Effect of pressure on the flow behavior of polybutene

The rheology of submicron thick polymer melt is examined under high normal pressure conditions by a recently developed photobleached‐fluorescence imaging velocimetry technique. In particular, the validity and limitation of Reynold equation solution, which suggests a linear through‐thickness velocity profile, is investigated. Polybutene (PB) is sheared between two surfaces in a point contact. The results presented in this work suggest the existence of a critical pressure below which the through‐thickness velocity profile is close to linear. At higher pressures however, the profile assumes a sigmoidal shape resembling partial plug flow. The departure of the sigmoidal profile from the linear profile increases with pressure, which is indicative of a second‐order phase/glass transition. The nature of the transition is confirmed independently by examining the pressure‐dependent dynamics of PB squeeze films. The critical pressure for flow profile transition varies with molecular weight, which is consistent with the pressure‐induced glass transition of polymer melt

USNWR College Rankings Reexamined

This paper extends Webster's [2001] analysis of the accuracy of the weighting scheme utilized by U.S. News & World Report (USNWR) to rank colleges and universities according to "widely accepted indicators of national excellence," which he found to be plagued by severe and pervasive multicollinearity.  As in the Webster study, we employ principal component analysis to assess the relative contributions of thirteen criteria used by USNWR in 2004 to rank "top schools" in the national university category.  Although USNWR continues to assign the greatest weight to peer assessment, this study confirms Webster's findings that average SAT/ACT scores of enrolled students is the most significant ranking criterion.  This paper also extends Webster's study by examining the reliability of the USNWR rankings, which have come under repeated criticism for their lack of consistency.  When compared with simulations generated from an estimated principal component regression model, the 2004 USNWR rankings are found to be increasingly more unreliable for lower ranked institutions.  The source of this inconsistency appears to be peer assessment, which is the only subjective criterion used in the USNWR ranking methodology.  This suggests that the rankings might be improved by lowering (or removing entirely) the relative contribution of peer assessment from the USNWR ranking methodology

Ectopic expression of the HLXB9 gene is associated with an altered nuclear position in t(7;12) leukaemias

This article is available open access through the publisher’s website at the link below. Copyright @ 2009 Macmillan Publishers Ltd.No abstract available (Letter to the editor).The Leukaemia Research Fun

An Interactive Procedure for Multiobjective Analysis of Water Resources Allocation

This paper reports on part of IIASA's research concerning regional water management planning, focusing on the Western Skane region in Southern Sweden. The IIASA studies are concerned with four issues of particular importance to water resources management, namely, conflict resolution, criteria of choice, uncertainty, and institutional arrangements. This paper is related primarily to the first two of these issues. An interactive procedure seeking the satisfactory nondominated solution of the multiobjective water resources allocation problem is discussed. It is based on the Powell method with penalty function for the solution of scalar optimization problem and on a constraint and weighting method, or actually a reference objective method, for the solution of the multiobjective optimization problem. Application of the procedure is illustrated by an example referring to the situation in the Kavlinge River system in the Western Skane, Sweden

Opinion formation models based on game theory

A way to simulate the basic interactions between two individuals with different opinions, in the context of strategic game theory, is proposed. Various games are considered, which produce different kinds of opinion formation dynamics. First, by assuming that all individuals (players) are equals, we obtain the bounded confidence model of continuous opinion dynamics proposed by Deffuant et al. In such a model a tolerance threshold is defined, such that individuals with difference in opinion larger than the threshold can not interact. Then, we consider that the individuals have different inclinations to change opinion and different abilities in convincing the others. In this way, we obtain the so-called ``Stubborn individuals and Orators'' (SO) model, a generalization of the Deffuant et al. model, in which the threshold tolerance is different for every couple of individuals. We explore, by numerical simulations, the dynamics of the SO model, and we propose further generalizations that can be implemented.Comment: 18 pages, 4 figure

Price discovery in the cryptocurrency option market : a univariate GARCH approach

Abstract:In this paper, two univariate generalised autoregressive conditional heteroskedasticity (GARCH) option pricing models are applied to Bitcoin and the Cryptocurrency Index (CRIX). The first model is symmetric and the other takes asymmetric effects into account. Furthermore, the accuracy of the GARCH option pricing model applied to Bitcoin is tested. Empirical results indicate that asymmetry is not an important factor to consider when pricing options on Bitcoin or CRIX, this is consistent with findings in the literature. In addition, the GARCH option pricing model provides realistic price discovery within the bid-ask spreads suggested by the market

Homotopy Theory of Strong and Weak Topological Insulators

We use homotopy theory to extend the notion of strong and weak topological insulators to the non-stable regime (low numbers of occupied/empty energy bands). We show that for strong topological insulators in d spatial dimensions to be "truly d-dimensional", i.e. not realizable by stacking lower-dimensional insulators, a more restrictive definition of "strong" is required. However, this does not exclude weak topological insulators from being "truly d-dimensional", which we demonstrate by an example. Additionally, we prove some useful technical results, including the homotopy theoretic derivation of the factorization of invariants over the torus into invariants over spheres in the stable regime, as well as the rigorous justification of replacing $T^d$ by $S^d$ and $T^{d_k}\times S^{d_x}$ by $S^{d_k+d_x}$ as is common in the current literature.Comment: 11 pages, 3 figure

Fast calculation of real fluid properties for steam turbine CFD analysis with the new IAPWS standard on the spline-based table look-Up method (SBTL)

Workshop byl částečně podpořen projektem CZ.1.07/2.3.00/20.0139. Tento projekt je spolufinancován Evropským sociálním fondem a státním rozpočtem České republiky