Design and Evaluation of a Differential Accelerometer for Drop-Tower Equivalence Principle Test with Rotating Masses

A differential accelerometer comprising of two rotating masses made of the same material is proposed for drop tower-based free-fall testing of the spin-spin force between the rotating mass and the Earth. The measurement is performed by placing the two concentric masses of very different momenta in a vacuum drop capsule which is falling freely in the Earth＇s gravitational field. A nonzero output of the differential aeeelerometer is an indication of possible violation of new equivalence principle （NEP）. We present the conceptual design of a modified free-fall NEP experiment which can be performed at the Belting drop tower. Design and evaluation of the differential accelerometer with a hybrid electrostatic/magnetic suspension system are presented to accommodate for operation on ground and drop-tower tests. Details specific to the measurement uncertainty are discussed to yield an NEP test accuracy of 7.2×10^-9.

Optical design and evaluation of Alvarez-type vision-training system

Myopia has become a noteworthy issue due to the increasing use of our eyes. We propose a continuous power variation vision-training device based on Alvarez lenses with the power ranging from -10D to ＋2D. First, we introduce the principle of Alvarez lenses and the evaluation method of dioptric power and astigmatism. Then, we optimize the optical system described by Zernike polynomials. Finally, we analyze the distributions of dioptric power and astigmatism with the overall surface analysis and fields of view（FOVs） analysis. The results show that the optical performance of an optimized system can meet the requirement within a 40° FOV.

Motivation effect of animated pedagogical agent's personality and feedback strategy types on learning in virtual training environment

Background The personality and feedback of an animated pedagogical agent(APA)are vital social-emotional features that render the agent perceptually believable.Their effects on learning during virtual training need to be examined.Methods In this paper,an explanation model is proposed to clarify the underlying mechanism of how these two features affect learners.Two studies were conducted to investigate the model.In Study 1,the effect of the APA's personality type and feedback strategy on flow experience and performance was reexamined,revealing significant effects of the feedback strategy on flow and performance and a marginally significant effect of the personality type on performance.To explore the mechanism behind these effects,a theoretical model is proposed by distinguishing between intrinsic and extrinsic motivation effects.In Study 2,the model was evaluated,and the APA's personality type was found to significantly influence the factors in the path of the extrinsic motivation effect rather than those in the path of the intrinsic motivation effect.Results In contrast,the feedback strategy affected factors in the path of the intrinsic motivation effect.Conclusions These results validated the proposed model.Further distinguishing the two motivation effects is necessary to understand the respective effects of an APA's personality and feedback features on learning experiences and outcomes.

Detection of scene-irrelevant head movements via eye-head coordination information

Background Accurate motion tracking in head-mounted displays(HMDs)has been widely used in immersive VR interaction technologies.However,tracking the head motion of users at all times is not always desirable.During a session of HMD usage,users may make scene-irrelevant head rotations,such as adjusting the head position to avoid neck pain or responding to distractions from the physical world.To the best of our knowledge,this is the first study that addresses the problem of scene-irrelevant head movements.Methods We trained a classifier to detect scene-irrelevant motions using temporal eye head-coordinated information sequences.To investigate the usefulness of the detection results,we propose a technique to suspend motion tracking in HMDs where scene-irrelevant motions are detected.Results/Conclusions Experimental results demonstrate that the scene-relevancy of movements can be detected using eye-head coordination information,and that ignoring scene-irrelevant head motions in HMDs improves user continuity without increasing sickness or breaking immersion.