scholarly journals Asynchronous c-VEP communication tools—efficiency comparison of low-target, multi-target and dictionary-assisted BCI spellers

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Felix W. Gembler ◽  
Mihaly Benda ◽  
Aya Rezeika ◽  
Piotr R. Stawicki ◽  
Ivan Volosyak
Keyword(s):  
Canonical Correlation ◽  
High Accuracy ◽  
Manual Control ◽  
Spatial Filters ◽  
Communication Tools ◽  
Free Communication ◽  
Computer Interfaces ◽  
The Mean ◽  
Efficiency Comparison ◽  
Control State

Abstract Keyboards and smartphones allow users to express their thoughts freely via manual control. Hands-free communication can be realized with brain–computer interfaces (BCIs) based on code-modulated visual evoked potentials (c-VEPs). Various variations of such spellers have been developed: Low-target systems, multi-target systems and systems with dictionary support. In general, it is not clear which kinds of systems are optimal in terms of reliability, speed, cognitive load, and visual load. The presented study investigates the feasibility of different speller variations. 58 users tested a 4-target speller and a 32-target speller with and without dictionary functionality. For classification, multiple individualized spatial filters were generated via canonical correlation analysis (CCA). We used an asynchronous implementation allowing non-control state, thus aiming for high accuracy rather than speed. All users were able to control the tested spellers. Interestingly, no significant differences in accuracy were found: 94.4%, 95.5% and 94.0% for 4-target spelling, 32-target spelling, and dictionary-assisted 32-target spelling. The mean ITRs were highest for the 32-target interface: 45.2, 96.9 and 88.9 bit/min. The output speed in characters per minute, was highest in dictionary-assisted spelling: 8.2, 19.5 and 31.6 characters/min. According to questionnaire results, 86% of the participants preferred the 32-target speller over the 4-target speller.

The solution of theoretical seismic problems by best rational function approximations for Laplace transform inversion

1975 ◽  
Vol 65 (4) ◽  
pp. 927-935
Author(s):  
I. M. Longman ◽  
T. Beer
Keyword(s):  
Laplace Transform ◽  
Rational Function ◽  
High Accuracy ◽  
Time Variable ◽  
Inversion Method ◽  
The Laplace Transform ◽  
Previously Treated ◽  
The Mean ◽  
Function Approximations ◽  
Laplace Transform Inversion

Abstract In a recent paper, the first author has developed a method of computation of “best” rational function approximations ḡn(p) to a given function f̄(p) of the Laplace transform operator p. These approximations are best in the sense that analytic inversion of ḡn(p) gives a function gn(t) of the time variable t, which approximates the (generally unknown) inverse f(t) of f̄(p in a minimum least-squares manner. Only f̄(p) but not f(t) is required to be known in order to carry out this process. n is the “order” of the approximation, and it can be shown that as n tends to infinity gn(t) tends to f(t) in the mean. Under suitable conditions on f(t) the convergence is extremely rapid, and quite low values of n (four or five, say) are sufficient to give high accuracy for all t ≧ 0. For seismological applications, we use geometrical optics to subtract out of f(t) its discontinuities, and bring it to a form in which the above inversion method is very rapidly convergent. This modification is of course carried out (suitably transformed) on f̄(p), and the discontinuities are restored to f(t) after the inversion. An application is given to an example previously treated by the first author by a different method, and it is a certain vindication of the present method that an error in the previously given solution is brought to light. The paper also presents a new analytical method for handling the Bessel function integrals that occur in theoretical seismic problems related to layered media.

MUSCLE RELAXATION CONTROLLED BY AUTOMATED ADMINISTRATION OF CISATRACURIUM

2006 ◽  
Vol 18 (06) ◽  
pp. 284-295 ◽  
Author(s):  
CHEN-TSE CHUANG ◽  
SHOU-ZEN FAN ◽  
JIANN-SHING SHIEH
Keyword(s):  
Fuzzy Logic ◽  
Time Delay ◽  
Automatic Control ◽  
Fuzzy Logic Controller ◽  
Muscle Relaxation ◽  
Manual Control ◽  
Logic Control ◽  
Long Term Effect ◽  
Clinical Control ◽  
The Mean

In this paper, the muscle relaxant agent (i.e., cisatracurium) and three clinical control methods (i.e., 13 patients undergoing intermitted bolus control, 15 patients undergoing intensive manual control and 15 patients) undergoing automatic fuzzy logic control (FLC), were used for maintaining depth of muscle relaxation (DOM) during surgery. Cisatracurium, a muscle relaxation drug with long-term effect, low metabolic loading, but long delay time, is widely used in operating rooms and ICUs. Meanwhile, the rules for the FLC were developed from the experimental experience of intensive manual control after learning from 15 patient trials. According to experts' experimental experience, our FLC inputs were chosen from T1% error and trend of T1% which differ from other previous studies on eliminating the effect of time delay from cisatracurium. In individual clinical experimental results, the mean(SD) of the mean T1% error in 13 patients for intermitted bolus control, in 15 patients for intensive manual control, and in 15 patients for automatic control was 8.76(1.46), 1.65(1.67), and 0.48(1.43), respectively. The t test results show that automatic control is not significantly different from intensive manual control. The results show that a simple fuzzy logic controller derived from anesthetists ' clinical trials can provide good accuracy without being affected by the pharmacological time delay problem.

A Dynamic Window Recognition Algorithm for SSVEP-Based Brain–Computer Interfaces Using a Spatio-Temporal Equalizer

2018 ◽  
Vol 28 (10) ◽  
pp. 1850028 ◽  
Author(s):  
Chen Yang ◽  
Xu Han ◽  
Yijun Wang ◽  
Rami Saab ◽  
Shangkai Gao ◽  
...  
Keyword(s):  
Correlation Analysis ◽  
Canonical Correlation Analysis ◽  
Canonical Correlation ◽  
Recognition Accuracy ◽  
Recognition Algorithm ◽  
Benchmark Dataset ◽  
Ease Of Use ◽  
Brain Computer Interfaces ◽  
Computer Interfaces ◽  
Spatio Temporal

The past decade has witnessed rapid development in the field of brain–computer interfaces (BCIs). While the performance is no longer the biggest bottleneck in the BCI application, the tedious training process and the poor ease-of-use have become the most significant challenges. In this study, a spatio-temporal equalization dynamic window (STE-DW) recognition algorithm is proposed for steady-state visual evoked potential (SSVEP)-based BCIs. The algorithm can adaptively control the stimulus time while maintaining the recognition accuracy, which significantly improves the information transfer rate (ITR) and enhances the adaptability of the system to different subjects. Specifically, a spatio-temporal equalization algorithm is used to reduce the adverse effects of spatial and temporal correlation of background noise. Based on the theory of multiple hypotheses testing, a stimulus termination criterion is used to adaptively control the dynamic window. The offline analysis which used a benchmark dataset and an offline dataset collected from 16 subjects demonstrated that the STE-DW algorithm is superior to the filter bank canonical correlation analysis (FBCCA), canonical variates with autoregressive spectral analysis (CVARS), canonical correlation analysis (CCA) and CCA reducing variation (CCA-RV) algorithms in terms of accuracy and ITR. The results show that in the benchmark dataset, the STE-DW algorithm achieved an average ITR of 134 bits/min, which exceeds the FBCCA, CVARS, CCA and CCA-RV. In off-line experiments, the STE-DW algorithm also achieved an average ITR of 116 bits/min. In addition, the online experiment also showed that the STE-DW algorithm can effectively expand the number of applicable users of the SSVEP-based BCI system. We suggest that the STE-DW algorithm can be used as a reliable identification algorithm for training-free SSVEP-based BCIs, because of the good balance between ease of use, recognition accuracy, ITR and user applicability.

scholarly journals Robust nonlinear canonical correlation analysis: application to seasonal climate forecasting

2008 ◽  
Vol 15 (1) ◽  
pp. 221-232 ◽  
Author(s):  
A. J. Cannon ◽  
W. W. Hsieh
Keyword(s):  
Correlation Analysis ◽  
Canonical Correlation Analysis ◽  
Canonical Correlation ◽  
Mean Squared Error ◽  
Synthetic Dataset ◽  
Model Parameters ◽  
Inverse Mapping ◽  
Seasonal Climate ◽  
The Mean ◽  
Improved Performance

Abstract. Robust variants of nonlinear canonical correlation analysis (NLCCA) are introduced to improve performance on datasets with low signal-to-noise ratios, for example those encountered when making seasonal climate forecasts. The neural network model architecture of standard NLCCA is kept intact, but the cost functions used to set the model parameters are replaced with more robust variants. The Pearson product-moment correlation in the double-barreled network is replaced by the biweight midcorrelation, and the mean squared error (mse) in the inverse mapping networks can be replaced by the mean absolute error (mae). Robust variants of NLCCA are demonstrated on a synthetic dataset and are used to forecast sea surface temperatures in the tropical Pacific Ocean based on the sea level pressure field. Results suggest that adoption of the biweight midcorrelation can lead to improved performance, especially when a strong, common event exists in both predictor/predictand datasets. Replacing the mse by the mae leads to improved performance on the synthetic dataset, but not on the climate dataset except at the longest lead time, which suggests that the appropriate cost function for the inverse mapping networks is more problem dependent.

Estimating central and peripheral respiratory resistance

1978 ◽  
Vol 45 (3) ◽  
pp. 375-380 ◽  
Author(s):  
R. L. Pimmel ◽  
M. J. Tsai ◽  
D. C. Winter ◽  
P. A. Bromberg
Keyword(s):  
Regression Equations ◽  
Respiratory Resistance ◽  
Added Resistance ◽  
Frequency Range ◽  
External Resistance ◽  
Control Data ◽  
Mean Values ◽  
External Resistor ◽  
The Mean ◽  
Control State

An analytic approach for fractionating total respiratory resistance into central (Rc) and peripheral (Rp) components is presented. In the analysis, linear regression equations relating the logarithm of the measured total resistance to the logarithm of frequency are derived for data spanning the frequency range 1–16 Hz. The computed slope and intercept are used to obtain estimates of the fraction of the resistance in the periphery (Fp) and of Rp and Rc. Data from anesthetized, closed-chested dogs in a control state and with an external resistor (1.37 cmH2O.1–1.s) were used to test the approach. Mean values +/- SE's for control data were: Fp = 0.400 +/- 0.039, Rp = 1.37 +/- 0.16 cm H2O.1–1.s, and Rc = 1.98 +/- 0.10 cmH2O.1–1.s. Mean values of Rp obtained with and without added resistance were not significantly different (P less than 0.1). The increase in the mean values of Rc represented 85% of the value of the added resistance but was significantly different from the known value of the external resistance (P less than 0.05). These data suggest that it may be possible to fractionate total respiratory resistance into central and peripheral components using the frequency dependence of forced oscillatory resistance.

21.—Riding Motion and Higher Cumulants in Crystallographic Models

1972 ◽  
Vol 70 ◽  
pp. 225-232
Author(s):  
G. S. Pawley
Keyword(s):  
Neutron Diffraction ◽  
Diffraction Study ◽  
Neutron Diffraction Study ◽  
High Accuracy ◽  
Vibrational Modes ◽  
Diffraction Experiment ◽  
Hydrogen Atoms ◽  
Curvilinear Motion ◽  
Higher Order Terms ◽  
The Mean

SynopsisThe motion of hydrogen atoms due to the internal vibrational modes of a molecule is large and curvilinear. Because of the curvilinear motion the mean displacements of these atoms cannot be described by ellipsoids alone, but higher order terms or cumulants are necessary. Equations determining these terms from the usual riding motion are presented. By analysing a neutron diffraction study of high accuracy it is shown that the size of these higher cumulants is sufficient for them to be determinable. For deuterated samples however really high accuracy will be necessary in the diffraction experiment.

The Difficulty of Remotely Negotiating Corners

2007 ◽  
Vol 51 (5) ◽  
pp. 489-493 ◽  
Author(s):  
Robert Pastel ◽  
Jacob Champlin ◽  
Matthew Harper ◽  
Nathan Paul ◽  
William Helton ◽  
...  
Keyword(s):  
Computer Games ◽  
Clinical Medicine ◽  
Remote Navigation ◽  
Computer Interfaces ◽  
Human Computer Interfaces ◽  
Index Of Difficulty ◽  
The Mean ◽  
Mean Time

Remote navigation, popular in computer games and prevalent in areas such as clinical medicine and teleoperations of robots and drones, uses human-computer interfaces for control. Usability studies of remote navigation interfaces require good metrics for evaluating interfaces, assessing users' capabilities, and determining the difficulty of the navigational task. We studied the time proficient users took to navigate virtual hovercrafts through virtual hallways with corners of various widths and discovered that the time to negotiate corners is inversely proportional to corner width. We derive and evaluate two models for the index of difficulty for negotiating corners. Both models fit the data well, with r2 greater than 0.85 for the mean time to negotiate corners verses corner width.

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