Abstract
Electrochemical reduction of CO
2
(CO
2
R) to formic acid upgrades waste CO
2
; however, up to now, chemical and structural changes to the electrocatalyst have often led to the deterioration ...of performance over time. Here, we find that alloying p-block elements with differing electronegativities modulates the redox potential of active sites and stabilizes them throughout extended CO
2
R operation. Active Sn-Bi/SnO
2
surfaces formed in situ on homogeneously alloyed Bi
0.1
Sn crystals stabilize the CO
2
R-to-formate pathway over 2400 h (100 days) of continuous operation at a current density of 100 mA cm
−2
. This performance is accompanied by a Faradaic efficiency of 95% and an overpotential of ~ −0.65 V. Operating experimental studies as well as computational investigations show that the stabilized active sites offer near-optimal binding energy to the key formate intermediate *OCHO. Using a cation-exchange membrane electrode assembly device, we demonstrate the stable production of concentrated HCOO
–
solution (3.4 molar, 15 wt%) over 100 h.
•We study a distributed flowshop problem with preventive maintenance.•We present a novel multi-start iterated greedy algorithm.•An improved NEH with dropout is proposed to generate searching ...starting-point.•A destruction with the tournament selection is well designed.•The effective of the iterated greedy is proved by extensive experiments.
In recent years, distributed scheduling problems have been well studied for their close connection with multi-factory production networks. However, the maintenance operations that are commonly carried out on a system to restore it to a specific state are seldom taken into consideration. In this paper, we study a distributed permutation flowshop scheduling problem with preventive maintenance operation (PM/DPFSP). A multi-start iterated greedy (MSIG) algorithm is proposed to minimize the makespan. An improved heuristic is presented for the initialization and re-initialization by adding a dropout operation to NEH2 to generate solutions with a high level of quality and disperstiveness. A destruction phase with the tournament selection and a construction phase with an enhanced strategy are introduced to avoid local optima. A local search based on three effective operators is integrated into the MSIG to reinforce local neighborhood solution exploitation. In addition, a restart strategy is adpoted if a solution has not been improved in a certain number of consecutive iterations. We conducted extensive experiments to test the performance of the presented MSIG. The computational results indicate that the presented MSIG has many promising advantages in solving the PM/DPFSP under consideration.
The distributed permutation flowshop scheduling problem (DPFSP) has been a hot issue in recent years. Due to the practical relevance of sequence-dependent setup time (SDST), we consider the DPFSP ...with SDST to minimize makespan. For the purpose, we propose three constructive heuristics and an effective discrete artificial bee colony (DABC) algorithm. All the heuristics are based on a greedy assignment rule and a local search of job blocks in each factory. In the local search, three different setup times are respectively considered for inserting a job block. In the DABC, to balance the local exploitation and the global exploration, we propose six composite neighborhood operators according to the problem characteristics. The first three are based on insertion and swap operators, and the second three have a close relationship with the critical factory. A problem-oriented local search method is developed to improve the best individual in the population. A comprehensive computational campaign against the closely related and state-of-the-art algorithms in the literature shows that both the proposed heuristics and DABC are very effective for solving the problem under consideration.
•We study a distributed permutation flowshop scheduling problem with sequence-dependent setup times.•Three effective constructive heuristics and a discrete bee colony optimization are presented.•Six problem-specified neighborhood operators are proposed.•A local search method based on job block is presented.•The effectiveness of the presented algorithms are demonstrated by the experimental results.
A highly efficient low-band-gap (1.2–0.8 eV) photoelectrode is critical for accomplishing efficient conversion of visible–near-infrared sunlight into storable hydrogen. Herein, we report an Sb2Se3 ...polycrystalline thin-film photocathode having a low band gap (1.2–1.1 eV) for efficient hydrogen evolution for wide solar-spectrum utilization. The photocathode was fabricated by a facile thermal evaporation of a single Sb2Se3 powder source onto the Mo-coated soda-lime glass substrate, followed by annealing under Se vapor and surface modification with an antiphotocorrosive CdS/TiO2 bilayer and Pt catalyst. The fabricated Sb2Se3(Se-annealed)/CdS/TiO2/Pt photocathode achieves a photocurrent density of ca. −8.6 mA cm–2 at 0 VRHE, an onset potential of ca. 0.43 VRHE, a stable photocurrent for over 10 h, and a significant photoresponse up to the near-infrared region (ca. 1040 nm) in near-neutral pH buffered solution (pH 6.5) under AM 1.5G simulated sunlight. The obtained photoelectrochemical performance is attributed to the reliable synthesis of a micrometer-sized Sb2Se3 (Se-annealed) thin film as photoabsorber and the successful construction of an appropriate p–n heterojunction at the electrode–liquid interface for effective charge separation. The demonstration of a low-band-gap and high-performance Sb2Se3 photocathode with facile fabrication might facilitate the development of cost-effective PEC devices for wide solar-spectrum utilization.
In this paper, a practical design to achieve bidirectional radiation and polarization conversion in a Fabry-Perot resonator antenna (FPRA) is proposed. The proposed design utilizes ...quasi-self-complementary and frequency-selective surfaces (SC-FSS) that are printed on a single dielectric substrate. The self-complementary surface (SCS) has been demonstrated to ensure a consistent 90° phase shift between orthogonal linear polarizations. Frequency-selective surface (FSS) is combined to enhance the reflection magnitude for high gain without affecting the polarization conversion characteristics. Based on the principle of symmetry, the SC-FSS unit is changed and modified to substitute the full reflection ground in the FPRA. This modification is initially proposed to realize bidirectional, circularly polarized (CP), and high-gain radiation in the FPRA. A 45° rotating patch antenna serves as the linearly polarized (LP) feed source. The impedance bandwidth of FPRA is 24.4-25.3 GHz. At 24.8 GHz, the maximum gain at theta = 0° and 180° is 14.2 dBi and 13 dBi, respectively. The polarization conversion bandwidth and 3 dB gain bandwidth are 24.4-25.2 GHz. The radiation properties in the upward and downward directions exhibit good consistency. Furthermore, the left-hand or right-hand CP radiation can be modified by altering the position of the feed, utilizing the same SC-FSS.
Abstract
Electrochemical CO
2
reduction (CO
2
R) to ethylene and ethanol enables the long-term storage of renewable electricity in valuable multi-carbon (C
2+
) chemicals. However, carbon–carbon ...(C–C) coupling, the rate-determining step in CO
2
R to C
2+
conversion, has low efficiency and poor stability, especially in acid conditions. Here we find that, through alloying strategies, neighbouring binary sites enable asymmetric CO binding energies to promote CO
2
-to-C
2+
electroreduction beyond the scaling-relation-determined activity limits on single-metal surfaces. We fabricate experimentally a series of Zn incorporated Cu catalysts that show increased asymmetric CO* binding and surface CO* coverage for fast C–C coupling and the consequent hydrogenation under electrochemical reduction conditions. Further optimization of the reaction environment at nanointerfaces suppresses hydrogen evolution and improves CO
2
utilization under acidic conditions. We achieve, as a result, a high 31 ± 2% single-pass CO
2
-to-C
2+
yield in a mild-acid pH 4 electrolyte with >80% single-pass CO
2
utilization efficiency. In a single CO
2
R flow cell electrolyzer, we realize a combined performance of 91 ± 2% C
2+
Faradaic efficiency with notable 73 ± 2% ethylene Faradaic efficiency, 31 ± 2% full-cell C
2+
energy efficiency, and 24 ± 1% single-pass CO
2
conversion at a commercially relevant current density of 150 mA cm
−2
over 150 h.
In this paper, we study the optimal ordering and inventory reallocation of the inventory service platform under the retailer demand information sharing. Due to the uncertainty of market demand, ...retailers’ demand information is likely to be inaccurate or even false. In this regard, retailers can reduce demand uncertainty by screening market signals. Therefore, based on the sharing of mean demand information and market signals, we explored the platform’s optimal ordering and inventory reallocation strategies, analyzed the retailer’s motivation for sharing false demand information, and proposed a corresponding penalty coordination mechanism. Our results show that the sharing of demand information and screening market signals reduces the uncertainty of market demand, thereby improving the accuracy of orders and increasing profit of the system. On the other hand, we find that the inventory reallocation strategy of the platform is affected by uncertain market information, but has nothing to do with the actual average demand and market signals shared by retailers. In this way, retailers will only share real information when the sharing system meets certain key conditions, otherwise they may share false demand information. The proposed punishment mechanism can encourage retailers to share their actual demand information with the platform.
Distributed scheduling problems have been an active research topic due to their close connection with the multifactory production environment in today’s decentralized economy. In this paper, the ...distributed permutation flowshop scheduling problem with preventive maintenance is studied with the goal of minimizing the total flowtime. A mathematical model and a hash map-based algorithm are presented to tackle the problem. The Nawaz–Enscore–Ham heuristic is improved and incorporated with the distributed Liu–Reeves heuristic to provide a promising initial solution in a finite number of steps. The proposed algorithm employs the data structure of the hash map to store all the candidate solutions in the form of key–value pairs. The selection, crossover, and mutation operators are also modified to expand the scope of exploration in the discrete domain. The local search hybridizes the job insertion operator and the job swap operator to further improve the obtained offspring solutions and utilizes the characteristic of the population hash map to reduce the efforts of solution evaluations. The candidate solution obtained by the local search is hashed by a rotating hash method and then placed at the node with the corresponding hash code. A series of experiments were conducted to verify the effectiveness of the hybrid local search operators and hash map strategy. Computational results indicate that the multiple strategies not only help to escape from the local optimization but also improve the computational efficiency. When compared with 10 state-of-the-art algorithms, the proposed algorithm generates an average relative percentage deviation of 0.134%, which is significant improvement.
•We study a distributed flowshop with preventive maintenance to minimize total flowtime.•We present a mathematical model for this problem.•A memetic algorithm is improved with a hash map based population.•A hybrid local search is well designed.•Experimental results demonstrate the effectiveness of the proposed algorithm.
A simple analytical approach for nonlinear analysis of the load–displacement response of a single pile is presented. Two models are adopted in the proposed approach. One model uses a softening ...nonlinear relationship to simulate the degradation behavior between the unit skin friction and the pile–soil relative displacement developed in the pile–soil interface, and the other model adopts a bilinear load–displacement relationship to capture the pile-end response. Based on the two proposed models, a highly effective computer program has been developed for nonlinear analysis of the load–settlement behavior of a single pile. Comparisons are made between the present method, other analytical methods, and a well-documented field experimental pile loading case. The results of the comparisons indicate that the proposed method is generally in good agreement with field-observed behavior and the calculated results derived from other approaches. A parametric study is conducted to assess the influence of the parameters related to the proposed model on the load–displacement response of a single pile.
Abstract Acidic CO 2 electroreduction (CO 2 R) using renewable electricity holds promise for high-efficiency generation of storable liquid chemicals with up to 100% CO 2 utilization. However, the ...strong parasitic hydrogen evolution reaction (HER) limits its selectivity and energy efficiency (EE), especially at ampere-level current densities. Here we present that enhancing CO 2 R intermediate coverage on catalysts promotes CO 2 R and concurrently suppresses HER. We identified and engineered robust Cu 6 Sn 5 catalysts with strong * OCHO affinity and weak * H binding, achieving 91% Faradaic efficiency (FE) for formic acid (FA) production at 1.2 A cm −2 and pH 1. Notably, the single-pass carbon efficiency reaches a new benchmark of 77.4% at 0.5 A cm −2 over 300 hours. In situ electrochemical Fourier-transform infrared spectroscopy revealed Cu 6 Sn 5 enhances * OCHO coverage ~2.8× compared to Sn at pH 1. Using a cation-free, solid-state-electrolyte-based membrane-electrode-assembly, we produce 0.36 M pure FA at 88% FE over 130 hours with a marked full-cell EE of 37%.
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