Browsing by Author "Chen, Yu"

Now showing 1 - 5 of 5

Cache Management Techniques for Privacy Preserving Location-based Services
(2008)
Chen, Yu
;
Bao, Jie
;
Ku, Wei-Shinn
;
Huang, Jiun-Long
;
資訊工程學系
In order to access location-based services, mobile users have to disclose their exact locations to service providers. However, adversaries could collect the location information for purposes against mobile users\' privacy. There are existing solutions for privacy protection by utilizing the K-anonymity model. However, the computational and communication costs are high. This research proposes cache management techniques for further improving user privacy protection, saving computational power, and decreasing communication costs.
Effective Promotion of Oxygen Reduction Reaction by in Situ Formation of Nanostructured Catalyst
(2019-08-01)
Chen, Yu
;
Yoo, Seonyoung
;
Zhang, Weilin
;
Kim, Jun Hyuk
;
Zhou, Yucun
Efficient electrocatalysts for oxygen reduction reaction (ORR) are critical to high-performance energy conversion and storage devices. As an important family of functional materials, alkaline earth metal oxides are generally considered inert toward electrochemical reactions. Here we report the remarkable enhancement of ORR activity and durability of electrodes enabled by surface modification with, a precursor of barium nitrate. During cell start-up process, an ORR active cobaltite catalyst was in situ formed on the electrode surface, as confirmed by scanning transmission electron microscopy (STEM) analysis. A combination of in situ/operando Raman and electrochemical impedance study suggests that the transition from nitrate to cobaltite may occur at similar to 565 degrees C. The peak power density of a single cell at 750 degrees C is increased from similar to 0.85 to similar to 1.15 W cm(-2) (35% increase) by the surface modification, demonstrating the remarkable enhancement of electrocatalytic activity under realistic operating conditions.
Hydrothermally Roughened Surface-Enhanced Raman Scattering-Active Substrates with Low Background Signals for Chemical Sensing Application
(2011-03-01)
Yang, Jung-Yen
;
Cheng, Hui-Wen
;
Chen, Yu
;
Li, Yiming
;
Lin, Chi-Hung
A low-cost, environment friendly and easily fabricated SERS-active substrate with low background signals has been developed by hydrothermal treatment of titanium thin films deposited on silicon substrate. Results from the experimental study revealed that Rhodamine 6G can be well resolved using gold-coated hydrothermally roughened TiO(2) substrates. The effect of surface enhancement by the hydrothermally roughened substrates enables rapid identification of Rhodamine 6G, and the enhancement capability is controllable by tuning the surface roughness of the substrates through varying treatment duration. The hydrothermally treated TiO(2) substrates also exhibit tunable wettability like that of the untreated ones.
Kinetic Competition Model and Size-Dependent Phase Selection in 1-D Nanostructures
(2012-06-01)
Chen, Yu
;
Lin, Yung-Chen
;
Huang, Chun-Wei
;
Wang, Chun-Wen
;
Chen, Lih-Juann
The first phase selection and the phase formation sequence between metal and silicon (Si) couples are indispensably significant to microelectronics. With increasing scaling of device dimension to nano regime, established thermodynamic and kinetic models in bulk and thin film fail to apply in 1-D nanostructures. Herein, we present an unique size-dependent first phase formation sequence in 1-D nanostructures, with Ni-Si as the model system. Interfacial-limited phase which forms the last in thin film, NiSi2, appears as the dominant first phase at 300-800 degrees C due to the elimination of continuous grain boundaries in 1-D suicides. On the other hand, theta-Ni2Si, the most competitive diffusion-limited phase takes over NiSi2 and wins out as the first phase in small diameter nanowires at 800 degrees C. Kinetic parameters extracted from in situ transmission electron microscope studies and a modified kinetic growth competition model quantitatively explain this observation. An estimated critical diameter from the model agrees reasonably well with observations.
UWB Printed Monopole Antenna with Radiation-Suppression in 5-GHz ISM Band
(2008)
Chen, Yu
;
Lin, Lieh-Chuan
;
Lin, Yu-De
;
Kitazawa, Toshihide
;
電信工程研究所