Browsing by Issue Date, starting with "2015-04-13"

Now showing 1 - 20 of 21989

Suppression of endurance degradation by utilizing oxygen plasma treatment in HfO2 resistive switching memory
(2015-04-13)
Chand, Umesh
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Huang, Chun-Yang
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Jieng, Jheng-Hong
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Jang, Wen-Yueh
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Lin, Chen-Hsi
Based on the phenomenon of endurance degradation problem caused by no sufficient oxygen ions for resistive switching, we use the oxygen plasma treatment in HfO2 layer to increase the extra available oxygen ions in resistive random access memory devices. To avoid the Ti top electrode directly absorbing the additional oxygen ions from HfO2 layer with oxygen plasma treatment, a thin HfO2 film is inserted to separate them. Therefore, the endurance degradation can be suppressed in the present structure. High speed (30 ns) and large endurance cycles (up to 10(10) cycles) are achieved in this device structure for next generation nonvolatile memory application. (C) 2015 AIP Publishing LLC.
Role of Sarcoplasmic Reticulum Calcium in Development of Secondary Calcium Rise and Early Afterdepolarizations in Long QT Syndrome Rabbit Model
(2015-04-13)
Chang, Po-Cheng
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Wo, Hung-Ta
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Lee, Hui-Ling
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Lin, Shien-Fong
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Wen, Ming-Shien
Background L-type calcium current reactivation plays an important role in development of early afterdepolarizations (EADs) and torsades de pointes (TdP). Secondary intracellular calcium (Ca-i) rise is associated with initiation of EADs. Objective To test whether inhibition of sarcoplasmic reticulum (SR) Ca2+ cycling suppresses secondary Ca-i rise and genesis of EADs. Methods Langendorff perfusion and dual voltage and Cai optical mapping were conducted in 10 rabbit hearts. Atrioventricular block (AVB) was created by radiofrequency ablation. After baseline studies, E4031, SR Ca2+ cycling inhibitors (ryanodine plus thapsigargin) and nifedipine were then administrated subsequently, and the protocols were repeated. Results At baseline, there was no spontaneous or pacing-induced TdP. After E4031 administration, action potential duration (APD) was significantly prolonged and the amplitude of secondary Cai rise was enhanced, and 7 (70%) rabbits developed spontaneous or pacing-induced TdP. In the presence of ryanodine plus thapsigargin, TdP inducibility was significantly reduced (2 hearts, 20%, p = 0.03). Although APD was significantly prolonged (from 298 +/- 30 ms to 457 +/- 75 ms at pacing cycle length of 1000 m, p = 0.007) by ryanodine plus thapsigargin, the secondary Ca-i rise was suppressed ( from 8.8 +/- 2.6% to 1.2 +/- 0.9%, p = 0.02). Nifedipine inhibited TdP inducibility in all rabbit hearts. Conclusion In this AVB and long QT rabbit model, inhibition of SR Ca2+ cycyling reduces the inducibility of TdP. The mechanism might be suppression of secondary Ca-i rise and genesis of EADs.
Vertical organic transistors withstanding high voltage bias
(2015-04-13)
Chang, Po-Yi
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Peng, Shao-Fu
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Chao, Yu-Chiang
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Lin, Hung-Cheng
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Zan, Hsiao-Wen
Vertical organic transistors withstanding high voltage bias were realized with an insulating silicon monoxide layer obliquely deposited on both the surface of the base electrode and sidewalls of the vertically oriented cylindrical nanopores. No noticeable insulating layer can be observed on the emitter electrode at the bottom of the cylindrical nanopores. The leakage current between the electrodes was suppressed and an operating voltage as high as 15V was obtained. An on/off current ratio of 10(3)-10(4) and an output current density of 5-10 mA/cm(2) were achieved. (c) 2015 AIP Publishing LLC.
Angular-Shaped 4,9-Dialkylnaphthodithiophene-Based Donor-Acceptor Copolymers for Efficient Polymer Solar Cells and High-Mobility Field-Effect Transistors
(2015-04-14)
Cheng, Sheng-Wen
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Tsai, Che-En
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Liang, Wei-Wei
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Chen, Yung-Lung
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Cao, Fong-Yi
Although the tetracyclic angular-shaped naphthodithiophenes (aNDTs) derivatives are an emergent building block for constructing promising semiconductor conjugated polymers, the absence of aliphatic side chains as solubilizing groups on the aNDTs greatly restricted their further application toward polymer synthesis. To create a new class of aNDT-based polymers for widespread applications in solution-processable OFETs and PSCs, side-chain engineering of the aNDT-based structures plays a pivotal role in improving solubility and optimizing electronic/steric properties associated with the resultant solar cell characteristics. In this research, we developed an efficient and straightforward methodology to construct the angular naphthodithophene core with regiospecific introduction of two aliphatic chains at its 4,9-positions via a base-induced double 6p-cyclization. For the first time, the corresponding 2,7-distannylated-4,9-dialkylated aNDT monomers were polymerized with FBT and DPP acceptors to make two new PaNDTDTFBT and PaNDTDPP donor-acceptor copolymers. The photovoltaic devices based on the PaNDTDTFBT:PC71BM blend not only showed a promising PCE of 6.52% with conventional configuration but also achieved a higher PCE of 6.86% with inverted configuration. Moreover, PaNDTDPP with strong intermolecular interaction achieved a high FET hole mobility of 0.202 cm(2) V-1 s(-1).
Novel thin-GaN LED structure adopted micro abraded surface to compare with conventional vertical LEDs in ultraviolet light
(2015-04-15)
Chiang, Yen Chih
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Lin, Chien Chung
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Kuo, Hao Chung
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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
In this study, novel thin-GaN-based ultraviolet light-emitting diodes (NTG-LEDs) were fabricated using wafer bonding, laser lift-off, dry etching, textured surface, and interconnection techniques. Placing PN electrodes on the same side minimized the absorption caused by electrodes in conventional vertical injection light-emitting diodes (V-LEDs) and the current spreading was improved. The light output power (700 mA) of the NTG-LEDs was enhanced by 18.3% compared with that of the V-LEDs, and the external quantum efficiency (EQE) of the NTG-LEDs was also relatively enhanced by 20.0% compared with that of a reference device. When the current operations were 1,500 mA, the enhancements of the light output power and EQE were 27.4% and 27.2%, respectively. Additionally, the efficiency droop was improved by more than 15% at the same current level.
百年長河看臺灣醫師地位的變化
(2015-04-15)
晏山农
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Shing-Tung Yau Center
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丘成桐中心
二○一四年深秋，台大医师柯文哲以压倒性票数登上台北市长高位。加上南台湾的赖清德、涂醒哲两个县市首长皆是医生出身，以致坊间有“医生治国”取代“律师治国”说法。实则，日治中期以后，医生就已是台湾社会的中流砥柱，战后台湾基层政治的主干─仕绅，如今柯文哲旋风其实是百年积累的结果，而非凭空产出。
Observation of Intrinsic Magnus Force and Direct Detection of Chirality in Superfluid He-3-A
(2015-04-15)
Ikegami, Hiroki
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Tsutsumi, Yasumasa
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Kono, Kimitoshi
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物理研究所
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Institute of Physics
We report details of the observation of the intrinsic Magnus (IM) force acting on negative and positive ions trapped just below a free surface of the A phase of superfluid He-3 (He-3-A). From the transport measurements of the ions along the surface, we found that the IM force acts on both the negative and positive ions. We also demonstrate that the transport measurements could distinguish whether the surface is composed of a chiral monodomain or multiple chiral domains. For multiple chiral domains, the current of the ions was found to be irreproducible and unstable, which was reasonably explained by the formation of the chiral domain structure and the dynamics of the chiral domain walls. For chiral monodomains, the appearance ratio of chirality emerging upon cooling through the superfluid transition temperature was found to depend on the direction of the external magnetic field, which implies the existence of an unknown coupling between the chirality and the magnetic field.
編輯曲線：天心惟微跨越兩個文化的嘗試
(2015-04-15)
編輯室
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Shing-Tung Yau Center
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丘成桐中心
《數理人文》做了新嘗試，想跨出數學成為真正包含數學、科學、歷史、文化議題的綜合雜誌。高水準的製作理念不變，也繼續提供讀者新知識、新發現、新反思的刺激。但是我們將試著不再局限於數學的視角，提供更完整的知識圖象。為這個想法定調的是第一篇文章，丘成桐的〈數理與人文〉是去年他在香港的講辭。丘先生有一個基本的看法，中國之所以很難出大數學家，和華人文化的教育系統文理分家太過嚴重有莫大的關係，缺乏博雅教育的涵養，讓數學家的養成缺乏關鍵的體系深度和宇宙關懷，而這是成為大數學家或大學問家的要件。
宇宙是怎麼來的？我們又是怎麼知道的？
(2015-04-15)
郭兆林
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Shing-Tung Yau Center
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丘成桐中心
大千世界怎麼來的？這個涉及起源與存在的重大問題，人類當然一直想知道答案。中西哲學家和宗教家對這個問題已經思辯了幾千年，不過以科學方法探討這個問題則是最近的事。儘管以前有盤古開天闢地等各種宇宙起源的說法，但並沒有任何哲學或是宗教的圖像，可以像物理學一般預測早期宇宙氦、重氫等含量，微波或重力波背等定量現象，然後用實驗方法加以檢驗。由於宇宙微波背景（Cosmic Microwave Background, 簡稱 CMB）與星系大尺度結構方面研究的大幅進展，物理學家現在知道，只要給定宇宙誕生一微秒時之初始條件，根據物理定律便可以演化成現在所見的宇宙。這初始條件是一種類似雜訊的密度微擾，一開始渺小的密度微擾在萬有引力吸聚下放大對比，形成現在所見星系、恆星等結構（圖 1）。現在宇宙學研究的重心，已經追溯到一微秒前到底發生什麼事，大霹靂本身的物理機制。而 CMB 在這方面的研究更將扮演極其獨特的角色。
Study of an electromagnetic control swing blade blower
(2015-04-15)
Li, Ai-Tsung
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Tseng, Hsuan-Kai
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Hsu, Ray-Quen
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機械工程學系
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Department of Mechanical Engineering
Investigation of an electromagnetically controlled swing blade blower is the major objectives of this study. A fan of this type consumes low power, emits little noise and vibration, and is small in size, which makes it suitable for application in consumer electronic products. It is based on the interaction between a permanent magnet and a magnetic coil field. This drives the fan blades, increasing the volume of wind flow. Therefore, the fan design is a major factor in the wind velocity. In this study, materials, fan shape, and the resonance frequency are the design parameters considered. With proper resonance frequency and blade shape, air flow can be greatly increased. Both numerical simulations and experimental analysis were carried out in this study. ANSYS software was used in a 2D simulation to predict the flow fields and compare the results with experiments to construct a simulation system. The simulation system was used to study various blade related parameters including materials, thickness, fan shape, resonance frequency, and fan tip displacement on the airflow wind velocity, while the power consumption was maintained within 0.25 W via electromagnetic actuator. Numerical simulations and experimental results show that trimming the fan blade area causes the resonance frequency and the tip displacement to increase. Therefore, with proper fan shape, the Aluminum 1050 fan obtained the highest wind velocity, up to 1.81 m/s. In sum, the numerical simulations and experimental results provide a better understanding of electromagnetic swing blade blower design. (C) 2015 Elsevier B.V. All rights reserved.
數理與人文
(2015-04-15)
丘成桐
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Shing-Tung Yau Center
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丘成桐中心
.創造力的來源除了個人的天賦與學養，更重要的是追求的熱情與文化的陶冶，數理與人文並無二致。 .作者以蘇軾〈洞仙歌〉、《紅樓夢》、虛數為例，說明數理與人文的高明學問，都需要高超的想像力、整體全景的架構能力、極致的完美化。 .中國科學家在原創性還比不上世界最先進的水準，原因之一是人文修養不夠，我們需要真正調和數理與人文的博雅教育。
20150415第四期目錄
(2015-04-15)
編輯室
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Shing-Tung Yau Center
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丘成桐中心
編輯曲線數理簡訊 [特稿] 數理與人文余英時印象 [專題] 宇宙是怎麼來的？聆聽宇宙絕對溫度十億分之一度下的量子模擬高溫超導的鐵器時代 [數] 涂林本事 [理]散射振幅給科學家的四則金玉良言 [人] 擇善固執的曲面探險家 [文] 胡適與巴斯德百年長河看臺灣醫師地位的變化
聆聽宇宙大密藏於微中子
(2015-04-15)
陳丕燊
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Shing-Tung Yau Center
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丘成桐中心
世界各地的古文明都有一個明顯的相似之處，那就是非常注重天象觀測。我們的祖先在尚無光害的古代用肉眼仰望蒼穹，那份感動、敬畏、和不可避免的疑問，就是人類探索宇宙的開端。幾千年來，從肉眼到望遠鏡，人類賴以探索宇宙的資訊，就是天體發出的光。
高溫超導的鐵器時代從「銅基超導」到「鐵基超導」
(2015-04-15)
吳茂昆
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Shing-Tung Yau Center
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丘成桐中心
.超導現象於 1911 年由荷蘭萊登大學的翁尼斯發現。到了 1986 年時，超導相變臨界溫度最高的超導體是鈮三鍺的 23.2K 。 .1986 年發現銅氧化物超導體，引發一連串研究高溫超導新材料的熱潮。目前的超導臨界溫度記錄是 164K。 .2008 年鐵硒超導體的發現開啟了鐵基超導系統的研究。鐵硒超導體的超導性可能來自於材料中的鐵空位排列方式。當這些鐵空位有序排列時，材料是莫特絕緣體。鐵空位若經熱處理而形成無序狀態時，材料變成導體，並在低溫出現超導性。
絕對溫度十億分之一度下的量子模擬
(2015-04-15)
金政
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陳勁豪
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Shing-Tung Yau Center
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丘成桐中心
近年來，冷原子的研究見證了一系列驚奇，並且開啟了一扇通往量子物理勝地的大門。這個領域宛如科學研究發現的天堂，因為幾乎所有東西都能精準控制，而且原子的運動完全遵循量子力學法則。從實驗物理學家的角度來看，這些冷原子的用途相當多元：它們既可以在某個實驗中模擬凝態材料裡的電子，也可以在另一個實驗中模擬交互作用的核子，甚至能化身為科學家在假想實驗中憑空創造出來的虛擬物體。在這個嶄新的量子奇境中，我們的想像力是僅有的疆界。
A Polarizer-Free Liquid Crystal Lens Exploiting an Embedded-Multilayered Structure
(2015-04-15)
Chen, Hung-Shan
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Wang, Yu-Jen
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Chang, Chia-Ming
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Lin, Yi-Hsin
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光電工程學系
Development of liquid crystal (LC) lenses is limited by the power law. The aperture size of LC lenses is traded for the lens power. In this letter, we prove theoretically and experimentally that the aperture size is not limited by the power law based on a polarizer-free LC lens exploiting an embedded-multilayered structure. By adding numbers of LC layers, the aperture size of the LC lens can be enlarged without lowering the tunable lens power. The optical theory of the polarization independence of the LC lens is derived. The wavefronts are measured after light propagates through the LC lens to discuss the polarization independence and image adjustment. The impact of this study is to show the possibility of LC lenses with large aperture size for wearable devices and ophthalmic applications.
涂林本事不可計算的一生功業
(2015-04-15)
庫珀 S. Barry Cooper、周樹靜
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Shing-Tung Yau Center
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丘成桐中心
.涂林以涂林機模型的觀點掌握可計算性的意義，而涂林機最後走出另一條歷史別徑，發展成日後的電腦。實際製作電腦的馮諾曼將此歸功於涂林。 .如同哥德爾不完備定理，涂林發現任何具有合理強度的數學理論都是不可判定的，亦即其中都包含了不可計算的定理，挫敗希爾伯特的樂觀思想。 .涂林晚期仍深入思考現實世界的問題，發展型態發生學的理論，解釋型態突現的機轉。另外更發展體稟與人造智慧的想法，發明影響深遠的涂林測試．
擇善固執的曲面探險家伊朗女數學家莫札卡尼
(2015-04-15)
蔻拉萊克 Erica Klarreich
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林奕君
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Shing-Tung Yau Center
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丘成桐中心
在八歲的年紀，莫札卡尼經常為自己編織一個優秀女孩如何冒險犯難的故事，每晚的睡前時光，她的女主角也許變成市長、環遊世界，或是完成其他偉大的使命。現在，37 歲的莫札卡尼是史丹福大學的數學教授，依舊在腦海中書寫著精巧複雜的故事。她的雄心壯志未曾改變，只是主要的角色不一樣了，變成雙曲面、模空間、動力系統。莫札卡尼認為從某方面來看，研究數學就像寫小說，「當中有很多角色，而且你會越來越了解他們，隨著劇情演變，當你回頭審視某個角色，他們早已和第一印象截然不同。」
余英時印象
(2015-04-15)
王汎森
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Shing-Tung Yau Center
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丘成桐中心
十六、七年前，當我在香港中文大學客座時，注意到余先生早期在香港報刊雜誌上發表過許多文章，我便開始零星的蒐集這方面的文字，並準備寫一篇長文（甚至是一本小書）來加以討論。而且我的討論將盡量不包含大家所熟知的學術論著—我的意思是余先生的學術論著早已為人們所熟知，不必再經過我的重述—可惜因為個人疏懶，這個願望遲遲未能實現。最近承《數理人文》出題讓我寫一篇「余英時印象」，因為時間比較倉促，我只先選擇一些生活上的印象下筆。
The size effect of titania-supported Pt nanoparticles on the electrocatalytic activity towards methanol oxidation reaction primarily via the bifunctional mechanism
(2015-04-15)
Ting, Chao-Cheng
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Liu, Chung-Hsuan
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Tai, Chun-Yen
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Hsu, Shih-Chieh
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Chao, Chih-Shuan
We prepared Pt nanoparticles of different particle sizes by plasma enhanced atomic layer deposition (PEALD) on the native oxide surface layer of Ti thin films, and investigated the Pt particle size effect on the electrocatalytic activity towards methanol oxidation reaction (MOR) in acidic media. The average Pt nanoparticles size ranges from 3 nm to 7 nm depending on the number of the PEALD reaction cycles. The electronic interaction between Pt nanoparticles and the TiO2 support is insignificant according to x-ray photoelectron spectroscopy analyses, suggesting that the influence of the Pt particle size on the electrocatalytic activity can be mainly described by the bifunctional mechanism. From cyclic voltammetry measurements, Pt particles of smaller size have a better CO tolerance in MOR. We proposed the reaction steps for the electrooxidation of CO adspecies on Pt nanoparticles on the basis of the bifunctional mechanism. The electrode with Pt nanoparticles of similar to 5 nm in size shows the best electrocatalytic performance in terms of CO tolerance and electrochemical stability. (C) 2015 Elsevier B.V. All rights reserved.