Surface acoustic waves in finite slabs of three-dimensional phononic crystals

We study theoretically, by means of layer-multiple-scattering techniques, the propagation of elastic waves through finite slabs of phononic crystals consisting of metallic spheres in a polyester matrix, embedded in air. In particular, we focus on the study of modes localized on the surfaces of the structure. Their origin and behavior, as well as the physical parameters that influence and determine their appearance, are investigated in detail. Our results reveal the existence of absolute phononic frequency gaps in these finite structures, and point out the possibility, under an appropriate choice of the parameters, of tunable regions of frequency free of propagating and/or surface-localized modes. © 2008 The American Physical Society.Peer Reviewe

An Integrative and Joint Approach to Climate Impacts, Hydrological Risks and Adaptation in the Indian Himalayan Region

Climate change has enormous impacts on the cryosphere In the Indian Himalayan Region (IHR) which have been increasingly documented over the past years. The effects of cryosphere change on people, ecosystems and economic sectors is less clear but bears important risks. Adaptation to changing conditions and risks is a priority for the region. Here we draw on experiences of Indo-Swiss collaborations in the field of climate change, cryosphere, risks and adaptation in the IHR. First, we provide a synthesis of the climate and cryosphere in the IHR, and related impacts on downstream communities and systems. Second, we analyze the associated risks from a conceptual and adaptation perspective. We then introduce concepts of co-production of knowledge as an approach to an inclusive and sustainable adaptation process which includes the development of future scenarios with a wide range of stakeholders. We visualize this approach using examples of the water resource sector

Debating dams: The World Commission on Dams 20 years on

The World Commission on Dams (WCD) was a global environmental governance forum that worked between 1998 and 2000 to try to resolve long-standing controversies between supporters and opponents of large dams. Its objectives were to assess the development effectiveness of large dams and to develop best practice guidelines for large dam construction and management, based on an extensive review of scientific evidence and wide-ranging stakeholder consultation. This paper reviews literature discussing the WCD, to understand its influence on the debate on large dams and beyond. We find that its influence is debated within four main contexts: (i) interpretations of stakeholder responses to the WCD report and recommendations; (ii) the persistence of the kinds of impacts of large dams that gave rise to the Commission’s work; (iii) the different visions for appropriate follow-up strategies; (iv) insights from the WCD experience in the context of global environmental governance. Within these four contexts, we identify diverse opinions and directions of post-WCD development and sources of disagreement on its merits and legacy, ranging from calls for its full implementation to dismissal and opposition. Commentators also differ in their assessment of whether the WCD sparked truly novel insights and propositions for dam decision-making or whether it simply represented one among many other elements in the broader debate on dams. Most commonly, the WCD’s work is cited in the context of persistent negative social and environmental impacts of dams: neither the impacts nor the controversy over large dams have ended