您当前的位置:首页 > 论文浏览



1. 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113下载量58 评论 0

2. 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2972下载量664 评论 0

3. chinaXiv:201806.00029 [pdf]


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


提交时间: 2018-06-12 来自合作期刊:《广西植物》 点击量458下载量48 评论 0

4. chinaXiv:201806.00020 [pdf]

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

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290下载量61 评论 0

5. chinaXiv:201806.00018 [pdf]


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301下载量61 评论 0

7. 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108下载量41 评论 0

8. 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86下载量34 评论 0

9. chinaXiv:201805.00407 [pdf]

Effects of grazing on net primary productivity, evapotranspiration and water use efficiency in the grasslands of Xinjiang

HUANG, Xiaotao; LUO, Geping; YE, Feipeng; HAN, Qifei
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等

Grazing is a main human activity in the grasslands of Xinjiang. It is vital to identify the effects of grazing on the sustainable utilization of local grasslands. However, the effects of grazing on net primary productivity (NPP), evapotranspiration (ET) and water use efficiency (WUE) in this region remain unclear. Using the spatial Biome-BGC grazing model, we explored the effects of grazing on NPP, ET and WUE across the different regions and grassland types in Xinjiang during 1979–2012. NPP, ET and WUE under the grazed scenario were generally lower than those under the ungrazed scenario, and the differences showed increasing trends over time. The decreases in NPP, ET and WUE varied significantly among the regions and grassland types. NPP decreased as follows: among the regions, Northern Xinjiang (16.60 g C/(m2•a)), Tianshan Mountains (15.94 g C/(m2•a)) and Southern Xinjiang (−3.54 g C/(m2•a)); and among the grassland types, typical grasslands (25.70 g C/(m2•a)), swamp meadows (25.26 g C/(m2•a)), mid-mountain meadows (23.39 g C/(m2•a)), alpine meadows (6.33 g C/(m2•a)), desert grasslands (5.82 g C/(m2•a)) and saline meadows (2.90 g C/(m2•a)). ET decreased as follows: among the regions, Tianshan Mountains (28.95 mm/a), Northern Xinjiang (8.11 mm/a) and Southern Xinjiang (7.57 mm/a); and among the grassland types, mid-mountain meadows (29.30 mm/a), swamp meadows (25.07 mm/a), typical grasslands (24.56 mm/a), alpine meadows (20.69 mm/a), desert grasslands (11.06 mm/a) and saline meadows (3.44 mm/a). WUE decreased as follows: among the regions, Northern Xinjiang (0.053 g C/kg H2O), Tianshan Mountains (0.034 g C/kg H2O) and Southern Xinjiang (0.012 g C/kg H2O); and among the grassland types, typical grasslands (0.0609 g C/kg H2O), swamp meadows (0.0548 g C/kg H2O), mid-mountain meadows (0.0501 g C/kg H2O), desert grasslands (0.0172 g C/kg H2O), alpine meadows (0.0121 g C/kg H2O) and saline meadows (0.0067 g C/kg H2O). In general, the decreases in NPP and WUE were more significant in the regions with relatively high levels of vegetation growth because of the high grazing intensity in these regions. The decreases in ET were significant in mountainous areas due to the terrain and high grazing intensity.

提交时间: 2018-05-18 来自合作期刊:《Journal of Arid Land》 点击量91下载量42 评论 0

10. chinaXiv:201804.02357 [pdf]

Diet characteristics of wild sheep (Ovis ammon darwini) in the Mengluoke Mountains, Xinjiang, China

LI Bang; XU Wenxuan; David A BLANK; WANG Muyang; YANG Weikang
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等

In most arid and semi-arid regions of the world, domestic livestock and native wildlife share pastures, and their competition for forage and habitat is thought to be a serious conservation issue. Moreover, unmanaged grazing by livestock can cause the population decline in wild ungulates. The diet of an animal species is a determining aspect of its ecological niche, and investigating its diet has been one of the initial steps in basic ecology study of a new species. To get an approximate understanding of the interspecific food relationships of argali (Ovis ammon darwini) between sexes, and sympatric domestic sheep and goats, we compared the diet compositions and diet-overlaps among these herbivores, i.e., male argali, female argali, domestic sheep, and domestic goats in the Mengluoke Mountains of Xinjiang, China by using micro-histological fecal analysis. Female argali, male argali, domestic sheep and domestic goat primarily consumed forbs (43.31%±4.86%), grass (36.02%±9.32%), forbs (41.01%±9.18%), and forbs (36.22%±10.61%), respectively in warm season. All these animals consumed mostly shrubs (female argali: 36.47%±7.56%; male argali: 47.28%±10.75%; domestic sheep: 40.46%±9.56%; and domestic goats: 42.88%±9.34%, respectively) in cold season. The diet-overlaps were relatively high among all species in cold season with values ranging from 0.88 to 0.94. Furthermore, Schoener’s index measured between each possible pair of 4 herbivores increased from the warm season to the cold season. The results illustrate that the high degree of diet-overlap of argali and domestic livestock (sheep and goat) may pose a threat to the survival of the argali in cold season. From the viewpoint of rangeland management and conservation of the endangered argali, the numbers of domestic sheep and goats should be limited in cold season to reduce food competition.

提交时间: 2018-04-24 来自合作期刊:《Journal of Arid Land》 点击量585下载量127 评论 0

12345678910  尾页  转到  [189 页/ 1886 条记录]