Tall Objects Research Articles

A Pneumatic Fingerless Soft Gripper for Envelope Gripping

In grasping operations, when facing unstructured environments, the use of soft-body grippers can be a good solution to the problem of grasping objects that are inconvenient to grasp due to their fragility and irregularity. However, as the soft-body gripper is composed of soft-body material, there are problems such as insufficient gripping power. The envelope-gripping method using a fingerless structure of the soft gripper has high gripping capacity. In this paper, a new type of pneumatic, soft-body, fingerless gripper (SFLG) is proposed based on envelope-type grasping. With its rigid connectors, it forms a soft-body gripper. By changing the air pressure and structure of the internal air cavity of the fingerless gripper, the degree of deformation can be controlled to achieve grasping of the object by the soft-body gripper. Experiments show that the soft-body gripper can grasp objects of different shapes and sizes. The SFLG can grasp objects up to 6 times higher than itself, and the soft gripper of this size can grasp objects up to 13 times heavier than itself. A pneumatic, fingerless, soft gripper has been designed to grasp small and heavy or tall objects in contrast to other fingerless soft grippers.

A stochastic world model on gravity for stability inference.

The fact that objects without proper support will fall to the ground is not only a natural phenomenon, but also common sense in mind. Previous studies suggest that humans may infer objects' stability through a world model that performs mental simulations with a priori knowledge of gravity acting upon the objects. Here we measured participants' sensitivity to gravity to investigate how the world model works. We found that the world model on gravity was not a faithful replica of the physical laws, but instead encoded gravity's vertical direction as a Gaussian distribution. The world model with this stochastic feature fit nicely with participants' subjective sense of objects' stability and explained the illusion that taller objects are perceived as more likely to fall. Furthermore, a computational model with reinforcement learning revealed that the stochastic characteristic likely originated from experience-dependent comparisons between predictions formed by internal simulations and the realities observed in the external world, which illustrated the ecological advantage of stochastic representation in balancing accuracy and speed for efficient stability inference. The stochastic world model on gravity provides an example of how a priori knowledge of the physical world is implemented in mind that helps humans operate flexibly in open-ended environments.

A stochastic world model on gravity for stability inference

The fact that objects without proper support will fall to the ground is not only a natural phenomenon, but also common sense in mind. Previous studies suggest that humans may infer objects’ stability through a world model that performs mental simulations with a priori knowledge of gravity acting upon the objects. Here we measured participants’ sensitivity to gravity to investigate how the world model works. We found that the world model on gravity was not a faithful replica of the physical laws, but instead encoded gravity’s vertical direction as a Gaussian distribution. The world model with this stochastic feature fit nicely with participants’ subjective sense of objects’ stability and explained the illusion that taller objects are perceived as more likely to fall. Furthermore, a computational model with reinforcement learning revealed that the stochastic characteristic likely originated from experience-dependent comparisons between predictions formed by internal simulations and the realities observed in the external world, which illustrated the ecological advantage of stochastic representation in balancing accuracy and speed for efficient stability inference. The stochastic world model on gravity provides an example of how a priori knowledge of the physical world is implemented in mind that helps humans operate flexibly in open-ended environments.

Interactions Between Lightning and Ship Traffic

AbstractIt is important to understand connections between society and the natural environment for anticipating hazards and anthropogenic effects on the Earth system. In this study, we conduct a detailed exploration of interactions between oceanic thunderstorms and maritime traffic. Shipping traffic produces aerosols that perturb the otherwise “clean” ocean environment. Prior work proposed these aerosol effects as the cause of increased lightning over certain shipping lanes. However, introducing tall grounded objects into a high electric field environment might also facilitate lightning discharges, as we see with upward lightning over land. We consider both possibilities. Our analyses of the thunderstorms responsible for enhanced lightning activity over the shipping lane with the clearest anthropogenic signal indicate that the enhancement results from an increased frequency of lightning‐producing storms. Observed variations in thunderstorm microphysics between the shipping lane and nearby oceans are small compared to natural factors such as the Indian monsoon, and are on the same scale as the local variability in the data. By contrast, matching lightning stroke data with ship transponder events in oceanic regions where public data are available reveals a strong signal from direct ship interactions. Lightning is 15× (66×) more likely to occur at a ship location compared to 2 km (25 km) away. These results highlight the central role of direct ship interactions in explaining lightning enhancements over shipping lanes. We also document the frequency of these direct lightning interactions across various categories of vessels and on individual ships present in the public data.

BISTATIC SCATTERING CHARACTERISTICS OF A WIND PARK TURBINE DERIVED FROM AN UAV-MOUNTED RECEIVER RECORDING C-BAND WEATHER RADAR SIGNALS

Abstract. As a result of increasing use of wind energy as a sustainable source of electricity, large Wind Parks with numerous Wind Turbines have been constructed. Wind turbines are extremely tall objects consisting of stationary and moving parts. The presence of wind turbines in the vicinity of weather radar systems can significantly impact their performance, leading to false alarms and errors in radar measurements. Accurate weather forecasting is challenging in this circumstance. Large Radar Cross Section (RCS) of wind turbines results in interference, also known asWind Turbine Clutter (WTC) orWind Turbine Interference (WTI), within and beyond the radar main beam, Multipath Interference (MPI), and phenomena referred to as ”shadowing effects” behind the wind turbines. These effects vary significantly in both time and space as a result of various wind turbine operations and meteorological conditions. It can often be difficult to distinguish wind turbine returns from weather-like signals. For the assessment of WTC or WTI, it is essential to understand the scattering properties of these wind turbines. In this paper, the bistatic scattering characteristics of a wind park turbine using a Unmanned Aerial Vehicle (UAV)-mounted receiver recording C-band weather radar signals were investigated by determining the average received power (PRxAvg (θs)) and RCS of wind turbine as a function of the scattering angle. For this purpose, the measurements and data provided by the German Meteorological Service (DWD, DeutscherWetterdienst) were utilised. The average received power as a function of scattering angle (θs) was calculated by using I-Q (In-phase and Quadrature) signals. Forward, back and side scattering of the calculated average received power were analysed separately. Moreover, Front-to-Back ratio, Front-to-Right side ratio and Front-to-Left side ratio were calculated and compared using forward, back and side scatter values. RCS values were also calculated depending on the scattering angle (θs) of the wind turbine.

Lightning Current Waveforms Inferred From Far-Field Waveforms for the Case of Strikes to Tall Objects

Electric and magnetic fields at far distances produced by lightning strikes to tall objects are different from those associated with lightning strikes to flat ground. Specifically, in the case of strikes to tall objects, the waveforms are oscillatory because of current reflections at the top and bottom of the tall object. In this article, a procedure to reconstruct the waveform of far electric field due to the lightning strike to flat ground from the corresponding waveform of far electric field due to a lightning strike to a tall object is proposed. Once the effect of tall strike object is removed from the measured field waveform, the channel-base current for the strike to flat ground is estimated. Further, the channel-base current waveform is used to find the waveform of current at any altitude along both the strike object and the lightning channel. Computations of far electric fields due to lightning strikes to tall objects are carried out using the finite-difference time-domain method in the two-dimensional cylindrical coordinate system. The lightning return stroke is represented by the transmission-line (TL) model, the modified TL model with linear current decay with height, or the modified TL model with exponential current decay with height.

Data-Driven Diffraction Loss Estimation for Future Intelligent Transportation Systems in 6G Networks

The advancement of 6G networks is driven by the need for customer-centric communication and network control, particularly in applications such as intelligent transport systems. These applications rely on outdoor communication in extremely high-frequency (EHF) bands, including millimeter wave (mmWave) frequencies exceeding 30 GHz. However, EHF signals face challenges such as higher attenuation, diffraction, and reflective losses caused by obstacles in outdoor environments. To overcome these challenges, 6G networks must focus on system designs that enhance propagation characteristics by predicting and mitigating diffraction, reflection, and scattering losses. Strategies such as proper handovers, antenna orientation, and link adaptation techniques based on losses can optimize the propagation environment. Among the network components, aerial networks, including unmanned aerial vehicles (UAVs) and electric vertical take-off and landing aircraft (eVTOL), are particularly susceptible to diffraction losses due to surrounding buildings in urban and suburban areas. Traditional statistical models for estimating the height of tall objects like buildings or trees are insufficient for accurately calculating diffraction losses due to the dynamic nature of user mobility, resulting in increased latency unsuitable for ultra-low latency applications. To address these challenges, this paper proposes a deep learning framework that utilizes easily accessible Google Street View imagery to estimate building heights and predict diffraction losses across various locations. The framework enables real-time decision-making to improve the propagation environment based on users’ locations. The proposed approach achieves high accuracy rates, with an accuracy of 39% for relative error below 2%, 83% for relative error below 4%, and 96% for both relative errors below 7% and 10%. Compared to traditional statistical methods, the proposed deep learning approach offers significant advantages in height prediction accuracy, demonstrating its efficacy in supporting the development of 6G networks. The ability to accurately estimate heights and map diffraction losses before network deployment enables proactive optimization and ensures real-time decision-making, enhancing the overall performance of 6G systems.

On the Use of Electromagnetic Models and the 3D-FDTD Method in the Evaluation of Radiations Due to Lightning Strikes to Tall Objects

The purpose of this paper is the investigation of the use of a lightning return stroke current electromagnetic model and the Finite Difference Time Domain (FDTD) method, in three dimensions, in order to study the Lightning Electromagnetic Pulse (LEMP) due to lightning strikes to tall objects (towers). The proposed approach and the developed code are validated by the comparison with the measured data taken obtained in the specialized literature. The evaluation of the LEMP propagation, in presence of different values of ground conductivity, is finally presented and discussed. It is found out that the use of electromagnetic models, which are close to the physical reality of the lightning phenomena, yields reasonably accurate results. The obtained simulation results, using a calculation code developed on Matlab, have turned out to be in very good agreement with measurement data. It has been found out also that the spatiotemporal current distribution along the tower and the lightning channel is influenced by the conductivity variation. Indeed, the LEMP propagation is significantly affected by both lightning current change and ground conductivity variation. It can be noted that the simulation results obtained can be exploited in order to study the coupling problems between LEMP due to lightning strikes to tall objects with different electrical, electronic and telecommunication systems.

Potential use of space-based lightning detection in electric power systems

• Operational space-based optical lightning detection provides new information useful for electrical power systems. • Flashes producing continuing currents can be identified from space-based lightning imagers. • Analyzed upward-triggering lightning flashes presents a common optical pattern. • Identification of potential upward-triggering lightning flashes is used to estimate the annual upward lightning frequency from tall towers (e.g. wind turbines). • Satellite total lightning data are used to evaluate the exposure of lightning of an overhead transmission line. Information about lightning activity and its parameters is necessary to design and evaluate the lightning protection of an electrical power system. This information can be obtained from ground-based lightning detection networks that provide information on cloud-to-ground lightning strikes with a location accuracy of few hundred meters. Recently, the first satellite-based lightning optical detectors are operating continuously from geostationary orbits. These imagers observe the luminosity escaping from clouds to detect and locate total lightning activity with a spatial accuracy of several kilometers. This allows delineating the initiation and propagation (sometimes over tens to hundreds of kilometers before striking the ground) not observable by the ground-based networks. In this paper, we explore the use of this new technology for lightning protection in power systems. We focus on tall objects such as wind turbines and overhead transmission lines. We show how the optical detections allow identifying lightning flashes that likely produce continuing currents. This provides additional information for the identification of dangerous events and also can be used to estimate the number of upward-flashes from tall objects triggered by a nearby flash. The analysis of a transmission line shows the concentration of faults in the areas of high total lightning flash density. We found regional variations of the optical energy of the flashes along the line.

Urban Road Safety Prediction: A Satellite Navigation Perspective

Predicting the safety of urban roads for navigation via global navigation satellite systems (GNSS) signals is considered. To ensure safe driving of automated vehicles, the vehicle must plan its trajectory to avoid navigating on unsafe roads (e.g., icy conditions, construction zones, narrow streets, etc.). Such information can be derived from the roads' physical properties, vehicle's capabilities, and weather conditions. From a GNSS-based navigation perspective, the reliability of GNSS signals in different locales, which is heavily dependent on the road layout within the surrounding environment, is crucial to ensure safe automated driving. An urban road environment surrounded by tall objects can significantly degrade the accuracy and availability of GNSS signals. This article proposes an approach to predict the reliability of GNSS-based navigation to ensure safe urban navigation. Satellite navigation reliability at a given location and time on a road is determined based on the probabilistic position error bound of the vehicle-mounted GNSS receiver. A metric for GNSS reliability for ground vehicles is suggested, and a method to predict the conservative probabilistic error bound of the GNSS navigation solution is proposed. A satellite navigation reliability map is generated for various navigation applications. As a case study, the reliability map is used in the proposed optimization problem formulation for automated ground vehicle safety-constrained path planning.

Monitoring the Geometry of Tall Objects in Energy Industry

The landscape shaped by the energy industry is rich in various slender structures, such as smokestacks, cooling towers, and others. It is thus becoming increasingly important to effectively monitor the geometrical condition of all types of such structures. Slender structures are deformed elastically under loads due to wind. A proper analysis of the changes and deformations of such structures requires a continuous ground-based measurement system which allows the movement of the structure to be measured in two horizontal directions, from a significant distance and with a possibly reduced number of stations. For this purpose, two methods were implemented: a linear terrestrial laser scanning method (TLS) and an optical, direct distance measurement method—tachymetry (TCH). The least squares method was used to fit rings on various levels of the structure and then the centers of the rings were identified. The comparison of the identified ring centers enabled the axis of the structure to be measured for deviation in two perpendicular directions. The methods were verified on actual structures: a smokestack 110 m in height, a cooling tower 60 m in height, and a wind turbine with the rotor axis at 149 m. The measurement results were compared with respect to the measurement time and the obtained accuracies at which the point locations were identified on the structure. The proposed methods are an effective tool for monitoring the condition of slender objects both during their operating life and after it. Regular monitoring of the geometric condition of slender structures in the energy industry limits the risk of major or catastrophic events, and as a result allows the safe and uninterrupted delivery of electric energy to clients.

Urbanistička analiza mogućnosti izgradnje objekata posebne namene - studija slučaja objekta kontrole letenja na aerodromu "Nikola Tesla" u Beogradu

The practice of implementing urban plans for the construction area of the City of Belgrade has shown that in some cases they do not contain enough elements to implement directly. This is especially true for special purpose sites and facilities, whose design and construction require the pre-definition of more detailed conditions and rules of landscaping and construction. In order to address such issues, the authors explore the practice of developing urban analyses in the case of the air traffic control facility at Belgrade's Nikola Tesla Airport. The paper presents the starting points for developing an urban analysis and excerpts from relevant planning documents, while analyzing the existing condition of the site. The basic results of the analysis show the available capabilities and capacity of the site. In particular, the paper analyzes how well the criteria for building a flight control tower, as a tall object and future location benchmark, were fulfilled. The findings underscore the importance of urban analysis as an instrument for implementing planning solutions for special purpose facilities, which by their nature are unique and of the utmost national importance. The authors also look at urban analysis as a scientific method, while laying out basic guidelines and emphasizing the need for further research.

On the Induced Currents to Wind Turbines by the Earth’s Atmospheric Electric Potential: Experiments With Drones

We live in an electrified atmosphere where a potential difference of about 250 kV is established between the ground and the ionosphere. The resulting potential gradient induces electric charges on the objects immersed in the atmosphere, which are more significant in tall objects. Several works have identified interferences to sensors in wind turbine rotor blades being attributed to electrostatic charging of blades. This paper presents a novel experiment using vertical wires lifted by a drone to study the currents resulting under fair-weather atmospheric conditions. Two current components are identified, one resulting in point/corona discharge and the other related to the movement. Based on the experimental results, a model for predicting induced currents on wind turbines is proposed, and estimates for thunderstorm conditions are made. The results presented in this paper are important for designing the electromagnetic compatibility measures to ensure the reliability of multi-megawatt wind turbines with blades equipped with active control systems and higher use of sensors.

Wind induced oscillation on a tall circular storage shell for various terrains

The wind is an important natural phenomenon, which adversely affects different structures, such as high-rise buildings, chimneys, tanks, silos, bridges etc. The effect of wind on tall circular storage shell structures becomes critical, especially when it is in empty condition. Wind induced radial, meridional and axial stresses can cause ovalling, buckling, rupture, overturning etc. on circular storage shells. Terrain, topography, surface roughness, wind velocity, etc. are some of the important factors which influences the wind pressure distribution on circular storage shells. Also, the wind-induced oscillation may lead to structural failure of such shells. Significantly, a small number of studies are there on the effect of these factors on the aerodynamic excitation of circular storage shells. These available scopes and the importance of the studies on circular shell under aerodynamic excitation draws the attention of the present authors to investigate in this field. In the present study the authors have conducted computational fluid dynamics analysis, fluid–structure interaction analysis and modal analysis on a tall circular storage shell with slenderness ratio 4.0 considering four different terrains as per IS 875, part 3, 2015. These terrains are open terrain (terrain 1), open terrain with well scattered low to mid-rise objects (terrain 2), terrain with numerous closely spaced low and mid-rise objects (terrain 3) and terrain with closely spaced tall objects (terrain 4). The atmospheric boundary for each terrain is simulated using power law. The effect of terrain variation is assessed through the variation in the mean, and fluctuating wind pressure coefficient distribution around the circumference of the tall shell. It is observed that the mean pressure coefficients decreases and the fluctuating pressure coefficients increases in the side region of the shell, with the change in terrain conditions from terrain 1 to terrain 4. The highest and lowest pressure fluctuations are observed in the side region and leeward region, respectively. The wind-induced oscillation of the tall shell in relation to the fluctuating pressure coefficients have been assessed and the deformation of the tall storage shell for six consecutive mode shapes have been highlighted for terrain 4, where the distribution of fluctuating pressure coefficients is highest in magnitude.

Building detection using a dense attention network from LiDAR and image data

Accurate building mapping using remote sensing data is challenging because of the complexity of building structures, particularly in populated cities. LiDAR data are widely used for building extraction because they provide height information, which can help distinguish buildings from other tall objects. However, tall trees and bridges in the vicinity of buildings can limit the application of LiDAR data, particularly in urban areas. Combining LiDAR and orthoimages can help in such situations, because orthoimages can provide information on the physical properties of objects, such as reflectance characteristics. One efficient way to combine these two data sources is to use convolutional neural networks (CNN). This study proposes a CNN architecture based on dense attention blocks for building detection in southern Toronto and Massachusetts. The stacking of information from multiple previous layers was inspired by dense attention networks (DANs). DAN blocks consist of batch normalization, convolution, dropout, and average pooling layers to extract high- and low-level features. Compared with two other widely used deep learning techniques, VGG16 and Resnet50, the proposed method has a simpler architecture and converges faster with higher accuracy. In addition, a comparison with the two other state-of-the-art deep learning methods, including U-net and ResUnet, showed that our proposed technique could achieve a higher F1-score, of 0.71, compared with 0.42 for U-net and 0.49 for ResUnet.

Through a Museum Window: Tacita Dean’s FILM (2011) and a Cinema of Dissensus

On a 13-meter-high white monolith screen, a succession of shots of tall objects, such as trees, a fountain, scaffolding, an industrial smokestack, a cathedral window and an escalator appear for a f...

An Extension of the Guided Wave M‐Component Model Taking Into Account the Presence of a Tall Strike Object

AbstractWe present in this paper an extension of the guided‐wave M‐component model of Rakov et al. considering the presence of a vertically elevated strike object. The tall object is represented as a lossless, uniform transmission line. Expressions for the current distribution along the channel and along the strike object are derived. Simulation results for the electric field at close (100 m), intermediate (15 km), and far (100 km) distance ranges are presented, considering fast and slow M‐component currents. The results show that, for very tall structures and fast M‐component waves, the presence of a tall strike object can result in a sharp peak superimposed on the M‐component electric field at intermediate and far distance ranges (e.g., 15 and 100 km). At close distances, the electric field of a fast M‐component is characterized by an initial negative excursion followed by a polarity change. It is shown that the presence of the tower results in a decrease of the negative initial excursion of the field. For slow M‐component waveforms or for moderately tall structures, the presence of the tall strike object can be disregarded in the M‐component field calculations. A discussion on the influence of the M‐wave channel height and velocity on the electric fields for fast M‐component currents is also presented. The study suggests a noticeable effect of the M‐wave velocity on the electric fields at all distance ranges. The variations of the wave velocity and channel length affect the time of appearance of the superimposed sharp peak on the electric fields. However, the sharp peak magnitude, which is due to the presence of the tower, is independent of the channel length and wave velocity. It is determined by the injected current and the reflection coefficients from the ground and tower top.

Computation of Electromagnetic Field Generated by Lightning Strikes to a Tall Object in Presence of a Vertically Stratified Ground Using the 3D-FDTD Method

In this paper, a study about lightning electromagnetic radiation in a complex geometry is presented. Indeed, it is about examining the effect of a vertically stratified ground presence on the electromagnetic field generated by lightning strikes to a tall object (tower), using the three dimension Finite Difference Time-Domain (3D-FDTD) method. The space-time distribution of the current along the lightning channel and along the tower is modeled and calculated using the Transmission Line (TL) model extended in order to include a tall strike object. The developed computing code is validated by the comparison with the results obtained in the specialized literature. In this comparison, a satisfactory agreement between results is observed. According to the obtained results it is shown that both up-ground and under-ground electromagnetic field components (vertical and horizontal electric field and azimuthal magnetic field) magnitudes are affected by the presence of the vertically stratified ground.

Effects of Surface and Top Wind Shear on the Spatial Organization of Marine Stratocumulus‐Topped Boundary Layers

AbstractThe convective nature of Stratocumulus topped boundary layers (STBL) involves the motion of updrafts and downdrafts, driven by surface fluxes and radiative cooling, respectively. The balance between shear and buoyant forcings at the surface can determine the organization of updrafts between cellular and roll structures. We investigate the effect of varying shear at the surface and top of the STBL using Large Eddy Simulations, taking DYCOMS II RF01 as a base case. We focus on spatial identification of the following features: coherent updrafts and downdrafts, and observe how they are affected by varying shear. Stronger surface shear organizes the updrafts in rolls, causes less well‐mixed thermodynamic profiles, and decreases cloud fraction and liquid water path (LWP). Stronger top shear also decreases cloud fraction and LWP more than surface shear, by thinning the cloud from the top. Features with stronger top than surface shear are associated with a net downward momentum transport and show early signs of decoupling. Classifying updrafts and downdrafts based on their vertical span and horizontal size confirms the dominance of tall objects spanning the whole STBL. Tall objects occupy 30% of the volume in the STBL, while short ones occupy less than 1%. For updraft and downdraft fluxes, these tall objects explain 65% of the vertical velocity variance and 83% of the buoyancy flux, on average. Stronger top shear also weakens the contribution of downdrafts to the turbulent fluxes and tilts the otherwise vertical development of updrafts.

MOBILE LASER SCANNING ELEVATION DATA ACCURACY IN CLOSED AND PARTIALLY OPEN SKY AREA

Mobile laser scanning is being used more often in Estonia and abroad to obtain geospatial information. As the system is still new and being upgraded, different methods are being used to find out how accurately the mobile laser scanner can measure in different conditions. In this article the mobile laser scanner accuracy is being examined depending on surrounding environment and the importance of postprocessing. Mobile laser scanning elevation data accuracy obtained in difficult conditions is being assessed. Difficult conditions are considered locations where there are tall objects that interrupt the satellite signals’ trajectory to the receiver. To determine the elevation accuracy of mobile laser scanner data, coordinates with the raw broadcast and final ephemerides with the combination of the GNSS receivers’ data that were installed in ideal and not ideal environmental conditions were computed. As a result of the study, the error of the elevation data in the first polygon, situated in difficult conditions was 7 mm when the Kunda reference station data was used with raw broadcast and final ephemerides. Error in the second polygon was accordingly 17 mm and 19 mm. When calculations were conducted using raw broadcast ephemerides in a base station in an imperfect environment, the error in the first polygon was 103 mm and in the second 75 mm. When the precise ephemerides were added to base station data, the error in the first polygon was 6 mm and in the second 21 mm. From the study results, it could be concluded that the mobile laser scanning system measures within 2 cm accuracy even in a complicated environment.