Stability of the crystal-melt system in the growing of large lithium niobate crystals by the low melt level Czochralski technique

The Lyapunov stability of the crystal-melt system and the solidification rate is studied for the growing of lithium niobate crystals by the low melt level Czochralski technique. The relaxation time is calculated as a function of growth conditions. The curves of transient processes are plotted at various variable perturbations. It is shown that, for optically homogeneous crystals to be produced, the stability of the solidification rate rather than the crystal-melt system as a whole should be ensured. The stability of the solidification rate is found to be maximal at the maximum temperature gradient at the solidification interface and the minimum melt level in a crucible.     

On the differential capacitance of the n- and p-type gallium arsenide electrode

Impedance measurements on the n- and p-type GaAs electrode show that in both cases, a depletion region exists under reverse bias. The capacitive behaviour of n-type GaAs is relatively simple and allows to determine the position of the conduction and valence band edge at the surface with respect to a reference electrode level. From the pH-dependence of this position, it follows that an acid-base equilibrium is established at the GaAs surface. The impedance behaviour of p-type GaAs is rather complex, and is interpreted on the basis of a model in which localized levels at large energy distance from the valence band edge are involved. The results indicate that the position of the band edges at the surface of GaAs in contact with a given electrolyte is essentially the same for n- and p-type material. The data obtained permit to explain qualitatively the electrochemical reactivity of the hexacyanoferrate (III) ion as well as the lack of reactivity of certain reducing agents at the GaAs electrode.     

The horizontal structure of the sound field in the ocean

Results of calculating the horizontal structure of acoustic field in the ocean with a canonical sound velocity profile are presented. The calculation is performed in the framework of geometrical acoustics by combining the fields of water-path rays at every point with allowance for their phases and amplitudes. The field distribution at a fixed depth is found to be not very informative: within a cycle length, it contains 1–3 maxima, which are mainly caused by the caustics present at the given depth. The width of caustics is ～0.1–1 km. Between the caustics, as well as in their absence, the field amplitude is much smaller than that in the regions of caustics and varies depending on the phases and amplitudes of rays arriving at a given point. The comparison of the calculated horizontal field structure with that obtained from full-scale measurements for the regions between the caustics is difficult because of the possible fluctuations of sound propagation conditions.     

Search for the critical point and the onset of deconfinement

A review of the current experimental situation on the search for a critical point in the QCD phase diagram and the onset of deconfinement is given. Ongoing (STAR, NA61), as well as previous (NA49) experiments are presented. Their main results up-to-now are summarized and their findings are put into a general context. The future experimental program (CBM at FAIR, MPD at NICA) is discussed as well.     

On the localization of plastic strain at the prefailure stage and the possibility of predicting the site and time of ductile rupture

The localization of macrodeformation during the transition from plastic flow to ductile rupture is studied for a wide class of metals. It is found that the mechanism behind this process is the same as that behind plastic deformation and as such can be described as a change in the type of localized deformation autowave in the following sequence: phase autowave → steady dissipative structure → collapse of autowave or its contraction at the site of ensuing failure. The kinetic characteristics of an autowave collapsing at the prefailure stage, which can be found experimentally, allow one to predict the spatio-temporal coordinates of rupture long before its signs appear.     

Application of the time-temperature superposition principle to the mechanical characterization of elastomeric adhesives for crash simulation purposes

In the automotive industry, finite element simulation is widely used to ensure crashworthiness. Mechanical material data over wide strain rate and temperature ranges are required as a basis. This work proposes a method reducing the cost of mechanical material characterization by using the time-temperature superposition principle on elastomeric adhesives. The method is based on the time and temperature interdependence which is characteristic for mechanical properties of polymers. Based on the assumption that polymers behave similarly at high strain rates and at low temperatures, a temperature-dominated test program is suggested, which can be used to deduce strain rate dependent material behavior at different reference temperatures. The temperature shift factor is found by means of dynamic mechanical analysis according to the WLF-equation, named after Williams, Landel and Ferry. The principle is applied to the viscoelastic properties as well as to the failure properties of the polymer. The applicability is validated with high strain rate tests.     

Using dileptons to probe the color glass condensate

The rapidity and transverse momentum dependence of the nuclear modification ratio for dilepton production at RHIC and LHC is presented, calculated in the color glass condensate (CGC) framework. The transverse momentum ratio is compared for two distinct dilepton mass values and a suppression of the Cronin peak is verified even for large mass. The nuclear modification ratio suppression in the dilepton rapidity spectra, as obtained experimentally for hadrons at RHIC, is verified for LHC energies at large transverse momentum, although not present at RHIC energies. The ratio between LHC and RHIC nuclear modification ratios is evaluated in the CGC, showing the large saturation effects at LHC compared with the RHIC results. These results consolidate the dilepton as a most suitable observable to investigate the QCD high density approaches.     

Pressure dependence of the radial breathing mode of carbon nanotubes: the effect of fluid adsorption

The pressure dependence of shifts in the vibrational modes of individual carbon nanotubes is strongly affected by the nature of the pressure transmitting medium as a result of adsorption at the nanotube surface. The adsorbate is treated as an elastic shell which couples with the radial breathing mode (RBM) of the nanotube via van der Waal interactions. Using analytical methods as well as molecular simulation, we observe a low frequency breathing mode for the adsorbed fluid at approximately 50 cm-1, as well as diameter dependent upshifts in the RBM frequency with pressure, suggesting metallic nanotubes may wet more than semiconducting ones.     

On the physical origin of conical bubble structure under an ultrasonic horn

The cavitation field generated by an ultrasonic horn at low frequency and high power is known to self-organize into a conical bubble structure. The physical mechanism at the origin of this bubble structure is investigated using numerical simulations and acoustic pressure measurements. The thin bubbly layer lying at horn surface is shown to act as a nonlinear thickness resonator that amplifies acoustic pressure and distorts acoustic waveform. This mechanism explains the self-stabilization of the conical bubble structure as well as the generation of shock wave and the focusing at very short distance.     

Dynamical approach to the cosmological constant

We consider a dynamical approach to the cosmological constant. There is a scalar field with a potential whose minimum occurs at a generic, but negative, value for the vacuum energy, and it has a nonstandard kinetic term whose coefficient diverges at zero curvature as well as the standard kinetic term. Because of the divergent coefficient of the kinetic term, the lowest energy state is never achieved. Instead, the cosmological constant automatically stalls at or near zero. The merit of this model is that it is stable under radiative corrections and leads to stable dynamics, despite the singular kinetic term. The model is not complete, however, in that some reheating is required. Nonetheless, our approach can at the very least reduce fine-tuning by 60 orders of magnitude or provide a new mechanism for sampling possible cosmological constants and implementing the anthropic principle.     

过苯胺黑聚合物的双极化子态

利用改进的Ginder-Epstein模型研究聚苯胺黑的双极化子态, 给出其键序波幅、芳环扭角、电子能级、理论吸收谱和电荷分布,并与极化子进行对比。结果发现双极化子激发能为3.08eV, 晶格驰豫宽度涉及12格点与极化子相当;键交错驰豫深度大约为极化子的2倍,畸变中心芳环扭角高达68.35°大于极化子中心扭角的2倍。两个能隙态几乎简并,吸收谱低能峰为1.6eV。     

Renormalization of the Mass Gap

We have explicitly shown that QCD is the color gauge invariant theory at non-zero mass gap as well. It has been defined as the value of the regularized full gluon self-energy at some finite point. The mass gap is mainly generated by the nonlinear interaction of massless gluon modes. All this allows one to establish the structure of the full gluon propagator in the explicit presence of the mass gap. In this case, the two independent general types of formal solutions for the full gluon propagator as a function of the regularized mass gap have been found. The nonlinear iteration solution at which the gluons remain massless is explicitly present. The existence of the solution with an effective gluon mass is also demonstrated.     

Precise predictions for the Higgs-boson masses in the NMSSM

The particle discovered in the Higgs-boson searches at the LHC with a mass of about \(125 \, \mathrm{GeV}\) can be identified with one of the neutral Higgs bosons of the Next-to-Minimal Supersymmetric Standard Model (NMSSM). We calculate predictions for the Higgs-boson masses in the NMSSM using the Feynman-diagrammatic approach. The predictions are based on the full NMSSM one-loop corrections supplemented with the dominant and sub-dominant two-loop corrections within the Minimal Supersymmetric Standard Model (MSSM). These include contributions at \(\mathcal {O}{(\alpha _t \alpha _s, \alpha _b \alpha _s, \alpha _t^2,\alpha _t\alpha _b)}\), as well as a resummation of leading and subleading logarithms from the top/scalar top sector. Taking these corrections into account in the prediction for the mass of the Higgs boson in the NMSSM that is identified with the observed signal is crucial in order to reach a precision at a similar level as in the MSSM. The quality of the approximation made at the two-loop level is analysed on the basis of the full one-loop result, with a particular focus on the prediction for the Standard Model-like Higgs boson that is associated with the observed signal. The obtained results will be used as a basis for the extension of the code FeynHiggs to the NMSSM.     

Highlights from the COMPASS experiment

The Compass experiment at CERN is studying the nucleon spin structure with a 160 GeV polarized muon beam and polarized targets as well as hadron structure with 190 GeV pion, kaon and proton beams. The paper gives an overview of the results for the helicity and transverse spin structure of the nucleon. A first result from the spectroscopy experiments, the observation of a resonance with exotic JPC = 1- + quantum numbers at 1660 MeV is also presented. The paper ends with an outlook to future measurements.     

基于节点拓扑特征的中国基金公司共持网络持股行为波动相关性

选取2003—2012年期间半年度中国基金公司持上市公司股票份额面板数据为样本数据,以基金公司为节点,以同一时刻共持同一家上市公司股票关系为边,以同一时刻共持的上市公司数量为权重,构建中国基金公司共持关系结构等价加权网络(简称共持网络).结合统计物理学等方法,分析了共持网络的拓扑结构稳定性及具有不同拓扑特征值的节点随时间演变过程中与共持网络中三类节点集合持股行为波动相关性.三类节点集合分别为t-1时刻基于某一股票形成的共持关系完全连通子图节点集合(第一类节点集合)、t-1时刻共持网络中非完全连通子图的节点集合(第二类节点集合)、t时刻新进入共持网络的节点集合(第三类节点集合).分析结果显示:1)节点与第二类节点集合持股行为波动呈正相关,且相关系数随着节点集聚系数的增强而增大;2)只有当节点的度和点强度值较高时,节点与第一类和第二类节点集合的持股行为呈正相关;3)不同拓扑特征条件下的节点与第三类节点集合的持股行为均不存在波动相关性.本文提供了一个研究持股行为相关性的新思路,并为进一步研究股票市场结构等价网络及节点重要性差异提供了基础.     

Finite-size behavior near the critical point of QCD phase-transition

It is pointed out that the finite-size effect is not negligible in locating the critical point of quantum colordynamics (QCD) phase transitions at current relativistic heavy ion collisions. The finite-size scaling form of the critical related observable is suggested. Its fixed point behavior at critical incident energy can be served as a reliable identification of a critical point and nearby boundary of QCD phase transition. How to experimentally find the fixed point behavior is demonstrated by using 3D-Ising model as an example. The validity of the method at finite detector acceptances at RHIC is also discussed.     

Enhancing the accelerated beam current in the booster synchrotron by optimizing the transport line beam propagation

In this paper, we present the results of transverse beam emittance and twiss parameter measurement of an electron beam, delivered by a 20 MeV microtron which is used as a pre-injector system for a booster synchrotron in the Indus Accelerator Facility at RRCAT Indore. Based on these measured beam parameters, beam optics of a transport line was optimized and its results are also discussed in this paper. This beam transport line is used to transport the electron beam from the 20 MeV microtron to the booster synchrotron. The booster synchrotron works as a main injector for Indus-1 and Indus-2 synchrotron radiation facilities. To optimize the beam optics of a transport line for proper beam transmission through the line as well as to match the beam twiss parameters at the beam injection point of another accelerator, it is necessary to know the transverse beam emittance and twiss parameters of the beam coming from the first one. A MATLAB-based GUI program has been developed to calculate the beam emittance and twiss parameters, using quadrupole scan method. The measured parameters have been used for beam transport line optimization and twiss parameters matching at booster injection point. After this optimization, an enhancement of ～50% beam current has been observed in the booster synchrotron.     

Half-Space Problem for the Discrete Boltzmann Equation: Condensing Vapor Flow in the Presence of a Non-condensable Gas

We consider a non-linear half-space problem related to the condensation problem for the discrete Boltzmann equation and extend some known results for a single-component gas to the case when a non-condensable gas is present. The vapor is assumed to tend to an assigned Maxwellian at infinity, as the non-condensable gas tends to zero at infinity. We assume that the vapor is completely absorbed and that the non-condensable gas is diffusively reflected at the condensed phase and that the vapor molecules leaving the condensed phase are distributed according to a given distribution. The conditions, on the given distribution, needed for the existence of a unique solution of the problem are investigated. We also find exact solvability conditions and solutions for a simplified six+four-velocity model, as the given distribution is a Maxwellian at rest, and study a simplified twelve+six-velocity model.     

Effect of the magnetic field from the accelerating system on the beam dynamics in the cyclotron

Magnetic components of the HF field in a cyclotron can change the transverse beam size and the phase width of bunches during acceleration. As a consequence, the phase portraits of the beam at the entrance to the electrostatic deflector and thus the efficiency of the extraction system can change. Expressions are obtained for the components of the magnetic field from the HF system in the vicinity of the cyclotron median plane. The effect of this field on the beam parameters during acceleration and at the entrance to the electrostatic deflector is shown by numerical simulation. For the C235 proton cyclotron, the beam parameter variation is as large as 50%.     

Entanglement between the future and the past in the quantum vacuum

We note that massless fields within the future and past light cone may be quantized as independent systems. The vacuum is shown to be a nonseparable state of these systems, exactly mirroring the known entanglement between the spacelike separated Rindler wedges. This leads to a notion of timelike entanglement. We describe an inertial detector which exhibits a thermal response to the vacuum when switched on at t=0, due to this property. The feasibility of detecting this effect is discussed, with natural experimental parameters appearing at the scale of 100?GHz.