Heuristic Reconstruction Research Articles

Unveiling wind-thrown trees: Detection and quantification of wind-thrown tree stems on UAV-orthomosaics based on UNet and a heuristic stem reconstruction

Severe storm events cause significant biomass losses in European forests. In addition to direct storm damage, biotic, abiotic, and market-related factors contribute to further damage with far-reaching effects on forest and nature conservation. These subsequent damages can be minimized if the amount of damaged timber and its spatial distribution are known and can be used to plan salvage operations. Traditional methods and satellite-based remote sensing can only delineate affected areas and estimate the amount of damaged timber. Aerial remote sensing can determine the spatial distribution of tree trunks with a detection rate of up to 92%, but it cannot quantify the volume of individual trunks. Newer UAV approaches are promising, but a methodology for quantifying fallen trees has not yet been published. This work addresses this gap by using UAVs orthomosaics and a hybrid heuristic and deep learning approach to capture the spatial distribution of tree trunks and estimate their volume while even reconstructing occluded stem parts. For the training of the deep learning model, high-resolution orthomosaics were used, in which 760 trunks were manually outlined and labeled. The method achieved an average stem detection rate DR25 of 92.6%. while an average classification error rate (CE) of 1.6% and a reconstruction error rate of 0.2% were reported. In the consecutive quantification of the stem volume, a relative bias rbias of −4.35% was reported for 560 reference stems at 15 investigation sites, whereas the result differ between the site (rbias= [−22.44%, 9.06%]) due weather conditions during the flight, stand parameters and the wind-throw pattern itself. The proposed method provides additional information for the management of wind-throw areas and the monitoring of biomass and carbon cycles, supports the understanding of wind-throw dynamics, and promotes the development of sustainable management strategies.

Mind Reasoning Manners: Enhancing Type Perception for Generalized Zero-Shot Logical Reasoning Over Text.

Logical reasoning task involves diverse types of complex reasoning over text, based on the form of multiple-choice question answering (MCQA). Given the context, question and a set of options as the input, previous methods achieve superior performances on the full-data setting. However, the current benchmark dataset has the ideal assumption that the reasoning type distribution on the train split is close to the test split, which is inconsistent with many real application scenarios. To address it, there remain two problems to be studied: 1) how is the zero-shot capability of the models (train on seen types and test on unseen types)? and 2) how to enhance the perception of reasoning types for the models? For problem 1, we propose a new benchmark for generalized zero-shot logical reasoning, named ZsLR. It includes six splits based on the three type sampling strategies. For problem 2, a type-aware model TaCo is proposed. It utilizes the heuristic input reconstruction and builds a text graph with a global node. Incorporating graph reasoning and contrastive learning, TaCo can improve the type perception in the global representation. Extensive experiments on both the zero-shot and full-data settings prove the superiority of TaCo over the state-of-the-art (SOTA) methods. Also, we experiment and verify the generalization capability of TaCo on other logical reasoning dataset.

Super-resolution visualization of chromatin loop folding in human lymphoblastoid cells using interferometric photoactivated localization microscopy

The three-dimensional (3D) genome structure plays a fundamental role in gene regulation and cellular functions. Recent studies in 3D genomics inferred the very basic functional chromatin folding structures known as chromatin loops, the long-range chromatin interactions that are mediated by protein factors and dynamically extruded by cohesin. We combined the use of FISH staining of a very short (33 kb) chromatin fragment, interferometric photoactivated localization microscopy (iPALM), and traveling salesman problem-based heuristic loop reconstruction algorithm from an image of the one of the strongest CTCF-mediated chromatin loops in human lymphoblastoid cells. In total, we have generated thirteen good quality images of the target chromatin region with 2–22 nm oligo probe localization precision. We visualized the shape of the single chromatin loops with unprecedented genomic resolution which allowed us to study the structural heterogeneity of chromatin looping. We were able to compare the physical distance maps from all reconstructed image-driven computational models with contact frequencies observed by ChIA-PET and Hi-C genomic-driven methods to examine the concordance between single cell imaging and population based genomic data.

Ultra-fast accurate reconstruction of spiking activity from calcium imaging data.

Calcium imaging provides an indirect observation of the underlying neural dynamics and enables the functional analysis of neuronal populations. However, the recorded fluorescence traces are temporally smeared, thus making the reconstruction of exact spiking activity challenging. Most of the established methods to tackle this issue are limited in dealing with issues such as the variability in the kinetics of fluorescence transients, fast processing of long-term data, high firing rates, and measurement noise. We propose a novel, heuristic reconstruction method to overcome these limitations. By using both synthetic and experimental data, we demonstrate the four main features of this method: 1) it accurately reconstructs both isolated spikes and within-burst spikes, and the spike count per fluorescence transient, from a given noisy fluorescence trace; 2) it performs the reconstruction of a trace extracted from 1,000,000 frames in less than 2 s; 3) it adapts to transients with different rise and decay kinetics or amplitudes, both within and across single neurons; and 4) it has only one key parameter, which we will show can be set in a nearly automatic way to an approximately optimal value. Furthermore, we demonstrate the ability of the method to effectively correct for fast and rather complex, slowly varying drifts as frequently observed in in vivo data. NEW & NOTEWORTHY Reconstruction of spiking activities from calcium imaging data remains challenging. Most of the established reconstruction methods not only have limitations in adapting to systematic variations in the data and fast processing of large amounts of data, but their results also depend on the user's experience. To overcome these limitations, we present a novel, heuristic model-free-type method that enables an ultra-fast, accurate, near-automatic reconstruction from data recorded under a wide range of experimental conditions.

A Heuristic Method for Power Pylon Reconstruction from Airborne LiDAR Data

Object reconstruction from airborne LiDAR data is a hot topic in photogrammetry and remote sensing. Power fundamental infrastructure monitoring plays a vital role in power transmission safety. This paper proposes a heuristic reconstruction method for power pylons widely used in high voltage transmission systems from airborne LiDAR point cloud, which combines both data-driven and model-driven strategies. Structurally, a power pylon can be decomposed into two parts: the pylon body and head. The reconstruction procedure assembles two parts sequentially: firstly, the pylon body is reconstructed by a data-driven strategy, where a RANSAC-based algorithm is adopted to fit four principal legs; secondly, a model-driven strategy is used to reconstruct the pylon head with the aid of a predefined 3D head model library, where the pylon head’s type is recognized by a shape context algorithm, and their parameters are estimated by a Metropolis–Hastings sampler coupled with a Simulated annealing algorithm. The proposed method has two advantages: (1) optimal strategies are adopted to reconstruct different pylon parts, which are robust to noise and partially missing data; and (2) both the number of parameters and their search space are greatly reduced when estimating the head model’s parameters, as the body reconstruction results information about the original point cloud, and relationships between parameters are used in the pylon head reconstruction process. Experimental results show that the proposed method can efficiently reconstruct power pylons, and the average residual between the reconstructed models and the raw data was smaller than 0.3 m.

Optimizing network attacks by artificial bee colony

Over the past few years, the task of conceiving effective attacks to complex networks has arisen as an optimization problem. Attacks are modelled as the process of removing a number k of vertices, from the graph that represents the network, and the goal is to maximise or minimise the value of a predefined metric over the graph. In this work, we present an optimization problem that concerns the selection of nodes to be removed to minimise the maximum betweenness centrality value of the residual graph. This metric evaluates the participation of the nodes in the communications through the shortest paths of the network.To address the problem we propose an artificial bee colony algorithm, which is a swarm intelligence approach inspired in the foraging behaviour of honeybees. In this framework, bees produce new candidate solutions for the problem by exploring the vicinity of previous ones, called food sources. The proposed method exploits useful problem knowledge in this neighbourhood exploration by considering the partial destruction and heuristic reconstruction of selected solutions. The performance of the method, with respect to other models from the literature that can be adapted to face this problem, such as sequential centrality-based attacks, module-based attacks, a genetic algorithm, a simulated annealing approach, and a variable neighbourhood search, is empirically shown.

Ultrafast CEST imaging

We describe a new MR imaging method for the rapid characterization or screening of chemical exchange saturation transfer (CEST) contrast agents. It is based on encoding the chemical shift dimension with an additional gradient as proposed in previous ultrafast CEST spectroscopy approaches, but extends these with imaging capabilities. This allows us to investigate multiple compounds simultaneously with an arbitrary sample tube arrangement. The technique requires a fast multislice readout to ensure the saturation is not lost during data acquisition due to T1 relaxation. We therefore employ radial subsampling, acquiring only 10 projections per CEST image with a 128×128 matrix. To recover the images, we use a heuristic reconstruction algorithm that incorporates low rank and limited object support as prior knowledge. This way, we are able to acquire a spectral CEST data set consisting of 15 saturation offsets more than 16 times faster than compared with conventional CEST imaging.

An Empirical Study of Reconstructing hv-Convex Binary Matrices from Horizontal and Vertical Projections

The reconstruction of hv-convex binary matrices (or equivalently, binary images) from their horizontal and vertical projections is proved to be NP-hard. In this paper we take a closer look at the difficulty of the problem. We investigate different heuristic reconstruction algorithms of the class, and compare them from the viewpoint of running-time and reconstruction quality. Using a large set of test images of different sizes and with varying number of components, we show that the reconstruction quality can depend not only on the size of the image, but on the number and location of its components, too. We also reveal that the reconstruction time can also be affected by the number of the so-called switching components present in the image.

New parasites and predators follow the introduction of two fish species to a subarctic lake: implications for food-web structure and functioning

Introduced species can alter the topology of food webs. For instance, an introduction can aid the arrival of free-living consumers using the new species as a resource, while new parasites may also arrive with the introduced species. Food-web responses to species additions can thus be far more complex than anticipated. In a subarctic pelagic food web with free-living and parasitic species, two fish species (arctic charr Salvelinus alpinus and three-spined stickleback Gasterosteus aculeatus) have known histories as deliberate introductions. The effects of these introductions on the food web were explored by comparing the current pelagic web with a heuristic reconstruction of the pre-introduction web. Extinctions caused by these introductions could not be evaluated by this approach. The introduced fish species have become important hubs in the trophic network, interacting with numerous parasites, predators and prey. In particular, five parasite species and four predatory bird species depend on the two introduced species as obligate trophic resources in the pelagic web and could therefore not have been present in the pre-introduction network. The presence of the two introduced fish species and the arrival of their associated parasites and predators increased biodiversity, mean trophic level, linkage density, and nestedness; altering both the network structure and functioning of the pelagic web. Parasites, in particular trophically transmitted species, had a prominent role in the network alterations that followed the introductions.Electronic supplementary materialThe online version of this article (doi:10.1007/s00442-012-2461-2) contains supplementary material, which is available to authorized users.

Quantitative biochronology of Devonian ammonoids from Morocco and proposals for a refined unitary association method

Monnet, C., Klug, C., Goudemand, N., De Baets, K. & Bucher, H. 2011: Quantitative biochronology of Devonian ammonoids from Morocco and proposals for a refined unitary association method. Lethaia, Vol. 44, pp. 469–489. Based on a rich dataset, the biostratigraphy of the late Emsian and the Eifelian (Early–Middle Devonian) ammonoids from the Moroccan Tafilalt is re-evaluated. We processed this dataset (comprising 53 species from 15 sections) with the unitary association method (UAM), by means of the UA-graph freeware. This led to the construction of a sequence of 17 UAs (maximal sets of actually or virtually coexisting taxa), which are grouped into 10 laterally reproducible association zones. This biostratigraphical subdivision of this interval is in some parts finer than the classically used empirical stratigraphical scheme and than a previous graphic correlation analysis. It enabled us to measure regional ammonoid diversity of this interval in detail. The UAM is a powerful biochronological method, which benefits from complementary tools to analyse conflicting inter-taxon stratigraphical relationships inherent to complex biostratigraphical datasets. In cases of under-constrained superpositional relationships between the taxa, the UAM can yield results, which are not parsimonious in terms of reconstructed virtual coexistences. We suggest several additions to complement the algorithmic steps of the method. The most important is the exhaustive or heuristic reconstruction of possible solutions resolving the observed biostratigraphical contradictions (conflicting inter-taxon superpositional relationships and cycles between maximal cliques) and the selection among the solutions of the most-parsimonious one(s) in terms of reconstructed virtual coexistences. Multiple equivalent results may then be processed with standard consensus techniques. Finally, the robustness of the results can be tested by bootstrapping methods to provide confidence estimates on the ranges and associations of studied taxa. □Ammonites, Anti-Atlas, biostratigraphy, correlation, zonation, diversity.

Heuristic optimization in penumbral image for high resolution reconstructed image

Penumbral imaging is a technique which uses the fact that spatial information can be recovered from the shadow or penumbra that an unknown source casts through a simple large circular aperture. The size of the penumbral image on the detector can be mathematically determined as its aperture size, object size, and magnification. Conventional reconstruction methods are very sensitive to noise. On the other hand, the heuristic reconstruction method is very tolerant of noise. However, the aperture size influences the accuracy and resolution of the reconstructed image. In this article, we propose the optimization of the aperture size for the neutron penumbral imaging.

Validation of an Output-Adaptive, Tetrahedral Cut-Cell Method for Sonic Boom Prediction

A cut-cell approach to computational fluid dynamics that uses the median dual of a tetrahedral background grid is described. The discrete adjoint is also calculated for an adaptive method to control error in a specified output. The adaptive method is applied to sonic boom prediction by specifying an integral of offbody pressure signature as the output. These predicted signatures are compared to wind-tunnel measurements to validate the method for sonic boom prediction. Accurate midfield sonic boom pressure signatures are calculated with the Euler equations without the use of hybrid grid or signature propagation methods. Highly refined, shock-aligned anisotropic grids are produced by this method from coarse isotropic grids created without prior knowledge of shock locations. A heuristic reconstruction limiter provides stable flow and adjoint solution schemes while producing similar signatures to Barth―Jespersen and Venkatakrishnan limiters. The use of cut cells with an output-based adaptive scheme automates the volume grid generation task after a triangular mesh is generated for the cut surface.

Penumbral imaging with multi-penumbral-apertures and its heuristic reconstruction for nuclear reaction region diagnostics

Imaging of nuclear reaction region is important to clarify heating mechanism in a fast-ignition plasma. The nuclear reaction region can be identified by hard x-ray and neutron images, which are emanated from the heated region. We proposed a novel penumbral imaging that is suitable for imaging quanta having strong penetrating power, such as hard x ray and neutron. Using multiple penumbral apertures arranged with M-sequence leads to two orders of magnitude higher detection efficiency than that with a single aperture. In addition, a heuristic method was introduced to a image reconstruction procedure for reducing artifacts caused by noise in a penumbral image. A proof-of-principle experiment indicates that the proposed imaging is superior to the conventional one.

A uniformly redundant imaging array of penumbral apertures coupled with a heuristic reconstruction for hard x-ray and neutron imaging

A coded imaging and decoding (image reconstruction) scheme was developed for diagnosing a hot and dense region emitting hard x-rays and neutrons in laser-fusion plasmas. Because the imager was a uniformly redundant array of penumbral aperture (URPA) arranged in an M-matrix, URPA leads to N times (N: the total number of apertures) enhancement of signal intensity in comparison with a single penumbral aperture. A recorded penumbral image was reconstructed by a computer-based heuristic method to reduce artifacts caused by noises contained in a penumbral image. Applicability of this technique was investigated by imaging x-rays emitted from laser-produced plasmas, demonstrating a spatial resolution of 16 microm. Under the present conditions, the spatial resolution was determined dominantly by a detector resolution (10.5 microm) and a signal-to-noise ratio of the obtained penumbral image.

Reconstruction of a uniform star object from interior x-ray data: uniqueness, stability and algorithm

In this paper we consider the problem of reconstructing a two-dimensional star-shaped object of uniform density from truncated projections of the object. In particular, we prove that such an object is uniquely determined by its parallel projections sampled over a full π angular range with a detector that only covers an interior field-of-view, even if the density of the object is not known a priori. We analyze the stability of this reconstruction problem and propose a reconstruction algorithm. Simulation experiments demonstrate that the algorithm is capable of reconstructing a star-shaped object from interior data, even if the interior region is much smaller than the size of the object. In addition, we present results for a heuristic reconstruction algorithm called DART, that was recently proposed. The heuristic method is shown to yield accurate reconstructions if the density is known in advance, and to have a very good stability in the presence of noisy projection data. Finally, the performance of the DBP and DART algorithms is illustrated for the reconstruction of real micro-CT data of a diamond.

Temporal resolved x-ray penumbral imaging technique using heuristic image reconstruction procedure and wide dynamic range x-ray streak camera

Temporal resolved x-ray penumbral imaging has been developed using an image reconstruction procedure of the heuristic method and a wide dynamic range x-ray streak camera (XSC). Reconstruction procedure of the penumbral imaging is inherently intolerant to noise, a reconstructed image is strongly distorted by artifacts caused by noise in a penumbral image. Statistical fluctuation in the number of detected photon is the dominant source of noise in an x-ray image, however acceptable brightness of an image is limited by dynamic range of an XSC. The wide dynamic range XSC was used to obtain penumbral images bright enough to be reconstructed. Additionally, the heuristic method was introduced in the penumbral image reconstruction procedure. Distortion of reconstructed images is sufficiently suppressed by these improvements. Density profiles of laser driven brominated plastic and tin plasma were measured with this technique.

Heuristic reconstructions of neutron penumbral images

Penumbral imaging is a technique of coded aperture imaging proposed for imaging of highly penetrating radiations. To date, the penumbral imaging technique has been successfully applied to neutron imaging in laser fusion experiments. Since the reconstruction of penumbral images is based on linear deconvolution methods, such as inverse filter and Wiener filer, the point spread function of apertures should be space invariant; it is also sensitive to the noise contained in penumbral images. In this article, we propose a new heuristic reconstruction method for neutron penumbral imaging, which can be used for a space-variant imaging system and is also very tolerant to the noise.

Classification of single-particle two-dimensional angular optical scattering patterns and heuristic scatterer reconstruction

Two-dimensional angular optical scattering (TAOS) is an experimental technique by which the azimuth- and polar-angle-dependent intensity patterns of monochromatic light scattered by isolated material particles are collected within a limited aperture. TAOS patterns are analyzed with the ultimate goal of estimating the class of shapes and the set of complex refractive indices to which the scatterer may belong. The implemented heuristic reconstruction procedure integrates experimental techniques and methods of data analysis. It consists of three stages: (1) TAOS patterns are classified by cluster analysis and classification is validated by principal components analysis, (2) prior information about the shape and refractive index of the particles is acquired from analytical electron microscopy and drives the computation of TAOS patterns by a T-matrix code, and (3) cluster analysis is repeated by including one computed pattern at a time and ranking it according to distance to a cluster. As a result, some simulated scatterers are found, the computed patterns of which merge with clusters of experimental patterns. Whereas the reconstruction of each individual scatterer from the available TAOS pattern would not have been feasible, possible scatterer classes are identified. The investigated material is tire dust from laboratory abrasion tests of aerodynamic size <10 μm.

Heuristic reconstruction of three-dimensional laser-imploded targets from x-ray pinhole images

Implosion symmetry has long been an important issue in inertial confinement fusion (ICF) research. In order to evaluate the implosion symmetry of ICF, a computer tomography (CT) technique developed for medical diagnostics is traditionally employed. This attempt was made to reconstruct the three-dimensional (3D) compressed core from several x-ray pinhole images. Unfortunately the reconstructed result is often constrained by the number of available pinhole images and is affected by the noise in them. In this article, we propose a heuristic method for 3D image reconstruction from a limited number of pinhole images and in the presence of noise. We represent the 3D compressed core as a summation of 3D Gaussian functions. The 3D image can be reconstructed by estimating the width and height of each Gaussian function. One heuristic method, simulated annealing, is used. The technique has been successfully applied to real laser–plasma experiments for the reconstruction of 3D compressed core utilizing only three x-ray pinhole images.

Das Brechungsgesetz in der Fassung von Snellius

A brief biographical introduction to Snellius (Snel van Royen) and his geodetic work is followed by a discussion of the historical background of his Amsterdam manuscript on optics. Here I present the first translation of the Latin original into any living language. It is preceded by a heuristic reconstruction of the path Snellius very likely took in finding the law of refraction named after him. My reconstruction essentially consists in the following five steps: Because of his geodetic work in which he pioneered the method of triangulation, Snellius already had considerable experience with trigonometric functions; indicative of this are the two allusions to geodesics in the Amsterdam manuscript, one of them directly before the law of refraction (see prop. 7 and prop. 22 of his book I). Other remarks in the manuscript reveal that Snellius had studied the existing literature on optics, particularly on refraction; various passages in the manuscript are analogous in formulation and sequence to other treatises as shown by his marginal notes and occasional references to other texts interspersed throughout the manuscript. Snellius showed special interest in Ibn al-Haitam's experimentum elegans (mentioned in prop. 22 of book I). He sought a geometrical description of the refractaria, (idem, prop. 36–39). This search led him to find the law of refraction in the secant form (idem, prop. 23).