Review of studies on target acquisition in virtual reality based on the crossing paradigm

Crossing is a fundamental paradigm for target selection in human-computer interaction systems.This paradigm was first introduced to virtual reality(VR)interactions by Tu et al.,who investigated its performance in comparison to pointing,and concluded that crossing is generally no less effective than pointing and has unique advantages.However,owing to the characteristics of VR interactions,there are still many factors to consider when applying crossing to a VR environment.Thus,this review summarizes the main techniques for object selection in VR and crossing-related studies.Then,factors that may affect crossing interactions are analyzed from the perspectives of the input space and visual space.The aim of this study is to provide a reference for future studies on target selection based on the crossing paradigm in virtual reality.

Efficient synthesis of cyclic carbonates under atmospheric CO_(2) by DMAP-based ionic liquids: the difference of inert hydrogen atom and active hydrogen atom in cation

The coupling reaction of carbon dioxide(CO_(2)) and epoxides is one of the most efficient pathways to achieve the carbon balance.However,to accomplish it under the mild conditions,especially under the atmospheric pressure,is still a perplexing problem.Three novel ionic liquids(ILs),[DMAPBrPC][TMGH],[DMAPBrPC][DBUH],and[DMAPBrPC][BTMA],are designed and synthesized.All of them display the excellent catalytic activity for the title reaction achieving the yield over 96.6% under the atmospheric CO_(2) pressure at 60℃.Interestingly,[DMAPBrPC][BTMA]with the inert hydrogen atom in cation exhibits the superior catalytic activity as compared to other two ILs with the protic hydrogen atom in cation along with the same anion.The active hydrogen atom in[DMAPBrPC][TMGH]and[DMAPBrPC][DBUH]would impede the–COO^(-)group to absorb CO 2,which is an unfavorable item for the reaction.Moreover,the strong hydrogen bond in[DMAPBrPC][TMGH]and[DMAPBrPC][DBUH]would lessen the nucleophilic ability of Br^(-) anion resulting in the inferior catalytic performance,which is further confirmed by the density functional theory(DFT)calculations.The cation without the active hydrogen atom could also be employed to design the ILs with the excellent catalytic feature when it is combined with the suitable anion.