strategy based on a combination of filtering and fuzzy logic controller is proposed. The main advantage of the proposed control strategy is that the peak current of the battery can be obviously reduced while ensuring the voltage of the supercapacitor fluctuates within a certain desired range. Second, a 30 kW rated power experimental platform is constructed, in which only one dc/dc converter is used to regulate the power flow between the battery and the supercapacitor. Finally, a corrected battery fade model, which can accurately match the studied battery, is used to analyze the battery fade behavior. The results reveal that the battery capacity fade cost of the hybrid energy storage system can be reduced by 44.42%, 30.44%, and 57.16% compared with the sole battery storage under new European drive cycle, highway driving cycle, and Indian urban driving cycle, three driving cycles, respectively.

In this paper, we present a diode-pump continuous wave laser amplifier chain where master the oscillator power amplifier (MOPA) architecture is used. The laser amplifier chain consists of two Yb:YAG surface-doped slab laser modules and the 1030nm fiber laser is used as seed. We theoretically calculate the conditions for obtaining high output laser power and systematically analyze the advantages of surface-doped slab. The maximum output power is 6.1 kW and the optical to optical conversion efficiency is 27% when the pump power is 22 kW at room temperature. The beam quality (β) is 2.8 times diffraction limit. These results demonstrate that the surface-doped slab structure has the potential to obtain high output laser power.

High-quality Pt-based catalysts are highly desirable for ethanol oxidation reaction (EOR), which is of critical importance for the commercial applications of direct ethanol fuel cells (DEFCs). However, most of the Pt-based catalysts have suffered from high cost and low operation durability. Herein a two-step method has been developed to synthesize porous Pt nanoframes decorated with Bi(OH)3, which show excellent catalytic activity and operation durability in both alkaline and acidic media. For example, the nanoframes show a mass activity of 6.87 A·mgPt−1 in alkaline media, which is 13.5-fold higher than that of commercial Pt/C. More importantly, the catalyst can be reactivated simply, which shows negligible activity loss after running for 180,000 s. Further in situ attenuated total reflection-infrared (ATR-IR) absorption spectroscopy and CO-stripping experiments indicate that surface Bi(OH)3 species can greatly facilitate the formation of adsorbed OH species and subsequently remove carbonaceous poison, resulting in a significantly enhanced stability towards EOR. This work may favor the tailoring of desired electrocatalysts with high activity and durability for future commercial application of DEFCs.

Valley-switching (VS) and zero-voltage switching (ZVS) improves overall efficiency in critical conduction mode (CRM) boost converters. To achieve VS/ZVS, off-time of the main switch is often extended to match the resonance period by circuit inductor and parasitic capacitors of switching components. In this article, a piecewise equivalent model for parasitic capacitors is proposed to derive analytical solutions of the resonant process, by which the numerical solutions of VS/ZVS time is calculated. To precisely achieve VS/ZVS in a boost converter, corresponding extended off-time based on the numerical solutions is implemented with an extended off-time (EOT) controller. The EOT controller makes the inductor volt-second unbalance in continuous conduction mode (CCM) operation during one switching cycle, leading to the convergence to CRM operation. The analytical and experimental results correct the results derived by conventional equivalent model for parasitic capacitors, which leads to deviated VS/ZVS boundary and wrongly calculated off-time. The proposed model and controller are verified in a non-synchronous CRM boost converter based on GaN high electron mobility transistor (HEMT) and SiC diode. With the derived extended off-time, a peak efficiency of 99.15% is achieved at output power level of 200W.

PdMn and PdFe nanoparticles supported reduced graphene oxide catalysts (RGO) are synthesized by sodium borohydride reduction using polyethylene glycol (PEG) as a protective agent. The prepared catalysts are used to electro-catalyse methanol under alkaline conditions. These catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The test results show that the dispersibility and size of the catalysts are modulated by the addition of the second metal. Cyclic voltammetry (CV) and chronoamperometry tests show that, compared with the Pd/RGO catalyst, the electrochemical activities of the PdMn/RGO and PdFe/RGO catalysts are enhanced, and their electrochemical stabilities are improved for methanol oxidation. Electrochemical tests show that PdMn/RGO and PdFe/RGO have lower initial potential for methanol oxidation than Pd/RGO, which indicates that the prepared Pd-based bimetallic catalysts have better electrochemical performance than Pd/RGO catalyst. Further, the electronic structure of Pd is also successfully changed, which has a significant impact on improving the stability and electrochemical activity for methanol oxidation. In summation, PdMn/RGO and PdFe/RGO catalysts show better electrochemical performance for methanol oxidation than the Pd/RGO catalyst.

The occurrence, distribution, ecological and health risk assessment of five antibiotics (CFM, ERY, LCM, SMD and SMX) in 32 drinking water reservoirs of a megacity (Shenzhen) in Guangdong–Hong Kong–Macao Greater Bay Area (GBA), were investigated. Among the above antibiotics, CFM was not detected, ERY, SMD, LCM and SMX were detected in 65.6%, 46.9%, 43.7% and 40.6% of samples, with concentrations of 1.594–7.605 ng·L−1, 0.335–6.695 ng·L−1, 0.288–7.878 ng·L−1 and 0.770–5.355 ng·L−1, respectively. The maximum concentration of ERY was detected in GT Reservoir, and those of the other 3 antibiotics were detected in SZ Reservoir. The ecological risk quotient (RQ) values for SMX in SZ, XL, YT, EJ, SY, TG, XK, GK, MK and GT reservoirs ranged from 0.1 to 1.0, indicating a median risk to aquatic organisms, the others posed insignificant risk or low risk. Considering the joint effects of detected antibiotics, the highest overall RQ value was 0.38, obtained in SZ Reservoir, in other words, it was exposed to greater risk. Based on health risk assessment, the health RQ values for the detected antibiotics were significantly lower than 0.01, indicating insignificant risk to human health. These findings could provide a scientific basis for the government to ensure the drinking water safety of a megacity in GBA.

Two-dimensional (2D) metal carbides, carbonitrides, and nitrides (MXenes) have recently emerged as promising candidates in catalysis due to their unique properties. In this work, we composited Ti3C...

The substitution of noble metal platinum catalyst is one of the important research contents for sustainable development and is also the key to the practical application of photoelectrochemical (PEC) hydrogen production. In this work, we loaded the 1T-2H mixed phase MoS2 on the hydrogenated anatase/rutile heterophase TiO2 (A-H-RTNA) by hydrothermal method to prepare a new MoS2/A-H-RTNA electrode material. The prepared material exhibited higher carrier density, lower PL intensity and higher conductivity than Pt/A-H-RTNA because 1T-MoS2 has more active sites and lower charge transfer resistance than Pt. With the bias voltage of −0.4 V, the optimized 16MoS2/A-H-RTNA as photocathode shows the largest PEC hydrogen production rate of 1840 mmol m−2 h−1, which is 2.9 and 2.2 times higher than those of A-H-RTNA (625 mmol m−2 h−1) and Pt/A-H-RTNA (848 mmol m−2 h−1), respectively. We innovatively used the prepared 16MoS2/A-H-RTNA film as counter electrode instead of Pt electrode to construct a PEC system without any noble-metal. The result demonstrates that the noble-metal-free MoS2 loaded on TiO2 electrode as counter electrode has 75% PEC activity of noble metal Pt electrode. This study develops a PEC method for hydrogen evolution, which no longer depends on precious metal platinum as cathode.

In this work, two-dimensional magnetic chitosan nanosheets (CSMNSs) for azo dye adsorption were successfully synthesised by a simple hydrothermal method. The as-prepared CSMNSs was characterised by scanning electron microscope, transmission electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis and vibrating sample magnetometer. Then, the CSMNSs as the dye adsorbent were applied to the removal of two kinds of azo dyes (methyl orange and amido black). The effect of solution pH and adsorbent dosage, adsorption isotherm, adsorption kinetics and the reusability of CSMNSs were examined. Adsorption isotherms obeyed Freundlich model and adsorption kinetics was described as pseudo-second-order model. Furthermore, the CSMNSs have the advantage of simple synthesis route, high absorption efficiency, rapid magnetic separation from aqueous solutions and excellent reusability. The CSMNSs as the dye adsorbent was applied to removal of azo dyes with broad prospects.

A facile method of loading CoSx nanosheet onto CdS nanorod has been designed, and the prepared CdS-CoSx composite catalyst exhibited significantly improved performance for photocatalytic hydrogen evolution compared with CdS catalyst. This composite catalyst was also used as a photoanode for photoelectrochemical (PEC) hydrogen production. The hydrogen production rate reached 168.6 μmol cm−2 h−1 (37.77 L m−2 h−1) under the simulated solar light, which is 2.7 times that of CdS and the same as that of CdS–Pt. In addition, in the Na2S–Na2SO3 system for PEC hydrogen production, an abnormal relationship between photocurrent and the hydrogen production yield was found. By designing a series of experiments, the photocatalytic and photoelectrochemical characteristics for hydrogen production were reasonably revealed for the first time. In this work, the prepared structured catalyst is easy to be recycled, and CoSx can replace precious metal Pt, showing a promising application.

Machine Learning as a Service (MLaaS) is enabling a wide range of smart applications on end devices. However, privacy-preserved computation is still expensive. Our investigation has found that the most time-consuming component of the HE-based linear computation is a series of Permutation (Perm) operations that are imperative for dot product and convolution in privacy-preserved MLaaS. To this end, we propose GALA: Greedy computAtion for Linear Algebra in privacy-preserved neural networks, which views the HE-based linear computation as a series of Homomorphic Add, Mult and Perm operations and chooses the least expensive operation in each linear computation step to reduce the overall cost. GALA makes the following contributions: (1) It introduces a row-wise weight matrix encoding and combines the share generation that is needed for the GC-based nonlinear computation, to reduce the Perm operations for the dot product; (2) It designs a first-Add-second-Perm approach (named kernel grouping) to reduce Perm operations for convolution. As such, GALA efficiently reduces the cost for the HE-based linear computation, which is a critical building block in almost all of the recent frameworks for privacy-preserved neural networks, including GAZELLE (Usenix Security'18), DELPHI (Usenix Security'20), and CrypTFlow2 (CCS'20). With its deep optimization of the HE-based linear computation, GALA can be a plug-and-play module integrated into these systems to further boost their efficiency. Our experiments show that it achieves a significant speedup up to 700x for the dot product and 14x for the convolution computation under different data dimensions. Meanwhile, GALA demonstrates an encouraging runtime boost by 2.5x, 2.7x, 3.2x, 8.3x, 7.7x, and 7.5x over GAZELLE and 6.5x, 6x, 5.7x, 4.5x, 4.2x, and 4.1x over CrypTFlow2, on AlexNet, VGG, ResNet-18, ResNet-50, ResNet-101, and ResNet-152, respectively.