Browsing by Author "Lee, Yu-Hsien"

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BARRIER-OVERPASSING TRANSPORTER
(2008-08-07)
Cheng, Pi-Ying
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Guo, Fang-Fu
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Wong, Kian-Poh
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Lin, I-Chung
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Lee, Yu-Hsien
The present invention discloses a barrier-overpassing transporter, which comprises: a support frame carrying a rider or another load; a sensing/adjusting module detecting a tilting state of the support frame and maintaining the support frame in a horizontal state; a ground contact module arranged below the support frame supporting an effective load and lifting the support frame to overpass a surface of a barrier; and a wireless transceiver module collecting and transmitting information to enable adjustments and activities responding to interior states of the transporter. Thereby, the present invention can provide a safe, stable, reliable, comfortable, convenient and low-cost barrier-overpassing transporter.
Beat of Frequency Modes with an Artificial Negative Frequency in Spectrogram Analysis
(2010-12-05)
Yabushita, Atsushi
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Kao, Chih-Hsien
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Lee, Yu-Hsien
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Kobayashi, Takayoshi
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電子物理學系
Spectrograms have been used for time-resolved analysis of Fourier power spectra in various fields We have performed spectrogram analysis for two neighboring modes and a low frequency mode changing gate width of the time gate function The obtained spectrogram of the former showed both amplitude and frequency modulations between two neighboring modes A contamination appearing on the spectrogram of the latter reflects an artifact showing beat between the signal mode and a negative frequency mode whose sign was inverted from the signal mode Surprising results from the amplitude and phase modulations were observed in the simulation even in the case of single mode This puzzling result was explained in terms of the interference between the single mode and the "negative" frequency composing the single mode with the corresponding positive frequency"
Development and demonstration of table-top synchronized fast-scan femtosecond time-resolved spectroscopy system by single-shot scan photo detector array
(2015-07-01)
Yabushita, Atsushi
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Kao, Chih-Hsien
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Lee, Yu-Hsien
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Kobayashi, Takayoshi
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電子物理學系
Ultrafast dynamics is generally studied by pump-probe method with laser pulse, which scans optical delay by motorized stage step by step. Using ultrashort laser pulse shorter than typical molecular vibration periods, the pump-probe measurement can study both of electronic dynamics and vibration dynamics simultaneously. The probe wavelength dependence of the ultrafast electronic and vibration dynamics (UEVD) helps us to distinguish the signal contributions from the dynamics of the electronic ground state and that of the electronic excited states, which elucidates primary reaction mechanism after photoexcitation. Meanwhile, the measurement time of UEVD spectroscopy takes too long time to be used in realistic application. In our previous work, we have developed multi-channel lock-in amplifying (MLA) detectors to study UEVD at all probe wavelengths simultaneously, and synchronized it with laser and fast-scan delay stage to scan the data in five seconds. It enabled us to study UEVD spectroscopy even for photo-fragile materials. However, the home-made MLA detectors required for the measurement is expensive and massive in size and weight, thus not suitable for general researchers in the field of ultrafast time-resolved spectroscopy. In the present work, we have developed a table-top synchronized fast-scan femtosecond time-resolved spectroscopy system using single shot scan line CCD. This system measures time-resolved trace at all probe wavelengths simultaneously in five seconds. The CCD-based fast-scan time-resolved spectroscopy system enables us to study ultrafast dynamics of various materials even biomaterials, which have been thought to be hard or even impossible to be studied in previous methods. (C) 2015 The Japan Society of Applied Physics
Development of a multiplex fast-scan system for ultrafast time-resolved spectroscopy
(2010-06-01)
Yabushita, Atsushi
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Lee, Yu-Hsien
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Kobayashi, Takayoshi
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電子物理學系
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Department of Electrophysics
A fast-scan method was developed to obtain time-resolved signals with femtosecond resolution over a picosecond range on the fly and in real time. Traditional fast-scan methods collect data at each probe wavelength one by one, which is time consuming and thus not possible for the study of photofragile materials. In this work, we have developed a system that performs fast scans with multiplex detection. Ultrafast time-resolved spectroscopy was demonstrated using the newly developed system. Femtosecond laser pulses have been used for pump-probe studies of ultrafast processes in various materials, and both electronic relaxation and vibrational dynamics have been studied. However, experiments have been limited in sensitivity and reliability because they are affected by the long-term instability of the ultrashort laser pulses and by the fragility of the samples. The instability of the sources hinders precise determination of electronic decay dynamics and introduces systematic errors. The fragility of the samples reduces their amount or concentration, and can lead to contamination of the materials even if they were pure before the measurement. These effects make it difficult to obtain reproducible and reliable experimental data. In the present work, we have developed a fast-scan pump-probe spectroscopic system that can complete a set of measurements in less than 2 min. Quantitative estimates of the signal reproducibility demonstrate that these measurements provide higher reproducibility and reliability than conventional measurements. (C) 2010 American Institute of Physics. [doi:10.1063/1.3455809]
Laser induced breakdown spectroscopy of pure aluminum with high temporal resolution
(2013-09-09)
Li, Yu-Tai
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Liu, Tze-An
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Chen, Chen-Wei
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Lee, Yu-Hsien
;
Yabushita, Atsushi
We report on a Laser Induced Breakdown Spectroscopy (LIBS) system with a very high temporal resolution, using femtosecond and picosecond pulse laser excitation of pure aluminum (Al). By using a 140 fs Ti:Sapphire laser in an ultrafast optical Kerr gate (OKG), we demonstrate LIBS sampling with a sub-ps time resolution (0.8 +/- 0.08 ps) in a 14 ns window. The width of the gating window in this system was as narrow as 0.8 ps, owing to the inclusion of a carbon disulfide (CS2) cell, which has a fast response and a large nonlinear coefficient. Furthermore, when using a 100 ps pulsed Nd:YAG laser and a fast photomultiplier tube (PMT) we demonstrate a LIBS system with a nanosecond time resolution (2.20 +/- 0.08 ns) in a microsecond window. With this sort of temporal resolution, a non-continuous decay in the Al signal could be observed. After 50 ns decay of the first peak, the second peak at 230 ns is started to perform. Experimental results with such short temporal windows in LIBS, in both nanosecond and microsecond ranges, are important for fast temporal evolution measurements and observations of early continuum emission in materials. (C) 2013 Optical Society of America
Novel Reversible Chemosensory Material Based on Conjugated Side-Chain Polymer Containing Fluorescent Pyridyl Receptor Pendants
(2011-07-21)
Chu, Hsuan-Chih
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Lee, Yu-Hsien
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Hsu, Shou-Jen
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Yang, Po-Jen
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Yabushita, Atsushi
A novel light-emitting monomer M1 and its side-chain polymer PI containing three conjugated aromatic pendants, including one pyridyl terminus, were successfully synthesized via Wittig and Pd-catalyzed Heck coupling reactions. The fluorescence of polymer P1 was efficiently quenched upon addition of different metal ions due to the facile energy transfers from the pendent groups of polymer PI to specific metal ions. Among these metal ions, PI exhibited extraordinary sensory selectivities for Ni(2+) and Cu(2+) ions over the other metal ions due to the stronger binding capabilities of Ni(2+) and Cu(2+) ions with polymer P1. From the time-resolved fluorescence (TRF) signals in photoluminescence spectra, the emergences of tau(1) decay components in polymer complexes (P1+Ni(2+)) and (P1-FCu(2+)) clearly indicated that their TRF traces consisted of two contributions, one from the complexes (tau(1)) and the other from free polymer P1 (tau(2)). Upon addition of Ni(2+) and Cu(2+) ions, polymer PI showed faster decay time constants (tau(1)) of metal ion quenching on TRF signals (i.e., better quenching efficiencies on photoluminescence) than its monomer M1. Furthermore, the on-off-on fluorescent switching behavior by adding a tridentate ligand 1,1,4,7,7-pentamethyl-diethylenetriamine (PMDTA) to the polymer complex (P1+Cu(2+)),for several successive cycles demonstrated a superior reusable chemosensor of P1 for further applications.
Quenching effects of gold nanoparticles in nanocomposites formed in water-soluble conjugated polymer nanoreactors
(2012-02-17)
Yang, Po-Jen
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Chu, Hsuan-Chih
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Lee, Yu-Hsien
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Kobayashi, Takayoshi
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Chen, Te-Cheng
In this paper we describe the first example of the in situ synthesis of gold nanoparticles (AuNPs) in the presence of a water-soluble conjugated polyfluorene (NPF) presenting pendent ammonium groups, with the polymer acting as an aqueous surfactant and providing fluorescent nanoreactors. Using this approach, we produced well-dispersed NPF-AuNP nanocomposites without the need for any additional reducing agents. The photoluminescence emission intensity of NPF-AuNP nanocomposite solution was quenched to a greater extent upon increasing the concentration of AuNPs, presumably through energy transfer or electron transfer from the fluorescent polymer to the metal nanoparticles. Through variations in the degrees of protonation and deprotonation of the amino groups of NPF at different values of pH, we found that the extent of quenching of AuNPs in NPF-AuNP nanocomposite solutions was directly related to the adsorption and desorption behavior of NPF on the metal surfaces. Transmission electron microscopy revealed that the greatest aggregation of AuNPs in the nanocomposite solution occurred at pH 3. suggesting that the ammonium groups (RNMe2 at pH 8.5; RNMe2H+ at pH 3) of the polymer side chains adsorbed onto the AuNP surfaces under these conditions. Distinct time-resolved fluorescence signals of the AuNP-quenched NPF polymers at different values of pH confirmed the interactions between these species. (C) 2012 Elsevier Ltd. All rights reserved.
Spectral phase retrieval of 8 fs optical pulses at 600nm by using a collinear autocorrelator with 300-mu m-thick lithium triborate crystals
(2011-06-01)
Hsu, Chen-Shao
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Lee, Yu-Hsien
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Yabushita, Atsushi
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Kobayashi, Takayoshi
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Yang, Shang-Da
We report on noniterative spectral phase retrieval of 1.1 nJ, 8 fs pulses at 600nm by using 300-mu m-thick lithium triborate crystals in a standard collinear autocorrelator with approximate to 2 min data acquisition time. This method is simple, sensitive, and immune to the spectral distortion and UV absorption of the linear and nonlinear optics. (C) 2011 Optical Society of America
Ultrafast photoexcited dynamics probe of blends of conjugated polymer poly{bi(dodecyl)thiophene-thieno[3,4-c]pyrrole-4,6-dione} and fullerenes for photovoltaic applications with broadband sub-10-fs visible pulse
(2016-03)
Kao, Chih-Hsien
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Yabushita, Atsushi
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Su, Yu-Wei
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Wei, Kung-Hwa
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Lee, Yu-Hsien
Conjugated polymers have been widely studied as active materials for organic solar cells, which are a promising replacement for silicon solar cells. A novel electron donor polymer of poly{bi(dodecyl)thiophene-thieno[3,4-c]pyrrole-4,6-dione} (PBTTPD) blended with an electron acceptor, [6,6]-phenyl C-71 butyric acid methyl ester (PC71BM), gave a device power conversion efficiency as high as 7.3%. In the present work, we performed time-resolved absorption change spectroscopy at various mixture ratios of PC71BM in the PBTTPD/PC71BM blend. Among the obtained time constants, the shortest (60 fs) and the longest (500 fs and 15 ps) were assigned to the production and relaxation of charge-transfer (CT) states, respectively. The PC71BM blended with PBTTPD was found to suppress interchain carrier transport and increase intrachain carrier transport. The prolonged lifetime of the CT state in the equally blended PBTTPD/PC71BM film increases the probability of charge separation and thus increases the power conversion efficiency of the device. (C) 2016 The Japan Society of Applied Physics