X

Summary

X, or x, is the 24th and third-to-last letter in the Latin alphabet, used in the modern English alphabet, the alphabets of other western European languages and others worldwide. Its name in English is "ex" (pronounced 'ɛks), plural exes. History In Ancient Greek, 'Χ' and 'Ψ' were among several variants of the same letter, used originally for /kʰ/ and later, in western areas such as Arcadia, as a simplification of the digraph 'ΧΣ' for /ks/. In the end, more conservative eastern forms became the standard of Classical Greek, and thus 'Χ' (Chi) stood for /kʰ/ (later /x/; palatalized to [ç] in Modern Greek before front vowels). However, the Etruscans had taken over 'Χ' from western Greek, and it therefore stands for /ks/ in Etruscan and Latin. The letter 'Χ' ~ 'Ψ' for /kʰ/ was a Greek addition to the alphabet, placed after the Semitic letters along with phi 'Φ' for /pʰ/. Pronunciation and use English In English orthography, is typically pronounced as t

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Intent Prediction Based on Biomechanical Coordination of EMG and Vision-Filtered Gaze for End-Point Control of an Arm Prosthesis

Iason Batzianoulis, Aude Billard, Nili Eliana Krausz, Silvestro Micera

We propose a novel controller for powered prosthetic arms, where fused EMG and gaze data predict the desired end-point for a full arm prosthesis, which could drive the forward motion of individual joints. We recorded EMG, gaze, and motion-tracking during pick-and-place trials with 7 able-bodied subjects. Subjects positioned an object above a random target on a virtual interface, each completing around 600 trials. On average across all trials and subjects gaze preceded EMG and followed a repeatable pattern that allowed for prediction.A computer vision algorithm was used to extract the initial and target fixations and estimate the target position in 2D space. Two SVRs were trained with EMG data to predict the x- and y- position of the hand; results showed that the y-estimate was significantly better than the x-estimate. The EMG and gaze predictions were fused using a Kalman Filter-based approach, and the positional error from using EMG-only was significantly higher than the fusion of EMG and gaze. The final target position Root Mean Squared Error (RMSE) decreased from 9.28 cm with an EMG-only prediction to 6.94 cm when using a gaze-EMG fusion. This error also increased significantly when removing some or all arm muscle signals. However, using fused EMG and gaze, there were no significant difference between predictors that included all muscles, or only a subset of muscles.

2020

The Chaining Lemma and Its Application

Sebastian Faust

We present a new information-theoretic result which we call the Chaining Lemma. It considers a so-called "chain" of random variables, defined by a source distribution X-(0) with high min-entropy and a number (say, t in total) of arbitrary functions (T-1,...,T-t) which are applied in succession to that source to generate the chain X-(0) (sic) X-(1) (sic) X-(2)...(sic) X-(t). Intuitively, the Chaining Lemma guarantees that, if the chain is not too long, then either (i) the entire chain is "highly random", in that every variable has high min-entropy; or (ii) it is possible to find a point j (1

Springer-Verlag Berlin2015

A Monte-Carlo approach for tracking mobile personnel

Volkan Cevher

In this paper, we propose a Monte-Carlo method based on the particle filter framework to track footfall locations generated by mobile personnel using seismic arrays. While the particle proposal function follows a simple bootstrap approach, the novelty in our algorithm comes from a unique weighting strategy that takes into account the sparse nature of the seismic footfall signal and is robust against missed detections and clutter which could appear in the form of other impulsive sources or other walkers. Our weighting strategy automatically makes use of the wavefront shape, either planar or circular, and assigns weights in x-y space. Data association is built into the system, eliminating the need to explicitly associate the received footfall impulses with different walkers. Hence our algorithm is ideal for tracking multiple mobile personnel. We also demonstrate the fusion of our system with range information available by means of radar. Fusion with radar improves x-y tracking when range resolution is lost due to a large distance between the target and the seismic array leading to planar wavefronts.

2007