Browsing by Author "Chen, Yu-Chih"

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Au-decorated Na(x)H(2-x)Ti(3)O(7) nanobelts exhibiting remarkable photocatalytic properties under visible-light illumination
(2010-06-18)
Pu, Ying-Chih
;
Chen, Yu-Chih
;
Hsu, Yung-Jung
;
材料科學與工程學系
;
Department of Materials Science and Engineering
We demonstrated for the first time that Na-intercalated H(2)Ti(3)O(7) (Na(x)H(2-x)Ti(3)O(7)) NBs, prepared in the typical alkaline hydrothermal process, can effectively absorb visible light to carry out photocatalytic reactions. With the capability of effective light absorption in visible range, Na(x)H(2-x)Ti(3)O(7) NBs performed much better in the photoclegradation of thionine than the other three counterpart products including H(2)Ti(3)O(7), mixed Na(2)Ti(6)O(13)/TiO(2) and anatase TiO(2) under visible-light irradiations. As compared to the relevant commercial products like P-25 TiO(2) and Na(2)Ti(3)O(7) powders, the as-synthesized Na(x)H(2-x)Ti(3)O(7) NBs exhibited superior photocatalytic efficiency under UV illumination, demonstrating their potential as an efficient photocatalyst in relevant redox reactions. A further enhancement in the photocatalytic activity can be achieved for Na(x)H(2-x)Ti(3)O(7) NBs when Au nanoparticles of suitable amount were deposited on their surfaces. This improvement is due to the band offsets between Na(x)H(2-x)Ti(3)O(7) and Au, which may promote charge carrier separation to favor the photocatalysis. The recycling test reveals that Au-decorated Na(x)H(2-x)Ti(3)O(7) NBs could be promisingly utilized in the long-term course of photocatalysis. Furthermore, the result of performance evaluation under natural sunlight shows that the current Au-decorated Na(x)H(2-x)Ti(3)O(7) NBs can be used as highly efficient photocatalysts which may practically harvest energy from sunlight. (C) 2010 Elsevier B.V. All rights reserved.
Au-decorated NaxH2-xTi3O7 nanobelts exhibiting remarkable photocatalytic properties under visible-light illumination
(2010-06-18)
Pu, Ying-Chih
;
Chen, Yu-Chih
;
Hsu, Yung-Jung
;
材料科學與工程學系
;
Department of Materials Science and Engineering
We demonstrated for the first time that Na-intercalated H2Ti3O7 (NaxH2-xTi3O7) NBs, prepared in the typical alkaline hydrothermal process, can effectively absorb visible light to carry out photocatalytic reactions. With the capability of effective light absorption in visible range, NaxH2-xTi3O7 NBs performed much better in the photoclegradation of thionine than the other three counterpart products including H2Ti3O7, mixed Na2Ti6O13/TiO2 and anatase TiO2 under visible-light irradiations. As compared to the relevant commercial products like P-25 TiO2 and Na2Ti3O7 powders, the as-synthesized NaxH2-xTi3O7 NBs exhibited superior photocatalytic efficiency under UV illumination, demonstrating their potential as an efficient photocatalyst in relevant redox reactions. A further enhancement in the photocatalytic activity can be achieved for NaxH2-xTi3O7 NBs when Au nanoparticles of suitable amount were deposited on their surfaces. This improvement is due to the band offsets between NaxH2-xTi3O7 and Au, which may promote charge carrier separation to favor the photocatalysis. The recycling test reveals that Au-decorated NaxH2-xTi3O7 NBs could be promisingly utilized in the long-term course of photocatalysis. Furthermore, the result of performance evaluation under natural sunlight shows that the current Au-decorated NaxH2-xTi3O7 NBs can be used as highly efficient photocatalysts which may practically harvest energy from sunlight. (C) 2010 Elsevier B.V. All rights reserved.
Brain tissue oxygen evaluation by wireless near-infrared spectroscopy
(2016-02-01)
Wang, Che-Chuan
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Kuo, Jinn-Rung
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Chen, Yu-Chih
;
Chio, Chung-Ching
;
Wang, Jhi-Joung
Background: Monitoring the partial pressure of oxygen in brain tissue (PbtO(2)) is an important tool for traumatic brain injury (TBI) but is invasive and inconvenient for real time monitoring. Near-infrared spectroscopy (NIRS), which can monitor hemoglobin parameters in the brain tissue, has been used widely as a noninvasive tool for assessing cerebral ischemia and hypoxia. Therefore, it may have the potential as a noninvasive tool for estimating the change of PbtO(2). In this study, a novel wireless NIRS system was designed to monitor hemoglobin parameters of rat brains under different impact strengths and was used to estimate the change of PbtO(2) noninvasively in TBI. Materials and methods: The proposed wireless NIRS system and a PbtO(2) monitoring system were used to monitor the oxygenation of rat brains under different impact strengths. Rats were randomly assigned to four different impact strength groups (sham, 1.6 atm, 2.0 atm, and 2.4 atm; n = 6 per group), and the relationships of concentration changes in oxyhemoglobin (HbO(2)), deoxyhemoglobin (HbR), and total hemoglobin (HbT), and PbtO(2) during and after TBI with different impact strengths were investigated. Triphenyltetrazolium chloride (TTC) staining was also used to evaluate infarction volume. Results: Concentration changes in HbO(2), HbR, and HbT dropped immediately after the impact, increased gradually, and then became stable. Changes in PbtO(2) had a similar tendency with the hemoglobin parameters. There was significant correlation between changes in PbtO(2) and HbO(2) (correlation = 0.76) but not with changes in HbR (correlation = 0.06). In triphenyltetrazolium chloride staining, the infarction volume was highly but negatively associated with oxygen-related parameters like PbtO(2) and HbO(2). Conclusions: Changes in HbO(2) under TBI was highly and positively correlated with changes in PbtO(2). By using the relative changes in HbO(2) as a reference parameter, the proposed
Evaluating performance of post-tensioned steel connections with strands and reduced flange plates
(2006-07-25)
Chou, Chung-Che
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Chen, Jun-Hen
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Chen, Yu-Chih
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Tsai, Keh-Chyuan
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土木工程學系
The seismic performance of post-tensioned steel connections for moment-resisting frames was examined experimentally and analytically. Cyclic tests were conducted on three full-scale subassemblies, which had two steel beams post-tensioned to a concrete-filled tube (CFT) column with high-strength strands to provide recentring response. Reduced flange plates (RFPs) welded to the column and bolted to the beam flange were used to increase the dissipation of energy. Test results indicated that (1) the proposed buckling-restrained RFP could dissipate energy in axial tension and compression, (2) the subassemblies could reach an interstorey drift of 4% without strength degradation, and (3) buckling of the beam occurred towards an interstorey drift of 5%, causing a loss of the strand force, the recentring response, and the moment capacity. A general-purpose non-linear finite element analysis program (ABAQUS) was used to perform a correlation study. The behaviour of the steel beam under both post-tensioning and flexural loadings was compared to the test results and predictions. Copyright (C) 2006 John Wiley & Sons, Ltd.
Evolution of carrier distribution and defects in InGaAsN/GaAs quantum wells with composition fluctuation
(2006-07-01)
Chen, Jenn-Fang
;
Hsiao, Ru-Shang
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Hsieh, Pei-Chen
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Chen, Yu-Chih
;
Wang, Jyh-Shyang
Carrier distribution and defect induction in In0.34Ga0.66As0.98N0.02/GaAs-single quantum wells grown by molecular beam epitaxy at low growth rates are investigated by frequency-dependent capacitance-voltage (C-V) and deep-level transient spectroscopy (DLTS). The C-V studies show that lowering the growth rate of the InGaAsN layer splits the carrier accumulation in the well into a central and two side peaks with different frequency dispersions. The DLTS studies show that a continuum of states (0-0.083eV) and a,deep trap at 0.21-0.25eV are responsible for the central and the side peaks, respectively. A comparison with photoluminescence (PL) spectra shows that these defects are induced by composition fluctuation. Lowering the growth rate degrades composition fluctuation by segregating the material into an InGaAsN phase and an N-depleted phase. Post-growth annealing can remove the deep trap and improve the InGaAsN emission, confirming that the deep trap degrades the InGaAsN phase. The feature of the continuum of states suggests that it may be the structural defects associated with lattice expansion or localized states introduced by composition fluctuation.
Interfacial Charge Carrier Dynamics of the Three-Component In2O3-TiO2-Pt Heterojunction System
(2012-02-02)
Chen, Yu-Chih
;
Pu, Ying-Chih
;
Hsu, Yung-Jung
;
材料科學與工程學系
;
Department of Materials Science and Engineering
The interfacial charge carrier dynamics of the three-component semiconductor semiconductor-metal heterojunction system were investigated and presented for the first time. The samples were prepared by selectively depositing Pt nanoparticles on the TiO2 surface of In2O3-decorated TiO2 nanobelts (In2O3-TiO2 nanobelts (NBs)) using the typical photodeposition method. For In2O3-TiO2 NBs, because of the difference in band structures between In2O3 and TiO2, the photoexcited electrons of In2O3 nanocrystals would preferentially transfer to TiO2 NBs to cause charge carrier separation. With the introduction of Pt on TiO2 surface, a fluent electron transfer from In2O3, through TiO2, and eventually to Pt was achieved, giving rise to the increasingly pronounced charge separation property for the as-prepared In2O3-TiO2-Pt NBs. The remarkable charge separation of the samples was revealed with the corresponding photocurrent measurements. Time-resolved photoluminescence spectra were measured to quantitatively analyze the electron transfer event between In2O3 and TiO2 for In2O3-TiO2 NBs and its dependence on Pt deposition. Upon the deposition of Pt, In2O3-TiO2 NBs showed an increased apparent electron-scavenging rate constant, fundamentally consistent with the result of their performance evaluation in photocatalysis. The current study provides a new paradigm for designing highly efficient three-component nanoheterojunction photocatalysts which can effectively produce chemical energy from absorbing light.
The Impact of Emergency Interventions and Patient Characteristics on the Risk of Heart Failure in Patients with Nontraumatic OHCA
(2019-12-16)
Chen, Cheng Hsu
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Chang, Chih-Yu
;
Yang, Mei-Chueh
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Wu, Jr-Hau
;
Liao, Ching-Hui
Background. Since out-of-hospital cardiac arrest- (OHCA-) related dysfunction (ischemic/reperfusion injury and inflammatory response) might result in long-term impairment, we suspect that new-onset heart failure might be common in long-term survivors. However, these relationships had not been well addressed, and we aimed to analyze the impact of emergency interventions and patient characteristics on the risk of new-onset heart failure in patients with nontraumatic OHCA. Methods. The Taiwanese government healthcare database contains data for 49,101 nontraumatic OHCA adult patients from 2011-2012, which were analyzed in this study. Nontraumatic OHCA patients who survived to the intensive care unit (ICU) were included as the study group (n = 7,321). Matched patients (n = 21,963) were recruited as a comparison group. Patients with any history of heart failure or cardiac arrest were not included in either group. All patients were followed-up for 6 months for the identification of new-onset heart failure. Adjustments were made for demographics, age, emergency interventions, and comorbidities as potential risk factors. Results. In all, 3.84% (n = 281) of OHCA patients suffered new-onset heart failure, while only 1.24% (n = 272) of matched patients in the comparison group suffered new-onset heart failure. Strong risk factors for heart failure were age (60-75 years, HR: 11.4; 95% CI: 9-14.4), medical history (myocardial infarction, HR: 2.47; 95% CI: 2.05-2.98 and cardiomyopathy, HR: 2.94; 95% CI: 1.45-5.94), and comorbidities during hospitalization (ischemic heart disease, HR: 4.5; 95% CI: 3.46-5.86). Only extracorporeal membrane oxygenation (ECMO) decreased the risk of heart failure. Most (53.6%) heart failure events occurred within 60 days after OHCA. Conclusion. An age from 61 to 75 years, a history of myocardial infarction or cardiomyopathy, and ischemic heart disease or infection as comorbidities occurring during hospitalization were strong risk factors for new-onset heart failure in OHCA patients. However, ECMO could decrease this risk. More importantly, most heart failure events occurred within 60 days after OHCA.
ZnO-graphene composites as practical photocatalysts for gaseous acetaldehyde degradation and electrolytic water oxidation
(2015-01-25)
Chen, Yu-Chih
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Katsumata, Ken-ichi
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Chiu, Yi-Hsuan
;
Okada, Kiyoshi
;
Matsushita, Nobuhiro
A facile, green one-pot hydrothermal method has been developed to prepare ZnO-reduced graphene oxide (rGO) composites with controllable rGO content. Time-resolved photoluminescence spectra revealed that an increased electron-transfer rate constant was observed for ZnO-rGO with increasing rGO contents, suggesting that an increased number of photoexcited charge carriers were separated and available for photocatalysis utilization. The photocatalytic properties of the ZnO-rGO composites were investigated by using gaseous acetaldehyde (CH3CHO), a typical volatile organic compound (VOC), as the test pollutant. This is the first time that ZnO-rGO composites have been used as photocatalysts for gaseous CH3CHO degradation. Compared to pure ZnO, ZnO-rGO composites with suitable rGO contents (1.0 and 3.0 wt%) displayed significantly enhanced photocatalytic activity in both CH3CHO degradation and CO2 generation. This enhancement was ascribed to the rGO support that can promote the carrier utilization efficiency of ZnO by readily accepting the photoexcited electrons from ZnO. As a result, abundant photogenerated holes remained on the ZnO and were available for participation in the CH3CHO photodegradation. Furthermore, the photoactivity of ZnO-rGO toward electrolytic water oxidation was evaluated. The results showed that ZnO-rGO composites achieved 50% increase in water oxidation current over pure ZnO under white light illumination. The demonstration from this work may facilitate the use of ZnO-rGO composites in photodegradation of VOCs as well as for photoelectrochemical applications, which is imperative from the environmental and energetic points of view. (C) 2014 Elsevier B.V. All rights reserved.
ZnSe center dot 0.5N(2)H(4) Hybrid Nanostructures: A Promising Alternative Photocatalyst for Solar Conversion
(2015-01-28)
Chen, Yu-Chih
;
Liu, Tao-Cheng
;
Hsu, Yung-Jung
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材料科學與工程學系
;
Department of Materials Science and Engineering
As the molecular precursor of ZnSe, ZnSe center dot 0.5N(2)H(4) inorganic-organic hybrids have received relatively less attention due to the feasibility of their further processing and decomposition into pure-phase ZnSe. Here we demonstrated that ZnSe center dot 0.5N(2)H(4) hybrid nanostructures, which were prepared using a facile hydrazine-assisted hydrothermal method, may practically harvest solar energy for photoconversion applications. By modulating the volume ratio of hydrazine hydrate to deionized water employed in the synthesis, the morphology of the grown ZnSe center dot 0.5N(2)H(4) can be varied, which included nanowires, nanobelts and nanoflakes. With the relatively long exciton lifetime and highly anisotropic structure, ZnSe center dot 0.5N(2)H(4) nanowires performed much better in the photodegradation of rhodamine B than the other two counterpart products. As compared to pure ZnSe nanoparticles and single-phase ZnSe nanowires obtained from further processing ZnSe center dot 0.5N(2)H(4), the ZnSe center dot 0.5N(2)H(4) hybrid nanowires exhibited superior photocatalytic performance under visible light illumination. The hybrid nanowires were further decorated with Au particles to endow them with structural and compositional diversities. Time-resolved photoluminescence spectra suggested that almost 40% of the photoexcited electrons in ZnSe center dot 0.5N(2)H(4) nanowires can be transported to the decorated Au, which enabled a fuller extent of participation of charge carriers in the photocatalytic process and thus conduced to a significant enhancement in the photocatalytic activity. The demonstrations from this work illustrate that ZnSe center dot 0.5N(2)H(4) hybrid nanostructures can serve as a versatile photocatalyst platform for advanced photocatalytic applications.