International Commission on Irrigation & Drainage Commission Interationale des Irrigation et du Drainage

Multilingual Technical Dictionary (MTD)
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Term No.Term Name/Term DescriptionAction
23
Average error
The mean of all the errors taken without regard to sign.
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82
Curve fitting
1 - The fitting of a mathematical curve to any statistical data, e.g. regression data or time series. 2 - The fitting of a mathematically specified frequency curve to a frequency distribution observed......
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106
Average sample number
The average number of sample units inspected per lot in reaching a decision to accept or reject. It is dependent on the actual quality level of the lot in question......
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107
Consecutive average, Moving average, or Consecutive mean
The mean of a small group of consecutive values, especially annual means, assigned to the middle time-term of the group in the process of smoothing, e.g. 5-year mean......
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113
Weighted average, or Weighted mean
An average of quantities that attaches a series of weights to it in order to make proper allowance for their relative importance. A value obtained by multiplying each of a series of values by its assigned weight and dividing the sum of those products by the sum of the weights. For example, a weighted arithmetic mean of x1, x2 ... xn with weights w1.....
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117
Average deviation, or Mean deviation
A measure of dispersion derived from the average deviation of observations from some central value, such deviations being absolute, i.e. without reference to algebric sign......
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134
Standardized averages, or Standardized means
A method of allowing or `adjusting` the effects of other variables, or for differences in the composition of the groups that are to be compared, by using a standard set of weights to combine the means of sub-groups into a single mean. Used mainly for the construction of index numbers......
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198
Maximum likelihood method
The method of estimating a parameter (or parameters) of a population by that value (or values) which maximizes (or maximize) the likelihood of a sample......
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243
Least square method
A method of determining the arbitrary constants in the equation of a curve, based upon the principle that the most probable value of a quantity to be deduced from a set of measurements is obtained by making the sum of the squares of the residual (deviations from it) a minimum......
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255
Goodness of fit
The goodness of agreement between an observed set of values and a second set of values which are derived wholly or partly on a hypothetical basis, that is to say, derived from the fitting of a model to the data. The excellence of fit is often measured by some criterion depending on the squares of the differences between observed and theoretical val.....
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265
Freehand method
A method of describing the relationship in a series of data, ordered in time or space, whereby the general trend is estimated by drawing a line freehand through or near the series of plotted observations. Hence `freehand fit`......
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266
Freehand fit
The fit or trend, obtained from the `freehand method`.
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267
Semi-average fit
When a straight line trend appears to fit the data well, the data may be divided into two equal parts and arithmetic means calculated for the first and second half, plotted and joined by a straight line which gives the `semi-average fit`. It is more objective than the freehand method, but because of its reliance on arithmetic means, it can be undul.....
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268
Moving average method of fit
The averaging at the central year of a series of overlapping means to smooth out, or damp down, undue high and low, short-term values. Hence, the `moving average fit`. (See also 279)......
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269
Least square fit
A straight or curvilinear trend to give the mean of the squared vertical deviations as minimum. See 244.
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279
Moving average
If a time series is x1,x2,...xn , and these are chosen set of weight
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1101
Average velocity (of groundwater)
The volume of groundwater passing through a unit cross-sectional area in unit time divided by the porosity of the water transmitting material......
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1171
Cloud-velocity gauging, Allen`s method of velocity gauging, Colour-velocity gauging
A method of determining the velocity of a slug of dye between two stations in the channel. This velocity, assumed to be the mean velocity of flow, multiplied by the cross-sectional area of the channel, gives the discharge. `Allen`s method` and `colour-velocity method` are different forms of cloud-velocity gauging......
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1199
Mean depth, or Average depth
The cross-sectional area of a stream channel or conduit divided by the surface width.
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1212
Mean velocity, Average velocity, Overall mean velocity
The velocity at a given section or reach of a stream obtained by dividing the discharge of the stream by the cross-sectional area at that section. .....
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1232
Integration method of velocity measurement
A means of determining the mean velocity at a vertical depth of a stream by noting the total number of revolutions of a current meter vane and the time consumed, while the meter is slowly lowered from the surface to the bed and returned one or more times......
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2062
Warping, or Commutation method
A process of allowing the tide to overflow low lying lands so as to deposit thereon the silt which it carries in suspension......
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2284
Method of independent variables, or Khosla`s method of determination of uplift pressures and exit gradients
It is an empirical method evolved by an Indian Engineer A N Khosla for determining uplift pressures with high accuracy for a weir founded on permeable soils. The complex foundation profile is broken up into a number of simple profiles, each of which is independently amenable to mathematical treatment......
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2566
Gravity method (two-dimensional method of analysis)
A method for stress analysis of gravity dams assuming the structure of the dam to be composed of vertical cantilever elements that act independently of each other while the vertical stress varies linearly......
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2567
Slab analogy method
A two-dimensional method of studying the non-linear distribution of stresses in a dam by considering the analogy between the stresses in a two-dimensional elastic body and the deflections of an unloaded slab of the same shape bent by forces and couples applied round its edges......
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