Indium as an efficient ohmic contact to N-face n-GaN of GaN-based vertical light-emitting diodes

We propose indium (In), a low work function and nitride-forming element, as an efficient ohmic contact layer to N-face n-GaN. While conventional Al-based ohmic contacts show severe degradation after annealing at 300 C, In-based ohmic contacts display considerable improvement in contact resistivity. The annealing-induced enhancement of ohmic behavior in In-based contacts is attributed to the formation of an InN interfacial layer, which is supported by x-ray photoemission spectroscopy measurements. These results suggest that In is of particular importance for application as reliable ohmic contacts to n-GaN of GaN-based vertical light-emitting diodes.open3

Effectiveness of a Virtual Reality Head-Mounted Display System-based Developmental Eye Movement Test

By transplanting the Developmental Eye Movement (DEM) test chart to a virtual reality head-mounted display (VR HMD) system, this study sought to evaluate the effectiveness of the DEM test for measuring dynamic visual acuity.Thirty-nine adults aged 20–39 years of both genders were the subjects of the study. After undergoing measurement of their visual function, through medical questionnaire, interpupillary distance, near point of convergence (NPC), near point of accommodation (NPA), and far and near phoria, the correlation between the tests was analyzed performing DEM vertical, horizontal test and VR HMD DEM (VHD) vertical, horizontal test.NPC and NPA decreased significantly after the VHD test, while phoria did not. The horizontal was quicker than the vertical in the DEM test, and vice versa in the VHD test. DEM was quicker than VHD in both the vertical and horizontal directions. There was no notable difference in error frequency between DEM and VHD. In terms of DEM and VHD test, there was no notable difference in the short-range IPD and subjective symptoms of the top 10 and bottom 10 subjects. There was also no notable difference between the exercise and non-exercise groups and the game and non-game groups.The performance time for VHD, in which the chart must be read while moving the body, was longer than that of DEM. Therefore, based on the consistency of the results of both tests and the lack of a difference in error frequency and subjective symptoms, the VHD equipment proposed in this thesis is as effective as dynamic visual acuity measurement equipment. In addition, the lack of a difference between the exercise and non-exercise groups and the game and non-game groups demonstrated that the amount of exercise and game by an ordinary person does not influence their dynamic visual function

Performance Comparison of Spectral Wave Models Based on Different Governing Equations Including Wave Breaking

The performance of three spectral wave models based on different types of governing equations, REF/DIF S, MIKE 21 BW module and SWAN, was compared by using four laboratory and field experimental data. The comparison was focused on accurate prediction of the measured wave height. Characteristics of the three wave models were discussed and their overall predictability of the measured data was evaluated by calculating mean absolute relative errors of wave height. All the numerical models simulated fairly well shoaling and breaking of waves propagating on a plane sloping beach, but the model accuracy was somewhat degenerated in simulating waves propagating over a barred beach. Among the three models, MIKE 21 BW was the most insensitive to the bathymetric change. Combined refraction-diffraction over a shoal without breaking was quite well simulated by the models, especially by REF/DIF S and MIKE 21 BW. When waves break over the shoal, however, all the models failed to reproduce the wave field behind the shoal. The agreement with data in simulating wave diffraction around breakwater was remarkably good for MIKE 21 BW, but very poor for other two models. Except the last simulation, the mean absolute relative errors of wave height from the three models ranged between 3 and 27%