scholarly journals Disaggregation of fixed time interval rainfall to continuous measured rainfall for the purpose of design rainfall estimation

Water SA ◽  
2018 ◽  
Vol 44 (4 October) ◽  
Author(s):  
OJ Gericke ◽  
JPJ Pietersen
Keyword(s):  
South Africa ◽  
Fixed Time ◽  
Estimation Methods ◽  
Time Interval ◽  
Rainfall Estimation ◽  
Fixed Time Interval ◽  
Design Rainfall ◽  
Thiessen Polygon ◽  
Continuous Measures

Design rainfall estimates are primarily used in single-event deterministic design flood estimation methods where estimates of the peak discharge are based on the critical storm duration or time of concentration (TC) of a catchment. Therefore, daily design rainfall depths used in flood estimations must either be decreased or increased from durations less than or longer than 24 hours to the design rainfall depths for a rainfall duration of TC. This paper presents the comparison of two South African methods used to convert or scale 1-day fixed time interval observed rainfall (08:00 to 08:00) to continuous measures of n-hour rainfall for selected TC durations at a quaternary catchment level, in the C5 secondary drainage region in South Africa as pilot case study. In each quaternary catchment, the annual maximum series (AMS) of the 1-day fixed time interval point rainfall were extracted, infilled, converted and scaled to appropriate continuous measures of TC-hour point rainfall using conversion factors (Adamson, 1981) and scaling factors (Smithers and Schulze, 2003), respectively. Thereafter, all the TC-hour observed point rainfall values were averaged to observed catchment rainfall at a quaternary catchment level using the Thiessen polygon method. In using the two methods to estimate continuous short-duration n-hour (TC ≤ 24 hours) and long-duration n-hour (TC > 24 hours) catchment rainfall from 1-day fixed time interval point rainfall, an acceptable (0.71 < r2 ≤ 0.86) and high (r2 ≥ 0.93) degree of association were achieved, respectively, despite the different approaches used in each method. Overall, the results confirmed that fixed time interval rainfall should be scaled to continuous measures of rainfall using the Smithers-Schulze scale invariance approach for various TC durations in the case study area. In comparison to the Adamson conversion methodology, the Smithers-Schulze scaling methodology is also based on a more extensive and recent rainfall database as incorporated in software for design rainfall estimation in modern flood hydrology practice in South Africa.

scholarly journals Improved bounds for the availability and unavailability in a fixed time interval for systems of maintained, interdependent components

1980 ◽  
Vol 12 (01) ◽  
pp. 200-221 ◽  
Author(s):  
B. Natvig
Keyword(s):  
Lower Bound ◽  
System Reliability ◽  
Nuclear Reactors ◽  
Random Variables ◽  
Fixed Time ◽  
Time Interval ◽  
Coherent System ◽  
Exact Results ◽  
Fixed Time Interval ◽  
Special Case

In this paper we arrive at a series of bounds for the availability and unavailability in the time interval I = [t A , t B ] ⊂ [0, ∞), for a coherent system of maintained, interdependent components. These generalize the minimal cut lower bound for the availability in [0, t] given in Esary and Proschan (1970) and also most bounds for the reliability at time t given in Bodin (1970) and Barlow and Proschan (1975). In the latter special case also some new improved bounds are given. The bounds arrived at are of great interest when trying to predict the performance process of the system. In particular, Lewis et al. (1978) have revealed the great need for adequate tools to treat the dependence between the random variables of interest when considering the safety of nuclear reactors. Satyanarayana and Prabhakar (1978) give a rapid algorithm for computing exact system reliability at time t. This can also be used in cases where some simpler assumptions on the dependence between the components are made. It seems, however, impossible to extend their approach to obtain exact results for the cases treated in the present paper.

A PROPOSED FORMULA FOR HORIZONTAL REVENUE ALLOCATION IN NIGERIA

2012 ◽  
Vol 29 (06) ◽  
pp. 1250033
Author(s):  
VIRTUE U. EKHOSUEHI ◽  
AUGUSTINE A. OSAGIEDE
Keyword(s):  
Optimal Control ◽  
Federal Government ◽  
Optimal Control Theory ◽  
Fixed Time ◽  
Tax Revenue ◽  
Time Interval ◽  
Fixed Time Interval ◽  
Hypothetical Data ◽  
Revenue Allocation ◽  
The Individual

In this study, we have applied optimal control theory to determine the optimum value of tax revenues accruing to a state given the range of budgeted expenditure on enforcing tax laws and awareness creation on the payment of the correct tax. This is achieved by maximizing the state's net tax revenue over a fixed time interval subject to certain constraints. By assuming that the satisfaction derived by the Federal Government of Nigeria on the ability of the individual states to generate tax revenue which is as near as the optimum tax revenue (via the state's control problem) is described by the logarithmic form of the Cobb–Douglas utility function, a formula for horizontal revenue allocation in Nigeria in its raw form is derived. Afterwards, we illustrate the use of the proposed horizontal revenue allocation formula using hypothetical data.

The evolution and measurement of a population of pairs

1995 ◽  
Vol 32 (04) ◽  
pp. 1048-1062 ◽  
Author(s):  
Eric Jakeman ◽  
Sean Phayre ◽  
Eric Renshaw
Keyword(s):  
Fixed Time ◽  
Statistical Properties ◽  
Time Interval ◽  
Fixed Time Interval ◽  
Analytical Results

The statistical properties of a population of immigrant pairs of individuals subject to loss through emigration are calculated. Exact analytical results are obtained which exhibit characteristic even–odd effects. The population is monitored externally by counting the number of emigrants leaving in a fixed time interval. The integrated statistics for this process are evaluated and it is shown that under certain conditions only even numbers of individuals will be observed.

scholarly journals Maximizing the Expected Duration of Owning a Relatively Best Object in a Poisson Process with Rankable Observations

2009 ◽  
Vol 46 (02) ◽  
pp. 402-414
Author(s):  
Aiko Kurushima ◽  
Katsunori Ano
Keyword(s):  
Poisson Process ◽  
Stopping Time ◽  
Fixed Time ◽  
Time Interval ◽  
Prior Density ◽  
Deterministic Equation ◽  
Fixed Time Interval ◽  
Unknown Number ◽  
Random Intensity ◽  
Time Selection

Suppose that an unknown number of objects arrive sequentially according to a Poisson process with random intensity λ on some fixed time interval [0,T]. We assume a gamma prior density G λ(r, 1/a) for λ. Furthermore, we suppose that all arriving objects can be ranked uniquely among all preceding arrivals. Exactly one object can be selected. Our aim is to find a stopping time (selection time) which maximizes the time during which the selected object will stay relatively best. Our main result is the following. It is optimal to select the ith object that is relatively best and arrives at some time s i (r) onwards. The value of s i (r) can be obtained for each r and i as the unique root of a deterministic equation.

The Hering-Breuer reflex in anesthetized infants: end-inspiratory vs. end-expiratory occlusion technique

1998 ◽  
Vol 84 (4) ◽  
pp. 1437-1446 ◽  
Author(s):  
K. Brown ◽  
J. Stocks ◽  
C. Aun ◽  
P. S. Rabbette
Keyword(s):  
Fixed Time ◽  
Inspiratory Effort ◽  
Stretch Receptor ◽  
Time Interval ◽  
Respiratory Drive ◽  
Inspiratory Time ◽  
Lung Inflation ◽  
Fixed Time Interval ◽  
Fixed Proportion ◽  
Occlusion Technique

Both end-inspiratory (EIO) and end-expiratory (EEO) occlusions have been used to measure the strength of the Hering-Breuer inflation reflex (HBIR) in infants. The purpose of this study was to compare both techniques in anesthetized infants. In each infant, HBIR activity was calculated as the relative prolongation of expiratory and inspiratory time during EIO and EEO, respectively. Respiratory drive was assessed from the change in airway pressure during inspiratory effort against the occlusion, both at a fixed time interval of 100 ms (P0.1) and a fixed proportion (10%) of the occluded inspiratory time (P10%). Twenty-two infants [age 14.3 ± 6.4 (SD) mo] were studied. No HBIR activity was present during EIO [−11.8 ± 15.9 (SD) %]. By contrast, there was significant, albeit weak, reflex activity during EEO [HBIR: 27.2 ± 17.4%]. A strong HBIR (up to 310%) was elicited in six of seven infants in whom EIO was repeated after lung inflation. P0.1 was similar during both types of occlusions, whereas mean ± SD P10% was lower during EEO than during EIO: 0.198 ± 0.09 vs. 0.367 ± 0.15 kPa, respectively ( P < 0.01). These data suggest a difference in the central integration of stretch receptor activity in infants during anesthesia compared with during sleep.

Estimated Forest Bird Densities by Variable Distance Point Counts

1985 ◽  
Vol 12 (2) ◽  
pp. 307 ◽  
Author(s):  
GH Pyke ◽  
HF Recher
Keyword(s):  
Fixed Time ◽  
Time Interval ◽  
Point Counts ◽  
Fixed Time Interval ◽  
Area Of Interest ◽  
Bird Density ◽  
Significant Movement ◽  
Stationary Observer ◽  
Variable Distance ◽  
Bird Distribution

During variable distance point counts a stationary observer records the species and distance for all birds detected during a fixed time interval. Such counts, repeated throughout the area of interest, can be used to estimate bird density so long as the following assumptions are made: (1) the distribution of birds is unaffected by the observer; (2) observers are certain of detecting near birds; (3) there is no error in measurement or estimation of distances; and (4) birds are stationary. Data collected during the present study indicated that at least two of these assumptions are not satisfied: estimates of distance based on sound are inaccurate and observers do not always detect near birds. No effect of observer presence on bird distribution was detected nor did there appear to be any significant movement of birds during counts. We recommend that bird counts be based only on sight detections and that, when bird movement is significant, instantaneous counts be used.

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