Collapsing Sub-Critical Bubbles

In the standard scenario, the electroweak phase transition is a first order phase transition which completes by the nucleation of critical bubbles. Recently, there has been speculation that the standard picture of the electroweak phase transition is incorrect. Instead, it has been proposed that throughout the phase transition appreciable amounts of both broken and unbroken phases of $SU(2)$ coexist in equilibrium. I argue that this can not be the case. General principles insure that the universe will remain in a homogenous state of unbroken $SU(2)$ until the onset of critical bubble production.Comment: 7 pages plus three figures. OHSTPY-HEP-T-92-016 A topdrawer file of the figures is appended to the en

Economic and environmental life cycle assessment of alternative mass timber walls to evaluate circular economy in building: MCDM method

The construction industry is one of the largest consumers of energy and materials, which leads to it being one of the highest sources of environmental emissions. Quantifying the impact of building materials is critical if strategies for mitigating environmental deterioration are to be developed. The lifecycle assessment (LCA) consequential methodology has been applied to evaluate different methods of constructing residential double-story buildings. The ReCiPe methodology has been used for life cycle inventory. Three different forms of mass timber construction have been considered including cross-laminated timber (CLT), nail-laminated timber (NLT), and dowel-laminated timber (DLT). These have been assessed as load-bearing panels or wood frame construction. We evaluated the global warming potential (GWP), embodied energy, and cost to identify the building type with the lowest impacts. The results revealed that total CO2 emissions for mass timbers for the construction stage are 130 CO2/M2, 118 CO2/M2, and 132 CO2/M2 of the panel for CLT, DLT, and NLT, respectively. The embodied energy emission is 1921 MJ/M2, 1902 MJ/M2, and 2130 MJ/M2 related to the CLT, DLT, and NLT, respectively, for this stage. The results also indicated that the carbon emission of DLT is lowest compared to the other two alternatives in the manufacturing and construction stages. However, when the entire life cycle is considered, NLT is the most favorable material. However, based on the life cycle cost (LCC), DLT has a lower cost. Finally, multiple-criteria decision-making (MCDM) was used to normalize the results and compare the alternatives. This showed DLT to be the best alternative, followed by CLT and NLT. In conclusion, the selection of building materials needs to prioritize regulations to reduce environmental and economic impacts

Comparative sustainability evaluation of two engineered wood-based construction materials: Life cycle analysis of CLT versus GLT

The environmental emissions and energy from construction activity and building materials contributes significantly to a building’s sustainability. Previous research dealing with wood or engineering wood’s energy requirements compared to reinforced concrete and steel structures has shown that embodied energy and embodied carbon is significantly lower in wood-based construction. This study has assessed the environmental impact and costs of glued laminated timber (GLT) or cross-laminated timber (CLT). Hardwood and softwood variants of both GLT and CLT were considered. We compared the life cycle costs (LCC) of these alternatives to discover the lowest cost. The comparative results indicated that GLT has higher emissions in Global warming potential (GWP), Terrestrial Ecotoxicity (TE), Land Use (LUP), and Ozone layer depletion (OLD), while CLT has higher impact in Human-Toxicity Potential (HTP), Fossil Depletion Potential (FDP). The results indicated that using CLT significantly reduces embodied energy by 40%. However, a comparison of costs showed that CLT is 7% more expensive than GLT. Establishing which material performs best based on environmental and economic criteria thus required further analysis. Thus, the multi-criteria decision making (MCDM) method was applied. This showed that CLT manufactured with softwood is the most sustainable choice among the alternatives considered. This study’s findings are important for aggregate level decision making of different wood materials for residential buildings

Life cycle assessment and economic analysis of Reusable formwork materials considering the circular economy

Economic development and population growth have impacted on fossil-based energy consumption, contributing to environmental pollution. Adopting circular economy research is more pressing than ever to ease pressure on the environment and the economy. Evaluating the best construction materials is not new. To date, many researchers have assessed materials using various criteria. Formwork differs from other construction materials in terms of serviceability and reusability. These materials may be reused multiple times (from 7 to around 50 times). This raises the question of which material is the best from a sustainability perspective. In this paper we have evaluated four of the most widely-used formwork materials used in the construction of buildings in Malaysia. These include plastic, steel, plywood and timber. Evaluations of life cycle assessment (LCA), embodied energy, and life cycle cost (LCC) were conducted from cradle to cradle. For a single use of formwork, timber is best in all categories except human non-carcinogenic toxicity. However, when 50 reuses are considered for the same wall a completely different result arises. In the environmental category, steel formwork produces the lowest emissions and impact in all categories except global warming potential (GWP). Plastic formwork has the lowest carbon emissions. In terms of embodied energy and cost, plastic formwork presents the best option being approximately 20% lower than steel formwork. Because of the inconsistency in the results for LCA, embodied energy, and LCC for 50-cycles of usage, a multi-criteria decision-making (MCDM) tool was used to normalize the results. The MCDM shows that plastic formwork is an ideal choice for sustainability among the alternatives considered

Recommending a new building structure to alleviate environmental impact in tropical climates: increasing the use of wood in construction

Purpose The construction sector is interested in considering environmental implications as necessary criteria for sustainability. In this regard, wood materials, especially engineering wood, are a promising choice for sustainable buildings. In some countries such as Malaysia, timber is rarely considered in the construction sector despite there being abundant access to wood. This is because of the scarcity of timber structures and the dominance of alternative materials such as steel and concrete. The cross-laminated timber-steel composite introduced in this research benefits both the wood and the steel markets leading to standardization and a more extensive market. At the same time, it contributes to environmentally friendly requirements. The main objective was to investigate timber applications in local construction and make proposals for its promotion. The new specimen described here could potentially enhance the strength of timber beams using steel plates. Four current structural methods have been chosen based on environmental and economic comparisons with a new composite structure. Methods The life cycle assessment (LCA) and life cycle cost (LCC) have been used to compare the performance of four current conventional structures. Results and discussion The results showed that the new proposed structure has lower emissions in all environmental categories, namely, Global Warming Potential (GWP), Human Carcinogenic Toxicity (HCT), Fossil Depletion Potential (FDP), Ozone Layer Depletion (OLD), Terrestrial Acidification (TA) and embodied energy. The results of the LCC are consistent with the environmental issue as the new composite has a lower cost over its entire life span. Conclusions The new structure provides a novel and sustainable alternative for the construction industry

The Anomalous Magnetic Moment of the Muon and Higgs-Mediated Flavor Changing Neutral Currents

In the two-Higgs doublet extension of the standard model, flavor-changing neutral couplings arise naturally. In the lepton sector, the largest such coupling is expected to be $\mu-\tau-\phi#. We consider the effects of this coupling on the anomalous magnetic moment of the muon. The resulting bound on the coupling, unlike previous bounds, is independent of the value of other unknown couplings. It will be significantly improved by the upcoming E821 experiment at Brookhaven National Lab.Comment: 7 pages Latex, 2 figure

Economic and environmental life cycle perspectives on two engineered wood products: Comparison of LVL and GLT construction materials

The embodied carbon of building materials and the energy consumed during construction have a significant impact on the environmental credentials of buildings. The structural systems of a building present opportunities to reduce environmental emissions and energy. In this regard, mass timber materials have considerable potential as sustainable materials over other alternatives such as steel and concrete. The aim of this investigation was to compare the environment impact, energy consumption, and life cycle cost (LCC) of different wood-based materials in identical single-story residential buildings. The materials compared are laminated veneer lumber (LVL) and glued laminated timber (GLT). GLT has less global warming potential (GWP), ozone layer depletion (OLD), and land use (LU), respectively, by 29%, 37%, and 35% than LVL. Conversely, LVL generally has lower terrestrial acidification potential (TAP), human toxicity potential (HTP), and fossil depletion potential (FDP), respectively, by 30%, 17%, and 27%. The comparative outcomes revealed that using LVL reduces embodied energy by 41%. To identify which of these materials is the best alternative, various environmental categories, embodied energy, and cost criteria require further analysis. Therefore, the multi-criteria decision-making (MCDM) method has been applied to enable robust decision-making. The outcome showed that LVL manufacturing using softwood presents the most sustainable choice. These research findings contribute to the body of knowledge about the use of mass timber in construction

Life Cycle Sustainability Assessment of Alternative Green Roofs – A Systematic Literature Review

There is general agreement on the importance of green roofs as ways of reducing GHG emissions, reducing overall costs and improving sustainability in urban areas. This systematic literature review highlights life cycle sustainability assessment as an essential criterion to evaluate green roofs. A bibliometric analysis was used to quantitatively review relevant literature. The Scopus database was chosen as a bibliographic database of academic publications. Thes period of search started from 2003 and final search was conducted on February 15, 2023. Based on further in-depth reading, 88 publication records which met the selection criteria, including 74 papers and 14 conference papers. Researchers from the United States contributed almost 31 % of the documents. We evaluated leading studies in this field and discussed assessment method, system boundaries and research gaps through a critical literature review and a systematic search review. Finally, we propose a framework and identify a gap and future research. The environmental aspect of green roofs have received more attention than economic issues. We found that most economic evaluations of green roofs are limited to their construction stage. As yet there is no comprehensive social study on green roofs. We considered a unified study of the economic, environmental impact and social evaluation of green roofs to be warranted. Additionally, various measurement methods should be used to assess the economic profitability of green roofs over the long term. In summary, this study provides a deeper understanding of the environmental, social, and economic performance of green roofs and identifies research gaps as well as future research directions