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"Maxima"
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Toward a New Flood Assessment Paradigm: From Exceedance Probabilities to the Expected Maximum Floods and Damages
To assess flood risks, we seek to estimate the probability distribution of the worst possible single‐event over a contiguous period of N years rather than the cumulative losses expected over a planning horizon. For this we use the probability distribution FN of extreme flood events over a multi‐year period, which is different from using the conventional single‐valued exceedance probability of 1/N years. FN can be used to estimate the hazard and then proceed to the estimation of risk, which we define as the “largest expected damage” over the set period. It also allows for a more coherent determination of design values, which descend from fully acknowledging the aleatoric uncertainty of the underlying natural river flow process. The epistemic uncertainty is removed by marginalizing the aleatoric‐epistemic uncertainty joint distribution over the parameter space. The advantage of the proposed Bayesian approach, which can be summarized in 12 steps, is demonstrated for the 2021 River Ahr flood in Germany, which caused casualties and huge material damage. Adopting the multi‐year maxima extreme value distribution can potentially lead to the reclassification of vulnerability levels for flood‐prone areas and reconsideration of current policy‐making and flood risk communication. Plain Language Summary To assess risks from extreme flood events, we seek to estimate the probability distribution of the worst possible single‐event over a contiguous period of for example, N = 100 or more year years and the cumulative losses expected over the planning horizon for a hydraulic protection measure. For this we use the probability distribution of extreme flood events over a multi‐year period, which is different from using the conventional single‐valued exceedance probability of 1/N years. This distribution can be used to estimate the “largest expected damage” over the entire planning horizon. It also allows for a more coherent determination of design values, which we obtain from fully acknowledging the climatological (and not epistemic) uncertainty of extreme flow events. The advantage of the proposed approach is demonstrated for the 2021 River Ahr flood in Germany, which caused casualties and huge material damage. Using the multi‐year maxima extreme value distribution instead of return periods should lead to a more consistent classification of vulnerability levels for flood‐prone areas and to reconsideration of current policy‐making and flood risk communication. Key Points Approach examines probability distribution of largest flood during a multi‐year planning horizon Yields different estimates of maximum flood in a multi‐year period than exceedance probabilities Bayesian inference enables consideration of both aleatory and epistemic uncertainties Expected maximum damages can be computed using expected maximum flood New assessment approach demonstrated through case study in Germany
Journal Article
Advanced Variable Step Size Incremental Conductance MPPT for a Standalone PV System Utilizing a GA-Tuned PID Controller
In this article, a novel maximum power point tracking (MPPT) controller for the fast-changing irradiance of photovoltaic (PV) systems is introduced. Our technique utilizes a modified incremental conductance (IC) algorithm for the efficient and fast tracking of MPP. The proposed system has a simple implementation, fast tracking, and achieved steady-state oscillation. Traditional MPPT techniques use a tradeoff between steady-state and transition-state parameters. The shortfalls of various techniques are studied. A comprehensive comparative study is done to test various existing techniques against the proposed technique. The common parameters discussed in this study are fast convergence, efficiency, and reduced oscillations. The proposed method successfully addresses these issues and improves the results significantly by using a proportional integral deferential (PID) controller with a genetic algorithm (GA) to predict the variable step size of the IC-based MPPT technique. The system is designed and tested against the perturbation and observation (P&O)-based MPPT technique. Our technique effectively detects global maxima (GM) for fast-changing irradiance due to the adopted GA-based tuning of the controller. A comparative analysis of the results proves the superior performance and capabilities to track GM in fewer iterations.
Journal Article
Calibration of seawater temperature and delta super(18)O sub(seawater) signals in Tridacna maxima's delta super(18)O sub(shell) record based on in situ data
The giant clam Tridacna maxima presents a strong potential for paleoclimatic reconstructions but its use remains limited by the fact that the relationship between the shell stable oxygen isotopes ratio ( delta super(18)O sub(shell)), the sea surface temperature (SST), and the stable oxygen isotopes ratio of seawater ( delta super(18)O sub(sw)) has not been calibrated yet. In this study, a T. maxima specimen was stained with calcein and grown in a tank for 1.5 yr. The tank seawater was monitored weekly for sea surface salinity, and the stable oxygen isotopes ratio of seawater ( delta super(18)O sub(sw)) and SST was recorded hourly. Microscopic observations of outer shell layer thin sections revealed micrometric, simple and complex, growth increments. The staining experiment demonstrated that these growth increments were deposited on a daily basis. The weekly delta super(18)O sub(shell) record showed that the shell was precipitated in isotopic equilibrium with seawater and that 63 % of the ( delta super(18)O sub(shell) - delta super(18)O sub(sw)) variations were explained by SST variations. A conventional linear function (1) linking T. maxima high-resolution delta super(18)O sub(shell) record, in situ delta super(18)O sub(sw), and SST data was calculated as where SST is in degree Celsius and Delta delta super(18)O is the difference between the stable oxygen isotopes ratio of the shell and of the seawater ( delta super(18)O sub(shell) - delta super(18)O sub(sw)), in ppt VPDB. The root mean square error of the SST reconstructed by this equation is plus or minus 1.41 degree C revealing the potential of T. maxima for paleoclimatic studies. An average SST = f( delta super(18)O sub(shell) - delta super(18)O sub(sw)) equation for giant clam is proposed by compiling the equations from the present study and previous works.This equation permits one to obtain SST records from isotopic values of giant clams species that have not been calibrated yet or from fossil giant species that do not have living modern conspecifics.
Journal Article
Covering Dimension of C-Algebras and 2-Coloured Classification
The authors introduce the concept of finitely coloured equivalence for unital ^*-homomorphisms between \\mathrm C^*-algebras, for which unitary equivalence is the 1-coloured case. They use this notion to classify ^*-homomorphisms from separable, unital, nuclear \\mathrm C^*-algebras into ultrapowers of simple, unital, nuclear, \\mathcal Z-stable \\mathrm C^*-algebras with compact extremal trace space up to 2-coloured equivalence by their behaviour on traces; this is based on a 1-coloured classification theorem for certain order zero maps, also in terms of tracial data. As an application the authors calculate the nuclear dimension of non-AF, simple, separable, unital, nuclear, \\mathcal Z-stable \\mathrm C^*-algebras with compact extremal trace space: it is 1. In the case that the extremal trace space also has finite topological covering dimension, this confirms the remaining open implication of the Toms-Winter conjecture. Inspired by homotopy-rigidity theorems in geometry and topology, the authors derive a \"homotopy equivalence implies isomorphism\" result for large classes of \\mathrm C^*-algebras with finite nuclear dimension.
eBook
Global urban population exposure to extreme heat
Increased exposure to extreme heat from both climate change and the urban heat island effect—total urban warming—threatens the sustainability of rapidly growing urban settlements worldwide. Extreme heat exposure is highly unequal and severely impacts the urban poor. While previous studies have quantified global exposure to extreme heat, the lack of a globally accurate, fine-resolution temporal analysis of urban exposure crucially limits our ability to deploy adaptations. Here, we estimate daily urban population exposure to extreme heat for 13,115 urban settlements from 1983 to 2016. We harmonize global, fine-resolution (0.05°), daily temperature maxima and relative humidity estimates with geolocated and longitudinal global urban population data. We measure the average annual rate of increase in exposure (person-days/year−1) at the global, regional, national, and municipality levels, separating the contribution to exposure trajectories from urban population growth versus total urban warming. Using a daily maximum wet bulb globe temperature threshold of 30 °C, global exposure increased nearly 200% from 1983 to 2016. Total urban warming elevated the annual increase in exposure by 52% compared to urban population growth alone. Exposure trajectories increased for 46% of urban settlements, which together in 2016 comprised 23% of the planet’s population (1.7 billion people). However, how total urban warming and population growth drove exposure trajectories is spatially heterogeneous. This study reinforces the importance of employing multiple extreme heat exposure metrics to identify local patterns and compare exposure trends across geographies. Our results suggest that previous research underestimates extreme heat exposure, highlighting the urgency for targeted adaptations and early warning systems to reduce harm from urban extreme heat exposure.
Journal Article
BEYOND GAUSSIAN APPROXIMATION
The Bonferroni adjustment, or the union bound, is commonly used to study rate optimality properties of statistical methods in high-dimensional problems. However, in practice, the Bonferroni adjustment is overly conservative. The extreme value theory has been proven to provide more accurate multiplicity adjustments in a number of settings, but only on an ad hoc basis. Recently, Gaussian approximation has been used to justify bootstrap adjustments in large scale simultaneous inference in some general settings when n ≫ (log p)⁷, where p is the multiplicity of the inference problem and n is the sample size. The thrust of this theory is the validity of the Gaussian approximation for maxima of sums of independent random vectors in high dimension. In this paper, we reduce the sample size requirement to n ≫ (log p)⁵ for the consistency of the empirical bootstrap and the multiplier/wild bootstrap in the Kolmogorov–Smirnov distance, possibly in the regime where the Gaussian approximation is not available. New comparison and anticoncentration theorems, which are of considerable interest in and of themselves, are developed as existing ones interweaved with Gaussian approximation are no longer applicable or strong enough to produce desired results.
Journal Article
An Efficient Algorithm for Automatic Peak Detection in Noisy Periodic and Quasi-Periodic Signals
We present a new method for automatic detection of peaks in noisy periodic and quasi-periodic signals. The new method, called automatic multiscale-based peak detection (AMPD), is based on the calculation and analysis of the local maxima scalogram, a matrix comprising the scale-dependent occurrences of local maxima. The usefulness of the proposed method is shown by applying the AMPD algorithm to simulated and real-world signals.
Journal Article
Comparison Between Maximum Annual and Peak Over Threshold Methods for the Determination of Extreme Waves in Moroccan Atlantic Coast
In this article, we present a study that focuses on forecasting the one hundred-years return period waves height using two methods; i) Peak Over Threshold (POT) and ii) Annual Maxima (MA). The analysis is carried out at three points at the Atlantic coast of northern Morocco. The results obtained by these two methods indicate a difference of less than 10 % and have shown that to ensure safe dimensioning of maritime structures, the application of the two statistical methods is necessary. This is explained by the drawbacks encountered in both methods. In the MA method, the inconvenience is linked to the choice of non-extreme events when no significant storm is recorded during one year, furthermore, the non-consideration of important events recorded in other year. In the second method (POT), the difficulty consists in the uncertainty of the calculations by the POT method due to the mistrust associated with the choice of the censoring threshold.
Journal Article
Effect of Ecklonia maxima seaweed extract on yield, mineral composition, gas exchange, and leaf anatomy of zucchini squash grown under saline conditions
The presence of NaCl in soil or water is one of the most critical environmental stresses limiting crop productivity worldwide. Seaweed extract (SWE) represents an important category of plant biostimulants able to improve crop tolerance to abiotic stresses, such as salinity. The current research aimed at elucidating the physiological and anatomical effects as well as the changes in mineral composition of greenhouse zucchini squash (
Cucurbita pepo
L.) treated with
Ecklonia maxima
SWE. Plants were sprayed every 2 weeks with a solution containing 3 mL L
−1
of SWE. Zucchini squash plants were supplied with four nutrient solutions: 1 (non-salt control), 20, 40, or 60 mM NaCl. Increased salinity in the nutrient solution triggered a decrease in marketable yield, shoot biomass, Soil Plant Analysis Development (SPAD) index, net CO
2
assimilation rate (
A
CO2
), transpiration rate (
E
), and leaf macronutrient concentration (P, K, Ca, and Mg), whereas it augmented Na and Cl concentrations in leaf tissue without altering PSII photochemistry. Anatomical changes in leaves, including an increase in lamina, palisade, spongy parenchyma thickness, and intercellular spaces, were recorded under saline conditions. Foliar application of SWE increased yield and shoot biomass by 12.0 and 17.4 %, respectively, as well as fruit dry matter and total soluble solid contents in comparison to untreated plants. This was associated with an improvement in
A
CO2
(+14 %), chlorophyll content (+8 %), and nutritional status (high K and low Na accumulation) in SWE-treated plants. The size of stomata was influenced by foliar application of SWE, since the smallest cell guard length and width were recorded in the leaves of SWE-treated plants. Finally, the phenolic compounds in both palisade and spongy parenchyma were higher in untreated than in SWE-treated plants.
Journal Article