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Literatura académica sobre el tema "Variations in flood activity"

Autor: Grafiati

Publicado: 25 de mayo de 2024

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Artículos de revistas sobre el tema "Variations in flood activity"

Liu, Yesen, Yaohuan Huang, Jinhong Wan, Zhenshan Yang y Xiaolei Zhang. "Analysis of Human Activity Impact on Flash Floods in China from 1950 to 2015". Sustainability 13, n.º 1 (28 de diciembre de 2020): 217. http://dx.doi.org/10.3390/su13010217.

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An early warning of a flash flood is essential to prevent the general public from the hazardous flooding events, however, the rapid variation of human activities has led to the uncertainty of risk in prone areas. The lack of a systematic record of flash flood events introduces challenges to flash flood-related research. Herein, we map spatial and temporal variations in flash floods in China from 1950 to 2015 and establish a general ordered logit model in a geographic information environment to estimate the association between the occurrence of flash flood events and natural conditions and the variation of human activities at the watershed level. The results showed that precipitation is an important cause of flash flooding, and demonstrate that anthropogenic intervention (heavy rainfall, density of villages, and vegetation cover) in the environment affect the likelihood of flash floods. We found that the likelihood of flash floods in China may increase with the air quality worsening and that the occurrence of flash floods is strongly correlated with vegetation cover. Our findings suggest a need for further investigation of the link between air quality and flash flooding in flood-prone areas.

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SHALTOUT, M. A. MOSALAM y M. T. Y. TADROS. "Variations of the solar activity and irradiance, and their influence on the flooding of the river Nile". MAUSAM 41, n.º 3 (24 de febrero de 2022): 53–62. http://dx.doi.org/10.54302/mausam.v41i3.2722.

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Autocorrelation and power spectra analysis are carried out for different lengths of time series Of the following data:(l) Solar activity (sunspot, faculae and radio flux on 2800 MHz);(2) Irradiance (solar Constant measured at earth's surface and by the artificial satellite (Nimbus- 7); (3) River Nile flood (old water level, maximum flood level, and the difference between the both levels) measured at Cairo. The results showing remarkable similarity between the power spectra of solar activity, irradiance (solar constant) and river Nile flood. We conclude that any short or long-term variations in the solar activity lead to similar variations in the solar constant. Also, annual and secular variations of solar activity yield information’s on the suspected annual and secular variations of the river Nile flood.

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Luz-Agostinho, KDG, AA Agostinho, LC Gomes, HF Júlio-Jr. y R. Fugi. "Effects of flooding regime on the feeding activity and body condition of piscivorous fish in the Upper Paraná River floodplain". Brazilian Journal of Biology 69, n.º 2 suppl (junio de 2009): 481–90. http://dx.doi.org/10.1590/s1519-69842009000300004.

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Flood pulses affect floodplain enrichment via the incorporation of nutrients and terrestrial biomass. As a result, they positively affect the body condition of aquatic organisms. This paper evaluates whether the absence of floods (resulting from dam control) affects the feeding activity and body condition of piscivorous fish. In addition, whether piscivores respond similarly to alterations in the flooding regime was assessed. Five piscivorous species were selected (Acestrorhynchus lacustris, Hoplias aff. malabaricus, Plagioscion squamosissimus, Rhaphiodon vulpinus, and Salminus brasiliensis). The fish were captured in four distinct years and in three river subsystems with differentiated water level fluctuations (Ivinheira = not regulated; Baía = regulated by the Paraná River level; Paraná = regulated by dams). Feeding activity and body condition were evaluated using the mean values of the standard residuals generated by regression models between body and stomach weights and standard length and body weight (all log-transformed). Differences among years and subsystems were evaluated via two-way analysis of variance. Pearson and Spearman correlations were performed between flooding attributes (duration, amplitude, timing, and daily variability) and feeding activity and body condition. Feeding activity differed across subsystems, whereas body condition varied across years, depending on the subsystem. Hoplias aff malabaricus (an ambusher adapted to starvation) presented feeding activity independent of the flooding regime and also presented better body condition in times of high water levels. Rhaphidon vulpinus exhibited variations in feeding activity but did not present alterations in body condition. The other species presented poorer body condition in years or subsystems with regular floods. Correlations identified that the duration and timing of floods had negative effects on body condition, whereas amplitude and mean annual water level improved feeding activity. Therefore, regular floods affect the feeding activity and body condition of piscivorous fish, and the response of each species depends on the existence or absence of pre-adaptation to long periods of starvation. Consequently, considering the role of the flood pulse in determining the availability of feeding resources for early life stages of piscivores, control of the flood pulse by dams is also disadvantageous for piscivorous fish.

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Vannière, B., M. Magny, S. Joannin, A. Simonneau, S. B. Wirth, Y. Hamann, E. Chapron, A. Gilli, M. Desmet y F. S. Anselmetti. "Orbital changes, variation in solar activity and increased anthropogenic activities: controls on the Holocene flood frequency in the Lake Ledro area, Northern Italy". Climate of the Past 9, n.º 3 (31 de mayo de 2013): 1193–209. http://dx.doi.org/10.5194/cp-9-1193-2013.

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Abstract. Two lacustrine sediment cores from Lake Ledro in northern Italy were studied to produce chronologies of flood events for the past 10 000 yr. For this purpose, we have developed an automatic method that objectively identifies the sedimentary imprint of river floods in the downstream lake basin. The method was based on colour data extracted from processed core photographs, and the count data were analysed to capture the flood signal. Flood frequency and reconstructed sedimentary dynamics were compared with lake-level changes and pollen inferred vegetation dynamics. The results suggest a record marked by low flood frequency during the early and middle Holocene (10 000–4500 cal BP). Only modest increases during short intervals are recorded at ca. 8000, 7500, and 7100 cal BP. After 4500–4000 cal BP, the record shows a shift toward increased flood frequency. With the exception of two short intervals around 2900–2500 and 1800–1400 cal BP, which show a slightly reduced number of floods, the trend of increasing flood frequency prevailed until the 20th century, reaching a maximum between the 16th and the 19th centuries. Brief-flood frequency increases recorded during the early and middle Holocene can be attributed to cold climatic oscillations. On a centennial time scale, major changes in flood frequency, such as those observed after ca. 4500/4000 and 500 cal BP, can be attributed to large-scale climatic changes such as the Neo-glacial and Little Ice Age, which are under orbital and possibly solar control. However, in the Bronze Age and during the Middle Ages and modern times, forest clearing and land use probably partially control the flood activity.

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Czymzik, M., R. Muscheler y A. Brauer. "Solar modulation of flood frequency in Central Europe during spring and summer on inter-annual to millennial time-scales". Climate of the Past Discussions 11, n.º 5 (13 de octubre de 2015): 4833–50. http://dx.doi.org/10.5194/cpd-11-4833-2015.

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Abstract. Solar influences on climate variability are one of the most controversially discussed topics in climate research. We analyze solar forcing of flood frequency in Central Europe on inter-annual to millennial time-scales using daily discharge data of River Ammer (southern Germany) back to AD 1926 and revisiting the 5500 year flood layer time-series from varved sediments of the downstream Lake Ammersee. Flood frequency in the discharge record is significantly correlated to changes in solar activity during solar cycles 16–23 (r = −0.47, p < 0.0001, n = 73). Flood layer frequency (n = 1501) in the sediment record depicts distinct multi-decadal variability and significant correlations to 10Be fluxes from a Greenland ice core (r = 0.45, p < 0.0001) and 14C production rates (r =0.36, p < 0.0001), proxy records of solar activity. Flood frequency is higher when solar activity is reduced. These correlations between flood frequency and solar activity might provide empirical support for the solar top-down mechanism expected to modify the mid-latitude storm tracks over Europe by model studies. A lag of flood frequency responses in the Ammer discharge record to changes in solar activity of about one to three years could be explained by a modelled ocean–atmosphere feedback delaying the atmospheric reaction to solar activity variations up to a few years.

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Vannière, B., M. Magny, S. Joannin, A. Simonneau, S. B. Wirth, Y. Hamann, E. Chapron, A. Gilli, M. Desmet y F. S. Anselmetti. "Orbital changes, variation in solar activity and increased anthropogenic activities: controls on the Holocene flood frequency in the Lake Ledro area, Northern Italy". Climate of the Past Discussions 8, n.º 5 (24 de septiembre de 2012): 4701–44. http://dx.doi.org/10.5194/cpd-8-4701-2012.

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Abstract. Two lacustrine sediment cores from Lake Ledro in Northern Italy were studied to produce chronologies of flood events for the past 10 000 yr. For this purpose, we have developed an automatic method that objectively identifies the sedimentary imprint of river floods in the downstream lake basin. The automatic counting of flood deposits was based on colour data extracted from processed core photographs, and the count data were processed to capture the flood signal. Automatic quantification was compared with naked-eye counting. Counts were performed twice on the proximal and distal cores to provide an objective and reproducible record of flood frequency. Geophysical and geochemical analyses made it possible to distinguish event deposits from background sedimentation. Flood frequency and reconstructed sedimentary dynamics were compared with lake-level changes and pollen dynamics inferred from vegetation data. The data suggest a record marked by low flood frequency during the early and middle Holocene (10 000–4500 cal BP). Only modest increases during short intervals are recorded at ca. 8000, 7500, and 7100 cal BP. The last third of the Holocene is characterised by a shift toward increased flood frequency at ca. 4500–4000 cal BP. With the exception of two short intervals around 2900–2500 and 1800–1400 cal BP, which show a slightly reduced number of floods, the trend of increasing flood frequency prevailed until the 20th century, reaching a maximum between the 16th and the 19th centuries. Brief-flood frequency increases recorded during the early and middle Holocene can be attributed to cold climatic oscillations. On a centennial time scale, major changes in flood frequency, such as those observed at ca. 4500 and 500 cal BP, can be attributed to large-scale climatic changes such as the Neo-glacial and Little Ice Age, which are under orbital and possibly solar control. The role of climate as the main forcing factor in flood activity is supported by the lake-level records: the major lake-level rises are synchronous with flood frequency increases. However, in the Bronze Age and during the Middle Ages and modern times, forest clearing and land use are indicated by pollen and archaeological data. These human activities have clearly affected the sediment record of flood activity, and they can partially explain the amplitude of the increases in flood activity.

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Zúñiga, Emmanuel, Víctor Magaña y Violeta Piña. "Effect of Urban Development in Risk of Floods in Veracruz, Mexico". Geosciences 10, n.º 10 (9 de octubre de 2020): 402. http://dx.doi.org/10.3390/geosciences10100402.

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Urban floods have adverse effects on the population and the economy, and they are increasing in frequency and magnitude. The State of Veracruz is the region of Mexico with the highest number of disasters, more than 50% of the total number nationwide, in the 1970–2015 period. During the 1990s, disasters in this region increased from 5 to 10 events per year, mostly in relation to intense rains and floods. This study analyzes the factors that increase the risk of urban floods in the regions: (i) the Pánuco River, (ii) the Papaloapan River, and (iii) the Coatzacoalcos River regions, combining hazard data and estimates of vulnerability factors. The 95th percentile of daily precipitation (P95) is used as a threshold of heavy rain, i.e., the natural hazard. Vulnerability is estimated in terms of the percentage of natural vegetation loss due to changes in land cover and land use in the hydrological basins and the expansion of the urban areas in the regions under study. The risk of flood was compared with records of flood events focusing on the low-frequency variations of risks and disaster activity. The trends in urban flood activity are related to the loss of natural vegetation and deterioration of the basins leading to a loss of infiltration, i.e., larger runoffs. Even when the intensity of precipitation in recent decades remains without clear trends, or shows negative tendencies in the number of intense events, the number of floods is higher mostly because of the deterioration of hydrologic basins. Therefore, the risk of flooding in the state of Veracruz is mainly related to environmental factors that result in vulnerability rather than changes in the trends of extreme precipitation activity. This result means that disaster risk reduction actions should be mainly related to rehabilitation of the basins.

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Barrera-Escoda, A. y M. C. Llasat. "The role of climatic factors in evolving flood patterns in a Mediterranean Region (1301–2012)". Hydrology and Earth System Sciences Discussions 11, n.º 8 (1 de agosto de 2014): 9145–82. http://dx.doi.org/10.5194/hessd-11-9145-2014.

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Abstract. Data on flood occurrence and flood impacts for the last seven centuries in the northeast Iberian Peninsula have been analysed in order to characterise long-term trends, anomalous periods and their relationship with different climatic factors such as precipitation, general circulation and solar activity. Catastrophic floods do not present a statistically significant trend, whereas extraordinary floods have seen a significant rise, especially from 1850 on, and were responsible for the total increase in flooding in the region. This rise can be mainly attributed to small coastal catchments, which have experienced a marked increase in developed land and population, resulting in changes in land use and greater vulnerability. Changes in precipitation alone cannot explain the variation in flood patterns, although a certain increase was shown in late summer–early autumn, when extraordinary floods are most frequently recorded. The relationship between North Atlantic circulation and floods is not as strong, due to the important role of mesoscale factors in heavy precipitation in the northwest of the Mediterranean region. However it can explain the variance to some extent, mainly in relation to the catastrophic floods experienced during the autumn. Solar activity has some impact on changes in catastrophic floods with cycles related to the Quasi-Biennial Oscillation and the Gleissberg solar cycle. In addition, anomalous periods of high flood frequency in autumn generally occurred during periods of increased solar activity. The physical influence of the latter in general circulation patterns, the high troposphere and the stratosphere, has been analysed in order to ascertain its role in causing floods.

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Czymzik, Markus, Raimund Muscheler y Achim Brauer. "Solar modulation of flood frequency in central Europe during spring and summer on interannual to multi-centennial timescales". Climate of the Past 12, n.º 3 (1 de abril de 2016): 799–805. http://dx.doi.org/10.5194/cp-12-799-2016.

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Abstract. Solar influences on climate variability are one of the most controversially discussed topics in climate research. We analyze solar forcing of flood frequency in central Europe during spring and summer on interannual to multi-centennial timescales, integrating daily discharge data of the River Ammer (southern Germany) back to AD 1926 (∼ solar cycles 16–23) and the 5500-year flood layer record from varved sediments of the downstream Ammersee. Flood frequency in the River Ammer discharge record is significantly correlated to changes in solar activity when the flood record lags the solar signal by 2–3 years (2-year lag: r = −0.375, p = 0.01; 3-year lag: r = −0.371, p = 0.03). Flood layer frequency in the Ammersee sediment record depicts distinct multi-decadal variations and significant correlations to a total solar irradiance reconstruction (r = −0.4, p < 0.0001) and 14C production rates (r = 0.37, p < 0.0001), reflecting changes in solar activity. On all timescales, flood frequency is higher when solar activity is reduced. In addition, the configuration of atmospheric circulation associated with periods of increased River Ammer flood frequency broadly resembles that during intervals of reduced solar activity, as expected to be induced by the so-called solar top-down mechanism by model studies. Both atmospheric patterns are characterized by an increase in meridional airflow associated with enhanced atmospheric blocking over central Europe. Therefore, the significant correlations as well as similar atmospheric circulation patterns might provide empirical support for a solar influence on hydroclimate extremes in central Europe during spring and summer by the so-called solar top-down mechanism.

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Suzuki, Yoshiaki, Ryuji Tada, Kana Nagashima, Takeshi Nakagawa, Katsuya Gotanda, Tsuyoshi Haraguchi y Gordon Schlolaut. "Extreme flood events and their frequency variations during the middle to late-Holocene recorded in the sediment of Lake Suigetsu, central Japan". Holocene 31, n.º 1 (8 de octubre de 2020): 121–33. http://dx.doi.org/10.1177/0959683620961497.

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Many studies are reconstructing flood records in the continental margins during the middle to late-Holocene. However, distinguishing the frequency and magnitude of flood events was difficult. Light gray event layers (GELs) in the sediment of Lake Suigetsu in Central Japan can solve this problem because they are recording the occurrence and magnitude of flood events during the last 80 years. Using these GELs, we aimed to reconstruct the frequency and magnitude of flood events during the last 8000 years. First, we verified whether GELs maintained the recording of flood events. We found that thin GELs (less than 40 mg/cm2 in mass) were rare, probably because of bioturbation, whereas thick GELs (larger than 40 mg/cm2 in mass) were rarely erased. We also found that GELs formed by the same amount of rainfall could have been thinner before 100 years ago. We revealed that the occurrence of extreme flood-origin event layers (EFELs: GELs thicker than 40 mg/cm2) during the last 8000 years may indicate the occurrence of extreme flood events (EFEs). Mass accumulation of EFELs may indicate the minimum estimation of rainfall on EFEs. There are several periods with higher frequency and magnitude of EFEs than those of the present level, agreeing with the periods of high flood activity in western Japan and East China. The frequency and magnitude of EFEs show different temporal variations. Northward and southward shifts in the westerly jet and monsoon fronts can partially explain such patterns.

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Tesis sobre el tema "Variations in flood activity"

Legrand, Caroline. "Simulation des variations de débits et de l’activité de crue du Rhône amont à partir de l’information atmosphérique de grande échelle sur le dernier siècle et le dernier millénaire". Electronic Thesis or Diss., Université Grenoble Alpes, 2024. http://www.theses.fr/2024GRALU011.

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Les crues sont des aléas naturels extrêmement destructeurs qui peuvent avoir des répercussionsconsidérables sur les écosystèmes et les sociétés. L’activité et l’intensité des crues pourraient êtreamplifiées par le changement climatique en cours. Quantifier les évolutions possibles pour les décenniesà venir est cependant difficile. L’approche classique consiste à estimer ces évolutions à partir deprojections hydrologiques obtenues par simulation à partir des scénarios météorologiques produitspour différents scénarios climatiques futurs. Ces scénarios météorologiques, qui doivent, entre autreschoses, être adaptés aux échelles spatiales et temporelles des bassins considérés, sont typiquementproduits avec des modèles de descente d’échelle à partir des conditions atmosphériques de grandeéchelle simulées par des modèles climatiques. Ces modèles de descente d’échelle sont soit dynamiquessoit statistiques. La possibilité de produire, avec ce type de modèles, des scénarios météorologiquespertinents est supposée acquise mais est rarement évaluée.Dans cette étude, nous avons évalué la capacité de deux chaînes de modélisation à reproduire,au cours du dernier siècle (1902-2009) et à partir de l’information atmosphérique de grande échelleuniquement, les variations temporelles observées des débits et des événements de crue du bassinversant du Rhône amont (10 900 km2). Les chaînes de modélisation sont constituées (i) de la réanalyseatmosphérique ERA-20C, (ii) soit du modèle de descente d’échelle statistique SCAMP, soit du modèlede descente d’échelle dynamique MAR et (iii) du modèle glacio-hydrologique GSM-SOCONT.Les évaluations sur les températures et les précipitations de bassin journalières soulignent la néces-sité d’une correction de biais pour les deux modèles de descente d’échelle. Pour éviter des simulationsnon pertinentes de la dynamique du manteau neigeux, en particulier pour les hautes altitudes, la cor-rection des biais est nécessaire non seulement pour les scénarios de précipitations et de températuresmais aussi pour les scénarios de gradients altimétriques de température pour la chaîne de descented’échelle dynamique.Les évaluations sur l’hydrologie des bassins montrent que les variations multi-échelles (journa-lières, saisonnières et interannuelles) observées des débits et les situations hydrologiques de bassefréquence (séquences d’étiage et événements de crue) sont globalement bien reproduites pour la pé-riode 1961-2009. Pour la première moitié du siècle, l’accord avec les débits de référence est plus faible,probablement en raison de la moindre qualité des données (données ERA-20C et de débits) et/ou decertaines hypothèses et choix de modélisation (e.g. calibration basée sur des signatures hydrologiques,hypothèse de stationnarité). Ces résultats ainsi que ceux sur les variations de l’activité de crue ob-tenus sur le siècle dernier permettent d’envisager l’utilisation des chaînes de modélisation pour descontextes climatiques différents.Dans une dernière partie, nous avons simulé les variations de l’activité de crue sur l’ensemble dudernier millénaire en utilisant les sorties d’un modèle climatique rendues disponibles par le projetPMIP (Paleoclimate Modelling Intercomparison Project). Les sorties du modèle climatique CESMLast Millennium Ensemble, composé de 12 membres, ont été statistiquement descendues en échelleau pas de temps journalier sur la période 850-2004 avec le modèle SCAMP (pour des raisons de coûtsde calcul) et utilisées comme forçages dans le modèle GSM-SOCONT.Les variations de l’activité de crue du Rhône amont simulées sur le dernier millénaire ont étécomparées à celles reconstituées à partir d’archives sédimentaires du lac du Bourget. Les résultatsobtenus suggèrent que les variations de l’activité de crue reconstituées sur cette période pourraientêtre liées à la variabilité interne du climat et non pas à un quelconque forçage atmosphérique degrande échelle
Floods are often destructive natural hazards that can have considerable implications on ecosystemsand societies. In many regions of the world, flood activity and intensity are expected to be amplifiedby the ongoing climate change. However, quantifying possible changes over the coming decades isdifficult. The classical approach is to estimate possible changes from hydrological projections obtainedby simulation using meteorological scenarios produced for different future climate scenarios. Amongother things, these meteorological scenarios have to be adapted to the spatial and temporal scalesof the considered basins. They are typically produced with downscaling models from the large-scaleatmospheric conditions simulated by climate models. Downscaling models are either dynamical orstatistical. The possibility of producing relevant meteorological scenarios with downscaling models istaken for granted, but is rarely assessed.In this study, we assessed the ability of two modelling chains to reproduce, over the last century(1902-2009) and from large-scale atmospheric information only, the observed temporal variations inflows and flood events in the Upper Rhône River catchment (10,900 km2). The modelling chains aremade up of (i) the ERA-20C atmospheric reanalysis, (ii) either the statistical downscaling modelSCAMP or the dynamical downscaling model MAR, and (iii) the glacio-hydrological model GSM-SOCONT.When compared to observations, the downscaled scenarios of daily temperatures and precipitationshighlight the need for a bias correction. This is the case for both downscaling models. For thedynamical downscaling chain, bias correction is additionally necessary for the temperature lapse ratescenarios to avoid irrelevant simulations of snowpack dynamics, particularly for high elevations.The observed multi-scale variations (daily, seasonal and interannual) in flows and low frequencyhydrological situations (low flow sequences and flood events) are generally well reproduced for theperiod 1961-2009. For the first half of the century, the agreement with the reference flows is wea-ker, probably due to lower data quality (ERA-20C and flow data) and/or certain assumptions andmodelling choices (e.g. calibration based on hydrological signatures, stationarity assumption). Theseresults, and those obtained over the last century on variations in flood activity, suggest that themodelling chains can be used in other climatic contexts.In the last part, we simulated variations in flood activity over the last millennium using cli-mate model outputs made available by the Paleoclimate Modelling Intercomparison Project (PMIP).Outputs from the climate model CESM Last Millennium Ensemble, made up of 12 members, werestatistically downscaled at the daily time step over the period 850-2004 with SCAMP (for reasons ofcomputational cost) and used as input to the GSM-SOCONT model.The simulated variations in flood activity in the Upper Rhône River over the last millennium werecompared with those reconstructed from the sediments cores of Lake Bourget. The results suggestthat the variations in flood activity reconstructed over this period could only be due to internalclimate variability and not to any large-scale atmospheric forcing

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Vye, Charlotte. "Flow Field Formation and Compositional Variations of Flood Basalt Eruptions". Thesis, Open University, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.518169.

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Characterisation of three lava flow fields from the Columbia River Basalt Group (CRBG), USA, reveals compositional heterogeneity on all scales, from adjacent lava lobes to the intra-crystal scale. Simple flow fields can be traced from vent areas to distal reaches, but those with multiple-layered lobes present a degree of complexity that make lava pathways and eruption sequences difficult to identify. A 3-D model based on field investigation of a single flow field establishes a volcanological context for geochemical sampling. Compositional v.ariation within each flow field suggests that small-scale geochemical heterogeneity is common within and between lobes of these flood basalt lavas. Lobe cores emplaced during the latter stages of an eruption have less evolved compositions and more enriched incompatible elements, suggesting progressive variation of magma composition caused by either recharge or sequential tapping of compositionally zoned magma. Progressive crustal contamination of magma during a single eruption is indicated by Re-Os isotope ratios. Initial 1870s/1880s ratios range from 1.405 in the earlier emplaced lava crust to 0.128 in the latter emplaced lava core. These values are more radiogenic than any known enriched sources (normative mantle -0.127, HIMU -0.15) consistent with previous data that indicate that neither an enriched source nor sub-continental lithospheric mantle can be the source of CRBG magma. Os isotope signatures can be explained by different degrees' of contamination of two isotopically distinct lithologies represented by the North American craton and Jurassic accreted terranes underlying the province. Intra-crystal Sr isotope analyses within a flow field record variable histories in an open magmatic system. Results suggest crystal residences in an increasingly contaminated melt within the crust with several recharge events of less-contaminated more primitive basaltic melt. Assembly of melt and crystal cargo occurred immediately prior to eruption without significant residence times in the final host magma. The combined compositional evidence suggests that an extensive shallow-crustal network of dykes and sills supplied magma to the CRBG eruptions.

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Eriksson, Tobias. "Variations in bioavailability of dissolved organic matter during a spring flood episode in northern Sweden /". Umeå : Swedish Univ. of Agricultural Sciences, 2004. http://epsilon.slu.se/9658927.pdf.

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Evans, S. T. "Variations in activity and psychological well-being in unemployed young adults". Thesis, University of Manchester, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.377464.

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Bourne, Geoffrey S. "Actinide and fission product activity variations in inter-tidal marine macrophytes". Thesis, Cardiff Metropolitan University, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.306854.

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Lachowycz, Stefan M. "Records of, and controls on, temporal variations in activity at arc volcanoes". Thesis, University of Oxford, 2016. https://ora.ox.ac.uk/objects/uuid:152a237e-76d1-409e-ba6d-fbb50da87b85.

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Many attributes of volcanic activity, whether physical, geochemical/petrological, or geophysical, change over timescales from minutes to millions of years. Understanding the nature of these variations and their controls is essential both for hazard assessment and to understand volcanic and magmatic processes. Arc volcanism entails a relatively broad range of eruption styles and magma compositions, and thus wide-ranging hazards and a variety of eruption records. Despite their significance, records of activity for many arc volcanoes are inadequately characterised, so any temporal variability is poorly constrained. In this thesis, I investigate temporal variations in different styles of activity (dome-forming, Plinian-style, and effusive/glaciovolcanic) on a range of timescales (days-years, millennia, and hundreds of ky, respectively), from diverse records (seismicity, tephra deposits, and effusive eruption products), at four arc volcanoes. I analyse seismic time-series from Soufrière Hills Volcano (Montserrat) and Volcán de Colima (Mexico) using two statistical techniques, identifying temporal variation in the extent of long-range correlations and randomness in these data, which has potential to inform real-time monitoring and constrain eruptive processes. I also present new composition data for and review previous studies of tephra deposits from Volcán Hudson (Chile), revising its explosive eruption history and finding previously unrecognised shifts in the magma composition erupted through the Holocene. I also describe and analyse sequences of lithofacies from effusive eruptions of a range of magma compositions from Volcán Sollipulli (Chile), inferring varying extents of interaction with ice during their emplacement, and so changes in eruption style through time. These case studies highlight the importance of detailed characterisation of temporally varying records of volcanic activity, and some of the limitations of and uncertainties in these records and their interpretation.

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Byrdina, Svetlana. "Anomalous Self-Potential variations related to activity of Merapi volcano (Central Java)". Paris, Institut de physique du globe, 2004. http://www.theses.fr/2004GLOB0006.

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La thèse est consacrée à l'analyse des données d'une surveillance continue du Potentiel Spontané (PS), obtenues sur le volcan Merapi, dans le but d'identifier les signaux de PS liées à l'activité volcanique. La comparaison dePS avec la météorologie montre que les propriétés les plus manifestes dans les données de PS sont produites par des variations d'infiltration d'eau de pluie et de pression atmosphérique. Les techniques spéciales de traitement des données ont été developpé pour reduire les effets météorologiquies. Pour identifier les signaux associés à l'activité volcanique, les séries temporelles de PS ont été comparées aux données de sismicité large bande. Un rapport statistiquement stable a été trouvé entre les signaux anormaux de PS et la sismicité de periode ultra-longue (ULP). L'occurrence des anomalies de PS liées à la sismicité ULP pourrait être provoquée par l'effet électro-cinétique du flux de fluide dans la proximité du dôme de lave
The thesis is devoted to the analysis of the continuous Self-Potential (SP) monitoring date registered on Merapi volcano, with the purpose to identify related to volcanic activity SP signals. The comparison between SP and meteorolopical parameters shows that the most prominent features in the SP data are produced by rain water infiltration and air pressure. Special techniques of data processing were developed to reduce the meteorological influence on the SP. To identify the signals associated with volcanic activity, the SP time series were compared to broadband seismicity. A statistically stable relationship was found between anomalous SP signals and ultra-long-period (ULP) seismicity with dominant periods <100s. In contrast, the anomalies were not present in ground temperature data nor in SP data recorded 1km from the summit. The occurrence of SP anomalies associated with ULP-seismicity might be caused by the electro-kinetic effect of fluid flow in subsurface near the lava dome

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Sahlén, Adam. "Muscle activity in m.pectoralis major during bench press variations in healthy young males". Thesis, Högskolan i Halmstad, Akademin för ekonomi, teknik och naturvetenskap, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-29361.

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Background. The bench press is a commonly used resistance training exercise for targeting the chest musculature. During hypertrophy training, different variations of bench press are often used to isolate different segments (pars clavicularis, pars sternocostalis and pars abdominals) of the chest muscle m.pectoralis major. Commonly used variations of the bench press are decline bench press (less than 0° from horizontal) and incline bench press (more than 0° from horizontal). Some research has been done into these variations of bench angle and their effect on muscle activation; however other commonly used bench angles is yet to be investigated. Aim. The aim of this study was to examine if there were any difference in muscle activity in the three segments of m.pectoralis majors while performing three different barbell bench press variations with different bench angles to obtain a greater understanding of m.pectoralis major activation and possibly optimize hypertrophy training in above mentioned muscles segments. Method. 13 healthy male (age: 23± 3.8 year and BMI: 24.3 ±1.8 kg/m2) participated in this single group study. EMG was used to measure muscle activity in m.pectoralis major's three segments. Test subjects performed 1 set of 6 repetitions on each bench press variation at a relative load of 6RM. An maximal voluntary isometric contraction (MVIC) test was performed and set as 100 percent reference value for comparison muscle activity in various angles. Results. While performing the decline bench press and the incline bench press, the muscle activity in pars clavicularis displayed a strong trend of a lower muscle activity (decline: p= 0.055 and incline: p=0.052) in comparison to the flat bench press. Muscle activity in pars sternocostalis while performing the incline bench press was significantly lower in comparison to the flat bench press (flat: p<0.001 and decline: p<0.001). Muscle activity in pars abdominals while performing the decline bench press was significantly higher (p=0.013) in comparison to the flat bench press. Muscle activity in pars abdominals while performing the incline bench press were significantly lower than both the flat and decline bench press (incline: p<0.001 and decline: p<0.001). Conclusion. For a better isolation of the pars abdominals segment, the decline bench press should be used. Muscle activity in pars sternocostalis did not show any significant difference between flat and decline bench press and could be isolated with either of these two exercises. The muscle activity in pars clavicularis showed a strong trend of higher activity while performing the flat bench press compared to the decline and incline bench press, however findings regarding the pars clavicularis differs between studies.

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Gäddnäs, Helena. "Long-term oral nicotine treatment and daily variations in brain monoamines and motor activity". Helsinki : University of Helsinki, 2002. http://ethesis.helsinki.fi/julkaisut/mat/farma/vk/gaddnas/.

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Harrington, Debra J. "Effect of river stage variations and flood events on trace metal mobilization and transport in the Apalachicola River Basin, NW Florida". Tallahassee, Fla. : Florida State University, 2001. http://purl.fcla.edu/fsu/lib/digcoll/etd/1191553.

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Libros sobre el tema "Variations in flood activity"

After the flood: The early post-flood history of Europe. Chichester: New Wine Press, 1995.

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Wilson, Robert M. On determining the rise, size, and duration classes of a sunspot cycle. Washington, D.C: National Aeronautics and Space Administration, 1996.

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H, Hathaway David, Reichmann Edwin J y George C. Marshall Space Flight Center., eds. On determining the rise, size, and duration classes of a sunspot cycle. Marshall Space Flight Center, Ala: National Aeronautics and Space Administration, 1996.

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Congdon, Peter. Towards fair shares: The nationalPCG funding scheme and variations in health activity. Barking: Public Health Directorate, Barking & Havering Health Authority, 1999.

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Van Allen, James Alfred, 1914-, ed. Cosmic rays, the sun, and geomagnetism: The works of Scott E. Forbush. Washington, D.C: American Geophysical Union, 1993.

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P, Kharin E., Semenov V. I͡U︡ y Rossiĭskai͡a︡ akademii͡a︡ nauk. Nat͡s︡ionalʹnyĭ geofizicheskiĭ komitet, eds. Hourly indices of geomagnetic activity for the middle latitudes: Catalogue 1964-1991. Moscow: Geophysical Committee, Russian Academy of Sciences, 1992.

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1941-, Stephenson F. Richard y Wolfendale A. W, eds. Secular solar and geomagnetic variations in the last 10,000 years. Dordrecht: Kluwer Academic Publishers, 1988.

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Damming the flood: Haiti and the politics of containment. London: Verso, 2010.

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George C. Marshall Space Flight Center, ed. North Atlantic basin tropical cyclone activity in relation to temperature and decadal-length oscillation patterns. Huntsville], Ala: National Aeronautics and Space Administration, Marshall Space Flight Center, 2009.

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Capítulos de libros sobre el tema "Variations in flood activity"

Fox, Peter. "Solar activity and irradiance variations". En Solar Variability and Its Effects on Climate, 141–70. Washington, D. C.: American Geophysical Union, 2004. http://dx.doi.org/10.1029/141gm12.

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Kazachevskaya, T. V., A. I. Lomovsky y A. A. Nusinov. "Solar EUV Flux Variations Near Activity Maxima". En The Sun as a Variable Star: Solar and Stellar Irradiance Variations, 77–80. Dordrecht: Springer Netherlands, 1994. http://dx.doi.org/10.1007/978-94-011-0950-5_12.

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Yoden, Shigeo y Kohei Yoshida. "Impacts of Solar Activity Variations on Climate". En Solar-Terrestrial Environmental Prediction, 445–59. Singapore: Springer Nature Singapore, 2023. http://dx.doi.org/10.1007/978-981-19-7765-7_15.

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Clément, Maéva. "Organising Political Violence: Radicalisation and Militancy as Narrative Activity". En Radicalization and Variations of Violence, 15–32. Cham: Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-031-27011-6_2.

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Emanuel, Kerry A. "Climate Variations and Hurricane Activity: Some Theoretical Issues". En Hurricanes, 55–65. Berlin, Heidelberg: Springer Berlin Heidelberg, 1997. http://dx.doi.org/10.1007/978-3-642-60672-4_3.

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Friis-Christensen, Eigil. "Solar Activity Variations and Possible Effects on Climate". En Space Storms and Space Weather Hazards, 231–50. Dordrecht: Springer Netherlands, 2001. http://dx.doi.org/10.1007/978-94-010-0983-6_9.

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Basu, Sarbani y H. M. Antia. "Possible Solar Cycle Variations in the Convection Zone". En Helioseismic Diagnostics of Solar Convection and Activity, 449–58. Dordrecht: Springer Netherlands, 2000. http://dx.doi.org/10.1007/978-94-011-4377-6_30.

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Abel, H. H., D. Klüßendorf, E. Koralewski, R. Krause y R. Droh. "Spectral Analysis of Heart Rate During Different States of Activity". En Temporal Variations of the Cardiovascular System, 99–116. Berlin, Heidelberg: Springer Berlin Heidelberg, 1992. http://dx.doi.org/10.1007/978-3-662-02748-6_5.

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Pronik, I. "Emission Lines Variations in the Spectra of Seyfert Galaxies Nuclei.Observational Data". En Observational Evidence of Activity in Galaxies, 169–84. Dordrecht: Springer Netherlands, 1987. http://dx.doi.org/10.1007/978-94-009-3851-9_25.

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Ruzmaikin, Alexander, Joan Feynman y Paul Robinson. "Long-Term Persistence of Solar Activity". En The Sun as a Variable Star: Solar and Stellar Irradiance Variations, 313. Dordrecht: Springer Netherlands, 1994. http://dx.doi.org/10.1007/978-94-011-0950-5_47.

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Actas de conferencias sobre el tema "Variations in flood activity"

Suri, Rajiv y Kevin Otto. "Evaluating Variation Reduction Process Control Strategies Through System Modeling". En ASME 1999 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1999. http://dx.doi.org/10.1115/imece1999-0761.

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Abstract This paper presents a method for using a system model to reduce end-of-line variation in a sheet stretch-forming manufacturing system. An integrated set of mathematical models representing the operations in a system can be effectively used to select among four variation reduction strategies: robust process design, input variation reduction, feed-forward control, and feedback control. To compare these alternatives, models that predict both quality characteristic nominal values and standard deviations of the work-in-process are required. Numerical simulation using these models allows for evaluation and comparison of each strategy prior to any activity on the shop floor. This approach is demonstrated on a sheet stretch-forming manufacturing system from the aerospace industry. A feed-forward strategy is selected as having the greatest potential for this system. A subsequent experimental validation on the shop floor showed a 30% reduction in strain variation on a batch of production parts.

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Werth, David y Matthew Havice. "A Review of Common Problems Observed in Cooling Water Intakes and the Use of Physical Models to Develop Effective Solutions". En ASME/JSME/KSME 2015 Joint Fluids Engineering Conference. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/ajkfluids2015-33776.

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Pump intake structures are a necessary component of the cooling water systems for power plants, process and manufacturing facilities, flood control and water/wastewater applications. Large cooling water systems often use substantial sea / river water intakes or cooling towers to provide the required cooling of the process or circulating water. These structures can be very large and often house multiple pump with capacities ranging in size from a few hundred m3/hr to 60,000 m3/hr or more. With such large flow rates care must be taken to ensure uniform flow to the pump to limit vortex activity, vibration, flow induced cavitation and performance problems. In many cases, a physical hydraulic model study is conducted to evaluate the overall approach flow and the performance of the intake. This paper presents a synopsis of several recent physical model studies and a review of recurring problems associated with common design features. This paper takes a closer look at stop log support walls, an intake design feature common to seawater intakes. This wall is often used to minimize the height of the stop logs. In applications with large variations of water level, such as a seawater intake, there are times when the support walls are submerged significantly, resulting in significant flow disturbances. A feature common to cooling towers is the use of 90-degree suction elbows to supply horizontal pumps. A review of short radius vs. long radius elbow performance is presented. Cooling towers often have another common feature which is a significant difference in depth between the cooling tower basin and the pump sump. This results in typical shallow basins and deeper sumps. A common problem is the utilization of minimum pump submergence to set the water levels without reference to the basin invert elevation. A discussion of choked flow conditions in cooling towers is presented. A final discussion is presented regarding cross-flow and the use of concentrated supply channels in cooling tower applications to facilitate the isolation of individual tower cells. This paper presents a synopsis of several recent physical model studies and a review of recurring problems associated with common intake design features. The results of several model studies are presented to demonstrate the negative impacts that these common intake features have on approach flow conditions. The intent of the paper is to provide the design engineer some additional guidance not offered in industry guidelines or standards with the hope of avoiding common problems which can be costly and difficult to remediate after the intake has been constructed.

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Homam, M. J. "Variations of ionospheric scintillations due to solar activity". En 2014 International Symposium on Antennas & Propagation (ISAP). IEEE, 2014. http://dx.doi.org/10.1109/isanp.2014.7026716.

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Mullayarov, V. A., V. I. Kozlov y R. R. Karimov. "Relation of thunderstorm activity to cosmic ray variations". En Eighth Joint International Symposium on Atmospheric and Ocean Optics: Atmospheric Physics, editado por Gelii A. Zherebtsov, Gennadii G. Matvienko, Viktor A. Banakh y Vladimir V. Koshelev. SPIE, 2002. http://dx.doi.org/10.1117/12.458516.

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Turuntaev, S. B., O. Y. Melchaeva, E. V. Zenchenko y E. I. Eremeeva. "Permeability Change Estimation from Microseismic Event Activity Variations". En ECMOR XIII - 13th European Conference on the Mathematics of Oil Recovery. Netherlands: EAGE Publications BV, 2012. http://dx.doi.org/10.3997/2214-4609.20143259.

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K. Petersen, U., R. J. Brown y M. S. Andersen. "Variations in Seismic Properties of Flood Basalts from Shallow Refraction Seismic Analysis". En 74th EAGE Conference and Exhibition incorporating EUROPEC 2012. Netherlands: EAGE Publications BV, 2012. http://dx.doi.org/10.3997/2214-4609.20148152.

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Ivanov-Kholodny, G. S. y V. E. Chertoprud. "Quasi-biennial variations in solar activity and geophysical processes". En Optical Monitoring of the Environment: CIS Selected Papers, editado por Nicholay N. Belov y Edmund I. Akopov. SPIE, 1993. http://dx.doi.org/10.1117/12.162192.

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Kozlova, I. A. "VARIATIONS OF RADON VOLUMETRIC ACTIVITY DURING SUCCESSIVE SEISMIC EVENTS". En 19th SGEM International Multidisciplinary Scientific GeoConference EXPO Proceedings. STEF92 Technology, 2019. http://dx.doi.org/10.5593/sgem2019/1.1/s05.125.

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Ptitsyna, N. G. y I. M. Demina. "MIDTERM OSCILLATIONS IN SOLAR ACTIVITY AND GEOMAGNETIC FIELD VARIATIONS". En All-Russia Conference on Solar and Solar-Terrestrial Physics. The Central Astronomical Observatory of the Russian Academy of Sciences at Pulkovo, 2023. http://dx.doi.org/10.31725/0552-5829-2023-273-276.

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Haralambous, H. y T. Leontiou. "Detection of TID activity from ionogram virtual height variations". En 2019 URSI Asia-Pacific Radio Science Conference (AP-RASC). IEEE, 2019. http://dx.doi.org/10.23919/ursiap-rasc.2019.8738172.

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Informes sobre el tema "Variations in flood activity"

Paul, A. K. Diurnal, Seasonal and Solar Activity Variations of F-Region Parameters. Fort Belvoir, VA: Defense Technical Information Center, marzo de 1994. http://dx.doi.org/10.21236/ada278106.

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Forbes, Jeffrey M. Thermosphere Structure Variations during High Solar and Magnetic Activity Conditions. Fort Belvoir, VA: Defense Technical Information Center, septiembre de 1985. http://dx.doi.org/10.21236/ada171350.

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Hammerstrom, Joseph A. y Pierre-Richard J. Cornely. Total Electron Content (TEC) Variations and Correlation with Seismic Activity over Japan. Journal of Young Investigators, octubre de 2016. http://dx.doi.org/10.22186/jyi.31.4.13-16.

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Akasofu, S. I. y L. C. Lee. A Study of the Relationship between Solar Activity and Interplanetary Field Variations. Fort Belvoir, VA: Defense Technical Information Center, febrero de 1986. http://dx.doi.org/10.21236/ada169983.

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Bojilova, Rumiana y Plamen Mukhtarov. Relationship Between Short-term Variations of Solar Activity and Critical Frequencies of the Ionosphere Represented by FoF2 and MUF3000. "Prof. Marin Drinov" Publishing House of Bulgarian Academy of Sciences, octubre de 2020. http://dx.doi.org/10.7546/crabs.2020.10.11.

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Lindberg, Laura D., Zoe H. Pleasure y Ayana Douglas-Hall. Assessing State-Level Variations in High School Students’ Sexual and Contraceptive Behavior: The 2019 Youth Risk Behavior Surveys. Guttmacher Institute, diciembre de 2020. http://dx.doi.org/10.1363/2020.32245.

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Key Points Sexual activity is a normal part of adolescent development, regardless of where young people live. ➔ There is greater variation between states in prescription method use than in condom use, suggesting that barriers to contraceptive care influence students’ method choice. ➔ High school students in Southern states tend to have higher rates of sexual activity but lower rates of contraceptive use than those in other U.S. regions. ➔ Recent patterns suggest that contraceptive use continues to be the main driver of declines in adolescent pregnancy. This report presents new state-level estimates of sexual activity and contraceptive use among high school students in the United States. The data are from the 2019 Youth Risk Behavior Surveillance System (YRBSS), which is managed by the U.S. Centers for Disease Control and Prevention (CDC). Because the 2019 YRBSS included more states than in prior years, we are able to better identify differences across states and regions, as well as describe recent trends. In particular, we examine variations in adolescents’ sexual activity and their use of condoms and of other contraceptive methods, because of their important implications for exposure to STIs and pregnancy. The YRBSS offers a unique opportunity to examine sexual and reproductive health at the state level among high school students.

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Robinson, Trina, Bryan Boruff, John Duncan, Kevin Murray, Jasper Schipperijn, Ben Beck, Gareth Stratton, Lucy Griffiths, Richard Fry y Hayley Christian. Understanding variations in the built environment over time to inform longitudinal studies of young children's physical activity behaviour - The BEACHES Project. Institute for Social Science Research, The University of Queensland, abril de 2024. http://dx.doi.org/10.14264/0ae8a48.

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Go, Eugenia, Kentaro Nakajima, Yasuyuki Sawada y Kiyoshi Taniguchi. On the Use of Satellite-Based Vehicle Flows Data to Assess Local Economic Activity: The Case of Philippine Cities. Asian Development Bank, marzo de 2022. http://dx.doi.org/10.22617/wps220079-2.

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Satellite image-derived vehicle counts were used to measure local economic activity following the opening of the new terminal at the Mactan-Cebu International Airport in the Philippines. Results reveal that the terminal’s opening has had positive impacts on Cebu’s local economy. A comparison of the vehicle count measure with luminosity-derived metrics suggests that the former is better at capturing seasonal and spatial variations in treatment effects, especially for beach tourism activities in Cebu.

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Or, Dani, Shmulik Friedman y Jeanette Norton. Physical processes affecting microbial habitats and activity in unsaturated agricultural soils. United States Department of Agriculture, octubre de 2002. http://dx.doi.org/10.32747/2002.7587239.bard.

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experimental methods for quantifying effects of water content and other dynamic environmental factors on bacterial growth in partially-saturated soils. Towards this end we reviewed critically the relevant scientific literature and performed theoretical and experimental studies of bacterial growth and activity in modeled, idealized and real unsaturated soils. The natural wetting-drying cycles common to agricultural soils affect water content and liquid organization resulting in fragmentation of aquatic habitats and limit hydraulic connections. Consequently, substrate diffusion pathways to soil microbial communities become limiting and reduce nutrient fluxes, microbial growth, and mobility. Key elements that govern the extent and manifestation of such ubiquitous interactions include characteristics of diffusion pathways and pore space, the timing, duration, and extent of environmental perturbations, the nature of microbiological adjustments (short-term and longterm), and spatial distribution and properties of EPS clusters (microcolonies). Of these key elements we have chosen to focus on a manageable subset namely on modeling microbial growth and coexistence on simple rough surfaces, and experiments on bacterial growth in variably saturated sand samples and columns. Our extensive review paper providing a definitive “snap-shot” of present scientific understanding of microbial behavior in unsaturated soils revealed a lack of modeling tools that are essential for enhanced predictability of microbial processes in soils. We therefore embarked on two pronged approach of development of simple microbial growth models based on diffusion-reaction principles to incorporate key controls for microbial activity in soils such as diffusion coefficients and temporal variations in soil water content (and related substrate diffusion rates), and development of new methodologies in support of experiments on microbial growth in simple and observable porous media under controlled water status conditions. Experimental efforts led to a series of microbial growth experiments in granular media under variable saturation and ambient conditions, and introduction of atomic force microscopy (AFM) and confocal scanning laser microscopy (CSLM) to study cell size, morphology and multi-cell arrangement at a high resolution from growth experiments in various porous media. The modeling efforts elucidated important links between unsaturated conditions and microbial coexistence which is believed to support the unparallel diversity found in soils. We examined the role of spatial and temporal variation in hydration conditions (such as exist in agricultural soils) on local growth rates and on interactions between two competing microbial species. Interestingly, the complexity of soil spaces and aquatic niches are necessary for supporting a rich microbial diversity and the wide array of microbial functions in unsaturated soils. This project supported collaboration between soil physicists and soil microbiologist that is absolutely essential for making progress in both disciplines. It provided a few basic tools (models, parameterization) for guiding future experiments and for gathering key information necessary for prediction of biological processes in agricultural soils. The project sparked a series of ongoing studies (at DTU and EPFL and in the ARO) into effects of soil hydration dynamics on microbial survival strategy under short term and prolonged desiccation (important for general scientific and agricultural applications).

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Day, Christopher M., Hiromal Premachandra y Darcy M. Bullock. Characterizing the Impacts of Phasing, Environment, and Temporal Factors on Pedestrian Demand at Traffic Signals. Purdue University, 2011. http://dx.doi.org/10.5703/1288284317352.

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There is a need for more and higher quality data on pedestrian demand patterns for a number of applications in planning, transportation engineering, public health, and other areas. It is particularly desirable to better characterize the influence of daily, weekly, and annual variations; the impact of weather and special events; and the effects of changes in pedestrian phasing. This paper proposes and demonstrates a methodology for quantifying the relative demand for pedestrian service at a signalized intersection by using the percent of signal cycles per hour in which the pedestrian phase was actuated. Although this performance measure does not by itself provide a pedestrian count, it can be used as a surrogate to characterize how pedestrian volumes vary due to operating conditions. More importantly, since this technique does not require new sensors, the data can be collected at thousands of intersections across the nation where pedestrian push buttons are in use. This paper documents findings from over a year of data collection at a signalized intersection on a college campus. The effects of daily/weekly/annual variations, special events, weather (temperature and precipitation), seasonal changes in activity patterns, and changes in pedestrian signal phasing are documented. A Tobit model is used to account for the influences of these variables and understand how they co-influence pedestrian activity. The implementation of an exclusive pedestrian phase is associated with a 9% increase in pedestrian phase utilization at the intersection. This change is associated with a decrease in user cost relative to performing midblock crossings. The modeled impact of snowfall events adds further insight by showing that as the user cost of making midblock crossings increases, pedestrian activity at the intersection increases.

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