Making things visual in science and engineeringbookmark_border

Traction unit scheduling in large railway networks involves complex operational constraints: multi-objective optimization produces feasible circulation plans under ideal assumptions, while simulation is required to assess their robustness under realistic operating conditions. A critical refinement mechanism relies on crossing operations, in which co-located traction units exchange their remaining schedules to reduce delay propagation. The space of possible crossing sequences, however, grows exponentially. Existing tools provide limited support for identifying promising candidates, evaluating their impact, and managing the resulting exploration. We present an interactive visual exploration approach that tightly couples schedule visualization, simulation-based evaluation, and a three-level guidance mechanism to support the systematic exploration and interactive optimization of traction unit circulation plans. The system renders the circulation plan in its domain-familiar form and integrates simulation results to expose delay propagation directly within the planning context. A three-level guidance framework aggregates crossing candidates spatially and ranks them by estimated impact on key performance indicators (KPIs) at an overview level, while exposing detailed per-candidate evaluation at a detail level to support informed decision-making. Applying a crossing change triggers an automatic schedule recomputation and re-simulation, with a provenance-based history mechanism enabling the non-linear exploration of alternative modification paths. We demonstrate the approach through real-world use case scenarios and report substantial reductions in the time and effort required to identify and evaluate promising schedule modifications compared to the current workflow.

This application paper presents DebrisTracer, a framework for the reliable tracking of debris in hypervelocity impact fast imaging. These noisy and highly specific datasets capture the ejection of a large number of debris fragments after the impact of a projectile launched at hypervelocity into a target material. The reliable estimation of debris mass and speed distributions is of major importance in aerospace applications. We document how to extend an off-the-shelf topology tracking framework based on critical point extraction and matching, in order to incorporate domain knowledge and physical assumptions. Our approach automatically produces an accurate and reliable debris tracking, enabling an interpretable visual analysis of this complex space-time phenomenon. Extensive experiments demonstrate the accuracy improvements provided by our approach over established tools used by domain experts in terms of physical validation, specifically via the prediction of the experimental ejected mass and crater depth profiles. We illustrate the utility of our approach across several use cases (with varying impact angles and physics). We show that our statistical summaries enable the visual identification of distinct regimes within the debris population, corroborating and refining prior expectations of domain experts. Our database and our C++ implementation are available at this address: https://github.com/tloloum/DebrisTracer.

Neural representation–based surrogate models have demonstrated remarkable performance in synthesizing ensemble data. However, existing approaches primarily focus on steady ensemble data and face challenges in extending to time-varying cases due to the limited expression of interpolable feature grids in parameter space. To address this limitation, we propose VQ-ANR, an attention-based neural representation with vector quantization for exploring time-varying ensemble data. Our framework consists of two stages: codebook construction and ensemble exploration. During codebook construction, we employ an autoencoder-decoder with vector quantization to map continuous data embeddings to a discrete codebook. In the ensemble exploration stage, given a parameter input, we develop an attention mechanism to query relevant data embeddings from the learned codebook. The retrieved embeddings, together with spatial coordinates, are then fed into an implicit neural representation for voxel prediction. We evaluate VQ-ANR across diverse time-varying ensemble datasets spanning astrophysics, cosmology, hydrodynamics, and ocean domains. Both quantitative and qualitative results demonstrate that VQ-ANR can significantly outperform state-of-the-art approaches, predict high-fidelity data, and effectively capture the underlying relationships among simulation parameters over time. The source code is available on https://github.com/huayuan4396/VQ-ANR.

Internal waves are large-amplitude gravity waves that occur below the ocean surface and propagate along interfaces separating water layers of different densities. Understanding their generation, propagation, and evolution is essential, as these waves play a vital role in the ocean system by contributing to nutrient transport, biological productivity, and the transfer of energy across the ocean and continental shelf. Domain scientists use high-resolution numerical ocean models, to study internal-wave dynamics and associated coastal and nearshore processes on hybrid computational grids. These models generate large-scale, three-dimensional spatiotemporal datasets that capture internal wave flow behavior and interactions with multiple ocean variables. These datasets are generally analyzed using command-line tools with limited interactivity. To address these challenges, we in collaboration with domain scientists designed a task-driven visualization methodology for analyzing multiscale, multivariate flow data on hybrid grids. The framework incorporates a hybrid-grid volumetric reconstruction method, enabling continuous 3D analysis and a coordinated multi-view design that supports interactive exploration of complex flow structures. An insight-based evaluation with domain experts demonstrates that the system enables the identification of previously difficult-to-observe phenomena, including transverse wave propagation, energy transport pathways, and shoaling-driven mixing. Beyond the application domain, our contributions provide generalizable techniques and design principles for visual analysis of multiscale, multivariate flow data on irregular grids.

Hairpin vortices are fundamental structures within turbulent boundary layers, playing a crucial role in energy dissipation, mixing, and momentum transport. However, accurately extracting these structures remains challenging due to their irregular shapes, varying scales, and entanglement with surrounding vortical structures. This paper presents a novel framework for the extraction of hairpin vortices from turbulent boundary layers. The method begins by identifying vortical regions and decomposing them into smaller segments using merge tree–based segmentation. A novel bottom-up rejoining approach is then introduced to group candidate segments according to the geometric and physical characteristics of hairpin vortices, resulting in regions that encompass complete hairpin vortex structures. These regions are subsequently refined and validated through skeleton analysis to detect the characteristic hairpin shape and are further confirmed using additional scalar-based criteria. Finally, smooth enclosing surfaces are generated for effective visualization. To enable quantitative evaluation, reference hairpin vortices are extracted from several flow datasets and used as ground truth. Compared with existing approaches, the proposed method eliminates manual parameter tuning, reduces under- and over-segmentation, and significantly improves both accuracy and computational efficiency. Demonstrations on multiple turbulent flow cases show that the method is robust and effective for hairpin vortex extraction under varying boundary layer conditions.