Critical Biot's number for Determination of the Sensitivity of Spherical Ceramics to Thermal Shock

A critical Blot number, which determines both the sensitivity of spherical ceramics to quenching and the durations of the temperature-wave propagation and the thermal stresses in the ceramics subjected to thermal shock, is theoretically obtained. The results prove that once the Blot number of a ceramic sphere is greater than the critical number, its thermal shock failure will be such a rapid process that the failure only occurs in the initial regime of heat conduction, whereas the thermal shock failure of the ceramic sphere is uncertain in the course of heat conduction. The presented results provide a guide to the selection of the ceramics applied in the thermostructural engineering with thermal shock.     

一维快装置中心反应率模拟计算的灵敏度和不确定度分析

采用广义微扰理论和离散纵标输运计算方法,推导了中心反应率比值对重要核反应参数的灵敏度的计算公式。以一维快基准装置Jezebel-Pu239为例,计算了其中心反应率比值对关键核数据的灵敏度,并结合多群协方差数据,分析了其中心反应率比值计算中由于核数据的不确定度所引入的不确定度及其来源。根据计算结果以及评价数据的协方差信息,建议对Pu-239的非弹截面数据进行更精细的评价,以期降低反应率比的模拟计算不确定度。On the base of the generalized perturbation theory and SN method, the theoretical model for calculating the sensitivity and uncertainty of reaction rates ratio (RRR) versus nuclear data is developed. Taking Jezebel-Pu239 critical benchmarking facility as an example, the sensitivity of F49/F25 ratio versus important nuclear data is calculated, as well as the uncertainty arising from the nuclear data. Basing on the sensitivity and uncertainty analysis as well as the covariance information of input evaluated data, refined evaluation of the inelastic data of Pu-239 is considered as a feasible measure to reduce the uncertainty of reaction rates ratios.     

Dynamical Critical Exponent for the Majority-Vote Model

We investigate the dynamical behavior of the isotropic majority-vote model on a square lattice using a combination of damage spreading and finite-size scaling methods. For initial damage D(0)1/2, the dynamical phase diagram exhibits a chaotic-frozen phase transition at a critical noise parameter q _c =0.0818±0.0002, while for D(0)1/2 the damage does not propagate for any value of the model's parameter 0q<1/2. From simulations at q _c , we find that the dynamical critical exponent is z=0.65±0.05.     

Mean-Field Critical Behavior for the Contact Process

The contact process is a model of spread of an infectious disease. Combining with the result of ref. 1, we prove that the critical exponents take on the mean-field values for sufficiently high dimensional nearest-neighbor models and for sufficiently spread-out models with d>4:()– _c as _c and ()( _c–)^–1 as _c, where () and () are the spread probability and the susceptibility of the infection respectively, and _c is the critical infection rate. Our results imply that the upper critical dimension for the contact process is at most 4.     

Forecast for the Next Eon: Applied Cosmology and the Long-Term Fate of Intelligent Beings

Cosmology seems extremely remote from everyday human practice and experience. It is usually taken for granted that cosmological data cannot rationally influence our beliefs about the fate of humanity—and possible other intelligent species—except perhaps in the extremely distant future, when the issue of heat death (in an ever-expanding universe) becomes actual. Here, an attempt is made to show that it may become a practical question much sooner, if an intelligent community wishes to maximize its creative potential. We estimate, on the basis of a greatly simplified model, the rate of loss of potentially useful information due to the delay in undertaking the colonization of the largest gravitationally bound structures in an accelerating universe. In addition, we argue for a natural cosmological extension of the classical taxonomy of advanced technological communities given by Kardashev. New developments in the fields of anthropic self-selection and physical eschatology give, for the first time, solid foundations to such results. This may open some new (and possibly urgent) issues in the areas of future policy making and transhumanist studies generally. It may also give us a slightly better perspective on the SETI endeavor.     

Critical indices for the charged Bose gas

A self-consistent version of the static random phase approximation leads to a quasi-particle energy satisfying ?(k)=Ak^v for small k, where v ≈ 1.8. The critical indices are those of an ideal Bose gas with this spectrum.     

Percus-Yevick equation for an inhomogeneous fluid: Critical region

The critical region of a locally nonuniform fluid with gaussian density inhomogeneity is investigated. Nonclassical behaviour is found; critical exponents agree very well with those obtained from the perturbation theory of liquids. The action of an external field shifts the critical region and weakens the critical behaviour. Discussed effects could be verified experimentally.     

Critical exponents for nuclear multifragmentation: dynamical lattice model

We present a dynamical and dissipative lattice model, designed to mimic nuclear multifragmentation. Monte Carlo simulations with this model show a clear signature of critical behaviour and reproduce experimentally observed correlations. In particular, using techniques devised for finite systems, we could obtain two of its critical exponents, whose values are in agreement with those of the universality class to which nuclear multifragmentation is supposed to belong.