Página 29 dos resultados de 476117 itens digitais encontrados em 0.050 segundos

## ‣ Vacuum energy and cosmological constant: View from condensed matter

Volovik, G. E.
Tipo: Artigo de Revista Científica
Português
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The condensed matter examples, in which the effective gravity appears in the low-energy corner as one of the collective modes of quantum vacuum, provide a possible answer to the question, why the vacuum energy is so small. This answer comes from the fundamental trans-Planckian'' physics of quantum liquids. In the effective theory of the low energy degrees of freedom the vacuum energy density is proportional to the fourth power of the corresponding Planck'' energy appropriate for this effective theory. However, from the exact Theory of Everything'' of the quantum liquid it follows that its vacuum energy density is exactly zero without fine tuning, if: there are no external forces acting on the liquid; there are no quasiparticles which serve as matter; no space-time curvature; and no boundaries which give rise to the Casimir effect. Each of these four factors perturbs the vacuum state and induces the nonzero value of the vacuum energy density of order of energy density of the perturbation. This is the reason, why one must expect that in each epoch the vacuum energy density is of order of matter density of the Universe, or/and of its curvature, or/and of the energy density of smooth component -- the quintessence.; Comment: RevTeX file...

## ‣ Ground-State Entanglement Bound for Quantum Energy Teleportation of General Spin-Chain Models

Hotta, Masahiro
Tipo: Artigo de Revista Científica
Português
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Many-body quantum systems in the ground states have zero-point energy due to the uncertainty relation. In many cases, the system in the ground state accompanies spatially-entangled energy density fluctuation via the noncommutativity of the energy density operators, though the total energy takes a fixed value, i.e. the lowest eigenvalue of the Hamiltonian. Quantum energy teleportation (QET) is protocols for extraction of the zero-point energy out of one subsystem using information of a remote measurement of another subsystem. From an operational viewpoint of protocol users, QET can be regarded as an effective rapid energy transportation without breaking all physical laws including causality and local energy conservation. In the protocols, the ground-state entanglement plays a crucial role. In this paper, we show analytically for a general class of spin-chain systems that the entanglement entropy is lower bounded by a positive quadratic function of the teleported energy between the regions of a QET protocol. This supports a general conjecture that ground-state entanglement is an evident physical resource for energy transportation in the context of QET. The result may also deepen our understanding of the energy density fluctuation in condensed matter systems from a new perspective of quantum information theory.; Comment: 24 pages...

## ‣ Neutrino factory in stages: Low energy, high energy, off-axis

Tang, Jian; Winter, Walter
Tipo: Artigo de Revista Científica
Português
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We discuss neutrino oscillation physics with a neutrino factory in stages, including the possibility of upgrading the muon energy within the same program. We point out that a detector designed for the low energy neutrino factory may be used off-axis in a high energy neutrino factory beam. We include the re-optimization of the experiment depending on the value of theta_13 found. As upgrade options, we consider muon energy, additional baselines, a detector mass upgrade, an off-axis detector, and the platinum (muon to electron neutrino) channels. In addition, we test the impact of Daya Bay data on the optimization. We find that for large theta_13 (theta_13 discovered by the next generation of experiments), a low energy neutrino factory might be the most plausible minimal version to test the unknown parameters. However, if a higher muon energy is needed for new physics searches, a high energy version including an off-axis detector may be an interesting alternative. For small theta_13 (theta_13 not discovered by the next generation), a plausible program could start with a low energy neutrino factory, followed by energy upgrade, and then baseline or detector mass upgrade, depending on the outcome of the earlier phases.; Comment: 23 pages...

## ‣ Energy Spectral Property in an Isolated CME-driven Shock

Wang, Xin; Yan, Yihua; Ding, Mingde; Wang, Na; Shan, Hao
Tipo: Artigo de Revista Científica
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Observations from multiple spacecraft show that there are energy spectral "breaks" at 1-10MeV in some large CME-driven shocks. However, numerical models can hardly simulate this property due to high computational expense. The present paper focuses on analyzing these energy spectral "breaks" by Monte Carlo particle simulations of an isolated CME-driven shock. Taking the Dec 14 2006 CME-driven shock as an example, we investigate the formation of this energy spectral property. For this purpose, we apply different values for the scattering time in our isolated shock model to obtain the highest energy "tails", which can potentially exceed the "break" energy range. However, we have not found the highest energy "tails" beyond the "break" energy range, but instead find that the highest energy "tails" reach saturation near the range of energy at 5MeV. So, we believe that there exists an energy spectral "cut off" in an isolated shock. If there is no interaction with another shock, there would not be formation of the energy spectral "break" property.; Comment: 10pages,4figures,Accepted in RAA

## ‣ Casimir Energy for a Coupled Fermion-Soliton System

Tipo: Artigo de Revista Científica
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In this paper we compute the Casimir energy for a coupled fermion-pseudoscalar field system. In the model considered in this paper the pseudoscalar field is \textit{static} and \textit{prescribed} with two adjustable parameters. These parameters determine the values of the field at infinity ($\pm \theta_0$) and its scale of variation ($\mu$). One can build up a field configuration with arbitrary topological charge by changing $\theta_0$, and interpolate between the extreme adiabatic and non-adiabatic regimes by changing $\mu$. This system is exactly solvable and therefore we compute the Casimir energy exactly and unambiguously by using an energy density subtraction scheme. We show that in general the Casimir energy goes to zero in the extreme adiabatic limit, and in the extreme non-adiabatic limit when the asymptotic values of the pseudoscalar field properly correspond to a configuration with an arbitrary topological charge. Moreover, in general the Casimir energy is always positive and on the average an increasing function of $\theta_0$ and always has local maxima when there is a zero mode, showing that these configurations are energetically unfavorable. We also compute and display the energy densities associated with the spectral deficiencies in both of the continua...

## ‣ Discarded low energy particles in extensive air shower simulations: Effect on the shower Energy Deposit

Tueros, M. J.
Tipo: Artigo de Revista Científica
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The simulation of particle cascades initiated in the atmosphere by ultra high energy cosmic ray particles involves the generation and propagation of a huge amount of particles. As it is unpractical to follow every particle to its end, particles below a certain energy ($E_{Cut}$) are discarded from the simulation. In this article we study in detail the influence that this cut has on the total energy deposited in the atmosphere by the particle cascade in AIRES simulations. The energy deposit is directly related to the emission of fluorescence light and is critical for the accurate simulation of shower signals in fluorescence detectors. Not correcting for the discarded particles introduces a bias on several shower observables related to the energy deposit that can range from 3 to 30% or more depending on the $E_{Cut}$ value used. A prescription for the correct treatment of these particles is proposed, and the resulting corrections to the total energy deposit are addressed, including a new universal parametrization of the mean energy deposit per particle. The low energy cut is introduced in the simulations to reduce the required CPU time per shower at the expense of simulation accuracy. We find that a 0.4 MeV cut for electrons and 0.9 MeV cut for gammas is an adequate compromise...

## ‣ Generic bottom-up building-energy models for developing regional energy transition scenarios

Knoeri, Christof; Goetz, Alessandra; Binder, Claudia R.
Tipo: Conferência ou Objeto de Conferência Formato: application/pdf
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Energy demand from buildings has the largest single share of the global final energy demand, but offers massive energy saving potentials through state-of-the-art technologies and behavioural changes. However, the required speed of technology adoption and behavioural changes to achieve such savings are largely uncertain and embedded in complex socio-technical system. Successful examples of achieving such systemic transition in the energy system are mostly found on the regional scale. Therefore a transition from the existing conventional centralized and mainly fossil fuelbased energy infrastructure towards a decentralized and renewable-based energy infrastructure is required. This research presents a generic bottom-up building-energy model for developing regional energy scenarios. Besides the development of regional scenarios, this model allows for analysing various detailed aspects of buildings' energy demand, such as retrofitting behaviour, technology adoption, and occupancy behaviour with agent-based modelling extensions.

## ‣ Modelling energy retrofit investments in the UK housing market: A microeconomic approach

Tipo: Article; accepted version
Português
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This is the author accepted manuscript. The final version is available from Emerald via http://dx.doi.org/10.1108/SASBE-03-2013-0016; Purpose - Improving the energy efficiency of the existing residential building stock has been identified as a key policy aim in many countries. This study reviews the extant literature on investment decisions in domestic energy efficiency and presents a model that is both grounded in microeconomic theory and empirically tractable. Design/methodology/approach ? This study develops a modified and extended version of an existing microeconomic model to embed the retrofit investment decision in a residential property market context, taking into account tenants? willingness to pay and cost-reducing synergies. A simple empirical test of the link between energy efficiency measures and housing market dynamics is then conducted. Findings - The empirical data analysis for England indicates that where house prices are low, energy efficiency measures tend to increase the value of a house more in relative terms compared to higher-priced regions. Secondly, where housing markets are tight, landlords and sellers will be successful even without investing in energy efficiency measures. Thirdly, where wages and incomes are low...

## ‣ Retrofitting the domestic built environment: investigating household perspectives towards energy efficiency technologies and behaviour

Pelenur, Marcos
Fonte: University of Cambridge; Department of Engineering Publicador: University of Cambridge; Department of Engineering
Tipo: Thesis; doctoral; PhD
Português
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Retrofitting the UK domestic built environment presents an excellent opportunity to improve its energy performance. However, retrofitting homes is a complex challenge conflated by multiple factors. Due to this complexity, a shortfall exists between the full potential and realised adoption of energy efficiency measures in the UK, a phenomenon termed the ?Energy Efficiency Gap?. While a number of technical or economic factors may help explain this gap, difficult to quantify factors, such as social motivations, barriers, and viewpoints towards energy are also significant and often under-emphasised in public policy. As such, in order to improve the understanding of the Energy Efficiency Gap and the uptake of future retrofit initiatives, this research adopted a socio-technical approach that considered social and technical retrofit factors together. Specifically, this research collected data from interviews, questionnaires, and a Q Study in the cities of Manchester and Cardiff, alongside a questionnaire that measured energy efficiency technology and behaviour preferences. An original contribution to knowledge was using the data to empirically identify motivations and barriers to adopting energy efficient technologies, as well as identifying household viewpoints towards energy use and linking them to retrofit technology and energy efficiency behaviour preferences. As a result of this research...

## ‣ Basic Research Needs for Solar Energy Utilization: report of the Basic Energy Sciences Workshop on Solar Energy Utilization, April 18-21, 2005

Lewis, Nathan S.; Crabtree, George
Fonte: US Department of Energy, Office of Basic Energy Science Publicador: US Department of Energy, Office of Basic Energy Science
Tipo: Book; NonPeerReviewed Formato: application/pdf
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This report of the Basic Energy Sciences Workshop on Solar Energy Utilization identifies the key scientific challenges and research directions that will enable efficient and economic use of the solar resource to provide a significant fraction of global primary energy by the mid 21st century. The report reflects the collective output of the workshop attendees, which included 200 scientists representing academia, national laboratories, and industry in the United States and abroad, and the U.S. Department of Energy’s Office of Basic Energy Sciences and Office of Energy Efficiency and Renewable Energy. Solar energy conversion systems fall into three categories according to their primary energy product: solar electricity, solar fuels, and solar thermal systems. Each of the three generic approaches to exploiting the solar resource has untapped capability well beyond its present usage. Workshop participants considered the potential of all three approaches, as well as the potential of hybrid systems that integrate key components of individual technologies into novel cross-disciplinary paradigms.

## ‣ Política energética no Brasil; Energy policies in Brazil

Goldemberg, José; Moreira, José Roberto
Tipo: info:eu-repo/semantics/article; info:eu-repo/semantics/publishedVersion; ; ; ; ; ; Formato: application/pdf; application/pdf
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ENERGIA é um ingrediente essencial para a vida na sociedade moderna. A ampliação da infra-estrututa energética do Brasil, tanto na sua produção como no consumo exigirá grandes investimentos. Daí a necessidade da presença do Governo no planejamento das atividades energéticas, que são geralmente implementados pela iniciativa privada. Esta presença é essencial para: 1. atender a demanda da sociedade por mais e melhores serviços de energia; 2. estimular a participação de fontes energéticas sustentáveis e duradouras; 3. priorizar o uso eficiente da energia para liberar capital aos setores mais produtivos da economia e preservar o meio ambiente; 4. utilizar o investimento em energia como fonte de geração de empregos e de estímulo à indústria nacional; 5. incorporar à matriz energética insumos importados quando isso resultar em vantagens comerciais e sociais ao país, inclusive através da abertura de exportação de produtos e serviços e, 6. produzir energia de diversas fontes, reduzindo o risco da eventual escassez de algumas delas de forma compatível com as reservas disponíveis no país.; ENERGY is an essential ingredient to life in modern society. The expansion of Brazil's energy infrastructure, both for production and consumption...

## ‣ The Impact of Appliance Efficiency on Building Energy Performance -A Case Study for a Tianjin Eco-city in China

Fan, Hua
Tipo: Masters' project Formato: 576675 bytes; application/pdf
Português
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Buildings consume approximately 40% of the total energy use in the world. A building is a complex system whose annual energy use consists of many factors. The top five end-uses of building energy are space heating, space cooling, water heating, lighting and electrical appliances. Over fifty countries have developed efficiency standards and energy labels for residential appliances and commercial equipment to reduce energy consumption of those end-users. However, studies rarely consider the appliance efficiency in a whole building system. For this project, I used a computer-based simulation program to evaluate the impact of appliance efficiency in buildings on the heating, ventilation and air conditioning systems (HVAC). I studied the Chinese energy efficiency standards for refrigerators, washing machines, televisions, computers and rice cookers, and evaluated their impacts on two residential building prototypes being designed in an eco-city being planned and under construction in China. I found that improved efficiency of refrigerators and washing machines decreased peak load and the energy use for space cooling, but increased the energy use for space heating. The improved efficiency cut overall energy consumption and could lead to total annual energy savings of \$1.2 million in Tianjin eco-city. Although several limitations exist in this project...

## ‣ Wood Energy in the Southeastern United States: A Strategy for Sustainable Growth

Palange, David
Tipo: Masters' project Formato: 748661 bytes; application/pdf
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Economic and environmental concerns over fossil fuels are placing the Southeast United States in a position to expand its use of wood biomass for energy. The region’s productive forestland, growing population, and wood products industry can help provide a sustainable, diverse and abundant supply of woody biomass much of which is currently unutilized. While federal and state policies are steering the use of wood toward large-scale production of cellulosic ethanol and electricity in the Southeast, the generation of thermal energy, the most efficient use of wood, appears to be undervalued. Three market segments that can benefit economically from biomass thermal energy are highlighted: institutions, agriculture, and industry. These segments are selected based on sustainability criteria that include a rapid payback period, high demand for thermal energy, efficient use of woody biomass, proximity to fuel source, and potential for repeatability across the region. Sensitivity analyses and case studies are used to support these findings. Critical factors for implementation of biomass thermal energy in the Southeast are also identified, revealing key economic, political and social barriers and drivers. Central barriers include the lack of a formal biomass market...

## ‣ Incentivizing Energy Efficiency In Public Buildings Through Information Disclosure: North Carolina Community Colleges As Case Study

Jackson, Charles
Tipo: Masters' project Formato: 1081410 bytes; application/pdf
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The energy efficiency gap, which describes the difference between current and socially optimal levels of energy efficiency, has persisted for decades, even as our nation’s energy intensity has improved. Economics literature tends to focus on informational, behavioral, and large-scale market failures when positing the causes of the gap. However, state and local policy failures may greatly contribute to the gap as well. Information disclosure policies are particularly well suited to narrow the energy efficiency gap, because they cost-effectively address behavioral and informational failures and can be easily implemented on the local level. The Federal Government has utilized such policies to vastly improve the energy efficiency of its buildings’ stock, but state and local governments have been slow to follow suit. This Master’s project investigates the potential of utilizing information disclosure policies to narrow the energy efficiency gap in public buildings at the local level by analyzing the North Carolina Community College System as a case study. First, analysis of the Toxics Release Inventory, the archetypal environmental information disclosure policy in the United States, yields recommendations for incentivizing energy efficiency in public buildings. Next...

## ‣ A Method for Measuring the Efficiency Gap between Average and Best Practice Energy Use: The ENERGY STAR Industrial Energy Performance Indicator

Boyd, Gale
Fonte: Journal of Industrial Ecology Publicador: Journal of Industrial Ecology
Tipo: Artigo de Revista Científica Formato: 410849 bytes; application/pdf
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A common feature distinguishing between parametric/statistical models and engineering economics models is that engineering models explicitly represent best practice technologies, whereas parametric/statistical models are typically based on average practice. Measures of energy intensity based on average practice are of little use in corporate management of energy use or for public policy goal setting. In the context of companyor plant-level indicators, it is more useful to have a measure of energy intensity that is capable of indicating where a company or plant lies within a distribution of performance. In other words, is the performance close to (or far from) the industry best practice? This article presents a parametric/statistical approach that can be used to measure best practice, thereby providing a measure of the difference, or "efficiency gap," at a plant, company, or overall industry level. The approach requires plant-level data and applies a stochastic frontier regression analysis used by the ENERGY STARTM industrial energy performance indicator (EPI) to energy intensity. Stochastic frontier regression analysis separates energy intensity into three components: systematic effects, inefficiency, and statistical (random) error. The article outlines the method and gives examples of EPI analysis conducted for two industries...

## ‣ Surface Energy Powered Processes upon Drop Coalescence

Liu, Fangjie
Tipo: Dissertação
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Surface energy-powered motion is useful for a variety of autonomous functions such as passive cooling and self-cleaning, where independence from external forces is highly desirable. Drop coalescence offers a convenient process to release surface energy, which can be harvested to power self-propelled fluid motion.

On superhydrophobic surfaces, out-of-plane jumping motion spontaneously results from drop coalescence. However, less than 4\% of the released surface energy is converted to useful kinetic energy giving rise to the jumping motion. Using three-dimensional interfacial flow simulations that are experimentally validated, we elucidate the mechanism of low energy conversion efficiency. The non-wetting substrate interferes with the expanding liquid bridge between the coalescing drops at a relatively late stage, forcing a small fraction of the merged drop to "bounce" back from the non-wetting substrate. The substrate breaks the symmetry of surface energy release, leading to self-propelled jumping that is perpendicular to the solid substrate. The intercepting substrate imparts a relatively small translational momentum on the overall merged drop, giving rise to a small energy conversion efficiency.

This mechanistic understanding has provided guidance on how to increase the energy conversion efficiency by changing the geometry of the intercepting solid surface...

## ‣ A Toolkit for Identifying Energy Savings at Colleges and Universities

Davis, Eliza
Tipo: Masters' project
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Across the country college and university leaders are beginning to recognize the financial and reputational benefits of saving energy and “going green”. However school administrators and other campus leaders face institutional, behavioral, and economic barriers to identifying energy-saving opportunities on their own. To address these challenges a “toolkit” was developed to help college and university leaders identify energy-saving upgrades and programs, calculate project costs and savings, and communicate the value of these investments to key stakeholders. The toolkit includes a menu of energy efficiency projects appropriate for college and university campuses as well as detailed explanations of how to calculate the expected project costs and savings. This resource walks users through the process of benchmarking and tracking campus energy use over time and introduces key calculations to consider for all energy investments such as net present value, payback period, and avoided greenhouse gas emissions. Additionally the toolkit addresses the importance of education and engagement for successful adoption of energy efficiency programs. Finally, the toolkit includes two case studies about identifying energy-saving projects at universities in North Carolina. This is a free and accessible guidebook designed for use by school administrators...

## ‣ Desenvolvimento de energias renováveis: comparativo dos cenários e das perspectivas de políticas públicas para alguns países da América Latina; Developing Renewable Energy: Comparative Scenarios and Public Policy Perspectives from some Latin American Countries

Lardizabal, Claudia Cecilia; Rosales, Ismene; Pasqual, Janaina Camile; Herrera, Gricelda; Mejia, Sandra; Cancino, Mariel Álvarez
Tipo: info:eu-repo/semantics/article; info:eu-repo/semantics/publishedVersion; ; Formato: application/pdf
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The energy matrix of Latin American and the Caribbean countries has one of the largest renewable energy components when compared to other regions of the world. Nonetheless, by 2009 nearly three-quarters of its structure corresponded to fossil fuels, with most of the countries being net importers of these fuels. This situation marks the region´s dependence on the effects of changes in energy commodities. Therefore, the opportunity lies in higher use of renewable energy sources that contribute to the country´s energy security and represent significant environmental benefits. The purpose of this paper is to provide a comparative analysis of current energy scenarios of six Latin American countries (Mexico, Honduras, Nicaragua, Brazil, Ecuador and Chile) in order to evaluate the policies, programs and strategies implemented in the search for greater participation of renewable energy. Considering the importance of the water-energy nexus that could serve to promote renewables under conditions of water scarcity, a qualitative data comparison was accomplished, considering energy consumption, CO2 emissions, GDP and water withdrawals per country. The authors conclude that, despite technological and financial constraints, all the involved countries are moving towards the substitution of a fossil fuel based matrix to a renewable one. This process could be seen as a result of clear policies and strategies that have been set...

## ‣ Limitations and improvements of the energy balance closure with reference to experimental data measured over a maize field

MASSERONI,DANIELE; CORBARI,CHIARA; MANCINI,MARCO
Fonte: Centro de Ciencias de la Atmósfera, UNAM Publicador: Centro de Ciencias de la Atmósfera, UNAM
Tipo: Artigo de Revista Científica Formato: text/html