Performance Evaluation of Cluster Validity Indices (CVIs) on Multi/Hyperspectral Remote Sensing Datasets

The number of clusters (i.e., the number of classes) for unsupervised classification has been recognized as an important part of remote sensing image clustering analysis. The number of classes is usually determined by cluster validity indices (CVIs). Although many CVIs have been proposed, few studies have compared and evaluated their effectiveness on remote sensing datasets. In this paper, the performance of 16 representative and commonly-used CVIs was comprehensively tested by applying the fuzzy c-means (FCM) algorithm to cluster nine types of remote sensing datasets, including multispectral (QuickBird, Landsat TM, Landsat ETM+, FLC1, and GaoFen-1) and hyperspectral datasets (Hyperion, HYDICE, ROSIS, and AVIRIS). The preliminary experimental results showed that most CVIs, including the commonly used DBI (Davies-Bouldin index) and XBI (Xie-Beni index), were not suitable for remote sensing images (especially for hyperspectral images) due to significant between-cluster overlaps; the only effective index for both multispectral and hyperspectral data sets was the WSJ index (WSJI). Such important conclusions can serve as a guideline for future remote sensing image clustering applications

Forward Modeling of Transducer Misalignment Effects in Ultrasonic Leaky Wave Measurements

Ultrasonic measurements performed with a pair of acoustic transducers in pitch-catch mode are of common use in the NDE field. In particular, for nearfield leaky wave (LW) measurements which are directed at precise determination of material properties of layered elastic structure in immersion. In LW measurements, the acoustic transducer beams are aligned at angles so as to phase match to one or several of the structure’s leaky (Rayleigh or Lamb) waves. The amplitude and phase of the scattered acoustic energy collected, and converted to an electrical voltage, by the phase-sensitive receiving transducer depends not only on the properties of the structure but also on the parameters of the transducers used, in particular, their apertures and alignment angles. Transducer alignment issues are especially important for transducers that radiate or receive over a narrow angular range

Variation in the Relationship of Wood Density With Growth In 40 Black Spruce (Picea Mariana) Families Grown in New Brunswick

This study examined variation in the relationship of wood density with growth traits (DBH, tree height, and bole volume) in 15-year-old half-sib families of black spruce (Picea mariana) grown on two different sites located in northern New Brunswick. Effect of genotype and environment on wood density was also briefly discussed. Although a moderately negative relationship between wood density and growth generally exists, the relationship, to some extent, varies with genotype and environment. A nonsignificant or even a weak positive relationship between wood density and growth can be found in some families. Moreover, the negative relationship between wood density and growth appears to be weaker in families growing in a more favorable environment. This study indicates that it is possible to select some families that not only grow fast, but also maintain high wood density

Shear-Wave Tomographic Images Of An Oil Reservoir At MIT's Michigan Test Site

We conducted a P- and S-wave crosswell survey with Conoco's orbital vibrator source and three-component receivers at M.LT.'s Michigan Test Site. The receiver and source wells bracket a known oil reservoir. Applying a nonlinear crosswell traveltime tomography method, we reconstruct the velocity structures in the oil reservoir using P- and S-wave data separately. The P-wave tomogram shows a similar image to the one by Matarese (1993), and it does not present much velocity variations in the oil producing zone. However, the S-wave tomogram clearly shows the image of the reservoir zone, which is characterized with low velocities in a pinnacle reef. The S-wave velocities in the reservoir are about 20% lower than those of the surrounding carbonates.Massachusetts Institute of Technology. Earth Resources Laboratory. Reservoir Delineation Consortiu

TEMPERA: Test-Time Prompting via Reinforcement Learning

Careful prompt design is critical to the use of large language models in zero-shot or few-shot learning. As a consequence, there is a growing interest in automated methods to design optimal prompts. In this work, we propose Test-time Prompt Editing using Reinforcement learning (TEMPERA). In contrast to prior prompt generation methods, TEMPERA can efficiently leverage prior knowledge, is adaptive to different queries and provides an interpretable prompt for every query. To achieve this, we design a novel action space that allows flexible editing of the initial prompts covering a wide set of commonly-used components like instructions, few-shot exemplars, and verbalizers. The proposed method achieves significant gains compared with recent SoTA approaches like prompt tuning, AutoPrompt, and RLPrompt, across a variety of tasks including sentiment analysis, topic classification, natural language inference, and reading comprehension. Our method achieves 5.33x on average improvement in sample efficiency when compared to the traditional fine-tuning methods

Prolonged mixed phase induced by high pressure in MnRuP

Hexagonally structured MnRuP was studied under high pressure up to 35 GPa from 5 to 300 K using synchrotron X-ray diffraction. We observed that a partial phase transition from hexagonal to orthorhombic symmetry started at 11 GPa. The new and denser orthorhombic phase coexisted with its parent phase for an unusually long pressure range, {\Delta}P ~ 50 GPa. We attribute this structural transformation to a magnetic origin, where a decisive criterion for the boundary of the mixed phase lays in the different distances between the Mn-Mn atoms. In addition, our theoretical study shows that the orthorhombic phase of MnRuP remains steady even at very high pressures up to ~ 250 GPa, when it should transform to a new tetragonal phase.Comment: 15 pages, 5 figures, supplementary materia