Browsing by Author "Huang, Chih-Hao"

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Asymptotic Distribution of The Number of Isolated Nodes in Wireless Ad Hoc Networks with Unreliable Nodes and Links
(2006)
Yi, Chih-Wei
;
Wan, Peng-Jun
;
Lin, Kuo-Wei
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Huang, Chih-Hao
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資訊工程學系
In randomly-deployed wireless ad hoc networks with reliable nodes and links, vanishment of isolated nodes asymptotically implies connectivity of networks. However, in a realistic system, nodes may become inactive, and links may become down. The inactive nodes and down links cannot take part in routing/relaying and thus may affect the connectivity. In this paper, we study the connectivity of a wireless ad hoc network that is composed of unreliable nodes and links by investigating the distribution of the number of isolated nodes in the network. We assume that the wireless ad hoc network consists of n nodes which are distributed independently and uniformly in a unit-area disk or square. Nodes are active independently with probability 0 < p(1) <= 1, and links are up independently with probability 0 < p(2) <= 1. A node is said to be isolated if it doesn't have an up link to an active node. We show that if all nodes have a maximum transmission radius r(n) = root ln n broken vertical bar xi/pi p(1)p2(n) for some constant xi, then the total number of isolated nodes is asymptotically Poisson with mean e(-xi) and the total number of isolated active nodes is also asymptotically Poisson with mean p(1)e(-xi). In addition, the work can be extended for secure wireless networks which adopt m-composite key predistribution schemes in which a node is said to be isolated if it doesn't have a secure link. Let p denote the probability of the event that two neighbor nodes have a secure link. We show that if all nodes have a maximum transmission radius r(n) = root ln n+xi/pi pn for some constant., then the total number of isolated nodes is asymptotically Poisson with mean
Dynamic Coupling of Optically Evolved Assembling and Swarming of Gold Nanoparticles with Photothermal Local Phase Separation of Polymer Solution
(2020-07-30)
Aibara, Issei
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Huang, Chih-Hao
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Kudo, Tetsuhiro
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Bresoli-Obach, Roger
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Hofkens, Johan
Optical trapping of gold nanoparticles (Au NPs) at a glass/solution interface initially generates a periodically aligned structure of a few NPs along the direction perpendicular to a linearly polarized laser. When the number of NPs was increased, this alignment was expanded to the outside of the irradiated focus, forming a single large assembly where the Au NPs dynamically fluctuated like a swarming of bees. The morphology was dumbbell-shape, consisting of two swarms at both sides of the focus, and its size reached about 10 mu m. This optically evolved assembling and swarming was studied in poly(N-isopropylacrylamide) (PNIPAM) solution, where liquid-liquid phase separation (LLPS) was induced by photothermal heating of the trapped Au NPs forming a microdroplet of highly concentrated PNIPAM. Dynamic coupling of the NPs assembling and swarming with the droplet formation of PNIPAM leads to cooperative optical evolution, through which the assembly was embedded in the single microdroplet.
Formation of porous carbon materials with in situ generated NaF nanotemplate
(2006-06-22)
Huang, Chih-Hao
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Chang, Yu-Hsu
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Wang, Hsiao-Wan
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Cheng, Soofin
;
Lee, Chi-Young
Porous carbon materials with pore sizes from 3 to 200 nm were synthesized by reacting hexafluorobenzene with Na liquid at 623 K. NaF crystals, a byproduct formed in the reaction, acted as nanotemplate to assist the pore formation. By employing hexafluorobenzene to react with Na incorporated within the channels ( diameter 200 nm) of anodized aluminum oxide ( AAO) membranes at 323- 623 K, the carbon material can be fabricated into aligned porous nanotube arrays ( ca. 250 nm in diameter, ca. 20 nm in wall thickness, ca. 0.06 mm in length, and ca. 3-90 nm in pore diameter). These materials were characterized by X-ray diffraction, scanning and transmission electron microscopy, X-ray energy dispersive spectroscopy, electron diffraction, thermal gravimetric analysis, and nitrogen physical adsorption experiments.
Phase segregation assisted morphology sculpting: Growth of graphite and silicon crystals via vapor-solid reactions
(2007-03-22)
Huang, Chih-Hao
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Chang, Yu-Hsu
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Lin, Huang-Kai
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Peng, Chih-Wei
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Chung, Wen-Sheng
Crystalline graphite and Si showing fertile morphologies are prepared via vapor-solid reaction growth (VSRG). By reacting CaC2 with vapors of CxCly (CxCly: CCl4, C2Cl4, C4Cl6, and C5Cl6), porous, fibrous, and planar graphite were obtained at 973-1023, 1073-1123, and 1123-1223 K, respectively. Employing SiCl4 to react with MxSiy (MxSiy: Mg2Si and CaSi2) generated many Si structures. These include clustered-particle and porous, wirelike, corallike, and planar or platelike at 1023, 1073, 1123, and 1223 K, respectively. The reaction products, the network solids (graphite and Si) and the ionic solids MCl2, phase-segregated into self-templating molds and casts and develop cooperatively into various three-dimensional structures. Final morphology of the network solids depends not only on the reaction temperature but their molar volume ratio to the MCl2 salt products.
Preparation of Mo2C@a-C core-shell powders via carburization of Mo particles by 1-chlorobutane and hexachlorobenzene
(2007-07-01)
Chien, Chun-Hsiung
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Sheng, Pei-Sun
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Wang, Chia-Hsin
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Huang, Chih-Hao
;
Lin, Huang-Kai
Mo2C@a-C core-shell powders were prepared by reacting Mo powders with gaseous 1-chlorobutane or hexachlorobenzene at 1173 K. The chlorinated reactants acted as the source of carbon for the carburization of Mo and the source of chlorine, which assists the etching of Mo to reduced particle sizes. (C) 2006 Elsevier B.V. All rights reserved.
Surface plasmon resonance effect on laser trapping and swarming of gold nanoparticles a an interface
(2020-09-14)
Huang, Chih-Hao
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Kudo, Tetsuhiro
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Bresoli-Obach, Roger
;
Hofkens, Johan
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Sugiyama, Teruki
Laser trapping at an interface is a unique platform for aligning and assembling nanomaterials outside the focal spot. In our previous studies, Au nanoparticles form a dynamically evolved assembly outside the focus, leading to the formation of an antenna-like structure with their fluctuating swarms. Herein, we unravel the role of surface plasmon resonance on the swarming phenomena by tuning the trapping laser wavelength concerning the dipole mode for Au nanoparticles of different sizes. We clearly show that the swarm is formed when the laser wavelength is near to the resonance peak of the dipole mode together with an increase in the swarming area. The interpretation is well supported by the scattering spectra and the spatial light scattering profiles from single nanoparticle simulations. These findings indicate that whether the first trapped particle is resonant with trapping laser or not essentially determines the evolution of the swarming. (C) 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement