Geometric Fitting Research Articles

Individual reversible plasticity as a genotype-level bet-hedging strategy.

Reversible plasticity in phenotypic traits allows organisms to cope with environmental variation within lifetimes, but costs of plasticity may limit just how well the phenotype matches the environmental optimum. An additional adaptive advantage of plasticity might be to reduce fitness variance, in other words: bet-hedging to maximize geometric (rather than simply arithmetic) mean fitness. Here, we model the evolution of plasticity in the form of reaction norm slopes, with increasing costs as the slope or degree of plasticity increases. We find that greater investment in plasticity (i.e. a steeper reaction norm slope) is favoured in scenarios promoting bet-hedging as a response to multiplicative fitness accumulation (i.e. coarser environmental grains and fewer time steps prior to reproduction), because plasticity lowers fitness variance across environmental conditions. In contrast, in scenarios with finer environmental grain and many time steps prior to reproduction, bet-hedging plays less of a role and individual-level optimization favours evolution of shallower reaction norm slopes. However, the opposite pattern holds if plasticity costs themselves result in increased fitness variation, as might be the case for production costs of plasticity that depend on how much change is made to the phenotype each time step. We discuss these contrasting predictions from this partitioning of adaptive plasticity into short-term individual benefits versus long-term genotypic (bet-hedging) benefits, and how this approach enhances our understanding of the evolution of optimum levels of plasticity in examples from thermal physiology to advances in avian lay dates.

An empirical test of the bet-hedging polyandry hypothesis: Female red flour beetles avoid extinction via multiple mating.

Bet‐hedging via polyandry (spreading the extinction risk of the female's lineage over multiple males) may explain the evolution of female multiple mating, which is found in a wide range of animal and plant taxa. This hypothesis posits that females can increase their fitness via polyandrous mating when “unsuitable” males (i.e., males causing reproductive failure for various reasons) are frequent in the population and females cannot discriminate such unsuitable mates. Although recent theoretical studies have shown that polyandry can operate as a bet‐hedging strategy, empirical tests are scarce. In the present study, we tested the bet‐hedging polyandry hypothesis by using the red flour beetle Tribolium castaneum. We compared female reproductive success between monandry and polyandry treatments when females mated with males randomly collected from an experimental population, including 20% irradiated (infertile) males. In addition, we evaluated geometric mean fitness across multiple generations as the index of adaptability of bet‐hedging traits. Polyandrous females showed a significantly higher egg hatching rate and higher geometric mean fitness than monandrous females. These results strongly support the bet‐hedging polyandry hypothesis.

A parameterized geometric fitting method for ellipse

This study presents an accurate and robust method for fitting noisy and occlusion elliptic data. The nonlinear issue of ellipse fitting is interpreted as a set of Levenberg–Marquardt iterations (LMIs) by minimizing the geometric distance. For each iteration of the geometric fitting, the representations of the parameterized ellipses are mapped to the geometric error distances, which are implemented latently by an orthogonal angle segmentation of the ellipses. Moreover, dimension reduction is utilized by the LMIs to avoid misconvergence and expensive computations. The method based on two recent representative algorithms is verified by simulation and real-world experiments. The results suggest that the saliency capability of the new method to fit ellipse-specific profiles with severe noise and occlusion, which is better than or equal to those of the reference approaches, has potential applications in quality monitoring, three-dimensional reconstruction, and instrument calibration.

A polybézier-based particle model for the DEM modeling of granular media

The discrete element method (DEM) has become a prominent tool for modeling granular media, whereas the development of versatile and efficient particle models for the modeling of irregular-shaped particles remains a heated topic and challenge. In this work, a new particle model based on polybézier curves to describe particle shapes is proposed for the modeling of smooth and irregular-shaped particles. In particular, cubic bézier curves are adopted because they have a fairly high degree of freedom in modeling curved geometries as well as a closed-form support function. With the particle geometry and support function derived from cubic polybézier curves, the Gilbert-Johnson-Keerthi algorithm is adopted to detect contacts, and the expanding polytope algorithm is adopted to resolve contact geometric features. To generate polybézier-based particle templates from images of particle shapes, a particle swarm optimization-based geometric fitting procedure is also developed. The effectiveness of the proposed particle model for shape representation is validated using a chart of particle shapes with various roundness and sphericity characteristics. DEM simulations of random packing and biaxial compression tests on polydispersed irregular-shaped particles are also presented, and the results show that the proposed model has fairly good computational efficiency and numerical stability.

Geometric least square curve fitting method for localization of wireless sensor network

In a wireless sensor network, the localized sensors are essential for efficient management of the network. In recent years, we have seen the implementation of various localization schemes. Few schemes presume to use mobile beacon because it has many potentialities. Despite many potentialities, the mobile beacon-based localization schemes suffer from two significant problems. First, the shorter beaconing interval increases the communication overhead and degrades the network lifetime. Second, the radio propagation irregularity minimizes the uniform coverage. For a better network lifetime, we need to reduce the communication overhead. Similarly, consistent coverage is improved through better path planning and enhanced beaconing range. However, most of the proposed geometric schemes in literature fails to address both the problems with better localization accuracy. In this paper, we address the underlying impact of shorter beaconing interval and the radio propagation irregularity. The proposed scheme utilizes the geometric least square curve fitting method for localization (GLSCFL). The results show that the proposed method provides better localization accuracy than other geometric schemes.

A Reconfigurable and Adjustable Compliance System for the Measurement of Interface Orthotic Properties.

A measurement system which provides INterface with Tunable Ergonomic properties using a Reconfigurable Framework with Adjustable Compliant Elements (INTERFACE system) is developed to implement the Rapid Evaluate and Adjust Device (READ) methodology. The geometry and stiffness of the Medial Longitudinal Arch (MLA) support provided by the INTERFACE system can be adjusted via linear actuators and tunable stiffness mechanisms, based on objective interface pressure/load distribution and subjective feedback evaluations. Validation tests were conducted on 13 subjects to measure the plantar pressure/load distribution and record the subjective feedback in different combinations of geometry and stiffness. The interface pressure/load distribution and subjective feedback of the support level indicate the efficacy of the adjustable geometry and stiffness. As the stiffness and geometrical height increased, the plantar loadings increased in the MLA region and decreased in the rear foot. Geometrical fitting can be achieved with the reconfigurable MLA support. The integration of locally adjustable stiffness makes it possible to fine tune the plantar pressure/load and provides the subjects with options of orthotic stiffness. The proposed INTERFACE system can be applied to conduct the measurement of the desired orthotic properties which satisfy the interface pressure/load requirement and the subject's comfort.

Efficient Deterministic Search With Robust Loss Functions for Geometric Model Fitting.

Geometric model fitting is a fundamental task in computer vision, which serves as the pre-requisite of many downstream applications. While the problem has a simple intrinsic structure where the solution can be parameterized within a few degrees of freedom, the ubiquitously existing outliers are the main challenge. In previous studies, random sampling techniques have been established as the practical choice, since optimization-based methods are usually too time-demanding. This prospective study is intended to design efficient algorithms that benefit from a general optimization-based view. In particular, two important types of loss functions are discussed, i.e., truncated and l1 losses, and efficient solvers have been derived for both upon specific approximations. Based on this philosophy, a class of algorithms are introduced to perform deterministic search for the inliers or geometric model. Recommendations are made based on theoretical and experimental analyses. Compared with the existing solutions, the proposed methods are both simple in computation and robust to outliers. Extensive experiments are conducted on publicly available datasets for geometric estimation, which demonstrate the superiority of our methods compared with the state-of-the-art ones. Additionally, we apply our method to the recent benchmark for wide-baseline stereo evaluation, leading to a significant improvement of performance. Our code is publicly available at https://github.com/AoxiangFan/EifficientDeterministicSearch.

Design for ergonomics in the bicycle industry: an engineering design concept

Bicycle manufacturing is an industry that has taken advantage of technological developments in materials and large-scale manufacturing for high-performance products. Higher-specification bicycles typically use fibre-reinforced composite frames that are optimised for structural performance and mass. Efforts have also been made to increase the comfort of a rider by increasing the vertical compliance of frames, but traditional fibre-reinforced composite moulding techniques restrict manufacturing flexibility in fitting frame geometry to match the requirements of an individual. Manufacturers typically subdivide their frames into sized-based grouping to reduce manufacturing, inventory and supply costs. For specific user fits, customised bicycles are produced, but only on a smaller scale. These improve comfort via improved geometric fit for the user, but typically do so at high cost, or by using sub-optimum material selections. In this paper, an innovative, segmented frame design concept is introduced to facilitate a design-for-ergonomics and mass-customisation approach in the high-volume, high-performance bicycle industry.

A Vision Measurement Method for the Gear Shaft Radial Runout With Line Structured Light

The gear shaft needs to measure its radial runout for straightening before finishing, while it is difficult to measure the gear shaft radial runout without rotating the gear shaft by the existing measurement technology, which results the measurement inefficient. Present work puts forward a method of measuring a gear shaft radial runout with line structured light vision. This method can measure the radial runout value and direction online for straightening the bending of the gear shaft. The center position of the gear shaft cross section is obtained by the ellipse geometric fitting on the laser plane to eliminate the influence of projection distortion. The measurement method is tested by a specialized experiment, and the experimental results show that measurements of the method meet the requirements of straightening the gear shaft. The method can realize online measurement of the gear shaft radial runout just by a single image without rotating the gear shaft, so it features fast measurement compared with the existing measurement technology.

Real-Time Vision-Based Pose Tracking of Spacecraft in Close Range Using Geometric Curve Fitting

This article presents a new framework of real-time vision-based pose tracking for spacecraft in close range using geometric fitting of the imaged geometric primitives (GPs) on the spacecraft. At the first time instant, the tracking is initialized with the template-based pose retrieval and GP-based pose determination. At each subsequent time instant, with the pose prediction from the extended Kalman filter (EKF) as initial value, the GPs are associated with the corresponding image data, and thereby the maximum-likelihood estimation (MLE) for spacecraft pose can be obtained in real time by geometrically fitting the GP projections over the corresponding image data with generalized expectation–maximization and M-estimation. Using the MLE, the EKF generates the final pose estimation and predicts the pose at the next time instant. The basic configurations of the GPs are investigated for the stability of tracking. Sufficient experiments validate the accuracy and the real-time performance of the proposed method.

Structural variability of CG-rich DNA 18-mers accommodating double T-T mismatches.

Solution and crystal data are reported for DNA 18-mers with sequences related to those of bacterial noncoding single-stranded DNA segments called repetitive extragenic palindromes (REPs). Solution CD and melting data showed that the CG-rich, near-palindromic REPs from various bacterial species exhibit dynamic temperature-dependent and concentration-dependent equilibria, including architectures compatible with not only hairpins, which are expected to be biologically relevant, but also antiparallel duplexes and bimolecular tetraplexes. Three 18-mer oligonucleotides named Hpar-18 (PDB entry 6rou), Chom-18 (PDB entry 6ros) and its brominated variant Chom-18Br (PDB entry 6ror) crystallized as isomorphic right-handed A-like duplexes. The low-resolution crystal structures were solved with the help of experimental phases for Chom-18Br. The center of the duplexes is formed by two successive T-T noncanonical base pairs (mismatches). They do not deform the double-helical geometry. The presence of T-T mismatches prompted an analysis of the geometries of these and other noncanonical pairs in other DNA crystals in terms of their fit to the experimental electron densities (RSCC) and their geometric fit to the NtC (dinucleotide conformational) classes (https://dnatco.datmos.org/). Throughout this work, knowledge of the NtC classes was used to refine and validate the crystal structures, and to analyze the mismatches.

Nb2O5-Li2O-Bi2O3-B2O3 novel glassy system: evaluation of optical, mechanical, and gamma shielding parameters

For the Nb2O5-Li2O-Bi2O3-B2O3 glass system, optical, structure, mechanical gamma, and neutron radiation shielding aspects were examined comprehensively. The two probabilities of the bandgaps, direct and indirect transition, were evaluated. The absorbance of the recent glasses was increased as Nb2O5 increased. Moreover, the peak shifted to a longer wavelength as Nb2O5 increased. Our results show a decreasing behavior of both kinds of the bandgap. Adopting XCOM within 0.04–15 MeV, LAC and MAC were evaluated for all samples and calculated MAC values are in excellent compliance with deduced FLUKA code respective MAC outcomes. Zeff, HVL, and MFP values were estimated. MAC, Zeff, HVL, and MFP values depended on glass components and energy. Moreover, using equivalent atomic numbers (Zeq) and the geometric progression fitting procedure, EABF values were calculated up to 40 mfp, within 0.015–15 MeV. Comparatively higher density (4.9454 g/cm3), greater LAC, MAC, Zeff, Zeq, and lower HVL, MFP, EABF values achieved for 10Nb2O5-10Li2O-30Bi2O3-50B2O3 glass indicated it as a better gamma shield. Furthermore, the calculated ΣR shows that the 10Nb2O5-10Li2O-30Bi2O3-50B2O3 sample has commensurately greater ΣR (= 0.1744 cm−1).

Seed germination of gynodioecious species: theoretical considerations and a comparison of females and hermaphrodites.

Better seed germination of females than of hermaphrodites is not a major contributor to the greater geometric lifetime fitness that females require to be maintained in a gynodioecious population. Gynodioecy is a sexually dimorphic breeding system in which females (F, male sterile) and hermaphrodites (H) coexist in the same population. For plants with nuclear (biparental) inheritance of male sterility, theory predicts that except when the product of selfing rate (s) and inbreeding depression (δ) in H is high (sδ > 0.50), F must compensate (female advantage) for the loss of gene transmission via pollen production by producing more or higher-quality offspring than H to be maintained in the population. For species with cytoplasmic (maternal) inheritance of male sterility, the female requires only a small compensation in seed production or some other offspring fitness trait to persist. Reallocation to seeds of resources saved by loss of pollen production is expected to increase the quantity (number) and/or quality (mass, germinability) of seeds produced by F, thus compensating for the lack of pollen production. The primary aim of our study was to compare seed germination of F and H via a literature review. Based on theoretical considerations, we hypothesized that seeds of F should germinate better or equally as well as those of H. We found that of 235 case studies for 47 species Fgerm > Hgerm in 48.1%, Fgerm = Hgerm in 38.3% and Fgerm < Hgerm in 13.6%. Our results are very similar to those of a previously published meta-analysis that included germination of F and H for 12 species. For 162 cases on seed size, F > H in 29.0%, F = H in 63.6% and F < H in 7.4%. Since [(Fgerm > Hgerm) < (Fgerm ≤ Hgerm)] and [(Fseedsize > Hseedsize) < (Fseedsize ≤ Hseedsize)], these results suggest that seed quality is not a major fitness component of female advantage.

Buildup with Bremsstrahlung in the Martian Atmosphere

Photon buildup is a function of energy, medium, and geometry and therefore must be specifically calculated for the case of interest. The Martian atmosphere, mostly comprising carbon dioxide, is becoming more relevant to radiation researchers and therefore warrants the study of this gas mixture’s buildup properties for ionizing photon flux resulting from the secondary effects of galactic cosmic rays and solar flares. Specifically, this work uses the MCNP6 code to develop energy absorption buildup factors in finite slab models for energies ranging from 40 keV to 15 MeV with Martian regolith as the backscattering medium. The Martian carbon dioxide cycle is accounted for by determining maximum and minimum mean densities as a function of orbital position. An isotropic point source model for the atmosphere is also developed using the geometric progression fitting function. Buildup is bounded to a factor of approximately 23 at 100 keV for normally incident photons at the top of the atmosphere. For conservatism, the design problem neglects coherent scattering but assumes bremsstrahlung effects and uses Klein-Nishina free-electron cross sections for Compton scattering.

Geometric Modelling for 3D Point Clouds of Elbow Joints in Piping Systems.

Pipe elbow joints exist in almost every piping system supporting many important applications such as clean water supply. However, spatial information of the elbow joints is rarely extracted and analyzed from observations such as point cloud data obtained from laser scanning due to lack of a complete geometric model that can be applied to different types of joints. In this paper, we proposed a novel geometric model and several model adaptions for typical elbow joints including the 90° and 45° types, which facilitates the use of 3D point clouds of the elbow joints collected from laser scanning. The model comprises translational, rotational, and dimensional parameters, which can be used not only for monitoring the joints’ geometry but also other applications such as point cloud registrations. Both simulated and real datasets were used to verify the model, and two applications derived from the proposed model (point cloud registration and mounting bracket detection) were shown. The results of the geometric fitting of the simulated datasets suggest that the model can accurately recover the geometry of the joint with very low translational (0.3 mm) and rotational (0.064°) errors when ±0.02 m random errors were introduced to coordinates of a simulated 90° joint (with diameter equal to 0.2 m). The fitting of the real datasets suggests that the accuracy of the diameter estimate reaches 97.2%. The joint-based registration accuracy reaches sub-decimeter and sub-degree levels for the translational and rotational parameters, respectively.

FAST AND REGULARIZED RECONSTRUCTION OF BUILDING FAÇADES FROM STREET-VIEW IMAGES USING BINARY INTEGER PROGRAMMING

Abstract. Regularized arrangement of primitives on building façades to aligned locations and consistent sizes is important towards structured reconstruction of urban environment. Mixed integer linear programing was used to solve the problem, however, it is extremely time consuming even for state-of-the-art commercial solvers. Aiming to alleviate this issue, we cast the problem into binary integer programming, which omits the requirements for real value parameters and is more efficient to be solved. Firstly, the bounding boxes of the primitives are detected using the YOLOv3 architecture in real-time. Secondly, the coordinates of the upper left corners and the sizes of the bounding boxes are automatically clustered in a binary integer programming optimization, which jointly considers the geometric fitness, regularity and additional constraints; this step does not require a priori knowledge, such as the number of clusters or pre-defined grammars. Finally, the regularized bounding boxes can be directly used to guide the façade reconstruction in an interactive environment. Experimental evaluations have revealed that the accuracies for the extraction of primitives are above 0.82, which is sufficient for the following 3D reconstruction. The proposed approach only takes about 10% to 20% of the runtime than previous approach and reduces the diversity of the bounding boxes to about 20% to 50%.

Cohort splitting from plastic bet-hedging: insights from empirical and theoretical investigations in a wolf spider

Bet-hedging strategies help organisms to decrease variance in their fitness in unpredictably changing environments, by which way lineage fitness can be maximized in the given environment. As one strategy, diversified bet-hedging helps to achieve that by increasing phenotypic variation in fitness-related traits. For example, in diversified tracking, parents may divide the developmental phenotypes of their offspring within broods, leading to cohort splitting among the progeny. Such diversification, though, should be probabilistic and sensitive to no external stimuli. However, it was recently highlighted that plasticity in response to environmental stimuli may be part of a more dynamic case of bet-hedging. Current understanding and empirical observations of such a plastic bet-hedging remain limited. Here I use a theoretical investigation relying on empirical grounds in a specific case of cohort splitting in the wolf spider Pardosa agrestis (Westring 1861). I investigated whether cohort splitting might be a bet-hedging strategy in females of P. agrestis, and whether it would be expected to be static or plastic bet-hedging. Results show that cohort splitting is likely a bet-hedging strategy in this species, by which females maximize their lineage fitness. Also, cohort splitting appears to arise from plastic bet-hedging, as in simulated populations where both static and plastic bet-hedging females occur, the latter have considerably higher geometric mean fitness. I discuss theoretical and empirical observations in light of the current theory, and draw predictions on specific aspects of this case of plastic bet-hedging.

Quantized Residual Preference Based Linkage Clustering for Model Selection and Inlier Segmentation in Geometric Multi-Model Fitting

In this paper, quantized residual preference is proposed to represent the hypotheses and the points for model selection and inlier segmentation in multi-structure geometric model fitting. First, a quantized residual preference is proposed to represent the hypotheses. Through a weighted similarity measurement and linkage clustering, similar hypotheses are put into one cluster, and hypotheses with good quality are selected from the clusters as the model selection results. After this, the quantized residual preference is also used to present the data points, and through the linkage clustering, the inliers belonging to the same model can be separated from the outliers. To exclude outliers as many as possible, an iterative sampling and clustering process is performed within the clustering process until the clusters are stable. The experiments undertake indicate that the proposed method performs even better on real data than the some state-of-the-art methods.

Two-step investigation on fabrication and characterization of iron-reinforced novel composite materials for nuclear-radiation shielding applications

In the present study, iron (Fe)-reinforced novel composite materials were produced as alternative shielding materials. In this context, linear attenuation coefficients and mass attenuation coefficients (MAC), half- and tenth-value layers, mean free path (MFP) and effective atomic number were determined. An experimental gamma-ray transmission setup was utilized for determination of MAC values. To confirm the consistency of experimental results, the obtained MAC values were compared with those produced using the WinXcom program and MCNPX Monte Carlo code. Moreover, exposure buildup factors and energy absorption buildup factors were calculated using a geometric progression fitting method. Relative dose distribution values of fabricated samples were calculated at 5, 10 and 20 MFP penetration depths up to 10 MeV. In addition to gamma-ray attenuation properties, basic interaction parameters of charged particles such as protons and alpha mass stopping powers, alpha projected ranges and proton projected ranges were determined in the 0.015–15 MeV energy range. Finally, variation of fast neutron removal cross-section versus increasing Fe concentration in composites was investigated. The composite with the highest Fe addition (20%) showed the best shielding capacity for gamma radiation.

The way of using recycled cardboard in the Production of sustainable furniture units

as the continuous decay of the cultivated areas, our environment also suffers from the great inflation in the amount of paper wastes resulting from various daily life activities and occupying the second place in value after iron wastes if compared to other wastes. The Egyptian annually consumption of paper is nearly 500,000 tons as mentioned in the pressreader in 2017.In an attempt to exploit this huge amount of paper wastes that could be considered as a fortune and a solution for an environmental problem, the research aims to discuss the ability of using recycled cardboard in the production of sustainable furniture units. Some computer programs and modern techniques can be used in the design and production of various and sustainable furniture units could be stated as the research hypothesis.The studies and experiments have concluded that the recycled cardboard sheets as well as the reused ones have proved to be highly endurance and compression resistant when used with specific geometrical fittings and constructions in a way that could easily lead to the production of a wide range of different and varied furniture units such as chairs, tables, benches and beds having compatible designs with the nature of the recycled cardboard which is used in the production and implementation of these units.