Evolution of the Dependence of Residual Lifetimes

We investigate the dependence properties of a vector of residual lifetimes by means of the copula associated with the conditional distribution function. In particular, the evolution of positive dependence properties (like quadrant dependence and total positivity) are analyzed and expressions for the evolution of measures of association are given

A model for the analysis of security policies in service function chains

Two emerging architectural paradigms, i.e., Software Defined Networking (SDN) and Network Function Virtualization (NFV), enable the deployment and management of Service Function Chains (SFCs). A SFC is an ordered sequence of abstract Service Functions (SFs), e.g., firewalls, VPN-gateways,traffic monitors, that packets have to traverse in the route from source to destination. While this appealing solution offers significant advantages in terms of flexibility, it also introduces new challenges such as the correct configuration and ordering of SFs in the chain to satisfy overall security requirements. This paper presents a formal model conceived to enable the verification of correct policy enforcements in SFCs. Software tools based on the model can then be designed to cope with unwanted network behaviors (e.g., security flaws) deriving from incorrect interactions of SFs in the same SFC

A multivariate analysis of tourists’ spending behaviour

According to the micro-economic theories regarding consumption behaviour, the determinants affecting the joint propensity of purchasing different goods and services are investigated. For this purpose, a copula-based model is suggested. This is in fact a suitable model to understand whether and how different expenditure categories are dependent with each other. A real application drawn from the tourism field is used to illustrate how the proposed approach works and to demonstrate its flexibility. The findings could guide local practitioners and managers in creating new promotional campaigns able to attract visitors willing to pay on a bundle of goods and services correlated with each other

Development of a 4-DoF Active Upper Limb Orthosis

In this paper, the designs and manufacturing process of a powered upper limb orthosis are presented. The orthosis is an exoskeleton worn on one arm by the user and fixed to the trunk. The orthosis’ architecture, design, and manufacturing process are presented and discussed. Estimations of the ranges of movement related to daily living activities are presented. The preliminary tests to verify the functionality of the design show encouraging results

On the return period and design in a multivariate framework

Abstract. Calculating return periods and design quantiles in a multivariate environment is a difficult problem: this paper tries to make the issue clear. First, we outline a possible way to introduce a consistent theoretical framework for the calculation of the return period in a multi-dimensional environment, based on Copulas and the Kendall's measure. Secondly, we introduce several approaches for the identification of suitable design events: these latter quantities are of utmost importance in practical applications, but their calculation is yet limited, due to the lack of an adequate theoretical environment where to embed the problem. Throughout the paper, a case study involving the behavior of a dam is used to illustrate the new concepts outlined in this work

An interview with Roger Cooke

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Start-up with or without inoculum? Analysis of an SMBR pilot plant.

This study analysed a submerged membrane bioreactor (SMBR) start-up with the purpose of determining the best conditions to carry it out. In order to do this, a hollow fibre membrane module was installed in a submerged configuration in a pilot aerobic reactor. The experiment was then divided in two phases, lasting 65 days each. During phase 1, the pilot plant was started-up without inoculum of activated sludge and no sludge, withdrawal was performed. Conversely, in phase 2, the MBR pilot plant was started-up with sludge inoculum and the sludge concentration was kept constant. In both phases, the volumetric loading rate applied to the pilot plant was kept constant. The authors analysed the difference in carbon removal performances, the evolution of floc sizes and the fouling rate in both phases. The results confirmed that MBRs can be quickly and easily started-up, but the initial start-up strategy can influence membrane fouling. More specifically, the carbon removal performances were similar in both phases, while the fouling rate increased faster during the start-up without inoculum, especially in terms of irreversible deposition of soluble compost on the membrane surface and into membrane pores.This study analysed a submerged membrane bioreactor (SMBR) start-up with the purpose of determining the best conditions to carry it out. In order to do this, a hollow fibre membrane module was installed in a submerged configuration in a pilot aerobic reactor. The experiment was then divided in two phases, lasting 65 days each. During phase 1, the pilot plant was started-up without inoculum of activated sludge and no sludge, withdrawal was performed. Conversely, in phase 2, the MBR pilot plant was started-up with sludge inoculum and the sludge concentration was kept constant. In both phases, the volumetric loading rate applied to the pilot plant was kept constant. The authors analysed the difference in carbon removal performances, the evolution of floc sizes and the fouling rate in both phases. The results confirmed that MBRs can be quickly and easily started-up, but the initial start-up strategy can influence membrane fouling. More specifically, the carbon removal performances were similar in both phases, while the fouling rate increased faster during the start-up without inoculum, especially in terms of irreversible deposition of soluble compost on the membrane surface and into membrane pores