The Effect of an Occluder on the Accuracy of Depth Perception in Optical See-Through Augmented Reality

Three experiments were conducted to study the effect of an occluder on the accuracy of nearield depth perception in optical-see-through augmented reality (AR). The first experiment was a duplicate experiment of the one in Edwards et al. [2004]. We found more accurate results than Edwards et al.’s work and did not find the occluder’s main effect or its two-way interaction effect with distance on the accuracy of observers’ depth matching. The second experiment was an updated version of the first one using a within-subject design and a more accurate calibration method. The results were that errors ranged from –5 to 3 mm when the occluder was present, –3 to 2 mm when the occluder was absent, and observers judged the virtual object to be closer after the presentation of the occluder. The third experiment was conducted on three subjects who were depth perception researchers. The result showed significant individual effects

Water–fertilizer coupling effect on the growth traits of winter wheat under conditions of light and small sprinklers

Light and small sprinklers were used to irrigate winter wheat fields. The distribution and migration of water and nitrogen in soil during winter wheat growth period were analyzed. Moreover, the growth traits of winter wheat were monitored. It is demonstrated that water–fertilizer coupling effect had a significant impact on the migration of water and nitrogen in soil and the growth traits of winter wheat under conditions of light and small sprinklers. Under the same condition of irrigation quota, although the content of moisture in soil was slightly reduced with the increase of the amount of fertilizer, the impact of the amount of fertilizer on the content of moisture in soil is much more insignificant than that of irrigation quota. The content of nitrate nitrogen (NO3--N) in soil was increased with an increasing amount of fertilizer, especially when the value of irrigation quota was low. On the other hand, under the same condition of amount of fertilizer, the content of nitrate nitrogen (NO3--N) in soil was decreased with an increasing value of irrigation quota, especially when the value of irrigation quota was high. Hence, an ultra-high value of irrigation quota will aggravate the leach of nitrate nitrogen in soil. The water–fertilizer coupling effect and yield of winter wheat could be optimized by improving irrigation scheme, optimizing irrigation quota, and optimizing the amount of fertilizer

Validation of geometric and dosimetric accuracy of edge accelerator gating with electromagnetic tracking: A phantom study

This work was to devise a comprehensive testing scheme to evaluate the geometric and dosimetric accuracy of the Edge accelerator gating with electromagnetic tracking (EMT) for its safety in clinical application. A CIRS thorax phantom was scanned with four-dimensional cone-beam CT (4D-CBCT) on an Edge accelerator while the simulated tumor was simultaneously tracked with an EMT system using Calypso. The geometric accuracy was validated by comparing the motion trajectories derived from Calypso and 4D-CBCT with the ground truth from motion control software. The two-dimensional and three-dimensional dynamic doses were measured with the Matrixx and ArcCHECK installed on a motion platform, both with and without EMT. For tumor motion with 5, 7.5 mm amplitudes, the average absolute differences of sample position between Calypso and the ground truth were 0.286±0.234 mm, 0.407±0.331 mm respectively. Dosimetric accuracy was validated with 3 mm/3% gamma criterion. The average gamma pass rates of 2D dynamic dose validation based on Matrixx were less than 46% without EMT, 97.3% using 2 mm gating limit, 96% using 3 mm gating limit and 93.4% using 5mm gating limit respectively. The mean 3D dynamic dose validation pass rates based on ArcCHECK were 65.9% without EMT, 96.2% using 3 mm gating limit, and 92.5% using 5 mm gating limit with EMT respectively. The geometric accuracy of the Calypso system in tracking the moving target area was stable at the submillimeter level. The dosimetric accuracy could be improved significantly with EMT using an appropriate gating limit