Geometric Issues Research Articles

Coordinate descent heuristics for the irregular strip packing problem of rasterized shapes

We consider the irregular strip packing problem of rasterized shapes, where a given set of pieces of irregular shapes represented in pixels should be placed into a rectangular container without overlap. The rasterized shapes provide simple procedures of the intersection test without any exceptional handling due to geometric issues, while they often require much memory and computational effort in high-resolution. To reduce the complexity of rasterized shapes, we propose a pair of scanlines representation called the double scanline representation that merges consecutive pixels in each row and column into strips with unit width, respectively. Based on this, we develop coordinate descent heuristics for the raster model that repeat a line search in the horizontal and vertical directions alternately, where we also introduce a corner detection technique used in computer vision to reduce the search space. Computational results for test instances show that the proposed algorithm obtains sufficiently dense layouts of rasterized shapes in high-resolution within a reasonable computation time.

Modelling on-demand preprocessing framework towards practical approach in clinical analysis of diabetic retinopathy

<p>Diabetic retinopathy (DR) refers to a complication of diabetes and a prime cause of vision loss in middle-aged people. A timely screening and diagnosis process can reduce the risk of blindness. Fundus imaging is mainly preferred in the clinical analysis of DR. However; the raw fundus images are usually subjected to artifacts, noise, low and varied contrast, which is very hard to process by human visual systems and automated systems. In the existing literature, many solutions are given to enhance the fundus image. However, such approaches are particular and limited to a specific objective that cannot address multiple fundus images. This paper has presented an on-demand preprocessing frame work that integrates different techniques to address geometrical issues, random noises, and comprehensive contrast enhancement solutions. The performance of each preprocessing process is evaluated against peak signal-to-noise ratio (PSNR), and brightness is quantified in the enhanced image. The motive of this paper is to offer a flexible approach of preprocessing mechanism that can meet image enhancement needs based on different preprocessing requirements to improve the quality of fundus imaging towards early-stage diabetic retinopathy identification.</p>

Scientific-theoretical foundations of primary school students to address geometric issues

In this article, in geometry lessons of primary school geometry, the theoretical and methodological aspects of the development of issues and increasing their interests have been stated in the science. The article also examines scientific and practical theories of great mathematical scientists and scientists on mathematical knowledge and the importance of today's education.

Seismic vulnerability assessment of the benedictine basilica typology in central Italy

The research deals with a methodology for the seismic vulnerability assessment of a set of historic churches characterized by a specific building typology and focuses on the mid-scale analysis which stands in between territorial level assessment and studies of single buildings. In particular, the proposed methodology allows to coordinate, connect and interpret apparently distant information, provided by accredited analysis tools from different scale of investigation on the seismic behaviour of historical constructions. A set of basilica churches, settled in central Italy, and stricken by the 2009 L'Aquila earthquake, has been analysed to uncover weaknesses related to the building typology by relating historical, environmental, geometrical, technological, and mechanical issues through a multi-discipline multi-scale innovative approach. All the churches belong to the Benedictine building culture and are built across a relatively limited territory; hence, they share the same architecture typology, while building technology can vary considerably due to the available environmental resources. Geometrical proportions and dimensions are investigated through appropriate morphological indexes, while masonry types through the Masonry Quality Index (MQI) method. First-level vulnerability indexes are determined on expeditious on site survey basis and most prone-to-activate kinematic mechanisms are hence deduced. Apse and façade constitute the macro-elements most prone to local mechanism activation. Also, the scale of the monument, associated to historical importance, quality of employed resources, and relevance of reworks, is central in determining homogeneity in the overall construction, quality of connections among the crucial macro-elements, and hence, their vulnerability. In the kinematic mechanism evaluation, the inclusion of frictional restraint forces simulating quality of connections between orthogonal walls proves effective in quantitatively translate observational data, although cautious calibration of the minimization procedure must be considered, especially for relatively small churches. • Novel methodology for assessment of seismic vulnerability of building typologies. • A set of basilica churches stricken by the 2009 L'Aquila earthquake has been analysed. • Analysed churches share common geometrical proportions, but scale and materials are different. • Apses and facades are the most vulnerable macro elements. • Vulnerability due to slenderness is not adequately compensated by wall-to-wall connections.

A Technical Review of Planet Smallsat Data: Practical Considerations for Processing and Using PlanetScope Imagery

With the ability to capture daily imagery of Earth at very high spatial resolutions, commercial smallsats are emerging as a key resource for the remote sensing community. Planet (Planet Labs, Inc., San Francisco, CA, USA) operates the largest constellation of Earth imaging smallsats, which have been capturing multispectral imagery for consumer use since 2016. Use of these images is growing in the remote sensing community, but the variation in radiometric and geometric quality compared to traditional platforms (i.e., Landsat, MODIS, etc.) means the images are not always ‘analysis ready’ upon download. Neglecting these variations can impact derived products and analyses. Users also must contend with constantly evolving technology, which improves products but can create discrepancies across sensor generations. This communication provides a technical review of Planet’s PlanetScope smallsat data streams and extant literature to provide practical considerations to the remote sensing community for utilizing these images in remote sensing research. Radiometric and geometric issues for researchers to consider are highlighted alongside a review of processing completed by Planet and innovations being developed by the user community to foster the adoption and use of these images for scientific applications.

A Recommender System for the Additive Manufacturing of Component Inventories Using Machine Learning

Abstract To appropriately leverage the benefits of additive manufacturing (AM), it would be advantageous if a printing could be guaranteed before allocating the necessary resources. Furthermore, when considering AM for an inventory of existing components traditionally fabricated through traditional means, such a guarantee could result in significant technical and economic advantages. To realize such advantages, this paper presents a platform that allows for a successful and efficient transition of part-inventories to AM. This is accomplished using a novel design recommender system supported by machine learning, capable of making suggestions towards effective design modifications. This system uses an automatic AM feasibility analysis of existing parts and a clustering of the parts based on similarities in their AM-feasibilities to develop a set of recommendations for those part clusters whose current designs are deemed as infeasible and/or inefficient for AM. The design modifications leverage a redesign algorithm to address not only problematic geometric issues but also potential infeasibilities associated with resource consumption. The utility of the presented modification algorithm is demonstrated using a number of case studies.

Enactive or symbolic representation? When the order alters the product

<p>This paper reviews a pedagogic exercise related to the degree of Architecture being taught at the University of Chile. This exercise, which is based on the action of folding paper, integrates knowledge areas from the project learning in initial phases. To illustrate this, in the methodology section, the applied didactic strategy together with its theoretical sustenance are described and then followed by both a review of the activities of the project itself and the learning results. The exercise addresses the multidisciplinary features of our field in Architecture, since it encourages students to directly and intuitively solve physical, structural, geometric, aesthetic and functional issues in an integral manner, appealing and adding to their already acquired ability to do and think in an enactive manner. The outcome of this exercise gets deep into the relationship among a number of aspects which include the type of representation incidence in the projecting operation (iconic, symbolic and enactive representations) and its directions, i.e., from enactive to symbolic representation and vice versa. Furthermore, it also lays out the didactic strategies and teaching contributions of the study case. To conclude, the relevance of this practical approach concerning the relationship between form with these three types of representation is discussed, so students may apply their knowledge and experience acquired during their life in the first stages of their architectural training at university.</p>

The response field and the saddle points of quantum mechanical path integrals

In quantum statistical mechanics, Moyal’s equation governs the time evolution of Wigner functions and of more general Weyl symbols that represent the density matrix of arbitrary mixed states. A formal solution to Moyal’s equation is given by Marinov’s path integral. In this paper we demonstrate that this path integral can be regarded as the natural link between several conceptual, geometric, and dynamical issues in quantum mechanics. A unifying perspective is achieved by highlighting the pivotal role which the response field, one of the integration variables in Marinov’s integral, plays for pure states even. The discussion focuses on how the integral’s semiclassical approximation relates to its strictly classical limit; unlike for Feynman type path integrals, the latter is well defined in the Marinov case. The topics covered include a random force representation of Marinov’s integral based upon the concept of “Airy averaging”, a related discussion of positivity-violating Wigner functions describing tunneling processes, and the role of the response field in maintaining quantum coherence and enabling interference phenomena. The double slit experiment for electrons and the Bohm–Aharonov effect are analyzed as illustrative examples. Furthermore, a surprising relationship between the instantons of the Marinov path integral over an analytically continued (“Wick rotated”) response field, and the complex instantons of Feynman-type integrals is found. The latter play a prominent role in recent work towards a Picard–Lefschetz theory applicable to oscillatory path integrals and the resurgence program.

Geometric issues of transforming a topographic surface into a design project

Natural relief adjustment for functional purpose - the task of vertical planning - is one of the main complexes of engineering preparation problems of urban areas, industrial sites, reclamation of irrigated land. Numerous methods of designing vertical levelling are aimed at building algorithms that would allow us to obtain an optimal solution in an automated mode. In the set of problems of engineering preparation of urban areas and industrial sites, vertical planning is defined as: a set of engineering and aesthetic measures aimed at adapting the natural relief for the needs of development and subsequent operation, taking into account the functional characteristics of the site a part of engineering preparation, which consists in providing a height arrangement of buildings and structures necessary for the best technological connection between individual objects, as well as a quick collection of atmospheric waters Reclamation of irrigated lands has specific requirements to design surface - maximum preservation of fertile layer, the satisfaction of cultivation technology conditions of different crops and irrigation technique. The main disadvantage of all known methods of designing vertical levelling is a cumbersome solution - a very labor-intensive way of successive approximation to an acceptable solution requires a large expenditure of computer time and subsequent manual revision. The article proposes one of the approaches to the design of levelling using geometric estimates.

Multicarrier Systems Over Underwater Acoustic Channels: A Performance Evaluation

The use of clean communication paths underwater can enable important applications not only for the human being. Predictions of water-observation systems (e.g., oxygen levels, climate recording, pollutant contents) and monitoring/imaging animal activity (e.g., fish, micro-organisms) could anticipate actions to preserve underwater life in case of natural disturbances. Thus, a well-designed underwater communication system goes beyond military and commercial applications, it is an agent to safeguard ocean and rivers lives. This work contributes to an underwater link design at evaluating the performance of two emerging waveforms techniques (OFDM and GFDM) and the classic FSK over an underwater acoustic channel. Large scale fading effects, including multipath fading, Doppler spread, and geometric issues are addressed. In addition to the well-known ability to combat multipath in electromagnetic channels, OFDM and GFDM are chosen due to their efficient use of bandwidth and higher data rate compared to the current underwater FSK modems. We analyze the performance of those techniques, as well as their similarities and differences in terms of the Bit Error Rate and Bitrate, evidencing that there is a performance tradeoff to be taken into account when choosing the waveform of submarine systems.

PO-1349: Geometric and dosimetric critical issues in iort by mobile linacs

PO-1349: Geometric and dosimetric critical issues in iort by mobile linacs

Comparison of the response to geometrical complexity of methods for unstationary simulations in discrete fracture networks with conforming, polygonal, and non-matching grids

The aim of this study is to compare numerical methods for the simulation of single-phase flow and transport in fractured media, described here by means of the discrete fracture network (DFN) model. A Darcy problem is solved to compute the advective field, then used in a subsequent time-dependent transport-diffusion-reaction problem. The numerical schemes are benchmarked in terms of flexibility in handling geometrical complexity, mass conservation, and stability issues for advection-dominated flow regimes. To this end, two benchmark cases, along with an additional one from a previous work, have been specifically designed and are here proposed and investigated, representing some of the most critical issues encountered in DFN simulations.

A comparison between LBW and hybrid laser-GMAW processes based on microstructure and weld geometry for hardenable steels

Welding processes are present in most industry sectors. Conventional arc welding processes, such as the gas metal arc welding (GMAW) process, have limitations when applied to join thick materials. In this scenario, the laser beam welding (LBW) process has proved to be an alternative to achieve high penetration depths, eliminating the need for joint beveling, although not without limitations. Proneness to surface and internal discontinuities are some of them. Recently, hybrid laser-arc welding (HLAW) process has come up as a promising joining process, combining the advantages of the GMAW and LBW processes on a single melting pool, counteracting defects, and enhancing process efficiency. Despite the high complexity of the hybrid process, its advantages derive not only from geometrical and mechanical issues but also from metallurgical features or characteristics. Twelve LBW and HLAW welding tests were performed using 5, 6, 7, 8, 9, and 10 kW of laser power. The HLAW results show higher robustness against weld defects, as well as greater penetration depths and bead widths then pure LBW. The microstructures in all regions of the welds were analyzed, showing their correlation between the welding parameters and processes performed. Due to a distinct thermal cycle resulting from the two simultaneous heat sources, the weld bead produced by the HLAW process presented reduction of 100 HV in the microhardness on the upper region and consequently reduction of its brittleness. The results obtained clearly indicate the metallurgical and operational advantages of the HLAW process compared with the individual LBW process.

History, Geometry and Stereotomy in the Vaults of the Halle au Blé

This paper analyses the history, cultural background, geometric configuration and stereotomic apparatus of one of the most interesting buildings in the urban landscape of Paris between the eighteenth and nineteenth centuries, the Halle au Ble in Rue de Viarmes, also known in English as Corn Exchange. This building, which over the years underwent several formal, functional and structural transformations, is particularly interesting to scholars because of the innovations researched and designed by the French architect Nicolas Le Camus de Mezieres, who tried to solve some novel geometric and constructive issues drawing from available treatises, probably most of all that of Frezier. His contribution to the Halle au Ble includes the invention of particular vaulted surfaces assembled by blending stone ashlars and bricks.

Third order open mapping theorems and applications to the end-point map**The first author has been supported by University of Padova STARS Project ‘Sub-Riemannian geometry and geometric measure theory issues: old and new’.

This paper is devoted to a third order study of the end-point map in sub-Riemannian geometry. We first prove third order open mapping results for maps from a Banach space into a finite dimensional manifold. In a second step, we compute the third order term in the Taylor expansion of the end-point map and we specialize the abstract theory to the study of length-minimality of sub-Riemannian strictly singular curves. We conclude with the third order analysis of a specific strictly singular extremal that is not length-minimizing.

Canopy Adjustment and Improved Cloud Detection for Remotely Sensed Snow Cover Mapping

AbstractMaps of snow cover serve as early indicators for hydrologic forecasts and as inputs to hydrologic models that inform water management strategies. Advances in snow cover mapping have led to increasing accuracy, but unsatisfactory treatment of vegetation's interference when mapping snow has led to maps that have limited utility for water forecasting. Vegetation affects snow mapping because ground surfaces not visible to the satellite produce uncertainty as to whether the ground is snow covered. At nadir, the forest canopy obscures the satellite view below the canopy. At oblique viewing angles, the forest floor is obscured by both the canopy and the projection of tree profiles onto the forest floor. We present a canopy correction method based on Moderate Resolution Imaging Spectroradiometer satellite imagery validated with field observations that mitigates geometric and georegistration issues associated with changing satellite acquisition angles in forested areas. The largest effect from a variable viewing zenith angle on the viewable gap fraction in forested areas occurs in moderately forested areas with 30–40% tree canopy coverage. Cloud cover frequently causes errors in snow identification, with some clouds identified as snow and some snow identified as cloud. A snow‐cloud identification method utilizes a time series of fractional vegetation and rock land‐surface data to flag snow‐cloud identification errors and improve snow‐map accuracy reducing bias by 20% over previous methods. Together, these contributions to snow‐mapping techniques could advance hydrologic forecasting in forested, snow‐dominated basins that comprise an estimated one fifth of Northern Hemisphere snow‐covered areas.

Electromagnetic flanging: from elementary geometries to aeronautical components

Aeronautical companies are manufacturing many components of small (less than 200 mm) and medium (between 200 mm and 1000 mm) sizes by flexforming. In order to diversify the production facilities of these components, these companies are interested in evaluating the ability of electromagnetic forming processes to produce small parts. This paper describes the design of a set of experiments of electromagnetic flanging with some elementary geometries, whose purpose is to enlighten several geometrical defect issues encountered, and to propose some solutions. A particular attention is first paid to the straight flange, which allows to analyse, understand and then correct the main defect issues that can occur during the forming. The proposed solutions consist of some particular design of the inductors and the dies, in order to adjust the profile of the loading and the kinematics of bending of the flange to obtain the desired final geometry. Next, curved flanges are addressed, and finally the forming of a model aeronautical part combining several elementary geometries of flange is described. Promising results are obtained. In these experiments, sheets of 1, 2 and 1.6 mm thickness made of aluminium alloy 2024-T4 and sheets of 0.5 mm thickness made of aluminium alloy 1050 are used. The geometric dispersions and the material soundness of the parts have been controlled. Besides, a numerical model of the model aeronautical part has been developed in the LS-DYNA computing environment, whose final purpose is to facilitate the design of the coil. The results of the numerical simulations are shown to be qualitatively in accordance with experimental results.

Geometric Design Issues and Safety Analysis of Two-way Rural Road Tunnels

Rural road tunnels may pose specific issues from several perspectives: mainly environmental, geotechnical/structural (excavation methods), economical. Geometric road design is then an often arduous task, which should be conducted by trying to make trade-offs between the different issues, and at the same time, it should be compliant to relevant standards and regulations. Nevertheless, the safety of road tunnels should be preserved, not only considering technological systems (e.g. ventilation systems, emergency exits and paths), but also regarding traditional road-safety issues related to road geometric features. In fact, the analysis of recent accident data related to two-way two-lane rural road tunnels has revealed that accident frequencies/rates in two-way two-lane rural road tunnels are comparable with those on the corresponding open sections, even with some differences concerning the accident types. Since road safety issues may be exacerbated by geometric design inaccuracies, some relevant road tunnel geometric issues are discussed in this study. These issues, scarcely treated in previous research and not addressed in detail in technical documents, emerge from the match between different design needs. In detail, those relate to: 1) the possible need for variable road tunnel cross-sections in case of lane/shoulder widenings for the sake of improving visibility or for other reasons, or in case of lay-bys, 2) the possible need for climbing/overtaking lanes in case of steep downhill or uphill slopes. An attempt at addressing the mentioned problems is provided, based on relevant existing research and technical documents. In particular, the preliminary design stages leading to a “WES” (Without Enlargement Solution) solution are described. Hence, besides enlarging the research body in this specific field, the study is also potentially deemed useful for practitioners who have to face similar design problems.

Design for Additive Manufacturing of Functionally Graded Lattice Structures: A Design Method with Process Induced Anisotropy Consideration

Lattice structures are well-known as a solution for designing parts with lightweight and multifunctional characteristics. Owing to the advancement of additive manufacturing (AM), the development of design methods for additively manufactured lattice structures has extensively progressed, especially for functionally graded lattice structures (FGLS). Despite plenty of available design frameworks, the application of AM constraints in the design of FGLS is limited to geometric issues. Further, there is a lack of design methods that consider the unique physical properties of additively manufactured parts, especially the anisotropic characteristics induced by AM processes. This paper proposes a novel method for the design of additively manufactured functionally graded lattice structures with the consideration of AM anisotropic properties. In addition, a customized anisotropic AM-Lattice material model that supports the design of FGLS through the density-variable topology optimization is proposed. Moreover, Fused Deposition Modeling (FDM) process in which the process-induced anisotropy of AM is clearly demonstrated is focused. The design method was validated by the three-point bending-beam design problem, a classical design problem for validating topology optimization. The results, showing agreements between simulations and experiments, prove the validity and practicality of the proposed method.

Dynamic and Proactive Risk-Based Methodology for Managing Excessive Geometric Variability Issues in Modular Construction Projects Using Bayesian Theory

AbstractManaging excessive geometric variability risks (i.e., out-of-tolerance and out-of-alignment issues) represents a major challenge in modular construction projects, owing to lack of accurate ...