Sub-nano Layers of Li, Be, and Al on the Si(100) Surface: Electronic Structure and Silicide Formation

Within the framework of the density functional theory and the pseudopotential method,the electronic structure calculations of the“metal-Si(100)”systems with Li,Be and Al as metal coverings of one to four monolayers(ML)thickness,were carried out.Calculations showed that band gaps of 1.02 eV,0.98 eV and 0.5 eV,respectively,appear in the densities of electronic states when the thickness of Li,Be and Al coverings is one ML.These gaps disappear with increasing thickness of the metal layers:first in the Li-Si system(for two ML),then in the Al-Si system(for three ML)and then in the Be-Si system(for four ML).This behavior of the band gap can be explained by the passivation of the substrate surface states and the peculiarities of the electronic structure of the adsorbed metals.In common the results can be interpreted as describing the possibility of the formation of a two-dimensional silicide with semiconducting properties in Li-Si(100),Be-Si(100)and Al-Si(100)systems.

The Complete Chromatic Number of Some Planar Graphs~*

Let G be a planar graph without cut vertex, let X_c(G) be the vertex, edge, face-complete chromatic number of G and let p=|V(G)|. This paper proves X_c(G)=Δ(G)+1 if G is an outerplanar graph with Δ(G)≥7, or a high degree planar graph with p≥9 and Δ(G)≥p-2 or a maximal planar graph with Δ(G)≥14.

DP-UserPro:differentially private user profile construction and publication

User profiles are widely used in the age of big data.However,generating and releasing user profiles may cause serious privacy leakage,since a large number of personal data are collected and analyzed.In this paper,we propose a differentially private user profile construction method DP-UserPro,which is composed of DP-CLIQUE and privately top-κtags selection.DP-CLIQUE is a differentially private high dimensional data cluster algorithm based on CLIQUE.The multidimensional tag space is divided into cells,Laplace noises are added into the count value of each cell.Based on the breadth-first-search,the largest connected dense cells are clustered into a cluster.Then a privately top-κtags selection approach is proposed based on the score function of each tag,to select the most importantκtags which can represent the characteristics of the cluster.Privacy and utility of DP-UserPro are theoretically analyzed and experimentally evaluated in the last.Comparison experiments are carried out with Tag Suppression algorithm on two real datasets,to measure the False Negative Rate(FNR)and precision.The results show that DP-UserPro outperforms Tag Suppression by 62.5%in the best case and 14.25%in the worst case on FNR,and DP-UserPro is about 21.1%better on precision than that of Tag Suppression,in average.