Multiple Use Management of Tropical Forests: On the Superiority of Land Use Specialization

One of the debates in tropical forest management centers on how to manage these resources for multiple uses. In fact, although the need to account for multiple values in forestry decisions is widely recognized, its implications for forest management are not clear. In particular, how is multiple-use to be achieved? Should management for multiple values be adopted on each forest management unit? Or should multiple use be attained at the landscape level, for example by dividing the landscape into units and manage each unit for a dominant use (e.g., timber production, conservation, etc.)? In tropical forest settings, where multiple use is often attained with less intensive harvesting and at the expenses of bringing larger – often virgin – areas into production, the circumstances under which multiple-use management is superior to dominant-use remain unclear. Past scholarly work has pointed to some circumstances under which dominant use may be superior to multiple (joint) use. The empirical significance of these circumstances has been quantified only in limited temperate settings. In this paper, we review two circumstances that are likely to yield to a non-convexity in the forest production set: the existence of large fixed costs associated with the production of one good (e.g., timber); and the existence of inefficiencies in the timber production process. The empirical significance of such circumstances is evaluated with the aid of a simulation model developed for a lowland tropical forest in peninsular Malaysia. Results suggest that, for certain benefits associated with forest diversity, specialized use (separation of conservation and timber production processes) is likely to be a strategy superior to multiple use.tropical forests, multiple use, specialization, non-convexities, biodiversity, carbon storage

A modelling technique for calculating stress intensity factors for structures reinforced by bonded straps. Part II: Validation

In this second part of the two-part paper validation of the 2D FE modelling technique described in the first part is presented for a range of test configurations. Each mechanism that influences crack growth behaviour of strap reinforced structures is modelled for different substrate geometries, strap materials and dimensions in order to test the accuracy and robustness of the methodology. First, calculated through-thickness strain energy release rate distribution is compared with the result of a 3D FE model to validate this 2D model. Second, calculated disbond areas, thermal residual stresses and their redistribution with crack propagation are validated against experimental measurements. Third, influence of geometric nonlinearity and the need to use the alternate analysis method described in part I are demonstrated by examples, and errors generated by not following this analysis rule are given. Finally, using the 2D model calculated stress intensity factors, fatigue crack growth rates and lives are predicted for different specimens, strap materials and applied stress levels and are compared with the experimental tests. Good or acceptable agreement has been achieved for each case

Promoting better logging practices in tropical forests

The study presented in this paper tests the empirical significance of several common recommendations for promoting better logging practices in tropicalforests: in particular, making concession agreements longer, linking renewal of those agreements to logging practices, and using performance bonds to encourage compliance with logging regulations. It assesses how these recommendations affect both the economics of timber harvesting and the provision of environmental benefits. With regard to the latter it focuses on carbon sequestration and biodiversity. It also examines the effects of timber fees and discount rates on economic and environmental outcomes. The study focuses on two aspects of logger behavior: choice of logging technology and compliance with prescribed minimum diameter cutting limits. The study analyzes loggers'decisions about technology and cutting limits in two scenarios: (i) the repeated harvesting of a given forest stand (virgin forest for the initial harvest, second growth forest for subsequent harvests), which occurs at a time delay of several decades (the cutting cycle); and (ii) the sequential harvesting of an annual series of different forest stands with identical characteristics (all virgin). The former gets at issues of sustainable forest management, while the latter gets at the mining of virgin timber stocks. In this way, the study examines both the long-run and short-run dynamics of logger behavior. The paper is organized as follows. The authors begin by describing the models of forest growth and logger behavior that comprise the simulation model. The description of the forest growth model includes the indicators used to predict the environmental impacts of logging, and the description of the model of logger behavior includes the regulatory instruments analyzed. Next, they present and discuss the simulation results, dealing with repeated harvesting and sequential harvesting in turn. In the final section the report highlights the principal conclusions that can be drawn from these results.Forests and Forestry,Environmental Economics&Policies,Water Conservation,Silviculture,Agribusiness,Environmental Economics&Policies,Agricultural Trade,Agribusiness,Forestry,Silviculture

The future prospects of muon colliders and neutrino factories

The potential of muon beams for high energy physics applications is described along with the challenges of producing high quality muon beams. Two proposed approaches for delivering high intensity muon beams, a proton driver source and a positron driver source, are described and compared. The proton driver concepts are based on the studies from the Muon Accelerator Program (MAP). The MAP effort focused on a path to deliver muon-based facilities, ranging from neutrino factories to muon colliders, that could span research needs at both the intensity and energy frontiers. The Low EMittance Muon Accelerator (LEMMA) concept, which uses a positron-driven source, provides an attractive path to very high energy lepton colliders with improved particle backgrounds. The recent study of a 14 TeV muon collider in the LHC tunnel, which could leverage the existing CERN injectors and infrastructure and provide physics reach comparable to the 100 TeV FCC-hh, at lower cost and with cleaner physics conditions, is also discussed. The present status of the design and R&D efforts towards each of these sources is described. A summary of important R&D required to establish a facility path for each concept is also presented.Comment: 29 pages, 17 figure

Nonlinear pulse shaping in optical fibres with a neural network

We use a machine-learning based paradigm to solve the direct and inverse problems relating to the shaping of optical pulses that occurs upon nonlinear propagation in optical fibres with a neural network

Il superamento del modello pianificatorio tradizionale

Il lavoro indica le traiettorie di superamentro del tradizionale modello pianificatorio dettato dalla legge urbanistica: centralit\ue0 della conoscenza, partecipazione, rivedibilit\ue0 delle scelte e ricerca di una maggior effettivit\ue0 sono i caratteri salienti della nuova stagione pianificatori