Optimization of Adaptive MTI Filter

Moving target indication (MTI) is an effective means for radar to find moving targets in clutter environment. This paper introduces the basic principles of MTI, how to avoid the blind speed problem and the optimization of MTI filter. Implementing the multi-notch adaptive moving target indication (AMTI) filter that designed by using the stagger code in varied cases, which is based on a feature vector method optimization.

Graph attention network for global search of atomic clusters:A case study of Ag_(n)(n=14-26)clusters

Due to coexistence of huge number of structural isomers,global search for the ground-state structures of atomic clusters is a challenging issue.The difficulty also originates from the computational cost of ab initio methods for describing the potential energy surface.Recently,machine learning techniques have been widely utilized to accelerate materials discovery and molecular simulation.Compared to the commonly used artificial neural network,graph network is naturally suitable for clusters with flexible geometric environment of each atom.Herein we develop a cluster graph attention network(CGANet)by aggregating information of neighboring vertices and edges using attention mechanism,which can precisely predict the binding energy and force of silver clusters with root mean square error of 5.4 meV/atom and mean absolute error of 42.3 meV/Å,respectively.As a proof-of-concept,we have performed global optimization of mediumsized Agn clusters(n=14–26)by combining CGANet and genetic algorithm.The reported ground-state structures for n=14–21,have been successfully reproduced,while entirely new lowest-energy structures are obtained for n=22–26.In addition to the description of potential energy surface,the CGANet is also applied to predict the electronic properties of clusters,such as HOMO energy and HOMO-LUMO gap.With accuracy comparable to ab initio methods and acceleration by at least two orders of magnitude,CGANet holds great promise in global search of lowest-energy structures of large clusters and inverse design of functional clusters.

The reactivity of O_(2) with copper cluster anions Cu_(n)^(-)(n = 7-20):Leveling effect of spin accommodation

The activation of molecular oxygen is an important step in metal-catalyzed oxidation reactions and a hot subject for the research of gas-phase metal clusters.It is known that the Ag and Au clusters readily re-act with O_(2)when they have open shell electronic structures.Distinct from this,here we observed Cu_(n)^(-)(n=7−20)clusters of both open and closed shells possess high reactivity with O_(2)with few exceptions.In a combination with ab initio calculations,we demonstrate that the activation of O_(2)on the even-and odd-sized Cu_(n)^(-)clusters follows the single and double electron transfer models,respectively.Such phe-nomenon of metal clusters with different basicity to activate oxygen is enabled by the leveling effect of spin accommodation.The activity of Cu_(n)^(-)clusters is correlated to the HOMO level,and for the close-shell clusters is also governed by the vertical spin excitation energy(VSE).In encountering the attack of dioxygen,the activity of the copper cluster anions not only depends on their basicity to donate electrons,but also closely associated with the cluster sizes.Small copper clusters Cu_(n)^(-)(n=7−13)can dissociate O_(2)spontaneously,while large clusters require extra energies and display close relationship between the reaction rates and electronic vertical detachment energies(VDE).Our work illuminates a novel reaction mechanism between Cu_(n)^(-)clusters and O_(2),which sheds light in manipulating the activity and stability of coinage clusters by controlling the spin and charge states.

Superatomic Signature and Reactivity of Silver Clusters with Oxygen:Double Magic Ag_(17)^– with Geometric and Electronic Shell Closure

Understanding the stability and reactivity of silver clusters toward oxygen provides insights to design new materials of coinage metals with atomic precision.Herein,we report a systematic study on anionic silver clusters,Ag_(n)^(−)(n=10-34),by reacting them with O_(2) under multiple-collision conditions.Mass spectrometry observation presents the odd-even alternation effect on the reaction rates of these Agn−clusters.