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With a view to the next generation of large space telescopes, we investigate guide-star-free, image-based aberration correction using a unimorph deformable mirror in a plane conjugate to the primary mirror. We designed and built a high-resolution imaging testbed to evaluate control algorithms. In this paper we use an algorithm based on the heuristic hill climbing technique and compare the correction in three different domains, namely the voltage domain, the domain of the Zernike modes, and the domain of the singular modes of the deformable mirror. Through our systematic experimental study, we found that successive control in two domains effectively counteracts uncompensated hysteresis of the deformable mirror.
Active optics is an enabling technology for future large space telescopes. Image-based wavefront control uses an image-sharpness metric to evaluate the optical performance. A control algorithm iteratively adapts a corrective element to maximize this metric, without reconstructing the wavefront. We numerically study a sharpness metric in the space of Zernike modes, and reveal that for large aberrations the Zernike modes are not orthogonal with respect to this metric. The findings are experimentally verified by using a unimorph deformable mirror as
corrective element. We discuss the implications for the correction process and the design of control algorithms.
Improving residential energy efficiency is widely recognized as one of the best strategies for reducing energy demand, combating climate change and increasing security of energy supply. However, progress has been slow to date due to a number of market and behavioural barriers that have not been adequately addressed by energy efficiency policies and programmes.
This study is based on updated findings of the European Futures for Energy Efficiency Project that responds to the EU Horizon 2020 Work Programme 2014-15 theme 'Secure, clean and efficient energy'. This article draws on five case studies from selected European countries - Finland, Italy, Hungary, Spain, and the UK - and evaluates recent energy efficiency developments in terms of indicators, private initiatives, and policy measures in the residential sector. Our analysis shows that the UK government has implemented a better range of policies, coupled with initiatives from the private sector, aimed at improving energy efficiency. However, its existing conditions appear to be more problematic than the other countries. On the other hand, the lack of effective and targeted policies in Finland resulted in increased energy consumption, while in Hungary, Spain and Italy some interesting initiatives, especially in terms of financial and fiscal incentives, have been found.
Technological solutions to the challenge of dangerous climate change are urgent and necessary but to be effective they need to be accompanied by reductions in the total level of consumption and production of goods and services. This is for three reasons. First, private consumption and its associated production are among the key drivers of greenhouse-gas (GHG) emissions, especially among highly emitting industrialized economies. There is no evidence that decoupling of the economy from GHG emissions is possible at the scale and speed needed. Second, investments in more sustainable infrastructure, including renewable energy, needed in coming decades will require extensive amounts of energy, largely from fossil sources, which will use up a significant share of the two-degree carbon budget. Third, improving the standard of living of the world’s poor will consume a major portion of the available carbon allowance. The scholarly community has a responsibility to put the issue of consumption and the associated production on the research and policy agenda.
The United Nations formulated the sustainable development goals (SDGs) in 2015 as a comprehensive global policy framework for addressing the most pressing social and environmental challenges currently facing humanity. In this paper, we analyse SDG 12, which aims to ‘‘ensure sustainable consumption and production patterns.’’ Despite long-standing political recognition of this objective, and ample scientific evidence both on its importance and on the efficacy of various ways of promoting it, the SDGs do not provide clear goals or effective guidance on how to accomplish this urgently needed transformation. Drawing from the growing body of research on sustainable consumption and production (SCP), the paper identifies two dominant vantage points—one focused on promoting more efficient production methods and products (mainly through technological improvement and informed consumer choice) and the other stressing the need to consider also overall volumes of consumption, distributional issues, and related social and institutional changes. We label these two approaches efficiency and systemic. Research shows that while the efficiency approach contains essential elements of a transition to sustainability, it is by itself highly unlikely to bring about sustainable outcomes. Concomitantly, research also finds that volumes of consumption and production are closely associated with environmental impacts, indicating a need to curtail these volumes in ways that safeguard social sustainability, which is unlikely to be possible without a restructuring of existing socioeconomic arrangements. Analysing how these two perspectives are reflected in the SDGs framework, we find that in its current conception, it mainly relies on the efficiency approach. On the basis of this assessment, we conclude that the SDGs represent a partial and inadequate conceptualisation of SCP which will hamper implementation. Based on this determination, this paper provides some suggestions on how governments and other actors involved in SDGs operationalisation could more effectively pursue SCP from a systemic standpoint and use the transformation of systems of consumption and production as a lever for achieving multiple sustainability objectives.
In this paper, we scrutinise the sharing economy from a moral householding perspective and evaluate the moral justifications for a sustainable form of the sharing economy. We consider the emergence of normative moral justifications through householding practices that rest on local mobilisation of people in defence of communities and commitments against the adverse impacts of neoliberal market capitalism.
Our perspective draws on Karl Polanyi's conceptualisation of householding, that is, autarchic, communistic provision in a closed community. Using timebanking as an example, we illustrate how a moral sharing economy can be mobilised in collective battles against the current neoliberal system of economic crisis. We contribute to the amassing sharing economy literature emphasising a central, yet missing element of the current discourse: householding as practices creating self-sufficiency and autonomy as well as combining both kin and stranger.
In this paper typical bypass efficiencies of sediment bypass tunnels (SBTs) used to counter reservoir sedimentation are described, distinguishing between two layouts of the tunnel intake. It results that SBTs are an effective measure to reduce the sedimentation of dam reservoirs, particularly of type (A) with intake at the reservoir head. The hydroabrasive wear of tunnel inverts is significant and
has to be mitigated by using adequate invert liners. The invert abrasion can be estimated based on an abrasion model where a correct input value of the bed material resistance coefficient is paramount to limit model uncertainties. Based on abrasion measurements at prototype SBTs typical values of the material resistance coefficient are recommended for high-strength concrete, natural stones and steel liners. The field experiences gathered so far and the comparison of various invert materials suggest granite pavers as a promising lining material for severe abrasion conditions.
Without adequate measures, reservoirs are not sustainable, neither the
reservoir itself due to continuous sedimentation, nor the downstream ecosystem due to altered sediment continuity. Appropriate actions are inevitable and require a systematic sedimentation management. Sediment bypassing constitutes one effective strategy that routes sediment load around reservoirs during floods. A sediment bypass system has the advantage that only newly entrained sediment is diverted from the upstream to the downstream reach thereby re-establishing sediment connectivity. Hence, such a system contributes to a sustainable water resources management while taking the downstream environment into consideration. This paper gives a state-of-the-art overview
encompassing design, bypass efficiency, hydraulics, challenges due to abrasion, positive effects on both downstream morphology and ecology, and makes design recommendations.
This paper describes the design of the new tunnel invert lining of the 9-foot tunnel at Mud Mountain Dam, Washington, USA. The tunnel diverts all bed load sediments into the tailwater. Major invert abrasion has been observed in the existing steel lining. The new invert design consists of 0.59 m2 and 0.79 m2 granite blocks that are 0.25 m thick and placed tightly together along the tunnel. Stability analysis showed factors of safety ranging from 1.2 to 2.6 against uplift. This will be achieved with strip drains placed in the bedding material along the tunnel. A service-design-life analysis was performed using abrasion prediction modelling.
This model was based on abrasion measurement data acquired from granite field tests at Pfaffensprung sediment bypass tunnel, Switzerland. The estimated annual abrasion depths for the granite were approximately 0.50 mm/year for average sediment transport conditions.