Browsing by Author "Chen, Y. -C."

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A comprehensive study of enhanced characteristics with localized transition in interface-type vanadium-based devices
(2020-06-01)
Lin, C. -Y.
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Chen, P. -H.
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Chang, T. -C.
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Huang, W. -C.
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Tan, Y. -F.
In this research, we investigated the conduction mechanism in metal-insulator transition (MIT) materials. Among these MIT materials (NbOx, NiOx, VOx, and TaS2), vanadium oxide-based selectors have been widely investigated because of their high switching speed (similar to 10-ns transition time), sufficient nonlinearity (>10(3)), and endurance stability (similar to 10(10)). Abnormal temperature-dependent degradation in the high resistive state was observed, as was studied in detail by a current fitting analysis and explored theoretically by electric (E-MIT) and thermal (T-MIT) modeling. The results suggest the existence of a MIT region located between the electrode and the localized filament. To improve the localized transition efficiency, we propose an enhanced-type MIT architecture to bypass the E-MIT and T-MIT universal rule with the novel structure of vanadium top electrode device. As compared with a vanadium oxide middle-layer device, the electrical transition efficiency is improved 2-fold as evidenced by thermal cycling material analysis, as well as boosting endurance reliability to 10(7) at 65 degrees C. Finally, for the first time, a potential neuromorphic computing application featuring a damping oscillator has been demonstrated in this enhanced-type MIT architecture, with a high damping ratio with 10-fold smaller area and 5-fold smaller energy than complementary metal-oxide-semiconductor (CMOS) devices. This presents a promising milestone for ultralow power neuromorphic system design and solutions in the near future. (C) 2020 Elsevier Ltd. All rights reserved.
Effect of atomic geometry on shot noise in aluminum quantum point contacts
(2006-06-01)
Yao, J.
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Chen, Y. -C.
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Di Ventra, M.
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Yang, Z. Q.
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電子物理學系
We investigate the role of atomic geometry on shot-noise properties of aluminum atomic contacts using first-principles calculations. We study both the effect of atomic separation in the wire as well as the geometry of the contacts. We find that shot noise, as opposed to conductance, is very sensitive to atomic details. In particular, the Fano factor for the asymmetric contact structures is more than double that of the symmetric ones due to increased backscattering, and is within the experimental range. These results indicate that shot noise may be used as a tool to infer the atomic geometries of quantum point contacts.
Electrically driven nanoarrow array green LED
(2012)
Chang, J. -R.
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Chang, S. -P.
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Chen, Y. -C.
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Sou, K. -P.
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Cheng, Y. -J.
An electrically driven nanopyramid green light emitting diode (LED) was demonstrated. The nanopyramid arrays were fabricated from a GaN substrate by patterned nanopillar etch, pillar side wall passivation, and epitaxial regrowth. Multiple quantum wells were selectively grown on the facets of the nanopyramids. The fabricated LED emits green wavelength under electrical injection. The emission exhibits a less carrier density dependent wavelength shift and higher internal quantum efficiency as compared with a reference c-plane sample at the same wavelength. It shows a promising potential for using nanopyramid in high In content LED applications.
Electrically driven nanopyramid green light emitting diode
(2012-02-06)
Chang, S. -P.
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Chen, Y. -C.
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Huang, J. -K.
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Cheng, Y. -J.
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Chang, J. -R.
An electrically driven nanopyramid green light emitting diode (LED) was demonstrated. The nanopyramid arrays were fabricated from a GaN substrate by patterned nanopillar etch, pillar side wall passivation, and epitaxial regrowth. Multiple quantum wells were selectively grown on the facets of the nanopyramids. The fabricated LED emits green wavelength under electrical injection. The emission exhibits a less carrier density dependent wavelength shift and higher internal quantum efficiency as compared with a reference c-plane sample at the same wavelength. It shows a promising potential for using nanopyramid in high In content LED applications. (C) 2012 American Institute of Physics. [doi:10.1063/1.3681363]
INTELLIGENT RADIOACTIVE WASTE MANAGEMENT PLATFORM FOR RADIOACTIVE WASTE STORAGE FACILITIES
(2013-06-01)
Chen, Y. -C.
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Yu, Y. S.
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Chen, R. -S.
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Chou, I-Hsin
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Sun, H. M.
Radioactive waste management is now a much discussed public issue, especially since the Taiwanese government announced that three operating nuclear power plants will be decommissioned on schedule. Safe, efficient, reliable, and sustainable solutions to the management of radioactive wastes are critical to the feasibility of the nuclear decommissioning project. Because of the lack of system integration within radioactive waste storage facilities, most of the radioactive waste information systems remain inconsistent. Therefore, the establishment of an intelligent integrated system that provides active assistance in tracing the processes of radioactive wastes is urgent. This study is based on the technology of radio frequency identification for detection of radioactive waste locations. An automatic identification mechanism can monitor the status of storage and instantly notify the relevant parties. Meanwhile, this platform also employs the software agent as the infrastructure to construct the integrated information system architecture; the software agent has been widely accepted as an effective method to integrate heterogeneous systems of the new paradigm. The overall framework will help enhance the monitoring performance for radioactive waste.
Liquid-phase and gas-phase investigation of biomolecules in a single experiment
(2013)
Huang, H. -Y.
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Lo, T. -J.
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Chen, Y. -C.
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Hu, J. -B.
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Urban, P. L.
Interrogating three-dimensional structures of biomolecules is instrumental to the fields of biochemistry and biophysics. Mass spectrometry is a technique that can provide important data on the molecular weight of protein molecules in the gas phase. However, the relationship between the structure of biomolecules in the native water-rich environment and the artificial gas-phase environment cannot always be established with high certainty. Here we communicate initial results obtained using a simple analytical approach which allows one to perform measurements of structural parameters of biomolecules in liquid phase and gas phase within a single experiment. Single-component samples are injected as plugs to a microscale capillary filled with aqueous medium and driven hydrodynamically. As they traverse the capillary, they undergo zone broadening. The extent of this broadening is measured at two points along the capillary by UV absorption detection, and used to compute hydrodynamic radii according to the Taylor dispersion analysis theory. Further downstream, the dispersed zones leave the capillary through the sharpened outlet aligned to the orifice of a mass spectrometer. This multiple detection strategy allows one to confront protein conformation in the liquid phase (deduced from the hydrodynamic size) and the gas phase (deduced from mass spectral patterns).
Multidie LED combined with homogenizing optics to improve frequency response and intensity for FLIM applications
(2017-06-01)
Liu, H. -T.
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Lin, W. -L.
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Feng, Y. -L.
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Lin, Y.
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Chen, Y. -C.
Application of light-emitting diodes (LEDs) in frequency-domain fluorescence lifetime imaging microscopy (FLIM) has been limited by the trade-off between modulation frequency and illumination intensity of LEDs, which affects the signal-to-noise ratio in fluorescence lifetime measurements. To increase modulation frequency without sacrificing output power of LEDs, we propose to use LEDs with multiple dice connected in series. The LED capacitance was reduced with series connection; therefore, the frequency response of multidie LED was significantly increased. LEDs in visible light, including blue, green, amber and red, were all applicable in FLIM. We also present a homogenizing optics design, so that multidie LEDs produced uniform illumination on the same focal spot. When the homogenizing optics was combined with multicolour emitters, it provides multiple colour selection in a compact and convenient design.
Normally-off operation AlGaN/GaN MOS-HEMT with high threshold voltage
(2010-09-02)
Chang, C. -T.
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Hsu, T. -H.
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Chang, E. Y.
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Chen, Y. -C.
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Trinh, H. -D.
Normally-off operation AlGaN/GaN high electron mobility transistors have been developed utilising a fluorine-based treatment technique combined with a metal-oxide-semiconductor gate architecture. Threshold voltage as high as 5.1 V was achieved by using an 16 nm-thick Al(2)O(3) gate oxide film. Additionally, the device performed a drain current density of 500 mA/mm and a peak transconductance of 100 mS/mm, which are comparable to the conventional normally-on devices.
Supporting vertical handover between universal mobile telecommunications system and wireless LAN for real-time services
(2008-01-01)
Liao, W. -K.
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Chen, Y. -C.
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電信工程研究所
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Institute of Communications Engineering
The provisioning of the seamless handovers for real-time services in-between UMTS/WLAN loose-interworking by the network-layer technologies has been studied. Issues are how to execute such a vertical handover in a fast and efficient manner as well as how to achieve it in a viable way. To resolve such issues, a novel scheme called 'designated crossover point' (DCP) within the existing IP end-to-end Quality of Servce (QoS) architecture has been proposed. The DCP is an agent at the edge router in the customer's premise to join the old RSVP signalling path and new RSVP signalling path. With the DCP in place, the vertical handover can be greatly accelerated. Besides, by enabling the DCP to handover to the edge router in the customer's network currently visited by the mobile, lower charging cost can be achieved. Finally, there is no modification required for the devices in the provider's network and thus the viability is much improved. It is then end up with a topology for resource management in IP backbone for UMTS/WLAN loose-interworking to support the idea of DCP. To determine when to perform the rerouting to remove the possible derouting caused by DCPs, use of an adaptive rule has been suggested. Simulation results show in general that the adaptive rule is effective.
WARD: a transmission control protocol-friendly stateless active queue management scheme
(2007-10-01)
Ho, C. -Y.
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Chan, Y. -C.
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Chen, Y. -C.
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資訊工程學系
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Department of Computer Science
In this article, the problem of providing a fair bandwidth allocation to the flows sharing a congested link in a router is investigated. Queue management, bandwidth share and congestion control are very important to both the robustness and fairness of the Internet. The buffer at the outgoing link is a simple FIFO, shared by packets belonging to the flows. A new transmission control protocol (TCP)-friendly router-based active queue management scheme, termed WARD, is proposed to approximate the fair queueing policy. WARD is a simple packet-dropping algorithm with a random mechanism which discriminates against flows that submit more packets per second than is allowed as their fair share. By doing this, it not only protects TCP connections from user datagram protocol flows, but also solves the problem of competing bandwidth among different TCP versions, such as TCP Vegas and TCP Reno. In addition, WARD works quite well for TCP flow isolation even with different round trip times. In other words, WARD improves the unfair bandwidth allocation properties. Furthermore, as it is stateless and easy to implement, WARD controls unresponsive or misbehaving flows with only a minimum overhead.