Shape Estimation Research Articles

Modeling forest canopy surface retrievals using very high-resolution spaceborne stereogrammetry: (II) optimizing acquisition configurations

The optimal configurations for very high-resolution (VHR, <2 m) spaceborne imagery collection to support stereogrammetry over complex forested terrain remain uncertain. We conducted a comprehensive sensitivity study of digital surface models (DSMs) derived from thousands of simulated along-track VHR stereopairs over two lidar-reconstructed forested scenes of closed and open canopies using the discrete anisotropic radiative transfer (DART) model. We evaluated the influence of convergence angle (CA), solar illumination, and image resolution on the derived DSM accuracy relative to the reference DSM and digital terrain model (DTM) products from airborne lidar data. Our results confirmed that the CA is the most critical acquisition parameter for DSM accuracy. Compared to the frequently used CA of ∼35∘ for along-track stereopair acquisitions by WorldView satellites, a smaller CA can provide better accuracy for forest canopy shape estimation by reducing occlusions and mitigating radiometric variance caused by the bidirectional reflectance characteristics of vegetation. For forested scenes over relatively flat terrain, oblique solar zenith angles (50−70∘) yielded more consistent DSMs with better accuracy, whereas images with a hotspot configuration generated elevations that were closer to the DTM. Image pairs with smaller ground sample distance (GSD) improved the DSM accuracy, and combinations of small (nadir) and large (off-nadir) GSDs had accuracy between those derived from homogeneous GSDs. These simulation results suggest that available global archives of DSMs from VHR stereo imagery collected under a range of acquisition configurations will yield inconsistent estimates of canopy surfaces. This study also provides a benchmark dataset and configuration guide for 1) selecting existing data to retrieve the forest canopy surface shape, and 2) defining requirements for future satellite missions to characterize the forest canopy surface using stereogrammetry.

Shape estimation of flexible ultrasound arrays using spatial coherence: A preliminary study

A flexible ultrasound array can potentially provide a larger field-of-view, enhanced imaging resolution, and less operator dependency compared to conventional rigid transducer arrays. However, such transducer arrays require information about relative element positions for beamforming and reconstructing geometrically accurate sonograms. In this study, we assess the potential utility of using spatial coherence of backscattered radiofrequency data to estimate transducer array shape (inverse problem). The methodology is evaluated through 1) simulation of flexible arrays and 2) blinded in vivo experiments using commercial rigid transducer arrays on various anatomical targets (shoulder, forearm, scapular, posterior calf muscles, and abdomen) and multi-purpose ultrasound phantoms. The average Euclidean error of shape estimation is below 0.1 wavelengths for simulated arrays and below 1.4 wavelengths (median: 0.58 wavelengths) for real arrays. The complex wavelet structural similarity index between the B-mode images reconstructed with estimated and ground truth array shapes is above 99 % and 96 %, for simulations and experiments, respectively. These findings suggest that optimizing for spatial coherence may be an effective way to estimate the unknown shape of conformal ultrasound arrays.

Geometric Modeling and Estimation of Robotic Fin Shape with Bending Actuators and Passive Elements

Geometric Modeling and Estimation of Robotic Fin Shape with Bending Actuators and Passive Elements

Effects of solidification conditions on the microstructural morphologies and strengths of hypereutectic high-chromium white cast iron castings

Although studies on hypereutectic high-Cr white cast iron (HCWCI) castings have been conducted to improve the toughnesses and quantify the microstructures of these castings, to date, only few studies have been reported on the quantitative influences of solidification conditions on the microstructures and mechanical properties of these castings. Accordingly, herein, the effects of solidification conditions on microstructural morphologies and strengths of hypereutectic HCWCI castings were investigated. Microstructural observation implied positive correlations between the minimum Feret diameter of primary M7C3 and length of M7C3 calculated from a three-dimensional geometric relationship under the approximation of the cylindrical shape of M7C3 and between experimental minimum Feret diameters of primary and eutectic M7C3. Additionally, the experimental minimum Feret diameter of primary M7C3 divided by the cube root of the volume fraction of M7C3 corresponded to the solidification velocity and temperature gradient obtained via solidification simulation. These results indicate that the parameters demonstrating three-dimensional morphologies of primary and eutectic M7C3 can be obtained by solidification simulation. Then, the strengths of the HCWCI castings were evaluated from the rule of mixtures considering the Stroh and Kelly–Tyson equations, where the volume fraction of M7C3 was acquired via thermodynamic calculations according to the chemical compositions of the castings and the strength of the matrix was substituted by the standard strengths of carbon steels under the same C equivalents as that of the matrix. The calculated strength exhibited almost the same magnitude and tendency as those of the experimental strength. The abovementioned findings reveal that not only the microstructural morphologies but also the strengths of the HCWCI castings can be estimated via computer-aided engineering. The results of this study can be utilized to predict the distributions of microstructural morphologies and strengths of the HCWCI castings.

OHO: A Multi-Modal, Multi-Purpose Dataset for Human-Robot Object Hand-Over.

In the context of collaborative robotics, handing over hand-held objects to a robot is a safety-critical task. Therefore, a robust distinction between human hands and presented objects in image data is essential to avoid contact with robotic grippers. To be able to develop machine learning methods for solving this problem, we created the OHO (Object Hand-Over) dataset of tools and other everyday objects being held by human hands. Our dataset consists of color, depth, and thermal images with the addition of pose and shape information about the objects in a real-world scenario. Although the focus of this paper is on instance segmentation, our dataset also enables training for different tasks such as 3D pose estimation or shape estimation of objects. For the instance segmentation task, we present a pipeline for automated label generation in point clouds, as well as image data. Through baseline experiments, we show that these labels are suitable for training an instance segmentation to distinguish hands from objects on a per-pixel basis. Moreover, we present qualitative results for applying our trained model in a real-world application.

Challenges of reliable AFM-tip shape reconstruction and approximation.

Reliable reconstruction of AFM tip geometry is not an easy task. The shape of the tip can be (partially) reconstructed from the AFM image of a calibration sample using a blind reconstruction method. The result is a range of the tip shapes (from unrealistically sharp to blunt). A criterion for selecting the true shape is proposed. It is based on reconstruction of the calibration relief. Further refining the probe geometry by indenting an elastic polymer is discussed. The choice of the test sample is another problem. In practice, the researcher has a small number of commercially available test gratings. Their limitations are highlighted. An approximation of tip geometry by a body of revolution is required in indentation experiments. A hyperboloid was found to be the closest approximation to the conventional probes. The contact area was obtained for the hyperboloids with different parameters indenting an elastic material. RESEARCH HIGHLIGHTS: Criteria for blind reconstruction algorithm of AFM tip shape. Pros and cons of tip shape calibration samples. Contact area of the elastic indentation by hyperbolic indenter.

CRITICAL BUCKLING LOAD SOLUTION OF THIN BEAM ON WINKLER FOUNDATION VIA POLYNOMIAL SHAPE FUNCTION IN STODOLA-VIANELLO ITERATION METHOD

The critical buckling load analysis of thin beam on Winkler foundation (BoWF) is crucial for BoWF subjected to in-plane compressive load. This paper presents the Stodola-Vianello method for the approximate solution of the governing ordinary differential equation (ODE). The Stodola-Vianello method expresses the ODE in iteration form after four successive integrations have been used in reformulating the equation. The problem then reduces to iteration in algebra. By deriving algebraic buckling shape functions that satisfy the boundary conditions, and substitution into the Stodola-Vianello iteration formula derived successive iterations of the buckling shape function would yield better approximations of the buckling shape. The existence condition for convergence which is the identity of the nth and (n +1) iterations are used to find the eigenvalue from which the buckling load is determined. The candidate problem solved is a BoWF with Dirichlet boundary conditions. It is found that one iteration yields sufficiently accurate buckling loads which differs from the exact solution by 0.129% for 0.0807% for and 0.0567% for where bl4 is a parameter measuring the beam structure – Winkler foundation interaction. The negligible difference in the critical buckling load found is because an approximate algebraic one-parameter shape function was used in the iteration. The paper has demonstrated the effectiveness of the Stodola-Vianello iteration for solving the stability of thin beam on Winkler foundation.

Autoregressive Based Vocal Tract Shape Modelling of Vowels in Speech Processing

In the present research article, which concentrates on the estimation of the vocal tract shape for the five vowels of Indian English in the current growing interest in the field of speech processing, with practical limitation of the data that can be collected and analysed. Speakers without the degree of control on articulators cannot produce the desired data. Here, we aim to design an approximate phonatory model by improving the present approach for acoustic calculation with a fully aerodynamic simulation, explicitly accounting for the propagation of sound along the tract, generating patterns of movement of simulated vocal tract articulators, and specifying the temporal relations among dynamically defined gestures that lead to a time-varying vocal tract filter function, and an acoustic waveform. The principle of phonetic distinctiveness and formants frequency spread is one of the crucial parameters that are measured and compared on intra, inter-speaker in actual speaker identification &amp; forensic applications.

Quantifying the Loss of Coral from a Bleaching Event Using Underwater Photogrammetry and AI-Assisted Image Segmentation

Detecting the impacts of natural and anthropogenic disturbances that cause declines in organisms or changes in community composition has long been a focus of ecology. However, a tradeoff often exists between the spatial extent over which relevant data can be collected, and the resolution of those data. Recent advances in underwater photogrammetry, as well as computer vision and machine learning tools that employ artificial intelligence (AI), offer potential solutions with which to resolve this tradeoff. Here, we coupled a rigorous photogrammetric survey method with novel AI-assisted image segmentation software in order to quantify the impact of a coral bleaching event on a tropical reef, both at an ecologically meaningful spatial scale and with high spatial resolution. In addition to outlining our workflow, we highlight three key results: (1) dramatic changes in the three-dimensional surface areas of live and dead coral, as well as the ratio of live to dead colonies before and after bleaching; (2) a size-dependent pattern of mortality in bleached corals, where the largest corals were disproportionately affected, and (3) a significantly greater decline in the surface area of live coral, as revealed by our approximation of the 3D shape compared to the more standard planar area (2D) approach. The technique of photogrammetry allows us to turn 2D images into approximate 3D models in a flexible and efficient way. Increasing the resolution, accuracy, spatial extent, and efficiency with which we can quantify effects of disturbances will improve our ability to understand the ecological consequences that cascade from small to large scales, as well as allow more informed decisions to be made regarding the mitigation of undesired impacts.

BOSS: Bones, organs and skin shape model

A virtual anatomical model of a patient can be a valuable tool for enhancing clinical tasks such as workflow automation, patient-specific X-ray dose optimization, markerless tracking, positioning, and navigation assistance in image-guided interventions. For these tasks, it is highly desirable that the patient’s surface and internal organs are of high quality for any pose and shape estimate. At present, the majority of statistical shape models (SSMs) are restricted to a small number of organs or bones or do not adequately represent the general population. To address this, we propose a deformable human shape and pose model that combines skin, internal organs, and bones, learned from CT images. By modeling the statistical variations in a pose-normalized space using probabilistic PCA while also preserving joint kinematics, our approach offers a holistic representation of the body that can be beneficial for automation in various medical applications. In an interventional setup, our model could, for example, facilitate automatic system/patient positioning, organ-specific iso-centering, automated collimation or collision prediction. We assessed our model’s performance on a registered dataset, utilizing the unified shape space, and noted an average error of 3.6 mm for bones and 8.8 mm for organs. By utilizing solely skin surface data or patient metadata like height and weight, we find that the overall combined error for bone-organ measurement is 8.68 mm and 8.11 mm, respectively. To further verify our findings, we conducted additional tests on publicly available datasets with multi-part segmentations, which confirmed the effectiveness of our model. In the diverse TotalSegmentator dataset, the errors for bones and organs are observed to be 5.10mm and 8.72mm, respectively. Our work shows that anatomically parameterized statistical shape models can be created accurately and in a computationally efficient manner. The proposed approach enables the construction of shape models that can be directly integrated into to various medical applications.

RGB-D-based categorical object pose and shape estimation: Methods, datasets, and evaluation

Recently, various methods for 6D pose and shape estimation of objects at a per-category level have been proposed. This work provides an overview of the field in terms of methods, datasets, and evaluation protocols. First, an overview of existing works and their commonalities and differences is provided. Second, we take a critical look at the predominant evaluation protocol, including metrics and datasets. Based on the findings, we propose a new set of metrics, contribute new annotations for the Redwood dataset, and evaluate state-of-the-art methods in a fair comparison. The results indicate that existing methods do not generalize well to unconstrained orientations and are actually heavily biased towards objects being upright. We provide an easy-to-use evaluation toolbox with well-defined metrics, methods, and dataset interfaces, which allows evaluation and comparison with various state-of-the-art approaches (https://github.com/roym899/pose_and_shape_evaluation).

The trade-sustainability nexus: the evolution of the European Commission’s trade and sustainable development discourse from 1993 to 2022

ABSTRACT This paper provides an in-depth analysis of the European Commission’s trade and sustainable development discourse from 1993 to 2022. By employing a discursive institutionalist framework and examining a comprehensive corpus of over 1,400 press documents, this study traces the discursive process that has created both significant changes to, and persistent elements in, the Commission’s trade-sustainability agenda. The analysis reveals noteworthy shifts within the discourse, notably a transition from a primary concern with labour and human rights during the 1990s to an increased focus on economic development and poverty reduction in the early 2000s. This was followed by a discernible move towards more stringent differentiation among developing countries and an amplified emphasis on reciprocity. In recent years, we are witnessing a strong focus on environmental and climate protection, labour rights, and enforceability. The findings underscore the enduring presence of trade-sustainability ideas within EU trade policy and their gradual evolution over time, while contributing to the literature on the role of ideas in shaping the Union’s external policies.

The World Economic Forum: An unaccountable force in global health governance?

AbstractThe World Economic Forum is a major player in global health governance, promoting the role of the private sector and specific public–private partnerships (PPPs). It exerts influence in three main ways: by exercising convening power, most notably in Davos where the most powerful representatives of the private sector meet with heads of governments and international organisations; by shaping ideas through its role as a think tank; by its engagement in PPPs, most recently as a founder member of CEPI (Coalition for Epidemic Preparedness Innovations). But its organisational status is ambiguous, and it appears to lack accountability—even to its own members, which casts doubt on the legitimacy of such an influential organisation.

A review of the Discrete Element Method/Modelling (DEM) in agricultural engineering

With the development of high-performance computing technology, the number of scientific publications regarding computational modelling of applications with the Discrete Element Method/Modelling (DEM) approaches in agricultural engineering has risen in the past decades. Many granular materials, e.g. grains, fruits and soils in agricultural engineering are processed, and thus a better understanding of these granular media with DEM is of great significance in design and optimization of tools and process in agricultural engineering. In this review, the theory and background of DEM have been introduced. Some improved contact models discussed in the literature for accurately predicting the contact force between two interacting particles have been compared. Accurate approximation of irregular particle shapes is of great importance in DEM simulations to model real particles in agricultural engineering. New algorithms to approximate irregular particle shapes, e.g. overlapping multi-sphere approach, ellipsoid, etc. have been summarized. Some remarkable engineering applications of the improved numerical models developed and implemented in DEM are discussed. Finally, potential applications of DEM and some suggested further work are addressed in the last section of this review.

Fault Delineation and Geological Carbon Storage (GCS) Characterization for the CCS and CCUS Facilities Based On Gravity Dataset. A Case Study in the Northern Part of East Java, Indonesia

lobal warming, the impact of greenhouse-gases emission has triggered climate change and caused various geological and hydro-meteorological disasters in the world. Most countries have carried out decarbonization efforts following the Paris Agreement, which aims to reduce carbon emissions from 29% of domestic effort up to 41% with international support by 2030. Sustainable Development Goal number 13 states combating climate change is a globally accepted framework adopted by the Indonesian Ministry of Development Planning. One aspect of decarbonization efforts involves establishing successful CCS/CCUS facilities, which requires readiness of geological carbon storage (GCS). The GCS has limited capacity, locate specifically underneath, and must consider nearby faulting system to avoid leakage and uncontrollable behavior after the injection phase of the liquefied (high-pressure) carbon. This study optimizes gravity dataset analysis to identify the existing faults and characterize the initial stage of proposed GCS in the northern part of East Java, Indonesia. Synthetic modeling of a strike slip fault was conducted to support data interpretation. The GCS characterizations, which include shape, depth, and storage capacity estimations, are inferred through 3D gravity inverse modeling. This study deduced the presence of a large-scale anticline closure without any intersecting of strike-slip fault in the area. The existing fault system is identified as the Baribis-Kendeng Reverse Fault Zone, trending west-east, and intersected by a sinistral strike-slip fault in the northeast-southwest direction. The study area is suggested as a potential GCS location with low-risk of leakage, located adjacent to the Central Processing Plant Gundih and Sukowati in East Java, Indonesia

Statistical analysis of measured underwater radiated noise from merchant ships using ship operational and design parameters.

Ships unintentionally radiate underwater noise mainly due to propeller cavitation under usual operations. In 2022, the International Maritime Organization started a review of the nonmandatory guidelines for the reduction of underwater radiated noise (URN) from ships. The characteristics of URN from ships have been studied for a long time, and quantitative variations in URN levels with ship size and speed have been reported. From the viewpoint of ship design, it is more reasonable that the effect of ship speed and draft is considered as the ratio to design speed and maximum draft, respectively. Therefore, in this study, underwater sound measurements were conducted in deep water (>300 m in depth) under a sea lane, and regression analysis was applied to the source levels of the URN from many merchant ships using ship length, ship speed ratio to design speed, and draft ratio to maximum draft. In this analysis, the source level is simplified based on the characteristics of URN due to propeller cavitation. This allows one coefficient to represent the approximate shape of the spectrum of URN level. Further, variations in the URN level for each ship type are discussed based on the results and comparisons with previous studies.

An accurate solution method for the dynamic characteristics of three-layered partial-interaction composite beams

In the dynamic analysis of three-layered partial interaction composite beams (PICBs), it is not clear whether the effects of shear deformation and rotary inertia all need to be considered, and the shear-locking problems often occurs in existing finite element methods. To improve computational efficiency, accuracy and stability, an analytical method is proposed by considering the shear slips at the interface and the independent rotary angles among the sub-elements. In the proposed method, a matrix containing the natural frequencies of the three-layered PICB is appropriately established by using the solutions to differential equations of motion rather than the shape function in finite element methods. The main improvement of the proposed method is the analyticity of solutions, which can effectively avoid shear-locking problems often mentioned in finite element methods and obtain accurate solutions due to no introduction of approximate shape functions. The present results agree well with the analytical and numerical results in the literature, which validates the accuracy of the proposed method. The effects of shear deformation and rotary inertia on the dynamic behaviors of three-layered PICBs are discussed. It reveals that the shear deformation can not be ignored but rotary inertia can be ignored in the dynamic analysis of three-layered PICBs, which can effectively reduce the computation complexity. In general, the proposed method has practical value in natural frequency analysis of the three-layered PICB with high computational efficiency, accuracy and stability.

Derivative shape estimations with resolved overlapped peaks and reduced noise for time signals encoded by NMR spectroscopy with and without water suppression

Derivative estimation in magnetic resonance spectroscopy (MRS) possesses several attractive features. It has the ability to enhance the inaccessible spectral details when time signals encoded by MRS are analyzed by nonderivative shape estimators. These unfolded subtle spectral features can be diagnostically relevant in differentiating between healthy and diseased tissues. Within the realm of shape estimators, the prerequisite for the success of MRS in the clinic is reliance upon accurate derivative signal processing. However, derivative processing of encoded time signals can be very challenging. The reason is that such spectra may suffer from severe numerical instabilities since even small perturbations (noise) in the input data could produce large errors in the predicted output data. Nevertheless, it is presently demonstrated that this obstacle can be surmounted by an adaptive optimization. The benefit is simultaneously increased resolution and reduced noise in quantitatively interpretable lineshapes. The illustrative spectra are reconstructed from time signals encoded by proton MRS with and without water suppression.

Estimation of the full shape of the crystalline lens from OCT: validation using stretched donor lenses.

Quantifying human crystalline lens geometry as a function of age and accommodation is important for improved cataract and presbyopia treatments. In previous works we presented eigenlenses as a basis of 3-D functions to represent the full shape of the crystalline lens ex vivo. Also, we presented the application of eigenlenses to estimate the full shape of the lens in vivo from 3-D optical coherence tomography (OCT) images, where only the central part of the lens -visible through the pupil- is available. The current work presents a validation of the use of eigenlenses to estimate in vivo the full shape of dis-accommodated lenses. We used 14 ex vivo crystalline lenses from donor eyes (11-54 y/o) mounted in a lens stretcher, and measured the geometry and the power of the lenses using a combined OCT and ray tracing aberrometry system. Ex vivo, the full extent of the lens is accessible from OCT because the incident light is not blocked by the iris. We measured in non-stretched (fully accommodated) and stretched (mimicking in vivo dis-accommodated lenses) conditions. Then, we simulated computationally in vivo conditions on the obtained ex vivo lenses geometry (assuming that just the portion of the lens within a given pupil is available), and estimated the full shape using eigenlenses. The mean absolute error (MAE) between estimated and measured lens' diameters and volumes were MAE = 0.26 ± 0.18 mm and MAE = 7.0 ± 4.5 mm3, respectively. Furthermore, we concluded that the estimation error between measured and estimated lenses did not depend on the accommodative state (change in power due to stretching), and thus eigenlenses are also useful for the full shape estimation of in vivo dis-accommodated lenses.

Where the rubber hits the road: how school leaders work with government-initiated policy within physical education

ABSTRACT Previous research has addressed how societal demands shape ideas about appropriate practices in physical education (PE) and the consequences for those involved and for society at large. It has also highlighted the influential role of groups and organisations, including PE teachers, in shaping PE practices. However, the significance of school leaders in driving change in PE practices has been largely overlooked, despite their crucial responsibilities in decision-making, division of labour, and resource allocation. To address this gap, this study answers the following research question: what types of institutional work do Swedish school leaders engage in as they navigate government-initiated policy? Guided by the institutional work perspective and data collected in semi-structured interviews with 13 school leaders, the thematic analysis reveals that school leaders engage in structural work, operational work, conceptual work, and relational work when navigating government-initiated policy. In more empirical terms, the results indicate that most of the power to shape the implementation process is passed on to PE teachers. This suggests that although school leaders have substantial control over strategic resources and wield other forms of power, they do not necessarily significantly influence practices and beliefs in PE. The theoretical significance of these findings lies in their ability to shed light on how changes occur and explain how such changes impact widely accepted norms, rules, and structures. In practice, knowledge of how ideas and practices guide future decisions can be used in efforts to support those working in, working with, or striving to develop PE, including decision-makers, school leaders, and PE teachers.