Browsing by Issue Date, starting with "2006-08-14"

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Comments on the high energy limit of bosonic open string theory
(2006-08-14)
Chan, Chuan-Tsung
;
Ho, Pei-Ming
;
Lee, Jen-Chi
;
Teraguchi, Shunsuke
;
Yang, Yi
In previous works, ratios among four-point scattering amplitudes at the leading order in the high-energy limit were derived for the bosonic open string theory. The derivation was based on Ward identities derived from the decoupling of zero-norm states and was purely algebraic. The only assumption of the derivation was that the momentum polarization can be approximated by the longitudinal polarization at high energies. In this paper, using the decoupling of spurious states, we reduce this assumption to a much weaker one which can be easily verified by simple power counting in most cases. For the special cases which are less obvious, we verify the new assumption for an example by saddle-point approximation. We also provide a new perspective to our previous results in terms of DDF states. In particular, we show that, by using DDF states, one can easily see that there is only one independent high energy scattering amplitude for each fixed mass level. (c) 2006 Elsevier B.V. All rights reserved.
一條黃昏
(2006-08-14)
管管
Rapid self-assembly of Ni nanodots on Si substrate covered by a less-adhesive and heat-accumulated SiO2 layers
(2006-08-14)
Lin, Gong-Ru
;
Kuo, Hao-Chung
;
Lin, Huang-Shen
;
Kao, Chih-Chiang
;
光電工程學系
Rapid self-aggregation of Ni nanodots on Si substrate covered with a thin SiO2 buffered layer is investigated. The Ni nanodots can hardly self-aggregate on highly heat-dissipated Si substrate with a thermal conductivity of 148 W/m K. Adding a 200-A-thick SiO2 buffer with an ultralow thermal conductivity of 1.35 W/m K prevents the formation of NiSi2 compounds, enhances the heat accumulation, and releases the adhesion at Ni/Si interface, which greatly accelerates the self-assembly of Ni nanodots. Dense Ni nanodots with size and density of 30 nm and 7x10(10) cm(-2), respectively, can be formatted after rapid thermal annealing at 850 degrees C for 22 s. (c) 2006 American Institute of Physics.
An efficient algorithm to find a double-loop network that realizes a given L-shape
(2006-08-14)
Chen, Chiuyuan
;
Lan, James K.
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Tang, Wen-Shiang
;
應用數學系
;
電信工程研究所
Double-loop networks have been widely studied as an architecture for local area networks. It is well known that the minimum distance diagram of a double-loop network yields an L-shape. Given a positive integer N, it is desirable to find a double-loop network with its diameter being the minimum among all double-loop networks with N nodes. Since the diameter of a double-loop network can be easily computed from its L-shape, one method is to start with a desirable L-shape and then find a double-loop network to realize it. This is a problem discussed by many authors [F Aguilo, M.A. Fiol, An efficient algorithm to find optimal double loop networks, Discrete Math. 138 (1995) 15-29, R.C. Chan, C.Y. Chen, ZX Hong, A simple algorithm to find the steps of double-loop networks, Discrete Appl. Math. 121 (2002) 61-72, C.Y. Chen, F.K. Hwang, The minimum distance diagram of double-loop networks, IEEE Trans. Comput. 49 (2000) 977-979, P. Esque, F Aguilo, M.A. Fiol, Double commutative-step diagraphs with minimum diameters, Discrete Math. 114 (1993) 147-157] and it has been open for a long time whether this problem can be solved in O(log N) time. In this paper, we will provide a simple and efficient 0 (log N)-time algorithm for solving this problem. (C) 2006 Elsevier B.V. All rights reserved.
Dielectric properties of nitric oxide-annealed gate oxides grown on nitrogen-implanted silicon substrates
(2006-08-14)
Chen, Y. Y.
;
Chien, C. H.
;
Lou, J. C.
;
電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
The characteristics of nitric oxide (NO)-annealed nitrided gate oxides grown on nitrogen-implanted silicon substrates (NIS) were studied in this paper. It was found that nitrogen accumulation occurred near the interface after NO-annealing, while NIS-grown nitrided oxide produced a uniform nitrogen distribution in the dielectric bulk. Moreover, it was found that the dielectric reliability is strongly dependent on the dosages used for NIS preparation. NIS with dosages smaller than 10(14) cm(-2) was found not to suppress the oxidation rate and to degrade the dielectric reliability. On the other hand, the samples with a dosage of 10(15) cm(-2) not only exhibited a significantly reduced oxidation rate, making it suitable for growing oxides of multiple thicknesses in sub-3 nm technologies meeting the Systems on Chip requirement, but also improved the dielectric reliability. NO-annealed NIS-grown nitrided oxides depict superior dielectric reliability and this technique appears to be suitable to replace the traditional SiO2 at 0.13 mu m technology node and beyond. (c) 2006 Elsevier B.V. All rights reserved.
Localized electrochemical oxidation of p-GaAs(100) using atomic force microscopy with a carbon nanotube probe
(2006-08-14)
Huang, Wu-Ping
;
Cheng, Hung-Hsiang
;
Jian, Sheng-Rui
;
Chuu, Der-San
;
Hsieh, Jin-Yuan
The nanometre-scale oxidation characteristics of a p-GaAs(100) surface are investigated by atomic force microscope (AFM) electrochemical nanolithography with a multiwalled carbon nanotube (MWCNT) probe. The electrochemical parameters, such as anodizing voltages, scanning rate and modulated voltages, and how they affect the creation and growth of the oxide nanostructures are explored. The present results reveal that the initial growth rate (similar to 600 nm s(-1) for 10 V) decreases rapidly as the electric field strength is decreased. The oxide practically ceases to grow as the electric field is reduced to the order of similar to 1.2 x 10(7) V cm(-1). Also, the oxide growth rate depends not only on the electric field strength but also on the applied anodizing voltage. The present results show that the height of the oxide structures can be significantly improved at an applied anodizing voltage of 10 V by using a CNT probe. In addition, Auger electron spectroscopy (AES) measurements performed in the present work confirm that modified structures replace the form of anodizing p-GaAs(100).
Suppression of interfacial reaction for HfO2 on silicon by pre-CF4 plasma treatment
(2006-08-14)
Lai, Chao Sung
;
Wu, Woei Cherng
;
Chao, Tien Sheng
;
Chen, Jian Hao
;
Wang, Jer Chyi
In this letter, the effects of pre-CF4 plasma treatment on Si for sputtered HfO2 gate dielectrics are investigated. The significant fluorine was incorporated at the HfO2/Si substrate interface for a sample with the CF4 plasma pretreatment. The Hf silicide was suppressed and Hf-F bonding was observed for the CF4 plasma pretreated sample. Compared with the as-deposited sample, the effective oxide thickness was much reduced for the pre-CF4 plasma treated sample due to the elimination of the interfacial layer between HfO2 and Si substrate. These improved characteristics of the HfO2 gate dielectrics can be explained in terms of the fluorine atoms blocking oxygen diffusion through the HfO2 film into the Si substrate. (c) 2006 American Institute of Physics.
Notes on high-energy limit of bosonic closed string scattering amplitudes
(2006-08-14)
Chan, Chuan-Tsung
;
Lee, Jen-Chi
;
Yang, Yi
;
電子物理學系
;
Department of Electrophysics
We study bosonic closed string scattering amplitudes in the high-energy limit. We find that the methods of decoupling of high-energy zero-norm states and the high-energy Virasoto constraints, which were adopted in the previous works to calculate the ratios among high-energy open string scattering amplitudes of different string states, persist for the case of closed string. However, we clarify the previous saddle-point calculation for high-energy open string scattering amplitudes and claim that only (t, u) channel of the amplitudes is suitable for saddle-point calculation. We then discuss three evidences to show that saddle-point calculation for high-energy closed string scattering amplitudes is not reliable. By using the relation of tree-level closed and open string scattering amplitudes of Kawai, Lewellen and Tye (KLT), we calculate the high-energy closed string scattering amplitudes for arbitrary mass levels. For the case of high-energy closed string four-tachyon amplitude, our result differs from the previous one of Gross and Mende, which is NOT consistent with KLT formula, by an oscillating factor. (c) 2006 Elsevier B.V. All rights reserved.
Prediction of protein subcellular localization
(2006-08-15)
Yu, Chin-Sheng
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Chen, Yu-Ching
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Lu, Chih-Hao
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Hwang, Jenn-Kang
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生物科技學系
Because the protein's function is usually related to its subcellular localization, the ability to predict subcellular localization directly from protein sequences will be useful for inferring protein functions. Recent years have seen a surging interest in the development of novel computational tools to predict subcellular localization. At present, these approaches, based on a wide range of algorithms, have achieved varying degrees of success for specific organisms and for certain localization categories. A number of authors have noticed that sequence similarity is useful in predicting subcellular localization. For example, Nair and Rost (Protein Sci 2002;11:2836-2847) have carried out extensive analysis of the relation between sequence similarity and identity in subcellular localization, and have found a close relationship between them above a certain similarity threshold. However, many existing benchmark data sets used for the prediction accuracy assessment contain highly homologous sequences-some data sets comprising sequences up to 80-90% sequence identity. Using these benchmark test data will surely lead to overestimation of the performance of the methods considered. Here, we develop an approach based on a two-level support vector machine (SVM) system: the first level comprises a number of SVM classifiers, each based on a specific type of feature vectors derived from sequences; the second level SVM classifier functions as the jury machine to generate the probability distribution of decisions for possible localizations. We compare our approach with a global sequence alignment approach and other existing approaches for two benchmark data sets-one comprising prokaryotic sequences and the other eukaryotic sequences. Furthermore, we carried out all-against-all sequence alignment for several data sets to investigate the relationship between sequence homology and subcellular localization. Our results, which are consistent with previous studies, indicate that the homology search approach performs well down to 30% sequence identity, although its performance deteriorates considerably for sequences sharing lower sequence identity. A data set of high homology levels will undoubtedly lead to biased assessment of the performances of the predictive approaches-especially those relying on homology search or sequence annotations. Our two-level classification system based on SVM does not rely on homology search; therefore, its performance remains relatively unaffected by sequence homology. When compared with other approaches, our approach performed significantly better. Furthermore, we also develop a practical hybrid method, which combines the two-level SVM classifier and the homology search method, as a general tool for the sequence annotation of subcellular localization.
Electronic transport characteristics in a one-dimensional constriction defined by a triple-gate structure
(2006-08-15)
Lee, Huang-Ming
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Muraki, Koji
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Chang, Edward Yi
;
Hirayama, Yoshiro
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材料科學與工程學系
We investigate the electronic transport characteristics of a one-dimensional (1D) narrow constriction defined in a GaAs/Al(x)Ga(1-x)As heterostructure by a simple triple-gate structure consisting of a pair of split gates and an additional surface Schottky gate (center gate) between them. Comparison between devices with and without a center gate reveals that the center gate, even when zero biased (V(CG)=0 V), significantly modifies the surface potential and facilitates the 1D confinement in a deep two-dimensional electron system. The pinch-off voltages at V(CG)=0 V for various channel widths W (=0.4-0.8 mu m) and lengths L (=0.2-2 mu m) are well described by the analytical formula based on the pinned-surface model [J. H. Davies , J. Appl. Phys. 77, 4504 (1995)]. Nonlinear transport spectroscopy with an additional dc bias shows that the lowest 1D subband energy separation (Delta E(1,2)) changes linearly with V(CG) and can be enhanced by 70% for V(CG)=0.8 V. A simple model assuming an infinitely long channel and no self-consistent potential well reproduces the overall behavior of the measured Delta E(1,2). In addition, effects of impurities, occasionally found for long-channel devices (L >= 1 mu m), are found to be greatly reduced by applying positive V(CG) and thereby enhancing Delta E(1,2). Data are also presented for the transport anomaly below the first conductance plateau, the so-called "0.7 anomaly," demonstrating that the triple-gate structure is useful for the study of density-dependent phenomena in a 1D system. (c) 2006 American Institute of Physics.
陪死刑犯之樹
(2006-08-15)
管管
光調制器與其所應用之光學多工／解多工器
(2006-08-16)
潘犀靈
;
趙如蘋
;
黃銘杰
;
藍玉屏
一種光學多工／解多工器，包括了分光元件和光調制單元。其中，分光元件用來將一主光束分成多道不同波長的子光束。然後這些子光束會分別對應入射到光調制單元上的其中一個畫素。而光調制單元則包括第一玻璃基板和第二玻璃基板，其中第一玻璃基板的第一側係接收對應之子光束，其第二側則與第二玻璃基板的第一側相對。第一玻璃基板的第二側上和第二玻璃基板的第一側上，都會形成電極和配向模。其中第一和第二玻璃基板上的電極係分別耦接驅動電壓和共同電壓。藉由控制驅動電壓，可以決定是否讓對應之子光束從第二玻璃基板的第二側出射。
紅外線影像位元壓縮與對比強化方法
(2006-08-16)
莊仁輝
;
王俊昌
本發明提供一種紅外線影像位元壓縮與對比強化方法，將高位元數之紅外線數位影像轉換成低位元數可顯示之灰階數位影像，其係利用直方圖之門檻值處理方式以強化影像之對比，可調整直方圖中各個強度所包含的影像像素(Pixels)之分佈數量，且對於不同景象的紅外線影像，皆可計算出不同的門檻值，以此門檻值對紅外線數位影像作不同的調整；另外，依據影像強度之平均區域標準差，進一步對門檻值作加權計算，重新調整影像直方圖分佈後，再進行位元壓縮轉換，以提升對比強化的效能。因此，本發明之影像處理效果，可避免因紅外線強度分佈多的物體對強度分佈少的物體所發生的影像擠壓現象，提升影像的可視對比，同時有效降低影像顯示的雜訊。
破天荒藝文界百人連署
(2006-08-16)
黃雅詩
渦輪解碼器之架構
(2006-08-16)
李鎮宜
;
林建青
;
施彥旭
本發明提出一種渦輪解碼器之架構，利用一最大後置機率解碼器自一共享記憶體讀取先驗資料，且先驗資料會先經過一讀取位址產生器重排位址後，再經過最大後置機率解碼器運算為數非本徵資料，並經過一寫入位址產生器重排位址，再寫入共享記憶體內，且本發明還設置一快取記憶體，藉此降低對外部記憶體的存取，進而降低功率消耗，且本發明可有效降低共享記憶體使用量，並降低電路複雜度，且可降低成本。
廢水混凝加藥之控制法
(2006-08-16)
江萬豪
;
黃志彬
;
蘇育俊
本發明係為一廢水混凝加藥之控制法，藉由直接滴定來決定加藥劑量，將混凝劑作為酸滴定藥劑，直接對氧化化學機械研磨廢水進行滴定加藥，至適當pH值時，滴定加藥停止，此時之加藥劑量為電性中和去穩之控制點，可精確控制加藥劑量，使加藥劑量降低，處理成本隨之降低，也不因於廢水進流濃度的變化而產生不能適用的情形，可不受限制而使用不同之混凝劑。
Probing field-induced submolecular motions in a ferroelectric liquid crystal mixture with time-resolved two-dimensional infrared spectroscopy
(2006-08-16)
Huang, Jung Y.
;
Shih, Wen-Tse
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光電工程學系
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Department of Photonics
Time-resolved two-dimensional infrared (2D IR) spectroscopy has been applied to analyse an electro-optic switching ferroelectric liquid crystal (FLC) mixture. The 2D IR correlation technique clearly shows that the Goldstone mode in the SmC* phase is suppressed by an applied electric field. The field-induced reorientation process initiates from intramolecular motions in about 10 mu s. The intramolecular motions then propagate from the molecular segments attached to the same molecule to those fragments on other surrounding molecules. During the field-induced switching, the IR dipoles undergo a collective reorientation but with hindered rotation about the molecular long axis.
Spin cloud induced around an elastic scatterer by the intrinsic spin Hall effect
(2006-08-18)
Mal'shukov, A. G.
;
Chu, C. S.
;
電子物理學系
;
Department of Electrophysics
Similar to the Landauer electric dipole created around an impurity by the electric current, a spin polarized cloud of electrons can be induced by the intrinsic spin Hall effect near a spin independent elastic scatterer. It is shown that in the ballistic range around the impurity, such a cloud appears in the case of Rashba spin-orbit interaction, even though the bulk spin Hall current is absent.
Defining equations of modular curves
(2006-08-20)
Yang, Yifan
;
應用數學系
;
Department of Applied Mathematics
We obtain defining equations of modular curves X-0(N), X-1(N), and X(N) by explicitly constructing modular functions using generalized Dedekind eta functions. As applications, we describe a method of obtaining a basis for the space of cusp forms of weight 2 on a congruence subgroup. We also use our model of X-0(37) to find explicit modular parameterization of rational elliptic curves of conductor 37. (C) 2005 Elsevier Inc. All rights reserved.
Absorption cross sections of NH3, NH2D, NHD2, and ND3 in the spectral range 140-220 nm and implications for planetary isotopic fractionation
(2006-08-20)
Cheng, Bing-Ming
;
Lu, Hsiao-Chi
;
Chen, Hong-Kai
;
Bahou, Mohammed
;
Lee, Yuan-Pern
Cross sections for photoabsorption of NH3, NH2D, NHD2, and ND3 in the spectral region 140-220 nm were determined at similar to 298 K using synchrotron radiation. Absorption spectra of NH2D and NHD2 were deduced from spectra of mixtures of NH3 and ND3, of which the equilibrium concentrations for all four isotopologues obey statistical distributions. Cross sections of NH2D, NHD2, and ND3 are new. Oscillator strengths, an integration of absorption cross sections over the spectral lines, for both A X and B X systems of NH3 agree satisfactorily with previous reports; values for NH2D, NHD2, and ND3 agree with quantum chemical predictions. The photolysis of NH3 provides a major source of reactive hydrogen in the lower stratosphere and upper troposphere of giant planets such as Jupiter. Incorporating the measured photoabsorption cross sections of NH3 and NH2D into the Caltech/JPL photochemical diffusive model for the atmosphere of Jupiter, we find that the photolysis efficiency of NH2D is lower than that of NH3 by as much as 30%. The D/H ratio in NH2D/NH3 for tracing the microphysics in the troposphere of Jupiter is also discussed.