An analysis of peer similarity for recommendations in P2P systems

In this paper, we propose a novel recommender framework for partially decentralized file sharing Peer-to-Peer systems. The proposed recommender system is based on user-based collaborative filtering. We take advantage from the partial search process used in partially decentralized systems to explore the relationships between peers. The proposed recommender system does not require any additional effort from the users since implicit rating is used. The recommender system also does not suffer from the problems that traditional collaborative filtering schemes suffer from like the Cold start and the Data sparseness. To measure the similarity between peers, we propose Files?? Popularity Based Recommendation (FP) and Asymmetric Peers?? Similarity Based Recommendation with File Popularity (ASFP). We also investigate similarity metrics that were proposed in other fields and adapt them to file sharing P2P systems. We analyze the impact of each similarity metric on the accuracy of the recommendations. Both weighted and non weighted approaches were studied.     

Isocyanate‐free Route to Starch‐graft‐Polycaprolactone via Carbonyldiimidazole (CDI)‐mediated End Group Conversion

This paper reports on the synthesis of biodegradable starch‐graft‐poly ϵ‐caprolactone (starch‐g‐PCL) in two steps. First, poly ϵ‐caprolactone (PCL) was modified on the terminal groups by using carbodiimidazole (CDI) as coupling agent. Then, the starch graft copolymers with PCL were prepared through a carbonate bond using carboimidazole function. Monofunctional and bifunctional reactive end‐group PCL terminated with carboimidazole groups were prepared and reacted with hydroxyl groups of starch. The resulting starch‐g‐PCL copolymers were characterized by FT‐IR, NMR, HR‐MAS‐NMR, DSC, MEB and XRD.     

Landfill leachate treatment with ozone and ozone/hydrogen peroxide systems

In the search for an efficient and economical method to treat a leachate generated from a controlled municipal solid waste landfill site (Jebel Chakir) in the region of greater Tunis in Tunisia, ozone alone and ozone combined with hydrogen peroxide were studied. The leachate was characterised by high COD, low biodegradability and intense dark colour. A purpose-built reactor, to avoid foaming, was used for the study. It was found that ozone efficacy was almost doubled when combined with hydrogen peroxide at 2g/L but higher H(2)O(2) concentrations gave lower performances. Enhancement in the leachate biodegradability from about 0.1 to about 0.7 was achieved by the O(3)/H(2)O(2) system. Insignificant changes in pH that may due to buffering effect of bicarbonate was found. A small decrease in sulphate concentrations were also observed. In contrast, chloride concentration declined at the beginning of the experiment then increased to reach its initial value. Estimates of the operating costs were made for comparison purposes and it was found that the O(3)/H(2)O(2) system at 2g/L H(2)O(2) gave the lowest cost of about 3.1TND( approximately 2.3USD)/kgCOD removed.     

Batch sorption dynamics and equilibrium for the removal of cadmium ions from aqueous phase using wheat bran

Studies on a batch sorption process using wheat bran as a low cost sorbent was investigated to remove cadmium ions from aqueous solution. The influence of operational conditions such as contact time, cadmium initial concentration, sorbent mass, temperature, solution initial pH, agitation speed and ionic strength on the sorption kinetics of cadmium was studied. Pseudo-second-order model was evaluated using the six linear forms as well as the non-linear curve fitting analysis method. Modeling of kinetic results shows that sorption process is best described by the pseudo-second-order model using the non-linear method. The sorption of cadmium was found to be dependent on initial concentration, sorbent mass, solution pH, agitation speed, temperature, ionic strength and contact time. The value of activation energy (12.38 kJ mol(-1)) indicates that sorption has a low potential barrier corresponding to a physical process. Sorption equilibrium isotherms at different temperatures was determined and correlated with common isotherm equations such as Langmuir and Freundlich models. It was found that the Langmuir model appears to well fit the isotherm data but a worse correlation was obtained by the Freundlich model. The five Langmuir linear equations as well as the non-linear curve fitting analysis method were discussed. Results show that the non-linear method may be a better way to obtain the Langmuir parameters. Thermodynamic parameters such as DeltaH degrees, DeltaS degrees and DeltaG degrees were calculated. These parameters indicate that the sorption of cadmium by wheat bran is a spontaneous process and physical in nature involving weak forces of attraction and is also endothermic.