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Based on first-principles calculations, symmetry analysis and model construction, we predict that Ho2CF2 hosts both straight and twisted Weyl nodal lines in its bulk phonon spectrum. We identify that the top two phonon bands entangle with each other, forming two straight Weyl nodal lines on the K–H and K′–H′paths at the Brillouin zone(BZ) boundary,and six twisted Weyl nodal lines within the BZ. All the Weyl nodal lines along the kz direction and across the entire BZ.The sym... 相似文献
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较早接受市场经济大潮洗礼的东部电视人在观念上革故鼎新,对新时期如何在市场经济条件下求得县级台的健康稳步发展有了既定的目标和切实可行的思路,这些都为西部电视的发展提供了可借鉴的经验,但是西部县级电视台基础设施落后、经营人才奇缺、经费筹集困难等因素仍是制约发展的重大障碍,西部电视人不得不面对市场化趋势的的难题,想方设法寻求破解之道。近两年,国家广电总局一再降低外资进入广电行业的门槛,这给一向吃独家饭的广电行业注入一江春水,眼光敏锐的广电经营人才以借船出海的战略,多方筹募资金壮大自己的实力,为进一步拓展生存空间… 相似文献
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实验表明掺杂是一种改善阻变存储器性能的有效手段,但其物理机理鲜有研究.本文采用第一性原理方法系统研究了过渡金属元素X(X=Mn,Fe,Co,Ni)掺杂对ZnO基阻变存储器中氧空位迁移势垒和形成能的影响.计算结果表明Ni掺杂可同时有效降低+1和+2价氧空位在掺杂原子附近的迁移势垒,X掺杂均减小了氧空位的形成能,特别是掺杂Ni时氧空位的形成能减小最为显著(比未掺杂时减少了64%).基于该结果制备了未掺杂和Ni掺杂ZnO阻变存储器,研究表明通过掺杂控制体系中氧空位的迁移势垒和形成能,可以有效改善器件的初始化过程、操作电压、保持性等阻变性能.研究结果有助于理解探究影响阻变的微观机制,并可为掺杂提高阻变存储器性能提供一定的理论指导. 相似文献
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In this paper, we provide a Word Emotion Topic (WET) model to predict the complex word emotion information from text, and discover the distribution of emotions among different topics. A complex emotion is defined as the combination of one or more singular emotions from following 8 basic emotion categories: joy, love, expectation, surprise, anxiety, sorrow, anger and hate. We use a hierarchical Bayesian network to model the emotions and topics in the text. Both the complex emotions and topics are drawn from raw texts, without considering any complicated language features. Our experiment shows promising results of word emotion prediction, which outperforms the traditional parsing methods such as the Hidden Markov Model and the Conditional Random Fields(CRFs) on raw text. We also explore the topic distribution by examining the emotion topic variation in an emotion topic diagram. 相似文献
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