Wyniki wyszukiwania - Biblioteka Nauki

1

Simulation of the granular flow of grinding media inside a ball mill

100%

Landowski B. , Kostek R.

Journal of Polish CIMAC

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2011

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tom Vol. 6, no 3

65-68

EN

The ball mills are often applied in mineral processing, they are e.g. an important part of the cement industry. A key factor, which influences the milling process, is the granular flow of grinding media. The flow determines: energy consumption, time of milling and capacity; thus there is a need to describe the phenomenon. The discrete element method - DEM is a computational method, which allows to simulation of the granular flow, thus it has been applied in this article. The received results of simulation have been compared with experimental results.

2

Simulation of the granular flow within an impact crusher

85%

Kostek R.

Inżynieria i Aparatura Chemiczna

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2009

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tom Nr 2

74-75

EN

Impact crushers are widely applied in mineral processing, recyclii and chemical industries, to name a few. The most important reseai issues in impact crushing are energy consumption, flow of materi impact, capacity and shape of a crushing chamber. The problems ; coupled together and influence each other. In this paper, a granu flow of particles through an impact crusher is presented. The flow w simulated with DEM.

PL

Kruszarki udarowe są szeroko stosowane w przetwórstwie minerałów, recyklingu oraz przemyśle chemicznym. Najważniejszymi zagadnieniami badawczymi dotyczącymi kruszarek udarowych są: zużycie energii, przepływ materiału, uderzenia, wydajność i kształt komory kruszenia. Zagadnienia te są wzajemnie sprzężone i wpływają na siebie. W artykule przedstawiono przepływ ziarnisty materiału rozdrabnianego przez kruszarkę udarową. Przepływ ten symulowano z wykorzystaniem metody elementów dyskretnych DEM.

3

Comparison of the Resampling Methods for Gridded DEM Downscaling

85%

Nguyen Q. M. , Nguyen T. T. H. , La P. H. , Duong T. T. N. , Nguyen T. M. H. , Vu V. A.

Inżynieria Mineralna

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2019

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tom R. 21, nr 2/2

240--248

EN

In this paper, a comparison and evaluation of three resampling methods for gridded DEM is implemented. The evaluation was based on the results of bilinear resampling, bi-cubic and Kriging resampling methods for an experiment using both degraded and sampled datasets at 20 m and 60 m spatial resolutions. The evaluation of the algorithms was accomplished comprehensively with visual and quantitative assessments. The visual assessment process was based on direct comparison of the same topographic features in different downscaled images, scatterplots and profiles. The quantitative assessment was based on the most commonly used parameters for DEM accuracy assessment such as root mean square errors (RMSEs), linear regression parameters m and b, and correlation coefficient R. Both visual and quantitative assessment revealed greater accuracy of the Kriging over the other two conventional methods.

4

Laboratoryjne badania przesypu przenośnika taśmowego w aspekcie weryfikacji dyskretnego modelu materiału transportowanego

85%

Kulinowski P. , Panek P. , Rubacha P.

Transport Przemysłowy i Maszyny Robocze

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2013

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tom Nr 4

6--11

PL

W artykule przedstawiono zagadnienia dotyczące wykorzystania metody elementów dyskretnych do modelowania zachowania się materiałów sypkich podczas transportu przenośnikami taśmowymi. Opisano stanowisko laboratoryjne do badania zachowania się materiałów sypkich w punktach przesypowych przenośników taśmowych oraz system pomiarowy, składający się z układu czujników tensometrycznych i kamery do szybkich zdjęć. W dalszej części przedstawiono metodykę badań oraz wyniki testów laboratoryjnych, które posłużyły do weryfikacji dyskretnego modelu materiału transportowanego zbudowanego w środowisku PFC3D, bazującego na metodzie elementów dyskretnych (DEM).

EN

In this paper some issues concerning the application of the Discrete Element Method (DEM) in modelling granular materials transported on conveyor belts have been discussed (presented). A test stand for examining the behavior of bulk materials in conveyor belt transfer chutes as well as a measuring assembly consisting of strain gauges and a high-speed camera have been described . The next part deals with the test method and test results, which were used to verify the discrete model of the handled material, modelled in PFC3D on the basis of the Discrete Element Method.

5

Numeryczne obliczenia oporów załadunku urobku na taśmę przenośnika z wykorzystaniem metody elementów dyskretnych

85%

Czuba W. , Kulinowski P.

Transport Przemysłowy i Maszyny Robocze

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2011

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tom Nr 2

5--10

PL

W artykule przedstawiono możliwość wykorzystania numerycznej metody analizy zachowania się ośrodków sypkich do analizy oporów ruchu występujących w stacjach przesypowych. Opisano metodę elementów dyskretnych (DEM), jej podstawowe założenia i algorytmy, a także przedstawiono wytyczne do kalibracji parametrów, przygotowania i prowadzenia badań symulacyjnych. W podsumowaniu porównano wyniki obliczeń uzyskane za pomocą analitycznych sposobów obliczania oporów załadunku z wynikami badań symulacyjnych przeprowadzonych w środowisku PFC3D z wykorzystaniem metody DEM.

EN

The article presents the possibility of using numerical methods for analysis of bulk materials behavior to calculate resistance to movement occurring in transfer stations. Paper describes the Discrete Element Method (DEM), its basic concepts and algorithms, and provides guidance for the calibration of parameters, preparation and conduct of simulations. In summary, comparison of the results of calculations obtained using the classical methods with the results of simulation studies carried out in an environment PFC3D using DEM method.

6

Wykorzystanie DEM do modelowania przepływu materiałów ziarnistych

85%

Walker P. , Doroszuk B. , Król R.

Transport Przemysłowy i Maszyny Robocze

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2018

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tom Nr 3

68--74

PL

W badaniach przepływu urobku w ciągłych systemach transportowych niezwykle trudno uwzględnić cząsteczkową budowę przenoszonego materiału. Różnice w rozmiarze i kształcie poszczególnych fragmentów urobku powinny być brane pod uwagę dla pełnego zrozumienia zjawisk zachodzących w czasie transportu. Metoda elementów dyskretnych DEM pozwala na zbadanie wybranych elementów ciągu transportowego, z uwzględnieniem specyficznej budowy transportowanego materiału oraz reakcji między jego fragmentami, traktując każdy element urobku osobno. Przedstawiono proces przygotowania symulacji DEM oraz wyniki badania zachowania się urobku o złożonej granulacji w czasie napełniania i opróżniania zbiornika przyszybowego kopalni podziemnej, a także wyznaczono czas przepływu pojedynczej cząstki urobku w postaci czytnika RFID (e-pelletu) przez zbiornik w zależności od stopnia jego wypełnienia.

EN

In research on the continuous transport system it is hard to take into account discrete construction of conveyed materiał. Differences in shape and size of each pieces of ore should be taken in to consideration for fuli understanding of phenomenon during transport. The Discreet element method (DEM) allows us to study what is happening with chosen elements of transport system including specific construction of the conveyed ore and also study the reactions between transported parts through treating all the elements separately. This paper presents the process of preparing the DEM simulation and results of research on various size ore flow during filling and emptying of underground mining large-capacity shaft station bunker. We also shows the analysis of flow time of pellets for various bunker fili levels.

7

Studies on Moisture Effects on Powder Flow and Mechanochemical Improvement of Powder Flowability

80%

Opaliński I. , Chutkowski M. , Stasiak M. , Leś K. , Olechowski M. , Przywara M.

Advances in Science and Technology. Research Journal

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2021

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tom Vol. 15, no 2

228--246

EN

Recent findings on some unsolved powder rheology problems and new challenges regarding mechanochemical powder processing and flow modelling are presented. There is remarkable difference in rheology when processing moist powders in static or dynamic conditions. Despite of regular trends of shear stress changes with humidity found in the both cases, some exceptions revealed the significant impact of particles size and their hygroscopic nature as example. Mechanochemical methods of high-energy interactive mixing of highly cohesive powders doped with nano-sized solid admixture enabled their flowability to be improved considerably. Using statistical approach, more general routine is proposed that allow the optimal mixing parameters to be reliably predicted with limited number of experiments needed. Ability to flow of some hygroscopic powders was examined with DEM method and extreme sensitivity of model output to input particle properties was found. The common DEM routine towards powder flow prediction is therefore suggested to be replaced with approach featuring in using DEM method to identify some unknown powder flow factors.

8

Model for the Volume-Area-Depth Relations of Midfield Ponds using LiDAR

80%

Fiedler M. , Antkowiak M. , Oliskiewicz-Krzywicka A. , Zbierska A.

Journal of Ecological Engineering

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2017

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tom Vol. 18, nr 6

36--42

EN

Small midfield ponds have important functions in the hydrology and ecology of hummocky areas of Poland. Because of their sensitivity to meteorological conditions, their number and hydroperiod are altered as a result of climate changes and agriculture pressure. Accurate estimation of the pond area and storage capacities requires up-to-date high-resolution elevation data. In this paper, we developed 0.2 m and 1.0 m bare-earth DEMs from LiDAR data and compared them with DEMs obtained from old bathymetric maps. Then, we calculated A-h and V-h relations and compared them with the relations derived from simplified models describing the pond shape. The analyses showed that LiDAR data are also useful for detecting changes in the ponds morphometry.

9

Visualization of Results Received with the Discrete Element Method

80%

Kostek R. , Munjiza A.

Computational Methods in Science and Technology

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2009

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tom Vol. 15, nr 2

151-160

EN

The output of discrete element simulations includes thousands of time-frames and millions of interacting particles (bodies) in each frame. A single simulation can include terabytes of results, which may lead to very large, very complex data sets. Visualizing them is coupled with difficulties caused by either the number of particles, the number of time-frames or complexities of “system variables”. In this work, an attempt has been made to present a data format and graphical template dedicated to discrete element visualization. The article presents a practical approach to the issues, that is the result of programming an open source 3D visualizer, called DEV_KM.

10

Changes of soil microrelief under the influence of simulated rainfall

80%

Baryła A. , Stańczyk T.

Infrastruktura i Ekologia Terenów Wiejskich

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2016

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tom nr IV/4

1723--1731

EN

Soil microrelief is one of the factors affecting wind and water erosion process. Spatial variability of soil surface (microrelief) influences initiation of the surface runoff and water flow mainly through depressions, where the runoff is delayed and infiltration increases owing to the interception of the flowing water. The research was conducted to assess the changes of relief of two soils (sandy loam and fine sand) under the influence of rainfall in a model experiment. The soil microrelief was determined by means of a contactless 3D scanner using the effect of line distortion as light beam illuminating the object surface (so called Moire pattern). On the basis of obtained results, maps of the differences in the scanned surface elevations were plotted in ArcGIS programme and the soil losses volume was computed. RR indicator calculated for sandy loam was decreasing with increasing depth of simulated rainfall. No such dependence was observed for loose sand.

11

Accuracy assessment of Digital Elevation Models using GPS

80%

Farah A. , Talaat A. , Farrag F. A.

Artificial Satellites : Journal of Planetary Geodesy

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2008

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tom Vol. 43, No. 4

151--161

EN

A Digital Elevation Model (DEM) is a digital representation of ground surface topography or terrain with different accuracies for different application fields. DEM have been applied to a wide range of civil engineering and military planning tasks. DEM is obtained using a number of techniques such as photogrammetry, digitizing, laser scanning, radar interferometry, classical survey and GPS techniques. This paper presents an assessment study of DEM using GPS (Stop&Go) and kinematic techniques comparing with classical survey. The results show that a DEM generated from (Stop&Go) GPS technique has the highest accuracy with a RMS error of 9.70 cm. The RMS error of DEM derived by kinematic GPS is 12.00 cm.

12

Use of geospatial tools in morphometric analysis and prioritisation of sub-catchments of the soundgrougrou (Casamance Basin)

80%

Faye C. , Ndiaye M.

Quaestiones Geographicae

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2021

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tom 40

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nr 3

65-84

EN

The prioritisation of catchments, particularly in the context of catchment plans and management programmes, is part of water resources development. In fact, morphometric analysis assisted by geospatial technology is carried out by prioritising sub-catchments according to their natural resource availability characteristics. Information on the geomorphology and erosion factors of the study area is used in the area in the preparation of local models of ungauged sub-catchments, which otherwise lack an adequate hydrological database. The objective of this paper is to use geographic information systems (GISs) in morphometric analysis to prioritise sub-catchments of the Soungrougrou (a tributary of the Casamance River). In this respect, the integrated methodology involving morphometric aspects from geospatial technology is used. To carry out the geospatial research, basic mathematical equations used in a GIS environment were used to measure a series of aspects of hydrology such as flow length, flow length ratio, bifurcation ratio, drainage density, drainage texture, flow frequency, elongation rate, circularity ratio, form factor, relief and relief ratio. The results divided the whole catchment into three priority areas, namely high, medium and low. The results are relevant for establishing soil and water conservation plans in the Soungrougrou basin, as well as adequate groundwater production and management. The high category (sub-basins 6, 8, 14, 17 and 18) is subject to maximum soil erosion, which requires immediate intervention to avoid possible natural hazards.

13

Modelling the structure of terrestrial landscapes in urban areas

80%

Krutskikh N.

Quaestiones Geographicae

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2021

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tom 40

|

nr 1

39-49

EN

The study of internal and external factors in the formation of an urban geosystem is determined by its complex structure and multiple connections. Based on geoinformation modelling, an analysis of the landscape structure of the city territory is carried out, which can be a basis for further geoecological research. Morphometric indicators, which make it possible to determine the elementary geochemical landscapes, are indicated according to the data of the digital elevation model. A standardised topographic position index (TPI) is used to determine locations. Spatial zoning according to the type of land use reflects the qualitative features of the external load and technogenic impact. The data on the composition of the lithogenic base show the properties of the depositing medium and determine the natural background. Number of categories of landscapes identified are 58, characterised by a homogeneous geological composition, technogenic load and conditions for the migration of matter. The ratios of various landscape zones have been calculated. The study area as a whole is characterised by the predominance of migration processes over accumulation.

14

The usage of DEM to create the 3D cadastre

80%

Sanecki J. , Klewski A. , Beczkowski K. , Pokonieczny K. , Stępień G.

Zeszyty Naukowe / Akademia Morska w Szczecinie

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2013

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tom nr 33 (105)

86--90

EN

The article presents the analysis of possibilities of using the Digital Elevation (Surface) Models for creation of the 3D cadastre. The authors present the characteristics and meaning of the three-dimensional modelling of objects in the context of solving problems occurring with the traditional two-dimensional cadastre. The paper presents imperfections of the 2D cadastre and indicates possibilities of their removal based on altitude data acquired from the laser scanning. It determines the accuracy of data obtained with lidar techniques and indicates their limitations in specifying the exceeding. As a result of the carried out analysis and theoretical considerations, the authors have indicated the potential possibilities of the usage of Digital Surface (Elevation) Models for the construction of the three-dimensional cadastre system.

15

Analysis of surface changes in the Walbrzych hard coal mining grounds (SW Poland) between 1886 and 2009

80%

Blachowski J. , Milczarek W.

Geological Quarterly

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2014

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tom Vol. 58, No. 2

353--368

EN

Underground coal mining causes surface changes such as subsidence and land transformation. The knowledge of the character of subsidence in the past and in the present provides useful information for example for spatial development. In this paper the methodology of determining surface height changes based on cartographic modelling in geographic information system (GIS) is presented. It has been applied to two test areas in a former coal basin in the Walbrzych region (SW Poland) that is characterised by complex geological conditions. In the result of a set of interpolation and map algebra operations surface height changes have been determined and the character of subsidence in a period of over 120 years (1886-2009) has been assessed. These results have been compared with the results of predictions based on the empirical Knothe theory of subsidence calculations using spatial statistics parameters. It has been found that theoretical modelling when applied in areas of complex mining and geological conditions produces lower subsidence values and more uniform subsidence surface than the applied method based on actual elevation data. The calculated surface height changes in the analysed period have been presented graphically and described.

16

Badania symulacyjne w projektowaniu głowicy dyskowej nowej generacji

71%

Stopka G.

Systemy Wspomagania w Inżynierii Produkcji

|

2019

|

tom Vol. 8, iss. 1

164--172

PL

W artykule przedstawiono koncepcję głowicy dyskowej nowej generacji oraz dotychczasowy zakres badań stanowiskowych związany z jej doświadczalną weryfikacją. Przedstawiono podstawowe zagadnienia będące przedmiotem aktualnych badań modelowych związanych z rozwojem konstrukcji głowicy, w tym modelowaniem dynamiki układu napędowego oraz symulacją obciążeń narzędzi dyskowych.

EN

he article presents a concept of the new generation mining head with disc tools and current scope of research related to experimenal verification. In the article the basic issues that are the subject of current simulation modeling are presented related to the development of the head construction, including modeling of dynamics of power transmission system and the simulation of disk tool loads.

17

Experimental and computational analysis of granular material flow in model silos

71%

Sielamowicz I. , Balevičius R.

IPPT Reports on Fundamental Technological Research

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2013

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tom nr 1

1--317

EN

The study described here was undertaken to explore the phenomena occurring in silo problems. For these problems, no experimental results exist, but simpler tests for validation can be used. This book identifies theses phenomena which are presented in two chapters. The first presents experimental investigations of granular material flows with a detailed description of phenomena occurring during filling and discharge processes in silo models. It also pertains to empirical descriptions of velocities and flow rates considered via statistical analysis. The experiments were conducted using a Digital Particle Image Velocimetry Optical Flow (DPIV OF). Applying this innovative technique allowed the obtaining and identification of a large volume of quantitative data characterizing the granular material flow, such as, velocities patterns within granular material, outflow rate, deformations, strains, dilation and stagnant zones boundaries; especially in the eccentric modes of flows for the plane silo models. The chapter also includes the analysis on verification of a Radial Flow assumption. The new mathematical description of kinematic parameter b for radial flow was applied with new formula for defining velocities in radial flows. Furthermore, the DPIV technique was applied to verify mass and volume conservation in the flowing material. The results obtained in this chapter serve as the basis of further verification via numerical simulations made by the Discrete Element Method (DEM). Hence, the second Chapter discusses implementation of DEM in simulation of the processes observed during the performed experiments. The presented DEM mathematical model was applied to verify the wall stress distributions, this is presented first with a limited number of particles and then with an increased number of particles. This approach made it possible to verify parameters or indicators derived from the well-known continuum-based methods. The computational analyses presented also provides a micromedianical insight into the filling and discharge of the granular materials in the 3D silo models. In particular, this chapter deals with the results of investigation of such specific phenomena known as "a free-fall arch", material dilation forming, porosity fields evolution, distribution of stress within the granular material, outflow rates and velocity profiles. The key finding of the analysis was the comparison of the measured wall pressure distribution in the experiments with those obtained numerically with DEM, Janssen solution and the Standard Eurocod 1. It was particularly demonstrated that the wall pressure calculated by the recommended formula in the design Standard gives lower values than those obtained from the experimental measurements. While a well known Janssen's theory cannot be expected to represent pressures during silo discharge. Also, the analysis of the influence of rolling friction on wall pressure and velocities distributions within the flowing granular material were considered in detail. Such important phenomena like a "pressure switch" were also successfully captured numerically and experimentally during the discharge process. Finally, the general conclusions arising from the study appear to be very useful for the designers of silo structures one of the most difficult tasks in the field of civil engineering.

PL

Podstawowym celem pracy jest opisanie zjawisk występujących w procesach technologicznych w silosach. Z uwagi na brak badań eksperymentalnych silosów w skali naturalnej badania tych zjawisk przeprowadza się w skali laboratoryjnej. W książce podjęto próbę zidentyfikowania niniejszych zjawisk a wyniki prac podano w dwóch odrębnych rozdziałach. Pierwszy z nich przedstawia wyniki badań eksperymentalnych płynięcia materiałów ziarnistych w czasie napełniania i opróżniania modelów silosu. Rozdział ten zawiera również empiryczne opisy prędkości i analizę wydatków wypływu wykonane metodami analizy statystycznej. Obrazy płynięcia materiału ziarnistego w modelach rejestrowano techniką cyfrową Digital Particle Image Velocimetry, Optical Flow, tzw. potokami optycznymi (DPIV OF). Zastosowanie tej innowacyjnej techniki pozwoliło na uzyskanie dużej ilości danych ilościowych charakteryzujących przepływy materiałów ziarnistych, takich jak: profile prędkości płynącego materiału ziarnistego, wartości wydatku wypływu, deformacje, odkształcenia, zakres stref zastoju w przepływach symetrycznych i niecentrycznych w płaskich modelach silosów. Rozdział pierwszy przedstawia również analizę weryfikacji założenia przepływu radialnego, gdzie podano nowy opis matematyczny parametru kinematycznego b dla przepływu radialnego, zastosowano nową formułę określenia prędkości w przepływach radialnych. Dzięki technice DPIV dokonano weryfikacji prawa zachowania masy i objętości w płynącym materiale. Wyniki przedstawione w tym rozdziale stały się podstawą do dalszej weryfikacji poprzez symulacje numeryczne wykonane metodą elementów dyskretnych (DEM). Rozdział drugi omawia zastosowanie metody DEM do symulacji procesów zarejestrowanych w czasie eksperymentów. Przedstawiony model matematyczny DEM wykorzystano do weryfikacji rozkładu naporów w ścianie, w pierwszej fazie analizy z mniejszą liczbą cząstek, a następnie z większą liczbą cząsteczek. Takie podejście pozwoliło na dokonanie oceny porównawczej różnych parametrów ze 8 Streszczenie znanymi rozwiązaniami mechaniki continuum oraz na zastosowanie podejścia mikromechaniki na ocenę procesów napełniania i opróżniania w trójwymiarowych modelach silosów. W rozdziale tym dalej omówiono wyniki symulacji konkretnych zjawisk, takich jak tworzące się zawieszenia w materiale, kształtowanie się stref rozluźniania materiału, ewolucję pola porowatości, rozkłady naprężeń w materiale, wartości wydatku wpływu i kształty profili prędkości. Finalnym ważkim wynikiem analizy było porównanie rozkładu ciśnienia pomierzonego eksperymentalnie w ścianie z wynikami analizy numerycznej metodą elementów dyskretnych DEM, a następnie z rozwiązaniem Janssena oraz zaleceniami normy Eurocod 1. Wykazano, że ciśnienie powstałe w ścianie w wyniku naporu materiału obliczone zgodnie z normą Eurokod 1 przedstawia niższe wartości niż te, które otrzymano w trakcie eksperymentów, a rozwiązanie Janssena nie podaje wartości ciśnień w czasie opróżniania silosu. Nadto, podano analizę wpływu tarcia tocznego na ciśnienia w ścianie i na rozkłady prędkości oraz zjawisko powstania „skoku ciśnień” w ścianie. W końcowej części monografii podano wnioski wypływające z badań, które mogą posłużyć projektantom konstrukcji silosów – jednym z najtrudniejszych zadań w zakresie inżynierii lądowej i wodnej

18

Photogrammetric reconstruction of changes in vertical river position using archival aerial photos: case study of the Czarny Dunajec River, Polish Carpathians

71%

Hajdukiewicz M. , Wyżga B. , Hajdukiewicz H. , Mikuś P.

Acta Geophysica

|

2019

|

tom Vol. 67, no. 4

1205--1221

EN

Rivers of the Polish Carpathians incised deeply during the twentieth century, but detailed information about the timing and amount of incision of their channels exists only for water-gauge cross sections. Applicability of photogrammetric extraction of digital elevation models (DEMs) from archival aerial photos for reconstructing changes in vertical river position was verifed in the study of a 3-km reach of the Czarny Dunajec River. DEMs extracted from a few sets of archival aerial photos from the years 1964–1994 together with recent orthophotos and DEMs were used in the analysis. Measurements taken in river cross sections spaced at 100-m intervals indicated that on average the lowest point of the channel bed lowered between 1964 and 2009 by 1.74±0.17 m, low-fow water surface by 1.57±0.07 m, active river channel by 1.54±0.12 m and the belt of river migration by 1.03±0.15 m. However, the change in vertical river position during the years 1964–2009 varied greatly along the reach, with the elevation of low-fow water surface lowered by up to 3.61±0.07 m in the upper part of the reach and increased by up to 1.34±0.07 m in its lower part. Combining the information about changes in vertical river position and the width of river migration belt yielded data about the change in sediment volume in the reach, with an average annual loss of sediment amounting to 256±37 m3 per 100-m channel segment. The study indicated that DEMs generated from archival aerial photos can be a useful tool in analysing recent vertical channel changes outside water-gauge stations.

19

Assessment of spatiotemporal changes of the length and starting date seasons in the west of Iran

71%

Nazripouya H. , Meshram S. G. , Bahramloo R. , Sepehri M. , Ali S. A. , Kushwaha N. L. , Kiani H. M. , Rodrigo-Comino J.

Acta Geophysica

|

2022

|

tom Vol. 70, no 6

2813--2825

EN

There is evidence that human activities are affecting global dynamics. The consequences of changes in the duration of the annual seasons and daily temperatures will imply drastic impacts on human and natural ecosystems. However, estimations related to the duration of the seasons considering the daily temperatures are scarce and could help to foresee negative effects with irreparable consequences. This study investigates the spatiotemporal variation of length and start date of each annual season based on temperature criteria by analyzing daily data of synoptic stations in western Iran from the period 1977–2015. Our results demonstrated that the starting date of summer shows a tendency advanced and the starting date of winter has been delayed. Moreover, spring is coming earlier. On the other hand, winter ends earlier and fall is delayed, with longer summers and shorter winters as a result. The starting date of summer differs from 0 to 2 d advanced in the southwest of the study area and 4–6 d advanced in the central and southeast parts. The starting date of winter on average has been delayed by 2 days and the length of the season has been shortened by 5 days. The changes for spring and fall are relatively smaller. Particularly, spring started earlier by 4.2 days but was extended by 1.8 days, and the fall season has started delayed by 0.8 days but extended by 0.4 days. This study provides simple information to stakeholders and policymakers so that they should focus on the issue and start developing efficient plans to reduce the negative impacts on the temperatures, shorter winters and the earlier spring, which could affect the floriation and animal behaviors among others.

20

Zastosowanie Metody Elementów Dyskretnych (DEM) do symulacji odstawy urobku przez ścianowy przenośnik zgrzebłowy

71%

Czuba W. , Gospodarczyk P. , Kulinowski P.

Symulacja w Badaniach i Rozwoju

|

2010

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tom Vol. 1, nr 3

213-221

PL

W referacie przedstawiono możliwość wykorzystania Metody Elementów Dyskretnych do numerycznej symulacji materiału sypkiego jako discontinuum. Metoda ta pozwala na modelowanie układów fizycznych składających się z wielu odrębnych elementów przez co znalazła zastosowanie w analizie procesów mechanicznych związanych z transportem urobku na różnego rodzaju przenośnikach. W opracowaniu przedstawiono wyniki symulacji ładowania urobku na ścianowy przenośnik zgrzebłowy i proces jego odstawy. Przeprowadzona analiza pokazała, że symulacja z wykorzystaniem metody DEM może być skutecznym narzędziem dla weryfikacji doboru parametrów konstrukcyjnych i ruchowych kombajnu i przenośnika w ścianowym kompleksie zmechanizowanym.

EN

This work presents the possibility of using Discrete Element Method for numerical simulation of bulk material as discontinuum. This method allows modeling of physical systems composed of many separate elements, therefore it found application in the analysis of mechanical processes associated with the transportation of excavated material on the various type of conveyors.