HyBoDT: Hybrid Bounded Distance Transforms of Trimmed NURBS Models

Distance field representation of objects in 3D space has several applications such as shape manipulation, graphics rendering, path planning, etc. Distance transforms (DTs) are discrete representations of distance fields in a regular voxel grid. The two main limitations of using distance transforms are that they are compute-intensive, and there are errors introduced while representing the object using DTs. In this work, we develop an hybrid GPU-accelerated marching wavefront method for computing DTs of models composed of trimmed NURBS surfaces with theoretical bounds. Our hybrid marching approach eliminates the error due to calculating approximate distances by marching. We also calculate the bounds on the error introduced due to the tessellation of the trimmed NURBS surfaces and calculate the propagation of these bounds in computing the DT. Finally, we present computation times for both 2D and 3D GPU DTs of test objects. We show that our GPU-accelerated approach is significantly faster than existing CPU-based methods.

Early linguistic experience shapes bilingual adults’ hearing for phonemes in both languages

How do bilinguals represent category structure for phonemes in early acquired languages? /b/ and /p/ voice onset times (VOTs) are earlier and closer together in English than in Mandarin. Hence the category boundary and the steepness of the transition can show ‘tuning’ to language-specific acoustic structure (i.e., earlier boundary and steeper slope for English). As preregistered, we mapped identification functions of early English-Mandarin bilingual adults (N=66) on a /b/ - /p/ VOT continuum in each language. Individual bilingual-balance was derived using principal component analysis and entered into GLMMs of categorical boundary and slope. As predicted, VOTs were earlier for English than Mandarin. Early bilingual-balance predicted the slope of the transition between categories: Those who heard more English from an earlier age showed steeper slopes than those who heard more Mandarin. Findings are consistent with discrete representations for each language, and transfer of category structure from the earlier acquired language.

Color Nameability Predicts Inference Accuracy in Spatial Visualizations

Color encoding is foundational to visualizing quantitative data. Guidelines for colormap design have traditionally emphasized perceptual principles, such as order and uniformity. However, colors also evoke cognitive and linguistic associations whose role in data interpretation remains underexplored. We study how two linguistic factors, name salience and name variation, affect people's ability to draw inferences from spatial visualizations. In two experiments, we found that participants are better at interpreting visualizations when viewing colors with more salient names (e.g., prototypical 'blue', 'yellow', and 'red' over 'teal', 'beige', and 'maroon'). The effect was robust across four visualization types, but was more pronounced in continuous (e.g., smooth geographical maps) than in similar discrete representations (e.g., choropleths). Participants' accuracy also improved as the number of nameable colors increased, although the latter had a less robust effect. Our findings suggest that color nameability is an important design consideration for quantitative colormaps, and may even outweigh traditional perceptual metrics. In particular, we found that the linguistic associations of color are a better predictor of performance than the perceptual properties of those colors. We discuss the implications and outline research opportunities. The data and materials for this study are available at https://osf.io/asb7n

Superstrings in thermal anti-de Sitter space

We revisit the calculation of the thermal free energy for string theory in three-dimensional anti-de Sitter spacetime with Neveu-Schwarz-Neveu-Schwarz flux. The path integral calculation is exploited to confirm the off-shell Hilbert space and we find that the Casimir of the discrete representations of the isometry group takes values in a half-open interval. We extend the free energy calculation to the case of superstrings, calculate the boundary toroidal twisted partition function in the Ramond-Ramond sector, and prove lower bounds on the boundary conformal dimension from the bulk perspective. We classify Ramond-Ramond ground states and construct their second quantized partition function. The partition function exhibits intriguing modular properties.

Shared or Separate Representations? The Spanish Palatal Nasal in Early Spanish/English Bilinguals

The purpose of this study is to examine phonetic interactions in early Spanish/English bilinguals to see if they have established a representation for the Spanish palatal nasal /ɲ/ (e.g., /kaɲon/ cañón ‘canyon’) that is separate from the similar, yet acoustically distinct English /n+j/ sequence (e.g., /kænjn̩/ ‘canyon’). Twenty heritage speakers of Spanish completed a delayed repetition task in each language, in which a set of disyllabic nonce words were produced in a carrier phrase. English critical stimuli contained an intervocalic /n+j/ sequence (e.g., /dɛnjɑ/ ‘denya’) and Spanish critical stimuli contained intervocalic /ɲ/ (e.g., /deɲja/ ‘deña’). We measured the duration and formant contours of the following vocalic portion as acoustic indices of the /ɲ/~/n+j/ distinction. The duration data and formant contour data alike show that early bilinguals distinguish between the Spanish /ɲ/ and English /n+j/ in production, indicative of the maintenance of separate representations for these similar sounds and thus a lack of interaction between systems for bilinguals in this scenario. We discuss these discrete representations in comparison to previous evidence of shared and separate representations in this population, examining a set of variables that are potentially responsible for the attested distinction.

Technical Note—Options Portfolio Selection

We develop a new method to optimize portfolios of options in a market where European calls and puts are available with many exercise prices for each of several potentially correlated underlying assets. We identify the combination of asset-specific option payoffs that maximizes the Sharpe ratio of the overall portfolio: such payoffs form the unique solution to a system of integral equations, which reduces to a linear matrix equation under discrete representations of the underlying probabilities. Even when risk-neutral volatilities are all higher than physical volatilities, it can be optimal to sell options on some assets while buying options on other assets, for which the positive hedging demand outweighs negative demand stemming from asset-specific returns.

Cerebellar degeneration selectively disrupts continuous mental operations

ABSTRACTInspired by computational models of how the cerebellum supports the coordination of movement, we propose a novel hypothesis to specify constraints on how this subcortical structure contributes to higher-level cognition. Specifically, we propose that the cerebellum helps facilitate dynamic continuous transformations of mental representations (CoRT). To test this hypothesis, we compared the performance of individuals with cerebellar degeneration (CD) on tasks that entail continuous movement-like mental operations with tasks that entail more discrete mental operations. In the first pair of experiments, individuals with CD were impaired on a mental rotation task, showing a slower rate of mental rotation compared to control participants. In contrast, the rate at which they scanned discrete representations in visual working memory was similar to that observed in the control group. In the second pair of experiments, we turned to mathematical cognition as a test of the generality of the CoRT hypothesis. Individuals with CD were selectively impaired in adding single-digit numbers, a task hypothesized to entail a mental operation involving continuous transformations along a mental number line. In contrast, their rate of performing arithmetic operations thought to involve retrieval from a look-up table was unimpaired. These results, obtained in disparate task domains, suggest a general role for the cerebellum in coordinating dynamic transformations in mental space, paralleling key features of computational theories concerning the cerebellum’s role in coordinated movement.

Discrete representations for Marchenko imaging of imperfectly sampled data

Marchenko imaging is based on integral representations for focusing functions and Green’s functions. In practice, the integrals are replaced by finite summations. This works well for regularly sampled data, but the quality of the results degrades in a case of imperfect sampling. We have developed discrete representations that account for imperfect sampling of the sources (or, via reciprocity, of the receivers). These representations contain point-spread functions that explain the blurring of the focusing functions and Green’s functions due to imperfect sampling. Deblurring the focusing functions and Green’s functions involves multidimensional deconvolution for the point-spread functions. The discrete representations form the basis for modifying Marchenko imaging to account for imperfectly sampled data, which is important for field data applications.