Chan-Su Lee

Classifying pathological gaits is crucial for identifying impairments in specific areas of the human body. Previous studies have extensively employed machine learning and deep learning (DL) methods, using various wearable (e.g., inertial sensors) and non-wearable (e.g., foot pressure plates and depth cameras) sensors. This study proposes early and late fusion methods through DL to categorize one normal and five abnormal (antalgic, lurch, steppage, stiff-legged, and Trendelenburg) pathological gaits. Initially, single-modal approaches were utilized: first, foot pressure data were augmented for transformer-based models; second, skeleton data were applied to a spatiotemporal graph convolutional network (ST-GCN). Subsequently, a multi-modal approach using early fusion by concatenating features from both the foot pressure and skeleton datasets was introduced. Finally, multi-modal fusions, applying early fusion to the feature vector and late fusion by merging outputs from both modalities with and without varying weights, were evaluated. The foot pressure-based and skeleton-based models achieved 99.04% and 78.24% accuracy, respectively. The proposed multi-modal approach using early fusion achieved 99.86% accuracy, whereas the late fusion method achieved 96.95% accuracy without weights and 99.17% accuracy with different weights. Thus, the proposed multi-modal models using early fusion methods demonstrated state-of-the-art performance on the GIST pathological gait database.

LEDs are widely used for both general and automotive lighting since their brightness can be easily regulated by controlling their on/off time using methods such as pulse width modulation (PWM). However, lighting control using PWM can cause temporal light artefacts, such as the phantom array effect, which affect human visual perception. In this study, we determined the influence of different colour temperatures on the visibility of the phantom array effect using five LEDs with different spectral distributions (red, green, blue, warm white and cool white) and frequencies of temporal modulation ranging from 1 kHz to 11 kHz. The threshold of the warm white LED was between that of the green and red LEDs, and threshold of the cool white LED was between that of the red and blue LEDs. The experimental results revealed a difference in the threshold frequency of the visibility of the phantom array effect, in accordance with the spectral distribution and the colour temperature of the light source.