Browsing by Issue Date, starting with "2016-03-02"

Now showing 1 - 20 of 17842

Antisite disorder driven spontaneous exchange bias effect in La2-xSrxCoMnO6 (0 <= x <= 1)
(2016-03-02)
Murthy, J. Krishna
;
Chandrasekhar, K. D.
;
Wu, H. C.
;
Yang, H. D.
;
Lin, J. Y.
Doping at the rare-earth site by divalent alkaline-earth ions in perovskite lattice has witnessed a variety of magnetic and electronic orders with spatially correlated charge, spin and orbital degrees of freedom. Here, we report an antisite disorder driven spontaneous exchange bias effect as a result of hole carrier (Sr2+) doping in La2-xSrxCoMnO6 (0 < x < 1) double perovskites. X-ray diffraction and Raman spectroscopy have evidenced an increase in disorder with the increase of Sr content up to x = 0.5 and thereby a decrease from x = 0.5 to 1. X-ray absorption spectroscopy has revealed that only Co is present in the mixed valence of Co2+ and Co3+ states with Sr doping to compensate the charge neutrality. Magnetotransport is strongly correlated with the increase of antisite disorder. The antisite disorder at the B-site interrupts the long-range ferromagnetic order by introducing various magnetic interactions and instigates reentrant glassy dynamics, phase separation and canted type antiferromagnetic behavior with the decrease of temperature. This leads to a novel magnetic microstructure with unidirectional anisotropy that causes a spontaneous exchange bias effect that can be tuned with the amount of antisite disorder.
Wide Range pH-Tolerable Silicon@Pyrite Cobalt Dichalcogenide Microwire Array Photoelectrodes for Solar Hydrogen Evolution
(2016-03-02)
Chen, Chihjung
;
Yang, Kai-Chih
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Basu, Mrinmoyee
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Lu, Tzu-Hsiang
;
Lu, Ying-Rui
This study employed silicon@cobalt dichalcogenide micro wires (MWs) as wide range pH-tolerable photocathode material for solar water splitting. Silicon microwire arrays were fabricated through lithography and dry etching technologies. Si@Co(OH)(2) MWs were utilized as precursors to synthesize Si@CoX2 (X = S or Se) photocathodes. Si@CoS2 and Si@CoSe2 MWs were subsequently prepared by thermal sulfidation and hydrothermal selenization reaction of Si@Co(OH)(2), respectively. The CoX2 outer shell served as cocatalyst to accelerate the kinetics of photogenerated electrons from the underlying Si MWs and reduce the recombination. Moreover, the CoX2 layer completely deposited on the Si surface functioned as a passivation layer by decreasing the oxide formation on Si MWs during solar hydrogen evolution. Si@CoS2 photocathode showed a photocurrent density of -3.22 mA cm(-2) at 0 V (vs RHE) in 0.5 M sulfuric acid electrolyte, and Si@CoSe2 MWs revealed moderate photocurrent density of -2.55 mA cm(-2). However, Si@CoSe2 presented high charge transfer efficiency in neutral and alkaline electrolytes. Continuous chronoamperometry in acid, neutral, and alkaline solutions was conducted at 0 V (vs RHE) to evaluate the photoelectrochemical durability of Si@CoX2 MWs. Si@CoS2 electrode showed no photoresponse after the chronoamperometry test because it was etched through the electrolyte. By contrast, the photocurrent density of Si@CoSe2 MWs gradually increased to -5 mA cm(-2) after chronoamperometry characterization owing to the amorphous structure generation.
Enhanced external quantum efficiency in GaN-based vertical-type light-emitting diodes by localized surface plasmons
(2016-03-03)
Yao, Yung-Chi
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Hwang, Jung-Min
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Yang, Zu-Po
;
Haung, Jing-Yu
;
Lin, Chia-Ching
Enhancement of the external quantum efficiency of a GaN-based vertical-type light emitting diode (VLED) through the coupling of localized surface plasmon (LSP) resonance with the wave-guided mode light is studied. To achieve this experimentally, Ag nanoparticles (NPs), as the LSP resonant source, are drop-casted on the most top layer of waveguide channel, which is composed of hydrothermally synthesized ZnO nanorods capped on the top of GaN-based VLED. Enhanced light-output power and external quantum efficiency are observed, and the amount of enhancement remains steady with the increase of the injected currents. To understand the observations theoretically, the absorption spectra and the electric field distributions of the VLED with and without Ag NPs decorated on ZnO NRs are determined using the finite-difference time-domain (FDTD) method. The results prove that the observation of enhancement of the external quantum efficiency can be attributed to the creation of an extra escape channel for trapped light due to the coupling of the LSP with wave-guided mode light, by which the energy of wave-guided mode light can be transferred to the efficient light scattering center of the LSP.
Capillary hydrodynamic chromatography reveals temporal profiles of cell aggregates
(2016-03-03)
Tang, Ya-Ru
;
Huang, Hsin-Yi
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Hu, Jie-Bi
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Rattinam, Rajesh
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Li, Chun-Hsien
Microbial cells are known to form aggregates. Such aggregates can be found in various matrices; for example, functional drinks. Capillary hydrodynamic chromatography (HDC) enables separation of particles by size using nanoliter-scale volumes of samples. Here we propose an approach based on HDC for characterisation of real samples containing aggregated and non-aggregated bacterial and fungal cells. Separation of cells and cell aggregates in HDC arises from the parabolic flow profile under laminar flow conditions. In the presented protocol, hydrodynamic separation is coupled with different on-line and offline detectors (light absorption/scattering and microscopy). The method has successfully been applied in the monitoring of dynamic changes in the microbiome of probiotic drinks. Chromatographic profiles of yogurt and kefir samples obtained at different times during fermentation are in a good agreement with microscopic images. Moreover, thanks to the implementation of an area imaging detector, capillary HDC could be multiplexed and used to profile spatial gradients in cell suspensions, which arise in the course of sedimentation of cells and cell aggregates. This result shows compatibility of sedimentation analysis and capillary HDC. We believe that the approach may find applications in the profiling of functional foods and other matrices containing aggregated bioparticles. (C) 2016 Elsevier B.V. All rights reserved.
Leveraging Strategic Detection Techniques for Smart Home Pricing Cyberattacks
(2016-03-04)
Liu, Yang
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Hu, Shiyan
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Ho, Tsung-Yi
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資訊工程學系
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Department of Computer Science
In this work, the vulnerability of the electricity pricing model in the smart home system is assessed. Two closely related pricing cyberattacks which manipulate the guideline electricity prices received at smart meters are considered and they aim at reducing the expense of the cyberattacker and increasing the peak energy usage in the local community. A single event detection technique which uses support vector regression and impact difference for detecting anomaly pricing is proposed. The detection capability of such a technique is still limited since it does not model the long term impact of pricing cyberattacks. This motivates us to develop a partially observable Markov decision process based detection algorithm, which has the ingredients such as reward expectation and policy transfer graph to account for the cumulative impact and the potential future impact due to pricing cyberattacks. Our simulation results demonstrate that the pricing cyberattack can reduce the cyberattacker\'s bill by 34.3 percent at cost of the increase of others\' bill by 7.9 percent, and increase the peak to average ratio (PAR) by 35.7 percent. Furthermore, the proposed long term detection technique has the detection accuracy of more than 97 percent with significant reduction in PAR and bill compared to repeatedly using the single event detection technique.
Manipulating mimicked magnetosome chains produced Using superparamagnetic microbeads in a confined space
(2016-03-05)
Li, Yan-Hom
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Su, Ting-Yu
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Chang, Tien-Li
;
Lee, Ya-Wei
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機械工程學系
In this study, we investigated the dynamics of microchains containing superparamagnetic microbeads under the influence of oscillating magnetic fields in a confined space. The behavior of constrained microchains was investigated experimentally. Chains in confined spaces were first formed using a static directional field or a permanent magnet and then manipulated using an additional dynamical perpendicular field. An oscillating chain in a confined space can be designed to mimic magnetosome chains synthesized by magnetotactic bacteria, which have been exploited recently for various applications in biological and medical sciences. The effects of crucial parameters, such as the lengths of particle chains and sizes of confined spaces, were thoroughly analyzed to observe the distinct behavior and investigate the dynamics of the constrained chains. (C) 2016 Elsevier B.V. All rights reserved.
交大e-News第204期-IBM攜手交通大學培育大數據分析人才
(2016-03-07)
國立交通大學秘書室
;
Secretariat
Plasmonic behaviors of metallic AZO thin film and AZO nanodisk array
(2016-03-07)
Lin, Jia-Yu
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Zhong, Kun-Da
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Lee, Po-Tsung
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光電工程學系
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光電工程研究所
Aluminum-doped zinc oxide (AZO) is well known as transparent conducting material for electro-optical devices, but is rarely used as plasmonic material, particularly on the localized surface plasmon resonance (LSPR) behavior of AZO nanostructure and its plasmonic devices. In this study, we systematically investigate the plasmonic behaviors of AZO thin films and patterned AZO nanostructures with various structural dimensions under different annealing treatments. We find that AZO film can possess highly-tunable, metal-like, and low-loss plasmonic property and the LSPR characteristic of AZO nanostructure is observed in the near-infrared (NIR) region under proper annealing conditions. Finally, environmental index sensing is performed to demonstrate the capability of AZO nanostructure for optical sensing application. High index sensitivity of 873 nm per refractive index unit (RIU) variation is obtained in experiment. (C) 2016 Optical Society of America
Optical design for a see-through head-mounted display with high visibility
(2016-03-07)
Zhao, Kai-Wei
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Pan, Jui-Wen
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光電系統研究所
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照明與能源光電研究所
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Institute of Photonic System
An optical design for a see-through head-mounted display with high visibility is described. This design, which is based on a light guide plate with triangular microstructures, can overcome the limitations of the balance in optical efficiency. The optical efficiency of the virtual image can be larger than the optical efficiency of the real image, which ensures high visibility. The visibility can be increased to 22 with this design, much higher than the visibility possible with previous designs for a see-through head-mounted display, making this suitable for daily application. (C) 2016 Optical Society of America
Heavy-flavor-conserving hadronic weak decays of heavy baryons
(2016-03-07)
Cheng, Hai-Yang
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Cheung, Chi-Yee
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Lin, Guey-Lin
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Lin, Yeu-Chung
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Yan, Tung-Mow
More than two decades ago, we studied heavy-flavor-conserving weak decays of heavy baryons within the framework that incorporates both heavy-quark and chiral symmetries. In view of the first observation of Xi(-)(b) -> Lambda(0)(b)pi(-) by LHCb recently, we have reexamin Xi(-)(b) -> Lambda(0)(b)pi(-) in the MIT bag and diquark models are consistent with experiment. The major theoretical uncertainty stems from the evaluation of baryon matrix elements. The branching fraction of Xi(c)-> Lambda(c)pi is predicted to be of order 10(-4). It is suppressed relative to B(Xi(b) -> Lambda(b)pi) owing to the shorter lifetime of Xi(c) relative to Xi(b) and the destructive nonspectator W-exchange contribution. The kinematically accessible weak decays of the sextet heavy baryon Omega(Q) are Omega(Q) -> Xi(Q)pi. Due to the absence of the B-6 - B-(3) over bar transition in the heavy quark limit and the B-6 - B-6 transition in the model calculations, Omega(Q) -> Xi(Q)pi vanish in the heavy quark limit.
Novel porphyrin-preparation, characterization, and applications in solar energy conversion
(2016-03-07)
Lu, Jianfeng
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Li, Hao
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Liu, Shuangshuang
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Chang, Yu-Cheng
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Wu, Hui-Ping
Porphyrins have been demonstrated as one of the most efficient sensitizers in dye-sensitized solar cells (DSSC). Herein, we investigated a series of porphyrin sensitizers functionalized with various pi-spacers, such as phenyl for LD14, thiophene for LW4, thiophene-phenyl for LW5, and 2,1,3-benzothiadiazole (BTD)-phenyl for LW24. Photo-physical investigation by means of time-resolved fluorescence and nanosecond transient absorption spectroscopy revealed an accelerated inner charge transfer in porphyrins containing the BTD-phenyl pi-spacer. Implementation of an auxiliary electron-deficient BTD unit to the porphyrin spacer also results in a broad light-harvesting ability extending up to 840 nm, contributing to an enhanced charge transfer character from the porphyrin ring to the anchoring group. When utilized as a sensitizer in DSSCs, the LW24 device achieved a power conversion efficiency of 9.2%, higher than those based on LD14 or LW5 porphyrins (PCE 9.0% or 8.2%, respectively) but lower than that of the LW4 device (PCE 9.5%). Measurements of transient photovoltage decays demonstrate that the LW24 device features the up-shifted potential band edge of the conduction band of TiO2, but involves serious charge recombination in the dye/TiO2 interface. The findings provide insights into the molecular structure and the charge-transfer characteristics for designing efficient porphyrin sensitizers for DSSC applications.
THz emission from organic cocrystalline salt: 2, 6-diaminopyridinium-4-nitrophenolate-4-nitrophenol
(2016-03-07)
Tu, Chien-Ming
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Chou, Li-Hsien
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Chen, Yi-Cheng
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Huang, Ping
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Rajaboopathi, M.
We report few-cycle THz pulses emission from a novel organic crystal 2,6-diaminopyridinium-4-nitrophenolate-4-nitrophenol (DAP(+)NP(-)NP). The observed amplitude of the THz electric field from a DAP(+)NP(-)NP crystal is comparable with that from a ZnTesingle crystal under the same optical pumping conditions. Both the waveform and spectra of the THz radiation from DAP(+)NP(-)NP are similar to those from ZnTe. We conclude that a high quality DAP(+)NP(-)NP crystal would be a high potential candidate in THz generation and applications. (C) 2016 Optical Society of America
The Efficacy of Acupuncture in Post-Operative Pain Management: A Systematic Review and Meta-Analysis
(2016-03-09)
Wu, Ming-Shun
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Chen, Kee-Hsin
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Chen, I-Fan
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Huang, Shihping Kevin
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Tzeng, Pei-Chuan
Background Postoperative pain resulting from surgical trauma is a significant challenge for healthcare providers. Opioid analgesics are commonly used to treat postoperative pain; however, these drugs are associated with a number of undesirable side effects. Objective This systematic review and meta-analysis evaluated the effectiveness of acupuncture and acupuncture-related techniques in treating postoperative pain. Data Source MEDLINE, Cochrane Library, and EMBASE databases were searched until Sep 30, 2014. Study Eligibility Criteria Randomized controlled trials of adult subjects (>= 18 years) who had undergone surgery and who had received acupuncture, electroacupuncture, or acupoint electrical stimulation for managing acute post-operative pain were included. Results We found that patients treated with acupuncture or related techniques had less pain and used less opioid analgesics on Day 1 after surgery compared with those treated with control (P < 0.001). Sensitivity analysis using the leave-one-out approach indicated the findings are reliable and are not dependent on any one study. In addition, no publication bias was detected. Subgroup analysis indicated that conventional acupuncture and transcutaneous electric acupoint stimulation (TEAS) were associated with less postoperative pain one day following surgery than control treatment, while electroacupuncture was similar to control (P = 0.116). TEAS was associated with significantly greater reduction in opioid analgesic use on Day 1 post surgery than control (P < 0.001); however conventional acupuncture and electroacupuncture showed no benefit in reducing opioid analgesic use compared with control (P >= 0.142). Conclusion Our findings indicate that certain modes of acupuncture improved postoperative pain on the first day after surgery and reduced opioid use. Our findings support the use of acupuncture as adjuvant therapy in treating postoperative pain.
Dielectric Engineering of a Boron Nitride/Hafnium Oxide Heterostructure for High-Performance 2D Field Effect Transistors
(2016-03-09)
Zou, Xuming
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Huang, Chun-Wei
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Wang, Lifeng
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Yin, Long-Jing
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Li, Wenqing
A unique design of a hexagonal boron nitride (h-BN)/HfO2 dielectric heterostructure stack is demonstrated, with few-layer h-BN to alleviate the surface optical phonon scattering, followed by high-kappa HfO2 deposition to suppress Coulombic impurity scattering so that high-performance top-gated two-dimensional semiconductor transistors are achieved. Furthermore, this dielectric stack can also be extended to GaN-based transistors to enhance their performance.
Optical properties of one- and two-dimensional excitons in m-plane ZnO/MgZnO multiple quantum wells
(2016-03-09)
Chen, H. R.
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Tsai, C. Y.
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Huang, Y. C.
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Kuo, C. C.
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Hsu, H. C.
Five pairs of ZnO/Zn0.9Mg0.1O multiple quantum wells (MQWs) with fixed barrier thickness of 55 nm and three well widths of 4, 8 and 16 nm have been grown on m-plane sapphires by pulsed laser deposition. Due to 2D quantum confinement with decreasing well width, the emission of excitons bound to the basal-plane stacking faults, which are one-dimensionally confined in MQWs, encounters larger blue shift than that of the near-band edge excitons. Furthermore, remarkably reducing coupling of free excitons with A1 longitudinal optical phonons is closely correlated with increasing exciton binding energy but enhanced coupling of E-2-low phonons is a result of increasing interaction with the interface phonons with decreasing well width.
Picosecond Motional Relaxation of Nanoparticles in Femtosecond Laser Trapping
(2016-03-10)
Muramatsu, Masayasu
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Shen, Tse-Fu
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Chiang, Wei-Yi
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Usman, Anwar
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Masuhara, Hiroshi
Repetitive drag and release dynamics by impnlsive force is characteristic of optical trapping by femtosecond laser pulses. We studied the dynamics utilizing double pulse train and found that trapped polystyrene particles are ejected repetitively from the focal spot and its frequencies become less for longer interval of the pulse trains. The ejection changes drastically in a few-ps interval region, although particles cannot move appreciable distance in such a short time. It means that displacement of particles by a conventional diffusive motion is not dominant and another fast process has an important role in femtosecond pulse trapping. We also revealed that the silica nanoparticles shows a decay at few-ps, indicating that the picosecond decay is not due to a material property but considered to be a general dynamics. We propose that a picosecond relaxation process of inertia force of particles is important for understanding laser trapping dynamics by femtosecond laser pulses.
Optimization of a guided-mode resonance filter by varying the thickness of the buffer layer
(2016-03-10)
Hsu, Hsiang I.
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Wu, Po-Tsung
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Huang, Cheng-Sheng
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機械工程學系
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Department of Mechanical Engineering
In this Letter, we demonstrate that by adjusting the thickness of the buffer layer, the optical responses of a guided-mode resonance filter (GMRF) can be improved for sensor applications. The GMRF is fabricated using a replica molding with a plastic substrate and a UV-curable polymer. SiO2 buffer layers of different thicknesses are deposited before the waveguide-layer deposition. The sensitivity of the GMRFs decreasds slightly with-increasing SiO2 layer thickness. By contrast, the full width at half-maximum reduces substantially with increasing SiO2 layer thickness, resulting in the improvement of the overall figure of merit.
Live無邊界　實況浪潮來襲
(2016-03-13)
吳偉立
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Department of Communication and Technology
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傳播與科技學系
簡述實況的概況，並且分析台灣觀看實況的情形。
熟男熟女　越老越美麗
(2016-03-13)
謝萱穎
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Department of Communication and Technology
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傳播與科技學系
社會大眾面對老化大多抱持抗拒、逃避的態度，因為無法對「變老」感同身受，反而因此衍生更多對熟齡的傷害。
「紫爆」來襲　空汙知多少
(2016-03-13)
鄭宇茹
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Department of Communication and Technology
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傳播與科技學系
空氣汙染影響的不只是我們的活動，還有健康，關注相關議題找出保護自己也保護環境的方法。