Browsing by Issue Date, starting with "2017-11-13"

Now showing 1 - 20 of 12767

Lasing on nonlinear localized waves in curved geometry
(2017-11-13)
Hong, Kou-Bin
;
Lin, Chun-Yan
;
Chang, Tsu-Chi
;
Liang, Wei-Hsuan
;
Lai, Ying-Yu
The use of geometrical constraints exposes many new perspectives in photonics and in the fundamental studies of nonlinear waves. By implementing surface structures in vertical cavity surface emitting lasers as manifolds for curved space, we experimentally study the impacts of geometrical constraints on nonlinear wave localization. We observe localized waves pinned to the maximal curvature in an elliptical-ring, and confirm the reduction in the localization length of waves by measuring near and far field patterns, as well as the corresponding energy-angle dispersion relation. Theoretically, analyses based on a dissipative model with a parabola curve give good agreement remarkably to experimental measurement on the reduction in the localization length. The introduction of curved geometry allows to control and design lasing modes in the nonlinear regime. (C) 2017 Optical Society of America
Effects of Position and Electronic Nature of Substituents on Cobalt-Porphyrin-Catalyzed Hydrogen Evolution Reaction
(2017-11-13)
Beyene, Belete B.
;
Mane, Sandeep B.
;
Leonardus, Mario
;
Hung, Chen-Hsiung
;
交大名義發表
Cobalt(II) porphyrins bearing ortho/para-amino and ortho-nitro groups at meso-phenyl rings have been prepared and employed for catalytic hydrogen generation. Electrochemical and catalytic studies show that position and electronic nature of the substituents strongly affect catalytic activity and overpotential of catalysis. Our study reveals that the complex with ortho-aminophenyl substituents on porphyrin core displays higher activity toward H-2 evolution with rate constant of 1.1 x 10(5) M-1 s(-1) at onset potential close to thermodynamic reduction potential of trifluoroacetic acid (TFA), and 89% efficiency. On the other hand, the reactions involving cobalt porphyrins with para-aminophenyl or ortho-nitrophenyl groups showed lower or no activity under the same experimental conditions, implying the significant role of pendant ortho-amino groups in accelerating the intramolecular proton transfer and the proton-hydride interactions to thermodynamically favor H-2 evolution.
Exploiting birefringent thermal lensing effect to manipulate polarization states of an Nd:YVO4 self-mode-locked laser
(2017-11-13)
Tuan, P. H.
;
Tsai, M. C.
;
Chen, Y. F.
;
電子物理學系
;
Department of Electrophysics
An Nd:YVO4 laser with a convex-plano cavity is systematically studied to demonstrate the manipulation of output polarization state by using the birefringent thermal lensing effect of the gain crystal. Based on the theoretical analysis of the cavity stability under the influence of thermal lens, the polarization state of output emission is experimentally confirmed that can be controlled to switch from pure pi- to pure sigma-polarization by simply varying the pump focus position from the tight-focusing to defocusing conditions. More importantly, it is found that there exists an adequate pump focus position within the switching region to lead the pi- and sigma-polarization to have balanced gain for achieving a stable self-mode-locked laser with orthogonally polarized components. Under the orthogonally polarized mode-locked operation, the pulse repetition rates are found to be 2.23 and 2.33 GHz for the pi- and sigma-polarization with pulse duration to be 16.1 and 15.1 ps, respectively. (C) 2017 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
Optimal coloring for data collection in tree-based wireless sensor networks
(2017-11-14)
Lo, Shih-Ming
;
Lin, Wu-Hsiung
;
Chen, Chiuyuan
;
Tseng, Yu-Ghee
;
應用數學系
Data collection is an important operation in a wireless sensor network (WSN). During data collection, the interference among nodes cannot be ignored. In a multi-hop WSN, one conventional way of defining interference neighbors is to prohibit a node from using the same time slot as those of its 1-hop and 2-hop neighbors. Recently, it is proved that for data collection in a WSN, since the set of communication nodes is limited and the transmission directions are toward the sink, a less strict set of interference neighbors can be defined [16]. The interference problem in a duty-cycle WSN (DC-WSN) with a corona structure is studied in [7]. In this paper, we solve the same problem by using the relaxed interference set defined in [16]. In particular, we give a complete classification of non-interference sets in 2-hop neighbors. We also propose a distributed 6-coloring algorithm. We prove a lower bound of six colors that every tree-based data collection algorithm requires in a dense DC-WSN, which proves our algorithm to be optimal. (C) 2017 Elsevier B.V. All rights reserved.
Equalization of PAM-4 Signal Generated by Silicon Microring Modulator for 64-Gbit/s Transmission
(2017-11-15)
Tzu, T. C.
;
Hsu, Y.
;
Chuang, C. Y.
;
Wu, X.
;
Chow, C. W.
We propose and demonstrate a 64-Gbit/s four-level pulse-amplitude-modulation transmission by using a limited modulation bandwidth silicon microring modulator (SiMRM) and the Volterra equalization scheme. Severe intersymbol interference caused by both the chromatic dispersion of the optical fiber and the bandwidth limitation of components can be compensated. Besides, several equalization schemes are compared and analyzed in terms of performance and complexity. In addition, the design and characteristics of the SiMRM used in the experiment are also discussed.
Extremality of numerical radii of matrix commutators and Jordan products
(2017-11-15)
Gau, Hwa-Long
;
Wang, Kuo-Zhong
;
應用數學系
;
Department of Applied Mathematics
It is known that the numerical radius of the commutator (resp., Jordan product) AB - BA (resp., AB + BA) of two n-by-n matrices A and B is related to those of A and B by w(AB +/- BA) <= 4w(A)w(B). In this paper, we give complete characterizations of A and B for which the equality is attained. The matrices involved can be considered as elaborate generalizations of the equality-attaining A = [0 a (0 0)] and B = [0 0 (b) (0)]. (C) 2017 Elsevier Inc. All rights reserved.
Numerical ranges of products of two positive contractions
(2017-11-15)
Gau, Hwa-Long
;
Wu, Pei Yuan
;
應用數學系
;
Department of Applied Mathematics
Let A and B be positive contractions on a Hilbert space. It was known before that the numerical range W(AB) of their product is contained in the rectangular region [-1/8,1] x [-1/4,1/4]. In this paper, we determine exactly when W(AB) touches on its four sides. This follows from the more general information on a containing region of W(AB) and on when they share a common tangent line. We also give an example of A and B on three-dimensional space for which W (AB) is not symmetric with respect to the x-axis. (C) 2017 Elsevier Inc. All rights reserved.
Supply chain optimization of forest biomass electricity and bioethanol coproduction
(2017-11-15)
Liu, Wan-Yu
;
Lin, Chun-Cheng
;
Yeh, Tzu-Lei
;
工業工程與管理學系
;
Department of Industrial Engineering and Management
To establish a systematic and efficient forest bioenergy supply chain management system, most previous related studies did not investigate a system that involves generating two or more types of energy simultaneously, and did not consider the carbon emissions caused by electricity power generation of forest biomass combustion. Consequently, this study addressed the problems regarding the tactical supply chain optimization of a forest biomass electricity and second-generation bioethanol coproduction plant. A mixed-integer linear programming model was employed to determine the optimal production strategies to maximize the profit and to minimize the carbon emissions cost. The advantages of coproduction include enabling equipment and facility sharing, reducing investment costs, and dispersing the risks that involve raw materials, leading to synergy. Empirical simulation results indicated that the coproduction model yielded more profit than the independently operated model. When electricity demand is reduced, the coproduction model mitigates its profit losses through an increase in its bioethanol production. However, when faced with an increase in carbon emission costs, the coproduction model loses its advantages. According to the sensitivity analysis, electricity prices are the most vital parameter to the profit of the model, followed sequentially by the higher heating value of raw materials and carbon emission costs. (C) 2017 Elsevier Ltd. All rights reserved.
Chemical structures of extra- and intra-cellular algogenic organic matters as precursors to the formation of carbonaceous disinfection byproducts
(2017-11-15)
Hua, Lap-Cuong
;
Lin, Jr-Lin
;
Chen, Pei-Chung
;
Huang, Chihpin
;
環境工程研究所
Algal eutrophication in reservoirs is frequently accompanied by a remarkable increase in the concentration of algogenic organic matter (AOM). Because AOM is well-known as an important precursor to disinfection by-products (DBPs) in drinking water, algal eutrophication poses severe concerns for public health. This study aimed to characterize the chemical properties of AOM from two major origins, i.e. extra-(EOM) and intracellular organic matter (IOM), of a commonly found green alga Chlorella sp. as precursors to trihalomethanes (THMs) and haloacetic acids (HAAs). Particularly, the corresponding relation between the chemical functional structure of EOM and IOM and their THM and HAA formation potential (THMFP and HAAFP) was comprehensively investigated. Results show that IOM chiefly comprised of aromatic and other aliphatic protein-like materials (high organic nitrogen content) those have high activity for chlorine substitution (high UV253/UV203 value) due to the high hydroxyl and amide contents in its chemical structures. EOM alternatively exhibited the characteristics of humic-and fulvic-like materials accompanying with high DOC/DON ratio and aromaticity. However, the chemical structure of EOM had a low tendency for chlorine substitution (low UV253/UV203 value); it was also accompanied by a considerable content of carboxylic moisture, which likely resulted in an unfavorable substitution reaction of EOM with chlorine. As a result, the carbonaceous DBP formation potential (C-DBPFP) showed that IOM yielded higher levels of both THMFP and HAAFP than that yielded by EOM.
恐懼的年代　
(2017-11-19)
戴葦婷
;
Department of Communication and Technology
;
傳播與科技學系
在景美人權文化園區走進那令人恐懼的年代。
多元文化大雜燴　西門鬧區
(2017-11-19)
黃郁庭
;
Department of Communication and Technology
;
傳播與科技學系
以照片呈現有著各式文化的西門町街頭。
於是我就這麼睡去
(2017-11-19)
郭庭芸
;
Department of Communication and Technology
;
傳播與科技學系
我總是在不應該睡著的時候睡著。以這樣的煩惱出發，我想做一些無理頭的插畫與小動畫。
漂流
(2017-11-19)
簡文怡
;
Department of Communication and Technology
;
傳播與科技學系
對世界的害怕需要一個出口，我們值得被溫柔地接住嗎？
堅持對的事　呂植的保育之路
(2017-11-19)
葉宜瑩
;
Department of Communication and Technology
;
傳播與科技學系
呂植為「山水自然保護中心」創辦人，早期因保育熊貓而聞名，現在將視野擴大到保育其他物種。
惜食減塑推手　黃尚衍
(2017-11-19)
簡嘉瑩
;
Department of Communication and Technology
;
傳播與科技學系
捨棄食材的華麗包裝，只剩對夢想的堅持和對這塊土地的熱愛。
夢
(2017-11-19)
巫尹文
;
Department of Communication and Technology
;
傳播與科技學系
送給一個月前為了夢想而哭泣的自己。
基因轉殖大突破　泡泡龍新契機
(2017-11-19)
謝瀚陞
;
Department of Communication and Technology
;
傳播與科技學系
基因轉殖的技術讓罕見的遺傳性疾病患者看到了機會的曙光。
創作者新天地　手感市集
(2017-11-19)
楊巧柔
;
Department of Communication and Technology
;
傳播與科技學系
好好手感微笑市集，於遊客眾多的新北投捷運站旁進行設攤，吸引路過遊客前來參觀選購，提供創作者管道進行商品展示與販售。
棉花糖女孩當道嗎？
(2017-11-19)
楊佩臻
;
Department of Communication and Technology
;
傳播與科技學系
近年來「棉花糖女孩」的形象似乎越來越受歡迎，自信散發出的美才是最重要的，然而，人們真的不再以「瘦」為美了嗎？
總編輯的話
(2017-11-19)
顏維萱
;
Department of Communication and Technology
;
傳播與科技學系
本期為喀報275期，稿件數量共19件；其中包含社會議題1篇，人物特寫3篇，科技新知1篇，文化現象2篇，照片故事6篇以及自由創作6篇。本期頭題為楊佩臻的文化現象——「棉花糖女孩當道嗎？」，探討用來形容女性微胖身形「棉花糖女孩」一詞，其流行是否取代了「瘦即是美」的審美價值。