Browsing by Author "Huang, Yu-Wei"

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A Study on Content Delivery Strategy for QoE Enhancement in P2P IPTV
(2014-01-01)
Huang, Yu-Wei
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Chen, Yaw-Chung
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資訊工程學系
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Department of Computer Science
Nowadays the peer-to-peer (P2P) systems have been widely deployed for the Internet television and live streaming. The real-time P2P service features advantages of scalability and heterogeneity in the existing network without modifying the underlay infrastructure. However, most of the common IPTV applications did not consider the user's surfing behavior which causes great burden to the IPTV streaming system. In addition, the high churn rate and insufficient upload capacity may lead to the unstable playback smoothness, and result in a poor quality of experience (QoE). In this paper, we propose a QoE-aware content delivery mechanism to distribute the important and instant data first. I-frame chunks near playback deadline are assigned the top priority. We discuss the comparison of overlay performance and demonstrate that the proposed scheme is workable via a series of experiments on OMNeT++.
Effect of hole blocking dielectric layer on microstructure and photoconducting properties of polycrystalline Se thin films
(2018-09-01)
Chang, Cheng-Yi
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Lin, Yi-Jie
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Huang, Yu-Wei
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Liao, Jye-Yow
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Lin, Jian-Siang
We fabricated polycrystalline selenium (c-Se) based photodetectors using three different dielectrics (HfO2, Al2O3 and SiO2) as the hole blocking layer (HBL), and studied the influence of the HBLs on the photoconducting performance of the photodetectors. The microstructure of the c-Se layer is greatly influenced by the nucleation behavior of the tellurium (Te) adhesion layer deposited between the c-Se layer and the HBLs. The photoconducting performance of the photodetectors is basically dependent on the barrier height at the junctions of the HBL with the tin-doped indium oxide (ITO) anode and with the c-Se layer. A higher barrier height at the HBL/ITO junction leads to a lower dark current density (I-D) of the photodetectors. However, the photodetector with the SiO2 HBL exhibits the largest I-D as the bias exceeds 2 V although it has the highest junction barrier height. We attribute the abnormity to the rugged morphology of the c-Se layer, which is a result of a less dense Te nucleation on the SiO2 HBL. The photocurrent density (I-ph) is inversely related to the junction barrier height at the HBL/c-Se contact. The c-Se photodetector with the HfO2 HBL has the largest I-Ph and the one with the SiO2 HBL has the smallest. The photodetector with the HfO2 HBL exhibits a quantum efficiency of 89% at 6 V.
Effect of Joint Shape Controlled by Thermocompression Bonding on the Reliability Performance of 60 mu m-pitch Solder Micro Bump Interconnections
(2014-01-01)
Huang, Yu-Wei
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Zhan, Chau-Jie
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Juang, Jing-Ye
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Lin Yu-Min
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Huang, Shin-Yi
Three dimensional integration circuits technology has received much attention recently since the demands of functionality and performance in microelectronic packaging for electronic products are rapidly increasing. For high-performance 3D chip stacking, high density interconnections are essential. In the current types of interconnects, solder micro bumps have been widely used and thermocompression bonding process are well adopted to form the connection between bumps. However, the prefect joint contour is difficult to obtain and control by such kind of bonding process in solder micro bump joints. For fine-pitch solder micro bump interconnections, the effect of joint shape on the reliability performances of the solder micro bump joints is not concluded yet till now and needs to be clarified. In this study, the effect of joint shape controlled by thermocompression bonding on the reliability performance of solder micro bump interconnections with a pitch of 60 mu m was discussed. The chip-to-chip test vehicle having more than 4000 solder micro bump interconnections with a bump pitch of 60 mu m was used in this study. A solder micro bump structure of Cu/SnAg having a thickness of 7 mu m/10 mu m was fabricated in both the silicon chip and substrate. To evaluate the effect of joint shape, four types of joint shape were controlled and made. The first type had a conventional shape of micro joint. Compared to the first one joint structure, the second type of joint structure showed the compressed shape. The third type of joint structure was the pillar-like micro joint while the fourth type of joint structure presented a neck shape having the highest joint height among all the joint structures tested. We used the fluxless thermocompression bonding process to form these four types of micro joints. After bonding process, the chip stack was assembled by capillary-type underfill. Reliability tests of temperature cycling test (TCT), high temperature storage (HTS) and electromigration test (EM) were selected to assess the effect of joint shape on the reliability properties of those four types of solder micro bump interconnections. The reliability results presented that all the types of joint structures could pass TCT of 1000 cycles and HTS of 1000 hours but high variation of daisy chain resistance more than 15% would happen in the neck-shape micro joint after TCT. For the neck-shape micro joint, the high variation of daisy chain resistance after TCT resulted from the cracking propagated along the interface of Cu UBM/Cu6Sn5 IMC and across the tin solder. The cracking situation was more serious as compared to the other three tested micro joints. The results of HTS revealed that resistance variation mainly depended on the micro structural evolution within micro joints tested. Electromigration test was conducted under the testing condition of 0.56 A/150 degrees C. A daisy chain structure was adopted. For both the pillar-shape and neck-shape micro joints, Cu UBM consumption and formation of large void were the major microstructure evolutions within the micro interconnections during EM testing. The conpressed-shape showed the longer electromigration lifetime among all the types of micro joints tested.
Electromigration in microbumps with Cu-Sn intermetallic compounds
(2016)
Chu, Yi-Cheng
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Zhan, Chau-Jie
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Lin, Han-Wen
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Huang, Yu-Wei
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Chen, Chih
The electromigration test of the microbump interconnects with Cu/Cu6Sn5/Cu structure is reported in this study. This Cu6Sn5 intermetallic compound layer was single-crystal like. The diameter of the microbumps in die-to-die stacking was 30 mu m. Test vehicles were applied by a current density of 2.2x10(5) A/cm(2) and settled on a hotplate at 150 degrees C. The resistances of the microbumps were simultaneously monitored by the four point probe during the test procedure. The Cu6Sn5 transformed into Cu3Sn in the early stage and porous Cu3Sn generated in the Cu6Sn5 layer at later stages. The morphology of porous Cu3Sn could be caused by the current direction. The decomposition of Cu6Sn5 into Cu3Sn and Sn occurs during the EM test. The migration of Sn atoms to the periphery of the under-bump-metallization was forced by the current stress, which may be the mechanism of the pore formation with the pore volume of 41.4%. More porous Cu3Sn was found in the cathode end which was an evidence of the EM effect. Finite element analysis was used to do some calculation based on theoretical stoichiometry and microstructures in the test results. The resistivity of porous Cu3Sn structure which was about 30 mu Omega-cm which was three times larger than that of Cu3Sn. The porous Cu3Sn may threaten the reliability issues of microbumps.
Optimal scheduling of a taxi fleet with mixed electric and gasoline vehicles to service advance reservations
(2018-08-01)
Lu, Chung-Cheng
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Yan, Shangyao
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Huang, Yu-Wei
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運輸與物流管理系註：原交通所+運管所
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Department of Transportation and Logistics Management
This study addresses the problem of scheduling a fleet of taxis that are appointed to solely service customers with advance reservations. In contrast to previous studies that have dealt with the planning and operations of a taxi fleet with only electric vehicles (EVs), we consider that most taxi companies may have to operate with fleets comprised of both gasoline vehicles (GVs) and plug-in EVs during the transition from GV to (complete) EV taxi fleets. This paper presents an innovative multi-layer taxi-flow time-space network which effectively describes the movements of the taxis in the dimensions of space and time. An optimization model is then developed based on the time-space network to determine an optimal schedule for the taxi fleet. The objective is to minimize the total operating cost of the fleet, with a set of operating constraints for the EVs and GVs included in the model. Given that the model is formulated as an integer multi-commodity network flow problem, which is characterized as NP-hard, we propose two simple but effective decomposition-based heuristics to efficiently solve the problem with practical sizes. Test instances generated based on the data provided by a Taiwan taxi company are solved to evaluate the solution algorithms. The results show that the gaps between the objective values of the heuristic solutions and those of the optimal solutions are less than 3%, and the heuristics require much less time to obtain the good quality solutions. As a result, it is shown that the model, coupled with the algorithms, can be an effective planning tool to assist the company in routing and scheduling its fleet to service reservation customers.
Photoconductive properties of polycrystalline selenium based lateral MISIM photodetectors of high quantum efficiency using different dielectrics as the charge blocking layer
(2019-07-01)
Chang, Cheng-Yi
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Huang, Yu-Wei
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Lin, Yi-Jie
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Liao, Jye-Yow
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Lin, Jian-Siang
We studied the photoconductive performance of polycrystalline selenium (pc-Se) based photodetectors with a lateral metal-insulator-semiconductor-insulator-metal (MISIM) device structure. The insulator layer is a 10 nm-thick Ga2O3, HfO2, or Al2O3 thin film, and used as a charge blocking layer (CBL) to suppress dark current injected from the Al electrodes. The dark current suppression primarily depends on the barrier height of the junctions between the CBLs and electrodes. The Ga2O3 CBL exhibits a poor dark current suppression compared to the HfO2 and the Al2O3 CBLs because of a lower electron barrier at the cathode. The lateral pc-Se photodetectors exhibit a very high internal photocurrent gain due to Fowler-Nordheim tunneling at relatively low applied voltages. The better crystallinity of pc-Se grains formed on the Ga2O3 CBL leads to a higher photoconversion efficiency for the MISIM-Ga2O3 photodetector. Compared with amorphous Se based lateral MISIM photodetectors, the pc-Se photodetectors demonstrate a uniform and much better photoconductive performance over the visible spectrum.