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Search Results: 1 - 10 of 224498 matches for " Yulia R. Gel "
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Identification of an unstable ARMA equation
Yulia R. Gel,Vladimir N. Fomin
Mathematical Problems in Engineering , 2001, DOI: 10.1155/s1024123x01001557
Abstract: Usually the coefficients in a stochastic time series model are partially or entirely unknown when the realization of the time series is observed. Sometimes the unknown coefficients can be estimated from the realization with the required accuracy. That will eventually allow optimizing the data handling of the stochastic time series.
Identification of an unstable ARMA equation
Gel Yulia R.,Fomin Vladimir N.
Mathematical Problems in Engineering , 2001,
Abstract: Usually the coefficients in a stochastic time series model are partially or entirely unknown when the realization of the time series is observed. Sometimes the unknown coefficients can be estimated from the realization with the required accuracy. That will eventually allow optimizing the data handling of the stochastic time series. Here it is shown that the recurrent least-squares (LS) procedure provides strongly consistent estimates for a linear autoregressive (AR) equation of infinite order obtained from a minimal phase regressive (ARMA) equation. The LS identification algorithm is accomplished by the Padé approximation used for the estimation of the unknown ARMA parameters.
lawstat: An R Package for Law, Public Policy and Biostatistics
Wallace Hui,Yulia R. Gel,Joseph L. Gastwirth
Journal of Statistical Software , 2008,
Abstract: We present a new R software package lawstat that contains statistical tests and procedures that are utilized in various litigations on securities law, antitrust law, equal employment and discrimination as well as in public policy and biostatistics. Along with the well known tests such as the Bartels test, runs test, tests of homogeneity of several sample proportions, the Brunner-Munzel tests, the Lorenz curve, the Cochran-Mantel-Haenszel test and others, the package contains new distribution-free robust tests for symmetry, robust tests for normality that are more sensitive to heavy-tailed departures, measures of relative variability, Levene-type tests against trends in variances etc. All implemented tests and methods are illustrated by simulations and real-life examples from legal cases, economics and biostatistics. Although the package is called lawstat, it presents implementation and discussion of statistical procedures and tests that are also employed in a variety of other applications, e.g., biostatistics, environmental studies, social sciences and others, in other words, all applications utilizing statistical data analysis. Hence, name of the package should not be considered as a restriction to legal statistics. The package will be useful to applied statisticians and "quantitatively alert practitioners" of other subjects as well as an asset in teaching statistical courses.
nparLD: An R Software Package for the Nonparametric Analysis of Longitudinal Data in Factorial Experiments
Kimihiro Noguchi,Yulia R. Gel,Edgar Brunner,Frank Konietschke
Journal of Statistical Software , 2012,
Abstract: Longitudinal data from factorial experiments frequently arise in various fields of study, ranging from medicine and biology to public policy and sociology. In most practical situations, the distribution of observed data is unknown and there may exist a number of atypical measurements and outliers. Hence, use of parametric and semi-parametric procedures that impose restrictive distributional assumptions on observed longitudinal samples becomes questionable. This, in turn, has led to a substantial demand for statistical procedures that enable us to accurately and reliably analyze longitudinal measurements in factorial experiments with minimal conditions on available data, and robust nonparametric methodology offering such a possibility becomes of particular practical importance. In this article, we introduce a new R package nparLD which provides statisticians and researchers from other disciplines an easy and user-friendly access to the most up-to-date robust rank-based methods for the analysis of longitudinal data in factorial settings. We illustrate the implemented procedures by case studies from dentistry, biology, and medicine.
The Impact of Levene's Test of Equality of Variances on Statistical Theory and Practice
Joseph L. Gastwirth,Yulia R. Gel,Weiwen Miao
Statistics , 2010, DOI: 10.1214/09-STS301
Abstract: In many applications, the underlying scientific question concerns whether the variances of $k$ samples are equal. There are a substantial number of tests for this problem. Many of them rely on the assumption of normality and are not robust to its violation. In 1960 Professor Howard Levene proposed a new approach to this problem by applying the $F$-test to the absolute deviations of the observations from their group means. Levene's approach is powerful and robust to nonnormality and became a very popular tool for checking the homogeneity of variances. This paper reviews the original method proposed by Levene and subsequent robust modifications. A modification of Levene-type tests to increase their power to detect monotonic trends in variances is discussed. This procedure is useful when one is concerned with an alternative of increasing or decreasing variability, for example, increasing volatility of stocks prices or "open or closed gramophones" in regression residual analysis. A major section of the paper is devoted to discussion of various scientific problems where Levene-type tests have been used, for example, economic anthropology, accuracy of medical measurements, volatility of the price of oil, studies of the consistency of jury awards in legal cases and the effect of hurricanes on ecological systems.
Using bootstrap for statistical inference on random graphs
Mary E. Thompson,Lilia Leticia Ramirez Ramirez,Vyacheslav Lyubchich,Yulia R. Gel
Statistics , 2014,
Abstract: In this paper, we propose new nonparametric approach to network inference that may be viewed as a fusion of block sampling procedures for temporally and spatially dependent processes with the classical network methodology. We develop estimation and uncertainty quantification procedures for network mean degree using a "patchwork" sample and nonparametric bootstrap, under the assumption of unknown degree distribution. We investigate asymptotic properties of the proposed patchwork bootstrap procedure and present cross-validation methodology for selecting an optimal patch size. We validate the new patchwork bootstrap on simulated networks with short and long tailed mean degree distributions, and revisit the Erdos collaboration data to illustrate the proposed methodology.
Influenza Forecasting with Google Flu Trends
Andrea Freyer Dugas, Mehdi Jalalpour, Yulia Gel, Scott Levin, Fred Torcaso, Takeru Igusa, Richard E. Rothman
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0056176
Abstract: Background We developed a practical influenza forecast model based on real-time, geographically focused, and easy to access data, designed to provide individual medical centers with advanced warning of the expected number of influenza cases, thus allowing for sufficient time to implement interventions. Secondly, we evaluated the effects of incorporating a real-time influenza surveillance system, Google Flu Trends, and meteorological and temporal information on forecast accuracy. Methods Forecast models designed to predict one week in advance were developed from weekly counts of confirmed influenza cases over seven seasons (2004–2011) divided into seven training and out-of-sample verification sets. Forecasting procedures using classical Box-Jenkins, generalized linear models (GLM), and generalized linear autoregressive moving average (GARMA) methods were employed to develop the final model and assess the relative contribution of external variables such as, Google Flu Trends, meteorological data, and temporal information. Results A GARMA(3,0) forecast model with Negative Binomial distribution integrating Google Flu Trends information provided the most accurate influenza case predictions. The model, on the average, predicts weekly influenza cases during 7 out-of-sample outbreaks within 7 cases for 83% of estimates. Google Flu Trend data was the only source of external information to provide statistically significant forecast improvements over the base model in four of the seven out-of-sample verification sets. Overall, the p-value of adding this external information to the model is 0.0005. The other exogenous variables did not yield a statistically significant improvement in any of the verification sets. Conclusions Integer-valued autoregression of influenza cases provides a strong base forecast model, which is enhanced by the addition of Google Flu Trends confirming the predictive capabilities of search query based syndromic surveillance. This accessible and flexible forecast model can be used by individual medical centers to provide advanced warning of future influenza cases.
Bio-Morphological Characters of Alien Legume Species, Influencing Their Invasion in Natural Plant Communities  [PDF]
Yulia Vinogradova
American Journal of Plant Sciences (AJPS) , 2016, DOI: 10.4236/ajps.2016.716209
Abstract: Five alien legume species, actively invading in natural plant communities in European part of Russia, were studied—Lupinus polyphyllus Lindl., Galega orientalis Lam., Robinia pseudoacacia L., Amorpha fruticosa L. and Caragana arborescens L. Distribution ranges (considering their invasive status) were mapped. Not a single bio-morphological character to forecast invasion success in natural plant communities within secondary distribution range was found. The data of key value/importance for explaining invasive success of the species studied were obtained. Two hypotheses— Propagule Pressure and Evolution of Invasiveness—were critically analyzed in view of the received data.
Reactions of chamois to human disturbance in Berchtesgaden National Park
B?gel, R.,H?rer, G.
Pirineos : Revista de Ecología de Monta?a , 2002,
Abstract: The objective of this study was to test whether the source and frequence of disturbance result in different behavioural responses of Chamois and if practical management guidelines can be drawn from these findings. The results clearly indicate that type and frequency of the disturbance have a strong influence on the behavioural response and that the disturbance tolerance varies with season, time of the day, sex and group size. Disturbances from flying resulted in a much stronger response than disturbances from the ground, and the response increased with velocity and/or noise level of the disturbance source. In areas with frequent disturbances the behavioural response was reduced when compared with remote areas, indicating habituation effects. While distance at first reaction and flight distance varied with disturbance intensity, the length of the flight path was not influenced by the disturbance type and frequency. Habitat use was also affected by disturbances: postdisturbance habitat types were mainly rocks and forests indicating a shift in habitat selection towards inaccessible habitat types or habitat types with good cover. [fr] Chez les chamois, nous avons étudié l’influence des différentes perturbations de diverses fréquences sur le comportement et nous nous sommes demandés si les résultats obtenus pouvaient orienter la gestion des populations. En effet, aussi bien le type que la fréquence de la perturbation ont influencé de manière significative le comportement. De plus, la tolérance aux perturbations varie avec la saison, l'heure du jour, le sexe et la taille du groupe. Les perturbations produites par des engins aériens ont provoqué une réponse beaucoup plus forte que celles provenant du terrain; la réponse étant augmentée avec la vitesse ou le degré du bruit de la source de perturbation. Là où les perturbations étaient fréquentes, la réponse se voyait réduite par rapport a des territoires éloignés, cela nous indiquant une habituation certaine. La distance de fuite et la distance de la première réaction ont suivi de près l'intensité de la perturbation; par contre, la longueur de la distance de fuite n'est pas influencée par le type de perturbation et la fréquence. L'utilisation de l'habitat était aussi affectée par les perturbations, ainsi les habitats choisis après la perturbation étaient les rochers et les forêts. Il y avait une préférence pour les habitats plus inaccessibles ou avec un meilleur recouvrement. [es] El objetivo del presente estudio es valorar si molestias de diferentes tipos y frecuencias producen diferentes respuestas en el compor
Hulusi GE?GEL,Fatma DEM?R
Journal of the Human and Social Science Researches (itobiad) , 2012,
Abstract: Cumhuriyet d nemiyle birlikte ocuk ve ocuk edebiyat daha ok nemsenmi ve bir ok yazar ocuk edebiyat alan nda eserler ortaya koymaya ba lam t r. Bu yazarlardan biri de, Muzaffer zgü’dür. Diyarbak r retmen Okulu’ndan mezun olduktan sonra uzun y llar retmenlik yapan yazar, kara mizah türünde yazarl k ya am na ba lar. Bu alanda yeti kinler i in bir ok ykü, roman ve oyunlar yazar. Daha sonra retmenlik mesle inden getirdi ideneyimlerle ocuk edebiyat alan na y nelerek ykü ve romanlardan olu an 76 eser meydana getirir. zgü’nün yeti kinler ve ocuklar i in yazd 65 ykü kitab nda ocuk ve e itim temas geni bir yer tutar. ocuklar zgü’nün eserlerinde vazge ilmez bir unsurdur. Yazar, yküleriyle ocuklar e itmeyi ve e lendirmeyi ama lar. zgü’nün eserlerinde ocuklara payla ma, yard mla ma, fedakarl k, eme e sayg , üretkenlik, gü süzden yana olma, vatan n sevme, evreye ve büyüklere sayg l olma gibi de erler verilmeye al l r. zgü’nün eserlerinde e itim konusu geni bir yer tuttu undan, e itimin en nemli iki unsuru da bu ykülerde kar m za s k a kar. Bu iki unsur retmen ve rencidir. ykülerde madd s k nt eken retmenler yer alsa da; okuyuculara rnek olmas a s ndan iyi, fedakar ve anlay l retmen tipleri daha ok anlat r. renci tipleri i in de ayn durum ge erlidir. Her tipte renci ykülerde yer al rken, o unlu u düzenli ve al kan renciler olu turur. Muzaffer zgü ykülerinde ocu u anlat rken, ocuk ve renci bütünlü ünü bozmaz. Ayn zamanda ykülerde yer alan ocuklar, o unlukla fakir ve al mak zorunda olan tiplerdir. ykülerin neredeyse hepsinde ocuk ve oyun kavram birlikte verilmi tir. Oyun, zgü’nün eserlerinde ocuktan ayr lmayan bir bütündür.
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