scholarly journals The impact of run-of-river dams on sediment longitudinal connectivity and downstream channel equilibrium

Geomorphology ◽  
2021 ◽  
Vol 376 ◽  
pp. 107568
Author(s):  
Francis J. Magilligan ◽  
Maura O. Roberts ◽  
Mackenzie Marti ◽  
Carl E. Renshaw
Keyword(s):  
Longitudinal Connectivity ◽  
The Impact ◽  
Run Of River

scholarly journals Desilting Basin Efficiency Estimation for Run-of-River Small Hydropower Plants

2019 ◽  
Vol 8 (4) ◽  
pp. 6389-6394
Keyword(s):  
Suspended Sediment ◽  
Suspended Sediment Concentration ◽  
Probabilistic Approach ◽  
Sediment Concentration ◽  
Operational Reliability ◽  
Maintenance Cost ◽  
Mathematical Function ◽  
Small Hydropower ◽  
The Impact ◽  
Run Of River

Suspended sediment concentration and discharge are important factors affecting the operational reliability of run-of-river small hydro power (SHP) plants. Elimination of sediment transported with the flow across the turbines of run-of-river plants is therefore a critical issue for the sustainability of the SHP industry. Comprise of a small diversion weir throughout a stream, the SHP plants does not have space to pile sediments but should be able to divert the incoming bed loads to the river downstream. Sediments in the water entering through the turbines with extreme velocity erode the contact surfaces of turbine mechanisms which results in reduced hydraulic efficiency and increased maintenance cost. Subsequently, desilting basins have become an essential part of the water conductor system of run-of-river SHP to reduce the impact of damage due to suspended sediment. Desilting basins are devised as settling basins to settle sediments larger than a targeted size. They are constructed just after power intake and discharge is despatched through them before pass into the head race tunnel. This study is aimed to estimate the sediment removal efficiency of SHP desilting basins based on data recorded at the intake of a run-of-river SHP. Considering the hydrological variability, probabilistic approach was used to obtain mathematical function for the probability density of suspended sediment concentration (SSC) based on the recorded data.

scholarly journals The Effects of Hydropower Plants on the Physicochemical Parameters of the Bystrzyca River in Poland

Energies ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 2075
Author(s):  
Paweł Tomczyk ◽  
Mirosław Wiatkowski
Keyword(s):  
Physicochemical Parameters ◽  
Renewable Energy Sources ◽  
Cumulative Effect ◽  
Ammonium Nitrogen ◽  
The European Union ◽  
Environmental Impact Assessments ◽  
Hydropower Plants ◽  
Odra River ◽  
The Impact ◽  
Run Of River

Currently, the literature lacks comprehensive studies on the impact of hydropower plants (HPs) on the environment, including studies focused on the physicochemical parameters of water. The aim of the article is to verify the current state of knowledge on the impact of run-of-river HPs on 17 physicochemical parameters of water. The article is in line with the recommendations of the European Union that the member states, under the common energy policy, should increase the share of renewable energy sources in the energy and perform environmental impact assessments of such facilities. As a result of the analysis carried out on three HPs (Sadowice, Skałka and Marszowice) located on the Bystrzyca River (a tributary of the Odra River in Poland), it was found that HPs affect the selected physicochemical parameters of the water, i.e., (p < 0.05): electrolytic conductivity (EC; Skałka, Marszowice HPs), pH (Skałka, Marszowice HPs); nitrate nitrogen (NO3-N; Marszowice HP), dissolved oxygen (DO; Marszowice HP) and ammonium nitrogen (NH4-N; Marszowice HP). The largest (>5%), statistically significant mean cumulative effect below Marszowice HP concerned NH4-N (−27.83%), DO (+14.04%) and NO3-N (+5.50%). In addition, it was observed that the effect of HPs increases in direct proportion to the damming height, and that run-of-river HPs have a lesser impact on the physicochemical parameters’ values than in storage HPs. Our results were in accordance with those of other scientists in terms of the increase in DO, the decrease in EC, and the decrease in total phosphorus concentrations below HPs.

scholarly journals Analyzing the Applicability of Random Forest-Based Models for the Forecast of Run-of-River Hydropower Generation

2021 ◽  
Vol 3 (4) ◽  
pp. 858-880
Author(s):  
Valentina Sessa ◽  
Edi Assoumou ◽  
Mireille Bossy ◽  
Sofia G. Simões
Keyword(s):  
Machine Learning ◽  
Time Series ◽  
Random Forest ◽  
Power Systems ◽  
Machine Learning Techniques ◽  
Climate Variables ◽  
Climate Data ◽  
Hydropower Generation ◽  
The Impact ◽  
Run Of River

Analyzing the impact of climate variables into the operational planning processes is essential for the robust implementation of a sustainable power system. This paper deals with the modeling of the run-of-river hydropower production based on climate variables on the European scale. A better understanding of future run-of-river generation patterns has important implications for power systems with increasing shares of solar and wind power. Run-of-river plants are less intermittent than solar or wind but also less dispatchable than dams with storage capacity. However, translating time series of climate data (precipitation and air temperature) into time series of run-of-river-based hydropower generation is not an easy task as it is necessary to capture the complex relationship between the availability of water and the generation of electricity. This task is also more complex when performed for a large interconnected area. In this work, a model is built for several European countries by using machine learning techniques. In particular, we compare the accuracy of models based on the Random Forest algorithm and show that a more accurate model is obtained when a finer spatial resolution of climate data is introduced. We then discuss the practical applicability of a machine learning model for the medium term forecasts and show that some very context specific but influential events are hard to capture.

Formation of Lunar Craters and Bright Rays as a Result of Meteorite Impacts

1962 ◽  
Vol 14 ◽  
pp. 415-418
Author(s):  
K. P. Stanyukovich ◽  
V. A. Bronshten
Keyword(s):  
Explosive Charge ◽  
The Moon ◽  
Meteorite Impacts ◽  
The Earth ◽  
Lunar Craters ◽  
The Impact

The phenomena accompanying the impact of large meteorites on the surface of the Moon or of the Earth can be examined on the basis of the theory of explosive phenomena if we assume that, instead of an exploding meteorite moving inside the rock, we have an explosive charge (equivalent in energy), situated at a certain distance under the surface.

The Geosciences Applied to Lunar Exploration

1962 ◽  
Vol 14 ◽  
pp. 169-257 ◽  
Author(s):  
J. Green
Keyword(s):  
Lunar Surface ◽  
Probable Mechanism ◽  
Point Of View ◽  
Lunar Exploration ◽  
Geological Model ◽  
Apply Geophysics ◽  
Surface Features ◽  
The Impact

The term geo-sciences has been used here to include the disciplines geology, geophysics and geochemistry. However, in order to apply geophysics and geochemistry effectively one must begin with a geological model. Therefore, the science of geology should be used as the basis for lunar exploration. From an astronomical point of view, a lunar terrain heavily impacted with meteors appears the more reasonable; although from a geological standpoint, volcanism seems the more probable mechanism. A surface liberally marked with volcanic features has been advocated by such geologists as Bülow, Dana, Suess, von Wolff, Shaler, Spurr, and Kuno. In this paper, both the impact and volcanic hypotheses are considered in the application of the geo-sciences to manned lunar exploration. However, more emphasis is placed on the volcanic, or more correctly the defluidization, hypothesis to account for lunar surface features.

Asteroid and Comet Impact Speeds upon Mars: Significance for Panspermia and the Supply of Organics

1997 ◽  
Vol 161 ◽  
pp. 197-201 ◽  
Author(s):  
Duncan Steel
Keyword(s):  
Probability Distributions ◽  
Regions Of Interest ◽  
Significant Fraction ◽  
Organic Chemicals ◽  
Impact Speed ◽  
The Mean ◽  
The Impact

AbstractWhilst lithopanspermia depends upon massive impacts occurring at a speed above some limit, the intact delivery of organic chemicals or other volatiles to a planet requires the impact speed to be below some other limit such that a significant fraction of that material escapes destruction. Thus the two opposite ends of the impact speed distributions are the regions of interest in the bioastronomical context, whereas much modelling work on impacts delivers, or makes use of, only the mean speed. Here the probability distributions of impact speeds upon Mars are calculated for (i) the orbital distribution of known asteroids; and (ii) the expected distribution of near-parabolic cometary orbits. It is found that cometary impacts are far more likely to eject rocks from Mars (over 99 percent of the cometary impacts are at speeds above 20 km/sec, but at most 5 percent of the asteroidal impacts); paradoxically, the objects impacting at speeds low enough to make organic/volatile survival possible (the asteroids) are those which are depleted in such species.

Organic Syntheses During the Impact of a Comet with a Gaseous Planet

1997 ◽  
Vol 161 ◽  
pp. 189-195
Author(s):  
Cesare Guaita ◽  
Roberto Crippa ◽  
Federico Manzini
Keyword(s):  
Polymeric Material ◽  
Molecular Form ◽  
Parent Compound ◽  
Blue Filter ◽  
Organic Syntheses ◽  
The Impact

AbstractA large amount of CO has been detected above many SL9/Jupiter impacts. This gas was never detected before the collision. So, in our opinion, CO was released from a parent compound during the collision. We identify this compound as POM (polyoxymethylene), a formaldehyde (HCHO) polymer that, when suddenly heated, reformes monomeric HCHO. At temperatures higher than 1200°K HCHO cannot exist in molecular form and the most probable result of its decomposition is the formation of CO. At lower temperatures, HCHO can react with NH3 and/or HCN to form high UV-absorbing polymeric material. In our opinion, this kind of material has also to be taken in to account to explain the complex evolution of some SL9 impacts that we observed in CCD images taken with a blue filter.

Hydrogen Cyanide Polymers from the Impact of Comet P/Shoemaker-Levy 9 on Jupiter

1997 ◽  
Vol 161 ◽  
pp. 179-187
Author(s):  
Clifford N. Matthews ◽  
Rose A. Pesce-Rodriguez ◽  
Shirley A. Liebman
Keyword(s):  
Amino Acids ◽  
Solar System ◽  
Hydrogen Cyanide ◽  
Nitrogen Heterocycles ◽  
Laboratory Studies ◽  
Heterogeneous Solids ◽  
The Many ◽  
Comet Halley ◽  
The Impact ◽  
By Products

AbstractHydrogen cyanide polymers – heterogeneous solids ranging in color from yellow to orange to brown to black – may be among the organic macromolecules most readily formed within the Solar System. The non-volatile black crust of comet Halley, for example, as well as the extensive orangebrown streaks in the atmosphere of Jupiter, might consist largely of such polymers synthesized from HCN formed by photolysis of methane and ammonia, the color observed depending on the concentration of HCN involved. Laboratory studies of these ubiquitous compounds point to the presence of polyamidine structures synthesized directly from hydrogen cyanide. These would be converted by water to polypeptides which can be further hydrolyzed to α-amino acids. Black polymers and multimers with conjugated ladder structures derived from HCN could also be formed and might well be the source of the many nitrogen heterocycles, adenine included, observed after pyrolysis. The dark brown color arising from the impacts of comet P/Shoemaker-Levy 9 on Jupiter might therefore be mainly caused by the presence of HCN polymers, whether originally present, deposited by the impactor or synthesized directly from HCN. Spectroscopic detection of these predicted macromolecules and their hydrolytic and pyrolytic by-products would strengthen significantly the hypothesis that cyanide polymerization is a preferred pathway for prebiotic and extraterrestrial chemistry.

Unusual Microstructure in Shock-Compacted Graphite

1970 ◽  
Vol 28 ◽  
pp. 474-475
Author(s):  
Lucien F. Trueb
Keyword(s):  
Mechanical Characteristic ◽  
Compression Wave ◽  
Gray Zone ◽  
Flyer Plate ◽  
Compacted Graphite ◽  
The Impact

Crushed and statically compressed Madagascar graphite that was explosively shocked at 425 kb by means of a planar flyer-plate is characterized by a black zone extending for 2 to 3 nun below the impact plane of the driver. Beyond this point, the material assumes the normal gray color of graphite. The thickness of the black zone is identical with the distance taken by the relaxation wave to overtake the compression wave.The main mechanical characteristic of the black material is its great hardness; steel scalpels and razor blades are readily blunted during attempts to cut it. An average microhardness value of 95-3 DPHN was obtained with a 10 kg load. This figure is a minimum because the indentations were usually cracked; 14.8 DPHN was measured in the gray zone.

Drug Induced Changes in Cell Organelles

1968 ◽  
Vol 26 ◽  
pp. 110-111
Author(s):  
Sarah A. Luse
Keyword(s):  
Clinical Medicine ◽  
Cell Organelles ◽  
Riboflavin Deficiency ◽  
Drug Induced ◽  
New Era ◽  
Health And Disease ◽  
In The Beginning ◽  
Cellular Pathology ◽  
Induced Changes ◽  
The Impact

In the mid-nineteenth century Virchow revolutionized pathology by introduction of the concept of “cellular pathology”. Today, a century later, this term has increasing significance in health and disease. We now are in the beginning of a new era in pathology, one which might well be termed “organelle pathology” or “subcellular pathology”. The impact of lysosomal diseases on clinical medicine exemplifies this role of pathology of organelles in elucidation of disease today.Another aspect of cell organelles of prime importance is their pathologic alteration by drugs, toxins, hormones and malnutrition. The sensitivity of cell organelles to minute alterations in their environment offers an accurate evaluation of the site of action of drugs in the study of both function and toxicity. Examples of mitochondrial lesions include the effect of DDD on the adrenal cortex, riboflavin deficiency on liver cells, elevated blood ammonia on the neuron and some 8-aminoquinolines on myocardium.

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