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1. chinaXiv:201807.00040 [pdf]

加速器的百年历程

朱雄伟
分类: 物理学 >> 核物理学

本文分析讨论了加速器的百年历史, 从思想的萌芽、理论的突破与准备、技术的准备与储存、实验的成功、加速器的未来与展望等几个方面进行了论述。

提交时间: 2018-07-10 点击量705下载量161 评论 0

2. chinaXiv:201806.00237 [pdf]

On the analytical solution of accelerating structure

朱雄伟
分类: 物理学 >> 核物理学

本文讨论了加速结构中的解析求解问题, 主要讨论了场和等效电路两种求解方法。

提交时间: 2018-06-20 点击量579下载量154 评论 0

3. chinaXiv:201804.01458 [pdf]

Comment on ”Integrability of the Rabi Model”

Degang Zhang
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等

In this Comment, I point out that the Braak's analytical solution doesn't exhibit the true energy spectrum of the Rabi model due to the derivation error in solving the time-independent Schrodinger equation.

提交时间: 2018-06-18 点击量333下载量181 评论 0

4. chinaXiv:201607.00046 [pdf]

Exact Solution for Three-Dimensional Ising Model

Zhang, Degang
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等

Three-dimensional Ising model in zero external field is exactly solved by operator algebras, similar to the Onsager's approach in two dimensions. The partition function of the simple cubic crystal imposed by the periodic boundary condition along both $(0 1 0)$ and $(0 0 1)$ directions and the screw boundary condition along the $(1 0 0)$ direction is calculated rigorously. In the thermodynamic limit an integral replaces a sum in the formula of the partition function. A order-disorder transition in the infinite crystal occurs at a temperature $T=T_c$ determined by the condition: $\sinh\frac{2J}{k_BT_c}\sinh\frac{2(J_1+J_2)}{k_BT_c}=1$, where $(J_1 J_2 J)$ are the interaction energies in three directions, respectively. The analytical expressions for the internal energy and the specific heat are also given. It is also shown that the thermodynamic properties of 3D Ising model with $J_1=J_2$ are connected to those in 2D Ising model with the interaction energies $(J_1 J_{2D})$ by the relation $(\frac{J_{2D}}{k_BT})^*=(\frac{J}{k_BT})^*-\frac{J_1}{k_BT}$, where $x^*=\frac{1}{2}{\rm ln coth} x={\rm tanh}^{-1}(e^{-2x})$.

提交时间: 2018-06-14 点击量3229下载量808 评论 0

5. chinaXiv:201806.00029 [pdf]

峨眉山世界遗产地植物多样性全球突出普遍价值及保护

姚小兰; 杜彦君; 郝国歉; 平晓鸽; 胡军华; 郝建锋
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等

世界遗产地对具有突出普遍价值的生物多样性和珍稀濒危物种及其栖息地等的保护具有重要作用。该文在申遗文本和大量文献资料的基础上,以峨眉山世界遗产地原生植物及植被群落为研究对象,从物种多样性、物种组成、植物区系、植被类型及垂直分布格局等方面,分析论证了峨眉山世界遗产地植物多样性的全球突出普遍价值,并简要概述了当前峨眉山世界遗产地植物受威胁状况以及在保护与发展中出现的问题。结果表明:(1)峨眉山世界遗产地目前拥有高等植物242科3200种以上,特有植物、孑遗植物种类丰富;(2)与中国其他湿润性亚热带山地森林垂直带谱相比,峨眉山亚热带森林植被类型完整,常绿阔叶林东部类型在山地垂直带谱中占据显著地位,海拔上限最高,跨度最大,具有典型的亚热带常绿阔叶林东部亚区森林群落特点;(3)植物区系复杂,既有热带、亚热带和温带植物区系成份,又有中国—日本与中国—喜马拉雅植物区系分布;(4)受人为活动(旅游发展、基础设施建设等)和自然扰动(气候变暖、地质灾害等)影响,峨眉山世界遗产地植物多样性下降明显,珍稀濒危植物受威胁程度增加,典型群落面积退化,稳定性降低。建议在划定珍稀植物保护区,对植物栖息地进行专门保护的基础上,开展植物多样性、环境因子、人为活动动态监测,预见性的保护其突出普遍价值,实现世界遗产地的可持续发展。

提交时间: 2018-06-12 来自合作期刊:《广西植物》 点击量1557下载量192 评论 0

6. chinaXiv:201806.00020 [pdf]

Synchrotron radiation intensity and energy of runaway electrons in EAST Tokamak.pdf

张永宽
Comment:已经在Chinese physics B上发表
分类: 物理学 >> 气体、等离子体、放电物理

A detailed analysis of the synchrotron radiation intensity and energy of runaway electrons are presented for EAST. In order to make the energy of the calculated runaway electrons more accurate, we take the shafranov shift into account. The results of the analysis show that the synchrotron radiation intensity and energy of runaway electrons did not reach the maximum at the same time. The energy of runaway electrons reached the maximum value first, and then the synchrotron radiation intensity of the runaway electrons reached the maximum. We also analyzed the runaway electrons density, and it shows the density of runaway electrons continuously increased. For this reason, although the energy of the runaway electrons drops but the synchrotron radiation intensity of the runaway electrons will continue rising for a while

提交时间: 2018-06-07 点击量456下载量157 评论 0

7. chinaXiv:201806.00018 [pdf]

规范势分解理论与整体拓扑问题.pdf

李希国
分类: 物理学 >> 基本粒子与场物理学

利用段一士提出的规范势可分解和具有内部结构的思想,使用几何代数方法对SO(n)群用单位矢量场进行了分解,给出了一般形式,并讨论这个分解的性质;由此给出了SU(2)群和U(1)群用单位矢量分解的形式,这正是著名物理学家法捷耶夫1999年所给出的结果。使用SO(n)群规范势分解的一般形式讨论了Gauss-Bonnet-Chern 密度的局域拓扑结构,其整体拓扑结构正好是Gauss—Bonnet-Chern 定理,由拓扑结构很容易得到Euler- Poincaré 示性数的Morse 理论形式。利用SU(2)群规范势分解研究了-1/2 Bose-Einstein 凝聚体,得到了一个新的环流条件,也是Mernin-Ho 关系的推广。最后,使用段一士发现的三维黎曼几何的Torsion 张量与U(1)规范理论的关系,使用U(1)规范势分解研究了位错线与link 数的关系。

提交时间: 2018-06-02 点击量552下载量193 评论 0

9. chinaXiv:201805.00405 [pdf]

Wind tunnel experiments on dust emissions from different landform types

WU, Wei; YAN, Ping; WANG, Yong; DONG, Miao; MENG, Xiaonan; JI, Xinran
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等

The measurement and assessment of dust emissions from different landforms are important to understand the atmospheric loading of PM10 (particulate matter ≤10 µm aerodynamic diameter) and to assess natural sources of dust; however, the methodology and technique for determining the dust still present significant research challenges. In the past, specialized field observation and field wind tunnel studies have been used to understand the dust emission. A series of wind tunnel tests were carried out to identify natural sources of dust and measure the magnitudes of dust emissions from different landforms. The method used in this study allowed the measurement of the PM10 emission rate using a laboratory based environmental boundary layer wind tunnel. Results indicated that PM10 emissions demonstrated strong temporal variation and were primarily driven by aerodynamic entrainment. Sand dunes, playa, and alluvial fans had the largest dust emission rates (0.8–5.4 mg/(m2•s)) while sandy gravel, Gobi desert and abandoned lands had the lowest emission rates (0.003–0.126 mg/(m2•s)). Dust emissions were heavily dependent on the surface conditions, especially the availability of loose surface dust. High dust emissions were a result of the availability of dust-particle materials for entrainment while low dust emissions were a result of surface crusts and gravel cover. Soil surface property (surface crusts and gravel cover) plays an important role in controlling the availability of dust-sized particles for entrainment. The dust emission rate depended not only on the surface conditions but also on the friction velocity. The emission rate of PM10 varies as a power function of the friction velocity. Although dynamic abrasion processes have a strong influence on the amount of dust entrainment, aerodynamic entrainment may provide an important mechanism for dust emissions. Large volumes of dust entrained by aerodynamic entrainment can not only occur at low shear velocity without saltation, but may dominate the entrainment process in many arid and semi-arid environments. So it may also be responsible for large magnitude dust storms. Playa and alluvial fan landforms, prior to developing a surface crust, may be the main sources of dust storms in Qinghai Province.

提交时间: 2018-05-18 来自合作期刊:《Journal of Arid Land》 点击量356下载量137 评论 0

10. chinaXiv:201805.00406 [pdf]

Solute transport characteristics of a deep soil profile in the Loess Plateau, China

WANG Jiao; SHAO Ming'an
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等

Understanding solute transport behaviors of deep soil profile in the Loess Plateau is helpful for ecological construction and agricultural production improvement. In this study, solute transport processes of a deep soil profile were measured by a conservative tracer experiment using 25 undisturbed soil cores (20 cm long and 7 cm diameter for each) continuously sampled from the surface downward to the depth of 500 cm in the Loess Plateau of China. The solute transport breakthrough curves (BTCs) were analyzed in terms of the convection-dispersion equation (CDE) and the mobile-immobile model (MIM). Average pore-water velocity and dispersion coefficient (or effective dispersion coefficient) were calculated using the CDE and MIM. Basic soil properties and water infiltration parameters were also determined to explore their influence on the solute transport parameters. Both pore-water velocity and dispersion coefficient (or effective dispersion coefficient) generally decreased with increasing depth, and the dispersivity fluctuated along the soil profile. There was a good linear correlation between log-transformed pore-water velocity and dispersion coefficient, with a slope of about 1.0 and an average dispersivity of 0.25 for the entire soil profile. Generally speaking, the soil was more homogeneous along the soil profile. Our results also show that hydrodynamic dispersion is the dominant mechanism of solute transport of loess soils in the study area.

提交时间: 2018-05-18 来自合作期刊:《Journal of Arid Land》 点击量330下载量140 评论 0

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