Browsing by Author "Chen, Chun-Hua"

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A facile dedoping approach for effectively tuning thermoelectricity and acidity of PEDOT:PSS films
(2014-03-01)
Tsai, Tsung-Che
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Chang, Hsiu-Cheng
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Chen, Chun-Hua
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Huang, Yi-Chia
;
Whang, Wha-Tzong
A facile approach namely controlling the pH level of 5 wt% dimethyl sulfoxide (DMSO) doped poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) solution with sodium hydroxide (NaOH) was utilized for the first time in successfully optimizing the thermoelectric conversion efficiency of PEDOT:PSS films. The largely varied Seebeck coefficients and electrical conductivities of the pH controlled PEDOT:PSS films which could thus construct a beneficial curve for locating the optimized power factor are clearly shown from the significant changes of the carrier concentration via the dedoping of PEDOT. The correlation between pH value and carrier concentration as well as the power factor is experimentally found with numerical description covering a full pH range. The applied technique and the resulting optimized thermoelectric properties and possible bio-compatibility not only provide a fundamental understanding of the thermoelectric conducting polymers but widely disclose a variety of potential applications in the future. (C) 2014 Elsevier B. V. All rights reserved.
A Facile Surface Treatment Utilizing Binary Mixtures of Ammonium Salts and Polar Solvents for Multiply Enhancing Thermoelectric PEDOT: PSS Films
(2014-12-01)
Tsai, Tsung-Che
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Chen, Tsung-Han
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Chang, Hsiu-Cheng
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Chen, Chun-Hua
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Huang, Yi-Chia
A Fuzzy Logic-Based Routing for Delay-Tolerant Heterogeneous Networks
(2009)
Huang, Chenn-Jung
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Shen, Hung-Yen
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Liao, Jia-Jian
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Hu, Kai-Wen
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Yang, Dian-Xiu
Delay Tolerant Network (DTN) is an intermittently connected mobile wireless network in which the connectivity between nodes changes frequently due to nodes\' movement. Recently, there have been a lot of researches working on this area. However, to the best of our knowledge, no work has addressed on the DTN routing which focuses on the heterogeneous network environment in the literature. In this work, we propose a prediction based routing protocol for the heterogeneous delay tolerant networks wherein edge servers are distributed over the borders of the different network domains. A location prediction algorithm based on the user online logs to intelligently estimate the most possible future location of the destination, if the destination is currently unavailable. Then an edge server selection algorithm based on fuzzy logic system is exploited to select the close-by intermediate node on the path to the destination so that the messages can be saved temporarily for the destination after the location of the destination is predicted. The experimental results exhibit that the proposed routing protocol can efficiently deliver the message under limited buffer space, comparing with two representative delay tolerant network routing protocols in the literature. The scalability of the proposed work is also confirmed in the simulations.
A hybrid priority-based video-on-demand resource sharing scheme
(2008-06-25)
Huang, Chenn-Jung
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Chuang, Yi-Ta
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Guan, Chih-Tai
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Luo, Yun-Cheng
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Hu, Kai-Wen
Video-on-demand (VoD) environments frequently batch video requests to decrease I/O demand and increase throughput. Since users may leave due to waiting too long, a good video scheduling policy has to consider not only the batch size, but also the user defection probabilities and waiting times. Moreover, a practical VoD resource sharing scheme should endeavor to provide some free streams to serve a high-priority clients requests immediately, since the high-priority clients might pay for the requested video. To tackle these problems, this work proposes a hybrid resource sharing model that integrates controlled multicasting and hatching. The proposed hybrid model applies a bandwidth borrowing and reserving scheme to give high-priority clients a prompt service, while still providing low-priority clients with a reasonable service. Furthermore, a novel probability model-based scheduling policy is proposed to alleviate the user defection behavior and unfairness issue. Experimental results demonstrate that the proposed resource sharing scheme is effective and feasible in terms of blocking probability of high-priority clients, the defection probability, service delay time and fairness to low-priority users. (C) 2008 Elsevier B.V. All rights reserved.
A SCALABLE ROUTING FOR DELAY-TOLERANT HETEROGENEOUS NETWORKS
(2012-01-01)
Huang, Chenn-Jung
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Chen, Heng-Ming
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Lin, Chin-Fa
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Liao, Jia-Jian
;
Hu, Kai-Wen
A Delay Tolerant Network (DTN) is an intermittently connected mobile wireless network in which the connectivity between nodes changes frequently, due to the nodes' movement. Recently, there have been a lot of researchers working in this area. However, to the best of our knowledge, no work has addressed itself specifically to DTN routing within heterogeneous network environments. In this work, we propose a prediction-based routing protocol for heterogeneous delay tolerant networks, wherein edge servers are distributed over the borders of the different network domains. First, a location prediction algorithm based on user online logs is used to intelligently estimate the most probable future location of a destination, if the destination is currently unavailable. Then, an edge server selection algorithm, based on fuzzy logic, is employed to select a close-by intermediate node along the path to the destination, so that messages can be saved temporarily once the destination's location has been predicted. The experimental results show that the proposed routing protocol can efficiently deliver a message under limited buffer space, compared with other two representative delay tolerant network routing protocols found in the literature. The scalability of the proposed model is also confirmed in the simulations.
Architecture controlled synthesis of flower-like In2O3 nanobundles with significantly enhanced ultraviolet scattering and ethanol sensing
(2012)
Lai, Hsiang-Yu
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Chen, Tsung-Han
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Chen, Chun-Hua
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材料科學與工程學系
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Department of Materials Science and Engineering
We have successfully synthesized novel needle-like and flower-like In2O3 nanobundles (NBs) composed of numerous parallel assembled nanoparticle chains via hydrolysis of InCl3 with NaBH4 in aqueous solution and subsequent heat treatment. These previously unknown nanostructures exhibit unusual optical and ethanol sensing properties. T-matrix simulation evidently explains the assembling effect on the significant scattering of UV-visible spectra including a characteristic peak in the UV region as well as the broadened edge toward the visible region for these two NBs. The greatly enhanced ethanol-sensing properties observed for the flower-like In2O3 NBs indicate that the dominant factors for sensing are not only the nanoparticle size but also the structural dimension and architecture of the nanoassembly.
Au-Pt-Pd spherically self-assembled nano-sieves as SERS sensors
(2020-11-30)
Chang, Fang-Ching
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Huang, Jing-Wen
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Chen, Chun-Hua
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材料科學與工程學系
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Department of Materials Science and Engineering
A series of unique granular and petaloid Au-capped Pt-Pd spherically-assembled nano-sieves (Au-PP SANSs) - with diameters smaller than 100 nm, combining quasi-regularly integrated surface-enhanced Raman scattering (SERS) active nanocrystals and a functional amphiphilic organic frame - have been successfully synthesized through a facile chemical route with a temperature-sensitive triblock copolymer soft template. Further, it has been demonstrated that they are potential candidates for developing highly-selective molecule-sieve assisted SERS sensors. The combination of the superposed inorganic and organic dual-core shell structures in Au-PP SANSs acts as a molecular sieve, which plays a crucial role in the promising chemical selectivity, which helps distinguish polar malachite green oxalate salt and non-polar thiabendazole molecules. (C) 2020 Elsevier B.V. All rights reserved.
Controlled synthesis and CO sensing potentials of size-tunable highly-uniform mesoporous Co3O4 nanospheres
(2020-03-05)
Chen, Kuan-Wei
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Tsai, Ju-Heng
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Chen, Chun-Hua
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材料科學與工程學系
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Department of Materials Science and Engineering
A series of highly-uniform and mesoporous Co3O4 nanospheres comprising porously-assembled tiny building blocks, and more importantly, with widely tunable sizes from 50 nm up to 500 nm were successfully synthesized for the first time via single facile polyol approach. The crucial synthesizing factors including molecular weight and concentrations of polyvinylpyrrolidone, the fraction of cobalt precursor, and the subsequent calcination temperature and time were systematically varied over a very wide range for extensively understanding their effects on growth mechanisms, uniformity and particularly the minimum assembled size. The present unique mesoporous nanoassemblies evidently lead to not only a higher surface-to-volume ratio for a variety of potential applications but a lower operating temperature for CO sensing compared with that reported for a variety of intrinsic or heterogeneous Co3O4 nanostructures. (C) 2019 Elsevier B.V. All rights reserved.
Controlled synthesis of Pt and Co3O4 dual-functionalized In2O3 nanoassemblies for room temperature detection of carbon monoxide
(2018-10-21)
Chen, Kuan-Wei
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Liu, Jen-Pu
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Hsu, Yu-Shan
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Liu, Chao-Heng
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Pai, Ying-Hao
We have designed and successfully synthesized innovative Pt and Co3O4 nanostructure co-decorated In2O3 nano-branches via stepwise facile chemical approaches for room-temperature CO gas sensing. The present results indicate that the combination of well-dispersed tiny Pt nanoparticles and the secondary oxide, p-type Co3O4, nanostructures with optimized fractions onto the n-type In2O3 nano-branches is an effective strategy which could lead to lowering the operating temperature to room temperature and significantly improving the sensitivity as well as the detection limit to a sub-ppm level, for meeting the requirement of advanced gas sensors for the next generation.
Copolymer and platinum ion assisted growth of functionalized gold nanonests
(2015-01-01)
Yang, Jing-Cyuan
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Chang, Yi-Hsiang
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Whang, Wha-Tzong
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Chen, Chun-Hua
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Wu, Ren-Jye
This paper describes a facile low-toxicity synthesis of two different types of Au nanonests and one binary Au-Pt core-shell nanonest with high yield and excellent uniformity in size and morphology using block copolymer P123 (EO20PO70EO20) as a soft template and the main reductant in an ice water bath. The introduction of a suitable second metallic source, i.e. Pt ions in the present case, was proven to be a unique strategy for effectively governing the reduction sites of P123 for Au nucleation, which leads to significant changes especially in the crystallite size of the grown Au nanonests. The Au nanonests exhibited a distinct morphology-dependent surface plasmon resonance (SPR) that is red-shifted by similar to 140 nm from the spherical particles wavelength, and significant surface-enhanced Raman scattering (SERS), allowing the rapid determination of rare malachite green oxalate (MGO).
Developing an Intelligent Diagnosis and Assessment E-learning Tool for Introductory Programming
(2008)
Huang, Chenn-Jung
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Chen, Chun-Hua
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Luo, Yun-Cheng
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Chen, Hong-Xin
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Chuang, Yi-Ta
Recently, a lot of open source e-learning platforms have been offered for free in the Internet. We thus incorporate the intelligent diagnosis and assessment tool into an open software e-learning platform developed for programming language courses, wherein the proposed learning diagnosis assessment tools based on text mining and machine learning techniques are employed to alleviate the loading of the teachers. Experiments were conducted in two introductory-undergraduate programming courses to examine the effectiveness of the proposed diagnosis and assessment tools. The learners' work including the source code and comments were processed by the proposed text mining and machine learning techniques. This system also provides immediate feedback and high-quality evaluation results to guide the learners with poor performance. Our experimental results reveal that the proposed work can effectively assist the low-ability learners.
Effect of Ionic Liquid on Structure and Properties of Polysquaraines
(2012-04-10)
Ho, Mei-Chan
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Chao, Ching-Hsun
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Chen, Chun-Hua
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Wu, Ren-Jye
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Whang, Wha-Tzong
Polycondensation of 4-bis[2-(1-methylpyrrol-2-yl)vinyl]-2,5-didodecyloxybenzene and squaric acid yielded the polysquaraine SQ with two isomeric subunits-1,3-addition (zwitterionic) and 1,2-addition (diketonic) moieties in the main chain structure. The former featured a C-O/C=O infrared (IR) absorption frequency at 1622 cm(-1); the latter, a C=O signal at 1716 cm(-1). Traditional synthesis yielded SQ as a powder with metallic luster that could not be cast as a polymer film from solution. When the ionic liquid [Oct(3)NMe][TfO] (IL) was present in the cosolvent of BuOH and benzene (1:3), however, the resulting SQI(x) polymers (x = 0.01-5 wt %) did not precipitate from solution, making it possible to cast continuous free-standing films with a large area (>1 X 1 cm(2)). A greater content of IL in the solution favored the formation of the 1,3-addition zwitterionic subunits in the SQI(x) polymer main chains, thereby changing the physical and optical properties of the polysquaraine, as evidenced in IR and optical absorption spectra. The features in the UV-Vis-NIR absorption spectra of SQ and SQL(x) were dependent on the IL concentration and the nature of the solvent. Among our synthesized SQI(x) polymers, SQI(0.01) and SQI(0.1) formed flexible free-standing films with metallic luster, smooth surfaces, and good semiconductivities (2.27 x 10(-5) and 4.74 x 10(-5) S/cm, respectively). X-ray diffraction patterns revealed that the presence of IL in the polymerization medium increased the SQI(x) interchain packing distance. SQI(0.01), and SQI(0.1) possessed thermal stabilities comparable with that of SQ. Our successful use of IL in the preparation of SQI(x) polymers appears to have great potential for application in ionic liquid-related organic or polymeric preparation and processing.
Electrospinning of magnesium-ion linked binder-less PEDOT:PSS nanofibers for sensing organic gases
(2015-09-01)
Huang, Yi-Chia
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Lo, Teng-Yuan
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Chen, Chun-Hua
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Wu, Kai-Hung
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Lin, Chien-Min
Controlled and continuous electrospinning of approximately pure poly(3,4-ethylenedioxythiophene): poly( styrenesulfonate) (PEDOT:PSS) nanofibers has been successfully realized for the first time by alternating the great amount of conventional carrier polymers with only slight doping of magnesium nitrate which acts as a polymer cross-linker for significantly enhancing the entanglement of PEDOT:PSS. In contrast to the less response of the bulky PEDOT:PSS film, the electrospun PEDOT:PSS nanofibers exhibit remarkably high sensitivities and responding speeds in respectively sensing gas molecules of dimethylformamide (DMF), dimethyl sulfoxide (DMSO) and propylene carbonate (PC). (C) 2015 Elsevier B.V. All rights reserved.
Enhanced thermoelectricity of three-dimensionally mesostructured BixSb2-xTe3 nanoassemblies: from micro-scaled open gaps to isolated sealed mesopores
(2017-03-07)
Chen, Tsung-Han
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Lin, Ping-Yu
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Chang, Hsiu-Cheng
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Chen, Chun-Hua
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材料科學與工程學系
We describe an innovative interfacial design concept and nanostructuring of novel BixSb2-xTe3 (BST) nanoassembled films comprising unique air-solid interfaces from micro-scaled open gaps to isolated sealed mesopores, and high-quality solid-solid ones including the coherent grain boundaries and specific twins, utilizing pulsed laser deposition (PLD), for potentially activating multiple thermoelectric enhancing mechanisms. The unusual mesopore embedded BST films exhibit the highest power factor of similar to 33 mu W cm(-1) K-2, which is comparable to or higher than the previously reported values for BST, and the corresponding relatively low thermal diffusivity in contrast to that for dense pore-less BST films evidently reveals the crucial role of the three-dimensionally and densely arranged air-solid interfaces in significantly arising the phonon scattering.
Facile growth of silver crystals with greatly varied morphologies by PEO-PPO-PEO tri-block copolymers
(2012)
Yang, Jing-Cyuan
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Chen, Chun-Hua
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Wu, Ren-Jye
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材料科學與工程學系
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Department of Materials Science and Engineering
Silver crystals with various novel nano-scale morphologies were synthesized from the reduction of silver nitrate (AgNO3) by ascorbic acid (AsA) in aqueous PEO-PPO-PEO tri-block copolymer (F127) solutions. The presence of only high-concentration AsA at the very initial stage of reduction acts as a key factor in forming distinct branched quasi-spherical Ag nanocrystals where coral-like and houseleek-like morphologies can be kinetically controlled via subsequent addition of F127. When AsA and F127 were mixed before the reduction, three-dimensional dendritic Ag nanocrystals with highly ordered dendrites were largely obtained. In contrast to these branched crystals prepared under low F127 concentration, the face-centered cubic (FCC) packed micelles at high F127 concentration, which provided orderly reaction spaces for AgNO3 and AsA reagents, dominated the growth of triangular and hexagonal prisms. The great variety in morphology is directly correlated with not only the concentration ratio between these reactants but the F127 induced kinetic mechanisms. Moreover, the greatly branched Ag nanocrystals exhibit significant surface-enhanced Raman scattering (SERS) for facilely, rapidly and effectively determining malachite green oxalate (MG) in aqueous solution. The present results provide valuable data not only for fundamental understanding of the directing effect of both F127 and AsA on the synthesis of Ag nanocrystals, but for advanced design and practical manufacturing of metals enhanced SERS sensors.
Facile Growth of Thermochromic VO2 Nanostructures with Greatly Varied Phases and Morphologies
(2013-03-04)
Wang, Ying-Ting
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Chen, Chun-Hua
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材料科學與工程學系
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Department of Materials Science and Engineering
We have successfully and reproducibly synthesized a variety of novel vanadium dioxide (VO2) nanostructures, including metastable monoclinic VO2(B) nanoneedles and nanocorals, orthorhombic VO2(O) nanoparticles, and monoclinic VO2(M) nanofacets by manipulating the aging time of a facile sol gel approach and the subsequent postannealing conditions. We envision that this previously unreported highly controlled synthesis and the resulting distinct morphologies of VO2 will not only provide a promising route for reliably selecting the phase, size, and morphology of these nanostructures, as well as achieving a fundamental understanding of their unusual temperature-dependent optical transmittance, but also facilitate the synthesis of functional VO2 nanostructures for a number of novel applications.
Facile Synthesis of Diamino-Modified Graphene/Polyaniline Semi-Interpenetrating Networks with Practical High Thermoelectric Performance
(2018-02-07)
Lin, Yen-Hao
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Lee, Tsung-Chi
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Hsiao, Yu-Sheng
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Ling, Wei-Keng
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Whang, Wha-Tzong
p-Phenediamino-modified graphene (PDG) has been newly synthesized via a facile green one-step chemical route as a functionalized graphene-based additive to copolymerize with aniline for fabricating innovative PDG/polyaniline conducting polymer composites containing very special semi-interpenetrating networks (S-IPNs). The S-IPNs not only provide additional pathways by creating chemically bonded PDG and PANI for smoothly transporting carriers but greatly reduce the amount of graphene required to less than a few percent could effectively improve the overall electrical conductivity, Seebeck coefficient, and thus the thermoelectric (TE) performance. The found optimized TE figure of merit (ZT) of 0.74 approaches a practical high level which is comparable or much higher than previously reported ones for TE polymers.
Functionalized Silica Nanoparticles by Nanometallic Ag Decoration for Optical Sensing of Organic Molecule
(2010-09-23)
Jean, Ren-Der
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Chiu, Kuo-Chuang
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Chen, Tsung-Han
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Chen, Chun-Hua
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Liu, Dean-Mo
Sensing technologies based on metallic nanoparticles, known as Ag, Au, and so on, have raised enormous interest for their extraordinary sensing resolution and sensitivity to analytes of chemical or biological importance under optical detection have received wide attention in recent decades. Currently, a discrete nanoparticle in a free-standing form, either being organically or biologically modified on the nanoparticle surface, on a given substrate surface region has been employed for photosensing purpose. However, metallic nanoparticles suffering from physical and chemical instability such as oxidation, interparticle coupling, agglomeration, and so on during the processing stages may render undesirable outcomes, which further results in poorer performance than the theoretical expectation. Here we propose a facile and elegant concept to prepare an Ag-decorated silica nanoparticle (hereinafter termed core-shell SiO(2)@Ag nanosphere) based on the modified Stober method. The Ag nanoparticles with an average size controlled at about 1, 3, and 5 nm deposited over the surface of the silica nanocarrier were well separated, making the resulting SiO(2)@Ag nanospheres. The nanospheres showed physically and optically stable surface plasmon resonance spectra and also demonstrated a relatively high Ag-sized dependent sensitivity to ppb level for the detection of analyte molecule, that is, melamine. Theoretical model fitting has been well managed to correlate the optical behavior of the nanosensors, and the outcomes strongly indicated a promising potential of the Ag-decorated SiO(2) core-shell nanospheres for sensory applications.
Great enhancements in the thermoelectric power factor of BiSbTe nanostructured films with well-ordered interfaces
(2013)
Chang, Hsiu-Cheng
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Chen, Chun-Hua
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Kuo, Yung-Kang
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材料科學與工程學系
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Department of Materials Science and Engineering
An innovative concept of twin-enhanced thermoelectricity was proposed to fundamentally resolve the high electrical resistance while not degrading the phonon scattering of the thermoelectric nanoassemblies. Under this frame, a variety of highly oriented and twinned bismuth antimony telluride (BixSb2-xTe3) nanocrystals were successfully fabricated by a large-area pulsed-laser deposition (PLD) technique on insulated silicon substrates at various deposition temperatures. The significant presence of the nonbasal- and basal-plane twins across the hexagonal BiSbTe nanocrystals, which were experimentally and systematically observed for the first time, evidently contributes to the unusually high electrical conductivity of similar to 2700 S cm(-1) and the power factor of similar to 25 mu W cm(-1) K-2 as well as the relatively low thermal conductivity of similar to 1.1 W m(-1) K-1 found in these nanostructured films.
Highly sensitive room-temperature CO gas sensors: Pt and Pd nanoparticle-decorated In2O3 flower-like nanobundles
(2012)
Lai, Hsiang-Yu
;
Chen, Chun-Hua
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材料科學與工程學系
;
Department of Materials Science and Engineering
We discovered a promising room-temperature CO sensing capability of Pt or Pd nanoparticle-functionalized In2O3 flower-like nanobundles (NBs) composed of parallel nanoparticle-chains. The highly branched In2O3 flower-like NBs synthesized through the process of hydrolysis of InCl3 in NaBH4 aqueous solution and the subsequent heat treatment provided an extremely porous matrix required for high-performance gas sensors. The Pt and Pd nanoparticles uniformly deposited on the In2O3 NBs evidently play a key role in enhancing the sensitivity and response, and most importantly lowering the operating temperature to 25 degrees C for the detection of CO gas. The present innovative hybrid nanostructures offer a potential platform for room-temperature oxide-based gas nanosensors. Moreover, the resulting sensing behaviours lead to a better understanding of using and designing such nanosensors for a number of gas sensory applications.