As immersive Virtual Reality (VR) applications become increasingly widespread, ensuring secure and usable authentication is critical. Traditional knowledge-based methods (e.g., passwords, PINs) suffer from memorability issues and are highly vulnerable to observation attacks such as Man-in-the-Room (MITR). Meanwhile, biometric and behavioral approaches raise concerns regarding practicality, privacy, and cross-platform deployment. We present SemanticAction, a semantic-driven, behavior-augmented authentication framework that integrates knowledge-based passwords with gesture-based behavioral biometrics. Passwords are encoded as scene-anchored directions executed through intuitive hand gestures, enabling semantic meaning to guide user interactions. To counter observation attacks, SemanticAction employs randomized scene prompts and decoy scenes, while a dual-constraint verification mechanism adapts to both cold-start/few-shot conditions. Two user studies provide initial evidence that SemanticAction can mitigate MITR attacks while alleviating memorability challenges, maintaining favorable usability and security performance even with limited behavioral data. This work offers early insights and practical design considerations for behavior-aware authentication in VR.

This article emphasizes the$H_{\infty }$control problem with convergence rate constraint for time-varying delay switched systems under the average dwell time switching signal. First, a novel criterion of asymptotic stability with$H_{\infty }$performance is advanced by introducing the method of average dwell time and the definition of asymptotic interval stability, which is more exact than the general stability criterion in estimating the convergence of the systems. Next, the technique of structuring$H_{\infty }$controller is derived from the stability analysis described above, which can constrain the rate of the system to equilibrium, and make it content the preset$H_{\infty }$performance. Finally, a numerical calculation and a water pollution control issue demonstrate the functionality of the technique.