KEYWORDS: 3D modeling, Detection and tracking algorithms, Skin, Pattern recognition, 3D acquisition, Cameras, Databases, Autoregressive models, Mobile devices, Target recognition
With enhanced processing capability of mobile platforms, augmented reality (AR) has been considered a promising technology for achieving enhanced user experiences (UX). Augmented reality is to impose virtual information, e.g., videos and images, onto a live-view digital display. UX on real-world environment via the display can be e ectively enhanced with the adoption of interactive AR technology. Enhancement on UX can be bene cial for digital learning systems. There are existing research works based on AR targeting for the design of e-learning systems. However, none of these work focuses on providing three-dimensional (3-D) object modeling for en- hanced UX based on interactive AR techniques. In this paper, the 3-D interactive augmented reality-enhanced learning (IARL) systems will be proposed to provide enhanced UX for digital learning. The proposed IARL systems consist of two major components, including the markerless pattern recognition (MPR) for 3-D models and velocity-based object tracking (VOT) algorithms. Realistic implementation of proposed IARL system is conducted on Android-based mobile platforms. UX on digital learning can be greatly improved with the adoption of proposed IARL systems.
Alternating-current (AC) driven light-emitting diodes (LEDs) have become the trend of solid-state lighting (SSL)
products. The junction temperature is an important index of LEDs reliability and efficiency. In other words, with proper
thermal management of AC LEDs lighting products, the high performance of SSL products will be achieved. In order to
obtain the junction temperature, we study and compare two published evaluating methods differentiating between the
measurements of DC and AC in this paper. The first method is in which a low reference current having a pulse width
was applied and the corresponding voltage across the device was measured and correlated to the junction temperature
(Tj). The second method is using an active heat sink for recovering the root mean square (RMS) current of the first half
cycle to estimate the junction temperature. The experimental evidence showed different aspects and variations of
evaluating the AC LEDs junction temperature. The variations of evaluating junction temperature were caused by the
switch time and phase of different source measurements in the first method and the capture time of the first half cycle in
the second method. With proper capture time, the rising junction temperature in the second method might be negligible.
The capability of high-power nitride-based light-emitting diodes (HPLED) to withstand electrostatic discharge
(ESD) is very important key index due to the horizontal structure of the insulating property of the sapphire substrate.
However, it is difficult to real-time monitor the damage caused by the ESD stress because it occurred in a very short
period. Current-voltage (I-V) curves and electroluminescence (EL) spectrum were applied to study the change during the
series ESD stress. Time-resolved optical beam induced current (TR-OBIC) was used to analyze the characteristics of the
delay time between normal region and the defect point caused by ESD stress. Transmission electron microscopy (TEM)
was used to compare to the difference in the distribution of damage region and investigate the failure modes. During the
series ESD stresses, V-shaped pits suffered from the high electrical field and the distance from multi-quantum well
(MQW). The bottom of V-shaped defect would be one of index to assess the ESD endurance of LED chips.
The die-attached quality and the thermal transient characteristics of high power flip chip light emitting diodes (LEDs)
are investigated using thermal transient tester. Various die-attached materials were utilized to compare the difference in
their thermal resistances and long term performance. By applying accelerated aging stress, the deterioration rates at the
die-attached layers were obtained. Numerical simulation provided further understanding of LED device temperature
distribution and also revealed that the thermal variance at the die-attached interface can be recognized within only few
milliseconds for the flip chip structure. The effects of bump arrangement and material were analyzed to achieve high
temperature uniformity and low thermal resistance for high power LEDs.
Alternating-current (AC) driven high-power light-emitting diodes (LEDs) have become available and introduced into
solid-state lighting (SSL) products. AC LEDs operate directly from a mains supply with no need of drivers, and thus can
simplify the design of SSL product and potentially increase product's reliability and lifetime. Similar to direct-current
(DC) LEDs the optical and electrical properties of AC LEDs are strongly dependent on the LED junction temperature. In
addition, the instantaneous junction temperature of an AC LED changes rapidly within an AC power cycle. Accurate
measurement of AC high-power LEDs is required for quality control and product qualifications such as the US Energy
Star. We have developed a simple, robust method for measurement of high-power AC LEDs at any specified junction
temperature under a normal AC operating condition. An active heat sink is used for setting and controlling the junction
temperature of the test AC LED. By using this measurement technique, the measurement of an AC LED also obtains the
thermal resistance between the LED junction and the LED heat sink.
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