WorldWideScience

Sample records for single-layer vegetated roof

  1. Water quality function of an extensive vegetated roof.

    Science.gov (United States)

    Todorov, Dimitar; Driscoll, Charles T; Todorova, Svetoslava; Montesdeoca, Mario

    2018-06-01

    In this paper we present the results of a four-year study of water quality in runoff from an extensive, sedum covered, vegetated roof on an urban commercial building. Monitoring commenced seven months after the roof was constructed, with the first growing season. Stormwater drainage quality function of the vegetated roof was compared to a conventional (impermeable, high-albedo) membrane roof in addition to paired measurements of wet and bulk depositions at the study site. We present concentrations and fluxes of nutrients and major solutes. We discuss seasonal and year-to-year variation in water quality of drainage from the vegetated roof and how it compares with atmospheric deposition and drainage from the impermeable roof. Drainage waters from the vegetated roof exhibited a high concentration of nutrients compared to atmospheric deposition, particularly during the warm temperature growing season. However, nutrient losses were generally low because of the strong retention of water by the vegetated roof. There was marked variation in the retention of nutrients by season due to variations in concentrations in drainage from the vegetated roof. The vegetated roof was a sink of nitrogen, total phosphorus and chloride, and a source of phosphate and dissolved inorganic and organic carbon. Chloride exhibited elevated inputs and leaching during the winter. The drainage from the vegetated and impermeable roofs met the United States Environmental Protection Agency freshwater standards for all parameters, except for total phosphorus. Copyright © 2017 Elsevier B.V. All rights reserved.

  2. Determining Thermal Specifications for Vegetated GREEN Roofs in Moderate Winter Climats

    NARCIS (Netherlands)

    Dr. Christoph Maria Ravesloot

    2015-01-01

    Because local weather conditions in moderate climates are changing constantly, heat transfer specifications of substrate and vegetation in vegetated green roofs also change accordingly. Nevertheless, it is assumed that vegetated green roofs can have a positive effect on the thermal performance of

  3. Water retention and evapotranspiration of green roofs and possible natural vegetation types

    NARCIS (Netherlands)

    Metselaar, K.

    2012-01-01

    Matching vegetation to growing conditions on green roofs is one of the options to increase biodiversity in cities. A hydrological model has been applied to match the hydrological requirements of natural vegetation types to roof substrate parameters and to simulate moisture stress for specific

  4. Use of endotrophic mycorhiza and soil microorganisms and vegetation establishment on mineral green roof substrate

    Energy Technology Data Exchange (ETDEWEB)

    Meyer, J. [GeoVerde Inc., Schaffhausen (Switzerland)

    2004-07-01

    Green roofs have the potential to introduce colour and nature into urban and industrial areas. This paper showed how the addition of soil microorganisms into a green roof substrate can help establish vegetation. Microorganisms help the roots exploit essential nutrient and water reserves in the substrate by making them more readily available to the plant. Microorganisms facilitate uniform germination, plant development at the young stage, and prolonged vegetation development on the roof. Soil microorganisms and mycorrhizal fungi can be added directly in to the seed blends. As the products are blended with the seed, they also fulfill the function of a seeding aid. Mycorrhizal and other soil fungi were examined on mineral roof substrates by means of dry and hydroseeding in greenhouse and field tests. Results of this developmental work and experiences from practical applications were presented. It was noted that vegetation on green roof areas must be able to withstand harsh environmental conditions. As such, the challenges include drought that causes water stress, warm and cold temperatures, wind, acid rain and air pollution. This paper also presented details of the following categories of green roof systems. Intensive green roofs are usually referred to as roof gardens. They are constructed over reinforced concrete decks and usually are accessible. Simple intensive green roofs are vegetated with lawns or ground covering plants. Regular maintenance including irrigation, fertilization and mowing is also required. Extensive green roofs are low maintenance and low weight. Growing media is usually composed of purely mineral material or a blend of mineral with a low proportion of organic matter. Substrate is low in nutrient content and the depth . Vegetation usually consists of succulents that require minimal maintenance. The requirements to install each of these types of green roof systems were also presented. 7 refs., 3 tabs.

  5. Urban particulate pollution reduction by four species of green roof vegetation in a UK city

    Science.gov (United States)

    Speak, A. F.; Rothwell, J. J.; Lindley, S. J.; Smith, C. L.

    2012-12-01

    Urban particulate pollution in the UK remains at levels which have the potential to cause negative impacts on human health. There is a need, therefore, for mitigation strategies within cities, especially with regards to vehicular sources. The use of vegetation as a passive filter of urban air has been previously investigated, however green roof vegetation has not been specifically considered. The present study aims to quantify the effectiveness of four green roof species - creeping bentgrass (Agrostis stolonifera), red fescue (Festuca rubra), ribwort plantain (Plantago lanceolata) and sedum (Sedum album) - at capturing particulate matter smaller than 10 μm (PM10). Plants were grown in a location away from major road sources of PM10 and transplanted onto two roofs in Manchester city centre. One roof is adjacent to a major traffic source and one roof is characterised more by urban background inputs. Significant differences in metal containing PM10 capture were found between sites and between species. Site differences were explained by proximity to major sources. Species differences arise from differences in macro and micro morphology of the above surface biomass. The study finds that the grasses, A. stolonifera and F. rubra, are more effective than P. lanceolata and S. album at PM10 capture. Quantification of the annual PM10 removal potential was calculated under a maximum sedum green roof installation scenario for an area of the city centre, which totals 325 ha. Remediation of 2.3% (±0.1%) of 9.18 tonnes PM10 inputs for this area could be achieved under this scenario.

  6. Spatially dependent biotic and abiotic factors drive survivorship and physical structure of green roof vegetation.

    Science.gov (United States)

    Aloisio, Jason M; Palmer, Matthew I; Giampieri, Mario A; Tuininga, Amy R; Lewis, James D

    2017-01-01

    Plant survivorship depends on biotic and abiotic factors that vary at local and regional scales. This survivorship, in turn, has cascading effects on community composition and the physical structure of vegetation. Survivorship of native plant species is variable among populations planted in environmentally stressful habitats like urban roofs, but the degree to which factors at different spatial scales affect survivorship in urban systems is not well understood. We evaluated the effects of biotic and abiotic factors on survivorship, composition, and physical structure of two native perennial species assemblages, one characterized by a mixture of C 4 grasses and forbs (Hempstead Plains, HP) and one characterized by a mixture of C 3 grasses and forbs (Rocky Summit, RS), that were initially sown at equal ratios of growth forms (5:1:4; grass, N-fixing forb and non-N-fixing forb) in replicate 2-m 2 plots planted on 10 roofs in New York City (New York, USA). Of 24 000 installed plants, 40% survived 23 months after planting. Within-roof factors explained 71% of variation in survivorship, with biotic (species identity and assemblage) factors accounting for 54% of the overall variation, and abiotic (growing medium depth and plot location) factors explaining 17% of the variation. Among-roof factors explained 29% of variation in survivorship and increased solar radiation correlated with decreased survivorship. While growing medium properties (pH, nutrients, metals) differed among roofs there was no correlation with survivorship. Percent cover and sward height increased with increasing survivorship. At low survivorship, cover of the HP assemblage was greater compared to the RS assemblage. Sward height of the HP assemblage was about two times greater compared to the RS assemblage. These results highlight the effects of local biotic and regional abiotic drivers on community composition and physical structure of green roof vegetation. As a result, initial green roof plant

  7. Portulaca grandiflora as green roof vegetation: Plant growth and phytoremediation experiments.

    Science.gov (United States)

    Vijayaraghavan, K; Arockiaraj, Jesu; Kamala-Kannan, Seralathan

    2017-06-03

    Finding appropriate rooftop vegetation may improve the quality of runoff from green roofs. Portulaca grandiflora was examined as possible vegetation for green roofs. Green roof substrate was found to have low bulk density (360.7 kg/m 3 ) and high water-holding capacity (49.4%), air-filled porosity (21.1%), and hydraulic conductivity (5270 mm/hour). The optimal substrate also supported the growth of P. grandiflora with biomass multiplication of 450.3% and relative growth rate of 0.038. Phytoextraction potential of P. grandiflora was evaluated using metal-spiked green roof substrate as a function of time and spiked substrate metal concentration. It was identified that P. grandiflora accumulated all metals (Al, Cd, Cr, Cu, Fe, Ni, Pb, and Zn) from metal-spiked green roof substrate. At the end of 40 days, P. grandiflora accumulated 811 ± 26.7, 87.2 ± 3.59, 416 ± 15.8, 459 ± 15.6, 746 ± 20.9, 357 ± 18.5, 565 ± 6.8, and 596 ± 24.4 mg/kg of Al, Cd, Cr, Cu, Fe, Ni, Pb and Zn, respectively. Results also indicated that spiked substrate metal concentration strongly influenced metal accumulation property of P. grandiflora with metal uptake increased and accumulation factor decreased with increase in substrate metal concentration. P. grandiflora also showed potential to translocate all the examined metals with translocation factor greater than 1 for Al, Cu, Fe, and Zn, indicating hyperaccumulation property.

  8. The Energy Impact in Buildings of Vegetative Solutions for Extensive Green Roofs in Temperate Climates

    Directory of Open Access Journals (Sweden)

    Benedetta Barozzi

    2016-08-01

    Full Text Available Many bibliographical studies have highlighted the positive effects of green roofs as technological solutions both for new and renovated buildings. The one-year experimental monitoring campaign conducted has investigated, in detail, some aspects related to the surface temperature variation induced by the presence of different types of vegetation compared to traditional finishing systems for flat roofs and their impact from an energy and environmental point of view. The results obtained underlined how an appropriate vegetative solution selection can contribute to a significant reduction of the external surface temperatures (10 °C–20 °C for I > 500 W/m2 and 0 °C–5 °C for I < 500 W/m2, regardless of the season compared to traditional flat roofs. During the winter season, the thermal gradients of the planted surface temperatures are close to zero compared to the floor, except under special improving conditions. This entails a significant reduction of the energy loads from summer air conditioning, and an almost conservative behavior with respect to that from winter heating consumption. The analysis of the inside growing medium temperatures returned a further interesting datum, too: the temperature gradient with respect to surface temperature (annual average 4 °C–9 °C is a function of solar radiation and involves the insulating contribution of the soil.

  9. The Soil-Root Strength Performance of Alternanthera Ficoidea and Zoysia Japonica as Green Roof Vegetation

    Directory of Open Access Journals (Sweden)

    Abdullah Muhamad Firdaurs

    2017-01-01

    Full Text Available The rise of awareness on environmentalism has demanded that all parties involved in built environment to implement green technology in their construction projects. Great care must be taken when designing a green roof system including the selection of plants and appropriate substrates. This study was performed to investigate the soil-root composite strength of two types of green roof vegetation (A. Ficoidea and Z. Japonica at different growth periods for up to 6 months. Both plants were planted in six plastic plots (45 cm × 29 cm × 13 cm containing a mixture of perlite, vermiculite and organic soil. Every two months, a series of direct shear tests were conducted on a sample from each species to determine the root-soil shear strength. The tests continued until the 6th month. The average results showed that Z. Japonica had higher soil-root shear strength (49.1 kPa compared to A. Ficoidea after two months of growth. In the 4th month however, A. Ficoidea managed to surpass Z. Japonica (28.7 kPa versus 18.5 kPa in terms of shear strength. However, their average peak shear strength decreased sharply compared to the previous month. Lastly, in six months, A. Ficoidea sustained a higher average peak soil shear strength (56.5 kPa compared to Z. Japonica (14.3 kPa. Therefore, it can be concluded that A. Ficoidea may offer a better soil reinforcement than Z. japonica and thus it could potentially be a good choice of green roof vegetation.

  10. Hyperspectral Monitoring of Green Roof Vegetation Health State in Sub-Mediterranean Climate: Preliminary Results.

    Science.gov (United States)

    Piro, Patrizia; Porti, Michele; Veltri, Simone; Lupo, Emanuela; Moroni, Monica

    2017-03-23

    In urban and industrial environments, the constant increase of impermeable surfaces has produced drastic changes in the natural hydrological cycle. Decreasing green areas not only produce negative effects from a hydrological-hydraulic perspective, but also from an energy point of view, modifying the urban microclimate and generating, as shown in the literature, heat islands in our cities. In this context, green infrastructures may represent an environmental compensation action that can be used to re-equilibrate the hydrological and energy balance and reduce the impact of pollutant load on receiving water bodies. To ensure that a green infrastructure will work properly, vegetated areas have to be continuously monitored to verify their health state. This paper presents a ground spectroscopy monitoring survey of a green roof installed at the University of Calabria fulfilled via the acquisition and analysis of hyperspectral data. This study is part of a larger research project financed by European Structural funds aimed at understanding the influence of green roofs on rainwater management and energy consumption for air conditioning in the Mediterranean area. Reflectance values were acquired with a field-portable spectroradiometer that operates in the range of wavelengths 350-2500 nm. The survey was carried out during the time period November 2014-June 2015 and data were acquired weekly. Climatic, thermo-physical, hydrological and hydraulic quantities were acquired as well and related to spectral data. Broadband and narrowband spectral indices, related to chlorophyll content and to chlorophyll-carotenoid ratio, were computed. The two narrowband indices NDVI 705 and SIPI turned out to be the most representative indices to detect the plant health status.

  11. A case study of air quality above an urban roof top vegetable farm

    International Nuclear Information System (INIS)

    Tong, Zheming; Whitlow, Thomas H.; Landers, Andrew; Flanner, Benjamin

    2016-01-01

    The effect of elevation and rooftop configuration on local air quality was investigated at the Brooklyn Grange rooftop farm during a short-term observational campaign. Using multiple particle counters and sonic anemometers deployed along vertical gradients, we found that PM 2.5 concentration decayed with height above the street. Samples adjacent to the street had the highest average PM 2.5 concentration and frequent stochastic spikes above background. Rooftop observations 26 m above ground showed 7–33% reductions in average PM 2.5 concentration compared with the curbside and had far fewer spikes. A relationship between the vertical extinction rate of PM 2.5 and atmospheric stability was found whereby less unstable atmosphere and greater wind shear led to greater PM 2.5 extinction due to damped vertical motion of air. - Highlights: • PM 2.5 concentrations on a rooftop farm were 7–33% lower than at ground level. • Rooftop plantings will remove less pollution due to the less steep concentration gradient. • Vegetables are exposed to less vehicular pollution on roofs than that at ground level. - PM 2.5 concentrations on a rooftop farm were 7–33% below those at ground level, and the vertical extinction rate of PM 2.5 varied with the atmospheric stability, and a perimeter wall was the dominant factor governing rooftop boundary layer thickness.

  12. Temperature and snowfall trigger alpine vegetation green-up on the world's roof.

    Science.gov (United States)

    Chen, Xiaoqiu; An, Shuai; Inouye, David W; Schwartz, Mark D

    2015-10-01

    Rapid temperature increase and its impacts on alpine ecosystems in the Qinghai-Tibetan Plateau, the world's highest and largest plateau, are a matter of global concern. Satellite observations have revealed distinctly different trend changes and contradicting temperature responses of vegetation green-up dates, leading to broad debate about the Plateau's spring phenology and its climatic attribution. Large uncertainties in remote-sensing estimates of phenology significantly limit efforts to predict the impacts of climate change on vegetation growth and carbon balance in the Qinghai-Tibetan Plateau, which are further exacerbated by a lack of detailed ground observation calibration. Here, we revealed the spatiotemporal variations and climate drivers of ground-based herbaceous plant green-up dates using 72 green-up datasets for 22 herbaceous plant species at 23 phenological stations, and corresponding daily mean air temperature and daily precipitation data from 19 climate stations across eastern and southern parts of the Qinghai-Tibetan Plateau from 1981 to 2011. Results show that neither the continuously advancing trend from 1982 to 2011, nor a turning point in the mid to late 1990s as reported by remote-sensing studies can be verified by most of the green-up time series, and no robust evidence for a warmer winter-induced later green-up dates can be detected. Thus, chilling requirements may not be an important driver influencing green-up responses to spring warming. Moreover, temperature-only control of green-up dates appears mainly at stations with relatively scarce preseason snowfall and lower elevation, while coupled temperature and precipitation controls of green-up dates occur mostly at stations with relatively abundant preseason snowfall and higher elevation. The diversified interactions between snowfall and temperature during late winter to early spring likely determine the spatiotemporal variations of green-up dates. Therefore, prediction of vegetation growth

  13. Sustainable roofs with real energy savings

    Energy Technology Data Exchange (ETDEWEB)

    Christian, J.E.; Petrie, T.W.

    1996-12-31

    This paper addresses the general concept of sustainability and relates it to the building owner`s selection of a low-slope roof. It offers a list of performance features of sustainable roofs. Experiences and data relevant to these features for four unique roofs are then presented which include: self-drying systems, low total equivalent warming foam insulation, roof coatings and green roofs. The paper concludes with a list of sustainable roofing features worth considering for a low-slope roof investment. Building owners and community developers are showing more interest in investing in sustainability. The potential exists to design, construct, and maintain roofs that last twice as long and reduce the building space heating and cooling energy loads resulting from the roof by 50% (based on the current predominant design of a 10-year life and a single layer of 1 to 2 in. (2.5 to 5.1 cm) of insulation). The opportunity to provide better low-slope roofs and sell more roof maintenance service is escalating. The general trend of outsourcing services could lead to roofing companies` owning the roofs they install while the traditional building owner owns the rest of the building. Such a situation would have a very desirable potential to internalize the costs of poor roof maintenance practices and high roof waste disposal costs, and to offer a profit for installing roofs that are more sustainable. 14 refs., 12 figs.

  14. Experience with single-layer rectal anastomosis.

    OpenAIRE

    Khubchandani, M; Upson, J

    1981-01-01

    Anastomotic dehiscence following resection of the large intestine is a serious complication. Satisfactory results of single-layer anastomosis depend upon meticulous technique and a scrupulously clean colon. Out of 65 single-layer anastomoses involving the rectum, significant leakage occurred in 4 patients. The results are reported in order to draw attention to the safety and efficacy of one-layer anastomosis.

  15. The implementation of biofiltration systems, rainwater tanks and urban irrigation in a single-layer urban canopy model

    Science.gov (United States)

    Demuzere, Matthias; Coutts, Andrew; Goehler, Maren; Broadbent, Ashley; Wouters, Hendrik; van Lipzig, Nicole; Gebert, Luke

    2015-04-01

    Urban vegetation is generally considered as a key tool to modify the urban energy balance through enhanced evapotranspiration (ET). Given that vegetation is most effective when it is healthy, stormwater harvesting and retention strategies (such as water sensitive urban design) could be used to support vegetation and promote ET. This study presents the implementation of a vegetated lined bio-filtration system (BFS) combined with a rainwater tank (RWT) and urban irrigation system in the single-layer urban canopy model Community Land Model-Urban. Runoff from roof and impervious road surface fractions is harvested and used to support an adequate soil moisture level for vegetation in the BFS. In a first stage, modelled soil moisture dynamics are evaluated and found reliable compared to observed soil moisture levels from biofiltration pits in Smith Street, Melbourne (Australia). Secondly, the impact of BFS, RWT and urban irrigation on ET is illustrated for a two-month period in 2012 using varying characteristics for all components. Results indicate that (i) a large amount of stormwater is potentially available for indoor and outdoor water demands, including irrigation of urban vegetation, (ii) ET from the BFS is an order of magnitude larger compared to the contributions from the impervious surfaces, even though the former only covers 10% of the surface fraction and (iii) attention should be paid to the cover fraction and soil texture of the BFS, size of the RWT and the surface fractions contributing to the collection of water in the RWT. Overall, this study reveals that this model development can effectuate future research with state-of-the-art urban climate models to further explore the benefits of vegetated biofiltration systems as a water sensitive urban design tool optimised with an urban irrigation system to maintain healthy vegetation.

  16. [A review of green roof performance towards management of roof runoff].

    Science.gov (United States)

    Chen, Xiao-ping; Huang, Pei; Zhou, Zhi-xiang; Gao, Chi

    2015-08-01

    Green roof has a significant influence on reducing runoff volume, delaying runoff-yielding time, reducing the peak flow and improving runoff quality. This paper addressed the related research around the world and concluded from several aspects, i.e., the definition of green roof of different types, the mechanism how green roof manages runoff quantity and quality, the ability how green roof controls roof runoff, and the influence factors of green roof toward runoff quantity and quality. Afterwards, there was a need for more future work on research of green roof toward roof runoff, i.e., vegetation selection of green roof, efficient construction model selection of green roof, the regulating characteristics of green roof on roof runoff, the value assessment of green roof on roof runoff, analysis of source-sink function of green roof on the water pollutants of roof runoff and the research on the mitigation measures of roof runoff pollution. This paper provided a guideline to develop green roofs aiming to regulating roof runoff.

  17. Simulation of green roof runoff under different substrate depths and vegetation covers by coupling a simple conceptual and a physically based hydrological model.

    Science.gov (United States)

    Soulis, Konstantinos X; Valiantzas, John D; Ntoulas, Nikolaos; Kargas, George; Nektarios, Panayiotis A

    2017-09-15

    In spite of the well-known green roof benefits, their widespread adoption in the management practices of urban drainage systems requires the use of adequate analytical and modelling tools. In the current study, green roof runoff modeling was accomplished by developing, testing, and jointly using a simple conceptual model and a physically based numerical simulation model utilizing HYDRUS-1D software. The use of such an approach combines the advantages of the conceptual model, namely simplicity, low computational requirements, and ability to be easily integrated in decision support tools with the capacity of the physically based simulation model to be easily transferred in conditions and locations other than those used for calibrating and validating it. The proposed approach was evaluated with an experimental dataset that included various green roof covers (either succulent plants - Sedum sediforme, or xerophytic plants - Origanum onites, or bare substrate without any vegetation) and two substrate depths (either 8 cm or 16 cm). Both the physically based and the conceptual models matched very closely the observed hydrographs. In general, the conceptual model performed better than the physically based simulation model but the overall performance of both models was sufficient in most cases as it is revealed by the Nash-Sutcliffe Efficiency index which was generally greater than 0.70. Finally, it was showcased how a physically based and a simple conceptual model can be jointly used to allow the use of the simple conceptual model for a wider set of conditions than the available experimental data and in order to support green roof design. Copyright © 2017 Elsevier Ltd. All rights reserved.

  18. Green roofs: roof system reducing heating and cooling costs

    Directory of Open Access Journals (Sweden)

    Konasova, Sarka

    2016-06-01

    Full Text Available Green roofs are among the passive building systems that contribute to the thermal stability of the rooms under the roof in both summer and winter. Green roofs can provide a significant contribution to the thermal balance of the protected space. Over the past ten years, many studies have been carried out to investigate the energy benefits of green roofs in terms of the energy performance of buildings. These studies show that the installation of vegetated cover can achieve energy savings for both winter heating and summer cooling. The green roof, as a thermal insulation, reduces the amount of building operating energy costs and reduces heat losses. This article summarizes current literature and points to situations in which green roofs can play an important role in saving energy for heating and cooling due to improved thermal insulating function of the roof, in case of extensive vegetation coverage without significant overloading of the roof structure and associated over-dimensioning. It is important to note that these energy savings always depend on the particular climate, the type of building and the availability and the type of roof structure.

  19. GREEN ROOFS — A GROWING TREND

    Science.gov (United States)

    One of the most interesting stormwater control systems under evaluation by EPA are “green roofs”. Green roofs are vegetative covers applied to building roofs to slow, or totally absorb, rainfall runoff during storms. While the concept of over-planted roofs is very ancient, the go...

  20. Tunneling spin injection into single layer graphene.

    Science.gov (United States)

    Han, Wei; Pi, K; McCreary, K M; Li, Yan; Wong, Jared J I; Swartz, A G; Kawakami, R K

    2010-10-15

    We achieve tunneling spin injection from Co into single layer graphene (SLG) using TiO₂ seeded MgO barriers. A nonlocal magnetoresistance (ΔR(NL)) of 130  Ω is observed at room temperature, which is the largest value observed in any material. Investigating ΔR(NL) vs SLG conductivity from the transparent to the tunneling contact regimes demonstrates the contrasting behaviors predicted by the drift-diffusion theory of spin transport. Furthermore, tunnel barriers reduce the contact-induced spin relaxation and are therefore important for future investigations of spin relaxation in graphene.

  1. Prolong Your Roof's Performance: Roof Asset Management.

    Science.gov (United States)

    Teitsma, Jerry

    2001-01-01

    Discusses the roof asset management process for maintaining a roof system's integrity and value in a cost-effective manner. Included is a breakdown of roofing surface characteristics for multiply and single ply roofing systems. (GR)

  2. Factors Influencing Arthropod Diversity on Green Roofs

    Directory of Open Access Journals (Sweden)

    Bracha Y. Schindler

    2011-01-01

    Full Text Available Green roofs have potential for providing substantial habitat to plants, birds, and arthropod species that are not well supported by other urban habitats. Whereas the plants on a typical green roof are chosen and planted by people, the arthropods that colonize it can serve as an indicator of the ability of this novel habitat to support a diverse community of organisms. The goal of this observational study was to determine which physical characteristics of a roof or characteristics of its vegetation correlate with arthropod diversity on the roof. We intensively sampled the number of insect families on one roof with pitfall traps and also measured the soil arthropod species richness on six green roofs in the Boston, MA area. We found that the number of arthropod species in soil, and arthropod families in pitfall traps, was positively correlated with living vegetation cover. The number of arthropod species was not significantly correlated with plant diversity, green roof size, distance from the ground, or distance to the nearest vegetated habitat from the roof. Our results suggest that vegetation cover may be more important than vegetation diversity for roof arthropod diversity, at least for the first few years after establishment. Additionally, we found that even green roofs that are small and isolated can support a community of arthropods that include important functional groups of the soil food web.

  3. Green roofs: potential at LANL

    Energy Technology Data Exchange (ETDEWEB)

    Pacheco, Elena M [Los Alamos National Laboratory

    2009-01-01

    Green roofs, roof systems that support vegetation, are rapidly becoming one of the most popular sustainable methods to combat urban environmental problems in North America. An extensive list of literature has been published in the past three decades recording the ecological benefits of green roofs; and now those benefits have been measured in enumerated data as a means to analyze the costs and returns of green roof technology. Most recently several studies have made substantial progress quantifying the monetary savings associated with storm water mitigation, the lessoning of the Urban Heat Island, and reduction of building cooling demands due to the implementation of green roof systems. Like any natural vegetation, a green roof is capable of absorbing the precipitation that falls on it. This capability has shown to significantly decrease the amount of storm water runoff produced by buildings as well as slow the rate at which runoff is dispensed. As a result of this reduction in volume and velocity, storm drains and sewage systems are relieved of any excess stress they might experience in a storm. For many municipalities and private building owners, any increase in storm water mitigation can result in major tax incentives and revenue that does not have to be spent on extra water treatments. Along with absorption of water, vegetation on green roofs is also capable of transpiration, the process by which moisture is evaporated into the air to cool ambient temperatures. This natural process aims to minimize the Urban Heat Island Effect, a phenomenon brought on by the dark and paved surfaces that increases air temperatures in urban cores. As the sun distributes solar radiation over a city's area, dark surfaces such as bitumen rooftops absorb solar rays and their heat. That heat is later released during the evening hours and the ambient temperatures do not cool as they normally would, creating an island of constant heat. Such excessively high temperatures induce heat

  4. Roof assembly

    CSIR Research Space (South Africa)

    De Villiers, A

    2010-01-01

    Full Text Available The objective of this chapter is to provide sustainability criteria for roof system design that can be used by planners, designers and developers as a planning, design and development guide for sustainable building projects....

  5. Green Roofs

    Energy Technology Data Exchange (ETDEWEB)

    None

    2004-08-01

    A New Technology Demonstration Publication Green roofs can improve the energy performance of federal buildings, help manage stormwater, reduce airborne emissions, and mitigate the effects of urban heat islands.

  6. Estimating Heat and Mass Transfer Processes in Green Roof Systems: Current Modeling Capabilities and Limitations (Presentation)

    Energy Technology Data Exchange (ETDEWEB)

    Tabares Velasco, P. C.

    2011-04-01

    This presentation discusses estimating heat and mass transfer processes in green roof systems: current modeling capabilities and limitations. Green roofs are 'specialized roofing systems that support vegetation growth on rooftops.'

  7. Green roof stormwater retention: effects of roof surface, slope, and media depth.

    Science.gov (United States)

    VanWoert, Nicholaus D; Rowe, D Bradley; Andresen, Jeffrey A; Rugh, Clayton L; Fernandez, R Thomas; Xiao, Lan

    2005-01-01

    Urban areas generate considerably more stormwater runoff than natural areas of the same size due to a greater percentage of impervious surfaces that impede water infiltration. Roof surfaces account for a large portion of this impervious cover. Establishing vegetation on rooftops, known as green roofs, is one method of recovering lost green space that can aid in mitigating stormwater runoff. Two studies were performed using several roof platforms to quantify the effects of various treatments on stormwater retention. The first study used three different roof surface treatments to quantify differences in stormwater retention of a standard commercial roof with gravel ballast, an extensive green roof system without vegetation, and a typical extensive green roof with vegetation. Overall, mean percent rainfall retention ranged from 48.7% (gravel) to 82.8% (vegetated). The second study tested the influence of roof slope (2 and 6.5%) and green roof media depth (2.5, 4.0, and 6.0 cm) on stormwater retention. For all combined rain events, platforms at 2% slope with a 4-cm media depth had the greatest mean retention, 87%, although the difference from the other treatments was minimal. The combination of reduced slope and deeper media clearly reduced the total quantity of runoff. For both studies, vegetated green roof systems not only reduced the amount of stormwater runoff, they also extended its duration over a period of time beyond the actual rain event.

  8. LENA Conversion Foils Using Single-Layer Graphene, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Our key innovation will be the use of single-layer graphene as LENA conversion foils, with appropriate microgrids and nanogrids to support the foils. Phase I...

  9. Functionalization of Single Layer MoS$_2$ Honeycomb Structures

    OpenAIRE

    Ataca, C.; Ciraci, S.

    2010-01-01

    Based on the first-principles plane wave calculations, we studied the functionalization of the two-dimensional single layer MoS$_2$ structure via adatom adsorption and vacancy defect creation. Minimum energy adsorption sites are determined for sixteen different adatoms, each gives rise to diverse properties. Bare, single layer MoS$_2$, which is normally a nonmagnetic, direct band gap semiconductor, attains a net magnetic moment upon adsorption of specific transition metal atoms, as well as si...

  10. Green roofs

    CSIR Research Space (South Africa)

    Van Wyk, Llewellyn V

    2010-04-01

    Full Text Available for green roofs. A typical method makes use of a studded membrane (resembling an egg box) laid on a suitable waterproofing which, together, provides the waterproofing and the water drainage. A Geotextile blanket is then laid on top of the studded... be advisable to lay a supporting layer between the insulation and the studded membrane to protect the insulation. A further variation is to replace the studded membrane with a gravel drainage layer followed by the growing medium. In this instance it would...

  11. Green roof valuation: a probabilistic economic analysis of environmental benefits.

    Science.gov (United States)

    Clark, Corrie; Adriaens, Peter; Talbot, F Brian

    2008-03-15

    Green (vegetated) roofs have gained global acceptance as a technologythat has the potential to help mitigate the multifaceted, complex environmental problems of urban centers. While policies that encourage green roofs exist atthe local and regional level, installation costs remain at a premium and deter investment in this technology. The objective of this paper is to quantitatively integrate the range of stormwater, energy, and air pollution benefits of green roofs into an economic model that captures the building-specific scale. Currently, green roofs are primarily valued on increased roof longevity, reduced stormwater runoff, and decreased building energy consumption. Proper valuation of these benefits can reduce the present value of a green roof if investors look beyond the upfront capital costs. Net present value (NPV) analysis comparing a conventional roof system to an extensive green roof system demonstrates that at the end of the green roof lifetime the NPV for the green roof is between 20.3 and 25.2% less than the NPV for the conventional roof over 40 years. The additional upfront investment is recovered at the time when a conventional roof would be replaced. Increasing evidence suggests that green roofs may play a significant role in urban air quality improvement For example, uptake of N0x is estimated to range from $1683 to $6383 per metric ton of NOx reduction. These benefits were included in this study, and results translate to an annual benefit of $895-3392 for a 2000 square meter vegetated roof. Improved air quality leads to a mean NPV for the green roof that is 24.5-40.2% less than the mean conventional roof NPV. Through innovative policies, the inclusion of air pollution mitigation and the reduction of municipal stormwater infrastructure costs in economic valuation of environmental benefits of green roofs can reduce the cost gap that currently hinders U.S. investment in green roof technology.

  12. Green roofs provide habitat for urban bats

    Directory of Open Access Journals (Sweden)

    K.L. Parkins

    2015-07-01

    Full Text Available Understanding bat use of human-altered habitat is critical for developing effective conservation plans for this ecologically important taxon. Green roofs, building rooftops covered in growing medium and vegetation, are increasingly important conservation tools that make use of underutilized space to provide breeding and foraging grounds for urban wildlife. Green roofs are especially important in highly urbanized areas such as New York City (NYC, which has more rooftops (34% than green space (13%. To date, no studies have examined the extent to which North American bats utilize urban green roofs. To investigate the role of green roofs in supporting urban bats, we monitored bat activity using ultrasonic recorders on four green and four conventional roofs located in highly developed areas of NYC, which were paired to control for location, height, and local variability in surrounding habitat and species diversity. We then identified bat vocalizations on these recordings to the species level. We documented the presence of five of nine possible bat species over both roof types: Lasiurus borealis, L. cinereus, L. noctivagans, P. subflavus,andE. fuscus. Of the bat calls that could be identified to the species level, 66% were from L. borealis. Overall levels of bat activity were higher over green roofs than over conventional roofs. This study provides evidence that, in addition to well documented ecosystem benefits, urban green roofs contribute to urban habitat availability for several North American bat species.

  13. Green roofs as a means of pollution abatement

    International Nuclear Information System (INIS)

    Rowe, D. Bradley

    2011-01-01

    Green roofs involve growing vegetation on rooftops and are one tool that can help mitigate the negative effects of pollution. This review encompasses published research to date on how green roofs can help mitigate pollution, how green roof materials influence the magnitude of these benefits, and suggests future research directions. The discussion concentrates on how green roofs influence air pollution, carbon dioxide emissions, carbon sequestration, longevity of roofing membranes that result in fewer roofing materials in landfills, water quality of stormwater runoff, and noise pollution. Suggestions for future directions for research include plant selection, development of improved growing substrates, urban rooftop agriculture, water quality of runoff, supplemental irrigation, the use of grey water, air pollution, carbon sequestration, effects on human health, combining green roofs with complementary related technologies, and economics and policy issues. - Green roofs can help mitigate air pollution, carbon dioxide emissions, sequester carbon, conserve energy, reduce the urban heat island, and improve water quality.

  14. Single-layer graphene on silicon nitride micromembrane resonators

    DEFF Research Database (Denmark)

    Schmid, Silvan; Bagci, Tolga; Zeuthen, Emil

    2014-01-01

    for exciting new devices, such as optoelectromechanical transducers. Here, we add a single-layer graphene on SiN micromembranes and compare electromechanical coupling and mechanical properties to bare dielectric membranes and to membranes metallized with an aluminium layer. The electrostatic coupling...

  15. Kernel Function Tuning for Single-Layer Neural Networks

    Czech Academy of Sciences Publication Activity Database

    Vidnerová, Petra; Neruda, Roman

    -, accepted 28.11. 2017 (2018) ISSN 2278-0149 R&D Projects: GA ČR GA15-18108S Institutional support: RVO:67985807 Keywords : single-layer neural networks * kernel methods * kernel function * optimisation Subject RIV: IN - Informatics, Computer Science http://www.ijmerr.com/

  16. Breakwater stability with damaged single layer armour units

    NARCIS (Netherlands)

    De Rover, R.; Verhagen, H.J.; Van den Berge, A.; Reedijk, B.

    2008-01-01

    The effect of single layer interlocking armour unit breakage on the hydraulic armour layer stability and potential damage progression is addressed in this paper. A 2-dimensional scale model of a rubble mound breakwater with an armour layer consisting of Xbloc armour units was tested. The residual

  17. Automatic settlement analysis of single-layer armour layers

    NARCIS (Netherlands)

    Hofland, B.; van gent, Marcel

    2016-01-01

    A method to quantify, analyse, and present the settlement of single-layer concrete armour layers of coastal structures is presented. The use of the image processing technique for settlement analysis is discussed based on various modelling
    studies performed over the years. The accuracy of the

  18. Composition and Diversity of Avian Communities Using a New Urban Habitat: Green Roofs

    Science.gov (United States)

    Washburn, Brian E.; Swearingin, Ryan M.; Pullins, Craig K.; Rice, Matthew E.

    2016-06-01

    Green roofs on buildings are becoming popular and represent a new component of the urban landscape. Public benefits of green roof projects include reduced stormwater runoff, improved air quality, reduced urban heat island effects, and aesthetic values. As part of a city-wide plan, several green roofs have been constructed at Chicago's O'Hare International Airport (ORD). Like some other landscaping features, green roofs on or near an airport might attract wildlife and thus increase the risk of bird-aircraft collisions. During 2007-2011, we conducted a series of studies to evaluate wildlife use of newly constructed green roofs and traditional (gravel) roofs on buildings at ORD. These green roofs were 0.04-1.62 ha in area and consisted of primarily stonecrop species for vegetation. A total of 188 birds were observed using roofs during this research. Of the birds using green roofs, 66, 23, and 4 % were Killdeer, European Starlings, and Mourning Doves, respectively. Killdeer nested on green roofs, whereas the other species perched, foraged, or loafed. Birds used green roofs almost exclusively between May and October. Overall, avian use of the green roofs was minimal and similar to that of buildings with traditional roofs. Although green roofs with other vegetation types might offer forage or cover to birds and thus attract potentially hazardous wildlife, the stonecrop-vegetated green roofs in this study did not increase the risk of bird-aircraft collisions.

  19. Environmental assessment of extensive green roofs in the UK

    Science.gov (United States)

    Ruan, Fei

    The advantages of the planted roofs are undoubtedly numerous from both the ecological and the social point of view. They act positively upon the climate of the city and its region, as well as upon the interior climate of the building beneath them. This dissertation, therefore, explores the environmental performance of the extensive green roofs in UK. The investigation was implemented in two phases: during the first phase, detailed introduction of green roofs with the emphasis on their thermal properties and behavior is provided with the support of literature review evidence. During the second phase of the study, the thermal properties of the green roof, as well as, the energy saving were examined, through two computer programs: Wufi and TAS. Two hypothetic models have been developed in these programs to evaluate thermal and energy performances of a building with a green roof, varying different parameters for the green roof or changing different internal condition for the building. The main conclusion of these analyses is that two parameters: vegetation solar absorptivity and water content of green roofs play significant role in the thermal performance of green roofs. Lower vegetation solar absorptivity and higher water content will help green roofs to further reduce the external heat flux and summer inward heat flux which consequently mitigate the urban heat island effect and summer energy consumption. On the other hand, in comparison with the traditional roofs, green roofs appear to have less heating loads but higher cooling loads when internal gain is higher. Finally, when comparing Wufi results to TAS results, both represent that featured as lower solar absorptivity and higher insulation value, green roofs do alleviate the urban heat island effect and reduce the heat flux through the roof. Nevertheless, by taking account of evaporative cooling effect of green roofs, Wufi provides a more accurate approach to simulate the performance of green roofs

  20. Thermoelectric properties of single-layered SnSe sheet

    Science.gov (United States)

    Wang, Fancy Qian; Zhang, Shunhong; Yu, Jiabing; Wang, Qian

    2015-09-01

    Motivated by the recent study of inspiring thermoelectric properties in bulk SnSe [Zhao et al., Nature, 2014, 508, 373] and the experimental synthesis of SnSe sheets [Chen et al., J. Am. Chem. Soc., 2013, 135, 1213], we have carried out systematic calculations for a single-layered SnSe sheet focusing on its stability, electronic structure and thermoelectric properties by using density functional theory combined with Boltzmann transport theory. We have found that the sheet is dynamically and thermally stable with a band gap of 1.28 eV, and the figure of merit (ZT) reaches 3.27 (2.76) along the armchair (zigzag) direction with optimal n-type carrier concentration, which is enhanced nearly 7 times compared to its bulk counterpart at 700 K due to quantum confinement effect. Furthermore, we designed four types of thermoelectric couples by assembling single-layered SnSe sheets with different transport directions and doping types, and found that their efficiencies are all above 13%, which are higher than those of thermoelectric couples made of commercial bulk Bi2Te3 (7%-8%), suggesting the great potential of single-layered SnSe sheets for heat-electricity conversion.Motivated by the recent study of inspiring thermoelectric properties in bulk SnSe [Zhao et al., Nature, 2014, 508, 373] and the experimental synthesis of SnSe sheets [Chen et al., J. Am. Chem. Soc., 2013, 135, 1213], we have carried out systematic calculations for a single-layered SnSe sheet focusing on its stability, electronic structure and thermoelectric properties by using density functional theory combined with Boltzmann transport theory. We have found that the sheet is dynamically and thermally stable with a band gap of 1.28 eV, and the figure of merit (ZT) reaches 3.27 (2.76) along the armchair (zigzag) direction with optimal n-type carrier concentration, which is enhanced nearly 7 times compared to its bulk counterpart at 700 K due to quantum confinement effect. Furthermore, we designed four types of

  1. Roofing research: a bibliography

    Energy Technology Data Exchange (ETDEWEB)

    Robinson, J.N.; Nichols, C.L.

    1981-04-01

    A listing, indexed by subject, primary author, and secondary authors, is presented of some 530 references in the literature related to roofing research - materials, construction, and in-service problems. Structural design of roofing systems is not covered.

  2. Green roofs as a means of pollution abatement.

    Science.gov (United States)

    Rowe, D Bradley

    2011-01-01

    Green roofs involve growing vegetation on rooftops and are one tool that can help mitigate the negative effects of pollution. This review encompasses published research to date on how green roofs can help mitigate pollution, how green roof materials influence the magnitude of these benefits, and suggests future research directions. The discussion concentrates on how green roofs influence air pollution, carbon dioxide emissions, carbon sequestration, longevity of roofing membranes that result in fewer roofing materials in landfills, water quality of stormwater runoff, and noise pollution. Suggestions for future directions for research include plant selection, development of improved growing substrates, urban rooftop agriculture, water quality of runoff, supplemental irrigation, the use of grey water, air pollution, carbon sequestration, effects on human health, combining green roofs with complementary related technologies, and economics and policy issues. Copyright © 2010 Elsevier Ltd. All rights reserved.

  3. Raman spectroscopy of boron-doped single-layer graphene.

    Science.gov (United States)

    Kim, Yoong Ahm; Fujisawa, Kazunori; Muramatsu, Hiroyuki; Hayashi, Takuya; Endo, Morinobu; Fujimori, Toshihiko; Kaneko, Katsumi; Terrones, Mauricio; Behrends, Jan; Eckmann, Axel; Casiraghi, Cinzia; Novoselov, Kostya S; Saito, Riichiro; Dresselhaus, Mildred S

    2012-07-24

    The introduction of foreign atoms, such as nitrogen, into the hexagonal network of an sp(2)-hybridized carbon atom monolayer has been demonstrated and constitutes an effective tool for tailoring the intrinsic properties of graphene. Here, we report that boron atoms can be efficiently substituted for carbon in graphene. Single-layer graphene substitutionally doped with boron was prepared by the mechanical exfoliation of boron-doped graphite. X-ray photoelectron spectroscopy demonstrated that the amount of substitutional boron in graphite was ~0.22 atom %. Raman spectroscopy demonstrated that the boron atoms were spaced 4.76 nm apart in single-layer graphene. The 7-fold higher intensity of the D-band when compared to the G-band was explained by the elastically scattered photoexcited electrons by boron atoms before emitting a phonon. The frequency of the G-band in single-layer substitutionally boron-doped graphene was unchanged, which could be explained by the p-type boron doping (stiffening) counteracting the tensile strain effect of the larger carbon-boron bond length (softening). Boron-doped graphene appears to be a useful tool for engineering the physical and chemical properties of graphene.

  4. Bandgap tunability at single-layer molybdenum disulphide grain boundaries

    KAUST Repository

    Huang, Yu Li

    2015-02-17

    Two-dimensional transition metal dichalcogenides have emerged as a new class of semiconductor materials with novel electronic and optical properties of interest to future nanoelectronics technology. Single-layer molybdenum disulphide, which represents a prototype two-dimensional transition metal dichalcogenide, has an electronic bandgap that increases with decreasing layer thickness. Using high-resolution scanning tunnelling microscopy and spectroscopy, we measure the apparent quasiparticle energy gap to be 2.40±0.05 eV for single-layer, 2.10±0.05 eV for bilayer and 1.75±0.05 eV for trilayer molybdenum disulphide, which were directly grown on a graphite substrate by chemical vapour deposition method. More interestingly, we report an unexpected bandgap tunability (as large as 0.85±0.05 eV) with distance from the grain boundary in single-layer molybdenum disulphide, which also depends on the grain misorientation angle. This work opens up new possibilities for flexible electronic and optoelectronic devices with tunable bandgaps that utilize both the control of two-dimensional layer thickness and the grain boundary engineering.

  5. New roof element system

    DEFF Research Database (Denmark)

    Ditlev, Jesper; Rudbeck, Claus Christian

    1997-01-01

    The aim of the project has been to develop an element system for warm deck roofs which, from a thermal and economical point of view, can deal with the future demands for heat loss coefficients for low slope roofs.......The aim of the project has been to develop an element system for warm deck roofs which, from a thermal and economical point of view, can deal with the future demands for heat loss coefficients for low slope roofs....

  6. Renovation of Roof Structure

    DEFF Research Database (Denmark)

    Kjærbye, Per Oluf H

    1997-01-01

    A 30 year old not-watertight roof based on wooden boards with roofing felt have been changed to a pitched structure with cementos plates. At the same time more thermal insulation has been placed.......A 30 year old not-watertight roof based on wooden boards with roofing felt have been changed to a pitched structure with cementos plates. At the same time more thermal insulation has been placed....

  7. An environmental cost-benefit analysis of alternative green roofing strategies

    Science.gov (United States)

    Richardson, M.; William, R. K.; Goodwell, A. E.; Le, P. V.; Kumar, P.; Stillwell, A. S.

    2016-12-01

    Green roofs and cool roofs are alternative roofing strategies that mitigate urban heat island effects and improve building energy performance. Green roofs consist of soil and vegetation layers that provide runoff reduction, thermal insulation, and potential natural habitat, but can require regular maintenance. Cool roofs involve a reflective layer that reflects more sunlight than traditional roofing materials, but require additional insulation during winter months. This study evaluates several roofing strategies in terms of energy performance, urban heat island mitigation, water consumption, and economic cost. We use MLCan, a multi-layer canopy model, to simulate irrigated and non-irrigated green roof cases with shallow and deep soil depths during the spring and early summer of 2012, a drought period in central Illinois. Due to the dry conditions studied, periodic irrigation is implemented in the model to evaluate its effect on evapotranspiration. We simulate traditional and cool roof scenarios by altering surface albedo and omitting vegetation and soil layers. We find that both green roofs and cool roofs significantly reduce surface temperature compared to the traditional roof simulation. Cool roof temperatures always remain below air temperature and, similar to traditional roofs, require low maintenance. Green roofs remain close to air temperature and also provide thermal insulation, runoff reduction, and carbon uptake, but might require irrigation during dry periods. Due to the longer lifetime of a green roof compared to cool and traditional roofs, we find that green roofs realize the highest long term cost savings under simulated conditions. However, using longer-life traditional roof materials (which have a higher upfront cost) can help decrease this price differential, making cool roofs the most affordable option due to the higher maintenance costs associated with green roofs

  8. Green roof Malta

    OpenAIRE

    Gatt, Antoine

    2015-01-01

    In Malta, buildings cover one third of the Island, leaving greenery in the dirt track. Green roofs are one way to bring plants back to urban areas with loads of benefits. Antoine Gatt, who manages the LifeMedGreenRoof project at the University of Malta, tells us more. http://www.um.edu.mt/think/green-roof-malta/

  9. EPA's Green Roof Research

    Science.gov (United States)

    This is a presentation on the basics of green roof technology. The presentation highlights some of the recent ORD research projects on green roofs and provices insight for the end user as to the benefits for green roof technology. It provides links to currently available EPA re...

  10. Single-layer MoS2 transistors.

    Science.gov (United States)

    Radisavljevic, B; Radenovic, A; Brivio, J; Giacometti, V; Kis, A

    2011-03-01

    Two-dimensional materials are attractive for use in next-generation nanoelectronic devices because, compared to one-dimensional materials, it is relatively easy to fabricate complex structures from them. The most widely studied two-dimensional material is graphene, both because of its rich physics and its high mobility. However, pristine graphene does not have a bandgap, a property that is essential for many applications, including transistors. Engineering a graphene bandgap increases fabrication complexity and either reduces mobilities to the level of strained silicon films or requires high voltages. Although single layers of MoS(2) have a large intrinsic bandgap of 1.8 eV (ref. 16), previously reported mobilities in the 0.5-3 cm(2) V(-1) s(-1) range are too low for practical devices. Here, we use a halfnium oxide gate dielectric to demonstrate a room-temperature single-layer MoS(2) mobility of at least 200 cm(2) V(-1) s(-1), similar to that of graphene nanoribbons, and demonstrate transistors with room-temperature current on/off ratios of 1 × 10(8) and ultralow standby power dissipation. Because monolayer MoS(2) has a direct bandgap, it can be used to construct interband tunnel FETs, which offer lower power consumption than classical transistors. Monolayer MoS(2) could also complement graphene in applications that require thin transparent semiconductors, such as optoelectronics and energy harvesting.

  11. Evaluation of Green Roof Water Quantity and Quality Performance in an Urban Climate

    Science.gov (United States)

    In this report we present an analysis of water benefits from an array of observed green roof and control (non-vegetated) roof project sites throughout NYC. The projects are located on a variety of building sites and represent a diverse set of available extensive green roof instal...

  12. Modeling a Hydrologically Optimal Green Roof Media Mixture

    Science.gov (United States)

    Background/Questions/MethodsA key environmental concern in managing urban ecosystems is controlling stormwater runoff to ameliorate pollution problems and sewage overflows. Vegetated green roofs have become an important green infrastructure tool to collect, store, and gradually r...

  13. Can green roof act as a sink for contaminants? A methodological study to evaluate runoff quality from green roofs.

    Science.gov (United States)

    Vijayaraghavan, K; Joshi, Umid Man

    2014-11-01

    The present study examines whether green roofs act as a sink or source of contaminants based on various physico-chemical parameters (pH, conductivity and total dissolved solids) and metals (Na, K, Ca, Mg, Al, Fe, Cr, Cu, Ni, Zn, Cd and Pb). The performance of green roof substrate prepared using perlite, vermiculite, sand, crushed brick, and coco-peat, was compared with local garden soil based on improvement of runoff quality. Portulaca grandiflora was used as green roof vegetation. Four different green roof configurations, with vegetated and non-vegetated systems, were examined for several artificial rain events (un-spiked and metal-spiked). In general, the vegetated green roof assemblies generated better-quality runoff with less conductivity and total metal ion concentration compared to un-vegetated assemblies. Of the different green roof configurations examined, P. grandiflora planted on green roof substrate acted as sink for various metals and showed the potential to generate better runoff. Copyright © 2014 Elsevier Ltd. All rights reserved.

  14. IMPROVED ROOF STABILIZATION TECHNOLOGIES

    Energy Technology Data Exchange (ETDEWEB)

    M.A. Ebadian, Ph.D.

    1999-01-01

    Many U.S. Department of Energy (DOE) remediation sites have performed roof repair and roof replacement to stabilize facilities prior to performing deactivation and decommissioning (D&D) activities. This project will review the decision criteria used by these DOE sites, along with the type of repair system used for each different roof type. Based on this information, along with that compiled from roofing experts, a decision-making tool will be generated to aid in selecting the proper roof repair systems. Where appropriate, innovative technologies will be reviewed and applied to the decision-making tool to determine their applicability. Based on the results, applied research and development will be conducted to develop a method to repair these existing roofing systems, while providing protection for the D and D worker in a cost-efficient manner.

  15. IMPROVED ROOF STABILIZATION TECHNOLOGIES

    International Nuclear Information System (INIS)

    Ebadian, M.A.

    1999-01-01

    Many U.S. Department of Energy (DOE) remediation sites have performed roof repair and roof replacement to stabilize facilities prior to performing deactivation and decommissioning (D and D) activities. This project will review the decision criteria used by these DOE sites, along with the type of repair system used for each different roof type. Based on this information, along with that compiled from roofing experts, a decision-making tool will be generated to aid in selecting the proper roof repair systems. Where appropriate, innovative technologies will be reviewed and applied to the decision-making tool to determine their applicability. Based on the results, applied research and development will be conducted to develop a method to repair these existing roofing systems, while providing protection for the D and D worker in a cost-efficient manner

  16. Green Roofs: Federal Energy Management Program (FEMP) Federal Technology Alert

    Energy Technology Data Exchange (ETDEWEB)

    Scholz-Barth, K.; Tanner, S.

    2004-09-01

    In a ''green roof,'' a layer of vegetation (e.g., a roof garden) covers the surface of a roof to provide shade, cooler indoor and outdoor temperatures, and effective storm-water management to reduce runoff. The main components are waterproofing, soil, and plants. There are two basic kinds: intensive and extensive. An intensive green roof often features large shrubs and trees, and it can be expensive to install and maintain. An extensive green roof features shallow soil and low-growing, horizontally spreading plants that can thrive in the alpine conditions of many rooftops. These plants do not require a lot of water or soil, and they can tolerate a significant amount of exposure to the sun and wind. This Federal Technology Alert focuses on the benefits, design, and implementation of extensive green roofs and includes criteria for their use on federal facilities.

  17. Yorktowne Square condominium green roof retrofit and stormwater management plan

    Energy Technology Data Exchange (ETDEWEB)

    Perry, M.D. [Building Logics Inc., Virginia Beach, VA (United States)

    2005-07-01

    This paper provided details of a green roof retrofit and and stormwater management plan developed for the Yorktowne Square Condominiums, a 15.3 acre site located in the highly developed county of Fairfax, Virginia. The 4700 square foot green roof system was installed as the first step to implement an effective stormwater management plan. The loss of forested areas and increased impervious surfaces in the region has meant that stormwater drainage in the region is increasingly allowing trash, sediment and other pollutants to enter the Chesapeake Bay. A lightweight EnviroTech green roof system was used to address structural concerns due to the age of the buildings. The specialized modified bitumen membrane incorporated waterproofing, root barrier, water retention and drainage systems in a single layer. The Yorktowne plan will reduce the nutrient load in the Chesapeake Bay and maintain the 40 per cent nutrient reduction goal agreed to in 1987, in addition to not using pesticides, fertilizers or herbicides. Studies have shown that the living roof has increased stormwater retention by up to 80 per cent. The roof has been the subject of television shows and newspaper articles. It was concluded that Yorktowne has become a model for residential and business communities by demonstrating how green roofs and other stormwater management designs can be implemented to improve water quality, decrease erosive stormwater, and conserve resources in the Chesapeake Bay watershed. 1 fig.

  18. Solution for Flat Roofs

    Directory of Open Access Journals (Sweden)

    Şt. Vasiliu

    2008-01-01

    Full Text Available Roofs are constructive subassemblies that are located at the top of buildings, which toghether with perimetral walls and some elements of the infrastructure belongs to the subsystem elements that close the building. An important share in the roofing is represented by the flat roofs. Flat roofs must meet the requirements of resistance to mechanical action, thermal insulation, acoustic and waterproof, fire resistance, durability and aesthetics. To meet these requirements is necessary an analysis of the component layers and materials properties that determine the durability of structural assembly.

  19. Single-layer graphene on silicon nitride micromembrane resonators

    Energy Technology Data Exchange (ETDEWEB)

    Schmid, Silvan; Guillermo Villanueva, Luis; Amato, Bartolo; Boisen, Anja [Department of Micro- and Nanotechnology, Technical University of Denmark, DTU Nanotech, Building 345 East, 2800 Kongens Lyngby (Denmark); Bagci, Tolga; Zeuthen, Emil; Sørensen, Anders S.; Usami, Koji; Polzik, Eugene S. [QUANTOP, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen (Denmark); Taylor, Jacob M. [Joint Quantum Institute/NIST, College Park, Maryland 20899 (United States); Herring, Patrick K.; Cassidy, Maja C. [School of Engineering and Applied Science, Harvard University, Cambridge, Massachusetts 02138 (United States); Marcus, Charles M. [Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen (Denmark); Cheol Shin, Yong; Kong, Jing [Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

    2014-02-07

    Due to their low mass, high quality factor, and good optical properties, silicon nitride (SiN) micromembrane resonators are widely used in force and mass sensing applications, particularly in optomechanics. The metallization of such membranes would enable an electronic integration with the prospect for exciting new devices, such as optoelectromechanical transducers. Here, we add a single-layer graphene on SiN micromembranes and compare electromechanical coupling and mechanical properties to bare dielectric membranes and to membranes metallized with an aluminium layer. The electrostatic coupling of graphene covered membranes is found to be equal to a perfectly conductive membrane, without significantly adding mass, decreasing the superior mechanical quality factor or affecting the optical properties of pure SiN micromembranes. The concept of graphene-SiN resonators allows a broad range of new experiments both in applied physics and fundamental basic research, e.g., for the mechanical, electrical, or optical characterization of graphene.

  20. Single-layer and integrated YBCO gradiometer coupled SQUIDs

    Energy Technology Data Exchange (ETDEWEB)

    Baer, L.R.; Daalmans, G.M.; Barthel, K.H.; Ferchland, L.; Selent, M.; Kuehnl, M.; Uhl, D. [Siemens AG, Central Research and Development, Paul-Gossen-Strasse 100, D-91052 Erlangen (Germany)

    1996-04-01

    For many SQUID applications such as biomagnetism or non-destructive evaluation it is convenient or even necessary to work without the restrictions of a magnetically shielded room. This contribution deals with two sensors appropriate for this purpose. In the first concept we present a flip chip arrangement of a single-layer flux transformer and a single-layer SQUID, taking advantage of a simple technology. The SQUID was prepared on a 15x15 mm{sup 2} SrTiO{sub 3} 24 deg. bicrystal and located in the common line of two-parallel-loop arrangements. The flipped antenna was designed as a two-parallel-loop gradiometer with 26 mm baseline on a 10x40 mm{sup 2} LaAlO{sub 3} single-crystal substrate. A field gradient sensitivity of 1 nT cm{sup -1}{phi}{sub 0} was obtained. We could demonstrate a field gradient resolution of 20 fT cm{sup -1} Hz{sup 1/2} at 1 kHz in an unshielded environment. In the second concept we integrated both the flux antenna and the SQUID on a SrTiO{sub 3} bicrystal. The tighter coupling scheme results in smaller devices for similar field gradient sensitivities. The integrated SQUID is designed as a 3x8 mm{sup 2} device on a 10x10 mm{sup 2} bicrystal substrate. The remaining space is used for test structures and SQUIDs without antennae, in order to control the technology as well as the SQUID design. Parallel processed dummy substrates were used to monitor the quality of film growth by x-ray analysis. The quality of our SQUID design will be discussed on the basis of the measured field gradient sensitivity and noise. The reliability of the devices is demonstrated by an NDE type measurement. (author)

  1. Vegetation

    DEFF Research Database (Denmark)

    Epstein, H.E.; Walker, D.A.; Bhatt, U.S.

    2012-01-01

    • Over the past 30 years (1982-2011), the Normalized Difference Vegetation Index (NDVI), an index of green vegetation, has increased 15.5% in the North American Arctic and 8.2% in the Eurasian Arctic. In the more southern regions of Arctic tundra, the estimated aboveground plant biomass has...... in vegetation (including shrub tundra expansion) and thunderstorm activity, each a result of Arctic warming, have created conditions that favor a more active Arctic fire regime....

  2. Million Solar Roofs

    Energy Technology Data Exchange (ETDEWEB)

    None

    2003-11-01

    Since its announcement in June 1997, the Million Solar Roofs Initiative has generated a major buzz in communities, states, and throughout the nation. With more than 300,000 installations, the buzz is getting louder. This brochure describes Million Solar Roofs activities and partnerships.

  3. Touch stimulated pulse generation in biomimetic single-layer graphene

    Science.gov (United States)

    Sul, Onejae; Chun, Hyunsuk; Choi, Eunseok; Choi, Jungbong; Cho, Kyeongwon; Jang, Dongpyo; Chun, Sungwoo; Park, Wanjun; Lee, Seung-Beck

    2016-02-01

    Detecting variation in contact pressure is a separate sensing mode in the human somatosensory system that differs from the detection of pressure magnitude. If pressure magnitude and variation sensing can be achieved simultaneously, an advanced biomimetic tactile system that better emulates human senses may be developed. We report on a novel single-layer graphene based artificial mechanoreceptor that generates a resistance pulse as the contact stimulus passes a specific threshold pressure, mimicking the generation of action potentials in a biological fast-adapting mechanoreceptor. The electric field from a flexible membrane gate electrode placed above a graphene channel raises the Fermi level from the valence band as pressure deflects the membrane. The threshold pressure is reached when the Fermi level crosses the Dirac point in the graphene energy band, which generates a sharp peak in the measured resistance. We found that by changing the gate potential it was possible to modulate the threshold pressure and using a series of graphene channels, a train of pulses were generated during a transient pressurizing stimulus demonstrating biomimetic behaviour.Detecting variation in contact pressure is a separate sensing mode in the human somatosensory system that differs from the detection of pressure magnitude. If pressure magnitude and variation sensing can be achieved simultaneously, an advanced biomimetic tactile system that better emulates human senses may be developed. We report on a novel single-layer graphene based artificial mechanoreceptor that generates a resistance pulse as the contact stimulus passes a specific threshold pressure, mimicking the generation of action potentials in a biological fast-adapting mechanoreceptor. The electric field from a flexible membrane gate electrode placed above a graphene channel raises the Fermi level from the valence band as pressure deflects the membrane. The threshold pressure is reached when the Fermi level crosses the Dirac

  4. Improved roof stabilization technologies

    International Nuclear Information System (INIS)

    Ebadian, M.A.

    1998-01-01

    Decontamination and decommissioning (D and D) activities require that personnel have access to all areas of structures, some of which are more than 40 years old. In many cases, these structures have remained in a standby condition for up to 10 years; few preventative maintenance activities have been performed on them because of lack of funding or a defined future plan of action. This situation has led to deteriorated building conditions, resulting in potential personnel safety hazards. In addition, leaky roofs allow water to enter the buildings, which can cause the spread of contamination and increase building deterioration, worsening the already unsafe working conditions. To ensure worker safety and facilitate building dismantlement, the assessment of roof stabilization techniques applicable to US Department of Energy (DOE) structures has become an important issue. During Fiscal year 1997 (FY97), a comprehensive reliability-based model for the structural stabilization analysis of roof system in complex structures was developed. The model consists of three major components: a material testing method, a deterministic structural computer model, and a reliability-based optimization, and probabilistic analyses of roof structures can be implemented. Given site-specific needs, this model recommends the most appropriate roof stabilization system. This model will give not only an accurate evaluation of the existing roof system in complex structures, but it will also be a reliable method to aid the decision-making process. This final report includes in its appendix a Users' Manual for the Program of Deterministic and Reliability Analysis of Roof Structures

  5. Improved roof stabilization technologies

    Energy Technology Data Exchange (ETDEWEB)

    Ebadian, M.A.

    1998-01-01

    Decontamination and decommissioning (D and D) activities require that personnel have access to all areas of structures, some of which are more than 40 years old. In many cases, these structures have remained in a standby condition for up to 10 years; few preventative maintenance activities have been performed on them because of lack of funding or a defined future plan of action. This situation has led to deteriorated building conditions, resulting in potential personnel safety hazards. In addition, leaky roofs allow water to enter the buildings, which can cause the spread of contamination and increase building deterioration, worsening the already unsafe working conditions. To ensure worker safety and facilitate building dismantlement, the assessment of roof stabilization techniques applicable to US Department of Energy (DOE) structures has become an important issue. During Fiscal year 1997 (FY97), a comprehensive reliability-based model for the structural stabilization analysis of roof system in complex structures was developed. The model consists of three major components: a material testing method, a deterministic structural computer model, and a reliability-based optimization, and probabilistic analyses of roof structures can be implemented. Given site-specific needs, this model recommends the most appropriate roof stabilization system. This model will give not only an accurate evaluation of the existing roof system in complex structures, but it will also be a reliable method to aid the decision-making process. This final report includes in its appendix a Users` Manual for the Program of Deterministic and Reliability Analysis of Roof Structures.

  6. Electrical and optical transport properties of single layer WSe2

    Science.gov (United States)

    Tahir, M.

    2018-03-01

    The electronic properties of single layer WSe2 are distinct from the famous graphene due to strong spin orbit coupling, a huge band gap and an anisotropic lifting of the degeneracy of the valley degree of freedom under Zeeman field. In this work, band structure of the monolayer WSe2 is evaluated in the presence of spin and valley Zeeman fields to study the electrical and optical transport properties. Using Kubo formalism, an explicit expression for the electrical Hall conductivity is examined at finite temperatures. The electrical longitudinal conductivity is also evaluated. Further, the longitudinal and Hall optical conductivities are analyzed. It is observed that the contributions of the spin-up and spin-down states to the power absorption spectrum depend on the valley index. The numerical results exhibit absorption peaks as a function of photon energy, ℏ ω, in the range ∼ 1.5 -2 eV. Also, the optical response lies in the visible frequency range in contrast to the conventional two-dimensional electron gas or graphene where the response is limited to terahertz regime. This ability to isolate carriers in spin-valley coupled structures may make WSe2 a promising candidate for future spintronics, valleytronics and optical devices.

  7. Plasmon enhanced terahertz emission from single layer graphene.

    Science.gov (United States)

    Bahk, Young-Mi; Ramakrishnan, Gopakumar; Choi, Jongho; Song, Hyelynn; Choi, Geunchang; Kim, Yong Hyup; Ahn, Kwang Jun; Kim, Dai-Sik; Planken, Paul C M

    2014-09-23

    We show that surface plasmons, excited with femtosecond laser pulses on continuous or discontinuous gold substrates, strongly enhance the generation and emission of ultrashort, broadband terahertz pulses from single layer graphene. Without surface plasmon excitation, for graphene on glass, 'nonresonant laser-pulse-induced photon drag currents' appear to be responsible for the relatively weak emission of both s- and p-polarized terahertz pulses. For graphene on a discontinuous layer of gold, only the emission of the p-polarized terahertz electric field is enhanced, whereas the s-polarized component remains largely unaffected, suggesting the presence of an additional terahertz generation mechanism. We argue that in the latter case, 'surface-plasmon-enhanced optical rectification', made possible by the lack of inversion symmetry at the graphene on gold surface, is responsible for the strongly enhanced emission. The enhancement occurs because the electric field of surface plasmons is localized and enhanced where the graphene is located: at the surface of the metal. We believe that our results point the way to small, thin, and more efficient terahertz photonic devices.

  8. Intrinsic Charge Carrier Mobility in Single-Layer Black Phosphorus.

    Science.gov (United States)

    Rudenko, A N; Brener, S; Katsnelson, M I

    2016-06-17

    We present a theory for single- and two-phonon charge carrier scattering in anisotropic two-dimensional semiconductors applied to single-layer black phosphorus (BP). We show that in contrast to graphene, where two-phonon processes due to the scattering by flexural phonons dominate at any practically relevant temperatures and are independent of the carrier concentration n, two-phonon scattering in BP is less important and can be considered negligible at n≳10^{13}  cm^{-2}. At smaller n, however, phonons enter in the essentially anharmonic regime. Compared to the hole mobility, which does not exhibit strong anisotropy between the principal directions of BP (μ_{xx}/μ_{yy}∼1.4 at n=10^{13} cm^{-2} and T=300  K), the electron mobility is found to be significantly more anisotropic (μ_{xx}/μ_{yy}∼6.2). Absolute values of μ_{xx} do not exceed 250 (700)  cm^{2} V^{-1} s^{-1} for holes (electrons), which can be considered as an upper limit for the mobility in BP at room temperature.

  9. Roof bolting equipment & technology

    Energy Technology Data Exchange (ETDEWEB)

    Fiscor, S.

    2009-04-15

    Technology provides an evaluator path to improvement for roof bolting machines. Bucyrus offers three different roof bolts models for various mining conditions. The LRB-15 AR is a single-arm boiler recommended for ranges of 32 inches and above; the dual-arm RB2-52A for ranges of 42 inches and above; and the dual-arm RB2-88A for ranges of 54 inches and above. Design features are discussed in the article. Developments in roof bolting technology by Joy Mining Machinery are reported. 4 photos.

  10. Do Looks Matter? A Case Study on Extensive Green Roofs Using Discrete Choice Experiments

    Directory of Open Access Journals (Sweden)

    Jan Vanstockem

    2018-01-01

    Full Text Available Extensive green roofs are a promising type of urban green that can play an important role in climate proofing and ultimately in the sustainability of our cities. Despite their increasingly widespread application and the growing scientific interest in extensive green roofs, their aesthetics have received limited scientific attention. Furthermore, several functional issues occur, as weedy species can colonize the roof, and extreme roof conditions can lead to gaps in the vegetation. Apart from altering the function of a green roof, we also expect these issues to influence the perception of extensive green roofs, possibly affecting their acceptance and application. We therefore assessed the preferences of a self-selected convenience sample of 155 Flemish respondents for visual aspects using a discrete choice experiment. This approach, combined with current knowledge on the psychological aspects of green roof visuals, allowed us to quantify extensive green roof preferences. Our results indicate that vegetation gaps and weedy species, together with a diverse vegetation have a considerable impact on green roof perception. Gaps were the single most important attribute, indicated by a relative importance of ca. 53%, with cost coming in at a close second at ca. 46%. Overall, this study explores the applicability of a stated preference technique to assess an often overlooked aspect of extensive green roofs. It thereby provides a foundation for further research aimed at generating practical recommendations for green roof construction and maintenance.

  11. Adaptable typologies for active roofs

    NARCIS (Netherlands)

    Quanjel, E.M.C.J.; Zeiler, W.

    2006-01-01

    The main objective of this part of the 6th framework Pan-European EUR-ACTIVE ROOF-er project is to improve the interaction between design participants of dynamic adaptable Active Roofs in product development and Active Roofs from an architects/ customers perspective. Improvements in Active Roof

  12. Green Roofs for Stormwater Management

    Science.gov (United States)

    This project evaluated green roofs as a stormwater management tool. Results indicate that the green roofs are capable of removing 40% of the annual rainfall volume from a roof through retention and evapotranspiration. Rainfall not retained by green roofs is detained, effectively...

  13. Ecological Impacts of Replacing Traditional Roofs with Green Roofs in Two Urban Areas

    Directory of Open Access Journals (Sweden)

    Timothy Carter

    2008-01-01

    Full Text Available Urban land cover is dominated by impervious surface that degrades both terrestrial and aquatic ecosystems relative to predevelopment conditions. There are significant opportunities for designers of urban landscapes to use alternative land covers that have multiple functions, benefiting both human and nonhuman components of the urban ecosystem. Vegetated (green roofs are one form of alternative land cover that has shown the potential to provide a variety of ecological benefits in urban areas. We evaluated how stormwater retention, building energy and temperature, and rooftop habitat are influenced by the use of green roofs using test plots in Georgia and Massachusetts. Green roofs were shown to recreate part of the predevelopment hydrology through increasing interception, stormwater storage, evaporation, and transpiration on the rooftop and worked extremely well for small storm events. Temperature reductions were found on the green rooftop as compared to an asphalt surface, although other roof technologies that minimize temperatures, such as lighter colored membranes, provide similar benefits. Novel habitat was created on the rooftop, although the extent of this habitat was limited in part by plant survivability and the need for additional water inputs for diverse plant communities to survive. Despite the challenges, the green roof benefits reported here suggest that green roofs can be used effectively as a multifunctional land cover in urban areas.

  14. Synthesis of PbI(2) single-layered inorganic nanotubes encapsulated within carbon nanotubes.

    Science.gov (United States)

    Cabana, Laura; Ballesteros, Belén; Batista, Eudar; Magén, César; Arenal, Raúl; Oró-Solé, Judith; Rurali, Riccardo; Tobias, Gerard

    2014-04-02

    The template assisted growth of single-layered inorganic nanotubes is reported. Single-crystalline lead iodide single-layered nanotubes have been prepared using the inner cavities of carbon nanotubes as hosting templates. The diameter of the resulting inorganic nanotubes is merely dependent on the diameter of the host. This facile method is highly versatile opening up new horizons in the preparation of single-layered nanostructures. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Solar power roof shingle

    Science.gov (United States)

    Forestieri, A. F.; Ratajczak, A. F.; Sidorak, L. G.

    1975-01-01

    Silicon solar cell module provides both all-weather protection and electrical power. Module consists of array of circular silicon solar cells bonded to fiberglass substrate roof shingle with fluorinated ethylene propylene encapsulant.

  16. Novel doping alternatives for single-layer transition metal dichalcogenides

    Science.gov (United States)

    Onofrio, Nicolas; Guzman, David; Strachan, Alejandro

    2017-11-01

    Successful doping of single-layer transition metal dichalcogenides (TMDs) remains a formidable barrier to their incorporation into a range of technologies. We use density functional theory to study doping of molybdenum and tungsten dichalcogenides with a large fraction of the periodic table. An automated analysis of the energetics, atomic and electronic structure of thousands of calculations results in insightful trends across the periodic table and points out promising dopants to be pursued experimentally. Beyond previously studied cases, our predictions suggest promising substitutional dopants that result in p-type transport and reveal interesting physics behind the substitution of the metal site. Doping with early transition metals (TMs) leads to tensile strain and a significant reduction in the bandgap. The bandgap increases and strain is reduced as the d-states are filled into the mid TMs; these trends reverse as we move into the late TMs. Additionally, the Fermi energy increases monotonously as the d-shell is filled from the early to mid TMs and we observe few to no gap states, indicating the possibility of both p- (early TMs) and n- (mid TMs) type doping. Quite surprisingly, the simulations indicate the possibility of interstitial doping of TMDs; the energetics reveal that a significant number of dopants, increasing in number from molybdenum disulfide to diselenide and to ditelluride, favor the interstitial sites over adsorbed ones. Furthermore, calculations of the activation energy associated with capturing the dopants into the interstitial site indicate that the process is kinetically possible. This suggests that interstitial impurities in TMDs are more common than thought to date and we propose a series of potential interstitial dopants for TMDs relevant for application in nanoelectronics based on a detailed analysis of the predicted electronic structures.

  17. Single-layer HDR video coding with SDR backward compatibility

    Science.gov (United States)

    Lasserre, S.; François, E.; Le Léannec, F.; Touzé, D.

    2016-09-01

    The migration from High Definition (HD) TV to Ultra High Definition (UHD) is already underway. In addition to an increase of picture spatial resolution, UHD will bring more color and higher contrast by introducing Wide Color Gamut (WCG) and High Dynamic Range (HDR) video. As both Standard Dynamic Range (SDR) and HDR devices will coexist in the ecosystem, the transition from Standard Dynamic Range (SDR) to HDR will require distribution solutions supporting some level of backward compatibility. This paper presents a new HDR content distribution scheme, named SL-HDR1, using a single layer codec design and providing SDR compatibility. The solution is based on a pre-encoding HDR-to-SDR conversion, generating a backward compatible SDR video, with side dynamic metadata. The resulting SDR video is then compressed, distributed and decoded using standard-compliant decoders (e.g. HEVC Main 10 compliant). The decoded SDR video can be directly rendered on SDR displays without adaptation. Dynamic metadata of limited size are generated by the pre-processing and used to reconstruct the HDR signal from the decoded SDR video, using a post-processing that is the functional inverse of the pre-processing. Both HDR quality and artistic intent are preserved. Pre- and post-processing are applied independently per picture, do not involve any inter-pixel dependency, and are codec agnostic. Compression performance, and SDR quality are shown to be solidly improved compared to the non-backward and backward-compatible approaches, respectively using the Perceptual Quantization (PQ) and Hybrid Log Gamma (HLG) Opto-Electronic Transfer Functions (OETF).

  18. Green roofs; Les toitures vegetalisees

    Energy Technology Data Exchange (ETDEWEB)

    Seghier, C.

    2006-03-15

    Impervious surface coverage keeps spreading in cities. Streets, sidewalks, parking lots and roofs are waterproof, meaning greater amounts of water to channel and treat and higher flood risks during heavy rainfalls. Green roofing can play a key part in addressing this alarming issue. There are three types of green roofs: extensive, semi-intensive and intensive. The extensive green roof technique uses a thin soil covering with a variety of species providing year-round plant coverage. The plants are not necessarily horticultural in which case routine maintenance is minimal. No watering is needed. Usually extensive green roofs create an ecosystem. The semi-intensive green roof technique uses a soil covering of average thickness and serves to create decorative roofing. Although maintenance is moderate, watering is essential. The intensive green roof technique produces a terrace roof garden. Another advantage of green roofs is they increase the life cycle of the sealing. Roof sealing protection may see the span of its life cycle, now at about fifteen years, doubled if the building has a green roof. planning professionals still know very little about green roofing solutions. Yet, green roofing provides unquestionable ecological qualities and thermal and acoustic performance that have proven to be environmentally friendly. Yet France lags behind northern European countries in green roofing. The Germans, Swiss, Austrians, Scandinavians and Dutch have been using the technique for more than twenty years. (A.L.B.)

  19. Plant species richness enhances nitrogen retention in green roof plots.

    Science.gov (United States)

    Johnson, Catherine; Schweinhart, Shelbye; Buffam, Ishi

    2016-10-01

    Vegetated (green) roofs have become common in many cities and are projected to continue to increase in coverage, but little is known about the ecological properties of these engineered ecosystems. In this study, we tested the biodiversity-ecosystem function hypothesis using commercially available green roof trays as replicated plots with varying levels of plant species richness (0, 1, 3, or 6 common green roof species per plot, using plants with different functional characteristics). We estimated accumulated plant biomass near the peak of the first full growing season (July 2013) and measured runoff volume after nearly every rain event from September 2012 to September 2013 (33 events) and runoff fluxes of inorganic nutrients ammonium, nitrate, and phosphate from a subset of 10 events. We found that (1) total plant biomass increased with increasing species richness, (2) green roof plots were effective at reducing storm runoff, with vegetation increasing water retention more than soil-like substrate alone, but there was no significant effect of plant species identity or richness on runoff volume, (3) green roof substrate was a significant source of phosphate, regardless of presence/absence of plants, and (4) dissolved inorganic nitrogen (DIN = nitrate + ammonium) runoff fluxes were different among plant species and decreased significantly with increasing plant species richness. The variation in N retention was positively related to variation in plant biomass. Notably, the increased biomass and N retention with species richness in this engineered ecosystem are similar to patterns observed in published studies from grasslands and other well-studied ecosystems. We suggest that more diverse plantings on vegetated roofs may enhance the retention capacity for reactive nitrogen. This is of importance for the sustained health of vegetated roof ecosystems, which over time often experience nitrogen limitation, and is also relevant for water quality in receiving waters

  20. Experimental research on the stability of armour and secondary layer in a single layered Tetrapod breakwater

    NARCIS (Netherlands)

    De Jong, W.; Verhagen, H.J.; Olthof, J.

    2004-01-01

    Physical model tests were done on an armour of Tetrapods, placed in a single layer. The objective of the investigations was to study the stability of the secondary layer, and to see if the material of this secondary layer could be washed out through the single layer of Tetrapods. It was concluded

  1. A theoretical study of pump–probe experiment in single-layer ...

    Indian Academy of Sciences (India)

    Home; Journals; Pramana – Journal of Physics; Volume 82; Issue 6. A theoretical study of pump–probe experiment in single-layer, bilayer and multilayer graphene ... Here we use it as a tool to study the phenomenon of anomalous Rabi oscillations in graphene that was predicted recently in single-layer graphene.

  2. Establishment and performance of an experimental green roof under extreme climatic conditions.

    Science.gov (United States)

    Klein, Petra M; Coffman, Reid

    2015-04-15

    Green roofs alter the surface energy balance and can help in mitigating urban heat islands. However, the cooling of green roofs due to evapotranspiration strongly depends on the climatic conditions, and vegetation type and density. In the Southern Central Plains of the United States, extreme weather events, such as high winds, heat waves and drought conditions pose challenges for successful implementation of green roofs, and likely alter their standard performance. The National Weather Center Experimental Green Roof, an interdisciplinary research site established in 2010 in Norman, OK, aimed to investigate the ecological performance and surface energy balance of green roof systems. Starting in May 2010, 26 months of vegetation studies were conducted and the radiation balance, air temperature, relative humidity, and buoyancy fluxes were monitored at two meteorological stations during April-October 2011. The establishment of a vegetative community trended towards prairie plant dominance. High mortality of succulents and low germination of grasses and herbaceous plants contributed to low vegetative coverage. In this condition succulent diversity declined. Bouteloua gracilis and Delosperma cooperi showed typological dominance in harsh climatic conditions, while Sedum species experienced high mortality. The plant community diversified through volunteers such as Euphorbia maculate and Portulaca maculate. Net radiation measured at a green-roof meteorological station was higher than at a control station over the original, light-colored roofing material. These findings indicate that the albedo of the green roof was lower than the albedo of the original roofing material. The low vegetative coverage during the heat and drought conditions in 2011, which resulted in the dark substrate used in the green roof containers being exposed, likely contributed to the low albedo values. Nevertheless, air temperatures and buoyancy fluxes were often lower over the green roof indicating

  3. Green roof systems: a study of public attitudes and preferences in southern Spain.

    Science.gov (United States)

    Fernandez-Cañero, Rafael; Emilsson, Tobias; Fernandez-Barba, Carolina; Herrera Machuca, Miguel Ángel

    2013-10-15

    This study investigates people's preconceptions of green roofs and their visual preference for different green roof design alternatives in relation to behavioral, social and demographical variables. The investigation was performed as a visual preference study using digital images created to represent eight different alternatives: gravel roof, extensive green roof with Sedums not in flower, extensive green roof with sedums in bloom, semi-intensive green roof with sedums and ornamental grasses, semi-intensive green roof with shrubs, intensive green roof planted with a lawn, intensive green roof with succulent and trees and intensive green roof with shrubs and trees. Using a Likert-type scale, 450 respondents were asked to indicate their preference for each digital image. Results indicated that respondents' sociodemographic characteristics and childhood environmental background influenced their preferences toward different green roof types. Results also showed that green roofs with a more careful design, greater variety of vegetation structure, and more variety of colors were preferred over alternatives. Copyright © 2013 Elsevier Ltd. All rights reserved.

  4. Evolution of Flat Roofs

    Directory of Open Access Journals (Sweden)

    Şt. Vasiliu

    2009-01-01

    Full Text Available Roofs are constructive subassembles that are located at the top of buildings, which toghether with perimetral walls and some elements of the infrastructure belongs to the subsystem elements that close the building. Roofs must meet resistance requirements to mechanical action, thermal insulating, waterproofing and acoustic, fire resistance, durability, economy and aesthetics. The man saw the need to build roofs from the oldest ancient times. Even if the design of buildings has an empirical character, are known and are preserved until today constructions that are made in antiquity, by the Egyptians, Greeks and Romans with architectural achievements, worthy of admiration and in present time. General composition of civil construction has been influenced throughout the evolution of construction history by the level of production forces and properties of building materials available in every historical epoch. For over five millennia, building materials were stone, wood and ceramic products (concrete was used by theRomans only as filling material.

  5. Green Roofs for Stormwater Runoff Control - Abstract

    Science.gov (United States)

    This project evaluated green roofs as a stormwater management tool. Specifically, runoff quantity and quality from green and flat asphalt roofs were compared. Evapotranspiration from planted green roofs and evaporation from unplanted media roofs were also compared. The influence...

  6. Monitoring of the Green Roofs Installation in Brno-City District, Czech Republic

    Science.gov (United States)

    Rebrova, Tatiana; Beckovsky, David; Selnik, Petr

    2017-12-01

    In spite of the rapidly growing interest to the green roofs, there is insufficient information about their local quantities and areas in Czech Republic as well as in Central Europe. There is a lack of technical information that leads to the further development, application and environmental contribution of green roofs under local climatic conditions. The purpose of the research is to follow the tendency of how the process of green roofs’ popularization is performed in the Czech Republic and to determine basic parameters of the installed green roofs. These parameters include total quantity, area and the most common roof vegetation type (extensive or intensive); how many green roofs were installed over the last years and as a result, how the proportion of the green roofs to the conventional ones is changing. For initial evaluation Brno-City District was chosen as the next stage of university environmental project EnviHUT following the genesis of green roofs under local weather conditions.

  7. Design methodology for innovative roofs

    NARCIS (Netherlands)

    Quanjel, E.M.C.J.; Zeiler, W.; Trum, H.M.G.J.

    2006-01-01

    Traditional roofs have primary, passive, functions such as protection against rain, wind, snow etc.. Nowadays, roofs are increasingly used as preferred location for additional functions such as photovoltaic systems, roof lights and safety devices. New approaches, on designing as well as assembling

  8. A field study to evaluate runoff quality from green roofs.

    Science.gov (United States)

    Vijayaraghavan, K; Joshi, U M; Balasubramanian, R

    2012-03-15

    Green (vegetated) roofs are emerging as practical strategies to improve the environmental quality of cities. However, the impact of green roofs on the storm water quality remains a topic of concern to city planners and environmental policy makers. This study investigated whether green roofs act as a source or a sink of various metals (Na, K, Ca, Mg, Al, Fe, Cu, Cd, Pb, Zn, Mn, Cr, Ni, Li and Co), inorganic anions (NO3-, NO2-, PO4(3-), SO4(2-), Cl-, F- and Br-) and cation (NH4+). A series of green roof assemblies were constructed. Four different real rain events and several artificial rain events were considered for the study. Results showed that concentrations of most of the chemical components in runoff were highest during the beginning of rain events and subsided in the subsequent rain events. Some of the important components present in the runoff include Na, K, Ca, Mg, Li, Fe, Al, Cu, NO3-, PO4(3-) and SO4(2-). However, the concentration of these chemical components in the roof runoff strongly depends on the nature of substrates used in the green roof and the volume of rain. Based on the USEPA standards for freshwater quality, we conclude that the green roof used in this study is reasonably effective except that the runoff contains significant amounts of NO3- and PO4(3-). Copyright © 2011 Elsevier Ltd. All rights reserved.

  9. Hydrological Performance of LECA-Based Roofs in Cold Climates

    Directory of Open Access Journals (Sweden)

    Vladimír Hamouz

    2018-03-01

    Full Text Available Rooftops represent a considerable part of the impervious fractions of urban environments. Detaining and retaining runoff from vegetated rooftops can be a significant contribution to reducing the effects of urbanization, with respect to increased runoff peaks and volumes from precipitation events. However, in climates with limited evapotranspiration, a non-vegetated system is a convenient option for stormwater management. A LECA (lightweight expanded clay aggregate-based roof system was established in the coastal area of Trondheim, Norway in 2016. The roof structure consists of a 200 mm-thick layer of LECA® lightweight aggregate, covered by a concrete pavement. The retention in the LECA-based roof was estimated at 9%, which would be equivalent to 0.27 mm/day for the entire period. The LECA-based configuration provided a detention performance for a peak runoff reduction of 95% (median and for a peak delay of 1 h and 15 min (median, respectively. The relatively high moisture levels in the LECA-based roof did not affect the detention performance. Rooftop retrofitting as a form of source control may contribute to a change in runoff characteristics from conventional roofs. This study of the LECA-based roof configuration presents data and performance indicators for stormwater urban planners with regard to water detention capability.

  10. Spatial environmental heterogeneity affects plant growth and thermal performance on a green roof

    Energy Technology Data Exchange (ETDEWEB)

    Buckland-Nicks, Michael; Heim, Amy; Lundholm, Jeremy, E-mail: jlundholm@smu.ca

    2016-05-15

    Green roofs provide ecosystem services, including stormwater retention and reductions in heat transfer through the roof. Microclimates, as well as designed features of green roofs, such as substrate and vegetation, affect the magnitude of these services. Many green roofs are partially shaded by surrounding buildings, but the effects of this within-roof spatial environmental heterogeneity on thermal performance and other ecosystem services have not been examined. We quantified the effects of spatial heterogeneity in solar radiation, substrate depth and other variables affected by these drivers on vegetation and ecosystem services in an extensive green roof. Spatial heterogeneity in substrate depth and insolation were correlated with differential growth, survival and flowering in two focal plant species. These effects were likely driven by the resulting spatial heterogeneity in substrate temperature and moisture content. Thermal performance (indicated by heat flux and substrate temperature) was influenced by spatial heterogeneity in vegetation cover and substrate depth. Areas with less insolation were cooler in summer and had greater substrate moisture, leading to more favorable conditions for plant growth and survival. Spatial variation in substrate moisture (7%–26% volumetric moisture content) and temperature (21 °C–36 °C) during hot sunny conditions in summer could cause large differences in stormwater retention and heat flux within a single green roof. Shaded areas promote smaller heat fluxes through the roof, leading to energy savings, but lower evapotranspiration in these areas should reduce stormwater retention capacity. Spatial heterogeneity can thus result in trade-offs between different ecosystem services. The effects of these spatial heterogeneities are likely widespread in green roofs. Structures that provide shelter from sun and wind may be productively utilized to design higher functioning green roofs and increase biodiversity by providing habitat

  11. Spatial environmental heterogeneity affects plant growth and thermal performance on a green roof

    International Nuclear Information System (INIS)

    Buckland-Nicks, Michael; Heim, Amy; Lundholm, Jeremy

    2016-01-01

    Green roofs provide ecosystem services, including stormwater retention and reductions in heat transfer through the roof. Microclimates, as well as designed features of green roofs, such as substrate and vegetation, affect the magnitude of these services. Many green roofs are partially shaded by surrounding buildings, but the effects of this within-roof spatial environmental heterogeneity on thermal performance and other ecosystem services have not been examined. We quantified the effects of spatial heterogeneity in solar radiation, substrate depth and other variables affected by these drivers on vegetation and ecosystem services in an extensive green roof. Spatial heterogeneity in substrate depth and insolation were correlated with differential growth, survival and flowering in two focal plant species. These effects were likely driven by the resulting spatial heterogeneity in substrate temperature and moisture content. Thermal performance (indicated by heat flux and substrate temperature) was influenced by spatial heterogeneity in vegetation cover and substrate depth. Areas with less insolation were cooler in summer and had greater substrate moisture, leading to more favorable conditions for plant growth and survival. Spatial variation in substrate moisture (7%–26% volumetric moisture content) and temperature (21 °C–36 °C) during hot sunny conditions in summer could cause large differences in stormwater retention and heat flux within a single green roof. Shaded areas promote smaller heat fluxes through the roof, leading to energy savings, but lower evapotranspiration in these areas should reduce stormwater retention capacity. Spatial heterogeneity can thus result in trade-offs between different ecosystem services. The effects of these spatial heterogeneities are likely widespread in green roofs. Structures that provide shelter from sun and wind may be productively utilized to design higher functioning green roofs and increase biodiversity by providing habitat

  12. Experimental Heat Transfer Study on Green Roofs in a Semiarid Climate during Summer

    Directory of Open Access Journals (Sweden)

    Roy J. Issa

    2015-01-01

    Full Text Available An experimental study was conducted on green roofs under the semiarid summer climatic conditions of West Texas to investigate the effect of soil type, moisture content, and the presence of a top soil grass layer on the conductive heat transfer through the roof. Two soil types were investigated: uniform sand and local silt clay. Tests were also conducted on a control roof. A dual-needle heat-pulse sensor was used to conduct thermal property tests on the soils. The tests reveal that unlike sand, the thermal conductivity of silt clay did not increase continuously with soil moisture. Better heat transfer conditions were achieved when the sand and silt clay roofs were watered to a water depth of 10 mm per day rather than double the amount of 20 mm per day. The roof with silt clay soil had the lowest fluctuation in inner temperature between daytime and nighttime. Green roofs with silt clay soil required more than twice the amount of soil moisture than green roofs with sand to achieve similar roof heat transfer rates. The best net heat flux gains for vegetated green roofs were 4.7 W/m2 for the sand roof and 7.8 W/m2 for the silt clay roof.

  13. Single-layer Ultralight, Flexible, Shielding Tension Shell System for Extreme Heat and Radiation

    Data.gov (United States)

    National Aeronautics and Space Administration — The objective of this project is to develop a flexible thermal protection system (FTPS) with a Boron Nitride Nanotube (BNNT)-based single-layer, lightweight,...

  14. Hydraulic Stability of Single-Layer Dolos and Accropode Armour Layers

    DEFF Research Database (Denmark)

    Christensen, M.; Burcharth, H. F.

    1995-01-01

    A new design for Dolos breakwater armour layers is presented: Dolos armour units are placed in a selected geometric pattern in a single layer. A series of model tests have been performed in order to determine the stability of such single-layer Dolos armour layers. The test results are presented...... and compared to the stability formula for the traditional double-layer, randomly placed Dolos armour layer design presented by Burcharth (1992). The results of a series of stability tests performed with Accropode® armour layers is presented and compared to the test results obtained with single-layer Dolos...... armour layers. Run-up and reflection are presented for both single-layer Dolos armour and Accropode armour....

  15. Rainwater runoff retention on an aged intensive green roof.

    Science.gov (United States)

    Speak, A F; Rothwell, J J; Lindley, S J; Smith, C L

    2013-09-01

    Urban areas are characterised by large proportions of impervious surfaces which increases rainwater runoff and the potential for surface water flooding. Increased precipitation is predicted under current climate change projections, which will put further pressure on urban populations and infrastructure. Roof greening can be used within flood mitigation schemes to restore the urban hydrological balance of cities. Intensive green roofs, with their deeper substrates and higher plant biomass, are able to retain greater quantities of runoff, and there is a need for more studies on this less common type of green roof which also investigate the effect of factors such as age and vegetation composition. Runoff quantities from an aged intensive green roof in Manchester, UK, were analysed for 69 rainfall events, and compared to those on an adjacent paved roof. Average retention was 65.7% on the green roof and 33.6% on the bare roof. A comprehensive soil classification revealed the substrate, a mineral soil, to be in good general condition and also high in organic matter content which can increase the water holding capacity of soils. Large variation in the retention data made the use of predictive regression models unfeasible. This variation arose from complex interactions between Antecedant Dry Weather Period (ADWP), season, monthly weather trends, and rainfall duration, quantity and peak intensity. However, significantly lower retention was seen for high rainfall events, and in autumn, which had above average rainfall. The study period only covers one unusually wet year, so a longer study may uncover relationships to factors which can be applied to intensive roofs elsewhere. Annual rainfall retention for Manchester city centre could be increased by 2.3% by a 10% increase in intensive green roof construction. The results of this study will be of particular interest to practitioners implementing greenspace adaptation in temperate and cool maritime climates. Copyright © 2013

  16. Effect of surface geometry and insolation on temperature profile of green roof in Saint-Petersburg environment

    Directory of Open Access Journals (Sweden)

    С. А. Игнатьев

    2016-08-01

    Full Text Available The paper addresses an issue of creating an environment favorable for the life in megacities by planting vegetation on the rooftops. It also provides information about rooftop greening practices adopted in other countries. The issues of ‘green roof’ building in climatic conditions of Saint Petersburg and roof vegetation impact on the urban ecosystem are examined. Vegetation composition quality- and quantity-wise has been proposed for the roof under research and a 3D model of this roof reflecting its geometric properties has been developed. A structure of roof covering and substrate qualitative composition is presented. An effect of rooftop geometry on the substrate temperature is explored. The annual substrate temperature and moisture content in different parts of the roof have been analyzed. Results of thermal imaging monitoring and insolation modelling for different parts of green roof surface are presented.

  17. Producing superhydrophobic roof tiles

    International Nuclear Information System (INIS)

    Carrascosa, Luis A M; Facio, Dario S; Mosquera, Maria J

    2016-01-01

    Superhydrophobic materials can find promising applications in the field of building. However, their application has been very limited because the synthesis routes involve tedious processes, preventing large-scale application. A second drawback is related to their short-term life under outdoor conditions. A simple and low-cost synthesis route for producing superhydrophobic surfaces on building materials is developed and their effectiveness and their durability on clay roof tiles are evaluated. Specifically, an organic–inorganic hybrid gel containing silica nanoparticles is produced. The nanoparticles create a densely packed coating on the roof tile surface in which air is trapped. This roughness produces a Cassie–Baxter regime, promoting superhydrophobicity. A surfactant, n-octylamine, was also added to the starting sol to catalyze the sol–gel process and to coarsen the pore structure of the gel network, preventing cracking. The application of ultrasound obviates the need to use volatile organic compounds in the synthesis, thereby making a ‘green’ product. It was also demonstrated that a co-condensation process effective between the organic and inorganic species is crucial to obtain durable and effective coatings. After an aging test, high hydrophobicity was maintained and water absorption was completely prevented for the roof tile samples under study. However, a transition from a Cassie–Baxter to a Wenzel state regime was observed as a consequence of the increase in the distance between the roughness pitches produced by the aging of the coating. (paper)

  18. Producing superhydrophobic roof tiles.

    Science.gov (United States)

    Carrascosa, Luis A M; Facio, Dario S; Mosquera, Maria J

    2016-03-04

    Superhydrophobic materials can find promising applications in the field of building. However, their application has been very limited because the synthesis routes involve tedious processes, preventing large-scale application. A second drawback is related to their short-term life under outdoor conditions. A simple and low-cost synthesis route for producing superhydrophobic surfaces on building materials is developed and their effectiveness and their durability on clay roof tiles are evaluated. Specifically, an organic-inorganic hybrid gel containing silica nanoparticles is produced. The nanoparticles create a densely packed coating on the roof tile surface in which air is trapped. This roughness produces a Cassie-Baxter regime, promoting superhydrophobicity. A surfactant, n-octylamine, was also added to the starting sol to catalyze the sol-gel process and to coarsen the pore structure of the gel network, preventing cracking. The application of ultrasound obviates the need to use volatile organic compounds in the synthesis, thereby making a 'green' product. It was also demonstrated that a co-condensation process effective between the organic and inorganic species is crucial to obtain durable and effective coatings. After an aging test, high hydrophobicity was maintained and water absorption was completely prevented for the roof tile samples under study. However, a transition from a Cassie-Baxter to a Wenzel state regime was observed as a consequence of the increase in the distance between the roughness pitches produced by the aging of the coating.

  19. Establishment and performance of an experimental green roof under extreme climatic conditions

    Energy Technology Data Exchange (ETDEWEB)

    Klein, Petra M., E-mail: pkklein@ou.edu [School of Meteorology, University of Oklahoma, Norman, OK (United States); Coffman, Reid, E-mail: rcoffma4@kent.edu [College of Architecture and Environmental Design, Kent State University, Kent, OH (United States)

    2015-04-15

    Green roofs alter the surface energy balance and can help in mitigating urban heat islands. However, the cooling of green roofs due to evapotranspiration strongly depends on the climatic conditions, and vegetation type and density. In the Southern Central Plains of the United States, extreme weather events, such as high winds, heat waves and drought conditions pose challenges for successful implementation of green roofs, and likely alter their standard performance. The National Weather Center Experimental Green Roof, an interdisciplinary research site established in 2010 in Norman, OK, aimed to investigate the ecological performance and surface energy balance of green roof systems. Starting in May 2010, 26 months of vegetation studies were conducted and the radiation balance, air temperature, relative humidity, and buoyancy fluxes were monitored at two meteorological stations during April–October 2011. The establishment of a vegetative community trended towards prairie plant dominance. High mortality of succulents and low germination of grasses and herbaceous plants contributed to low vegetative coverage. In this condition succulent diversity declined. Bouteloua gracilis and Delosperma cooperi showed typological dominance in harsh climatic conditions, while Sedum species experienced high mortality. The plant community diversified through volunteers such as Euphorbia maculate and Portulaca maculate. Net radiation measured at a green-roof meteorological station was higher than at a control station over the original, light-colored roofing material. These findings indicate that the albedo of the green roof was lower than the albedo of the original roofing material. The low vegetative coverage during the heat and drought conditions in 2011, which resulted in the dark substrate used in the green roof containers being exposed, likely contributed to the low albedo values. Nevertheless, air temperatures and buoyancy fluxes were often lower over the green roof indicating

  20. Establishment and performance of an experimental green roof under extreme climatic conditions

    International Nuclear Information System (INIS)

    Klein, Petra M.; Coffman, Reid

    2015-01-01

    Green roofs alter the surface energy balance and can help in mitigating urban heat islands. However, the cooling of green roofs due to evapotranspiration strongly depends on the climatic conditions, and vegetation type and density. In the Southern Central Plains of the United States, extreme weather events, such as high winds, heat waves and drought conditions pose challenges for successful implementation of green roofs, and likely alter their standard performance. The National Weather Center Experimental Green Roof, an interdisciplinary research site established in 2010 in Norman, OK, aimed to investigate the ecological performance and surface energy balance of green roof systems. Starting in May 2010, 26 months of vegetation studies were conducted and the radiation balance, air temperature, relative humidity, and buoyancy fluxes were monitored at two meteorological stations during April–October 2011. The establishment of a vegetative community trended towards prairie plant dominance. High mortality of succulents and low germination of grasses and herbaceous plants contributed to low vegetative coverage. In this condition succulent diversity declined. Bouteloua gracilis and Delosperma cooperi showed typological dominance in harsh climatic conditions, while Sedum species experienced high mortality. The plant community diversified through volunteers such as Euphorbia maculate and Portulaca maculate. Net radiation measured at a green-roof meteorological station was higher than at a control station over the original, light-colored roofing material. These findings indicate that the albedo of the green roof was lower than the albedo of the original roofing material. The low vegetative coverage during the heat and drought conditions in 2011, which resulted in the dark substrate used in the green roof containers being exposed, likely contributed to the low albedo values. Nevertheless, air temperatures and buoyancy fluxes were often lower over the green roof indicating

  1. Diverse and tunable electronic structures of single-layer metal phosphorus trichalcogenides for photocatalytic water splitting

    International Nuclear Information System (INIS)

    Liu, Jian; Li, Xi-Bo; Wang, Da; Liu, Li-Min; Lau, Woon-Ming; Peng, Ping

    2014-01-01

    The family of bulk metal phosphorus trichalcogenides (APX 3 , A = M II , M 0.5 I M 0.5 III ; X = S, Se; M I , M II , and M III represent Group-I, Group-II, and Group-III metals, respectively) has attracted great attentions because such materials not only own magnetic and ferroelectric properties, but also exhibit excellent properties in hydrogen storage and lithium battery because of the layered structures. Many layered materials have been exfoliated into two-dimensional (2D) materials, and they show distinct electronic properties compared with their bulks. Here we present a systematical study of single-layer metal phosphorus trichalcogenides by density functional theory calculations. The results show that the single layer metal phosphorus trichalcogenides have very low formation energies, which indicates that the exfoliation of single layer APX 3 should not be difficult. The family of single layer metal phosphorus trichalcogenides exhibits a large range of band gaps from 1.77 to 3.94 eV, and the electronic structures are greatly affected by the metal or the chalcogenide atoms. The calculated band edges of metal phosphorus trichalcogenides further reveal that single-layer ZnPSe 3 , CdPSe 3 , Ag 0.5 Sc 0.5 PSe 3 , and Ag 0.5 In 0.5 PX 3 (X = S and Se) have both suitable band gaps for visible-light driving and sufficient over-potentials for water splitting. More fascinatingly, single-layer Ag 0.5 Sc 0.5 PSe 3 is a direct band gap semiconductor, and the calculated optical absorption further convinces that such materials own outstanding properties for light absorption. Such results demonstrate that the single layer metal phosphorus trichalcogenides own high stability, versatile electronic properties, and high optical absorption, thus such materials have great chances to be high efficient photocatalysts for water-splitting

  2. Modelling reduction of urban heat load in Vienna by modifying surface properties of roofs

    Science.gov (United States)

    Žuvela-Aloise, Maja; Andre, Konrad; Schwaiger, Hannes; Bird, David Neil; Gallaun, Heinz

    2018-02-01

    The study examines the potential of urban roofs to reduce the urban heat island (UHI) effect by changing their reflectivity and implementing vegetation (green roofs) using the example of the City of Vienna. The urban modelling simulations are performed based on high-resolution orography and land use data, climatological observations, surface albedo values from satellite imagery and registry of the green roof potential in Vienna. The modelling results show that a moderate increase in reflectivity of roofs (up to 0.45) reduces the mean summer temperatures in the densely built-up environment by approximately 0.25 °C. Applying high reflectivity materials (roof albedo up to 0.7) leads to average cooling in densely built-up area of approximately 0.5 °C. The green roofs yield a heat load reduction in similar order of magnitude as the high reflectivity materials. However, only 45 % of roof area in Vienna is suitable for greening and the green roof potential mostly applies to industrial areas in city outskirts and is therefore not sufficient for substantial reduction of the UHI effect, particularly in the city centre which has the highest heat load. The strongest cooling effect can be achieved by combining the green roofs with high reflectivity materials. In this case, using 50 or 100 % of the green roof potential and applying high reflectivity materials on the remaining surfaces have a similar cooling effect.

  3. Toronto green roof construction standard

    International Nuclear Information System (INIS)

    Aster, D.

    2007-01-01

    Toronto City Council adopted a green roof strategy in February 2006. This paper reviewed the by-law governing the strategy as well as the work in progress to develop minimum standards for the design and construction of green roofs in Toronto. The strategy included a series of recommendations regarding the installation of green roofs on city buildings; a pilot grant program; using the development process to encourage green roofs; and, public education and promotion. It was noted that compared to Europe, the development of standards for green roofs in North America is in its early stages. As an emerging sustainable technology, there currently are no standards incorporated into Ontario's Building Code against which Toronto can measure the design and construction of green roofs. Therefore this paper included an analysis detailing how the recommended design requirements were able to support the City's green roof policy objectives and integrate the performance criteria for green roofs previously established and supported by Toronto City Council. The key policy objectives of the City's green roof strategy were to reduce the urban heat island effect; to address stormwater management implications in terms of quality and quantity; to improve the energy budgets of individual buildings; and, to improve air quality

  4. Modelling of green roofs' hydrologic performance using EPA's SWMM.

    Science.gov (United States)

    Burszta-Adamiak, E; Mrowiec, M

    2013-01-01

    Green roofs significantly affect the increase in water retention and thus the management of rain water in urban areas. In Poland, as in many other European countries, excess rainwater resulting from snowmelt and heavy rainfall contributes to the development of local flooding in urban areas. Opportunities to reduce surface runoff and reduce flood risks are among the reasons why green roofs are more likely to be used also in this country. However, there are relatively few data on their in situ performance. In this study the storm water performance was simulated for the green roofs experimental plots using the Storm Water Management Model (SWMM) with Low Impact Development (LID) Controls module (version 5.0.022). The model consists of many parameters for a particular layer of green roofs but simulation results were unsatisfactory considering the hydrologic response of the green roofs. For the majority of the tested rain events, the Nash coefficient had negative values. It indicates a weak fit between observed and measured flow-rates. Therefore complexity of the LID module does not affect the increase of its accuracy. Further research at a technical scale is needed to determine the role of the green roof slope, vegetation cover and drying process during the inter-event periods.

  5. 30 CFR 75.205 - Installation of roof support using mining machines with integral roof bolters.

    Science.gov (United States)

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Installation of roof support using mining... Roof Support § 75.205 Installation of roof support using mining machines with integral roof bolters. When roof bolts are installed by a continuous mining machine with intregal roof bolting equipment: (a...

  6. Morphology and atomic-scale structure of single-layer WS2 nanoclusters.

    Science.gov (United States)

    Füchtbauer, Henrik G; Tuxen, Anders K; Moses, Poul G; Topsøe, Henrik; Besenbacher, Flemming; Lauritsen, Jeppe V

    2013-10-14

    Two-dimensional sheets of transition metal (Mo and W) sulfides are attracting strong attention due to the unique electronic and optical properties associated with the material in its single-layer form. The single-layer MoS2 and WS2 are already in widespread commercial use in catalytic applications as both hydrotreating and hydrocracking catalysts. Consequently, characterization of the morphology and atomic structure of such particles is of utmost importance for the understanding of the catalytic active phase. However, in comparison with the related MoS2 system only little is known about the fundamental properties of single-layer WS2 (tungstenite). Here, we use an interplay of atom-resolved Scanning Tunneling Microscopy (STM) studies of Au(111)-supported WS2 nanoparticles and calculated edge structures using Density Functional Theory (DFT) to reveal the equilibrium morphology and prevalent edge structures of single-layer WS2. The STM results reveal that the single layer S-W-S sheets adopt a triangular equilibrium shape under the sulfiding conditions of the synthesis, with fully sulfided edges. The predominant edge structures are determined to be the (101[combining macron]0) W-edge, but for the smallest nanoclusters also the (1[combining macron]010) S-edges become important. DFT calculations are used to construct phase diagrams of the WS2 edges, and describe their sulfur and hydrogen coordination under different conditions, and in this way shed light on the catalytic role of WS2 edges.

  7. Two-dimensional modeling of water and heat fluxes in green roof substrates

    Science.gov (United States)

    Suarez, F. I.; Sandoval, V. P.

    2016-12-01

    Due to public concern towards sustainable development, greenhouse gas emissions and energy efficiency, green roofs have become popular in the last years. Green roofs integrate vegetation into infrastructures to reach additional benefits that minimize negative impacts of the urbanization. A properly designed green roof can reduce environmental pollution, noise levels, energetic requirements or surface runoff. The correct performance of green roofs depends on site-specific conditions and on each component of the roof. The substrate and the vegetation layers strongly influence water and heat fluxes on a green roof. The substrate is an artificial media that has an improved performance compared to natural soils as it provides critical resources for vegetation survival: water, nutrients, and a growing media. Hence, it is important to study the effects of substrate properties on green roof performance. The objective of this work is to investigate how the thermal and hydraulic properties affect the behavior of a green roof through numerical modeling. The substrates that were investigated are composed by: crushed bricks and organic soil (S1); peat with perlite (S2); crushed bricks (S3); mineral soil with tree leaves (S4); and a mixture of topsoil and mineral soil (S5). The numerical model utilizes summer-arid meteorological information to evaluate the performance of each substrate. Results show that the area below the water retention curve helps to define the substrate that retains more water. In addition, the non-linearity of the water retention curve can increment the water needed to irrigate the roof. The heat propagation through the roof depends strongly on the hydraulic behavior, meaning that a combination of a substrate with low thermal conductivity and more porosity can reduce the heat fluxes across the roof. Therefore, it can minimize the energy consumed of an air-conditioner system.

  8. Application of green blue roof to mitigate heat island phenomena and resilient to climate change in urban areas: A case study from Seoul, Korea

    OpenAIRE

    Shafique Muhammad; Kim Reeho

    2017-01-01

    Green blue roof has the potential to reduce the surface temperature of the building in the urban areas. Green blue roof is a new innovative low impact development (LID) practice that has exhibited an option to mitigate the heat island phenomena in urban area. This is the modified form of green roof that has ability to store rainwater in vegetation, soil layer and increases the evapotranspiration rate which decreases the temperature of an area. For this purpose, green blue roof is installed at...

  9. Developing resilient green roofs in a dry climate.

    Science.gov (United States)

    Razzaghmanesh, M; Beecham, S; Brien, C J

    2014-08-15

    Living roofs are an emerging green infrastructure technology that can potentially be used to ameliorate both climate change and urban heat island effects. There is not much information regarding the design of green roofs for dry climates and so the aim of this study was to develop low maintenance and unfertilized green roofs for a dry climate. This paper describes the effects of four important elements of green roofs namely slope, depth, growing media and plant species and their possible interactions in terms of plant growth responses in a dry climate. Sixteen medium-scale green roofs were set up and monitored during a one year period. This experiment consisted of twelve vegetated platforms and four non-vegetated platforms as controls. The design for the experiment was a split-split-plot design in which the factors Slope (1° and 25°) and Depth (100mm, 300 mm) were randomized to the platforms (main plots). Root depth and volume, average height of plants, final dry biomass and ground cover, relative growth rate, final dry shoot-root ratio, water use efficiency and leaf succulence were studied during a twelve month period. The results showed little growth of the plants in media type A, whilst the growth was significant in both media types B and C. On average, a 90% survival rate of plants was observed. Also the growth indices indicated that some plants can grow efficiently in the harsh environment created by green roofs in a dry climate. The root growth pattern showed that retained water in the drainage layer is an alternative source of water for plants. It was also shown that stormwater can be used as a source of irrigation water for green roofs during six months of the year at the study site. In summary, mild sloping intensive systems containing media type C and planted with either Chrysocephalum apiculatum or Disphyma crassifolium showed the best performance. Copyright © 2014 Elsevier B.V. All rights reserved.

  10. Leaf Roof - Designing Luminescent Solar Concentrating PV Roof Tiles

    NARCIS (Netherlands)

    Reinders, Angelina H.M.E.; Doudart de la Gree, G.; Papadopoulos, A..; Rosemann, A.; Debije, M.G.; Cox, M.; Krumer, Zachar

    2016-01-01

    The Leaf Roof project on the design features of PV roof tiles using Luminescent Solar Concentrator (LSC) technology [1] has resulted in a functional prototype. The results are presented in the context of industrial product design with a focus on the aesthetic aspects of LSCs [2]. This paper outlines

  11. Nontraumatic orbital roof encephalocele.

    Science.gov (United States)

    Hoang, Amber; Maugans, Todd; Ngo, Thang; Ikeda, Jamie

    2017-02-01

    Intraorbital meningoencephaloceles occur most commonly as a complication of traumatic orbital roof fractures. Nontraumatic congenital orbital meningoncephaloceles are very rare, with most secondary to destructive processes affecting the orbit and primary skull defects. Treatment for intraorbital meningoencephaloceles is surgical repair, involving the excision of herniated brain parenchyma and meninges and reconstruction of the osseous defect. Most congenital lesions present in infancy with obvious globe and orbital deformities; we report an orbital meningoencephalocele in a 3-year-old girl who presented with ptosis. Copyright © 2017 American Association for Pediatric Ophthalmology and Strabismus. Published by Elsevier Inc. All rights reserved.

  12. Selective exfoliation of single-layer graphene from non-uniform graphene grown on Cu

    International Nuclear Information System (INIS)

    Lim, Jae-Young; Lee, Jae-Hyun; Jang, Hyeon-Sik; Whang, Dongmok; Joo, Won-Jae; Hwang, SungWoo

    2015-01-01

    Graphene growth on a copper surface via metal-catalyzed chemical vapor deposition has several advantages in terms of providing high-quality graphene with the potential for scale-up, but the product is usually inhomogeneous due to the inability to control the graphene layer growth. The non-uniform regions strongly affect the reliability of the graphene in practical electronic applications. Herein, we report a novel graphene transfer method that allows for the selective exfoliation of single-layer graphene from non-uniform graphene grown on a Cu foil. Differences in the interlayer bonding energy are exploited to mechanically separate only the top single-layer graphene and transfer this to an arbitrary substrate. The dry-transferred single-layer graphene showed electrical characteristics that were more uniform than those of graphene transferred using conventional wet-etching transfer steps. (paper)

  13. Fabrication of a single layer graphene by copper intercalation on a SiC(0001) surface

    International Nuclear Information System (INIS)

    Yagyu, Kazuma; Tochihara, Hiroshi; Tomokage, Hajime; Suzuki, Takayuki; Tajiri, Takayuki; Kohno, Atsushi; Takahashi, Kazutoshi

    2014-01-01

    Cu atoms deposited on a zero layer graphene grown on a SiC(0001) substrate, intercalate between the zero layer graphene and the SiC substrate after the thermal annealing above 600 °C, forming a Cu-intercalated single layer graphene. On the Cu-intercalated single layer graphene, a graphene lattice with superstructure due to moiré pattern is observed by scanning tunneling microscopy, and specific linear dispersion at the K ¯ point as well as a characteristic peak in a C 1s core level spectrum, which is originated from a free-standing graphene, is confirmed by photoemission spectroscopy. The Cu-intercalated single layer graphene is found to be n-doped

  14. Single layer of Ge quantum dots in HfO2for floating gate memory capacitors.

    Science.gov (United States)

    Lepadatu, A M; Palade, C; Slav, A; Maraloiu, A V; Lazanu, S; Stoica, T; Logofatu, C; Teodorescu, V S; Ciurea, M L

    2017-04-28

    High performance trilayer memory capacitors with a floating gate of a single layer of Ge quantum dots (QDs) in HfO 2 were fabricated using magnetron sputtering followed by rapid thermal annealing (RTA). The layer sequence of the capacitors is gate HfO 2 /floating gate of single layer of Ge QDs in HfO 2 /tunnel HfO 2 /p-Si wafers. Both Ge and HfO 2 are nanostructured by RTA at moderate temperatures of 600-700 °C. By nanostructuring at 600 °C, the formation of a single layer of well separated Ge QDs with diameters of 2-3 nm at a density of 4-5 × 10 15 m -2 is achieved in the floating gate (intermediate layer). The Ge QDs inside the intermediate layer are arranged in a single layer and are separated from each other by HfO 2 nanocrystals (NCs) about 8 nm in diameter with a tetragonal/orthorhombic structure. The Ge QDs in the single layer are located at the crossing of the HfO 2 NCs boundaries. In the intermediate layer, besides Ge QDs, a part of the Ge atoms is segregated by RTA at the HfO 2 NCs boundaries, while another part of the Ge atoms is present inside the HfO 2 lattice stabilizing the tetragonal/orthorhombic structure. The fabricated capacitors show a memory window of 3.8 ± 0.5 V and a capacitance-time characteristic with 14% capacitance decay in the first 3000-4000 s followed by a very slow capacitance decrease extrapolated to 50% after 10 years. This high performance is mainly due to the floating gate of a single layer of well separated Ge QDs in HfO 2 , distanced from the Si substrate by the tunnel oxide layer with a precise thickness.

  15. Thermal vibration of a rectangular single-layered graphene sheet with quantum effects

    International Nuclear Information System (INIS)

    Wang, Lifeng; Hu, Haiyan

    2014-01-01

    The thermal vibration of a rectangular single-layered graphene sheet is investigated by using a rectangular nonlocal elastic plate model with quantum effects taken into account when the law of energy equipartition is unreliable. The relation between the temperature and the Root of Mean Squared (RMS) amplitude of vibration at any point of the rectangular single-layered graphene sheet in simply supported case is derived first from the rectangular nonlocal elastic plate model with the strain gradient of the second order taken into consideration so as to characterize the effect of microstructure of the graphene sheet. Then, the RMS amplitude of thermal vibration of a rectangular single-layered graphene sheet simply supported on an elastic foundation is derived. The study shows that the RMS amplitude of the rectangular single-layered graphene sheet predicted from the quantum theory is lower than that predicted from the law of energy equipartition. The maximal relative difference of RMS amplitude of thermal vibration appears at the sheet corners. The microstructure of the graphene sheet has a little effect on the thermal vibrations of lower modes, but exhibits an obvious effect on the thermal vibrations of higher modes. The quantum effect is more important for the thermal vibration of higher modes in the case of smaller sides and lower temperature. The relative difference of maximal RMS amplitude of thermal vibration of a rectangular single-layered graphene sheet decreases monotonically with an increase of temperature. The absolute difference of maximal RMS amplitude of thermal vibration of a rectangular single-layered graphene sheet increases slowly with the rising of Winkler foundation modulus.

  16. Chemical etching of copper foils for single-layer graphene growth by chemical vapor deposition

    Science.gov (United States)

    Yoshihara, Naoki; Noda, Masaru

    2017-10-01

    Chemical etching on copper surface is essential as a pre-treatment for single-layer graphene growth by chemical vapor deposition (CVD). Here, we investigated the effect of chemical etching treatment on copper foils for single-layer graphene CVD growth. The chemical etching conditions, such as the type of chemical etchants and the treatment time, were found to strongly influence the graphene domain size. Moreover, a drastic change in the layer structure of graphene sheets, which was attributed to the surface morphology of the etched copper foil, was confirmed by graphene transmittance and Raman mapping measurements.

  17. Habitat connectivity shapes urban arthropod communities: the key role of green roofs.

    Science.gov (United States)

    Braaker, S; Ghazoul, J; Obrist, M K; Moretti, M

    2014-04-01

    The installation of green roofs, defined here as rooftops with a shallow soil cover and extensive vegetation, has been proposed as a possible measure to mitigate the loss of green space caused by the steady growth of cities. However, the effectiveness of green roofs in supporting arthropod communities, and the extent to which they facilitate connectivity of these communities within the urban environment is currently largely unknown. We investigated the variation of species community composition (beta diversity) of four arthropod groups with contrasting mobility (Carabidae, Araneae, Curculionidae, and Apidae) on 40 green roofs and 40 extensively managed green sites on the ground in the city of Zurich, Switzerland. With redundancy analysis and variation partitioning, we (1) disentangled the relative importance of local environmental conditions, the surrounding land cover composition, and habitat connectivity on species community composition, (2) searched for specific spatial scales of habitat connectivity for the different arthropod groups, and (3) discussed the ecological and functional value of green roofs in cities. Our study revealed that on green roofs community composition of high-mobility arthropod groups (bees and weevils) were mainly shaped by habitat connectivity, while low-mobility arthropod groups (carabids and spiders) were more influenced by local environmental conditions. A similar but less pronounced pattern was found for ground communities. The high importance of habitat connectivity in shaping high-mobility species community composition indicates that these green roof communities are substantially connected by the frequent exchange of individuals among surrounding green roofs. On the other hand, low-mobility species communities on green roofs are more likely connected to ground sites than to other green roofs. The integration of green roofs in urban spatial planning strategies has great potential to enable higher connectivity among green spaces, so

  18. Water quality and quantity investigation of green roofs in a dry climate.

    Science.gov (United States)

    Beecham, S; Razzaghmanesh, M

    2015-03-01

    Low-energy pollutant removal strategies are now being sought for water sensitive urban design. This paper describes investigations into the water quality and quantity of sixteen, low-maintenance and unfertilized intensive and extensive green roof beds. The factors of Slope (1° and 25°), Depth (100 mm and 300 mm), Growing media (type A, type B and type C) and Species (P1, P2 and P3) were randomized according to a split-split plot design. This consisted of twelve vegetated green roof beds and four non-vegetated beds as controls. Stormwater runoff was collected from drainage points that were installed in each area. Samples of run-off were collected for five rainfall events and analysed for water retention capacity and the water quality parameters of NO₂, NO₃, NH₄, PO₄, pH, EC, TDS, Turbidity, Na, Ca, Mg and K. The results indicated significant differences in terms of stormwater water quality and quantity between the outflows of vegetated and non-vegetated systems. The water retention was between 51% and 96% and this range was attributed to the green roof configurations in the experiment. Comparing the quality of rainfall as inflow, and the quality of runoff from the systems showed that green roofs generally acted as a source of pollutants in this study. In the vegetated beds, the intensive green roofs performed better than the extensive beds with regard to outflow quality while in the non-vegetated beds, the extensive beds performed better than intensive systems. This highlights the importance of vegetation in improving water retention capacity as well as the role of vegetation in enhancing pollutant removal in green roof systems. In addition growing media with less organic matter had better water quality performance. Comparison of these results with national and international standards for water reuse confirmed that the green roof outflow was suitable for non-potable uses such as landscape irrigation and toilet flushing. Copyright © 2014 Elsevier Ltd. All

  19. Spatial environmental heterogeneity affects plant growth and thermal performance on a green roof.

    Science.gov (United States)

    Buckland-Nicks, Michael; Heim, Amy; Lundholm, Jeremy

    2016-05-15

    Green roofs provide ecosystem services, including stormwater retention and reductions in heat transfer through the roof. Microclimates, as well as designed features of green roofs, such as substrate and vegetation, affect the magnitude of these services. Many green roofs are partially shaded by surrounding buildings, but the effects of this within-roof spatial environmental heterogeneity on thermal performance and other ecosystem services have not been examined. We quantified the effects of spatial heterogeneity in solar radiation, substrate depth and other variables affected by these drivers on vegetation and ecosystem services in an extensive green roof. Spatial heterogeneity in substrate depth and insolation were correlated with differential growth, survival and flowering in two focal plant species. These effects were likely driven by the resulting spatial heterogeneity in substrate temperature and moisture content. Thermal performance (indicated by heat flux and substrate temperature) was influenced by spatial heterogeneity in vegetation cover and substrate depth. Areas with less insolation were cooler in summer and had greater substrate moisture, leading to more favorable conditions for plant growth and survival. Spatial variation in substrate moisture (7%-26% volumetric moisture content) and temperature (21°C-36°C) during hot sunny conditions in summer could cause large differences in stormwater retention and heat flux within a single green roof. Shaded areas promote smaller heat fluxes through the roof, leading to energy savings, but lower evapotranspiration in these areas should reduce stormwater retention capacity. Spatial heterogeneity can thus result in trade-offs between different ecosystem services. The effects of these spatial heterogeneities are likely widespread in green roofs. Structures that provide shelter from sun and wind may be productively utilized to design higher functioning green roofs and increase biodiversity by providing habitat

  20. Modeling of 1-D nitrate transport in single layer soils | Dike | Journal ...

    African Journals Online (AJOL)

    The transport of nitrate in laboratory single soil columns of sand, laterite and clay were investigated after 21 days. The 1-D contaminant transport model by Notodarmojo et al (1991) for single layer soils were calibrated and verified using field data collected from a refuse dump site at avu, owerri, Imo state. The experimental ...

  1. Single-layer skull approximations perform well in transcranial direct current stimulation modeling

    NARCIS (Netherlands)

    Rampersad, S.M.; Stegeman, D.F.; Oostendorp, T.F.

    2013-01-01

    In modeling the effect of transcranial direct current stimulation, the representation of the skull is an important factor. In a spherical model, we compared a realistic skull modeling approach, in which the skull consisted of three isotropic layers, to anisotropic and isotropic single-layer

  2. Single Layered Versus Double Layered Intestinal Anastomosis: A Randomized Controlled Trial

    Science.gov (United States)

    Mohapatra, Vandana; Singh, Surendra; Rath, Pratap Kumar; Behera, Tapas Ranjan

    2017-01-01

    Introduction Gastrointestinal anastomosis is one of the most common procedures being performed in oesophagogastric, hepatobiliary, bariatric, small bowel and colorectal surgery; however, the safety and efficacy of single layer or double layer anastomotic technique is still unclear. Aim To assess and compare the efficacy, safety and cost effectiveness of single layered versus double layered intestinal anastomosis. Materials and Methods This prospective, double-blind, randomized controlled comparative study comprised of patients who underwent intestinal resection and anastomosis. They were randomly assigned to undergo either single layered extra-mucosal anastomosis (Group-A) or double layered intestinal anastomosis (Group-B). Primary outcome measures included average time taken for anastomosis, postoperative complications, mean duration of hospital stay and cost of suture material used; secondary outcome measures assessed the postoperative return of bowel function. Statistical analysis was done by Chi-square test and student t-test. Results A total of 97 participants were randomized. Fifty patients were allocated to single layered extramucosal continuous anastomosis (Group-A) and 47 patients to double layered anastomosis (Group-B). The patients in each group were well matched for age, sex and diagnosis. The mean time taken for anastomosis (15.12±2.27 minutes in Group-A versus 24.38±2.26 minutes in Group-B) and the length of hospital stay (5.90±1.43 days in Group-A versus 7.29±1.89 days in Group-B) was significantly shorter in Group-A {p-value anastomosis. However, there was no significant difference in the complication rates between the two groups. Conclusion It can be concluded that single layered extramucosal continuous intestinal anastomosis is equally safe and perhaps more cost effective than the conventional double layered method and may represent the optimal choice for routine surgical practice. PMID:28764239

  3. Diffusion of Supercritical Fluids through Single-Layer Nanoporous Solids: Theory and Molecular Simulations.

    Science.gov (United States)

    Oulebsir, Fouad; Vermorel, Romain; Galliero, Guillaume

    2018-01-16

    With the advent of graphene material, membranes based on single-layer nanoporous solids appear as promising devices for fluid separation, be it liquid or gaseous mixtures. The design of such architectured porous materials would greatly benefit from accurate models that can predict their transport and separation properties. More specifically, there is no universal understanding of how parameters such as temperature, fluid loading conditions, or the ratio of the pore size to the fluid molecular diameter influence the permeation process. In this study, we address the problem of pure supercritical fluids diffusing through simplified models of single-layer porous materials. Basically, we investigate a toy model that consists of a single-layer lattice of Lennard-Jones interaction sites with a slit gap of controllable width. We performed extensive equilibrium and biased molecular dynamics simulations to document the physical mechanisms involved at the molecular scale. We propose a general constitutive equation for the diffusional transport coefficient derived from classical statistical mechanics and kinetic theory, which can be further simplified in the ideal gas limit. This transport coefficient relates the molecular flux to the fluid density jump across the single-layer membrane. It is found to be proportional to the accessible surface porosity of the single-layer porous solid and to a thermodynamic factor accounting for the inhomogeneity of the fluid close to the pore entrance. Both quantities directly depend on the potential of mean force that results from molecular interactions between solid and fluid atoms. Comparisons with the simulations data show that the kinetic model captures how narrowing the pore size below the fluid molecular diameter lowers dramatically the value of the transport coefficient. Furthermore, we demonstrate that our general constitutive equation allows for a consistent interpretation of the intricate effects of temperature and fluid loading

  4. 30 CFR 75.204 - Roof bolting.

    Science.gov (United States)

    2010-07-01

    ... anchor trailing cables or used for any other purpose that could affect the tension of the bolt. Hanging... tension ranges for roof bolts as specified in the roof control plan shall maintain the integrity of the.... (4) In each roof bolting cycle, the actual torque or tension of the first tensioned roof bolt...

  5. The properties degradation of exposed GFRP roof

    Science.gov (United States)

    Zainudin, Mohammad; Diharjo, Kuncoro; Kaavessina, Mujtahid; Setyanto, Djoko

    2018-02-01

    There is much consideration of roof selection as a protector of a building against the outside weather, such as lightweight, strong stiff, corrosion resistant and guarantee for the availability of products. Based on these considerations, glass fiber reinforced polymer (GFRP) roof is a roof which can fulfill the requirement. The objective of this research is to investigate the degradation of physical and mechanical properties of GFRP roof exposed in outside weather. This GFRP roof composite was produced using a sheet molding compound (SMC) supplied by PT Intec Persada, Tangerang, Indonesia. There are two kinds GFRP roofs evaluated in this research that are GFRP roof exposed within 7 years and new GFRP roof that has not been exposed. The GFRP roofs were cut manually for preparing the specimens for hardness test, tensile test, SEM and FTIR test. The results show that the GFRP roof exposed within 7 years had the degradation of properties compared to the new GFRP roof. The exposed GFRP roof had lower strength and hardness compared to the new GFRP roof. The SEM observation indicates that exposed GFRP roof had the debonding of fiber on the surface, and in contrast, there are no debonding of fiber in the new GFRP roof surface. It can be recommended that the exposed GFRP roof may be repaired to enhance its performance and can re-increase its properties using the coating.

  6. Green Roofs for Stormwater Runoff Control

    Science.gov (United States)

    This project evaluated green roofs as a stormwater management tool. Specifically, runoff quantity and quality from green and flat asphalt roofs were compared. Evapotranspiration from planted green roofs and evaporation from unplanted media roofs were also compared. The influence...

  7. The green roof dilemma - discussion of Francis and Lorimer (2011).

    Science.gov (United States)

    Henry, Alexandre; Frascaria-Lacoste, Nathalie

    2012-08-15

    Urban ecosystems are the most complex mosaics of vegetative land cover that can be found. In a recent paper, Francis and Lorimer (2011) evaluated the reconciliation potential of living roofs and walls. For these authors, these two techniques for habitat improvement have strong potential for urban reconciliation ecology. However they have some ecological and societal limitations such as the physical extreme environmental characteristics, the monetary investment and the cultural perceptions of urban nature. We are interested in their results and support their conclusions. However, for a considerable time, green roofs have been designed to provide urban greenery for buildings and the green roof market has only focused on extensive roof at a restricted scale within cities. Thus, we have strong doubts about the relevance of their use as possible integrated elements of the network. Furthermore, without dynamic progress in research and the implementation of well-thought-out policies, what will be the real capital gain from green roofs with respect to land-use complementation in cities? If we agree with Francis and Lorimer (2011) considering that urban reconciliation ecology between nature and citizens is a current major challenge, then "adaptive collaborative management" is a fundamental requirement. Copyright © 2012 Elsevier Ltd. All rights reserved.

  8. ENERGY STAR Certified Roof Products

    Data.gov (United States)

    U.S. Environmental Protection Agency — Certified models meet all ENERGY STAR requirements as listed in the Version 3.0 ENERGY STAR Program Requirements for Roof Products that are effective as of July 1,...

  9. High Throughput Characterization of Epitaxially Grown Single-Layer MoS2

    Directory of Open Access Journals (Sweden)

    Foad Ghasemi

    2017-03-01

    Full Text Available The growth of single-layer MoS2 with chemical vapor deposition is an established method that can produce large-area and high quality samples. In this article, we investigate the geometrical and optical properties of hundreds of individual single-layer MoS2 crystallites grown on a highly-polished sapphire substrate. Most of the crystallites are oriented along the terraces of the sapphire substrate and have an area comprised between 10 µm2 and 60 µm2. Differential reflectance measurements performed on these crystallites show that the area of the MoS2 crystallites has an influence on the position and broadening of the B exciton while the orientation does not influence the A and B excitons of MoS2. These measurements demonstrate that differential reflectance measurements have the potential to be used to characterize the homogeneity of large-area chemical vapor deposition (CVD-grown samples.

  10. Edge structures and properties of triangular antidots in single-layer MoS2

    KAUST Repository

    Gan, Li Yong

    2016-08-30

    Density functional theory and experiments are employed to shed light on the edge structures of antidots in O etched single-layer MoS2. The equilibrium morphology is found to be the zigzag Mo edge with each Mo atom bonded to two O atoms, in a wide range of O chemical potentials. Scanning electron microscopy shows that the orientation of the created triangular antidots is opposite to the triangular shape of the single-layer MoS2 samples, in agreement with the theoretical predictions. Furthermore, edges induced by O etching turn out to be p-doped, suggesting an effective strategy to realize p-type MoS2 devices. Published by AIP Publishing.

  11. Quantum Hall states of atomic Bose gases: Density profiles in single-layer and multilayer geometries

    International Nuclear Information System (INIS)

    Cooper, N. R.; Lankvelt, F. J. M. van; Reijnders, J. W.; Schoutens, K.

    2005-01-01

    We describe the density profiles of confined atomic Bose gases in the high-rotation limit, in single-layer and multilayer geometries. We show that, in a local-density approximation, the density in a single layer shows a landscape of quantized steps due to the formation of incompressible liquids, which are analogous to fractional quantum Hall liquids for a two-dimensional electron gas in a strong magnetic field. In a multilayered setup we find different phases, depending on the strength of the interlayer tunneling t. We discuss the situation where a vortex lattice in the three-dimensional condensate (at large tunneling) undergoes quantum melting at a critical tunneling t c 1 . For tunneling well below t c 1 one expects weakly coupled or isolated layers, each exhibiting a landscape of quantum Hall liquids. After expansion, this gives a radial density distribution with characteristic features (cusps) that provide experimental signatures of the quantum Hall liquids

  12. White-light-emitting diode based on a single-layer polymer

    Science.gov (United States)

    Wang, B. Z.; Zhang, X. P.; Liu, H. M.

    2013-05-01

    A broad-band light-emitting diode was achieved in a single-layer device based on pure poly(9,9'-dioctylfluorene-co-bis-N,N'-(4-butylphenyl)-bis-N,N'-phenyl-1,4-phenylenediamine) (PFB). Electromer emission was observed in the red with a center wavelength of about 620 nm in electroluminescence (EL) spectrum. This kind of emission exhibits strong dependence on the thickness of the PFB layer, so that the shape of the EL spectrum may be adjusted through changing the thickness of the active polymer layer to balance between the intrinsic PFB emission in the blue and the electromer emission in the red. Thus, white light emission may be achieved from such a single-layer single-material diode.

  13. Edge structures and properties of triangular antidots in single-layer MoS{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Gan, Li-Yong, E-mail: ganly@swjtu.edu.cn, E-mail: iamyccheng@njtech.edu.cn, E-mail: udo.schwingenschlogl@kaust.edu.sa [Key Laboratory of Advanced Technology of Materials (Ministry of Education), Superconductivity and New Energy R& D Center, Southwest Jiaotong University, Chengdu, Sichuan 610031 (China); Cheng, Yingchun, E-mail: ganly@swjtu.edu.cn, E-mail: iamyccheng@njtech.edu.cn, E-mail: udo.schwingenschlogl@kaust.edu.sa; Huang, Wei [Key Laboratory of Flexible Electronics (KLOFE) and Institute of Advanced Materials (IAM), Jiangsu National Synergetic Innovation Center for Advanced Materials - SICAM, Nanjing Tech University - NanjingTech, 30 South Puzhu Road, Nanjing 211816 (China); Schwingenschlögl, Udo, E-mail: ganly@swjtu.edu.cn, E-mail: iamyccheng@njtech.edu.cn, E-mail: udo.schwingenschlogl@kaust.edu.sa [Physical Science and Engineering Division (PSE), King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900 (Saudi Arabia); Yao, Yingbang [Advanced Nanofabrication and Imaging Core Lab, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900 (Saudi Arabia); School of Materials and Energy, Guangdong University of Technology, Guangdong 510006 (China); Zhao, Yong [Key Laboratory of Advanced Technology of Materials (Ministry of Education), Superconductivity and New Energy R& D Center, Southwest Jiaotong University, Chengdu, Sichuan 610031 (China); School of Physical Science and Technology, Southwest Jiaotong University, Chengdu, 610031 Sichuan (China); Zhang, Xi-xiang [Physical Science and Engineering Division (PSE), King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900 (Saudi Arabia); Advanced Nanofabrication and Imaging Core Lab, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900 (Saudi Arabia)

    2016-08-29

    Density functional theory and experiments are employed to shed light on the edge structures of antidots in O etched single-layer MoS{sub 2}. The equilibrium morphology is found to be the zigzag Mo edge with each Mo atom bonded to two O atoms, in a wide range of O chemical potentials. Scanning electron microscopy shows that the orientation of the created triangular antidots is opposite to the triangular shape of the single-layer MoS{sub 2} samples, in agreement with the theoretical predictions. Furthermore, edges induced by O etching turn out to be p-doped, suggesting an effective strategy to realize p-type MoS{sub 2} devices.

  14. Persistent Charge-Density-Wave Order in Single-Layer TaSe2.

    Science.gov (United States)

    Ryu, Hyejin; Chen, Yi; Kim, Heejung; Tsai, Hsin-Zon; Tang, Shujie; Jiang, Juan; Liou, Franklin; Kahn, Salman; Jia, Caihong; Omrani, Arash A; Shim, Ji Hoon; Hussain, Zahid; Shen, Zhi-Xun; Kim, Kyoo; Min, Byung Il; Hwang, Choongyu; Crommie, Michael F; Mo, Sung-Kwan

    2018-02-14

    We present the electronic characterization of single-layer 1H-TaSe 2 grown by molecular beam epitaxy using a combined angle-resolved photoemission spectroscopy, scanning tunneling microscopy/spectroscopy, and density functional theory calculations. We demonstrate that 3 × 3 charge-density-wave (CDW) order persists despite distinct changes in the low energy electronic structure highlighted by the reduction in the number of bands crossing the Fermi energy and the corresponding modification of Fermi surface topology. Enhanced spin-orbit coupling and lattice distortion in the single-layer play a crucial role in the formation of CDW order. Our findings provide a deeper understanding of the nature of CDW order in the two-dimensional limit.

  15. Interactions between C and Cu atoms in single-layer graphene: direct observation and modelling.

    Science.gov (United States)

    Kano, Emi; Hashimoto, Ayako; Kaneko, Tomoaki; Tajima, Nobuo; Ohno, Takahisa; Takeguchi, Masaki

    2016-01-07

    Metal doping into the graphene lattice has been studied recently to develop novel nanoelectronic devices and to gain an understanding of the catalytic activities of metals in nanocarbon structures. Here we report the direct observation of interactions between Cu atoms and single-layer graphene by transmission electron microscopy. We document stable configurations of Cu atoms in the graphene sheet and unique transformations of graphene promoted by Cu atoms. First-principles calculations based on density functional theory reveal a reduction of energy barrier that caused rotation of C-C bonds near Cu atoms. We discuss two driving forces, electron irradiation and in situ heating, and conclude that the observed transformations were mainly promoted by electron irradiation. Our results suggest that individual Cu atoms can promote reconstruction of single-layer graphene.

  16. Identification of excitons, trions and biexcitons in single-layer WS{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Plechinger, Gerd; Nagler, Philipp; Kraus, Julia; Paradiso, Nicola; Strunk, Christoph; Schueller, Christian; Korn, Tobias [Institut fuer Experimentelle und Angewandte Physik, Universitaet Regensburg, 93040, Regensburg (Germany)

    2015-08-15

    Single-layer WS{sub 2} is a direct-gap semiconductor showing strong excitonic photoluminescence features in the visible spectral range. Here, we present temperature-dependent photoluminescence measurements on mechanically exfoliated single-layer WS{sub 2}, revealing the existence of neutral and charged excitons at low temperatures as well as at room temperature. By applying a gate voltage, we can electrically control the ratio of excitons and trions and assert a residual n-type doping of our samples. At high excitation densities and low temperatures, an additional peak at energies below the trion dominates the photoluminescence, which we identify as biexciton emission. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  17. Phonon-limited mobility in n-type single-layer MoS2 from first principles

    DEFF Research Database (Denmark)

    Kaasbjerg, Kristen; Thygesen, Kristian S.; Jacobsen, Karsten W.

    2012-01-01

    We study the phonon-limited mobility in intrinsic n-type single-layer MoS2 for temperatures T > 100 K. The materials properties including the electron-phonon interaction are calculated from first principles and the deformation potentials and Frohlich interaction in single-layer MoS2 are establish...

  18. Initial experience with application of single layer modified Kugel mesh for inguinal hernia repair: Case series of 72 consecutive patients

    Directory of Open Access Journals (Sweden)

    Pao-Hwa Chen

    2017-03-01

    Conclusion: The postoperative complication and recurrence rates of single-layer MK mesh herniorrhaphy was comparable with previously reported tension-free repair. Single-layer application is safe and feasible. A longer follow-up period and larger study group with a control group are needed to verify our method.

  19. Model for a collimated spin wave beam generated by a single layer, spin torque nanocontact

    OpenAIRE

    Hoefer, M. A.; Silva, T. J.; Stiles, M. D.

    2007-01-01

    A model of spin torque induced magnetization dynamics based upon semi-classical spin diffusion theory for a single layer nanocontact is presented. The model incorporates effects due to the current induced Oersted field and predicts the generation of a variety of spatially dependent, coherent, precessional magnetic wave structures. Directionally controllable collimated spin wave beams, vortex spiral waves, and localized standing waves are found to be excited by the interplay of the Oersted fie...

  20. Doping-controlled phase transitions in single-layer MoS2

    Science.gov (United States)

    Zhuang, Houlong L.; Johannes, Michelle D.; Singh, Arunima K.; Hennig, Richard G.

    2017-10-01

    The electronic properties of single-layer MoS2 make it an ideal two-dimensional (2D) material for application in electronic devices. Experiments show that MoS2 can undergo structural phase transitions. Applications of single-layer MoS2 will require firm laboratory control over the phase formation. Here we compare the stability and electronic structure of the three experimentally observed single-layer MoS2 phases, 2 H ,1 T , and 1 T' , and an in-plane metal/semiconductor heterostructure. We reveal by density-functional theory calculations that charge doping can induce the phase transition of single-layer MoS2 from the 2 H to the 1 T structure. Further, the 1 T structure undergoes a second phase transition due to the occurrence of a charge-density wave (CDW). By comparing the energies of several possible resulting CDW structures, we find that the 1 T' orthorhombic structure is the most stable one, consistent with experimental observations and previous theoretical studies. We show that the underlying CDW transition mechanism is not due to Fermi surface nesting, but nonetheless, can be controlled by charge doping. In addition, the stability landscape is highly sensitive to charge doping, which can be used as a practical phase selector. We also provide a prescription for obtaining the 1 T' structure via growth or deposition of MoS2 on a Hf substrate, which transfers electrons uniformly and with minimal structural distortion. Finally, we show that lateral heterostructures formed by the 2 H and 1 T' structures exhibit a low interfacial energy of 0.17 eV/Å, a small Schottky barrier of 0.3 eV for holes, and a large barrier of 1.6 eV for electrons.

  1. Growth of high-crystalline, single-layer hexagonal boron nitride on recyclable platinum foil.

    Science.gov (United States)

    Kim, Gwangwoo; Jang, A-Rang; Jeong, Hu Young; Lee, Zonghoon; Kang, Dae Joon; Shin, Hyeon Suk

    2013-04-10

    Hexagonal boron nitride (h-BN) is gaining significant attention as a two-dimensional dielectric material, along with graphene and other such materials. Herein, we demonstrate the growth of highly crystalline, single-layer h-BN on Pt foil through a low-pressure chemical vapor deposition method that allowed h-BN to be grown over a wide area (8 × 25 mm(2)). An electrochemical bubbling-based method was used to transfer the grown h-BN layer from the Pt foil onto an arbitrary substrate. This allowed the Pt foil, which was not consumed during the process, to be recycled repeatedly. The UV-visible absorption spectrum of the single-layer h-BN suggested an optical band gap of 6.06 eV, while a high-resolution transmission electron microscopy image of the same showed the presence of distinct hexagonal arrays of B and N atoms, which were indicative of the highly crystalline nature and single-atom thickness of the h-BN layer. This method of growing single-layer h-BN over large areas was also compatible with use of a sapphire substrate.

  2. Learning rate and attractor size of the single-layer perceptron

    International Nuclear Information System (INIS)

    Singleton, Martin S.; Huebler, Alfred W.

    2007-01-01

    We study the simplest possible order one single-layer perceptron with two inputs, using the delta rule with online learning, in order to derive closed form expressions for the mean convergence rates. We investigate the rate of convergence in weight space of the weight vectors corresponding to each of the 14 out of 16 linearly separable rules. These vectors follow zigzagging lines through the piecewise constant vector field to their respective attractors. Based on our studies, we conclude that a single-layer perceptron with N inputs will converge in an average number of steps given by an Nth order polynomial in (t/l), where t is the threshold, and l is the size of the initial weight distribution. Exact values for these averages are provided for the five linearly separable classes with N=2. We also demonstrate that the learning rate is determined by the attractor size, and that the attractors of a single-layer perceptron with N inputs partition R N +R N

  3. Laser-assisted fabrication of single-layer flexible touch sensor

    Science.gov (United States)

    Son, Seokwoo; Park, Jong Eun; Lee, Joohyung; Yang, Minyang; Kang, Bongchul

    2016-10-01

    Single-layer flexible touch sensor that is designed for the indium-tin-oxide (ITO)-free, bendable, durable, multi-sensible, and single layer transparent touch sensor was developed via a low-cost and one-step laser-induced fabrication technology. To this end, an entirely novel approach involving material, device structure, and even fabrication method was adopted. Conventional metal oxides based multilayer touch structure was substituted by the single layer structure composed of integrated silver wire networks of sensors and bezel interconnections. This structure is concurrently fabricated on a glass substitutive plastic film via the laser-induced fabrication method using the low-cost organometallic/nanoparticle hybrid complex. In addition, this study addresses practical solutions to heterochromia and interference problem with a color display unit. As a result, a practical touch sensor is successfully demonstrated through resolving the heterochromia and interference problems with color display unit. This study could provide the breakthrough for early realization of wearable device.

  4. Modeling Košice Green Roofs Maps

    Directory of Open Access Journals (Sweden)

    Poorova Zuzana

    2017-06-01

    Full Text Available The need to house population in urban areas is expected to rise to 66% in 2050, according to United Nations. The replacement of natural permeable green areas with concrete constructions and hard surfaces will be noticed. The densification of existing built-up areas is responsible for the decreasing vegetation, which results in the lack of evapotranspiration cooling the air. Such decreasing vegetation causes urban heat islands. Since roofs and pavements have a very low albedo, they absorb a lot of sunlight. Several studies have shown that natural and permeable surfaces, as in the case of green roofs, can play crucial role in mitigating this negative climate phenomenon and providing higher efficiency for the building, leading to savings. Such as water saving, what is the main idea of this research.

  5. Modeling Košice Green Roofs Maps

    Science.gov (United States)

    Poorova, Zuzana; Vranayova, Zuzana

    2017-06-01

    The need to house population in urban areas is expected to rise to 66% in 2050, according to United Nations. The replacement of natural permeable green areas with concrete constructions and hard surfaces will be noticed. The densification of existing built-up areas is responsible for the decreasing vegetation, which results in the lack of evapotranspiration cooling the air. Such decreasing vegetation causes urban heat islands. Since roofs and pavements have a very low albedo, they absorb a lot of sunlight. Several studies have shown that natural and permeable surfaces, as in the case of green roofs, can play crucial role in mitigating this negative climate phenomenon and providing higher efficiency for the building, leading to savings. Such as water saving, what is the main idea of this research.

  6. Dynamic Simulation of the Green Roofs Impact on Building Energy Performance, Case Study of Antananarivo, Madagascar

    Directory of Open Access Journals (Sweden)

    Hery Tiana Rakotondramiarana

    2015-05-01

    Full Text Available Green roofs improve building energy performance and constitute an alternative to sustainable buildings. A green roof model is dynamically coupled with a building thermal model to assess its energy performance that takes into account the indoor air temperature dynamic changes. Under the climate conditions in Antananarivo, we compared green and conventional roofs. The present study shows that green roofs protect the roof structure under extreme temperature and large temperature fluctuations. For the case of Antananarivo, the amplitude of the temperature fluctuations at the top face of the support is reduced by 28 °C when using green roof. The impact of the green roof on indoor air temperature and energy demand is investigated. The vegetation decreases the maximum indoor air temperature and improves the building thermal comfort during summer days. It has no effect on the minimum indoor air temperature, but additional soil thickness can increase it. In addition, a global sensitivity analysis, which is carried out on the proposed model without considering any specific weather data, allows us to identify the most influential parameters on the energy demand. It has been found that green roofs have almost insignificant thermal impact in insulated buildings; however, their potential prevails over the building envelope and weather characteristics in the case of non-insulated building.

  7. Ecological and Energy Efficiency Impacts of Urban Roofs and Pavements

    Energy Technology Data Exchange (ETDEWEB)

    Moll, Gary; Beattie, Jeff

    1999-07-01

    AMERICAN FORESTS is a national leader in analyzing urban ecosystem structure, function and value using GIS technology. After conducting Urban Ecosystem Analyses in several US cities, the organization has developed a desktop computer software program that allows this technology to be transferred to local government and be used on a personal computer. This user-friendly version can be used by local planners and political leaders to make well-informed decisions about the planning and development process. AMERJCAN FORESTS' current GIS-based analyses address the effects of vegetation on air quality energy conservation and stormwater management. This project will expand the interpretive capabilities of the program to include thermal and energy-use response to the use of different roofing surfaces. The program currently analyzes the impacts of trees on home air-conditioning use, and the roof surface module will be an important complementary component. Research has shown that roof products which reflect the sun's heat back into the atmosphere impose lower cooling costs on buildings than roof products which absorb the sun's heat slowly and release it. Reflectance, or albedo, is often higher in lighter-colored products, although the use of certain materials can make a dark-colored roof more reflective. A considerable amount of research has been done in this area by scientists from the Department of Energy, particularly the Lawrence Berkeley Laboratories (LBL), the Florida Solar Energy Center and others. This project makes use of research and modeling results from Lawrence Berkeley Laboratories, in Berkeley, California. This research associates a specific reduction in energy-use with a change of roofing products.

  8. Retrofitted green roofs and walls and improvements in thermal comfort

    Science.gov (United States)

    Feitosa, Renato Castiglia; Wilkinson, Sara

    2017-06-01

    Increased urbanization has led to a worsening in the quality of life for many people living in large cities in respect of the urban heat island effect and increases of indoor temperatures in housing and other buildings. A solution may be to retrofit existing environments to their former conditions, with a combination of green infrastructures applied to existing walls and rooftops. Retrofitted green roofs may attenuate housing temperature. However, with tall buildings, facade areas are much larger compared to rooftop areas, the role of green walls in mitigating extreme temperatures is more pronounced. Thus, the combination of green roofs and green walls is expected to promote a better thermal performance in the building envelope. For this purpose, a modular vegetated system is adopted for covering both walls and rooftops. Rather than temperature itself, the heat index, which comprises the combined effect of temperature and relative humidity is used in the evaluation of thermal comfort in small scale experiments performed in Sydney - Australia, where identical timber framed structures prototypes (vegetated and non-vegetated) are compared. The results have shown a different understanding of thermal comfort improvement regarding heat index rather than temperature itself. The combination of green roof and walls has a valid role to play in heat index attenuation.

  9. System for monitoring of green roof performance: use of weighing roof segment and non-invasive visualization

    Science.gov (United States)

    Jelinkova, Vladmira; Dohnal, Michal; Picek, Tomas; Sacha, Jan

    2015-04-01

    Understanding the performance of technogenic substrates for green roofs is a significant task in the framework of sustainable urban planning and water/energy management. The potential retention and detention of the anthropogenic, light weight soil systems and their temporal soil structure changes are of major importance. A green roof test segment was built to investigate the benefits of such anthropogenic systems. Adaptable low-cost system allows long-term monitoring of preferred characteristics. Temperature and water balance measurements complemented with meteorological observations and knowledge of physical properties of the substrates provide basis for detailed analysis of thermal and hydrological regime in green roof systems. The first results confirmed the benefits of green roof systems. The reduction of temperature fluctuations as well as rainfall runoff was significant. Depending on numerous factors such substrate material or vegetation cover the test green roof suppressed the roof temperature amplitude for the period analyzed. The ability to completely prevent (light rainfall events) or reduce and delay (medium and heavy rainfall events) the peak runoff was also analyzed. Special attention is being paid to the assessment of soil structural properties related to possible aggregation/disaggregation, root growth, weather conditions and associated structural changes using non-invasive imaging method. X-ray computed microtomography of undisturbed soil samples (taken from experimental segments) is used for description of pore space geometry, evaluation of surface to volume ratio, additionally for description of cracks and macropores as a product of soil flora and fauna activity. The information from computed tomography imaging will be used for numerical modeling of water flow in variable saturated porous media. The research was realized as a part of the University Centre for Energy Efficient Buildings supported by the EU and with financial support from the Czech

  10. Advanced Energy Efficient Roof System

    Energy Technology Data Exchange (ETDEWEB)

    Jane Davidson

    2008-09-30

    Energy consumption in buildings represents 40 percent of primary U.S. energy consumption, split almost equally between residential (22%) and commercial (18%) buildings.1 Space heating (31%) and cooling (12%) account for approximately 9 quadrillion Btu. Improvements in the building envelope can have a significant impact on reducing energy consumption. Thermal losses (or gains) from the roof make up 14 percent of the building component energy load. Infiltration through the building envelope, including the roof, accounts for an additional 28 percent of the heating loads and 16 percent of the cooling loads. These figures provide a strong incentive to develop and implement more energy efficient roof systems. The roof is perhaps the most challenging component of the building envelope to change for many reasons. The engineered roof truss, which has been around since 1956, is relatively low cost and is the industry standard. The roof has multiple functions. A typical wood frame home lasts a long time. Building codes vary across the country. Customer and trade acceptance of new building products and materials may impede market penetration. The energy savings of a new roof system must be balanced with other requirements such as first and life-cycle costs, durability, appearance, and ease of construction. Conventional residential roof construction utilizes closely spaced roof trusses supporting a layer of sheathing and roofing materials. Gypsum board is typically attached to the lower chord of the trusses forming the finished ceiling for the occupied space. Often in warmer climates, the HVAC system and ducts are placed in the unconditioned and otherwise unusable attic. High temperature differentials and leaky ducts result in thermal losses. Penetrations through the ceilings are notoriously difficult to seal and lead to moisture and air infiltration. These issues all contribute to greater energy use and have led builders to consider construction of a conditioned attic. The

  11. Performance Analysis of Cool Roof, Green Roof and Thermal Insulation on a Concrete Flat Roof in Tropical Climate

    OpenAIRE

    Zingre, Kishor T.; Yang, Xingguo; Wan, Man Pun

    2015-01-01

    In the tropics, the earth surface receives abundant solar radiation throughout the year contributing significantly to building heat gain and, thus, cooling demand. An effective method that can curb the heat gains through opaque roof surfaces could provide significant energy savings. This study investigates and compares the effectiveness of various passive cooling techniques including cool roof, green roof and thermal insulation for reducing the heat gain through a flat concrete roof in tropic...

  12. Habitat connectivity and local conditions shape taxonomic and functional diversity of arthropods on green roofs.

    Science.gov (United States)

    Braaker, Sonja; Obrist, Martin Karl; Ghazoul, Jaboury; Moretti, Marco

    2017-05-01

    Increasing development of urban environments creates high pressure on green spaces with potential negative impacts on biodiversity and ecosystem services. There is growing evidence that green roofs - rooftops covered with vegetation - can contribute mitigate the loss of urban green spaces by providing new habitats for numerous arthropod species. Whether green roofs can contribute to enhance taxonomic and functional diversity and increase connectivity across urbanized areas remains, however, largely unknown. Furthermore, only limited information is available on how environmental conditions shape green roof arthropod communities. We investigated the community composition of arthropods (Apidae, Curculionidae, Araneae and Carabidae) on 40 green roofs and 40 green sites at ground level in the city of Zurich, Switzerland. We assessed how the site's environmental variables (such as area, height, vegetation, substrate and connectivity among sites) affect species richness and functional diversity using generalized linear models. We used an extension of co-inertia analysis (RLQ) and fourth-corner analysis to highlight the mechanism underlying community assemblages across taxonomic groups on green roof and ground communities. Species richness was higher at ground-level sites, while no difference in functional diversity was found between green roofs and ground sites. Green roof arthropod diversity increased with higher connectivity and plant species richness, irrespective of substrate depth, height and area of green roofs. The species trait analysis reviewed the mechanisms related to the environmental predictors that shape the species assemblages of the different taxa at ground and roof sites. Our study shows the important contribution of green roofs in maintaining high functional diversity of arthropod communities across different taxonomic groups, despite their lower species richness compared with ground sites. Species communities on green roofs revealed to be characterized

  13. IDENTIFYING ROOF FALL PREDICTORS USING FUZZY CLASSIFICATION

    International Nuclear Information System (INIS)

    Bertoncini, C. A.; Hinders, M. K.

    2010-01-01

    Microseismic monitoring involves placing geophones on the rock surfaces of a mine to record seismic activity. Classification of microseismic mine data can be used to predict seismic events in a mine to mitigate mining hazards, such as roof falls, where properly bolting and bracing the roof is often an insufficient method of preventing weak roofs from destabilizing. In this study, six months of recorded acoustic waveforms from microseismic monitoring in a Pennsylvania limestone mine were analyzed using classification techniques to predict roof falls. Fuzzy classification using features selected for computational ease was applied on the mine data. Both large roof fall events could be predicted using a Roof Fall Index (RFI) metric calculated from the results of the fuzzy classification. RFI was successfully used to resolve the two significant roof fall events and predicted both events by at least 15 hours before visual signs of the roof falls were evident.

  14. Single-layer centrifugation through colloid selects improved quality of epididymal cat sperm.

    Science.gov (United States)

    Chatdarong, K; Thuwanut, P; Morrell, J M

    2010-06-01

    The objectives were to determine the: 1) extent of epithelial and red blood cell contamination in epididymal cat sperm samples recovered by the cutting method; 2) efficacy of simple washing, single-layer centrifugation (SLC), and swim-up for selecting epididymal cat sperm; and 3) effects of freezing and thawing on cat sperm selected by various techniques. Ten unit samples were studied; each contained sperm from the cauda epididymides of four cats (total, approximately 200 x 10(6) sperm) and was equally allocated into four treatments: 1) simple washing, 2) single-layer centrifugation through colloid prior to cryopreservation (SLC-PC), 3) single-layer centrifugation through colloid after cryopreservation (SLC-AC), and 4) swim-up. Centrifugation (300 x g for 20 min) was done for all methods. The SLC-PC had a better recovery rate than the SLC-AC and swim-up methods (mean+/-SD of 16.4+/-8.7, 10.7+/-8.9, and 2.3+/-1.7%, respectively; Pblood cell contamination than simple washed samples (0.02+/-0.01, 0.02+/-0.04, 0.03+/-0.04, and 0.44+/-0.22 x 10(6) cells/mL, respectively; P0.05), SLC-PC yielded the highest percentage of sperm with normal midpieces and tails (P0.05). In conclusion, both SLC-PC and swim-up improved the quality of epididymal cat sperm, including better morphology, membrane and DNA integrity, and removal of cellular contamination. However, SLC had a better sperm recovery rate than swim-up. 2010 Elsevier Inc. All rights reserved.

  15. Spin effects in MoS{sub 2} and WS{sub 2} single layers

    Energy Technology Data Exchange (ETDEWEB)

    Kioseoglou, G. [Department of Materials Science and Technology, University of Crete, Heraklion (Greece); Institute of Electronic Structure and Laser (IESL), Foundation for Research and Technology Hellas (FORTH), Heraklion, Crete (Greece); Korkusinski, M. [Quantum Theory Group, Emerging Technologies Division, National Research Council, Ottawa, ON (Canada); Scrace, T. [University at Buffalo, SUNY, Buffalo, NY (United States); Hanbicki, A.T.; Currie, M.; Jonker, B.T.; Petrou, A. [Naval Research Laboratory, Washington, DC (United States); Hawrylak, P. [Quantum Theory Group, Emerging Technologies Division, National Research Council, Ottawa, ON (Canada); Department of Physics, University of Ottawa, ON (Canada)

    2016-01-15

    Replacing the two sublattices of carbon atoms in graphene with transition metal atoms and chalcogenide dimers results in single layers of transition metal dichalcogenides (TMDCs). TMDCs are promising new materials for light and energy harvesting, transistors, sensors and quantum information processing. One way to access the distinctive functionality of these materials is via their optical selection rules. In particular, light with positive or negative helicity is absorbed differently, therefore, understanding the interaction of circularly polarized light with various TMDCs should enable future applications. Using the examples of MoS{sub 2} and WS{sub 2} we summarize some recent results that illustrate the potential of these materials. First, when optically excited with circularly polarized light, single layers of MoS{sub 2} can emit light with an appreciable polarization. Depolarization mechanisms can be subsequently explored by monitoring the polarization of emitted photoluminescence as a function of the excess energy supplied to the system. As the energy of the pumping light increases further from the emission channel, the emission quickly becomes depolarized. The dominant relaxation mechanism is identified as phonon-assisted intervalley scattering. In single layers of WS{sub 2} containing electron gas, the main emission channel is from negatively charged excitons, or trions. In the presence of a two-dimensional electron gas this trion emission is circularly polarized at zero magnetic field, even when excited with linearly polarized light. This spontaneous circular polarization of the trion has a linear dependence on magnetic field and can be attributed to the existence of a valley polarized state of the two-dimensional electron gas. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  16. Exploring single-layered SnSe honeycomb polymorphs for optoelectronic and photovoltaic applications

    Science.gov (United States)

    Ul Haq, Bakhtiar; AlFaify, S.; Ahmed, R.; Butt, Faheem K.; Laref, A.; Shkir, Mohd.

    2018-02-01

    Single-layered tin selenide that shares the same structure with phosphorene and possesses intriguing optoelectronic properties has received great interest as a two-dimensional material beyond graphene and phosphorene. Herein, we explore the optoelectronic response of the newly discovered stable honeycomb derivatives (such as α , β , γ , δ , and ɛ ) of single-layered SnSe in the framework of density functional theory. The α , β , γ , and δ derivatives of a SnSe monolayer have been found to exhibit an indirect band gap, however, the dispersion of their band-gap edges demonstrates multiple direct band gaps at a relatively high energy. The ɛ -SnSe, however, features an intrinsic direct band gap at the high-symmetry Γ point. Their energy band gaps (0.53, 2.32, 1.52, 1.56, and 1.76 eV for α -, β -, γ -, δ -, and ɛ -SnSe, respectively), calculated at the level of the Tran-Blaha modified Becke-Johnson approach, mostly fall right in the visible range of the electromagnetic spectrum and are in good agreement with the available literature. The optical spectra of these two-dimensional (2D) SnSe polymorphs (besides β -SnSe) are highly anisotropic and possess strictly different optical band gaps along independent diagonal components. They show high absorption in the visible and UV ranges. Similarly, the reflectivity, refraction, and optical conductivities inherit strong anisotropy from the dielectric functions as well and are highly visible-UV polarized along the cartesian coordinates, showing them to be suitable for optical filters, polarizers, and shields against UV radiation. Our investigations suggest these single-layered SnSe allotropes as a promising 2D material for next-generation nanoscale optoelectronic and photovoltaic applications beyond graphene and phosphorene.

  17. Valley polarization in magnetically doped single-layer transition-metal dichalcogenides

    KAUST Repository

    Cheng, Yingchun

    2014-04-28

    We demonstrate that valley polarization can be induced and controlled in semiconducting single-layer transition-metal dichalcogenides by magnetic doping, which is important for spintronics, valleytronics, and photonics devices. As an example, we investigate Mn-doped MoS2 by first-principles calculations. We study how the valley polarization depends on the strength of the spin orbit coupling and the exchange interaction and discuss how it can be controlled by magnetic doping. Valley polarization by magnetic doping is also expected for other honeycomb materials with strong spin orbit coupling and the absence of inversion symmetry.

  18. Atomic-scale structure of single-layer MoS2 nanoclusters

    DEFF Research Database (Denmark)

    Helveg, S.; Lauritsen, J. V.; Lægsgaard, E.

    2000-01-01

    We have studied using scanning tunneling microscopy (STM) the atomic-scale realm of molybdenum disulfide (MoS2) nanoclusters, which are of interest as a model system in hydrodesulfurization catalysis. The STM gives the first real space images of the shape and edge structure of single-layer MoS2 n...... nanoparticles synthesized on Au(lll), and establishes a new picture of the active edge sires of the nanoclusters. The results demonstrate a way to get detailed atomic-scale information on catalysts in general....

  19. Single layer graphene electrodes for quantum dot-light emitting diodes

    Science.gov (United States)

    Yan, Long; Zhang, Yu; Zhang, Xiaoyu; Zhao, Jia; Wang, Yu; Zhang, Tieqiang; Jiang, Yongheng; Gao, Wenzhu; Yin, Jingzhi; Zhao, Jun; Yu, William W.

    2015-03-01

    Single layer graphene was employed as the electrode in quantum dot-light emitting diodes (QD-LEDs) to replace indium tin oxide (ITO). The graphene layer demonstrated low surface roughness, good hole injection ability, and proper work function matching with the poly (3,4-ethylenedioxythiophene):poly (styrenesulfonate) layer. Together with the hole transport layer and electron transport layer, the fabricated QD-LED showed good current efficiency and power efficiency, which were even higher than an ITO-based similar device under low current density. The result indicates that graphene can be used as anodes to replace ITO in QD-LEDs.

  20. Highly simplified small molecular phosphorescent organic light emitting devices with a solution-processed single layer

    Directory of Open Access Journals (Sweden)

    Zhaokui Wang

    2011-09-01

    Full Text Available A highly simplified single layer solution-processed phosphorescent organic light emitting device (PHOLED with the maximum ηP 11.5 lm/W corresponding to EQE 9.6% has been demonstrated. The solution-processed device is shown having comparable even exceeding device performance to vacuum-processed PHOLED. The simplified device design strategy represents a pathway toward large area, low cost and high efficiency OLEDs in the future. The charge injection and conduction mechanisms in two solution- and vacuum-processed devices are also investigated by evaluating the temperature dependence of current density – voltage characteristics.

  1. Hot trends in design : chic sustainability, unique driving factors and boutique green roofs

    Energy Technology Data Exchange (ETDEWEB)

    Velazquez, L.S. [American Society of Landscape Architects, Washington, DC (United States)]|[Greenroofs.com, Alpharetta, GA (United States); Kiers, K. [Greenroofs.com, Alpharetta, GA (United States)

    2007-07-01

    Green roofs are well known for their ecological benefits but less for their architectural usage. Green roofs offer more to the urban landscape than simply ecological, economic and aesthetic attributes of storm water management, temperature and energy reduction, and provision of additional green space. This paper focused on the top ten architectural trends in vegetated rooftop design. It addressed issues regarding client demands for green roofs and questioned if green roofs should be defined solely by their function as an ecological cover. The top ten trends revealed out-of-the ordinary applications, specialty designs and unusual projects on the boards. The paper looked beyond storm water and heat islands, and explored plans for innovative recreation, including a rooftop ski slope in Delft, the Netherlands, and a converted helipad turned into temporary grass tennis court in Dubai. The paper also presented less typical green roof market drivers, such as a doggie green space for a 10-year old, 9-pound Yorkie and a rooftop garden with plants from the Bible as a teaching laboratory for ministers. Other proposed projects that were discussed included plans for rice paddies on rooftop farms in China and the Vancouver Olympic Village with 50 per cent green roof coverage. The top ten list was organized under the following topics: boutique green roofs; sports and recreation; living roofs and living walls; eco resorts, hotels and therapeutic gardens; food on the roof; cutting edge applications; government and big box applications, cool green residences; mega green roofs; and, visionary proposed projects. 77 refs., 77 figs.

  2. Green Roof Potential in Arab Cities

    OpenAIRE

    Attia, Shady

    2014-01-01

    Urban green roofs have long been promoted as an easy and effective strategy for beautifying the built environment and increasing investment opportunity. The building roof is very important because it has a direct impact on thermal comfort and energy conservation in and around buildings. Urban green roofs can help to address the lack of green space in many urban areas. Urban green roofs provides the city with open spaces that helps reduce urban heat island effect and provides the human populat...

  3. The influence of dual-substrate-layer extensive green roofs on rainwater runoff quantity and quality.

    Science.gov (United States)

    Wang, Xiaoou; Tian, Yimei; Zhao, Xinhua

    2017-08-15

    This study investigates the ability of dual-substrate-layer extensive green roofs to retain rainwater and reduce pollutant leaching. The substrates in dual-substrate-layer green roofs consist of an upper organic nutrition layer for plant growth and a lower inorganic adsorption layer for water retention and pollutant reduction. One traditional single-substrate-layer extensive green roof was built for comparison with dual-substrate-layer green roofs. During the experimental period, dual-substrate-layer green roofs supported better natural vegetation growth, with coverage exceeding 90%, while the coverage in single-substrate-layer green roof was over 80%. Based on the average retention value of the total rainfall for four types of simulated rains (the total rainfall depth (mm) was 43.2, 54.6, 76.2 and 86.4, respectively), the dual-substrate-layer green roofs, which used the mixture of activated charcoal with perlite and vermiculite as the adsorption substrate, possessed better rainfall retention performance (65.9% and 55.4%) than the single-substrate-layer green roof (52.5%). All of the dual-substrate-layer green roofs appeared to be sinks for organics, heavy metals and all forms of nitrogen in all cases, while acted as sources of phosphorus contaminants in the case of heavy rains. In consideration of the factors of water retention, pollution reduction and service life of the green roof, a mixture of activated charcoal and/or pumice with perlite and vermiculite is recommended as the adsorption substrate. The green roofs were able to mitigate mild acid rain, raising the pH from approximately 5.6 in rainfall to 6.5-7.6 in green roof runoff. No signs of a first flush effect for phosphate, total phosphorus, ammonia nitrogen, nitrate nitrogen, total nitrogen, organics, zinc, lead, chromium, manganese, copper, pH or turbidity were found in the green roof runoff. Cost analysis further proved the practicability of dual-substrate-layer green roofs in retaining rainwater, and

  4. Strength Comparison of Flawed Single-Layer and Multilayer AISI 301 Stainless Steel Pressure Vessels at Cryogenic Temperatures

    National Research Council Canada - National Science Library

    Pierce, William

    1965-01-01

    An experimental investigation was conducted to determine the strengths of single-layer and multilayer scale model tanks of AISI 301 stainless steel containing sharp notches and having the same total wall thickness...

  5. Effect of Substrate Permittivity and Thickness on Performance of Single-Layer, Wideband, U-Slot Antennas on Microwave Substrates

    National Research Council Canada - National Science Library

    Natarajan, V; Chatterjee, D

    2004-01-01

    This paper presents effects of substrate permittivity and thickness on the performance characteristics like impedance bandwidth, radiation efficiency and gain of a single-layer, wideband, U-slot antenna...

  6. Aesthetic design and green roofs

    Energy Technology Data Exchange (ETDEWEB)

    Oberlander, C.H.; Whitelaw, E. [Cornelia Hahn Oberlander Landscape Architects, Vancouver, BC (United States)

    2005-07-01

    This paper illustrated several recent approaches to aesthetically pleasing designs in different climatic zones by a renowned Canadian landscape architect. It was argued that landscape architects should join with researchers to find new alternatives to the sedums and grasses typically used in green roof systems. Buildings reviewed in the study included the new Canadian Chancery in Washington DC; the Library Square in Vancouver; the Portland Hotel in Vancouver; a therapeutic garden at the Vancouver General Hospital and a provincial courthouse complex. All designs used a combination of intensive and extensive roof garden techniques, as well as vertical landscaping features. It was suggested that as cities grow vertically, more and more rooftops will be seen. While some will not be accessible, other roof gardens will be subject to intensive use, constituting a unique urban facade. Extensive research and planning for projects will allow for the correct determination of plants and roof landscape structures. It was concluded that patterned landscapes where the eye can explore and make sense of shapes and gradations of colour as well as as textures are restorative and uplifting to many people. 4 refs., 9 figs.

  7. Electronic origin of high-temperature superconductivity in single-layer FeSe superconductor.

    Science.gov (United States)

    Liu, Defa; Zhang, Wenhao; Mou, Daixiang; He, Junfeng; Ou, Yun-Bo; Wang, Qing-Yan; Li, Zhi; Wang, Lili; Zhao, Lin; He, Shaolong; Peng, Yingying; Liu, Xu; Chen, Chaoyu; Yu, Li; Liu, Guodong; Dong, Xiaoli; Zhang, Jun; Chen, Chuangtian; Xu, Zuyan; Hu, Jiangping; Chen, Xi; Ma, Xucun; Xue, Qikun; Zhou, X J

    2012-07-03

    The recent discovery of high-temperature superconductivity in iron-based compounds has attracted much attention. How to further increase the superconducting transition temperature (T(c)) and how to understand the superconductivity mechanism are two prominent issues facing the current study of iron-based superconductors. The latest report of high-T(c) superconductivity in a single-layer FeSe is therefore both surprising and significant. Here we present investigations of the electronic structure and superconducting gap of the single-layer FeSe superconductor. Its Fermi surface is distinct from other iron-based superconductors, consisting only of electron-like pockets near the zone corner without indication of any Fermi surface around the zone centre. Nearly isotropic superconducting gap is observed in this strictly two-dimensional system. The temperature dependence of the superconducting gap gives a transition temperature T(c)~ 55 K. These results have established a clear case that such a simple electronic structure is compatible with high-T(c) superconductivity in iron-based superconductors.

  8. Single layer porous media with entrapped minerals for microscale studies of multiphase flow.

    Science.gov (United States)

    Liefferink, R W; Naillon, A; Bonn, D; Prat, M; Shahidzadeh, N

    2018-03-27

    The behaviour of minerals (i.e. salts) such as sodium chloride and calcite in porous media is very important in various applications such as weathering of artworks, oil recovery and CO2 sequestration. We report a novel method for manufacturing single layer porous media in which minerals can be entrapped in a controlled way in order to study their dissolution and recrystallization. In addition, our manufacturing method is a versatile tool for creating monomodal, bimodal or multimodal pore size microporous media with controlled porosity ranging from 25% to 50%. These micromodels allow multiphase flows to be quantitatively studied with different microscopy techniques and can serve to validate numerical models that can subsequently be extended to the 3D situation where visualization is experimentally difficult. As an example of their use, deliquescence (dissolution by moisture absorption) of entrapped NaCl crystals is studied; our results show that the invasion of the resulting salt solution is controlled by the capillary pressure within the porous network. For hydrophilic porous media, the liquid preferentially invades the small pores whereas in a hydrophobic network the large pores are filled. Consequently, after several deliquescence/drying cycles in the hydrophilic system, the salt is transported towards the outside of the porous network via small pores; in hydrophobic micromodels, no salt migration is observed. Numerical simulations based on the characteristics of our single layer pore network agree very well with the experimental results and give more insight into the dynamics of salt transport through porous media.

  9. Charge transferred doping of single layer graphene by mono-dispersed manganese-oxide nanoparticles adsorption

    Science.gov (United States)

    Phan, Thanh Luan; Kang, Myunggoo; Choi, Soo Ho; Kim, You Joong; Jung, Hyun; Yoon, Im Taek; Yang, Woochul

    2017-10-01

    We report an efficient and controllable method to introduce p-type doping in graphene by decoration with Mn3O4 nanoparticles (NPs) on mechanically exfoliated single layer graphene. A monolayer of Mn3O4 NPs, with a diameter in the range of 5-10 nm, was decorated on a graphene film using an ex-situ method, whereas by controlling the coverage of the NPs on the graphene surface, the carrier concentration could be continually adjusted. The p-type of the NP-decorated single layer graphene was confirmed by the Raman G-band. It was found that the carrier concentration could be gradually adjusted up to 26.09 × 1012 cm-2, with 90% coverage of Mn3O4 NPs. The Dirac point of the pristine graphene at the gate bias of 27 V shifted to 150 V for Mn3O4 NP decorated graphene. The p-type graphene doped with Mn3O4 NPs demonstrated significant high air-stability, even under an oxygen atmosphere for 60 days. This approach allows for the opportunity for simple, scalable, and highly stable doping of graphene for future high-performance electronic device applications.

  10. Strong piezoelectricity in single-layer graphene deposited on SiO2 grating substrates.

    Science.gov (United States)

    da Cunha Rodrigues, Gonçalo; Zelenovskiy, Pavel; Romanyuk, Konstantin; Luchkin, Sergey; Kopelevich, Yakov; Kholkin, Andrei

    2015-06-25

    Electromechanical response of materials is a key property for various applications ranging from actuators to sophisticated nanoelectromechanical systems. Here electromechanical properties of the single-layer graphene transferred onto SiO2 calibration grating substrates is studied via piezoresponse force microscopy and confocal Raman spectroscopy. The correlation of mechanical strains in graphene layer with the substrate morphology is established via Raman mapping. Apparent vertical piezoresponse from the single-layer graphene supported by underlying SiO2 structure is observed by piezoresponse force microscopy. The calculated vertical piezocoefficient is about 1.4 nm V(-1), that is, much higher than that of the conventional piezoelectric materials such as lead zirconate titanate and comparable to that of relaxor single crystals. The observed piezoresponse and achieved strain in graphene are associated with the chemical interaction of graphene's carbon atoms with the oxygen from underlying SiO2. The results provide a basis for future applications of graphene layers for sensing, actuating and energy harvesting.

  11. Epitaxial Single-Layer MoS2 on GaN with Enhanced Valley Helicity

    KAUST Repository

    Wan, Yi

    2017-12-19

    Engineering the substrate of 2D transition metal dichalcogenides can couple the quasiparticle interaction between the 2D material and substrate, providing an additional route to realize conceptual quantum phenomena and novel device functionalities, such as realization of a 12-time increased valley spitting in single-layer WSe2 through the interfacial magnetic exchange field from a ferromagnetic EuS substrate, and band-to-band tunnel field-effect transistors with a subthreshold swing below 60 mV dec−1 at room temperature based on bilayer n-MoS2 and heavily doped p-germanium, etc. Here, it is demonstrated that epitaxially grown single-layer MoS2 on a lattice-matched GaN substrate, possessing a type-I band alignment, exhibits strong substrate-induced interactions. The phonons in GaN quickly dissipate the energy of photogenerated carriers through electron–phonon interaction, resulting in a short exciton lifetime in the MoS2/GaN heterostructure. This interaction enables an enhanced valley helicity at room temperature (0.33 ± 0.05) observed in both steady-state and time-resolved circularly polarized photoluminescence measurements. The findings highlight the importance of substrate engineering for modulating the intrinsic valley carriers in ultrathin 2D materials and potentially open new paths for valleytronics and valley-optoelectronic device applications.

  12. Tuning the band structure and superconductivity in single-layer FeSe by interface engineering.

    Science.gov (United States)

    Peng, R; Xu, H C; Tan, S Y; Cao, H Y; Xia, M; Shen, X P; Huang, Z C; Wen, C H P; Song, Q; Zhang, T; Xie, B P; Gong, X G; Feng, D L

    2014-09-26

    The interface between transition metal compounds provides a rich playground for emergent phenomena. Recently, significantly enhanced superconductivity has been reported for single-layer FeSe on Nb-doped SrTiO3 substrate. Yet it remains mysterious how the interface affects the superconductivity. Here we use in situ angle-resolved photoemission spectroscopy to investigate various FeSe-based heterostructures grown by molecular beam epitaxy, and uncover that electronic correlations and superconducting gap-closing temperature (Tg) are tuned by interfacial effects. Tg up to 75 K is observed in extremely tensile-strained single-layer FeSe on Nb-doped BaTiO3, which sets a record high pairing temperature for both Fe-based superconductor and monolayer-thick films, providing a promising prospect on realizing more cost-effective superconducting device. Moreover, our results exclude the direct correlation between superconductivity and tensile strain or the energy of an interfacial phonon mode, and highlight the critical and non-trivial role of FeSe/oxide interface on the high Tg, which provides new clues for understanding its origin.

  13. Gold Dispersion and Activation on the Basal Plane of Single-Layer MoS2

    KAUST Repository

    Merida, Cindy S.

    2017-12-09

    Gold islands are typically associated with high binding affinity to adsorbates and catalytic activity. Here we present the growth of such dispersed nanoscale gold islands on single layer MoS2, prepared on an inert SiO2/Si support by chemical vapor deposition (CVD). This study offers a combination of growth process development, optical characterization, photoelectron spectroscopy at sub-micron spatial resolution, and advanced density functional theory modeling for detailed insight into the electronic interaction between gold and single-layer MoS2. In particular, we find the gold density of states in Au/MoS2/SiO2/Si to be far less well-defined than Au islands on other 2-dimensional materials such as graphene, for which we also provide data. We attribute this effect to the presence of heterogeneous Au adatom/MoS2-support interactions within the nanometer-scale gold cluster. As a consequence, theory predicts that CO will exhibit adsorption energies in excess of 1 eV at the Au cluster edges, where the local density of states is dominated by Au 5dz2 symmetry.

  14. Quality of bull spermatozoa after preparation by single-layer centrifugation.

    Science.gov (United States)

    Goodla, Lavanya; Morrell, Jane M; Yusnizar, Yulnawati; Stålhammar, Hans; Johannisson, Anders

    2014-01-01

    The present study aimed to evaluate the effect of single-layer centrifugation (SLC) through a species-specific colloid (Androcoll-B; patent pending, J. M. Morrell) on bull sperm quality. Computer-assisted sperm analysis of motility and flow cytometric analysis of sperm viability (SYBR-14/propidium iodide staining), chromatin integrity (acridine orange staining), reactive oxygen species production [Hoechst 33258-hydroethidine-2',7'-dichlorodihydrofluorescein diacetate (HO-HE-DCFDA) staining], mitochondrial membrane potential (staining with JC-1 probe), and protein tyrosine phosphorylation (specific antibody staining) were performed on unselected and SLC-selected sperm samples. Single-layer centrifugation of bull spermatozoa resulted in the selection of a sperm population that had high mitochondrial membrane potential, a higher content of phosphorylated protein, and more reactive oxygen species than control samples. Sperm chromatin damage was lower in the SLC samples although sperm viability and motility did not differ between SLC samples and controls. These observations suggest that SLC of bull semen in a soybean-containing extender improved some, but not all, parameters of sperm quality. Copyright © 2014 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

  15. Evaluation of Roof Bolting Requirements Based on In-Mine Roof Bolter Drilling

    Energy Technology Data Exchange (ETDEWEB)

    Syd S. Peng

    2005-10-01

    Roof bolting is the most popular method for underground openings in the mining industry, especially in the bedded deposits such as coal. In fact, all U.S. underground coal mine entries are roof-bolted as required by law. However, roof falls still occur frequently in the roof bolted entries. The two possible reasons are: the lack of knowledge of and technology to detect the roof geological conditions in advance of mining, and lack of roof bolting design criteria for modern roof bolting systems. This research is to develop a method for predicting the roof geology and stability condition in real time during roof bolting operation. Based on this information, roof bolting design criteria for modern roof bolting systems will be developed for implementation in real time. For the prediction of roof geology and stability condition in real time, a micro processor was used and a program developed to monitor and record the drilling parameters of roof bolter. These parameters include feed pressure, feed flow (penetration rate), rotation pressure, rotation rate, vacuum pressure, oil temperature of hydraulic circuit, and signals for controlling machine. From the results of a series of laboratory and underground tests so far, feed pressure is found to be a good indicator for identifying the voids/fractures and estimating the roof rock strength. The method for determining quantitatively the location and the size of void/fracture and estimating the roof rock strength from the drilling parameters of roof bolter was developed. Also, a set of computational rules has been developed for in-mine roof using measured roof drilling parameters and implemented in MRGIS (Mine Roof Geology Information System), a software package developed to allow mine engineers to make use of the large amount of roof drilling parameters for predicting roof geology properties automatically. For the development of roof bolting criteria, finite element models were developed for tensioned and fully grouted bolting

  16. Single Layer Nanomaterials: The Chemical Vapor Deposition Synthesis and Atomic Scale Characterization of Hexagonal Boron Nitride and Graphene

    OpenAIRE

    Gibb, Ashley L

    2015-01-01

    The design of novel nanomaterials with tunable geometries and properties has transformed chemistry and physics in recent years. In particular, recent advances in the isolation of two-dimensional films have inspired the exploration and development of stable, self-supporting single layer systems. Most notably graphene, a single layer of hexagonal sp2 carbon, has attracted interest due to intriguing electronic, optical, and mechanical properties. Hexagonal boron nitride (h-BN) is a closely relat...

  17. Magneto-transport in the zero-energy Landau level of single-layer and bilayer graphene

    International Nuclear Information System (INIS)

    Zeitler, U; Giesbers, A J M; Elferen, H J van; Kurganova, E V; McCollam, A; Maan, J C

    2011-01-01

    We present recent low-temperature magnetotransport experiments on single-layer and bilayer graphene in high magnetic field up to 33 T. In single layer graphene the fourfold degeneracy of the zero-energy Landau level is lifted by a gap opening at filling factor ν = 0. In bilayer graphene, we observe a partial lifting of the degeneracy of the eightfold degenerate zero-energy Landau level.

  18. AN AUTOMATED METHOD FOR 3D ROOF OUTLINE GENERATION AND REGULARIZATION IN AIRBONE LASER SCANNER DATA

    Directory of Open Access Journals (Sweden)

    S. N. Perera

    2012-07-01

    Full Text Available In this paper, an automatic approach for the generation and regularization of 3D roof boundaries in Airborne Laser scanner data is presented. The workflow is commenced by segmentation of the point clouds. A classification step and a rule based roof extraction step are followed the planar segmentation. Refinement on roof extraction is performed in order to minimize the effect due to urban vegetation. Boundary points of the connected roof planes are extracted and fitted series of straight line segments. Each line is then regularized with respect to the dominant building orientation. We introduce the usage of cycle graphs for the best use of topological information. Ridge-lines and step-edges are basically extracted to recognise correct topological relationships among the roof faces. Inner roof corners are geometrically fitted based on the closed cycle graphs. Outer boundary is reconstructed using the same concept but with the outer most cycle graph. In here, union of the sub cycles is taken. Intermediate line segments (outer bounds are intersected to reconstruct the roof eave lines. Two test areas with two different point densities are tested with the developed approach. Performance analysis of the test results is provided to demonstrate the applicability of the method.

  19. Green roofs for a drier world: effects of hydrogel amendment on substrate and plant water status.

    Science.gov (United States)

    Savi, Tadeja; Marin, Maria; Boldrin, David; Incerti, Guido; Andri, Sergio; Nardini, Andrea

    2014-08-15

    Climate features of the Mediterranean area make plant survival over green roofs challenging, thus calling for research work to improve water holding capacities of green roof systems. We assessed the effects of polymer hydrogel amendment on the water holding capacity of a green roof substrate, as well as on water status and growth of Salvia officinalis. Plants were grown in green roof experimental modules containing 8 cm or 12 cm deep substrate (control) or substrate mixed with hydrogel at two different concentrations: 0.3 or 0.6%. Hydrogel significantly increased the substrate's water content at saturation, as well as water available to vegetation. Plants grown in 8 cm deep substrate mixed with 0.6% of hydrogel showed the best performance in terms of water status and membrane integrity under drought stress, associated to the lowest above-ground biomass. Our results provide experimental evidence that polymer hydrogel amendments enhance water supply to vegetation at the establishment phase of a green roof. In particular, the water status of plants is most effectively improved when reduced substrate depths are used to limit the biomass accumulation during early growth stages. A significant loss of water holding capacity of substrate-hydrogel blends was observed after 5 months from establishment of the experimental modules. We suggest that cross-optimization of physical-chemical characteristics of hydrogels and green roof substrates is needed to improve long term effectiveness of polymer-hydrogel blends. Copyright © 2014 Elsevier B.V. All rights reserved.

  20. Cladonia lichens on extensive green roofs: evapotranspiration, substrate temperature, and albedo.

    Science.gov (United States)

    Heim, Amy; Lundholm, Jeremy

    2013-01-01

    Green roofs are constructed ecosystems that provide ecosystem services in urban environments. Shallow substrate green roofs subject the vegetation layer to desiccation and other environmental extremes, so researchers have evaluated a variety of stress-tolerant vegetation types for green roof applications. Lichens can be found in most terrestrial habitats.  They are able to survive extremely harsh conditions, including frequent cycles of desiccation and rehydration, nutrient-poor soil, fluctuating temperatures, and high UV intensities. Extensive green roofs (substrate depth green roofs.  In a modular green roof system, we tested the effect of Cladonia lichens on substrate temperature, water loss, and albedo compared to a substrate-only control. Overall, the Cladonia modules had significantly cooler substrate temperatures during the summer and significantly warmer temperatures during the fall.  Additionally, the Cladonia modules lost significantly less water than the substrate-only control. This implies that they may be able to benefit neighboring vascular plant species by reducing water loss and maintaining favorable substrate temperatures.

  1. PREDICTING THERMAL PERFORMANCE OF ROOFING SYSTEMS IN SURABAYA

    Directory of Open Access Journals (Sweden)

    MINTOROGO Danny Santoso

    2015-07-01

    Full Text Available Traditional roofing systems in the developing country likes Indonesia are still be dominated by the 30o, 45o, and more pitched angle roofs; the roofing cover materials are widely used to traditional clay roof tiles, then modern concrete roof tiles, and ceramic roof tiles. In the 90’s decay, shop houses are prosperous built with flat concrete roofs dominant. Green roofs and roof ponds are almost rarely built to meet the sustainable environmental issues. Some tested various roof systems in Surabaya were carried out to observe the roof thermal performances. Mathematical equation model from three references are also performed in order to compare with the real project tested. Calculated with equation (Kabre et al., the 30o pitched concrete-roof-tile, 30o clay-roof-tile, 45o pitched concrete-roof-tile are the worst thermal heat flux coming to room respectively. In contrast, the bare soil concrete roof and roof pond system are the least heat flux streamed onto room. Based on predicted calculation without insulation and cross-ventilation attic space, the roof pond and bare soil concrete roof (greenery roof are the appropriate roof systems for the Surabaya’s climate; meanwhile the most un-recommended roof is pitched 30o or 45o angle with concrete-roof tiles roofing systems.

  2. Generating realistic roofs over a rectilinear polygon

    KAUST Repository

    Ahn, Heekap

    2011-01-01

    Given a simple rectilinear polygon P in the xy-plane, a roof over P is a terrain over P whose faces are supported by planes through edges of P that make a dihedral angle π/4 with the xy-plane. In this paper, we introduce realistic roofs by imposing a few additional constraints. We investigate the geometric and combinatorial properties of realistic roofs, and show a connection with the straight skeleton of P. We show that the maximum possible number of distinct realistic roofs over P is ( ⌊(n-4)/4⌋ (n-4)/2) when P has n vertices. We present an algorithm that enumerates a combinatorial representation of each such roof in O(1) time per roof without repetition, after O(n 4) preprocessing time. We also present an O(n 5)-time algorithm for computing a realistic roof with minimum height or volume. © 2011 Springer-Verlag.

  3. Orbital roof encephalocele mimicking a destructive neoplasm.

    Science.gov (United States)

    Alsuhaibani, Adel H; Hitchon, Patrick W; Smoker, Wendy R K; Lee, Andrew G; Nerad, Jeffrey A

    2011-01-01

    The purpose of this case report is to report an orbital roof encephalocele mimicking a destructive orbital neoplasm. Orbital roof encephalocele is uncommon but can mimic neoplasm. One potential mechanism for the orbital roof destruction is a post-traumatic "growing orbital roof fracture." The growing fracture has been reported mostly in children but can occur in adults. Alternative potential etiologies for the encephalocele are discussed, including Gorham syndrome. Orbital roof encephalocele is uncommon in adults, and the findings can superficially resemble an orbital neoplasm. Radiographic and clinical features that might suggest the correct diagnosis include a prior history of trauma, overlying frontal lobe encephalomalacia without significant mass effect or edema, and an orbital roof defect. The "growing fracture" mechanism may be a potential explanation for the orbital roof destruction in some cases.

  4. Green roof impact on the hydrological cycle components

    Science.gov (United States)

    Lamera, Carlotta; Rulli, Maria Cristina; Becciu, Gianfranco; Rosso, Renzo

    2013-04-01

    In the last decades the importance of storm water management in urban areas has increased considerably, due to both urbanization extension and to a greater concern for environment pollution. Traditional storm water control practices, based on the "all to the sewer" attitude, rely on conveyance to route storm water runoff from urban impervious surfaces towards the nearby natural water bodies. In recent years, infiltration facilities are receiving an increasing attention, due to their particular efficiency in restoring a balance in hydrological cycle quite equal to quite pre-urbanization condition. In particular, such techniques are designed to capture, temporarily retain and infiltrate storm water, promote evapotranspiration and harvest water at the source, encouraging in general evaporation, evapotranspiration, groundwater recharge and the re-use of storm water. Green roofs are emerging as an increasingly popular Sustainable Urban Drainage Systems (SUDS) technique for urban storm water management. Indeed, they are able to operate hydrologic control over storm water runoff: they allow a significant reduction of peak flows and runoff volumes collected by drainage system, with a consequent reduction of flooding events and pollution masses discharges by CSO. Furthermore green roofs have a positive influence on the microclimate in urban areas by helping in lower urban air temperatures and mitigate the heat island effect. Last but not least, they have the advantage of improving the thermal insulation of buildings, with significant energy savings. A detailed analysis of the hydrological dynamics, connected both with the characteristics of the climatic context and with the green roof technical design, is essential in order to obtain a full characterization of the hydrologic behavior of a green roof system and its effects on the urban water cycle components. The purpose of this paper is to analysis the hydrological effects and urban benefits of the vegetation cover of a

  5. Performance of dryland and wetland plant species on extensive green roofs.

    Science.gov (United States)

    MacIvor, J Scott; Ranalli, Melissa A; Lundholm, Jeremy T

    2011-04-01

    Green roofs are constructed ecosystems where plants perform valuable services, ameliorating the urban environment through roof temperature reductions and stormwater interception. Plant species differ in functional characteristics that alter ecosystem properties. Plant performance research on extensive green roofs has so far indicated that species adapted to dry conditions perform optimally. However, in moist, humid climates, species typical of wetter soils might have advantages over dryland species. In this study, survival, growth and the performance of thermal and stormwater capture functions of three pairs of dryland and wetland plant species were quantified using an extensive modular green roof system. Seedlings of all six species were germinated in a greenhouse and planted into green roof modules with 6 cm of growing medium. There were 34 treatments consisting of each species in monoculture and all combinations of wet- and dryland species in a randomized block design. Performance measures were survival, vegetation cover and roof surface temperature recorded for each module over two growing seasons, water loss (an estimate of evapotranspiration) in 2007, and albedo and water capture in 2008. Over two seasons, dryland plants performed better than wetland plants, and increasing the number of dryland species in mixtures tended to improve functioning, although there was no clear effect of species or habitat group diversity. All species had survival rates >75 % after the first winter; however, dryland species had much greater cover, an important indicator of green roof performance. Sibbaldiopsis tridentata was the top performing species in monoculture, and was included in the best treatments. Although dryland species outperformed wetland species, planting extensive green roofs with both groups decreased performance only slightly, while increasing diversity and possibly habitat value. This study provides further evidence that plant composition and diversity can

  6. Negative quantum capacitance induced by midgap states in single-layer graphene.

    Science.gov (United States)

    Wang, Lin; Wang, Yang; Chen, Xiaolong; Zhu, Wei; Zhu, Chao; Wu, Zefei; Han, Yu; Zhang, Mingwei; Li, Wei; He, Yuheng; Xiong, Wei; Law, Kam Tuen; Su, Dangsheng; Wang, Ning

    2013-01-01

    We demonstrate that single-layer graphene (SLG) decorated with a high density of Ag adatoms displays the unconventional phenomenon of negative quantum capacitance. The Ag adatoms act as resonant impurities and form nearly dispersionless resonant impurity bands near the charge neutrality point (CNP). Resonant impurities quench the kinetic energy and drive the electrons to the Coulomb energy dominated regime with negative compressibility. In the absence of a magnetic field, negative quantum capacitance is observed near the CNP. In the quantum Hall regime, negative quantum capacitance behavior at several Landau level positions is displayed, which is associated with the quenching of kinetic energy by the formation of Landau levels. The negative quantum capacitance effect near the CNP is further enhanced in the presence of Landau levels due to the magnetic-field-enhanced Coulomb interactions.

  7. Effect of humid-thermal environment on wave dispersion characteristics of single-layered graphene sheets

    Science.gov (United States)

    Ebrahimi, Farzad; Dabbagh, Ali

    2018-04-01

    In the present article, the hygro-thermal wave propagation properties of single-layered graphene sheets (SLGSs) are investigated for the first time employing a nonlocal strain gradient theory. A refined higher-order two-variable plate theory is utilized to derive the kinematic relations of graphene sheets. Here, nonlocal strain gradient theory is used to achieve a more precise analysis of small-scale plates. In the framework of the Hamilton's principle, the final governing equations are developed. Moreover, these obtained equations are deemed to be solved analytically and the wave frequency values are achieved. Some parametric studies are organized to investigate the influence of different variants such as nonlocal parameter, length scale parameter, wave number, temperature gradient and moisture concentration on the wave frequency of graphene sheets.

  8. Large theoretical thermoelectric power factor of suspended single-layer MoS{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Babaei, Hasan, E-mail: babaei@illinois.edu, E-mail: babaei@auburn.edu [Mechanical Science and Engineering Department, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801-2906 (United States); Mechanical Engineering Department, Auburn University, Auburn, Alabama 36849-5341 (United States); Khodadadi, J. M. [Mechanical Engineering Department, Auburn University, Auburn, Alabama 36849-5341 (United States); Sinha, Sanjiv [Mechanical Science and Engineering Department, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801-2906 (United States)

    2014-11-10

    We have calculated the semi-classical thermoelectric power factor of suspended single-layer (SL)- MoS{sub 2} utilizing electron relaxation times derived from ab initio calculations. Measurements of the thermoelectric power factor of SL-MoS{sub 2} on substrates reveal poor power factors. In contrast, we find the thermoelectric power factor of suspended SL-MoS{sub 2} to peak at ∼2.8 × 10{sup 4} μW/m K{sup 2} at 300 K, at an electron concentration of 10{sup 12} cm{sup −2}. This figure is higher than that in bulk Bi{sub 2}Te{sub 3}, for example. Given its relatively high thermal conductivity, suspended SL-MoS{sub 2} may hold promise for in-plane thin-film Peltier coolers, provided reasonable mobilities can be realized.

  9. Moisture barrier properties of single-layer graphene deposited on Cu films for Cu metallization

    Science.gov (United States)

    Gomasang, Ploybussara; Abe, Takumi; Kawahara, Kenji; Wasai, Yoko; Nabatova-Gabain, Nataliya; Thanh Cuong, Nguyen; Ago, Hiroki; Okada, Susumu; Ueno, Kazuyoshi

    2018-04-01

    The moisture barrier properties of large-grain single-layer graphene (SLG) deposited on a Cu(111)/sapphire substrate are demonstrated by comparing with the bare Cu(111) surface under an accelerated degradation test (ADT) at 85 °C and 85% relative humidity (RH) for various durations. The change in surface color and the formation of Cu oxide are investigated by optical microscopy (OM) and X-ray photoelectron spectroscopy (XPS), respectively. First-principle simulation is performed to understand the mechanisms underlying the barrier properties of SLG against O diffusion. The correlation between Cu oxide thickness and SLG quality are also analyzed by spectroscopic ellipsometry (SE) measured on a non-uniform SLG film. SLG with large grains shows high performance in preventing the Cu oxidation due to moisture during ADT.

  10. Single layered flexible photo-detector based on perylene/graphene composite through printed technology

    Science.gov (United States)

    Ali, Shawkat; Bae, Jinho; Lee, Chong Hyun

    2015-07-01

    In this paper, a single layered passive photo sensor based on perylene/graphene composite is proposed, which is deposited in comb type silver electrodes separated as 50 μm spacing. To increase an electrical conductivity of the proposed sensor, perylene and graphene are blended. Photo sensing layer (120nm thick) and Silver electrodes (50 μm width, 350 nm thick) are deposited on poly(ethylene terephthalate) (PET) substrate through electro-hydrodynamic (EHD) system. The proposed photo sensor detects a terminal resistance inversely varied by an incident light in the range between 78 GΩ in dark and 25 GΩ at light intensity of 400lux. The device response is maximum at 465 nm ~ 535 nm wavelength range at blue light. The device exhibited bendability up to 4mm diameter for 1000 endurance cycles. The surface morphology analysis is carried out with FE-SEM and microscope.

  11. A visualization method for probing grain boundaries of single layer graphene via molecular beam epitaxy

    Science.gov (United States)

    Zhan, Linjie; Wan, Wen; Zhu, Zhenwei; Zhao, Zhijuan; Zhang, Zhenhan; Shih, Tien-Mo; Cai, Weiwei

    2017-07-01

    Graphene, a member of layered two-dimensional (2D) materials, possesses high carrier mobility, mechanical flexibility, and optical transparency, as well as enjoying a wide range of promising applications in electronics. Adopting the chemical vaporization deposition method, the majority of investigators have ubiquitously grown single layer graphene (SLG), which inevitably involves polycrystalline properties. Here we demonstrate a simple method for the direct visualization of arbitrarily large-size SLG domains by synthesizing one-hundred-nm-scale MoS2 single crystals via a high-vacuum molecular beam epitaxy process. The present study based on epitaxial growth provides a guide for probing the grain boundaries of various 2D materials and implements higher potentials for the next-generation electronic devices.

  12. Probing Critical Point Energies of Transition Metal Dichalcogenides: Surprising Indirect Gap of Single Layer WSe 2

    KAUST Repository

    Zhang, Chendong

    2015-09-21

    By using a comprehensive form of scanning tunneling spectroscopy, we have revealed detailed quasi-particle electronic structures in transition metal dichalcogenides, including the quasi-particle gaps, critical point energy locations, and their origins in the Brillouin zones. We show that single layer WSe surprisingly has an indirect quasi-particle gap with the conduction band minimum located at the Q-point (instead of K), albeit the two states are nearly degenerate. We have further observed rich quasi-particle electronic structures of transition metal dichalcogenides as a function of atomic structures and spin-orbit couplings. Such a local probe for detailed electronic structures in conduction and valence bands will be ideal to investigate how electronic structures of transition metal dichalcogenides are influenced by variations of local environment.

  13. Polarized dependence of nonlinear susceptibility in a single layer graphene system in infrared region

    Energy Technology Data Exchange (ETDEWEB)

    Solookinejad, G., E-mail: ghsolooki@gmail.com

    2016-09-15

    In this study, the linear and nonlinear susceptibility of a single-layer graphene nanostructure driven by a weak probe light and an elliptical polarized coupling field is discussed theoretically. The Landau levels of graphene can be separated in infrared or terahertz regions under the strong magnetic field. Therefore, by using the density matrix formalism in quantum optic, the linear and nonlinear susceptibility of the medium can be derived. It is demonstrated that by adjusting the elliptical parameter, one can manipulate the linear and nonlinear absorption as well as Kerr nonlinearity of the medium. It is realized that the enhanced Kerr nonlinearity can be possible with zero linear absorption and nonlinear amplification at some values of elliptical parameter. Our results may be having potential applications in quantum information science based on Nano scales devices.

  14. Tensile loading induced phase transition and rippling in single-layer MoS2

    Science.gov (United States)

    Bao, Hongwei; Huang, Yuhong; Yang, Zhi; Miao, Yaping; Chu, Paul K.; Xu, Kewei; Ma, Fei

    2017-05-01

    Molecular dynamics (MD) simulation is performed to study the structural evolution of single-layer MoS2 nanosheets under tensile loading and a phase transition from hexagonal structure to quadrilateral one is observed at a large strain when loaded along the zigzag direction but not along the armchair direction. Density functional theory (DFT) calculation illustrates that the newly generated quadrilateral phase is metallic. Further loading along the zigzag direction promotes an inhomogeneous distribution of lateral and shear stress around the phase boundaries due to local mechanical mismatch. As a result, periodic rippling parallel to the loading direction emerges and the wavelength and wave height change with strain according to λ∼ε-1/4 and h∼ε1/4. Accordingly, a graded distribution of strain can be produced or modulated by a simple tensile loading and the strategy might be utilized to enhance the photoelectrical properties of 2D materials and design strain-tunable nanodevices.

  15. Effect of quenched disorder on charge-orbital-spin ordering in single-layer manganites

    International Nuclear Information System (INIS)

    Uchida, Masaya; Mathieu, Roland; He, Jinping; Kaneko, Yoshio; Tokura, Yoshinori; Asamitsu, Atsushi; Kumai, Reiji; Tomioka, Yasuhide; Matsui, Yoshio

    2006-01-01

    Structural and magnetic properties have been investigated for half-doped single-layer manganites RE 0.5 Sr 1.5 MnO 4 [RE=La, (La, Pr), Pr, Nd, Sm, and Eu]. Analyses of electron diffraction and ac susceptibility measurements have revealed that the long-range charge-orbital ordering (CO-OO) state as observed in La 0.5 Sr 1.5 MnO 4 is suppressed for the other materials: the CO-OO transition temperature, as well as the correlation length decreases with a decrease in the cation size of RE. Such a short-range CO-OO state shows a spin-glass behavior at low temperatures. A new electronic phase diagram is established with quenched disorder as the control parameter. (author)

  16. Biomimetic plasmonic color generated by the single-layer coaxial honeycomb nanostructure arrays

    Science.gov (United States)

    Zhao, Jiancun; Gao, Bo; Li, Haoyong; Yu, Xiaochang; Yang, Xiaoming; Yu, Yiting

    2017-07-01

    We proposed a periodic coaxial honeycomb nanostructure array patterned in a silver film to realize the plasmonic structural color, which was inspired from natural honeybee hives. The spectral characteristics of the structure with variant geometrical parameters are investigated by employing a finite-difference time-domain method, and the corresponding colors are thus derived by calculating XYZ tristimulus values corresponding with the transmission spectra. The study demonstrates that the suggested structure with only a single layer has high transmission, narrow full-width at half-maximum, and wide color tunability by changing geometrical parameters. Therefore, the plasmonic colors realized possess a high color brightness, saturation, as well as a wide color gamut. In addition, the strong polarization independence makes it more attractive for practical applications. These results indicate that the recommended color-generating plasmonic structure has various potential applications in highly integrated optoelectronic devices, such as color filters and high-definition displays.

  17. Thermal vibration of rectangular single-layered black phosphorus predicted by orthotropic plate model

    Science.gov (United States)

    Zhang, Yiqing; Wang, Lifeng; Jiang, Jingnong

    2018-03-01

    Vibrational behavior is very important for nanostructure-based resonators. In this work, an orthotropic plate model together with a molecular dynamics (MD) simulation is used to investigate the thermal vibration of rectangular single-layered black phosphorus (SLBP). Two bending stiffness, two Poisson's ratios, and one shear modulus of SLBP are calculated using the MD simulation. The natural frequency of the SLBP predicted by the orthotropic plate model agrees with the one obtained from the MD simulation very well. The root of mean squared (RMS) amplitude of the SLBP is obtained by MD simulation and the orthotropic plate model considering the law of energy equipartition. The RMS amplitude of the thermal vibration of the SLBP is predicted well by the orthotropic plate model compared to the MD results. Furthermore, the thermal vibration of the SLBP with an initial stress is also well-described by the orthotropic plate model.

  18. Water desalination with a single-layer MoS2 nanopore

    Science.gov (United States)

    Heiranian, Mohammad; Farimani, Amir Barati; Aluru, Narayana R.

    2015-01-01

    Efficient desalination of water continues to be a problem facing the society. Advances in nanotechnology have led to the development of a variety of nanoporous membranes for water purification. Here we show, by performing molecular dynamics simulations, that a nanopore in a single-layer molybdenum disulfide can effectively reject ions and allow transport of water at a high rate. More than 88% of ions are rejected by membranes having pore areas ranging from 20 to 60 Å2. Water flux is found to be two to five orders of magnitude greater than that of other known nanoporous membranes. Pore chemistry is shown to play a significant role in modulating the water flux. Pores with only molybdenum atoms on their edges lead to higher fluxes, which are ∼70% greater than that of graphene nanopores. These observations are explained by permeation coefficients, energy barriers, water density and velocity distributions in the pores. PMID:26465062

  19. Large theoretical thermoelectric power factor of suspended single-layer MoS2

    International Nuclear Information System (INIS)

    Babaei, Hasan; Khodadadi, J. M.; Sinha, Sanjiv

    2014-01-01

    We have calculated the semi-classical thermoelectric power factor of suspended single-layer (SL)- MoS 2 utilizing electron relaxation times derived from ab initio calculations. Measurements of the thermoelectric power factor of SL-MoS 2 on substrates reveal poor power factors. In contrast, we find the thermoelectric power factor of suspended SL-MoS 2 to peak at ∼2.8 × 10 4 μW/m K 2 at 300 K, at an electron concentration of 10 12 cm −2 . This figure is higher than that in bulk Bi 2 Te 3 , for example. Given its relatively high thermal conductivity, suspended SL-MoS 2 may hold promise for in-plane thin-film Peltier coolers, provided reasonable mobilities can be realized

  20. The strain rate effect on the buckling of single-layer MoS2.

    Science.gov (United States)

    Jiang, Jin-Wu

    2015-01-15

    The Euler buckling theory states that the buckling critical strain is an inverse quadratic function of the length for a thin plate in the static compression process. However, the suitability of this theory in the dynamical process is unclear, so we perform molecular dynamics simulations to examine the applicability of the Euler buckling theory for the fast compression of the single-layer MoS2. We find that the Euler buckling theory is not applicable in such dynamical process, as the buckling critical strain becomes a length-independent constant in the buckled system with many ripples. However, the Euler buckling theory can be resumed in the dynamical process after restricting the theory to an individual ripple in the buckled structure.

  1. Growth and electronic structure of single-layered transition metal dichalcogenides

    DEFF Research Database (Denmark)

    Dendzik, Maciej

    2016-01-01

    The discovery of graphene has opened a novel research direction focused on the properties of 2D materials. Transition metal dichalcogenides (TMDCs) were quickly identified as important materials due to the great variety of electronic properties that they manifest – properties that are markedly...... different from graphene’s. For example, semiconducting TMDCs undergo an indirectdirect band gap transition when thinned to a single layer (SL); this results in greatly enhanced photoluminescence, making those materials attractive for applications in optoelectronics. Furthermore, metallic TMDCs can host...... TMDCs is directly studied with angle-resolved photoemission spectroscopy (ARPES) and x-ray photoelectron spectroscopy (XPS) techniques. Experimental results are compared with density-functional theory calculations (DFT), both for a free-standing layer and for a layer adsorbed on a metallic substrate...

  2. Trends in the design, construction and operation of green roofs to improve the rainwater quality. State of the art

    Directory of Open Access Journals (Sweden)

    Jair Andrés Morales Mojica

    2017-07-01

    Full Text Available The green roofs appear as technology for the improvement water quality. This article identifies trends in the conditions of design, construction and operation of green roofs, which aim is to improve the quality of rainwater. A literature review was carried out in order to collect 45 original research papers from databases as Scopus, Science Direct, and Redalyc. From the information collected trends in increments and reductions in the concentrations of the main water quality parameters, seasons of the year with the best results, types of green roofs , types of substrate and most common components, construction trends (dimensions, inclination, Materials and layers and vegetation used in these systems have been determined. The results show that green roofs have the ability to neutralize acid rain. Extensive type roofs are the ones most commonly used, due to its characteristics of construction, functionality and low maintenance requirements.

  3. Anomalous photoluminescence thermal quenching of sandwiched single layer MoS_2

    KAUST Repository

    Tangi, Malleswararao

    2017-09-22

    We report an unusual thermal quenching of the micro-photoluminescence (µ-PL) intensity for a sandwiched single-layer (SL) MoS2. For this study, MoS2 layers were chemical vapor deposited on molecular beam epitaxial grown In0.15Al0.85N lattice matched templates. Later, to accomplish air-stable sandwiched SL-MoS2, a thin In0.15Al0.85N cap layer was deposited on the MoS2/In0.15Al0.85N heterostructure. We confirm that the sandwiched MoS2 is a single layer from optical and structural analyses using µ-Raman spectroscopy and scanning transmission electron microscopy, respectively. By using high-resolution X-ray photoelectron spectroscopy, no structural phase transition of MoS2 is noticed. The recombination processes of bound and free excitons were analyzed by the power-dependent µ-PL studies at 77 K and room temperature (RT). The temperature-dependent micro photoluminescence (TDPL) measurements were carried out in the temperature range of 77 – 400 K. As temperature increases, a significant red-shift is observed for the free-exciton PL peak, revealing the delocalization of carriers. Further, we observe unconventional negative thermal quenching behavior, the enhancement of the µ-PL intensity with increasing temperatures up to 300K, which is explained by carrier hopping transitions that take place between shallow localized states to the band-edges. Thus, this study renders a fundamental insight into understanding the anomalous thermal quenching of µ-PL intensity of sandwiched SL-MoS2.

  4. Single-Layer Plication for Repair of Diastasis Recti: The Most Rapid and Efficient Technique.

    Science.gov (United States)

    Gama, Luiz José Muaccad; Barbosa, Marcus Vinicius Jardini; Czapkowski, Adriano; Ajzen, Sergio; Ferreira, Lydia Masako; Nahas, Fábio Xerfan

    2017-06-01

    Plication of the anterior rectus sheath is the most commonly used technique for repair of diastasis recti, but is also a time-consuming procedure. The aim of this study was to compare the efficacy and time required to repair diastasis recti using different plication techniques. Thirty women with similar abdominal deformities, who had had at least one pregnancy, were randomized into three groups to undergo abdominoplasty. Plication of the anterior rectus sheath was performed in two layers with 2-0 monofilament nylon suture (control group) or in a single layer with either a continuous 2-0 monofilament nylon suture (group I) or using a continuous barbed suture (group II). Operative time was recorded. All patients underwent ultrasound examination preoperatively and at 3 weeks and 6 months postoperatively to monitor for diastasis recurrence. The force required to bring the anterior rectus sheath to the midline was measured at the supraumbilical and infraumbilical levels. Patient age ranged from 26 to 50 years and body mass index from 20.56 to 29.17 kg/m2. A significant difference in mean operative time was found between the control and study groups (control group, 35 min:22 s; group I, 14 min:22 s; group II, 15 min:23 s; P < 0.001). Three patients in group II had recurrence of diastasis. There were no significant within- and between-group differences in tensile force on the aponeurosis. Plication of the anterior rectus sheath in a single-layer with a continuous suture showed to be an efficient and rapid technique for repair of diastasis recti. © 2017 The American Society for Aesthetic Plastic Surgery, Inc. Reprints and permission: journals.permissions@oup.com

  5. Polyurethane adhesives in flat roofs

    OpenAIRE

    Bogárová Markéta; Stodůlka Jindřich; Šuhajda Karel

    2017-01-01

    It is necessary to stabilize individual layers of flat roofs, mainly because of wind suction. Apart from anchoring and surcharge, these layers can be secured by bonding. At present gluing is an indispensable and widely used stabilization method. On our market we can found many types of adhesives, most widely used are based on polyurethane. This paper focuses on problematic about stabilization thermal insulation from expanded polystyrene to vapor barrier from bitumen. One of the main issues is...

  6. Million Solar Roofs Flyer (Revision)

    Energy Technology Data Exchange (ETDEWEB)

    2000-11-01

    The Million Solar Roofs Initiative, announced in June 1997, assists businesses and communities in installing solar energy systems on one million buildings across the United States by 2010. The US Department of Energy leads this trailblazing initiative by partnering with the building industry, local governments, state agencies, the solar industry, electric service providers, and non-governmental organizations to remove barriers and strengthen the demand for solar technologies.

  7. Polyurethane adhesives in flat roofs

    Directory of Open Access Journals (Sweden)

    Bogárová Markéta

    2017-01-01

    Full Text Available It is necessary to stabilize individual layers of flat roofs, mainly because of wind suction. Apart from anchoring and surcharge, these layers can be secured by bonding. At present gluing is an indispensable and widely used stabilization method. On our market we can found many types of adhesives, most widely used are based on polyurethane. This paper focuses on problematic about stabilization thermal insulation from expanded polystyrene to vapor barrier from bitumen. One of the main issues is to calculate the exact amount of adhesive, which is required to guarantee the resistance against wind suction. In this problematic we can not find help neither in technical data sheets provided by the manufactures. Some of these data sheets contain at least information about amount of adhesive depending on location in roof plane and building height, but they do not specify the strength of such connection. It was therefore resorted to select several representatives polyurethane adhesives and their subsequent testing on specimens simulating the flat roof segment. The paper described the test methodology and results for two types of polyurethane adhesives.

  8. Demonstration of energy savings of cool roofs

    Energy Technology Data Exchange (ETDEWEB)

    Konopacki, S.; Gartland, L.; Akbari, H. [Lawrence Berkeley National Lab., CA (United States). Environmental Energy Technologies Div.; Rainer, L. [Davis Energy Group, Davis, CA (United States)

    1998-06-01

    Dark roofs raise the summertime air-conditioning demand of buildings. For highly-absorptive roofs, the difference between the surface and ambient air temperatures can be as high as 90 F, while for highly-reflective roofs with similar insulative properties, the difference is only about 20 F. For this reason, cool roofs are effective in reducing cooling energy use. Several experiments on individual residential buildings in California and Florida show that coating roofs white reduces summertime average daily air-conditioning electricity use from 2--63%. This demonstration project was carried out to address some of the practical issues regarding the implementation of reflective roofs in a few commercial buildings. The authors monitored air-conditioning electricity use, roof surface temperature, plenum, indoor, and outdoor air temperatures, and other environmental variables in three buildings in California: two medical office buildings in Gilroy and Davis and a retail store in San Jose. Coating the roofs of these buildings with a reflective coating increased the roof albedo from an average of 0.20--0.60. The roof surface temperature on hot sunny summer afternoons fell from 175 F--120 F after the coating was applied. Summertime average daily air-conditioning electricity use was reduced by 18% (6.3 kWh/1000ft{sup 2}) in the Davis building, 13% (3.6 kWh/1000ft{sup 2}) in the Gilroy building, and 2% (0.4 kWh/1000ft{sup 2}) in the San Jose store. In each building, a kiosk was installed to display information from the project in order to educate and inform the general public about the environmental and energy-saving benefits of cool roofs. They were designed to explain cool-roof coating theory and to display real-time measurements of weather conditions, roof surface temperature, and air-conditioning electricity use. 55 figs., 15 tabs.

  9. Habitat connectivity and local conditions shape taxonomic and functional diversity of arthropods on green roofs

    NARCIS (Netherlands)

    Braaker, Sonja; Obrist, Martin Karl; Ghazoul, Jaboury; Moretti, Marco

    2017-01-01

    Increasing development of urban environments creates high pressure on green spaces with potential negative impacts on biodiversity and ecosystem services. There is growing evidence that green roofs – rooftops covered with vegetation – can contribute mitigate the loss of urban green spaces by

  10. Giant magnetoimpedance effect in sputtered single layered NiFe film and meander NiFe/Cu/NiFe film

    International Nuclear Information System (INIS)

    Chen, L.; Zhou, Y.; Lei, C.; Zhou, Z.M.; Ding, W.

    2010-01-01

    Giant magnetoimpedance (GMI) effect on NiFe thin film is very promising due to its application in developing the magnetic field sensors with highly sensitivity and low cost. In this paper, the single layered NiFe thin film and NiFe/Cu/NiFe thin film with a meander structure are prepared by the MEMS technology. The influences of sputtering parameters, film structure and conductor layer width on GMI effect in NiFe single layer and meander NiFe/Cu/NiFe film are investigated. Maximum of the GMI ratio in single layer and sandwich film is 5% and 64%, respectively. The results obtained are useful for developing the high-performance magnetic sensors based on NiFe thin film.

  11. Realistic roofs over a rectilinear polygon

    KAUST Repository

    Ahn, Heekap

    2013-11-01

    Given a simple rectilinear polygon P in the xy-plane, a roof over P is a terrain over P whose faces are supported by planes through edges of P that make a dihedral angle π/4 with the xy-plane. According to this definition, some roofs may have faces isolated from the boundary of P or even local minima, which are undesirable for several practical reasons. In this paper, we introduce realistic roofs by imposing a few additional constraints. We investigate the geometric and combinatorial properties of realistic roofs and show that the straight skeleton induces a realistic roof with maximum height and volume. We also show that the maximum possible number of distinct realistic roofs over P is ((n-4)(n-4)/4 /2⌋) when P has n vertices. We present an algorithm that enumerates a combinatorial representation of each such roof in O(1) time per roof without repetition, after O(n4) preprocessing time. We also present an O(n5)-time algorithm for computing a realistic roof with minimum height or volume. © 2013 Elsevier B.V.

  12. A two-stage storage routing model for green roof runoff detention.

    Science.gov (United States)

    Vesuviano, Gianni; Sonnenwald, Fred; Stovin, Virginia

    2014-01-01

    Green roofs have been adopted in urban drainage systems to control the total quantity and volumetric flow rate of runoff. Modern green roof designs are multi-layered, their main components being vegetation, substrate and, in almost all cases, a separate drainage layer. Most current hydrological models of green roofs combine the modelling of the separate layers into a single process; these models have limited predictive capability for roofs not sharing the same design. An adaptable, generic, two-stage model for a system consisting of a granular substrate over a hard plastic 'egg box'-style drainage layer and fibrous protection mat is presented. The substrate and drainage layer/protection mat are modelled separately by previously verified sub-models. Controlled storm events are applied to a green roof system in a rainfall simulator. The time-series modelled runoff is compared to the monitored runoff for each storm event. The modelled runoff profiles are accurate (mean Rt(2) = 0.971), but further characterization of the substrate component is required for the model to be generically applicable to other roof configurations with different substrate.

  13. Tuning Electronic Structure of Single Layer MoS2through Defect and Interface Engineering.

    Science.gov (United States)

    Chen, Yan; Huang, Shengxi; Ji, Xiang; Adepalli, Kiran; Yin, Kedi; Ling, Xi; Wang, Xinwei; Xue, Jianmin; Dresselhaus, Mildred; Kong, Jing; Yildiz, Bilge

    2018-03-27

    Transition-metal dichalcogenides (TMDs) have emerged in recent years as a special group of two-dimensional materials and have attracted tremendous attention. Among these TMD materials, molybdenum disulfide (MoS 2 ) has shown promising applications in electronics, photonics, energy, and electrochemistry. In particular, the defects in MoS 2 play an essential role in altering the electronic, magnetic, optical, and catalytic properties of MoS 2 , presenting a useful way to engineer the performance of MoS 2 . The mechanisms by which lattice defects affect the MoS 2 properties are unsettled. In this work, we reveal systematically how lattice defects and substrate interface affect MoS 2 electronic structure. We fabricated single-layer MoS 2 by chemical vapor deposition and then transferred onto Au, single-layer graphene, hexagonal boron nitride, and CeO 2 as substrates and created defects in MoS 2 by ion irradiation. We assessed how these defects and substrates affect the electronic structure of MoS 2 by performing X-ray photoelectron spectroscopy, Raman and photoluminescence spectroscopies, and scanning tunneling microscopy/spectroscopy measurements. Molecular dynamics and first-principles based simulations allowed us to conclude the predominant lattice defects upon ion irradiation and associate those with the experimentally obtained electronic structure. We found that the substrates can tune the electronic energy levels in MoS 2 due to charge transfer at the interface. Furthermore, the reduction state of CeO 2 as an oxide substrate affects the interface charge transfer with MoS 2 . The irradiated MoS 2 had a faster hydrogen evolution kinetics compared to the as-prepared MoS 2 , demonstrating the concept of defect controlled reactivity in this phase. Our findings provide effective probes for energy band and defects in MoS 2 and show the importance of defect engineering in tuning the functionalities of MoS 2 and other TMDs in electronics, optoelectronics, and

  14. EVALUATION OF ROOF BOLTING REQUIREMENTS BASED ON IN-MINE ROOF BOLTER DRILLING

    Energy Technology Data Exchange (ETDEWEB)

    Syd S. Peng

    2003-07-15

    Roof bolting is the most popular method for underground openings in the mining industry, especially in the bedded deposits such as coal, potash, salt etc. In fact, all U.S. underground coal mine entries are roof-bolted as required by law. However, roof falls still occur frequently in the roof bolted entries. The two possible reasons are: the lack of knowledge of and technology to detect the roof geological conditions in advance of mining, and lack of roof bolting design criteria for modern roof bolting systems. This research is to develop a method for predicting the roof geology and stability condition in real time during roof bolting operation. Based on such information, roof bolting design criteria for modern roof bolting systems will be developed for implementation in real time. In this quarter, the field, theoretical and programming works have been performed toward achieving the research goals set in the proposal. The selected site and the field testing plan enabled us to test all three aspects of roof geological features. The development of the data interpretation methodologies and the geology mapping computer program have also been preceding well.

  15. Monolithic-Structured Single-Layered Textile-Based Dye-Sensitized Solar Cells

    Science.gov (United States)

    Yun, Min Ju; Cha, Seung I.; Kim, Han Seong; Seo, Seon Hee; Lee, Dong Y.

    2016-10-01

    Textile-structured solar cells are frequently discussed in the literature due to their prospective applications in wearable devices and in building integrated solar cells that utilize their flexibility, mechanical robustness, and aesthetic appearance, but the current approaches for textile-based solar cells—including the preparation of fibre-type solar cells woven into textiles—face several difficulties from high friction and tension during the weaving process. This study proposes a new structural concept and fabrication process for monolithic-structured textile-based dye-sensitized solar cells that are fabricated by a process similar to the cloth-making process, including the preparation of wires and yarns that are woven for use in textiles, printed, dyed, and packaged. The fabricated single-layered textile-based dye-sensitized solar cells successfully act as solar cells in our study, even under bending conditions. By controlling the inter-weft spacing and the number of Ti wires for the photoelectrode conductor, we have found that the performance of this type of dye-sensitized solar cell was notably affected by the spacing between photoelectrodes and counter-electrodes, the exposed areas of Ti wires to photoelectrodes, and photoelectrodes’ surface morphology. We believe that this study provides a process and concept for improved textile-based solar cells that can form the basis for further research.

  16. Field electron emission characteristics and physical mechanism of individual single-layer graphene.

    Science.gov (United States)

    Xiao, Zhiming; She, Juncong; Deng, Shaozhi; Tang, Zikang; Li, Zhibing; Lu, Jianming; Xu, Ningsheng

    2010-11-23

    Due to its difficulty, experimental measurement of field emission from a single-layer graphene has not been reported, although field emission from a two-dimensional (2D) regime has been an attractive topic. The open surface and sharp edge of graphene are beneficial for field electron emission. A 2D geometrical effect, such as massless Dirac fermion, can lead to new mechanisms in field emission. Here, we report our findings from in situ field electron emission characterization on an individual singe-layer graphene and the understanding of the related mechanism. The measurement of field emission from the edges was done using a microanode probe equipped in a scanning electron microscope. We show that repeatable stable field emission current can be obtained after a careful conditioning process. This enables us to examine experimentally the typical features of the field emission from a 2D regime. We plot current versus applied field data, respectively, in ln(I/E(3/2)) ∼ 1/E and ln(I/E(3)) ∼ 1/E(2) coordinates, which have recently been proposed for field emission from graphene in high- and low-field regimes. It is observed that the plots all exhibit an upward bending feature, revealing that the field emission processes undergo from a low- to high-field transition. We discuss with theoretical analysis the physical mechanism responsible for the new phenomena.

  17. Pregnancy rates after artificial insemination with cooled stallion spermatozoa either with or without single layer centrifugation.

    Science.gov (United States)

    Morrell, J M; Richter, J; Martinsson, G; Stuhtmann, G; Hoogewijs, M; Roels, K; Dalin, A-M

    2014-11-01

    A successful outcome after artificial insemination with cooled semen is dependent on many factors, the sperm quality of the ejaculate being one. Previous studies have shown that spermatozoa with good motility, normal morphology, and good chromatin integrity can be selected by means of colloid centrifugation, particularly single layer centrifugation (SLC) using species-specific colloids. The purpose of the present study was to conduct an insemination trial with spermatozoa from "normal" ejaculates, i.e., from stallions with no known fertility problem, to determine whether the improvements in sperm quality seen in SLC-selected sperm samples compared with uncentrifuged controls in laboratory tests are reflected in an increased pregnancy rate after artificial insemination. In a multicentre study, SLC-selected sperm samples and uncentrifuged controls from eight stallions were inseminated into approximately 10 mares per treatment per stallion. Ultrasound examination was carried out approximately 16 days after insemination to detect an embryonic vesicle. The pregnancy rates per cycle were 45% for controls and 69% for SLC-selected sperm samples, which is statistically significant (P < 0.0018). Thus, the improvement in sperm quality reported previously for SLC-selected sperm samples is associated with an increase in pregnancy rate, even for ejaculates from stallions with no known fertility problem. Copyright © 2014 Elsevier Inc. All rights reserved.

  18. Monolithic-Structured Single-Layered Textile-Based Dye-Sensitized Solar Cells

    Science.gov (United States)

    Yun, Min Ju; Cha, Seung I.; Kim, Han Seong; Seo, Seon Hee; Lee, Dong Y.

    2016-01-01

    Textile-structured solar cells are frequently discussed in the literature due to their prospective applications in wearable devices and in building integrated solar cells that utilize their flexibility, mechanical robustness, and aesthetic appearance, but the current approaches for textile-based solar cells—including the preparation of fibre-type solar cells woven into textiles—face several difficulties from high friction and tension during the weaving process. This study proposes a new structural concept and fabrication process for monolithic-structured textile-based dye-sensitized solar cells that are fabricated by a process similar to the cloth-making process, including the preparation of wires and yarns that are woven for use in textiles, printed, dyed, and packaged. The fabricated single-layered textile-based dye-sensitized solar cells successfully act as solar cells in our study, even under bending conditions. By controlling the inter-weft spacing and the number of Ti wires for the photoelectrode conductor, we have found that the performance of this type of dye-sensitized solar cell was notably affected by the spacing between photoelectrodes and counter-electrodes, the exposed areas of Ti wires to photoelectrodes, and photoelectrodes’ surface morphology. We believe that this study provides a process and concept for improved textile-based solar cells that can form the basis for further research. PMID:27708359

  19. Investigating change of properties in gallium ion irradiation patterned single-layer graphene

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Quan, E-mail: wangq@mail.ujs.edu.cn [School of Mechanical Engineering, Jiangsu University, Zhenjiang 212013 (China); Key Laboratory of Nanodevices and Applications, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences (China); Dong, Jinyao; Bai, Bing [School of Mechanical Engineering, Jiangsu University, Zhenjiang 212013 (China); Xie, Guoxin [State Key Laboratory of Tribology, Tsinghua University, Beijing 100084 (China)

    2016-10-14

    Besides its excellent physical properties, graphene promises to play a significant role in electronics with superior properties, which requires patterning of graphene for device integration. Here, we presented the changes in properties of single-layer graphene before and after patterning using gallium ion beam. Combined with Raman spectra of graphene, the scanning capacitance microscopy (SCM) image confirmed that a metal–insulator transition occurred after large doses of gallium ion irradiation. The changes in work function and Raman spectra of graphene indicated that the defect density increased as increasing the dose and a structural transition occurred during gallium ion irradiation. The patterning width of graphene presented an increasing trend due to the scattering influence of the impurities and the substrate. - Highlights: • The scanning capacitance microscopy image confirmed a metal–insulator transition occurred after large doses of gallium ion irradiation. • The changes indicated the defect density increased as increasing the dose and a structural transition occurred during gallium ion irradiation. • The patterning width of graphene presented a increasing trend due to the scattering influence of the impurities and the substrate.

  20. First-principles study of single-layer C-terminated BN quantum dots

    Science.gov (United States)

    Qu, Li-Hua; Zhang, Jian-Min; Xu, Ke-Wei

    2013-09-01

    We present a first-principles study of the structural, electronic and magnetic properties of single-layer C-terminated BN quantum dots (QDs) under different hydrotreating conditions. The morphologies of QDs with fully hydrogenated edges change slightly. For the fully bared cases, the edged C-C bonds become short and protrudent edged C atoms relax inwards therefore edged zigzag C chain tends to a straight line. The cases of the partially passivated by hydrogen atom at apex, the apex C atom is not relaxed inwards and a new C-C bond is formed. The fully hydrogenated QDs especially N-rich cases are energetically more favorable than those with bared or partially hydrogenated ones. The C-terminated BN-QDs have no magnetic moment when their protrudent edged C atoms are fully passivated by hydrogen atoms, while those with bared or partially hydrogenated edges possess magnetic moments and especially for N-rich cases their magnetic moments increase with increasing QD size n for either bared or partially hydrogenated edges. The band gap of the fully hydrogenated QDs decreases oscillatorily with increasing QD size n. Moreover, for the same size n, the energy gap is wider under N-rich condition than under B-rich condition.

  1. A single-layer, planar, optofluidic Mach–Zehnder interferometer for label-free detection†

    Science.gov (United States)

    Lapsley, Michael Ian; Chiang, I.-Kao; Zheng, Yue Bing; Ding, Xiaoyun; Mao, Xiaole

    2014-01-01

    We have developed a planar, optofluidic Mach–Zehnder interferometer for the label-free detection of liquid samples. In contrast to most on-chip interferometers which require complex fabrication, our design was realized via a simple, single-layer soft lithography fabrication process. In addition, a single-wavelength laser source and a silicon photodetector were the only optical equipment used for data collection. The device was calibrated using published data for the refractive index of calcium chloride (CaCl2) in solution, and the biosensing capabilities of the device were tested by detecting bovine serum albumin (BSA). Our design enables a refractometer with a low limit of detection (1.24 × 10−4 refractive index units (RIU)), low variability (1 × 10−4 RIU), and high sensitivity (927.88 oscillations per RIU). This performance is comparable to state-of-the-art optofluidic refractometers that involve complex fabrication processes and/or expensive, bulky optics. The advantages of our device (i.e. simple fabrication process, straightforward optical equipment, low cost, and high detection sensitivity) make it a promising candidate for future mass-producible, inexpensive, highly sensitive, label-free optical detection systems. PMID:21479332

  2. A single-layer, planar, optofluidic Mach-Zehnder interferometer for label-free detection.

    Science.gov (United States)

    Lapsley, Michael Ian; Chiang, I-Kao; Zheng, Yue Bing; Ding, Xiaoyun; Mao, Xiaole; Huang, Tony Jun

    2011-05-21

    We have developed a planar, optofluidic Mach-Zehnder interferometer for the label-free detection of liquid samples. In contrast to most on-chip interferometers which require complex fabrication, our design was realized via a simple, single-layer soft lithography fabrication process. In addition, a single-wavelength laser source and a silicon photodetector were the only optical equipment used for data collection. The device was calibrated using published data for the refractive index of calcium chloride (CaCl(2)) in solution, and the biosensing capabilities of the device were tested by detecting bovine serum albumin (BSA). Our design enables a refractometer with a low limit of detection (1.24 × 10(-4) refractive index units (RIU)), low variability (1 × 10(-4) RIU), and high sensitivity (927.88 oscillations per RIU). This performance is comparable to state-of-the-art optofluidic refractometers that involve complex fabrication processes and/or expensive, bulky optics. The advantages of our device (i.e. simple fabrication process, straightforward optical equipment, low cost, and high detection sensitivity) make it a promising candidate for future mass-producible, inexpensive, highly sensitive, label-free optical detection systems. © The Royal Society of Chemistry 2011

  3. Broadband photodetector based on carbon nanotube thin film/single layer graphene Schottky junction

    Science.gov (United States)

    Zhang, Teng-Fei; Li, Zhi-Peng; Wang, Jiu-Zhen; Kong, Wei-Yu; Wu, Guo-An; Zheng, Yu-Zhen; Zhao, Yuan-Wei; Yao, En-Xu; Zhuang, Nai-Xi; Luo, Lin-Bao

    2016-12-01

    In this study, we present a broadband nano-photodetector based on single-layer graphene (SLG)-carbon nanotube thin film (CNTF) Schottky junction. It was found that the as-fabricated device exhibited obvious sensitivity to a wide range of illumination, with peak sensitivity at 600 and 920 nm. In addition, the SLG-CNTF device had a fast response speed (τr = 68 μs, τf = 78 μs) and good reproducibility in a wide range of switching frequencies (50-5400 Hz). The on-off ratio, responsivity, and detectivity of the device were estimated to be 1 × 102, 209 mAW-1 and 4.87 × 1010 cm Hz1/2 W-1, respectively. What is more, other device parameters including linear performance θ and linear dynamic range (LDR) were calculated to be 0.99 and 58.8 dB, respectively, which were relatively better than other carbon nanotube based devices. The totality of the above study signifies that the present SLG-CNTF Schottky junction broadband nano-photodetector may have promising application in future nano-optoelectronic devices and systems.

  4. Adhesion and migration of CHO cells on micropatterned single layer graphene

    Science.gov (United States)

    Keshavan, S.; Oropesa-Nuñez, R.; Diaspro, A.; Canale, C.; Dante, S.

    2017-06-01

    Cell patterning technology on single layer graphene (SLG) is a fairly new field that can find applications in tissue engineering and biomaterial/biosensors development. Recently, we have developed a simple and effective approach for the fabrication of patterned SLG substrates by laser micromachining, and we have successfully applied it for the obtainment of geometrically ordered neural networks. Here, we exploit the same approach to investigate the generalization of the cell response to the surface cues of the fabricated substrates and, contextually, to quantify cell adhesion on the different areas of the patterns. To attain this goal, we tested Chinese hamster ovary (CHO) cells on PDL-coated micropatterned SLG substrates and quantified the adhesion by using single cell force spectroscopy (SCFS). Our results indicate higher cell adhesion on PDL-SLG, and, consequently, an initial CHO cell accumulation on the graphene areas, confirming the neuronal behaviour observed previously; interestingly, at later time point in culture, cell migration was observed towards the adjacent SLG ablated regions, which resulted more favourable for cell proliferation. Therefore, our findings indicate that the mechanism of interaction with the surface cues offered by the micropatterned substrates is strictly cell-type dependent.

  5. Compact Single-Layer Traveling-Wave Antenna DesignUsing Metamaterial Transmission Lines

    Science.gov (United States)

    Alibakhshikenari, Mohammad; Virdee, Bal Singh; Limiti, Ernesto

    2017-12-01

    This paper presents a single-layer traveling-wave antenna (TWA) that is based on composite right/left-handed (CRLH)-metamaterial (MTM) transmission line (TL) structure, which is implemented by using a combination of interdigital capacitors and dual-spiral inductive slots. By embedding dual-spiral inductive slots inside the CRLH MTM-TL results in a compact TWA. Dimensions of the proposed CRLH MTM-TL TWA is 21.5 × 30.0 mm2 or 0.372λ0 × 0.520λ0 at 5.2 GHz (center frequency). The fabricated TWA operates over 1.8-8.6 GHz with a fractional bandwidth greater than 120%, and it exhibits a peak gain and radiation efficiency of 4.2 dBi and 81%, respectively, at 5 GHz. By avoiding the use of lumped components, via-holes or defected ground structures, the proposed TWA design is economic for mass production as well as easy to integrate with wireless communication systems.

  6. Substitutional impurity in single-layer graphene: The Koster–Slater and Anderson models

    Energy Technology Data Exchange (ETDEWEB)

    Davydov, S. Yu., E-mail: sergei-davydov@mail.ru [Russian Academy of Sciences, Ioffe Physical–Technical Institute (Russian Federation)

    2016-06-15

    The Koster–Slater and Anderson models are used to consider substitutional impurities in free-standing single-layer graphene. The density of states of graphene is described using a model (the M model). For the nitrogen and boron impurities, the occupation numbers and the parameter η which defines the fraction of delocalized electrons of the impurity are determined. In this case, experimental data are used for both determination of the model parameters and comparison with the results of theoretical estimations. The general features of the Koster–Slater and Anderson models and the differences between the two models are discussed. Specifically, it is shown that the band contributions to the occupation numbers of a nitrogen atom in both models are comparable, whereas the local contributions are substantially different: the local contributions are decisive in the Koster–Slater model and negligible in the Anderson model. The asymptotic behavior of the wave functions of a defect is considered in the Koster–Slater model, and the electron states of impurity dimers are considered in the Anderson model.

  7. Determination of band offsets at GaN/single-layer MoS2 heterojunction

    KAUST Repository

    Tangi, Malleswararao

    2016-07-25

    We report the band alignment parameters of the GaN/single-layer (SL) MoS2 heterostructure where the GaN thin layer is grown by molecular beam epitaxy on CVD deposited SL-MoS2/c-sapphire. We confirm that the MoS2 is an SL by measuring the separation and position of room temperature micro-Raman E1 2g and A1 g modes, absorbance, and micro-photoluminescence bandgap studies. This is in good agreement with HRTEM cross-sectional analysis. The determination of band offset parameters at the GaN/SL-MoS2 heterojunction is carried out by high-resolution X-ray photoelectron spectroscopy accompanying with electronic bandgap values of SL-MoS2 and GaN. The valence band and conduction band offset values are, respectively, measured to be 1.86 ± 0.08 and 0.56 ± 0.1 eV with type II band alignment. The determination of these unprecedented band offset parameters opens up a way to integrate 3D group III nitride materials with 2D transition metal dichalcogenide layers for designing and modeling of their heterojunction based electronic and photonic devices.

  8. Single Layer Bismuth Iodide: Computational Exploration of Structural, Electrical, Mechanical and Optical Properties

    Science.gov (United States)

    Ma, Fengxian; Zhou, Mei; Jiao, Yalong; Gao, Guoping; Gu, Yuantong; Bilic, Ante; Chen, Zhongfang; Du, Aijun

    2015-12-01

    Layered graphitic materials exhibit new intriguing electronic structure and the search for new types of two-dimensional (2D) monolayer is of importance for the fabrication of next generation miniature electronic and optoelectronic devices. By means of density functional theory (DFT) computations, we investigated in detail the structural, electronic, mechanical and optical properties of the single-layer bismuth iodide (BiI3) nanosheet. Monolayer BiI3 is dynamically stable as confirmed by the computed phonon spectrum. The cleavage energy (Ecl) and interlayer coupling strength of bulk BiI3 are comparable to the experimental values of graphite, which indicates that the exfoliation of BiI3 is highly feasible. The obtained stress-strain curve shows that the BiI3 nanosheet is a brittle material with a breaking strain of 13%. The BiI3 monolayer has an indirect band gap of 1.57 eV with spin orbit coupling (SOC), indicating its potential application for solar cells. Furthermore, the band gap of BiI3 monolayer can be modulated by biaxial strain. Most interestingly, interfacing electrically active graphene with monolayer BiI3 nanosheet leads to enhanced light absorption compared to that in pure monolayer BiI3 nanosheet, highlighting its great potential applications in photonics and photovoltaic solar cells.

  9. Investigating change of properties in gallium ion irradiation patterned single-layer graphene

    International Nuclear Information System (INIS)

    Wang, Quan; Dong, Jinyao; Bai, Bing; Xie, Guoxin

    2016-01-01

    Besides its excellent physical properties, graphene promises to play a significant role in electronics with superior properties, which requires patterning of graphene for device integration. Here, we presented the changes in properties of single-layer graphene before and after patterning using gallium ion beam. Combined with Raman spectra of graphene, the scanning capacitance microscopy (SCM) image confirmed that a metal–insulator transition occurred after large doses of gallium ion irradiation. The changes in work function and Raman spectra of graphene indicated that the defect density increased as increasing the dose and a structural transition occurred during gallium ion irradiation. The patterning width of graphene presented an increasing trend due to the scattering influence of the impurities and the substrate. - Highlights: • The scanning capacitance microscopy image confirmed a metal–insulator transition occurred after large doses of gallium ion irradiation. • The changes indicated the defect density increased as increasing the dose and a structural transition occurred during gallium ion irradiation. • The patterning width of graphene presented a increasing trend due to the scattering influence of the impurities and the substrate.

  10. Two-band induced superconductivity in single-layer graphene and topological insulator bismuth selenide

    Science.gov (United States)

    Talantsev, E. F.; Crump, W. P.; Tallon, J. L.

    2018-01-01

    Proximity-induced superconductivity in single-layer graphene (SLG) and in topological insulators represent almost ideal examples of superconductivity in two dimensions. Fundamental mechanisms governing superconductivity in the 2D limit are of central interest for modern condensed-matter physics. To deduce fundamental parameters of superconductor/graphene/superconductor and superconductor/bismuth selenide/superconductor junctions we investigate the self-field critical currents in these devices using the formalism of the Ambegaokar–Baratoff model. Our central finding is that the induced superconducting state in SLG and bismuth selenide each exhibits gapping on two superconducting bands. Based on recent results obtained on ultra-thin films of natural superconductors, including single-atomic layer of iron selenide, double and triple atomic layers of gallium, and several atomic layer tantalum disulphide, we conclude that a two-band induced superconducting state in SLG and bismuth selenide is part of a wider, more general multiple-band phenomenology of currently unknown origin.

  11. Band Alignment at GaN/Single-Layer WSe2 Interface

    KAUST Repository

    Tangi, Malleswararao

    2017-02-21

    We study the band discontinuity at the GaN/single-layer (SL) WSe2 heterointerface. The GaN thin layer is epitaxially grown by molecular beam epitaxy on chemically vapor deposited SL-WSe2/c-sapphire. We confirm that the WSe2 was formed as an SL from structural and optical analyses using atomic force microscopy, scanning transmission electron microscopy, micro-Raman, absorbance, and microphotoluminescence spectra. The determination of band offset parameters at the GaN/SL-WSe2 heterojunction is obtained by high-resolution X-ray photoelectron spectroscopy, electron affinities, and the electronic bandgap values of SL-WSe2 and GaN. The valence band and conduction band offset values are determined to be 2.25 ± 0.15 and 0.80 ± 0.15 eV, respectively, with type II band alignment. The band alignment parameters determined here provide a route toward the integration of group III nitride semiconducting materials with transition metal dichalcogenides (TMDs) for designing and modeling of their heterojunction-based electronic and optoelectronic devices.

  12. A single-layer tilting actuator with multiple close-gap electrodes

    International Nuclear Information System (INIS)

    Shmilovich, T; Krylov, S

    2009-01-01

    We report on the design, fabrication and characterization of a novel tilting electrostatic actuator, fabricated by using a single layer of a silicon on insulator (SOI) wafer and investigate, both theoretically and experimentally, the electromechanical behavior of the device. The actuator incorporates high aspect ratio comb-like electrodes oriented in the direction parallel to the rotation axis of the tilting element. An increase in the tilting angle is accompanied by a decrease in the distance between the electrodes and by an increase of the actuating torque. Simultaneously, the overlap area between electrodes located farther apart the axis shrinks, resulting in a 'restoring' torque in the opposite direction. The electromechanical behavior and stability of the device were investigated using a simplified model of the actuator and verified by a coupled three-dimensional simulation. Model results suggest that by changing the design parameters, the actuator characteristic can be tailored in a large range. Devices of three different configurations incorporating elastic torsion axes or bending flexures were fabricated and characterized and both static and resonant responses, typical for parametrically excited nonlinear oscillators, were registered. Theoretical and experimental results indicate that the suggested architecture can be efficiently used for the static and dynamic operation of electrostatic tilting devices

  13. Single-layer tungsten oxide as intelligent photo-responsive nanoagents for permanent male sterilization.

    Science.gov (United States)

    Liu, Zhen; Liu, Xianjun; Ran, Xiang; Ju, Enguo; Ren, Jinsong; Qu, Xiaogang

    2015-11-01

    Permanent male sterilization has been recognized as useful tools for the development of neuter experimental animals and fattening livestock, as well as efficient control of pet overpopulation. Traditional routes such as surgical ways, chemical injections, and anti-fertility vaccines have addressed these crucial problems with idea outcomes. However, these routes usually bring out serious pain and infection towards animals, as well as induce long-term adverse reaction and immune suppression. Thus, a convenient, but non-surgical strategy for male sterilization under a mild manner is highly desirable. Here, for the first time, we demonstrate a novel platform for male sterilization by using single-layer WO2.72 nanosheets as smart photo-responsive sterilants. Upon a 980 nm irradiation, these nanoagents can possess intrinsic NIR-induced hyperthermia and sensitize the formation of singlet oxygen due to the cooperation of photothermal and photodynamic effects. Mechanism of cellular injury can be attributed to the denaturation of protein and apoptosis-related death. Moreover, long-term toxicity and possible metabolism route after testicular injection are discussed, indicating the neglectable systemic toxicity and high bio-compatibility of our nanoagents. Overall, our strategy can extremely overcome the shortcomings in various routine routes and suggest the new biological application of nanomaterials. Copyright © 2015 Elsevier Ltd. All rights reserved.

  14. Unexpected strong magnetism of Cu doped single-layer MoS₂ and its origin.

    Science.gov (United States)

    Yun, Won Seok; Lee, J D

    2014-05-21

    The magnetism of the 3d transition-metal (TM) doped single-layer (1L) MoS2, where the Mo atom is partially replaced by the 3d TM atom, is investigated using the first-principles density functional calculations. In a series of 3d TM doped 1L-MoS2's, the induced spin polarizations are negligible for Sc, Ti, and Cr dopings, while the induced spin polarizations are confirmed for V, Mn, Fe, Co, Ni, Cu, and Zn dopings and the systems become magnetic. Especially, the Cu doped system shows unexpectedly strong magnetism although Cu is nonmagnetic in its bulk state. The driving force is found to be a strong hybridization between Cu 3d states and 3p states of neighboring S, which results in an extreme unbalanced spin-population in the spin-split impurity bands near the Fermi level. Finally, we also discuss further issues of the Cu induced magnetism of 1L-MoS2 such as investigation of additional charge states, the Cu doping at the S site instead of the Mo site, and the Cu adatom on the layer (i.e., 1L-MoS2).

  15. Engineering of electronic properties of single layer graphene by swift heavy ion irradiation

    Science.gov (United States)

    Kumar, Sunil; Kumar, Ashish; Tripathi, Ambuj; Tyagi, Chetna; Avasthi, D. K.

    2018-04-01

    In this work, swift heavy ion irradiation induced effects on the electrical properties of single layer graphene are reported. The modulation in minimum conductivity point in graphene with in-situ electrical measurement during ion irradiation was studied. It is found that the resistance of graphene layer decreases at lower fluences up to 3 × 1011 ions/cm2, which is accompanied by the five-fold increase in electron and hole mobilities. The ion irradiation induced increase in electron and hole mobilities at lower fluence up to 1 × 1011 ions/cm2 is verified by separate Hall measurements on another irradiated graphene sample at the selected fluence. In contrast to the adverse effects of irradiation on the electrical properties of materials, we have found improvement in electrical mobility after irradiation. The increment in mobility is explained by considering the defect annealing in graphene after irradiation at a lower fluence regime. The modification in carrier density after irradiation is also observed. Based on findings of the present work, we suggest ion beam irradiation as a useful tool for tuning of the electrical properties of graphene.

  16. Single track and single layer formation in selective laser melting of niobium solid solution alloy

    Directory of Open Access Journals (Sweden)

    Yueling GUO

    2018-04-01

    Full Text Available Selective laser melting (SLM was employed to fabricate Nb-37Ti-13Cr-2Al-1Si (at% alloy, using pre-alloyed powders prepared by plasma rotating electrode processing (PREP. A series of single tracks and single layers under different processing parameters was manufactured to evaluate the processing feasibility by SLM, including laser power, scanning speed, and hatch distance. Results showed that continuous single tracks could be fabricated using proper laser powers and scanning velocities. Both the width of a single track and its penetration depth into a substrate increased with an increase of the linear laser beam energy density (LED, i.e., an increase of the laser power and a decrease of the scanning speed. Nb, Ti, Si, Cr, and Al elements distributed heterogeneously over the melt pool in the form of swirl-like patterns. An excess of the hatch distance was not able to interconnect neighboring tracks. Under improper processing parameters, a balling phenomenon occurred, but could be eliminated with an increased LED. This work testified the SLM-processing feasibility of Nb-based alloy and promoted the application of SLM to the manufacture of niobium-based alloys. Keywords: Additive manufacturing, Melt pool, Niobium alloy, Powder metallurgy, Selective laser melting

  17. Abrupt change of luminescence spectrum in single-layer phosphorescent polymer light emitting diode

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, X.; Lee, D.-H.; Chae, H. [School of Chemical Engineering, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of); Cho, S.M., E-mail: sungmcho@skku.edu [School of Chemical Engineering, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of); Advanced Materials and Process Research Center for IT, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of)

    2012-01-15

    PVK-based single-layer phosphorescent polymer OLEDs (organic light emitting diodes) with different rubrene concentrations were fabricated and examined for the Foerster energy transfer from phosphorescent FIrpic dye to rubrene. We found out that at a certain rubrene concentration the energy transfer occurs abruptly and the transfer shows an abnormal evolution of electroluminescence (EL) spectrum due to the coincidence of peak wavelengths of bis[(4,6-difluorophenyl)-pyridinato-N,C{sup 2'}](picolinate) iridium(III) (FIrpic) emission and 5,6,11,12-tetraphenylnaphthacene (rubrene) absorption. With the calculation of Foerster radius and average distance between FIrpic molecules, we have related the calculated ratio between the number of FIrpic molecules within to that out of Foerster radius with the degree of Foerster energy transfer from EL spectra measured in the experiment. Experimental results were found to fit well with the predicted results especially at low rubrene concentrations. - Highlights: > Foerster energy transfer between FIrpic and rubrene. > Energy transfer shows an abnormal evolution of emission spectrum. > Calculated Foerster radius and degree of energy transfer by a simple model.

  18. A single-layer peptide nanofiber for enhancing the cytotoxicity of trastuzumab (anti-HER)

    Energy Technology Data Exchange (ETDEWEB)

    Malik, Ruchi; Wagh, Anil; Qian, Steven; Law, Benedict, E-mail: Shek.law@ndsu.edu [College of Pharmacy, Nursing, and Allied Sciences, North Dakota State University, Department of Pharmaceutical Sciences (United States)

    2013-06-15

    A multivalent system is often employed to enhance the effectiveness of a targeted therapy. In the present study, we report a single-layer peptide nanofiber (NFP) as a multivalent targeting platform to improve the cytotoxicity of trastuzumab (anti-HER), a monoclonal antibody targeting the human epidermal growth factor receptor 2 (HER-2) in approximately 20 % of breast cancer patients. The trastuzumab-conjugated nanofiber (anti-HER/NFP) was 100 Multiplication-Sign 4 nm in size and was assembled from multiple peptide units (mPEG-BK(FITC)SGASNRA-kldlkldlkldl-CONH{sub 2}). The optimized preparation was attached with approximately 10 antibodies at the surface. Because of an increase in the multivalency, anti-HER/NFP was able to truncate more cell surface HER-2 and, thus, showed an enhanced cytotoxicity toward HER-2 positive SKBr-3 human breast cancer as compared to the free anti-HER. Western blot analysis and fluorescence microscopic studies confirmed that there was a significant downregulation of the HER-2 level and also inhibition of the cell survival cell signaling pathways including the phosphatidylinositol 3-kinase (PI3K) and the mitogen activated protein kinase (MAPK) pathway. Our data suggested that NFP can be useful as a multivalent platform for immunotherapy, especially in combination with other chemotherapeutic agents in the future.

  19. The Stability of New Single-Layer Combined Lattice Shell Based on Aluminum Alloy Honeycomb Panels

    Directory of Open Access Journals (Sweden)

    Caiqi Zhao

    2017-11-01

    Full Text Available This article proposes a new type of single-layer combined lattice shell (NSCLS; which is based on aluminum alloy honeycomb panels. Six models with initial geometric defect were designed and precision made using numerical control equipment. The stability of these models was tested. The results showed that the stable bearing capacity of NSCLS was approximately 16% higher than that of a lattice shell with the same span without a reinforcing plate. At the same time; the properties of the NSCLS were sensitive to defects. When defects were present; its stable bearing capacity was decreased by 12.3% when compared with the defect-free model. The model with random defects following a truncated Gaussian distribution could be used to simulate the distribution of defects in the NSCLS. The average difference between the results of the nonlinear analysis and the experimental results was 5.7%. By calculating and analyzing nearly 20,000 NSCLS; the suggested values of initial geometric defect were presented. The results of this paper could provide a theoretical basis for making and revising the design codes for this new combined lattice shell structure.

  20. Effect of cushioned or single layer semen centrifugation before sex sorting on frozen stallion semen quality.

    Science.gov (United States)

    Mari, G; Bucci, D; Love, C C; Mislei, B; Rizzato, G; Giaretta, E; Merlo, B; Spinaci, M

    2015-04-01

    The aim of this study was to compare the effect of presorting centrifugation (cushioned [CC] or single-layer colloid [SLC]), with simple dilution (SD), on the quality of sex-sorted stallion semen before and after sorting and after freezing and thawing. Four ejaculates from each of two fertile stallions were collected 1 week apart and evaluated for percent total sperm motility (TM), percent viable acrosome-intact sperm (VAI), and DNA quality (percentage of DNA fragmentation index). Freezing caused, independently from CC and SLC treatments, a significant decrease of TM (P < 0.05) and VAI (P < 0.05) in both unsorted and sorted semen. On the other hand, sorting did not impair TM and VAI and, interestingly, improved DNA quality in all treatments only before freezing (28 vs 13, 28 vs 10, 22 vs 7 in SD, CC, and SLC for unsorted vs sorted groups, respectively; P < 0.05); this positive effect was lost in the same samples after freezing and thawing, suggesting that the freezing process reduces the DNA quality of sex-sorted sperm. Our results suggest that CC and SLC are not able to select those spermatozoa that possess a better ability to withstand sperm processing associated with sperm sorting and freezing. Copyright © 2015 Elsevier Inc. All rights reserved.

  1. Single layer centrifugation-selected boar spermatozoa are capable of fertilization in vitro

    Science.gov (United States)

    2013-01-01

    Background Good quality spermatozoa are important to achieve fertilization, viable embryos and offspring. Single Layer Centrifugation (SLC) through a colloid (Androcoll-P) selects good quality spermatozoa. However, it has not been established previously whether porcine spermatozoa selected by this method maintain their fertility. Methods The semen was prepared either by SLC or by standard centrifugation (control) and used for in vitro fertilization (IVF) at oocyte:spermatozoa ratios of 1:50; 1:100 and 1:300 (or 4 x 103, 8 x 103 and 24 x 103 spermatozoa/ml) to evaluate their subsequent ability to generate blastocysts. In addition, sperm motility was assessed by computer assisted sperm motility analysis. Results Total and progressive motility were significantly higher in sperm samples prepared by SLC compared to uncentrifuged samples. Sperm binding ability, polyspermy, cleavage and blastocyst rates were affected by the oocyte:sperm ratio, but not by sperm treatment. Conclusion The use of SLC does not adversely affect the in vitro fertilizing and embryo-generating ability of the selected spermatozoa compared to their unselected counterparts, but further modifications in the IVF conditions would be needed to improve the monospermy in IVF systems. Since SLC did not appear to have a negative effect on sperm fertilizing ability, and may in fact select for spermatozoa with a greater potential for fertilization, an in vivo trial to determine the usefulness of this sperm preparation technique prior to artificial insemination is warranted. PMID:23497680

  2. Local Electronic Structure of a Single-Layer Porphyrin-Containing Covalent Organic Framework

    KAUST Repository

    Chen, Chen

    2017-12-20

    We have characterized the local electronic structure of a porphyrin-containing single-layer covalent organic framework (COF) exhibiting a square lattice. The COF monolayer was obtained by the deposition of 2,5-dimethoxybenzene-1,4-dicarboxaldehyde (DMA) and 5,10,15,20-tetrakis(4-aminophenyl) porphyrin (TAPP) onto a Au(111) surface in ultrahigh vacuum followed by annealing to facilitate Schiff-base condensations between monomers. Scanning tunneling spectroscopy (STS) experiments conducted on isolated TAPP precursor molecules and the covalently linked COF networks yield similar transport (HOMO-LUMO) gaps of 1.85 ± 0.05 eV and 1.98 ± 0.04 eV, respectively. The COF orbital energy alignment, however, undergoes a significant downward shift compared to isolated TAPP molecules due to the electron-withdrawing nature of the imine bond formed during COF synthesis. Direct imaging of the COF local density of states (LDOS) via dI/dV mapping reveals that the COF HOMO and LUMO states are localized mainly on the porphyrin cores and that the HOMO displays reduced symmetry. DFT calculations reproduce the imine-induced negative shift in orbital energies and reveal that the origin of the reduced COF wave function symmetry is a saddle-like structure adopted by the porphyrin macrocycle due to its interactions with the Au(111) substrate.

  3. Performance assessment of a single-layer moisture store-and-release cover system at a mine waste rock pile in a seasonally humid region (Nova Scotia, Canada).

    Science.gov (United States)

    Power, Christopher; Ramasamy, Murugan; Mkandawire, Martin

    2018-03-03

    Cover systems are commonly applied to mine waste rock piles (WRPs) to control acid mine drainage (AMD). Single-layer covers utilize the moisture "store-and-release" concept to first store and then release moisture back to the atmosphere via evapotranspiration. Although more commonly used in semi-arid and arid climates, store-and-release covers remain an attractive option in humid climates due to the low cost and relative simplicity of installation. However, knowledge of their performance in these climates is limited. The objective of this study was to assess the performance of moisture store-and-release covers at full-scale WRPs located in humid climates. This cover type was installed at a WRP in Nova Scotia, Canada, alongside state-of-the-art monitoring instrumentation. Field monitoring was conducted over 5 years to assess key components such as meteorological conditions, cover material water dynamics, net percolation, surface runoff, pore-gas, environmental receptor water quality, landform stability and vegetation. Water balances indicate small reductions in water influx to the waste rock (i.e., 34 to 28% of precipitation) with the diminished AMD release also apparent by small improvements in groundwater quality (increase in pH, decrease in sulfate/metals). Surface water quality analysis and field observations of vegetative/aquatic life demonstrate significant improvements in the surface water receptor. The WRP landform is stable and the vegetative cover is thriving. This study has shown that while a simple store-and-release cover may not be a highly effective barrier to water infiltration in humid climates, it can be used to (i) eliminate contaminated surface water runoff, (ii) minimize AMD impacts to surface water receptor(s), (iii) maintain a stable landform, and (iv) provide a sustainable vegetative canopy.

  4. Hydrological performance of dual-substrate-layer green roofs using porous inert substrates with high sorption capacities.

    Science.gov (United States)

    Wang, Xiaoou; Tian, Yimei; Zhao, Xinhua; Peng, Chenrui

    2017-06-01

    Given that the common medium in existing green roofs is a single layer composed of organic and inorganic substrates, seven pilot-scale dual-substrate-layer extensive green roofs (G1-G7), which include nutrition and adsorption substrate layers, were constructed in this study. The effectiveness of porous inert substrates (activated charcoal, zeolite, pumice, lava, vermiculite and expanded perlite) used as the adsorption substrate for stormwater retention was investigated. A single-substrate-layer green roof (G8) was built for comparison with G1-G7. Despite the larger total rainfall depth (mm) of six types of simulated rains (43.2, 54.6, 76.2, 87.0, 85.2 and 86.4, respectively), the total percent retention of G1-G7 varied between 14% and 82% with an average of 43%, exhibiting better runoff-retaining capacity than G8 based on the maximum potential rainfall storage depth per unit height of adsorption substrate. Regression analysis showed that there was a logarithmic relationship between cumulative rainfall depth with non-zero runoff and stormwater retention for G1-G4 and a linear relationship for G5-G8. To enhance the water retention capacity and extend the service life of dual-substrate-layer extensive green roofs, the mixture of activated charcoal and/or pumice with expanded perlite and/or vermiculite is more suitable as the adsorption substrate than the mixture containing lava and/or zeolite.

  5. Integrated roof wind energy system

    Directory of Open Access Journals (Sweden)

    Moonen S.P.G.

    2012-10-01

    Full Text Available Wind is an attractive renewable source of energy. Recent innovations in research and design have reduced to a few alternatives with limited impact on residential construction. Cost effective solutions have been found at larger scale, but storage and delivery of energy to the actual location it is used, remain a critical issue. The Integrated Roof Wind Energy System is designed to overcome the current issues of urban and larger scale renewable energy system. The system is built up by an axial array of skewed shaped funnels that make use of the Venturi Effect to accelerate the wind flow. This inventive use of shape and geometry leads to a converging air capturing inlet to create high wind mass flow and velocity toward a vertical-axis wind turbine in the top of the roof for generation of a relatively high amount of energy. The methods used in this overview of studies include an array of tools from analytical modelling, PIV wind tunnel testing, and CFD simulation studies. The results define the main design parameters for an efficient system, and show the potential for the generation of high amounts of renewable energy with a novel and effective system suited for the built environment.

  6. Sloshing impact in roofed tanks

    International Nuclear Information System (INIS)

    Uras, R.A.

    1995-01-01

    A large number of high-level waste (HLW) storage tanks exists in various tank farms. Seismic activities at those locations may cause significant sloshing in HLW tanks. These tanks are covered to avoid any spilling during large amplitude earthquakes. However, large amplitude sloshing may result in impact on the cover or the roof of the tank. Hence, a better understanding of the impact phenomenon is necessary to assess the safety of the tanks currently in existence, and to establish design guidelines for future designs. A pressure based formulation is derived to model sloshing impact in roofed tanks. It is incorporated into Argonne's in-house finite element code FLUSTR-ANL. A numerical test case with a harmonic input excitation is studied. The simulation results indicate that linear behavior is preserved beyond the first impact, and some mesh distortion is observed following a stronger second impact. During the impact, the displacement of the contacting surface nodes remains constant, and the velocities are reduced to zero. An identification of impacting nodes is possible from the dynamic pressures induced in surface elements

  7. Plasma process-induced latent damage on gate oxide - demonstrated by single-layer and multi-layer antenna structures

    NARCIS (Netherlands)

    Wang, Zhichun; Ackaert, Jan; Salm, Cora; Kuper, F.G.

    2001-01-01

    In this paper, by using both single-layer (SL) and multi-layer (ML) or stacked antenna structures, a simple experimental method is proposed to directly demonstrate the pure plasma process-induced latent damage on gate oxide without any impact of additional defects generated by normal constant

  8. Integral design of active energy roofs

    NARCIS (Netherlands)

    Quanjel, E.M.C.J.

    2006-01-01

    A wide variety of new products, such as photovoltaic (PV) systems and solar collectors, roof lights, ventilation devices, insulation and safety devices, is finding its way into the roofing industry. As a result many problems occurred, resulting in poor quality, unsafe working conditions and high

  9. Do green roofs cool the air?

    NARCIS (Netherlands)

    Solcerova, A.; van de Ven, F.H.M.; Wang, Mengyu; Rijsdijk, Michiel; van de Giesen, N.C.

    2017-01-01

    Rapid urbanization and an increasing number and duration of heat waves poses a need to mitigate extremely high temperatures. One of the repeatedly suggested measures to moderate the so called urban heat island are green roofs. This study investigates several extensive sedum-covered green roofs in

  10. Wind loads on solar energy roofs

    NARCIS (Netherlands)

    Geurts, C.P.W.; Bentum, C.A. van

    2007-01-01

    This paper presents an overview of the wind loads on roofs, equipped with solar energy products, so called Active Roofs. Values given in this paper have been based on wind tunnel and full scale measurements, carried out at TNO, and on an interpretation of existing rules and guidelines. The results

  11. Comparative study of hand sewn single layer anastomosis of dog's bowel Estudo comparativo das anastomoses manuais em plano único do intestino delgado de cães

    OpenAIRE

    João Luiz Moreira Coutinho Azevedo; Octávio Hypólito; Otávio Cansanção Azevedo; Otávio Monteiro Becker Jr.; Dalmer Faria Freire

    2008-01-01

    BACKGROUND: Two-layer intestinal anastomosis increases the inflammatory response while single-layer anastomosis results in a better wound healing. However the four main kinds of stitches which may be chosen in performing single layer intestinal sutures never before had been comparatively studied. AIM: To compare the four more commonly used types of single layer surgical anastomosis sutures of the digestive tract. METHODS: Six mongrel dogs were operated, each one receiving two anastomosis: one...

  12. [Single-layer colonic anastomoses using polyglyconate (Maxon) vs. two-layer anastomoses using chromic catgut and silk. Experimental study].

    Science.gov (United States)

    García-Osogobio, Sandra Minerva; Takahashi-Monroy, Takeshi; Velasco, Liliana; Gaxiola, Miguel; Sotres-Vega, Avelina; Santillán-Doherty, Patricio

    2006-01-01

    The safety of an intestinal anastomosis is usually measured by its complication rate, especially the incidence of anastomotic leakage. A wide variety of methods have been described to reestablish intestinal continuity including single-layer continuous or two-layer interrupted anastomosis. To evaluate if the single-layer continuous anastomosis using polygluconate is safer and reliable than two-layer interrupted anastomosis with chromic catgut and silk. A prospective, experimental, randomized and comparative analysis was conducted in 20 dogs. They were divided in two groups; group 1 underwent two-layer interrupted anastomosis and group 2 underwent sigle-layer continuous technique. Anastomoses were timed. Both groups were under observation. Anastomotic leakage, and other complications were evaluated. The animals were sacrified and the anastomosis was taken out together with 10 cm of colon on both sides of the anastomosis. Breaking strength, histologic evaluation and hydroxyproline determination were performed. Ten two-layer anastomosis and ten single-layer anastomosis were performed. A median of 25 minutes (range: 20-30 minutes) was required to construct the anastomoses in group 1 versus 20 minutes (range: 12-25 minutes) in group 2. All animals survived and no leakage was observed. Wound infection ocurred in four dogs (20%). Median breaking strength was 230 mm Hg in group 1 and 210 mm Hg in group 2. Hydroxyproline concentration was 8.94 mg/g in group 1 (range: 5.33-16.71) and 9.94 mg/g in group 2 (range: 2.96-21.87). There was no difference among groups about the inflammatory response evaluated by pathology. There was no statistical significance in any variable evaluated. CONCLUIONS: This study demonstrates that a single-layer continuous is similar in terms of safety to the two-layer technique, but because of its facility to perform, the single-layer technique could be superior.

  13. Seamless lamination of a concave-convex architecture with single-layer graphene

    Science.gov (United States)

    Park, Ji-Hoon; Lim, Taekyung; Baik, Jaeyoon; Seo, Keumyoung; Moon, Youngkwon; Park, Noejung; Shin, Hyun-Joon; Kyu Kwak, Sang; Ju, Sanghyun; Real Ahn, Joung

    2015-10-01

    Graphene has been used as an electrode and channel material in electronic devices because of its superior physical properties. Recently, electronic devices have changed from a planar to a complicated three-dimensional (3D) geometry to overcome the limitations of planar devices. The evolution of electronic devices requires that graphene be adaptable to a 3D substrate. Here, we demonstrate that chemical-vapor-deposited single-layer graphene can be transferred onto a silicon dioxide substrate with a 3D geometry, such as a concave-convex architecture. A variety of silicon dioxide concave-convex architectures were uniformly and seamlessly laminated with graphene using a thermal treatment. The planar graphene was stretched to cover the concave-convex architecture, and the resulting strain on the curved graphene was spatially resolved by confocal Raman spectroscopy; molecular dynamic simulations were also conducted and supported the observations. Changes in electrical resistivity caused by the spatially varying strain induced as the graphene-silicon dioxide laminate varies dimensionally from 2D to 3D were measured by using a four-point probe. The resistivity measurements suggest that the electrical resistivity can be systematically controlled by the 3D geometry of the graphene-silicon dioxide laminate. This 3D graphene-insulator laminate will broaden the range of graphene applications beyond planar structures to 3D materials.Graphene has been used as an electrode and channel material in electronic devices because of its superior physical properties. Recently, electronic devices have changed from a planar to a complicated three-dimensional (3D) geometry to overcome the limitations of planar devices. The evolution of electronic devices requires that graphene be adaptable to a 3D substrate. Here, we demonstrate that chemical-vapor-deposited single-layer graphene can be transferred onto a silicon dioxide substrate with a 3D geometry, such as a concave-convex architecture. A

  14. Design of a Single-Layer Microchannel for Continuous Sheathless Single-Stream Particle Inertial Focusing.

    Science.gov (United States)

    Zhang, Yan; Zhang, Jun; Tang, Fei; Li, Weihua; Wang, Xiaohao

    2018-02-06

    High-throughput, high-precision single-stream focusing of microparticles has a potentially wide range of applications in biochemical analysis and clinical diagnosis. In this work, we develop a sheathless three-dimensional (3D) particle-focusing method in a single-layer microchannel. This novel microchannel consists of periodic high-aspect-ratio curved channels and straight channels. The proposed method takes advantage of both the curved channels, which induce Dean flow to promote particle migration, and straight channels, which suppress the remaining stirring effects of Dean flow to stabilize the achieved particle focusing. The 3D particle focusing is demonstrated experimentally, and the mechanism is analyzed theoretically. The effects of flow rate, particle size, and cycle number on the focusing performance were also investigated. The experimental results demonstrate that polystyrene particles with diameters of 5-20 μm can be focused into a 3D single file within seven channel cycles, with the focusing accuracy up to 98.5% and focusing rate up to 98.97%. The focusing throughput could reach up to ∼10 5 counts/min. Furthermore, its applicability to biological cells is also demonstrated by 3D focusing of HeLa and melanoma cells and bovine blood cells in the proposed microchannel. The proposed sheathless passive focusing scheme, featuring a simple channel structure, small footprint (9 mm × 1.2 mm), compact layout, and uncomplicated fabrication procedure, holds great promise as an efficient 3D focusing unit for the development of next-generation on-chip flow cytometry.

  15. Determination of the optimized single-layer ionospheric height for electron content measurements over China

    Science.gov (United States)

    Li, Min; Yuan, Yunbin; Zhang, Baocheng; Wang, Ningbo; Li, Zishen; Liu, Xifeng; Zhang, Xiao

    2018-02-01

    The ionosphere effective height (IEH) is a very important parameter in total electron content (TEC) measurements under the widely used single-layer model assumption. To overcome the requirement of a large amount of simultaneous vertical and slant ionospheric observations or dense "coinciding" pierce points data, a new approach comparing the converted vertical TEC (VTEC) value using mapping function based on a given IEH with the "ground truth" VTEC value provided by the combined International GNSS Service Global Ionospheric Maps is proposed for the determination of the optimal IEH. The optimal IEH in the Chinese region is determined using three different methods based on GNSS data. Based on the ionosonde data from three different locations in China, the altitude variation of the peak electron density (hmF2) is found to have clear diurnal, seasonal and latitudinal dependences, and the diurnal variation of hmF2 varies from approximately 210 to 520 km in Hainan. The determination of the optimal IEH employing the inverse method suggested by Birch et al. (Radio Sci 37, 2002. doi: 10.1029/2000rs002601) did not yield a consistent altitude in the Chinese region. Tests of the method minimizing the mapping function errors suggested by Nava et al. (Adv Space Res 39:1292-1297, 2007) indicate that the optimal IEH ranges from 400 to 600 km, and the height of 450 km is the most frequent IEH at both high and low solar activities. It is also confirmed that the IEH of 450-550 km is preferred for the Chinese region instead of the commonly adopted 350-450 km using the determination method of the optimal IEH proposed in this paper.

  16. Electronic and optical properties of vacancy defects in single-layer transition metal dichalcogenides

    Science.gov (United States)

    Khan, M. A.; Erementchouk, Mikhail; Hendrickson, Joshua; Leuenberger, Michael N.

    2017-06-01

    A detailed first-principles study has been performed to evaluate the electronic and optical properties of single-layer (SL) transition metal dichalcogenides (TMDCs) (M X 2 ; M = transition metal such as Mo, W, and X = S, Se, Te), in the presence of vacancy defects (VDs). Defects usually play an important role in tailoring electronic, optical, and magnetic properties of semiconductors. We consider three types of VDs in SL TMDCs: (i) X vacancy, (ii) X2 vacancy, and (iii) M vacancy. We show that VDs lead to localized defect states (LDS) in the band structure, which in turn gives rise to sharp transitions in in-plane and out-of-plane optical susceptibilities, χ∥ and χ⊥. The effects of spin-orbit coupling (SOC) are also considered. We find that SOC splitting in LDS is directly related to the atomic number of the transition metal atoms. Apart from electronic and optical properties we also find magnetic signatures (local magnetic moment of ˜μB ) in MoSe2 in the presence of the Mo vacancy, which breaks the time-reversal symmetry and therefore lifts the Kramers degeneracy. We show that a simple qualitative tight-binding model (TBM), involving only the hopping between atoms surrounding the vacancy with an on-site SOC term, is sufficient to capture the essential features of LDS. In addition, the existence of the LDS can be understood from the solution of the two-dimensional Dirac Hamiltonian by employing infinite mass boundary conditions. In order to provide a clear description of the optical absorption spectra, we use group theory to derive the optical selection rules between LDS for both χ∥ and χ⊥.

  17. Parametric study of roof diaphragm stiffness requirements

    International Nuclear Information System (INIS)

    Jones, W.D.; Tenbus, M.A.

    1991-01-01

    A common assumption made in performing a dynamic seismic analysis for a building is that the roof/floor system is open-quotes rigidclose quotes. This assumption would appear to be reasonable for many of the structures found in nuclear power plants, since many of these structures are constructed of heavily reinforced concrete having floor/roof slabs at least two feet in thickness, and meet the code requirements for structural detailing for seismic design. The roofs of many Department of Energy (DOE) buildings at the Oak Ridge Y-12 Plant in Oak Ridge, Tennessee, have roofs constructed of either metal, precast concrete or gypsum plank deck overlaid with rigid insulation, tar and gravel. In performing natural phenomena hazard assessments for one such facility, it was assumed that the existing roof performed first as a flexible diaphragm (zero stiffness) and then, rigid (infinitely stiff). For the flexible diaphragm model it was determined that the building began to experience significant damage around 0.09 g's. For the rigid diaphragm model it was determined that no significant damage was observed below 0.20 g's. A Conceptual Design Report has been prepared for upgrading/replacing the roof of this building. The question that needed to be answered here was, open-quotes How stiff should the new roof diaphragm be in order to satisfy the rigid diaphragm assumption and, yet, be cost effective?close quotes. This paper presents a parametric study of a very simple structural system to show that the design of roof diaphragms needs to consider both strength and stiffness (frequency) requirements. This paper shows how the stiffness of a roof system affects the seismically induced loads in the lateral, vertical load resisting elements of a building and provides guidance in determining how open-quotes rigidclose quotes a roof system should be in order to accomplish a cost effective design

  18. The Perception of Malaysian Architects towards the Implementation of Green Roofs: A Review of Practices, Methodologies and Future Research

    Directory of Open Access Journals (Sweden)

    Zahir M.H. Md.

    2014-01-01

    Full Text Available The implementation of green roofs or vegetated roof as a sustainable tool to mitigate the Urban Heat Island effect is relatively new in Malaysia. Although it has not been tested on an urban scale, many research findings have indicated that green roofs can contribute towards enhancing the environmental and aesthetical quality of the built environment. It was hypothesized that the low application of green roofs in the Malaysian construction industry is due to the lack of awareness, understanding and experience in its benefits especially among building practitioners. As a result, this research was initiated to determine the perception and understanding of Malaysian architects in green roofs implementation issues, as well as to identify their level of acceptance and readiness. This paper reviews practices and different research approaches in understanding the factors that influence architect’s perception towards the implementation of green roofs in the Malaysian construction industry. Architects were chosen as the only respondents due to their intensive involvement in the conceptualisation, planning, design and construction stage of a built environment project. Extensive literature review was conducted to explore past experiences in green roof implementation and to develop the theoretical framework for this research.

  19. Design and Development of Low P-Emission Substrate for the Protection of Urban Water Bodies Collecting Green Roof Runoff

    Directory of Open Access Journals (Sweden)

    Agnieszka Karczmarczyk

    2017-10-01

    Full Text Available Urbanization leads to higher phosphorus (P concentration in urban catchments. Among different stormwater retention measures, green roofs are the least efficient in phosphorus retention. Moreover, much research has shown that green roofs act as sources of phosphorus, and they can emit P in significant loads. In this study low P emission green roof substrate was developed based on the proposed step by step procedure for the selection of materials including laboratory tests, column experiments, and the monitoring of the open air green roof model. Developed substrate is the mixture of crushed red brick (35% of volume, crushed limestone (20% of volume, and sand (45% of volume, and is characterized by a bulk density of 1.52 g/cm3, water permeability of 9 mm/min, water capacity of 24.6% of volume, and granulometric composition that meets the Landscaping and Landscape Development Research Society (FLL guidelines. Limestone was added to limit the potential P leaching from crushed red brick and vegetated mate consisted of Sedum album, Sedum acre, Sedum kamtschaticum, Sedum spurium, Sedum reflexum, Sedum sexangulare, Dianthus deltoides, Dianthus carthusianorum, and Thymus vulgaris. The open air model experiment was run for 319 days, from March 2015 to February 2016. The total water runoff from the green roof model amounted to 43.3% of runoff from the reference roof. The only one runoff event polluted with phosphorus was connected with the outflow of melted snow from an unfreezing green roof model.

  20. SOLAR RADIATION ESTIMATION ON BUILDING ROOFS AND WEB-BASED SOLAR CADASTRE

    Directory of Open Access Journals (Sweden)

    G. Agugiaro

    2012-07-01

    Full Text Available The aim of this study is the estimation of solar irradiance on building roofs in complex Alpine landscapes. Very high resolution geometric models of the building roofs are generated by means of advanced automated image matching methods. Models are combined with raster and vector data sources to estimate the incoming solar radiation hitting the roofs. The methodology takes into account for atmospheric effects, site latitude and elevation, slope and aspect of the terrain as well as the effects of shadows cast by surrounding buildings, chimneys, dormers, vegetation and terrain topography. An open source software solution has been developed and applied to a study area located in a mountainous site and containing some 1250 residential, commercial and industrial buildings. The method has been validated by data collected with a pyranometer and results made available through a prototype WebGIS platform.

  1. Decision Guide for Roof Slope Selection

    Energy Technology Data Exchange (ETDEWEB)

    Sharp, T.R.

    1988-01-01

    This decision guide has been written for personnel who are responsible for the design, construction, and replacement of Air Force roofs. It provides the necessary information and analytical tools for making prudent and cost-effective decisions regarding the amount of slope to provide in various roofing situations. Because the expertise and experience of the decision makers will vary, the guide contains both basic slope-related concepts as well as more sophisticated technical data. This breadth of information enables the less experienced user to develop an understanding of roof slope issues before applying the more sophisticated analytical tools, while the experienced user can proceed directly to the technical sections. Although much of this guide is devoted to the analysis of costs, it is not a cost-estimating document. It does, however, provide the reader with the relative costs of a variety of roof slope options; and it shows how to determine the relative cost-effectiveness of different options. The selection of the proper roof slope coupled with good roof design, a quality installation, periodic inspection, and appropriate maintenance and repair will achieve the Air Force's objective of obtaining the best possible roofing value for its buildings.

  2. Nutrient trading and green roof initiatives

    Energy Technology Data Exchange (ETDEWEB)

    Evans, D.; Stevenson, H.; Leeth, S. [McGuireWoods LLP, Richmond, VA (United States)

    2005-07-01

    Green roofs help to reduce urban stormwater runoff by reducing the impervious surfaces within a site, and can help to reduce the nutrient concentrations of runoff volumes that contribute to poor water quality in lakes and coastal waters. This paper investigated the use of green roof systems with reference to Virginia's new nutrient trading scheme in the Chesapeake Bay watershed. The scheme was established as part of a plan to allow facilities to obtain allocations to offset waste load allocations or permitted capacity. A review of the trading scheme and its relationship to various statutes and regulations was provided. Results of the study showed that green roofs are a viable option for controlling and reducing nutrient input to the bay and its tributaries. The state of Virginia has noted its interest in promoting alternative means of addressing stormwater quantity and quality. However, additional economic and policy support is needed at the federal, state, and local level to promote the use of green roofs. Grants and low-interest loans for the construction of green roofs are needed, as well as laws supporting or requiring green roofs where feasible. Local laws providing density bonuses for the use of green roofs may also increase interest in the technology. It was also noted that individual green roof projects that do not wish to be included in the allocations systems can offer project sponsors the opportunity to generate revenues from the sale of credits and offsets. It was concluded that Virginia's water quality permitting and nutrient trading program may provide an important vehicle for promoting and increasing the use of green roofs in the state. 14 refs.

  3. A learning rule for very simple universal approximators consisting of a single layer of perceptrons.

    Science.gov (United States)

    Auer, Peter; Burgsteiner, Harald; Maass, Wolfgang

    2008-06-01

    One may argue that the simplest type of neural networks beyond a single perceptron is an array of several perceptrons in parallel. In spite of their simplicity, such circuits can compute any Boolean function if one views the majority of the binary perceptron outputs as the binary output of the parallel perceptron, and they are universal approximators for arbitrary continuous functions with values in [0,1] if one views the fraction of perceptrons that output 1 as the analog output of the parallel perceptron. Note that in contrast to the familiar model of a "multi-layer perceptron" the parallel perceptron that we consider here has just binary values as outputs of gates on the hidden layer. For a long time one has thought that there exists no competitive learning algorithm for these extremely simple neural networks, which also came to be known as committee machines. It is commonly assumed that one has to replace the hard threshold gates on the hidden layer by sigmoidal gates (or RBF-gates) and that one has to tune the weights on at least two successive layers in order to achieve satisfactory learning results for any class of neural networks that yield universal approximators. We show that this assumption is not true, by exhibiting a simple learning algorithm for parallel perceptrons - the parallel delta rule (p-delta rule). In contrast to backprop for multi-layer perceptrons, the p-delta rule only has to tune a single layer of weights, and it does not require the computation and communication of analog values with high precision. Reduced communication also distinguishes our new learning rule from other learning rules for parallel perceptrons such as MADALINE. Obviously these features make the p-delta rule attractive as a biologically more realistic alternative to backprop in biological neural circuits, but also for implementations in special purpose hardware. We show that the p-delta rule also implements gradient descent-with regard to a suitable error measure

  4. Single layer and multilayer wear resistant coatings of (Ti,Al)N: a review

    International Nuclear Information System (INIS)

    PalDey, S.; Deevi, S.C.

    2003-01-01

    periodicity of 5-10 nm allow creation of coatings with different properties than PVD deposited single layered thick coatings with columnar grain structure. A range of (Ti,Al)N based multilayers containing layers of (Ti,Al)CN, (Ti,Nb)N, TiN, AlN/TiN, CrN, Mo and WC are also reviewed. It is now possible to design new wear resistant or functional coatings based on a multilayer or a multicomponent system to meet the demanding applications of advanced materials

  5. Temporal variations in the potential hydrological performance of extensive green roof systems

    Science.gov (United States)

    De-Ville, Simon; Menon, Manoj; Stovin, Virginia

    2018-03-01

    Existing literature provides contradictory information about variation in potential green roof hydrological performance over time. This study has evaluated a long-term hydrological monitoring record from a series of extensive green roof test beds to identify long-term evolutions and sub-annual (seasonal) variations in potential hydrological performance. Monitoring of nine differently-configured extensive green roof test beds took place over a period of 6 years in Sheffield, UK. Long-term evolutions and sub-annual trends in maximum potential retention performance were identified through physical monitoring of substrate field capacity over time. An independent evaluation of temporal variations in detention performance was undertaken through the fitting of reservoir-routing model parameters. Aggregation of the resulting retention and detention variations permitted the prediction of extensive green roof hydrological performance in response to a 1-in-30-year 1-h summer design storm for Sheffield, UK, which facilitated the comparison of multi and sub-annual hydrological performance variations. Sub-annual (seasonal) variation was found to be significantly greater than long-term evolution. Potential retention performance increased by up to 12% after 5-years, whilst the maximum sub-annual variation in potential retention was 27%. For vegetated roof configurations, a 4% long-term improvement was observed for detention performance, compared to a maximum 63% sub-annual variation. Consistent long-term reductions in detention performance were observed in unvegetated roof configurations, with a non-standard expanded-clay substrate experiencing a 45% reduction in peak attenuation over 5-years. Conventional roof configurations exhibit stable long-term hydrological performance, but are nonetheless subject to sub-annual variation.

  6. Plant species and functional group combinations affect green roof ecosystem functions.

    Science.gov (United States)

    Lundholm, Jeremy; Macivor, J Scott; Macdougall, Zachary; Ranalli, Melissa

    2010-03-12

    Green roofs perform ecosystem services such as summer roof temperature reduction and stormwater capture that directly contribute to lower building energy use and potential economic savings. These services are in turn related to ecosystem functions performed by the vegetation layer such as radiation reflection and transpiration, but little work has examined the role of plant species composition and diversity in improving these functions. We used a replicated modular extensive (shallow growing- medium) green roof system planted with monocultures or mixtures containing one, three or five life-forms, to quantify two ecosystem services: summer roof cooling and water capture. We also measured the related ecosystem properties/processes of albedo, evapotranspiration, and the mean and temporal variability of aboveground biomass over four months. Mixtures containing three or five life-form groups, simultaneously optimized several green roof ecosystem functions, outperforming monocultures and single life-form groups, but there was much variation in performance depending on which life-forms were present in the three life-form mixtures. Some mixtures outperformed the best monocultures for water capture, evapotranspiration, and an index combining both water capture and temperature reductions. Combinations of tall forbs, grasses and succulents simultaneously optimized a range of ecosystem performance measures, thus the main benefit of including all three groups was not to maximize any single process but to perform a variety of functions well. Ecosystem services from green roofs can be improved by planting certain life-form groups in combination, directly contributing to climate change mitigation and adaptation strategies. The strong performance by certain mixtures of life-forms, especially tall forbs, grasses and succulents, warrants further investigation into niche complementarity or facilitation as mechanisms governing biodiversity-ecosystem functioning relationships in green

  7. Green roof rainfall-runoff modelling: is the comparison between conceptual and physically based approaches relevant?

    Science.gov (United States)

    Versini, Pierre-Antoine; Tchiguirinskaia, Ioulia; Schertzer, Daniel

    2017-04-01

    Green roofs are commonly considered as efficient tools to mitigate urban runoff as they can store precipitation, and consequently provide retention and detention performances. Designed as a compromise between water holding capacity, weight and hydraulic conductivity, their substrate is usually an artificial media differentiating significantly from a traditional soil. In order to assess green roofs hydrological performances, many models have been developed. Classified into two categories (conceptual and physically based), they are usually applied to reproduce the discharge of a particular monitored green roof considered as homogeneous. Although the resulted simulations could be satisfactory, the question of robustness and consistency of the calibrated parameters is often not addressed. Here, a modeling framework has been developed to assess the efficiency and the robustness of both modelling approaches (conceptual and physically based) in reproducing green roof hydrological behaviour. SWMM and VS2DT models have been used for this purpose. This work also benefits from an experimental setup where several green roofs differentiated by their substrate thickness and vegetation cover are monitored. Based on the data collected for several rainfall events, it has been studied how the calibrated parameters are effectively linked to their physical properties and how they can vary from one green roof configuration to another. Although both models reproduce correctly the observed discharges in most of the cases, their calibrated parameters exhibit a high inconsistency. For a same green roof configuration, these parameters can vary significantly from one rainfall event to another, even if they are supposed to be linked to the green roof characteristics (roughness, residual moisture content for instance). They can also be different from one green roof configuration to another although the implemented substrate is the same. Finally, it appears very difficult to find any

  8. Impact- and earthquake- proof roof structure

    International Nuclear Information System (INIS)

    Shohara, Ryoichi.

    1990-01-01

    Building roofs are constituted with roof slabs, an earthquake proof layer at the upper surface thereof and an impact proof layer made of iron-reinforced concrete disposed further thereover. Since the roofs constitute an earthquake proof structure loading building dampers on the upper surface of the slabs by the concrete layer, seismic inputs of earthquakes to the buildings can be moderated and the impact-proof layer is formed, to ensure the safety to external conditions such as earthquakes or falling accidents of airplane in important facilities such as reactor buildings. (T.M.)

  9. 30 CFR 75.213 - Roof support removal.

    Science.gov (United States)

    2010-07-01

    ... mining experience shall perform permanent roof support removal work. (b) Prior to the removal of... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Roof support removal. 75.213 Section 75.213... MANDATORY SAFETY STANDARDS-UNDERGROUND COAL MINES Roof Support § 75.213 Roof support removal. (a)(1) All...

  10. 30 CFR 75.206 - Conventional roof support.

    Science.gov (United States)

    2010-07-01

    ... HEALTH MANDATORY SAFETY STANDARDS-UNDERGROUND COAL MINES Roof Support § 75.206 Conventional roof support. (a) Except in anthracite mines using non-mechanized mining systems, when conventional roof support... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Conventional roof support. 75.206 Section 75...

  11. Green Roofs and Green Walls for Biodiversity Conservation: A Contribution to Urban Connectivity?

    Directory of Open Access Journals (Sweden)

    Flavie Mayrand

    2018-03-01

    Full Text Available Green roofs and walls have recently emerged as conservation tools, and they offer promising additional opportunities to enhance biodiversity in cities. However, their ecological conditions remain poorly considered when planning wildlife corridors. To discuss the role of vegetated buildings in landscape connectivity, we reviewed the ecological and technical specificities of green walls and green roofs in light of the key factors concerning urban wildlife (patch size, quality, abundance, and isolation. Green roofs and walls show limited patch sizes, distinct habitat quality at the building scale, and limited redundancy of patch quality within the landscape. We also highlight that the abundance of roof and wall patches is often low. Future research is needed to establish if walls can be vertical corridors for wildlife, thereby reducing the isolation of green roofs. We argue that creating 3D ecological connectivity within the city requires substantial modifications of the design and maintenance of existing green building systems. We suggest that research is needed to integrate the biotic and abiotic characteristics of green buildings to make them more closely resemble those of open green spaces.

  12. Magneto-electroluminescence effects in the single-layer organic light-emitting devices with macrocyclic aromatic hydrocarbons

    Directory of Open Access Journals (Sweden)

    S.-T. Pham

    2018-02-01

    Full Text Available Magneto-electroluminescence (MEL effects are observed in single-layer organic light-emitting devices (OLEDs comprising only macrocyclic aromatic hydrocarbons (MAHs. The fluorescence devices were prepared using synthesized MAHs, namely, [n]cyclo-meta-phenylene ([n]CMP, n = 5, 6. The MEL ratio of the resulting OLED is 1%–2% in the spectral wavelength range of 400-500 nm, whereas it becomes negative (−1.5% to −2% in the range from 650 to 700 nm. The possible physical origins of the sign change in the MEL are discussed. This wavelength-dependent sign change in the MEL ratio could be a unique function for future single-layer OLEDs capable of magnetic-field-induced color changes.

  13. Novel single-layer gas diffusion layer based on PTFE/carbon black composite for proton exchange membrane fuel cell

    Energy Technology Data Exchange (ETDEWEB)

    Chen-Yang, Y.W.; Hung, T.F.; Yang, F.L. [Department of Chemistry and Center for Nanotechnology, Chung Yuan Christian University, Chung-Li 32023 (China); Huang, J. [Yeu Ming Tai Chemical Industrial Co., Ltd, Taichung 40768 (China)

    2007-11-08

    A series of poly(tetrafluoroethylene)/carbon black composite-based single-layer gas diffusion layers (PTFE/CB-GDLs) for proton exchange membrane fuel cell (PEMFC) was successfully prepared from carbon black and un-sintered PTFE, which included powder resin and colloidal dispersion, by a simple inexpensive method. The scanning electron micrographs of PTFE/CB-GDLs indicated that the PTFE resins were homogeneously dispersed in the carbon black matrix and showed a microporous layer (MPL)-like structure. The as-prepared PTFE/CB-GDLs exhibited good mechanical property, high gas permeability, and sufficient water repellency. The best current density obtained from the PEMFC with the single-layer PTFE/CB-GDL was 1.27 and 0.42 A cm{sup -2} for H{sub 2}/O{sub 2} and H{sub 2}/air system, respectively. (author)

  14. Improving the light-emitting properties of single-layered polyfluorene light-emitting devices by simple ionic liquid blending

    Science.gov (United States)

    Horike, Shohei; Nagaki, Hiroto; Misaki, Masahiro; Koshiba, Yasuko; Morimoto, Masahiro; Fukushima, Tatsuya; Ishida, Kenji

    2018-03-01

    This paper describes an evaluation of ionic liquids (ILs) as potential electrolytes for single-layered light-emitting devices with good emission performance. As optoelectronic devices continue to grow in abundance, high-performance light-emitting devices with a single emission layer are becoming increasingly important for low-cost production. We show that a simple technique of osmosing IL into the polymer layer can result in high luminous efficiency and good response times of single-layered light-emitting polymers, even without the additional stacking of charge carrier injection and transport layers. The IL contributions to the light-emission of the polymer are discussed from the perspectives of energy diagrams and of the electric double layers on the electrodes. Our findings enable a faster, cheaper, and lower-in-waste production of light-emitting devices.

  15. Structure and Electronic Properties of In Situ Synthesized Single-Layer MoS2 on a Gold Surface

    DEFF Research Database (Denmark)

    Sørensen, Signe Grønborg; Füchtbauer, Henrik Gøbel; Tuxen, Anders Kyrme

    2014-01-01

    with scanning tunneling microscopy and X-ray photoelectron spectroscopy characterization of two-dimensional single-layer islands of MoS2 synthesized directly on a gold single crystal substrate. Thanks to a periodic modulation of the atom stacking induced by the lattice mismatch, we observe a structural buckling...... structure appears modified at the band gap edges. This electronic effect is further modulated by the moiré periodicity and leads to small substrate-induced electronic perturbations near the conduction band minimum in the band gap of MoS2. The results may be highly relevant in the context of nanopatterned......When transition metal sulfides such as MoS2 are present in the single-layer form, the electronic properties change in fundamental ways, enabling them to be used, e.g., in two-dimensional semiconductor electronics, optoelectronics, and light harvesting. The change is related to a subtle modification...

  16. A meta-analytic review of the effectiveness of single-layer clothing in preventing exposure from pesticide handling.

    Science.gov (United States)

    Miguelino, Eric S

    2014-01-01

    This review summarizes available information on the penetration of pesticides through single-layer clothing by pesticide handlers and introduces epidemiological and observational studies on pesticide exposure. The data for this report were taken from peer-reviewed articles, publicly available government reports, and publicly available government reviews of registrant-submitted data and information. The arithmetic mean of calculated clothing penetration was obtained for various parts of the body (upper arm, lower arm, chest/torso, back/torso, upper leg, and lower leg) that were exposed to pesticide. The range of pesticide penetration to the various parts of the body through single-layer clothing during mixing, loading, and application (MLA) activities was found to be 6.2% ± 5.7% to 21.4% ± 6.7%, which demonstrates a potential for increased and unintentional pesticide exposures. Based on this evaluation, some accepted default values for protection against pesticide exposure may be overestimated.

  17. Spin-dependent electron-phonon coupling in the valence band of single-layer WS2

    DEFF Research Database (Denmark)

    Hinsche, Nicki Frank; Ngankeu, Arlette S.; Guilloy, Kevin

    2017-01-01

    The absence of inversion symmetry leads to a strong spin-orbit splitting of the upper valence band of semiconducting single-layer transition-metal dichalchogenides such as MoS2 or WS2. This permits a direct comparison of the electron-phonon coupling strength in states that only differ by their spin....... Here, the electron-phonon coupling in the valence band maximum of single-layer WS2 is studied by first-principles calculations and angle-resolved photoemission. The coupling strength is found to be drastically different for the two spin-split branches, with calculated values of λK=0.0021 and 0.......40 for the upper and lower spin-split valence band of the freestanding layer, respectively. This difference is somewhat reduced when including scattering processes involving the Au(111) substrate present in the experiment but it remains significant, in good agreement with the experimental results....

  18. Metal and nutrient dynamics on an aged intensive green roof.

    Science.gov (United States)

    Speak, A F; Rothwell, J J; Lindley, S J; Smith, C L

    2014-01-01

    Runoff and rainfall quality was compared between an aged intensive green roof and an adjacent conventional roof surface. Nutrient concentrations in the runoff were generally below Environmental Quality Standard (EQS) values and the green roof exhibited NO3(-) retention. Cu, Pb and Zn concentrations were in excess of EQS values for the protection of surface water. Green roof runoff was also significantly higher in Fe and Pb than on the bare roof and in rainfall. Input-output fluxes revealed the green roof to be a potential source of Pb. High concentrations of Pb within the green roof soil and bare roof dusts provide a potential source of Pb in runoff. The origin of the Pb is likely from historic urban atmospheric deposition. Aged green roofs may therefore act as a source of legacy metal pollution. This needs to be considered when constructing green roofs with the aim of improving pollution remediation. Copyright © 2013 Elsevier Ltd. All rights reserved.

  19. Single-layer ZnS supported on Au(111): A combined XPS, LEED, STM and DFT study

    Science.gov (United States)

    Deng, Xingyi; Sorescu, Dan C.; Lee, Junseok

    2017-04-01

    Single-layer of ZnS, consisting of one atomic layer of ZnS(111) plane, has been grown on Au(111) and characterized using X-ray photoelectron spectroscopy (XPS), low energy electron diffraction (LEED) and scanning tunneling microscopy (STM). While the LEED measurement indicates a coincidence structure of ZnS-(3×3)/Au(111)-(4×4), high resolution STM images reveal hexagonal unit cells of 6.7×6.7 Å2 and 11.6×11.6 Å2, corresponding to √3 and 3 times the unit cell of the ideal zincblende ZnS-(1×1), respectively, depending on the tunneling conditions. Calculations based on density functional theory (DFT) indicate a significantly reconstructed non-planar structure of ZnS single-layer on Au(111) with 2/3 of the S anions being located nearly in the plane of the Zn cations and the rest 1/3 of the S anions protruding above the Zn plane. The calculated STM image shows similar characteristics to those of the experimental STM image. Additionally, the DFT calculations reveal the different bonding nature of the S anions in ZnS single-layer supported on Au(111).

  20. Roof instability characteristics and pre-grouting of the roof caving zone in residual coal mining

    Science.gov (United States)

    Zhao, Tong; Liu, Changyou

    2017-12-01

    Abandoned roadways and roof caving zones are commonly found in residual coal, and can destroy the integrity of the coal seam and roof. Resulting from mining-induced stress, continuous collapse and fracture instability in roof caving zones (RCZs) jeopardize the safety and efficiency of residual coal mining. Based on the engineering geology conditions of remining face 3101 in Shenghua Mine, the roof fracture and instability features of the RCZ were analyzed through physical simulation, theoretical analysis, and field measurements. In this case, influenced by the RCZ, the main roof across the RCZ fractured and rotated towards the goaf, greatly increasing the working resistance, and crushing the supports. The sudden instability of the coal pillars weakened its support of the main roof, thus resulting in long-key blocks across the RCZ and hinged roof structures, which significantly decreased the stability of the underlying immediate roof. This study establishes a mechanical model for the interactions between the surrounding rock and the supports in the RCZ, determines the reasonable working resistance, and examines the use of pre-grouting solidification restoration technology (PSRT) to solidify the RCZ and reinforce the coal pillars—thus increasing their bearing capacity. Field measurements revealed no roof flaking, inhomogeneous loading or support crushing, indicating that the PSRT effectively controlled the surrounding rock of the RCZ.

  1. ROOF GARDENS AS LANDSCAPING IN MODERN TIMES

    Directory of Open Access Journals (Sweden)

    Vaska Sandeva

    2017-02-01

    Full Text Available As we know we live in a process of industrialization and massive building of residential buildings, both individually and as a collective housing. Given all that happens even with the procedural other things to come up with all this, the country remains less green space that is required for a single environment, so the roof gardens are the best choice for all of this to get a beautiful country. For roof gardens should be given the explanation that, roof gardens, call it beautiful, flat roofs, and with gentle slope, with rich composition intensively maintained and often impose a constructive adaptation of the building and benefits by the architectural beauty, insulation, absorption. Commonly found in urban areas and almost always are placed foliage with not very high growth.

  2. Million Solar Roofs: Partners Make Markets

    Energy Technology Data Exchange (ETDEWEB)

    2004-06-01

    Million Solar Roofs (MSR) Partners Make Markets Executive Summary is a summary of the MSR Annual Partnership Update, a report from all the partners and partnerships who participate in the MSR Initiative.

  3. Solar performance of hemispherical vault roofs

    Energy Technology Data Exchange (ETDEWEB)

    Gomez-Munoz, V.M. [Instituto Politecnico Nacional, La Paz, Baja California Sur (Mexico). Centro Interdisciplinario de Ciencias Marinas; Porta-Gandara, M.A. [Centro de Investigaciones Biologicas del Noroeste S.C., Baja California Sur (Mexico); Heard, C. [Instituto Mexinano de Petroleo (Mexico)

    2003-12-01

    In hot climates, the improvement of comfort by passive solar techniques is a very important issue. In many parts of the world such as the Middle East, vault roofs are widely used in construction. The solar and energy performance of a hemispherical vault roof is studied, including the auto-shading instant effect during several days for different latitudes and throughout the year also. The results are compared with the standard horizontal flat roofing used in the typical modern low-cost housing in Mexico. The hemispherical vault receives around 35% less energy than the flat roof between the equinoxes, besides having other advantages such as a greater ceiling height, natural ventilation and illumination possibilities, and structural stability. (author)

  4. MC Contracting, Paint, & Roofing, LLC Information Sheet

    Science.gov (United States)

    MC Contracting, Paint, & Roofing, LLC, d/b/a M.C. Painting & Contractor and M.C. Painting Group (the Company) is located in Philadelphia, Pennsylvania. The settlement involves renovation activities conducted at property constructed prior to 1978.

  5. Sloshing impact in roofed tanks

    International Nuclear Information System (INIS)

    Uras, R.A.

    1995-01-01

    A large number of high-level waste (HLW) storage tanks exists in various tank farms. Seismic activities at those locations may cause significant sloshing in HLW tanks. These tanks are covered to avoid any spilling during large amplitude earthquakes. However, large amplitude sloshing may result in impact on the cover or the roof of the tank. Hence, a better understanding of the impact phenomenon is necessary to assess the safety of the tanks currently in existence, and to establish design guidelines for future designs. A pressure based formulation is derived to model sloshing impact in roared tanks. It is incorporated into Argonne's in-house finite element code FLUSTR-ANL. A numerical test case with a harmonic input excitation is studied. The simulation results indicate that linear behavior is preserved beyond the first impact, and some mesh distortion is observed following a stronger second impact. During the impact, the displacement of the contacting surface nodes remains constant, and the velocities are reduced to zero. An identification of impacting nodes is possible from the dynamic pressures induced in surface elements

  6. The Influence of green areas and roof albedos on air temperatures during Extreme Heat Events in Berlin, Germany

    Directory of Open Access Journals (Sweden)

    Sebastian Schubert

    2013-04-01

    Full Text Available The mesoscale atmospheric model COSMO-CLM (CCLM with the Double Canyon Effect Parametrization Scheme (DCEP is applied to investigate possible adaption measures to extreme heat events (EHEs for the city of Berlin, Germany. The emphasis is on the effects of a modified urban vegetation cover and roof albedo on near-surface air temperatures. Five EHEs with a duration of 5 days or more are identified for the period 2000 to 2009. A reference simulation is carried out for each EHE with current vegetation cover, roof albedo and urban canopy parameters (UCPs, and is evaluated with temperature observations from weather stations in Berlin and its surroundings. The derivation of the UCPs from an impervious surface map and a 3-D building data set is detailed. Characteristics of the simulated urban heat island for each EHE are analysed in terms of these UCPs. In addition, six sensitivity runs are examined with a modified vegetation cover of each urban grid cell by -25%, 5% and 15%, with a roof albedo increased to 0.40 and 0.65, and with a combination of the largest vegetation cover and roof albedo, respectively. At the weather stations' grid cells, the results show a maximum of the average diurnal change in air temperature during each EHE of 0.82 K and -0.48 K for the -25% and 15% vegetation covers, -0.50 K for the roof albedos of 0.65, and -0.63 K for the combined vegetation and albedo case. The largest effects on the air temperature are detected during midday.

  7. Research on the compressive strength of a passenger vehicle roof

    Science.gov (United States)

    Zhao, Guanglei; Cao, Jianxiao; Liu, Tao; Yang, Na; Zhao, Hongguang

    2017-05-01

    To study the compressive strength of a passenger vehicle roof, this paper makes the simulation test on the static collapse of the passenger vehicle roof and analyzes the stress and deformation of the vehicle roof under pressure in accordance with the Roof Crush Resistance of Passenger Cars (GB26134-2010). It studies the optimization on the major stressed parts, pillar A, pillar B and the rail of roof, during the static collapse process of passenger vehicle roof. The result shows that the thickness of pillar A and the roof rail has significant influence on the compressive strength of the roof while that of pillar B has minor influence on the compressive strength of the roof.

  8. Cladonia lichens on extensive green roofs: evapotranspiration, substrate temperature, and albedo [v1; ref status: indexed, http://f1000r.es/2ha

    Directory of Open Access Journals (Sweden)

    Amy Heim

    2013-12-01

    Full Text Available Green roofs are constructed ecosystems that provide ecosystem services in urban environments. Shallow substrate green roofs subject the vegetation layer to desiccation and other environmental extremes, so researchers have evaluated a variety of stress-tolerant vegetation types for green roof applications. Lichens can be found in most terrestrial habitats.  They are able to survive extremely harsh conditions, including frequent cycles of desiccation and rehydration, nutrient-poor soil, fluctuating temperatures, and high UV intensities. Extensive green roofs (substrate depth <20cm exhibit these harsh conditions, making lichens possible candidates for incorporation into the vegetation layer on extensive green roofs.  In a modular green roof system, we tested the effect of Cladonia lichens on substrate temperature, water loss, and albedo compared to a substrate-only control. Overall, the Cladonia modules had significantly cooler substrate temperatures during the summer and significantly warmer temperatures during the fall.  Additionally, the Cladonia modules lost significantly less water than the substrate-only control. This implies that they may be able to benefit neighboring vascular plant species by reducing water loss and maintaining favorable substrate temperatures.

  9. Cladonia lichens on extensive green roofs: evapotranspiration, substrate temperature, and albedo [v2; ref status: indexed, http://f1000r.es/2v4

    Directory of Open Access Journals (Sweden)

    Amy Heim

    2014-01-01

    Full Text Available Green roofs are constructed ecosystems that provide ecosystem services in urban environments. Shallow substrate green roofs subject the vegetation layer to desiccation and other environmental extremes, so researchers have evaluated a variety of stress-tolerant vegetation types for green roof applications. Lichens can be found in most terrestrial habitats.  They are able to survive extremely harsh conditions, including frequent cycles of desiccation and rehydration, nutrient-poor soil, fluctuating temperatures, and high UV intensities. Extensive green roofs (substrate depth <20cm exhibit these harsh conditions, making lichens possible candidates for incorporation into the vegetation layer on extensive green roofs.  In a modular green roof system, we tested the effect of Cladonia lichens on substrate temperature, water loss, and albedo compared to a substrate-only control. Overall, the Cladonia modules had significantly cooler substrate temperatures during the summer and significantly warmer temperatures during the fall.  Additionally, the Cladonia modules lost significantly less water than the substrate-only control. This implies that they may be able to benefit neighboring vascular plant species by reducing water loss and maintaining favorable substrate temperatures.

  10. Peculiarities of superconductivity in the single-layer FeSe /SrTi O3 interface

    Science.gov (United States)

    Gor'kov, Lev P.

    2016-02-01

    Observation of replica bands in the angle-resolved photoemission spectroscopy (ARPES) spectra of single-layer FeSe on a strontium titanate substrate revealed a phonon component contribution to mechanisms behind its high-Tc superconductivity. We study the interaction of the in-layer FeSe electrons with the electric potential of the longitudinal (LO) modes at the surface of bulk SrTi O3 . A two-dimensional system of charges at the FeSe /SrTi O3 interface includes both the itinerant and the immobile electrons. The latter significantly change the interface characteristics, increasing screening at the substrate surface and thereby reducing the strength of the electron-LO-phonon interaction. In what follows, the dielectric constant serves as a free parameter and is determined using the ARPES measurements of the replicas. Two-dimensional Coulomb screening is accounted for in the random-phase approximation. It is shown that the model is applicable over the entire range of the parameters typical for current experiments. The estimates from this model make possible the conclusion that the LO-phonon-mediated pairing alone cannot account for the temperatures of the superconducting transitions Tc in the single-layer FeSe /SrTi O3 reported in these experiments. This does not exclude that the LO-phonon mechanisms can become more significant in differently and better prepared single-layer FeSe films. Available experiments are briefly discussed. Thus far no measurements exist on the dependence of Tc on the concentration of electrons doped into the in-layer FeSe band.

  11. [Observation of single-layered inverted internal limiting membrane flap technique for macular hole with retinal detachment in high myopia].

    Science.gov (United States)

    Xu, C Z; Wu, J H; He, J W; Feng, C

    2017-05-11

    Objective: To compare the outcome of pars plana vitrectomy (PPV) with a single-layered inverted internal limiting membrane (ILM) flap versus PPV with ILM peeling for the treatment of macular hole associated retinal detachment (MHRD) in high myopia. Methods: In a retrospective cohort study, PPV with 2 kinds of adjuvant surgical procedures were used in 35 moderately high myopia eyes with MHRD. These eyes were divided into 2 groups: group 1 (17 eyes) receiving PPV and ILM peeling and group 2 (18 eyes) receiving PPV with a single-layered inverted ILM flap. Anatomical reattachment of the retina, macular hole closure, and best-corrected visual acuity (BCVA) were measured at 6 months after surgery. Results: The retina was successfully reattached in all cases. The difference of the retinal reattachment rate between the two groups was not statistically significant (Fisher's exact test, P= 1.000). The rate of macular hole closure was 47.1% in group 1 (8 eyes) and 88.9% in group 2 (16 eyes). The difference of the macular hole closure rate between the two groups was statistically significant (Fisher's exact test, P= 0.012). Significant improvement in logarithm of minimal angle of resolution (logMAR) BCVA was achieved in both groups. There was no difference in the initial, final, or improved logMAR BCVA in the 2 groups. Conclusion: Single-layered inverted ILM flap technique effectively helps close the macular hole in moderately high myopia with MHRD. This may prevent the possible redetachment from the macular hole. (Chin J Ophthalmol, 2017, 53: 338 - 343) .

  12. Laboratory Tests of Substrate Physical Properties May Not Represent the Retention Capacity of Green Roof Substrates In Situ

    Directory of Open Access Journals (Sweden)

    Christopher Szota

    2017-11-01

    Full Text Available Green roofs can be used to reduce the volume of polluted stormwater that is generated by cities. Modelling rainfall retention is critical, but green roof water balance models often rely on the physical properties of substrates. In these models, substrate water holding capacity (WHC determines the depth of water which can be stored before runoff is generated; whereas, the permanent wilting point (PWP limits evapotranspiration. The WHC and PWP, as well as plant available water (PAW; where PAW = WHC − PWP, as determined from laboratory tests, may not truly reflect how substrates perform on green roofs. We therefore ran a simulated rainfall experiment on green roof modules to (i compare the rainfall retention of vegetated and non-vegetated substrates with different WHC and PAW, and (ii relate retention to substrate storage capacity, as calculated from laboratory measures of WHC and PAW. We found that the PAW of a substrate is a better indicator of evapotranspiration and retention when compared with WHC. However, we also found that substrates always retained less water than their calculated storage capacity would suggest, most likely being due to their high permeability. Our results indicate that using laboratory-derived measures of WHC and PAW in green roof models may be over-estimating both evapotranspiration and rainfall retention.

  13. THE INFLUENCE THE EXTENSIVE GREEN ROOFS ON THE OUTFLOW RAINWATER TO THE SEWAGE SYSTEM

    Directory of Open Access Journals (Sweden)

    Maciej Mrowiec

    2015-10-01

    Full Text Available In times of rapid urbanization and climate change has drawn more attention to stormwater runoff to sewer systems. The phenomenon of flooding in urban areas have become increasingly common as a result of heavy rains. Sewage systems in such a short time are not able to accept such a large amount of rainwater flowing on the site, which we experience the phenomenon of rainfall flowing down the street in excessive amounts. The problem of such phenomena can be solved by the development of green roof technology. Even in its simplest form that extensive green roof is able to delay outflow, and store in its entirety falling falls on the area. Everything depends on the layers and the size of the roof. The research study presented at two mini green roof, an area of 1.44 m2. Both cases have different layers. One of them has a layer of non-woven filter layer, the substrate and vegetation. The second station is built of layers of drainage, filter layer, a layer of substrate and vegetation. For experimental purposes a rain shower were used for testing, which allows to calibrate the right amount of water at a specified time. In the research of precipitation 10, 15 and 20-minute tested. On the bench number 1 a reduction in the range of 48.9 to 97.5% was achieved. The second experiment stand showed a higher retention capacity ranged from 74.5 to 94.7%. We concluded that the use of extensive green roofs in cities can help reduce storm water runoff from impervious surfaces.

  14. Classification of Roof Materials Using Hyperspectral Data

    Science.gov (United States)

    Chisense, C.

    2012-07-01

    Mapping of surface materials in urban areas using aerial imagery is a challenging task. This is because there are numerous materials present in relatively small regions. Hyperspectral data features a fine spectral resolution and thus has a significant capability for automatic identification and mapping of urban surface materials. In this study an approach for identification of roof surface materials using hyperspectral data is presented. The study is based on an urban area in Ludwigsburg, Germany, using a HyMap data set recorded during the HyMap campaign in August, 2010. Automatisierte Liegenschaftskarte (ALK) vector data with a building layer is combined with the HyMap data to limit the analysis to roofs. A spectral library for roofs is compiled based on field and image measurements. In the roof material identification process, supervised classification methods, namely spectral angle mapper and spectral information divergence and the object oriented ECHO (extraction and classification of homogeneous objects) approach are compared. In addition to the overall shape of spectral curves, position and strength of absorptions features are used to enhance material identification. The discriminant analysis feature extraction method is applied to the HyMap data in order to identify features (band combinations) suitable for discriminating between the target classes. The identified optimal features are used to create a new data set which is later classified using the ECHO classifier. The classification results with respect to material types of roofs are presented in this study. The most important results are evaluated using orthophotos, probability maps and field visits.

  15. Retention capacity of extensive green roofs

    Directory of Open Access Journals (Sweden)

    Sobczyk Małgorzata

    2016-09-01

    Full Text Available Climate change causes a more frequent occurrence of extreme events. The result of these phenomena is the occurrence of floods and flooding, and periods of drought. Particularly unfavorable is intensive rainfall over the urban catchments. To prevent the negative consequences of these phenomena, unconventional solutions should be used. The use of green roofs in urban areas will serve the sustainable development of cities and the impact on local ecological changes. The study was performed at two green roof platforms 1.2×1.2×0.1 m each. An analysis was performed at different intensities given for precipitation. 20 min for the rain to stop was observed from 68 to 100% precipitation. The study was divided into two parts. The first part of the study has been performed in the dry period. In contrast, another round of tests was repeated in other conditions after rainfall. The amount of water at two experimental green roofs platforms before the test was 11.0 dm3. The research relates to the impact of green roofs on local hydrological changes. Development of technologies for green roofs had a positive impact on mitigating the effects of climate change associated with the occurrence of flooding the city.

  16. Self-assembly surface modified indium-tin oxide anodes for single-layer light-emitting diodes

    CERN Document Server

    Morgado, J; Charas, A; Matos, M; Alcacer, L; Cacialli, F

    2003-01-01

    We study the effect of indium-tin oxide surface modification by self assembling of highly polar molecules on the performance of single-layer light-emitting diodes (LEDs) fabricated with polyfluorene blends and aluminium cathodes. We find that the efficiency and light-output of such LEDs is comparable to, and sometimes better than, the values obtained for LEDs incorporating a hole injection layer of poly(3,4-ethylene dioxythiophene) doped with polystyrene sulphonic acid. This effect is attributed to the dipole-induced work function modification of indium-tin oxide.

  17. Effect of ethanethiolate spacer on morphology and optical responses of Ag nanoparticle array-single layer graphene hybrid systems

    Czech Academy of Sciences Publication Activity Database

    Sutrová, Veronika; Šloufová, I.; Melníková Komínková, Zuzana; Kalbáč, Martin; Pavlova, Ewa; Vlčková, B.

    2017-01-01

    Roč. 33, č. 50 (2017), s. 14414-14424 ISSN 0743-7463 R&D Projects: GA ČR(CZ) GA15-01953S; GA MŠk(CZ) LM2015073 Grant - others:GA MŠk(CZ) CZ.02.1.01/0.0/0.0/16_013/0001821 Institutional support: RVO:61389013 ; RVO:61388955 Keywords : Ag nanoparticle * single layer graphene * ethanethiol Subject RIV: JI - Composite Materials; CF - Physical ; Theoretical Chemistry (UFCH-W) OBOR OECD: Composites (including laminates, reinforced plastics, cermets, combined natural and synthetic fibre fabrics; Physical chemistry (UFCH-W) Impact factor: 3.833, year: 2016

  18. Self-assembly surface modified indium-tin oxide anodes for single-layer light-emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Morgado, Jorge [Instituto de Telecomunicacoes and Departamento de Engenharia Quimica, Instituto Superior Tecnico, Avenida Rovisco Pais, P-1049-001 Lisbon (Portugal); Barbagallo, Nunzio [Instituto de Telecomunicacoes and Departamento de Engenharia Quimica, Instituto Superior Tecnico, Avenida Rovisco Pais, P-1049-001 Lisbon (Portugal); Charas, Ana [Instituto de Telecomunicacoes and Departamento de Engenharia Quimica, Instituto Superior Tecnico, Avenida Rovisco Pais, P-1049-001 Lisbon (Portugal); Matos, Manuel [Departamento de Engenharia Quimica, Instituto Superior de Engenharia de Lisboa, Rua Conselheiro Emidio Navarro-1, P-1949-001 Lisbon (Portugal); Alcacer, Luis [Instituto de Telecomunicacoes and Departamento de Engenharia Quimica, Instituto Superior Tecnico, Avenida Rovisco Pais, P-1049-001 Lisbon (Portugal); Cacialli, Franco [Department of Physics and Astronomy, University College London, Gower Street, London, WC1E 6BT (United Kingdom)

    2003-03-07

    We study the effect of indium-tin oxide surface modification by self assembling of highly polar molecules on the performance of single-layer light-emitting diodes (LEDs) fabricated with polyfluorene blends and aluminium cathodes. We find that the efficiency and light-output of such LEDs is comparable to, and sometimes better than, the values obtained for LEDs incorporating a hole injection layer of poly(3,4-ethylene dioxythiophene) doped with polystyrene sulphonic acid. This effect is attributed to the dipole-induced work function modification of indium-tin oxide.

  19. Model for a collimated spin-wave beam generated by a single-layer spin torque nanocontact

    Science.gov (United States)

    Hoefer, M. A.; Silva, T. J.; Stiles, M. D.

    2008-04-01

    A model of spin-torque-induced magnetization dynamics based on semiclassical spin diffusion theory for a single-layer nanocontact is presented. The model incorporates effects due to the current-induced Oersted field and predicts the generation of a variety of spatially dependent, coherent, precessional magnetic wave structures. Directionally controllable collimated spin-wave beams, vortex spiral waves, and localized standing waves are found to be excited by the interplay of the Oersted field and the orientation of an applied field. These fields act as a spin-wave “corral” around the nanocontact that controls the propagation of spin waves in certain directions.

  20. Anisotropic Young's Modulus for Single-Layer Black Phosphorus: The Third Principle Direction Besides Armchair and Zigzag

    OpenAIRE

    Jiang, Jin-Wu

    2015-01-01

    We derive an analytic formula for the Young's modulus in single-layer black phosphorus using the valence force field model. By analyzing the directional dependence for the Young's modulus, we explore the third principle direction with direction angle phi_tp = 0.268pi besides armchair and zigzag directions. The maximum Young's modulus value is in the third principle direction. More specifically, the Young's modulus is 52.2 N/m, 85.4 N/m, and 111.4 N/m in the armchair direction, zigzag directio...

  1. Roofing as a source of nonpoint water pollution.

    Science.gov (United States)

    Chang, Mingteh; McBroom, Matthew W; Scott Beasley, R

    2004-12-01

    Sixteen wooden structures with two roofs each were installed to study runoff quality for four commonly used roofing materials (wood shingle, composition shingle, painted aluminum, and galvanized iron) at Nacogdoches, Texas. Each roof, either facing NW or SE, was 1.22 m wide x 3.66 m long with a 25.8% roof slope. Thus, there were 32 alternatively arranged roofs, consisting of four roof types x two aspects x four replicates, in the study. Runoff from the roofs was collected through galvanized gutters, downspouts, and splitters. The roof runoff was compared to rainwater collected by a wet/dry acid rain collector for the concentrations of eight water quality variables, i.e. Cu(2+), Mn(2+), Pb(2+), Zn(2+), Mg(2+), Al(3+), EC and pH. Based on 31 storms collected between October 1997 and December 1998, the results showed: (1) concentrations of pH, Cu, and Zn in rainwater already exceed the EPA freshwater quality standards even without pollutant inputs from roofs, (2) Zn and Cu, the two most serious pollutants in roof runoff, exceeded the EPA national freshwater water quality standards in virtually 100% and more than 60% of the samples, respectively, (3) pH, EC, and Zn were the only three variables significantly affected by roofing materials, (4) differences in Zn concentrations were significant among all roof types and between all roof runoff and rainwater samples, (5) although there were no differences in Cu concentrations among all roof types and between roof runoff and rainwater, all means and medians of runoff and rainwater exceeded the national water quality standards, (6) water quality from wood shingles was the worst among the roof types studied, and (7) although SE is the most frequent and NW the least frequent direction for incoming storms, only EC, Mg, Mn, and Zn in wood shingle runoff from the SE were significantly higher than those from the NW; the two aspects affected no other elements in runoff from the other three roof types. Also, Zn concentrations from

  2. Weathering of Roofing Materials-An Overview

    Energy Technology Data Exchange (ETDEWEB)

    Berdahl, Paul; Akbari, Hashem; Levinson, Ronnen; Miller, William A.

    2006-03-30

    An overview of several aspects of the weathering of roofing materials is presented. Degradation of materials initiated by ultraviolet radiation is discussed for plastics used in roofing, as well as wood and asphalt. Elevated temperatures accelerate many deleterious chemical reactions and hasten diffusion of material components. Effects of moisture include decay of wood, acceleration of corrosion of metals, staining of clay, and freeze-thaw damage. Soiling of roofing materials causes objectionable stains and reduces the solar reflectance of reflective materials. (Soiling of non-reflective materials can also increase solar reflectance.) Soiling can be attributed to biological growth (e.g., cyanobacteria, fungi, algae), deposits of organic and mineral particles, and to the accumulation of flyash, hydrocarbons and soot from combustion.

  3. Growing vertical ZnO nanorod arrays within graphite: efficient isolation of large size and high quality single-layer graphene.

    Science.gov (United States)

    Ding, Ling; E, Yifeng; Fan, Louzhen; Yang, Shihe

    2013-07-18

    We report a unique strategy for efficiently exfoliating large size and high quality single-layer graphene directly from graphite into DMF dispersions by growing ZnO nanorod arrays between the graphene layers in graphite.

  4. Analytical and molecular dynamics studies on the impact loading of single-layered graphene sheet by fullerene

    Science.gov (United States)

    Hosseini-Hashemi, Shahrokh; Sepahi-Boroujeni, Amin; Sepahi-Boroujeni, Saeid

    2018-04-01

    Normal impact performance of a system including a fullerene molecule and a single-layered graphene sheet is studied in the present paper. Firstly, through a mathematical approach, a new contact law is derived to describe the overall non-bonding interaction forces of the "hollow indenter-target" system. Preliminary verifications show that the derived contact law gives a reliable picture of force field of the system which is in good agreements with the results of molecular dynamics (MD) simulations. Afterwards, equation of the transversal motion of graphene sheet is utilized on the basis of both the nonlocal theory of elasticity and the assumptions of classical plate theory. Then, to derive dynamic behavior of the system, a set including the proposed contact law and the equations of motion of both graphene sheet and fullerene molecule is solved numerically. In order to evaluate outcomes of this method, the problem is modeled by MD simulation. Despite intrinsic differences between analytical and MD methods as well as various errors arise due to transient nature of the problem, acceptable agreements are established between analytical and MD outcomes. As a result, the proposed analytical method can be reliably used to address similar impact problems. Furthermore, it is found that a single-layered graphene sheet is capable of trapping fullerenes approaching with low velocities. Otherwise, in case of rebound, the sheet effectively absorbs predominant portion of fullerene energy.

  5. First-principles study of thermal expansion and thermomechanics of single-layer black and blue phosphorus

    International Nuclear Information System (INIS)

    Sun, Hongyi; Liu, Gang; Li, Qingfang; Wan, X.G.

    2016-01-01

    The linear thermal expansion coefficients (LTEC) and thermomechanics of single-layer black and blue phosphorus are systematically studied using first-principles based on quasiharmonic approximation. We find the thermal expansion of black phosphorus is very anisotropic. The LTEC along zigzag direction has a turning from negative to positive at around 138 K, while the LTEC along armchair direction is positive (except below 8 K) and about 2.5 times larger than that along zigzag direction at 300 K. For blue phosphorus, the LTEC is negative in the temperature range from 0 to 350 K. In addition, we find that the Young's modulus and Poisson's ratio of black phosphorus along zigzag direction are 4 to 5 times larger than those along armchair direction within considered temperature range, showing a remarkable anisotropic in-plane thermomechanics property. The mechanisms of these peculiar thermal properties are also explored. This work provides a theoretical understanding of the thermal expansion and thermomechanics of this single layer phosphorus family, which will be useful in nanodevices. - Highlights: • The thermal properties of black and blue phosphorus are studied. • Black phosphorus shows remarkable anisotropic thermal expansion and thermomechanics properties. • Blue phosphorus shows novel negative thermal expansion. • The thermal expansion properties are well analyzed by grüneisen theory.

  6. A development of simulation and analytical program for through-diffusion experiments for a single layer of diffusion media

    International Nuclear Information System (INIS)

    Sato, Haruo

    2001-01-01

    A program (TDROCK1. FOR) for simulation and analysis of through-diffusion experiments for a single layer of diffusion media was developed. This program was made by Pro-Fortran language, which was suitable for scientific and technical calculations, and relatively easy explicit difference method was adopted for an analysis. In the analysis, solute concentration in the tracer cell as a function of time that we could not treat to date can be input and the decrease in the solute concentration as a function of time by diffusion from the tracer cell to the measurement cell, the solute concentration distribution in the porewater of diffusion media and the solute concentration in the measurement cell as a function of time can be calculated. In addition, solution volume in both cells and diameter and thickness of the diffusion media are also variable as an input condition. This simulation program could well explain measured result by simulating solute concentration in the measurement cell as a function of time for case which apparent and effective diffusion coefficients were already known. Based on this, the availability and applicability of this program to actual analysis and simulation were confirmed. This report describes the theoretical treatment for the through-diffusion experiments for a single layer of diffusion media, analytical model, an example of source program and the manual. (author)

  7. Alkali (Li, K and Na) and alkali-earth (Be, Ca and Mg) adatoms on SiC single layer

    Science.gov (United States)

    Baierle, Rogério J.; Rupp, Caroline J.; Anversa, Jonas

    2018-03-01

    First-principles calculations within the density functional theory (DFT) have been addressed to study the energetic stability, and electronic properties of alkali and alkali-earth atoms adsorbed on a silicon carbide (SiC) single layer. We observe that all atoms are most stable (higher binding energy) on the top of a Si atom, which moves out of the plane (in the opposite direction to the adsorbed atom). Alkali atoms adsorbed give raise to two spin unpaired electronic levels inside the band gap leading the SiC single layer to exhibit n-type semiconductor properties. For alkaline atoms adsorbed there is a deep occupied spin paired electronic level inside the band gap. These finding suggest that the adsorption of alkaline and alkali-earth atoms on SiC layer is a powerful feature to functionalize two dimensional SiC structures, which can be used to produce new electronic, magnetic and optical devices as well for hydrogen and oxygen evolution reaction (HER and OER, respectively). Furthermore, we observe that the adsorption of H2 is ruled by dispersive forces (van der Waals interactions) while the O2 molecule is strongly adsorbed on the functionalized system.

  8. Design of single-layer high-efficiency transmitting phase-gradient metasurface and high gain antenna

    Science.gov (United States)

    Zhang, Di; Yang, Xiaoqing; Su, Piqiang; Luo, Jiefang; Chen, Huijie; Yuan, Jianping; Li, Lixin

    2017-12-01

    In this paper, based on rotation phase-gradient principle, a single-layer, high-efficiency transmitting metasurface is designed and applied to high-gain antenna. In the case of circularly polarized incident wave, the PCR (polarization conversions ratio) of the metasurface element is greater than 90% in the band of 9.11–10.48 GHz. The transmitting wave emerges an anomalous refraction when left-handed circularly polarized wave are incident perpendicularly to the 1D phase-gradient metasurface, which is composed of cycle arrangement of 6 units with step value of 30°. The simulated anomalous refraction angle is 40.1°, coincided with the theoretical design value (40.6°). For further application, the 2D focused metasurface is designed to enhance the antenna performance while the left-handed circularly polarized antenna is placed at the focus. The simulated max gain is increased by 12 dB (182%) and the half-power beamwidth is reduced by 74.6°. The measured results are coincided with the simulations, which indicates the antenna has high directivity. The designed single-layer transmission metasurface has advantages of thin thickness (only 1.5 mm), high efficiency and light weight, and will have important application prospects in polarization conversion and beam control.

  9. The wind resistance of asphalt roofing shingles

    Science.gov (United States)

    Dixon, Craig Robert

    Asphalt shingle roofing is the leading cause of hurricane wind-related insured losses in residential buildings. Damage statistics generated from recent hurricanes indicate shingle roofs sustain damage in wind velocities below design-level with damage frequency increasing with shingle roof age. The objective of this dissertation is the identification of primary mechanisms triggering the failure of shingle roof systems in wind. The research goal is to reduce future shingle roof wind damage and improve our ability to predict asphalt shingle wind resistance. Five studies comprising this dissertation addressed the adhesive consistency and strength of aged asphalt shingles, system-level wind resistance, and the load model underpinning the ASTM D7158 wind test standard. The most significant and unexpected finding was partially unsealed shingles on field, hip, and ridge locations on Florida and Texas homes. Location on the shingle's sealant strip where unsealed and failure mode were consistent at each location. Total quantity of partially unsealed shingles in the field of the roof significantly increased with age, aligning with damage statistics. Full-scale wind tunnel tests demonstrate partially unsealed shingles are more vulnerable than fully sealed due to increased distributed force on sealant strip and concentrated force at the adhered and non-adhered interface. Uplift resistance was measured in artificially and naturally aged shingles. For artificially aged shingles, one of three products evaluated had statistically significant decreases in mean uplift resistance as exposure time increased. However, resistance was above design-level at all exposure test intervals. Naturally aged shingles also had resistance above design-level. Combined results demonstrate that reduced uplift capacity can occur, but high initial bond strength promotes long-term uplift resistance. Wind loads exerted on the shingles sealant strip load path were directly measured on fully sealed and

  10. 49 CFR 238.123 - Emergency roof access.

    Science.gov (United States)

    2010-10-01

    ... material shall conspicuously mark the line along which the roof skin shall be cut; and (2) A sign plate... CAUTION—WARN PASSENGERS BEFORE CUTTING CUT ALONG DASHED LINE TO GAIN ACCESS ROOF CONSTRUCTION—[STATE...

  11. COMPUTATIONAL INVESTIGATIONS OF DEFORMATED STRESS STATE OF THE SHELL ROOF

    Directory of Open Access Journals (Sweden)

    Yarov Vaycheslav Alekseevich

    2012-09-01

    Full Text Available Computational investigations of the new design concept of monolithic shell roof of the construction were made. Theoretical data of deformated stress state of the shell roof is found.

  12. Decoupling factors affecting plant diversity and cover on extensive green roofs.

    Science.gov (United States)

    MacIvor, J Scott; Margolis, Liat; Puncher, Curtis L; Carver Matthews, Benjamin J

    2013-11-30

    Supplemental irrigation systems are often specified on green roofs to ensure plant cover and growth, both important components of green roof performance and aesthetics. Properties of the growing media environment too can alter the assemblage of plant species able to thrive. In this study we determine how plant cover, above ground biomass and species diversity are influenced by irrigation and growing media. Grass and forb vegetative cover and biomass were significantly greater in organic based growing media but there was no effect of supplemental irrigation, with two warm season grasses dominating in those treatments receiving no supplemental irrigation. On the other hand, plant diversity declined without irrigation in organic media, and having no irrigation in inorganic growing media resulted in almost a complete loss of cover. Sedum biomass was less in inorganic growing media treatments and species dominance shifted when growing media organic content increased. Our results demonstrate that supplemental irrigation is required to maintain plant diversity on an extensive green roof, but not necessarily plant cover or biomass. These results provide evidence that planting extensive green roofs with a mix of plant species can ensure the survival of some species; maintaining cover and biomass when supplemental irrigation is turned off to conserve water, or during extreme drought. Crown Copyright © 2013. Published by Elsevier Ltd. All rights reserved.

  13. Probabilistic economic analysis of green roof benefits for policy design

    International Nuclear Information System (INIS)

    Clark, C.; Adriaens, P.; Talbot, B.

    2006-01-01

    The installation costs of green roofs continue to deter widespread use of green roof technology. Analyses of the boundary conditions for the cost differential between a green roof and a conventional roof are usually compared to environmental benefits such as storm water reduction and building energy savings. However, evidence is emerging that green roofs may play a role in urban air quality improvement. This paper discussed a methodology for developing probabilistic ranges of benefits and cost analyses. A probabilistic analysis was conducted to prepare a generalized cost-benefit analysis for application to a range of green roof projects. Environmental benefits of roof greening were quantified on a per unit surface area to assess environmental impact at the building scale. Parameters included conventional and green roof installation costs; storm water fees and fee reductions for green roofs; energy costs due to heat flux and the resultant savings through the installation of a green roof and the additional economic valuation of the public health benefits due to air pollution mitigation. Results were then integrated into an economic model to determine the length of time required for a return on investment in a green roof, assuming that a traditional roof would require replacement after 20 years. A net present value analysis was performed for an average-sized university roof. Results of the study showed that a valuation of environmental benefits can reduce the time required for a return on investment in a moderately priced green roof. While reduced installation costs reduced the time required for a return on investment, optimizing the green roof system for maximum environmental benefit had a greater potential to provide a higher return. It was concluded that the benefit of improved air quality should not be ignored by green roof policy-makers as a valuation tool. 10 refs., 3 tabs., 1 fig

  14. 30 CFR 75.211 - Roof testing and scaling.

    Science.gov (United States)

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Roof testing and scaling. 75.211 Section 75.211 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR COAL MINE SAFETY AND HEALTH MANDATORY SAFETY STANDARDS-UNDERGROUND COAL MINES Roof Support § 75.211 Roof testing and scaling. (a) A...

  15. Substrate Composition and Depth Affect Soil Moisture Behavior and Plant-Soil Relationship on Mediterranean Extensive Green Roofs

    Directory of Open Access Journals (Sweden)

    Julie Chenot

    2017-10-01

    Full Text Available The Mediterranean basin is extremely vulnerable to climate change, and one of the areas most impacted by human water demand. Yet the green roofs increasingly created both for aesthetic reasons and to limit pollution and urban runoff are themselves very water-demanding. Successful green roof installation depends on the establishment of the vegetation, and the substrate is the key element: it conserves water, and provides the nutrients and physical support indispensable for plant growth. Since typical Mediterranean plant communities require no maintenance, this study seeks to develop techniques for creating maintenance- and watering-free horizontal green roofs for public or private buildings in a Mediterranean context. The innovative aspect of this study lies in creating two soil mixes, fine elements (clay and silt and coarse elements (pebbles of all sizes, in two different thicknesses, to assess vegetation development. Monitoring of substrate moisture was carried out and coupled with local rainfall measurements during summer and autumn. As expected, substrate moisture is mainly influenced by substrate depth (the deeper, the moister and composition (the finer the particles (clays and silts, the higher the moisture content. Vegetation cover impacts moisture to a lesser extent but is itself affected by the composition and depth of the substrates. These results are subsequently discussed with relation to the issue of sustainable green roofs in Mediterranean climates. Considering applications of our results, for an optimal colonization of a Mediterranean vegetation, a substrate thickness of 15 cm composed mainly of fine elements (75% clay-silt and 25% pebble-sand would be recommended in green roofs.

  16. Collaborative integral design of active roofs

    NARCIS (Netherlands)

    Zeiler, W.; Quanjel, E.M.C.J.; Borsboom, W.A.

    2009-01-01

    The application of photo-voltaic elements is the most economical on the roof. Still this often leads to severe problems due to poor coordination of all the design and practical aspects involved. This paper describes the research methodology, based on Methodical Design, as used in a design approach

  17. One Roof Judicial System in Indonesia

    Directory of Open Access Journals (Sweden)

    - Sufiarina

    2012-09-01

    Full Text Available Judicial power as an independent and autonomous power must be free from any intervention and power, thus ensuring that judges possess independence and impartiality in handling cases. One of the measures for enhancing the independence and autonomy of the judiciary is by placing it under the one roof judicial arrangement developed by the Supreme Court, both from the judicial as well as the non-judicial technical aspects. Up to the present time, endeavors for bringing the four court jurisdictions under the one roof judicial arrangement developed by the Supreme Court have not been completely materialized, due to the existing dualism in judicial power at various courts. The objective of this research is to understand the developments in the endeavors towards bringing the Indonesian judicial system under the one roof judicial arrangement developed by the Supreme Court. The type of research applied is descriptive normative juridical research, namely legal research based on examining secondary data. As the research results indicate, the one roof system developed by the Supreme Court is already being implemented, with the exception of the Military Court and the Tax Court within the State Administration Court jurisdiction.

  18. Accidents due to falls from roof slabs.

    Science.gov (United States)

    Rudelli, Bruno Alves; Silva, Marcelo Valerio Alabarce da; Akkari, Miguel; Santili, Claudio

    2013-01-01

    CONTEXT AND OBJECTIVE Falls from the roof slabs of houses are accidents of high potential severity that occur in large Brazilian cities and often affect children and adolescents. The aims of this study were to characterize the factors that predispose towards this type of fall involving children and adolescents, quantify the severity of associated lesions and suggest preventive measures. DESIGN AND SETTING Descriptive observational prospective longitudinal study in two hospitals in the metropolitan region of São Paulo. METHODS Data were collected from 29 cases of falls from roof slabs involving children and adolescents between October 2008 and October 2009. RESULTS Cases involving males were more prevalent, accounting for 84%. The predominant age group was schoolchildren (7 to 12 years old; 44%). Leisure activities were most frequently being practiced on the roof slab at the time of the fall (86%), and flying a kite was the most prevalent game (37.9%). In 72% of the cases, the children were unaccompanied by an adult responsible for them. Severe conditions such as multiple trauma and traumatic brain injuries resulted from 79% of the accidents. CONCLUSION Falls from roof slabs are accidents of high potential severity, and preventive measures aimed towards informing parents and guardians about the dangers and risk factors associated with this type of accident are needed, along with physical protective measures, such as low walls around the slab and gates with locks to restrict free access to these places.

  19. Accidents due to falls from roof slabs

    Directory of Open Access Journals (Sweden)

    Bruno Alves Rudelli

    Full Text Available CONTEXT AND OBJECTIVE Falls from the roof slabs of houses are accidents of high potential severity that occur in large Brazilian cities and often affect children and adolescents. The aims of this study were to characterize the factors that predispose towards this type of fall involving children and adolescents, quantify the severity of associated lesions and suggest preventive measures. DESIGN AND SETTING Descriptive observational prospective longitudinal study in two hospitals in the metropolitan region of São Paulo. METHODS Data were collected from 29 cases of falls from roof slabs involving children and adolescents between October 2008 and October 2009. RESULTS Cases involving males were more prevalent, accounting for 84%. The predominant age group was schoolchildren (7 to 12 years old; 44%. Leisure activities were most frequently being practiced on the roof slab at the time of the fall (86%, and flying a kite was the most prevalent game (37.9%. In 72% of the cases, the children were unaccompanied by an adult responsible for them. Severe conditions such as multiple trauma and traumatic brain injuries resulted from 79% of the accidents. CONCLUSION Falls from roof slabs are accidents of high potential severity, and preventive measures aimed towards informing parents and guardians about the dangers and risk factors associated with this type of accident are needed, along with physical protective measures, such as low walls around the slab and gates with locks to restrict free access to these places.

  20. Load-Bearing Capacity of Roof Trusses

    DEFF Research Database (Denmark)

    Sørensen, John Dalsgaard; Damkilde, Lars; Munch-Andersen, J.

    2004-01-01

    systems such as roof trusses are established and statistical characteristics of the load bearing capacity are determined. The results show that there is a significant increase in the characteristic (nominal) value and a reduction in the coefficient of variation (COV) for typical loads such as permanent...

  1. Rating system for coal mine roofs

    CSIR Research Space (South Africa)

    Canbulat, I

    2002-09-01

    Full Text Available It is standard practice in the majority of rock engineering applications to use a rock mass classification method to evaluate the condition of rock, i.e. to quantify, in an objective manner, the characteristics of good or bad roof. These rockmass...

  2. The 3rd power unit roofing decontamination

    International Nuclear Information System (INIS)

    Samojlenko, Yu.N.; Golubev, V.V.

    1989-01-01

    The most features of the 3rd power unit (PU) roofing decontamination are described: 1) the most active materials were thrown into the 4th PU ruins before the Ukrytie construction completion; 2) the decontamination was fulfilled using remote-controlled mechanisms and manual devices (the main part). 6 figs.; 1 tab

  3. Pluralism and Prayer under One Roof.

    Science.gov (United States)

    McMurtrie, Beth

    1999-01-01

    Reports on increasing efforts by colleges and universities to meet the spiritual needs of minority students by providing religious centers where students of all faiths can worship under one roof. Examples include the Massachusetts Institute of Technology, Mount Holyoke College (Massachusetts), and Johns Hopkins University (Maryland). (DB)

  4. Evolution of cool-roof standards in the United States

    Energy Technology Data Exchange (ETDEWEB)

    Akbari, Hashem; Akbari, Hashem; Levinson, Ronnen

    2008-07-11

    Roofs that have high solar reflectance and high thermal emittance stay cool in the sun. A roof with lower thermal emittance but exceptionally high solar reflectance can also stay cool in the sun. Substituting a cool roof for a noncool roof decreases cooling-electricity use, cooling-power demand, and cooling-equipment capacity requirements, while slightly increasing heating-energy consumption. Cool roofs can also lower citywide ambient air temperature in summer, slowing ozone formation and increasing human comfort. Provisions for cool roofs in energy-efficiency standards can promote the building- and climate-appropriate use of cool roofing technologies. Cool-roof requirements are designed to reduce building energy use, while energy-neutral cool-roof credits permit the use of less energy-efficient components (e.g., larger windows) in a building that has energy-saving cool roofs. Both types of measures can reduce the life-cycle cost of a building (initial cost plus lifetime energy cost). Since 1999, several widely used building energy-efficiency standards, including ASHRAE 90.1, ASHRAE 90.2, the International Energy Conservation Code, and California's Title 24 have adopted cool-roof credits or requirements. This paper reviews the technical development of cool-roof provisions in the ASHRAE 90.1, ASHRAE 90.2, and California Title 24 standards, and discusses the treatment of cool roofs in other standards and energy-efficiency programs. The techniques used to develop the ASHRAE and Title 24 cool-roof provisions can be used as models to address cool roofs in building energy-efficiency standards worldwide.

  5. CLASSIFICATION OF ROOF MATERIALS USING HYPERSPECTRAL DATA

    Directory of Open Access Journals (Sweden)

    C. Chisense

    2012-07-01

    Full Text Available Mapping of surface materials in urban areas using aerial imagery is a challenging task. This is because there are numerous materials present in relatively small regions. Hyperspectral data features a fine spectral resolution and thus has a significant capability for automatic identification and mapping of urban surface materials. In this study an approach for identification of roof surface materials using hyperspectral data is presented. The study is based on an urban area in Ludwigsburg, Germany, using a HyMap data set recorded during the HyMap campaign in August, 2010. Automatisierte Liegenschaftskarte (ALK vector data with a building layer is combined with the HyMap data to limit the analysis to roofs. A spectral library for roofs is compiled based on field and image measurements. In the roof material identification process, supervised classification methods, namely spectral angle mapper and spectral information divergence and the object oriented ECHO (extraction and classification of homogeneous objects approach are compared. In addition to the overall shape of spectral curves, position and strength of absorptions features are used to enhance material identification. The discriminant analysis feature extraction method is applied to the HyMap data in order to identify features (band combinations suitable for discriminating between the target classes. The identified optimal features are used to create a new data set which is later classified using the ECHO classifier. The classification results with respect to material types of roofs are presented in this study. The most important results are evaluated using orthophotos, probability maps and field visits.

  6. Phase manipulation of Goos–Hänchen shifts in a single-layer of graphene nanostructure under strong magnetic field

    Science.gov (United States)

    Solookinejad, Gh; Jabbari, M.; Panahi, M.; Ahmadi Sangachin, E.

    2017-11-01

    In this paper, we discuss the phase management of Goos–Hänchen (GH) shifts of a probe light through a cavity with a single-layer graphene nanostructure under a strong magnetic field. By using the quantum mechanical density matrix formalism we study the GH shifts of reflected and transmitted light beams. It is realized that negative or positive GH shifts can be achieved simultaneously by tuning some controllable parameters such as relative phase and the Rabi frequency of the applied fields. Moreover, the thickness effect of the cavity structure is considered as an effective parameter for adjusting the GH shifts of reflected and transmitted light beams. We find that by choosing suitable parameters, a maximum negative shift of 4.5 mm and positive shift of 5.4 mm are possible for GH shifts in reflected and transmitted light. Our proposed model may be useful for developing all-optical devices in the infrared region.

  7. p-wave triggered superconductivity in single-layer graphene on an electron-doped oxide superconductor.

    Science.gov (United States)

    Di Bernardo, A; Millo, O; Barbone, M; Alpern, H; Kalcheim, Y; Sassi, U; Ott, A K; De Fazio, D; Yoon, D; Amado, M; Ferrari, A C; Linder, J; Robinson, J W A

    2017-01-19

    Electron pairing in the vast majority of superconductors follows the Bardeen-Cooper-Schrieffer theory of superconductivity, which describes the condensation of electrons into pairs with antiparallel spins in a singlet state with an s-wave symmetry. Unconventional superconductivity was predicted in single-layer graphene (SLG), with the electrons pairing with a p-wave or chiral d-wave symmetry, depending on the position of the Fermi energy with respect to the Dirac point. By placing SLG on an electron-doped (non-chiral) d-wave superconductor and performing local scanning tunnelling microscopy and spectroscopy, here we show evidence for a p-wave triggered superconducting density of states in SLG. The realization of unconventional superconductivity in SLG offers an exciting new route for the development of p-wave superconductivity using two-dimensional materials with transition temperatures above 4.2 K.

  8. Controlling the formation of wrinkles in a single layer graphene sheet subjected to in-plane shear

    KAUST Repository

    Duan, Wen Hui

    2011-08-01

    The initiation and development of wrinkles in a single layer graphene sheet subjected to in-plane shear displacements are investigated. The dependence of the wavelength and amplitude of wrinkles on the applied shear displacements is explicitly obtained with molecular mechanics simulations. A continuum model is developed for the characteristics of the wrinkles which show that the wrinkle wavelength decreases with an increase in shear loading, while the amplitude of the wrinkles is found to initially increase and then become stable. The propagation and growth process of the wrinkles in the sheet is elucidated. It is expected that the research could promote applications of graphenes in the transportation of biological systems, separation science, and the development of the fluidic electronics. © 2011 Elsevier Ltd. All rights reserved.

  9. Phase transitions and optical properties of the semiconducting and metallic phases of single-layer MoS₂.

    Science.gov (United States)

    Fair, K M; Ford, M J

    2015-10-30

    We report density functional theory calculations for single layer MoS2 in its 2H, semiconducting and 1T metallic phases in order to understand the relative stability of these two phases and transition between them in the presence of adsorbed lithium atoms and under compressive strain. We have determined the diffusion barriers between the two phases and demonstrate how the presence of Li adatoms or strain can significantly reduce these barriers. We show that the 2H and 1T structures have the same energy under 15% biaxial, compressive strain. This is the same strain value posited by Lin et al (2014 Nat. Nanotechnology 9 391-396) for their intermediate α phase. Calculations of the 1T and 2H permittivity and electron energy loss spectrum are also performed and characterized.

  10. 1617 nm emission control of an Er:YAG laser by a corrugated single-layer resonant grating mirror.

    Science.gov (United States)

    Aubourg, Adrien; Rumpel, Martin; Didierjean, Julien; Aubry, Nicolas; Graf, Thomas; Balembois, François; Georges, Patrick; Ahmed, Marwan Abdou

    2014-02-01

    A resonant grating mirror (RGM) that combines a single layer planar waveguide and a subwavelength grating is used to simultaneously control the beam quality, the spectral bandwidth, and the polarization state of an Er:YAG laser. This simple device is compared to classical methods using several intracavity components: an etalon for wavelength selection, a thin film polarizer for polarization selection, and an aperture for spatial filtering. It is demonstrated that the RGM provides the same polarization purity, an enhanced spectral filtering, and a significant improvement of the beam quality. In CW operation, the Er:YAG laser with a RGM emits an output power of 1.4 W at 1617 nm with a M2 of 1.4.

  11. Highly balanced single-layer high-temperature superconductor SQUID gradiometer freely movable within the Earth's magnetic field

    International Nuclear Information System (INIS)

    Schultze, Volkmar; IJsselsteijn, Rob; May, Torsten; Meyer, Hans-Georg

    2003-01-01

    We developed a gradiometer system based on a single-layer high-temperature superconductor dc superconducting quantum interference device (SQUID), which can be freely moved within the Earth's magnetic field during measurement. The problem of circumferential shielding currents in the parallel gradiometer pick-up loop is solved by the use of an appropriately designed magnetometer SQUID integrated on the gradiometer chip. The magnetometer's feedback coil of the flux-locked loop is laid out as a small Helmholtz coil pair, thus keeping the homogeneous magnetic field constant for both the magnetometer and the gradiometer. Therefore, the balance of the directly coupled gradiometer SQUID is enhanced from 100 up to 3800. The noise limited magnetic field gradient resolution of 45 pT m -1 Hz -1/2 is preserved down to frequencies of several Hz even after strong motion in the Earth's magnetic field

  12. The Self-Drying Concept for Flat Roofs

    DEFF Research Database (Denmark)

    Korsgaard, Vagn; Bunch-Nielsen, Tommy; Rode, Carsten

    1996-01-01

    ways. From the interior by diffusion and convection. During construction from moist materials or rain. Later on, rain water may enter through leaks in the roofing.From laboratory experiment, computer calculations and practical experience it is concluded, that the Self-Drying Roof concept works for both...... moisture levels low within a roof assembly by providing a path for moisture to periodically escape. A design strategy that assumes roof assemblies may get wet and permits them to dry, presents a more forgiving and perhaps less costly alternative.Moisture may enter a roof assembly in a number of different...

  13. Analysis of current-driven oscillatory dynamics of single-layer homoepitaxial islands on crystalline conducting substrates

    Science.gov (United States)

    Dasgupta, Dwaipayan; Kumar, Ashish; Maroudas, Dimitrios

    2018-03-01

    We report results of a systematic study on the complex oscillatory current-driven dynamics of single-layer homoepitaxial islands on crystalline substrate surfaces and the dependence of this driven dynamical behavior on important physical parameters, including island size, substrate surface orientation, and direction of externally applied electric field. The analysis is based on a nonlinear model of driven island edge morphological evolution that accounts for curvature-driven edge diffusion, edge electromigration, and edge diffusional anisotropy. Using a linear theory of island edge morphological stability, we calculate a critical island size at which the island's equilibrium edge shape becomes unstable, which sets a lower bound for the onset of time-periodic oscillatory dynamical response. Using direct dynamical simulations, we study the edge morphological dynamics of current-driven single-layer islands at larger-than-critical size, and determine the actual island size at which the migrating islands undergo a transition from steady to time-periodic asymptotic states through a subcritical Hopf bifurcation. At the highest symmetry of diffusional anisotropy examined, on {111} surfaces of face-centered cubic crystalline substrates, we find that more complex stable oscillatory states can be reached through period-doubling bifurcation at island sizes larger than those at the Hopf points. We characterize in detail the island morphology and dynamical response at the stable time-periodic asymptotic states, determine the range of stability of these oscillatory states terminated by island breakup, and explain the morphological features of the stable oscillating islands on the basis of linear stability theory.

  14. Hydrological performance of an extensive green roof: a case study from the central Europe (Bustehrad, Czech Republic)

    Science.gov (United States)

    Tománková, Klára; Sněhota, Michal; Jelínková, Vladimíra

    2016-04-01

    Extensive green roofs with a thin growing medium require minimal maintenance, and in general no irrigation. The proper functioning of such systems rests with their structural constituents, especially with the substrate used for planting. An extensive green roof with poorly developed vegetation and with a soil layer of a maximum thickness of 5 cm mixed with local stripped topsoil with crushed bricks and green waste was studied with respect to the hydrological behavior. The substrate classified as loam comprises a significant proportion of very fine particles and thus it is prone to clogging up of soil pores and forming of fissures on the surface. The green roof studied is well equipped for measuring meteorological data including air temperature, wind speed and direction, net radiation, relative humidity, and rainfall intensity. The meteorological information on the site is completed by soil temperature measurement. The 12 m long transect is equipped with eight time domain reflectometry probes (TDR) to monitor soil water content. Soil physical properties (bulk density, porosity, grain size distribution) and soil hydraulic characteristics (soil water retention curve) were obtained. The numerical modeling of transient soil water movement in the green roof substrate was performed using a two-dimensional model based on the Richards' equation. Results were compared with the soil water content data acquired. Six alternative scenarios were formulated to discuss possible improvement of green roof functioning and four selected scenarios were simulated. The study helped us to improve our understanding of the flow processes through the green roof soil system under study. The alternative scenario simulations allowed hydrological assessment of roof construction amendments. The research was realized as a part of the University Centre for Energy Efficient Buildings supported by the EU and with financial support from the Czech Science Foundation under project number 14-10455P.

  15. Establishing green roof infrastructure through environmental policy instruments.

    Science.gov (United States)

    Carter, Timothy; Fowler, Laurie

    2008-07-01

    Traditional construction practices provide little opportunity for environmental remediation to occur in urban areas. As concerns for environmental improvement in urban areas become more prevalent, innovative practices which create ecosystem services and ecologically functional land cover in cities will be in higher demand. Green roofs are a prime example of one of these practices. The past decade has seen the North American green roof industry rapidly expand through international green roof conferences, demonstration sites, case studies, and scientific research. This study evaluates existing international and North American green roof policies at the federal, municipal, and community levels. Green roof policies fall into a number of general categories, including direct and indirect regulation, direct and indirect financial incentives, and funding of demonstration or research projects. Advantages and disadvantages of each category are discussed. Salient features and a list of prompting standards common to successfully implemented green roof strategies are then distilled from these existing policies. By combining these features with data collected from an experimental green roof site in Athens, Georgia, the planning and regulatory framework for widespread green roof infrastructure can be developed. The authors propose policy instruments be multi-faceted and spatially focused, and also propose the following recommendations: (1) Identification of green roof overlay zones with specifications for green roofs built in these zones. This spatial analysis is important for prioritizing areas of the jurisdiction where green roofs will most efficiently function; (2) Offer financial incentives in the form of density credits and stormwater utility fee credits to help overcome the barriers to entry of the new technology; (3) Construct demonstration projects and institutionalize a commitment greening roofs on publicly-owned buildings as an effective way of establishing an educated

  16. Green roof and storm water management policies: monitoring experiments on the ENPC Blue Green Wave

    Science.gov (United States)

    Versini, Pierre-Antoine; Gires, Auguste; Fitton, George; Tchiguirinskaia, Ioulia; Schertzer, Daniel

    2015-04-01

    Currently widespread in new urban projects, green roofs have shown a positive impact on urban runoff at the building/parcel scale. Nevertheless, there is no specific policy promoting their implementation neither in Europe nor in France. Moreover they are not taken into account (and usually considered as an impervious area) in the sizing of a retention basin for instance. An interesting example is located in the heart of the Paris-East Cluster for Science and Technology (Champs-sur-Marne, France). Since 2013 a large (1 ha) wavy-form vegetated roof (called bleu green wave) is implemented. Green roof area and impervious areas are connected to a large retention basin, which has been oversized. The blue green wave represents a pioneering site where an initially amenity (decorative) design project has been transformed into a research oriented one. Several measurement campaigns have been conducted to investigate and better understand the hydrological behaviour of such a structure. Rainfall, humidity, wind velocity, water content and temperature have been particularly studied. The data collected are used for several purposes: (i) characterize the spatio-temporal variability of the green roof response, (ii) calibrate and validate a specific model simulating its hydrological behavior. Based on monitoring and modeling results, green roof performances will be quantified. It will be possible to estimate how they can reduce stormwater runoff and how these performances can vary in space and in time depending on green roof configuration, rainfall event characteristics and antecedent conditions. These quantified impacts will be related to regulation rules established by stormwater managers in order to connect the parcel to the sewer network. In the particular case of the building of a retention basin, the integration of green roof in the sizing of the basin will be studied. This work is funded by the European Blue Green Dream project (http://bgd.org.uk/, funded by Climate

  17. EXTRUDED POLYSTYRENE FOAM IN FLAT ROOFS

    Directory of Open Access Journals (Sweden)

    Zhukov Aleksey Dmitrievich

    2014-09-01

    Full Text Available In our article we prove the necessity of applying thermal insulation with low water absorption and resistance and preserving mechanical and thermophysical properties in corrosive environment in flat roofs, where there is always a danger of penetrating condensed moisture into the structure. As such material we offered extruded polystyrene foam - heat-insulating polymer material with uniformly distributed closed cells. The products are used in the form of slab insulation and special items - for forming slopes and venting.

  18. Installation of a Roof Mounted Photovoltaic System

    Science.gov (United States)

    Lam, M.

    2015-12-01

    In order to create a safe and comfortable environment for students to learn, a lot of electricity, which is generated from coal fired power plants, is used. Therefore, ISF Academy, a school in Hong Kong with approximately 1,500 students, will be installing a rooftop photovoltaic (PV) system with 302 solar panels. Not only will these panels be used to power a classroom, they will also serve as an educational opportunity for students to learn about the importance of renewable energy technology and its uses. There were four different options for the installation of the solar panels, and the final choice was made based on the loading capacity of the roof, considering the fact that overstressing the roof could prove to be a safety hazard. Moreover, due to consideration of the risk of typhoons in Hong Kong, the solar panel PV system will include concrete plinths as counterweights - but not so much that the roof would be severely overstressed. During and after the installation of the PV system, students involved would be able to do multiple calculations, such as determining the reduction of the school's carbon footprint. This can allow students to learn about the impact renewable energy can have on the environment. Another project students can participate in includes measuring the efficiency of the solar panels and how much power can be produced per year, which in turn can help with calculate the amount of money saved per year and when we will achieve economic parity. In short, the installation of the roof mounted PV system will not only be able to help save money for the school but also provide learning opportunities for students studying at the ISF Academy.

  19. Effective roof support for tabular stopes.

    CSIR Research Space (South Africa)

    Ottermann, RW

    2002-09-01

    Full Text Available on surface in the laboratory and in a mock-up stope. A risk analysis, in which technical, logistical and economical aspects were assessed, was done to determine the critical areas of the system. The tests and risk assessment of the roof support system... IN MOCK-UP STOPE............................................................................. 29 5.2.1 University of Pretoria mock-up stope......................................................29 5.2.2 Kloof mine mock-up stope...

  20. Creating a marketplace for green roofs in Chicago

    International Nuclear Information System (INIS)

    Vitt Sale, L.; Berkshire, M.

    2004-01-01

    Since 2003, the Chicago Department of Planning and Development has been encouraging city developers to consider installing green roofs on buildings in Chicago, with the belief that this practice results in mitigation of the urban heat island effect, cleaner runoff leaving green roofs, sound attenuation, aesthetic value, oxygen production, and mitigation of carbon dioxide emissions. However, the benefits to developers, which include reduced stormwater runoff, extended roof life and energy savings, in total do not offset the first cost premium of a green roof. Despite this, and with no mandate requiring green roofs, the marketplace is growing. After seeing green roofs on a tour in Europe, the mayor of Chicago encouraged the first design and installation of a 20,300 square foot demonstration green roof in Chicago, and other city-sponsored pilot projects followed shortly after. Since then, the number of green roofs in Chicago has grown to over one million square feet. A map of Chicago showing locations of most of the projects was presented. It was suggested that lower prices for green roofs, higher energy costs and an inclination to invest in long-term strategies would accelerate the market. In an effort to engage the public in dialogue, the Department of Planning and Development held seminars to promote the benefits of green roofs . Participants had many questions about the applicability of green roofs to Chicago, expressing skepticism that Chicago's climate would provide the same benefits as in Europe. Other concerns were expressed regarding the devaluation of property values resulting from placing green roofs on buildings; doubts about roof leaks; maintenance practices; and, bugs and mold. Since the first cost premium of the system remains a question, most participants expressed interest in some kind of incentive program, but remained open-minded if benefits could be proved. 6 figs

  1. Single layers and multilayers of GaN and AlN in square-octagon structure: Stability, electronic properties, and functionalization

    Science.gov (United States)

    Gürbüz, E.; Cahangirov, S.; Durgun, E.; Ciraci, S.

    2017-11-01

    Further to planar single-layer hexagonal structures, GaN and AlN can also form free-standing, single-layer structures constructed from squares and octagons. We performed an extensive analysis of dynamical and thermal stability of these structures in terms of ab initio finite-temperature molecular dynamics and phonon calculations together with the analysis of Raman and infrared active modes. These single-layer square-octagon structures of GaN and AlN display directional mechanical properties and have wide, indirect fundamental band gaps, which are smaller than their hexagonal counterparts. These density functional theory band gaps, however, increase and become wider upon correction. Under uniaxial and biaxial tensile strain, the fundamental band gaps decrease and can be closed. The electronic and magnetic properties of these single-layer structures can be modified by adsorption of various adatoms, or by creating neutral cation-anion vacancies. The single-layer structures attain magnetic moment by selected adatoms and neutral vacancies. In particular, localized gap states are strongly dependent on the type of vacancy. The energetics, binding, and resulting electronic structure of bilayer, trilayer, and three-dimensional (3D) layered structures constructed by stacking the single layers are affected by vertical chemical bonds between adjacent layers. In addition to van der Waals interaction, these weak vertical bonds induce buckling in planar geometry and enhance their binding, leading to the formation of stable 3D layered structures. In this respect, these multilayers are intermediate between van der Waals solids and wurtzite crystals, offering a wide range of tunability.

  2. Stormwater runoff mitigation and nutrient leaching from a green roof designed to attract native pollinating insects

    Science.gov (United States)

    Fogarty, S.; Grogan, D. S.; Hale, S. R.

    2013-12-01

    A green roof is typically installed for one of two reasons: to mitigate the 'urban heat island' effect, reducing ambient temperatures and creating energy savings, or to reduce both the quantity and intensity of stormwater runoff, which is a major cause of river erosion and eutrophication. The study of green roofs in the United States has focused on commercial systems that use a proprietary expanded shale or clay substrate, along with succulent desert plants (mainly Sedum species). The green roof has the potential not only to provide thermal insulation and reduce storm runoff, but also to reclaim some of the natural habitat that has been lost to the built environment. Of special importance is the loss of habitat for pollinating insects, particularly native bees, which have been in decline for at least two decades. These pollinators are essential for crop production and for the reproduction of at least 65% of wild plants globally. Our study involves the installation of a small (4ft by 4ft), self-designed green roof system built with readily available components from a hardware store. The garden will be filled with a soilless potting mix, combined with 15% compost, and planted with grasses and wildflowers native to the Seacoast, New Hampshire region. Some of the plant species are used by bees for nesting materials, while others provide food in the form of nectar, pollen, and seeds for bees, butterflies, hummingbirds, and granivorous birds. We monitor precipitation on the roof and runoff from the garden on a per storm basis, and test grab samples of runoff for dissolved organic nitrogen and phosphorous. Runoff and nutrient concentration results are compared to a non-vegetated roof surface, and a proprietary Green Grid green roof system. This project is designed to address three main questions of interest: 1) Can these native plant species, which potentially provide greater ecosystem services than Sedum spp. in the form of food and habitat, survive in the conditions on

  3. EVALUATION OF ROOF BOLTING REQUIREMENTS BASED ON IN-MINE ROOF BOLTER DRILLING

    Energy Technology Data Exchange (ETDEWEB)

    Syd S. Peng

    2005-01-15

    In this quarter, the field, theoretical and programming works have been performed toward achieving the research goals set in the proposal. The main accomplishments in this quarter included: (1) one more field test has been conducted in an underground coal mine, (2) optimization studies of the control parameters have been conducted, (3) method to use torque to thrust ratio as indicator of rock relative hardness has also been explored, and (4) about 98% of the development work for the roof geology mapping program, MRGIS, has completed, (5) A real time roof geology mapping system for roof bolters in limestone mine, including a special version of the geology mapping program and hardware, has already been verified to perform very well in underground production condition.

  4. Density functional theory study of chemical sensing on surfaces of single-layer MoS2 and graphene

    International Nuclear Information System (INIS)

    Mehmood, F.; Pachter, R.

    2014-01-01

    In this work, density functional theory (DFT) calculations have been used to investigate chemical sensing on surfaces of single-layer MoS 2 and graphene, considering the adsorption of the chemical compounds triethylamine, acetone, tetrahydrofuran, methanol, 2,4,6-trinitrotoluene, o-nitrotoluene, o-dichlorobenzene, and 1,5-dicholoropentane. Physisorption of the adsorbates on free-standing surfaces was analyzed in detail for optimized material structures, considering various possible adsorption sites. Similar adsorption characteristics for the two surface types were demonstrated, where inclusion of a correction to the DFT functional for London dispersion was shown to be important to capture interactions at the interface of molecular adsorbate and surface. Charge transfer analyses for adsorbed free-standing surfaces generally demonstrated very small effects. However, charge transfer upon inclusion of the underlying SiO 2 substrate rationalized experimental observations for some of the adsorbates considered. A larger intrinsic response for the electron-donor triethylamine adsorbed on MoS 2 as compared to graphene was demonstrated, which may assist in devising chemical sensors for improved sensitivity

  5. Electronic evidence of an insulator-superconductor crossover in single-layer FeSe/SrTiO3 films.

    Science.gov (United States)

    He, Junfeng; Liu, Xu; Zhang, Wenhao; Zhao, Lin; Liu, Defa; He, Shaolong; Mou, Daixiang; Li, Fangsen; Tang, Chenjia; Li, Zhi; Wang, Lili; Peng, Yingying; Liu, Yan; Chen, Chaoyu; Yu, Li; Liu, Guodong; Dong, Xiaoli; Zhang, Jun; Chen, Chuangtian; Xu, Zuyan; Chen, Xi; Ma, Xucun; Xue, Qikun; Zhou, X J

    2014-12-30

    In high-temperature cuprate superconductors, it is now generally agreed that superconductivity is realized by doping an antiferromagnetic Mott (charge transfer) insulator. The doping-induced insulator-to-superconductor transition has been widely observed in cuprates, which provides important information for understanding the superconductivity mechanism. In the iron-based superconductors, however, the parent compound is mostly antiferromagnetic bad metal, raising a debate on whether an appropriate starting point should go with an itinerant picture or a localized picture. No evidence of doping-induced insulator-superconductor transition (or crossover) has been reported in the iron-based compounds so far. Here, we report an electronic evidence of an insulator-superconductor crossover observed in the single-layer FeSe film grown on a SrTiO3 substrate. By taking angle-resolved photoemission measurements on the electronic structure and energy gap, we have identified a clear evolution of an insulator to a superconductor with increasing carrier concentration. In particular, the insulator-superconductor crossover in FeSe/SrTiO3 film exhibits similar behaviors to that observed in the cuprate superconductors. Our results suggest that the observed insulator-superconductor crossover may be associated with the two-dimensionality that enhances electron localization or correlation. The reduced dimensionality and the interfacial effect provide a new pathway in searching for new phenomena and novel superconductors with a high transition temperature.

  6. Electronic evidence of an insulator–superconductor crossover in single-layer FeSe/SrTiO3 films

    Science.gov (United States)

    He, Junfeng; Liu, Xu; Zhang, Wenhao; Zhao, Lin; Liu, Defa; He, Shaolong; Mou, Daixiang; Li, Fangsen; Tang, Chenjia; Li, Zhi; Wang, Lili; Peng, Yingying; Liu, Yan; Chen, Chaoyu; Yu, Li; Liu, Guodong; Dong, Xiaoli; Zhang, Jun; Chen, Chuangtian; Xu, Zuyan; Chen, Xi; Ma, Xucun; Xue, Qikun; Zhou, X. J.

    2014-01-01

    In high-temperature cuprate superconductors, it is now generally agreed that superconductivity is realized by doping an antiferromagnetic Mott (charge transfer) insulator. The doping-induced insulator-to-superconductor transition has been widely observed in cuprates, which provides important information for understanding the superconductivity mechanism. In the iron-based superconductors, however, the parent compound is mostly antiferromagnetic bad metal, raising a debate on whether an appropriate starting point should go with an itinerant picture or a localized picture. No evidence of doping-induced insulator–superconductor transition (or crossover) has been reported in the iron-based compounds so far. Here, we report an electronic evidence of an insulator–superconductor crossover observed in the single-layer FeSe film grown on a SrTiO3 substrate. By taking angle-resolved photoemission measurements on the electronic structure and energy gap, we have identified a clear evolution of an insulator to a superconductor with increasing carrier concentration. In particular, the insulator–superconductor crossover in FeSe/SrTiO3 film exhibits similar behaviors to that observed in the cuprate superconductors. Our results suggest that the observed insulator–superconductor crossover may be associated with the two-dimensionality that enhances electron localization or correlation. The reduced dimensionality and the interfacial effect provide a new pathway in searching for new phenomena and novel superconductors with a high transition temperature. PMID:25502774

  7. High performance of low band gap polymer-based ambipolar transistor using single-layer graphene electrodes.

    Science.gov (United States)

    Choi, Jong Yong; Kang, Woonggi; Kang, Boseok; Cha, Wonsuk; Son, Seon Kyoung; Yoon, Youngwoon; Kim, Hyunjung; Kang, Youngjong; Ko, Min Jae; Son, Hae Jung; Cho, Kilwon; Cho, Jeong Ho; Kim, BongSoo

    2015-03-18

    Bottom-contact bottom-gate organic field-effect transistors (OFETs) are fabricated using a low band gap pDTTDPP-DT polymer as a channel material and single-layer graphene (SLG) or Au source/drain electrodes. The SLG-based ambipolar OFETs significantly outperform the Au-based ambipolar OFETs, and thermal annealing effectively improves the carrier mobilities of the pDTTDPP-DT films. The difference is attributed to the following facts: (i) the thermally annealed pDTTDPP-DT chains on the SLG assume more crystalline features with an edge-on orientation as compared to the polymer chains on the Au, (ii) the morphological features of the thermally annealed pDTTDPP-DT films on the SLG electrodes are closer to the features of those on the gate dielectric layer, and (iii) the SLG electrode provides a flatter, more hydrophobic surface that is favorable for the polymer crystallization than the Au. In addition, the preferred carrier transport in each electrode-based OFET is associated with the HOMO/LUMO alignment relative to the Fermi level of the employed electrode. All of these experimental results consistently explain why the carrier mobilities of the SLG-based OFET are more than 10 times higher than those of the Au-based OTFT. This work demonstrates the strong dependence of ambipolar carrier transport on the source/drain electrode and annealing temperature.

  8. Single-layer 2nd-order high-T{sub c} SQUID gradiometer for use in unshielded environments

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Soon-Gul; Park, Seung Moon; Kang, Chan Seok [Korea University, Chungnam (Korea, Republic of); Kim, In-Seon [Korea Research Institute of Standards and Science, Daejon (Korea, Republic of); Kim, Sang-Jae [Cheju National University, Cheju (Korea, Republic of)

    2006-05-15

    We have studied the fabrication of second-order SQUID gradiometers from single-layer high-T{sub c} film and the feasibility of using those gradiometers in magnetocardiography. The gradiometer contains three parallel-connected pickup loops that are directly coupled to a step-edge junction SQUID with the coupling polarity of the center loop opposite to those of the two side loops. For a well-balanced gradiometer with a balancing factor of 10{sup 3}, we achieved an unshielded gradient noise of 0.84 pT/cm{sup 2}/Hz{sup 1/2} at 1 Hz, which corresponds to an equivalent field noise of 280 fT/Hz{sup 1/2}. A gradiometer with a 5.8-mm baseline successfully recorded the magnetocardic signals of a human subject, demonstrating the feasibility of using the device in biomagnetism. We have also studied the use of submicron YBCO bridges as Josephson elements of long-baseline gradiometers. The bridges were fabricated from 3-{mu}m-wide, 300-nm-thick YBCO lines with a thin layer of Au on top by using a focused-ion-beam (FIB) patterning method. The temperature-dependent critical currents, I{sub c}(T), and the normal state resistances, R{sub N}(T), showed SIS-type behaviors, which are believed to be due to naturally formed grain boundaries.

  9. Timing and Distribution of Single-Layered Ejecta Craters Imply Sporadic Preservation of Tropical Subsurface Ice on Mars

    Science.gov (United States)

    Kirchoff, Michelle R.; Grimm, Robert E.

    2018-01-01

    Determining the evolution of tropical subsurface ice is a key component to understanding Mars's climate and geologic history. Study of an intriguing crater type on Mars—layered ejecta craters, which likely form by tapping subsurface ice—may provide constraints on this evolution. Layered ejecta craters have a continuous ejecta deposit with a fluidized-flow appearance. Single-layered ejecta (SLE) craters are the most common and dominate at tropical latitudes and therefore offer the best opportunity to derive new constraints on the temporal evolution of low-latitude subsurface ice. We estimate model formation ages of 54 SLE craters with diameter (D) ≥ 5 km using the density of small, superposed craters with D D 1 km indicates that ice could be preserved as shallow as 100 m or less at those locations. Finally, there is a striking spatial mixing in an area of highlands near the equator of layered and radial (lunar-like ballistic) ejecta craters; the latter form where there are insufficient concentrations of subsurface ice. This implies strong spatial heterogeneity in the concentration of tropical subsurface ice.

  10. Dual functional porous anti-reflective coatings with a photocatalytic effect based on a single layer system

    Science.gov (United States)

    Jilavi, M. H.; Mousavi, S. H.; Müller, T. S.; de Oliveira, P. W.

    2018-05-01

    Anti-reflection and photocatalytic properties are desirable for improving the optical properties of electronic devices. We describe a method of fabrication a single-layer, anti-reflective (AR) thin film with an additional photocatalytic property. The layer is deposited on glass substrates by means of a low-cost dip-coating method using a SiO2-TiO2 solution. A comparative study was undertaken to investigate the effects of TiO2 concentrations on the photocatalytic properties of the film and to determine the optimal balance between transmittance and photocatalysis. The average transmittance increases from T = 90.51% to T = 95.46 ± 0.07% for the wavelengths between 380 and 1200 nm. The structural characterization indicated the formation of thin, porous SiO2-TiO2 films with a roughness of less than 7.5 nm. The quality of the samples was evaluated by a complete test program of the mechanical, chemical and accelerated weathering stability. This results open up new possibilities for cost-effective AR coatings for the glass and solar cell industries.

  11. Development and characterization of light-emitting diodes (LEDs) based on ruthenium complex single layer for transparent displays

    Energy Technology Data Exchange (ETDEWEB)

    Santos, G.; Fonseca, F.; Andrade, A.M. [Laboratorio de Microelectronica, Departamento de Engenharia de Sistemas Electronicos, Escola Politecnica da Universidade de Sao Paulo (Brazil); Patrocinio, A.O.T.; Mizoguchi, S.K.; Murakami Iha, N.Y. [Laboratorio de Fotoquimica Inorganica e Conversao de Energia, Instituto de Quimica da Universidade de Sao Paulo (Brazil); Peres, M.; Monteiro, T.; Pereira, L. [Departamento de Fisica e I3N, Universidade de Aveiro (Portugal)

    2008-08-15

    In this work, two ruthenium complexes,[Ru(bpy){sub 3}](PF{sub 6}){sub 2} and[Ru(ph2phen){sub 3}](PF{sub 6}){sub 2} in poly(methylmethacrylate) matrix were employed to build single-layer light-emitting electrochemical cells by spin coating on indium tin oxide substrate. In both cases the electroluminescence spectra exhibit a relatively broad band with maxima near to 625 nm and CIE (x,y) color coordinates of (0.64,0.36), which are comparable with the photoluminescence data in the same medium. The best result was obtained with the[Ru(bpy){sub 3}](PF{sub 6}){sub 2} device where the optical output power approaches 10{mu}W at the band maximum with a wall-plug efficiency higher than 0.03%. The lowest driving voltage is about 4 V for an electrical current of 20 mA. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  12. Room-temperature superparamagnetism due to giant magnetic anisotropy in Mo S defected single-layer MoS2

    Science.gov (United States)

    Khan, M. A.; Leuenberger, Michael N.

    2018-04-01

    Room-temperature superparamagnetism due to a large magnetic anisotropy energy (MAE) of a single atom magnet has always been a prerequisite for nanoscale magnetic devices. Realization of two dimensional (2D) materials such as single-layer (SL) MoS2, has provided new platforms for exploring magnetic effects, which is important for both fundamental research and for industrial applications. Here, we use density functional theory (DFT) to show that the antisite defect (Mo S ) in SL MoS2 is magnetic in nature with a magnetic moment μ of  ∼2 μB and, remarkably, exhibits an exceptionally large atomic scale MAE =\\varepsilon\\parallel-\\varepsilon\\perp of  ∼500 meV. Our calculations reveal that this giant anisotropy is the joint effect of strong crystal field and significant spin–orbit coupling (SOC). In addition, the magnetic moment μ can be tuned between 1 μB and 3 μB by varying the Fermi energy \\varepsilonF , which can be achieved either by changing the gate voltage or by chemical doping. We also show that MAE can be raised to  ∼1 eV with n-type doping of the MoS2:Mo S sample. Our systematic investigations deepen our understanding of spin-related phenomena in SL MoS2 and could provide a route to nanoscale spintronic devices.

  13. Single-layer centrifugation separates spermatozoa from diploid cells in epididymal samples from gray wolves, Canis lupus (L.).

    Science.gov (United States)

    Muñoz-Fuentes, Violeta; Linde Forsberg, Catharina; Vilà, Carles; Morrell, Jane M

    2014-09-15

    Sperm samples may be used for assisted reproductive technologies (e.g., farmed or endangered species) or as a source of haploid DNA or sperm-specific RNA. When ejaculated spermatozoa are not available or are very difficult to obtain, as is the case for most wild endangered species, the epididymides of dead animals (e.g., animals that have been found dead, shot by hunters or poachers, or that that require euthanasia in zoological collections) can be used as a source of sperm. Such epididymal sperm samples are usually contaminated with cellular debris, erythrocytes, leukocytes, and sometimes also bacteria. These contaminants may be sources of reactive oxygen species that damage spermatozoa during freezing or contribute undesired genetic material from diploid cells. We used single-layer centrifugation through a colloid formulation, Androcoll-C, to successfully separate wolf epididymal spermatozoa from contaminating cells and cellular debris in epididymal samples harvested from carcasses. Such a procedure may potentially be applied to epididymal sperm samples from other species. Copyright © 2014 Elsevier Inc. All rights reserved.

  14. Planar heterostructures of single-layer transition metal dichalcogenides: Composite structures, Schottky junctions, tunneling barriers, and half metals

    Science.gov (United States)

    Aras, Mehmet; Kılıç, ćetin; Ciraci, S.

    2017-02-01

    Planar composite structures formed from the stripes of transition metal dichalcogenides joined commensurately along their zigzag or armchair edges can attain different states in a two-dimensional (2D), single-layer, such as a half metal, 2D or one-dimensional (1D) nonmagnetic metal and semiconductor. Widening of stripes induces metal-insulator transition through the confinements of electronic states to adjacent stripes, that results in the metal-semiconductor junction with a well-defined band lineup. Linear bending of the band edges of the semiconductor to form a Schottky barrier at the boundary between the metal and semiconductor is revealed. Unexpectedly, strictly 1D metallic states develop in a 2D system along the boundaries between stripes, which pins the Fermi level. Through the δ doping of a narrow metallic stripe one attains a nanowire in the 2D semiconducting sheet or narrow band semiconductor. A diverse combination of constituent stripes in either periodically repeating or finite-size heterostructures can acquire critical fundamental features and offer device capacities, such as Schottky junctions, nanocapacitors, resonant tunneling double barriers, and spin valves. These predictions are obtained from first-principles calculations performed in the framework of density functional theory.

  15. Single-layer ionic conduction on carboxyl-terminated silane monolayers patterned by constructive lithography.

    Science.gov (United States)

    Berson, Jonathan; Burshtain, Doron; Zeira, Assaf; Yoffe, Alexander; Maoz, Rivka; Sagiv, Jacob

    2015-06-01

    Ionic transport plays a central role in key technologies relevant to energy, and information processing and storage, as well as in the implementation of biological functions in living organisms. Here, we introduce a supramolecular strategy based on the non-destructive chemical patterning of a highly ordered self-assembled monolayer that allows the reproducible fabrication of ion-conducting surface patterns (ion-conducting channels) with top -COOH functional groups precisely definable over the full range of length scales from nanometre to centimetre. The transport of a single layer of selected metal ions and the electrochemical processes related to their motion may thus be confined to predefined surface paths. As a generic solid ionic conductor that can accommodate different mobile ions in the absence of any added electrolyte, these ion-conducting channels exhibit bias-induced competitive transport of different ionic species. This approach offers unprecedented opportunities for the realization of designed ion-conducting systems with nanoscale control, beyond the inherent limitations posed by available ionic materials.

  16. Efficient Nitrogen Doping of Single-Layer Graphene Accompanied by Negligible Defect Generation for Integration into Hybrid Semiconductor Heterostructures.

    Science.gov (United States)

    Sarau, George; Heilmann, Martin; Bashouti, Muhammad; Latzel, Michael; Tessarek, Christian; Christiansen, Silke

    2017-03-22

    While doping enables application-specific tailoring of graphene properties, it can also produce high defect densities that degrade the beneficial features. In this work, we report efficient nitrogen doping of ∼11 atom % without virtually inducing new structural defects in the initial, large-area, low defect, and transferred single-layer graphene. To shed light on this remarkable high-doping-low-disorder relationship, a unique experimental strategy consisting of analyzing the changes in doping, strain, and defect density after each important step during the doping procedure was employed. Complementary micro-Raman mapping, X-ray photoelectron spectroscopy, and optical microscopy revealed that effective cleaning of the graphene surface assists efficient nitrogen incorporation accompanied by mild compressive strain resulting in negligible defect formation in the doped graphene lattice. These original results are achieved by separating the growth of graphene from its doping. Moreover, the high doping level occurred simultaneously with the epitaxial growth of n-GaN micro- and nanorods on top of graphene, leading to the flow of higher currents through the graphene/n-GaN rod interface. Our approach can be extended toward integrating graphene into other technologically relevant hybrid semiconductor heterostructures and obtaining an ohmic contact at their interfaces by adjusting the doping level in graphene.

  17. Study of the mechanical properties of single- layer and multi-layer metallic coatings with protective-decorative applications

    Directory of Open Access Journals (Sweden)

    Cherneva Sabina

    2018-01-01

    Full Text Available Single thin coating of matt nickel (Nimat, a mirror bright copper (Cubright, a mirror bright nickel (Nibright and their combinations were electrochemically deposited on brass substrate with thickness 500 μm. The basic aim was electrodeposition of two-layer Cubright/Nimat and Nibright/Cubright systems, and three-layer Nibright Cubrigh/Nimat system, which are among the most widely applied protective and decorative systems in light and medium operating conditions of corrosion. The thicknesses of the obtained films varied from 1 μm to 3.25 μm. They were investigated via nanoindentation experiments, in order to characterize their basic physical and mechanical characteristics, related with their good adhesion and corrosion protective ability, as well as ensuring the integrity of the system “protective coating/substrate” to possible mechanical, dynamic and/or thermal stresses. As a result, load-displacement curves were obtained and indentation hardness and indentation modulus were calculated using the Oliver & Pharr approximation method. The dependence of the indentation modulus and the indentation hardness on the depth of the indentation, surface morphology and structure of the obtained coatings, their texture and surface roughness were investigated too. The obtained results showed that the three-layer Nibright/Cubright /Niimat/CuZn37 system has highest indentation modulus and indentation hardness, following by two-layer Nibright/Cubright system and single layer coatings.

  18. Junctionless Diode Enabled by Self-Bias Effect of Ion Gel in Single-Layer MoS2 Device.

    Science.gov (United States)

    Khan, Muhammad Atif; Rathi, Servin; Park, Jinwoo; Lim, Dongsuk; Lee, Yoontae; Yun, Sun Jin; Youn, Doo-Hyeb; Kim, Gil-Ho

    2017-08-16

    The self-biasing effects of ion gel from source and drain electrodes on electrical characteristics of single layer and few layer molybdenum disulfide (MoS 2 ) field-effect transistor (FET) have been studied. The self-biasing effect of ion gel is tested for two different configurations, covered and open, where ion gel is in contact with either one or both, source and drain electrodes, respectively. In open configuration, the linear output characteristics of the pristine device becomes nonlinear and on-off ratio drops by 3 orders of magnitude due to the increase in "off" current for both single and few layer MoS 2 FETs. However, the covered configuration results in a highly asymmetric output characteristics with a rectification of around 10 3 and an ideality factor of 1.9. This diode like behavior has been attributed to the reduction of Schottky barrier width by the electric field of self-biased ion gel, which enables an efficient injection of electrons by tunneling at metal-MoS 2 interface. Finally, finite element method based simulations are carried out and the simulated results matches well in principle with the experimental analysis. These self-biased diodes can perform a crucial role in the development of high-frequency optoelectronic and valleytronic devices.

  19. Single-layer 2nd-order high-Tc SQUID gradiometer for use in unshielded environments

    International Nuclear Information System (INIS)

    Lee, Soon-Gul; Park, Seung Moon; Kang, Chan Seok; Kim, In-Seon; Kim, Sang-Jae

    2006-01-01

    We have studied the fabrication of second-order SQUID gradiometers from single-layer high-T c film and the feasibility of using those gradiometers in magnetocardiography. The gradiometer contains three parallel-connected pickup loops that are directly coupled to a step-edge junction SQUID with the coupling polarity of the center loop opposite to those of the two side loops. For a well-balanced gradiometer with a balancing factor of 10 3 , we achieved an unshielded gradient noise of 0.84 pT/cm 2 /Hz 1/2 at 1 Hz, which corresponds to an equivalent field noise of 280 fT/Hz 1/2 . A gradiometer with a 5.8-mm baseline successfully recorded the magnetocardic signals of a human subject, demonstrating the feasibility of using the device in biomagnetism. We have also studied the use of submicron YBCO bridges as Josephson elements of long-baseline gradiometers. The bridges were fabricated from 3-μm-wide, 300-nm-thick YBCO lines with a thin layer of Au on top by using a focused-ion-beam (FIB) patterning method. The temperature-dependent critical currents, I c (T), and the normal state resistances, R N (T), showed SIS-type behaviors, which are believed to be due to naturally formed grain boundaries.

  20. Colloid single-layer centrifugation improves post-thaw donkey (Equus asinus) sperm quality and is related to ejaculate freezability.

    Science.gov (United States)

    Ortiz, I; Dorado, J; Acha, D; Gálvez, M J; Urbano, M; Hidalgo, M

    2015-01-01

    The aim of this study was to determine whether colloid single-layer centrifugation (SLC) improves post-thaw donkey sperm quality and if this potential enhancement is related to ejaculate freezability. Semen from Andalusian donkeys was frozen following a standard protocol. SLC was performed on frozen-thawed semen and post-thaw sperm parameters were compared with uncentrifuged samples. Sperm quality was estimated by integrating in a single value sperm motility (assessed by computer-assisted sperm analysis), morphology and viability (evaluated under brightfield or fluorescence microscopy). Sperm freezability was calculated as the relationship between sperm quality obtained before freezing and after thawing. Ejaculates were classified into low, medium and high freezability groups using the 25th and 75th percentiles as thresholds. All sperm parameters were significantly (P<0.01) higher in SLC-selected samples in comparison to uncentrifuged frozen-thawed semen and several kinematic parameters were even higher than those obtained in fresh semen. The increment of sperm parameters after SLC selection was correlated with ejaculate freezability, obtaining the highest values after SLC in semen samples with low freezability. We concluded that, based on the sperm-quality parameters evaluated, SLC can be a suitable procedure to improve post-thaw sperm quality of cryopreserved donkey semen, in particular for those ejaculates with low freezability.

  1. 49 CFR 571.216a - Standard No. 216a; Roof crush resistance; Upgraded standard.

    Science.gov (United States)

    2010-10-01

    .... Definitions. Altered roof means the replacement roof on a motor vehicle whose original roof has been removed, in part or in total, and replaced by a roof that is higher than the original roof. The replacement... document, except that the length of the lower leg and thigh segments of the H-point machine are adjusted to...

  2. Roof weakness: fossilization and (cyclic) regenerative hydrated sulphates

    Energy Technology Data Exchange (ETDEWEB)

    Zodrow, E.L.; McCandlish, K.

    1978-08-01

    Roof instability at two Cape Breton mines is attributed mainly to the oxidation of pyrite in the coal seam. It is predicted that rock falls should occur in areas which have been exposed to the air for a long time if the roof is composed of shale containing pyrite and fossils. Roof bolting may contribute to the problem by affecting the passage of water and air through the shale.

  3. Bamboo Fibre Reinforced Cement Used as a Roofing Sheet | Alade ...

    African Journals Online (AJOL)

    ... bamboo fibre-roofing sheet could be used as a low cost roofing sheet. It is however imperative that the roofing system should be at slope of 45o – 60o to ensure speedy flow of water down the slope and also reduce the shock effect when a lateral load falls on it. Journal of Civil Engineering Research and Practice Vol.1(2)

  4. Observation and Estimation of Evapotranspiration from an Irrigated Green Roof in a Rain-Scarce Environment

    Directory of Open Access Journals (Sweden)

    Youcan Feng

    2018-03-01

    Full Text Available While the rain-driven evapotranspiration (ET process has been well-studied in the humid climate, the mixed irrigation and rain-driven ET process is less understood for green roof implementations in dry regions, where empirical observations and model parameterizations are lacking. This paper presents an effort of monitoring and simulating the ET process for an irrigated green roof in a rain-scarce environment. Annual ET rates for three weighing lysimeter test units with non-vegetated, sedums, and grass covers were 2.01, 2.52, and 2.69 mm d−1, respectively. Simulations based on the three Penman–Monteith equation-derived models achieved accuracy within the reported range of previous studies. Compared to the humid climate, the overestimation of high ET rates by existing models is expected to cause a larger error in dry environments, where the enhanced ET process caused by repeated irrigations overlapped with hot, dry conditions often occurs during summer. The studied sedum species did not show significantly lower ET rates than native species, and could not effectively take advantage of the deep moisture storage. Therefore, native species, instead of the shallow-rooted species commonly recommended in humid climates, might be a better choice for green roofs in rain-scarce environments.

  5. Single layers of WS2 nanoplates embedded in nitrogen-doped carbon nanofibers as anode materials for lithium-ion batteries

    Science.gov (United States)

    Yu, Sunmoon; Jung, Ji-Won; Kim, Il-Doo

    2015-07-01

    Single layers of WS2 nanoplates are uniformly embedded in nitrogen-doped carbon nanofibers (WS2@NCNFs) via a facile electrospinning method. Crystallization of the single-layered WS2 nanoplates and in situ nitrogen doping into the carbon nanofibers were simultaneously accomplished during a two-step heat treatment. The distinctive structure of the WS2@NCNFs enables outstanding electrochemical performances.Single layers of WS2 nanoplates are uniformly embedded in nitrogen-doped carbon nanofibers (WS2@NCNFs) via a facile electrospinning method. Crystallization of the single-layered WS2 nanoplates and in situ nitrogen doping into the carbon nanofibers were simultaneously accomplished during a two-step heat treatment. The distinctive structure of the WS2@NCNFs enables outstanding electrochemical performances. Electronic supplementary information (ESI) available: Experimental section, SEM images of WS2 powder and ground WS2 powder, TEM image and SAED pattern of the WS2 powder, Raman spectra of the WS2 powder, CV curves of the WS2 powder, voltage profiles of the WS2 powder, schematic diagram of WS2@NCNFs undergoing lithium storage reactions, electrochemical performance of NCNFs, morphologies and EDS mapping of WS2@NCNFs after cycling, and a table of contributions of NCNFs to the specific capacity. See DOI: 10.1039/c5nr02425k

  6. Effect of non-sperm cells removal with single-layer colloidal centrifugation on myeloperoxidase concentration in post-thaw equine semen.

    Science.gov (United States)

    Ponthier, Jérôme; Teague, Sheila R; Franck, Thierry Y; de la Rebière, Geoffroy; Serteyn, Didier D; Brinsko, Steven P; Love, Charles C; Blanchard, Terry L; Varner, Dickson D; Deleuze, Stéfan C

    2013-12-01

    Myeloperoxidase (MPO) is a pro-oxidant enzyme contained in and released by neutrophils during degranulation or after lysis. Post-thaw semen contains MPO and its concentration is associated with decreased sperm motility. Recently, MPO concentration in post-thaw semen was shown to be associated with the presence of non-sperm cells (NSC). The objective of this study was to evaluate the effect of a single-layer colloidal centrifugation before cryopreservation on NSC and MPO concentrations in equine semen. The experimental design consisted of freezing semen with or without previous centrifugation through two concentrations of single-layer colloid media. Non-sperm cells and MPO concentrations were assessed in pellet and upper layer at each step of the procedure and MPO was detected in cells by immunocytochemistry. Single-layer colloid centrifugation decreased NSC and MPO concentrations in post-thaw semen. The MPO concentration was correlated with concentration of NSC in the upper layer of the supernatant. In post-thaw semen, with or without previous single-layer colloid centrifugation, MPO concentration was correlated with concentration of NSC. Overall, neutrophils were rarely observed and NSC were mainly epithelial cells or cellular debris, as demonstrated by MPO immunocytochemistry. At all steps of the semen processing and cryopreservation, MPO immunostaining was clearly identified only on NSC. In conclusion, our study shows that NSC present in fresh semen release MPO during freezing. Copyright © 2013 Elsevier Inc. All rights reserved.

  7. Double-layer versus single-layer bone-patellar tendon-bone anterior cruciate ligament reconstruction: a prospective randomized study with 3-year follow-up.

    Science.gov (United States)

    Mei, Xiaoliang; Zhang, Zhenxiang; Yang, Jingwen

    2016-12-01

    To evaluate the clinical results of a randomized controlled trial of single-layer versus double-layer bone-patellar tendon-bone (BPTB) anterior cruciate ligament (ACL) reconstruction. Fifty-eight subjects who underwent primary ACL reconstruction with a BPTB allograft were prospectively randomized into two groups: single-layer reconstruction (n = 31) and double-layer reconstruction (n = 27). The following evaluation methods were used: clinical examination, KT-1000 arthrometer measurement, muscle strength, Tegner activity score, Lysholm score, subjective rating scale regarding patient satisfaction and sports performance level, graft retear, contralateral ACL tear, and additional meniscus surgery. Forty-eight subjects (24 in single-layer group and 24 in double-layer group) who were followed up for 3 years were evaluated. Preoperatively, there were no differences between the groups. At 3-year follow-up, the Lachman and pivot-shift test results were better in the double-layer group (P = 0.019 and P reconstruction, double-layer BPTB reconstruction was significantly better than single-layer reconstruction regarding anterior and rotational stability at 3-year follow-up. The results of KT measurements and the Lachman and pivot-shift tests were significantly better in the double-layer group, whereas there was no difference in the anterior drawer test results. The Tegner score was also better in the double-layer group; however, there were no differences in the other subjective findings.

  8. Aromatic structure degradation of single layer graphene on an amorphous silicon substrate in the presence of water, hydrogen and Extreme Ultraviolet light

    NARCIS (Netherlands)

    Mund, Baibhav Kumar; Sturm, J.M.; Lee, Christopher James; Bijkerk, Frederik

    2018-01-01

    In this paper we study the reaction of water and graphene under Extreme Ultraviolet (EUV) irradiation and in the presence of hydrogen. In this work, single layer graphene (SLG) on amorphous Si as an underlying substrate was dosed with water (0.75 ML) and exposed to EUV (λ = 13.5 nm, 92 eV) with

  9. Phosphate Leaching from Green Roof Substrates—Can Green Roofs Pollute Urban Water Bodies?

    Directory of Open Access Journals (Sweden)

    Agnieszka Karczmarczyk

    2018-02-01

    Full Text Available Green roofs are an effective stormwater measure due to high water retention capacity and the ability of delaying stormwater runoff. However, low importance is still given to the pollutant leaching potential of substrates used in green roof construction. The aim of the study is to estimate the concentrations and loads of P-PO43− in runoff from extensive and intensive substrates. To achieve this goal, several commonly-used fresh substrates were analyzed for P-PO43− leaching potential in different scale experiments, from laboratory batch tests, leaching column experiments, and long-term monitoring of open air green roof containers. The results of the study confirmed that fresh green roof substrates contain phosphorus in significant amounts of 17–145 mg∙P-PO43−/kg and, thus, can contribute to eutrophication of freshwater ecosystems. High correlation between phosphate content estimated by HCl extraction and cumulative load in leachate tests suggests that the batch HCl extraction test can be recommended for the comparison and selection of substrates with low potential P leaching. Volume-weighted mean concentrations and UALs of P-PO43− leaching from fresh substrates were higher in cases of intensive substrates, but there was no clear relationship between substrate type and the observed P-PO43− concentration range. To avoid increasing eutrophication of urban receivers the implementation of P reduction measures is strongly recommended.

  10. Roof renovation of buildings 128 and 129

    CERN Multimedia

    2015-01-01

    The roof renovation of buildings 128 and 129 is scheduled to take place from 17 August to 15 October 2015.   During this period, access to the "raw material" workshop will be limited and controlled due to asbestos removal. Collecting your orders directly from the building will be difficult, or even impossible, and urgent requests will be difficult to carry out. We therefore ask you to create your requests via EDH, so that delivery may be carried out as soon as possible. Thank you for your understanding. GS Department

  11. Full-thickness skin wound healing using autologous keratinocytes and dermal fibroblasts with fibrin: bilayered versus single-layered substitute.

    Science.gov (United States)

    Idrus, Ruszymah Bt Hj; Rameli, Mohd Adha bin P; Low, Kiat Cheong; Law, Jia Xian; Chua, Kien Hui; Latiff, Mazlyzam Bin Abdul; Saim, Aminuddin Bin

    2014-04-01

    Split-skin grafting (SSG) is the gold standard treatment for full-thickness skin defects. For certain patients, however, an extensive skin lesion resulted in inadequacies of the donor site. Tissue engineering offers an alternative approach by using a very small portion of an individual's skin to harvest cells for propagation and biomaterials to support the cells for implantation. The objective of this study was to determine the effectiveness of autologous bilayered tissue-engineered skin (BTES) and single-layer tissue-engineered skin composed of only keratinocytes (SLTES-K) or fibroblasts (SLTES-F) as alternatives for full-thickness wound healing in a sheep model. Full-thickness skin biopsies were harvested from adult sheep. Isolated fibroblasts were cultured using medium Ham's F12: Dulbecco modified Eagle medium supplemented with 10% fetal bovine serum, whereas the keratinocytes were cultured using Define Keratinocytes Serum Free Medium. The BTES, SLTES-K, and SLTES-F were constructed using autologous fibrin as a biomaterial. Eight full-thickness wounds were created on the dorsum of the body of the sheep. On 4 wounds, polyvinyl chloride rings were used as chambers to prevent cell migration at the edge. The wounds were observed at days 7, 14, and 21. After 3 weeks of implantation, the sheep were euthanized and the skins were harvested. The excised tissues were fixed in formalin for histological examination via hematoxylin-eosin, Masson trichrome, and elastin van Gieson staining. The results showed that BTES, SLTES-K, and SLTES-F promote wound healing in nonchambered and chambered wounds, and BTES demonstrated the best healing potential. In conclusion, BTES proved to be an effective tissue-engineered construct that can promote the healing of full-thickness skin lesions. With the support of further clinical trials, this procedure could be an alternative to SSG for patients with partial- and full-thickness burns.

  12. Predicting Single-Layer Technetium Dichalcogenides (TcX₂, X = S, Se) with Promising Applications in Photovoltaics and Photocatalysis.

    Science.gov (United States)

    Jiao, Yalong; Zhou, Liujiang; Ma, Fengxian; Gao, Guoping; Kou, Liangzhi; Bell, John; Sanvito, Stefano; Du, Aijun

    2016-03-02

    One of the least known compounds among transition metal dichalcogenides (TMDCs) is the layered triclinic technetium dichalcogenides (TcX2, X = S, Se). In this work, we systematically study the structural, mechanical, electronic, and optical properties of TcS2 and TcSe2 monolayers based on density functional theory (DFT). We find that TcS2 and TcSe2 can be easily exfoliated in a monolayer form because their formation and cleavage energy are analogous to those of other experimentally realized TMDCs monolayer. By using a hybrid DFT functional, the TcS2 and TcSe2 monolayers are calculated to be indirect semiconductors with band gaps of 1.91 and 1.69 eV, respectively. However, bilayer TcS2 exhibits direct-bandgap character, and both TcS2 and TcSe2 monolayers can be tuned from semiconductor to metal under effective tensile/compressive strains. Calculations of visible light absorption indicate that 2D TcS2 and TcSe2 generally possess better capability of harvesting sunlight compared to single-layer MoS2 and ReSe2, implying their potential as excellent light-absorbers. Most interestingly, we have discovered that the TcSe2 monolayer is an excellent photocatalyst for splitting water into hydrogen due to the perfect fit of band edge positions with respect to the water reduction and oxidation potentials. Our predictions expand the two-dimensional (2D) family of TMDCs, and the remarkable electronic/optical properties of monolayer TcS2 and TcSe2 will place them among the most promising 2D TMDCs for renewable energy application in the future.

  13. Sperm yield after single layer centrifugation with Androcoll-E is related to the potential fertility of the original ejaculate.

    Science.gov (United States)

    Morrell, J M; Stuhtmann, G; Meurling, S; Lundgren, A; Winblad, C; Macias Garcia, B; Johannisson, A

    2014-05-01

    Many attempts have been made to identify laboratory tests that are predictive of sperm fertility, both to improve the quality of stallion semen doses for artificial insemination (AI) and to identify potential breeding sires if no fertility data are available. Sperm quality at the stud is mostly evaluated by assessing subjective motility, although this parameter can be poorly indicative of fertility. Sperm morphology and chromatin integrity in Swedish stallions are correlated to pregnancy rate after AI. Because single layer centrifugation (SLC) selects for spermatozoa with normal morphology and good chromatin, retrospective analysis was carried out to investigate whether sperm yield after SLC is linked to potential fertility. Commercial semen doses for AI from 24 stallions (five stallions with four ejaculates each, 19 stallions with three ejaculates each; n = 77) obtained during the breeding season were cooled, and sent overnight to the Swedish University of Agricultural Sciences in an insulated box for evaluation, with other doses being sent to studs for commercial AI. On arrival at Swedish University of Agricultural Sciences, the semen was used for SLC and also for evaluation of sperm motility, membrane integrity, chromatin integrity, and morphology. The seasonal pregnancy rates for each stallion were available. The yield of progressively motile spermatozoa after SLC (calculated as a proportion of the initial load) was found to be highly correlated with pregnancy rate (r = 0.75; P centrifugation is fast (30 minutes) and does not require expensive equipment, whereas other assays require a flow cytometer and/or specialist skills. An additional option could be to transport semen doses to a laboratory for SLC if the stud personnel do not want to perform the procedure themselves. Copyright © 2014 Elsevier Inc. All rights reserved.

  14. A green roof grant program for Washington DC

    International Nuclear Information System (INIS)

    Johnson, P.A.

    2007-01-01

    The Chesapeake Bay Foundation (CBF) began its green roof demonstration project with $300,000 in funding provided by the DC Water and Sewer Authority. This paper reviewed the history of the project, its goals and early findings. The main objective was to demonstrate the technical, policy and economic feasibility of installing green roofs on commercial buildings in Washington DC and to promote green roofs as a means to manage storm water and improve water quality through the reduction of excessive runoff. The CBF has issued grants for the installation of 7 green roofs varying in size, design, location, and use. The projects included both new and existing structures designed to improve storm-water management in an urban area with significant pollution stress on the adjacent rivers. This paper provided technical, cost, and performance evaluations of each roof. A public outreach segment provided information to decision-makers to encourage more widespread replication of green roof technology throughout the metropolitan area. Much of the District of Columbia is served by a combined sewer system that becomes overloaded and discharges raw sewage into adjacent rivers during even moderately heavy rains. An average of 75 overflow events each year result in 1.5 billion gallons discharged into the Anacostia River. The installation of green roofs on buildings in the combined sewer area would retain storm water during these heavy rains and reduce the amount of overflow discharges. Apartments, as well as commercial and government buildings with mostly flat roofs are the most likely candidates for green roofs. The demonstration roofs are intended to become models, which all building owners could use as a guide for future plans for construction or re-construction to expand green roof coverage in Washington DC. It was emphasized that although such large-scale replication will take time and financial investments, it is achievable given enough political will and commercial awareness of

  15. Predictive Service Life Tests for Roofing Membranes

    Science.gov (United States)

    Bailey, David M.; Cash, Carl G.; Davies, Arthur G.

    2002-09-01

    The average service life of roofing membranes used in low-slope applications on U.S. Army buildings is estimated to be considerably shorter than the industry-presumed 20-year design life, even when installers carefully adhere to the latest guide specifications. This problem is due in large part to market-driven product development cycles, which do not include time for long-term field testing. To reduce delivery costs, contractors may provide untested, interior membranes in place of ones proven satisfactory in long-term service. Federal procurement regulations require that roofing systems and components be selected according to desired properties and generic type, not brand name. The problem is that a material certified to have satisfactory properties at installation time will not necessarily retain those properties in service. The overall objective of this research is to develop a testing program that can be executed in a matter of weeks to adequately predict a membrane's long-term performance in service. This report details accelerated aging tests of 12 popular membrane materials in the laboratory, and describes outdoor experiment stations set up for long-term exposure tests of those same membranes. The laboratory results will later be correlated with the outdoor test results to develop performance models and predictive service life tests.

  16. Roof Deformation Characteristics and Preventive Techniques Using a Novel Non-Pillar Mining Method of Gob-Side Entry Retaining by Roof Cutting

    OpenAIRE

    Yajun Wang; Yubing Gao; Eryu Wang; Manchao He; Jun Yang

    2018-01-01

    A new non-pillar mining technology, gob-side entry retaining by roof cutting (GERRC), different from the conventional gob-side entry retaining formed by a roadside filling support, is introduced in this study. In the new technology, roof cutting is conducted so that the roof plate forms a short cantilever beam structure within a certain range above the retained entry, thus changing the stress boundary condition of the roof structure. To explore the deformation characteristics of the roof unde...

  17. Using Cool Roofs to Reduce Energy Use, Greenhouse Gas Emissions, and Urban Heat-island Effects: Findings from an India Experiment

    Energy Technology Data Exchange (ETDEWEB)

    Akbari, Hashem; Xu, Tengfang; Taha, Haider; Wray, Craig; Sathaye, Jayant; Garg, Vishal; Tetali, Surekha; Babu, M. Hari; Reddy, K. Niranjan

    2011-05-25

    Cool roofs, cool pavements, and urban vegetation reduce energy use in buildings, lower local air pollutant concentrations, and decrease greenhouse gas emissions from urban areas. This report summarizes the results of a detailed monitoring project in India and related simulations of meteorology and air quality in three developing countries. The field results quantified direct energy savings from installation of cool roofs on individual commercial buildings. The measured annual energy savings potential from roof-whitening of previously black roofs ranged from 20-22 kWh/m2 of roof area, corresponding to an air-conditioning energy use reduction of 14-26% in commercial buildings. The study estimated that typical annual savings of 13-14 kWh/m2 of roof area could be achieved by applying white coating to uncoated concrete roofs on commercial buildings in the Metropolitan Hyderabad region, corresponding to cooling energy savings of 10-19%. With the assumption of an annual increase of 100,000 square meters of new roof construction for the next 10 years in the Metropolitan Hyderabad region, the annual cooling energy savings due to whitening concrete roof would be 13-14 GWh of electricity in year ten alone, with cumulative 10-year cooling energy savings of 73-79 GWh for the region. The estimated savings for the entire country would be at least 10 times the savings in Hyderabad, i.e., more than 730-790 GWh. We estimated that annual direct CO2 reduction associated with reduced energy use would be 11-12 kg CO2/m2 of flat concrete roof area whitened, and the cumulative 10-year CO2 reduction would be approximately 0.60-0.65 million tons in India. With the price of electricity estimated at seven Rupees per kWh, the annual electricity savings on air-conditioning would be approximately 93-101 Rupees per m2 of roof. This would translate into annual national savings of approximately one billion Rupees in year ten, and cumulative 10-year savings of over five billion Rupees for cooling

  18. Building Integrated Photovoltaic (BIPV) Roofs for Sustainability and Energy Efficiency

    Science.gov (United States)

    2013-09-10

    Angeles, the costs were slightly affected by the distance from the manufacturing plant , but the roof at Site II (NAS Patuxent River) is 73% larger than...linear feet of fascia trim, and reinforcement of six (6) damaged roofing beams. The PV produced 60,708 kWh over the demonstration period of two (2

  19. New typologies for active roofs; An integral approach

    NARCIS (Netherlands)

    Zeiler, W.; Quanjel, E.M.C.J.; Borsboom, W.; Spoorenberg, H.

    2006-01-01

    A wide variety of new products, such as photovoltaic (PV) systems and solar collectors, roof lights, ventilation devices, insulation and safety devices, is finding its way into the roofing industry. As a result many problems occurred, resulting in poor quality, unsafe working conditions and high

  20. New typologies for active roofs; an integral approach

    NARCIS (Netherlands)

    Quanjel, E.M.C.J.; Borsboom, W.A.; Spoorenberg, H.H.R.

    2006-01-01

    A wide variety of new products, such as photovoltaic (PV) systems and solar collectors, roof lights, ventilation devices, insulation and safety devices, is finding its way into the roofing industry. As a result many problems occurred, resulting in poor quality, unsafe working conditions and high

  1. Causes of falls of roof in South African collieries

    CSIR Research Space (South Africa)

    Van der Merwe, JN

    2001-08-01

    Full Text Available The main objective of this research was to determine the causes of falls of roof in South African collieries. Sixteen major roof falls were investigated in detail and their causes established. This data was supplemented by mapping a large number...

  2. Demonstration of Three Corrosion-Resistant Sustainable Roofing Systems

    Science.gov (United States)

    2013-06-01

    the location to demonstrate (1) a heat-resistant metal shingle roofing sys- tem with above-sheathing ventilation (ASV), (2) a sloped-roof conversion...3 2.2.1 Stone-coated metal shingle system with ASV...10 2.3.1 Stone-coated metal shingle system with ASV ......................................................... 10

  3. Comparative Study Of Asbestos And Rice Husk As Roofing Materials

    African Journals Online (AJOL)

    The need to get a replacement for asbestos as a roofing material cannot be overemphasized. Therefore, the researcher in this study critically analyses the characteristics of rice husk as compared to the characteristics of asbestos. Series of tests were carried out on rice husk roofing sheet while the results of tests carried out ...

  4. Installation, care, and maintenance of wood shake and shingle roofs

    Science.gov (United States)

    Tony Bonura; Jack Dwyer; Arnie Nebelsick; Brent Stuart; R. Sam Williams; Christopher Hunt

    2011-01-01

    This article gives general guidelines for selection, installation, finishing, and maintenance of wood shake and shingle roofs. The authors have gathered information from a variety of sources: research publications on wood finishing, technical data sheets from paint manufacturers, installation instructions for shake and shingle roofs, and interviews with experts having...

  5. Insulation of inaccessible roof constructions. Isolering af utilgaengelige tagkonstruktioner

    Energy Technology Data Exchange (ETDEWEB)

    Naumann, P.

    1992-10-01

    There are approximately 5 million m[sup 3] of uninsulated mansard roofs, roof space and sloping walls in Denmark. The humidity content after insulation with ventilationed insulation material is presented. Measurement of the humidity 2 years after the insulation has taken place and guidelines for reinsulation are given. (CLS).

  6. Variability of Rain Water Quality due to Roof Characteristics | Utsev ...

    African Journals Online (AJOL)

    It was discovered that, the period of rainfall, environmental factors, type and age of roofing materials have varying effects on the characteristics of rainwater. From the experimental result, the roof drainage water quality in Gboko can be used as grey water for domestic purposes but requires treatment to be used as drinking ...

  7. U-value measurements on a roof window

    DEFF Research Database (Denmark)

    Duer, Karsten

    1998-01-01

    This report describes the results of the U-value measurements performed on a roof window. The work is as a part of the development of an ISO/CEN standard measuring procedure for roof windows.The measurements have been performed using the procedures given in ISO 12567 draft version 1998...

  8. Green roof hydrologic performance and modeling: a review.

    Science.gov (United States)

    Li, Yanling; Babcock, Roger W

    2014-01-01

    Green roofs reduce runoff from impervious surfaces in urban development. This paper reviews the technical literature on green roof hydrology. Laboratory experiments and field measurements have shown that green roofs can reduce stormwater runoff volume by 30 to 86%, reduce peak flow rate by 22 to 93% and delay the peak flow by 0 to 30 min and thereby decrease pollution, flooding and erosion during precipitation events. However, the effectiveness can vary substantially due to design characteristics making performance predictions difficult. Evaluation of the most recently published study findings indicates that the major factors affecting green roof hydrology are precipitation volume, precipitation dynamics, antecedent conditions, growth medium, plant species, and roof slope. This paper also evaluates the computer models commonly used to simulate hydrologic processes for green roofs, including stormwater management model, soil water atmosphere and plant, SWMS-2D, HYDRUS, and other models that are shown to be effective for predicting precipitation response and economic benefits. The review findings indicate that green roofs are effective for reduction of runoff volume and peak flow, and delay of peak flow, however, no tool or model is available to predict expected performance for any given anticipated system based on design parameters that directly affect green roof hydrology.

  9. Extensive Green Roof Research Program at Colorado State University

    Science.gov (United States)

    In the high elevation, semi-arid climate of Colorado, green roofs have not been scientifically tested. This research examined alternative plant species, media blends, and plant interactions on an existing modular extensive green roof in Denver, Colorado. Six plant species were ev...

  10. 40 CFR 65.44 - External floating roof (EFR).

    Science.gov (United States)

    2010-07-01

    ... they are closed. (iii) Except for automatic bleeder vents, rim space vents, roof drains, and leg... and rim space vents shall be equipped with a gasket. (v) Each roof drain that empties into the stored... shall be designed to extend into the stored liquid and the other end shall extend a minimum vertical...

  11. Requirements of inverted roofs with a drainage layer

    DEFF Research Database (Denmark)

    Leimer, Hans-Peter; Rode, Carsten; Künzel, Hartwig

    2005-01-01

    This contribution illustrates the application of the standard EN ISO 6946 regarding the heat loss of an inverted roof for different regions of Europe. An addendum to the standard (EN ISO 6946:1996/A1, 2003) introduces a correction to the thermal transmittance of inverted roofs due to rain water f...

  12. Comparative properties of ceramic-based roofing sheets from local ...

    African Journals Online (AJOL)

    Ceramic roofing sheets were fabricated in the laboratory by using ideal raw materials. The fabricating materials are coiled coconut fibre, palm fruit fibre, fresh water, river sand, polymeric dust, saw dust and cement. The resulting product was compared with factory -produced ceramic-based roofing sheets that are easily ...

  13. Thermal analysis of building roof assisted with water heater and ...

    Indian Academy of Sciences (India)

    D Prakash

    2018-03-14

    Mar 14, 2018 ... Thermal analysis; building roof; solar water heating system; roof insulation; numerical simulation. 1. Introduction. Nowadays, residential buildings are consuming a signifi- cant percentage of energy for lighting, cooling of buildings and for home appliances. Also, the ever-growing popula- tion increases the ...

  14. Hygrothermal Performance of West Coast Wood Deck Roofing System

    Energy Technology Data Exchange (ETDEWEB)

    Pallin, Simon B. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Kehrer, Manfred [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Desjarlais, Andre Omer [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2014-02-01

    Simulations of roofing assemblies are necessary in order to understand and adequately predict actual the hygrothermal performance. At the request of GAF, simulations have been setup to verify the difference in performance between white and black roofing membrane colors in relation to critical moisture accumulation for traditional low slope wood deck roofing systems typically deployed in various western U.S. Climate Zones. The performance of these roof assemblies has been simulated in the hygrothermal calculation tool of WUFI, from which the result was evaluated based on a defined criterion for moisture safety. The criterion was defined as the maximum accepted water content for wood materials and the highest acceptable moisture accumulation rate in relation to the risk of rot. Based on the criterion, the roof assemblies were certified as being either safe, risky or assumed to fail. The roof assemblies were simulated in different western climates, with varying insulation thicknesses, two different types of wooden decking, applied with varying interior moisture load and with either a high or low solar absorptivity at the roof surface (black or white surface color). The results show that the performance of the studied roof assemblies differs with regard to all of the varying parameters, especially the climate and the indoor moisture load.

  15. Common Causes of Leakages in Parapet Roof Construction in Ghana

    African Journals Online (AJOL)

    In Ghana, especially Kumasi, the second largest city after Accra, the country\\'s capital, parapet roof construction became fashionable in building construction in the 1970\\'s. It entailed hiding the roofs of buildings from view behind parapet walls. This concept is popularly known as “Bohyemu”, literally meaning “construct it ...

  16. Design strategies for integration of green roofs in sustainable housing

    Directory of Open Access Journals (Sweden)

    Avi Friedman

    2015-12-01

    Full Text Available Green roofs are the integration of plant material and its supporting structures in buildings. Such an approach provides a habitat for local flora and fauna, helps manage storm water, reduces heat demand in winter and the cooling load in the summer, enhances the aesthetic values of dwellings, provides the occupants with comfort and amenities and strengthens environmental responsibility. Because roofs represent approximately 40 percent to 50 percent of the surfaces in urban areas, green roofs have an important role in drainage and as a result water management as well. In fact, when a green roof is installed on 50 percent or more of the roof’s surface, it guarantees 2 points and can contribute 7 additional points toward LEED certification - almost 20 percent of the required rating. This paper classifies green roofs and offers strategies for their integration in residential buildings and examines their benefits, construction principles and applications.

  17. Modelling of green roof hydrological performance for urban drainage applications

    DEFF Research Database (Denmark)

    Locatelli, Luca; Mark, Ole; Mikkelsen, Peter Steen

    2014-01-01

    Green roofs are being widely implemented for stormwater management and their impact on the urban hydrological cycle can be evaluated by incorporating them into urban drainage models. This paper presents a model of green roof long term and single event hydrological performance. The model includes...... surface and subsurface storage components representing the overall retention capacity of the green roof which is continuously re-established by evapotranspiration. The runoff from the model is described through a non-linear reservoir approach. The model was calibrated and validated using measurement data...... from 3 different extensive sedum roofs in Denmark. These data consist of high-resolution measurements of runoff, precipitation and atmospheric variables in the period 2010–2012. The hydrological response of green roofs was quantified based on statistical analysis of the results of a 22-year (1989...

  18. Thermal Behavior of Green Roofs Applied to Tropical Climate

    Directory of Open Access Journals (Sweden)

    Grace Tibério Cardoso

    2013-01-01

    Full Text Available The main goal of this paper is to present results on an experimental field about the green roofs thermal behavior, compared to other traditional roof covering systems. On the one hand, it intends to describe shortly the constructive system of a green roof with a lightweight building system, which has a sustainable building materials character and, on the other, it worries with the water reuse and with the run-off delay. The main methodological procedure adopted to study the thermal behavior of green roof was installing thermocouples to collect surface temperatures and indoor air, later comparing them with existing prototypes in an experimental plot. The thermal behavior analysis of cover systems was assessed by a representative episode of the climate fact, based on the dynamic climate approach. The experimental results from internal air temperature measurements show that the green roofs applied to warm and dry climates also provide an interesting time lag with surface and internal air temperature reduction.

  19. Experimental analysis of green roof substrate detention characteristics.

    Science.gov (United States)

    Yio, Marcus H N; Stovin, Virginia; Werdin, Jörg; Vesuviano, Gianni

    2013-01-01

    Green roofs may make an important contribution to urban stormwater management. Rainfall-runoff models are required to evaluate green roof responses to specific rainfall inputs. The roof's hydrological response is a function of its configuration, with the substrate - or growing media - providing both retention and detention of rainfall. The objective of the research described here is to quantify the detention effects due to green roof substrates, and to propose a suitable hydrological modelling approach. Laboratory results from experimental detention tests on green roof substrates are presented. It is shown that detention increases with substrate depth and as a result of increasing substrate organic content. Model structures based on reservoir routing are evaluated, and it is found that a one-parameter reservoir routing model coupled with a parameter that describes the delay to start of runoff best fits the observed data. Preliminary findings support the hypothesis that the reservoir routing parameter values can be defined from the substrate's physical characteristics.

  20. Preparation and applications of mechanically exfoliated single-layer and multilayer MoS₂ and WSe₂ nanosheets.

    Science.gov (United States)

    Li, Hai; Wu, Jumiati; Yin, Zongyou; Zhang, Hua

    2014-04-15

    Although great progress has been achieved in the study of graphene, the small current ON/OFF ratio in graphene-based field-effect transistors (FETs) limits its application in the fields of conventional transistors or logic circuits for low-power electronic switching. Recently, layered transition metal dichalcogenide (TMD) materials, especially MoS2, have attracted increasing attention. In contrast to its bulk material with an indirect band gap, a single-layer (1L) MoS2 nanosheet is a semiconductor with a direct band gap of ~1.8 eV, which makes it a promising candidate for optoelectronic applications due to the enhancement of photoluminescence and high current ON/OFF ratio. Compared with TMD nanosheets prepared by chemical vapor deposition and liquid exfoliation, mechanically exfoliated ones possess pristine, clean, and high-quality structures, which are suitable for the fundamental study and potential applications based on their intrinsic thickness-dependent properties. In this Account, we summarize our recent research on the preparation, characterization, and applications of 1L and multilayer MoS2 and WSe2 nanosheets produced by mechanical exfoliation. During the preparation of nanosheets, we proposed a simple optical identification method to distinguish 1L and multilayer MoS2 and WSe2 nanosheets on a Si substrate coated with 90 and 300 nm SiO2. In addition, we used Raman spectroscopy to characterize mechanically exfoliated 1L and multilayer WSe2 nanosheets. For the first time, a new Raman peak at 308 cm(-1) was observed in the spectra of WSe2 nanosheets except for the 1L WSe2 nanosheet. Importantly, we found that the 1L WSe2 nanosheet is very sensitive to the laser power during characterization. The high power laser-induced local oxidation of WSe2 nanosheets and single crystals was monitored by Raman spectroscopy and atomic force microscopy (AFM). Hexagonal and monoclinic structured WO3 thin films were obtained from the local oxidization of single- to triple

  1. Entire cities could benefit from green roofs : Heleen Mees is investigating how five metropolises are greenifying their roofs

    NARCIS (Netherlands)

    Mees, Heleen

    Rotterdam is making good progress with its creation of green roofs. Heleen Mees, researcher at Utrecht University, drew this conclusion from her research, in which she compared the green roof policy of four different cities with that of Rotterdam. Rotterdam awards grants to those wishing to create a

  2. Analysis of the impact of thermal resistance of the roof on the performance of photovoltaic roof tiles

    Science.gov (United States)

    Kurz, Dariusz; Nawrowski, Ryszard

    2017-10-01

    The paper explores the issues related to the impact of thermal resistance of the roof on the electrical parameters of photovoltaic roof tiles. The methodology of determination of the thermal resistance and thermal transmittance factor was presented in accordance with the applicable legal regulations and standards. A test station was presented for the purpose of measurement of the parameters of photovoltaic roof tiles depending on the structure of the roof substrate. Detailed analysis of selected building components as well as their impact on the design thermal resistance factor and thermal transmittance factor was carried out. Results of our own studies, which indicated a relation between the type of the roof structure and the values of the electricity generated by photovoltaic tiles, were presented. Based on the calculations, it was concluded that the generated outputs in the respective constructions differ by maximum 6%. For cells with the highest temperature, the performance of the PV roof tiles on the respective roof constructions fell within the range between 0.4% and 1.2% (depending on the conducted measurement) and amounted to 8.76% (in reference to 9.97% for roof tiles with the lowest temperature).

  3. Analysis of the impact of thermal resistance of the roof on the performance of photovoltaic roof tiles

    Directory of Open Access Journals (Sweden)

    Kurz Dariusz

    2017-01-01

    Full Text Available The paper explores the issues related to the impact of thermal resistance of the roof on the electrical parameters of photovoltaic roof tiles. The methodology of determination of the thermal resistance and thermal transmittance factor was presented in accordance with the applicable legal regulations and standards. A test station was presented for the purpose of measurement of the parameters of photovoltaic roof tiles depending on the structure of the roof substrate. Detailed analysis of selected building components as well as their impact on the design thermal resistance factor and thermal transmittance factor was carried out. Results of our own studies, which indicated a relation between the type of the roof structure and the values of the electricity generated by photovoltaic tiles, were presented. Based on the calculations, it was concluded that the generated outputs in the respective constructions differ by maximum 6%. For cells with the highest temperature, the performance of the PV roof tiles on the respective roof constructions fell within the range between 0.4% and 1.2% (depending on the conducted measurement and amounted to 8.76% (in reference to 9.97% for roof tiles with the lowest temperature.

  4. Stormwater quality from extensive green roofs in a subtropical region

    Science.gov (United States)

    Onis Pessoa, Jonas; Allasia, Daniel; Tassi, Rutineia; Vaz Viega, Juliana; Fensterseifer, Paula

    2016-04-01

    Green roofs have increasingly become an integral part of urban environments, mainly due to their aesthetic benefits, thermal comfort and efficiency in controlling excess runoff. However, the effects of this emerging technology in the qualitative characteristics of rainwater is still poorly understood. In this study was evaluated the effect of two different extensive green roofs (EGRs) and a traditional roof built with corrugated fiber cement sheets (control roof) in the quality of rainwater, in a subtropical climate area in the city of Santa Maria, in southern Brazil. The principal variant between the two EGRs were the type of plant species, time since construction, soil depth and the substrate characteristics. During the monitoring period of the experiment, between the months of April and December of 2015 fourteen rainfall events were selected for qualitative analysis of water from the three roofs and directly from rainfall. It was analyzed physical (turbidity, apparent color, true color, electrical conductivity, total solids, dissolved solids, suspended solids and temperature), chemical (pH, phosphate, total nitrogen, nitrate, nitrite, chloride, sulfate, BOD, iron and total hardness), heavy metals (copper, zinc, lead and chromium) and microbiological parameters (total coliforms and E. coli). It was also characterized the substrates used in both extensive green roofs. The results showed that the quality of the water drained from EGR s was directly influenced by their substrates (in turn containing significant levels of nutrients, organic matter and some metals). The passage of rainwater through green roofs and control roof resulted in the elevation of pH, allowing the conversion of the slightly acidic rainfall into basic water. Similarly, on both types of roofs occurred an increase of the values of most of the physical, chemical and microbiological parameters compared to rainwater. This same trend was observed for heavy metals, although with a much smaller degree

  5. EVALUATION OF ROOF BOLTING REQUIREMENTS BASED ON IN-MINE ROOF BOLTER DRILLING

    Energy Technology Data Exchange (ETDEWEB)

    Syd S. Peng

    2005-04-15

    In this quarter, the field, theoretical and programming works have been performed toward achieving the research goals set in the proposal. The main accomplishments in this quarter included: (1) one more field test has been conducted in an underground coal mine, (2) optimization studies of the control parameters have been conducted, (3) the relationship among feed pressure, penetration rate and rotation rate seems to be a good indicator for estimating rock strength when both penetration rate and rotation rate are controlled or kept constant, (4) the empirical equations for eliminating the machine effect on drilling parameters were developed and verified, and (5) a real time roof geology mapping system for roof bolters in limestone mine, including a special version of the geology mapping program and hardware, performs very well in underground production condition.

  6. Self-Assembly of Single-Layer CoAl-Layered Double Hydroxide Nanosheets on 3D Graphene Network Used as Highly Efficient Electrocatalyst for Oxygen Evolution Reaction.

    Science.gov (United States)

    Ping, Jianfeng; Wang, Yixian; Lu, Qipeng; Chen, Bo; Chen, Junze; Huang, Ying; Ma, Qinglang; Tan, Chaoliang; Yang, Jian; Cao, Xiehong; Wang, Zhijuan; Wu, Jian; Ying, Yibin; Zhang, Hua

    2016-09-01

    A non-noble metal based 3D porous electrocatalyst is prepared by self-assembly of the liquid-exfoliated single-layer CoAl-layered double hydroxide nanosheets (CoAl-NSs) onto 3D graphene network, which exhibits higher catalytic activity and better stability for electrochemical oxygen evolution reaction compared to the commercial IrO2 nanoparticle-based 3D porous electrocatalyst. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Raman excitation profiles of hybrid systems constituted by single-layer graphene and free base phthalocyanine: Manifestations of two mechanisms of graphene-enhanced Raman scattering

    Czech Academy of Sciences Publication Activity Database

    Uhlířová, T.; Mojzeš, P.; Melníková Komínková, Zuzana; Kalbáč, Martin; Sutrová, Veronika; Šloufová, I.; Vlčková, B.

    2017-01-01

    Roč. 48, č. 10 (2017), s. 1270-1281 ISSN 0377-0486 R&D Projects: GA ČR(CZ) GA15-01953S Institutional support: RVO:61388955 ; RVO:61389013 Keywords : graphene -enhanced Raman scattering * single-layer graphene * free base phthalocyanine * Raman excitation profiles * photoinduced charge transfer Subject RIV: CF - Physical ; Theoretical Chemistry; CD - Macromolecular Chemistry (UMCH-V) OBOR OECD: Physical chemistry; Polymer science (UMCH-V) Impact factor: 2.969, year: 2016

  8. Raman excitation profiles of hybrid systems constituted by single-layer graphene and free base phthalocyanine: Manifestations of two mechanisms of graphene-enhanced Raman scattering

    Czech Academy of Sciences Publication Activity Database

    Uhlířová, T.; Mojzeš, P.; Melníková Komínková, Zuzana; Kalbáč, Martin; Sutrová, Veronika; Šloufová, I.; Vlčková, B.

    2017-01-01

    Roč. 48, č. 10 (2017), s. 1270-1281 ISSN 0377-0486 R&D Projects: GA ČR(CZ) GA15-01953S Institutional support: RVO:61388955 ; RVO:61389013 Keywords : graphene-enhanced Raman scattering * single-layer graphene * free base phthalocyanine * Raman excitation profiles * photoinduced charge transfer Subject RIV: CF - Physical ; Theoretical Chemistry; CD - Macromolecular Chemistry (UMCH-V) OBOR OECD: Physical chemistry; Polymer science (UMCH-V) Impact factor: 2.969, year: 2016

  9. A retrospective study comparing the outcome of horses undergoing small intestinal resection and anastomosis with a single layer (Lembert) or double layer (simple continuous and Cushing) technique.

    Science.gov (United States)

    Close, Kristyn; Epstein, Kira L; Sherlock, Ceri E

    2014-05-01

    To (1) compare postoperative complications and survival in horses after small intestinal resection and anastomosis using 2 anastomosis techniques (single layer Lembert; double layer simple continuous oversewn with Cushing), and (2) to compare outcome by anastomosis type (jejunoileostomy; jejunojejunostomy). Retrospective case series. Horses (n = 53). Medical records (July 2006-July 2010) of all horses that had small intestinal resection and anastomosis. Horses were divided into groups based on technique and type of anastomosis. Comparisons of pre- and intraoperative findings (disease severity), postoperative complications, and survival rates were made between groups. There were no differences in disease severity, postoperative complications, or survival between single layer (n = 23) or double layer (n = 31) anastomoses. There were no differences in disease severity or survival between jejunoileostomy (n = 16) or jejunojejunostomy (n = 38). There was a higher incidence of postoperative colic in hospital after jejunoileostomy (13/16) compared with jejunojejunostomy (18/38) (P = .0127). Postoperative complications and survival are comparable between horses undergoing single layer and double layer small intestinal end-to-end anastomoses. With the exception of increased postoperative colic in the hospital, postoperative complications and survival after jejunoileostomy and jejunojejunostomy are also comparable. © Copyright 2014 by The American College of Veterinary Surgeons.

  10. Common electronic origin of superconductivity in (Li,Fe)OHFeSe bulk superconductor and single-layer FeSe/SrTiO3 films.

    Science.gov (United States)

    Zhao, Lin; Liang, Aiji; Yuan, Dongna; Hu, Yong; Liu, Defa; Huang, Jianwei; He, Shaolong; Shen, Bing; Xu, Yu; Liu, Xu; Yu, Li; Liu, Guodong; Zhou, Huaxue; Huang, Yulong; Dong, Xiaoli; Zhou, Fang; Liu, Kai; Lu, Zhongyi; Zhao, Zhongxian; Chen, Chuangtian; Xu, Zuyan; Zhou, X J

    2016-02-08

    The mechanism of high-temperature superconductivity in the iron-based superconductors remains an outstanding issue in condensed matter physics. The electronic structure plays an essential role in dictating superconductivity. Recent revelation of distinct electronic structure and high-temperature superconductivity in the single-layer FeSe/SrTiO3 films provides key information on the role of Fermi surface topology and interface in inducing or enhancing superconductivity. Here we report high-resolution angle-resolved photoemission measurements on the electronic structure and superconducting gap of an FeSe-based superconductor, (Li0.84Fe0.16)OHFe0.98Se, with a Tc at 41 K. We find that this single-phase bulk superconductor shows remarkably similar electronic behaviours to that of the superconducting single-layer FeSe/SrTiO3 films in terms of Fermi surface topology, band structure and the gap symmetry. These observations provide new insights in understanding high-temperature superconductivity in the single-layer FeSe/SrTiO3 films and the mechanism of superconductivity in the bulk iron-based superconductors.

  11. Chemical composition of water from roofs in Gdansk, Poland

    Energy Technology Data Exchange (ETDEWEB)

    Tsakovski, Stefan, E-mail: stsakovski@chem.uni-sofia.b [Chair of Physical Chemistry, Faculty of Chemistry, University of Sofia, J Bourchier Blvd. 1, 1164 Sofia (Bulgaria); Tobiszewski, Marek [Department of Analytical Chemistry, Chemical Faculty, Gdansk University of Technology (GUT), 11/12 G. Narutowicza St., 80-952 Gdansk (Poland); Simeonov, Vasil, E-mail: vsimeonov@chem.uni-sofia.b [Chair of Analytical Chemistry, Faculty of Chemistry, University of Sofia, 1164 Sofia (Bulgaria); Polkowska, Zaneta [Department of Analytical Chemistry, Chemical Faculty, Gdansk University of Technology (GUT), 11/12 G. Narutowicza St., 80-952 Gdansk (Poland); Namiesnik, Jacek, E-mail: chemanal@pg.gda.p [Department of Analytical Chemistry, Chemical Faculty, Gdansk University of Technology (GUT), 11/12 G. Narutowicza St., 80-952 Gdansk (Poland)

    2010-01-15

    This study deals with the assessment of roof runoff waters from the region of Gdansk collected during the winter season (2007/2008). The chemical analysis includes 16 chemical variables: major ions, PAHs and PCBs measured at 3 sampling sites for 6-14 rain events. Although the data set is of limited volume the statistical data treatment using self-organizing maps (SOM) reveals the main factors controlling roof runoff water quality even for a data set with small dimension. This effort for explanation of the identified factors by the possible emission sources of the urban environment and air-particulate formation seems to be very reliable. Additionally to the roof runoff water quality factors the rain events patterns are found: 'background' group of events and groups formally named 'PAHs', 'PCBs' and 'air-borne particles' - dominated events. The SOM classification results give an opportunity to uncover the role of roof 'impact' on the runoff waters. Rain runoff water quality is described by four latent factors and the 'roof' impact is uncovered. - Identification of the urban roof runoff water quality factors and 'roof' impact by self-organizing map classification.

  12. Comparative life cycle assessment of standard and green roofs.

    Science.gov (United States)

    Saiz, Susana; Kennedy, Christopher; Bass, Brad; Pressnail, Kim

    2006-07-01

    Life cycle assessment (LCA) is used to evaluate the benefits, primarily from reduced energy consumption, resulting from the addition of a green roof to an eight story residential building in Madrid. Building energy use is simulated and a bottom-up LCA is conducted assuming a 50 year building life. The key property of a green roof is its low solar absorptance, which causes lower surface temperature, thereby reducing the heat flux through the roof. Savings in annual energy use are just over 1%, but summer cooling load is reduced by over 6% and reductions in peak hour cooling load in the upper floors reach 25%. By replacing the common flat roof with a green roof, environmental impacts are reduced by between 1.0 and 5.3%. Similar reductions might be achieved by using a white roof with additional insulation for winter, but more substantial reductions are achieved if common use of green roofs leads to reductions in the urban heat island.

  13. Multi functional roof structures of the energy efficient buildings

    Directory of Open Access Journals (Sweden)

    Krstić Aleksandra

    2006-01-01

    Full Text Available Modern architectural concepts, which are based on rational energy consumption of buildings and the use of solar energy as a renewable energy source, give the new and significant role to the roofs that become multifunctional structures. Various energy efficient roof structures and elements, beside the role of protection, provide thermal and electric energy supply, natural ventilation and cooling of a building, natural lighting of the indoor space sunbeam protection, water supply for technical use, thus according to the above mentioned functions, classification and analysis of such roof structures and elements are made in this paper. The search for new architectural values and optimization in total energy balance of a building or the likewise for the urban complex, gave to roofs the role of "climatic membranes". Contemporary roof forms and materials clearly exemplify their multifunctional features. There are numerous possibilities to achieve the new and attractive roof design which broadens to the whole construction. With such inducement, this paper principally analyze the configuration characteristics of the energy efficient roof structures and elements, as well as the visual effects that may be achieved by their application.

  14. Typology of Retractable Roof Structures in Stadiums and Sports Halls

    Directory of Open Access Journals (Sweden)

    Andrej Mahovič

    2015-10-01

    Full Text Available Retractable roof structures are one of the four fundamental systems (in addition to the playing area, stands and facade in a stadium and sports hall. The roof protects users against various weather conditions and creates optimum circumstances for carrying out different activities. Stadiums and sports halls with retractable roof structures can host a greater variety of activities, improve the quality of their implementation and the quality of visitors’ experience, and affect the perception and experience of people using or observing such buildings. A retractable roof structure allows for natural lighting and ventilation of the venue, gives optimal conditions for grass growth on the playing field, and reduces costs of use and maintenance of the building. Different typologies of movement of roof structures (frequency of opening and closing, design of the structure, and methods of movement are categorised in terms of their architectural and structural design. Application of different retractable roof systems worldwide is indicator of their effectiveness and efficiency, and is basis for use of movement also in other fundamental systems of stadiums and sports halls. Research and identification of characteristics of retractable roof structures lead to the design of new moving systems that can with the application of the moving principle change the purpose of movable elements or assume the characteristics of other fundamental systems.

  15. Hydrological Modelling and Parameter Identification for Green Roof

    Science.gov (United States)

    Lo, W.; Tung, C.

    2012-12-01

    Green roofs, a multilayered system covered by plants, can be used to replace traditional concrete roofs as one of various measures to mitigate the increasing stormwater runoff in the urban environment. Moreover, facing the high uncertainty of the climate change, the present engineering method as adaptation may be regarded as improper measurements; reversely, green roofs are unregretful and flexible, and thus are rather important and suitable. The related technology has been developed for several years and the researches evaluating the stormwater reduction performance of green roofs are ongoing prosperously. Many European counties, cities in the U.S., and other local governments incorporate green roof into the stormwater control policy. Therefore, in terms of stormwater management, it is necessary to develop a robust hydrologic model to quantify the efficacy of green roofs over different types of designs and environmental conditions. In this research, a physical based hydrologic model is proposed to simulate water flowing process in the green roof system. In particular, the model adopts the concept of water balance, bringing a relatively simple and intuitive idea. Also, the research compares the two methods in the surface water balance calculation. One is based on Green-Ampt equation, and the other is under the SCS curve number calculation. A green roof experiment is designed to collect weather data and water discharge. Then, the proposed model is verified with these observed data; furthermore, the parameters using in the model are calibrated to find appropriate values in the green roof hydrologic simulation. This research proposes a simple physical based hydrologic model and the measures to determine parameters for the model.

  16. Effects of Solar Photovoltaic Panels on Roof Heat Transfer

    Science.gov (United States)

    Dominguez, A.; Klessl, J.; Samady, M.; Luvall, J. C.

    2010-01-01

    Building Heating, Ventilation and Air Conditioning (HVAC) is a major contributor to urban energy use. In single story buildings with large surface area such as warehouses most of the heat enters through the roof. A rooftop modification that has not been examined experimentally is solar photovoltaic (PV) arrays. In California alone, several GW in residential and commercial rooftop PV are approved or in the planning stages. With the PV solar conversion efficiency ranging from 5-20% and a typical installed PV solar reflectance of 16-27%, 53-79% of the solar energy heats the panel. Most of this heat is then either transferred to the atmosphere or the building underneath. Consequently solar PV has indirect effects on roof heat transfer. The effect of rooftop PV systems on the building roof and indoor energy balance as well as their economic impacts on building HVAC costs have not been investigated. Roof calculator models currently do not account for rooftop modifications such as PV arrays. In this study, we report extensive measurements of a building containing a flush mount and a tilted solar PV array as well as exposed reference roof. Exterior air and surface temperature, wind speed, and solar radiation were measured and thermal infrared (TIR) images of the interior ceiling were taken. We found that in daytime the ceiling surface temperature under the PV arrays was significantly cooler than under the exposed roof. The maximum difference of 2.5 C was observed at around 1800h, close to typical time of peak energy demand. Conversely at night, the ceiling temperature under the PV arrays was warmer, especially for the array mounted flat onto the roof. A one dimensional conductive heat flux model was used to calculate the temperature profile through the roof. The heat flux into the bottom layer was used as an estimate of the heat flux into the building. The mean daytime heat flux (1200-2000 PST) under the exposed roof in the model was 14.0 Watts per square meter larger than

  17. Roof Deformation Characteristics and Preventive Techniques Using a Novel Non-Pillar Mining Method of Gob-Side Entry Retaining by Roof Cutting

    Directory of Open Access Journals (Sweden)

    Yajun Wang

    2018-03-01

    Full Text Available A new non-pillar mining technology, gob-side entry retaining by roof cutting (GERRC, different from the conventional gob-side entry retaining formed by a roadside filling support, is introduced in this study. In the new technology, roof cutting is conducted so that the roof plate forms a short cantilever beam structure within a certain range above the retained entry, thus changing the stress boundary condition of the roof structure. To explore the deformation characteristics of the roof under this special condition, a short cantilever beam mechanical model was established and solved using energy theory and displacement variational methods. Meanwhile, a theoretical and analytical control solution for roof deformation was obtained and verified via field-measured results. Based on the aforementioned calculation, the relationship between the roof deformation and main influence parameters was explored. It was concluded that the rotation of the upper main roof and width of the retained entry had the most significant impacts on roof deformation. Bolt and cable support and temporary support in the entry had a non-obvious influence on the roof deformation and could not prevent the given deformation that was caused by the rotation of the upper main roof. Based on comprehensive theoretical analysis and calculation results, ideas and countermeasures to control short cantilever roof deformation—that is, designing a reasonable height of roof cutting and a controlled width of retaining entry—were proposed and tested. Field monitoring shows that the entry control effects were satisfactory.

  18. Diaphragm Effect of Steel Space Roof Systems in Hall Structures

    Directory of Open Access Journals (Sweden)

    Mehmet FENKLİ

    2015-09-01

    Full Text Available Hall structures have been used widely for different purposes. They have are reinforced concrete frames and shear wall with steel space roof systems. Earthquake response of hall structures is different from building type structures. One of the most critical nodes is diaphragm effect of steel space roof on earthquake response of hall structures. Diaphragm effect is depending on lateral stiffness capacity of steel space roof system. Lateral stiffness of steel space roof system is related to modulation geometry, support conditions, selected sections and system geometry. In current paper, three representative models which are commonly used in Turkey were taken in to account for investigation. Results of numerical tests were present comparatively

  19. MODELING OF STORM WATER RUNOFF FROM GREEN ROOFS

    Directory of Open Access Journals (Sweden)

    Ewa Burszta-Adamiak

    2014-10-01

    Full Text Available Apart from direct measurements, modelling of runoff from green roofs is valuable source of information about effectiveness of this type of structure from hydrological point of view. Among different type of models, the most frequently used are numerical models. They allow to assess the impact of green roofs on decrease and attenuation of runoff, reduction of peak runoff and value of water retention. This paper presents preliminary results of research on computing the rate of runoff from green roofs using GARDENIA model. The analysis has been carried out for selected rainfall events registered during measuring campaign on pilot-scale green roofs. Obtained results are promising and show good fit between observed and simulated runoff.

  20. Optimal Adoption of Green Roofs: Hydrology and Public Finance Applications

    National Research Council Canada - National Science Library

    Stumme, Luke D

    2008-01-01

    ... infrastructure to convey and treat stormwater discharge. A municipality can introduce planned percentages of green roof coverage which will diminish infrastructure improvement costs over time and increase the population's sustainable footprint...

  1. Home advantage in retractable-roof baseball stadia.

    Science.gov (United States)

    Romanowich, Paul

    2012-10-01

    This study examined whether the home advantage varies for open-air, domed, or retractable-roof baseball stadia, and whether having the roof open or closed affects the home advantage in retractable-roof baseball stadia. Data from Major League Baseball (MLB) games played between 2001 and 2009 were analyzed for whether or not the presence of a home-advantage was dependent on the type of home stadium used. Home advantage was robust for all three types of stadia. A significant effect of stadium type on home advantage was found, with a greater home advantage for teams playing home games in domed stadia relative to open-air stadia, replicating a previous study. There was a greater home advantage for teams playing home games in domed stadia relative to retractable-roof stadia. No other differences in the home advantage were found; results are discussed in terms of familiarity with the facility.

  2. 40 CFR 63.1042 - Standards-Separator fixed roof.

    Science.gov (United States)

    2010-07-01

    ..., as applicable, to the separator. (ii) To remove accumulated sludge or other residues from the bottom... roof and its closure devices shall be designed to form a continuous barrier over the entire surface...

  3. 40 CFR 63.902 - Standards-Tank fixed roof.

    Science.gov (United States)

    2010-07-01

    ... tank. (ii) To remove accumulated sludge or other residues from the bottom of tank. (2) Opening of a... specifications: (1) The fixed roof and its closure devices shall be designed to form a continuous barrier over...

  4. The gastrocoel roof plate in embryos of different frogs.

    Science.gov (United States)

    Sáenz-Ponce, Natalia; Santillana-Ortiz, Juan-Diego; del Pino, Eugenia M

    2012-02-01

    The morphology of the gastrocoel roof plate and the presence of cilia in this structure were examined in embryos of four species of frogs. Embryos of Ceratophrys stolzmanni (Ceratophryidae) and Engystomops randi (Leiuperidae) develop rapidly, provide comparison for the analysis of gastrocoel roof plate development in the slow-developing embryos of Epipedobates machalilla (Dendrobatidae) and Gastrotheca riobambae (Hemiphractidae). Embryos of the analyzed frogs develop from eggs of different sizes, and display different reproductive and developmental strategies. In particular, dorsal convergence and extension and archenteron elongation begin during gastrulation in embryos of rapidly developing frogs, as in Xenopus laevis. In contrast, cells that involute during gastrulation are stored in the large circumblastoporal collar that develops around the closed blastopore in embryos of slow-developing frogs. Dorsal convergence and extension only start after blastopore closure in slow-developing frog embryos. However, in the neurulae, a gastrocoel roof plate develops, despite the accumulation of superficial mesodermal cells in the circumblastoporal collar. Embryos of all four species develop a ciliated gastrocoel roof plate at the beginning of neurulation. Accordingly, fluid-flow across the gastrocoel roof plate is likely the mechanism of left-right asymmetry patterning in these frogs, as in X. laevis and other vertebrates. A ciliated gastrocoel roof plate, with a likely origin as superficial mesoderm, is conserved in frogs belonging to four different families and with different modes of gastrulation. Copyright © 2011 International Society of Differentiation. Published by Elsevier B.V. All rights reserved.

  5. Green roofs and implementing the goals of Smart Growth

    International Nuclear Information System (INIS)

    Loder, A.; Peck, S.W.

    2004-01-01

    Smart Growth is a movement developed by city planners to counteract urban sprawl and inner-city deterioration. This paper explored the use of green roofs as a tangible means to attain the following 4 main goals of Smart Growth: (1) support infill development which refers to the concentration of development in already existing nodes and corridors served by public transit, (2) make cities more liveable, healthy, and environmentally sustainable, (3) create new green space and habitat for biodiversity preservation, and (4) support efficient and green infrastructure. It was suggested that few technologies provide such a wide range of opportunity as green roofs do to generate tangible social, economic and environmental benefits. Roof space represents 15 to 35 per cent of the total land area in a city. In addition to providing stormwater management, green roofs contribute to a reduction of the urban heat island, bringing nature back into the city. It was noted that generating new accessible and inaccessible green space is consistent with the needs and desires or urban dwellers. The extent to which green roofs can provide public benefits depends on the type of design. Green roofs not only cool the buildings they sit upon, but generate cooling for the surrounding area that can result in reduced energy consumption and improvements in air quality. 64 refs., 2 figs

  6. Proposed Measures to Protect Temporary Roofs from Unwanted Heat Gains

    Directory of Open Access Journals (Sweden)

    Omar S. Asfour

    2017-06-01

    Full Text Available This study focuses on the uncompleted multi-storey residential buildings located in hot climates. This construction pattern is common in the case of incremental housing, where additional floors are added to the building as housing needs grow. Top roofs in these buildings are usually left without thermal insulation until the rest of upper floors are erected. This causes higher thermal discomfort in the top flats compared to the lower ones. Thus, the aim of this study is to investigate thermal effect of some proposed temporary measures that are intended to protect these roofs from unwanted heat gains until the rest of storeys are constructed. This has been carried out using thermal modelling to find out the effect of these measures on the amount of heat transfer through the roof in both summer and winter times. The analysis showed that it is possible to achieve competent thermal protection of the top roof compared to the layered thermal insulation using simple, cost-effective, and reversible measures. Among the examined measures, covering the roof with white foldable sheets and the use of pergolas have been found to be the most effective measures. In both cases, a reduction of 38% in conductive heat transfer through the top roof in summer was observed compared to the unprotected modelling case.

  7. Reliability Analysis of a Green Roof Under Different Storm Scenarios

    Science.gov (United States)

    William, R. K.; Stillwell, A. S.

    2015-12-01

    Urban environments continue to face the challenges of localized flooding and decreased water quality brought on by the increasing amount of impervious area in the built environment. Green infrastructure provides an alternative to conventional storm sewer design by using natural processes to filter and store stormwater at its source. However, there are currently few consistent standards available in North America to ensure that installed green infrastructure is performing as expected. This analysis offers a method for characterizing green roof failure using a visual aid commonly used in earthquake engineering: fragility curves. We adapted the concept of the fragility curve based on the efficiency in runoff reduction provided by a green roof compared to a conventional roof under different storm scenarios. We then used the 2D distributed surface water-groundwater coupled model MIKE SHE to model the impact that a real green roof might have on runoff in different storm events. We then employed a multiple regression analysis to generate an algebraic demand model that was input into the Matlab-based reliability analysis model FERUM, which was then used to calculate the probability of failure. The use of reliability analysis as a part of green infrastructure design code can provide insights into green roof weaknesses and areas for improvement. It also supports the design of code that is more resilient than current standards and is easily testable for failure. Finally, the understanding of reliability of a single green roof module under different scenarios can support holistic testing of system reliability.

  8. EVALUATION OF ROOF BOLTING REQUIREMENTS BASED ON IN-MINE ROOF BOLTER DRILLING

    Energy Technology Data Exchange (ETDEWEB)

    Syd S. Peng

    2003-01-15

    In this quarter, the field, theoretical and programming works have been performed toward achieving the research goals set in the proposal. The main accomplishments in this quarter included: (1) laboratory tests have been conducted, (2) with the added trendline analysis method, the accuracy of the data interpretation methodology will be improved and the interfaces and voids can be more reliably detected, (3) method to use torque to thrust ratio as indicator of rock relative hardness has also been explored, and (4) about 80% of the development work for the roof geology mapping program, MRGIS, has completed.

  9. EVALUATION OF ROOF BOLTING REQUIREMENTS BASED ON IN MINE ROOF BOLTER DRILLING

    Energy Technology Data Exchange (ETDEWEB)

    Syd S. Peng

    2003-10-15

    In this quarter, the field, theoretical and programming works have been performed toward achieving the research goals set in the proposal. The main accomplishments in this quarter included: (1) laboratory tests have been conducted, (2) with the added trendline analysis method, the accuracy of the data interpretation methodology will be improved, (3) method to use torque to thrust ratio as indicator of rock relative hardness has also been explored, and (3) about one half of the development work for the roof geology mapping program, MRGIS, has completed.

  10. The Effect of Medium Cultures on Water Use and Charactristic of Gazania Flowers (Gazania hybrida in Green Roof.

    Directory of Open Access Journals (Sweden)

    Tahereh Bahrami

    2017-02-01

    Full Text Available Introduction: Green roof is one of the newest phenomenons in architecture and urbanism that refers to the sustainable development concepts and it will be usable for increasing landscape design, improving quality of the environment and reduction in energy consumption. Ensure of existing adequate green landscape in urban areas and improving access to natural areas surrounding the cities can help to offset negative effects of urban life. The use of green roof technology in cities is one of advanced techniques of green landscape. A green or living roof is a roof of a building that is partially or completely covered with vegetation and a growing medium on top view of buildings. Green roof layers that considered for roof side consist of protection layer, drainage layer, growing medium and plant layer. Medium layer is the medium culture of green roof that plants are begins to grow in it. This space should enable to save enough minerals and water for conserve of green-roof plants. All kinds of plants can growth on the green roof, but there are some constraints in creative of design because of roots dimension, plant canopy, necessary volume of soil, suitable direction to light, good weather, weight of designed structures, budget of repairing and keeping. Materials and Methods: To evaluate the effect of some culture medium on water consumption, vegetative and reproductive traits of Gazania (Gazania hybrida in condition of green roof a factorial experiment was conducted based on a completely randomized design with nine treatments and three replications in 2014. Treatments were three levels of vermicompost (zero, 5%, and 10% and rice hull (zero, 7, and 14%. Seedlings of plants cultivated in the media mixture of coco peat 15%, perlite 15%, leaf 10%, manure 10%, and filed soil 50%. The container had 60 × 60 ×25 cm dimensions that placed on the roof of greenhouse building with four meters height. The measured traits was number, average, and diameter of

  11. Sheffield's Green Roof Forum: a multi-stranded programme of green roof infrastructure development for the UK's greenest city

    International Nuclear Information System (INIS)

    Dunnett, N.

    2006-01-01

    Sheffield, United Kingdom (UK) was the world centre for the steel and cutlery industries. However, those industries have been in decline and the city has been in the process of re-inventing itself over the past 20 years. Sheffield is now known as the UK's greenest city in terms of the amount of woodland, parkland and open spaces within its city limits. The city of Sheffield has also developed a unique partnership approach to promote green roof infrastructure as the most visible and high-profile signal of intent and symbol of low environmental impact building design and construction. This partnership involves Sheffield's Green Roof Forum, comprising the University of Sheffield's multi-disciplinary centre of excellence in green roof research; Sheffield City Council; Groundwork Sheffield, an urban economic and environmental regeneration agency; and city Architects and developers. This partnership meets six times a year to raise the profile of green roofs within the city and region, and to develop strategies to increase the uptake and implementation of green roof infrastructure in the region. This paper discussed the partnership, the Green Room Forum, accomplishments to date in promoting green roofs in the city, and the strategy for the Sheffield region to become a leader in green roof implementation and associated green technologies. The strategy is presented in two parts: consultation and research to identify the nature of market failure and devising methods to overcome that failure. The green roof strategy is being implemented through a program entitled Building Greener, Building Smarter and consists of four inter-linked strands. These strands were discussed in detail and included getting buy-in, demonstrating benefit, establishing the business case, and changing plans and practices. 3 tabs., 1 ref

  12. Alveolar ridge preservation with an open-healing approach using single-layer or double-layer coverage with collagen membranes.

    Science.gov (United States)

    Choi, Ho-Keun; Cho, Hag-Yeon; Lee, Sung-Jo; Cho, In-Woo; Shin, Hyun-Seung; Koo, Ki-Tae; Lim, Hyun-Chang; Park, Jung-Chul

    2017-12-01

    The aim of this prospective pilot study was to compare alveolar ridge preservation (ARP) procedures with open-healing approach using a single-layer and a double-layer coverage with collagen membranes using radiographic and clinical analyses. Eleven molars from 9 healthy patients requiring extraction of the maxillary or mandibular posterior teeth were included and allocated into 2 groups. After tooth extraction, deproteinized bovine bone mineral mixed with 10% collagen was grafted into the socket and covered either with a double-layer of resorbable non-cross-linked collagen membranes (DL group, n=6) or with a single-layer (SL group, n=5). Primary closure was not obtained. Cone-beam computed tomography images were taken immediately after the ARP procedure and after a healing period of 4 months before implant placement. Radiographic measurements were made of the width and height changes of the alveolar ridge. All sites healed without any complications, and dental implants were placed at all operated sites with acceptable initial stability. The measurements showed that the reductions in width at the level 1 mm apical from the alveolar crest (including the bone graft) were -1.7±0.5 mm in the SL group and -1.8±0.4 mm in the DL group, and the horizontal changes in the other areas were also similar in the DL and SL groups. The reductions in height were also comparable between groups. Within the limitations of this study, single-layer and double-layer coverage with collagen membranes after ARP failed to show substantial differences in the preservation of horizontal or vertical dimensions or in clinical healing. Thus, both approaches seem to be suitable for open-healing ridge preservation procedures.

  13. Comparison of light out-coupling enhancements in single-layer blue-phosphorescent organic light emitting diodes using small-molecule or polymer hosts

    Energy Technology Data Exchange (ETDEWEB)

    Chang, Yung-Ting [Institute of Chemistry, Academia Sinica, Taipei, Taiwan 11529, Taiwan (China); Department of Electrical Engineering, Graduate Institute of Photonics and Optoelectronics, National Taiwan University, Taipei, Taiwan 10617, Taiwan (China); Liu, Shun-Wei [Department of Electronic Engineering, Mingchi University of Technology, New Taipei, Taiwan 24301, Taiwan (China); Yuan, Chih-Hsien; Lee, Chih-Chien [Department of Electronic Engineering, National Taiwan University of Science and Technology, Taipei, Taiwan 10607, Taiwan (China); Ho, Yu-Hsuan; Wei, Pei-Kuen [Research Center for Applied Science Academia Sinica, Taipei, Taiwan 11527, Taiwan (China); Chen, Kuan-Yu [Chilin Technology Co., LTD, Tainan City, Taiwan 71758, Taiwan (China); Lee, Yi-Ting; Wu, Min-Fei; Chen, Chin-Ti, E-mail: cchen@chem.sinica.edu.tw, E-mail: chihiwu@cc.ee.ntu.edu.tw [Institute of Chemistry, Academia Sinica, Taipei, Taiwan 11529, Taiwan (China); Wu, Chih-I, E-mail: cchen@chem.sinica.edu.tw, E-mail: chihiwu@cc.ee.ntu.edu.tw [Department of Electrical Engineering, Graduate Institute of Photonics and Optoelectronics, National Taiwan University, Taipei, Taiwan 10617, Taiwan (China)

    2013-11-07

    Single-layer blue phosphorescence organic light emitting diodes (OLEDs) with either small-molecule or polymer hosts are fabricated using solution process and the performances of devices with different hosts are investigated. The small-molecule device exhibits luminous efficiency of 14.7 cd/A and maximum power efficiency of 8.39 lm/W, which is the highest among blue phosphorescence OLEDs with single-layer solution process and small molecular hosts. Using the same solution process for all devices, comparison of light out-coupling enhancement, with brightness enhancement film (BEF), between small-molecule and polymer based OLEDs is realized. Due to different dipole orientation and anisotropic refractive index, polymer-based OLEDs would trap less light than small molecule-based OLEDs internally, about 37% better based simulation results. In spite of better electrical and spectroscopic characteristics, including ambipolar characteristics, higher carrier mobility, higher photoluminescence quantum yield, and larger triplet state energy, the overall light out-coupling efficiency of small molecule-based devices is worse than that of polymer-based devices without BEF. However, with BEF for light out-coupling enhancement, the improved ratio in luminous flux and luminous efficiency for small molecule based device is 1.64 and 1.57, respectively, which are significantly better than those of PVK (poly-9-vinylcarbazole) devices. In addition to the theoretical optical simulation, the experimental data also confirm the origins of differential light-outcoupling enhancement. The maximum luminous efficiency and power efficiency are enhanced from 14.7 cd/A and 8.39 lm/W to 23 cd/A and 13.2 lm/W, respectively, with laminated BEF, which are both the highest so far for single-layer solution-process blue phosphorescence OLEDs with small molecule hosts.

  14. Vegetable Fermentation

    OpenAIRE

    Eifert, Joell

    2014-01-01

    People have been fermenting vegetables for centuries to increase the stability of fresh foods, to make the foods safer to eat in the absence of refrigeration and to enhance their flavor. Today, vegetable fermentation is done on a large-scale setting in factories as well as in households across the world. In the United States, the primary vegetables fermented are cucumbers (pickles), cabbage (sauerkraut and Kimchi) and olives. In many parts of the world, especially in developing countries wher...

  15. Inclusion of cool roofs in nonresidential Title 24 prescriptive requirements

    Energy Technology Data Exchange (ETDEWEB)

    Levinson, Ronnen; Akbari, Hashem; Konopacki, Steve; Bretz, Sarah

    2002-12-15

    Roofs that have high solar reflectance (high ability to reflect sunlight) and high thermal emittance (high ability to radiate heat) tend to stay cool in the sun. The same is true of low-emittance roofs with exceptionally high solar reflectance. Substituting a cool roof for a noncool roof tends to decrease cooling electricity use, cooling power demand, and cooling-equipment capacity requirements, while slightly increasing heating energy consumption. Cool roofs can also lower the ambient air temperature in summer, slowing ozone formation and increasing human comfort. DOE-2.1E building energy simulations indicate that use of a cool roofing material on a prototypical California nonresidential building with a low-sloped roof yields average annual cooling energy savings of approximately 300 kWh/1000 ft2 [3.2 kWh/m2], average annual natural gas deficits of 4.9 therm/1000 ft2 [5.6 MJ/m2], average source energy savings of 2.6 MBTU/1000 ft2 [30 MJ/m2], and average peak power demand savings of 0. 19 kW/1000 ft2 [2.1 W/m2]. The 15-year net present value (NPV) of energy savings averages $450/1000 ft2 [$4.90/m2] with time dependent valuation (TDV), and $370/1000 ft2 [$4.00/m2] without TDV. When cost savings from downsizing cooling equipment are included, the average total savings (15-year NPV + equipment savings) rises to $550/1000 ft2 [$5.90/m2] with TDV, and to $470/1000 ft2 [$5.00/m2] without TDV. Total savings range from 0.18 to 0.77 $/ft2 [1.90 to 8.30 $/m2] with TDV, and from 0.16 to 0.66 $/ft2 [1.70 to 7.10 $/m2] without TDV, across California's 16 climate zones. The typical cost premium for a cool roof is 0.00 to 0.20 $/ft2 [0.00 to 2.20 $/m2]. Cool roofs with premiums up to $0.20/ft2 [$2.20/m2] are expected to be cost effective in climate zones 2 through 16; those with premiums not exceeding $0.18/ft2 [$1.90/m2] are expected to be also cost effective in climate zone 1. Hence, this study recommends that the year-2005 California building energy efficiency code (Title

  16. Temperature reduction in attic and ceiling via insulation of several passive roof designs

    Energy Technology Data Exchange (ETDEWEB)

    Ong, K.S., E-mail: Ong.Kok.Seng@eng.monash.edu.m [Monash University Sunway Campus, Jalan Lagoon Selatan, 46150 Bandar Sunway (Malaysia)

    2011-06-15

    Research highlights: {yields} Six passive roof designs were tested simultaneously outdoors. {yields} Roof, attic and ceiling temperatures were determined. {yields} Solar collector roof design provided the coolest attic and ceiling. {yields} Placing insulation under roof is preferred to above ceiling. -- Abstract: High ambient temperatures coupled with high humidity lead to uncomfortable conditions that are non-conducive for human comfort and productivity. Heat transmission through the roof could be reduced by providing insulation in the attic under the roof or above the ceiling. A roof solar collector could provide both ventilation and cooling in the attic. Several laboratory sized units of passive roof designs were constructed and tested side-by-side under outdoor conditions to obtain temperature data of the roof, attic and ceiling in order to compare their performances.

  17. Temperature reduction in attic and ceiling via insulation of several passive roof designs

    International Nuclear Information System (INIS)

    Ong, K.S.

    2011-01-01

    Research highlights: → Six passive roof designs were tested simultaneously outdoors. → Roof, attic and ceiling temperatures were determined. → Solar collector roof design provided the coolest attic and ceiling. → Placing insulation under roof is preferred to above ceiling. -- Abstract: High ambient temperatures coupled with high humidity lead to uncomfortable conditions that are non-conducive for human comfort and productivity. Heat transmission through the roof could be reduced by providing insulation in the attic under the roof or above the ceiling. A roof solar collector could provide both ventilation and cooling in the attic. Several laboratory sized units of passive roof designs were constructed and tested side-by-side under outdoor conditions to obtain temperature data of the roof, attic and ceiling in order to compare their performances.

  18. Releasability of asbestos fibers from weathered roof cement.

    Science.gov (United States)

    Oberta, Andrew F; Poye, Lee; Compton, Steven P

    2018-03-26

    Chrysotile asbestos fibers were added to roofing products, including roof cement, for several decades. The fibers were described as "encapsulated" and therefore incapable of being released, an assertion that is disproved by the study reported herein. Three test panels of roof cement from the original container were exposed to ambient weathering in 2015 and 2016. Two panels were then sampled using the ASTM D5755 microvacuum method. Sampling revealed a light brown sub-layer under the dark brown surface layer, both of which crumbled and became friable during sampling. Analysis of the microvacuum samples with transmission electron microscopy showed that the material on the two panels contained 4,432,000 and 3,320,000 asbestos structures per cm² with nearly all of the structures consisting of fibers less than 5 µm long. Energy dispersive spectrometry determined that none of the fibers reported were coated with asphalt. The presence of free fibers were confirmed by direct examination of the surfaces of the panels and of dust released from handling the panels via scanning electron microscopy. This study confirmed the releasability of uncoated asbestos fibers from dried roof cement that was indicated in two previous studies published in 2007 and 2010. These results suggest that the finding of the 5th Circuit Court in 1997 that uncoated airborne asbestos fibers cannot be released from roof cement, and therefore do not present a potential exposure by inhalation, was erroneous in retrospect. Theexemption of roof cement from regulation under the Occupational Safety and Health Administration Construction Industry Standard for asbestos by the Court should not be relied on by employers of workers who remove weathered asbestos-containing roof cement, and precautions should be taken against exposure to airborne asbestos fibers during this work.

  19. Manipulating soil microbial communities in extensive green roof substrates.

    Science.gov (United States)

    Molineux, Chloe J; Connop, Stuart P; Gange, Alan C

    2014-09-15

    There has been very little investigation into the soil microbial community on green roofs, yet this below ground habitat is vital for ecosystem functioning. Green roofs are often harsh environments that would greatly benefit from having a healthy microbial system, allowing efficient nutrient cycling and a degree of drought tolerance in dry summer months. To test if green roof microbial communities could be manipulated, we added mycorrhizal fungi and a microbial mixture ('compost tea') to green roof rootzones, composed mainly of crushed brick or crushed concrete. The study revealed that growing media type and depth play a vital role in the microbial ecology of green roofs. There are complex relationships between depth and type of substrate and the biomass of different microbial groups, with no clear pattern being observed. Following the addition of inoculants, bacterial groups tended to increase in biomass in shallower substrates, whereas fungal biomass change was dependent on depth and type of substrate. Increased fungal biomass was found in shallow plots containing more crushed concrete and deeper plots containing more crushed brick where compost tea (a live mixture of beneficial bacteria) was added, perhaps due to the presence of helper bacteria for arbuscular mycorrhizal fungi (AMF). Often there was not an additive affect of the microbial inoculations but instead an antagonistic interaction between the added AM fungi and the compost tea. This suggests that some species of microbes may not be compatible with others, as competition for limited resources occurs within the various substrates. The overall results suggest that microbial inoculations of green roof habitats are sustainable. They need only be done once for increased biomass to be found in subsequent years, indicating that this is a novel and viable method of enhancing roof community composition. Copyright © 2014 Elsevier B.V. All rights reserved.

  20. Comparison of Software Models for Energy Savings from Cool Roofs

    Energy Technology Data Exchange (ETDEWEB)

    New, Joshua Ryan [ORNL; Miller, William A [ORNL; Huang, Yu (Joe) [White Box Technologies; Levinson, Ronnen [Lawrence Berkeley National Laboratory (LBNL)

    2014-01-01

    A web-based Roof Savings Calculator (RSC) has been deployed for the United States Department of Energy as an industry-consensus tool to help building owners, manufacturers, distributors, contractors and researchers easily run complex roof and attic simulations. This tool employs modern web technologies, usability design, and national average defaults as an interface to annual simulations of hour-by-hour, whole-building performance using the world-class simulation tools DOE-2.1E and AtticSim in order to provide estimated annual energy and cost savings. In addition to cool reflective roofs, RSC simulates multiple roof and attic configurations including different roof slopes, above sheathing ventilation, radiant barriers, low-emittance roof surfaces, duct location, duct leakage rates, multiple substrate types, and insulation levels. A base case and energy-efficient alternative can be compared side-by-side to estimate monthly energy. RSC was benchmarked against field data from demonstration homes in Ft. Irwin, California; while cooling savings were similar, heating penalty varied significantly across different simulation engines. RSC results reduce cool roofing cost-effectiveness thus mitigating expected economic incentives for this countermeasure to the urban heat island effect. This paper consolidates comparison of RSC s projected energy savings to other simulation engines including DOE-2.1E, AtticSim, Micropas, and EnergyPlus, and presents preliminary analyses. RSC s algorithms for capturing radiant heat transfer and duct interaction in the attic assembly are considered major contributing factors to increased cooling savings and heating penalties. Comparison to previous simulation-based studies, analysis on the force multiplier of RSC cooling savings and heating penalties, the role of radiative heat exchange in an attic assembly, and changes made for increased accuracy of the duct model are included.

  1. Experimental study on foam coverage on simulated longwall roof

    Science.gov (United States)

    Reed, W.R.; Zheng, Y.; Klima, S.; Shahan, M.R.; Beck, T.W.

    2018-01-01

    Testing was conducted to determine the ability of foam to maintain roof coverage in a simulated longwall mining environment. Approximately 27 percent of respirable coal mine dust can be attributed to longwall shield movement, and developing controls for this dust source has been difficult. The application of foam is a possible dust control method for this source. Laboratory testing of two foam agents was conducted to determine the ability of the foam to adhere to a simulated longwall face roof surface. Two different foam generation methods were used: compressed air and blower air. Using a new imaging technology, image processing and analysis utilizing ImageJ software produced quantifiable results of foam roof coverage. For compressed air foam in 3.3 m/s (650 fpm) ventilation, 98 percent of agent A was intact while 95 percent of agent B was intact on the roof at three minutes after application. At 30 minutes after application, 94 percent of agent A was intact while only 20 percent of agent B remained. For blower air in 3.3 m/s (650 fpm) ventilation, the results were dependent upon nozzle type. Three different nozzles were tested. At 30 min after application, 74 to 92 percent of foam agent A remained, while 3 to 50 percent of foam agent B remained. Compressed air foam seems to remain intact for longer durations and is easier to apply than blower air foam. However, more water drained from the foam when using compressed air foam, which demonstrates that blower air foam retains more water at the roof surface. Agent A seemed to be the better performer as far as roof application is concerned. This testing demonstrates that roof application of foam is feasible and is able to withstand a typical face ventilation velocity, establishing this technique’s potential for longwall shield dust control. PMID:29563765

  2. An Integrative Analysis of an Extensive Green Roof System: A Case Study of the Schleman Green Roof

    Science.gov (United States)

    Hoover, F.; Bowling, L. C.

    2013-12-01

    In urban environments where populations continue to rise, the need for affective stormwater management and runoff control methods is ever prevalent. Increased population growth and city expansion means greater impervious surfaces and higher rates of stormwater runoff. In well-established cities, this proves particularly difficult due to a constraining built environment and limited pervious spaces, even in cities as small as 40,000 residents. Work to reduce runoff in combined sewer systems (CSS) and municipal separated storm sewer systems (MS4) by use of best-management practices is one route currently under investigation. The Purdue University campus is making efforts to reduce their impact on the West Lafayette CSS and MS4. Green roofs are one management practice being used for runoff mitigation. Specifically, Schleman Hall, an administrative student affairs building, has a small green roof located on the second floor installed in 2008. In cooperation with Purdue Physical Facilities, monitoring and analysis for the Schleman extensive green roof at Purdue University was performed from June 2012 to December 2012. The objective was to determine the stormwater retention, output water quality and net present value for the 165 m2 roof. The results from the water balance analysis revealed retention rates on average of 58% of precipitation per rain event, where retention included soil moisture, evaporation and detention/depression storage. The water quality metrics tested were Nitrate-Nitrite (NO2-NO3), Orthophosphate (PO4), Ammonia-Ammonium ion (NH3-NH4), Sulfate (SO4), total suspended solids (TSS) and pH. The pollutant concentration and load results varied, but the pH levels from precipitation increased in all samples after passing through the substrate. SO4 and PO4 results yielded higher concentrations and loads in the green roof output than the control output and precipitation, while NO2-NO3 and NH3-NH4 yielded concentrations and loads that were reduced by the green

  3. Analysis of the Umbrella Roof for lifting

    International Nuclear Information System (INIS)

    Shaaban, A.

    1983-01-01

    In addition to supporting the dead loads and the operational loads, the Umbrella Roof (UR) has two major functions to which it was designed. First is to allow access for repair and removal of any of the TF coils, the upper PF coils and the Vacuum Vessel sections; and second, is to reproduce the exact positioning of the upper PF coils every time the UR is placed over the Tokamac. To provide these functions, the UR is designed to be lifted as one integrated structure to which the upper PF coils are attached. In order to ensure precise positioning of the UR, a redundant system of 13 guide pins were provided on the bottom of the radial beams, and four shear lugs were provided atop the central column. Mating reciprocals with very close tolerance for the guide pins were provided in the tops of the 13 peripheral columns. To meet close tolerances and to accommodate such high redundancy in match points, accurate analysis was necessary by which the center of gravity of the UR can be located and the deflection of all match points can be computed. Also stress analysis of the members of the UR was necessary because when the UR is lifted it is denied the midpoint support over the center column; and also the beams of the UR are not interconnected by moment-capable joints, thus if provisions are not made to support every radial beam, those which are not supported would yield and collapse. In this paper, the lifting schemes proposed for the UR are discussed and the results of the analysis performed for the elected scheme are presented. Also presented is a unique application of the NASTRAN code by which the center of gravity of the UR was located by allowing a refined model of the UR to swing until it came to rest under an arbitrary lift point

  4. Interactions between Cool Roofs and Urban Irrigation: Do Cooling Strategies Reduce Water Consumption in the San Francisco Bay Area?

    Science.gov (United States)

    Vahmani, P.; Jones, A. D.

    2016-12-01

    California has experienced progressive drought since 2012, with 2012-2014 constituting a nearly 10,000-year drought event, resulting in a suite of policies with the goal of reducing water consumption. At the same time, climate warming effects of accelerated urbanization along with projected global climate change raise an urgent need for sustainable mitigation and adaptation strategies to cool urban climates. In this study, for the first time, we assess the overarching benefits of cooling strategies on urban water consumption. We employ a satellite-supported regional climate-modeling framework over the San Francisco Bay Area to assess the effects of cool roofs on urban irrigation, a topic of increasing importance as it accounts for a significant fraction of urban water use particularly in arid and semi-arid regions. We use a suit of climatological simulations at high (1.5 km) spatial resolution, based on a Weather Research and Forecasting (WRF)-Urban Canopy Model (UCM) modeling framework, reinforced with remotely sensed observations of Green Vegetation Fraction (GVF), leaf area index (LAI), and albedo. Our analysis shows that widespread incorporation of cool roofs would result in a mean daytime cooling of about 0.7° C, which in turn results in roughly 4% reduction in irrigation water, largely due to decreases in surface evapotranspiration rates. We further investigate the critical interactions between cool roofs, wind, and sea-breeze patterns as well as fog formation, a dominant weather pattern in San Francisco Bay area.

  5. Growing substrates for aromatic plant species in green roofs and water runoff quality: pilot experiments in a Mediterranean climate.

    Science.gov (United States)

    Monteiro, Cristina M; Calheiros, Cristina S C; Palha, Paulo; Castro, Paula M L

    2017-09-01

    Green roof technology has evolved in recent years as a potential solution to promote vegetation in urban areas. Green roof studies for Mediterranean climates, where extended drought periods in summer contrast with cold and rainy periods in winter, are still scarce. The present research study assesses the use of substrates with different compositions for the growth of six aromatic plant species - Lavandula dentata, Pelargonium odoratissimum, Helichrysum italicum, Satureja montana, Thymus caespititius and T. pseudolanuginosus, during a 2-year period, and the monitoring of water runoff quality. Growing substrates encompassed expanded clay and granulated cork, in combination with organic matter and crushed eggshell. These combinations were adequate for the establishment of all aromatic plants, allowing their propagation in the extensive system located on the 5th storey. The substrate composed of 70% expanded clay and 30% organic matter was the most suitable, and crushed eggshell incorporation improved the initial plant establishment. Water runoff quality parameters - turbidity, pH, conductivity, NH 4 + , NO 3 - , PO 4 3- and chemical oxygen demand - showed that it could be reused for non-potable uses in buildings. The present study shows that selected aromatic plant species could be successfully used in green roofs in a Mediterranean climate.

  6. Quality Assessment of Roof Planes Extracted from Height Data for Solar Energy Systems by the EAGLE Platform

    Directory of Open Access Journals (Sweden)

    Simon Schuffert

    2015-12-01

    Full Text Available Due to the increasing scarcity of fossil fuels and the upwards trend in energy costs over time, many countries—especially in Europe—have begun to modify their energy policies aiming to increase that percentage obtained from renewable energies. The EAGLE (FP7 program, European Commission has developed a web-based platform to promote renewable energy systems (RES in the public and private sectors, and to deliver a comprehensive information source for all interested users. In this paper, a comprehensive quality assessment of extracted roof planes suitable for solar energy installations (photovoltaic, solar thermal from height data derived automatically from both LiDAR (Light Detection and Ranging and aerial images will be presented. A shadow analysis is performed regarding the daily path of the sun including the shading effects of nearby objects (chimneys, dormers, vegetation, buildings, topography, etc.. A quality assessment was carried out for both LiDAR and aerial images of the same test sites in UK and Germany concerning building outline accuracy, extraction rate of roof planes and the accuracy of their geometric parameters (inclination and aspect angle, size. The benefit is an optimized system to extract roof planes for RES with a high level of detail, accuracy and flexibility (concerning different commonly available data sources including an estimation of quality of the results which is important for individual house owners as well as for regional applications by governments or solar energy companies to judge their usefulness.

  7. Reaching state-of-the art requirements for MIM capacitors with a single-layer anodic Al2O3 dielectric and imprinted electrodes

    Science.gov (United States)

    Hourdakis, Emmanouel; Nassiopoulou, Androula G.

    2017-07-01

    Metal-Insulator-Metal (MIM) capacitors with a high capacitance density and low non-linearity coefficient using a single-layer dielectric of barrier-type anodic alumina (Al2O3) and an imprinted bottom Al electrode are presented. Imprinting of the bottom electrode aimed at increasing the capacitor effective surface area by creating a three-dimensional MIM capacitor architecture. The bottom Al electrode was only partly nanopatterned so as to ensure low series resistance of the MIM capacitor. With a 3 nm thick anodic Al2O3 dielectric, the capacitor with the imprinted electrode showed a 280% increase in capacitance density compared to the flat electrode capacitor, reaching a value of 20.5 fF/μm2. On the other hand, with a 30 nm thick anodic Al2O3 layer, the capacitance density was 7.9 fF/μm2 and the non-linearity coefficient was as low as 196 ppm/V2. These values are very close to reaching all requirements of the last International Technology Roadmap for Semiconductors for MIM capacitors [ITRS, http://www.itrs2.net/2013-itrs.html for ITRS Roadmap (2013)], and they are achieved by a single-layer dielectric instead of the complicated dielectric stacks of the literature. The obtained results constitute a real progress compared to previously reported results by our group for MIM capacitors using imprinted electrodes.

  8. Copper-vapor-assisted chemical vapor deposition for high-quality and metal-free single-layer graphene on amorphous SiO2 substrate.

    Science.gov (United States)

    Kim, Hyungki; Song, Intek; Park, Chibeom; Son, Minhyeok; Hong, Misun; Kim, Youngwook; Kim, Jun Sung; Shin, Hyun-Joon; Baik, Jaeyoon; Choi, Hee Cheul

    2013-08-27

    We report that high-quality single-layer graphene (SLG) has been successfully synthesized directly on various dielectric substrates including amorphous SiO2/Si by a Cu-vapor-assisted chemical vapor deposition (CVD) process. The Cu vapors produced by the sublimation of Cu foil that is suspended above target substrates without physical contact catalyze the pyrolysis of methane gas and assist nucleation of graphene on the substrates. Raman spectra and mapping images reveal that the graphene formed on a SiO2/Si substrate is almost defect-free and homogeneous single layer. The overall quality of graphene grown by Cu-vapor-assisted CVD is comparable to that of the graphene grown by regular metal-catalyzed CVD on a Cu foil. While Cu vapor induces the nucleation and growth of SLG on an amorphous substrate, the resulting SLG is confirmed to be Cu-free by synchrotron X-ray photoelectron spectroscopy. The SLG grown by Cu-vapor-assisted CVD is fabricated into field effect transistor devices without transfer steps that are generally required when SLG is grown by regular CVD process on metal catalyst substrates. This method has overcome two important hurdles previously present when the catalyst-free CVD process is used for the growth of SLG on fused quartz and hexagonal boron nitride substrates, that is, high degree of structural defects and limited size of resulting graphene, respectively.

  9. Phase diagram and electronic indication of high-temperature superconductivity at 65 K in single-layer FeSe films.

    Science.gov (United States)

    He, Shaolong; He, Junfeng; Zhang, Wenhao; Zhao, Lin; Liu, Defa; Liu, Xu; Mou, Daixiang; Ou, Yun-Bo; Wang, Qing-Yan; Li, Zhi; Wang, Lili; Peng, Yingying; Liu, Yan; Chen, Chaoyu; Yu, Li; Liu, Guodong; Dong, Xiaoli; Zhang, Jun; Chen, Chuangtian; Xu, Zuyan; Chen, Xi; Ma, Xucun; Xue, Qikun; Zhou, X J

    2013-07-01

    The recent discovery of possible high-temperature superconductivity in single-layer FeSe films has generated significant experimental and theoretical interest. In both the cuprate and the iron-based high-temperature superconductors, superconductivity is induced by doping charge carriers into the parent compound to suppress the antiferromagnetic state. It is therefore important to establish whether the superconductivity observed in the single-layer sheets of FeSe--the essential building blocks of the Fe-based superconductors--is realized by undergoing a similar transition. Here we report the phase diagram for an FeSe monolayer grown on a SrTiO3 substrate, by tuning the charge carrier concentration over a wide range through an extensive annealing procedure. We identify two distinct phases that compete during the annealing process: the electronic structure of the phase at low doping (N phase) bears a clear resemblance to the antiferromagnetic parent compound of the Fe-based superconductors, whereas the superconducting phase (S phase) emerges with the increase in doping and the suppression of the N phase. By optimizing the carrier concentration, we observe strong indications of superconductivity with a transition temperature of 65±5 K. The wide tunability of the system across different phases makes the FeSe monolayer ideal for investigating not only the physics of superconductivity, but also for studying novel quantum phenomena more generally.

  10. Comparison of Single-Layer and Double-Layer Anti-Reflection Coatings Using Laser-Induced Damage Threshold and Photothermal Common-Path Interferometry

    Directory of Open Access Journals (Sweden)

    Caspar Clark

    2016-05-01

    Full Text Available The dielectric thin-film coating on high-power optical components is often the weakest region and will fail at elevated optical fluences. A comparison of single-layer coatings of ZrO2, LiF, Ta2O5, SiN, and SiO2 along with anti-reflection (AR coatings optimized at 1064 nm comprised of ZrO2 and Ta2O5 was made, and the results of photothermal common-path interferometry (PCI and a laser-induced damage threshold (LIDT are presented here. The coatings were grown by radio frequency (RF sputtering, pulsed direct-current (DC sputtering, ion-assisted electron beam evaporation (IAD, and thermal evaporation. Test regimes for LIDT used pulse durations of 9.6 ns at 100 Hz for 1000-on-1 and 1-on-1 regimes at 1064 nm for single-layer and AR coatings, and 20 ns at 20 Hz for a 200-on-1 regime to compare the //ZrO2/SiO2 AR coating.

  11. Investigation of the single layer model of GPS ionospheric data processing using IRI-90 and the attached diffusive equilibrium model of plasmaspheric electron density

    Directory of Open Access Journals (Sweden)

    L. Bànyai

    1997-06-01

    Full Text Available The single layer model of GPS ionospheric data processing is compared with the International Reference Ionosphere í 1990 and the attached Diffusive Equilibrium model of Plasmasphere (IRI-90+DEP which proved to be a good supplement to GPS data processing. These models can be used to estimate the single layer height and to improve the mapping function in day-time. The code delays estimated from IRI-90+DEP models are compared with GPS measurements carried out by TurboRogue receiver. These models can be used to estimate the preliminary receiver biases especially in the case of cross-correlation tracking mode. The practical drawback of the IRI-90 model is the sharp discontinuity of the ion components during sunset and sunrise at an elevation of 1000 km, because it also causes a sharp discontinuity in the TEC values computed from the DEP model. The GPS data may be a good source to improve the topside region of the IRI model estimating smooth TEC transition before and after sunrise in the plasmasphere.

  12. A comparative analysis of selected parameters of roofing used in the Polish construction industry

    Directory of Open Access Journals (Sweden)

    Radziszewska-Zielina Elżbieta

    2014-06-01

    Full Text Available Roofing is an important element in the construction of the roof. It is also one of the essential elements of the whole building. The choice of roofing should depend on technical parameters that affect the quality of the materials used and the price. The present paper is a comparative analysis of the properties of five roofing materials selected as examples with respect to twelve parameters. As can be seen from the comparative analysis of the roofing parameters, roofing tile is by far the best material, receiving the highest score in the ranking

  13. Portland's experience with land use tools to promote green roofs

    International Nuclear Information System (INIS)

    Johnson, M.

    2004-01-01

    In the late 1990s, the City of Portland, Oregon faced environmental challenges that prompted the City to mandate environmentally sensitive development. Several programs were developed in response to these challenges, some of which resulted in the creation of land use policies and incentives that promote green roofs. Zoning code provisions were adopted in 2001 to promote eco-roofs in an effort to reduce stormwater runoff, mitigate urban heat island effects, provide habitat for birds, and improve air quality and energy efficiency. The Central City Fundamental Design Guidelines were also revised to encourage eco-roof development. In 2002, the South Waterfront Plan was created to integrate ecological design into an urban environment through sustainability principles and practices. Land use tools were developed to introduce developers to an approach that reduced energy costs and stormwater costs, while also contributing to a project's marketability. These tools were created with the support of programs and policies such as the CSO (Combined Sewer Overflow) Program; eco-roof research which began in 1995 to determine the stormwater management potential of eco-Green roofs; technical assistance to encourage and highlight sustainable development practices; the Stormwater Management Manual that set standards for the amount and quality of stormwater runoff leaving development sites; the G/Rated Program that offers resources for green building practices; the Green Investment Fund that supports the G/Rated Program; and, the Portland Development Commission Green Building Policy financing tool for earth-friendly designs and materials. 34 refs., 2 figs

  14. Retention performance of green roofs in three different climate regions

    Science.gov (United States)

    Sims, Andrew W.; Robinson, Clare E.; Smart, Charles C.; Voogt, James A.; Hay, Geoffrey J.; Lundholm, Jeremey T.; Powers, Brandon; O'Carroll, Denis M.

    2016-11-01

    Green roofs are becoming increasingly popular for moderating stormwater runoff in urban areas. This study investigated the impact different climates have on the retention performance of identical green roofs installed in London Ontario (humid continental), Calgary Alberta (semi-arid, continental), and Halifax Nova Scotia (humid, maritime). Drier climates were found to have greater percent cumulative stormwater retention with Calgary (67%) having significantly better percent retention than both London (48%) and Halifax (34%). However, over the same study period the green roof in London retained the greatest depth of stormwater (598 mm), followed by the green roof in Halifax (471 mm) and then Calgary (411 mm). The impact of climate was largest for medium sized storms where the antecedent moisture condition (AMC) at the beginning of a rainfall event governs retention performance. Importantly AMC was a very good predictor of stormwater retention, with similar retention at all three sites for a given AMC, emphasizing that AMC is a relevant indicator of retention performance in any climate. For large rainfall events (i.e., >45 mm) green roof average retention ranged between 16% and 29% in all cities. Overall, drier climates have superior retention due to lower AMC in the media. However, moderate and wet climates still provide substantial total volume reduction benefits.

  15. A pilot study to evaluate runoff quantity from green roofs.

    Science.gov (United States)

    Lee, Ju Young; Lee, Min Jung; Han, Mooyoung

    2015-04-01

    The use of green roofs is gaining increased recognition in many countries as a solution that can be used to improve environmental quality and reduce runoff quantity. To achieve these goals, pilot-scale green roof assemblies have been constructed and operated in an urban setting. From a stormwater management perspective, green roofs are 42.8-60.8% effective in reducing runoff for 200 mm soil depth and 13.8-34.4% effective in reducing runoff for 150 mm soil depth. By using Spearman rank correlation analysis, high rainfall intensity was shown to have a negative relationship with delayed occurrence time, demonstrating that the soil media in green roofs do not efficiently retain rainwater. Increasing the number of antecedent dry days can help to improve water retention capacity and delay occurrence time. From the viewpoint of runoff water quality, green roofs are regarded as the best management practice by filtration and adsorption through growth media (soil). Copyright © 2015 Elsevier Ltd. All rights reserved.

  16. Empirically Derived Strength of Residential Roof Structures for Solar Installations.

    Energy Technology Data Exchange (ETDEWEB)

    Dwyer, Stephen F.; Sanchez, Alfred; Campos, Ivan A.; Gerstle, Walter H.

    2014-12-01

    Engineering certification for the installation of solar photovoltaic (PV) modules on wood roofs is often denied because existing wood roofs do not meet structural design codes. This work is intended to show that many roofs are actually sufficiently strong given the conservatism in codes, documented allowable strengths, roof structure system effects, and beam composite action produced by joist-sheathing interaction. This report provides results from a testing program to provide actual load carrying capacity of residential rooftops. The results reveal that the actual load carrying capacity of structural members and systems tested are significantly stronger than allowable loads provided by the International Residential Code (IRC 2009) and the national structural code found in Minimum Design Loads for Buildings and Other Structures (ASCE 7-10). Engineering analysis of residential rooftops typically ignores the system affects and beam composite action in determining rooftop stresses given a potential PV installation. This extreme conservatism combined with conservatism in codes and published allowable stress values for roof building materials (NDS 2012) lead to the perception that well built homes may not have adequate load bearing capacity to enable a rooftop PV installation. However, based on the test results presented in this report of residential rooftop structural systems, the actual load bearing capacity is several times higher than published values (NDS 2012).

  17. Effect of Composite Action on the Strength of Wood Roofs

    Directory of Open Access Journals (Sweden)

    Ivan A. Campos Varela

    2015-01-01

    Full Text Available Engineering certification for the installation of solar photovoltaic modules on wood roofs is often denied because existing wood roofs do not meet current building codes. Rather than requiring expensive structural retrofits, we desire to show that many roofs are actually sufficiently strong if the effect of composite action produced by joist-sheathing interaction is considered. In a series of laboratory experiments using a limited number of two-by-four wood joists with and without sheathing panels, conventionally sheathed stud-grade joists, surprisingly, exhibited between 18% and 63% higher nominal strength than similar bare joists. To explain this strength increase, a simple model was developed to predict the strengths of the nailed partially composite sections, but the model only justifies a 1.4% to 3.8% increase in bending strength of joists with an allowable bending strength of 1000 psi. More testing is indicated to resolve this discrepancy between laboratory results and analytical modeling results. In addition to elucidating nonlinear partial composite behavior of existing roof systems, this paper shows that, with minor changes in roof framing practices, strength increases of 70% or more are achievable, compared to the strengths of conventionally sheathed joists.

  18. A fuzzy approach to selecting roof supports in longwall mining

    Directory of Open Access Journals (Sweden)

    Yetkin, M. E.

    2016-05-01

    Full Text Available As a decision-making problem, selecting proper machines and equipment plays a key role for mining sites and companies. Many factors affect this decision, and values belonging to these factors can be expressed numerically and/or non-numerically. In order to make the most appropriate decision, engineers must carry out an evaluation process that comprises all criteria that might affect decision-making. To achieve this, multi-criteria decision-making tools are used. As a result of technological developments, coal outputs in longwall mining have risen tremendously over the last decades, and longwall mechanisation has become unavoidable. The significance of powered roof supports in particular increases day- by-day, since the rate of roof support has to be in accordance with the rate of face advance in longwalls. In this study, an integrated fuzzy analytic hierarchy process and fuzzy goal programming model is used to select the most suitable powered roof supports. The procedure is applied to a real-life underground coal mine that is operated using the longwall method. Seven alternative powered roof supports are compared with each other, taking a total of 24 decision criteria under four main topics into account. In conclusion, the most suitable roof supports for the mine under study are determined and recommended to the decision-makers of the system.

  19. Evaluating Cool Impervious Surfaces: Application to an Energy-Efficient Residential Roof and to City Pavements

    Science.gov (United States)

    Rosado, Pablo Javier

    Summer urban heat island (UHI) refers to the phenomenon of having higher urban temperatures compared to the those in surrounding suburban and rural areas. Higher urban air temperatures lead to increased cooling demand, accelerates the formation of smog, and contributes to the generation of greenhouse gas emissions. Dark-colored impervious surfaces cover a significant fraction of an urban fabric, and as hot and dry surfaces, are a major contributor to the UHI effect. Adopting solar-reflective ("cool") roofs and cool pavements, and increasing the urban vegetation, are strategies proven to mitigate urban heat islands. These strategies often have an "indirect" effect (ambient cooling) and "direct" effect (change in solar energy flux entering the conditioned space) on the energy use of buildings. This work investigates some elements of the UHI mitigation strategies, specifically the annual direct effect of a cool roof, and the direct and indirect effects of cool pavements. The first topic researched in this paper consists in an experimental assessment of the direct effects from replacing a conventional dark roof with a highly energy-efficient cool roof. The study measures and calculates the annual benefits of the cool roof on the cooling and heating energy uses, and the associated emission reductions. The energy savings attributed to the cool roof are validated by measuring the difference between the homes in the heat loads that entered the conditioned space through the ceiling and HVAC ducts. Fractional annual cooling energy savings (26%) were 2.6 times the 10% daily cooling energy savings measured in a previous study that used a white coating to increase the albedo of an asphalt shingle roof by the same amount (0.44). The improved cooling energy savings (26% vs. 10%) may be attributed to the cool tile's above-sheathing ventilation, rather than to its high thermal mass. The roof also provided energy savings during the heating season, yielding fractional annual gas

  20. EVALUATION OF ROOF BOLTING REQUIREMENTS BASED ON IN-MINE ROOF BOLTER DRILLING

    Energy Technology Data Exchange (ETDEWEB)

    Syd S. Peng

    2004-04-15

    A one-year non-cost extension has been granted for this project. In this quarter, the field, theoretical and programming works have been performed toward achieving the research goals set in the proposal. The main accomplishments in this quarter included: (1) laboratory tests have been conducted, (2) with the added trendline analysis method, the accuracy of the data interpretation methodology will be improved and the interfaces and voids can be more reliably detected, (3) method to use torque to thrust ratio as indicator of rock relative hardness has also been explored, and (3) about 80% of the development work for the roof geology mapping program, MRGIS, has completed and a special version of the program is in the field testing stage.

  1. EVALUATION OF ROOF BOLTING REQUIREMENTS BASED ON IN-MINE ROOF BOLTER DRILLING

    Energy Technology Data Exchange (ETDEWEB)

    Syd S. Peng

    2004-09-15

    In this quarter, the field, theoretical and programming works have been performed toward achieving the research goals set in the proposal. The main accomplishments in this quarter included: (1) two more sets of field tests have been conducted in an underground coal mine, (2) optimization studies of the control parameters have been conducted, (3) method to use torque to thrust ratio as indicator of rock relative hardness has also been explored, and (3) about 97% of the development work for the roof geology mapping program, MRGIS, has completed, (4) A special version of the geology mapping program for a limestone mine has been developed. The field test for the software and hardware has been successfully finished.

  2. Plant functional traits predict green roof ecosystem services.

    Science.gov (United States)

    Lundholm, Jeremy; Tran, Stephanie; Gebert, Luke

    2015-02-17

    Plants make important contributions to the services provided by engineered ecosystems such as green roofs. Ecologists use plant species traits as generic predictors of geographical distribution, interactions with other species, and ecosystem functioning, but this approach has been little used to optimize engineered ecosystems. Four plant species traits (height, individual leaf area, specific leaf area, and leaf dry matter content) were evaluated as predictors of ecosystem properties and services in a modular green roof system planted with 21 species. Six indicators of ecosystem services, incorporating thermal, hydrological, water quality, and carbon sequestration functions, were predicted by the four plant traits directly or indirectly via their effects on aggregate ecosystem properties, including canopy density and albedo. Species average height and specific leaf area were the most useful traits, predicting several services via effects on canopy density or growth rate. This study demonstrates that easily measured plant traits can be used to select species to optimize green roof performance across multiple key services.

  3. Building Integrated Photovoltaic (BIPV) Roofs for Sustainability and Energy Efficiency

    Science.gov (United States)

    2014-04-01

    In addition, the emergence of new CIGS and CdTe PV modules and vendors have led to a much more diverse group of designs since this study started and...California CdTe Cadmium Telluride CIGS Copper Indium Gallium Di-Selenide DC Direct Current DoD Department of Defense DOE Department of...roof and PV system installed separately. The form of BIPV roof in this study used amorphous silicon (a-Si) PV modules adhered to a reflective polyvinyl

  4. Single-Sided Natural Ventilation through a Velux Roof Window

    DEFF Research Database (Denmark)

    Li, Zhigang; Nielsen, Peter Vilhelm; Fransson, J.

    2004-01-01

    This paper investigates the single-sided natural ventilation through a VELUX centre pivot roof window under natural weather conditions. The aim of the investigation is to develop an empirical formulation for air flow rate through a roof window based on CFD and tracer gas decay measurement methods....... CFD can separate buoyancy and wind effects in the calculation of the air flow rate through a window opening, but it is difficult to isolate wind effect from buoyancy forces during measurements. The ?Warren-plot? method can be used to separate and analyse the measured data which are dominated by stack...

  5. Retention performance of green roofs in representative climates worldwide

    Science.gov (United States)

    Viola, F.; Hellies, M.; Deidda, R.

    2017-10-01

    The ongoing process of global urbanization contributes to an increase in stormwater runoff from impervious surfaces, threatening also water quality. Green roofs have been proved to be innovative stormwater management measures to partially restore natural states, enhancing interception, infiltration and evapotranspiration fluxes. The amount of water that is retained within green roofs depends not only on their depth, but also on the climate, which drives the stochastic soil moisture dynamic. In this context, a simple tool for assessing performance of green roofs worldwide in terms of retained water is still missing and highly desirable for practical assessments. The aim of this work is to explore retention performance of green roofs as a function of their depth and in different climate regimes. Two soil depths are investigated, one representing the intensive configuration and another representing the extensive one. The role of the climate in driving water retention has been represented by rainfall and potential evapotranspiration dynamics. A simple conceptual weather generator has been implemented and used for stochastic simulation of daily rainfall and potential evapotranspiration. Stochastic forcing is used as an input of a simple conceptual hydrological model for estimating long-term water partitioning between rainfall, runoff and actual evapotranspiration. Coupling the stochastic weather generator with the conceptual hydrological model, we assessed the amount of rainfall diverted into evapotranspiration for different combinations of annual rainfall and potential evapotranspiration in five representative climatic regimes. Results quantified the capabilities of green roofs in retaining rainfall and consequently in reducing discharges into sewer systems at an annual time scale. The role of substrate depth has been recognized to be crucial in determining green roofs retention performance, which in general increase from extensive to intensive settings. Looking at the

  6. Preliminary Guidelines for Maintenance of Polyurethane Foam (PUF) Roofing Systems.

    Science.gov (United States)

    1984-03-01

    establish effective procedures for maintenance of PUF roofing systems. Libr , -Card - Naval Civil Engineering Laboratory PRELIMINARY GUIDELINES FOR...attempted. 1.2.3 Insulation Board. If the roof deck is smooth rather than irregular, as with some metal decks, a patch can be made using PUF or other...VA FNIFI .-NNI (TO (Mfr. Norfolk N\\X 6fDF)P 0W. Corona . C-N (SA Ass Conmn D~es & (io~i IF.NIA) I) R Ilihner Xaiinjton. I)( (MI A lDcs &k 0 n’t.T NI IW

  7. Water Runoff Properties for Expanded Clay LWA in Green Roofs

    OpenAIRE

    Eriksson, Anders Olof

    2013-01-01

    A lightweight aggregate (LWA) is a material that has a lower density than rock aggregates. There are many civil engineering application possibilities for LWA. A potential field of application for expanded clay LWA is as a storm water retaining layer in green roofs. In order to design reliable structures of green roofs, more knowledge about the characteristics of the material is needed. The purpose of this master thesis was to test if the software SEEP/W is an appropriate tool for simulation o...

  8. TV borehole inspection and vacuum testing of roof strata

    International Nuclear Information System (INIS)

    Herget, G.

    1982-01-01

    To improve quality control of roof conditions, a program was carried out at Elliot Lake uranium mines in Ontario, Canada to test a portable TV camera system. This camera has a 29 mm diameter probe and is capable of identifying crack locations, crack width and approximate dip direction. The extent of fractures in the roof was checked with the aid of a vacuum system by placing packers in various boreholes and checking for communication. The removal of some rock bolts indicated an increase in fracture extent

  9. Identification of causes of unsafe acts or neglect resulting in roof or sidewall accidents.

    CSIR Research Space (South Africa)

    Hamilton-Atwell, A

    1997-10-01

    Full Text Available the cause was roof and sidewall accidents. The primary objective of this project was to identify the causes of unsafe acts or neglect resulting in roof and sidewall accidents in coal mines....

  10. Field Testing Unvented Roofs with Asphalt Shingles in Cold and Hot-Humid Climates

    Energy Technology Data Exchange (ETDEWEB)

    Ueno, Kohta [Building Science Corporation, Westford, MA (United States); Lstiburek, Joseph W. [Building Science Corporation, Westford, MA (United States)

    2015-09-01

    Test houses with unvented roof assemblies were built to measure long-term moisture performance, in the Chicago area (5A) and the Houston area (2A). The Chicago-area test bed had seven experimental rafter bays, including a control vented compact roof, and six unvented roof variants with cellulose or fiberglass insulation. The interior was run at 50% RH. The Houston-area roof was an unvented attic insulated with spray-applied fiberglass. Most ridges and hips were built with a diffusion vent detail, capped with vapor permeable roof membrane. In contrast, the diffusion vent roofs had drier conditions at the roof peak in wintertime, but during the summer, RHs and MCs were higher than the unvented roof (albeit in the safe range).

  11. Accurate and Automatic Building Roof Extraction Using Neighborhood Information of Point Clouds

    Directory of Open Access Journals (Sweden)

    ZHAO Chuan

    2017-09-01

    Full Text Available High accuracy building roof extraction from LiDAR data is the key to build topological relationship of building roofs and reconstruct buildings. Aiming at the poor adaptation and low extraction precision of existing roof extraction methods for complex building, an accurate and automatic building roof extraction method using neighborhood information of point clouds is proposed. Point clouds features are calculated by principle component analysis, and reliable seed points are selected after feature histogram construction. Initial roof surfaces are extracted quickly and precisely by the proposed local normal vector distribution density-based spatial clustering of applications with noise (LNVD-DBSCAN. Roof competition problem is solved effectively by the poll model based on neighborhood information. Experimental results show that the proposed method can extract building roofs automatically and precisely, and has preferable adaptation to buildings with different complexity, which is able to provide reliable roof information for building reconstruction.

  12. Wieslander Vegetation

    Data.gov (United States)

    California Department of Resources — Digital version of the 1945 California Vegetation Type Maps by A. E. Wieslander of the U.S. Forest Service. Source scale of maps are 1:100,000. These compiled maps...

  13. Kuchler Vegetation

    Data.gov (United States)

    California Department of Resources — Digital version of potential natural plant communites as compiled and published on 'Map of the Natural Vegetation of California' by A. W. Kuchler, 1976. Source map...

  14. Wieslander Vegetation

    Data.gov (United States)

    California Natural Resource Agency — Digital version of the 1945 California Vegetation Type Maps by A. E. Wieslander of the U.S. Forest Service. Source scale of maps are 1:100,000. These compiled maps...

  15. Kuchler Vegetation

    Data.gov (United States)

    California Natural Resource Agency — Digital version of potential natural plant communites as compiled and published on 'Map of the Natural Vegetation of California' by A. W. Kuchler, 1976. Source map...

  16. Separating drought effects from roof artifacts on ecosystem processes in a grassland drought experiment.

    Science.gov (United States)

    Vogel, Anja; Fester, Thomas; Eisenhauer, Nico; Scherer-Lorenzen, Michael; Schmid, Bernhard; Weisser, Wolfgang W; Weigelt, Alexandra

    2013-01-01

    1: Given the predictions of increased drought probabilities under various climate change scenarios, there have been numerous experimental field studies simulating drought using transparent roofs in different ecosystems and regions. Such roofs may, however, have unknown side effects, called artifacts, on the measured variables potentially confounding the experimental results. A roofed control allows the quantification of potential artifacts, which is lacking in most experiments. 2: We conducted a drought experiment in experimental grasslands to study artifacts of transparent roofs and the resulting effects of artifacts on ecosystems relative to drought on three response variables (aboveground biomass, litter decomposition and plant metabolite profiles). We established three drought treatments, using (1) transparent roofs to exclude rainfall, (2) an unroofed control treatment receiving natural rainfall and (3) a roofed control, nested in the drought treatment but with rain water reapplied according to ambient conditions. 3: Roofs had a slight impact on air (+0.14°C during night) and soil temperatures (-0.45°C on warm days, +0.25°C on cold nights), while photosynthetically active radiation was decreased significantly (-16%). Aboveground plant community biomass was reduced in the drought treatment (-41%), but there was no significant difference between the roofed and unroofed control, i.e., there were no measurable roof artifact effects. 4: Compared to the unroofed control, litter decomposition was decreased significantly both in the drought treatment (-26%) and in the roofed control treatment (-18%), suggesting artifact effects of the transparent roofs. Moreover, aboveground metabolite profiles in the model plant species Medicago x varia were different from the unroofed control in both the drought and roofed control treatments, and roof artifact effects were of comparable magnitude as drought effects. 5: Our results stress the need for roofed control treatments

  17. Rational Geometrical Characters of Saddle Shape Cable Roof Supported by Tensioned Cables

    OpenAIRE

    Rocēns, K; Pakrastiņš, L; Serdjuks, D

    1999-01-01

    The saddle shape cable roof, which is supported by tension cables, is considered in the paper. The roof is kinematics invariable because of prestressing of rectangular (orthogonal) cable net The correlation between the main geometrical characters of the cable roof and weight of the cable net which is divided by the area covered by the cable roof, was ascertained by a numeral experiment. The main geometrical characters are the initial curvatures of stressing, suspension and tension cables and ...

  18. Digging the New York City Skyline: soil fungal communities in green roofs and city parks.

    Science.gov (United States)

    McGuire, Krista L; Payne, Sara G; Palmer, Matthew I; Gillikin, Caitlyn M; Keefe, Dominique; Kim, Su Jin; Gedallovich, Seren M; Discenza, Julia; Rangamannar, Ramya; Koshner, Jennifer A; Massmann, Audrey L; Orazi, Giulia; Essene, Adam; Leff, Jonathan W; Fierer, Noah

    2013-01-01

    In urban environments, green roofs provide a number of benefits, including decreased urban heat island effects and reduced energy costs for buildings. However, little research has been done on the non-plant biota associated with green roofs, which likely affect their functionality. For the current study, we evaluated whether or not green roofs planted with two native plant communities in New York City functioned as habitats for soil fungal communities, and compared fungal communities in green roof growing media to soil microbial composition in five city parks, including Central Park and the High Line. Ten replicate roofs were sampled one year after planting; three of these roofs were more intensively sampled and compared to nearby city parks. Using Illumina sequencing of the fungal ITS region we found that green roofs supported a diverse fungal community, with numerous taxa belonging to fungal groups capable of surviving in disturbed and polluted habitats. Across roofs, there was significant biogeographical clustering of fungal communities, indicating that community assembly of roof microbes across the greater New York City area is locally variable. Green roof fungal communities were compositionally distinct from city parks and only 54% of the green roof taxa were also found in the park soils. Phospholipid fatty acid analysis revealed that park soils had greater microbial biomass and higher bacterial to fungal ratios than green roof substrates. City park soils were also more enriched with heavy metals, had lower pH, and lower quantities of total bases (Ca, K, and Mg) compared to green roof substrates. While fungal communities were compositionally distinct across green roofs, they did not differentiate by plant community. Together, these results suggest that fungi living in the growing medium of green roofs may be an underestimated component of these biotic systems functioning to support some of the valued ecological services of green roofs.

  19. Pemanfaatan Green Roof sebagai Media Filter Air Hujan di Kota Pontianak

    OpenAIRE

    Uria Karlena Sely Sakong

    2013-01-01

    Penelitian ini bertujuan untuk mempelajari pengaruh green roof terhadap kualitas air hujan di KotaPontianak. Pengaruh tersebut dipelajari dengan cara membandingkan antara kualitas air hujan yang melewatigreen roof dengan kualitas air yang tidak melewati green roof. Penelitian diawali dengan merancang danmembuat model green roof. Pengambilan sampel dilakukan sebanyak empat kali dan diuji di laboratoriumterhadap parameter pH, kekeruhan, Pb terlarut dan E.Col...

  20. R&D for a single-layer $Nb_{3}Sn$ common coil dipole using the react-and-wind fabrication technique

    CERN Document Server

    Ambrosio, G; Barzi, E; Bauer, P; Chichili, D R; Ewald, K D; Fehér, S; Imbasciati, L; Kashikhin, V V; Limon, P J; Litvinenko, L; Novitski, I; Rey, J M; Scanlan, R M; Yadav, S; Yamada, R; Zlobin, A V

    2002-01-01

    A dipole magnet based on the common coil design, using prereacted Nb /sub 3/Sn superconductor, is under development at Fermilab, for a future Very Large Hadron Collider. This magnet has some innovative design and technological features such as single layer coils, a 22 mm wide 60-strand Rutherford type cable and stainless steel collars reinforced by horizontal bridges inserted between coil blocks. Both left and right coils are wound simultaneously into the collar structure and then impregnated with epoxy. In order to optimize the design and fabrication techniques an R&D program is underway. The production of cables with the required characteristics was shown possible. Collar laminations were produced, assembled and tested in order to check the effectiveness of the bridges and the validity of the mechanical design. A mechanical model consisting in a 165 mm long section of the magnet straight section was assembled and tested. This paper summarizes the status of the program, and reports the results of fabrica...

  1. NMR studies of Borrelia burgdorferi OspA, a 28 kDa protein containing a single-layer {beta}-sheet

    Energy Technology Data Exchange (ETDEWEB)

    Pham, Thuy-Nga; Koide, Shohei

    1998-05-15

    The crystal structure of outer surface protein A (OspA) from Borrelia burgdorferi contains a single-layer {beta}-sheet connecting the N- and C-terminal globular domains. The central {beta}-sheet consists largely of polar amino acids and it is solvent-exposed on both faces, which so far appears to be unique among known protein structures. We have accomplished nearly complete backbone H, C and N and C{sup ;}/H{sup {beta}} assignments of OspA (28 kDa) using standard triple resonance techniques without perdeuteration. This was made possible by recording spectra at a high temperature (45 {sup o}C ). The chemical shift index and {sup 15}N T{sub 1}/T{sub 2} ratios show that both the secondary structure and the global conformation of OspA in solution are similar to the crystal structure, suggesting that the unique central {beta}-sheet is fairly rigid.

  2. Remote N2 plasma treatment to deposit ultrathin high-k dielectric as tunneling contact layer for single-layer MoS2 MOSFET

    Science.gov (United States)

    Qian, Qingkai; Zhang, Zhaofu; Hua, Mengyuan; Wei, Jin; Lei, Jiacheng; Chen, Kevin J.

    2017-12-01

    Remote N2 plasma treatment is explored as a surface functionalization technique to deposit ultrathin high-k dielectric on single-layer MoS2. The ultrathin dielectric is used as a tunneling contact layer, which also serves as an interfacial layer below the gate region for fabricating top-gate MoS2 metal–oxide–semiconductor field-effect transistors (MOSFETs). The fabricated devices exhibited small hysteresis and mobility as high as 14 cm2·V‑1·s‑1. The contact resistance was significantly reduced, which resulted in the increase of drain current from 20 to 56 µA/µm. The contact resistance reduction can be attributed to the alleviated metal–MoS2 interface reaction and the preserved conductivity of MoS2 below the source/drain metal contact.

  3. Who governs climate adaptation? Getting green roofs for stormwater retention off the ground

    NARCIS (Netherlands)

    Mees, H.L.P.; Driessen, P.P.J.; Runhaar, H.A.C.; Stamatelos, J.

    2013-01-01

    Green roofs are an innovative solution for urban stormwater management. This paper examines governance arrangements for green roofs as a ‘no-regrets’ climate adaptation measure in five cities. We analysed who governs green roofs, why and with what outcome. Our results show that hierarchical and

  4. Wind loads on stand-off photovoltaic systems on pitched roofs

    NARCIS (Netherlands)

    Geurts, C.P.W.; Blackmore, P.

    2013-01-01

    Stand-off photovoltaic systems are a popular measure for retrofitting of existing pitched roofs.Panels are generally mounted parallel to the existing roof coverings,usually roofing tiles.Full scale and wind tunnel experiments have been performed to determine the net uplift loads on these systems,

  5. Cool roofs and the influence on the energy consumption under Danish conditions

    DEFF Research Database (Denmark)

    Brandt, Erik; Bunch-Nielsen, Tommy; Juhl, Lasse

    Experience from countries in warm climates has shown that the color of the roofing material has a significant effect on the energy consumption of the building. Especially changing from black to white roofing material provides reduction in energy consumption. The investigated roofs have been with ...

  6. Evaluation of Green Roof Plants and Materials for Semi-Arid Climates

    Science.gov (United States)

    Abstract While green roof systems have proven to be highly effective in the evaporative cooling of buildings, reduction of roof top temperatures, protection of roof membranes from solar radiation degradation, reducing stormwater runoff, as well as beautification of the urban roo...

  7. Green Roofs: A Part of Green Infrastructure Strategy for Urban Areas

    Science.gov (United States)

    This is a presentation on the basics of green roof technology. The presentation highlights some of the recent ORD research projects on green roofs and provides insight for the end user as to the benefits for green roof technology. It provides links to currently available EPA rep...

  8. 30 CFR 75.209 - Automated Temporary Roof Support (ATRS) systems.

    Science.gov (United States)

    2010-07-01

    ... of temporary support shall be used, as specified in the roof control plan, when— (1) Mining... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Automated Temporary Roof Support (ATRS) systems... COAL MINE SAFETY AND HEALTH MANDATORY SAFETY STANDARDS-UNDERGROUND COAL MINES Roof Support § 75.209...

  9. Green roofs: A possible best management practice for enhancing ...

    African Journals Online (AJOL)

    City expansion typically erodes the natural ability of the locale to perform its ecosystem services. This paper discusses green roofs and their potential benefits for Ghanaian cities in terms of improving environmental quality. Limited analysis shows that daily minimum temperatures of cities like Accra are rising faster than the ...

  10. Asphalt and Wood Shingling. Roofing Workbook and Tests.

    Science.gov (United States)

    Brown, Arthur

    This combination workbook and set of tests contains materials on asphalt and wood shingling that have been designed to be used by those studying to enter the roofing and waterproofing trade. It consists of seven instructional units and seven accompanying objective tests. Covered in the individual units are the following topics: shingling…

  11. Roofing: Workbook and Tests. First-Aid Training.

    Science.gov (United States)

    California State Dept. of Education, Sacramento. Bureau of Publications.

    This workbook on first aid is one of a series of nine individual units of instruction for roofing apprenticeship classes in California. The workbook covers 12 topics: introduction to first-aid practices; burns; skeletal injuries; spinal injuries; wounds, bleeding, and bruises; emergencies of the heart and blood circulation system; breathing and…

  12. Pressing process improvements for roofing tiles using porous moulds

    NARCIS (Netherlands)

    Dortmans, L.J.M.G.; Bos, B.; Fischer, H.R.

    2010-01-01

    Roofing tiles are traditionally produced via pressing using plaster of Paris moulds. A replacement of such moulds by porous PMMA based moulds increases production speed and the durability of the moulds, however results in a non-acceptable surface finish due to enhanced adhesion of the clay to the

  13. Evaluation of green roof characteristics in green building assessment

    Directory of Open Access Journals (Sweden)

    Sekulić Mirjana

    2013-01-01

    Full Text Available Methodology of building evaluation based on green building characteristics is rapidly gaining momentum, mainly in foreign, but also in domestic building practice. This methodology is being carried out through different Green Building Certification Systems, which are complex evaluation mechanisms based on numerous criteria of sustainability, addressing both ecological issues, but also economic and social ones. Green roof represents one of the 'must have' features of contemporary buildings aiming to gain green label. This paradigm is based on their numerous characteristics which contribute to different aspects of building sustainability, among which are savings in energy and water consumption, but also ecological balance and quality of built environment. Criteria used for evaluation of green roof solutions and their overall contribution to the building, are integral part of all of the mentioned certification systems, but the way they are structured and formulated inside each system varies significantly, hence causing differences in evaluation results. This paper presents the analysis of green roof related criteria of three characteristic green building certification systems: LEED, BREEAM and CASBEE. These systems are chosen primarily because of the different evaluation methodology, but also because of their market prevalence and perspectives of usage in the domestic practice. Conclusions driven from these analyses and comparisons provide insight into main aspect of green roof planning and construction which are relevant for the overall building sustainability assessment.

  14. Green Roof Research through EPA's Regional Applied Research Effort - slides

    Science.gov (United States)

    The U.S. Environmental Protection Agency’s (EPA) Regional Applied Research Effort (RARE) allows the Regions of the EPA to choose research projects to be performed in partnership with EPA’s Office of Research and Development (ORD). Over the last decade, several green roof projects...

  15. Empirical Strengths of Concrete Roof Slabs After 34 Years Service ...

    African Journals Online (AJOL)

    This paper examines the strengths of four reinforced concrete roof slabs which have been in service for over 34years. The non-destructive test hammer was used to obtain data for the empirical determination of the practical strengths of the existing structures. A total of 110 tests were performed on each slab at 11 points ...

  16. Survey of the Pagoda Timber Roof in Derneburg Castle

    Science.gov (United States)

    Perria, E.; Sieder, M.; Hoyer, S.; Krafczyk, C.

    2017-05-01

    The work analyses the historical roof of Derneburg Castle, in the municipality of Holle, Hildesheim's district, Lower Saxony, Germany. The roof is assembled according to Laves Balken's system (Laves beam's system), developed by the architect Georg Ludwig Friedrich Laves (1788-1864). The system has the peculiarity to consist of beams that are split along the half of the cross section, and maintained diverged by wooden wedges, distributed along the length of the beam. The system increases the height of the beam, and elevates the bending capacity of it (Weber, 1964). The work has been developed in the frame of an interdisciplinary project in the fields of architecture, engineering and photogrammetry. Main aim of the project is the developing of a structural model to understand the load-carrying capacity of Laves Balken's system from the laser-scanning model. For this reason, extensive surveys and photo documentation were collected on three areas of the roof construction, characterized by three peculiar usage of Laves Balken's system. The work presents the survey of the pagoda-roof that covers the tower of the castle, and problems that can be encountered during the survey of very complex timber constructions.

  17. 30 CFR 75.221 - Roof control plan information.

    Science.gov (United States)

    2010-07-01

    ... installation and spacing of supports for each method of mining used. (6) When an ATRS system is used, the... of pillar recovery, and the sequence of mining pillars. (9) A list of all support materials required... mining approaches within 150 feet of an outcrop. (12) A description of the roof and rib support necessary...

  18. Field Testing Unvented Roofs with Asphalt Shingles in Cold and Hot-Humid Climates

    Energy Technology Data Exchange (ETDEWEB)

    Ueno, Kohta [National Renewable Energy Lab. (NREL), Golden, CO (United States); Lstiburek, Joseph W. [National Renewable Energy Lab. (NREL), Golden, CO (United States)

    2015-09-01

    Insulating roofs with dense-pack cellulose (instead of spray foam) has moisture risks, but is a lower cost approach. If moisture risks could be addressed, buildings could benefit from retrofit options, and the ability to bring HVAC systems within the conditioned space. Test houses with unvented roof assemblies were built to measure long-term moisture performance, in the Chicago area (5A) and the Houston area (2A). The Chicago-area test bed had seven experimental rafter bays, including a control vented compact roof, and six unvented roof variants with cellulose or fiberglass insulation. The interior was run at 50% RH. All roofs except the vented cathedral assembly experienced wood moisture contents and RH levels high enough to constitute failure. Disassembly at the end of the experiment showed that the unvented fiberglass roofs had wet sheathing and mold growth. In contrast, the cellulose roofs only had slight issues, such as rusted fasteners and sheathing grain raise. The Houston-area roof was an unvented attic insulated with spray-applied fiberglass. Most ridges and hips were built with a diffusion vent detail, capped with vapor permeable roof membrane. Some ridge sections were built as a conventional unvented roof, as a control. In the control unvented roofs, roof peak RHs reached high levels in the first winter; as exterior conditions warmed, RHs quickly fell. In contrast, the diffusion vent roofs had drier conditions at the roof peak in wintertime, but during the summer, RHs and MCs were higher than the unvented roof (albeit in the safe range).

  19. Green roofs'retention performances in different climates

    Science.gov (United States)

    Viola, Francesco; Hellies, Matteo; Deidda, Roberto

    2017-04-01

    The ongoing process of global urbanization contributes to increasing stormwater runoff from impervious surfaces, threatening also water quality. Green roofs have been proved to be an innovative stormwater management tool to partially restore natural state, enhancing interception, infiltration and evapotranspiration fluxes. The amount of water that is retained within green roofs depends mainly on both soil properties and climate. The evaluation of the retained water is not trivial since it depends on the stochastic soil moisture dynamics. The aim of this work is to explore performances of green roofs, in terms of water retention, as a function of their depth considering different climate regimes. The role of climate in driving water retention has been mainly represented by rainfall and potential evapotranspiration dynamics, which are simulated by a simple conceptual weather generator at daily time scale. The model is able to describe seasonal (in-phase and counter-phase) and stationary behaviors of climatic forcings. Model parameters have been estimated on more than 20,000 historical time series retrieved worldwide. Exemplifying cases are discussed for five different climate scenarios, changing the amplitude and/or the phase of daily mean rainfall and evapotranspiration forcings. The first scenario represents stationary climates, in two other cases the daily mean rainfall or the potential evapotranspiration evolve sinusoidally. In the latter two cases, we simulated the in-phase or in counter-phase conditions. Stochastic forcings have been then used as an input to a simple conceptual hydrological model which simulate soil moisture dynamics, evapotranspiration fluxes, runoff and leakage from soil pack at daily time scale. For several combinations of annual rainfall and potential evapotranspiration, the analysis allowed assessing green roofs' retaining capabilities, at annual time scale. Provided abacus allows a first approximation of possible hydrological benefits

  20. A Case Study of Effective Support Working Resistance and Roof Support Technology in Thick Seam Fully-Mechanized Face Mining with Hard Roof Conditions

    Directory of Open Access Journals (Sweden)

    Wei-bin Guo

    2017-06-01

    Full Text Available This paper presents the engineering geological properties and roof control tecnology for a thick coal seam fully-mechanized face mining with hard roof conditions (THC at the Jinhuagong Coal Mine (JCM, northwest China. The effective support working resistance and appropriate roof control technology are two critical factors for safe and productive mining in the THC. The load-estimate-method (LOEM is the effective method to determine the support working resistance for normal working conditions (the mining height less than 3.5 m. In order to prevent support crushing accidents from happening and to ensure the safety and high-efficiency in the THC, the LOEM was modified based on the structure of the overlying strata in the THC. The strata which can form the voussoir beam structure in normal working conditions and will break in the form of cantilever beam in the THC is defined as the key strata in the immediate roof. Therefore, the hanging length of the key strata in the immediate roof was considered in the LOEM. Furthermore, a method for calculating the hanging length of the key strata in the immediate roof and its influencing factors were proposed using cantilever beam theory analysis of the structure of the overlying strata. Moreover, in order to fully fill the goaf area with caving roof to reduce the energy accumulation of main roof movement, it was decided to apply destress blasting technique (DEBT at the JCM to control the large hanging length of the hard roof, so as to reduce the impact of the hard main roof movement on the working face. The key technique parameters of the roof caving borehole were also proposed. The obtained results demonstrated that the theoretical analysis is reasonable, and the chosen support type and the DEBT could meet the roof control requirements. The THC has achieved safety and high-efficiency mining.