Internal union dynamics during a strike: A quasi-experimental study.

Hypothesized that union members on strike will (a) give a higher evaluation of the union and of the leadership, (b) evaluate the benefit package more highly after the strike, (c) become more militant against the employer during the strike, (d) report more willingness to participate in union activities, and (e) show more intraunion cohesion during the strike. Random samples of members of 9 local unions (3 each from Ford, General Motors, and Chrysler) were surveyed on 4 occasions: before the 1976 bargaining, during the strike at Ford, after settlement of the national contract, and 7 mo after the strike ended. Usable responses from a questionnaire totaled 1,182 (405 strikers, 777 nonstrikers). With the exception of greater intraunion cohesion during the strike, all hypotheses were confirmed. (18 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Distributed MST for constant diameter graphs

This paper considers the problem of distributively constructing a minimum-weight spanning tree (MST) for graphs of constant diameter in the bounded-messages model, where each message can contain at most B bits for some parameter B. It is shown that the number of communication rounds necessary to compute an MST for graphs of diameter 4 or 3 can be as high as and , respectively. The asymptotic lower bounds hold for randomized algorithms as well. On the other hand, we observe that O(log n) communication rounds always suffice to compute an MST deterministically for graphs with diameter 2, when B = O(log n). These results complement a previously known lower bound of for graphs of diameter Ω(log n). An extended abstract of this work appears in Proceedings of 20th ACM Symposium on Principles of Distributed Computing, August 2001.     

On the complexity of distributed stable matching with small messages

We consider the distributed complexity of the stable matching problem (a.k.a. “stable marriage”). In this problem, the communication graph is undirected and bipartite, and each node ranks its neighbors. Given a matching of the nodes, a pair of unmatched nodes is called blocking if they prefer each other to their assigned match. A matching is called stable if it does not induce any blocking pair. In the distributed model, nodes exchange messages in each round over the communication links, until they find a stable matching. We show that if messages may contain at most B bits each, then any distributed algorithm that solves the stable matching problem requires ${\Omega(\sqrt{n/B\log n})}We consider the distributed complexity of the stable matching problem (a.k.a. “stable marriage”). In this problem, the communication graph is undirected and bipartite, and each node ranks its neighbors. Given a matching of the nodes, a pair of unmatched nodes is called blocking if they prefer each other to their assigned match. A matching is called stable if it does not induce any blocking pair. In the distributed model, nodes exchange messages in each round over the communication links, until they find a stable matching. We show that if messages may contain at most B bits each, then any distributed algorithm that solves the stable matching problem requires W(?{n/Blogn}){\Omega(\sqrt{n/B\log n})} communication rounds in the worst case, even for graphs of diameter O(log n), where n is the number of nodes in the graph. Furthermore, the lower bound holds even if we allow the output to contain O(?n){O(\sqrt n)} blocking pairs, and if a pair is considered blocking only if they like each other much more then their assigned match.     

INVESTIGATION OF THE K2 ALGORITHM IN LEARNING BAYESIAN NETWORK CLASSIFIERS

We experimentally study the K2 algorithm in learning a Bayesian network (BN) classifier for image detection of cytogenetic abnormalities. Starting from an initial BN structure, the K2 algorithm searches the BN structure space and selects the structure maximizing the K2 metric. To improve the accuracy of the K2-based BN classifier, we investigate the K2 algorithm initial ordering, search procedure, and metric. We find that BN structures learned using random initial orderings, orderings based on expert knowledge, or a scatter criterion are comparable and lead to similar classification accuracies. Replacing the K2 search with hill-climbing search improves the accuracy as does the inclusion of hidden nodes in the BN structure. Also, we demonstrate that though the maximization of the K2 metric solicits structures providing improved inference, these structures contribute to only limited classification accuracy.     

Approximating the Visible Region of a Point on a Terrain

Given a terrain and a point p on or above it, we wish to compute the region R _p that is visible from p. We present a generic radar-like algorithm for computing an approximation of R _p . The algorithm interpolates the visible region between two consecutive rays (emanating from p) whenever the rays are close enough; that is, whenever the difference between the sets of visible segments along the cross sections in the directions specified by the rays is below some threshold. Thus the density of the sampling by rays is sensitive to the shape of the visible region. We suggest a specific way to measure the resemblance (difference) and to interpolate the visible region between two consecutive rays. We also present an alternative algorithm, which uses circles of increasing radii centered at p instead of rays emanating from p. Both algorithms compute a representation of the (approximated) visible region that is especially suitable for is-visible-from-p queries, i.e., given a query point q on the terrain determine whether q is visible from p. Finally, we report on the experiments that we performed with these algorithms and with their corresponding fixed versions, using a natural error measure. Our main conclusion is that the radar-like algorithm is significantly better than the others.     

Freeze concentration of milk and saline solutions in a liquid–solid fluidized bed: Part I. Experimental

Fluidized bed freeze concentration is a novel technique that uses a fluidized bed heat exchanger (FBHE) to concentrate liquids through the process of freeze concentration. Ice formed on the cooled surface of the vertical heat exchanger is removed by particles fluidized inside the FBHE. In this paper, the operating conditions are reported for freeze concentration of saline solutions and milk in FBHE. The operation was tested with equilateral 4 mm and then 5 mm particles at different bed porosities, cooling rates and NaCl and milk concentrations. Experiments with NaCl solutions showed that the 5 mm particles were more aggressive than 4 mm in removing ice from the heat exchanger wall. Whilst particle size was considered responsible for this, the particle shape could have played a major role. A theoretical analysis on effect of FBHE parameters showed the size of particles to exert influence on FBHE performance. The result from experiments with skim milk and whole milk maintained the conclusions formed previously with NaCl experiments with regard to the effect of tested parameters on operational stability. However, the ice formed from milk was more difficult to remove than the ice formed from NaCl solutions. Whole milk showed even more resistance to ice removal. Skim milk was freeze concentrated from 13% to 27% TS content in these experiments. Installing a wash screen further improved the purity of separated ice.     

Scheduling multipacket frames with frame deadlines

We consider scheduling information units called frames, each with a delivery deadline. Frames consist of packets, which arrive online in a roughly periodic fashion, and compete on allocation of transmission slots. A frame is deemed useful only if all its packets are delivered before its deadline. We focus on a “proportional” variant, where the value of each frame is proportional to its size, but the sizes and periods of the frames are arbitrary. We give a constant-competitive algorithm for this setting, assuming bounded jitter and some slack in the frames’ deadlines, the latter of which is necessary. Using standard techniques, our algorithm yields polylog-competitive algorithms for general instances with slack and bounded jitter.     

On the Galerkin/Finite-Element Method for the Serre Equations

A highly accurate numerical scheme is presented for the Serre system of partial differential equations, which models the propagation of dispersive shallow water waves in the fully-nonlinear regime. The fully-discrete scheme utilizes the Galerkin / finite-element method based on smooth periodic splines in space, and an explicit fourth-order Runge–Kutta method in time. Computations compared with exact solitary and cnoidal wave solutions show that the scheme achieves the optimal orders of accuracy in space and time. These computations also show that the stability of this scheme does not impose very restrictive conditions on the temporal stepsize. In addition, solitary, cnoidal, and dispersive shock waves are studied in detail using this numerical scheme for the Serre system and compared with the ‘classical’ Boussinesq system for small-amplitude shallow water waves. The results show that the interaction of solitary waves in the Serre system is more inelastic. The efficacy of the numerical scheme for modeling dispersive shocks is shown by comparison with asymptotic results. These results have application to the modeling of shallow water waves of intermediate or large amplitude.     

Icarus’ predicament: Managing the pathologies of overspecification and overdesign

The phenomenon of overspecification and overdesign is well known in all industries: developing features that are not needed by the customer causes excess development efforts, missed due dates, terminated projects and higher lifecycle costs. The paper defines the phenomena, exploring inherent causes and prescribes solutions for both business-to-business and business-to-customer industries. It presents illustrative cases of overspecification and overdesign, proposes a self-assessment to determine the severity of these phenomena in an organization and resolves the conflicts driving these phenomena. Solutions suggested include adapting Simon’s satisficer approach, resolving the marketing conflict by focusing on the 20% of features that account for 80% of the value, breaking the assumption that overspecification is beneficial for future growth potential, resolving the product manager’s conflict via a global system view, implementing the 25/25 principle, freezing and stabilizing the specifications, constraining developer time to eliminate spontaneous overdesign, and piecemeal feature launch.