Optimization of Pt atom utilization efficiency is critical for the development of proton-exchange-membrane fuel *** we aim to develop an efficient oxygen reduction reaction(ORR)catalyst with a low Pt content through t...
详细信息
Optimization of Pt atom utilization efficiency is critical for the development of proton-exchange-membrane fuel *** we aim to develop an efficient oxygen reduction reaction(ORR)catalyst with a low Pt content through the concurrent modification of Pt-Co alloy catalysts and carbon *** the present study,ultrafine Pt-Co alloy nanoparticles are successfully synthesized and stabilized by topological carbon defects via adopting the ammonia thermal *** the low Pt loading,the obtained catalyst exhibits an impressive half-wave potential of 0.926 V versus the reversible hydrogen electrode in 0.1 M HClO_(4)***,the durability testing using the timed-current method demonstrates a tiny loss of only 3.6%after 12 *** experimental results and theoretical calculations demonstrate that topological carbon defects significantly enhance the charge transfer processes at the alloy/carbon interface,contributing to the strong electronic metal-support interactions between the Pt-Co alloy nanoparticles and topological carbon *** interactions,along with the alloy effect,play a crucial role in promoting the ORR performance in acidic media.
Covert communication is considered a promising technology for hiding transmission processes and activities from malicious eavesdropping. With the development of detection technology, the traditional point-to-point cov...
详细信息
High-voltage aqueous zinc ion batteries(AZIBs) with a high-safety near-neutral electrolyte is of great significance for practical sustainable application; however, they suffer from anode and electrode/electrolyte in...
详细信息
High-voltage aqueous zinc ion batteries(AZIBs) with a high-safety near-neutral electrolyte is of great significance for practical sustainable application; however, they suffer from anode and electrode/electrolyte interfacial incompatibility. Herein, a conversion-type anode chemistry with a low anodic potential, which is guided by the Gibbs free energy change of conversion reaction, was designed for high-voltage near-neutral AZIBs. A reversible conversion reaction between ZnC2O4·2H2O particles and three-dimensional Zn metal networks well-matched in CH3COOLi-based electrolyte was revealed. This mechanism can be universally validated in the battery systems with sodium or iodine ions. More importantly, a cathodic crowded micellar electrolyte with a water confinement effect was proposed in which lies the core for the stability and reversibility of the cathode under an operating platform voltage beyond 2.0 V, obtaining a capacity retention of 95% after 100 cycles. Remarkably, the scientific and technological challenges from the coin cell to Ah-scale battery, sluggish kinetics of the solid-solid electrode reaction, capacity excitation under high loading of active material, and preparation complexities associated with large-area quasi-solid electrolytes,were explored, successfully achieving an 88% capacity retention under high loading of more than 20 mg cm-2and particularly a practical 1.1 Ah-level pouch cell. This work provides a path for designing low-cost, eco-friendly and high-voltage aqueous batteries.
The logical-physical dual-layer network is standardized in this paper, and three attack modes-random attack, maximum betweenness attack, and minimum betweenness attack are used to simulate and analyze the network resi...
详细信息
This paper proposes an event-triggered stochastic model predictive control for discrete-time linear time-invariant(LTI) systems under additive stochastic disturbances. It first constructs a probabilistic invariant set...
详细信息
This paper proposes an event-triggered stochastic model predictive control for discrete-time linear time-invariant(LTI) systems under additive stochastic disturbances. It first constructs a probabilistic invariant set and a probabilistic reachable set based on the priori knowledge of system *** with enhanced robust tubes, the chance constraints are then formulated into a deterministic form. To alleviate the online computational burden, a novel event-triggered stochastic model predictive control is developed, where the triggering condition is designed based on the past and future optimal trajectory tracking errors in order to achieve a good trade-off between system resource utilization and control performance. Two triggering parameters σ and γ are used to adjust the frequency of solving the optimization problem. The probabilistic feasibility and stability of the system under the event-triggered mechanism are also examined. Finally, numerical studies on the control of a heating, ventilation, and air conditioning(HVAC) system confirm the efficacy of the proposed control.
Noble metal nanocavities have been widely demonstrated to possess great potential applications in nanooptics and nanophotonics due to their extraordinary localized surface plasmon ***,most metal nanocrystals synthesiz...
详细信息
Noble metal nanocavities have been widely demonstrated to possess great potential applications in nanooptics and nanophotonics due to their extraordinary localized surface plasmon ***,most metal nanocrystals synthesized by chemical methods often suffer from truncation with different degrees due to oxidation and dissolution of metal atoms at corner and *** investigate the influence of shape truncation on the plasmonic properties of single Ag nanowire on Au film nanocavity using the finite difference time domain *** the Ag nanowire(the circumradius R_(2)=50 nm)is gradually truncated from pentagonal to circular geometry,the scattering peak position of the nanocavity shows prominent blue shift from 962 nm to 608 nm,suggesting a nonnegligible role of truncation on plasmonic *** electric field strength and charge distribution of the structure reveal the evolution from dipole mode to quadrupole *** is also found that the plasmon resonance wavelength is linearly dependent on the truncation ratio R_(1)/R_(2)(R_(1) is the inradius)and the modulation slope is also reliable to the size of Ag *** observations could shed light on developing high-performance tunable optical nano-devices in future.
With the rapid development of the electronics industry,the demand for dielectric materials with high permittivities,low losses,and excellent electrical breakdown strengths prepared via low-temperature fabrication tech...
详细信息
With the rapid development of the electronics industry,the demand for dielectric materials with high permittivities,low losses,and excellent electrical breakdown strengths prepared via low-temperature fabrication techniques is ***,we propose a one-step cold sintering process route to improve the comprehensive performance of BaTiO_(3)−based ceramics by integrating polyetherimide(PEI).Dense BaTiO_(3)–PEI nanocomposites can be prepared via a cold sintering process at 250℃ using Ba(OH)_(2)∙8H_(2)O and H_(2)TiO_(3) as the transient liquid *** grain growth of BaTiO_(3) is inhibited,and thin PEI layers less than 10 nm in size are located at the grain *** dissolution‒precipitation process triggered by the transient liquid phase and viscous flow assisted by PEI dominates the cold sintering mechanism of the(1−x)BaTiO_(3)–xPEI *** dielectric properties are stable over a broad temperature range up to 200℃.Compared with BaTiO_(3),80%BaTiO_(3)–20%PEI has superior performance,with a relative permittivity of 163 and a low dielectric loss of 0.014,and the electrical breakdown strength is increased by 80.65%compared with BaTiO_(3).Overall,the cold sintering process provides a potential way to develop dielectric nanocomposites with excellent comprehensive performance.
Polyolefin vitrimers are polymer networks bearing reversible covalent crosslinking points, enabling them to be reprocessed and recycled. In this contribution, a series of polyolefin vitrimers were designed based on th...
详细信息
Polyolefin vitrimers are polymer networks bearing reversible covalent crosslinking points, enabling them to be reprocessed and recycled. In this contribution, a series of polyolefin vitrimers were designed based on the acetoacetate-functionalized polyolefin copolymers, which were produced through the direct copolymerization of ethylene with polar comonomers using a phosphinesulfonate palladium catalyst. The pendant acetoacetate group could mediate several characteristic reactions, such as the Michael addition reaction, ketone-amine condensation and metal coordination reaction. As such, structurally adjustable polyolefin vitrimers can be accessed by introducing various dynamic crosslinking bonds, including disulfide exchange, transamination of vinylogous urethane and labile metal coordination bond. The utilization of different crosslinking reactions and the mole ratio of crosslinkers significantly impact the material properties of the resultant polymers. Specifically, the generated polyolefin vitrimers demonstrated excellent reprocessability and closed-loop recycling properties. The study in this work provides an efficient strategy to access various polyolefin vitrimers.
Optimizing multistage processes,such as distillation or absorption,is a complex mixed-integer nonlinear programming(MINLP)*** integer into continuous variables and solving the easier nonlinear programming(NLP)problem ...
详细信息
Optimizing multistage processes,such as distillation or absorption,is a complex mixed-integer nonlinear programming(MINLP)*** integer into continuous variables and solving the easier nonlinear programming(NLP)problem is an optimization idea for the multistage *** this article,we propose a relaxation method based on the efficiency *** the efficiency parameter is 1or 0,the proposed model is equivalent to the complete existence or inexistence of the equilibrium *** non-integer efficiency represents partial existence.A multi-component absorption case shows a natural penalty for non-integer efficiency,which can assist the efficiency parameter converging to 0 or ***,its penalty is weaker than the existing relaxation models,such as the bypass efficiency *** a simple distillation case,we show that this property can weaken the nonconvexity of the optimization problem and increase the probability of obtaining better optimization results.
Complex networks are becoming more complex because of the use of many components with diverse technologies. In fact, manual configuration that makes each component interoperable has breed latent danger to system secur...
详细信息
Complex networks are becoming more complex because of the use of many components with diverse technologies. In fact, manual configuration that makes each component interoperable has breed latent danger to system security. There is still no comprehensive review of these studies and prospects for further research. According to the complexity of component configuration and difficulty of security assurance in typical complex networks, this paper systematically reviews the abstract models and formal analysis methods required for intelligent configuration of complex networks, specifically analyzes, and compares the current key technologies such as configuration semantic awareness, automatic generation of security configuration, dynamic deployment, and verification evaluation. These technologies can effectively improve the security of complex networks intelligent configuration and reduce the complexity of operation and maintenance. This paper also summarizes the mainstream construction methods of complex networks configuration and its security test environment and detection index system, which lays a theoretical foundation for the formation of the comprehensive effectiveness verification capability of configuration security. The whole lifecycle management system of configuration security process proposed in this paper provides an important technical reference for reducing the complexity of network operation and maintenance and improving network security.
暂无评论