Browsing by Issue Date, starting with "2007-09-05"

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交大e-News第009期
(2007-09-05)
Secretariat
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國立交通大學秘書室
Relaxation-induced lattice misfits and their effects on the emission properties of InAs quantum dots
(2007-09-05)
Chen, J. F.
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Wang, Y. Z.
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Chiang, C. H.
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Hsiao, R. S.
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Wu, Y. H.
Strain relaxation in InAs/InGaAs quantum dots (QDs) is shown to introduce misfits in the QD and neighboring GaAs bottom layer. A capacitance -voltage profiling shows an electron accumulation peak at the QD with a long emission time, followed by additional carrier depletion caused by the misfits in the GaAs bottom layer. The emission-time increase is explained by the suppression of tunneling for the QD excited states due to the additional carrier depletion. As a result, electrons are thermally activated from the QD states to the GaAs conduction band, consistent with observed emission energies of 0.160 and 0.068 eV which are comparable to the confinement energies of the QD electron ground and first-excited states, respectively, relative to the GaAs conduction band. This is in contrast to non-relaxed samples in which emission energy of 60 meV is observed, corresponding to the emission from the QD ground state to the first-excited state.
Relaxation dynamics of ruthenium complexes in solution, PMMA and TiO2 films: The roles of self-quenching and interfacial electron transfer
(2007-09-06)
Chang, Chih-Wei
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Chou, Chung Kuang
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Chang, I-Jy
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Lee, Yuan-Pern
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Diau, Eric Wei-Guang
The relaxation dynamics of two transition-metal complexes, [Ru(bpy)(3)](2+) and [Ru(bpy)(3)(mcbpy)](2+), in ethanol solution and in poly(methyl methacrylate) (PMMA) and TiO2 films have been investigated with time-resolved emission and femtosecond transient absorption spectroscopy. The emission lifetime of a degassed [Ru(bpy)3]21 solution in ethanol was determined to be 700 ns; to describe the self-quenching kinetics due to aggregation, three decay coefficients, 5.3, 70, and 220 ns, were obtained for the [Ru(bPY)(3)](2+)/PMMA film. The electron transfer through space in a [Ru(bpy)(3)](2+)/TiO2 film competed with intrinsic intersystem crossing (similar to 100 fs) and vibrational relaxation (similar to 6 ps) in solid films. For the [Ru(bpy)(2)(mcbpy)](2+)/TiO2 film, although the relaxation for electron transfer through bonds was more rapid than electron transfer through space, both processes occur on similar time scales. Through ferntosecond transient absorption measurements, we provide important dynamical evidence for the interfacial electron transfer in both forward and backward directions. We conclude that in dye-sensitized solar-cell applications processes for interfacial electron transfer are significant not only through bonds but also through space.
Architecture of a n-type metal-oxide-semiconductor transistor with a compressive strained silicon-germanium channel fabricated on a silicon (110) substrate
(2007-09-06)
Luo, Guangli
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Chien, Chao-Hsin
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Yang, Tsung-Hsi
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Chang, Chun-Yen
The present invention discloses an architecture of a NMOS transistor with a compressive strained Si—Ge channel fabricated on a silicon (110) substrate, which comprises: a p-silicon (110) substrate, two n+ ion-implanted regions functioning as the source and the drain respectively, a compressive strained Si—Ge channel layer, and a gate structure. The compressive strained Si—Ge channel layer is grown on the p-silicon (110) substrate to reduce the electron conductivity effective mass in the [1_l -10] crystallographic direction and to promote the electron mobility in the [1-10] crystallographic direction. Thus, the present invention can improve the electron mobility of a NMOS transistor via the channels fabricated on the silicon (110) substrate. Further, the NMOS transistor of the present invention can combine with a high-speed PMOS transistor on a silicon (110) substrate to form a high-performance CMOS transistor on the same silicon (110) substrate.
Kaluza-Klein higher-derivative induced gravity
(2007-09-07)
Kao, W. F.
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物理研究所
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Institute of Physics
The existence and stability analysis of an inflationary solution in a ( D + 4)dimensional anisotropic-induced gravity is presented in this paper. Nontrivial conditions in the field equations are shown to be compatible with a cosmological model in which the 4-dimension external space evolves inflationary while the D-dimension internal one is static. In particular, only two additional constraints on the coupling constants are derived from the abundant field equations and perturbation equations. In addition, a compact formula for the non-redundant ( 4 + D)-dimensional Friedmann equation is also derived for convenience. Possible implications are also discussed in this paper.
Nonlinear responses of degenerate two-level systems to intense few-cycle pulses
(2007-09-07)
Nagaya, Kuninobu
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Zhu, Chaoyuan
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Lin, Sheng Hsien
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應用化學系
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應用化學系分子科學碩博班
Population transfers in degenerate (or almost degenerate) two-level systems interacting with the few-cycle laser pulse are investigated. A simple and analytical formula of nonadiabatic transition probability is derived with completely degenerate condition, demonstrating the sensitive dependence of the transition probability on the phase of the few-cycle pulses. As one of the applications of this formula, a new way of controlling the nuclear wave packet dynamics at a potential curve crossing by 1 cycle laser pulse is proposed. (C) 2007 American Institute of Physics.
Protein subcellular localization prediction based on compartment-specific features and structure conservation
(2007-09-08)
Su, Emily Chia-Yu
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Chiu, Hua-Sheng
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Lo, Allan
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Hwang, Jenn-Kang
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Sung, Ting-Yi
Background: Protein subcellular localization is crucial for genome annotation, protein function prediction, and drug discovery. Determination of subcellular localization using experimental approaches is time-consuming; thus, computational approaches become highly desirable. Extensive studies of localization prediction have led to the development of several methods including composition-based and homology-based methods. However, their performance might be significantly degraded if homologous sequences are not detected. Moreover, methods that integrate various features could suffer from the problem of low coverage in high-throughput proteomic analyses due to the lack of information to characterize unknown proteins. Results: We propose a hybrid prediction method for Gram-negative bacteria that combines a one-versus-one support vector machines ( SVM) model and a structural homology approach. The SVM model comprises a number of binary classifiers, in which biological features derived from Gram-negative bacteria translocation pathways are incorporated. In the structural homology approach, we employ secondary structure alignment for structural similarity comparison and assign the known localization of the top-ranked protein as the predicted localization of a query protein. The hybrid method achieves overall accuracy of 93.7% and 93.2% using ten-fold cross-validation on the benchmark data sets. In the assessment of the evaluation data sets, our method also attains accurate prediction accuracy of 84.0%, especially when testing on sequences with a low level of homology to the training data. A three-way data split procedure is also incorporated to prevent overestimation of the predictive performance. In addition, we show that the prediction accuracy should be approximately 85% for non-redundant data sets of sequence identity less than 30%. Conclusion: Our results demonstrate that biological features derived from Gram-negative bacteria translocation pathways yield a significant improvement. The biological features are interpretable and can be applied in advanced analyses and experimental designs. Moreover, the overall accuracy of combining the structural homology approach is further improved, which suggests that structural conservation could be a useful indicator for inferring localization in addition to sequence homology. The proposed method can be used in large-scale analyses of proteomes.
Computing wave functions of nonlinear Schrodinger equations: A time-independent approach
(2007-09-10)
Chang, S.-L.
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Chien, C.-S.
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Jeng, B.-W.
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應用數學系
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Department of Applied Mathematics
We present a novel algorithm for computing the ground-state and excited-state solutions of M-coupled nonlinear Schrodinger equations (MCNLS). First we transform the MCNLS to the stationary state ones by using separation of variables. The energy level of a quantum particle governed by the Schrodinger eigenvalue problem (SEP) is used as an initial guess to computing their counterpart of a nonlinear Schrodinger equation (NLS). We discretize the system via centered difference approximations. A predictor-corrector continuation method is exploited as an iterative method to trace solution curves and surfaces of the MCNLS, where the chemical potentials are treated as continuation parameters. The wave functions can be easily obtained whenever the solution manifolds are numerically traced. The proposed algorithm has the advantage that it is unnecessary to discretize or integrate the partial derivatives of wave functions. Moreover, the wave functions can be computed for any time scale. Numerical results on the ground-state and excited-state solutions are reported, where the physical properties of the system such as isotropic and nonisotropic trapping potentials, mass conservation constraints, and strong and weak repulsive interactions are considered in our numerical experiments. (C) 2007 Elsevier Inc. All rights reserved.
White p-i-n organic light-emitting devices with high power efficiency and stable color
(2007-09-10)
Ho, Meng-Huan
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Hsu, Shih-Feng
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Ma, Jia-Wei
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Hwang, Shiao-Wen
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Yeh, Pu-Cheng
Highly efficient p-i-n two-component white organic light-emitting devices have been fabricated with a thin dual emission layer system comprised of one codeposited emitting layer with blue and yellow dyes and one blue emitting layer, which gives rise to a balance white emission. The p-i-n white device achieved an electroluminescence efficiency of 10 cd/A and a power efficiency of 9.3 lm/W at 1000 cd/m(2) and a low voltage of 3.4 V with a Commission Internationale de l'Eclairage coordinates of (0.32, 0.43). The electroluminescent color of this p-i-n white organic light-emitting diode device has been shown to be immune to drive current density variations.
Acoustic and optical phonon assisted formation of biexcitons
(2007-09-10)
Pan, Ching-Ju
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Lin, Kuo-Feng
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Hsieh, Wen-Feng
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光電工程學系
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Department of Photonics
Efficient exciton relaxation is required for bounding two cooled excitons to form biexciton. Acoustic and optical phonon scatterings playing key roles in exciton relaxation are responsible for formation of biexcitons at various temperatures. Using ZnO powders, the authors observed a sublinear dependence on excitation power at low temperature, in which the relaxation process involves only emission of acoustic phonons due to the excitons having kinetic energy lower than those of the optical phonons. However, the exponent comes near theoretical value of 2 for participation of optical phonons when the exciton kinetic energy approaches to the energy of the lowest optical phonon.
Wide-ratio broadband SiGe HBT regenerative frequency divider enhanced by differential TIA load
(2007-09-13)
Wei, H.-J.
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Meng, C.
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Chang, Y.-W.
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電信工程研究所
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Institute of Communications Engineering
Well-aligned ternary Cd1-xZnxS nanowire Arrays and their composition-dependent field emission properties
(2007-09-13)
Lin, Yi-Feng
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Hsu, Yung-Jung
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Lu, Shih-Yuan
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Chen, Kuan-Tsung
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Tseng, Tseung-Yuen
Well-aligned plain CdS and ternary Cd1-xZnxS nanowire arrays were successfully fabricated via a noncatalytic and template-free metal-organic chemical vapor deposition process. The nanowires were grown on a 1 mu m thick buffer layer formed in situ on the surface of silicon substrates. These nanowires were 20-40 nm in diameter and 500-900 nm in length. High-resolution transmission electron microscopy analyses revealed that the nanowires were single-cry stalline and grew along the [0001] direction of the hexagonal crystalline phase. The photoluminescence characterizations showed near band edge emissions at 535, 498, and 473 nm for the US nanowire arrays and Cd1-xZnxS nanowire arrays with x values of 0.21 and 0.44, respectively, demonstrating clear color tunability achieved with the composition adjustment of the alloy nanowires. The same morphology. and single-crystallinity of these three nanowire arrays enabled investigation of the composition-dependent field emission characteristics of the nanowire arrays for the first time, excluding interferences originating from morphology and crystallinity related factors. The plain CdS nanowire arrays exhibited better field emission properties, a lower turn-on field, and a higher field enhancement factor than the ternary Cd1-xZnxS nanowire arrays, for which the lower resistivity of the CdS nanowires may have played an important role. An important parameter, the absolute field enhancement factor (beta(0)), to more intrinsically quantify the field emission performance of the plain US and ternary Cd1-xZnxS nanowires arrays was also studied. The values of beta(0) decreased with increasing Zn content in the ternary products. The high beta(0) values of the US based nanowire arrays, comparable to that of carbon nanotubes grown on silicon wafers, made these nanowire arrays a promising candidate material for high-performance field emitting devices.
A Method For Predicting Inductance And Self-Resonant Frequency Of A Spiral Inductor
(2007-09-13)
Chen, Chien-Chang
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Cheng, Yu-Ting
In this invention, a closed-form integral model for on-chip freely suspended rectangular spiral inductor is presented. The model of this invention bases on the Kramers-Kronig relations, field theory, and solid state physics to characterize a spiral inductor which RFIC designers could easily have the optimal design utilizing this analytical method. Meanwhile, this model can provide satisfactory prediction to the inductance and self-resonant frequency of the spiral inductor without complicated geometry analysis. Furthermore, unlike conventional formulations only based on circuit parameters, this model could safely predict the inductance and the self-resonant frequency when altering the material (excluding ferromagnetic materials) of a spiral inductor.
High strength and high toughness alloy with low density and the method of making
(2007-09-13)
Liu, Tzeng-Feng
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Lee, Jian-Wei
The present invention relates to a high strength and high toughness alloy with a low density and the method of making thereof. The alloy essentially comprises 15 to 33 wt % of manganese, 6 to 10 wt % of aluminum, 0.6 to 1.2 wt % of carbon, 0.1 to 1.0 wt % of silicon, and the balance of iron. The alloy has excellent properties of a density of 6.6 to 6.9 g/cm3, an elongation of 25 to 70%, and a tensile strength of 100 to 190 ksi. In particularly, and the alloy is useful for golf club heads with excellent properties. Further, the use of the alloy reduces pits and defects generated during the electroplating process of the heads. Therefore, the defect rate of the product is remarkably decreased so that the cost is reduced.
Dynamics of the F-2+CH3SCH3 reaction: A molecule-molecule reaction without entrance barrier
(2007-09-14)
Lu, Yu-Ju
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Lee, Lance
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Pan, Jun-Wei
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Witek, Henryk A.
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Lin, Jim J.
The F-2+CH3SCH3 reaction was studied with crossed molecular beam techniques and high level ab initio calculations. Significant reactivity was observed even at low collision energies, consistent with the negligible barrier height obtained from the ab initio calculations. All experimental findings are consistent with a weakly bound reaction intermediate of F-F-S(CH3)(2) structure, which possesses a special type of three-center four-electron bonding. Analogous intermediates can also explain the reactions of F-2 with CH3SH and CH3SSCH3.
Efficient algorithms for regular expression constrained sequence alignment
(2007-09-15)
Chung, Yun-Sheng
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Lu, Chin Lung
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Tang, Chuan Yi
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生物科技學系
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Department of Biological Science and Technology
Imposing constraints is an effective means to incorporate biological knowledge into alignment procedures. As in the PROSITE database, functional sites of proteins can be effectively described as regular expressions. In an alignment of protein sequences it is natural to expect that functional motifs should be aligned together. Due to this motivation, Arslan introduced the regular expression constrained sequence alignment problem and proposed an algorithm which, if implemented naively, can take time and space up to O(vertical bar Sigma vertical bar V-2 vertical bar vertical bar(4)n(2)) and O(vertical bar Sigma vertical bar(2)vertical bar V vertical bar(4)n), respectively, where Sigma is the alphabet, n is the sequence length, and V is the set of states in an automaton equivalent to the input regular expression. In this paper we propose a more efficient algorithm solving this problem which takes O(vertical bar V vertical bar(3)n(2)) time and O(vertical bar V vertical bar(2n)) space in the worst case. If vertical bar V vertical bar = O(log n) we propose another algorithm with time complexity O(vertical bar V vertical bar(2)log vertical bar V vertical bar n(2)). The time complexity of our algorithms is independent of Sigma, which is desirable in protein applications where the formulation of this problem originates; a factor of vertical bar Sigma vertical bar(2) = 400 in the time complexity of the previously proposed algorithm would significantly affect the efficiency in practice. (c) 2007 Elsevier B.V All rights reserved.
Optical method for measuring the azimuthal anchoring strength of liquid crystals using pitch values determined in imperfect samples
(2007-09-15)
Tang, Tsung-Ta
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Wu, Hsin-Ying
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Lin, Chia-Jen
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Pan, Ru-Pin
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電子物理學系
An improved Grandjean-Cano wedge method for measuring the pitch of a chiral nematic liquid crystal is demonstrated. This method is easy to implement and can yield results of high accuracy when it is used for measuring the liquid crystal surface anchoring strength.(C) 2007 American Institute of Physics.
Methods of achieving linear index-change response for narrow-band fiber Bragg grating sequential writing
(2007-09-15)
Hsu, Kuei-Chu
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Sheu, Lih-Gen
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Hsiang, Wei-Wei
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Lai, Yinchieh
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光電工程學系
This investigation elucidates the refractive index-change response of the photosensitive optical fiber to exposed UV flux. The nonlinear U-V photosensitivity deforms the index profile of FBGs on the tail edges where the writing UV flux is low. Pre-UV treatment eliminates the nonlinear index-change response and ensures the linearity of the response of subsequent grating writing. A new method that involves interference between two unequal beams in a single writing scan is proposed and demonstrated to be able to improve the index profile and the spectral response of fabricated FBGs. The procedure is stable for writing weak fiber Bragg gratings with pre-designed index profiles. (c) 2007 Elsevier B.V. All rights reserved.
聲源能量分佈可視化系統及其方法
(2007-09-16)
白明憲
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林家鴻
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甯攸威
本發明提供一種聲源能量分佈可視化系統及其方法,其係在求得波傳遞矩陣與窗口矩陣後,透過將波傳遞矩陣進行反逆運算,以及將反逆運算結果與窗口矩陣作相乘運算,把相乘運算結果由頻率域轉換成時間域後,建立起聲源能量分佈重建器,而在進一步利用陣列式麥克風接收聲源訊號,且使用多通道擷取裝置將聲源訊號轉換成數位聲源訊號後,讓數位聲源訊號與聲源能量分佈重建器作旋積運算,而得到一可視化之聲源能量分佈。因此,本發明提供一種聲源能量分佈可視化系統及其方法,其可獲得近場及遠場之穩態與非穩態聲源的能量分佈情形,或是任一頻帶內的聲源能量分佈情況。
低密度高強度高韌性合金材料及其製法
(2007-09-16)
劉增豐
;
李堅瑋
本發明係關於一種低密度、高强度、高韌性之合金材料及其製法。該合金材料其主要包含15~33重量百分比之錳、6~10重量百分比之鋁、0.6~1.2重量百分比之碳、0.1~1.0重量百分比之矽及其餘比例以鐵為基材之合金材料,其具有6.6~6.9g/cm^3的密度、25~70%的延伸率或100~190ksi的抗拉强度等極佳的性質,故使得該合金材料可達到高强度、低密度、高延展性及優異表面性質之高爾夫桿頭設計目的,且該合金材料更可降低高爾夫桿頭在電鍍過程中所產生的孔蝕孔洞及缺陷的發生,因此大幅降低產品的不良率及成本。