532 research outputs found
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Learning Curves For Energy Technology: A Critical Assessment
In this paper, which forms a chapter in the forthcoming Book ĂąÂÂDelivering a Low Carbon Electricity System: Technologies, Economics and PolicyĂąÂÂ, Jamasb and Kohler revisit the literature on learning curves and their application to energy technology and climate change policy analysis and modeling. The academic literature and policy documents have in recent years embraced the learning curves and applied the concept to technology analysis and forecasting cost reductions. We argue that learning curves have often been used or assumed uncritically in technology analysis and draw parallels between the use of learning rates in energy technological progress and climate change modeling to that of discount rates in social cost benefit analysis. The paper discusses that care needs to be taken in applying learning curves, originally developed as an empirical tool to assess the effect of learning by doing in manufacturing, to analysis innovation and technical change. Finally, we suggest some potential extensions of learning curves, e.g. by incorporating R&D and diffusion effects into learning models, and other areas where learning curves may potentially be a useful tool in energy technology policy and analysis
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The impact of a seasonally ice free Arctic Ocean on the temperature, precipitation and surface mass balance of Svalbard
The observed decline in summer sea ice extent since the 1970s is predicted to continue until the Arctic Ocean is seasonally ice free during the 21st Century. This will lead to a much perturbed Arctic climate with large changes in ocean surface energy ïŹux. Svalbard, located on the present day sea ice edge, contains many low lying ice caps and glaciers and is expected to experience rapid warming over the 21st Century. The total sea level rise if all the land ice on Svalbard were to melt completely is 0.02 m.
The purpose of this study is to quantify the impact of climate change on Svalbardâs surface mass balance (SMB) and
to determine, in particular, what proportion of the projected changes in precipitation and SMB are a result of changes to the Arctic sea ice cover. To investigate this a regional climate model was forced with monthly mean climatologies of sea surface temperature (SST) and sea ice concentration for the periods 1961â1990 and 2061â2090 under two emission scenarios. In a novel forcing experiment, 20th Century SSTs and 21st Century sea ice were used to force one simulation to investigate the role of sea ice forcing. This experiment results in a 3.5 m water equivalent increase in Svalbardâs SMB compared to the present day. This is because over 50 % of the projected increase in winter precipitation over Svalbard under the A1B emissions scenario is due to an increase in lower atmosphere moisture content associated with evaporation from the ice free ocean. These results indicate that increases in precipitation due to sea ice decline may act to moderate mass loss from Svalbardâs glaciers due to future Arctic warming
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Expenditure on Environmentally Sensitive Goods and Services: Household Spending in Europe
Expenditure on environmentally sensitive goods and services has been analysed for the member states of the EEC, using the EUROSTAT Family Budgets data based on surveys carried out in 1988. Some data are also available from Germany, Finland, Norway, Sweden and Switzerland. The groups with low average expenditures spend a higher proportion of their budget on energy than those with high expenditures, but a lower proportion on transport, especially vehicle purchases. However, all groups spend a much higher proportion of expenditure on transport than on energy, although purchased (i.e. non-private motoring and public) transport is a small proportion of transport spending, even for low expenditure groups. Pensioners spend a relatively high proportion of their budgets on package tours, especially compared to the other 'at risk' groups
Cavity-assisted measurement and coherent control of collective atomic spin oscillators
We demonstrate continuous measurement and coherent control of the collective
spin of an atomic ensemble undergoing Larmor precession in a high-finesse
optical cavity. The coupling of the precessing spin to the cavity field yields
phenomena similar to those observed in cavity optomechanics, including cavity
amplification, damping, and optical spring shifts. These effects arise from
autonomous optical feedback onto the atomic spin dynamics, conditioned by the
cavity spectrum. We use this feedback to stabilize the spin in either its high-
or low-energy state, where, in equilibrium with measurement back-action
heating, it achieves a steady-state temperature, indicated by an asymmetry
between the Stokes and anti-Stokes scattering rates. For sufficiently large
Larmor frequency, such feedback stabilizes the spin ensemble in a nearly pure
quantum state, in spite of continuous measurement by the cavity field.Comment: 5 pages, 4 figures, and supplemental materia
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Electricity Network Scenarios for Great Britain in 2050
The next fifty years are likely to see great developments in the technologies deployed in electricity systems, with consequent changes in the structure and operation of power networks. This paper, which forms a chapter in the forthcoming book Future Electricity Technologies and Systems, develops and presents six possible future electricity industry scenarios for Great Britain, focussed on the year 2050. The paper draws upon discussions of important technologies presented by expert authors in other chapters of the book to consider the impact of different combinations of key influences on the nature of the power system in 2050. For each scenario there is a discussion of the effects of the key parameters, with a description and pictorial illustration. Summary tables identify the role of the technologies presented in other chapters of the book, and list important figures of interest, such as the capacity and energy production of renewable generation technologies
Complex networks of interacting stochastic tipping elements: cooperativity of phase separation in the large-system limit
Tipping elements in the Earth System receive increased scientific attention
over the recent years due to their nonlinear behavior and the risks of abrupt
state changes. While being stable over a large range of parameters, a tipping
element undergoes a drastic shift in its state upon an additional small
parameter change when close to its tipping point. Recently, the focus of
research broadened towards emergent behavior in networks of tipping elements,
like global tipping cascades triggered by local perturbations. Here, we analyze
the response to the perturbation of a single node in a system that initially
resides in an unstable equilibrium. The evolution is described in terms of
coupled nonlinear equations for the cumulants of the distribution of the
elements. We show that drift terms acting on individual elements and offsets in
the coupling strength are sub-dominant in the limit of large networks, and we
derive an analytical prediction for the evolution of the expectation (i.e., the
first cumulant). It behaves like a single aggregated tipping element
characterized by a dimensionless parameter that accounts for the network size,
its overall connectivity, and the average coupling strength. The resulting
predictions are in excellent agreement with numerical data for Erd\"os-R\'enyi,
Barab\'asi-Albert and Watts-Strogatz networks of different size and with
different coupling parameters
Tracking evaporative cooling of a mesoscopic atomic quantum gas in real time
The fluctuations in thermodynamic and transport properties in many-body
systems gain importance as the number of constituent particles is reduced.
Ultracold atomic gases provide a clean setting for the study of mesoscopic
systems; however, the detection of temporal fluctuations is hindered by the
typically destructive detection, precluding repeated precise measurements on
the same sample. Here, we overcome this hindrance by utilizing the enhanced
light--matter coupling in an optical cavity to perform a minimally invasive
continuous measurement and track the time evolution of the atom number in a
quasi two-dimensional atomic gas during evaporation from a tilted trapping
potential. We demonstrate sufficient measurement precision to detect atom
number fluctuations well below the level set by Poissonian statistics.
Furthermore, we characterize the non-linearity of the evaporation process and
the inherent fluctuations of the transport of atoms out of the trapping volume
through two-time correlations of the atom number. Our results establish coupled
atom--cavity systems as a novel testbed for observing thermodynamics and
transport phenomena in mesosopic cold atomic gases and, generally, pave the way
for measuring multi-time correlation functions of ultracold quantum gases.Comment: Significantly extended discussion of Fig. 4. Accepted for publication
in Phys. Rev.
An ectomycorrhizal fungus alters sensitivity to jasmonate, salicylate, gibberellin, and ethylene in host roots.
The phytohormones jasmonate, gibberellin, salicylate, and ethylene regulate an interconnected reprogramming network integrating root development with plant responses against microbes. The establishment of mutualistic ectomycorrhizal symbiosis requires the suppression of plant defense responses against fungi as well as the modification of root architecture and cortical cell wall properties. Here, we investigated the contribution of phytohormones and their crosstalk to the ontogenesis of ectomycorrhizae (ECM) between grey poplar (Populus tremula x alba) roots and the fungus Laccaria bicolor. To obtain the hormonal blueprint of developing ECM, we quantified the concentrations of jasmonates, gibberellins, and salicylate via liquid chromatography-tandem mass spectrometry. Subsequently, we assessed root architecture, mycorrhizal morphology, and gene expression levels (RNA sequencing) in phytohormone-treated poplar lateral roots in the presence or absence of L. bicolor. Salicylic acid accumulated in mid-stage ECM. Exogenous phytohormone treatment affected the fungal colonization rate and/or frequency of Hartig net formation. Colonized lateral roots displayed diminished responsiveness to jasmonate but regulated some genes, implicated in defense and cell wall remodelling, that were specifically differentially expressed after jasmonate treatment. Responses to salicylate, gibberellin, and ethylene were enhanced in ECM. The dynamics of phytohormone accumulation and response suggest that jasmonate, gibberellin, salicylate, and ethylene signalling play multifaceted roles in poplar L. bicolor ectomycorrhizal development
Scanning cavity microscopy of a single-crystal diamond membrane
Spin-bearing color centers in the solid state are promising candidates for the realization of quantum networks and distributed quantum computing. A remaining key challenge is their efficient and reliable interfacing to photons. Incorporating minimally processed membranes into open-access microcavities represents a promising route for Purcellenhanced spin-photon interfaces: it enables significant emission enhancement and efficient photon collection, minimizes deteriorating influence on the quantum emitter, and allows for full spatial and spectral tunability, key for controllably addressing suitable emitters with desired optical and spin properties. Here, we study the properties of a high-finesse fiber Fabry-PĂ©rot microcavity with integrated single-crystal diamond membranes by scanning cavity microscopy. We observe spatially resolved the effects of the diamond-air interface on the cavity mode structure: a strong correlation of the cavity finesse and mode structure with the diamond thickness and surface topography, significant transverse-mode mixing under diamond-like conditions, and mode-character-dependent polarization-mode splitting. Our results reveal the influence of the diamond surface on the achievable Purcell enhancement, which helps to clarify the route towards optimized spin-photon interfaces
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