基于广电网络的地震预警技术

地震会造成大量的人员伤亡和财产损失,而依靠目前的技术还不足以预测地震的发生。最有效的减灾措施是当地震发生时,通过技术手段向非震中区域发出预警,在地震波到达之前,提早采取避震措施。四川广电网络开发和部署了基于广电网络的地震预警系统,经过实际运行,取得了良好的效果。本文介绍了该系统的原理、实现方案、实测技术指标以及演进路线等。     

铁磁半导体 花落两维里

正三十余载觅磁稀今看低维若鹜依极限少层铬锗碲双重调控又双极载流双子两极缘电荷惺惺共自旋量子以为多靓颖其实几负丽人娟——带隙铁磁~1)1引子自古人类视觉追求立体、丰满、洞透,当下物理追求平面、细微、对称破缺。后者为之欲生欲死的对象之一就是"二维"这个字眼。她真是让人又爱又恨。爱者赞其丰富物理,可上天入地无所不能而酣畅淋漓。恨者斥其不可捉摸而迁怒于"炒作概念",就如朗道不喜、墨敏(Mermin)证毕一般,仅此而已。窃以为,二维材料的     

基于Android的违章举报界面设计

本文介绍了一款基于Android的违章举报App的用户界面,其设计原则遵循Google发布的Material Design规范,通过合理的界面布局和设计元素,在实现所需功能的同时,带来较为良好的用户体验.     

Tailoring electronic properties of two-dimensional antimonene with isoelectronic counterparts

Using ab initio density functional theory calculations, we explore the three most stable structural phases, namely, α,β, and cubic(c) phases, of two-dimensional(2D) antimonene, as well as its isoelectronic counterparts SnTe and InI. We find that the band gap increases monotonically from Sb to SnTe to InI along with an increase in ionicity, independent of the structural phases. The band gaps of this material family cover the entire visible-light energy spectrum, ranging from 0.26 eV to 3.37 eV, rendering them promising candidates for optoelectronic applications. Meanwhile, band-edge positions of these materials are explored and all three types of band alignments can be achieved through properly combining antimonene with its isoelectronic counterparts to form heterostructures. The richness in electronic properties for this isoelectronic material family sheds light on possibilities to tailor the fundamental band gap of antimonene via lateral alloying or forming vertical heterostructures.     

基于混沌理论与DNA动态编码的卫星图像加密算法

针对卫星图像在传输、存储过程中涉及的信息安全问题,该文提出一种新型的基于混沌理论与DNA动态编码的卫星图像加密算法。首先,提出一种改进型无限折叠混沌映射,拓宽了原有无限折叠混沌映射的混沌区间。之后,结合改进型Chebyshev混沌映射与SHA-256哈希算法,生成加密算法的密钥流,提升算法的明文敏感性。然后,利用混沌系统的状态值对Hilbert局部置乱后的像素进行DNA编码,实现DNA动态编码,解决了DNA编码规则较少所带来的容易受到暴力攻击的弱点。最后,使用混沌序列完成进一步混沌加密,从而彻底混淆原始像素信息,增加加密算法的随机性与复杂性,得到密文图像。实验结果表明,该算法具有较好的加密效果和应对各种攻击的能力。     

Theoretical study of thermoelectric properties of MoS2

We systematically studied the thermoelectric properties of MoS2 with doping based on the Boltzmann transport theory and first-principles calculations. We obtained an optimal doping region(around 1019cm 3) for thermoelectric properties along in-plane and cross-plane directions. MoS2in the optimal doping region has a vanishingly small anisotropy of thermopower possibly due to the decoupling of in-plane and cross-plane conduction channels, but big anisotropies of electrical conductivity σ and electronic thermal conductivity κearising from the anisotropic electronic scattering time. The κeis comparable to the lattice counterpart κlin the plane, while κldominates over κeacross the plane. The figure of merit ZT can reach 0.1 at around 700 K with in-plane direction preferred by doping.