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1. chinaXiv:202010.00037 [pdf]

Performance and uncertainty analysis of a short-term climate reconstruction based on multi-source data in the Tianshan Mountains region, China

LI,Xuemei; SIMONOVIC,Slobodan P; LI,Lanhai; ZHANG,Xueting; QIN,Qirui
Subjects: Geosciences >> History of Geosciences

Short-term climate reconstruction, i.e., the reproduction of short-term (several decades) historical climatic time series based on the relationship between observed data and available longer-term reference data in a certain area, can extend the length of climatic time series and offset the shortage of observations. This can be used to assess regional climate change over a much longer time scale. Based on monthly grid climate data from a Coupled Model Inter-comparison Project phase 5 (CMIP5) dataset for the period of 1850–2000, the Climatic Research Unit (CRU) dataset for the period of 1901–2000 and the observed data from 53 meteorological stations located in the Tianshan Mountains region (TMR) of China during the period of 1961–2011, we calibrated and validated monthly average temperature (MAT) and monthly accumulated precipitation (MAP) in the TMR using the delta, physical scaling (SP) and arti?cial neural network (ANN) methods. Performance and uncertainty during the calibration (1971–1999) and verification (1961–1970) periods were assessed and compared using traditional performance indices and a revised set pair analysis (RSPA) method. The calibration and verification processes were subjected to various sources of uncertainty due to the influence of different reconstructed variables, different data sources, and/or different methods used. According to traditional performance indices, both the CRU and CMIP5 datasets resulted in satisfactory calibrated and verified MAT time series at 53 meteorological stations and MAP time series at 20 meteorological stations using the delta and SP methods for the period of 1961–1999. However, the results differed from those obtained by the RSPA method. This showed that the CRU dataset produced a low degree of uncertainty (positive connection degree) during the calibration and verification of MAT using the delta and SP methods compared to the CMIP5 dataset. Overall, the calibrated and verified MAP had a high degree of uncertainty (negative connection degree) regardless of the dataset or reconstruction method used. Therefore, the reconstructed time series of MAT for the period of 1850 (or 1901)–1960 based on the CRU and CMIP5 datasets using the delta and SP methods could be used for further study. The results of this study will be useful for short-term (several decades) regional climate reconstruction and longer-term (100 a or more) assessments of regional climate change.

submitted time 2020-10-20 From cooperative journals:《Journal of Arid Land》 Hits137Downloads76 Comment 0

2. chinaXiv:201911.00009 [pdf]

一种替代彩虹模型的惯性系非洛仑兹变换模型

胡锦文
Subjects: Physics >> Geophysics, Astronomy, and Astrophysics

在洛伦兹破缺模型中,彩虹模型通常被讨论,因为彩虹模型可以使一个粒子的能量有一个极限,而不是由洛伦兹变换中得到的无限大,这在量子引力理论中被认为是必要的。然而,本文表明一开始并没有必要限制光速是一个常数,当我们约定如下三个原则:(1)我们可以用校准的时钟定义整个空间的同时性,(2)时空是均匀的,空间各向同性和(3)所有的惯性系统是等价的。基于上述三原则,我们可以构造一个通用坐标变换来满足惯性系统的对称性,并可以在惯性系统之间构建一个non-Lorentz变换使得粒子的能量有一个极限值,就像和彩虹模型一样。此外,在最近的论文中,作为一种超高能量尺度的测试,彩虹模型被用来研究伽马射线爆发,如GRB 160509A事件,它强烈地表明了光速的变化与光子能量之间存在线性关系。所以我们也分析了同样的事件,我们发现我们的模型也支持彩虹模型的结论,我们的模型和彩虹模型之间有一定的相关性。最后,我们简要讨论了如何在未来的高能粒子实验中验证这两个模型。

submitted time 2019-11-09 Hits12944Downloads940 Comment 0

3. chinaXiv:201910.00060 [pdf]

Reinvestigation of the scaling law of the windblown sand launch velocity with a wind tunnel experiment

ZHANG Yang1; LI Min; WANG Yuan; YANG Bin
Subjects: Environmental Sciences, Resource Sciences >> Basic Disciplines of Environmental Science and Technology

Windblown sand transport is a leading factor in the geophysical evolution of arid and semi-arid regions. The evolution speed is usually indicated by the sand transport rate that is a function of launch velocity of sand particle, which has been investigated by the experimental measurement and numerical simulation. However, the obtained results in literatures are inconsistent. Some researchers have discovered a relation between average launch velocity and wind shear velocity, while some other researchers have suggested that average launch velocity is independent of wind shear velocity. The inconsistence of launch velocity leads to a controversy in the scaling law of the sand transport rate in the windblown case. On the contrary, in subaqueous case, the scaling law of the sand transport rate has been widely accepted as a cubic function of fluid shear velocity. In order to explain the debates surrounding the windblown case and the difference between windblown and subaquatic cases, this study reinvestigates the scaling law of the vertical launch velocity of windblown transported sand particles by using a dimensional analysis in consideration of the compatibility of the characteristic time of sand particle motion and that of air flow. Then a wind tunnel experiment is conducted to confirm the revisited scaling law, where the sand particle motion pictures are recorded by a high-speed camera and then the launch velocity is solved by the particle tracking velocimetry. By incorporating the results of dimensional analysis and wind tunnel experiment, it can be concluded that, the ratio of saltons number to reptons number determines the scaling law of sand particle launch velocity and that of sand transport rate, and using this ratio is able to explain the discrepancies among the classical models of steady sand transport. Moreover, the resulting scaling law can explain the sand sieving phenomenon: a greater fraction of large grains is observed as the distance to the wind tunnel entrance becomes larger.

submitted time 2019-10-26 From cooperative journals:《Journal of Arid Land》 Hits505Downloads180 Comment 0

4. chinaXiv:201904.00075 [pdf]

A non-Lorentz transformation corresponding to the symmetry of inertial systems as an alternative to the rainbow model.pdf

胡锦文
Subjects: Physics >> Geophysics, Astronomy, and Astrophysics

在Lorentz破缺模型中,通常会讨论彩虹模型,因为彩虹模型可以使粒子的能量具有极限而不是与Lorentz变换相对应的具有无限值,而这在量子引力中被认为是必需的。然而,本文表明,当我们只是坚持时空是均匀的,空间是各向同性的并且所有惯性系统都是等价时,并没有必要将光速限制为常数。并且由于光速的变化,我们可以完全构造惯性系统的坐标变换,使粒子的能量有一个极限,而这与彩虹模型相同。 此外,在最近的论文中,作为超高能量尺度的测试,彩虹模型用于研究伽马射线爆,例如GRB 160509A事件,该事件强烈暗示光速随其能量变化的线性形式。所以我们也分析了这个事件,发现我们的模型和彩虹模型之间存在联系。最后,我们简要讨论了如何在超高能量级的未来粒子实验中验证这两个模型。

submitted time 2019-04-03 Hits13100Downloads886 Comment 0

5. chinaXiv:201902.00059 [pdf]

西双版纳地区主要森林植被乔木多样性的时间变化

杨建波; 马友鑫; 白杨; 曹慧
Subjects: Biology >> Botany >> Applied botany

生物多样性评估为区域可持续发展提供重要参考。为了评估云南省西双版纳森林植被乔木多样性的时间变化,通过样方调查收集了该地区 4 种主要森林植被(热带雨林、热带季节性湿润林、热带山地常绿阔叶林和暖热性针叶林)乔木多样性数据;结合遥感影像提取了该地区 4 种森林植被在 1992、2000、2009 和 2016 年 4 个时期的分布;用 Simpson,Shannon-Wiener 和 Scaling 物种多样性指数对比 4 种森林植被乔木均匀度差异;利用Scaling生态多样性指数和灰色关联评价模型,评估该地区在 4 个时期的森林乔木多样性的时间变化。结果表明:(1)森林面积比例变化有先减少后增加的趋势,表现为由 1992 年的 65.5%减少至 2000 年的 53.42%,减少到 2009 年的 52.49%,再增至 2016 年的 54.73%,但是热带雨林呈持续减少的趋势;(2)4 种森林植被对乔木多样性的贡献有明显差异,均匀度排序是热带雨林>热带山地(低山)常绿阔叶林>暖热性针叶林>热带季节性湿润林,丰富度排序是热带雨林>热带山地(低山)常绿阔叶林>热带季节性湿润林>暖热性针叶林,对乔木多样性贡献的排序是热带雨林>热带山地(低山)常绿阔叶林>热带季节性湿润林>暖热性针叶林;(3)热带雨林和热带季节性湿润林乔木多样性呈现持续减少趋势,4 个时期西双版纳森林植被乔木多样性排序为 1992 年>2009 年>2016 年>2000 年。研究表明,经济活动是影响西双版纳生物多样性的重要原因,保护热带雨林对维持该地区生物多样性具有重要意义。

submitted time 2019-02-25 From cooperative journals:《广西植物》 Hits780Downloads462 Comment 0

6. chinaXiv:201711.02792 [pdf]

2017-Fe05Co05Si.pdf

张蕾
Subjects: Physics >> Condensed Matter: Electronic Structure, Electrical, Magnetic, and Optical Properties

The magnetic entropy change [ΔSM(T;H)] around the phase transition temperature TC is investigated by the scaling method for Fe0:5Co0:5Si, which exhibits a skyrmion phase below TC. The parameters of ΔSM(T;H) exhibit field dependent behaviors. The ΔSM(T;H) curves under high field can be well scaled into a single universal curve independent of external field and temperature. However, ΔSM(T;H) curves under low field become divergent just below TC, which indicates a characteristic of first-order transition. The scaling investigation of ΔSM(T;H) curves indicates that the phase transition in Fe0:5Co0:5Si is of a weak first-order type in low field region, while it is driven into a second-order one under high field. This weak first-order phase transition in low field region resembles that in typical skyrmion system MnSi which is caused by the critical fluctuation. The result suggests that critical fluctuation plays an important role in the phase transition and formation of skyrmion state.

submitted time 2017-11-27 Hits2306Downloads1168 Comment 0

7. chinaXiv:201711.02790 [pdf]

2017-CrNbS.pdf

张蕾
Subjects: Physics >> Condensed Matter: Electronic Structure, Electrical, Magnetic, and Optical Properties

The magnetism of the single crystal Cr1=3NbS2, which exhibits chiral soliton lattice (CSL) state, is investigated. The magnetization displays strong magnetic anisotropy when the field is applied perpendicularly and parallel to the c-axis in low field region (H < HS, HS is the saturation field). The critical exponents of Cr1=3NbS2 are obtained as β = 0.370(4), γ = 1.380(2), and δ = 4.853(6), which are close to the theoretical prediction of three-dimensional Heisenberg model. Based on the scaling equation and the critical exponents, the H ? T phase diagram in the vicinity of the phase transition is constructed, where two critical points are determined. One is a tricrtical point which locates at the intersection between the CSL, forced ferromagnetic (FFM), and paramagnetic (PM) states. The other one is a critical point situated at the boundaries between CSL, helimagnetic (HM), and PM states.

submitted time 2017-11-27 Hits2220Downloads1124 Comment 0

8. chinaXiv:201711.02797 [pdf]

Critical phenomenon in the itinerant ferromagnet Cr11Ge19 studied by scaling of the magnetic entropy change

张蕾
Subjects: Physics >> Condensed Matter: Electronic Structure, Electrical, Magnetic, and Optical Properties

Critical phenomenon of the noncentrosymmetric Cr11Ge19, which exhibits an itinerant ferromagnetic ground state, is investigated by scaling of the magnetic entropy change [ΔSM(T;H)]. It is found that parameters #14;FWHM (the full width at half maximum), ?ΔSmax M (the maximum of the magnetic entropy change), and RCP (the relative cooling power) of ΔSM(T) are governed by the power law of critical exponents. With the critical exponents, ΔSM(T;H) curves are scaled into a universal curve independent of temperature and field, which suggests that the magnetic transition is of a second order type. The universal collapse of ΔSM(T;H) indicates that the critical behavior of Cr11Ge19 can be well described by the scaling laws for the critical phenomenon. Moreover, the ΔSM follows the power law of Hn with n(T;H) = dlnjΔSMj=dln(H). The temperature dependence of n values reach minimum at #24; 71.5 K. Based on the magnetic specific change ΔCp(T;H), the actual magnetic transition temperature is strictly determined as TC = 71:3 #6; 0:2 K for the single crystal Cr11Ge19.

submitted time 2017-11-27 Hits2161Downloads1150 Comment 0

9. chinaXiv:201710.00002 [pdf]

在液滴作用下悬浮薄膜的毛细皱纹标度律

孙博华
Subjects: Physics >> Electromagnetism, Optics, Acoustics, Heat Transfer, Classical Mechanics, and Fluid Dynamics

研究意义: 悬浮于液体的薄膜在其上有个液滴(drop),由于液滴的表面张力的作用,薄膜会发生皱纹。皱纹的长度和数量对于测量和标定薄膜材料的性能非常有意义。 J. Huang, M. Juszkiewicz, W. H. de Jeu, E. Cerda, T.Emrick, N. Menon and T. P. Russell在 Science, 317, 650(2007) 通过细致的实验,并通过曲线拟合得到了薄膜皱纹长度和数量的经验表达式,2010年D. Vella, M. Adda-Bedia and E. Cerda, Soft Matter 6,5778 (2010),利用圆形薄板理论进行了解析和数值分析,从理论上部分地验证了 Huang et al(2007)的经验公式。 存在的问题是: 1. 目前得到的经验表达式是否是普遍适用的结果? 2.如果不是普遍适用,那么在什么情况下可以使用这些经验公式? 3.目前的结果都是在各向同性薄膜的情况下获得的结果,那么对于正交各向同性薄膜的情况如何把现有表达式推广到正交各向同性薄膜? 4.Huang (2007), Vella (2010)和其他成果都是只是研究静态情况,而实际情况是,表面张力的作用是一个动力学的过程,随着时间的发展,皱纹长度和数量要发生变化,如何在静态成果的基础上,推广到皱纹动力学? 5.另外,液滴的半径如果超过毛细尺度,重力就起主导作用,就必须考虑重力的影响(之前的论文都没有考虑),这时的皱纹长度和数量与时间的关系满足什么标度律? 本文的工作: 首先我们使用量纲分析方法,推导出皱纹长度和数量的一般关系,发现皱纹长度和数量由二个组合无量纲参数的联合作用控制,在一般非线性变形的情况下,没有普遍适用的规律(标度律),只有在线性小变形的情况,才有普遍适用的标度律。 在小变形的情况下,皱纹长度主要有薄膜面内刚度与表面张力之比控制,其物理意义就是,在液滴薄膜张力一定的情况下,薄膜面内拉伸性能越好皱纹越长,反之,越短。皱纹数量取决于液滴的半径和薄膜弯曲刚度与表面张力之比,薄膜越容易弯曲皱纹越多,反之,越少。这里的结果完全符合物理观察。 对于小变形情况,我们把各向同性薄膜的情况推广到正交各向同性的情况。 对于皱纹动力学问题,我们利用Tanner的液滴半径随时间的标度律,结合我们得到的结果,成功地得到了皱纹长度和数量的动力学结果。以前没有看到皱纹动力学的结果。 最后,我们给出了重力主导的皱纹长度和数量的表达式,发现在重力主导的情况下,皱纹长度和数量对于给定的问题,是一个常数。以前没有看到重力主导情况下的皱纹结果。

submitted time 2017-09-30 Hits10919Downloads1303 Comment 0

10. chinaXiv:201612.00445 [pdf]

Structure function of holographic quark-gluon plasma: Sakai-Sugimoto model versus its non-critical version

Bu,YY; Yang,JM
Subjects:

Motivated by recent studies of deep inelastic scattering (DIS) off the N=4N=4\mathcal{N}=4 super-Yang-Mills (SYM) plasma, holographically dual to AdS5×S5AdS5×S5AdS_5\times S^5 black hole, we in this note use the spacelike flavor current to probe the inter

submitted time 2016-12-28 Hits616Downloads322 Comment 0

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