Motivating participation in social computing applications: a user modeling perspective

The explosive growth of Web-based social applications over the last 10?years has led people to engage in online communities for various purposes: to work, learn, play, share time and mementos with friends and family and engage in public action. Social Computing Applications (SCA) allow users to discuss various topics in online forums, share their thoughts in blogs, share photos, videos, bookmarks, and connect with friends through social networks. Yet, the design of successful social applications that attract and sustain active contribution by their users still remains more of an art than a science. My research over the last 10?years has been based on the hypothesis that it is possible to incorporate mechanisms and tools in the design of the social application that can motivate users to participate, and more generally, to change their behavior in a desirable way, which is beneficial for the community. Since different people are motivated by different things, it can be expected that personalizing the incentives and the way the rewards are presented to the individual, would be beneficial. Also since communities have different needs in different phases of their existence, it is necessary to model the changing needs of communities and adapt the incentive mechanisms accordingly, to attract the kind of contributions that are beneficial. Therefore User and Group (Community) Modeling is an important area in the design of incentive mechanisms. This paper presents an overview of different approaches to motivate users to participate. These approaches are based on various theories from the area of social psychology and behavioral economics and involve rewards mechanisms, reputation, open group user modeling, and social visualization. Future trends are outlined towards convergence with the areas of persuasive systems design, adaptive/personalized systems, and intelligent social learning environments.     

Modeling the efficacy of persuasive strategies for different gamer types in serious games for health

Persuasive games for health are designed to alter human behavior or attitude using various Persuasive Technology (PT) strategies. Recent years have witnessed an increasing number of such games, which treat players as a monolithic group by adopting a one-size-fits-all design approach. Studies of gameplay motivation have shown that this is a bad approach because a motivational approach that works for one individual may actually demotivate behavior in others. In an attempt to resolve this weakness, we conducted a large-scale study on 1,108 gamers to examine the persuasiveness of ten PT strategies that are commonly employed in persuasive game design, and the receptiveness of seven gamer personalities (gamer types identified by BrianHex) to the ten PT strategies. We developed models showing the receptiveness of the gamer types to the PT strategies and created persuasive profiles, which are lists of strategies that can be employed to motivate behavior for each gamer type. We then explored the differences between the models and, based on the results, proposed two approaches for data-driven persuasive game design. The first is the one-size-fits-all approach that will motivate a majority of gamers, while not demotivating any player. The second is the personalized approach that will best persuade a particular type of gamer. We also compiled a list of the best and the worst strategies for each gamer type. Finally, to bridge the gap between game design and PT researchers, we map common game mechanics to the persuasive system design strategies.     

On‐site wastewater treatment using reactive filter media

The aim of this study is to reduce the phosphate concentration in treated wastewater using a small amount of the reactive filter media, Filtralite P. Biologically treated wastewater was passed through a filter with 215 g of Filtralite P. In the laboratory, the phosphate removal efficiency was 51% at a flow speed of 0.87 m/h. Under real conditions, in an experimental stand filled with 0.5 m³ of Filtralite P, the phosphate removal efficiency was 85% and the removal efficiency of total suspended solids was 57% after a 5‐month period. The residual phosphate concentration in the filtrate from the experimental stand was 1 mg/L of PO₄‐P after the 5‐month period. The experimental filtration plant was buried in the ground, and it did not freeze and worked well under winter conditions. The results of this study can be useful in the design and development of tertiary wastewater treatment plants in view of their sustainability potential.     

Effect of AMC on fixed‐rate traffic with hard delay constraints in mobile broadband systems

The adaptive modulation and coding (AMC) technique, which has been adopted by advanced mobile telecommunication systems, supports a flexible response to the random radio behaviour. As a result, the attained transmission rate over a wireless link is time varying. Hence, resource demands are not deterministic but fluctuating even for calls with constant bit rate service requirements. Consequently, constant bit rate calls are susceptible to a forced call termination because of insufficient resources not only in a target cell during inter‐cell handoffs but also in a serving cell during radio link deterioration. Furthermore, call blocking and dropping probabilities depend on radio propagation conditions among other factors and therefore they are dissimilar throughout a service area. The latter leads to unfairness problems. We analytically measure the impact of AMC on fixed‐rate service with hard delay constraints such as voice for different signal, mobility and traffic conditions. We consider a reference case (call requests are admitted into the system provided there are enough free resources) and two classes of admission control approaches: traditional (only inter‐cell handoffs are prioritised) and modified (all ongoing calls are prioritised). The reported results reveal conditions for which AMC affects voice call performance and can serve as guidelines on admission control design. Copyright © 2013 John Wiley & Sons, Ltd.     

Electronmicroscope investigations of the initial stages of silver electrodeposition

The processes of silver electrodeposition have been investigated electron-microscopically. Conclusions are drawn on the actual mechanism of growth of silver crystallites under potentiostatic conditions. An interaction between the separate crystallites during growth has been found to exist and the results obtained show that this interaction leads to a decrease in the rate of growth.     

INDOLE-3-ACETIC ACID PRODUCTION BY GEL-ENTRAPPED BACILLUS THURINGIENSIS IN THE PRESENCE OF ROCK PHOSPHATE ORE

Bacillus thuringiensis in entrapped in k-carrageenan was capable of producing indole-3-acetic acid (IAA) in the presence of rock phosphate ore (RPO). After five repeated batch fermentation experiments, an average of 6.9 mg/L IAA was recorded in the presence of 1.5 g/L RPO and 4.7 mg/L IAA in the RPO-free control. The bacterium simultaneously solubilized phosphates with a maximum soluble P of 115 mg/L and 150 mg/L after the fourth batch cycle in 1.5 and 3.0 g/L RPO amendment, respectively. Addition of tryptophan to the media increased IAA production to 13.9 and 20.7 mg/L per batch on RPO-free and 1.5 g/L RPO-supplemented media with poor bacterial growth and RPO solubilization.     

Modified silica gel with 5-amino-1,3,4-thiadiazole-2-thiol for heavy metal ions removal

A two sorbents was to synthesize for heavy metals removal: silica gel modified with 5-amino-1,3,4-thiadiazole-2-thiol (S5A) and pure silica gel. Modification of silica gel is achieved by tetraethyl orthosilicate (TEOS) preliminary hydrolyzed at room temperature. 5-Amino-1,3,4-thiadiazole-2-thiol is added, with continuous stirring with a magnetic stirrer, to the hydrolyzed TEOS. Pure silica gel (sample SG) is obtained by the classical sol–gel method using the same conditions and initial component ratios. The sorbents have been characterized as to their surface area, pore volumes, content of the functional groups, IR spectra, sulfur and nitrogen content. Their sorption properties to heavy (Cu(II), Co(II), Ni(II), Cd(II), Pb(II) and Hg(II) metals are investigated. The investigations indicate that modified silica gel is characterized by a relatively higher sorption capacity than is the unmodified one. The highest sorption capacity belongs to Hg(II) in presence of unmodified silica gel due to which this sorbent can be used for selective extraction of mercury ions from aqueous solutions.     

Investigation of electron beam melting and refining of titanium and tantalum scrap

In this paper obtained experimental and theoretical data for Ti and Ta electron beam melting regeneration from waste products are presented. Different technological regimes and methods are realized and the obtained results are discussed. Element analyses of the impurities’ concentration of the materials before electron beam melting and refining (EBMR) and of the ingots after EBMR are compared. Statistical approach is applied for optimization of process parameters for Ti. Material losses less than 1% and oxygen concentration less than 400 ppm after EBMR of Ti scrap are achieved at 11.5–12 kW beam power and 0.09–0.14 mm/s casting velocity. The optimal process conditions and purification data for Ti refining by minimization of all impurities’ concentrations and the material losses at the same time are obtained at 11.25 kW electron beam power and 0.0835 mm/s casting velocity. For the performed experiments the best purification of Ta (99.985) is obtained at 24 kW beam power and 0.029 mm/s casting velocity, the residence times on the front side of the feeding block and in the liquid metal pool are 2 min and 5 min, respectively.     

Alkylation of poly(n-vinylpyrrolidone-co-vinylamine) with esters of phosphorous acids

Alkylation of amino groups bounded to a polymer chain with esters of phosphorous acids was studied in order to obtain physiologically active polymers. Poly(N-vinyl-pyrrolidone-co-vinylamine) was chosen as a polymer-carrier. The phosphorous acid esters used were dimethyl hydrogen phosphonate, dimethyl methanephosphonate, trimethyl phosphate and bis-(2-chloroethyl)-hydrogen phosphonate. The composition and structure of the isolated final products was proved by IR- and NMR-spectroscopy and elemental analysis. It is established that alkylation takes place to various extents. The obtained alkylated phosphorous-containing polymers exhibit herbicidal activity and could find application as plant growth retardants.