Trade-offs between multifunctionality and profit in tropical smallholder landscapes

Land-use transitions can enhance the livelihoods of smallholder farmers but potential economic-ecological trade-offs remain poorly understood. Here, we present an interdisciplinary study of the environmental, social and economic consequences of land-use transitions in a tropical smallholder landscape on Sumatra, Indonesia. We find widespread biodiversity-profit trade-offs resulting from land-use transitions from forest and agroforestry systems to rubber and oil palm monocultures, for 26,894 aboveground and belowground species and whole-ecosystem multidiversity. Despite variation between ecosystem functions, profit gains come at the expense of ecosystem multifunctionality, indicating far-reaching ecosystem deterioration. We identify landscape compositions that can mitigate trade-offs under optimal land-use allocation but also show that intensive monocultures always lead to higher profits. These findings suggest that, to reduce losses in biodiversity and ecosystem functioning, changes in economic incentive structures through well-designed policies are urgently needed

Performance of a Single Server Queue Supported by an Intermittent Server

International audienceThis chapter concerns the situation of a queue with one regular single server supported by an additional intermittent server who, in order to decrease the mean response time, i) leaves the back office to join the first server when the number of customers reaches the threshold K, ii) leaves the front office when he has no more customers to serve. This study produces a closed form solution for the steady state probability distribution and for different metrics such as expected response times for customers or expectation of busy periods. Then, for a given value of K, the influence of the intermittent server on the response time is exhibited. The consequences on the primary task of the intermittent server are investigated through metrics such as mean working and pseudo-idle periods. Finally, a cost function is proposed from which an optimal value of the threshold K is obtained

Availability Modeling and Evaluation of a Network Service Deployed via NFV

The Network Function Virtualization (NFV) has been conceived as an enabler of novel network infrastructures and services that can be deployed by combining virtualized network elements. In particular, NFV is suited to boost the deployment flexibility of Service Function Chains (SFCs). In this paper, we address an availability evaluation of a chain of network nodes implementing a SFC managed by the Virtualized Infrastructure Manager (VIM), responsible for handling and controlling the system resources. A double-layer model is adopted, where Reliability Block Diagram describes the high-level dependencies among the architecture components, and Stochastic Reward Networks model the probabilistic behavior of each component. In particular, a steady-state availability analysis is carried out to characterize the minimal configuration of the overall system guaranteeing the so-called “five nines” requirement, along with a sensitivity analysis to evaluate the system robustness with respect to variations of some key parameters

Integrated Analysis of Concurrent Distributed Systems using Markovian Process Algebra

this paper [1] and the three technical reports (TR-94-10, 94-11 and 94-12) by the same authors

Adaptive Multiscale Methods for the Numerical Treatment of Systems of PDEs

These notes are concerned with numerical analysis issues arising in the solution of certain systems involving stationary and instationary linear variational problems. Standard examples are second order elliptic boundary value problems, where particular emphasis is placed on the treatment of essential boundary conditions, and linear parabolic equations. These operator equations serve as a core ingredient for control problems where in addition to the state, the solution of the PDE, a control is to be determined which together with the state minimizes a certain tracking-type objective functional. Having assured that the variational problems are well-posed, we discuss numerical schemes based on B-splines and B-spline-type wavelets as a particular multiresolution discretization methodology. The guiding principle is to devise fast and efficient solution schemes which are optimal in the number of arithmetic unknowns. We discuss optimal conditioning of the system matrices, numerical stability of discrete formulations, and adaptive approximations

Towards Guaranteed Quality and Dependability of Information Services

The impressive advances in global networking and information technology provide great opportunities for all kinds of ubiquitous information services, ranging from digital libraries and information discovery to virtual-enterprise workflows and electronic commerce. However, many of these services too often exhibit rather poor quality and are thus unsuitable for mission-critical applications. In this paper I would like to encourage more intensive research efforts towards service quality guarantees, the ultimate goal being the ability to construct and deploy truly dependable systems with provable correctness, continuous availability, and predictable performance. The paper aims to sort out some of the issues towards these elusive goals, mainly by discussing a case study on workflow management. I will point out various assets that can be leveraged, most notably, from database and TP technology and also mathematical modeling and reasoning, and I will outline some research directions that I wo..