Browsing by Issue Date, starting with "2020-05-25"

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Experimental investigation on heat transfer enhancement with twisted tape having various V-cut configurations
(2020-05-25)
Chu, Wen-Xiao
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Tsai, Ching-An
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Lee, Bing-Hung
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Cheng, Kai-Yueh
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Wang, Chi-Chuan
This paper experimentally investigates the thermo-hydraulic performance of tubes with various twisted tapes (TTs) with the Reynolds number ranging from 4000 to 10,000 (at the turbulent transition region). The Nusselt number (Nu) and friction factor (f) of the tested plain tube shows good agreement with the Gnielienski and Filonenko equations. The average deviations are within 9.5% and 2.8%, respectively. For the successive TT tube, the existing correlation which includes the effect of gap between the TT insert and tube can well predict the present measurement, and the deviation upon Nu and f is within +/- 10%. Meanwhile, the successive TT with the twisted ratio of 4 can achieve the highest comprehensive thermal performance (CTP) by 1.08-1.10. Yet the Nu and f will simultaneously drop by 6.7% and 11.6% when raising the gap ratio from 0.043 to 0.135. The CTP is also pronouncedly reduced and can be negatively reversed than the plain tube at the turbulent transition region. On the other hand, it is validated that the U-cut and isosceles V-cut configurations might provide similar improvement on Nu and f compared to the successive TT. The obtuse V-cut configuration shows more pronounced improvement on Nu and f, and yields the highest CTP of 1.18-1.23 within the test range. The existing correlations applicable for the V-cut TTs are unable to predict the present measurements accurately.
Photocatalytic activity enhancement of Bi2WO6 nanoparticles by Ag doping and Ag nanoparticles modification
(2020-05-25)
Nguyen Dang Phu
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Luc Huy Hoang
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Pham Van Hai
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Tran Quang Huy
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Chen, Xiang-Bai
Bi2WO6 nanoparticles doped with Ag, and modified with Ag nanoparticles, were successfully prepared using a two-step microwave assisted and hydrothermal synthesis. With Ag doping, the Bi ions were substituted by the dopant Ag ions in the host lattice structure of Bi2WO6. With Ag nanoparticles modification, the Ag nanoparticles grew on the surface of the Bi2WO6 nanoparticles without changing the host lattice structure. The photocatalytic activities of the samples were studied by visible light irradiation of rhodamine B. Both the Ag doping and the Ag nanoparticles modification enhanced the photocatalytic activity of the Bi2WO6 nanoparticles. Moreover, Ag nanoparticles modification produced a more than two times higher enhancement of the photocatalytic activity than the Ag doping method. Furthermore, a mechanism of the significant photocatalytic activity enhancement by Ag nanoparticles modification is proposed. (C) 2020 Elsevier B.V. All rights reserved.
A thermodynamic and kinetic study of the antioxidant activity of natural hydroanthraquinones
(2020-05-26)
Vo, Quan V.
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Nguyen Minh Thong
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Trinh Le Huyen
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Pham Cam Nam
;
Nguyen Minh Tam
Novel hydroanthraquinones isolated from marine algal-derived endophytic fungus Talaromyces islandicus EN-501 exhibited promising antioxidant properties in preliminary studies, raising the prospect of adapting these compounds for therapeutic use in diseases caused by oxidative stress. For medicinal applications it is beneficial to develop a full understanding of the antioxidant activity of these compounds. In this study, the hydroperoxide radical scavenging activity of five natural hydroanthraquinones was evaluated by kinetic and thermodynamic calculations. The results showed that the radical scavenging of these hydroanthraquinones in the gas phase and in lipid solvents was defined by the formal hydrogen transfer mechanism, that for the polar environments was decided by the sequential proton loss electron transfer pathway. The hydroanthraquinones exhibited good hydroperoxide scavenging activity in both polar and non-polar media. The overall rate constant values for the radical scavenging reaction were in the range of 3.42 x 10(1) to 2.60 x 10(5) M-1 s(-1) and 3.80 x 10(6) to 5.87 x 10(7) M-1 s(-1) in pentyl ethanoate and water solvents, respectively. Thus the activity of 8-hydroxyconiothyrinone B (1) is about 2.6 and 444.6 times higher than that of Trolox in the studied solvents, identifying 8-hydroxyconiothyrinone B as a promising antioxidant.
Structural Colors Enabled by Lattice Resonance on Silicon Nitride Metasurfaces
(2020-05-26)
Yang, Jhen-Hong
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Babicheva, Viktoriia E.
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Yu, Min-Wen
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Lu, Tien-Chang
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Lin, Tzy-Rong
Artificial color pixels based on dielectric Mie resonators are appealing for scientific research as well as practical design. Vivid colors are imperative for displays and imaging. Dielectric metasurface-based artificial pixels are promising candidates for developing flat, flexible, and/or wearable displays. Considering the application feasibility of artificial color pixels, wide color gamuts are crucial for contemporary display technology. To achieve a wide color gamut, ensuring the purity and efficiency of nanostructure resonance peaks in the visible spectrum is necessary for structural color design. Low-loss dielectric materials are suitable for achieving vivid colors with structural color pixels. However, high-order Mie resonances prevent color pixels based on dielectric metasurfaces from efficiently generating highly saturated colors. In particular, fundamental Mie resonances (electric/magnetic dipole) for red can result in not only a strong resonance peak at 650 nm but also high-order Mie resonances at shorter wavelengths, which reduces the saturation of the target color. To address these problems, we fabricated silicon nitride metasurfaces on quartz substrates and applied Rayleigh anomalies at relatively short wavelengths to successfully suppress high-order Mie resonances, thus creating vivid color pixels. We performed numerical design, semianalytic considerations, and experimental proof-of-concept examinations to demonstrate the performance of the silicon nitride metasurfaces. Apart from traditional metasurface designs that involve transmission and reflection modes, we determined that lateral light incidence on silicon nitride metasurfaces can provide vivid colors through long-range dipole interactions; this can thus extend the applications of such surfaces to eyewear displays and guided-wave illumination techniques.
SiCxNy-based resistive and threshold switching by using single precursor plasma-enhanced atomic layer deposition
(2020-05-26)
Hsu, Yu-Lin
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Chang, Yao-Feng
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Chung, Wei-Min
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Chen, Ying-Chen
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Lin, Chao-Cheng
In this work, SiCxNy-based resistive switching memory by using a single precursor for the back end of line (BEOL) integration has been investigated. SiCxNy films were deposited on the aluminum (Al) substrates using plasma enhanced atomic layer deposition (PEALD) method. The effects of SiCxNy chemical structure with respect to resistive switching characteristics have been studied, and the results suggest that the resistive switching mechanism is dominated by the interfacial Schottky junction with SiCxNy composition. This work not only demonstrates a PEALD method in fabricating SiCxNy-based electronics active devices but also provides additional insights into the interaction between the electrical and chemical structures in bi-functional resistive switching or threshold switching behavior. A demonstrated PEALD tool with simple single-precursor for SiCxNy deposition shows excellent feasibility to be used as functional memory and selector devices, further giving the potential pathway for advanced BEOL process integration.
Direct observation of dynamic thermal lensing in nanoscale surfaces/interfaces of end-pumped Nd:YVO4 laser
(2020-05-26)
Lin, Shou-Tai
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Hung, Wei-Kuo
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Zhuo, Guan-Yu
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Wang, Hsien-Yi
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Chan, Ming-Che
This work describes non-invasive observations of dynamic thermal lensing in an end-pumped Nd:YVO4 laser. Measurements were obtained with a nanoscale optical ruler created using chromatic aberrations, pinholes, dispersive gratings, and position-sensitive detectors. This study reports on variations in thermally induced oscillations and on underdamping behavior in the regime of high pump power. Dynamic data related to the thermal behavior can be used to study the balance between driving forces (pumping and thermal stresses) and damping losses (cooling and output coupling). The non-invasive nature of the proposed scheme along with its sub-100-nm axial resolution, sub-millisecond time resolution, and simple configuration makes it widely applicable for studying heat-related phenomena within laser crystals. The preliminary results show that such non-invasive methods could be used to detect thermally induced nanoscale deformations in integrated circuits, high-power optoelectronic devices, and optical devices with high-power illumination.
Scanning Moire Fringe Method: A Superior Approach to Perceive Defects, Interfaces, and Distortion in 2D Materials
(2020-05-26)
Lin, Yung-Chang
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Ji, Hyun Goo
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Chang, Li-Jen
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Chang, Yao-Pang
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Liu, Zheng
Scanning moire fringe (SMF) is a widely utilized technique for the precise measurement of the strain field in semiconductor transistors and heterointerfaces. With the growing challenges of traditional chip scaling, two-dimensional (2D) materials turn out to be ideal candidates for incorporation into semiconductor devices. Therefore, a method to efficiently locate defects and grain boundaries in 2D materials is highly essential. Here, we present a demonstration of using the SMF method to locate the domain boundaries at the nearly coherent interfaces with sub-angstrom spatial resolution under submicron fields of views. The strain field of small angle grain boundary and lateral heterojunction are instantaneously found and precisely determined by a quick SMF method without any atomic resolution images.
Accounting for air pollution emissions and transport policy in the measurement of the efficiency and effectiveness of bus transits
(2020-05-27)
Kang, Chao-Chung
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Feng, Cheng-Min
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Liao, Bo-Ruei
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Khan, Haider A.
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運輸與物流管理系註：原交通所+運管所
This study presents a two-stage network performance evaluation model that determines the efficiency and effectiveness of bus transit systems. The model accounts for non-storable service features, undesirable outputs, and transport policy factors. The Taipei bus transit system is presented as an empirical case to measure the performance of bus transits with and without consideration of carbon dioxide (CO2) emissions and the transfer of riders. The results show that CO2 emissions and the transfer of riders are important factors for a performance evaluation model. Failure to include these results in an incomplete evaluation. Rather than focusing solely on marketable outputs, government agencies and managers must consider undesirable outputs or transport policy factors that relate to bus transits when measuring the efficiency and effectiveness of bus transits.
Photo-induced electrodeposition of metallic nanostructures on graphene
(2020-05-28)
Xia, Kangwei
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Chiang, Wei-Yi
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de la Rosa, Cesar Javier Lockhart
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Fujita, Yasuhiko
;
Toyouchi, Shuichi
Graphene, a single atomic layer of sp(2)hybridized carbon, is a promising material for future devices due to its excellent optical and electrical properties. Nevertheless, for practical applications, it is essential to deposit patterned metals on graphene in the micro and nano-meter scale in order to inject electrodes or modify the 2D film electrical properties. However, conventional methods for depositing patterned metals such as lift-off or etching leave behind contamination. This contamination has been demonstrated to deteriorate the interesting properties of graphene such as its carrier mobility. Therefore, to fully exploit the unique properties of graphene, the controlled and nano-patterned deposition of metals on graphene films without the use of a sacrificial resist is of significant importance for graphene film functionalization and contact deposition. In this work, we demonstrate a practical and low-cost optical technique of direct deposition of metal nano-patterned structures without the need for a sacrificial lift-off resist. The technique relies on the laser induced reduction of metal ions on a graphene film. We demonstrate that this deposition is optically driven, and the resolution is limited only by the diffraction limit of the light source being used. Patterned metal features as small as 270 nm in diameter are deposited using light with a wavelength of 532 nm and a numerical aperture of 1.25. Deposition of different metals such as Au, Ag, Pd, Pb and Pt is shown. Additionally, change in the Fermi level of the graphene film through the nano-patterned metal is demonstrated through the electrical characterization of four probe field effect transistors.
Quantum yields of singlet and triplet chemiexcitation of dimethyl 1,2-dioxetane: ab initio nonadiabatic molecular dynamic simulations
(2020-05-28)
Yue, Ling
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Yu, Le
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Xu, Chao
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Zhu, Chaoyuan
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Liu, Yajun
The global nonadiabatic switching on-the-fly trajectory surface hopping simulation at the 8SA-CASSCF quantum level has been performed to estimate the quantum yield of chemiexcitation for the uncatalyzed decomposition reaction of the open-shell biradical trans-3,4-dimethyl-1,2-dioxetane system. The present ab initio nonadiabatic molecular dynamic simulation involving both conical intersection and intersystem crossing is to compute for the first time the population evolution of quantum yields at the four lowest singlet and four lowest triplet states. The simulated results demonstrate not only the stepwise dissociation of O-O and C-C bond breaking, but also confirm the existence of a biradical entropic trap which is responsible for chemiexcitation. The simulated quantum yield of the triplet chemiexcitation phi(T1) = 0.266 +/- 0.096 agrees with the experimental value of 0.20 +/- 0.04 very well. The present nonadiabatic molecular dynamic simulation of dimethyl 1,2-dioxetanes provides a further advanced understanding and stepping stone for future studies on chemi- and bio-luminescence.
陽明與華碩AICS推動「華陽計畫」，為台灣智慧醫療培育專才
(國立陽明大學, 2020-05-29)
陽明電子報編輯小組
醫療人工智慧如何更有效的掌握醫療大數據，創造多元而有價值的照護體系，備受期待。華碩AI研發中心AICS於5月19日宣布與國立陽明大
45周年校慶日，郭校長率年輕教師韓園獻花
(國立陽明大學, 2020-05-29)
陽明電子報編輯小組
5月15日是陽明45周年校慶日，郭旭崧校長特地邀請45歲以下的年輕老師，一起到韓園獻花，向創校的韓偉院長致意；一方面緬懷陽明創校
Organ-on-a-Chip: Opportunities for Assessing the Toxicity of Particulate Matter
(2020-05-29)
Yang, Jia-Wei
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Shen, Yu-Chih
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Lin, Ko-Chih
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Cheng, Sheng-Jen
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Chen, Shiue-Luen
Recent developments in epidemiology have confirmed that airborne particulates are directly associated with respiratory pathology and mortality. Although clinical studies have yielded evidence of the effects of many types of fine particulates on human health, it still does not have a complete understanding of how physiological reactions are caused nor to the changes and damages associated with cellular and molecular mechanisms. Currently, most health assessment studies of particulate matter (PM) are conducted through cell culture or animal experiments. The results of such experiments often do not correlate with clinical findings or actual human reactions, and they also cause difficulty when investigating the causes of air pollution and associated human health hazards, the analysis of biomarkers, and the development of future pollution control strategies. Microfluidic-based cell culture technology has considerable potential to expand the capabilities of conventional cell culture by providing high-precision measurement, considerably increasing the potential for the parallelization of cellular assays, ensuring inexpensive automation, and improving the response of the overall cell culture in a more physiologically relevant context. This review paper focuses on integrating the important respiratory health problems caused by air pollution today, as well as the development and application of biomimetic organ-on-a-chip technology. This more precise experimental model is expected to accelerate studies elucidating the effect of PM on the human body and to reveal new opportunities for breakthroughs in disease research and drug development.
【完美求職系列講座】斜槓青年真本事，成功的意願
(國立陽明大學, 2020-05-29)
陽明電子報編輯小組
斜槓世代來臨，你，準備好了嗎？你希望你的人生是直線進行嗎.
【109年實驗動物福祉和動物權】
(國立陽明大學, 2020-05-29)
陽明電子報編輯小組
課程內容為有關動物保護法，實驗動物相關福祉和動物權之介紹。
「敘事心理學讀書會」讀書筆記
(國立陽明大學, 2020-05-29)
許伶楓
;
陽明電子報編輯小組
【陽明45周年校慶五大特展】
(國立陽明大學, 2020-05-29)
陽明電子報編輯小組
歡慶45周年校慶，校慶期間特推出五大特展，完整呈現陽明45年來的成長與成果，希望讓所有陽明人一起感受「陽明45．展翅飛舞」的...
人社院嚴偉哲老師獲選科技部「年度十大科研破壞性創新論文」
(國立陽明大學, 2020-05-29)
陽明電子報編輯小組
本校人社中心嚴偉哲（Jonathon Hricko）副教授與中正大學哲學系陳瑞麟講座教授，合著之〈實驗個體化與哲學的零散論證〉（Experime...
【高中生大數據能力探索】養成班
(國立陽明大學, 2020-05-29)
陽明電子報編輯小組
隨著AI人工智慧的發展，大數據探索能力愈來愈重要。為了讓高中
Formation and IR spectrum of monobridged Si2H4 isolated in solid argon
(2020-05-29)
Lin, Shu-Yu
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Chou, Sheng-Lung
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Lin, Meng-Yeh
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Huang, Wen-Jian
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Huang, Tzu-Ping
The infrared (IR) spectrum of monobridged Si2H4 (denoted as mbr-Si2H4) isolated in solid Ar was recorded, and a set of lines (in the major matrix site) observed at 858.3 cm(-1), 971.5 cm(-1), 999.2 cm(-1), 1572.7 cm(-1), 2017.7 cm(-1), 2150.4 cm(-1), and 2158.4 cm(-1) were characterized. The species was produced by the electron bombardment of an Ar matrix sample containing a small proportion of SiH4 during matrix deposition. Upon photolysis of the matrix samples using 365 nm and 160 nm light, the content of mbr-Si2H4 increased. The band positions, relative intensity ratios, and D-isotopic shift ratios of the observed IR features are generally in good agreement with those predicted by the B3LYP/aug-cc-pVTZ method. In addition, the photochemistry of the observed products was discussed.