Browsing by Issue Date, starting with "2020-03-23"

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Unidirectional Charge Transport via Ripplonic Polarons in a Three-Terminal Microchannel Device
(2020-03-23)
Badrutdinov, A. O.
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Rees, D. G.
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Lin, J. Y.
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Smorodin, A., V
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Konstantinov, D.
We study the transport of surface electrons on superfluid helium through a microchannel structure in which the charge flow splits into two branches, one flowing straight and one turned at 90 degrees. According to Ohm's law, an equal number of charges should flow into each branch. However, when the electrons are dressed by surface excitations (ripplons) to form polaronlike particles with sufficiently large effective mass, all the charge follows the straight path due to momentum conservation. This surface-wave induced transport is analogous to the motion of electrons coupled to surface acoustic waves in semiconductor 2DEGs.
Facile and One-Step in Situ Synthesis of Pure Phase Mesoporous Li2MnSiO4/CNTs Nanocomposite for Hybrid Supercapacitors
(2020-03-23)
Kumar, Nagesh
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Singh, Meetesh
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Kumar, Amit
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Tseng, Tseung-Yuen
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Sharma, Yogesh
In material sciences, synergistic effect and nanostructuring are the two factors which enable researchers to look beyond the conventionally defined categories of the materials. Here, we report the synthesis mechanism of pure phase mesoporous Li2MnSiO4 (LMS) with a high specific surface area by varying the concentration of metal precursors and solvents in one-step hydrothermal technique. Furthermore, the effect of MWCNTs addition on the electrochemical performance of LMS is studied. The quantitative contribution of current generating from EDLC and/or the surface pseudocapacitance reactions, and the current caused by diffusion-controlled redox reactions in the total current is also evaluated. The pure phase LMS/CNTs nanocomposite with 2% MWCNTs (abbreviated as LMS2C) is found to be the best supercapacitor material among studied nanocomposites as it exhibits specific capacitance of similar to 290 F g(-1) @ 1 A g(-1), good rate capability, small relaxation time constant (tau = 87 ms), and higher diffusion coefficient of electrolytic cations (D-k(+) = 9.4 x 10(-9) cm(2) s(-1)) in 2 M KOH aqueous electrolyte. A hybrid supercapacitor cell (HSC) designed using LMS2C as positive and activated carbon as negative electrodes shows the maximum energy density of 31 W h kg(-1), which is much higher than several recently reported hybrid supercapacitor systems. Two series connected HSCs can power a drone motor and light up 8 red LEDs for more than 3 min, indicating practical applicability of our designed hybrid supercapacitor system.
An In-situ and Direct Confirmation of Super-Planckian Thermal Radiation Emitted From a Metallic Photonic-Crystal at Optical Wavelengths
(2020-03-23)
Lin, Shawn-Yu
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Hsieh, Mei-Li
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John, Sajeev
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Frey, B.
;
Bur, James A.
Planck's law predicts the distribution of radiation energy, color and intensity, emitted from a hot object at thermal equilibrium. The Law also sets the upper limit of radiation intensity, the blackbody limit. Recent experiments reveal that micro-structured tungsten can exhibit significant deviation from the blackbody spectrum. However, whether thermal radiation with weak non-equilibrium pumping can exceed the blackbody limit in the far field remains un-answered experimentally. Here, we compare thermal radiation from a micro-cavity/tungsten photonic crystal (W-PC) and a blackbody, which are both measured from the same sample and also in-situ. We show that thermal radiation can exceed the blackbody limit by >8 times at lambda = 1.7 mu m resonant wavelength in the far-field. Our observation is consistent with a recent calculation by Wang and John performed for a 2D W-PC filament. This finding is attributed to non-equilibrium excitation of localized surface plasmon resonances coupled to nonlinear oscillators and the propagation of the electromagnetic waves through non-linear Bloch waves of the W-PC structure. This discovery could help create super-intense narrow band thermal light sources and even an infrared emitter with a laser-like input-output characteristic.
Heat Transfer of Semicrystalline Nylon Nanofibers
(2020-03-24)
Chien, Hsin-Che
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Peng, Wei-Tsu
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Chiu, Te-Hsuan
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Wu, Pei-Hsiu
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Liu, Yueh-Ju
Polymers are generally regarded as thermal insulators. The efficient heat transfer observed in the low-dimensional polymers in the literature mainly result from the larger crystallinity or improved polymer chain orientation in the low-dimensional polymers. However, the role of the amorphous domain on heat transfer in polymers remains unexplored. In this work, we report that the semicrystalline nylon polymer nanofibers can exhibit a very large thermal conductivity of 59.1 +/- 3.1 W m(-1) K-1 and the heat transfer in the semicrystalline polymer nanofibers was time-dependent. The thermal conductivity of the nanofibers could be modulated to span 3 orders of magnitude from being nearly insulated (similar to 0.27 +/- 0.02 W m(-1) K-1) to being highly thermal conductive after annealing (similar to 59.1 +/- 3.1 W m(-1) K-1). The time-dependent thermal conductivity was observed at a temperature lower than the gamma transition temperature of the polymer and was a result of the physical aging of the semicrystalline polymer. A phenomenological model was adopted to explain the time-dependent heat transfer of the semicrystalline nanofibers. The physical aging reduced the configuration disorder in the polymer and caused the heat transfer of the semicrystalline polymer to increase during the annealing process.
Exploring career commitment and turnover intention of high-tech personnel: a socio-cognitive perspective
(2020-03-25)
Lin, Chieh-Peng
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經營管理研究所
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Institute of Business and Management
Drawing upon social cognitive theory, this study presents psychosocial functioning in which personal factors and social influences jointly influence career commitment as a mediator and then turnover intention as an outcome among high-tech personnel. Based on a two-wave survey of working professionals in high-tech industry, this study's empirical results find that passion, social support, and perceived self-centered leadership indirectly relate to turnover intention through the full mediation of career commitment. At the same time, the effects of job self-efficacy and social support on career commitment are moderated respectively by passion. Finally, managerial implications and research limitations are discussed.
Combinational Approach To Realize Highly Efficient Light-Emitting Electrochemical Cells
(2020-03-25)
Yi, Rong-Huei
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Lo, Chieh-Liang
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Luo, Dian
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Lin, Chien-Hsiang
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Weng, Shu-Wen
Light-emitting electrochemical cells (LECs) show high technical potential for display and lighting utilizations owing to the superior properties of solution processability, low operation voltage, and employing inert cathodes. For maximizing the device efficiency, three approaches including development of efficient emissive materials, optimizing the carrier balance, and maximizing the light extraction have been reported. However, most reported works focused on only one of the three optimization approaches. In this work, a combinational approach is demonstrated to optimize the device efficiency of LECs. A sophisticatedly designed yellow complex exhibiting a superior steric hindrance and a good carrier balance is proposed as the emissive material of light-emitting electrochemical cells and thus the external quantum efficiency (EQE) is up to 13.6%. With an improved carrier balance and reduced self-quenching by employing the host-guest strategy, the device EQE can be enhanced to 16.9%. Finally, a diffusive layer embedded between the glass substrate and the indium-tin-oxide layer is utilized to scatter the light trapped in the layered device structure, and consequently, a high EQE of 23.7% can be obtained. Such an EQE is impressive and consequently proves that the proposed combinational approach including adopting efficient emissive materials, optimizing the carrier balance, and maximizing the light extraction is effective in realizing highly efficient LECs.
Lattice distortion effect on elastic anisotropy of high entropy alloys
(2020-03-25)
Yen, Chao-Chun
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Huang, Guan-Rong
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Tan, Yun-Cheng
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Yeh, Han-Wen
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Luo, Da-Ji
The superior mechanical properties of high-entropy alloys (HEAs) have made an outstanding success in materials science and engineering. Studies to date have been devoted to what the severe lattice distortion induces. However, most researchers focus on its stimulation to plastic deformation instead of scrutinizing the variations on elasticity. Compared with conventional alloys, HEAs may perform disproportionate elasticity with uneven local lattice strain resulting from the severe lattice distortion. Therefore, it is necessary to survey its influence on the mechanical properties of HEAs systematically. In this study, the Lennard-Jones (LJ) potential, the embedded atom method (EAM) potential, and the modified embedded atom method (MEAM), are respectively conducted to investigate the lattice distortion effect on Young's modulus E (hkl) and Poisson's ratio nu (hkl, theta) along [100], [110], and [111] loading directions for several fcc metals composed of 1 similar to 5 atomic types, including Ni, Ni98W2, Ni96W4, FeCrNi, and CoNiCrFeMn HEAs. Also, a method is used to analyze the performance of the individual element on the elastic properties in the HEA environment. As a result, it can be unveiled that the effect of electron density inconsistency is more dominant than the effect of lattice distortion associated with the atomic size difference. The electronic configuration in the HEA environment plays a major role in elastic anisotropy while the difference of the atomic radii does the minor one. The anisotropy of CoNiCrFeMn HEA analyzed by this work is also consistent with in-situ neutron diffraction measurements. (C) 2019 Elsevier B.V. All rights reserved.
Evolving Crystal Morphology of Potassium Chloride Controlled by Optical Trapping
(2020-03-26)
Cheng, An-Chieh
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Masuhara, Hiroshi
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Sugiyama, Teruki
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交大名義發表
;
應用化學系
Dynamic morphology evolution of potassium chloride (KCl) crystals was demonstrated by surface optical trapping with a focused continuous-wave near-infrared laser. Optical trapping at an air/solution interface triggered the crystallization, and then, the dynamic change in crystal morphology was observed in real time. We observed three different crystal morphologies of needle, rectangle, and cubic at the early stage of crystallization. As the laser power increases, the probability of generation of a cubic crystal increases, especially upon the irradiation with linear polarization. We also found laser polarization-dependent morphology evolution by the continuous irradiation to the generated crystals. Upon linearly polarized laser irradiation, the stepwise morphology evolves from needle to rectangle, and eventually to cubic, which is an equilibrium shape of KCl crystals. Meanwhile, circularly polarized laser irradiation only induced morphology evolution from needle to rectangle, without morphology change into cubic, because the rectangle crystal was dissolved while the crystal was rotating. It was made possible to observe such a unique morphological evolution due to the spatiotemporal controllability of our crystallization method. The dynamics and mechanism of these intriguing phenomena are discussed from the perspective of a dense cluster domain formed by optical trapping before nucleation.
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(國立陽明大學, 2020-03-27)
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【藝文中心展覽延期公告】
(國立陽明大學, 2020-03-27)
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陽明大學109年暑期營隊起跑囉！！
(國立陽明大學, 2020-03-27)
陽明電子報編輯小組
暑期即將來臨，本校各研習營係以推廣醫學教育、生物醫學教育及人文教育等領域為目的，將於今年7月10日至8月8日區分成四大營隊，以協助學生確立其生涯志向，歷年來活動成效深獲社會各界之肯定。參與對象包括高中及大專院校學生，學員透過暑期營隊課程，學習不同領域的專業知識，並提前體驗大學生活，更藉此充實暑假。
【109學年度宿舍幹部選舉】
(國立陽明大學, 2020-03-27)
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正向視壓，成功釋壓
(國立陽明大學, 2020-03-27)
程千芳
;
陽明電子報編輯小組