Browsing by Author "Chen, Ching-Yu"

Now showing 1 - 5 of 5

A Scalable Complex Event Analytical System with Incremental Episode Mining over Data Streams
(2016)
Tseng, Jerry C. C.
;
Gu, Jia-Yuan
;
Tseng, Vincent S.
;
Wang, P. F.
;
Chen, Ching-Yu
Episode pattern mining is a very powerful technique to get high-valued information for people to solve real-life cross-disciplinary problems, such as for the analysis of manufacturing, stock markets, weather records and so on. As data grows, the mining process must be re-triggered again and again to obtain the most updated information. However, periodically re-mining the full dataset is not cost-effective, and thus a number of incremental mining approaches arise for the growing data. However, to our best knowledge, there exist few studies targeted on the problem of incremental episode mining. Moreover, streaming data of complex events is more and more popular because digital sensors always collect data around us in this big data age. Now the challenge is not only mining valuable episode patterns of incremental dataset, but also mining episode patterns over data streams of complex events. To address this research problem, we adopt the Lambda Architecture to design a scalable complex event analytical system that could be used to facilitate the incremental episode mining process over complex event sequences of data streams. Apache Spark and Apache Spark Streaming are applied as the development framework of the batch layer and the speed layer, respectively. To take both the efficiency and accuracy into consideration, we develop a series of modules and three algorithms, namely, batch episode mining, delta episode mining and pattern merging. Results from the experimental validation on a real dataset show that the proposed system carries high scalability and delivers excellent performance in terms of efficiency and accuracy.
Effects of growth temperature on InN/GaN nanodots grown by metal organic chemical vapor deposition
(2008-05-15)
Chang, Wen-Hao
;
Ke, Wen-Cheng
;
Yu, Shu-Hung
;
Lee, Lin
;
Chen, Ching-Yu
InN nanodots grown on GaN by metal organic chemical vapor deposition using conventional growth mode as well as flow-rate modulation epitaxy at various growth temperatures (550-730 degrees C) were investigated. We found that different precursor injection schemes together with the effect of growth temperatures greatly influenced the surface morphology of InN nanodots and their photoluminescence (PL) properties. The sample grown at around 650 degrees C showed the highest growth rate. For samples grown at higher temperatures, the residual carrier concentration was reduced and the PL efficiency was improved. Furthermore, we found that the growth of InN nanodots is still sustainable even at a temperature higher than 700 degrees C while retaining their optical quality. (c) 2008 American Institute of Physics.
Enhanced external quantum efficiency in GaN-based vertical-type light-emitting diodes by localized surface plasmons
(2016-03-03)
Yao, Yung-Chi
;
Hwang, Jung-Min
;
Yang, Zu-Po
;
Haung, Jing-Yu
;
Lin, Chia-Ching
Enhancement of the external quantum efficiency of a GaN-based vertical-type light emitting diode (VLED) through the coupling of localized surface plasmon (LSP) resonance with the wave-guided mode light is studied. To achieve this experimentally, Ag nanoparticles (NPs), as the LSP resonant source, are drop-casted on the most top layer of waveguide channel, which is composed of hydrothermally synthesized ZnO nanorods capped on the top of GaN-based VLED. Enhanced light-output power and external quantum efficiency are observed, and the amount of enhancement remains steady with the increase of the injected currents. To understand the observations theoretically, the absorption spectra and the electric field distributions of the VLED with and without Ag NPs decorated on ZnO NRs are determined using the finite-difference time-domain (FDTD) method. The results prove that the observation of enhancement of the external quantum efficiency can be attributed to the creation of an extra escape channel for trapped light due to the coupling of the LSP with wave-guided mode light, by which the energy of wave-guided mode light can be transferred to the efficient light scattering center of the LSP.
Optical Properties of Uncapped InN Nanodots Grown at Various Temperatures
(2009-03-01)
Chen, Ching-Yu
;
Lee, Ling
;
Tai, Shin-Kai
;
Fu, Shao-Fu
;
Ke, Wen-Cheng
Photoluminescence (PL) measurements were employed to investigate the emission properties of uncapped InN nanodot samples grown at temperature from 550 to 725 degrees C. Our results indicate that once the In droplets are formed, the optical properties of InN dots deteriorate markedly. As for those droplet-free samples grown at temperatures >= 600 degrees C, good luminescence properties are obtained. The corresponding 20 K PL peak energy is found to be almost constant at approximately 0.77 eV with a slow increase in its linewidth from 71 to 74 meV. A strong temperature-induced energy blue shift at approximately 20 to 280 K is considered to be partially connected to the band-filling effects of thermally stimulated surface electrons. (C) 2009 The Japan Society of Applied Physics
Structural and optical properties of InN/GaN nanodots grown by metalorganic chemical vapor deposition
(2008)
Chang, Wen-Hao
;
Lee, Lin
;
Chen, Ching-Yu
;
Tsai, Wen-Che
;
Lin, Hsuan
InN nanodots grown on GaN by metalorganic chemical vapor deposition (MOCVD) using conventional growth mode as well as flow-rate modulation epitaxy (FME) at various growth temperatures (550-730 degrees C) were investigated. We found that different precursor injection schemes together with the effect of growth temperatures greatly influenced the surface morphology of InN dots and their photoluminescence (PL) properties. The best growth efficiency of InN was achieved by FME at around 650 degrees C. The residual carrier concentration and PL efficiency was also be improved when a high growth temperature was used. Our results indicated that InN nanodots can be grown at a temperature even higher than 700 degrees C while maintain their optical quality. (C) 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.