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1.
Several theoretical aspects in leading (1-loop) and higher (2-loop) order as well as various approaches of extracting leading
twist-2 parton distributions from structure function measurements are discussed and summarized. Their implications for the
small-x region (x⩽10−2) are analyzed and compared with alternative approaches where higher twist contributions (‘fans’) are added to the twist-2
LO terms in the evolution equations. The second part of these lectures deals with longitudinally polarized parton distributions
related to the structure functiong
1, in particular with various scenarios to explain the total spin structure of nucleons, including the gluon anomaly as well.
Specific (realistic) tests for discriminating between these alternatives are discussed as well asx-dependent expectations, in particular for neutron targets in connection with the Bjorken sum rule. Furthermore, various theoretical
expectations and sum rules for the transverse (chiral-even) structure functiong
2 are presented and very recent developments of transverse chiral-odd (‘transversity’) distributions are briefly discussed. 相似文献
2.
以有限温度Brueckner-Hartree-Fock(BHF)方法为基础,利用质量算子的空穴线展开,计算了不同温度和密度下的核物质中单核子势和核子有效质量,特别是研究和讨论了基态关联效应和三体核力贡献对热核物质中单核子势的影响. 研究表明,基态关联和三体核力对单核子势的密度和温度依赖性均有重要影响. 基态关联导致的重排修正具有排斥性,大大减弱了低动量区域单核子势的吸引性,而且基态关联效应对单核子势的贡献随密度增大而增强,随温度升高而减弱. 三体核力对基态关联的影响是导致单核子势中重排项贡献减小. 在高密
关键词:
有限温度BHF方法
质量算子空穴线展开
重排修正
单核子势
有效质量 相似文献
3.
《中国物理 B》2021,30(7):74201-074201
Single pixel imaging is a novel imaging technique, and it becomes a focus of research in recent years due to its advantages such as high lateral resolution and high robustness to noise. Imaging speed is one of the critical shortcomings, which limits the further development and applications of this technique. In this paper, we focus on the issues of imaging efficiency of a single pixel imaging system. We propose semi-continuous wavelet transform(SCWT) protocol and introduce the protocol into the single pixel imaging system. The proposed protocol is something between continuous wavelet transform and discrete wavelet transform, which allows the usage of those smooth(usually non-orthogonal, and they have advantages in representing smooth signals compressively, which can improve the imaging speed of single pixel imaging) wavelets and with limited numbers of measurements. The proposed imaging scheme is studied, and verified by simulations and experiments. Furthermore, a comparison between our proposed scheme and existing imaging schemes are given. According to the results, the proposed SCWT scheme is proved to be effective in reconstructing a image compressively. 相似文献
4.
5.
Magdy E. Amin 《Physics letters. A》2004,320(5-6):338-346
The limit distribution of the layer block spin variables of the mean spherical model under Neumann–Dirichlet boundary conditions is investigated in the presence of an inhomogeneous external field which changes sign at distance Lx (0x1) from the Neumann boundary. The behaviour of the equation of state is studied in different temperature and field regimes: high-temperature bulk limit, critical finite-size scaling regime, and low-temperature moderate-field regime. A new classes of critical behaviour for the characteristic function of the limit distributions are obtained and studied in the three different regimes. 相似文献
6.
The hot rotating compound systems formed in heavy ion collisions are studied using the statistical theory with a view to determine
the spin and temperature dependence of nuclear shapes. Shape transitions are observed for these systems at particular spin
values. The neutron and proton separation energies for heavier high spin systems have been evaluated. Results are presented
for
70
170
Yb and
78
194
Pt. 相似文献
7.
针对0.13 μm CMOS(Complementary Metal-Oxide-Semiconductor)体硅外延工艺下FPGA(Field Programmable Gate Arrays)配置片反熔丝PROM(Programmable-Read-Only-Memory)进行了单粒子效应(Single Event Effects SEEs)的加速器地面模拟试验研究。以PROM的存储容量、数据类型和工艺差异性为研究变量,考核与验证其在不同种类和能量粒子入射的系列性加速器地面SEEs模拟试验。研究结果表明,相对于8 Mbits PROM而言,空片16 Mbits PROM抗辐射性能最优,且从翻转饱和截面上说,16 Mbits的PROM具备更高的可靠性,优于国外同系列的芯片类型,试验用PROM芯片的单粒子锁定阈值>99.0 MeV·cm2/mg。另一方面,研究0.13 μm CMOS普通与深阱工艺技术下PROM芯片单粒子翻转效应异同性的实验数据表明,在高LET(Linear Energy Transfer)处的两者抗辐射性能并无明显变化,但是低LET处(LET翻转阈值)的加固效果较为明显,即抗辐射技术能力主要体现在LET翻转阈值的提升而非翻转截面的减小。Single event effects (SEEs) have been characterized and investigated on one-time configured devices for field-programmable-gate-arrays (FPGA) of programmable-read-only-memory (PROM) in 0.13 μm Complementary Metal-Oxide-Semiconductor (CMOS) technology.The variables of their memory size,written data and technology have been taken into consideration as the key parameters affecting the SEEs sensitivity when testing and verifying the reliability/radiation tolerance on self-made PROMs by heavy ions.The results show that,16 Mbits PROM within blanked data has been studied that it has better performance to radiation tolerance as compared with the 8 Mbits PROMs.Additionally,16 Mbits PROMs have the higher reliability,if based on the viewpoint of the saturated single event upset cross-section.To the single event latchup,16 Mbits PROMs were exposed to a total fluence of 107 ions/cm2 at the linear energy transfer (LET) of 99.0 MeV·cm2/mg and no obvious fluctuation of current has been observed.Additionally,as comparing the zone of high LET value,0.13 μm CMOS transistors with deep-well technology present a better radiation hardened approach than normal technology,especially in improving the threshold of LET at the zone of low LET value. 相似文献
8.
WANG Yan-Zhao ZHANG Hong-Fei GAO Yong-Hua HOU Zhao-Yu DONG Jian-Min DUAN Chun-Gui ZUO Wei 《中国物理C(英文版)》2009,33(4):263-268
Extended quark distribution functions are presented obtained by fitting a large amount of experi-mental data of the ι-A DIS process on the basis of an improved nuclear density model. The experimental data of ι-A DIS processes with A≥ 3 in the region 0.0010 ≤ x ≤ 0.9500 are quite satisfactorily described by using the extended formulae. Our knowledge of the influence of nuclear matter on the quark distributions is deepened. 相似文献
9.
The fixed-trace ensemble of random complex matrices is the fundamental model that excellently describes the entanglement in the quantum states realized in a coupled system by its strongly chaotic dynamical evolution [see H. Kubotani, S. Adachi, M. Toda, Phys. Rev. Lett. 100 (2008) 240501]. The fixed-trace ensemble fully takes into account the conservation of probability for quantum states. The present paper derives for the first time the exact analytical formula of the one-body distribution function of singular values of random complex matrices in the fixed-trace ensemble. The distribution function of singular values (i.e. Schmidt eigenvalues) of a quantum state is so important since it describes characteristics of the entanglement in the state. The derivation of the exact analytical formula utilizes two recent achievements in mathematics, which appeared in 1990s. The first is the Kaneko theory that extends the famous Selberg integral by inserting a hypergeometric type weight factor into the integrand to obtain an analytical formula for the extended integral. The second is the Petkovšek–Wilf–Zeilberger theory that calculates definite hypergeometric sums in a closed form. 相似文献
10.
Extended quark distribution functions are presented obtained by fitting a large amount of experimental data of the l-A DIS process on the basis of an improved nuclear density model. The experimental data of l-A DIS processes with A≥3 in the region 0.0010≤x≤0.9500 are quite satisfactorily described by using the extended formulae. Our knowledge of the influence of nuclear matter on the quark distributions is deepened. 相似文献
11.
Liu Shenggang 《International Journal of Infrared and Millimeter Waves》1981,2(6):1253-1262
The problems concerning the specification of electron equilibrium distribution function for the kinetic theory of ECRM are investigated in this paper. After detailed analysis of the published equilibium distribution functions, several conclusion have been achieved. 相似文献
12.
根据非线性局部Lyapunov向量方法和增长模繁殖方法,选取Lorenz63模型和Lorenz96模型的不同状态为例,对集合预报与单一预报的预报技巧开展了对比研究.结果表明:与单一预报比较,集合预报的均方根误差和型异常相关有明显改善,随预报时间推移,改善效果越显著,且集合平均优于单一预报的实验个例数逐渐增多.就概率分布(f)而言,单一预报状态的f与真实状态基本一致,不随时间变化;而集合平均预报状态的f则随时间呈现出值域变窄、峰值变大的特点.表明随预报时间的延长,单一预报状态为混沌吸引子上的随机状态,而集合平均预报状态为吸引子子集上的随机状态,这可能是集合平均误差小于单一预报的原因. 相似文献
13.
Robert Eckardt Jörg Hansper Manfred F. Gari 《Zeitschrift für Physik A Hadrons and Nuclei》1992,343(4):443-449
In a re-analysis of nucleon form factors in perturbative quantum chromodynamics we examine the
-dependence of the nucleon quark distribution amplitude by means of some model distribution amplitudes. We point out some problems that arise in the determination of the
-evolution of the distribution amplitude. Our suggestions to cure these problems are discussed and resulting nucleon quark distribution amplitudes are presented. These give reasonable agreement with the available data for the form factors.Work is supported by Deutsche Forschungsgemeinschaft (Ga 153-13-1) and partially by NATO (0581/87) 相似文献
14.
磁镊是一种高精度的单分子技术,它用磁场对连有生物大分子的超顺磁球产生磁力,通过追踪磁球的位置来测量生物大分子的长度信息.磁镊包括横向磁镊和纵向磁镊.纵向磁镊空间精度高,但昂贵;横向磁镊简单便宜,但由于受其成像原理的限制,一般情况下只能连接较长的DNA等生物大分子,且其空间精度较差,进而限制了其应用范围.为了解决这个问题,本文改进了横向磁镊,用片层光照明的方法使光线主要被磁球散射,从而能够直接观察到吸附在样品槽侧壁上的磁球,这使得测量短连接的底物成为可能.对于实际应用的检测,首先测试了包含270 bp发卡结构的0.5μm双链DNA,用其中发卡结构的"折叠-去折叠"跳变过程证明了改进后的横向磁镊的确可以追踪短DNA等生物大分子.然后,进一步用16μm的λ-DNA检验了实验系统.最后,将新型横向磁镊与普通横向磁镊及纵向磁镊在小力和大力条件下拉伸不同长度DNA的噪声进行了比较,发现改进后的横向磁镊在空间精度上明显优于普通横向磁镊,与纵向磁镊相比也无明显差异.以上结果证明了改进后的横向磁镊的精度优势,并扩展了横向磁镊的应用范围. 相似文献
15.
采用1948—2005年NCEP/NCAR全球温度资料构建温度关联矩阵,研究表明:为了滤除关联“噪声”,采用信度为001的统计检验是比较合适的.对日温度序列做step=5d,10d,…的滑动平均继而构建关联矩阵发现:365—730d可能是温度场时间尺度上的一个转折点;全球平均关联系数Cglobal的总体变化趋势是随step的增加而增大,但趋势逐渐变缓;相关系数绝对值大于03的正负强关联点对数也随之增加;位于赤道东太平洋海域的正关联中心(区域Ⅰ)(1625°W—775°E,75°N—125°S)和位于北太平洋海域的负关联中心(区域Ⅱ)(1575°W—325°E,275°—475°N )是值得重点关注的两个区域,二者之间存在较强的负相关;取长度为10 a滑动窗口研究Cglobal随时间的演变特征发现,Cglobal在1981—1987a之间发生了明显的跃变,并且这一跃变可能是年代际尺度上的行为;区域Ⅰ和Ⅱ对这一跃变也有清晰的反映,区域Ⅱ的跃变略滞后于区域Ⅰ;与此同时北太平洋海域关联系数的最小值点随时间演变还出现了明显的“位移”.
关键词:
温度场
关联矩阵
时间尺度
跃变 相似文献
16.
17.
移动通信应用为人类移动规律的研究提供了独特的数据来源. 本文通过城市手机用户的分布数据,研究城市移动人群的整体动力学行为. 借助随机矩阵理论的方法,通过比较移动人群数据与随机数据在互相关矩阵谱分布上的差异,发现移动人群数据互相关矩阵的相关系数均值、最大本征值及其对应的本征向量明显偏离于随机互相关矩阵的分布,指出这种差异体现了城市移动人群的整体行为特性,且这种差异在不同时间段也会有所不同. 研究结果体现出相关系数的均值和最大本征值的波动趋势,并指出本征向量成员权重的时空模式与城市移动人群整体行为特征的波动过
关键词:
随机矩阵理论
移动人群
宏观行为 相似文献
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压缩测量矩阵的构造是压缩感知的核心工作之一.循环矩阵由于其对应离散卷积且具有快速算法被广泛应用于压缩测量矩阵.本文力图将混沌的优点和循环矩阵的优点相结合,提出基于混沌序列的循环压缩测量矩阵.混沌循环测量矩阵元素的产生仅需要利用混沌的内在确定性,即利用混沌映射公式、初始值以及一定的采样间隔就可以产生独立同分布的随机序列;同时混沌序列的外在随机性可以满足压缩测量矩阵对随机性的要求.本文给出了使用Cat混沌映射时混沌循环测量矩阵的构造方法,以及该矩阵RIPless特性的检验.研究了采用构造的混沌循环测量矩阵对一维和二维信号进行压缩测量的效果,并与采用传统的循环测量矩阵的效果进行了比较.结果表明,混沌循环测量矩阵对于一维和二维信号都具有很好的恢复效果,且对二维信号的恢复性能要优于已有的循环矩阵.从相图角度分析了混沌循环测量矩阵优于已有的循环矩阵的机理,指出混沌的内在确定性和外在随机性的有机结合是所构造的混沌循环测量矩阵性能优于传统的循环矩阵的本质性原因. 相似文献