Добірка наукової літератури з теми "Threshold exceedance"
Оформте джерело за APA, MLA, Chicago, Harvard та іншими стилями
Ознайомтеся зі списками актуальних статей, книг, дисертацій, тез та інших наукових джерел на тему "Threshold exceedance".
Біля кожної праці в переліку літератури доступна кнопка «Додати до бібліографії». Скористайтеся нею – і ми автоматично оформимо бібліографічне посилання на обрану працю в потрібному вам стилі цитування: APA, MLA, «Гарвард», «Чикаго», «Ванкувер» тощо.
Також ви можете завантажити повний текст наукової публікації у форматі «.pdf» та прочитати онлайн анотацію до роботи, якщо відповідні параметри наявні в метаданих.
Статті в журналах з теми "Threshold exceedance":
1
Flunker, John C., Christopher Zuidema, Jihoon Jung, Edward Kasner, Martin Cohen, Edmund Seto, Elena Austin, and June T. Spector. "Potential Impacts of Different Occupational Outdoor Heat Exposure Thresholds among Washington State Crop and Construction Workers and Implications for Other Jurisdictions." International Journal of Environmental Research and Public Health 19, no. 18 (September 14, 2022): 11583. http://dx.doi.org/10.3390/ijerph191811583.
Анотація:
Occupational heat exposure is associated with substantial morbidity and mortality among outdoor workers. We sought to descriptively evaluate spatiotemporal variability in heat threshold exceedances and describe potential impacts of these exposures for crop and construction workers. We also present general considerations for approaching heat policy-relevant analyses. We analyzed county-level 2011–2020 monthly employment (Bureau of Labor Statistics Quarterly Census of Employment and Wages) and environmental exposure (Parameter-elevation Relationships on Independent Slopes Model (PRISM)) data for Washington State (WA), USA, crop (North American Industry Classification System (NAICS) 111 and 1151) and construction (NAICS 23) sectors. Days exceeding maximum daily temperature thresholds, averaged per county, were linked with employment estimates to generate employment days of exceedances. We found spatiotemporal variability in WA temperature threshold exceedances and crop and construction employment. Maximum temperature exceedances peaked in July and August and were most numerous in Central WA counties. Counties with high employment and/or high numbers of threshold exceedance days, led by Yakima and King Counties, experienced the greatest total employment days of exceedances. Crop employment contributed to the largest proportion of total state-wide employment days of exceedances with Central WA counties experiencing the greatest potential workforce burden of exposure. Considerations from this analysis can help inform decision-making regarding thresholds, timing of provisions for heat rules, and tailoring of best practices in different industries and areas.
2
GREENWOOD, PRISCILLA E., and PETR LANSKY. "INFORMATION CONTENT IN THRESHOLD DATA WITH NON-GAUSSIAN NOISE." Fluctuation and Noise Letters 07, no. 01 (March 2007): L79—L89. http://dx.doi.org/10.1142/s0219477507003702.
Анотація:
If data is binary, it is probable that the combination of a signal of interest plus a noise has been simplified by a thresholding mechanism, as in, e.g., a neuron firing mechanism. For identifying optimal signal or coding range of binary data, Fisher information is an attractive measure. A general formula allows the signal level or signal range producing the most information-rich data to be identified if the noise distribution is known. In this paper we study the information content of binary data resulting from threshold exceedance of a signal plus an arbitrary type of noise. For a specified parametric family of distributions a fixed proportion of exceedances is optimal for any combination of signal, threshold, and noise amplitude. If the ratio of noise to signal level is constant, Fisher information is unimodal for many noise distributions. The results extend to the case of a random signal and to inter-exceedance-interval data. The family of gamma noise distributions is used for illustration.
3
Zhang, Sen, Gaetano Pecoraro, Qigang Jiang, and Michele Calvello. "Definition of Rainfall Thresholds for Landslides Using Unbalanced Datasets: Two Case Studies in Shaanxi Province, China." Water 15, no. 6 (March 10, 2023): 1058. http://dx.doi.org/10.3390/w15061058.
Анотація:
The Lueyang and Xunyang counties in the Shaanxi province (China) are highly susceptible to rainfall-induced landslides. Rainfall thresholds are the most used tool to predict the occurrence of rainfall-induced landslides over large areas. However, the definition of robust thresholds may be difficult for unbalanced datasets, for which the number of non-landslide observations is much higher than the number of landslide observations. This study aims at defining adequate rainfall thresholds for the two study areas using landslide datasets that are strongly unbalanced in terms of occurrences vs. non-occurrences. Two types of rainfall thresholds are determined using a frequentist method at several non-exceedance and exceedance probabilities, separately considering rainfall events responsible for landslides (positive thresholds) and rainfall events not responsible for landslides (negative thresholds). The comparison between the two sets of thresholds shows that the method based on non-triggering events allows defining rainfall thresholds characterized by lower uncertainties and a better performance than the ones defined considering the triggering events, in both the study areas. In particular, the best-performing thresholds are the negative threshold defined at 15% exceedance probability for the Lueyang county and the negative threshold defined at 20% exceedance probability for the Xunyang county.
4
Deidda, R. "A multiple threshold method for fitting the generalized Pareto distribution and a simple representation of the rainfall process." Hydrology and Earth System Sciences Discussions 7, no. 4 (July 23, 2010): 4957–94. http://dx.doi.org/10.5194/hessd-7-4957-2010.
Анотація:
Abstract. Previous studies indicate the generalized Pareto distribution (GPD) as a suitable distribution function to reliably describe the exceedances of daily rainfall records above a proper optimum threshold, which should be selected as small as possible to retain the largest sample while assuring an acceptable fitting. Such an optimum threshold may differ from site to site, affecting consequently not only the GPD scale parameter, but also the probability of threshold exceedance. Thus a first objective of this paper is to derive some expressions to parameterize a simple threshold-invariant three-parameter distribution function which is able to describe zero and non zero values of rainfall time series by assuring a perfect overlapping with the GPD fitted on the exceedances of any threshold larger than the optimum one. Since the proposed distribution does not depend on the local thresholds adopted for fitting the GPD, it will only reflect the on-site climatic signature and thus appears particularly suitable for hydrological applications and regional analyses. A second objective is to develop and test the Multiple Threshold Method (MTM) to infer the parameters of interest on the exceedances of a wide range of thresholds using again the concept of parameters threshold-invariance. We show the ability of the MTM in fitting historical daily rainfall time series recorded with different resolutions. Finally, we prove the supremacy of the MTM fit against the standard single threshold fit, often adopted for partial duration series, by evaluating and comparing the performances on Monte Carlo samples drawn by GPDs with different shape and scale parameters and different discretizations.
5
Deidda, R. "A multiple threshold method for fitting the generalized Pareto distribution to rainfall time series." Hydrology and Earth System Sciences 14, no. 12 (December 14, 2010): 2559–75. http://dx.doi.org/10.5194/hess-14-2559-2010.
Анотація:
Abstract. Previous studies indicate the generalized Pareto distribution (GPD) as a suitable distribution function to reliably describe the exceedances of daily rainfall records above a proper optimum threshold, which should be selected as small as possible to retain the largest sample while assuring an acceptable fitting. Such an optimum threshold may differ from site to site, affecting consequently not only the GPD scale parameter, but also the probability of threshold exceedance. Thus a first objective of this paper is to derive some expressions to parameterize a simple threshold-invariant three-parameter distribution function which assures a perfect overlapping with the GPD fitted on the exceedances over any threshold larger than the optimum one. Since the proposed distribution does not depend on the local thresholds adopted for fitting the GPD, it is expected to reflect the on-site climatic signature and thus appears particularly suitable for hydrological applications and regional analyses. A second objective is to develop and test the Multiple Threshold Method (MTM) to infer the parameters of interest by using exceedances over a wide range of thresholds applying again the concept of parameters threshold-invariance. We show the ability of the MTM in fitting historical daily rainfall time series recorded with different resolutions and with a significative percentage of heavily quantized data. Finally, we prove the supremacy of the MTM fit against the standard single threshold fit, often adopted for partial duration series, by evaluating and comparing the performances on Monte Carlo samples drawn by GPDs with different shape and scale parameters and different discretizations.
6
Roy, Ritu, Dewan Mohammad Enamul Haque, Shamima Ferdousi Sifa, Sumya Tasnim, Tonoy Mahmud, and Tanzim Hayat. "Empirical Approach Based Rainfall Threshold Estimation for Landslide Occurrence in Cox's Bazar District, Bangladesh." Dhaka University Journal of Earth and Environmental Sciences 11, no. 1 (February 1, 2023): 81–94. http://dx.doi.org/10.3329/dujees.v11i1.63713.
Анотація:
Rainfall threshold estimation empirically to forecast rainfall-induced landslide events provides crucial information to reduce landslide impact. The landslide events triggered by rainfall are common in Cox's Bazar district, especially during the monsoon season. Geological settings and climatic conditions make this area more landslide-prone leading to huge losses of lives and property. Establishing an effective early warning system based on a rainfall threshold value has become a top priority to save people's lives, the economy, and the environment. We have employed three empirical approaches to estimate rainfall thresholds. Intensity-Duration, Event-Duration, and Antecedent Rainfall thresholds are the most conventional rainfall methods to identify the lowest amount of rainfall that triggers landslide. The Intensity-Duration (ID) and Event-Duration (ED) rainfall threshold equations are calculated using a simple power-law curve. For 5% exceedance probability level ID defined as: T5: I = 3.63 D-0.1313 & ED as T5: E = 3.63 D0.8687. Similarly, for 1% exceedance probability level ID defined as: T1: I= 2.78 D-0.1313 & T1: E = 2.78 D0.8687 for ED. Both 1% and 5% rainfall threshold equations are the minimum rainfall threshold equations. Since the 5% exceedance probability threshold line delineates the lower end of all the observed data points for landslide events, it is considered the minimum threshold line for Cox's Bazar. According to the 5% exceedance probability level threshold equation, mean intensity of 2.39 mmh-1 or 57.4 mm cumulated rainfall in 24 hours is required to initiate a landslide event. Whereas, for longer duration events such as 120h, rainfall intensity of 1.93 mmh-1 or continuous rainfall of 232 mm appears to be sufficient in landslide initiation. There is a less than 5% chance of a landslide below this threshold limit. In the context of 3-day and 5-day antecedent rainfall thresholds, we found that a minimum of 130 mm in 72 h (3-day) and 210 mm in 120 h (5-day) could initiate a landslide event. We have compared our thresholds with a few global and local rainfall threshold estimates. The Dhaka University Journal of Earth and Environmental Sciences, Vol. 11(1), 2022: 81-94
7
Schönenberg-Tu, Anna-Li, Dirk Cysarz, Benjamin Petzold, Carl Benjamin Blümel, Christa Raak, Oliver Fricke, Friedrich Edelhäuser, and Wolfram Scharbrodt. "Pressure Time Dose as a Representation of Intracranial Pressure Burden and Its Dependency on Intracranial Pressure Waveform Morphology at Different Time Intervals." Sensors 23, no. 19 (September 24, 2023): 8051. http://dx.doi.org/10.3390/s23198051.
Анотація:
Intracranial pressure (ICP) burden or pressure time dose (PTD) is a valuable clinical indicator for pending intracranial hypertension, mostly based on threshold exceedance. Pulse frequency and waveform morphology (WFM) of the ICP signal contribute to PTD. The temporal resolution of the ICP signal has a great influence on PTD calculation but has not been systematically studied yet. Hence, the temporal resolution of the ICP signal on PTD calculation is investigated. We retrospectively analysed continuous 48 h ICP recordings with high temporal resolution obtained from 94 patients at the intensive care unit who underwent neurosurgery due to an intracranial haemorrhage and received an intracranial pressure probe (43 females, median age: 72 years, range: 23 to 88 years). The cumulative area under the curve above the threshold of 20 mmHg was compared for different temporal resolutions of the ICP signal (beat-to-beat, 1 s, 300 s, 1800 s, 3600 s). Events with prolonged ICP elevation were compared to those with few isolated threshold exceedances. PTD increased for lower temporal resolutions independent of WFM and frequency of threshold exceedance. PTDbeat-to-beat best reflected the impact of frequency of threshold exceedance and WFM. Events that could be distinguished in PTDbeat-to-beat became magnified more than 7-fold in PTD1s and more than 104 times in PTD1h, indicating an overestimation of PTD. PTD calculation should be standardised, and beat-by-beat PTD could serve as an easy-to-grasp indicator for the impact of frequency and WFM of ICP elevations on ICP burden.
8
Aranda, Diana, Jose V. Lopez, Helena M. Solo-Gabriele, and Jay M. Fleisher. "Using probabilities of enterococci exceedance and logistic regression to evaluate long term weekly beach monitoring data." Journal of Water and Health 14, no. 1 (September 14, 2015): 81–89. http://dx.doi.org/10.2166/wh.2015.030.
Анотація:
Recreational water quality surveillance involves comparing bacterial levels to set threshold values to determine beach closure. Bacterial levels can be predicted through models which are traditionally based upon multiple linear regression. The objective of this study was to evaluate exceedance probabilities, as opposed to bacterial levels, as an alternate method to express beach risk. Data were incorporated into a logistic regression for the purpose of identifying environmental parameters most closely correlated with exceedance probabilities. The analysis was based on 7,422 historical sample data points from the years 2000–2010 for 15 South Florida beach sample sites. Probability analyses showed which beaches in the dataset were most susceptible to exceedances. No yearly trends were observed nor were any relationships apparent with monthly rainfall or hurricanes. Results from logistic regression analyses found that among the environmental parameters evaluated, tide was most closely associated with exceedances, with exceedances 2.475 times more likely to occur at high tide compared to low tide. The logistic regression methodology proved useful for predicting future exceedances at a beach location in terms of probability and modeling water quality environmental parameters with dependence on a binary response. This methodology can be used by beach managers for allocating resources when sampling more than one beach.
9
Engler, C., W. Birmili, G. Spindler та A. Wiedensohler. "Analysis of exceedances in the daily PM<sub>10</sub> mass concentration (50 μg m<sup>−3</sup>) at a roadside station in Leipzig, Germany". Atmospheric Chemistry and Physics 12, № 21 (5 листопада 2012): 10107–23. http://dx.doi.org/10.5194/acp-12-10107-2012.
Анотація:
Abstract. Five years of PM10 and PM2.5 ambient air measurements at a roadside, an urban, and a regional background site in Leipzig (Germany) were analyzed for violations of the legal PM10 limit value (EC, 1999). The annual mean PM10 concentrations at the three sites were well below the legal threshold of 40 μg m−3 (32.6, 22.0 and 21.7 μg m−3, respectively). At roadside, the daily maximum value of 50 μg m−3 was exceeded on 232 days (13% of all days) in 2005–2009, which led to a violation of the EC directive in three out of five years. We analysed the meteorological factors and local source contributions that eventually led to the exceedances of the daily limit value. As noted in other urban environments before, most exceedance days were observed in the cold season. Exceedance days were most probable under synoptic situations characterised by stagnant winds, low temperatures and strong temperature inversions in winter time. However, these extreme situations accounted for only less than half of the exeedance days. We also noticed a significant number of exceedance days that occurred in the cold season under south-westerly winds, and in the warm season in the presence of easterly winds. Our analysis suggests that local as well as regional sources of PM are equally responsible for exceedances days at the roadside site. The conclusion is that a combined effort of local, national and international reduction measures appears most likely to avoid systematic exceedances of the daily limit value in the future.
10
Kang, Daiwen, Rohit Mathur, Kenneth Schere, Shaocai Yu, and Brian Eder. "New Categorical Metrics for Air Quality Model Evaluation." Journal of Applied Meteorology and Climatology 46, no. 4 (April 1, 2007): 549–55. http://dx.doi.org/10.1175/jam2479.1.
Анотація:
Abstract Traditional categorical metrics used in model evaluations are “clear cut” measures in that the model’s ability to predict an “exceedance” is defined by a fixed threshold concentration and the metrics are defined by observation–forecast sets that are paired both in space and time. These metrics are informative but limited in evaluating the performance of air quality forecast (AQF) systems because AQF generally examines exceedances on a regional scale rather than a single monitor. New categorical metrics—the weighted success index (WSI), area hit (aH), and area false-alarm ratio (aFAR)—are developed. In the calculation of WSI, credits are given to the observation–forecast pairs within the observed exceedance region (missed forecast) or the forecast exceedance region (false alarm), depending on the distance of the points from the central line (perfect observation–forecast match line or 1:1 line on scatterplot). The aH and aFAR are defined by matching observed and forecast exceedances within an area (i.e., model grid cells) surrounding the observation location. The concept of aH and aFAR resembles the manner in which forecasts are usually issued. In practice, a warning is issued for a region of interest, such as a metropolitan area, if an exceedance is forecast to occur anywhere within the region. The application of these new categorical metrics, which are supplemental to the traditional counterparts (critical success index, hit rate, and false-alarm ratio), to the Eta Model–Community Multiscale Air Quality (CMAQ) forecast system has demonstrated further insight into evaluating the forecasting capability of the system (e.g., the new metrics can provide information about how the AQF system captures the spatial variations of pollutant concentrations).
Дисертації з теми "Threshold exceedance":
1
Squintu, Antonello Angelo. "Daily temperature trends in Trentino Alto Adige over the last century." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amslaurea.unibo.it/8310/.
Анотація:
Numerosi lavori apparsi sulla letteratura scientifica negli ultimi decenni hanno evidenziato come, dall’inizio del XX secolo, la temperatura media globale sia aumentata. Tale fenomeno si è fatto più evidente dagli anni ’80, infatti ognuno degli ultimi tre decenni risulta più caldo dei precedenti. L’Europa e l’area mediterranea sono fra le regioni in cui il riscaldamento risulta più marcato, soprattutto per le temperature massime (dal 1951 sono cresciute di +0.39 °C per decennio) che hanno mostrato trend maggiori delle minime. Questo comportamento è stato osservato anche a scala nazionale (+0.25°C/dec per le massime e +0.20°C/dec per le minime). Accanto all’aumento dei valori medi è stato osservato un aumento (diminuzione) degli eventi di caldo (freddo) estremo, studiati attraverso la definizione di alcuni indici basati sui percentili delle distribuzioni. Resta aperto il dibattito su quali siano le cause delle variazioni negli eventi estremi: se le variazioni siano da attribuire unicamente ad un cambiamento nei valori medi, quindi ad uno shift rigido della distribuzione, o se parte del segnale sia dovuto ad una variazione nella forma della stessa, con un conseguente cambiamento nella variabilità. In questo contesto si inserisce la presente tesi con l’obiettivo di studiare l’andamento delle temperature giornaliere sul Trentino-Alto-Adige a partire dal 1926, ricercando cambiamenti nella media e negli eventi estremi in due fasce altimetriche. I valori medi delle temperature massime e minime hanno mostrato un evidente riscaldamento sull’intero periodo specialmente per le massime a bassa quota (`0.13 ̆ 0.03 °C/dec), con valori più alti per la primavera (`0.22 ̆ 0.05 °C/dec) e l’estate (`0.17 ̆ 0.05 °C/dec). Questi trends sono maggiori dopo il 1980 e non significativi in precedenza. L’andamento del numero di giorni con temperature al di sopra e al di sotto delle soglie dei percentili più estremi (stimate sull’intero periodo) indica un chiaro aumento degli estremi caldi, con valori più alti per le massime ad alta quota ( fino a +26.8% per il 99-esimo percentile) e una diminuzione degli estremi freddi (fino a -8.5% per il primo percentile delle minime a bassa quota). Inoltre, stimando anno per anno le soglie di un set di percentili e confrontando i loro trend con quelli della mediana, si è osservato, unicamente per le massime, un trend non uniforme verso temperature più alte, con i percentili più bassi (alti) caratterizzati da trend inferiori (superiori) rispetto a quello della mediana, suggerendo un allargamento della PDF.
2
Cotsakis, Ryan. "Sur la géométrie des ensembles d'excursion : garanties théoriques et computationnelles." Electronic Thesis or Diss., Université Côte d'Azur, 2024. http://www.theses.fr/2024COAZ5007.
Анотація:
L'ensemble d'excursion EX(u) d'un champ aléatoire réel X sur R^d à un niveau de seuil u ∈ R est le sous-ensemble du domaine R^d où X dépasse u. Ainsi, l'ensemble d'excursion est aléatoire, et sa distribution à un niveau fixe u est déterminée par la distribution de X. Étant des sous-ensembles de R^d, les ensembles d'excursions peuvent être étudiés en termes de leurs propriétés géométriques comme moyen d'obtenir des informations partielles sur les propriétés de distribution des champs aléatoires sous-jacents.Cette thèse examine :(a) comment les mesures géométriques d'un ensemble d'excursion peuvent être déduites à partir d'un échantillon discret de l'ensemble d'excursion, et(b) comment ces mesures peuvent être liées aux propriétés distributionnelles du champ aléatoire à partir duquel l'ensemble d'excursion a été obtenu. Chacun de ces points est examiné en détail dans le Chapitre 1, qui fournit un aperçu global des résultats trouvés tout au long du reste de ce manuscrit. Les mesures géométriques que nous étudions (pour les ensembles d'excursion et les sous-ensembles déterministes de R^d) lors de l'adressage du point (a) sont la mesure de la surface de dimension (d−1), le reach, et le rayon de r-convexité. Chacune de ces quantités peut être liée à la régularité de la frontière de l'ensemble, ce qui est souvent difficile à déduire à partir d'échantillons discrets de points.Pour résoudre ce problème, nous apportons les contributions suivantes au domaine de la géométrie computationnelle :- Dans le Chapitre 2, nous identifions le facteur de biais qui correspond aux algorithmes de comptage local pour calculer la mesure de la surface de dimension (d − 1) des ensembles d'excursion sur une grande classe de pavages de R^d. Le facteur de biais dépend uniquement de la dimension d et non de la géométrie précise du pavage.- Dans le Chapitre 3, nous introduisons un algorithme de comptage pseudo-local pour calculer le périmètre des ensembles d'excursion en deux dimensions. L'algorithme proposé est convergent multigrille (multigrid convergent en anglais) et comporte un hyper paramètre réglable pouvant être choisi automatiquement à partir d'informations accessibles.- Dans le Chapitre 4, nous introduisons le β-reach en tant que généralisation du reach, et l'utilisons pour prouver la cohérence d'un estimateur du reach des sous-ensembles fermés de R^d. De même, nous définissons un estimateur cohérent du rayon de r-convexité des sous-ensembles fermés de R^d. De nouvelles relations théoriques sont établies entre le reach et le rayon de r-convexité. Nous étudions également comment ces mesures géométriques des ensembles d'excursion sont liées à la distribution du champ aléatoire.- Dans le Chapitre 5, nous introduisons l'extremal range : une statistique géométrique locale qui caractérise l'étendue spatiale des dépassements de seuil à un niveau fixe u ∈ R. La distribution de l'extremal range est entièrement déterminée par la distribution de l'ensemble d'excursion au niveau u. Nous montrons comment l'extremal range est liée distributionnellement aux volumes intrinsèques de l'ensemble d'excursion. De plus, le comportement limite de l'extremal range aux grands seuils est étudié en relation avec la stabilité des peaks-over-threshold du champ aléatoire sous-jacent. Enfin, la théorie est appliquée à des données climatiques réelles pour mesurer le degré d'indépendance asymptotique présent et sa variation dans l'espace.Des perspectives sur la manière dont ces résultats peuvent être améliorés et étendus sont fournies dans le Chapitre 6The excursion set EX(u) of a real-valued random field X on R^d at a threshold level u ∈ R is the subset of the domain R^d on which X exceeds u. Thus, the excursion set is random, and its distribution at a fixed level u is determined by the distribution of X. Being subsets of R^d, excursion sets can be studied in terms of their geometrical properties as a means of obtaining partial information about the distributional properties of the underlying random fields.This thesis investigates(a) how the geometric measures of an excursion set can be inferred from a discrete sample of the excursion set, and(b) how these measures can be related back to the distributional properties of the random field from which the excursion set was obtained.Each of these points are examined in detail in Chapter 1, which provides a broad overview of the results found throughout the remainder of this manuscript. The geometric measures that we study (for both excursion sets and deterministic subsets of R^d) when addressing point (a) are the (d − 1)-dimensional surface area measure, the reach, and the radius of r-convexity. Each of these quantities can be related to the smoothness of the boundary of the set, which is often difficult to infer from discrete samples of points. To address this problem, we make the following contributions to the field of computational geometry:• In Chapter 2, we identify the bias factor in using local counting algorithms for computing the (d − 1)-dimensional surface area of excursion sets over a large class of tessellations of R^d. The bias factor is seen to depend only on the dimension d and not on the precise geometry of the tessellation.• In Chapter 3, we introduce a pseudo-local counting algorithm for computing the perimeter of excursion sets in two-dimensions. The proposed algorithm is multigrid convergent, and features a tunable hyperparameter that can be chosen automatically from accessible information.• In Chapter 4, we introduce the β-reach as a generalization of the reach, and use it to prove the consistency of an estimator for the reach of closed subsets of R^d. Similarly, we define a consistent estimator for the radius of r-convexity of closed subsets of R^d. New theoretical relationships are established between the reach and the radius of r-convexity.We also study how these geometric measures of excursion sets relate to the distribution of the random field.• In Chapter 5, we introduce the extremal range: a local, geometric statistic that characterizes the spatial extent of threshold exceedances at a fixed level threshold u ∈ R. The distribution of the extremal range is completely determined by the distribution of the excursion set at the level u. We show how the extremal range is distributionally related to the intrinsic volumes of the excursion set. Moreover, the limiting behavior of the extremal range at large thresholds is studied in relation to the peaks-over-threshold stability of the underlying random field. Finally, the theory is applied to real climate data to measure the degree of asymptotic independence present, and its variation throughout space.Perspectives on how these results may be improved and expanded upon are provided in Chapter 6
3
Silva, Domingos José Lopes da. "Estatística de extremos: limites da performance humana - estudo com lançadores e saltadores do atletismo." Doctoral thesis, Universidade de Évora, 2020. http://hdl.handle.net/10174/28600.
Анотація:
Eventos extremos são raros, mas quando ocorrem têm um enorme impacto social e uma atenção
mediática considerável. São exemplo os recordes no mundo do desporto – raros de acontecerem, mas
quando ocorrem não apenas são divulgados nos mais variados meios de comunicação social, como são
motivo de modificação da metodologia de treino e do comportamento do atleta. Como prever esta
ocorrência? Qual a probabilidade de ocorrência? Qual a magnitude da ocorrência? Quanto tempo de
espera? A teoria de valores extremos, baseada no teorema dos tipos extremais de Fisher-Tippett-
Gnedenko, proporciona um rigoroso quadro de análise dos valores extremos, estimando a probabilidade
de ocorrência de eventos que estão para além da amostra disponível. Assim, sob a questão “qual o limite
da performance humana?”, este trabalho no domínio da Estatística de Extremos tem aplicações ao
desporto de alto rendimento, particularmente às especialidades de lançamentos e saltos do atletismo.
Foram utilizadas as metodologias: (i) r-maiores observações, (ii) excessos acima de um limiar, e (iii)
máximos de blocos não-estacionários. Decidida a distribuição limite do máximo associado ao evento
em estudo e o modelo que melhor se adequa aos dados disponíveis, a estimação pontual dos parâmetros
extremais foi realizada por máxima verosimilhança e a estimação intervalar pelo método delta e pela
função profile log-likelihood. Em cada método foram testados diversos modelos. Recorremos a técnicas
gráficas, estabilidade dos erros-padrão, intervalos de confiança, testes de hipóteses e algumas métricas
de erro, para verificação do ajustamento dos modelos aos dados disponíveis. Estamos particularmente
interessados na estimação de quantis extremais, probabilidades de excedência, limite superior do
suporte, níveis de retorno e período de retorno. Os resultados mostram que nos lançamentos do martelo,
disco e dardo feminino existe uma forte probabilidade de se conseguir um novo recorde do mundo e que
nos lançamentos masculinos tal probabilidade é reduzida. Com exceção do triplo-salto, nas restantes
especialidades de saltos, o período de retorno (i.e., número de máximos individuais) até à ocorrência de
um novo recorde do mundo é menor nas mulheres do que nos homens; ABSTRACT:
Statistics of Extremes: limits of human performance - study with throwers and jumpers
in athletics
Extreme events are rare, but when they do occur, they have an enormous social impact and they receive
a considerable media attention. Such is the case of world records in sport – they rarely happen, but when
they do, not only are they disclosed by all media, but they also cause changes in the training methodology
and in the athlete's behaviour. How to predict this occurrence? What is the probability of occurrence?
What is the magnitude of the occurrence? How long is the wait? The extreme value theory, based on the
Fisher-Tippett-Gnedenko theorem, provides a rigorous framework for analysing extreme values,
estimating the probability of the occurrence of events that are beyond the sample. Thus, research within
the area of Extreme Statistics provide information to answer the question “what is the limit of human
performance?” in the framework of high-performance sport, particularly in the case of the specialties of
throwing and jumping in athletics. The methodologies used were: (i) r-largest order statistics, (ii) peaks
over threshold, and (iii) non-stationary annual maximum. Once decided the limit distribution of the
maximum associated with the event under study and the model that best fits the available data, the point
estimation of the extremal parameters were performed by maximum likelihood estimation, with Nelder-
Mead or BFGS optimization and the interval estimation using the delta method and the profile loglikelihood
function. In each method, several models were tested. We used graphical techniques, stability
of standard errors, confidence intervals, hypothesis tests and some error metrics, to verify if the models
fit the available data. We were particularly interested in the estimation of extreme quantiles, exceedance
probability, right endpoint, return levels and return period. The results suggest that in hammer, discus
and javelin throwing there are a strong probability of a new world record will be achieved. In the case
of male, throwing events, the forecast of a new world record being achieved with reduced probability.
With exception of triple-jump, in all other jumping specialities, the return period (i.e., number of
individual maximums) until the occurrence of a new world record is shorter in women than in men.
4
Deviney, Frank A. "Hierarchical continuous time Markov chain models for threshold exceedance." 2009. http://wwwlib.umi.com/dissertations/fullcit/3393526.
5
Khuluse, Sibusisiwe Audrey. "Modelling heavy rainfall over time and space." Thesis, 2011. http://hdl.handle.net/10539/10005.
Анотація:
Extreme Value Theory nds application in problems concerning low probability but high
consequence events. In hydrology the study of heavy rainfall is important in regional
ood
risk assessment. In particular, the N-year return level is a key output of an extreme value
analysis, hence care needs to be taken to ensure that the model is accurate and that the
level of imprecision in the parameter estimates is made explicit.
Rainfall is a process that evolves over time and space. Therefore, it is anticipated that
at extreme levels the process would continue to show temporal and spatial correlation. In
this study interest is in whether any trends in heavy rainfall can be detected for the Western
Cape. The focus is on obtaining the 50-year daily winter rainfall return level and investigating
whether this quantity is homogenous over the study area. The study is carried out in
two stages.
In the rst stage, the point process approach to extreme value theory is applied to arrive
at the return level estimates at each of the fteen sites. Stationarity is assumed for the
series at each station, thus an issue to deal with is that of short-range temporal correlation of
threshold exceedances. The proportion of exceedances is found to be smaller (approximately
0.01) for stations towards the east such as Jonkersberg, Plettenbergbay and Tygerhoek.
This can be attributed to rainfall values being mostly low, with few instances where large
amounts of rainfall were observed. Looking at the parameters of the point process extreme
value model, the location parameter estimate appears stable over the region in contrast to
the scale parameter estimate which shows an increase towards in a south easterly direction.
While the model is shown to t exceedances at each station adequately, the degree of uncertainty
is large for stations such as Tygerhoek, where the maximum observed rainfall value is
approximately twice as large as the high rainfall values. This situation was also observed at
other stations and in such cases removal of these high rainfall values was avoided to minimize
the risk of obtaining inaccurate return level estimates. The key result is an N-year rainfall
return level estimate at each site. Interest is in mapping an estimate of the 50-year daily
winter rainfall return level, however to evaluate the adequacy of the model at each site the
25-year return level is considered since a 25 year return period is well within the range of the
observed data. The 25-year daily winter rainfall return level estimate for Ladismith is the
smallest at 22:42 mm. This can be attributed to the station's generally low observed winter
rainfall values. In contrast, the return level estimate for Tygerhoek is high, almost six times
larger than that of Ladismith at 119:16 mm. Visually design values show di erences between
sites, therefore it is of interest to investigate whether these di erences can be modelled.
The second stage is the geostatistical analysis of the 50-year 24-hour rainfall return level The aim here is to quantify the degree of spatial variation in the 50-year 24-hour rainfall
return level estimates and to use that association to predict values at unobserved sites within
the study region. A tool for quantifying spatial variation is the variogram model. Estimation
of the parameters of this model require a su ciently large sample, which is a challenge in
this study since there is only fteen stations and therefore only fteen observations for the
geostatistical analysis. To address this challenge, observations are expanded in space and
time and then standardized and to create a larger pool of data from which the variogram is
estimated. The obtained estimates are used in ordinary and universal kriging to derive the
50-year 24-hour winter rainfall return level maps. It is shown that 50-year daily winter design
rainfall over most of the Western Cape lies between 40 mm and 80 mm, but rises sharply as
one moves towards the east coast of the region. This is largely due to the in
uence of large
design values obtained for Tygerhoek. In ordinary kriging prediction uncertainty is lowest
around observed values and is large if the distance from these points increases. Overall, prediction
uncertainty maps show that ordinary kriging performs better than universal kriging
where a linear regional trend in design values is included.
6
Baki, Zhuldyzay. "Local Likelihood Approach for High-Dimensional Peaks-Over-Threshold Inference." Thesis, 2018. http://hdl.handle.net/10754/627878.
Анотація:
Global warming is affecting the Earth climate year by year, the biggest difference being observable in increasing temperatures in the World Ocean. Following the long- term global ocean warming trend, average sea surface temperatures across the global tropics and subtropics have increased by 0.4–1◦C in the last 40 years. These rates become even higher in semi-enclosed southern seas, such as the Red Sea, threaten- ing the survival of thermal-sensitive species. As average sea surface temperatures are projected to continue to rise, careful study of future developments of extreme temper- atures is paramount for the sustainability of marine ecosystem and biodiversity. In this thesis, we use Extreme-Value Theory to study sea surface temperature extremes from a gridded dataset comprising 16703 locations over the Red Sea. The data were provided by Operational SST and Sea Ice Analysis (OSTIA), a satellite-based data system designed for numerical weather prediction. After pre-processing the data to account for seasonality and global trends, we analyze the marginal distribution of ex- tremes, defined as observations exceeding a high spatially varying threshold, using the Generalized Pareto distribution. This model allows us to extrapolate beyond the ob- served data to compute the 100-year return levels over the entire Red Sea, confirming the increasing trend of extreme temperatures. To understand the dynamics govern- ing the dependence of extreme temperatures in the Red Sea, we propose a flexible local approach based on R-Pareto processes, which extend the univariate Generalized Pareto distribution to the spatial setting. Assuming that the sea surface temperature varies smoothly over space, we perform inference based on the gradient score method
over small regional neighborhoods, in which the data are assumed to be stationary in space. This approach allows us to capture spatial non-stationarity, and to reduce the overall computational cost by taking advantage of distributed computing resources. Our results reveal an interesting extremal spatial dependence structure: in particular, from our estimated model, we conclude that significant extremal dependence prevails for distances up to about 2500 km, which roughly corresponds to the Red Sea length.
Книги з теми "Threshold exceedance":
1
Leeuw, Frank de. Air pollution by ozone in the European Union: Exceedance of ozone threshold values in 1995 and Summer 1996. Copenhagen: European Environmental Agency, 1997.
2
McGettigan, M. F. Ozone monitoring results and EU threshold exceedances for Ireland in 1995. Dublin: Environmental Protection Agency, 1996.
3
Jaroslav, Fiala, and European Environment Agency, eds. Air pollution by ozone in Europe in summer 2002: Overview of exceedances of EC ozone threshold values during the summer season April-August 2002. Luxembourg: Office for Official Publications, 2003.
4
Agency, European Environment, ed. Air pollution by ozone in Europe in summer 2003: Overview of exceedances of EC ozone threshhold values during the summer season April-August 2003 and comparisions with previous years. Luxembourg: Office for Official Publications of the European Communities, 2003.
5
Huffaker, Ray, Marco Bittelli, and Rodolfo Rosa. Capstone: Application of NLTS to Real-World Data. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198782933.003.0010.
Анотація:
This chapter investigates the use of Extreme Value Statistics (EVS) to probabilistically model extreme events separated as unstructured noise in signal processing. We apply a version of EVS that computes the likelihood of extreme discrepancies exceeding a selected threshold value within a given time interval. In theory, exceedances follow a Generalized Pareto (GP) distribution, and we run diagnostics to determine how well the data actually fit this distribution. If we find a reasonable fit, we can invert the GP distribution to solve for quantiles providing a useful noise diagnostic: return level plots. Return level plots show the return periods expected before particular extreme noise levels return levels are realized.
Частини книг з теми "Threshold exceedance":
1
Debry, Édouard, Vivien Mallet, Laure Malherbe, Frédérik Meleux, Bertrand Bessagnet, and Laurence Rouïl. "Ensemble Forecasting Coupled with Data Assimilation, and Threshold Exceedance Detection on Prev’Air." In Air Pollution Modeling and its Application XXII, 211–14. Dordrecht: Springer Netherlands, 2013. http://dx.doi.org/10.1007/978-94-007-5577-2_36.
2
Droit, Julie, Mohamed El Fadili, and Marion Messager. "Assessment of the chemical quality of sediments in the maritime port of Reunion. Concentrations in trace metals and natural geochemical backgrounds." In Ninth International Symposium “Monitoring of Mediterranean Coastal Areas: Problems and Measurement Techniques”, 456–60. Florence: Firenze University Press, 2022. http://dx.doi.org/10.36253/979-12-215-0030-1.41.
Анотація:
The analyzes carried out in the marine sediments sampled in the port and coastal areas of Reunion show, for certain metallic trace elements, significant variations in their contents and regular overruns of the regulatory thresholds for the management of dredged sediments. Several studies show that the volcanic nature of Reunion Island is the cause of high concentrations of metals in the soil. The objective of this study is to define, whether the observed exceedances of the management thresholds for dredged sediments are due to the geology of the island or to contributions of anthropogenic origin.
3
Gariano, Stefano Luigi, Massimo Melillo, Maria Teresa Brunetti, Sumit Kumar, Rajkumar Mathiyalagan, and Silvia Peruccacci. "Challenges in Defining Frequentist Rainfall Thresholds to Be Implemented in a Landslide Early Warning System in India." In Progress in Landslide Research and Technology, Volume 1 Issue 1, 2022, 409–16. Cham: Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-031-16898-7_27.
Анотація:
AbstractIn India, rainfall-induced landslides cause a high toll in terms of fatalities and damages. Therefore, the adoption of tools to predict the occurrence of such phenomena is urgent. For the purpose, the LANDSLIP project aimed at developing a landslide early warning system (LEWS) to forecast the occurrence of rainfall-induced landslides in two Indian pilot areas: Darjeeling and Nilgiris. Rainfall thresholds are a widely used tool to define critical probability levels for the possible occurrence of landslides in large areas, and are particularly suitable to be implemented in LEWSs.In this work, we exploited two catalogues of 84 and 116 rainfall conditions likely responsible for landslide triggering in Darjeeling and Nilgiris, respectively. Adopting a frequentist statistical method and using an automatic tool, we determined rainfall thresholds at different non-exceedance probabilities for the two pilot areas. Despite the daily temporal resolution of rainfall data and the spatial and temporal distribution of the documented landslides, the thresholds calculated for the two areas have acceptable uncertainties and were implemented in the LANDSLIP LEWS prototype. We expect that the new thresholds and the whole system will contribute to mitigate the landslide risk in the study areas.
4
Johansson, M., R. Suutari, J. Bak, G. Lövblad, M. Posch, D. Simpson, J. P. Tuovinen, and K. Tørseth. "The Importance of Nitrogen Oxides for the Exceedance of Critical Thresholds in the Nordic Countries." In Acid rain 2000, 1739–44. Dordrecht: Springer Netherlands, 2001. http://dx.doi.org/10.1007/978-94-007-0810-5_137.
5
Ogutu, Carolyne, and Antony Rono. "On Modelling Extreme Damages from Natural Disasters in Kenya." In Natural Hazards - Impacts, Adjustments and Resilience. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.94578.
Анотація:
We seek to develop a distribution to model the extreme damages resulting from Natural Disasters in Kenya.The distribution is based on the Compound Extreme Value Distribution, which takes into account both the distributions of the frequency of occurrence and magnitude of the events. Threshold modelling is employed, where the extreme damages are identified as the points that lie above a sufficiently high threshold. The distribution of the number of the exceedance is found to be Negative Binomial, while that of the severity is approximated by a Generalised Pareto Distribution. Maximum likelihood estimation is used to estimate the parameters, and the log-likelihood is maximised using numerical methods. Probability weighted moments estimation is used to determine the starting values for the iterations. Prediction study is then carried out to investigate the performance of the proposed distribution in predicting future events.
6
Besche, Fabian, Helen Seitzer, and Michael Windzio. "Diffusion of Mass Education." In The Oxford Handbook of Education and Globalization, 615—C29P97. Oxford University Press, 2023. http://dx.doi.org/10.1093/oxfordhb/9780197570685.013.19.
Анотація:
Abstract In this chapter, we investigate the diffusion of mass education. We define the establishment of a “mass education system” in a country as an exceedance of the threshold of an overall enrolment of 40% in primary education for boys and girls combined. We focus on countries’ interrelations to explain the institutional development of mass education. What effects do networks of cultural and colonial linkages have on the emergence of national mass education systems? Our theoretical considerations follow sociological functionalism and neoinstitutionalism, but enhance these concepts with a focus on global “cultural spheres,” which we assume are of particular importance for the global diffusion of mass education. We apply social network analysis to describe global cultures in a nonessentialist way and apply network diffusion models in order to estimate the effects of contagion on the emergence of mass education in 156 countries around the world from 1880 to 2010.
7
Kelly, Kaitlyn R., and Bryan W. Brooks. "Global Aquatic Hazard Assessment of Ciprofloxacin: Exceedances of Antibiotic Resistance Development and Ecotoxicological Thresholds." In Progress in Molecular Biology and Translational Science, 59–77. Elsevier, 2018. http://dx.doi.org/10.1016/bs.pmbts.2018.07.004.
8
Calatayud, Alexandra. "Atmospheric Pollution." In The Yearbook of European Environmental Law, 211–24. Oxford University PressOxford, 2006. http://dx.doi.org/10.1093/oso/9780199289271.003.0007.
Анотація:
Abstract Similarly to 2003, most of the developments on air pollution for 2004 involve old initiatives and no significant new proposals. Among the old legislative dossiers of great importance is the draft Fourth Air Quality Daughter Directive relating to Heavy Metals and Polycyclic Aromatic Hydrocarbons. This Directive is the last in the set of legislation that had to be adopted pursuant to Directive 96/62/EC on Ambient Air Quality and Management (Air Quality Framework Directive), and is an important element of the overall strategy to improve air quality in the European Union (EU). Other dossiers to look out for include the Directive on Paints and Solvents, aimed at reducing volatile organic compounds (VOCs), and the draft Directive on Sulphur-Free Shipping Fuel. On the international arena, a key development will be how the question of methyl bromide phase-out is dealt with in the extraordinary and the regular Meeting of the Parties (MOP) of the Montreal Protocol, which both take place this year. In 2004, the European Commission (Commission) published the required guidance for the implementation of Directive 2002/3/EC relating to Ozone in Ambient Air (Ozone Directive). The Commission Decision contains advice on the development of short-term action plans that must be drawn up in the event of exceedances of ozone alert thresholds, as well as on strategies to measure ozone precursors. It provides for geographical differences, regional extension, duration of possible measures, and gives examples of short-term actions. In the case of guidance on monitoring levels, the Decision supplies recommendations for the location of the mandatory measuring station.
9
Bugalho, Lourdes, Luisa Mendes, Maria José Monteiro, Paulo Pinto, João Rio, and Manuel João Lopes. "Monitoring wildfire smoke dispersion using concentrations of PM10 and PM2.5." In Advances in Forest Fire Research 2022, 298–303. Imprensa da Universidade de Coimbra, 2022. http://dx.doi.org/10.14195/978-989-26-2298-9_47.
Анотація:
Portugal as a member of the European Union (EU) follows the air quality legislation regulated by Directive 2008/50/EC that states that “Member States shall ensure that timely information about actual or predicted exceedances of alert thresholds, and any information threshold is provided to the publicâ€. The southern European countries have biogenic contributions, mainly resulting from the long-distance transport of particulate matter, originated in arid regions, and from large forest fires, whose pollutants loads cannot be imposed limits. These sources lead to an additional contribution of atmospheric pollutants mainly during the spring and summer seasons. Climate change is increasing the vulnerability of the environment to extreme events, such as those that enhance the likelihood of forest fires. Due to the forecast increase in temperatures and decrease in precipitation and humidity it is likely there will be an increase in the frequency and intensity of forest fires in certain regions of the Mediterranean basin as is the case of Portugal. Monitoring the concentration of particles matters in the network of air quality stations can be a way of detecting the dispersion of smoke and giving possible alerts to affected populations. The analysis of PM10 and PM2.5 of the air quality network stations, from June to October, in the period 2010-2020, showed very high concentration values coincident with the years and periods of forest fires. This data was analysed for all stations by considering the average value of the concentration in the 2 days before the day of registration of fires with burned area, daily and by district, greater than 500ha, on the day of the fire occurrence and on two days later. Back trajectory analysis was performed using HYSPLIT Model to confirm the origin of the particles observed at the stations. It was observed that the percentage increase in the daily average value of PM10 concentration, between one day before and the day of the event, is variable but with 26% as an average value for the wildfire above 500ha district daily value, in the period 2010-2020 . This difference depends on the proximity of the forest fire, the area burned as an indication of its strength, the stability of the atmosphere and the height of the boundary layer. Dust episodes with origin in the deserts in Northern Africa often affect the southern regions of Portugal which leads to an increase the concentration of PM10 and PM2.5 particles. The days with high values of PM10 particles (and PM2.5), in the summer months, were studied in order to distinguish the days that could be related to dust particles, in general larger particles, from those which referred to smoke particles from forest fires, usually smaller particles. For this purpose, the relationship between the concentrations of PM2.5 in relation to PM10, in the data coincidence period, was considered. For the large fires of 2017, a more detailed assessment of these characteristics was made by studying the optical thickness of the aerosols and the Angstrom exponent of the VIIRS radiometer on board the Suomi NPP satellite.
10
Castel-Clavera, Jorge, François Pimont, Thomas Opitz, Julien Ruffault, and Jean-Luc Dupuy. "Modelling the influence of regional landscape drivers on spatio-temporal patterns of wildfire activity." In Advances in Forest Fire Research 2022, 1228–33. Imprensa da Universidade de Coimbra, 2022. http://dx.doi.org/10.14195/978-989-26-2298-9_186.
Анотація:
Identifying the drivers of fire activity’s spatio-temporal variability is challenging in densely populated and fire prone landscapes. Human usage and climate affect the local fire regime in contrasting ways. The identification of these drivers is further complicated due to the stochastic nature of fire activity. Fire regimes in Mediterranean France show contrasted spatial patterns and temporal changes at decadal scales. While overall, the number of fires decreased over the last thirty years, certain zones suffered local increases in fire activity. To describe and understand the drivers of those changes and the spatial variability, we introduced several improvements in the Firelihood model - a probabilistic framework capable of prediction fire occurrence of >1ha fires, and exceedance probabilities of 10 and 100 ha thresholds - by incorporating Land-Use Land-Cover (LULC) explanatory variables, as well as by enhancing its spatio-temporal components to account for unexplained variability in models. The novel model - fitted on a 2km-pixel grid, but relying on variables aggregated at various spatial aggregations (2, 4, 8 and 16km) - is used to explain the observed spatial patterns of fire activity during the last 27 years, as well as the regional and local changes observed between two decades with contrasted fire activities by running counterfactual scenarios. LULC variables, including road density, wildland-urban interface, or expert-based fuel type rating explain a significant part (as much as fire-weather) of the variability in fire occurrence (>1ha), thereby reducing the effect of unexplained spatial variability. The selected occurrence model uses only 2km-resolution variables, as local factors have a high influence on fire ignition and initial spread. The occurrence of larger fire (>10 ha or >100 ha) is largely driven by fire-weather, followed by unexplained spatial variability; selected models for larger fires uses a few LULC variables aggregated at 4, 8 and/or 16 km. This indicates the influence of surrounding factors on fire size extension. The spatial effect for fire occurrence presents contrasted hot and cold-spots throughout the area, while it has a clear east to west decreasing trend for fire size. Regarding temporal changes in fire activity between the two decades, changes in fire weather induced a strong increase in fire probability in many hot spots throughout the region, but this effect was overcompensated by a negative trend associated with unexplained temporal factors (and of larger magnitude than fire weather). LULC variables had negligible effect on the fire regime’s temporal trends. Moreover, an east-to-west gradient appears for the spatial trends of the larger fires, and for the temporal trends in all sizes, highlighting the increase in fire activity in the western side of the region. Those results suggest that observed temporal changes in fire activity are the result of a changing socio-economic or policy frame, probably related to reinforced suppression policies following the year 2003, and the increasing agricultural abandonment.
Тези доповідей конференцій з теми "Threshold exceedance":
1
Scanlan, Kirk M., Michael T. Hendry, and C. Derek Martin. "Evaluating the Equivalency Between Track Quality Indices and the Minimum Track Geometry Threshold Exceedances Along a Canadian Freight Railway." In 2016 Joint Rail Conference. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/jrc2016-5748.
Анотація:
Railway regulators require that track geometry measurements meet a specific set of minimum safety thresholds. A proper interpretation of track geometry survey data is fundamental for the detection of track exceeding these thresholds and in need of corrective maintenance. Irregular track geometry independent of the minimum safety thresholds can also be used as evidence of degradation in the railway foundation. Therefore, multiple evaluation methods must be applied to the track geometry survey data when assessing foundation degradation. In this study, we compare multiple track geometry evaluation methods in order to assess if they equally identify sections of irregular track geometry along a 335 kilometer section of a Canadian freight railway. The track geometry evaluation methods investigated are the Transport Canada Class 5 minimum safety threshold exceedances and three literature-suggested track quality indices; the Overall Track Geometry Index, the Polish J Index and the Swedish Q Index. Furthermore, this study also investigates the ability of the track quality indices to provide additional insight into track geometry variability in sections without a minimum safety threshold exceedance. The track under investigation is not a Class 5, however, Class 5 minimum safety thresholds were used to produce enough threshold exceedances to allow for the comparison to the track quality indices. The results of the analysis reveal that while the large-scale variability in the three track quality indices is similar, the individual equivalency with the occurrence of Class 5 threshold exceedances is highly variable. Furthermore, only the Overall Track Geometry Index demonstrates the potential to provide consistent additional track geometry variability information.
2
Marinos, George, Manos Karvounis, and Ioannis Athanasiadis. "Survival Analysis as a Risk Stratification Tool for Threshold Exceedance Forecasting." In 15th International Conference on Knowledge Management and Information Systems. SCITEPRESS - Science and Technology Publications, 2023. http://dx.doi.org/10.5220/0012234700003598.
3
Chua, Terence Jie, Wenhan Yu, Chang Liu, and Jun Zhao. "Detection of Uncertainty in Exceedance of Threshold (DUET): An Adversarial Patch Localizer." In 2022 IEEE/ACM International Conference on Big Data Computing, Applications and Technologies (BDCAT). IEEE, 2022. http://dx.doi.org/10.1109/bdcat56447.2022.00010.
4
Keshavarzian, Alireza, and Shahrokh Valaee. "Raster: Representation Learning for Time Series Classification using Scatter Score and Randomized Threshold Exceedance Rate." In 2023 IEEE 33rd International Workshop on Machine Learning for Signal Processing (MLSP). IEEE, 2023. http://dx.doi.org/10.1109/mlsp55844.2023.10285973.
5
Johnson, B. C., and G. E. Apostolakis. "The Limit Exceedance Factor Importance Measure: An Application to the Prism Reactor Design." In 17th International Conference on Nuclear Engineering. ASMEDC, 2009. http://dx.doi.org/10.1115/icone17-75128.
Анотація:
Probabilistic Risk Assessment has several different standard importance measures for structures, systems, and components (SSCs). These importance measures are Risk Achievement Worth (RAW), Risk Reduction Worth (RRW), and Fussell-Vesely (FV). In particular, RAW and FV have been used to identify SSCs of low risk significance. However, when designing a conceptual reactor with a safety goal in mind such as those proposed in various technology neutral frameworks, these importance measures are quite crude. RAW is defined such that a component is always in the failed state, and a designer may not be looking to remove a system but to simplify it to improve economics. The Limit Exceedance Factor has been developed as a more informative importance measure when there is a goal in mind. It is defined as the factor by which the failure probability of a component may be multiplied by such that the end state (e.g. core damage) frequency exceeds a limit. With a living PRA available throughout the design process, it could allow a designer to know how much room there is for possible simplification in redundant systems. Alternatively, in the case where a system does not meet the frequency limit it can show which systems might be ideal targets for improvement to reach the limit. For a sodium-cooled fast reactor design, using the goals and limits outlined in NUREG-1860 (Technology Neutral Framework), one end state that must stay below a threshold is a very large release due to an energetic scenario. Several SSCs can be identified as risk insignificant with RAW values below two. The other SSCs tend to have very high RAW values on the order of one thousand. When the LEF is applied to the SSCs that seem to be very important using traditional importance measures, we see that some may actually have a fairly wide margin from their cited failure probabilities and still maintain the frequency goal.
6
Arena, Felice, Giuseppe Barbaro, and Alessandra Romolo. "Return Period of a Sea Storm With at Least Two Waves Higher Than a Fixed Threshold." In ASME 2009 28th International Conference on Ocean, Offshore and Arctic Engineering. ASMEDC, 2009. http://dx.doi.org/10.1115/omae2009-80031.
Анотація:
The analytical solution for the return period R≥2′ (H) of a sea storm having at least two individual waves higher than a fixed level H, is obtained. This solution is based on the application of the Boccotti’s Equivalent Triangular Storm model for the representation of actual storms. One of the corollaries of the solution gives the exact expression for the probability that at least two waves higher than level H are produced during the lifetime of a structure. The previous solution of R≥2′ (H) and the relative probability of exceedance can be effectively applied for the risk analysis of ocean structures. The results obtained show an excellent agreement with those achieved by considering the different approach, proposed by Arena and Pavone (2009), for the calculation of the return period R≥2 (H).
7
Moriarty, Patrick J., William E. Holley, and Sandy Butterfield. "Probabilistic Methods for Predicting Wind Turbine Design Loads." In ASME 2003 Wind Energy Symposium. ASMEDC, 2003. http://dx.doi.org/10.1115/wind2003-864.
Анотація:
Further study of probabilistic methods for predicting extreme wind turbine loading was performed on two large-scale wind turbine models with stall and pitch regulation. Long-term exceedance probability distributions were calculated using maxima extracted from time series simulations of in-plane and out-of-plane blade loads. It was discovered that using a threshold on the selection of maxima increased the accuracy of the fitted distribution in following the trends of the largest extreme values for a given wind condition. The optimal threshold value for in-plane and out-of-plane blade loads was found to be the mean value plus 1.4 times the standard deviation of the original time series for the quantity of interest. When fitting a distribution to a given data set, the higher-order moments were found to have the greatest amount of uncertainty and also the largest influence on the extrapolated long-term load’s. This uncertainty was reduced by using large data sets, smoothing of the moments between wind conditions and parametrically modeling moments of the distribution. A deterministic turbulence model using the 90th percentile level of the conditional turbulence distribution given mean wind speed was used to greatly simplify the calculation of the long-term probability distribution. Predicted extreme loads using this simplified distribution were equal to or more conservative than the loads predicted by the full integration method.
8
Driessen, Tom, Lokin Prasad, Pavlo Bazilinskyy, and Joost De Winter. "Identifying Lane Changes Automatically using the GPS Sensors of Portable Devices." In 13th International Conference on Applied Human Factors and Ergonomics (AHFE 2022). AHFE International, 2022. http://dx.doi.org/10.54941/ahfe1002433.
Анотація:
Mobile applications that provide GPS-based route navigation advice or driver diagnostics are gaining popularity. However, these applications currently do not have knowledge of whether the driver is performing a lane change. Having such information may prove valuable to individual drivers (e.g., to provide more specific navigation instructions) or road authorities (e.g., knowledge of lane change hotspots may inform road design). The present study aimed to assess the accuracy of lane change recognition algorithms that rely solely on mobile GPS sensor input. Three trips on Dutch highways, totaling 158 km of driving, were performed while carrying two smartphones (Huawei P20, Samsung Galaxy S9), a GPS-equipped GoPro Max, and a USB GPS receiver (GlobalSat BU343-s4). The timestamps of all 215 lane changes were manually extracted from the forward-facing GoPro camera footage, and used as ground truth. After connecting the GPS trajectories to the road using Mapbox Map Matching API (2022), lane changes were identified based on the exceedance of a lateral translation threshold in set time windows. Different thresholds and window sizes were tested for their ability to discriminate between a pool of lane change segments and an equally-sized pool of no-lane-change segments. The overall accuracy of the lane-change classification was found to be 90%. The method appears promising for highway engineering and traffic behavior research that use floating car data, but there may be limited applicability to real-time advisory systems due to the occasional occurrence of false positives.
9
Reid, Stuart, and Arvid Naess. "Influence on Structural Reliability of Uncertain Extreme Value Estimates." In ASME 2017 36th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/omae2017-62709.
Анотація:
Loads for the purpose of structural design are often based on estimated extreme values of time-varying loads based on limited amounts of data. Uncertainty in the estimation of the design loads inevitably leads to uncertainty in the resultant levels of structural reliability. In this paper, uncertainty is assessed for estimates of extreme wind loads calculated using statistical methods based on the average conditional exceedance rate (ACER), fitting of a Gumbel distribution and Peaks-Over-Threshold (POT). The ACER method gave the best results, but all the methods gave results which would normally be considered to be sufficiently accurate for engineering applications. However, for structures designed on the basis of the estimated values of V100 or V500, the uncertainty in the estimated design loads produced very uncertain probabilities of failure with a significant increase in their expected value. It is concluded that the uncertain distribution of the probabilities of failure must be taken into account when evaluating structural safety and a ‘fiducial confidence function’ is proposed for this purpose.
10
Harper, William V., David J. Stucki, Thomas A. Bubenik, Clifford J. Maier, David A. R. Shanks, and Neil A. Bates. "Improved Comparison of ILI Data and Field Excavations." In 2012 9th International Pipeline Conference. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/ipc2012-90440.
Анотація:
The importance of comparing in-line inspection (ILI) calls to excavation data should not be underestimated. Neither should it be undertaken without a solid understanding of the methodologies being employed. Such a comparison is not only a key part of assessing how well the tool performed, but also for an API 1163 evaluation and any subsequent use of the ILI data. The development of unity (1-1) plots and the associated regression analysis are commonly used to provide the basis for predicting the likelihood of leaks or failures from unexcavated ILI calls. Combining such analysis with statistically active corrosion methods into perhaps a probability of exceedance (POE) study helps develop an integrity maintenance plan for the years ahead. The theoretical underpinnings of standard regression analysis are based on the assumption that the independent variable (often thought of as x) is measured without error as a design variable. The dependent variable (often labeled y) is modeled as having uncertainty or error. Pipeline companies may run their regressions differently, but ILI to field excavation regressions often use the ILI depth as the x variable and field depth as the y variable. This is especially the case in which a probability of exceedance analysis is desired involving transforming ILI calls to predicted depths for a comparison to a threshold of interest such as 80% wall thickness. However, in ILI to field depth regressions, both the measured depths can have error. Thus, the underlying least squares regression assumptions are violated. Often one common result is a regression line that has a slope much less than the ideal 1-1 relationship. Reduced Major Axis (RMA) Regression is specifically formulated to handle errors in both the x and y variables. It is not commonly found in the standard literature but has a long pedigree including the 1995 text book Biometry by Sokal and Rohlf in which it appears under the title of Model II regression. In this paper we demonstrate the potential improvements brought about by RMA regression. Building on a solid comparison between ILI data and excavations provides the foundation for more accurate predictions and management plans that reliably provide longer range planning. This may also result in cost savings as the time between ILI runs might be lengthened due to a better analysis of such important data.