Exploiting semantic proximities for content search over p2p networks

In this paper, we address the issue of content search over peer-to peer networks. We use the concept of semantic proximity that exploits the commonalities of interests exhibited among peer users so as to decompose the network into semantic clusters. We initially define search entropy, as a metric indicating the average number of packets required to locate the requested content. Then, spectral clustering is used to organize the peer nodes into semantic clusters so that (a) the probability that a node locates content within its own cluster is maximized, while simultaneously; (b) the respective probability of finding this content outside this cluster is minimized. The proposed semantic partitioning algorithm is then extended into a hierarchical two-tier scheme, in which practical issues arising for the deployment of a peer-to-peer (p2p) application can be more easily addressed. After the system has been initialized, a dynamic algorithm places new users that join the p2p network into appropriately selected clusters and also handles peer departures without the need for matrix eigen decomposition process which is necessary for the assessment of the initial static partitioning. Our experimental results validate that (a) our static partitioning outperforms traditional and novel search techniques and (b) our dynamic algorithm is able to efficiently track the system’s progression maintaining the search entropy close to the initially assessed levels.     

CFD simulation of magnetorheological fluid journal bearings

Magnetorheological fluid journal bearing can be controlled by a steady magnetic field doing that very effective for attenuating and controlling the performance of the rotor bearing systems.An integrated simulation study, of a magnetorheological (MRF) fluid journal bearing, via computational fluid dynamics (CFD) and finite element method (FEM) is presented in this paper. The journal bearing characteristics such as, eccentricity, attitude angle, oil flow and friction coefficients are calculated and presented as functions of the magnetic field, and L/D bearing ratios.A specific procedure in order to simulate an MRF bearing operated in high eccentricity ratios is also presented and the meshing requirements are discussed.     

How to improve the peer review method: Free-selection vs assigned-pair protocol evaluated in a computer networking course

This study provides field research evidence on the efficiency of a “free-selection” peer review assignment protocol as compared to the typically implemented “assigned-pair” protocol. The study employed 54 sophomore students who were randomly assigned into three groups: Assigned-Pair (AP) (the teacher assigns student works for review to student pairs), Free-Selection (FS) (students are allowed to freely explore and select peer work for review), and No Review (NR) (control group). AP and FS student groups studied and reviewed peer work in the domain of Computer Networking, supported by a web-based environment designed to facilitate the two peer review protocols. Our results indicate that students following the Free Selection protocol demonstrate (a) better domain learning outcomes, and (b) better reviewer skills, compared to the AP condition. Overall, the study analyzes the benefits and shortcomings of the FS vs AP review assignment protocol, providing evidence that the FS condition can be multiply beneficial to students who engage in peer review activities.     

Detecting Collaborations in Text Comparing the Authors' Rhetorical Language Choices in The Federalist Papers

In author attribution studies function words or lexical measures areoften used to differentiate the authors' textual fingerprints. Thesestudies can be thought of as quantifying the texts, representing thetext with measured variables that stand for specific textual features.The resulting quantifications, while proven useful for statisticallydifferentiating among the texts, bear no resemblance to the understanding a human reader – even an astute one – would develop whilereading the texts. In this paper we present an attribution study that,instead, characterizes the texts according to the representationallanguage choices of the authors, similar to a way we believe close humanreaders come to know a text and distinguish its rhetorical purpose. Fromour automated quantification of The Federalist papers, it isclear why human readers find it impossible to distinguish the authorshipof the disputed papers. Our findings suggest that changes occur in theprocesses of rhetorical invention when undertaken in collaborativesituations. This points to a need to re-evaluate the premise ofautonomous authorship that has informed attribution studies of The Federalist case.     

Assessing the Variable Molecular Architecture of Poly(ethylene terephthalate) Under Reactive Modification by Melt and Dilute Solution Rheology

Two simple methods are described that utilize melt or dilute solution rheology in characterizing transfomations in molecular architecture induced on an originally linear PET during the early stages of reactive extrusion. A plausible senario for the shape variation and relative difficulty of the new polymers formed is assumed, from which expressions for the evolving melt and intrinsic viscosity of the reacting PET are derived. The model is tested using two separate sets of viscometric data refering to PET modified at various degrees. Quantitative agreement is found between the two methods in estimating the composition of the various types of PET species present.

     

Design of a Six-Sector Switched Parasitic Planar Array Using the Method of Genetic Algorithms

Switched parasitic planar arrays, as possible implementations of smart antennas, and an efficient method of designing them are presented in this paper. The radiation pattern of an array can be controlled by a digital word, the insertion of which in the antenna feeding circuit achieves electronic beam steering. The 1s and the 0s in the digital word represent the active and short-circuited elements in the array, respectively. The aim of the design is to cover the azimuth plane with six radiation patterns, each one having 3 dB beamwidth equal to 60° and relative sidelobe level not more than –3 dB. The well-known genetic algorithms are used tooptimize the antenna performance, determining the element positions and voltage phase values. This is made feasible by selecting the digital words, among the 2^N–1 available (N-number of elements), which maximize theobjective function containing the pattern requirements of the design. The numerical results presented show a possible application of this idea. An array of seven identical dipoles /2 offers diagrams, with an average 3 dB beamwidth equal to 63°. Relative sidelobe levels lower than –3 dB are obtained. Simulations at different frequencies prove that thearraydesigned here is a narrowband one and its bandwidth is 2.5% of the carrier frequency.     

Bladder wall dosimetry for 131I administered activities

Detailed dosimetric calculations of bladder dose from 131I accumulations are presented, using Monte Carlo simulations and the dynamic bladder model proposed in the recent revision of MIRD Pamphlet No 14. Penetrating radiation and electron dose to the bladder wall inner surface, as well as within the bladder wall, per unit of 131I activity accumulated in the bladder, are calculated for various bladder filling volumes. The effect of backscatter was taken into account for photon dose calculations while electron dose was determined for all the beta spectral components of 131I. Dosimetric results were used to derive simple parameterisation functions of photon and electron dose with respect to bladder filling volume in combination with any bladder physiology model. Calculations of bladder dose per unit of 131I-OIH and 131I-NaI administered activity, using the derived parametrisations, differ by less than 12% from corresponding results given in the recent revision of MIRD Pamphlet No 14.