scholarly journals Energetic analysis of hard facing and weld cladding of an air powered drop hammer damaged ram

2010 ◽  
Vol 14 (suppl.) ◽  
pp. 269-284
Author(s):  
Vukic Lazic ◽  
Milorad Jovanovic ◽  
Aleksandar Sedmak ◽  
Srbislav Aleksandrovic ◽  
Dragan Milosavljevic ◽  
...  
Keyword(s):  
Thermal Fatigue ◽  
Complex Geometry ◽  
Impact Compression ◽  
Temperature Changes ◽  
Drop Hammer ◽  
Cyclic Temperature ◽  
Energetic Analysis ◽  
Weld Cladding ◽  
Variable Impact

This paper studies problems of hard facing of damaged and initially cracked mechanical engineering heavy parts of complex geometry such as large rams of air powered drop hammers. During long-term exploitation, these parts are subjected to thermal fatigue due to cyclic temperature changes and variable impact compression. Taking into consideration high ram costs and difficulties to purchase ram, the necessity of its reparation becomes obvious. The choices of the most suitable technologies of hard facing and welding of an initially cracked ram are also studied here. Besides the techno-economic analysis, an energetic analysis is performed as an additional criterion in assessment of the proposed technology.

scholarly journals Membrane Homeoviscous Adaptation in Sinorhizobium Submitted to a Stressful Thermal Cycle Contributes to the Maintenance of the Symbiotic Plant–Bacteria Interaction

2021 ◽  
Vol 12 ◽  
Author(s):  
Natalia Soledad Paulucci ◽  
Adriana Belén Cesari ◽  
María Alicia Biasutti ◽  
Marta Susana Dardanelli ◽  
María Angélica Perillo
Keyword(s):  
Lipid Bilayers ◽  
Sinorhizobium Meliloti ◽  
Symbiotic Interaction ◽  
Homeoviscous Adaptation ◽  
Temperature Changes ◽  
Thermal Changes ◽  
Cyclic Temperature ◽  
The One ◽  
Term Response

Here, we estimate fast changes in the fluidity of Sinorhizobium meliloti membranes submitted to cyclic temperature changes (10°C–40°C–10°C) by monitoring the fluorescence polarization (P) of DPH and TMA-DPH of the whole cell (WC) as well as in its outer (OM) and inner (IM) membranes. Additionally, the long-term response to thermal changes is demonstrated through the dynamics of the phospholipid and fatty acid composition in each membrane. This allowed membrane homeoviscous adaptation by the return to optimal fluidity levels as measured by the PDPH/TMA-DPH in WC, OM, IM, and multilamellar vesicles of lipids extracted from OM and IM. Due to probe-partitioning preferences and membranes’ compositional characteristics, DPH and TMA-DPH exhibit different behaviors in IM and OM. The rapid effect of cyclic temperature changes on the P was the opposite in both membranes with the IM being the one that exhibited the thermal behavior expected for lipid bilayers. Interestingly, only after the incubation at 40°C, cells were unable to recover the membrane preheating P levels when cooled up to 10°C. Solely in this condition, the formation of threads and nodular structures in Medicago sativa infected with S. meliloti were delayed, indicating that the symbiotic interaction was partially altered but not halted.

scholarly journals The Impact of Selected Atmospheric Conditions on the Process of Abrasive Wear of CFRP

Materials ◽  
2020 ◽  
Vol 13 (18) ◽  
pp. 3965 ◽  
Author(s):  
Aneta Krzyzak ◽  
Damian Racinowski ◽  
Robert Szczepaniak ◽  
Mateusz Mucha ◽  
Ewelina Kosicka
Keyword(s):  
Abrasive Wear ◽  
Atmospheric Conditions ◽  
Carbon Fabric ◽  
Temperature Changes ◽  
Cyclic Temperature ◽  
Research Findings ◽  
Long Term Impact ◽  
The Impact ◽  
Thermal Shocks

The aim of this study was to examine the impact of weathering and thermal shocks on the abrasive wear of epoxy resin composites reinforced with carbon fabric that are commonly used in aviation. The composite was exposed to degradation in an apparatus simulating weathering and thermal shocks and then subjected to an abrasion process, with and without the presence of water. The abrasive wear was controlled by checking the weight loss as well as by visual inspection. The research findings indicated a significant effect of the presence of water in the process of friction upon the deterioration of composite resistance to abrasion with regard to dry friction. The long-term impact of rapid cyclic temperature changes (temperature difference: from −56.5 °C to +60 °C) and a combined effect of UV-A (0.83 W/m2), along with condensation of vapor and an increased ambient temperature (above 50 °C), influenced an improvement in resistance to abrasive wear. The environment of thermal shocks diminished abrasive wear to a much smaller extent than after exploitation in an environment of weathering but both environments contributed to the degradation of the surface layer. Additionally, the environment with UV-A radiation resulted in exposure of the composite reinforcement already after four months of environmental impact.

Modeling of unforced demand response programs

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Hassan Jalili ◽  
Pierluigi Siano
Keyword(s):  
Demand Response ◽  
Load Shifting ◽  
Response Models ◽  
Temperature Changes ◽  
Proposed Model ◽  
Equipment Failures ◽  
Demand Response Programs ◽  
Simultaneous Implementation ◽  
Long Term Studies

Abstract Demand response programs are useful options in reducing electricity price, congestion relief, load shifting, peak clipping, valley filling and resource adequacy from the system operator’s viewpoint. For this purpose, many models of these programs have been developed. However, the availability of these resources has not been properly modeled in demand response models making them not practical for long-term studies such as in the resource adequacy problem where considering the providers’ responding uncertainties is necessary for long-term studies. In this paper, a model considering providers’ unavailability for unforced demand response programs has been developed. Temperature changes, equipment failures, simultaneous implementation of demand side management resources, popular TV programs and family visits are the main reasons that may affect the availability of the demand response providers to fulfill their commitments. The effectiveness of the proposed model has been demonstrated by numerical simulation.

scholarly journals Maps, trends, and temperature sensitivities—phenological information from and for decreasing numbers of volunteer observers

2021 ◽  
Author(s):  
Ye Yuan ◽  
Stefan Härer ◽  
Tobias Ottenheym ◽  
Gourav Misra ◽  
Alissa Lüpke ◽  
...  
Keyword(s):  
Climate Change ◽  
Time Series ◽  
Strong Decrease ◽  
Temperature Changes ◽  
Interpolation Accuracy ◽  
Observation Network ◽  
Shiny App ◽  
Long Term Trends ◽  
Autumn And Winter

AbstractPhenology serves as a major indicator of ongoing climate change. Long-term phenological observations are critically important for tracking and communicating these changes. The phenological observation network across Germany is operated by the National Meteorological Service with a major contribution from volunteering activities. However, the number of observers has strongly decreased for the last decades, possibly resulting in increasing uncertainties when extracting reliable phenological information from map interpolation. We studied uncertainties in interpolated maps from decreasing phenological records, by comparing long-term trends based on grid-based interpolated and station-wise observed time series, as well as their correlations with temperature. Interpolated maps in spring were characterized by the largest spatial variabilities across Bavaria, Germany, with respective lowest interpolated uncertainties. Long-term phenological trends for both interpolations and observations exhibited mean advances of −0.2 to −0.3 days year−1 for spring and summer, while late autumn and winter showed a delay of around 0.1 days year−1. Throughout the year, temperature sensitivities were consistently stronger for interpolated time series than observations. Such a better representation of regional phenology by interpolation was equally supported by satellite-derived phenological indices. Nevertheless, simulation of observer numbers indicated that a decline to less than 40% leads to a strong decrease in interpolation accuracy. To better understand the risk of declining phenological observations and to motivate volunteer observers, a Shiny app is proposed to visualize spatial and temporal phenological patterns across Bavaria and their links to climate change–induced temperature changes.

scholarly journals Cities Exacerbate Climate Warming

Urban Science ◽  
2021 ◽  
Vol 5 (1) ◽  
pp. 27
Author(s):  
Lahouari Bounoua ◽  
Kurtis Thome ◽  
Joseph Nigro
Keyword(s):  
Surface Temperature ◽  
Land Surface ◽  
Large Scale ◽  
Climate Models ◽  
Warming Trend ◽  
Climate Mitigation ◽  
Temperature Changes ◽  
Surface Warming ◽  
The Us

Urbanization is a complex land transformation not explicitly resolved within large-scale climate models. Long-term timeseries of high-resolution satellite data are essential to characterize urbanization within land surface models and to assess its contribution to surface temperature changes. The potential for additional surface warming from urbanization-induced land use change is investigated and decoupled from that due to change in climate over the continental US using a decadal timescale. We show that, aggregated over the US, the summer mean urban-induced surface temperature increased by 0.15 °C, with a warming of 0.24 °C in cities built in vegetated areas and a cooling of 0.25 °C in cities built in non-vegetated arid areas. This temperature change is comparable in magnitude to the 0.13 °C/decade global warming trend observed over the last 50 years caused by increased CO2. We also show that the effect of urban-induced change on surface temperature is felt above and beyond that of the CO2 effect. Our results suggest that climate mitigation policies must consider urbanization feedback to put a limit on the worldwide mean temperature increase.

scholarly journals The role of frost cracking in local denudation of steep Alpine rockwalls over millennia (Eiger, Switzerland)

2020 ◽  
Vol 8 (3) ◽  
pp. 637-659
Author(s):  
David Mair ◽  
Alessandro Lechmann ◽  
Romain Delunel ◽  
Serdar Yeşilyurt ◽  
Dmitry Tikhomirov ◽  
...  
Keyword(s):  
Swiss Alps ◽  
Rock Fall ◽  
Temperature Changes ◽  
Rock Face ◽  
Temperature Conditions ◽  
Denudation Rates ◽  
Reconstructed Temperature ◽  
Cryogenic Processes

Abstract. Denudation of steep rockwalls is driven by rock fall processes of various sizes and magnitudes. Rockwalls are sensitive to temperature changes mainly because thermo-cryogenic processes weaken bedrock through fracturing, which can precondition the occurrence of rock fall. However, it is still unclear how the fracturing of rock together with cryogenic processes impacts the denudation processes operating on steep rockwalls. In this study, we link data on long-term rockwall denudation rates at the Eiger (Central Swiss Alps) with the local bedrock fabric and the reconstructed temperature conditions at these sites, which depend on the insolation pattern. We then estimate the probability of bedrock for failure through the employment of a theoretical frost cracking model. The results show that the denudation rates are low in the upper part of the NW rockwall, but they are high both in the lower part of the NW rockwall and on the SE face, despite similar bedrock fabric conditions. The frost cracking model predicts a large difference in cracking intensity from ice segregation where the inferred efficiency is low in the upper part of the NW rockwall but relatively large on the lower section of the NW wall and on the SE rock face of the Eiger. We explain this pattern by the differences in insolation and temperature conditions at these sites. Throughout the last millennium, temperatures in bedrock have been very similar to the present. These data thus suggest the occurrence of large contrasts in microclimate between the NW and SE walls of the Eiger, conditioned by differences in insolation. We use these contrasts to explain the relatively low denudation rates in the upper part of the NW rockwall and the rapid denudation in the SW face and in the lower part of the NW rock face where frost cracking is more efficient.

Multi-cell thermogalvanic systems for harvesting energy from cyclic temperature changes

2018 ◽  
Vol 399 ◽  
pp. 429-435 ◽  
Author(s):  
Patrick A. Linford ◽  
Lin Xu ◽  
Botao Huang ◽  
Yang Shao-Horn ◽  
Carl V. Thompson
Keyword(s):  
Temperature Changes ◽  
Cyclic Temperature
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