Dynamic bonding of metallic nanocontacts: Insights from experiments and atomistic simulations

The conductance across an atomically narrow metallic contact can be measured by using scanning tunneling microscopy. In certain situations, a jump in the conductance is observed right at the point of contact between the tip and the surface, which is known as “jump to contact” (JC). Such behavior provides a way to explore, at a fundamental level, how bonding between metallic atoms occurs dynamically. This phenomenon depends not only on the type of metal but also on the geometry of the two electrodes. For example, while some authors always find JC when approaching two atomically sharp tips of Cu, others find that a smooth transition occurs when approaching a Cu tip to an adatom on a flat surface of Cu. In an attempt to show that all these results are consistent, we make use of atomistic simulations; in particular, classical molecular dynamics together with density functional theory transport calculations to explore a number of possible scenarios. Simulations are performed for two different materials: Cu and Au in a [100] crystal orientation and at a temperature of 4.2 K. These simulations allow us to study the contribution of short- and long-range interactions to the process of bonding between metallic atoms, as well as to compare directly with experimental measurements of conductance, giving a plausible explanation for the different experimental observations. Moreover, we show a correlation between the cohesive energy of the metal, its Young's modulus, and the frequency of occurrence of a jump to contact.

Germany's energy transformation: difficult beginnings. OSW Report, March 2013

Initiated in May 2011, several months after the Fukushima nuclear disaster, Germany’s energy transformation (Energiewende) has been presented as an irrevocable plan, and – due to the speed of change required – it represents a new quality in Germany’s energy strategy. Its main objectives include: nuclear energy being phased out by 2022, the development of renewable energy sources (OZE), the expansion of transmission networks, the construction of new conventional power plants and an improvement in energy efficiency.The cornerstone of the strategy is the development of renewable energy. Under Germany's amended renewable energy law, the proportion of renewable energy in electricity generation is supposed to increase steadily from the current level of around 20% to approximately 38% in 2020. In 2030, renewable energy is expected to account for 50% of electricity generation. This is expected to increase to 65% in 2040 and to as much as 80% in 2050. The impact of the Energiewende is not limited to the sphere of energy supplies. In the medium and long term, it will change not only to the way the German economy operates, but also the functioning of German society and the state. Facing difficulties with the expansion of transmission networks, the excessive cost of building wind farms, and problems with the stability of electricity supplies, especially during particularly cold winters, the federal government has so far tended to centralise power and limit the independence of the German federal states with regard to their respective energy policies, justifying this with the need for greater co-ordination. The Energiewende may also become the beginning of a "third industrial revolution", i.e. a transition to a green economy and a society based on sustainable development. This will require a new "social contract" that will redefine the relations between the state, society and the economy. Negotiating such a contract will be one of the greatest challenges for German policy in the coming years.

The Energy Performance of Buildings: Promises Still Unfulfilled. Egmont Paper No. 78, May 2015

EXECUTIVE SUMMARY All observers agree that energy efficiency must be the cornerstone of any serious EU energy strategy. In this general context, the EU building sector is critical. It represents about 40% of EU final energy consumption (residential houses, public/private offices, commercial buildings, etc.) and approximately 36% of EU CO2 emissions. This is massive. The EU has certainly not been inactive in this field. The Energy Performance in Buildings Directive 2002/91/EC (EPBD) was the first and the main instrument to address the problem of the energy performance of buildings. It has established numerous principles: a reliable methodology which enables the calculation and rating of the energy performance of buildings; minimum energy performance standards for new buildings and existing buildings under major renovation; energy performance certificates; regular inspection of heating and air-conditioning systems; and, finally, quality standards for inspections and energy performance certificates. They were strengthened in 2010 by the recast Directive 2010/31/EU. This directive also introduces a decisive concept for the development of the building sector: ‘nearly zeroenergy buildings’. In 2012, the new Energy Efficiency Directive 2012/27/EU dealt with other aspects. In the building sector, three of them are particularly important. They concern: (1) the establishment of long-term strategies for mobilizing investment in the renovation of the national building stocks; (2) the introduction of energy saving schemes for ‘designated’ energy companies with a view to reducing consumption among ‘final consumers’ by 1.5% annually; and (3), as an option, the setting up of an Energy Efficiency National Fund to support energy efficiency initiatives. This paper also briefly examines the different instruments put in place to disseminate information and consultation, and the EU funding for energy efficiency in buildings. Results, however, have remained limited until now. The improvement of the energy performance of buildings and the rhythm of renovation remain extremely weak. Member States’ unwillingness to timely and properly transpose and implement the Directives continues despite the high degree of flexibility permitted. The decentralized approach chosen for some specific aspects and the differentiation in the application of EPBD standards between Member States do not appear optimal either. Adequate financial schemes remain rare. The permanent deficit of qualified and trained personnel and the inertia of public authorities to make the public understand the stakes in this domain remain problematic. Hence the need to take new initiatives to reap the benefits that the building sector is meant to bring.

The investigation of energy efficiency measures in the traditional buildings in Oporto World Heritage Site

Background The improvement of energy efficiency in buildings is widely promoted as a measure to mitigate climate change through the reduction of CO2 emissions. Thermal regulations worldwide promote it, for both new and existing buildings. Among the existing stock, traditional and historic buildings pose the additional challenge of heritage conservation. Their energy efficiency upgrade raises the risk of provoking negative impacts on their significance. Aims and Methodology This research used an approach based on impact assessment methodologies, defining an inital baseline scenario for both heritage and energy, from which the appropriate improvement solutions were identified and assessed. The measures were dynamically simulated and the results for energy, CO2, cost and comfort compared with the initial scenario, and then being further assessed for their heritage impact to eventually determine the most feasible solutions. To test this method, ten case studies, representative of the identified typological variants, were selected among Oporto’s traditional buildings located in the World Heritage Site. Findings and Conclusions The fieldwork data revealed that the energy consumption of these dwellings was below the European average. Additionally, the households expressed that their home comfort sensation was overall positive. The simulations showed that the introduction of insulation and solar thermal panels were ineffective on these cases in terms of energy, cost and comfort. At the same time, these measures pose a great risk to the buildings heritage value. The most efficient solutions were obtained from behavioural changes and DHW retrofit. The study reinforced the idea that traditional buildings performed better than expected and can be retrofitted and updated at a low-cost and with passive solutions. The use of insulation and solar panels should be disregarded.

Modeling and validation of the thermal behavior of buildings for the development of demand response methods

The representation of the thermal behaviour of the building is achieved through a relatively simple dynamic model that takes into account the effects due to the thermal mass of the building components. The model of a intra-floor apartment has been built in the Matlab-Simulink environment and considers the heat transmission through the external envelope, wall and windows, the internal thermal masses, (i.e. furniture, internal wall and floor slabs) and the sun gain due to opaque and see-through surfaces of the external envelope. The simulations results for the entire year have been compared and the model validated, with the one obtained with the dynamic building simulation software Energyplus.

On the initiation of boudinage and folding instabilities in layered elasto-visco-plastic solids - Insights from natural microstructures and numerical simulations

The present understanding of the initiation of boudinage and folding structures is based on viscosity contrasts and stress exponents, considering an intrinsically unstable state of the layer. The criterion of localization is believed to be prescribed by geometry-material interactions, which are often encountered in natural structures. An alternative localization phenomenon has been established for ductile materials, in which instability emerges for critical material parameters and loading rates from homogeneous conditions. In this thesis, conditions are sought under which this type of instability prevails and whether localization in geological materials necessarily requires a trigger by geometric imperfections. The relevance of critical deformation conditions, material parameters and the spatial configuration of instabilities are discussed in a geological context. In order to analyze boudinage geometries, a numerical eigenmode analysis is introduced. This method allows determining natural frequencies and wavelengths of a structure and inducing perturbations on these frequencies. In the subsequent coupled thermo-mechanical simulations, using a grain size evolution and end-member flow laws, localization emerges when material softening through grain size sensitive viscous creep sets in. Pinch-and-swell structures evolve along slip lines through a positive feedback between the matrix response and material bifurcations inside the layer, independent from the mesh-discretization length scale. Since boudinage and folding are considered to express the same general instability, both structures should arise independently of the sign of the loading conditions and for identical material parameters. To this end, the link between material to energy instabilities is approached by means of bifurcation analyses of the field equations and finite element simulations of the coupled system of equations. Boudinage and folding structures develop at the same critical energy threshold, where dissipative work by temperature-sensitive creep overcomes the diffusive capacity of the layer. This finding provides basis for a unified theory for strain localization in layered ductile materials. The numerical simulations are compared to natural pinch-and-swell microstructures, tracing the adaption of grain sizes, textures and creep mechanisms in calcite veins. The switch from dislocation to diffusion creep relates to strain-rate weakening, which is induced by dissipated heat from grain size reduction, and marks the onset of continuous necking. The time-dependent sequence uncovers multiple steady states at different time intervals. Microstructurally and mechanically stable conditions are finally expressed in the pinch-and-swell end members. The major outcome of this study is that boudinage and folding can be described as the same coupled energy-mechanical bifurcation, or as one critical energy attractor. This finding allows the derivation of critical deformation conditions and fundamental material parameters directly from localized structures in the field.

Socio-technical transitions and policy change - Advocacy coalitions in Swiss energy policy

Policies and politics are an integral part of socio-technical transitions but have not received much attention in the transitions literature so far. Drawing on the advocacy coalition framework, our paper addresses this gap with a study on actors and coalitions in Swiss energy policy. Our results show that advocacy coalitions in Switzerland have largely remained stable despite the Fukushima shock. However, heterogeneity of beliefs has increased and in 2013, even a majority of actors expressed their support for the energy transition – an indication that major policy change might be ahead. It seems that in socio-technical transitions, changes in the policy issue and in the actor base also work toward policy change, next to changes in core beliefs. We make suggestions how the advocacy coalition framework can inform analysis and theory building in transition studies. We also present first ideas about the interplay of socio-technical systems and policy systems.

All-weather home building manual /

"Contract H-2047R."

Formerly utilized MED/AEC sites remedial action program : radiological survey of the Building Site 421, United States Watertown Arsenel, Watertown, MA /

Feb. 1980.

State solar energy legislation of 1976 : a review of statutes relating to buildings /

Mode of access: Internet.

State solar energy legislation of 1977 : a review of statutes relating to buildings /

Feb. 1979.

Technical guidelines for energy conservation : final report for period December 1975 to March 1977.

"Technical portion of a two-report Energy Conservation effort prepared by the staff of the Center for Building Technology of the National Bureau of Standards (NBS) for the Air Force Civil Engineering Center (AFCEC), Tyndall AFB, Florida."

Retrofitting an existing wood-frame residence for energy conservation : an experimental study /

Includes bibliographical references.

Energy conservation in buildings : an economics guidebook for investment decisions /

Issued May 1980.

Window design strategies to conserve energy /

"CODEN: BSSNBV."