Human resources allocation for aircraft maintenance with predefined sequence

There are always large-scale items in the maintenances schedule of aircraft system, many of which have been fixed to be done in predefined sequences, which leads the workflow to be sys-tematically complex and makes this kind of problem quite different from all sorts of existing job-selection modes. On the other hand, the human resources are always limited and men have different working capabilities on different items, which make the allocation operation of human resources be much roomy. However, the final total time span of maintenance is often required to be as short as possible in many practices, in order to suffer only the lowest cost of loss while the system is stopping. A new model for op-timizing the allocation if aircraft maintenance human resources with the constraint of predefined sequence is presented. The ge-netic algorithm is employed to find the optimal solution that holds the shortest total time span of maintenance. To generate the ul-timate maintenance work items and the human resource array, the sequences among all maintenance work items are considered firstly, the work item array is then generated through traversal with the constraint of maintenance sequence matrix, and the human resources are finally allocated according to the work item array with the constraint of the maintenance capability. An example is demonstrated to show that the model and algorithm behave a satisfying performance on finding the optimal solution as expected.

Parallel Construction Heuristic Combined with Constraint Propagation for the Car Sequencing Problem

For the car sequencing（CS） problem, the draw-backs of the ＂sliding windows＂ technique used in the objective function have not been rectified, and no high quality initial solution has been acquired to accelerate the improvement of the solution quality. Firstly, the objective function is improved to solve the double and bias counting of violations broadly discussed. Then, a new method combining heuristic with constraint propagation is proposed which constructs initial solutions under a parallel framework. Based on constraint propagation, three filtering rules are designed to intersecting with three greedy functions, so the variable domain is narrowed in the process of the construction. The parallel framework is served to show its robustness in terms of the quality of the solution since it greatly increases the performance of obtaining the best solution. In the computational experiments, 109 instances of 3 sets from the CSPLib＇ s benchmarks are used to test the performance of the proposed method. Experiment results show that the proposed method outperforms others in acquiring the best-known results for 85 best-known results of 109 are obtained with only one construction. The proposed research provides an avenue to remedy the deficiencies of ＂sliding windows＂ technique and construct high quality initial solutions.

Recent advances for Zn-gas batteries beyond Zn-air/oxygen battery

Zn-gas batteries have attracted great attention in the area of energy conversion and storage owing to their high theoretical energy density in the past decades.In addition to the most widely researched Znair/oxygen battery,other novel Zn-gas batteries such as Zn-CO_(2),Zn-N_(2) and Zn-NO batteries as“killing two birds with one stone”strategy have emerged to provide energy power and upgrade the pollutant/useless gases simultaneously.This technology becomes more appealing as a low-cost and controllable method to produce value-added chemicals and fuels(such as CO,HCOO^(-),CH_(4),NH_(3))at the cathode driven by surplus electricity.However,there is an absence of a guide for the selection of catalyst and the construction of energy system.Herein,we overview recent achievements in typical Zn-gas batteries beyond Zn-air/oxygen,mainly including Zn-CO_(2),Zn-N_(2) and Zn-NO batteries.The energy storage mechanism of these novel Zn-gas batteries has been clearly elaborated.Then,the produced value-added chemicals and the design of cathodic catalyst materials are summarized.Lastly,the remaining challenges and possible directions of Zn-gas batteries,such as highly reduced products,high yield rate and remarkable battery performance,in the future are discussed.

Cathode Engineering for High Energy Density Aqueous Zn Batteries

CONSPECTUS:Frequent safety accidents of lithium-ion batteries(LIBs)originating from the utilization of flammable electrolytes urges the battery community to develop a safe substitute.This safety background is a boom for aqueous batteries(ABs)which employ aqueous electrolytes to address safety concerns.Recently,ABs have experienced a rapid advance because various battery chemistries have been successively developed,e.g.,aqueous Zn batteries(AZBs),aqueous LIBs,aqueous sodium-ion battery,etc.Impeded by the narrow voltage window of aqueous electrolytes,however,the majorities of cathode materials with high operation potential employed in traditional nonaqueous batteries are excluded from the range of ABs cathodes,leading to a low energy density.Directly using metal as an anode is likely to improve the energy density,whereas most of the reported metal anodes,e.g.,lithium,sodium,magnesium,etc.,cannot run in aqueous electrolytes.One exceptional case is the Zn metal anode that permits theoretically high energy density AZBs due to triple merits:(1)the Zn metal anode exhibits a low redox potential(−0.76 V vs standard hydrogen electrode,SHE),taking the best advantage of the limited voltage window of aqueous electrolytes;(2)Zn metal anode with mild protection can easily maintain its chemical stability in aqueous medium;(3)Zn metal anode releases a high specific capacity of 820 mAh g^(−1).AZBs thus exhibit a rapid development,especially in developing high specific capacity cathode materials such as MnO_(2)and V_(2)O_(5),and the corresponding structure modification.Despite these spurring achievements,the overall energy density of the whole AZB device is still unsatisfactory.

Building durable aqueous K-ion capacitors based on MXene family

Obtaining stable aqueous K-ion capacitors is still challenging due to the cathode materials tended to structurally collapse after long-term cycling during large-radius K-ion insertion/extraction.In this work,three different typical MXene electrodes,i.e.,Nb_(2)C,Ti_(2)C,and Ti_(3)C_(2) were individually investigated upon their electrochemical behaviors for potassium-ion(K-ion)storage.All these MXene materials exhibited pseudocapacitive-dominated behaviors,fast kinetics,and durable K-ion storage,delivering superior performance compared with other K-ion host materials.According to the experimental results,it could be ascribed to the intrinsically large interlayer distance for K-ion transport and the superb structural stability of MXene even subjected to long-term potassiation/depotassiation process.

Organic materials-based cathode for zinc ion battery

The quest for advanced energy storage devices with cheaper,safer,more resource-abundant storage has triggered intense research into zinc ion batteries(ZIBs).Among them,organic materials as cathode materials for ZIBs have attracted great interest due to their flexible structure designability,high theoretical capacity,environmental friendliness,and sustainability.Although numerous organic electrode materials have been studied and different redox mechanisms have been proposed in the past decade,their electrochemical performance still needs further improvement,and the mechanisms require further exploration.This paper provides a systematical overview of three types of organic materials(bipolar-type conductive polymer,n-type conjugated carbonyl compounds,and p-type material)on the energy storage mechanisms and distinct characteristics.We then focus on discussing the design strategies to improve electrochemical performance.Furthermore,the challenges and future research directions are discussed to provide a foundation for further developing organic-based ZIBs.

Recent advances and future perspectives for aqueous zinc-ion capacitors

Ion-hybrid capacitors are expected to combine the high specific energy of battery-type materials and the superior specific power of capacitor-type materials and are considered as a promising energy storage technique.In particular,aqueous zinc-ion capacitors(ZIC),possessing the merits of high safety,cost-efficiency and eco-friendliness,have been widely explored with various electrode materials and electrolytes to obtain excellent electrochemical performance.In this review,we first summarize the research progress on enhancing the specific capacitance of capacitor-type materials and review the research on improving the cycling capability of battery-type materials under high current densities.Then,we look back on the effects of electrolyte engineering on the electrochemical performance of ZIC.Finally,we propose research challenges and development directions for ZIC.This review provides guidance for the design and construction of high-performance ZIC.