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Volumen 18 (2010): Heft 2 (June 2010)

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Zeitschriftendaten
Format
Zeitschrift
eISSN
1338-3973
ISSN
1210-3896
Erstveröffentlichung
23 May 2011
Erscheinungsweise
4 Hefte pro Jahr
Sprachen
Englisch

Suche

Volumen 28 (2020): Heft 2 (June 2020)

Zeitschriftendaten
Format
Zeitschrift
eISSN
1338-3973
ISSN
1210-3896
Erstveröffentlichung
23 May 2011
Erscheinungsweise
4 Hefte pro Jahr
Sprachen
Englisch

Suche

9 Artikel
access type Uneingeschränkter Zugang

Numerical Modeling of a Punch Penetration Test Using the Discrete Element Method

Online veröffentlicht: 06 Jul 2020
Seitenbereich: 1 - 7

Zusammenfassung

Abstract

Understanding the brittleness of rock has a crucial importance in rock engineering applications such as the mechanical excavation of rock. In this study, numerical modeling of a punch penetration test is performed using the Discrete Element Method (DEM). The Peak Strength Index (PSI) as a function of the brittleness index was calculated using the axial load and a penetration graph obtained from numerical models. In the first step, the numerical model was verified by experimental results. The results obtained from the numerical modeling showed a good agreement with those obtained from the experimental tests. The propagation path was also simulated using Voronoi meshing. The fracture was created under the indenter in the first step, and then radial fractures were propagated. The effects of confining pressure and strength parameters on the PSI were subsequently investigated. The numerical results showed that the PSI increases with enhancing the confining pressure and the strength parameter of the rock, including cohesion and the friction angle. A new relationship between the strength parameters and PSI was also introduced based on two variable regressions of the numerical results.

Schlüsselwörter

  • PunchPenetrationTest
  • Indentation Test
  • Peak Slope Index
  • Brittleness
  • DEM
access type Uneingeschränkter Zugang

Assessing the Effect of Turning Vehicles and Pedestrians on the Safety of an Urban Road Section (Using Examples from the Commonwealth of Independent States)

Online veröffentlicht: 06 Jul 2020
Seitenbereich: 8 - 17

Zusammenfassung

Abstract

The article is devoted to an analysis of accidents involving pedestrians in traffic. An analysis of the statistical data of accidents involving pedestrians in the Republic of Belarus has been made. The main patterns and trends of accidents involving pedestrians are identified. A detailed analysis of the accident rate at pedestrian crossings and intersections was carried out, which made it possible to establish the most dangerous types of collisions during the interaction of transport and pedestrian flows. Experimental studies of collision situations were also carried out, which made it possible to establish the dependence of the violation rate on the composition of the right-handed traffic flow, on the type of traffic signal that regulates traffic on the right, as well as on the size of groups of pedestrians in front of cars.

Schlüsselwörter

  • Roadtraffic
  • Pedestrian
  • Traffic conflicts
  • Crosswalk
  • Traffic light intersection
  • Road accidents
  • Risk
access type Uneingeschränkter Zugang

A Web-Based 3D Simulation Platform Aimed at Policy Makers for Estimating the Effects of Urban Heat Islands

Online veröffentlicht: 06 Jul 2020
Seitenbereich: 18 - 22

Zusammenfassung

Abstract

The prediction of microclimate effects within an urban context through simulations has previously been done through elaborate software packages that offer accurate results but require extensive domain knowledge and time for the preparation of a model. In day-to-day policymaking, however, these efforts may turn out to be a major limiting factor: Policymakers and city administrators need a quick tool that can predict the effects of urban interventions in a variety of possible scenarios rather than a full-fledged simulation study for a limited set of specific interventions. In our work, we have been seeking to address this mismatch in expectations by using the best of both worlds: We have approximated results from a full-fledged simulation that uses a Cellular Automaton running within a 3D city visualization. Policymakers can edit the urban context by changing cell types (placement of greenery, etc.), thus leading to scenarios that can be compared to the status quo. As a matter of fact, policymakers can use these comparisons to argue for measures that mitigate the effects of heat islands, without requiring extensive domain knowledge or the effort to prepare a simulation model.

Schlüsselwörter

  • Pixel/Voxel based approach
  • Summer overheating
  • Mitigation
  • Urban greenery
  • Decision support
access type Uneingeschränkter Zugang

Experimental Study on the Placement of the Angle and the Distance of Parallel Skimming Walls to Reduce Inlet Sediment in a Lateral Intake

Online veröffentlicht: 06 Jul 2020
Seitenbereich: 23 - 29

Zusammenfassung

Abstract

Parallel skimming walls are regarded as one of the more efficient methods for controlling inlet sediment to a lateral intake. The present study attempts to experimentally scrutinize the impact of the angles of parallel skimming walls (θ), the corresponding distance (b), and the discharge variations of the main channel of the inlet sediment for the control of an intake. First, the impacts of parallel skimming walls incorporating three angles (θ = 0°, 15°, 30°), located in the front section of the intake and the distance between the walls (b=10 cm, 20 cm, 30 cm), were studied. A dimensional analysis showed the dimensionless extraction ratios and the relation between the variables in a laboratory. The results indicate that parallel skimming walls lead to average decreases of 69%, 41% and 26% in the amount of inlet sediment to the intake, for walls with angles of 0°, 15° and 30°, respectively. With regard to the distance between the walls, average decreases of 58%, 70% and 86% were observed for walls with placement distances of b/H=2.5, b/H=5 and b/ H=7.5, respectively.

Schlüsselwörter

  • LateralIntake
  • River Engineering
  • Sediment Control
  • Skimming Walls
access type Uneingeschränkter Zugang

Monitoring Changes in the Morphology and Storage of a Small Water Reservoir: A Case Study from Vrbovce, Slovakia

Online veröffentlicht: 06 Jul 2020
Seitenbereich: 30 - 35

Zusammenfassung

Abstract

One of the most profound problems in the operation of water reservoirs is their siltation by sediments coming from agricultural land. The siltation of water reservoirs can significantly shorten their life spans and prevent them from effectively fulfilling their functions. Therefore, accurate monitoring of the current state and dynamics of siltation processes is critical to maintaining their economic, environmental, and societal functions. This study presents a simple method to evaluate the sedimentation rate of a small water reservoir in Slovakia. The method is based on comparing the results from two bathymetric surveys that were carried out in 2017 and 2019 using an ultrasonic acoustic doppler current profiler (ADCP), which was originally developed to measure river discharges. A raster map of the thickness of the sediment in the reservoir was assembled by subtracting the two bathymetric surveys from each other. The analysis of the results showed that the mean annual sedimentation rate of the reservoir is only 101 m3/year, representing a mean increment in sediment thickness of 1.4 cm. The method described showed promising results and could be applied to numerous small water reservoirs of a similar size across Slovakia.

Schlüsselwörter

  • ADCP
  • Water reservoir
  • Bathymetry
  • Sedimentation
access type Uneingeschränkter Zugang

Reclaimed Asphalt Pavement (RAP) Based on a Geospatial Information System (GIS)

Online veröffentlicht: 06 Jul 2020
Seitenbereich: 36 - 42

Zusammenfassung

Abstract

A Geospatial Information System (GIS) is a system designed to capture, store, manipulate, analyze, manage, and present spatial or geospatial data. Reclaimed Asphalt Pavement (RAP) based on the GIS is one of the indirect and efficient methods in identifying areas. In this work, an analytical computational process combined with a spatial analysis was used to identify pavement zones for a city. The zoning results were categorized in four classes, including very high, high, medium risk, and low risk zones. The high and very high risk zones have been considered as a whole. The work circumstances include the Mean Profile Depth (MPD) data as a function of the number of wheel passes and the temperature; ten (10) specimens were selected from a set of 23 specimens. The results showed a good correlation between the parameters, including the number of wheels passing, the temperature, and the MPD.

Schlüsselwörter

  • Pavement
  • Geospatial Information Systems (GIS)
  • Regression
  • Analytical computational process
access type Uneingeschränkter Zugang

A New Method to Describe the Combined Effect of Draught and Radiant Thermal Asymmetry on Human Work Performance

Online veröffentlicht: 06 Jul 2020
Seitenbereich: 43 - 49

Zusammenfassung

Abstract

Human resources are the most important elements of economic units; thus, the efficiency of human work is of crucial importance. Work efficiency can be achieved only in an environment offering optimal thermal comfort. The present study makes use of human subject experiments in order to investigate the joint effect of draughts and warm ceilings on work performance. During the experiments, 10 thermal environments with 5 radiant thermal asymmetries and 2 draught rates were investigated. The most important outcome of the research is the presentation of the combined effect of a draught and a warm ceiling on work performance.

Schlüsselwörter

  • Thermalcomfort
  • Productivity
  • Radiant thermal asymmetry
  • Draught
  • Joint effect
  • Human subject measurement
access type Uneingeschränkter Zugang

Durability of FRP Reinforcements and Long-Term Properties

Online veröffentlicht: 06 Jul 2020
Seitenbereich: 50 - 55

Zusammenfassung

Abstract

Although fiber-reinforced polymers (FRPs) have achieved increasing popularity in strengthening concrete structures and reinforcing new ones, there is to date insufficient knowledge about their long-term behavior. The long-term properties of FRPs specified in design codes lead to the low utilization capacity of these materials and are not supposed to be correct according to the actual behavior of structures reinforced with FRPs after 20 or 30 years of their use. Environmental impact reduction factors limit the mechanical properties of FRP composites in a range from 0.95 for CFRP to 0.5 for GFRP; the creep rupture factor is from 0.9 to 0.2. The paper summarizes previous research and experimental studies on the long-term properties of FRP reinforcements and also their comparison with the actual structures in which this reinforcement has been used; it presents the first part of an experimental investigation with comparative calculations.

Schlüsselwörter

  • GFRPreinforcement
  • Long-term properties
  • Creep-rupture
  • Long-term reduction factors
access type Uneingeschränkter Zugang

Detection of Changes in Hydrological Time Series During Recent Decades

Online veröffentlicht: 06 Jul 2020
Seitenbereich: 56 - 62

Zusammenfassung

Abstract

An analysis of a hydrological time-series data offers the possibility of detecting changes that have arisen due to climate change or change in land use. This paper deals with the detection of changes in the hydrological time data series. The trend analysis was applied at 58 stage-discharge gauging stations that are located throughout Slovakia, with the measurement period from 1962 to 2017. The Mann-Kendall test show a declining trends in the summer and a few rising trends in the winter in discharges. In the town of Banská Bystrica at a station on the Hron River, decades of discharges, air temperatures, and precipitation totals were analyzed. The five decades from the 1960s to the 2000s were used. The hydrological time data series were also analyzed by the Pettitt’s test, which is used to detect change points. The decadal analysis at the Banská Bystrica station shows an increase in the air temperature but insignificant changes in discharges and precipitation. Pettitt’s test identified many change points in the 1990s in the air temperature.

Schlüsselwörter

  • Trendanalysis
  • Discharge
  • Change point
9 Artikel
access type Uneingeschränkter Zugang

Numerical Modeling of a Punch Penetration Test Using the Discrete Element Method

Online veröffentlicht: 06 Jul 2020
Seitenbereich: 1 - 7

Zusammenfassung

Abstract

Understanding the brittleness of rock has a crucial importance in rock engineering applications such as the mechanical excavation of rock. In this study, numerical modeling of a punch penetration test is performed using the Discrete Element Method (DEM). The Peak Strength Index (PSI) as a function of the brittleness index was calculated using the axial load and a penetration graph obtained from numerical models. In the first step, the numerical model was verified by experimental results. The results obtained from the numerical modeling showed a good agreement with those obtained from the experimental tests. The propagation path was also simulated using Voronoi meshing. The fracture was created under the indenter in the first step, and then radial fractures were propagated. The effects of confining pressure and strength parameters on the PSI were subsequently investigated. The numerical results showed that the PSI increases with enhancing the confining pressure and the strength parameter of the rock, including cohesion and the friction angle. A new relationship between the strength parameters and PSI was also introduced based on two variable regressions of the numerical results.

Schlüsselwörter

  • PunchPenetrationTest
  • Indentation Test
  • Peak Slope Index
  • Brittleness
  • DEM
access type Uneingeschränkter Zugang

Assessing the Effect of Turning Vehicles and Pedestrians on the Safety of an Urban Road Section (Using Examples from the Commonwealth of Independent States)

Online veröffentlicht: 06 Jul 2020
Seitenbereich: 8 - 17

Zusammenfassung

Abstract

The article is devoted to an analysis of accidents involving pedestrians in traffic. An analysis of the statistical data of accidents involving pedestrians in the Republic of Belarus has been made. The main patterns and trends of accidents involving pedestrians are identified. A detailed analysis of the accident rate at pedestrian crossings and intersections was carried out, which made it possible to establish the most dangerous types of collisions during the interaction of transport and pedestrian flows. Experimental studies of collision situations were also carried out, which made it possible to establish the dependence of the violation rate on the composition of the right-handed traffic flow, on the type of traffic signal that regulates traffic on the right, as well as on the size of groups of pedestrians in front of cars.

Schlüsselwörter

  • Roadtraffic
  • Pedestrian
  • Traffic conflicts
  • Crosswalk
  • Traffic light intersection
  • Road accidents
  • Risk
access type Uneingeschränkter Zugang

A Web-Based 3D Simulation Platform Aimed at Policy Makers for Estimating the Effects of Urban Heat Islands

Online veröffentlicht: 06 Jul 2020
Seitenbereich: 18 - 22

Zusammenfassung

Abstract

The prediction of microclimate effects within an urban context through simulations has previously been done through elaborate software packages that offer accurate results but require extensive domain knowledge and time for the preparation of a model. In day-to-day policymaking, however, these efforts may turn out to be a major limiting factor: Policymakers and city administrators need a quick tool that can predict the effects of urban interventions in a variety of possible scenarios rather than a full-fledged simulation study for a limited set of specific interventions. In our work, we have been seeking to address this mismatch in expectations by using the best of both worlds: We have approximated results from a full-fledged simulation that uses a Cellular Automaton running within a 3D city visualization. Policymakers can edit the urban context by changing cell types (placement of greenery, etc.), thus leading to scenarios that can be compared to the status quo. As a matter of fact, policymakers can use these comparisons to argue for measures that mitigate the effects of heat islands, without requiring extensive domain knowledge or the effort to prepare a simulation model.

Schlüsselwörter

  • Pixel/Voxel based approach
  • Summer overheating
  • Mitigation
  • Urban greenery
  • Decision support
access type Uneingeschränkter Zugang

Experimental Study on the Placement of the Angle and the Distance of Parallel Skimming Walls to Reduce Inlet Sediment in a Lateral Intake

Online veröffentlicht: 06 Jul 2020
Seitenbereich: 23 - 29

Zusammenfassung

Abstract

Parallel skimming walls are regarded as one of the more efficient methods for controlling inlet sediment to a lateral intake. The present study attempts to experimentally scrutinize the impact of the angles of parallel skimming walls (θ), the corresponding distance (b), and the discharge variations of the main channel of the inlet sediment for the control of an intake. First, the impacts of parallel skimming walls incorporating three angles (θ = 0°, 15°, 30°), located in the front section of the intake and the distance between the walls (b=10 cm, 20 cm, 30 cm), were studied. A dimensional analysis showed the dimensionless extraction ratios and the relation between the variables in a laboratory. The results indicate that parallel skimming walls lead to average decreases of 69%, 41% and 26% in the amount of inlet sediment to the intake, for walls with angles of 0°, 15° and 30°, respectively. With regard to the distance between the walls, average decreases of 58%, 70% and 86% were observed for walls with placement distances of b/H=2.5, b/H=5 and b/ H=7.5, respectively.

Schlüsselwörter

  • LateralIntake
  • River Engineering
  • Sediment Control
  • Skimming Walls
access type Uneingeschränkter Zugang

Monitoring Changes in the Morphology and Storage of a Small Water Reservoir: A Case Study from Vrbovce, Slovakia

Online veröffentlicht: 06 Jul 2020
Seitenbereich: 30 - 35

Zusammenfassung

Abstract

One of the most profound problems in the operation of water reservoirs is their siltation by sediments coming from agricultural land. The siltation of water reservoirs can significantly shorten their life spans and prevent them from effectively fulfilling their functions. Therefore, accurate monitoring of the current state and dynamics of siltation processes is critical to maintaining their economic, environmental, and societal functions. This study presents a simple method to evaluate the sedimentation rate of a small water reservoir in Slovakia. The method is based on comparing the results from two bathymetric surveys that were carried out in 2017 and 2019 using an ultrasonic acoustic doppler current profiler (ADCP), which was originally developed to measure river discharges. A raster map of the thickness of the sediment in the reservoir was assembled by subtracting the two bathymetric surveys from each other. The analysis of the results showed that the mean annual sedimentation rate of the reservoir is only 101 m3/year, representing a mean increment in sediment thickness of 1.4 cm. The method described showed promising results and could be applied to numerous small water reservoirs of a similar size across Slovakia.

Schlüsselwörter

  • ADCP
  • Water reservoir
  • Bathymetry
  • Sedimentation
access type Uneingeschränkter Zugang

Reclaimed Asphalt Pavement (RAP) Based on a Geospatial Information System (GIS)

Online veröffentlicht: 06 Jul 2020
Seitenbereich: 36 - 42

Zusammenfassung

Abstract

A Geospatial Information System (GIS) is a system designed to capture, store, manipulate, analyze, manage, and present spatial or geospatial data. Reclaimed Asphalt Pavement (RAP) based on the GIS is one of the indirect and efficient methods in identifying areas. In this work, an analytical computational process combined with a spatial analysis was used to identify pavement zones for a city. The zoning results were categorized in four classes, including very high, high, medium risk, and low risk zones. The high and very high risk zones have been considered as a whole. The work circumstances include the Mean Profile Depth (MPD) data as a function of the number of wheel passes and the temperature; ten (10) specimens were selected from a set of 23 specimens. The results showed a good correlation between the parameters, including the number of wheels passing, the temperature, and the MPD.

Schlüsselwörter

  • Pavement
  • Geospatial Information Systems (GIS)
  • Regression
  • Analytical computational process
access type Uneingeschränkter Zugang

A New Method to Describe the Combined Effect of Draught and Radiant Thermal Asymmetry on Human Work Performance

Online veröffentlicht: 06 Jul 2020
Seitenbereich: 43 - 49

Zusammenfassung

Abstract

Human resources are the most important elements of economic units; thus, the efficiency of human work is of crucial importance. Work efficiency can be achieved only in an environment offering optimal thermal comfort. The present study makes use of human subject experiments in order to investigate the joint effect of draughts and warm ceilings on work performance. During the experiments, 10 thermal environments with 5 radiant thermal asymmetries and 2 draught rates were investigated. The most important outcome of the research is the presentation of the combined effect of a draught and a warm ceiling on work performance.

Schlüsselwörter

  • Thermalcomfort
  • Productivity
  • Radiant thermal asymmetry
  • Draught
  • Joint effect
  • Human subject measurement
access type Uneingeschränkter Zugang

Durability of FRP Reinforcements and Long-Term Properties

Online veröffentlicht: 06 Jul 2020
Seitenbereich: 50 - 55

Zusammenfassung

Abstract

Although fiber-reinforced polymers (FRPs) have achieved increasing popularity in strengthening concrete structures and reinforcing new ones, there is to date insufficient knowledge about their long-term behavior. The long-term properties of FRPs specified in design codes lead to the low utilization capacity of these materials and are not supposed to be correct according to the actual behavior of structures reinforced with FRPs after 20 or 30 years of their use. Environmental impact reduction factors limit the mechanical properties of FRP composites in a range from 0.95 for CFRP to 0.5 for GFRP; the creep rupture factor is from 0.9 to 0.2. The paper summarizes previous research and experimental studies on the long-term properties of FRP reinforcements and also their comparison with the actual structures in which this reinforcement has been used; it presents the first part of an experimental investigation with comparative calculations.

Schlüsselwörter

  • GFRPreinforcement
  • Long-term properties
  • Creep-rupture
  • Long-term reduction factors
access type Uneingeschränkter Zugang

Detection of Changes in Hydrological Time Series During Recent Decades

Online veröffentlicht: 06 Jul 2020
Seitenbereich: 56 - 62

Zusammenfassung

Abstract

An analysis of a hydrological time-series data offers the possibility of detecting changes that have arisen due to climate change or change in land use. This paper deals with the detection of changes in the hydrological time data series. The trend analysis was applied at 58 stage-discharge gauging stations that are located throughout Slovakia, with the measurement period from 1962 to 2017. The Mann-Kendall test show a declining trends in the summer and a few rising trends in the winter in discharges. In the town of Banská Bystrica at a station on the Hron River, decades of discharges, air temperatures, and precipitation totals were analyzed. The five decades from the 1960s to the 2000s were used. The hydrological time data series were also analyzed by the Pettitt’s test, which is used to detect change points. The decadal analysis at the Banská Bystrica station shows an increase in the air temperature but insignificant changes in discharges and precipitation. Pettitt’s test identified many change points in the 1990s in the air temperature.

Schlüsselwörter

  • Trendanalysis
  • Discharge
  • Change point

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