Consulta: subjectFacets:"Trend"
Registros recuperados: 13
Data/hora: 09/06/2024 06:01:27

Analisis de tendencia en el modelo autoregresivo bajo innovaciones con distribuciones normal y otras
Provedor de dados: 32
Autores: Maza Cantellano, Pablo.
Se analiza la tendencia en el modelo autorregresivo. Se propone el nivel de tendencia y se  observa si las pruebas de Mann-Kendall y el coeficiente de correlación de Pearson la detectan,  variando el tamaño de muestra, el valor del término autorregresivo, el nivel de significancia y el  tipo de distribución que siguen las innovaciones, la cual puede ser Exponencial, Pareto, de Valor  Extremo Generalizado Tipo I o Normal. El proceso es aplicado a datos simulados sin transformar  y a datos transformados con sus rangos. Los resultados sugieren que cuando se utiliza la  transformación del rango se obtiene la mejor potencia, aunque no existen notables diferencias  entre ambas pruebas puede decirse que la mejor es la prueba de Mann-Kendall, dado que es  menos...
Tipo: Tesis
Palavras-chave: Tendencia; Autorregresivo; Mann-Kendall; Coeficiente de correlación de Pearson; Transformación del rango; Maestría; Estadística; Trend; Autorregressive; Mann-Kendall; Pearson correlation coefficient; Range transformation.
Ano: 2008
URL: http://hdl.handle.net/10521/1506

Antarctic icebergs: A significant natural ocean sound source in the Southern Hemisphere
Provedor de dados: 5
Autores: Matsumoto, Haru; Bohnenstiehl, Delwayne R.; Tournadre, Jean; Dziak, Robert P.; Haxel, Joseph H.; Lau, T. -k. A.; Fowler, Matt; Salo, Sigrid A.
In late 2007, two massive icebergs, C19a and B15a, drifted into open water and slowly disintegrated in the southernmost Pacific Ocean. Archived acoustic records show that the high-intensity underwater sounds accompanying this breakup increased ocean noise levels at mid-to-equatorial latitudes over a period of ∼1.5 years. More typically, seasonal variations in ocean noise, which are characterized by austral summer-highs and winter-lows, appear to be modulated by the annual cycle of Antarctic iceberg drift and subsequent disintegration. This seasonal pattern is observed in all three Oceans of the Southern Hemisphere. The life cycle of Antarctic icebergs affects not only marine ecosystem but also the sound environment in far-reaching areas and must be...
Tipo: Text
Palavras-chave: Antarctica; Iceberg; Ocean noise; Seasonality; Trend.
Ano: 2014
URL: http://archimer.ifremer.fr/doc/00205/31613/30035.pdf

A growing oceanic carbon uptake: Results from an inversion study of surface pCO(2) data
Provedor de dados: 5
Autores: Majkut, Joseph D.; Sarmiento, J. L.; Rodgers, K. B.
Concerted community efforts have been devoted to producing an authoritative climatology of air-sea CO2 fluxes, but identifying decadal trends in CO2 fluxes has proven to be more challenging. The available surface pCO(2) estimates are too sparse to separate long-term trends from decadal and seasonal variability using simple linear models. We introduce Markov Chain Monte Carlo sampling as a novel technique for estimating the historical pCO(2) at the ocean surface. The result is a plausible history of surface pCO(2) based on available measurements and variability inferred from model simulations. Applying the method to a modern database of pCO(2) data, we find that two thirds of the ocean surface is trending toward increasing uptake of CO2, with a mean (year...
Tipo: Text
Palavras-chave: Carbon; Assimilation; LDEO2010; Trend.
Ano: 2014
URL: https://archimer.ifremer.fr/doc/00290/40156/38724.pdf

Les surcotes et les décotes marines à Brest, étude statistique et évolution
Provedor de dados: 5
Autores: Bouligand, R; Pirazzoli, Pa.
Sea surges (positive or negative) are short-period events (several hours to several days) among the most extreme oceanic phenomena resulting from climatic variability. A statistical study of hourly tide-gauge records at Brest does not allow any clear trend in long-term variations of these extreme sea levels to be detected. However, the frequency of extreme positive sea surges has increased recently (1953-1994), whereas extreme and sub-extreme negative sea surges has decreased. Such trends for the highest values strengthen the prevalence of positive sea surges over negative ones. The general evolution appears to be organised around several time scales, with a strong interannual variability superimposed on periods of amplification or regression of decennial...
Tipo: Text
Palavras-chave: Niveau marin; Surcotes et décotes marines; Fréquence; Évolution; Brest; Sea level; Positive and negative sea surges; Frequency; Trend; Brest.
Ano: 1999
URL: http://archimer.ifremer.fr/doc/00325/43617/43918.pdf

Analyse des tendances des séries temporelles de la concentration en azote minéral dissous dans les trois principaux estuaires de la façade Manche-Atlantique
Provedor de dados: 5
Autores: Gailhard, Isabelle.
Estuaries are areas which, from their structure, their fonctioning, and their localisation, are subject to significant contribution of nutrients. One of the objectif of the RNO, the French network for coastal water quality monitoring, is to assess the levels and trends of nutrient concentrations in estuaries. A linear model was used in order to describe and to explain the total dissolved nitrogen concentration evolution in the three most important estuaries on the Chanel-Atlantic front (Seine, Loire and Gironde). As a first step, the selection of a reliable data set was performed. Then total dissolved nitrogen evolution schemes in estuary environment were graphically studied, and allowed a resonable choice of covariables. The salinity played a major role...
Tipo: Text
Palavras-chave: Nutriments; Estuaire; Loire; Seine; Gironde; Schéma de dilution; Modèle linéaire; Tendance; Nutrients; Estuary; Seine; Loire; Gironde; Dilution schema; Linear mode1; Trend.
Ano: 2000
URL: http://archimer.ifremer.fr/doc/00079/19070/16665.pdf

Market Instability in a New Era of Corn, Soybean, and Wheat Prices
Provedor de dados: 31
Autores: Irwin,   Scott H.; Good,   Darrel L.
Tipo: Journal Article
Palavras-chave: Grain; Price; Increase; Trend; Demand and Price Analysis; Marketing; Q11; Q13.
Ano: 2009
URL: http://purl.umn.edu/94694

Characteristics of Price Fluctuation of Agricultural Products in China
Provedor de dados: 31
Autores: Guo,   Xiao-hui; Ge,   Dang-qiao.
This paper introduces the basic trend of the price of agricultural products in China, and analyzes the causation of rigid rise of agricultural product price. We also study on the fluctuation characteristics of the prices of Chinese and classification agricultural products.
Tipo: Thesis or Dissertation
Palavras-chave: Agricultural product price; Fluctuation characteristics; Trend; China; Agricultural and Food Policy; Demand and Price Analysis; Food Consumption/Nutrition/Food Safety; Marketing; Research Methods/ Statistical Methods; Resource /Energy Economics and Policy.
Ano: 2009
URL: http://purl.umn.edu/53515

Weather Effects on Trend, Variance and Distribution of Crop Yield
Provedor de dados: 31
Autores: Yu,   Tian; Babcock,   Bruce A.
Favorable weather conditions for dryland crop production, including a proper amount of heat and rainfall during the growing season, are critical factors determining yield outcomes. Weather conditions however, are randomly distributed across regions and over time, thus influencing the temporal and geographical patterns of measured crop yield. Failure to account for weather factors when estimating crop yield distributions, time trends or productivity gains can lead to spurious conclusions regarding technology improvement, yield risk and skewness of yield. This paper addresses some limitations in the literature that result from not taking into account weather, and proposes an approach to incorporate weather into modeling yield.
Tipo: Conference Paper or Presentation
Palavras-chave: Corn yield; Distribution; Trend; Yield risk; Agricultural Finance.
Ano: 2010
URL: http://purl.umn.edu/60908

MODELOS DE SÉRIES TEMPORAIS APLICADOS À SÉRIE DOS ÍNDICES DE PREÇOS AO CONSUMIDOR NA REGIÃO DE LAVRAS, MG, NO PERÍODO DE 1992 A 1999
Provedor de dados: 31
Autores: Silva,   Roberta Bessa Veloso; Ferreira,   Daniel Furtado; Safadi,   Thelma.
This piece of work was carried out objectifying to adjust the time series models to the series of price indexes for the consumer ( PIC ) of Lavras MG. It aimed at verifying the occurrence of differences in trend as for the period which preceeded, as well as for the one which succeeded the Plano Real, and if there was a simple linear trend along with Plano Real ( 1994-1999 ) as well as if any seasonality occurred. It also objectified to comparing the series of both Lavras and the Federal District. It was verified that there was no trend along the whole series, nor there was any seasonality, notwithstanding the fact that a level change occurred, which was characterized as an intervention, rather than a trend. It was necessary to fit a model featuring an...
Tipo: Journal Article
Palavras-chave: Price index to the consumer; Trend; Seasonality; Forecast.
Ano: 2000
URL: http://purl.umn.edu/43355

Agricultural yield expectations under climate change - a Bayesian approach
Provedor de dados: 31
Autores: Krause,   Jette.
In the years to come, German wheat, corn and aggregated cereal yields can be expected to show growing deviations from a linearly increasing trend. This results from the Bayesian Updating approach I apply to agricultural yield data. The updating procedure is carried out on a set of hypotheses on yield development, which are weighted in the light of yield data from 1950 through 2006. All hypotheses share the assumption of a linear yield trend with normally distributed variance of actual data from this trend, but differ in regard to possible future developments. The set of hypotheses allows for both the trend and the variance of data to stay unchanged, increase or decrease by 20 per cent from one period to the next. As a result, yield expectations converge to...
Tipo: Conference Paper or Presentation
Palavras-chave: Bayesian updating; Agricultural yields; Expectation; Risk; Climate change; Trend; Variance; Volatility; Crop Production/Industries; Environmental Economics and Policy.
Ano: 2007
URL: http://purl.umn.edu/9273

Generalized least squares for trend estimation of summarized dose–response data
Provedor de dados: 31
Autores: Orsini,   Nicola; Bellocco,   Rino; Greenland,   Sander.
This paper presents a command, glst, for trend estimation across different exposure levels for either single or multiple summarized case–control, incidence-rate, and cumulative incidence data. This approach is based on constructing an approximate covariance estimate for the log relative risks and estimating a corrected linear trend using generalized least squares. For trend analysis of multiple studies, glst can estimate fixed- and random-effects metaregression models.
Tipo: Journal Article
Palavras-chave: Glst; Dose–response data; Generalized least squares; Trend; Meta-analysis; Metaregression; Research Methods/ Statistical Methods.
Ano: 2006
URL: http://purl.umn.edu/117556

Have Biotech Seeds Increased Maize Yields?
Provedor de dados: 31
Autores: Xu,   Zheng; Hennessy,   David A.; Moschini,   GianCarlo.
Corn yield is determined by soils, weather, seed used and other technology choices. Global population and per capita income growth trends as well as demand from the energy sector have placed great stress on cropland use. Global cropland acres and/or yield per acre will need to increase. Whether new seed technologies have enhanced corn yield is a controversial issue. We study U.S. county corn yields 1964-2008, controlling for location effects, fertilization technologies and weather. We find evidence that trend yield growth has been fastest in the Central Corn Belt, genetic modification technologies have increased trend yield, and this increase has been largest in the Central Corn Belt.
Tipo: Conference Paper or Presentation
Palavras-chave: Biotechnology; Corn Yield; Trend; Regional Effects; Weather; Fertilization.; Crop Production/Industries; Industrial Organization; Research and Development/Tech Change/Emerging Technologies; L65; Q16.
Ano: 2010
URL: http://purl.umn.edu/61303

World and regional trends in maize production, productivity and demand
Provedor de dados: 106
Autores: Harrington, L.W.
4 ill., 11 tables
Palavras-chave: Corn; Maize; Production; Productivity; Demand; Supply; Utilization; Facts; Trend; ข้าวโพด; การผลิต; ผลผลิต; อุปสงค์; อุปทาน; แนวโน้ม.
Ano: 1989
URL: http://anchan.lib.ku.ac.th/agnet/handle/001/4322