Browsing by Issue Date, starting with "2017-04-05"

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Broadband Omnidirectional Light Trapping in Gold-Decorated ZnO Nanopillar Arrays
(2017-04-05)
Chang, Yuan-Ming
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Lin, Man-Ling
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Lai, Tung-Yen
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Chen, Chang-Hung
;
Lee, Hsin-Yi
The photoluminescence (PL) and reflectivity characteristics of zinc oxide nanopillars- (ZnO-NPs) grown on indium tin oxide (ITO)-coated glasses were investigated. The room temperature PL showed bright -white -light emission for the undoped ZnO-NPs grown at 600 degrees C, suggesting the close relation between the optical characteristic and "the growth conditions being, carried out for,obtaining the present ZnO-NPs. The reflectivity of the as -grown ZnO-NPs array was about, similar to 29% with the wavelength of the incident light ranging from 200 to 1800 nm. Nevertheless, the reflectance reduced significantly to less than 9.9% when a layer of gold (Au) was deposited on ZnO=NPg by sputtering for 5 min, corresponding to more than 65% reduction in Au -coated ZnQ-NPs (Au/ZnO-NPs). Moreover, the angle -resolved reflectance measurement's on the present Au/ZnO-NPs array show an omnidirectional light -trapping characteristic. These remarkable characteristics, broadband and omnidirectional light -trapping -of Ati/ZnO-NPs, are attributed to the extended effective optical path of the incident light due to subwavelength scattering resulting,from the presence of Au nanoparticics.
Surface Engineering of Polycrystalline Silicon for Long-Term Mechanical Stress Endurance Enhancement in Flexible Low Temperature Poly-Si Thin-Film Transistors
(2017-04-05)
Chen, Bo-Wei
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Chang, Ting-Chang
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Chang, Kuan-Chang
;
Hung, Yu-Ju
;
Huang, Shin-Pin
The surface morphology in polycrystalline silicon (poly-Si) film is an issue regardless of whether conventional excimer laser annealing (ELA) or the newer metal-induced lateral crystallization (MILC) process is used. This paper investigates the stress distribution while undergoing longterm mechanical stress and the influence of stress on electrical characteristics. Our simulated results show that the nonuniform stress in the gate insulator is more pronounced near the polysilicon/gate insulator edge and at the two sides of the polysilicon protrusion. This stress results in defects in the gate insulator and leads to a nonuniform degradation phenomenon, which affects both the performance and the reliability in thin-film transistors (TFTs). The degree of degradation is similar regardless of bending axis (channel-length axis, channel-width axis) or bending type (compression, tension), which means that the degradation is dominated by the protrusion effects. Furthermore, by utilizing long-term electrical bias stresses after undergoing long-tern bending stress, it is apparent that the carrier injection is severe in the subchannel region, which confirms that the influence of protrusions is crucial. To eliminate the influence of surface morphology in poly-Si, three kinds of laser energy density were used during crystallization to control the protrusion height. The device with the lowest protrusions demonstrates the smallest degradation after undergoing long-term bending.
Biocompatible D-A Semiconducting Polymer Nanoparticle with Light-Harvesting Unit for Highly Effective Photoacoustic Imaging Guided Photothermal Therapy
(2017-04-05)
Zhang, Jinfeng
;
Yang, Caixia
;
Zhang, Rui
;
Chen, Rui
;
Zhang, Zhenyu
The development of nanotheranostic agents that integrate diagnosis and therapy for effective personalized precision medicine has obtained tremendous attention in the past few decades. In this report, biocompatible electron donor-acceptor conjugated semiconducting polymer nanoparticles (PPor-PEG NPs) with light-harvesting unit is prepared and developed for highly effective photoacoustic imaging guided photothermal therapy. To the best of our knowledge, it is the first time that the concept of light-harvesting unit is exploited for enhancing the photoacoustic signal and photothermal energy conversion in polymer-based theranostic agent. Combined with additional merits including donor-acceptor pair to favor electron transfer and fluorescence quenching effect after NP formation, the photothermal conversion efficiency of the PPor-PEG NPs is determined to be 62.3%, which is the highest value among reported polymer NPs. Moreover, the as-prepared PPor-PEG NP not only exhibits a remarkable cell-killing ability but also achieves 100% tumor elimination, demonstrating its excellent photothermal therapeutic efficacy. Finally, the as-prepared water-dispersible PPor-PEG NPs show good biocompatibility and biosafety, making them a promising candidate for future clinical applications in cancer theranostics.
Microscopic solvation environments in a prototype room-temperature ionic liquid as elucidated by resonance Raman spectroscopy of iodine and bromine
(2017-04-05)
Saha, Satyen
;
Okajima, Hajime
;
Homma, Osamu
;
Hamaguchi, Hiro-o
;
應用化學系分子科學碩博班
Microscopic solvation environments in a prototype ionic liquid, bmimTf(2)N; 1-buty1-3-methyl-imidazoliumbis(trifluoromethanesulfonyl)imide, have been studied with the use of halides, X-2 and X-n(-) (X = I, Br; n = 3,5), as molecular probes. Resonance Raman spectroscopy has been used to detect these halogen species existing in bmimTf(2)N as well as in reference solvents including heptane, cyclohexane, KX/H2O and benzene. In heptane and cyclohexane, only free X-2 species are detected. In KX/H2O, only X-n(-) and, in benzene, only benzene-X-2 complexes are detected. On the contrary, free X-2 and X-n(-) are concomitantly detected in bmimTf(2)N, indicating that there are two distinct solvation environments in bmimTf(2)N, non-polar environments that solvate free X-2 and polar environments that stabilize X-n(-) These two distinct solvation environments are most likely to arise from microscopic structural heterogeneity of ionic liquids. (C) 2016 Elsevier B.V. All rights reserved.
交大e-News第229期-彈性學習、深化跨域交通大學第二專長、ICT工坊培育多元人才
(2017-04-06)
國立交通大學秘書室
;
Secretariat
Measurement of electron antineutrino oscillation based on 1230 days of operation of the Daya Bay experiment
(2017-04-06)
An, F. P.
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Balantekin, A. B.
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Band, H. R.
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Bishai, M.
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Blyth, S.
A measurement of electron antineutrino oscillation by the Daya Bay Reactor Neutrino Experiment is described in detail. Six 2.9-GWth nuclear power reactors of the Daya Bay and Ling Ao nuclear power facilities served as intense sources of nu((e) over bar)'s. Comparison of the (v) over bare rate and energy spectrum measured by antineutrino detectors far from the nuclear reactors (similar to 1500-1950 m) relative to detectors near the reactors (similar to 350-600 m) allowed a precise measurement of (v) over bar (e) disappearance. More than 2.5 million (v) over bar (e) inverse beta-decay interactions were observed, based on the combination of 217 days of operation of six antineutrino detectors (December, 2011-July, 2012) with a subsequent 1013 days using the complete configuration of eight detectors (October, 2012-July, 2015). The (v) over bar (e) rate observed at the far detectors relative to the near detectors showed a significant deficit, R = 0.949 +/- 0.002(stat) +/- 0.002(syst). The energy dependence of (v) over bar (e) disappearance showed the distinct variation predicted by neutrino oscillation. Analysis using an approximation for the three-flavor oscillation probability yielded the flavor-mixing angle sin(2)2 theta(13) = 0.0841 +/- 0.0027(stat) +/- 0.0019(syst) and the effective neutrino mass-squared difference of broken vertical bar Delta m(ee)(2)vertical bar = (2.50 +/- 0.06(stat) +/- 0.06(syst)) x 10(-3) eV(2). Analysis using the exact three-flavor probability found Delta m(32)(2) = (2.45 +/- 0.06(stat) +/- 0.06d(syst)) x 10(-3) eV(2) assuming the normal neutrino mass hierarchy and Delta m(32)(2) = (-2.56 +/- 0.06(stat) +/- 0.06(syst)) x 10(-3) eV(2) for the inverted hierarchy.
Valence- and element-dependent water oxidation behaviors: in situ X-ray diffraction, absorption and electrochemical impedance spectroscopies
(2017-04-07)
Hsu, Chia-Shuo
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Suen, Nian-Tzu
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Hsu, Ying-Ya
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Lin, Hsuan-Yu
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Tung, Ching-Wei
Metal oxides of the spinel family have shown great potential towards the oxygen evolution reaction (OER), but the fundamental OER mechanism of spinel oxides is still far from being completely understood, especially for the role of the metal ions. Owing to various coordinated sites of divalent/trivalent metals ions and surface conditions (morphology and defects), it is a great challenge to have a fair assessment of the electrocatalytic performance of spinel systems. Herein, we demonstrated a series of MFe2O4 (M = Fe, Co, Ni, Zn) with a well-controlled morphology to achieve a comprehensive study of electrocatalytic activity toward OER. By utilizing several in situ analyses, we could conclude a universal rule that the activities for OER in the metal oxide systems were determined by the occurrence of a phase transformation, and this structural transformation could work well in both crystallographic sites (Td and Oh sites). Additionally, the divalent metal ion significantly dominated the formation of oxyhydroxide through an epitaxial relationship, which depended on the atomic arrangement at the interface of spinel and metal oxyhydroxide, while trivalent metal ions remained unchanged as a host lattice. The metal oxyhydroxide was formed during a redox reaction rather than being formed during OER. The occurrence of the redox reaction seems to accompany a remarkable increase in resistance and capacitance might result from the structural transformation from spinel to metal oxyhydroxide. We believe that the approaching strategies and information obtained in the present study can offer a guide to designing a promising electrocatalytic system towards the oxygen evolution reaction and other fields.
Non-interferometric phase retrieval using refractive index manipulation
(2017-04-07)
Chen, Chyong-Hua
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Hsu, Hsin-Feng
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Chen, Hou-Ren
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Hsieh, Wen-Feng
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光電工程學系
We present a novel, inexpensive and non-interferometric technique to retrieve phase images by using a liquid crystal phase shifter without including any physically moving parts. First, we derive a new equation of the intensity-phase relation with respect to the change of refractive index, which is similar to the transport of the intensity equation. The equation indicates that this technique is unneeded to consider the variation of magnifications between optical images. For proof of the concept, we use a liquid crystal mixture MLC 2144 to manufacture a phase shifter and to capture the optical images in a rapid succession by electrically tuning the applied voltage of the phase shifter. Experimental results demonstrate that this technique is capable of reconstructing high-resolution phase images and to realize the thickness profile of a microlens array quantitatively.
The effect of asymmetrical electrode form after negative bias illuminated stress in amorphous IGZO thin film transistors (vol 110, 103502, 2017)
(2017-04-10)
Su, Wan-Ching
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Chang, Ting-Chang
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Liao, Po-Yung
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Chen, Yu-Jia
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Chen, Bo-Wei
Synthesis and Characterization of an Exact Polystyrene-graft-polyisoprene: A Failure of Size Exclusion Chromatography Analysis
(2017-04-11)
Lee, Sanghoon
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Lee, Hyojoon
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Chang, Taihyun
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Hirao, Akira
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應用化學系
An exact polystyrene-graft-polyisoprene (PS-g-PI) synthesized by iterative anionic polymerization and graft reaction using diphenylethylene functional groups was characterized by liquid chromatography. As-prepared graft copolymer contains various byproducts other than the target PS-g-PI. After the fractionation by size exclusion chromatography (SEC), the PS-g-PI appears quite homogeneous by SEC analysis, but the temperature gradient interaction chromatography (TGIC) separation with respect to the PI branch number showed a significantly wide distribution in the number of PI grafts. The resolved TGIC peaks were fractionated, and the molecular weight of each block (backbone or branches) was estimated by liquid chromatography at critical condition (LCCC) analysis at the critical adsorption condition of the opposite block. The composition determined by LCCC analysis and H-1 NMR analysis yielded a reasonably self-consistent result. Through this study, we demonstrated that SEC analysis of this type of branched copolymers can lead to erroneous result and needs to be done with proper caution.
Enhanced hydrogen generation from formic acid by a biomimetic ruthenium complex with a covalently bonded phosphine ligand
(2017-04-13)
Chen, Mei-Hua
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Lin, Jia-Hoa
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Li, Chuen-Ru
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Gliniak, Jacek
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Chang, Chin-Hao
A series of [Ru-2(CO)(5)(mu-SCH2CH2CH2S)PXS] complexes (Ru-2-S-2-PXS, X = phosphine ligands, S = 1-8) have been synthesized and evaluated for their photocatalytic H-2 generation efficiencies from formic acid decomposition. The [Ru-2(CO)(5)(mu-SCH2CH2CH2S)P(o-C6H4CH3)(3)] (Ru-2-S-2-PX4) catalyst + P(CH3)(3) ligand exhibited a high turnover frequency of 15,840h(-1) and turnover number of 24,536. A mechanistic investigation of the Ru-2-S-2-PX4 + FA/TEA catalyzed photocatalytic H-2 generation reaction using ATR-IR, EI-MS, and NMR techniques suggested that when Ru2-S2-PX4 was photoirradiated, the P(o-C6H4CH3)(3) was dissociated from the complex to form a new species, [Ru-2(CO)(5)(mu-SCH2CH2CH2S)]* (I). The free P(o-C6H4CH3)(3) then attacks a second molecule of Ru-2-S-2-PX4 to form Ru-2-S-2-(PX4)(2) and release of free CO, which is then combined with species I to form Ru-2-S-2. Subsequent attachment of formate ion to species Ru-2-S-2-PX4, Ru-2-S-2, and Ru-2-S-2-(PX4)(2) to form [Ru-2(CO)(5)(mu-SCH(2)CH(2)CH(2)SA]-HC00(-) (II), Ru-2-S-2-HCOO- (II') and Ru-2-S-2-PX4-HCOO- (II"), respectively. Rearrangement of complex II (or II' or II") and evolution of CO2 generate a transient complex [Ru-2(CO)(5)(mu-SCH2CH2CH2S)H (III), which then undergoes a protonation process to yield complex [Ru-2(CO)(5)(mu-SCH2CH2CH2S)H-2] (IV). Release of H-2 and re-incorporation of the formate anion as well as evolution of CO2 regenerates the active complex III and the cycle begins again. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
MASTER-SLAVE FLIP-FLOP
(2017-04-13)
Shyh-Jye JOU
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Chia-Hsiang YANG
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Wei-Chang LIU
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Chi-Wei LO
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Ching-Da CHAN
A master-slave flip-flop includes a master latch, a slave latch, a first logic gate and a signal transition detector. The first logic gate is receiving a reference clock and a first control clock, and outputting a first trigger signal to control one of the master latch and the slave latch, which are connected with a logic circuit, to switch to an opaque state or a transparent state, wherein the other one of the master latch and the slave latch is switched to an opaque state or a transparent state according to the reference clock. The above-mentioned master-slave flip-flop can correct sampling when a timing error occurs.
Enhanced optical absorption and photocatalytic H-2 production activity of g-C3N4/TiO2 heterostructure by interfacial coupling: A DFT plus U study
(2017-04-13)
Lin, Yanming
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Shi, Hailong
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Jiang, Zhenyi
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Wang, Guanshi
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Zhang, Xiaodong
The electronic and optical properties of g-C3N4/TiO2 heterostructure are investigated using spin-polarized DFT+U calculations. The equilibrium spacing (1.94 angstrom) and binding energy (24 meV/angstrom(2)) show that g-C3N4/TiO2 is a van der Waals heterostructure. And the calculated band gap of g-C3N4/TiO2 is significantly reduced compared with TiO2. Therefore, the visible light response of g-C3N4/TiO2 heterostructure is remarkably improved. Besides, the predicted type II band alignment would ensure that the electrons can migrate from g-C3N4 monolayer to anatase TiO2 (101) surface, which leads oxidation and redox reactions can occur on g-C3N4 and TiO2, respectively. Finally, a built-in electric field within the interface region will be set. Above processes can benefit the separation of photoexcited carriers and enhance the hydrogen-evolution activity. In addition, compared with TiO2, g-C3N4/TiO2 with higher conduction band minimum energy can effectively produce higher-energy electrons to reduce hydrogen ions. Moreover, the influence of composite distance and the number of g-C3N4 layers are also investigated systematically. The results indicate that the optical absorption is enhanced over the whole spectrum with the increase of the number of g-C3N4 layers. Similar visible light enhancing is also found when the composite distance is decreased. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
Catalytic Nanoreactors of Au@Fe3O4 Yolk-Shell Nanostructures with Various Au Sizes for Efficient Nitroarene Reduction
(2017-04-13)
Lin, Fang-hsin
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Doong, Ruey-an
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環境工程研究所
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Institute of Environmental Engineering
Au@Fe3O4 yolk shell nanocatalysts based on the thermal decomposition of iron pentacarbonyl in the presence of 2.5-10-nm Au core nanoparticles were successfully fabricated for the catalytic reduction of nitroarenes. The particle sizes of the Au@Fe3O4 nanostructures were in the range 8-15 nm, with Fe3O4 shell layer thicknesses of 2.0-2.4 nm. The Fe3O4 layer not only can form a magnetic shell for recovery but also enables the protection of the catalytic activity of the Au core nanoparticles toward the reduction of nitrobenzene derivatives including 2-nitrophenol, 4-nitrophenol, 4-nitrotoluene, and 1-chloro-4-nitrobenzene in the presence of NaBH4. The catalytic performance of Au@Fe3O4 is highly dependent on the particle size of the Au core materials and the substituent groups of the nitroarenes. The reduction rates of nitroarenes with electron-withdrawing groups were found to be 2.3-2.6 times higher than those of nitroarenes with electron-donating groups. In addition, the reduction of nitroarenes by the Au@Fe3O4 yolk shell nanocatalysts was found to be a surface-mediated reaction, and the relationship rate and the initial NaBH4 concentration was found to follow Langmuir Hinshelwood kinetics. Moreover, the yolk shell nanoparticles showed good separation ability and reusability, as they could be repeatedly applied for the nearly complete reductions of 4-nitrophenol and 1-chloro-4-nitrobenzene for at least five successive cycles. These unique properties make Au@Fe3O4 nanocatalysts an ideal platform for tailoring yolk shell nanoreactors with various active materials and also for studying various heterogeneous catalytic processes.
Infrared absorption of methanol-water clusters (CH3OH)(n)(H2O), n=1-4, recorded with the VUV-ionization/IR-depletion technique
(2017-04-14)
Lee, Yu-Fang
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Kelterer, Anne-Marie
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Matisz, Gergely
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Kunsagi-Mate, Sandor
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Chung, Chao-Yu
We recorded infrared (IR) spectra in the CH- and OH-stretching regions of size-selected clusters of methanol (M) with one water molecule (W), represented as MnW, n = 1-4, in a pulsed supersonic jet using the photoionization/IR-depletion technique. Vacuum ultraviolet emission at 118 nm served as the source of ionization in a time-of-flight mass spectrometer to detect clusters M-n W as protonated forms Mn-1 WH+. The variations in intensities of Mn-1 WH+ were monitored as the wavelength of the IR laser light was tuned across the range 2700-3800 cm(-1). IR spectra of size-selected clusters were obtained on processing of the observed action spectra of the related cluster-ions according to a mechanism that takes into account the production and loss of each cluster due to IR photodissociation. Spectra of methanol-water clusters in the OH region show significant variations as the number of methanol molecules increases, whereas those in the CH region are similar for all clusters. Scaled harmonic vibrational wavenumbers and relative IR intensities predicted with the M06-2X/aug-cc-pVTZ method for the methanol-water clusters are consistent with our experimental results. For dimers, absorption bands of a structure WM with H2O as a hydrogen-bond donor were observed at 3570, 3682, and 3722 cm(-1), whereas weak bands of MW with methanol as a hydrogen-bond donor were observed at 3611 and 3753 cm(-1). For M2W, the free OH band of H2O was observed at 3721 cm(-1), whereas a broad feature was deconvoluted to three bands near 3425, 3472, and 3536 cm(-1), corresponding to the three hydrogen-bonded OH-stretching modes in a cyclic structure. For M3W, the free OH shifted to 3715 cm(-1), and the hydrogen-bonded OH-stretching bands became much broader, with a weak feature near 3179 cm(-1) corresponding to the symmetric OH-stretching mode of a cyclic structure. For M4W, the observed spectrum agrees unsatisfactorily with predictions for the most stable cyclic structure, indicating significant contributions from branched isomers, which is distinctly different from M-5 of which the cyclic form dominates. Published by AIP Publishing.
Infrared spectra of HSCS+, c-HSCS, and HCS2- produced on electron bombardment of CS2 in solid para-hydrogen
(2017-04-14)
Tsuge, Masashi
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Lee, Yuan-Pern
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應用化學系
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應用化學系分子科學碩博班
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Department of Applied Chemistry
We report infrared (IR) spectra of HSCS+, c-HSCS, HCS2-, and other species produced on electron bombardment of a mixture of CS2 and para-hydrogen (p-H-2) during deposition at 3.2 K. After maintenance of the deposited matrix in darkness for 12 h, the intensities of the absorption lines of HSCS+ at 2477.2 (v(1)), 1525.6 (v(2)), and 919.6 cm(-1) (v(3)) decreased through neutralization of HSCS+ with trapped electrons. During this period, the intensities of the lines of HCS2- at 2875.7 (v(1)), 1249.9 (v(5)), 1003.2 (v(6)), and 814.3 cm (1) (v(4)) increased due to reaction between H and CS2 . The intensities of the lines observed at 2312.7 and 889.0 cm(-1), which are assigned to the c-HSCS radical, increased after maintenance in darkness and greatly diminished after irradiation at 373 nm. The IR spectra of HSCS+, HCS2-, and c-HSCS are reported for the first time. The IR absorption lines of the t-HSCS radical, t-HC(S) SH, and c-HC(S) SH were also identified; their wavenumbers are similar to those reported for these species in an Ar matrix. The corresponding spectra of the C-13, S-34, and D isotopic variants of these species were observed. The assignments were made according to the expected chemical behavior, predicted potential energies of associated reactions, and a comparison of observed and predicted wavenumbers and their C-13, S-34, and D isotopic ratios. In contrast to the observed significant red shifts of the OH-stretching wavenumbers of HOCO+ and HOCS+ in solid p-H-2 compared to those in the gaseous phase due to proton sharing with H-2, the wavenumber of the HS-stretching mode of HSCS+ in solid p-H-2 (2477.2 cm(-1)) is similar to the anharmonic wavenumber of HSCS+ (2424 cm(-1)) predicted with the B3LYP/aug-cc-pVTZ method, indicating that the sharing of a proton between HSCS+ and neighboring H-2 molecules is insignificant.
A flexible and miniaturized hair dye based photodetector via chemiluminescence pathway
(2017-04-15)
Lin, Ching-Chang
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Sun, Da-Shiuan
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Lin, Ya-Lin
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Tsai, Tsung-Tso
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Cheng, Chieh
A flexible and miniaturized metal semiconductor metal (MSM) biomolecular photodetector was developed as the core photocurrent system through chemiluminescence for hydrogen peroxide sensing. The flexible photocurrent sensing system was manufactured on a 30-mu m-thick crystalline silicon chip by chemical etching process, which produced a flexible silicon chip. A surface texturization design on the flexible device enhanced the light-trapping effect and minimized reflectivity losses from the incident light. The model protein streptavidin bound to horseradish peroxidase (HRP) was successfully immobilized onto the sensor surface through high-affinity conjugation with biotin. The luminescence reaction occurred with luminol, hydrogen peroxide and HRP enzyme, and the emission of light from the catalytic reaction was detected by underlying flexible photodetector. The chemiluminescence in the miniaturized photocurrent sensing system was successfully used to determine the hydrogen peroxide concentration in real-time analyses. The hydrogen peroxide detection limit of the flexible MSM photodetector was 2.47 mM. The performance of the flexible MSM photodetector maintained high stability under bending at various bending radii. Moreover, for concave bending, a significant improvement in detection signal intensity (14.5% enhancement compared with a flat configuration) was observed because of the increased photocurrent, which was attributed to enhancement of light trapping. Additionally, this detector was used to detect hydrogen peroxide concentrations in commercial hair dye products, which is a significant issue in the healthcare field. The development of this novel, flexible and miniaturized MSM biomolecular photodetector with excellent mechanical flexibility and high sensitivity demonstrates the applicability of this approach to future wearable sensor development efforts.
Real-Time and Noncontact Impulse Radio Radar System for mu m Movement Accuracy and Vital-Sign Monitoring Applications
(2017-04-15)
Hung, Wei-Ping
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Chang, Chia-Hung
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Lee, Tsern-Huei
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電信工程研究所
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Institute of Communications Engineering
In this paper, a real-time, contactless pulse-based ultra-wideband (UWB) radar sensor was used to precisely detect the movement of the robotic arm, heartbeats, and respiration activities. To increase the object tracking resolution, an algorithm using adaptive and digitalized post-calibration techniques were proposed and tested. Both the radiated and reflected analog pulses were converted to digital signals by a low-noise comparator and its buffer for the time interval and distance detection. Moreover, the dynamic and calibrated tracking mechanism was incorporated into the algorithm for improving tracking accuracy and to continuously localize an object's vibration. The measured performance revealed that the proposed method successfully achieved mu m movement precision, thus providing its excellent tracking ability. We performed three different experimental tests to demonstrate the UWB radar's viability. First, the radar was employed to detect the undesired structural vibration of a delta robotic arm, which was subjected to high acceleration and structural flexibility. The measured results indicated that the accuracy of 100 mu m can be achieved at a 10 Hz vibration frequency. Next, the apnea alarm was tested, which included an embedded sensitive sensor in the smart mattress in order to execute long-term physiological monitoring. The apnea was mitigated by auto-adjusting the patient's sleeping posture on the mattress when the UWB sensor detected the apnea condition. The final experiment using the radar sensor was to monitor human vital signs, such as heart and breathing rates, simultaneously. In comparison with a commercial electrocardiography instrument, this radar sensor measured 73.2 bpm with only 1.2% deviation. Our results shown that the contactless UWB sensor performs superbly and is well-suited for monitoring physiological parameters.
Microstructural analysis and molecular dynamics modeling of shape memory alloys
(2017-04-15)
Yang, Chia-Wei
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Tsou, Nien-Ti
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材料科學與工程學系
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Department of Materials Science and Engineering
Molecular dynamics (MD) is an effective tool for studying the microstructures in shape memory alloys at the atomic level. However, microstructural analysis of the results generated by MD is typically done by examining lattice constants or monoclinic angles, and only a limited set of the crystal variants can be identified. In the current work, a numerical method that can identify the crystal variants and multiple phases is proposed. By observing the pattern of the components in the transformation matrix of the lattice in the crystal, the corresponding variant of the lattice can be determined. The method is then applied to study the martensitic transformation induced by temperature and ultrahigh shear strain, and the resulting microstructures are verified by literature. Moreover, the microstructural evolution and the volume fraction variation of the crystal variants under ultrahigh shear strain are examined. The observed multiple stages of phase transitions imply that the current method is able to identify the austenitic, orthorhombic, trigonal (R phase), monoclinic, and body-centered orthorhombic crystal systems simultaneously. The proposed method also reveals that the nanometer-sized R phase is a transition zone that maintains the compatibility between the two phases in the different crystal systems. The proposed method is rapid, accurate, and sufficiently versatile to be applicable to other crystal systems and related materials. (C) 2017 Elsevier B.V. All rights reserved.
Nonlinear Absorption Spectroscopy of Porphyrin J-aggregates in Aqueous Solution: Evidence for Control of Degree of Association by Light-Induced Force
(2017-04-15)
Shirakawa, Masayuki
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Nakata, Kazuaki
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Suzuki, Masaya
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Kobayashi, Takayoshi
;
Tokunaga, Eiji
Spectroscopic evidence was obtained for molecular aggregation states to be controlled by the irradiation of light, which is off-resonant below the peak absorption energies of both monomers and well-grown J-aggregates. In low (undersaturated)-concentration aqueous solutions of porphyrin molecules (tetraphenyl porphyrin tetrasulfonic acid; TPPS) where the monomer absorbance dominates, irradiation with a 532nm laser induces a decrease in the monomer absorbance and an increase in the aggregate absorbance. The increase in the absorbance of J-aggregates occurs in a broad spectral range associated with the increase in the number of not only variously sized oligomer aggregates but also aggregates structurally different from well-grown stable J-aggregates. In high-concentration solutions where the J-aggregate absorbance dominates, a blue shift of the absorption peak of J-aggregates is induced at the same 532nm irradiation, corresponding to a decrease in the aggregation number or in the association energy. By contrast, for spincoated polymer films of monomers and J-aggregates where molecules are immobile, these features are not observed. It is remarkable that the gradient force potential is smaller by more than seven orders of magnitude than the kinetic energy of the thermal motion of the molecule at room temperature, but the absorption change in solution indicating the increase in the number of aggregates is as large as Delta A similar to 10(-3) in magnitude.