Distance semantics for database repair

In many scenarios, a database instance violates a given set of integrity constraints. In such cases, it is often required to repair the database, that is, to restore its consistency. A primary motif behind the repairing approaches is the principle of minimal change, which is the aspiration to keep the recovered data as faithful as possible to the original (inconsistent) database. In this paper, we represent this qualitative principle quantitatively, in terms of distance functions and some underlying metrics, and so introduce a general framework for repairing inconsistent databases by distance-based considerations. The uniform way of representing repairs and their semantics clarifies the essence behind several approaches to consistency restoration in database systems, helps to compare the underlying formalisms, and relates them to existing methods of defining belief revision operators, merging data sets, and integrating information systems.      

Triplet State Interrogation in Supersonic Beams by Surface Electron Ejection

Recently, we have developed an experimental method for the detection of triplet states generated by laser excitation in supersonic beams. It is based on electron ejection from low work-function surfaces by metastable triplet states. We have detected both directly laser-excited triplets and triplets generated via intersystem crossing from laser-excited singlet states. Here, we review the applications of this method and discuss its mechanism. By comparing the laser-induced fluorescence (LIF) spectrum and Surface Electron Ejection by Laser-Excited Metastables (SEELEM), we have measured relative triplet formation quantum yields for several aromatic compounds. By utilizing a detector mounted on a translational stage, we could vary the distance between the pulsed laser excitation and the detector and measure the decay rates of triplets in molecular beams. The major advantage of the method is in extending the measurement of triplet lifetimes to the ∼ 1-ms range. The combination of LIF, SEELEM, and fluorescence quantum yields enabled us to discriminate between intersystem crossing and internal conversion in isoquinoline. SEELEM is now being utilized in studying the spectroscopy and the dynamics of directly laser-excited triplet states. Although the oscillator strength of the lowest triplet state of pyrazine is about 10⁻⁸, we have measured the spectrum and the decay rates of its various vibronic levels. Our results support the notion that surface Penning ionization is the mechanism of SEELEM. The detector is insensitive to vibrational energy (thus enabling the distinction between intersystem crossing and internal conversion). The detection sensitivity of triplets rises with the excess electronic energy and with the lowering of the surface work-function.     

Simplified Analytical Treatment of Defect Equilibria: Applications to Oxides with Multivalent Dopants

A simplified analytical treatment of rather complex defect equilibria involving systems with multivalent dopants is presented. This approach is first demonstrated for the case of Gd₂Ti₂O₇; doped with multiple valent donors, in which the effects of variations in donor ionization levels and in the equilibrium constants on the defect equilibria are examined. The conductivity data of U doped CeO₂ are then evaluated, leading to equilibrium constants in good agreement with previous results, but allowing a more complete analysis.     

HRM in project groups: The effect of project duration on team development effectiveness

The literature has found contradictory results regarding the impact of human resource management on project success. This paper focuses on one important human resource management process – team development – to investigate its importance in the project environment. Results show that most team development practices that work well in the operational business environment do not have a significant influence on project success. However, project duration was found to moderate the relationship between team development and project success: the effectiveness of team development increases in longer projects. The paper identifies and analyzes team development practices that have a positive impact on project success exclusively in long projects.     

Improving Social Recommender Systems

Recommender systems play a significant role in reducing information overload for people visiting online sites, but their accuracy could be improved by using data from online social networks and electronic communication tools.     

Easy on that trigger dad: a study of long term family photo retrieval

We examine the effects of new technologies for digital photography on people’s longer term storage and access to collections of personal photos. We report an empirical study of parents’ ability to retrieve photos related to salient family events from more than a year ago. Performance was relatively poor with people failing to find almost 40% of pictures. We analyze participants’ organizational and access strategies to identify reasons for this poor performance. Possible reasons for retrieval failure include: storing too many pictures, rudimentary organization, use of multiple storage systems, failure to maintain collections and participants’ false beliefs about their ability to access photos. We conclude by exploring the technical and theoretical implications of these findings.     

Effect of Initial Particle and Agglomerate Size on the Elastic Moduli of Porous Yttria (Y2O3)

The present study shows the effect of porosity on the dynamic elastic moduli of partially dense yttria (Y₂O₃). This article reveals that the sound velocities and the elastic moduli of the porous samples depend not only on density, but also upon the reciprocal of the initial particle and agglomerate size. These findings explain some of the variation in the elastic moduli found especially, but not only, for highly porous yttria.     

Transport of testosterone and estrogen from dairy-farm waste lagoons to groundwater

Although concentrated animal feeding operations constantly generate physiologically active steroidal hormones, little is known of their environmental fate. Estrogen and testosterone concentrations in groundwater and their distribution in sediments below a dairy-farm wastewater lagoon were therefore determined and compared to a reference site located upgradient of the farm. Forward simulations of flow as well as estrogen and testosterone transport were conducted based on data from the sediment profile obtained during drilling of a monitoring well belowthe dairy-farm waste lagoon. Testosterone and estrogen were detected in sediments to depths of 45 and 32 m, respectively. Groundwater samples were directly impacted by the dairy farm, as evidenced by elevated concentrations of nitrate, chloride, testosterone, and estrogen as compared to the reference site. Modeling potential transport of hormones in the vadose zone via advection, dispersion, and sorption could not explain the depths at which estrogen and testosterone were found, suggesting that other transport mechanisms influence hormone transport under field conditions. These mechanisms may involve interactions between hormones and manure as well as preferential flow paths, leading to enhanced transport rates. These types of interactions should be further investigated to understand the processes regulating hormone transport in the subsurface environment and parametrized to forecast long-term fate and transport of steroidal hormones.