Browsing by Issue Date, starting with "2005-03-17"

Now showing 1 - 20 of 67003

Femtosecond fluorescence dynamics of rotation-restricted azobenzenophanes: new evidence on the mechanism of trans -> cis photoisomerization of azobenzene
(2005-03-17)
Lu, YC
;
Diau, EWG
;
Rau, H
;
應用化學系分子科學碩博班
;
Institute of Molecular science
The ultrafast relaxation dynamics of two rotation-restricted (azobenzeno-2S-phane and azobenzeno-4S-phane) and one rotation-free (4,4'-dimethylazobenzene) azobenzene derivatives were investigated using femtosecond fluorescence up-conversion on both S-1(n,pi*) and S-2(pi,pi*) excitations. On S-2 excitation, pulse-limited kinetics with a decay coefficient of similar to 100 fs corresponding to ultrafast S-2-> S-1 relaxation is found to be common for all molecules under investigation regardless of the molecular structure. This indicates that a direct rotational. relaxation on the S-2 surface is unfavorable. On S-1 excitation, we observed biphasic fluorescence decay with a femtosecond component attributed to the decay of the Franck-Condon state prepared by excitation and a picosecond component attributed to the deactivation of the relaxed molecule on the S, surface. This picosecond component is slowed by at least a factor of 2 for the rotation-restricted 2S-bridged molecule compared to that of the rotation-free molecule; for the even stronger rotation-restricted azobenzeno-4S-phane, the decrease is by a factor of 10. These differences in deactivation suggest that the relaxed states and probably the trajectories for rotation-free and rotation-restricted molecules are different on the S, surface, which should be important for the quantum yield of photoisomerization.
Singlemode (SMSR > 40 dB) proton-implanted photonic crystal vertical-cavity surface-emitting lasers
(2005-03-17)
Yang, HPD
;
Lai, FI
;
Chang, YH
;
Yu, HC
;
Sung, CP
A proton-implanted photonic crystal vertical-cavity surface-emitting laser for fibre optic applications is demonstrated. Ultra-low threshold current of about 1.25 mA, single fundamental mode (SMSR > 40 dB) CW output power of over 1 mW, with a pulsed output power exceeding 2 mW has been achieved in the 850 nm range.
A quantum corrected energy-transport model for nanoscale semiconductor devices
(2005-03-20)
Chen, RC
;
Liu, JL
;
應用數學系
;
Department of Applied Mathematics
An energy transport model coupled with the density gradient method as quantum mechanical corrections is proposed and numerically investigated. This new model is comprehensive in both physical and mathematical aspects. It is capable of describing hot electron transport as well as significant quantum mechanical effects for advanced devices with dimensions comparable to the de Broglie wave-length. The model is completely self-adjoint for all state variables and hence provides many appealing mathematical features such as global convergence, fast iterative solution, and highly parallelizable. Numerical simulations on diode and MOSFET with the gate length down to 34 nm using this model have been performed and compared with that using the classical transport model. It is shown that the I V characteristics of this short-channel device is significantly corrected by the density-gradient equations with current drive reduced by up to 60% comparing with that of the classical model along. Moreover, a 2D quantum layer, which is only a fraction of the length scale of inversion layer, is also effectively captured by this new model with very fine mesh near the interface produced by an adaptive finite element method. (c) 2004 Elsevier Inc. All rights reserved.
可調式準直器與具有此種可調式準直器之濺鍍設備
(2005-03-21)
李承士
;
張翼
一種可調式準直器與具有此種可調式準直器之濺鍍設備，其可調式準直器係由可調式本體、第一準直元件以及第二準直元件所構成。可調式本體具有一內部空間，且其有上部、下部以及上部與下部之間的調整器，這個調整器可調整上部與下部之相對間距。第一準直元件是固設於上部之內部空間中，俾使第一準直元件隨上部移動，而第二準直元件係位於第一準直器下方並固設於下部之內部空間中，俾使第二準直元件隨上部移動。當可調式準直器應用於濺鍍設備時，能藉由調整上部與下部的相對間距來控制入射的濺鍍材料分子角度。
Field emission of carbon nanotubes on anodic aluminum oxide template with controlled tube density
(2005-03-21)
Chen, PL
;
Chang, JK
;
Kuo, CT
;
Pan, FM
;
材料科學與工程學系
The tube number density of aligned carbon nanotubes (CNTs) grown over the nanoporous anodic aluminum oxide (AAO) template can be directly controlled by adjusting the CH4/H-2 feed ratio during the CNT growth. We ascribe the variation of the tube density as a function of the CH4/H-2 feed ratio to the kinetic competition between outgrowth of cobalt-catalyzed CNTs from the AAO pore bottom and deposition of the amorphous carbon (a-C) overlayer on the AAO template. A pore-filling ratio of 18% to 82% for the nanotubes overgrown out of nanopores on the AAO template can be easily achieved by adjusting the CH4/H-2 feed ratio. Enhanced field emission properties of CNTs were obtained by lowering the tube density on AAO. However, at a high CH4 concentration, a-C by-product deposit on the CNT surface can degrade the field emission property due to a high energy barrier and significant potential drop at the emission site. (C) 2005 American Institute of Physics.
Two-color resonant four-wave mixing spectroscopy of highly predissociated levels in the (A)over-tilde(2)A(1) state of CH3S
(2005-03-22)
Liu, CP
;
Reid, SA
;
Lee, YP
;
應用化學系
;
Department of Applied Chemistry
We report results of two-color resonant four-wave mixing experiments on highly predissociated levels of the methylthio (or thiomethoxy) radical CH3S in its first excited electronic state A (2)A(1). Following photolysis of jet-cooled dimethyl disulfide at 248 nm, the spectra were measured with a hole-burning scheme in which the probe laser excited specific rotational transitions in band 3(3). The spectral simplification afforded by the two-color method allows accurate determination of line positions and homogeneous linewidths, which are reported for the C-S stretching states 3(v)(v=3-7) and combination states 1(1)3(v)(v=0-2), 2(1)3(v)(v=3-6), and 1(1)2(1)3(v)(v=0,1) involving the symmetric CH3 stretching (nu(1)) mode and the CH3 umbrella (nu(2)) mode. The spectra show pronounced mode specificity, as the homogeneous linewidth of levels with similar energies varies up to two orders of magnitude; nu(3) is clearly a promoting mode for dissociation. Derived vibrational wave numbers omega(1)('), omega(2)('), and omega(3)(') of the A state agree satisfactorily with ab initio predictions.
Head-related transfer function (HRTF) synthesis based on a three-dimensional array model and singular value decomposition
(2005-03-22)
Bai, MR
;
Ou, KY
;
機械工程學系
;
Department of Mechanical Engineering
An external ear model based on a three-dimensional array beamformer is presented to synthesize the head-related transfer functions (HRTFs). The array coefficients are calculated by matching the measured HRTFs with a frequency-domain template. In light of the characteristics of human hearing, a non-uniform sampling technique is also devised to reduce the problem to a manageable size. The model-matching problem is then solved, by using singular value decomposition procedure. Numerical simulations are carried out to investigate various array configurations in relation to approximation performance. A subjective experiment of sound localization is undertaken to demonstrate the validity of the proposed technique. From the results, the proposed beamformer-based technique proves to be an effective method for modeling the HRTFs. (C) 2004 Elsevier Ltd. All rights reserved.
陳庭詩紀念揭幕管管一封信真情動人
(2005-03-24)
李友煌
上午中午下午和晚上
(2005-03-24)
管管
An improvement of the Yang-Shieh password authentication schemes
(2005-03-25)
Yang, CC
;
Wang, RC
;
Chang, TY
;
資訊工程學系
;
Department of Computer Science
Recently, Yang and Shieh proposed two password authentication schemes by employing smart cards. One is a timestamp-based password authentication scheme and the other is a nonce-based password authentication scheme. In 2002, Chan and Cheng pointed Out that Yang and Shieh's timestamp-based password authentication scheme was vulnerable to the forgery attack. However, in 2003, Sun and Yell pointed Out that Chan and Cheng's attack was unreasonable. At the same time, Sun and Yell pointed out that Yang and Shieh's password authentication schemes were still Vulnerable to the forgery attack. In this paper, we shall improve Yang and Shieh's schemes to resist Sun and Yell's attack. (C) 2004 Elsevier Inc. All rights reserved.
93學年度第12次行政主管會報
(國立陽明大學, 2005-03-31)
陽明電子報編輯小組
時間：94年3月9日(週三)上午8時30分整地點：行政大樓2樓會議室
神奇的北一段（下）
(國立陽明大學, 2005-03-31)
陽明電子報編輯小組
一大早起來，發現我的嘴腫得像香腸那麼大，原來我的嘴唇曬傷了！！！夏天爬山時太陽可毒辣的很，所以防曬的功夫可偷懶不得。今天終於要走那傳說中「走一步，退三步」的碎石坡了，我一面擔心自己的體力，卻又不想說放棄，因為都來到這裡了，怎可錯過台灣三尖之一的中央尖呢.....
和春天有約
(國立陽明大學, 2005-03-31)
陽明電子報編輯小組
不經意間，就和春天訂下了這一場不見不散的約會。
西非照片集錦 (二)
(國立陽明大學, 2005-03-31)
陽明電子報編輯小組
記錄時間：2005 / 01 / 27 至 2005 / 02 / 02 這天一早的工作是跟門診，病人還是如往常一樣的多寡，十個上下，在約莫收班的時候總會多跑出幾個。突然一通電話響，把我們叫了過去：這是服務於外科的黃醫療團團長打的電話，他認為我們到的時間夠久了，也差不多要介紹給友誼醫院院長之類的行政長官認識。不巧，由於沒有事先約，撲了個空，只看到空空蕩蕩「高級座椅」，橫在我們面前。只好與秘書打個招呼，說著下次再拜訪.....
通識中心公佈英語演講比賽優勝者名單
(國立陽明大學, 2005-03-31)
陽明電子報編輯小組
恭喜陽明英語大學備稿演講比賽優勝者第一名 (獎金1500元)：蔡佳君(Chai Kia Chin)／牙醫系二年級第二名 (獎金1200元)：王嘉鐸(Edward Wang)／醫學系一年級第三名 (獎金1000元)：謝岱君(Sharon Hsieh)／護理系三年級恭喜陽明英語大學英語演講社Table Topics演講比賽優勝者第一名：蔡佳君(Chai Kia Chin)／牙醫系二年級第二名：鄭名淵(Tim Chen)／生科系二年級第三名：簡杏宜(Hani Chien)／牙醫系二年級
93學年度第4次(擴大)行政會議
(國立陽明大學, 2005-03-31)
陽明電子報編輯小組
時間：94年3月16日(星期三)上午九時整地點：本校會議中心第二會議室
跨領域研究及腦力激盪座談會
(國立陽明大學, 2005-03-31)
陽明電子報編輯小組
＜研發處／代轉訊息＞本校奈米科技中心之影像核心設施（目前位於研究大樓四樓429之一，可參閱網頁 http://www.ym.edu.tw/ustymu）之各項建置日益完善，為強化榮陽校區與各合作醫院同仁（尤其是具生醫背景之研究工作者）對此設施之瞭解與應用，我們計畫與儀器中心合作
「音樂之旅—自我成長工作坊」活動報導
(國立陽明大學, 2005-03-31)
陽明電子報編輯小組
每個學期山腰上的家都會為陽明人精心規劃二至三個工作坊，熟門熟路的學生還會在開學初就迫不及待到山腰拿愛相隨，把自己的充電時間留下來。這學期的主題是音樂之旅(3/12-13)和傾聽自然(4/9)，都非常難得的邀請到大師級的人物.
春耕
(國立陽明大學, 2005-03-31)
陽明電子報編輯小組
民國73年5月間，當時服役中的第二屆校友洪耀欽，於探望病榻中的故前院長韓偉教授後，寫信致意並親筆繪贈一幅水彩畫「春耕」。韓院長收到信及畫作後，立即手諭將「此信及此畫放在校史室供賞閱」，其欣慰之情溢於言表。韓偉院長稍後於同年8月4日辭世.....
唭哩岸的女兒 - 自生植物花季
(國立陽明大學, 2005-03-31)
李榮文
又是清明時節了，唭哩岸山自生植物經過雨霧的滋潤，會在清明過後大量吐出美麗的花朵。粉紅色系桃金孃，白色系的小花鼠刺等開滿山野，吸引大批甲蟲、蝴蝶來此覓食，食物鏈中的掠食者鳥類燕子等也會大量的在山頭上穿梭捕食昆蟲。因此，清明到端午之間是唭哩岸山春季花季最集中的期間，也是賞蟲、賞鳥的好季節