713 resultados para Mangshan loess


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Muddy floods occur when rainfall generates runoff on agricultural land, detaching and transporting sediment into the surrounding natural and built environment. In the Belgian Loess Belt, muddy floods occur regularly and lead to considerable economic costs associated with damage to property and infrastructure. Mitigation measures designed to manage the problem have been tested in a pilot area within Flanders and were found to be cost-effective within three years. This study assesses whether these mitigation measures will remain effective under a changing climate. To test this, the Water Erosion Prediction Project (WEPP) model was used to examine muddy flooding diagnostics (precipitation, runoff, soil loss and sediment yield) for a case study hillslope in Flanders where grass buffer strips are currently used as a mitigation measure. The model was run for present day conditions and then under 33 future site-specific climate scenarios. These future scenarios were generated from three earth system models driven by four representative concentration pathways and downscaled using quantile mapping and the weather generator CLIGEN. Results reveal that under the majority of future scenarios, muddy flooding diagnostics are projected to increase, mostly as a consequence of large scale precipitation events rather than mean changes. The magnitude of muddy flood events for a given return period is also generally projected to increase. These findings indicate that present day mitigation measures may have a reduced capacity to manage muddy flooding given the changes imposed by a warming climate with an enhanced hydrological cycle. Revisions to the design of existing mitigation measures within existing policy frameworks are considered the most effective way to account for the impacts of climate change in future mitigation planning. 

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The sixth in a series, this bulletin further compiles the reports on completed research done for the Iowa State Highway Research Board under its Project HR-1, The loess and glacial till materials of Iowa; an investigation of their physical and chemical properties and techniques for processing them to increase their all-weather stability for road construction. The research, started in 1950, has been conducted by the Iowa Engineering Experiment Station at Iowa State University under its Project 283-S.

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This bulletin is a further compilation of the reports on completed research done for the Iowa State Highway Research Board Project HR-1 The loess and glacial till materials of Iowa; an investigation of their physical and chemical properties and techniques for processing them to increase their all-weather stability for road construction. The research, started in 1950, was done by the Iowa Engineering Experiment Station at Iowa State University under its project 283-S. The project was supported by funds from the Iowa State Highway Commission.

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This is the fourth publication in a series of compilations of the reports on research completed for the Iowa State Highway Commission. This research was done for the Iowa State Highway Research Board Project HR-1. The Loess and Glacial Till Materials of Iowa; an Investigation of Their Physical and Chemical Properties and Techniques for Processing Them to Increase Their All-Weather Stability for Road Construction. The research, started in 1950, was done by the Iowa Engineering Experiment Station under its project 283-S. The project was supported by funds from the Iowa State Highway Commission.

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This is the fifth publication in a series of compilations of the reports on research completed for the Iowa State Highway Commission. This research was done for the Iowa State Highway Research Board Project HR-1, "The Loess and Glacial Till Materials of Iowa; an Investigation of Their Physical and Chemical Properties and Techniques for Processing Them to Increase Their All-Weather Stability for Road Construction." The research, started in 1950, was done by the Iowa Engineering Experiment Station under its project 283-S. The project was supported by funds from the Iowa State Highway Commission. The principal objectives of the project may be summed up as follows: 1. To determine by means of both field and laboratory studies the areal and stratigraphic variation in the physical and chemical properties of the loess and glacial till materials of Iowa. 2. To develop new equipment and methods for evaluating physical and chemical properties of soil where needed. 3. To correlate fundamental soil properties with the performance of soils in the highway structure. 4. To develop a scientific approach to the problem of soil stabilization based on the relationships between the properties of the soils and those of the admixtures. 5. To determine the manner in which the loess and glacial till materials of Iowa can be processed for optimum performance as highway embankments, sub-grades, base courses, and surface courses.

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Al desarrollar el proyecto «Limos Cuaternarios» se encontró que dentro de la Formación Libertad se incluían dos lodolitas diferentes: una, derivada de la meteorización de un loess finiplioceno, sin gravilla, con menos de 20 % de arena y con illita como mineral arcilloso dominante, a la que se propone mantener como Formación Libertad. A la otra lodolita, derivada de rocas básicas con alto porcentaje de arena, minerales ferromagnesianos en esa fracción, abundante gravilla (30-50 %) y montmorillonita como mineral arcilloso dominante, se propone denominarla Formación La Carolina. En realidad se trata de unidades edafoestratigráficas. Las diferencias mineralógicas sugieren una concentración diferente en oligoelementos que podría resultar en un comportamiento disímil de la fertilidad natural. La distribución actual puede definirse a partir de las asociaciones de suelos relevados en la Carta de Suelos a escala 1/1.000.000 de Uruguay.

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In the first paragraphs of this paper a survey of the most ap- proved paleowind indicators is given. Methods, limitations and Problems of their Interpretation are discussed. The following indicators and their attributes are considered: loess, sandy loess (attributes: Sediment thickness, grain size, mineral compo- sition, sediment structure and morphology), paleosoils, vulcano- eolian Sediments, deep sea Sediments and paleo snowlines. In the second part of this paper the wind regimes predominating in Europe during the Weichselian glacial maximum are recon- structed based on information from more than 170 publications with interpretations of paleowind indicators. The results are presented in two survey maps. The most significant result is to indicate two competing wind regimes existing during the glacial maximum. In the immediate vicinity of the Fennoscandian glaciation and in eastern Europe paleowind indicators document easterly and north easterly anti- cyclonic winds; in central and Western Europe they show westerly winds originated in cyclones coming from the North Atlantic. Some modifications of the wind pattern are induced by local and regional morphological conditions (e.g. the Upper Rhine valley, the east rim of the Carpathian Mountains). In general and compared with previous investigations the study points to a more differentiated pattern of atmospheric circula- tion during the Weichselian Pleniglacial influenced by variing topographical, paleoecological and meteorological factors.

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Uma avaliação das metodologias de análise e recolha de dados aplicadas pelo Programa NOCTUAPortugal é de extrema importância para se apurar se estas são as mais indicadas em estudos de citizen science. Comparou-se os resultados de diferentes metodologias analíticas de estimação das tendências populacionais das espécies de aves noturnas durante o período de realização do Programa NOCTUA-Portugal (análise gráfica simples, modelos lineares generalizados (GLM-Poisson e GLMM), modelos aditivos generalizados (GAM-LOESS e GAM-mgcv) e software TRIM). Analisou-se a metodologia de censo de modo a avaliar o número de registos face à duração dos pontos de escuta, comparar a eficiência do ponto de deteção com outros estudos, variação das respostas ao longo da noite e efeito da época do ano, vento, nebulosidade e luminosidade da lua. Os resultados mostraram que a metodologia analítica mais indicada era o GLMM e que não era necessário realizar nenhum ajuste em particular na metodologia de censo; Trends in nocturnal birds in Portugal Methods and analysis of a volunteer-based monitoring program ABSTRACT: An evaluation of the methodologies of analysis and data collection applied by NOCTUA-Portugal Program is extremely important to determine whether these are the most suitable in citizen science studies. We compared the results of different analytical methodologies to estimate population trends of the species of nocturnal birds during the period of the NOCTUA-Portugal Program (simple graphical analysis, generalized linear models (GLM-Poisson and GLMM), generalized additive models (GAM-LOESS and GAMmgcv) and software TRIM). We analyzed the field methodology to assess the effect of point duration on the number of records, compared the point count efficiency with other sources, the variation of responses throughout the night, the effect of time of year, wind, cloud cover and moon luminosity. The results showed that the most suitable analytical methodology was the GLMM and it was not necessary to make any particular adjustment in the field methodology.