Silane‐modified PVC pervaporation membranes for bromoform/water separation

The transport properties of a unique family of silane‐modified poly(vinyl chloride) (PVC) pervaporation membranes for the separation of halogenated hydrocarbons from water were investigated. The PVC was modified by using a vinyl silane to improve its resistance to attack by halogenated hydrocarbons and to increase the flux. Two preparation routes were used: Route i included an initiator to promote the vinyl reaction before the hydrolysis and condensation of the methoxy silane group, whereas Route ni did not. The structures of the membranes were characterized and related to the transport properties, as derived from batch pervaporation experiments. The permeability of unmodified PVC membranes increases with exposure to haloorganics at low concentrations. Initially, the modified membranes exhibited a higher permeability than PVC and a lower selectivity. At long pervaporation times, the silane‐modified membranes exhibited a higher selectivity than PVC. The different preparation routes led to different morphologies, which affected the performance of the membranes; Route ni membranes exhibited higher permeabilities and selectivity than Route i membranes. Rubbery polydimethylsiloxane membranes were resistant to haloorganics but their high water permeability and low selectivity make them unsuitable for this pervaporative separation. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1429–1438, 2001     

A shift in task routines during the learning of a motor skill: Group-averaged data may mask critical phases in the individuals' acquisition of skilled performance.

The authors describe a transient phase during training on a movement sequence wherein, after an initial improvement in speed and decrease in variability, individual participants' performance showed a significant increase in variability without change in mean performance speed. Subsequent to this phase, as practice continued, variability again decreased, performance significantly exceeded the gains predicted by extrapolation of the initial learning curve, the type of errors committed changed, and performance became more coherent. The transient phase of increased variability may reflect a mixture of 2 (or more) performance routines before the more effective one is set and mastered, presumably the setting up of a sequence-specific representation. Both group and individual analyses indicated a departure from the single process (e.g., power-law) model of learning. However, although similar phases appeared in the mean group data, there was little correspondence to individual participants' time courses, and the individuals' gains in the second low-variability phase were masked. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Leontief Meets Markov: Sectoral Vulnerabilities Through Circular Connectivity

Economists have been aware of the mapping between an Input-Output (I-O, hereinafter) table and the adjacency matrix of a weighted digraph for several decades (Solow, Econometrica 20(1):29–46, 1952). An I-O table may be interpreted as a network in which edges measure money flows to purchase inputs that go into production, whilst vertices represent economic industries. However, only recently the language and concepts of complex networks (Newman 2010) have been more intensively applied to the study of interindustry relations (McNerney et al. Physica A Stat Mech Appl, 392(24):6427–6441, 2013). The aim of this paper is to study sectoral vulnerabilities in I-O networks, by connecting the formal structure of a closed I-O model (Leontief, Rev Econ Stat, 19(3):109–132, 1937) to the constituent elements of an ergodic, regular Markov chain (Kemeny and Snell 1976) and its chance process specification as a random walk on a graph. We provide an economic interpretation to a local, sector-specific vulnerability index based on mean first passage times, computed by means of the Moore-Penrose inverse of the asymmetric graph Laplacian (Boley et al. Linear Algebra Appl, 435(2):224–242, 2011). Traversing from the most central to the most peripheral sector of the economy in 60 countries between 2005 and 2015, we uncover cross-country salient roles for certain industries, pervasive features of structural change and (dis)similarities between national economies, in terms of their sectoral vulnerabilities.

     

Building user argumentative models

Knowing how a user builds his/her arguments during a discussion gives useful advantages if we want to assist the user or analyse his/her argumentative skills. This paper presents a novel mechanism to build user argumentative models, which captures the argumentative style to generate arguments. To this end, we observe how users generate arguments, and apply a generalised association rules algorithm to discover rules for argument generation. These rules depict the argumentative style of the user. They are composed of an antecedent, which represents the conditions to build an argument, and a consequent, which represents such argument. To evaluate this proposal, we show results obtained in the domain of meeting scheduling. We discovered interesting rules from a group of users discussing in that domain, and checked that about 60% of the arguments that users had generated in a test situation can be also generated from the rules previously learnt, at least partially. Finally, although this work focuses on modelling users’ argumentative style, we discuss how this promising approach could be applied in different knowledge domains.     

Incentive compatible regression learning

We initiate the study of incentives in a general machine learning framework. We focus on a game-theoretic regression learning setting where private information is elicited from multiple agents with different, possibly conflicting, views on how to label the points of an input space. This conflict potentially gives rise to untruthfulness on the part of the agents. In the restricted but important case when every agent cares about a single point, and under mild assumptions, we show that agents are motivated to tell the truth. In a more general setting, we study the power and limitations of mechanisms without payments. We finally establish that, in the general setting, the VCG mechanism goes a long way in guaranteeing truthfulness and economic efficiency.     

Distributed shortest-path protocols for time-dependent networks

 This paper addresses algorithms for networks whose behavior changes with time according to known functions. Because the computation depends on the same functions it attempts to compute, its execution must obey strict timing constraints. When distributed versions of such algorithms are considered, a key difficulty is how to transfer local timing functions among the participating nodes. To that end it is necessary to characterize the parameterization of the functions and accommodate this parameterization in the computation. In particular, we consider the shortest-path problem in networks in which the delay of the edges changes with time according to continuous functions. We present distributed protocols for finding the shortest and minimum delay path under various waiting constraints. We investigate and analyze protocols that exchange local time-delay functions only within limited intervals yet allow every node to calculate its representation in the shortest path in time for it to be used. Received: November 1992 / Accepted: December 1995     

Specifying and analyzing early requirements in Tropos

We present a framework that supports the formal verification of early requirements specifications. The framework is based on Formal Tropos, a specification language that adopts primitive concepts for modeling early requirements (such as actor, goal, and strategic dependency), along with a rich temporal specification language. We show how existing formal analysis techniques, and in particular model checking, can be adapted for the automatic verification of Formal Tropos specifications. These techniques have been implemented in a tool, called the T-Tool, that maps Formal Tropos specifications into a language that can be handled by the NuSMV model checker. Finally, we evaluate our methodology on a course-exam management case study. Our experiments show that formal analysis reveals gaps and inconsistencies in early requirements specifications that are by no means trivial to discover without the help of formal analysis tools.

Close-packed noncircular nanodevice pattern generation by self-limiting ion-mill process

We describe a self-limiting, low-energy argon-ion-milling process that enables noncircular device patterns, such as squares or hexagons, to be formed using precursor arrays of uniform circular openings in poly(methyl methacrylate) defined using electron beam lithography. The proposed patterning technique is of particular interest for bit-patterned magnetic recording medium fabrication, where square magnetic bits result in improved recording system performance. Bit-patterned magnetic medium is among the primary candidates for the next generation magnetic recording technologies and is expected to extend the areal bit density limits far beyond 1 Tbit/in(2). The proposed patterning technology can be applied either for direct medium prototyping or for manufacturing of nanoimprint lithography templates or ion beam lithography stencil masks that can be utilized in mass production.     

The flow of an elastico-viscous fluid past a stretching sheet with partial slip

Summary An analysis is carried out to study the flow characteristics in an elastico-viscous fluid (Walters' liquid-B model) over a stretching sheet with partial slip. The flow is generated due to linear stretching of the sheet. Using suitable similarity transformations on the highly non-linear partial differential equations we derive exact analytical solution with appropriate boundary conditions. The important finding in this communication is the effect of partial slip on the velocity and skin friction coefficient.