Comparative study on the effects of groupware and conventional technologies on the efficiency of collaborative writing

In this paper the concept of efficiency in collaborative writing is considered in detail and a definition of efficiency is proposed. The definition of efficiency leads to the development of a research framework that delineates five operational measures of efficiency: (a) writing activities efficiency, (b) coordination efficiency, (c) quality of output, (d) absence of breakdowns, and (e) satisfaction with group performance. A comparative study is subsequently presented on the effects that groupware and conventional technologies have on the effciency of collaborative writing. The hypothesis is advanced that groupware can improve the efficiency of collaborative writing over conventional technologies. The results seem to support the hypothesis and indicate that (a) the groupware system examined in this study (MUCH system) offers efficiency benefits in terms of coordination, (b) MUCH users tend to face communication breakdowns while users of conventional technologies tend to face task-related breakdowns, (c) the documents produced with MUCH are of higher content quality, more coherent, and of higher rhetorical effectiveness than the documents produced with conventional technologies, and (d) the comparison of MUCH with conventional technologies shows no significant difference in terms of their effects on group performance satisfaction.     

An expertext system for collaborative authoring

This paper describes the principles behind and the design and implementation of a collaborative expertext authoring tool. The system presented aims to act as an intelligent assistant. It is based on a model of writing as a problem-solving activity, constrained by goal and audience, in which success depends on allowing the user to witch at will between the different phases of the task. Key to achieving this role is its ability to make explicit the implicit semantics of associative links in the hypertext. In order to guide the user, a knowledge base is provided by the system which an author can edit and which determines how the hypertext network is edited and traversed in the course of generating linear documents. In this way, minor modifications of the knowledge base can readily lead to significant reorganization of a document.     

Surface photovoltage spectroscopy on Cu(In,Ga)(S,Se)2/ZnS‐nanodot/In2S3 systems

Single layers and combined layer systems with Cu(In,Ga)(S,Se)₂, ZnS‐nanodot (nd) and In₂S₃ layers were investigated by surface photovoltage spectroscopy in the Kelvin‐probe arrangement and compared with the open‐circuit voltage (V_OC) of solar cells. The In₂S₃ and ZnS‐nd layers were prepared by the spray ion layer gas reaction (ILGAR) technique from Indium chloride (InCl₃), Indium acetylacetonate (In(acac)₃) and Zinc acetylacetonate, respectively. The surface photovoltage signals of Cu(In,Ga)(S,Se)₂ were larger for the Cu(In,Ga)(S,Se)₂/ZnS‐nd/In₂S₃ than for the Cu(In,Ga)(S,Se)₂/In₂S₃ layer system showing that a ZnS‐nd layer additionally passivated the Cu(In,Ga)(S,Se)₂ surface. ILGAR In₂S₃ deposition from InCl₃ precursor solution led to a modification of surface defects of ZnS‐nd and to generation of defect states below the band gap of Cu(In,Ga)(S,Se)₂, which has not been observed for deposition from Indium acetylacetonate precursor. Defect generation during ILGAR In₂S₃ deposition with InCl₃ precursor resulted in a lower V_OC of Cu(In,Ga)(S,Se)₂/ZnS‐nd/In₂S₃/ZnO : Al solar cells. Copyright © 2012 John Wiley & Sons, Ltd.     

Novel structural properties of the lead–vanadate–tellurate glass ceramics

In this paper, we have examined and analyzed the effects of systematic intercalation of the lead ions on vanadate–tellurate glass ceramics with interesting results. The structural properties of the lead–vanadate–tellurate glass ceramics of compositions xPbO·(100 − x)[6TeO₂·4V₂O₅], x = 0 − 100 mol%, are reported for the first time. It has been shown by X-ray diffraction that single-phase homogeneous glasses with a random network structure can be obtained in this system. Among these unconventional lead–vanadate–tellurate glass ceramics, we found that network formers are good host material for lead ions and are capable to intercalate a variety of species such as Te₂V₂ ⁵⁺O₉, Pb₃(V⁵⁺O₄)₂, Pb₂V₂ ⁵⁺O₇, and V₂O₅-rich amorphous phase. On the other hand, these glass ceramics contain V⁴⁺ and V⁵⁺ ions necessary for the electrical conduction. Based on these experimental results, we propose that the V⁴⁺=O bonds are created by two different mechanisms: the first of reduction of V⁵⁺ ions to V⁴⁺ ions and thus of creation of V⁴⁺=O bonds.     

Compulsive buying: a new disorder?

Despite its high frequency and its severe financial, social and personal complications, compulsive buying is rarely described in the psychiatric literature. We reviewed all the published papers on this syndrome to describe its clinical features, epidemiology and response to drug or psychological treatment. Psychiatric comorbidity is also reviewed and nosologic implications are analyzed.     

Determination of total nitrogen in sediments and plants using persulfate digestion. An evaluation and comparison with the Kjeldahl procedure

Accuracy and precision of the persulfate and Kjeldahl determinations of total nitrogen in solid samples were assessed with certified standards, plant material and river sediments. Accuracy determined with the certified reference materials was within an acceptable range to assure quality control for routine laboratory analyses. In addition, results obtained by examining plant samples indicated that TPN and TKN were not significantly different. Precision for analyses of all samples was high; however a direct comparison of plant material indicated that TPN (RSD = 5.3%) was more precise than TKN (RSD = 8.4%). TPN is a reasonable alternative to the standard TKN procedure for analysis of sediment and plant materials. The TPN method would increase the feasibility of conducting replicate analyses and would result in increased quality control.     

View selection for <Emphasis Type="Italic">real</Emphasis> conjunctive queries

Given a query workload, a database and a set of constraints, the view-selection problem is to select views to materialize so that the constraints are satisfied and the views can be used to compute the queries in the workload efficiently. A typical constraint, which we consider in the present work, is to require that the views can be stored in a given amount of disk space. Depending on features of SQL queries (e.g., the DISTINCT keyword) and on whether the database relations on which the queries are applied are sets or bags, the queries may be computed under set semantics, bag-set semantics, or bag semantics. In this paper we study the complexity of the view-selection problem for conjunctive queries and views under these semantics. We show that bag semantics is the “easiest to handle” (we show that in this case the decision version of view selection is in NP), whereas under set and bag-set semantics we assume further restrictions on the query workload (we only allow queries without self-joins in the workload) to achieve the same complexity. Moreover, while under bag and bag-set semantics filtering views (i.e., subgoals that can be dropped from the rewriting without impacting equivalence to the query) are practically not needed, under set semantics filtering views can reduce significantly the query-evaluation costs. We show that under set semantics the decision version of the view-selection problem remains in NP only if filtering views are not allowed in the rewritings. Finally, we investigate whether the cgalg algorithm for view selection introduced in Chirkova and Genesereth (Linearly bounded reformulations of conjunctive databases, pp. 987–1001, 2000) is suitable in our setting. We prove that this algorithm is sound for all cases we examine here, and that it is complete under bag semantics for workloads of arbitrary conjunctive queries and under bag-set semantics for workloads of conjunctive queries without self-joins. Rada Chirkova’s work on this material has been supported by the National Science Foundation under Grant No. 0307072. The project is co-funded by the European Social Fund (75%) and National Resources (25%)- Operational Program for Educational and Vocational Training II (EPEAEK II) and particularly the program PYTHAGORAS. A preliminary version of this paper appears in F. Afrati, R. Chirkova, M. Gergatsoulis, V. Pavlaki. Designing Views to Efficiently Answer Real SQL Queries. In Proc. of SARA 2005, LNAI Vol. 3607, pages 332-346, Springer-Verlag, 2005.     

Preparation of TiO2/carbon nanotubes photocatalysts: The influence of the method of oxidation of the carbon nanotubes on the photocatalytic activity of the nanocomposites

A method for the preparation of efficient TiO₂/multi-wall carbon nanotubes nanocomposite photocatalysts by precipitation of anatase TiO₂ nanoparticles onto differently oxidized carbon nanotubes is presented. The precursor compound titanium(IV) bromide was hydrolyzed producing pure anatase phase TiO₂ nanoparticles decorated on the surface of the oxidized carbon nanotubes. The oxidative treatment of the carbon nanotubes influenced the type, quantity and distribution of oxygen-containing functional groups, which had a significant influence on the electron transfer properties, i.e., the photocatalytic activity of the synthesized nanocomposites. The results of C.I. Reactive Orange 16 photodegradation in the presence of all the synthesized nanocomposites showed their better photocatalytic activity in comparison to the commercial photocatalyst Degussa P-25.