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A return period, also known as a recurrence interval or repeat interval, is an average time or an estimated average time between events such as earthquakes, floods, [1] landslides, [2] or river discharge flows to occur. It is a statistical measurement typically based on historic data over an extended period, and is used usually for risk analysis.
There is a large number of empirical approaches that relate the intensity (I), the duration (t) and the return period (p), from fits to power laws such as: Sherman's formula, [8] with three parameters (a, c and n), which are a function of the return period, p: = (+)
Hudson's equation, also known as Hudson formula, is an equation used by coastal engineers to calculate the minimum size of riprap (armourstone) required to provide satisfactory stability characteristics for rubble structures such as breakwaters under attack from storm wave conditions.
H s = Significant wave height at the toe of the construction Δ = relative density of the stone (= (ρ s-ρ w)/ρ w) where ρ s is the density of the stone and ρ w is the density of the water d n50 = nominal stone diameter α = breakwater slope P = notional permeability S = Damage number N = number of waves in the storm ξ m = the Iribarren ...
After these subspaces are identified, a frequency estimation function is used to find the component frequencies from the noise subspace. The most popular methods of noise subspace based frequency estimation are Pisarenko's method, the multiple signal classification (MUSIC) method, the eigenvector method, and the minimum norm method.
[2] [3] [4] It has an integrated spreadsheet for data input and can import files in several formats (Excel, SPSS, CSV, ...). MedCalc includes basic parametric and non-parametric statistical procedures and graphs such as descriptive statistics , ANOVA , Mann–Whitney test , Wilcoxon test , χ 2 test , correlation , linear as well as non-linear ...
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The formula to calculate surface wave magnitude is: [3] = + (), where A is the maximum particle displacement in surface waves (vector sum of the two horizontal displacements) in μm, T is the corresponding period in s (usually 20 ± 2 seconds), Δ is the epicentral distance in °, and