Low-flow analysis with a conditional Weibull Tail Model

1996 ◽  
Vol 32 (6) ◽  
pp. 1749-1760 ◽  
Author(s):  
S. Rocky Durrans
Keyword(s):  
Flow Analysis ◽  
Low Flow

scholarly journals Frequency Analysis of Low Flows

1985 ◽  
Vol 16 (2) ◽  
pp. 105-128 ◽  
Author(s):  
G. V. Loganathan ◽  
C. Y. Kuo ◽  
T. C. McCormick
Keyword(s):  
Lower Bounds ◽  
Frequency Analysis ◽  
Probability Distributions ◽  
Flow Analysis ◽  
Extreme Value ◽  
Low Flow ◽  
Type Iii ◽  
Low Flows ◽  
Pearson Type

The transformations (i) SMEMAX (ii) Modified SMEMAX (iii) Power and Probability Distributions (iv) Weibull (α,β,γ) or Extreme value type III (v) Weibull (α,β,0) (vi) Log Pearson Type III (vii) Log Boughton are considered for the low flow analysis. Also, different parameter estimating procedures are considered. Both the Weibull and log Pearson can have positive lower bounds and thus their use in fitting low flow probabilities may not be physically justifiable. A new derivation generalizing the SMEMAX transformation is proposed. A new estimator for the log Boughton distribution is presented. It is found that the Boughton distribution with Cunnane's plotting position provides a good fit to low flows for Virginia streams.

scholarly journals Research Trends of Hydrological Drought: A Systematic Review

Water ◽  
2019 ◽  
Vol 11 (11) ◽  
pp. 2252 ◽  
Author(s):  
Hasrul Hazman Hasan ◽  
Siti Fatin Mohd Razali ◽  
Nur Shazwani Muhammad ◽  
Asmadi Ahmad
Keyword(s):  
Systematic Review ◽  
Scientific Evidence ◽  
Flow Analysis ◽  
Hydrological Drought ◽  
Low Flow ◽  
Drought Severity ◽  
Spatial And Temporal Variability ◽  
Drought Vulnerability ◽  
Regional Modelling ◽  
Drought Assessment

The frequency and severity of global drought-induced impacts have led to raising awareness of the need for improved river management. Although academic publications on drought have proliferated, a systematic review of literature has not yet been conducted to identify trends, themes, key topics, and authorships. This study aims to evaluate the scientific evidence for the hydrological drought characteristics and the methodologies by performing as a framework. This systematic review performed three-stage screening of literature review for current applicable hydrological drought studies that have been conducted since the year of 2000 concerning methodologies, literature research gaps, and trends, and contribute to future studies. The analysis shows the increasing trends of research and publications in the hydrological drought assessment. The primary research themes are hydrological drought is drought severity, drought vulnerability, and drought forecast. Despite the current research findings, spatial and temporal variability, low flow analysis and regional modelling are the most important to encourage a holistic approach and international collaborations. The finding identified the shortcomings of most research, which are the use of non-standardized methodological and distinct sample sizes, resulting in data summary challenges and unrealistic comparisons.

New double-tracer digital radiography for analysis of spatial and temporal myocardial flow heterogeneity

2001 ◽  
Vol 280 (1) ◽  
pp. H465-H474 ◽  
Author(s):  
Takeshi Matsumoto ◽  
Hiroyuki Tachibana ◽  
Yasuo Ogasawara ◽  
Fumihiko Kajiya
Keyword(s):  
Digital Radiography ◽  
Flow Analysis ◽  
Flow Distribution ◽  
Low Flow ◽  
Flow Heterogeneity ◽  
S Period ◽  
And Control ◽  
Imaging Plates ◽  
Myocardial Flow ◽  
Microsphere Embolization

A new high-resolution digital radiographic technique based on the deposition of125I- and 3H-labeled desmethylimipramine (IDMI and HDMI, respectively) was developed for the assessment of spatial and temporal myocardial flow heterogeneity at a microvascular level. The density distributions of two tracers, or relative flow distributions, were determined by subtraction digital radiography using two imaging plates of different sensitivity. The regions resolved are comparable in size to vascular regulatory units (400 × 400 μm2). This method was applied to the measurement of within-layer myocardial flow distributions in Langendorff-perfused rabbit hearts. The validity of this method was confirmed by the strong correlation between regional densities of two tracers injected simultaneously ( r = 0.89 ± 0.03, n = 8). The temporal flow stability was evaluated by a 90-s continuous IDMI injection and subsequent bolus HDMI injection ( n = 8). Regional densities of the two tracers were fairly correlated ( r = 0.86 ± 0.03), indicating that the spatial pattern of flow distribution was stable even at a microvascular level over a 90-s period. The effect of microsphere embolization on the flow distribution was also investigated by the sequential injections of IDMI, 15-μm microspheres, and HDMI at 20-s intervals ( n = 8). Microembolization increased the coefficient of variation of tracer density from 19 to 25% ( P < 0.05), whereas the regional densities of two tracers were still correlated substantially, as in the case of no embolization ( r = 0.84 ± 0.06). Thus the microsphere embolization enhanced flow heterogeneity with increasing flow differences between control high-flow and control low-flow regions but rather maintained the pattern of flow distribution. In conclusion, double-tracer digital radiography will be a promising method for the spatial and temporal myocardial flow analysis at microvascular levels.

scholarly journals Low Flow Analysis and Possible Impact of the Mekong River

2012 ◽  
Vol 1 ◽  
pp. 309-317
Author(s):  
Kunatip Raviwan ◽  
Supasit Konyai
Keyword(s):  
Flow Analysis ◽  
Mekong River ◽  
Low Flow

High Pressure Fan Design for Biogas Plants

2009 ◽  
Author(s):  
Philipp Epple ◽  
Mihai Miclea ◽  
Harald Schmidt ◽  
Antonio Delgado ◽  
Hans Russwurm
Keyword(s):  
High Pressure ◽  
High Pressures ◽  
Thermal Power ◽  
Flow Analysis ◽  
Single Stage ◽  
Low Flow ◽  
Operating Point ◽  
Flow Rates ◽  
New Class ◽  
Biogas Plants

High pressure fans for thermal power generation stations, especially biogas plants, usually operate in a spiral casing at high pressures of about p = 12.000–15.000 Pa and low flow rates of around Q = 100–600 m3/s. The motor drive has a constant speed of 3.000 l/min. This corresponds to specific speeds of nq = 3–6 min−1, which is already beyond the conventional range of single stage radial machines. Nowadays these fans for biogas plants usually operate at higher flow rates than specified or are multiple stage radial fans. Therefore a new class of radial impellers has been developed. These single stage impellers have a unique high pressure at a low flow rate operating point. In this work several impellers of this new class have been designed and validated with a commercial Navier-Stokes solver (ANSYS CFX). The design process is described in detail. It is based on a new extended analytical and numerical design method. It is shown that the prescribed unusual operating point can be achieved with single stage radial impellers. An in detail flow analysis is given showing the fundamental flow physics of these impellers.

scholarly journals Comparison of Distribution Methods of Low Flow Analysis for Bandar Segamat, Johor

2015 ◽  
Vol 773-774 ◽  
pp. 1266-1270
Author(s):  
Yuliarahmadila Erfen ◽  
Mohd Shalahuddin Adnan ◽  
Noorfathiah Che Ali ◽  
Nurul Farehah Amat ◽  
Zawani Mohd Zahudi
Keyword(s):  
Stream Flow ◽  
Transition Period ◽  
Monsoon Season ◽  
Flow Analysis ◽  
Gumbel Distribution ◽  
Low Flow ◽  
Flow Data ◽  
Type Iii ◽  
Pearson Type ◽  
Pearson Type Iii Distribution

During the monsoon season, certain areas in Malaysia are experiencing a flood. While during the transition period Malaysia is experiencing a drought. This phenomenon could lead to severe disaster and precaution monitoring is needed to avoid this occurrences. Low flow during the dry season could lead to several negative effects on the river ecosystem. Thus, this study was conducted to determine the low flow frequency and intensity for the Segamat city. The duration for 2 years to 100 years based on the previous 20 years of stream flow data were used to calculated. Stream flow data were obtained from the Department of Irrigation and Drainage (DID). Two prominent distribution analyses methods known as Gumbel Distribution and Log pearson Type III Distribution were applied. The distribution results were validated using Root Mean Square Error (RMSE) and California method and Weibull method are selected. Based on the analyses results, it clearly shows that the distibution of low flow are between 1 m3/s to 10 m3/s. The flow are significantly correlate with the rainfall intensity. RMSE was selected based on the lowest value of 0.721 for the Gumble Distribution and 1.831 for Log Pearson Type III Distribution. Chi-square test shows a good agreement for Gumble Distribution (7.615<12.59) and Log Pearson Type III(5.201<11.07) using 5% significant level. The confident level form both tests are valid (p>0.05), thus, this results could be used for further analyses to alleviate the low flow in the study area.

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