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关键词： 量子力学  

ISBN: (纸本)9787568538381

摘要： 本书为理工科物理类规划教材, 本书分为11章, 本书系统阐述传统量子力学的基本概念和基本原理的同时, 把量子态的纠缠性、不可克隆性、量子力学的非局域性等概念引入量子力学的理论体系, 并介绍了量子力学的新进展和量子通信、量子计算及其物理实现、量子密码、量子测量等量子信息学的基本内容, 以更新和丰富量子力学的内容。

关键词： 纳米材料 物理学 研究 英文  

ISBN: (纸本)9787548749783

摘要： 自旋电子学是基于对电子的自旋属性调控从而实现信息的处理和存储等目标而发展的新兴学科。与以电荷属性为基础的传统电子学器件和材料相比，自旋电子学器件和材料具有低功耗、非易失性、高速等优点而具有重要的应用前景。在理论研究中，双探针系统被广泛用于描述分子器件和纳米器件。许多研究表明，纳米器件的输运特性不仅取决于所采用的纳米材料，而且还取决于电极及其之间的耦合。本文主要对低维纳米结模型器件中的电荷和自旋输运进行了理论研究。在简要回顾纳米器件中量子传输的基本理论方法后，深入探讨了分子器件中的开关比、自旋过滤以及自旋极化等，并给出相应的输运量子调控的理论机理。

摘要： In this thesis, a theoretical study is presented based on the first-principles calculation of four main topics on the controllable mass-gapped Dirac cone (MGDC) mechanism of graphene using spin-dependent potentials in graphene- based magnetic junctions. Using a specific stacking configuration design at the interface of graphene sandwiching with magnetic materials, MGDC of graphene can be open and close depending on the magnetic alignment of the upper and lower magnetic materials. A systematic study within spin-polarized generalized-gradient approximation on the interface is presented to understand the influence of physical and chemical properties at the interface that affect the optimum control of MGDC of graphene and its efficiency as a spintronic device. By understanding the origin and characteristics of controllable MGDC of graphene, a successful graphene-based magnetic junction device with high spintronic performance can be created. At the beginning of this thesis (chapter 1), the introduction to magnetic junctions, their development, and the recent consideration of 2D materials- based magnetic junctions for spintronic devices is presented. The problems that need to be solved, the aims of the research, and the strategy for address- ing the problem are also presented. Afterward, the theoretical basis of the computational method used in the research and the physics of graphene and its characters in magnetic junction is discussed in chapter 2. Next, Chapter 3 presents the theoretical framework of the considered design and the computa- tional approach strategy in the simulation. In the first study (Chapter 4), Ni(111)/graphene/Ni(111) magnetic junc- tion is proposed. Ni(111) slabs are used due to their similar structures to graphene, that is, having the smallest lattice mismatch among transition met- als. In this proposed system, the MGDC of graphene can be controlled using the magnetic alignment of the Ni slabs. When the magnetic moments of the upper and lower Ni(1

关键词： 自旋转移力矩   磁导率   微磁学模拟   微波磁损耗  

摘要： 基于微磁学模拟结果，发现由于单根纳米线两端处磁矩矢量方向与极化电流密度(J)方向的不一致，导致电子的自旋转移力矩（STT）只能作用于纳米线两端的磁矩。通过提高极化电流的自旋极化率(P)，这个简化模型的微波磁谱中处在18 GHz的微波磁损耗可以得到明显的抑制，同时发现与微波损耗对应的自然共振频率大小却不受STT影响。在STT效应作用下，负的磁导率虚部也是可实现的。另外，模拟结果表明通过提高STT效应中非绝热效应项中的值，18GHz处的微波磁损耗可以得到显著的增强。基于STT效应中不同力矩的来源对磁化强度进动过程的有效阻尼常数(ɑe)的影响，上述的结果可以得到合理的解释：绝热力矩能降低ɑe数值，因而能抑制微波磁损耗的大小；非绝热力矩能提高ɑe数值，因而能增强微波磁损耗。我们的研究结果展示了一个创新性的、能主动地调控微波磁损耗的方法。

摘要： 近日,中国科学技术大学中国科学院微观磁共振重点实验室彭新华研究组在自旋量子精密测量领域取得重要进展,首次提出和验证了Floquet自旋量子放大技术,该技术克服了以往只在单个频率处量子放大的局限性,实现了多频段极弱磁场信号的量子放大,灵敏度达到了飞特斯拉水平.相关研究成果于6月9日以"Floquet Spin Amplification"为题在线发表于著名国际学术期刊《Physical Review Letters》上[***.128,233201(2022)],并被选为"编辑推荐(Editors' Suggestion)"文章.

关键词： 磁共振成像   快速恢复快速自旋回波序列   快速自旋回波序列   婴幼儿   头颅  

摘要： 目的 研究MR 2种T2 WI序列快速恢复快速自旋回波(TSE DRIVE)和快速自旋回波(TSE)在婴幼儿头颅检查中的优劣性及临床应用价值.方法 随机选取行婴幼儿头颅MRI检查的患者69例,扫描序列包括T2 WI TSE DRIVE及T2 WI TSE,对2种序列进行图像质量分析,比较2种序列图像信噪比(SNR)、对比噪声比(CNR)、特异吸收率(SAR)值的差异,分析2种序列在显示颅内解剖结构及病灶方面显示能力.结果 69例患者中,主观评价图像质量评分方面:T2 WI TSE DRIVE序列评分[(2.812±0.522)分]高于T2 WI TSE序列评分[(2.522±0.720)分],差异有统计学意义(χ2=9.066,P<0.05).客观评价SNR、CNR方面:在显示侧脑室后角区T2 WI TSE DRIVE序列SNR明显高于T2 WI TSE序列,差异有显著统计学意义(F=79.356,P<0.001),在显示额叶白质区T2 WI TSE DRIVE序列SNR与T2 WI TSE序列无统计学意义(P>0.05),T2 WI TSE DRIVE序列CNR明显高于T2 WI TSE序列,差异有显著统计学意义(F=61.022,P<0.001).SAR值方面:T2WI TSE DRIVE、T2WI TSE分别为(2.6±0.08)W/kg、(2.4±0.05)W/kg.结论 T2WI TSE DRIVE序列可以用来增强具有较长T2弛豫时间的脑脊液强度,使重复时间缩短,提高图像分辨率,在显示颅内细微结构、灰白质交界、髓鞘化发育等方面有明显优势,图像效果优于T2 WI TSE序列,可以作为婴幼儿颅脑T2 WI首选序列.

关键词： breakage rate   calcined coal gangue   ceramic proppant   machanical property   structural strength   α-Fe2O3  

摘要： The exploitation of combustible gas and the recycle of solid waste are important measures to respond the national policy of low-carbon development and energy transformation. In this paper, ceramic particle proppant was synthesized by the solid waste material of calcined coal gangue for realizing the efficient exploitation of coalbed methane. By adjusting the synthetic conditions, the mechanical properties of the material were finally strengthened for the efficient exploitation of coalbed methane. The experimental results show that the proper addition of calcined coal gangue can effectively adjust the anti-crushing strength of ceramic proppant, and the lowest crushing rate is 3. 66% at 42 MPa and 7. 97% at 52 MPa, respectively. After the interfacial corrosion treatment of ceramic proppant, it is found that the uniform distribution of Fe element is conducive to the generation of molten liquid in proppant and structural densification. Moreover, the microstructural stress generated by the gap filling of the α-Fe₂O₃ particle during the process of grain nucleation and growth. The material structure has been strengthened through the dispersive α-Fe₂O₃ particle, which significantly improves the mechanical properties and crushing resistance of ceramic proppant. © 2023 Bulletin of the Chinese Ceramic Society. All rights reserved.

关键词： Floquet physics   periodically driven quantum systems   Floquet ETH   dynamical freezing   Floquet MBL   emergent conservation law   Floquet scars  

摘要： Equilibrium statistical mechanics rests on the assumption of chaotic dynamics of a system modulo the conservation laws of local observables: extremization of entropy immediately gives Gibbs' ensemble (GE) for energy conserving systems and a generalized version of it (GGE) when the number of local conserved quantities is more than one. Through the last decade, statistical mechanics has been extended to describe the late-time behaviour of periodically driven (Floquet) quantum matter starting from a generic state. The structure built on the fundamental assumptions of ergodicity and identification of the relevant conservation laws in this inherently non-equilibrium setting. More recently, it has been shown that the statistical mechanics of Floquet systems has a much richer structure due to the existence of emergent conservation laws: these are approximate but stable conservation laws arising due to the drive, and are not present in the undriven system. Extensive numerical and analytical results support perpetual stability of these emergent (though approximate) conservation laws, probably even in the thermodynamic limit. This banks on the recent finding of a sharp threshold for Floquet thermalization in clean, interacting non-integrable Floquet systems. This indicates to the possibility of stable Floquet phases of matter in disorder-free systems. This review intends to give a self-contained theoretical overview of these developments for a broad physics audience. We conclude by briefly surveying the current experimental scenario.

关键词： 表象脚本技术   积极表象训练   抑郁   行为激活  

摘要： 目的:探索表象脚本技术的积极表象训练对中学生抑郁个体抑郁与行为激活的效果。方法:对96名中学生抑郁个体进行不等组对照实验研究:表象干预组36人进行两周的表象脚本技术的积极表象干预;空白组30人在实验过程中不实施任何干预;活动提醒组30人通过每日活动提醒完成任务(活动任务不需要心理表象)。使用贝克抑郁量表第二版和抑郁行为激活量表对三组被试进行前后测及一个月追踪。结果:行为激活量表得分的组别和时间交互作用显著[F(4,134)=17.96,P<0.001,η_(p)^(2)=0.349],抑郁得分的组别和时间交互作用显著[F(4,138)=13.99,P<0.001,η_(p)^(2)=0.289]。结论:线上的表象脚本技术的积极表象干预方法,对改善中学生抑郁个体的抑郁情绪及提高其行为激活水平是有效的。

关键词： 固态原子自旋   磁传感   类环形磁耦合天线   微波非均匀性  

摘要： 固态原子自旋磁传感器具有磁灵敏度高、体积小等优势,在精密测量领域具有很好的发展前景。面向高灵敏度固态原子自旋磁传感器对大功率高均匀微波激发天线的需求,设计了一种类环形磁耦合天线结构,通过增加不规则移相回路和环形开口结构使微波场在环形天线中心处叠加,产生大功率高均匀微波场。实验中,通过仿真得到该结构S_(11)参数为-20.8dB,微波非均匀性小于6%。同时,通过与传统环形天线对比测试,该类环形天线使固态原子自旋ODMR谱对比度提升了330%,相应的磁传感灵敏度提升了约450%,实现了对固态原子自旋磁传感结构的灵敏度提升,为高灵敏固态原子自旋传感测量技术提供了技术支撑。