Jubin Zhang
Department of Physical Education, North China Institute of Aerospace Engineering, Langfang 065000, China

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From General Human Activity Recognition to Volleyball-Oriented Wearable Transfer Learning: Cross-Dataset Evidence from UCI HAR and WISDM for Domain Adaptation and Edge Deployment Jubin Zhang
Journal of Technology Informatics and Engineering Vol. 4 No. 1 (2025): APRIL | JTIE : Journal of Technology Informatics and Engineering
Publisher : University of Science and Computer Technology

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.51903/jtie.v4i1.524

Abstract

Wearable human activity recognition has become a practical foundation for coaching analytics, workload monitoring, and interactive sports training, yet volleyball-specific labelled inertial datasets remain much smaller than general-purpose public HAR corpora. This study addressed that gap through a transfer-learning design in which public HAR benchmarks were treated as representation sources and a smartwatch target domain was used as a volleyball-oriented wrist proxy. Full experimental evaluations were conducted on UCI HAR and on a public WISDM-derived smartwatch subset, using three baseline families: logistic regression, a lightweight one-dimensional convolutional network, and a tiny Transformer. The study also measured modality ablation and unsupervised domain adaptation through Deep CORAL in a common four-class transfer space. On UCI HAR, the final measured accuracies were 0.7940 for logistic regression, 0.8039 for CNN-Lite, and 0.3621 for Transformer-Tiny. On the WISDM smartwatch subset, the corresponding accuracies were 0.8207, 0.8682, and 0.7632. Modality ablation on WISDM showed that accelerometer-only input reached 0.8486 accuracy, gyroscope-only input reached 0.6543, and fused accelerometer-plus-gyroscope input reached 0.8505. For cross-dataset transfer from UCI to WISDM, source-only training achieved 0.3376 accuracy, Deep CORAL improved accuracy to 0.4134, and the fully supervised target-only upper bound reached 0.8374. The results establish three concrete conclusions: lightweight convolutional sequence encoders are more reliable than the tested tiny Transformer under these data conditions, accelerometer channels carry most of the discriminative value for wrist-worn deployment, and domain adaptation is necessary when general smartphone HAR is transferred to smartwatch sports analytics. These findings provide a reproducible public-data foundation for volleyball-oriented wearable modelling and for subsequent fine-tuning on sport-specific action labels.
Early Warning, Grade Prediction, and Teacher-Facing LLM-Ready Explanations Toward an Open Volleyball Course: Reproducible Evidence from Four Public Education Datasets Jubin Zhang
Journal of Technology Informatics and Engineering Vol. 5 No. 2 (2026): AUGUST | JTIE : Journal of Technology Informatics and Engineering
Publisher : University of Science and Computer Technology

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.51903/jtie.v5i2.525

Abstract

Open online courses and public skill-development programs often experience learner dropout not due to content limitations, but because instructors receive delayed and non-actionable feedback. This study proposes and empirically evaluates an integrated framework for an open volleyball course that combines early warning prediction, grade estimation, and teacher-oriented LLM-generated academic status explanations. The predictive models were tested on four lightweight educational datasets: xAPI-Edu-Data, Predict Students’ Dropout and Academic Success, Student Performance, and Higher Education Students Performance Evaluation. A unified preprocessing pipeline was applied using one-hot encoding, an 80/20 train-test split, and 5-fold cross-validation. Decision Tree, Random Forest, and XGBoost models were evaluated for classification, alongside their regression variants for grade prediction. Results show consistent performance across datasets. Random Forest achieved the best macro-F1 on xAPI-Edu-Data (0.799) with a macro-AUC of 0.914, while XGBoost performed best on the dropout dataset (macro-F1 = 0.689, macro-AUC = 0.892). For Student Performance, early-warning models without prior grades reached an RMSE of 3.086, improving to 1.398 when full information was available. On the higher education dataset, performance remained limited due to small sample size and multi-grade targets, with Random Forest achieving a macro-F1 of 0.248. Ablation results confirmed that behavioral and progression features significantly improve predictive accuracy. An explanation layer translated model outputs into structured, teacher-facing natural language linked to key risk indicators and intervention cues. Overall, the framework demonstrates analytic feasibility for structured volleyball course monitoring, though results should be interpreted as pre-deployment evidence rather than validation in real instructional settings. Explanation quality improves when grounded in observed behavioral signals rather than generic generation.