Block Geometry Research Articles

BENCHMARKING THE OPTICAL RESOLVING POWER OF UAV BASED CAMERA SYSTEMS

Abstract. UAV based imaging and 3D object point generation is an established technology. Some of the UAV users try to address (very) highaccuracy applications, i.e. inspection or monitoring scenarios. In order to guarantee such level of detail and accuracy high resolving imaging systems are mandatory. Furthermore, image quality considerably impacts photogrammetric processing, as the tie point transfer, mandatory for forming the block geometry, fully relies on the radiometric quality of images. Thus, empirical testing of radiometric camera performance is an important issue, in addition to standard (geometric) calibration, which normally is covered primarily. Within this paper the resolving power of ten different camera/lens installations has been investigated. Selected systems represent different camera classes, like DSLRs, system cameras, larger format cameras and proprietary systems. As the systems have been tested in wellcontrolled laboratory conditions and objective quality measures have been derived, individual performance can be compared directly, thus representing a first benchmark on radiometric performance of UAV cameras. The results have shown, that not only the selection of appropriate lens and camera body has an impact, in addition the image pre-processing, i.e. the use of a specific debayering method, significantly influences the final resolving power.

UAV CAMERAS: OVERVIEW AND GEOMETRIC CALIBRATION BENCHMARK

Abstract. Different UAV platforms and sensors are used in mapping already, many of them equipped with (sometimes) modified cameras as known from the consumer market. Even though these systems normally fulfil their requested mapping accuracy, the question arises, which system performs best? This asks for a benchmark, to check selected UAV based camera systems in well-defined, reproducible environments. Such benchmark is tried within this work here. Nine different cameras used on UAV platforms, representing typical camera classes, are considered. The focus is laid on the geometry here, which is tightly linked to the process of geometrical calibration of the system. In most applications the calibration is performed in-situ, i.e. calibration parameters are obtained as part of the project data itself. This is often motivated because consumer cameras do not keep constant geometry, thus, cannot be seen as metric cameras. Still, some of the commercial systems are quite stable over time, as it was proven from repeated (terrestrial) calibrations runs. Already (pre-)calibrated systems may offer advantages, especially when the block geometry of the project does not allow for a stable and sufficient in-situ calibration. Especially for such scenario close to metric UAV cameras may have advantages. Empirical airborne test flights in a calibration field have shown how block geometry influences the estimated calibration parameters and how consistent the parameters from lab calibration can be reproduced.

PERFORMANCE ASSESSMENT OF INTEGRATED SENSOR ORIENTATION WITH A LOW-COST GNSS RECEIVER

Abstract. Mapping with Micro Aerial Vehicles (MAVs whose weight does not exceed 5 kg) is gaining importance in applications such as corridor mapping, road and pipeline inspections, or mapping of large areas with homogeneous surface structure, e.g. forest or agricultural fields. In these challenging scenarios, integrated sensor orientation (ISO) improves effectiveness and accuracy. Furthermore, in block geometry configurations, this mode of operation allows mapping without ground control points (GCPs). Accurate camera positions are traditionally determined by carrier-phase GNSS (Global Navigation Satellite System) positioning. However, such mode of positioning has strong requirements on receiver’s and antenna’s performance. In this article, we present a mapping project in which we employ a single-frequency, low-cost (

EXPLORATION OF STUDENTS KNOWLEDGE CONSTRUCTION PROCESS ON GEOMETRY THROUGT RANDOM THINKING STYLE AND SPATIAL ABILITY OF MENTAL ROTATION LEVEL

The purpose of the study was to determine students’ knowledge construction process in random thinking style including concrete random (CR) and abstract random (AR) where spatial ability was at the mental rotation level in resolving non-routine issues related to the block geometry. This was an exploratory study with a qualitative approach, in which the researcher himself was the main instrument. Data ware collected through the provision of math construction tes (MCT) and unstructured interviews. The subjects of the study consisted of two students, one concrete random (CR) and one abstract random (AR). The subjects were chosen by testing the thinking style and spatial ability tests. The results of the study showed that (1) CR in problem identification indicator was able to understand the problem well and gave clear verbal response and had a process of assimilation for a long time in understanding the information, relations, and brought the situation of the problem in the form of images; whereas, the indicator of the problem solving process could be completed well but it had accommodation when determining the completion and fnding the value of unknown variable. This accommodation process lasted longer and let to the completion and the right answers as well as using procedural and meta-cognition knowledge to solve the problem; (2) AR in problem identification indicator was able to understand the problem well and gave clear verbal response and had a process of assimilation in understanding the information, relations, and brought the situation of the problem into a more complex form; whereas, the indicator of the problem solving process could be complete well in number 1 question and different assimilation process occurs in number 2 question. The accommodation process occurred on the phases of information simplification into the form of equations and finding the variable value by means of substitution between exsisting equations. This accommodation process lasted longer and led to the completion and the right answers as well as used factual and conceptual knowledge to solve the problem

Rectangular Blocks vs Polygonal Walls in Archaeoseismology

Collapsed or deformed walls in ancient structures constitute important evidence in archaeoseismology, where damage is interpreted in terms of earthquake ground motion. A large variety of wall types have been developed during the millennia in different cultural backgrounds. Often walls with polygonal-shaped building blocks are regarded as more earthquake-resistant than a wall consisting of rectangular elements and, as is sometimes speculated, that the irregular wall types were intentionally developed for that purpose. We use simply structured discrete element models of four walls with different block geometries, perfect rectangular, an Inka-type structure and two polygonal designs, to test their dynamic behavior. In addition to an analytic calculation of ground motion, we use measured strong motion signals as boundary conditions for the 3D wall models with varying height to width ratios. At peak ground accelerations between 1.0 and 9.0 m/s 2 and major frequencies of 0.5 to 3 Hz, numeric experiments with the horizontally applied analytic ground motions result in clear differences in the resistance of the four wall types with the rectangular block wall being most vulnerable. For more complex measured 3D motions the Inka-type wall proves more stable than the rectangular block wall; however, height to width ratio still has equally strong influence on the stability. Internal deformation of non-collapsed walls shows some correlation with the parameters of the driving motion. For simple impulsive ground motions, a peak ground displacement threshold exists between toppling and remaining upright for all four models but peak acceleration cannot be reliably back calculated.

Molecular engineering of chiral colloidal liquid crystals using DNA origami.

Establishing precise control over the shape and the interactions of the microscopic building blocks is essential for design of macroscopic soft materials with novel structural, optical and mechanical properties. Here, we demonstrate robust assembly of DNA origami filaments into cholesteric liquid crystals, one-dimensional supramolecular twisted ribbons and two-dimensional colloidal membranes. The exquisite control afforded by the DNA origami technology establishes a quantitative relationship between the microscopic filament structure and the macroscopic cholesteric pitch. Furthermore, it also enables robust assembly of one-dimensional twisted ribbons, which behave as effective supramolecular polymers whose structure and elastic properties can be precisely tuned by controlling the geometry of the elemental building blocks. Our results demonstrate the potential synergy between DNA origami technology and colloidal science, in which the former allows for rapid and robust synthesis of complex particles, and the latter can be used to assemble such particles into bulkmaterials.

Tectonic control of complex slope failures in the Ameka River Valley (Lower Gibe Area, central Ethiopia): Implications for landslide formation

Even though major faults represent important landslide controlling factors, the role the tectonic setting in actively spreading rifts plays in the development of large complex landslides is seldom discussed. The Ameka complex landslide area is located on the eastern scarp of the Gibe Gorge, approximately 45km to the west of the Main Ethiopian Rift and 175km to the southwest of Addis Ababa. Investigation of the complex landslide failures required a combination of satellite and airborne data-based geomorphology, geological field survey complemented with structural analysis, radiocarbon geochronology and vertical electric sounding. The obtained observations confirmed the multiphase evolution of the landslide area. We have documented that, apart from climatic and lithological conditions, the main triggering factor of the Ameka complex landslide is the tectonic development of this area. The ~E–W extension along the ~NNE–SSW trending Main Ethiopian Rift is associated with the formation of numerous parallel normal faults, such as the Gibe Gorge fault and the almost perpendicular scissor faults. The geometry of the slid blocks of coherent lithology have inherited the original tectonic framework, which suggests the crucial role tectonics play in the fragmentation of the compact rock-masses, and the origin and development of the Ameka complex landslide area. Similarly, the main scarps were also parallel to the principal tectonic features. The local tectonic framework is dominated by faults of the same orientation as the regional structures of the Main Ethiopian Rift. Such parallel tectonic frameworks display clear links between the extension of the Main Ethiopian Rift and the tectonic development of the landslide area. The Ameka complex landslide developed in several episodes over thousands of years. According to the radiocarbon data, the last of the larger displaced blocks (representing only 2% of the total area) most likely slid down in the seventh century AD. The main scarps, namely the high scarps in the western part, are unstable over the long term and toppling and falling-type slope movements can be expected here in the future.

Investigation of rock fragmentation during rockfalls and rock avalanches via 3‐D discrete element analyses

AbstractThis paper investigates the characteristics of dynamic rock fragmentation and its influence on the postfailure fragment trajectory. A series of numerical simulations by discrete element method (DEM) were performed for a simple rock block and slope geometry, where a particle agglomerate of prismatic shape is released along a sliding plane and subsequently collides onto a flat horizontal plane at a sharp kink point. The rock block is modeled as an assembly of bonded spherical particles with fragmentation arising from bond breakages. Bond strength and stiffness were calibrated against available experimental data. We analyzed how dynamic fragmentation occurs at impact, together with the generated fragment size distributions and consequently their runout for different slope topographies. It emerges that after impact, the vertical momentum of the granular system decreases sharply to nil, while the horizontal momentum increases suddenly and then decreases. The sudden boost of horizontal momentum can effectively facilitate the transport of fragments along the bottom floor. The rock fragmentation intensity is associated with the input energy and increases quickly with the slope angle. Gentle slopes normally lead to long spreading distance and large fragments, while steep slopes lead to high momentum boosts and impact forces, with efficient rock fragmentation and fine deposits. The fragment size decreases, while the fracture stress and fragment number both increase with the impact loading strain rate, supporting the experimental observations. The fragment size distributions can be well fitted by the Weibull's distribution function.

Updating the coal quality parameters in multiple production benches based on combined material measurement: a full case study

An efficient resource model updating framework concept was proposed aiming for the improvement of raw material quality control and process efficiency in any type of mining operation. The concept integrates sensor data measured online on the production line into the resource or grade/quality control model and continuously provides locally more accurate estimates. The concept has been applied in a lignite field with the aim of identifying local impurities in a coal seam and to improve the prediction of coal quality attributes in neighbouring blocks. A significant improvement was demonstrated which led to better coal quality management. So far, the proposed concept and the application in coal mining was limited to a case where online measurements were unambiguously trackable due to a single extraction face being the point of origin for the material. This contribution presents an extension to the case, where characteristics from blended material, originating from two or three simultaneously operating extraction faces, are measured. The challenge tackled in this contribution is the updating of local coal quality estimates in different production benches based on measurements of a blended material stream. For a practical application of the updating concept, which is based on the Ensemble Kalman Filter, a simple method for generating prior ensemble members based on block geometries defined in the short-term model and the variogram, is discussed. This method allows for a fast, semi-automated and rather simple generation of prior models instead of generating a fully simulated deposit model using conditional simulation in geostatistics. It should foster operational implementation in an industrial environment. The main purpose of this article is to investigate the applicability of the developed framework with a simplified prior resource model. In addition to this any model improvements due to the integration of sensor data obtained by observing a blend of coal from multiple extraction faces is investigated.

Engineering geological and geotechnical analysis of a rock slide in the quarry Frauenmühle near Metten (Lower Bavaria)

AbstractIn spring 2008 a rock slide detached from one of the walls in the quarry ”Frauenmühle“ locally used as climbing park, mobilizing a volume of 50 m3. The binary granite is relative fresh on the bottom of the walls, but the weathering increases significantly to the natural surface. The bedrock shows an orthogonal joint system enabling the so‐called ”Wollsackverwitterung“. Mapping of the joints followed by a kinematic analysis of the quarry wall by DIPS (Rocscience) indicates the slope failure to be of a planar sliding type on a medium‐steep dipping plane. As the contributing factor for the slide, weathering along the plane has to be considered. Thereby the destruction of rock bridges downgrades the overall shear strength. A stability analysis based on the reconstructed block geometry and the determined shear parameters verifies the instability of the block. For today's situation, the kinematic analysis detects some critical intersections of joints being able to generate slide wedges.

Numerical investigation of laminar forced convection heat transfer in rectangular channels with different block geometries using nano-fluids

This research investigates the laminar steady-forced convection heat transfer of a Cu-water nanofluid in a 2-D horizontal channel with different block geometries attached to the bottom wall. The block geometries assumed in this research are triangular and curve blocks. The governing equations associated with the required boundary conditions are solved using finite volume method based on the SIMPLE technique and the effects of Reynolds number, nanofluid volume fraction, block geometry, and the numbers of blocks on the local and average Nusselt numbers are explored. The obtained results show that nanoparticles can effectively enhance the heat transfer in a channel. Furthermore, the local and average Nusselt number distribution is strongly dependent on the block geometry. As observed, the heat transfer augments with the increase in the Reynolds number and nanofluid volume fraction for both block geometries. It is also concluded that the average Nusselt number of the curve block is higher than that of the triangular block for different Reynolds numbers which declares the importance of the block geometry in the heat transfer enhancement.

Potential energy landscapes of tetragonal pyramid molecules

Hiraoka et al. have developed a self-assembling system referred to as a nanocube (Hiraoka et al., 2008). In the present contribution a coarse-grained model for this system is analysed, focusing on how the potential energy landscape for self-assembly is related to the geometry of the building blocks. We find that six molecules assemble to form various clusters, with cubic and sheet structures the most stable. The relative stability is determined by the geometry of the building blocks.

Material development for a sustainable precast concrete block pavement

Abstract Portland cement concrete (PCC) and asphalt concrete (AC) are the most common roadway and highway construction materials which are more suitable for continuous slab pavements. The durability of these materials is highly dependent on construction quality and techniques, and both materials are difficult to repair. Heavy rain storms in India have recently revealed several roadway pavement failures and resulted in significant repair costs. Interlocking block type pavements are simpler to construct and maintain than both PCC and AC pavements but, have only been used for slower traffic roads due to weak interlocking at the joints. To improve the quality of block pavements, blocks made of PCC with waste tire crumb rubber partially replacing river sand (fine aggregate) are suggested. The joint interlocks can be further improved by modifying the block geometry. The material is completely recycled and is deemed more superior than concrete pavements when repair and construction techniques and costs are concerned. This paper presents the material characterization of Rubberized Concrete Blocks (RCBs) using crumb rubber particle size ranging from 0.075 mm to 4.75 mm to partially replace the fine aggregates. It also discusses the advantages of RCB over continuous material pavements.

Sensitivity analysis of urban morphology factors regarding solar energy potential of buildings in a Brazilian tropical context

Today, 75% of global energy consumption occurs in cities. On the topic of climate change, adapting urban settlements to face this growing demand is a priority issue, especially for fast-growing cities in developing countries such as Brazil. Planning the urban morphology of the built environment is a key issue in shifting to a climate adapted urban environment. This paper addresses an important threefold energy challenge of tropical cities: the major potential of harnessing solar energy as renewable resource for local electricity production and the energy-saving paradox of reducing the undesirable solar heat gains in buildings while providing satisfactory levels of daylight. It aims at measuring the effect size of urban form factors regarding these energy goals. This study applies the Design Of Experiments (DOE) approach. A DOE analysis is a statistical technique that provides a set measure of how design parameters are correlated and the effective contribution of each one to a given response of interest. This study proposes a fractional factorial DOE method coupled to a Simplified Radiosity Algorithm (SRA) aiming to evaluate the irradiation availability on building envelopes while taking a large representative sample of contrasted urban block geometries into account. The buildings’ envelope solar irradiation availability assesses a set of energy-related morphological parameters. Results indicate a significant impact of the aspect ratio, the distance between buildings and the surface equivalent albedo. Establishing high values of street aspect ratio may cut solar irradiation on roofs by 130kWh/m2year, while increasing the plot ratio may only yield 26kWh/m2year. The results also point out important first order interaction effects between certain variables.

Design and Engineering of a Dry Assembled Glass Block Pedestrian Bridge

Inspired by the glass masonry technique developed by the TU Delft Glass and Transparency Lab for the Crystal House in Amsterdam, a 14 meter span pedestrian bridge is envisioned, also consisting of cast glass elements. In contrast to the Crystal House project that employs an adhesively bonded glass block system, here dry assembly of the glass elements is proposed to allow for a demountable structure. To achieve this, a constant compression force is introduced in the bridge through its arch-shape. This compression force and a special interlocking geometry of the blocks will ensure the stability of the structure, like a medieval stone arch. The paper will discuss the exploratory design and engineering leading up to the construction of the first 3 meter span mock-up. This includes studies on the visual appearance of the bridge, studies on the glass block geometry, calculations on stresses in the glass elements, experiments on force transfer through dry-connected elements and mould design for casting of the complex geometries of the glass elements.

ChemInform Abstract: Constraining the Coordination Geometries of Lanthanide Centers and Magnetic Building Blocks in Frameworks: A New Strategy for Molecular Nanomagnets

AbstractReview: 50 refs.

DEM-Aided Bundle Adjustment With Multisource Satellite Imagery: ZY-3 and GF-1 in Large Areas

In this letter, a new digital elevation model (DEM)-aided bundle block adjustment (BBA) method is proposed which utilizes a rational-polynomial-coefficient affine transformation model and a preconditioned conjugate gradient (PCG) algorithm with multisource satellite imagery (ZY-3 and GF-1) for producing and updating ortho maps of large areas. To deal with the weak geometry of the large blocks, a reference DEM is used in this method as an additional constraint in the BBA. The PCG algorithm is applied to solve the large normal matrix produced by the massive data of the large areas. Our proposed method was tested on three blocks of real data collected by GF-1 panchromatic and multispectral sensors and ZY-3 three-line-camera sensors. The preliminary results show that the proposed method can achieve an accuracy of better than 0.5 pixels in planimetry and is suitable for wide application in ortho-map production. It also has great potential for the ortho-map production of superlarge areas such as the country of China as one block.

Implicit Discrete Element Analysis of a Masonry Cupola Under Seismic Loads

In the current study, the dynamic mechanical behaviour of a masonry cupola composed of non-convex discrete elements is investigated. This cupola is designed in innovative and modern ways and was recently constructed with stone blocks in the south of France. The necessity of applying an accurate numerical modelling method being able to take into account the real geometry of each non-convex block is also presented and discussed. The stability state of this masonry structure, by considering the different levels of seismic loads is studied. In addition, the effects of changes in the contact condition between blocks, or the blocks and the structure foundation, are comprehensively investigated.

Analytical Method for Calculating the Volume of Rock Blocks Using Available Mapping Data Field

The calculation of the volumes of rock blocks delimited by discontinuity planes in rock masses is essential for the design of excavations and supports, applied to various engineering activities, like mining and tunneling. Furthermore, the block volumes control the rock mass behavior. If very small blocks are predominant, the rock mass tends to act as a continuum media and exhibit failure through the rock material. In case of prevalence of large blocks the rock mass acts as a discrete block set and failure through discontinuities can occur. There are many analytical methods in technical literature to calculate the volume of rock blocks but most of them are not realistic in relation to data input. In some cases a detailed knowledge of block geometry is required; such condition is rarely available in a field survey. This paper presents an analytical solution for block volume calculation using an easily obtained data in the field. Tetrahedral, tabular or prismatic blocks can be considered. An extension of the solution for polyhedral blocks is also presented.

Seismic resistance of dry stone arches under in-plane seismic loading

The aim of this study is to investigate the seismic resistance of dry stone arches under in-plane seismic loading. For that purpose, several numerical analyses were performed using the combined finite-discrete element method (FDEM). Twelve types of arches with different ratios of a rise at the mid-span to the span, different thicknesses of stone blocks and different numbers of stone blocks in the arch were subjected to an incremental dynamic analysis based on excitation from three real horizontal and vertical ground motions. The minimum value of the failure peak ground acceleration that caused the collapse of the arch was adopted as a measure of the seismic resistance. In this study, the collapse mechanisms of each type of stone arch, as well as the influence of the geometry of stone blocks and stone arches on the seismic resistance of structures were observed. The conclusions obtained on the basis of the performed numerical analyses can be used as guidelines for the design of dry stone arches.