Characterizing peers communities and dynamics in a P2P live streaming system

Despite the large number of works devoted to understand P2P live streaming applications, most of them put forth so far rely on characterizing the static view of these systems. In this work, we characterize the SopCast, one of the most important P2P live streaming applications. We focus on its dynamics behavior as well as on the community formation phenomena. Our results show that SopCast presents a low overlay topology diameter and low end-to-end shortest path. In fact, diameter is smaller than 6 hops in almost 90 % of the observation time. More than 96 % of peers’ end-to-end connections present only 3 hops. These values combined may lead to low latencies and a fast streaming diffusion. Second, we show that communities in SopCast are well defined by the streaming data exchange process. Moreover, the SopCast protocol does not group peers according to their Autonomous System. In fact, the probability that a community contains 50 % of its members belonging to the same AS (when we observe the largest AS of our experiments) is lower then 10 %. Peers exchange more data with partners belonging to the same community instead of peers inside the same AS. For the largest AS we have, less than 18 % of peer traffic has been exchanged with another AS partners. Finally, our analysis provides important information to support the future design of more efficient P2P live streaming systems and new protocols that exploit communities’ relationships.     

Assessment of the Impact of Stormwater Characteristics on Clogging in Stormwater Filters

Hydraulic conductivity of granular filter media and its evolution over time is a key design parameter for stormwater filtration and infiltration systems that are now widely used in management of polluted urban runoff. In fact, clogging of filter media is recognised as the main limiting factor of these stormwater treatment systems. This paper focuses on the effect of stormwater characteristics on the clogging of stormwater filters. Effect of five different operational regimes has been tested in this study of sediment concentration; pollutant concentrations; stormwater sediment size; loading rate and stormwater loading/dosing regime and compared with the Base case. For each operational condition, five column replicates were tested. Results suggest that sediment concentration in stormwater is a significant parameter affecting hydraulic and treatment performance, eventually affecting longevity of these stormwater treatment systems. Further, the size of sediments (and their relation to the size of filter media grains) in stormwater was found to be an important parameter to be considered in design of coarse filters with high infiltration rates that are used for stormwater treatment. As expected, the addition of metals and nutrients had limited or no contribution to changes in hydraulic or sediment removal performance of the studied stormwater filters. Whilst loading rate was found to be an important parameter affecting the hydraulic and treatment performance of these systems, any variation in the stormwater loading regime had a limited effect on their performance. This study therefore develops an understanding of the effect of catchment characteristics on design of filters and hence their longevity and maintenance needs.     

Integrating the implementation of the European Union Water Framework Directive and Floods Directive in Ireland

Water Framework Directive (WFD) statutory authorities and stakeholders in Ireland are now challenged with the issue of how the proposed programmes of measures in the newly required River Basin Management Plans - designed to protect and restore good ecology by reverting as closely as possible back to natural conditions - are to be implemented in a way that concurrently complies with other existing and emerging intersecting European Union legislation, such as the Floods Directive (FD). The WFD is driven largely by ecological considerations, whereas the FD and other legislation are more geared towards protecting physical property and mitigating public safety risks. Thus many of the same waterbodies, especially heavily modified waterbodies, arguably have somewhat competing policy objectives put upon them. This paper explores the means by which Ireland might best achieve the highest degrees of cost effectiveness, economic efficiency and institutional durability in pursuing the common and overarching objective of the WFD and FD - to ensure Irish waterways are put to their highest valued uses.     

Feasibility of UASB/trickling filter systems without final clarifiers for the treatment of domestic wastewater in small communities in Brazil

The paper analyses the concept and performance of different configurations of compact UASB/TF systems, without the final clarification stage, in relation to the removal of organic matter. The experiments were carried out in two sets of UASB/TF systems operating without secondary clarifiers, as follows: (i) four shallow (2.50 m height) TFs, each one filled with a different packing material; and (ii) two deep (4.20 m height) TFs, one filled with polyethylene corrugated sheets and the other with mixed polyethylene and sponge sheets. For the conditions tested (different packing material in shallow and deep TF), the UASB/TF systems had consistently complied (90 to 100% of the results) with the Brazilian discharge standards regarding to BOD, COD, and TSS parameters. The average BOD, COD and TSS effluent concentrations stayed below 40 mg BOD L(-1), 100 mg COD L(-1) and 50 mg TSS L(-1), respectively. UASB/TF systems can constitute an attractive alternative for domestic wastewater treatment in small communities in developing countries, especially considering its operational simplicity and very low running costs.     

Preventing Youth Pregnancy: Dialogue and Deliberation in a Science Museum Exhibit

ABSTRACT

In this article, we explore how visitors engage with a science museum exhibit that displays controversial topics. Through a case study methodology, we focus on the Brazilian exhibit Preventing Youth Pregnancy that delves into teen pregnancy, sexual practices, and sexually transmitted diseases. Using the lens of science communication (an emergent field of research) we explore (a) communication patterns established between the exhibit and the public and (b) the dimensions of engagement that visitors experienced. Data were collected through observations and interviews with visitors, field notes, exit comment cards, and interviews with staffers. Our findings revealed the potential of articulating different models of science communication and exposed a visitor experience in which informed decision making, sharing of personal stories, co-production of knowledge, and learning how to care (and act) were at play while negotiating the complexities of the issues raised by the displays.     

Forecasting binary longitudinal data by a functional PC-ARIMA model

In order to forecast time evolution of a binary response variable from a related continuous time series a functional logit model is proposed. The estimation of this model from discrete time observations of the predictor is solved by using functional principal component analysis and ARIMA modelling of the associated discrete time series of principal components. The proposed model is applied to forecast the risk of drought from El Niño phenomenon.     

A review on the combination of binary classifiers in multiclass problems

Several real problems involve the classification of data into categories or classes. Given a data set containing data whose classes are known, Machine Learning algorithms can be employed for the induction of a classifier able to predict the class of new data from the same domain, performing the desired discrimination. Some learning techniques are originally conceived for the solution of problems with only two classes, also named binary classification problems. However, many problems require the discrimination of examples into more than two categories or classes. This paper presents a survey on the main strategies for the generalization of binary classifiers to problems with more than two classes, known as multiclass classification problems. The focus is on strategies that decompose the original multiclass problem into multiple binary subtasks, whose outputs are combined to obtain the final prediction.     

Modeling and solving the rooted distance-constrained minimum spanning tree problem

In this paper we discuss models and methods for solving the rooted distance constrained minimum spanning tree problem which is defined as follows: given a graph G=(V,E)$G=(V,E)$ with node set V={0,1,…,n}$V=\{0,1,\dots ,n\}$ and edge set E$E$, two integer weights, a cost _ce$c_e$ and a delay _we$w_e$ associated with each edge e$e$ of E$E$, and a natural (time limit) number H$H$, we wish to find a spanning tree T$T$ of the graph with minimum total cost and such that the unique path from a specified root node, node 0, to any other node has total delay not greater than H$H$. This problem generalizes the well known hop-constrained spanning tree problem and arises in the design of centralized networks with quality of service constraints and also in package shipment with service guarantee constraints. We present three theoretically equivalent modeling approaches, a column generation scheme, a Lagrangian relaxation combined with subgradient optimization procedure, both based on a path formulation of the problem, and a shortest path (compact) reformulation of the problem which views the underlying subproblem as defined in a layered extended graph. We present results for complete graph instances with up to 40 nodes. Our results indicate that the layered graph path reformulation model is still quite good when the arc weights are reasonably small. Lagrangian relaxation combined with subgradient optimization procedure appears to work much better than column generation and seems to be a quite reasonable approach to the problem for large weight, and even small weight, instances.     

Thionine immobilized in crosslinked chitosan films

Redox and acid–base properties of thionine immobilized in crosslinked chitosan films are analyzed. The experimental conditions for the preparation of the films are described. Results obtained with cyclic voltammetry, spectroelectrochemistry and spectrophotometry indicate that the immobilized dye retains the redox and acid–base activity of free thionine. An acid dissociation constant (K_a) for the immobilized dye of K_a = 2.7 × 10⁻¹¹ was obtained.

Due to the stable and reversible pH dependent optical signal of the studied film, this membrane can be used as a building component of an optical pH sensor.