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Procena koeficijenta opterećenja zagađenjem površinskog oticaja sa ruralnih površina
Get PDFVarious polluting compounds accumulate on rural surfaces. These compounds get washed off the surface during rainy periods and carried by the surface runoff. Concentrations of quality parameters are constantly changing, which is why the assessment of the value of load coefficient represents a significant challenge. This paper presents the detennination of the pollution load coefficient of surface runoff in an experimental rural watershed in southern Serbia. The obtained results and suggestions for improving future research have also been covered
Parametarsko modelovanje srednjevekovnih portala Raških crkava
Get PDFU ovom radu zasnovanom na geometrijskim pravilnostima arhitektonskog dizajna, istražuju se mogućnosti načina kreiranja digitalnih parametarskih modela portala crkava u Raškoj (srednjevekovna teritorija Srbije). U literaturi, ovi portali su prepoznati kao romanički, prema karakterističnom dizajnu i geometriji. Rad je nastavak istraživanja autora na analizama šest izabranih portala, u kontekstu njihovog arhitektonskog dizajna i geometrije. Na osnovu definisanih dimenzionih parametara i geometrije oblika elemenata jednog portala, kreirani su odgovarajući 3D modeli elemenata, kroz nekoliko faza, obradom u različitim programskim paketima. Kroz modelovanje izabranog portala pokazan je postupak koji kombinuje tri programska paketa: AutoCAD, SolidWorks i ArchiCAD. Cilj rada je doprinos u sferi kreiranja digitalnih biblioteka elemenata izabranog tipa portala, u okviru Heritage Building Information Modelling-a (HBIM-informaciono modelovanje istorijskih objekata)
Merenje protoka na prilazima cevnih turbina uz pomoć EM senzora brzine: Hidraulička analiza izmerenih brzina
Get PDFU okviru postupka revitalizacije cevnih agregata na HE Đerdap 2, projektovan je i primenjen inovativni sistem za merenje protoka na turbinama metodom brzina-proticajni presek. Okosnicu sistema čine 15 elektro magnetnih (EM) senzora brzina, horizontalno postavljenih na čelični ram koji se podiže po celom proticajnom preseku. Imajući u vidu da se radi o novorazvijenim merilima brzine, redudantna merenja brzina se vrše preko dva ADV (eng. Acoustic Doppler Velocimeter) merila. U sklopu svakog merenja protoka, odnosno jedne merne sesije, pomoću EM senzora se snimi (mapira) celokupno polje brzina u proticajnom preseku i to za sve tri komponente vektora, dok preko ADV senzora se beleže redudantni podaci o rasporedu sve tri komponente brzine u dve vertikale proticajnog preseka. Koriste se dva režima merenja: inkrementalni, kao primarni, gde se ram podiže u inkrementima i zadržava na izabranim kotama u periodu od minimum 10 minuta, i kontinualni gde se ram podiže konstantnom brzinom po celom proticajnom preseku. Merni sistem je u periodu od 2020-2023 godine primenjen na 6 (od 10) agregata HE Đerdap 2, beležeći protoke pri različitim uslovima rada i koristeći oba režima merenja. U ovom radu se daje poseban osvrt na hidrauličku analizu izmerenog rasporeda brzina u proticajnom preseku. Razmatraju se karakteristike u rasporedu sve tri komponente vektora brzina pri različitim radnim protocima, različitim uslovima rada susednih agregata kao i za različite položaje agregata u sklopu dispozicije HE Đerdap 2.Within the scope of the turbine revitalization process on the HPP Iron Gate 2, an innovative discharge measurement system based on the velocity-area method, was designed and applied. The core of the system is made up from 15 electromagnetic (EM) velocity sensors, horizontally distributed on the steel frame which is traversed across the flow area. As the EM velocity sensors are novel by design, redundant velocity measurements are made with two Acoustic Doppler Velocimeters (ADV). With each discharge measurement, or within each measurement session, EM sensors map the whole velocity field within the flow cross section, for all three velocity components, while ADV sensors capture redundant velocity component measurements in two verticals of the flow area. Two measurement modes were developed: incremental, primary, where the steel frame is traversed in increments and held at chosen depths for a period of at least 10 minutes, and continuous where the steel frame is traversed with constant speed across the whole cross-section. The measurement system was applied on 6 (out of 10) turbines of HPP Iron Gate 2, during the 2020-2023 period, capturing discharges at various operating conditions and by using both measurement modes. In this paper, hydraulic analysis of the measured velocity fields is carried on. Characteristics in the distribution of all three velocity components due to the different discharge values, neighboring turbine operating modes and turbine positions, are discussed
River Flow Monitoring: The Influence of Graphical Enhancement Techniques on Image Velocimetry Performances
No full textImage velocimetry techniques for river flow monitoring have progressively spread due to the advantages of such methods with respect to traditional approaches. Image-based techniques can nonintrusively provide river discharge, with accuracy depending on several factors (e.g., environmental and hydraulic conditions, processing software, etc.). A key stage of image-based techniques workflow is frames pre-processing. In particular, graphical enhancement is often needed to maximize contrast between tracer and background, improving software capability to detect and track the tracer motion. This work aims to investigate the influence of graphical enhancement methods on the results of image-based analyses, comparing traditional and less common algorithms. Analyses were conducted on videos acquired during a measurement campaign on two rivers in Sicily (Italy), where simultaneous ADCP reference measurements were also collected. Different graphic filters were applied to frames and the enhanced sequences were then processed using two optical software programs (i.e., PIVlab and SSIMS-Flow). Performances are evaluated in terms of errors in surface velocity and discharge assessment, using ADCP measurements as benchmark. Results confirm the overall high potential of image-based techniques and provide insights on the importance of using the appropriate enhancement filters based on the selected processing software and environmental conditions at
recording time
Comparison of Different Numerical Methods in Modeling of Debris Flows—Case Study in Selanac (Serbia)
No full textFlow-type landslides are not typical in this region of the Balkans. However, after the Tamara cyclone event in 2014, numerous such occurrences have been observed in Serbia. This paper presents the initial results of a detailed investigation into debris flows in Serbia, comparing findings from two programs: RAMMS DBF and Geoflow SPH. Located in Western Serbia, the Selanac debris flow is a complex event characterized by significant depths in the initial block and entrainment zone. Previous field investigations utilized ERT surveys, supplemented by laboratory tests, to characterize material behavior. Approximately 450,000 m3 of material began to flow following an extreme precipitation period, ultimately traveling 1.2 km to the deposition zone. For validation purposes, ERT profiles from both the deposition zone and the source area were utilized, with particular attention given to areas where entrainment was substantial, as this had a significant impact on the final models. The first objective of this research is to conduct a detailed investigation of debris flow using field investigations: geophysical (ERT) and aerial photogrammetry. The second objective is to evaluate the capacity of two debris flow propagation models to simulate the reality of these phenomena. The GeoFlow-SPH code overestimated the maximum propagation thickness in comparison to the RAMMS model. The numerical results regarding final depths closely align, especially when considering the estimated average depth in the deposition zone. The results confirm the necessity of using multiple simulation codes to more accurately predict specific events.This article belongs to the Special Issue Recent Advances in Modeling, Assessment, and Mitigation of Landslide Hazards
Defining the functioning of developed karst systems through extreme climatic event analysis, application to the Krupaja Spring, Serbia
No full textThis paper aims to characterize the functioning of a karst system through spatial and temporal modeling based on time series of precipitation and discharge of karst springs. Long-term, continuous daily monitoring (2009–2020) of rainfall and discharge of the Krupaja Spring, which drains the Beljanica karst massif (Serbia), has enabled a much better understanding of the role and development of fossil karst channels within a karst system. Special emphasis is given to the data relating to extreme events, in this case the extreme discharges of 31 m3/s caused by Cyclone Tamara in 2014. According to historical records, until 2009, discharges greater than 2.8 m3/s have never been recorded at the Krupaja Spring. Newer, and very precise monitoring data indicated that the yields of this spring typically range up to a maximum of 13 m3/s. The sudden filling of the karst system made it possible for the discharge (of an already-saturated karst system) to increase from 5.7 to 31 m3/s in just 16 h. The use of data from extreme weather events can greatly contribute to a greater knowledge of speleogenesis in karst systems. The Krupaja Spring karst system features entire networks of karst conduits that are almost or completely inactive during medium and even high groundwater levels. The activation of these channels, often filled with various clay deposits, can generally be linked to extreme climatic events, where spring flow discharge increases by five to six times higher than normal conditions, accompanied by extreme water turbidity
Application of adaptive neuro-fuzzy inference systems (ANFIS) for short-term flow prediction of karst springs
No full textUpravljanje vodoprivrednim sistemima u karstnim područjima predstavlja izazov zbog kompleksnih hidrogeoloških karakteristika i neizvesnosti u ulaznim podacima. Tradicionalne metode modeliranja često ne uspevaju da obuhvate sve karakteristike ovih sistema, zbog čega se sve češće analizira mogućnost korišćenja tehnika mašinskog učenja. U ovom radu analizirana je mogućnost primene adaptivnog neuro-fazi sistema zaključivanja (ANFIS) za predikciju protoka na vrelu Bune u Istočnoj Hercegovini (Bosna i Hercegovina). ANFIS kombinuje prednosti neuronskih mreža i fazi logike, omogućavajući precizno modeliranje nelinearnih funkcija kroz Sugeno fazi sistem zaključivanja. Za predviđanje protoka na vrelu Bune korišćeni su podaci o dnevnim padavinama i protocima na slivu u periodu od 13 godina. Model je obučavan hibridnim algoritmom učenja koji integriše opadajući gradijent i metod najmanjih kvadrata. Dobijeni rezultati pokazuju visok nivo tačnosti modela. Naknadna analiza značajnosti ulaznih parametara pokazala je da se izbacivanjem određenih promenljivih može poboljšati efikasnost modela bez gubitka na tačnosti. Sprovedene analize sugerišu da se ANFIS model može koristiti kao efikasan alat za hidrološku prognozu u složenim karstnim područjima.Managing water resource systems in karst areas poses a challenge due to complex hydrogeological characteristics and uncertainties in input data. Traditional modeling methods often fail to capture all the features of these systems, which is why the use of machine learning techniques is increasingly being analyzed. In this paper, the application of the Adaptive Neuro-Fuzzy Inference System (ANFIS) for predicting flow at the Buna spring in Eastern Herzegovina (Bosnia and Herzegovina) is analyzed. ANFIS combines the advantages of neural networks and fuzzy logic, allowing precise modeling of nonlinear functions through the Sugeno fuzzy inference system. Data on daily precipitation and flows in the catchment area, over a period of 13 years, were used. The model was trained with a hybrid learning algorithm that integrates gradient descent and the least squares method. The obtained results show a high level of model accuracy. Subsequent analysis of the significance of input parameters showed that the efficiency of the model can be improved by excluding certain variables, without losing accuracy. These results suggest that ANFIS can be used as an effective tool for hydrological forecasting in complex karst areas
Regional Debris Flow Hazard Assessment of the Grdelica Gorge (Serbia)
No full textRoad infrastructure development is currently very intensive in Serbia. One such example is the Grdelica Gorge, where a new highway was aligned and put into service in 2019. The
Gorge has provided a very challenging engineering environment imposing high levels of several hazard types: floods; slides; debris flows; and rockfalls. In this work, the debris flow hazard for the first 15 km of the road route was in focus. The assessment included an expert-driven analysis for identifying potential source areas, coupled with deterministic modelling of the flowing process originating from these source areas, resulting in detailed simulations of the final runout distance, height of deposit, and flow velocity, which are all reliable parameters for mitigating the hazard across the road alignment. A combination of geomorphological criteria, processed in a GIS environment was used to narrow down the search of source areas containing loose, erodible material which easily mobilizes under saturated conditions. The criteria were calibrated by the outlines of the available inventory, acquired by remote sensing techniques. The Digital Terrain Model with 12.5 m resolution was used for running RApid Mass Movement Simulation (RAMMS), using estimated bulk density and friction coefficients as input parameters. Since there was no recent debris flow in the area for the appropriate back-analysis of these parameters, experience-and lab-based estimations were used. Several simulations have reached the road alignment, wherein a few imposed significant threats with respect to deposit height and velocity that require additional attention
Debris-flow Susceptibility Assessment in Flow-R: Ribnica River Case Study
No full textDebris flows are among the most dangerous
erosional geohazards due to the fast rate of movement and
long runout zones. Even though the initiation can be
triggered in mountainous areas, inhabited and with steep
slopes, their propagation and deposition can endanger not
only buildings and infrastructure in the urbanized areas,
but also threaten human lives. As these initiation areas
usually represent unattainable terrains with rapid
vegetation cover development, field observations and
aerial photo analysis become high-demanding tasks.
Consequently, medium-to-regional scale susceptibility
assessments are increasing in interest. They allow for
efficient and effective identification of the most
endangered zones and can be used to propose where
further detailed studies should take place. In those terms,
since it can be challenging to obtain enough data for larger
regions, empirical models with low data requirements
represent an adequate solution to the susceptibility
modelling problem. In this paper, a medium-scale debris
flow susceptibility assessment has been carried out along
the Ribnica River in western Serbia. Both the source areas
and the propagation extent have been identified with the
Flow-R empirical model based on simple probabilistic and
energy calculations. The key input data used to investigate
debris flow susceptibility in the study area was 10 m
resolution DEM. The combination of DEM, its associated
morphological derivates, landuse and lithology datasets,
with Holmgren’s modified propagation algorithm and the
angle of reach, allowed for the 1:25000 susceptibility
assessment. The results are reasonable and can be of great
use for determining the areas that need to be prioritized
for further detailed studies
Hipoteza Nikiforova i slučajni grafovi
No full textU ovom radu govori se o neorijentisanim grafovima bez petlji i njihovom spektru. Šatenove
p-norme predstavljaju zbir p-tih stepena singularnih vrednosti grafa stepenovan sa 1
p , specijalan
slučaj Šatenove norme za p = 1 je baš energija grafa. Vladimir Nikiforov je postavio hipotezu
da od svih neorijentisanih grafova bez petlji sa n qvorova najve u vrednost Xatenove norme za
p > 2 ima komletan graf. Poxto je spektar kompletnog grafa poznat dokazivanje ove hipoteze postaje
dokazivanje odre ene nejednakosti. Ova hipoteza je dokazana da va i za tri specijalne klase grafova,
to su: stabla, jako regularni grafovi s
kod kojih se
postiže maksimalna energija i grafovi kod kojih je p paran broj. Tako
đe navode se i neka uopštenja
vezana za slučajne grafove. Nađena je gornja ocena za geometrijsku sredinu singularnih vrednosti
slučajnog grafa i izračunata je srednja vrednost p-tih stepena singularnih vrednosti sluqajnog
grafa