Browsing by Issue Date, starting with "2018-07-09"

Now showing 1 - 20 of 10298

Establishment of the relationship between the electron energy and the electron injection for AlGaN based ultraviolet light-emitting diodes
(2018-07-09)
Zhang, Zi-Hui
;
Tian, Kangkai
;
Chu, Chunshuang
;
Fang, Mengqian
;
Zhang, Yonghui
This work establishes the relationship between the electron energy and the electron concentration within the multiple quantum wells (MQWs) for AlGaN based deep ultraviolet light-emitting diodes (DUV LEDs). The electron energy of different values can be obtained by modulating the Si doping concentration in the n-AlGaN layer and/or engineering the polarization induced interface charges. The modulated Si doping concentration in the n-AlGaN layer will cause the interface depletion region within which the electric field can be generated and then tunes the electron energy. The polarization induced charges and the polarization induced electric field can be obtained by stepwisely reducing the AlN composition for the n-AlGaN layer along the [0001] orientation. We find that the electron concentration in the MQWs can be increased once the electron energy is reduced to a proper level, which correspondingly improves the external quantum efficiency (EQE) for DUV LEDs. According to our investigations, it is more advisable to adopt the n-AlGaN layer with the stepwise AlN composition, which can make both the EQE and the wall plug efficiency high. (C) 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
Equivalence between Clar covering polynomials of single zigzag chains and tiling polynomials of 2 x n rectangles
(2018-07-10)
Langner, Johanna
;
Witek, Henryk A.
;
應用化學系
;
應用化學系分子科學碩博班
;
Department of Applied Chemistry
This paper offers a formal explanation of a rather puzzling and surprising equivalence between the Clar covering polynomials of single zigzag chains and the tiling polynomials of 2 x n rectangles for tilings using 1 x 2, 2 x 1 and 2 x 2 tiles. It is demonstrated that the set of Clar covers of single zigzag chains N(n - 1) is isomorphic to the set of filings of a 2 x n rectangle. In particular, this isomorphism maps Clar covers of N(n - 1) with k aromatic sextets to tilings of a 2 x n rectangle using k square 2 x 2 tiles. The proof of this fact is an application of the recently introduced interface theory of Clar covers. The existence of a similar relationship between the Clar covers of more general benzenoid structures and more general tilings of rectangles remains an interesting open problem in chemical graph theory. (C) 2018 Elsevier B.V. All rights reserved.
Joint server and network optimization toward load-balanced service chaining
(2018-07-10)
Minh-Tuan Thai
;
Lin, Ying-Dar
;
Lai, Yuan-Cheng
;
交大名義發表
;
資訊工程學系
Prior service chaining systems address server and network load balancing issues individually, which may not ensure efficient system performance. To this end, in this paper, we study the design, implementation, complexity analysis, and evaluation of Nearest First and Local-Global Transformation algorithm, which jointly supports server and network load balancing for chaining virtualized network functions (VNFs) in data center environment. The algorithm firstly constructs service chains by a greedy strategy, which both considers server and network latency. Then a searching technique, which replaces a selected VNF with another candidate and swaps the order of VNFs in service chains, is applied to improve the solutions. We have implemented the algorithm using Software-defined networking and OpenFlow concepts. The numerical results indicate that, compared with a sequential approach, Nearest First and Local-Global Transformation increases the system bandwidth utilization up to 45%. The results also show that it is worth applying the second phase of our algorithm since it considerably enhances the system performance by 20%.
Fully Depleted Ti-Nb-Ta-Zr-O Nanotubes: Interfacial Charge Dynamics and Solar Hydrogen Production
(2018-07-11)
Chiu, Yi-Hsuan
;
Lai, Ting-Hsuan
;
Chen, Chun-Yi
;
Hsieh, Ping-Yen
;
Ozasa, Kazunari
Poor kinetics of hole transportation at the electrode/electrolyte interface is regarded as a primary cause for the mediocre performance of n-type TiO2 photoelectrodes. By adopting nanotubes as the electrode backbone, light absorption and carrier collection can be spatially decoupled, allowing n-type TiO2, with its short hole diffusion length, to maximize the use of the available photoexcited charge carriers during operation in photoelectrochemical (PEC) water splitting. Here, we presented a delicate electrochemical anodization process for the preparation of quaternary Ti-Nb-Ta-Zr-O mixed-oxide (denoted as TNTZO) nanotube arrays and demonstrated their utility in PEC water splitting. The charge transfer dynamics for the electrodes was investigated using time-resolved photoluminescence, electrochemical impedance spectroscopy, and the decay of open-circuit voltage analysis. Data reveal that the superior photoactivity of TNTZO over pristine TiO2 originated from the introduction of Nd, Ta, and Zr elements, which enhanced the amount of accessible charge carriers, modified the electronic structure, and improved the hole injection kinetics for expediting water splitting. By modulating the water content of the electrolyte employed in the anodization process, the wall thickness of the grown TNTZO nanotubes can be reduced to a size smaller than that of the depletion layer thickness, realizing a fully depleted state for charge carriers to further advance the PEC performance. Hydrogen evolution tests demonstrate the practical efficacy of TNTZO for realizing solar hydrogen production. Furthermore, with the composition complexity and fully depleted band structure, the present TNTZO nanotube arrays may offer a feasible and universal platform for the loading of other semiconductors to construct a sophisticated heterostructure photoelectrode paradigm, in which the photoexcited charge carriers can be entirely utilized for efficient solar-to-fuel conversion.
Solution-Processed High-Performance Tetrathienothiophene-Based Small Molecular Blends for Ambipolar Charge Transport
(2018-07-11)
Vegiraju, Sureshraju
;
Lin, Chih-Yu
;
Priyanka, Pragya
;
Huang, Deng-Yi
;
Luo, Xian-Lun
Four soluble dialkylated tetrathienoacene (TTAR)-based small molecular semiconductors featuring the combination of a TTAR central core, pi-conjugated spacers comprising bithiophene (bT) or thiophene (T), and with/without cyanoacrylate (CA) end-capping moieties are synthesized and characterized. The molecule DbT-TTAR exhibits a promising hole mobility up to 0.36 cm(2) V-1 s(-1) due to the enhanced crystallinity of the microribbon-like films. Binary blends of the p-type DbT-TTAR and the n-type dicyanomethylene substituted dithienothiophene-quinoid (DTTQ-11) are investigated in terms of film morphology, microstructure, and organic field-effect transistor (OFET) performance. The data indicate that as the DbT-TTAR content in the blend film increases, the charge transport characteristics vary from unipolar (electron-only) to ambipolar and then back to unipolar (hole-only). With a 1:1 weight ratio of DbT-TTAR DTTQ-11 in the blend, well-defined pathways for both charge carriers are achieved and resulted in ambipolar transport with high hole and electron mobilities of 0.83 and 0.37 cm(2) V-1 s(-1), respectively. This study provides a viable way for tuning microstructure and charge carrier transport in small molecules and their blends to achieve high-performance solution-processable OFETs.
3D surface morphology imaging of opaque microstructures via light-field microscopy
(2018-07-12)
Da Sie, Yong
;
Lin, Chun-Yu
;
Chen, Shean-Jen
;
光電學院
;
College of Photonics
Observing dynamic micro-scale phenomena occurring at millisecond time scales, such as organism activity, micron particle flows, or any opaque object observation, requires volumetric microscopy techniques able to achieve high data acquisition rates while maintaining contrast so that measurement of fine micro-scale features is possible. In realizing this purpose, the light-field (LF) technique has already been used on three-dimensional (3D) scene capturing and even for microscopic visualizations. In studying the ability and feasibility of 3D surface morphology reconstruction via LF microscopy, we adopted a lab-made LF microscope and integrated a four-dimensional Fourier slice algorithm and a Markov random field propagation algorithm. Furthermore, for numerical comparison and quantized analysis, the Tenengrad function was utilized to calculate the average contrast of the region of interest. Reflective US Air Force targets and 3D photolithography-made micro-scaffolds coated with 50 nm nickel thin films were adopted for system alignment and calibration. The experimental results demonstrate that the developed LF microscope with the signal processing algorithms can observe the 3D surface morphology of opaque microstructures with one snapshot, and has been preliminary applied to Brownian motion observation with 30 Hz volumetric image rate.
A Nanostructuring Method to Decouple Electrical and Thermal Transport through the Formation of Electrically Triggered Conductive Nanofilaments
(2018-07-12)
Retamal, Jose Ramon Duran
;
Kang, Chen-Fang
;
Lien, Der-Hsien
;
Kuo, Wei-Cheng
;
Juang, Zhen-Yu
Transforming thermal energy into electric energy and vice versa needs the decoupling of electrical transport from thermal transport. An innovative strategy is proposed by forming/disrupting electrically triggered conductive nanofilaments within semiconducting thin films to switch thermoelectric properties between two states without further material modification and manufacturing processes. It can also controllably adjust the degree of decoupling, providing a potential resolution and performance adjustability for heat/coldness control or power consumption reduction on demand.
Comparison of oxidation in uni-directionally and randomly oriented Cu films for low temperature Cu-to-Cu direct bonding
(2018-07-13)
Tseng, Chih-Han
;
Tu, K. N.
;
Chen, Chih
;
材料科學與工程學系
;
國際半導體學院
Cu-to-Cu direct bonding has attracted attention because it has been implemented in CMOS image sensors. Prior to the bonding, the oxides on the Cu surface needs to be removed, yet the surface may oxidize right after cleaning. Thus, oxidation is an inherent issue in the application of Cu direct bonding. Our previous study reported that Cu direct bonding can be achieved below 250 degrees C by using (111)-oriented nanotwinned Cu because it has the fastest surface diffusivity. However, the oxidation behavior of the nanotwinned Cu is unclear. Here, we examined the oxidation behavior of highly (111) and (200) oriented, and randomly-oriented Cu films at temperatures ranging from 120 to 250 degrees C. Transmission electron microscopy was used to measure the oxide thickness. The results show that the oxidation rate of (111)-oriented nanotwinned Cu has the lowest oxidation rate among them. Together, it is unique to possess the combination of the fastest surface diffusivity and the lowest oxidation rate.
歐拉的學伴:威伊，我的父親
(國立交通大學丘成桐中心, 2018-07-15)
席爾薇威伊
;
趙學信
;
Sylvie Weil
作者簡介:席爾薇‧威伊曾在巴納德學院、本寧頓學院和亨特學院以及紐約市立大學研究生中心任教法國文學
《論語》的閱讀與理解
(國立交通大學丘成桐中心, 2018-07-15)
蔣紹愚
《論語》是一部影響極大的著作，研究《論語》對研究中國古代文化有十分重要的意義。但要研究《論語》，首先要對《論語》有正確的解讀。《論語》中很多文句，歷來有多種不同的解釋，究竟哪一種對？怎樣理解才符合《論語》的原意？這往往需要從語法、辭彙和語音方面對這些文句作深入的分析。下面就我在閱讀《論語》過程中遇到的幾個問題作一些分析。
中英名詞對照
(國立交通大學丘成桐中心, 2018-07-15)
中英名詞對照
士族門第如何看待數學？
(國立交通大學丘成桐中心, 2018-07-15)
洪萬生
著者簡介:洪萬生為臺灣師大數學系退休教授，臺灣HPM發起人，強調數學史在數學教育中的功能，更是臺灣數學科普推手，近年來推動以文學小說促進數學普及。
中國應當建造巨型對撞機嗎？
(國立交通大學丘成桐中心, 2018-07-15)
霍金
;
凱恩
;
鮮于中之
;
Stephen Hawking
;
Gordon Kane
霍金（1942 年1 月8 日∼2018 年3 月14 日），英國著名物理學家與宇宙學家，被譽為繼愛因斯坦後最傑出的理論物理學家之一。1974 年獲選為英國皇家學會院士，是當時最年輕的院士。1992 年當選美國科學院外籍院士，1979 年至2009 年擔任劍橋大學的盧卡斯數學教授，生前任職劍橋大學理論宇宙學中心研究主任。凱恩，美國密西根大學魏斯科普夫（Victor Weisskopf）特聘教授，密西根理論物理中心榮譽主任。曾獲美國物理學會頒發的利林菲爾德獎（2012 年）與櫻井獎（2017 年）。
數學與疫苗如何確保你遠離流感？:簡單的數學揭示：如何以不需要全面的疫苗接種阻止疾病以指數形式散播，從而避免流行病爆發
(國立交通大學丘成桐中心, 2018-07-15)
洪納
;
紀露結
;
Patrick Honner
作者洪納在布魯克林科技高中教授數學和計算機科學，他還擔任該校的教學教練。他是「為美國教數學」（Math for America）的專家級講師，而獲頒2 013 年美國的數學和科學教學卓越總統獎。他經常發表數學和教學的文章和演講。
半個古典詩人的獨白
(國立交通大學丘成桐中心, 2018-07-15)
丁邦新
宋朝的大詩人陸游有一首詩說：「衣上征塵雜酒痕，遠遊無處不銷魂。此身合是詩人未？細雨騎驢入劍門。」（劍門道中道遇微雨）「衣服上征戰的塵土夾雜著酒痕，我遠離家鄉到處遊歷，沒有一個地方不令我感動莫名。我自己究竟算不算得上是一個詩人？騎着毛驢，冒着細雨，慢慢地走入了劍門。」像陸游這樣的愛國詩人，劉大杰說他是南宋詩壇的領袖，他還自問究竟算不算得上是一個詩人，我今天來講這個題目，自封為半個詩人，其實還把自己說得太高了。但是說我是四分之一個詩人或者五分之一個詩人，又好像有點不大成話。各位知道我是研究中國音韻學和方言學的，暫且算是半個詩人吧！我今天想講的一部分是研究，一部分是創作。先講研究，後談創作。希望從兩者彼此的影響裡談一點個人的淺見。
只有詠唱才能學會詠唱（上）::悼威廉‧瑟斯頓（1946~2012）
(國立交通大學丘成桐中心, 2018-07-15)
噶拜
;
科寇夫
;
翁秉仁
;
David Gabai
;
Steve Kerckhoff
瑟斯頓（William Paul Thurston，大家都叫他比爾）是一位卓越的數學家，他的工作和思想澈底改變許多數學領域的風貌，包括葉層論（foliation）、泰希穆勒理論（Teichmüller theory）、曲面自同構（automorphism）、三維拓樸、接觸結構（contact structure）、雙曲幾何、有理映射、圓裝填（circle packing）、不可壓縮曲面（incompressible surface）、三維流形之幾何化等等。瑟斯頓的影響遠遠超過他曾提出的傑出洞見、定理或猜想。比爾改變了人們思考與看待事物的方式，大方分享他那種好玩、很奇特、近似魔術，有時又顯得雜沓的數學思路。
讓研究和生活結合在一起:王慕道教授訪談
(國立交通大學丘成桐中心, 2018-07-15)
李瑩英
;
黃國卿
受訪者簡介:臺灣大學數學系畢業，哈佛大學數學博士。曾任教於史丹福大學，目前為哥倫比亞大學教授。研究興趣包括微分幾何、離散群、偏微分方程和廣義相對論。曾獲2007 年陳省身獎、2010 年晨興數學金獎、2012 年傅斯年獎。
編輯曲線
(國立交通大學丘成桐中心, 2018-07-15)
編輯室
本期內容:從大自然掘取數學問題
淺議現代數學物理對數學的影響
(國立交通大學丘成桐中心, 2018-07-15)
孔良
從上個世紀80 年代以來，數學物理，特別是量子場論和弦論，對數學的很多領域都產生了影響。，本文以不進入任何具體細節的方式，試圖在哲學層面來解析這個潮流的根源和特點，以期得到以上問題的一個解答。當然我們的真正目的並不是去解答這個「膚淺」的問題，而是瞭解藏在現象背後的深層原因，從而瞭解我們在歷史脈絡裡的位置和時代賦予我們的機遇和使命。
從大自然掘取數學問題:姚鴻澤院士訪談
(國立交通大學丘成桐中心, 2018-07-15)
翁秉仁
;
馮肅媛
受訪者簡介: 姚鴻澤為臺灣大學數學系畢業，普林斯頓大學數學博士。曾任教於紐約大學、史丹福大學，目前為哈佛大學教授。研究領域為數學物理。2000 年麥克阿瑟獎、2001 年晨興數學金獎、2002 年中研院院士，2003 年美國國家科學院院士。