The combination of surface enhanced Raman spectroscopy and an ionic liquid as a model system to study the adhesion interface between sulfur and brass

The adhesion of steel cord to rubber is very important for the quality of reinforced rubber products, e.g. tyres. Therefore, steel cord is often plated with brass, which will lead to Cu_xS bonds after reaction with sulfur compounds in the rubber. A unique in‐situ analytical method has been developed to investigate the sulfur–brass interface: the sulfuring process has been simulated via a heating process in a water‐free transparent ionic liquid with added sulfur and the reaction at the brass‐coated steel cord has been monitored in real time with Raman spectroscopy. The grown Cu_xS film seems to be similar to the layers at the steel cord interface in real rubber materials. The model system can also be used to perform electrochemical measurements at the same time. The thickness of the Cu_xS layer has been estimated from the measured current during a cathodic stripping process. Copyright © 2013 John Wiley & Sons, Ltd.     

Exact value of the correlation factor for the divacancy mechanism in FCC crystals: the end of a long quest

Using a double Laplace and Fourier transform of the transport equation for the divacancy, we obtain the exact values of the return probabilities of the vacancy in the close vicinity of the tracer atom. The final value falls within the confidence interval determined by Monte-Carlo simulations of previous investigators, and last but not least, the diagonal elements t₁₁ and t₂₂ of the T matrix are shown to be equal. Future developments of the method are presented.     

Experiments on the interactions between impurities and solitary waves in lattice model

The interactions between solitary waves and impurities have been studied experimentally in a 1D nonlinear coupled pendulum chain under vertical excitation. The mass and the coupling are unique, except a single pendulum with length impurity in the chain. The experiment reveals: the long impurity repels breather and attracts kink while the short one attracts breather and repels kink under higher frequency driving, and the long impurity attracts breather and repels kink while the short one repels breather and attracts kink under the lower frequency driving. These results prove the current theoretical prediction based on continuum-limit approximation.     

晶格不具备五度及六度以上对称轴的双轴证明是正确的

指出晶格不具备五度及六度以上对称轴的双轴证明是正确的     

Ferromagnetism in the Hubbard model: instability of the Nagaoka state on the triangular,honeycomb and kagome lattices

In order to analyse the lattice dependence of ferromagnetism in the two-dimensional Hubbard model we investigate the instability of the fully polarised ferromagnetic ground state (Nagaoka state) on the triangular, honeycomb and kagome lattices. We mainly focus on the local instability, applying single spin flip variational wave functions which include majority spin correlation effects. The question of global instability and phase separation is addressed in the framework of Hartree-Fock theory. We find a strong tendency towards Nagaoka ferromagnetism on the non-bipartite lattices (triangular, kagome) for more than half filling. For the triangular lattice we find the Nagaoka state to be unstable above a critical density of n = 1.887 at U = ∞, thereby significantly improving former variational results. For the kagome lattice the region where ferromagnetism prevails in the phase diagram widely exceeds the flat band regime. Our results even allow the stability of the Nagaoka state in a small region below half filling. In the case of the bipartite honeycomb lattice several disconnected regions are left for a possible Nagaoka ground state.     

Experimental study on the micromechanical behavior of a PBX simulant using SEM and digital image correlation method

The micro-scale mechanical behavior of a polymer-bonded explosive (PBX) simulant was experimentally studied using a scanning electron microscope (SEM) imaging system and digital image correlation (DIC) method. The semi-circular bend (SCB) test was chosen for the study. During the testing, a series of SEM images of the specimen was acquired in situ. The natural micro-structural features of the specimen were used as random speckle pattern for DIC analysis. The displacement and strain fields at the area of interest were obtained by DIC. The deformation and damage of PBX were analyzed. Heterogeneous strain fields demonstrated the damage evolution underneath the specimen surface and predicted possible micro-crack growth. Based on the contour plots of the correlation coefficient, the formation and extension of microscopic cracks were quantitatively analyzed.     

Intermediate Energy Reactions Versus Heavy-Ion Fusion: Light Particle Emission and Post-Saddle Friction in the Presence of Deformation Effects *

A decaying nucleus undergoes a change in deformation when it fissions. This affects the particle emission in the fission process. Using the dynamical Langevin model, we investigate the role of deformation in the sensitivity of post-saddle neutrons and light charged particles (LCPs) to the post-saddle friction strength ($beta$) for heavy nuclei $^{240}$Am produced with different initial conditions: (i) a low excitation energy $E^*$ and a large spin $ell$ (provided via a fusion mechanism) and (ii) a high $E^*$ and a large $ell$ as well as a higher $E^*$ but a small $ell$ (provided in peripheral and near-central intermediate energy heavy-ion reactions, respectively). It is shown that deformation obviously enhances the sensitivity of post-saddle neutrons to $beta$ at intermediate-energy peripheral collisions and that for case (i), the drop of LCPs emission due to deformation makes post-saddle LCPs to be almost insensitive to $beta$, but for case (ii) LCPs still have a significant change with $beta$. Furthermore, we find that post-saddle LCPs display a greater sensitivity to $beta$ for near-central collisions than for peripheral collisions. These results suggest that given the deformation effects, to better probe post-saddle dissipation properties with neutrons (LCPs) in experiments, it is best to choose those excited heavy nuclear systems populated in peripheral (near-central) collisions at intermediate energies.     

The effect of a constant number of particles on the pair correlation function and the density profile in a one-dimensional lattice gas

A one-dimensional lattice gas (Ising model) of lengthL and with nearest-neighbor couplingJ is considered in a canonical ensemble with fixed number of particlesN=L/2. Exact expressions and asymptotic forms for largeL are derived for the density-density correlation function, using periodic boundary conditions, and for the density (magnetization) profile, using antisymmetric boundary conditions. The density-density correlation function,g, assumes for temperaturesT> T, withT = 2J(_BlnL)^–1 and forL large, the formg(x) =g ^gc(x) +BL ^–1 +a(x)L ^–1 +O(L^–2) wherex is a distance between considered lattice sites,B is known from earlier work of Lebowitz and Percus,(1b) anda(x) decays exponentially forx . For TT, the correlation function and the density profile behave differently, the latter exhibiting a step in the middle of the interface.     

Effect of time delay in FitzHugh-Nagumo neural model with correlations between multiplicative and additive noises

We study the effect of time delay in the FitzHugh-Nagumo neural model with correlations between multiplicative and additive noise terms. Based on the corresponding Fokker-Planck equation, the explicit expressions of the stationary probability distribution function (SPDF), the mean first passage time (MFPT) and the signal-to-noise ratio (SNR) are obtained, respectively. Research results show that: (i) the system undergoes a succession of two phase transitions (i.e., the reentrance phenomenon) as the noise correlation parameter is increased and a (single) phase transition as the time delay is increased. (ii) The MFPT as a function of the multiplicative noise intensity exhibits a maximum. This maximum for MFPT identifies the noise enhanced stability (NES) effect, the noise correlation parameter intensifies the NES effect while the time delay, and the additive noise intensity weakens it. (iii) The existence of a maximum in the SNR as a function of the multiplicative noise intensity is the identifying characteristic of the stochastic resonance (SR) phenomenon, the noise correlation parameter enhances the SR while the time delay, and the additive noise intensity weaken it.     

Helix-coil transition in the case of interaction between two chains

Based on the generalized model of polypeptide chain the helix-coil transition in two chains, which are interacting abreast, is studied. There are four types of interaction (hh, hc, ch, cc). The Hamiltonian of system includes the basic Hamiltonian for two chains and the term which is responsible for interactions. It is shown that, when the energy of one type interaction (hh, cc) is more than the energy of mixed-type interaction (hc, ch), the correlation length grows sharply and melting interval becomes narrower. The system has a nontrivial behavior when the energy of mixed-type interactions (hc, ch) is higher than that of the one-type interaction (hh, cc). In this case one can observe the growth of the correlation length, and the melting curve has a two-stage character. The portion of junctions and the average length of helical fractions show that the merging and breakup of helical fractions take place.     

Correlation between the Optical Properties and Structure of GRS-Active Substrates Based on Silver Films

The relationship between the optical properties of GRS-active substrates based on silver films and the parameters of their surface roughness have been studied by methods of mathematical statistics (correlation, regression, and factor analyses). The equations of nonlinear regression connecting these quantities were obtained. It is established that most correlatable are the maximum value of the optical density with the distance between islands and with the coefficient of their shape, and also its relation to the halfwidth of the optical density band of a silver film with the mentioned characteristics of the islands.     

Effects of correlations between the real and imaginary parts of quantum noise on intensity fluctuation for a saturation laser model

This paper studies the effects of cross-correlations between the real and imaginary parts of quantum noise on the laser intensity in a saturation laser model. It derives the analytic expressions of the intensity correlation function ${C(\tau)}$ and the associated relaxation time ${T({C})}$ in the case of a stable locked phase resulting from the cross-correlation ${\lambda_q}$ between the real and imaginary parts of quantum noise. Based on numerical computations it finds that the presence of cross correlations between the real and imaginary parts of quantum noise slow down the decay of intensity fluctuation, i.e., it causes the increase of intensity fluctuation.     

Effects of correlations between the real and imaginary parts of quantum noise on intensity fluctuation for a saturation laser model

This paper studies the effects of cross-correlations between the real and imaginary parts of quantum noise on the laser intensity in a saturation laser model. It derives the analytic expressions of the intensity correlation function C（τ） and the associated relaxation time T（C） in the case of a stable locked phase resulting from the cross-correlation λq between the real and imaginary parts of quantum noise. Based on numerical computations it finds that the presence of cross correlations between the real and imaginary parts of quantum noise slow down the decay of intensity fluctuation, i.e., it causes the increase of intensity fluctuation.     

The effect of stochastic accelerating and delay probability with the velocity and the gap between vehicles on traffic flow

This paper proposes a new combined cellular automaton (CA) model considering the driver behavior of stochastic acceleration and delay with the velocity of the preceding vehicle and the gap between the successive vehicles based on the WWH model and the noise-first NaSch model. It introduces the delay probability varying with the gap, adds the anticipation headway and increases the acceleration with a certain probability. Through these simulations, not only can the metastable state and start--stop wave be obtained but also the synchronized flow which the wide moving jam results in. Moreover, the effect of stochastic acceleration and delay on traffic flow is discussed by analyzing the correlation of traffic data. This indicates that synchronized flow easily emerges in the critical area between free flow and synchronized flow when acceleration and delay are synchronized or their probability is close to 0.5.     

不同土壤类型的粗糙地面与其下方埋藏目标复合电磁散射研究

利用MOM研究了不同土壤类型的一维有耗介质粗糙地面与其下方二维埋藏目标的复合电磁散射问题,在数值计算中,引入了锥形入射波以减少粗糙面模拟中由于人为截断所引起的计算误差.当给定入射波频率、土壤成分及土壤温度和土壤湿度后,可以根据相关模型计算出土壤的相对介电常数.数值结果以二维无限长导体圆柱为例,利用 Monte Carlo方法统计计算了双站复合散射截面随土壤类型、土壤湿度、入射波频率及均方根高度等的变化情况,并做了详细分析及讨论.该研究结果对于探地雷达在民用、军事、工业等多领域的应用具有一定的理论指导价值. 关键词： 粗糙地面 土壤类型 相对介电常数 四成分模型     

Temperature variation of the Debye-Waller factors of Ba++ and F− ions in BaF2 powder by x-ray diffraction

The temperature variation of the Debye-Waller factors of Ba⁺⁺ and F⁻ ions in BaF₂ powder has been studied using x-ray powder diffraction over the temperature range 77°–298°K. A continuous flow cryostat has been specially fabricated for this purpose for the YPC 50 NM powder diffractometer available in the department. The Debye-Waller factors of Ba⁺⁺ and F⁻ between room temperature and 879°K have been measured using single crystal neutron diffraction by Cooperet al. Theoretical lattice dynamics shell model calculations using a 7-parameter model in a quasiharmonic approximation have been done over a temperature range 77° to 879°K. The theoretical values have been compared with the present x-ray measurements and the single crystal neutron diffraction values and the results are discussed.     

Random walk properties of lattices and correlation factors for diffusion via the vacancy mechanism in crystals

Random walk properties and correlation factors for diffusion via the vacancy mechanism are calculated and compared for various three-dimensional lattices. By applying the theory of random walks on an imperfect lattice, the correlation factor for impurity diffusion is calculated rigorously for the five jump frequency model in the fee lattice.Presented at the Symposium on Random Walks, Gaithersburg, MD, June 1982.     

光度法对不同土地利用类型河流在不同水期氮磷分布特性及定量源解析研究

氮和磷是水环境生物生长和繁殖必须的营养成分,影响水体初级生产力的水平,且水体富营养化水平与氮磷形态密切相关,随着水体环境的改变,沉积物会向水体释放氮磷,造成二次污染。同时,对外源氮磷污染来源的贡献进行定量识别,可有效管理和控制水体氮磷污染负荷。毗河和石亭江是沱江的重要支流,影响着长江母亲河的水质。采用钼锑抗分光光度法和连续提取法研究在枯水期和丰水期毗河和石亭江水体和表层沉积物中总氮(TN)、总磷(TP)及各形态氮磷的分布特性,对比不同土地利用类型河流氮磷行为特性及释放风险,并采用Multiple Linear Regression of the Absolute Principal Component Scores(APCS-MLR)受体模型进行氮磷污染源的识别和量化。研究结果表明：(1)研究区水体和表层沉积物中氮磷均处于不同程度的污染水平,水体枯水期TP的主要贡献者是颗粒态无机磷(PIP)和颗粒态有机磷(POP),而丰水期却是颗粒态无机磷(PIP)和溶解态无机磷(DIP),两水期水体中TN的主要贡献者是硝态氮(NO^-₃-N)和有机氮(ON)...     

传感器和Origin7.0软件在电脑控制光强与距离关系的实验中应用

研究用电脑控制光强与距离关系的实验中,用光强传感器测量光的照度,电脑软件采集光照度与距离的数据,用Origin7.0软件处理实验数据,得到受光物体的照度与距离的平方成反比。