同时考虑传染媒介和传播延迟的复杂网络病毒传播行为研究

提出一种新的流行病传播模型,基于平均场理论,研究传染媒介和传播延迟同时存在对网络中流行病传播行为的影响.理论分析和仿真结果表明,传染媒介和传播延迟同时存在显著增强了网络中流行病爆发的危险性,并加速了流行病的传播.研究还发现,对于给定的有效传播率,均匀网络中流行病的感染程度分别与传染媒介的传染概率和传播延迟呈对数关系,无标度网络中流行病的感染程度与传染媒介的传染概率呈幂率关系,而与传播延迟之间则存在线性关系。     

复杂网络中考虑不完全免疫的病毒传播研究

复杂网络中不完全免疫包括免疫失败和免疫失效两种情况,本文研究两者同时存在对网络病毒传播行为的影响,基于平均场理论,提出一种新的传播模型.理论分析表明,免疫失败和免疫失效同时存在显著降低了网络的传播临界值,增强了病毒的感染程度.根据传播临界值与免疫节点密度、免疫成功率以及免疫失效率之间的关系,给出有效控制网络病毒传播的策略.通过数值仿真进行验证。     

A Class of Rumor Spreading Models with Population Dynamics

Based on the characteristics of rumor spreading in online social networks, this paper proposes a new rumor spreading model. This is an improved SIS rumor spreading model in online social networks that combines the transmission dynamics and population dynamics with consideration of the impact of both of the changing number of online social network users and different levels of user activity. We numerically simulate the rumor spreading process. The results of numerical simulation show that the improved SIS model can successfully characterize the rumor spreading behavior in online social networks. We also give the effective strategies of curbing the rumor spreading in online social networks.     

A Novel LO Power Injection Method for SIS Mixers

We propose a novel LO power injection method developed for SIS mixers in this paper. Based on the feature of extremely small LO power requirements of SIS quantum mixing, the new method fulfills SIS pumping through a DC/IF route based built-in LO path, which is composed of an additional LO waveguide and the existing microstrip choke filter on the junction substrate. With the new method, traditional external LO diplexers(e.g., crossguide-couplers or beamsplitters) become unnecessary, resulting in a lower loss, compact, and stable receiver system. Experiments at 110- and 230 GHz bands have shown that the present method is efficient in coupling sufficient pumping power to SIS junctions from general LO sources, and the receiver sensitivities have a further improvement of about 10 K. We expect this method is also able to be applied into submillimeter wave band for SIS mixers.     

Sexually transmitted infections and the marriage problem

We study an SIS epidemiological model for a sexually transmitted infection in a monogamous population where the formation and breaking of couples is governed by individual preferences. The mechanism of couple recombination is based on the so-called bar dynamics for the marriage problem. We compare the results with those of random recombination – where no individual preferences exist – for which we calculate analytically the infection incidence and the endemic threshold. We find that individual preferences give rise to a large dispersion in the average duration of different couples, causing substantial changes in the incidence of the infection and in the endemic threshold. Our analysis yields also new results on the bar dynamics, that may be of interest beyond the field of epidemiological models.     

Epidemic spreading on networks with vaccination

In this paper, a new susceptible-infected-susceptible (SIS) model on complex networks with imperfect vaccination is proposed. Two types of epidemic spreading patterns (the recovered individuals have or have not immunity) on scale-free networks are discussed. Both theoretical and numerical analyses are presented. The epidemic thresholds related to the vaccination rate, the vaccination-invalid rate and the vaccination success rate on scale-free networks are demonstrated, showing different results from the reported observations. This reveals that whether or not the epidemic can spread over a network under vaccination control is determined not only by the network structure but also by the medicine's effective duration. Moreover, for a given infective rate, the proportion of individuals to vaccinate can be calculated theoretically for the case that the recovered nodes have immunity. Finally, simulated results are presented to show how to control the disease prevalence.     

Systematics of elliptic flow in heavy-ion collisions

We analyze elliptic flow from SIS to RHIC energies systematically in a realistic dynamical cascade model. We compare our results with the recent data from STAR and PHOBOS collaborations on elliptic flow of charged particles at midrapidity in Au+ Au collisions at RHIC. In the analysis of elliptic flow at RHIC energy, we find a good fitting with data at 1.5 times a scaling factor to our model, which characterizes that the model is required to have extra pressure generated from the subsequent parton scattering after the initial minijet production. In energy dependence of elliptic flow, we notice re-hardening nature at RHIC energies. Both these two observations would probably imply the possible formation of quark-gluon plasma.     

Periodic Wave of Epidemic Spreading in Community Networks

It was reported by Cummings ef al. [Nature 427 （2004） 344] that there are periodic waves in the spatiotemporal data of epidemics. For understanding the mechanism, we study the epidemic spreading on community networks by both the SIS model and the SIRS model. We find that with the increase of infection rate, the number of total infected nodes may be stabilized at a fixed point, oscillatory waves, and periodic cycles. Moreover, the epidemic spreading in the SIS model can be explained by an analytic map.     

Epidemic threshold and immunization on generalized networks

The susceptible–infected–susceptible (SIS) model is widely adopted in the studies of epidemic dynamics. When it is applied on contact networks, these networks mostly consist of nodes connected by undirected and unweighted edges following certain statistical properties, whereas in this article we consider the threshold and immunization problem for the SIS model on generalized networks that may contain different kinds of nodes and edges which are very possible in the real situation. We proved that an epidemic will become extinct if and only if the spectral radius of the corresponding parameterized adjacent matrix (PAM) is smaller than 1. Based on this result, we can evaluate the efficiency of immune strategies and take several prevailing ones as examples. In addition, we also develop methods that can precisely find the optimal immune strategies for networks with the given PAM.     

Analysis of epidemic models with demographics in metapopulation networks

In this paper, two susceptible–infected–susceptible (SIS) epidemic models are presented and analyzed by reaction–diffusion processes with demographics in metapopulation networks. Firstly, an SIS model with constant-inputting is discussed. The model has a disease-free equilibrium, which is locally asymptotically stable when the basic reproduction number is less than unity, otherwise it is unstable. It has an endemic equilibrium, which is globally asymptotically stable. Secondly, in another SIS model, the birth rate is the form of Logistic. Similarly, the stability of disease-free equilibrium and endemic equilibrium is also proved. Finally, numerical simulations are performed to illustrate the analytical results.     

Scaled model measurements of the sandwiched V-antenna

At frequencies above a few hundred GHz, waveguide mixer blocks become extremely difficult to build, so open structure feeds may be more appropriate. One promising planar antenna structure, which can easily be integrated with SIS junctions, is the sandwiched V-antenna. The antenna is completely enclosed in dielectric by placing it between substrate and superstrate blocks. Using a model scaled to a center frequency of 10 GHz, we investigated the beam pattern as a function of frequency, and measured its dependence on gaps between the super-and substrates. We plan to test the structure at a frequency of 345 GHz and to compare it with waveguide horn antennas for possible use in submillimeter astronomical receivers. The antenna patterns and analysis in this work are substantially more extensive than earlier published results.     

The extinction and persistence of the stochastic SIS epidemic model with vaccination

In this paper, we discuss the dynamics of a stochastic SIS epidemic model with vaccination. When the noise is large, the infective decays exponentially to zero regardless of the magnitude of _R0$R_0$. When the noise is small, sufficient conditions for extinction exponentially and persistence in the mean are established. The results are illustrated by computer simulations.     

Epidemics and chaotic synchronization in recombining monogamous populations

We analyze the critical transitions (a) to endemic states in an SIS epidemiological model, and (b) to full synchronization in an ensemble of coupled chaotic maps, on networks where, at any given time, each node is connected to just one neighbour. In these “monogamous” populations, the lack of connectivity in the instantaneous interaction pattern—that would prevent both the propagation of an infection and the collective entrainment into synchronization—is compensated by occasional random reconnections which recombine interacting couples by exchanging their partners. The transitions to endemic states and to synchronization are recovered if the recombination rate is sufficiently large, thus giving rise to a bifurcation as this rate varies. We study this new critical phenomenon both analytically and numerically.     

基于元胞自动机考虑传播延迟的复杂网络病毒传播研究

基于元胞自动机,研究传播延迟对复杂网络病毒传播动力学行为的影响,提出一种新的易染状态-感染状态-易染状态(SIS)传播模型.研究表明,传播延迟的存在显著降低了网络的传播临界值,增强了网络中病毒爆发的危险性.研究还发现,随着传播延迟的增大,病毒的感染程度以及传播速率都明显增大.此外,SIS传播模型不仅能够反映病毒的平均传播趋势,而且可以描述病毒随时间的动态演化过程以及病毒的爆发和消亡等概率事件,从而有效地克服了利用平均场方法构建的微分方程模型只能反映病毒平均传播趋势的局限性.同时,还给出有效控制网络中病毒传 关键词： 复杂网络 病毒传播 元胞自动机 传播延迟     

Negative-index dispersion and accidental mode degeneracy in an asymmetric spoof-insulator-spoof waveguide

It has been recently demonstrated that negative-index dispersion and mode degeneracy can be achieved by manipulating a spoof-insulator-spoof(SIS) waveguide. In this paper, we propose a new SIS waveguide, which is composed of two spoof surface plasmon polaritons(SSPPs) waveguides drilled with periodic rhomboidal grooves. Both the symmetric and asymmetric cases are investigated. Our simulation results show that the asymmetric SIS waveguides are more significant.By tailoring the tilt of the rhomboidal grooves, the negative-index dispersion can be achieved and the microwave band gap(MBG) can be effectively modulated. At a critical tilt, there appears an accidental mode degeneracy at the edge of the first Brillouin zone. The excitation and propagation of the two coupled modes sustained by the asymmetric SIS waveguides are also demonstrated.     

Integrated Josephson effect suppression electromagnets for sis receivers

We describe a method for integrating a Josephson current suppression electromagnet along with a superconductor-insulator-superconductor (SIS) mixer. In this technique, circuitry already in place for matching the SIS mixing device with the antenna is used as the conductor for an electromagnet. Reduced cost and size are among the advantages achieved by elimination of external magnets.     

A Low Noise NbTiN-Based 850 GHz SIS Receiver for the Caltech Submillimeter Observatory

We have developed a niobium titanium nitride (NbTiN) based superconductor-insulator-superconductor (SIS) receiver to cover the 350 micron atmospheric window. This frequency band lies entirely above the energy gap of niobium (700 GHz), a commonly used SIS superconductor. The instrument uses an open structure twin-slot SIS mixer that consists of two Nb/AlN/NbTiN tunnel junctions, NbTiN thin-film microstrip tuning elements, and a NbTiN ground plane. The optical configuration is very similar to the 850 GHz waveguide receiver that was installed at the Caltech Submillimeter Observatory (CSO) in 1997. To minimize front-end loss, we employed reflecting optics and a cooled beamsplitter at 4 K. The instrument has an uncorrected receiver noise temperature of 205K DSB at 800 GHz and 410K DSB at 900 GHz. The degradation in receiver sensitivity with frequency is primarily due to an increase in the mixer conversion loss, which is attributed to the mismatch between the SIS junction and the twin-slot antenna impedance. The overall system performance has been confirmed through its use at the telescope to detect a wealth of new spectroscopic lines.     

Probing string fragmentation in nuclear matter: Lepton-nucleus scattering

We introduce a new model for the fragmentation of strings in a “medium” of hadronic objects. These objects may be hadrons, resonances, or string pieces from the fragmentation of other strings. As a first application we treat the fragmentation of a string inside a nuclear medium, taking into account interactions of the fragmenting string with spectator nucleons (spectators of the hard process which created the string in the first place). We compare with neutrino-neon data.     

An Integrated Sideband-Separating SIS Mixer Based on Waveguide Split Block for 100 GHz Band with 4.0–8.0 GHz IF

We have developed an integrated sideband-separating SIS mixer for the 100 GHz band based on the waveguide split block. The measured receiver noise temperatures with 4.0–8.0 GHz IF are less than 60 K in the LO frequency range of 90–110 GHz, and a minimum value of around 45 K is achieved at 100 GHz. The image rejection ratios are more than 10 dB in the frequency range of 90–110 GHz. We have installed the sideband-separating SIS mixer into an atmospheric ozone-measuring system at Osaka Prefecture University and successfully observed an ozone spectrum at 110 GHz in SSB mode. This experimental result indicates that the sideband-separating SIS mixer is very useful for astronomical observation as well as atmospheric observation.     

Influence of Chiral Mean Field on Kaon In-plane Flow in Heavy Ion Collisions

The influence of the chiral mean field on the K⁺ in-plane flow in heavy ion collisions at SIS energy is investigated within covariant kaon dynamics. For the kaon mesons inside the nuclear medium a quasi-particle picture including scalar and vector fields is adopted and compared to the standard treatment with a static potential. It is confirmed that a Lorentz force from spatial component of the vector field provides an important contribution to the in-medium kaon dynamics and strongly counterbalances the influence of the vector potential on the K⁺ in-plane flow. The calculated results show that the new FOPI data can be reasonably described using the Brown & Rho parametrization, which partly takes into account the correction of higher order contributions in the chiral expansion. This indicates that one can abstract the information on the kaon potential in a nuclear medium from the analysis of the K⁺ in-plane flow.