A
bstract
By taking the ultra-spinning limit as a simple solution-generating trick, a novel class of ultra-spinning charged black hole solutions has been constructed from Chow’s rotating charged ...black hole with two equal-charge parameters in six-dimensional
N
= 4 gauged supergravity theory. We investigate their thermodynamical properties and then demonstrate that all thermodynamical quantities completely obey both the differential first law and the Bekenstein-Smarr mass formula. For the six-dimensional ultra-spinning Chow’s black hole with only one rotation parameter, we show that it does not always obey the reverse isoperimetric inequality, thus it can be either sub-entropic or super-entropic, depending upon the ranges of the mass parameter and especially the charge parameter. This property is obviously different from that of the six-dimensional singly-rotating Kerr-AdS super-entropic black hole, which always strictly violates the RII. For the six-dimensional doubly-rotating Chow’s black hole but ultra-spinning only along one spatial axis, we point out that it may also obey or violate the RII, and can be either super-entropic or sub-entropic in general.
This study examines potential future changes of precipitation in China based on Coupled Model Intercomparison Project Phase 5 (CMIP5) climate model projections for the medium (RCP4.5) and high ...(RCP8.5) emission scenarios. We first evaluate the biases of climate model output and correct the biases through quantile mapping. After bias correction, we examine the changes in mean precipitation as well as shifts in its frequency distribution. We also evaluate the changes in extreme precipitation based on frequency analysis techniques. Our results show that by the end of the century, mean precipitation is going to increase by 8% (12%) under RCP4.5 (RCP8.5) scenarios, resulted from a combination of an increase in precipitation intensity and a slight decrease in precipitation frequency. Spatially, precipitation is projected to increase more in northern China than southern China, and the increase is the least in the southeast. Seasonally, precipitation is projected to increase more in fall and winter, and less in spring and summer. The precipitation intensity distribution is likely to shift towards more heavy events, with a decrease in the contribution from light events and a significant increase in contribution from heavy events. Extreme precipitation is going to increase at much higher rates than mean precipitation, and the increase is more spatially uniform. Changes in annual and seasonal precipitation are closely linked with temperature change. Total precipitation increases at 2.6% (1.9%) per degree warming under RCP4.5 (RCP8.5), but extreme precipitation has much higher sensitivities ranging 4.5–6.5% per degree warming for events of various return intervals. The percentage increase per degree is generally smaller for RCP8.5 than RCP4.5 scenarios, suggesting a reduced sensitivity at higher temperature. In addition, the precipitation increase seems to be linked with changes in the atmospheric circulations that transport moisture in different regions in China. These changes have significant implications for the management of water resources and water‐related hazards.
This figure shows the projected percentage change between 1971–2000 and 2071–2100 under the medium (RCP4.5) and high (RCP8.5) climate change scenarios for precipitation mean, frequency, and intensity in China. It shows a general increase in precipitation and decrease in frequency, leading to a greater increase in precipitation intensity. The frequency distribution is going to shift towards more intense precipitation, with an even greater increase for extreme precipitation.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
A three-dimensional numerical model of water-cooled PV/T system with cooling channel above PV panel was built to analyze the influences of mass flow rate, cooling channel height, inlet water ...temperature and solar radiation intensity on heat transfer characteristics of cooling channel and performance of system. The Nusselt numbers of bottom and top surfaces of cooling channel were calculated, and the energy and exergy efficiencies of PV/T system were obtained. Results show that the Nusselt numbers of bottom and top surfaces perform opposite trend along the flow direction, and the convection heat transfer of bottom surface is better than that of top surface for almost all of cases. There is opposite direction of heat transfer within a certain distance from the entrance when inlet temperature of cooling medium is less than ambient temperature. As for system performance, both thermal efficiency and thermal exergy efficiency have greater variation amplitude when compared with electric efficiency and electric exergy efficiency respectively. The overall exergy efficiency of system achieves maximum at the mass flow rate of 0.003 kg/s and cooling channel height of 5 mm. Besides, the performance between the present system and traditional system was compared and some different conclusions have been drawn.
•A numerical model of water-cooled PV/T system with cooling channel above PV panel.•The heat transfer characteristics of cooling channel and parametric analysis.•The energy and exergy efficiencies of system and the optimal parameters.•The performance comparison between the present system and traditional system.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
•δ18O, δ2H, and d-excess of groundwater and stream show spatial variation.•This study presents the first groundwater and stream isoscape of Ethiopia.•The isotopic composition of groundwater is biased ...towards the wet season isotopes in precipitation.•High-intensity storms are an important source of groundwater recharge.
Sustainable water resource management requires a clear understanding of the spatial variation and seasonal recharge of groundwater and their links to local precipitation. A combined spatial analysis of the stable isotope composition of groundwater, surface water, and precipitation could help to understand groundwater sources and recharge processes. In this study, we collected 297 groundwater and stream water samples across Ethiopia and analyzed them for the oxygen and hydrogen isotope ratios. The isotope data were then interpolated into isoscapes for the entire country using the Cokriging method based on their spatial autocorrelation and covariance with elevation, annual mean precipitation, and temperature. These are the first groundwater and stream isoscapes for Ethiopia. By comparing the spatial isotopic distribution of the two water resources with local precipitation, we showed distinct groundwater recharge patterns in different regions in terms of their water sources, timing, seasonality, and the degree of surface and groundwater interaction. We found that the groundwater recharge was generally biased towards the main rainy season. However, in the relatively dry southeastern Ethiopia, groundwater could receive significant input from infrequent high-intensity rainfalls associated with tropical cyclones, but additional precipitation and groundwater isotope data are needed to further test our hypothesis in this data-poor region. Overall, this study has largely expanded the spatial coverage of water stable isotope data and filled significant data gaps in Ethiopia, which could be used to provide vital information in the arid and semi-arid parts of the country where water resources are critical in climate change adaptation strategies.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Stable isotopes of oxygen (δ18O) and hydrogen (δD) in precipitation can be used as dual conservative tracers in the hydrologic cycle and help to understand hydrological and atmospheric processes. ...Although long-term monthly precipitation global isotope datasets are available in some locations, currently there are limited daily precipitation isotope data, particularly in the Midwest region of the USA. In this study we report a daily precipitation δ18O and δD dataset from March 2014–December 2017 in Dayton, Ohio, the USA. The daily δ18O and δD vary from −28.0 to 0.4‰, and −214.0 to 9.0‰ respectively. The data exhibit strong seasonality with lower δ18O and δD values in the winter and higher values in the summer. The precipitation isotopic values are mainly controlled by temperature, and show no correlation with precipitation amount and relative humidity. However, δ18O-temperature relationship varies among different seasons. The correlation is the strongest in winter (R2 = 0.56), weaker in spring (R2 = 0.28) and fall (R2 = 0.24), and almost non-existent in summer (R2 = 0.1). The slope values also vary with highest value in winter (0.68‰/OC) and much smaller in other seasons. The HYSPLIT back trajectory analyses show that Pacific, Gulf of Mexico, Arctic and Continental moistures are the main sources for southwestern Ohio with different seasonal contributions. The isotopic compositions of precipitation from different sources show small intra-season variations but large seasonal variability. Our daily-resolved dataset provides new insights into the main controls on the isotopic composition of precipitation and its seasonal variations, which could help to understand atmospheric processes and enable their proper use in interpretation of paleoclimate proxies, particularly those with seasonal bias.
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•δ18O shows seasonality with high values in the summer and low values in the winter.•Precipitation isotopic composition is mainly controlled by temperature.•The δ18O-T relationship varies seasonally with highest slope in winter.•Dayton gets moisture from Pacific, Gulf of Mexico, Arctic and Continental sources.•δ18O from different sources are similar within a season but vary seasonally.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
It is demonstrated that the generic four-dimensional Taub-Newman-Unti-Tamburino (Taub-NUT) spacetimes can be perfectly described in terms of three or four different kinds of thermodynamic hairs: the ...Komar mass (M=m), the "angular momentum" (Jn=mn), the gravitomagnetic charge (N=n), and/or the dual (magnetic) mass (M˜=n). In other words, the NUT charge is a thermodynamic multihair which means that it simultaneously has both rotation-like and electromagnetic charge-like characteristics; this is in sharp contrast with the previous knowledge that it has only one physical feature, or that it is purely a single solution parameter. To arrive at this novel result, we put forward a simple, systematic way to investigate the consistent thermodynamic first law and Bekenstein-Smarr mass formulas of all four-dimensional spacetimes that contain a nonzero NUT charge, facilitated by first deriving a meaningful Christodoulou-Ruffini-type squared-mass formula. In this way, not only can the elegant Bekenstein-Hawking one-quarter area-entropy relation be naturally restored in the Lorentzian and Euclidian sectors of generic Taub-NUT-type spacetimes without imposing any constraint condition, but also the physical meaning of the NUT parameter as a poly-facet can be completely clarified in the thermodynamic sense for the first time.
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CMK, CTK, FMFMET, IJS, NUK, PNG, UM
Recently, the so-called “consistent thermodynamics” of the Lorentzian Reissner-Nordström (RN)-NUT-AdS4 spacetimes has been pursued by a lot of efforts via different means. Among these attempts, we ...had proposed a novel idea that “The NUT charge is a thermodynamical multihair” to successfully tackle with the subject. In this paper, we will adopt this strategy to reconsider the mass formulas of the RN-NUT-AdS4 solutions but written in an alternative form, which had not been studied before in any existing literature and might be a most appropriate ansatz for the higher dimensional multiply NUTty-charged AdS spacetimes without any constraint condition. Here, we shall discuss the Christodoulou-Ruffini-like squared mass formula and the first law as well as the Bekenstein-Smarr mass formula by introducing the secondary hair Jn=Mn. For the sake of generality, we have introduced a dimensionless constant w into the constant factor Ξ in the solution expression so that when w=1, all obtained results can reproduce those delivered in our previous work.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
As an ecologically sensitive region, the humid‐to‐arid climate transition zone in the eastern and central north China (ECNC) has experienced varied vegetation change in recent decades, but the exact ...impacts of climate change and human activities remain uncertain. Based on the Normalized Difference Vegetation Index (NDVI), we established the trend of vegetation change in the past three decades (1982–2013) in the ECNC, and examined the impact of climate and nonclimate factors on vegetation growth within the different eco‐regions. For the study period, the climate in ECNC became significantly warmer and slightly drier, and the overall NDVI increased significantly, but with great spatial variations. Our results suggest that temperature increase has promoted vegetation growth in places that are colder and/or wetter, and with higher vegetation coverage. Precipitation increase has promoted vegetation growth in drier places with sparse vegetation and inhibited growth in wet places with high vegetation coverage. As different eco‐regions typically have different vegetation coverage and occupy different climate zones, their response to climate change also varies. For the study period, increasing temperature and decreasing precipitation promoted vegetation growth in the forest of northern ECNC. Increasing temperature and precipitation led to NDVI increase in the grassland in the south, whereas grassland in the north and west showed no significant change despite temperature increase and precipitation decrease. Cropland responded mostly positively to temperature increase, although correlations between NDVI and climate factors were generally weaker. Using multiple regression models, we found that 60% of the NDVI increase was attributed to climate factors whereas the remaining 40% was likely caused by human activities. Although farming practices and crop rotations might have caused significant decrease in NDVI in small areas, human impact largely led to significant NDVI increase in the grass‐crop transition zones, most likely due to ecological restoration programs.
This figure shows the predominant increasing trends of the growing season vegetation for the study region, and the increasing NDVI was due to a combination of climate (a) and human factors (b). Overall, 60% of the NDVI increase was attributed to climate factors (modelled) whereas the remaining 40% was likely caused by human activities (residual). Climate change led to varied responses in vegetation of different types because of different environmental conditions.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
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