Overcoming Spatial Constraints in VR:A Survey of Redirected Walking Techniques

As the virtual reality(VR)technology strives to provide immersive and natural user experiences,the challenge of aligning vast virtual environments with limited physical spaces remains significant.This survey comprehensively explores the advancements in redirected walking(RDW)techniques aimed at overcoming spatial constraints in VR.RDW addresses this by subtly manipulating users’physical movements to allow for seamless navigation within constrained areas.The survey delves into gain perception mechanisms,detailing how slight discrepancies between virtual and real-world movements can be utilized without user awareness,thus extending the effective navigable space.Various RDW control algorithms for gain-based RDW are analyzed,highlighting their implementation and effectiveness in maintaining immersion and minimizing perceptual disturbances.Furthermore,novel methods extending beyond traditional gain-based techniques are discussed,showcasing innovative approaches that further refine VR interactions.The practical implications of RDW in enhancing safety and reducing physical collisions in VR environments are underscored,alongside its potential to improve user experience by aligning virtual exploration more closely with natural human behavior patterns.Through a thorough review of existing literature and recent advancements,this survey provides a systematic understanding for researchers,developers,and industry professionals.It underscores the importance of RDW in the future of VR,emphasizing RDW's role in making VR more accessible and practical across various applications,from education and training to therapy and entertainment.The paper concludes with a forward-looking perspective on the continued evolution and potential of RDW in revolutionizing virtual reality experiences.

Evaluation of remediation process with soapberry derived saponin for removal of heavy metals from contaminated soils in Hai-Pu, Taiwan

The use of a biodegradable natural plant-based surfactant extracted from soapberry is proposed for the remediation of Ni, Cr and Mn from industrial soil site in Hai-Pu, Taiwan. Batch experiments were performed under variation of fundamental factors （saponin concentration, pH, and incubation time） for metal remediation. Removal of Ni and Mn were increased with increasing saponin concentration （0.015-0.150 g/L）, whereas the removal of Cr was increased upto 0.075 g/L saponin. The Ni, Cr and Mn were removed significantly （p 〈 0.05） at near to the neutral and slightly acidic （pH 5 to 8） conditions. Removal efficiency of Ni （99%） from the soil was found to be greater than that of Cr （73%） or Mn （25%） in the presence of saponin at a concentration of 0.150 g/L at pH 5. The removal percentage increased with incubation time where the removal of Ni was faster than that of Cr and Mn. The result indicates the feasibility of cco-friendly removal of heavy metal （Ni, Cr and Mn） from industrial soil by soil washing process in presence of plant derived saponin.