Rapid 4D FWI using a local wave solver

Much of the computational cost involved in full-waveform inversion comes from the solution of the wave equation in a large domain. These computations must be done for the entire domain through which we expect waves to pass for a particular survey, despite the fact that our region of interest is often significantly smaller. In addition to the wasted time spent propagating waves through less important parts of the model, computing updates on the entire domain may result in slower convergence of the inversion algorithm due to the larger model space. This can be especially important in 4D seismic monitoring, where we often see the majority of changes within a small subregion of the total domain, such as the reservoir. We present a local wave solver that accurately computes the solution of the wave equation within only a subdomain of the region covered by the survey, representing a significant cost saving in the computation of full-waveform inversion. We also show how this solver can improve the resulting velocity estimates in full-waveform inversion for time-lapse applications and observe that the local solver requires fewer iterations to converge than does the full-domain solver

Coupling a Local Elastic Solver to a Background Acoustic Model to Estimate Phase Variation

In characterizing reservoirs, we are often interested in detailed elastic parameters about only a very limited part of the subsur-face. To that end, we introduce a local solver which uses an acoustic solver to propagate the wavefield to a sub-domain on which we use a local elastic solver. This avoids the use of an expensive full domain elastic solver while still incorporating elastic physics in the region where it is most important. We apply the local solver to modeling phase variation with angle

An efficient coupled acoustic-elastic local solver applied to phase inversion

In characterizing reservoirs, we are often interested in retrieving detailed elastic parameters for only a very limited part of the subsurface. One way of doing so involves studying the seismic reflection response within the region of interest. To that end, we introduce a local solver that uses an acoustic solver to propagate the wavefield to a subdomain on which we use a local elastic solver. This avoids the use of an expensive full-domain elastic solver while still incorporating elastic physics in the region where it is most important. We then study whether this modeled phase is sufficiently accurate for recovering important subsurface reservoir properties in an inversion procedure

A numerically exact local solver applied to salt boundary inversion in seismic full-waveform inversion

In a set of problems ranging from 4-D seismic to salt boundary estimation, updates to the velocity model often have a highly localized nature. Numerical techniques for these applications such as full-waveform inversion (FWI) require an estimate of the wavefield to compute the model updates. When dealing with localized problems, it is wasteful to compute these updates in the global domain, when we only need them in our region of interest. This paper introduces a local solver that generates forward and adjoint wavefields which are, to machine precision, identical to those generated by a full-domain solver evaluated within the region of interest. This means that the local solver computes all interactions between model updates within the region of interest and the inhomogeneities in the background model outside. Because no approximations are made in the calculation of the forward and adjoint wavefields, the local solver can compute the identical gradient in the region of interest as would be computed by the more expensive full-domain solver. In this paper, the local solver is used to efficiently generate the FWI gradient at the boundary of a salt body. This gradient is then used in a level set method to automatically update the salt boundary

Resolving References in Visually-Grounded Dialogue via Text Generation

Vision-language models (VLMs) have shown to be effective at image retrieval based on simple text queries, but text-image retrieval based on conversational input remains a challenge. Consequently, if we want to use VLMs for reference resolution in visually-grounded dialogue, the discourse processing capabilities of these models need to be augmented. To address this issue, we propose fine-tuning a causal large language model (LLM) to generate definite descriptions that summarize coreferential information found in the linguistic context of references. We then use a pretrained VLM to identify referents based on the generated descriptions, zero-shot. We evaluate our approach on a manually annotated dataset of visually-grounded dialogues and achieve results that, on average, exceed the performance of the baselines we compare against. Furthermore, we find that using referent descriptions based on larger context windows has the potential to yield higher returns.Comment: Published at SIGDIAL 202

Toward target-oriented FWI: An exact local wave solver applied to salt boundary inversion

Seismic full waveform inversion (FWI) uses the gradient of the objective function for computing model updates. This requires computation of the forward and adjoint wavefields on the current model estimate. Calculating the gradient on the full computational domain is wasteful when it is only required in a limited region of interest, as is the case in 4D seismic and salt boundary estimation, for example. In this paper, a local solver is introduced that accurately computes, up to machine precision, all the wavefield interactions between model updates restricted to a region of interest and inhomogeneities in the background model outside. The local solver therefore generates exactly the same forward and adjoint wavefields in the region of interest that a full domain solver would have generated. In this paper, the exact local gradient at the boundary of a salt body is computed from these exact local wavefields. A level set method uses this gradient to automatically update the local salt boundary estimate

Collecting Visually-Grounded Dialogue with A Game Of Sorts

An idealized, though simplistic, view of the referring expression production and grounding process in (situated) dialogue assumes that a speaker must merely appropriately specify their expression so that the target referent may be successfully identified by the addressee. However, referring in conversation is a collaborative process that cannot be aptly characterized as an exchange of minimally-specified referring expressions. Concerns have been raised regarding assumptions made by prior work on visually-grounded dialogue that reveal an oversimplified view of conversation and the referential process. We address these concerns by introducing a collaborative image ranking task, a grounded agreement game we call "A Game Of Sorts". In our game, players are tasked with reaching agreement on how to rank a set of images given some sorting criterion through a largely unrestricted, role-symmetric dialogue. By putting emphasis on the argumentation in this mixed-initiative interaction, we collect discussions that involve the collaborative referential process. We describe results of a small-scale data collection experiment with the proposed task. All discussed materials, which includes the collected data, the codebase, and a containerized version of the application, are publicly available.Comment: Published at LREC 202

Exploring the Effect of Gestures and Adaptive Tutoring on Children’s Comprehension of L2 Vocabularies

de Wit J, Schodde T, Willemsen B, et al. Exploring the Effect of Gestures and Adaptive Tutoring on Children’s Comprehension of L2 Vocabularies. In: Proceedings of the Workshop R4L at ACM/IEEE Human-Robot Interaction 2017. 2017