分类: 图书馆学、情报学 >> 图书馆学 提交时间: 2016-07-31
摘要: 本文从全人教育的角度,分析香港城市大学邵逸夫图书馆的馆藏、空间和 服务,提出发展全人教育型图书馆的差异化服务模式。其中包括:发掘差异化学科资源需求,根据需求差异配置不同资源,根据差异资源开展各类研究、教学、学习服务,以及整合各类差异化服务发展全人教育型图书馆。
分类: 图书馆学、情报学 >> 图书馆学 提交时间: 2016-07-31
摘要: 过文献分析法、观察法以及社会网络分析法,描绘了图书馆内部员工的人际网络关系图:威胁组织的次级团体、硬性的组织关系、软性的社团关系。在此基础上,讨论了非正式社团对正式组织的影响。建议未来运用社会关系网络的方法来进行“软硬兼施”的人力资源管理,以提升图书馆团队的团结士气、和谐文化和工作效率。
分类: 物理学 >> 基本粒子与场物理学 提交时间: 2016-07-26
摘要: Kibble mechanism drastically underestimates the production of point-like topological defects, as confirmed recently in atomic and condensed matter systems If non-thermally produced, they can be cosmological dark matter of mass 1-10 PeV or heavier If thermalized, skyrimon of mass 1-10 TeV is also a viable dark matter candidate, whose decay may explain e(+/-) spectra in cosmic rays recently measured by PAMELA, FERMI, and HESS Collaborations Models that produce magnetic monopoles below the inflation scale, such as Pati-Salam unification, are ruled out unless new annihilation mechanism for monopoles is introduced (C) 2010 Elsevier B V All rights reserved
分类: 物理学 >> 基本粒子与场物理学 提交时间: 2016-07-25
摘要: In the presence of background fields that spontaneously violate Lorentz invariance, a matter-antimatter asymmetry can be generated even in thermal equilibrium. In this paper we systematically investigate models of this type, showing that either high-energy or electroweak versions of baryogenesis are possible, depending on the dynamics of the Lorentz-violating fields. In addition to the previously studied models of spontaneous baryogenesis and quintessential baryogenesis, we identify two scenarios of interest: baryogenesis from a weak-scale pseudo-Nambu-Goldstone boson with intermediate-scale baryon-number violation, and sphaleron-induced baryogenesis driven by a constant-magnitude vector with a late-time phase transition.
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: 2016-07-19
摘要: We explore the possibility that the observed baryon asymmetry of the Universe is the result of an earlier phase transition in which an extended gauge sector breaks down into the SU(3)(C)xSU(2)(L)xU(1)(Y) of the standard model. Our proto-typical example is the topflavor model, in which there is a separate SU(2)(1) for the third generation from the SU(2)(2) felt by the first two generations. We show that the breakdown of SU(2)(1)xSU(2)(2)-> SU(2)(L) results in lepton number being asymmetrically distributed throughout the three families, and provided the SM electroweak phase transition is not strongly first order, results in a nonzero baryon number, which for parameter choices that can be explored at the LHC may explain the observed baryon asymmetry.
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: 2016-07-19
摘要: We study the properties of g(1), the first excited state of the gluon in representative variants of the Randall-Sundrum (RS) model with the standard model (SM) fields in the bulk. We find that measurements of the coupling to light quarks (from the inclusive cross section for pp -> g(1)-> t (t) over bar), the coupling to bottom quarks (from the rate of pp -> g(1)b), as well as the overall width can provide powerful discriminants between the models. In models with large brane kinetic terms, the g(1) resonance can even potentially be discovered decaying into dijets against the large QCD background. We also derive bounds based on existing Tevatron searches for resonant t (t) over bar production and find that they require M(g)(1)greater than or similar to 950 GeV. In addition, we explore the pattern of interference between the g(1) signal and the nonresonant SM background, defining an asymmetry parameter for the invariant mass distribution. The interference probes the relative signs of the couplings of the g(1) to light quark pairs and to t (t) over bar, and thus provides an indication that the top is localized on the other side of the extra dimension from the light quarks, as is typical in the RS framework.
分类: 物理学 >> 基本粒子与场物理学 提交时间: 2016-07-13
摘要: In this paper, we will illustrate how computer algebra system Cadabra is used in computing the supersymmetric amplitude in pure spinor formalism and provide the source code that computes the tree-level massless 5-gluon amplitude.
分类: 物理学 >> 凝聚态:结构、力学和热性能 提交时间: 2016-07-12
摘要: A robust solid state diffusion joining technique for SiC ceramics was designed with thickness-controlled Ti interlayer formed by Physical Vapor Deposition method and joined by Electric Field-Assisted Sintering Technology. The interface reaction and phase revolution process were investigated in details, and was analyzed in term of equilibrium phase diagram and also concentration-dependent potential diagram of Ti-Si-C ternary system. Interestingly, on the same joining conditions (fixed temperature and annealing duration), the thickness of Ti interlayer determined the concentration and distribution of reactants of Si and C elements in the resultant joint layer, and the respective diffusion distance of Si and C into Ti interlayer dramatically differentiated during the short joining process (only 5 min). In the case of 100nm thickness Ti interlayer, the C concentration saturated quickly in the joint layer and benefited the formation of TiC phase and following Ti3SiC2 phase. When the Ti thickness increase to 1μm, Si atoms easily diffuse through the diluted Ti-C alloy (dense TiC phase not formed), and amount of Ti5Si3 brittle phase was preferential formed. When the thickness of Ti interlayer is 100nm, SiC ceramics were successfully joined at low temperature of 1000°C for 20min with a flexural strength of 168.2MPa which satisfies the application in corrosion environment. All above findings revealed the importance of diffusion kinetics of reactants on the final composition in the solid state reaction, especially in the joining technique for the covalent SiC ceramics. The well-controlled composition in the joint layer of SiC couples will find its application merits in the harsh service environments, such as nuclear cladding for accident-tolerant fuel (ATF) in the environment of steam corrosion, high neutron irradiation, high temperature, etc.).
分类: 数学 >> 控制和优化 分类: 数学 >> 计算数学 提交时间: 2016-07-11
摘要: In this paper, we construct and analyze an efficient m-step Levenberg-Marquardt method for nonlinear equations. The main advantage of this method is that the m-step LM method could save more Jacobian calculations with frozen $(J_k^TJ_k+\lambda_kI)^{-1}J_k^T$ at every iteration. Under the local error bound condition which is weaker than nonsingularity, the m-step LM method has been proved to have $(m+1)$th convergence order. The global convergence has also been given by trust region technique. Numerical results show that the m-step LM method is efficient and could save many calculations of the Jacobian especially for large scale problems.
分类: 物理学 >> 基本粒子与场物理学 提交时间: 2016-07-11
摘要: We explore the possibility that the right-handed top quark is composite. We examine the consequences that compositeness would have on t (t) over bar production at the Tevatron, and derive a weak constraint on the scale of compositeness of order a few hundred GeV from the t (t) over bar inclusive cross section. More detailed studies of differential properties of t (t) over bar production could potentially improve this limit. We find that a composite top can result in an enhancement of the t (t) over bart (t) over bar production rate at the LHC (of as much as 10(3) compared to the Standatd Model four top rate). We explore observables which allow us to extract the four top rate from the backgrounds, and show that the LHC can either discover or constrain top compositeness for wide ranges of parameter space.
分类: 物理学 >> 基本粒子与场物理学 提交时间: 2016-07-11
摘要: We study the decay of a Z' boson into two Z bosons by extending the Landau-Yang theorem to a parent particle decaying into two Z bosons. For a spin-1 parent the theorem predicts that (1) there are only two possible couplings and (2) the normalized differential cross section depends on kinematics only through a phase shift in the azimuthal angle between the two decay planes of the Z boson. When the parent is a Z' the two possible couplings are anomaly induced and CP violating, respectively. At the CERN Large Hadron Collider their effects could be disentangled when both Z bosons decay leptonically.
分类: 物理学 >> 基本粒子与场物理学 提交时间: 2016-07-11
摘要: If a new massive vector boson with nonzero axial couplings to fermions will be observed at LHC, then an upper limit on the scale of new physics could be derived from unitarity of S matrix. The new physics will involve either new massive fermions, or scalars, or even a strongly coupled sector. We derive a model independent bound on the scale of new physics. If M-G/g(A) < 3 TeV and the fermion is a top quark, the upper limit is 78 TeV.
分类: 物理学 >> 基本粒子与场物理学 提交时间: 2016-07-08
摘要: Motivated by the recent observation of the high energy electron and positron excesses in cosmic ray by PAMELA and ATIC/PPB-BETS, we suggest an anomaly-free scenario for the universal extra dimension that localizes the standard model quarks and splits the spectrum of Kaluza-Klein (KK) quarks from KK leptons. When the SM quarks are "well localized" at the boundaries, the most stringent bound of the model (1/R > 510 GeV) comes from the resonance search for the Tevatron dijet channels. Even at the early stage of LHC, one can discover the second KK gluon for masses up to 4 TeV.
分类: 物理学 >> 基本粒子与场物理学 提交时间: 2016-07-08
摘要: We explicitly show that split-universal extra dimension (split-UED), a recently suggested extension of universal extra dimension (UED) model, can nicely explain recent anomalies in cosmic-ray positrons and electrons observed by PAMELA and ATIC/PPB-BETS. Kaluza-Klein (KK)dark matters mainly annihilate into leptons because the hadronic branching fraction is highly suppressed by large KK quark masses and the antiproton flux agrees very well with the observation where no excess is found. The flux of cosmic gamma-rays from pion decay is also highly suppressed and hardly detected in low energy region (E-gamma less than or similar to 20GeV). Collider signatures of colored KK particles at the LHC, especially q(1)q(1) production, are studied in detail. Due to the large split in masses of KK quarks and other particles, hard p(T) jets and missing E-T are generated, which make it possible to suppress the standard model background and discover the signals.
分类: 物理学 >> 基本粒子与场物理学 提交时间: 2016-07-08
摘要: We discuss general on-shell couplings of a scalar with two Z bosons using an operator analysis. In addition to the operator that originated from the Higgs mechanism, two dimension-five operators, one CP even and one CP odd, are generated only at the loop level. Simple formulas are derived for the differential decay distributions when the Z pair subsequently decays into four leptons by computing the helicity amplitudes, from which it is shown the CP-odd operator merely induces a phase shift in the azimuthal angular distribution between the two decay planes of the Z bosons. We also investigate new physics scenarios giving rise to loop-induced decays of a scalar into the ZZ pair, and argue that the total decay width of such a scalar would be an order-of-magnitude smaller than that of a Higgs boson, should such decays be observed in the early running of the LHC. Therefore, the total decay width alone is a strong indicator of the Higgs nature, or the lack thereof, of a scalar resonance in ZZ final states. In addition, we study the possibility of using the azimuthal angular distribution to disentangle effects among all three operators.
分类: 物理学 >> 基本粒子与场物理学 提交时间: 2016-07-08
摘要: A flavor-nonuniversal chiral color model is introduced. It is used for comparison to the recent data on (p) over barp -> (t) over bart. We concluded that the data are consistent with interpretation as an axigluon exchange within 1 sigma and a unique rise and fall behavior is predicated with regard to the asymmetry A(FB)(t) as a function of t (t) over bar invariant mass, which can distinguish our model from others before one discovers the axigluon resonance. Further aspects of the model are discussed. (C) 2009 Elsevier B.V. All rights reserved.
分类: 物理学 >> 基本粒子与场物理学 提交时间: 2016-07-08
摘要: We consider the recent measurement of the top quark forward-backward asymmetry at the Fermilab Tevatron, which shows a discrepancy of slightly more than 2 sigma compared to the standard model prediction. We find that t-channel exchange of a color sextet or triplet scalar particle can explain the measurement, while leaving the cross section for t (t) over bar production within measured uncertainties. Such particles have good discovery prospects by study of the kinematic structure of t (t) over bar + jets at the LHC.
分类: 物理学 >> 交叉学科物理及相关领域的科学与技术 提交时间: 2016-07-07
摘要: 由于现实社会中,并不是每个“海盗”都是绝对理性的,而且等级制度也存在一定的摘要:由于现实社会中,并不是每个“海盗”都是绝对理性的,而且等级制度也存在一定的弹性,因此本文对海盗分金差分方程模型做进一步的分数阶差分理论推广,采用 Caputo 型分数阶差分,构建海盗分金分数阶差分模型,并证明 Cauchy 初值问题解的存在唯一性和解对初值的依赖性;当分数阶差分退化到一阶差分时,解是完全一致的;从而,在理论和实际意义方面对海盗分金问题的分数阶模型的推广做出了合理的解释。
分类: 数学 >> 应用数学 提交时间: 2016-07-07
摘要: 自博弈论中有趣的海盗分金问题(Pirate Game(PG))提出以来,其在理论分析上,仅摘要:自博弈论中有趣的海盗分金问题(Pirate Game(PG))提出以来,其在理论分析上,仅限于逆向递推法和数列递推法。本文首先借鉴这两种方法建立一阶差分模型;而后,考虑到每个海盗不是绝对理性的,等级高的海盗需要依赖等级低一级的海盗的决策而做出最优决策,建立二阶时滞差分模型,在数学原理上对 PG 做深入分析:当τ= 0 时,与实际情况偏差较大;当时滞量 τ=1 时,模型的解和一阶差分模型的解一致,即在现实生活中也存在着做决策时直接咨询自己的第一副手的社会群体。从而,在现代分析方法的层次上,本文给出一个 PG 的新的合理的数学解释。
分类: 数学 >> 数学(综合) 提交时间: 2016-07-05
摘要: In this paper, the Pazy's Fixed Point Theorems of monotone $\alpha-$nonexpansive mapping $T$ are proved in a uniformly convex Banach space $E$ with the partial order ``$\leq$". That is, we obtain that the fixed point set of $T$ with respect to the partial order ``$\leq$" is nonempty whenever the Picard iteration $\{T^nx_0\}$ is bounded for some comparable initial point $x_0$ and its image $Tx_0$. When restricting the demain of $T$ to the cone $P$, a monotone $\alpha-$nonexpansive mapping $T$ has at least a fixed point if and only if the Picard iteration $\{T^n0\}$ is bounbed. Furthermore, with the help of the properties of the normal cone $P$, the weakly and strongly convergent theorems of the Picard iteration $\{T^nx_0\}$ are showed for finding a fixed point of $T$ with respect to the partial order ``$\leq$" in uniformly convex ordered Banach space.