Tuning Oxygen Vacancies in Ultrathin TiO2 Nanosheets to Boost Photocatalytic Nitrogen Fixation up to 700 nm

Dinitrogen reduction to ammonia using transition metal catalysts is central to both the chemical industry and the Earth's nitrogen cycle. In the Haber–Bosch process, a metallic iron catalyst and high temperatures (400 °C) and pressures (200 atm) are necessary to activate and cleave N?N bonds, motivating the search for alternative catalysts that can transform N₂ to NH₃ under far milder reaction conditions. Here, the successful hydrothermal synthesis of ultrathin TiO₂ nanosheets with an abundance of oxygen vacancies and intrinsic compressive strain, achieved through a facile copper‐doping strategy, is reported. These defect‐rich ultrathin anatase nanosheets exhibit remarkable and stable performance for photocatalytic reduction of N₂ to NH₃ in water, exhibiting photoactivity up to 700 nm. The oxygen vacancies and strain effect allow strong chemisorption and activation of molecular N₂ and water, resulting in unusually high rates of NH₃ evolution under visible‐light irradiation. Therefore, this study offers a promising and sustainable route for the fixation of atmospheric N₂ using solar energy.     

Gate‐Tunable and Multidirection‐Switchable Memristive Phenomena in a Van Der Waals Ferroelectric

Memristive devices have been extensively demonstrated for applications in nonvolatile memory, computer logic, and biological synapses. Precise control of the conducting paths associated with the resistance switching in memristive devices is critical for optimizing their performances including ON/OFF ratios. Here, gate tunability and multidirectional switching can be implemented in memristors for modulating the conducting paths using hexagonal α‐In₂Se₃, a semiconducting van der Waals ferroelectric material. The planar memristor based on in‐plane (IP) polarization of α‐In₂Se₃ exhibits a pronounced switchable photocurrent, as well as gate tunability of the channel conductance, ferroelectric polarization, and resistance‐switching ratio. The integration of vertical α‐In₂Se₃ memristors based on out‐of‐plane (OOP) polarization is demonstrated with a device density of 7.1 × 10⁹ in.^?2 and a resistance‐switching ratio of well over 10³. A multidirectionally operated α‐In₂Se₃ memristor is also proposed, enabling the control of the OOP (or IP) resistance state directly by an IP (or OOP) programming pulse, which has not been achieved in other reported memristors. The remarkable behavior and diverse functionalities of these ferroelectric α‐In₂Se₃ memristors suggest opportunities for future logic circuits and complex neuromorphic computing.     

A Compromise Programming to Task Assignment Problem in Software Development Project

The scheduling process that aims to assign tasks to members is a difficult job in project management. It plays a prerequisite role in determining the project’s quality and sometimes winning the bidding process. This study aims to propose an approach based on multi-objective combinatorial optimization to do this automatically. The generated schedule directs the project to be completed with the shortest critical path, at the minimum cost, while maintaining its quality. There are several real-world business constraints related to human resources, the similarity of the tasks added to the optimization model, and the literature’s traditional rules. To support the decision-maker to evaluate different decision strategies, we use compromise programming to transform multi-objective optimization (MOP) into a single-objective problem. We designed a genetic algorithm scheme to solve the transformed problem. The proposed method allows the incorporation of the model as a navigator for search agents in the optimal solution search process by transferring the objective function to the agents’ fitness function. The optimizer can effectively find compromise solutions even if the user may or may not assign a priority to particular objectives. These are achieved through a combination of non-preference and preference approaches. The experimental results show that the proposed method worked well on the tested dataset.     

Effects of the stress state on plastic deformation and ductile failure: Experiment and numerical simulation using a newly designed tension‐shear specimen

The stress state is one of the most notable factors that dominates the initiation of ductile fracture. To examine the effects of the stress state on plasticity and ductile failure, a new tension‐shear specimen that can cover a wide range of stress triaxialities was designed. A fracture locus was constructed in the space of ductility and stress triaxiality for two typical steels based on a series of tests. It is observed that the equivalent plastic strain at failure exhibits a nonmonotonic variation with increasing the value of stress triaxiality. A simple damage model based on the ductility exhaustion concept was used to simulate the failure behaviour, and a good agreement is achieved between simulation results and experimental data. It is further shown that consideration of fracture locus covering a wide range of stress triaxialities is a key to an accurate prediction.     

Uniform Luminous Perovskite Nanofibers with Color‐Tunability and Improved Stability Prepared by One‐Step Core/Shell Electrospinning

A one‐step core/shell electrospinning technique is exploited to fabricate uniform luminous perovskite‐based nanofibers, wherein the perovskite and the polymer are respectively employed in the core and the outer shell. Such a coaxial electrospinning technique enables the in situ formation of perovskite nanocrystals, exempting the needs of presynthesis of perovskite quantum dots or post‐treatments. It is demonstrated that not only the luminous electrospun nanofibers can possess color‐tunability by simply tuning the perovskite composition, but also the grain size of the formed perovskite nanocrystals is largely affected by the perovskite precursor stoichiometry and the polymer solution concentration. Consequently, the optimized perovskite electrospun nanofiber yields a high photoluminescence quantum yield of 30.9%, significantly surpassing the value of its thin‐film counterpart. Moreover, owing to the hydrophobic characteristic of shell polymer, the prepared perovskite nanofiber is endowed with a high resistance to air and water. Its photoluminescence intensity remains constant while stored under ambient environment with a relative humidity of 85% over a month and retains intensity higher than 50% of its initial intensity while immersed in water for 48 h. More intriguingly, a white light‐emitting perovskite‐based nanofiber is successfully fabricated by pairing the orange light‐emitting compositional perovskite with a blue light‐emitting conjugated polymer.     

Development of an automatic arc welding system using a sliding mode control

This paper describes the development of an automatic welding control system for alternating current shield metal arc welding. This method could replace manual operations which require a well-trained technician. We have derived a mathematical model of the welding control system and identified system parameters. An adaptive sliding mode controller, estimates the bound of uncertainties, and modulates the rate of the electrode feed mechanism that regulates the arc current. The electrode feed-rate mechanism with this controller is driven by an AC servomotor, which can compensate for both the molten part of the electrode and undesirable fluctuations in the arc length during the welding process. The method can be easily applied to any welding system in which the electrode is consumed during the welding process. By maintaining the magnitude of the arc current at the desired value and the stability of the arc length, excellent welding performance is obtained. The simulation and the experimental results both show that this automatic welding control system, based on the adaptive sliding mode controller, can perform effectively.     

Modeling and Investigation of the Stability of a Multicutter Turning Process by a Trace

The results of modeling and investigation of the stability of a continuous multicutter turning process are presented. The mathematical modeling is based on an equation for the formation of new surfaces, on equations of motion, and on the fractional-rational cutting law. The influence of the parameters of the technological system on the stability of the continuous cutting mode is analyzed.     

A study of boundary lubrication thin filmsproduced from a perfluoropolyalkylether fluid on M-50 surfaces.II. Humidity effect and topography studies

Tribology experiments under controlled humidity were conductedusing a Cameron-Plint tribometer with an M-50 cylinder slidingon an M-50 flat specimen in the presence of a linearperfluoropolyalkylether fluid. The tests were conducted at 100,70, 59, 10, 7 and 5% relative humidities. The surface thin filmsformed on the M-50 flat specimen were studied by grazing-angle-microscope/FTIR technique. A thicker surface filmof R_fCOOH was observed for the tests conducted atrelative humidities equal to or larger than 15%. A monodentatemodel discussed in the preceding paper was adopted to be thesurface film configuration. For the lower humidity tests, anultra-thin surface film of R_fCOOH-type was observed.An asymmetrical bridging model was proposed to account for thisobservation. In addition, the_asym,OCO band shifted to lower wavenumbers as the relative humidity of the controlled environmentwas decreased. These band shifts at different humidities warrantthe use of the multilayer model over the metal soap model toaccount for the experimentalobservation. Topographical and frictional image studies on thecylinder wear scars tested at 100, 98, 70, 59, 15 and 5% relativehumidities have been carried out using atomic force andfrictional force microscopies. Residual surface features werefound to be present on those specimens tested at 100, 98, 70, 59and 15% relative humidities. These findings are complementarywith the results obtained from the M-50 flat specimens studiedby GAM/FTIR technique.     

多台机组巡检与异常状态诊断

作者在上海金山石化总厂芳烃厂长达两年的压缩机组的状态监测中总结了一套对设备的监测方法.全文包括四个部分:1.前言 对金山石化所监测的设备作了概述.2.多台机组定期巡检 对电机—往复式压缩机组,蒸汽透平—汽轮压缩机组,电机—螺杆压缩机组等大机组进行了定期定点的振动值监测,噪声监测和电气参数监测.3.设备异常状态的诊断,采用相关与们分析方法对GB-302/B电机的异常状态进行诊断.4.大修后开车保护性监测.文章所总结的方法,为大中型工矿企业多台设备的现代化管理,提供一套实用有效的参考模式,有学术与实用价值.