Correlations between Horn fractions, satisfiability and solver performance for fixed density random 3-CNF instances

An enhanced concept of sub-optimal reverse Horn fraction of a CNF-formula was introduced in [18]. It was shown that this fraction is very useful in effectively (almost) separating 3-colorable random graphs with fixed node-edge density from the non-3-colorable ones. A correlation between this enhanced sub-optimal reverse Horn fraction and satisfiability of random 3-SAT instances with a fixed density was observed. In this paper, we present experimental evidence that this correlation scales to larger-sized instances and that it extends to solver performances as well, both of complete and incomplete solvers. Furthermore, we give a motivation for various phases in the algorithm aHS, establishing the enhanced sub-optimal reverse Horn fraction, and we present clear evidence for the fact that the observed correlations are stronger than correlations between satisfiability and sub-optimal MAXSAT-fractions established similarly to the enhanced sub-optimal reverse Horn fraction. The latter observation is noteworthy because the correlation between satisfiability and the optimal MAXSAT-fraction is obviously 100%. AMS subject classification 90C05, 03B99, 68Q01, 68W01     

Improved Competitive Guarantees for QoS Buffering

We consider a network providing Differentiated Services (DiffServ), which allow Internet Service Providers (ISPs) to offer different levels of Quality of Service (QoS) to different traffic streams. We study two types of buffering policies that are used in network switches supporting QoS. In the FIFO type, packets must be transmitted in the order they arrive. In the uniform bounded delay type, there is a maximal delay time associated with the switch and each packet must be transmitted within this time, or otherwise it is dropped. In both models the buffer space is limited, and packets are lost when the buffer overflows. Each packet has an intrinsic value, and the goal is to maximize the total value of transmitted packets. Our main contribution is an algorithm for the FIFO model with arbitrary packet values that for the first time achieves a competitive ratio better than 2, namely 2-ε for a constant ε gt; 0. We also describe an algorithm for the uniform bounded delay model which simulates our algorithm for the FIFO model, and show that it achieves the same competitive ratio.     

Multi-fidelity optimization of laminated conical shells for buckling

Optimum laminate configuration for minimum weight of filament-wound laminated conical shells is investigated subject to a buckling load constraint. In the case of a composite laminated conical shell, due to the manufacturing process, the thickness and the ply orientation are functions of the shell coordinates, which ultimately results in coordinate dependence of the stiffness matrices (A,B,D). These effects influence both the buckling load and the weight of the structure and complicate the optimization problem considerably. High computational cost is involved in calculating the buckling load by means of a high-fidelity analysis, e.g. using the computer code STAGS-A. In order to simplify the optimization procedure, a low-fidelity model based on the assumption of constant material properties throughout the shell is adopted, and buckling loads are calculated by means of a low-fidelity analysis, e.g. using the computer code BOCS. This work proposes combining the high-fidelity analysis model (based on exact material properties) with the low-fidelity model (based on nominal material properties) by using correction response surfaces, which approximate the discrepancy between buckling loads determined from different fidelity analyses. The results indicate that the proposed multi-fidelity approaches using correction response surfaces can be used to improve the computational efficiency of structural optimization problems.     

On‐the‐job Innovation: The Impact of Job Design and Human Resource Management through Production Ownership

A growing number of practitioners and academics endorse that the ability of organizations to foster, develop and use the innovative potential of their employees contributes to organizational success. Yet empirical investigation of individual innovation processes is lacking. In this research we address the question of whether both more flexibility in an employees’ job design and commitment‐oriented HRM activities promote individual innovative work behaviour. Findings suggest that a multifunctional job design and the perceived HRM system promote employee involvement in innovative activities through increased feelings of ownership for work‐related issues and problems.     

Technologies towards patterned optical foils applied to transflective LCDs

Abstract— For better front‐of‐screen performance for transflective LCDs, a technology with extra free optimization parameters for the optical stack is needed. Thin wet coatable retarders which enable adjustment of the optical activity on the (sub)pixel level have been developed. Isotropic domains have been created in nematic retardation films by thermal patterning or photopatterning. Employing such a patterned retarder in a transflective LCD leads to an LCD that is lighter and thinner with good reflectivity, high transmission, and low chromaticity at all gray levels and wide viewing angles. The patterned thin‐film technology has been proven to be versatile and applicable in various LCD designs.     

On the Expressiveness of Higher Dimensional Automata: (Extended Abstract)

In this paper I compare the expressive power of several models of concurrency based on their ability to represent causal dependence. To this end, I translate these models, in behaviour preserving ways, into the model of higher dimensional automata, which is the most expressive model under investigation. In particular, I propose four different translations of Petri nets, corresponding to the four different computational interpretations of nets found in the literature.I also extend various equivalence relations for concurrent systems to higher dimensional automata. These include the history preserving bisimulation, which is the coarsest equivalence that fully respects branching time, causality and their interplay, as well as the ST-bisimulation, a branching time respecting equivalence that takes causality into account to the extent that it is expressible by actions overlapping in time. Through their embeddings in higher dimensional automata, it is now well-defined whether members of different models of concurrency are equivalent.     

Statistical Modeling of the Serviceability of Sewage Pumps

Sewage pumping stations represent an element of the sewer system, which is directly responsible for affecting serviceability; i.e., failing pumps may result in combined sewer overflows or flooding. However, failures of sewage pumps are not yet incorporated in sewer assessments due to lack of data. This paper presents the analysis of pump failure data provided by two sewer management authorities in The Netherlands. Pump failures have been studied accounting for the nature of the failures, the operation and maintenance procedures of the management authority, the aging of the pumps, and the changes in the environment of pumps. The analysis shows that sewage pumps fail relatively often due to the composition of sewage and the discontinuous operation of the pumps. The interarrival time and the duration of failures are highly variable and independent of the specific function of the pump. Resulting pump failure characteristics are applied in a Monte Carlo simulation to calculate the impact of failures on combined sewer overflow volumes. The results indicate that the serviceability of sewer systems is significantly affected by failing pumps. Therefore, including pump availability in sewer system assessments should be considered.     

Flow-Induced Failure of Cable-Tied Blocks

An experimental study of flow-induced failure of cable-tied blocks is presented. The particular failure mechanism studied is overturning and rolling up of the leading edge of a cable-tied block mat. Individual blocks were investigated also. The block size, flow depth, and block (mat) protrusion above the surrounding bed were systematically varied. The results are presented in terms of the critical dimensionless shear stress θc for block (mat) failure. A relationship between θc, block size and block protrusion, and flow depth is given.     

Understanding smoking cessation: The role of smokers' quit history.

Many studies have found smokers' quit history to correlate with quitting smoking, but little is known about the psychological processes explaining this relationship. This study uses the integrative model of behavioral prediction to examine how quit history affects quit intention. Data from 3,428 Dutch smokers demonstrate that quit history affects (a) beliefs about quitting and (b) the degree to which self-efficacy predicts quit intention. It seems that a relatively unsuccessful history of prior quit attempts reduces self-efficacy over quitting and strengthens the relationship of self-efficacy with the intention to quit. The results are used to call for more process-oriented research in order to advance our understanding of the relationship between quit history and quit intention. (PsycINFO Database Record (c) 2010 APA, all rights reserved)