Browsing by Issue Date, starting with "2006-08-15"

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Prediction of protein subcellular localization
(2006-08-15)
Yu, Chin-Sheng
;
Chen, Yu-Ching
;
Lu, Chih-Hao
;
Hwang, Jenn-Kang
;
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
;
Muraki, Koji
;
Chang, Edward Yi
;
Hirayama, Yoshiro
;
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
;
光電工程學系
;
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.
Nonlinear dynamics in thin-slice Nd : YAG ceramic lasers: Coupled local-mode laser model
(2006-08-21)
Otsuka, Kenju
;
Narita, Tatsuro
;
Miyasaka, Yoshihiko
;
Lin, Chi-Ching
;
Ko, Jing-Yuan
The authors propose a coupled spatially distributed local-mode laser model for understanding self-induced high-speed modulations in Nd:YAG ceramic lasers with laser-diode end pumping, which critically depend on pump positions. In addition to complicated high-speed modulations, quasiperiodic and chaotic relaxation oscillations have been demonstrated experimentally and reproduced by numerical simulation of the model of coupled local-mode lasers. Q-switching-like periodic spiking pulsations have been also observed and reproduced numerically by assuming saturable absorber type of inclusions in grain boundaries.
Effects of strain on the electronic structures and T-C's of the La0.67Ca0.33MnO3 and La0.8Ba0.2MnO3 thin films deposited on SrTiO3
(2006-08-21)
Chou, Hsiung
;
Tsai, M. -H.
;
Yuan, F. P.
;
Hsu, S. K.
;
Wu, C. B.
The strain effects on the electronic structures of La0.67Ca0.33MnO3 (LCMO) and La0.8Ba0.2MnO3 (LBMO) thin films have been studied by O K-edge x-ray absorption near edge structure (XANES) spectroscopy. For LCMO, the first-principles calculations reveal that the features in the XANES spectra are associated with hybridized states between O 2p and Mn minority-spin 3d t(2g) and e(g), La 5d/Ca 3d, and Mn 4s/Ca 4p states. An analysis of these features shows that the tensile strain decreases substantially La-O and Ca-O hybridization and T-C for LCMO. For LBMO, the small compressive strain enhances slightly La-O and Ba-O hybridization and T-C. (c) 2006 American Institute of Physics.
Thermal stability of Ti/Pt/Cu Schottky contact on InAlAs layer
(2006-08-21)
Lien, Yi-Chung
;
Chang, Edward Yi
;
Chen, Szu-Hung
;
Chu, Li-Hsin
;
Chen, Po-Chou
Electrical characteristics and thermal stability of the Ti/Pt/Cu Schottky contact on InAlAs were investigated. The Ti/Pt/Cu Schottky contact had comparable electrical properties compared to the conventional Ti/Pt/Au contact after annealing. As judged from the material analysis, the Ti/Pt/Cu on InAlAs after 350 degrees C annealing showed no diffusion sign into the InAlAs. After 400 degrees C annealing, the interfacial mixing of Cu and the underlying layers occurred and resulted in the formation of Cu4Ti. The results show that Ti/Pt/Cu Schottky contact using platinum as the diffusion barrier is very stable up to 350 degrees C annealing and can be used for InAlAs/InGaAs high-electron mobility transistors and monolithic microwave integrated circuits. (c) 2006 American Institute of Physics.
具有防止源汲極區摻雜離子在接面區外擴散的電晶體結構及其製作方法
(2006-08-21)
羅廣禮
;
楊宗
;
張翼
;
張俊彥
本發明係揭露一種具有防止源汲極區摻雜離子在接面區外擴散的電晶體結構及其製作方法，其係於半導體基底上形成材質為具有摻雜離子的含碳-矽化鍺(SiGe：C)嵌入式源汲極，利用碳能夠抑制摻雜離子擴散的特性，來形成兼具低接觸電阻與能抑制摻雜離子擴散的源汲極區，進而提高元件的可靠度。
磁光式之近場光學光儲存元件
(2006-08-21)
徐文祥
;
謝漢萍
;
孫翊庭
本發明係提供一種磁光式之近場光學光儲存元件，係先利用犧牲層製作空氣軸承結構；再定義一初始小孔，並以電鍍法縮小該孔至奈米等級，再以兩次之厚膜光阻層配合兩次電鍍製程，製作高深寬比之金屬線圈結構與金屬內連線；可有效利用面積與降低電阻，最後利用微影製程中對不同區域的不同曝光量控制，定義單層光阻形成具有特定尺寸且不同厚度之結構，接著配合回流(reflow)即可利用一連續製程製作出結合超半球固態浸沒式透鏡(solid immersion lens)、奈米微孔、金屬線圈、空氣軸承之磁光(MO)讀取頭，而不需精密昂貴的設備，並可批次大量生產，免去組裝的步驟，並且不用高精密度之儀器即可製作，達到高資料儲存與複寫。
隨機存取記憶體陣列結構
(2006-08-21)
鄭東栓
;
黃威
本發明提供一種隨機存取記憶體陣列結構，其係將一隨機存取記憶體陣列結構分成複數個資料區塊，每一資料區塊以陣列方式排列，且每一資料區塊連接有一及閘及電源閘，利用一編碼裝置使一數據資料進行儲存或讀取動作。本發明能有效使電路減少漏電流的產生，進而大幅降低動態功率之消耗。
Identification of mechanical properties of elastically restrained laminated composite plates using vibration data
(2006-08-22)
Lee, C. R.
;
Kam, T. Y.
;
機械工程學系
;
Department of Mechanical Engineering
A nondestructive evaluation method using vibration data to determine mechanical properties (material and spring constants) of elastically restrained laminated composite plates is presented. The Rayleigh-Ritz method in which a set of Legendre's polynomials is adopted to approximate the plate deflection is used to determine the theoretical natural frequencies of the elastically restrained laminated composite plates. A number of natural frequencies extracted from the impulse vibration test data of the laminated composite plates supported by elastic restraints at both the edges and centers of the plates are used in the present method to determine the mechanical properties of the plates. The sum of the squared differences function which measures the differences between the experimentally and theoretically predicted natural frequencies of the elastically restrained laminated composite plates is established. The identification of the plate mechanical properties is then formulated as a constrained minimization problem in which the mechanical properties are determined by making the sum of the squared differences function a global minimum. The feasibility and accuracy of the proposed method are studied by means of several numerical examples on the mechanical properties identification of elastically restrained laminated composite plates with different layups made of various composite materials. Experimental investigation of the mechanical properties identification of several elastically restrained laminated composite plates has been performed to illustrate the applications of the present method. It has been shown that the present method can produce good estimates of the mechanical properties of the elastically restrained laminated composite plates in an efficient and effective way. (c) 2006 Elsevier Ltd. All rights reserved.
A computational study on the kinetics and mechanism for the unimolecular decomposition of o-nitrotoluene
(2006-08-24)
Chen, S. C.
;
Xu, S. C.
;
Diau, E.
;
Lin, M. C.
;
應用化學系分子科學碩博班
The kinetics and mechanism for the unimolecular decomposition of o-nitrotoluene (o-CH3C6H4NO2) have been studied computationally at the G2M(RCC, MP2)//B3LYP/6-311G(d, p) level of theory in conjunction with rate constant predictions with RRKM and TST calculations. The results of the calculations reveal 10 decomposition channels for o-nitrotoluene and its six isomeric intermediates, among them four channels give major products: CH3C6H4 + NO2, C6H4C(H) ON (anthranil) + H2O, CH3C6H4O (o-methyl phenoxy) + NO, and C6H4C(H-2) NO + OH. The predicted rate constants in the 500-2000 K temperature range indicate that anthranil production, taking place initially by intramolecular H-abstraction from the CH3 group by NO2 followed by five-membered ring formation and dehydration, dominates at temperatures below 1000 K, whereas NO2 elimination becomes predominant above 1100 K and CH3C6H4O formation by the nitro-nitrite isomerization/decomposition process accounts for only 5-11% of the total product yield in the middle temperature range 800-1300 K. The branching ratio for CH2C6H4NO formation by the decomposition process of CH2C6H4N(O)OH is negligible. The predicted high-pressure-limit rate constants with the rate expression of 4.10 x 10(17) exp[-37000/T] s(-1) for the NO2 elimination channel and 9.09 x 10(12) exp[-25800/T] s(-1) for the H2O elimination channel generally agree reasonably with available experimental data. The predicted high-pressure-limit rate constants for the NO and OH elimination channels are represented as 1.49 x 10(14) exp[-30000/T] and 1.31 x 10(15) exp[-38000/T] s(-1), respectively.