Browsing by Issue Date, starting with "2010-09-27"

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Tunable Kondo-Luttinger systems far from equilibrium
(2010-09-27)
Chung, C. -H.
;
Latha, K. V. P.
;
Le Hur, K.
;
Vojta, M.
;
Woelfle, P.
We theoretically investigate the nonequilibrium current through a quantum dot coupled to one-dimensional electron leads, utilizing a controlled frequency-dependent renormalization group approach. We compute the nonequilibrium conductance for large bias voltages and address the interplay between decoherence, Kondo entanglement, and Luttinger physics. The combined effect of large bias voltage and strong interactions in the leads, known to stabilize two-channel Kondo physics, results in nontrivial modifications in the conductance. Interestingly, these unusual changes in the conductance persist in the presence of a finite channel asymmetry.
Tunable Kondo-Luttinger systems far from equilibrium
(2010-09-27)
Chung, C. -H.
;
Latha, K. V. P.
;
Le Hur, K.
;
Vojta, M.
;
Woelfle, P.
We theoretically investigate the nonequilibrium current through a quantum dot coupled to one-dimensional electron leads, utilizing a controlled frequency-dependent renormalization group approach. We compute the nonequilibrium conductance for large bias voltages and address the interplay between decoherence, Kondo entanglement, and Luttinger physics. The combined effect of large bias voltage and strong interactions in the leads, known to stabilize two-channel Kondo physics, results in nontrivial modifications in the conductance. Interestingly, these unusual changes in the conductance persist in the presence of a finite channel asymmetry.
Intra- and intersite electronic excitations in multiferroic TbMnO(3) probed by resonant inelastic x-ray scattering
(2010-09-27)
Chen, J. M.
;
Lee, J. M.
;
Huang, S. W.
;
Lu, K. T.
;
Jeng, H. T.
Mn 3d valence states and elementary electronic excitations in single-crystalline TbMnO(3) were probed with resonant inelastic x-ray scattering (RIXS) (or resonant x-ray emission spectroscopy, RXES), polarized x-ray absorption spectra and ab initio electron-structure calculations. Polarized Mn K-edge x-ray absorption spectra of TbMnO(3) crystals exhibit a significant anisotropy along three crystallographic directions, particularly for the white-line region. The 1s3p-RXES spectra obtained at the Mn K edge reveal that the quadrupolar Raman regime is restricted predominantly to below the pre-edge peak whereas the fluorescence regime starts from the first pre-edge peak of 1s -> 3d transitions, indicating a relatively delocalized character of unoccupied Mn 3d states. The additional K beta emission profile at energy loss similar to 62 eV is attributed to the off-site dipole Mn 1s-Mn' 3d and/or Mn 1s-Tb 5d transitions, originating from hybridization between Mn 4p states and neighboring Mn' 3d/Tb 5d states. The off-site dipole transition makes a considerable contribution to the pre-edge region of Mn K-edge spectrum. Three prominent RIXS features at similar to 2.9, 7, and 11 eV were observed. Based on GGA+U calculations, the 7 eV region corresponds to transitions from O 2p states to unoccupied minority Mn 3d states, whereas the 11 eV band is ascribed to transitions from the O 2p band to the empty Tb 5d band. The broad 2.9 eV band is attributed to the coexistence of on-site Mn 3d-Mn 3d and off-site Mn 3d-Mn' 3d transitions.
Study on dispersion-induced phase noise in an optical OFDM radio-over-fiber system at 60-GHz band
(2010-09-27)
Wei, Chia Chien
;
Chen, Jason (Jyehong)
;
光電工程學系
;
Department of Photonics
While coherency between an RF-tone and OFDM signals in RoF systems at 60 GHz is de-correlated by fiber dispersion, both phase rotation term (PRT) on each subcarrier and inter-carrier interference (ICI) between subcarriers are induced at a receiver. We analytically calculate the powers of PRT and ICI under different parameters, such as subcarrier number, modulation format, laser linewidth and transmission distance. Moreover, dispersion-induced ICI is shown to be non-Gaussian distributed by its kurtosis, and its distribution depends on system parameters. Therefore, using only the power of ICI cannot predict accurate bit error rate (BER) and corresponding power penalty. We propose to use t-distribution to fit the distribution of ICI, and it can be used to compute BER precisely. (C) 2010 Optical Society of America
Clean sub-8-fs pulses at 400 nm generated by a hollow fiber compressor for ultraviolet ultrafast pump-probe spectroscopy
(2010-09-27)
Liu, Jun
;
Okamura, Kotaro
;
Kida, Yuichiro
;
Teramoto, Takahiro
;
Kobayashi, Takayoshi
Clean 7.5 fs pulses at 400 nm with less than 3% energy in tiny satellite pulses were obtained by spectral broadening in a hollow fiber and dispersive compensating using a prism pair together with a deformable mirror system. As an example, this stable and clean pulse was used to study the ultrafast pump-probe spectroscopy of photoactive yellow protein. Moreover, the self-diffraction signal shows a smoothed and broadened laser spectrum and is expected to have a further clean laser pulse, which makes it more useful in the ultrafast pump-probe spectroscopy in the future. (C) 2010 Optical Society of America
Intra- and intersite electronic excitations in multiferroic TbMnO3 probed by resonant inelastic x-ray scattering
(2010-09-27)
Chen, J. M.
;
Lee, J. M.
;
Huang, S. W.
;
Lu, K. T.
;
Jeng, H. T.
Mn 3d valence states and elementary electronic excitations in single-crystalline TbMnO3 were probed with resonant inelastic x-ray scattering (RIXS) (or resonant x-ray emission spectroscopy, RXES), polarized x-ray absorption spectra and ab initio electron-structure calculations. Polarized Mn K-edge x-ray absorption spectra of TbMnO3 crystals exhibit a significant anisotropy along three crystallographic directions, particularly for the white-line region. The 1s3p-RXES spectra obtained at the Mn K edge reveal that the quadrupolar Raman regime is restricted predominantly to below the pre-edge peak whereas the fluorescence regime starts from the first pre-edge peak of 1s -> 3d transitions, indicating a relatively delocalized character of unoccupied Mn 3d states. The additional K beta emission profile at energy loss similar to 62 eV is attributed to the off-site dipole Mn 1s-Mn' 3d and/or Mn 1s-Tb 5d transitions, originating from hybridization between Mn 4p states and neighboring Mn' 3d/Tb 5d states. The off-site dipole transition makes a considerable contribution to the pre-edge region of Mn K-edge spectrum. Three prominent RIXS features at similar to 2.9, 7, and 11 eV were observed. Based on GGA+U calculations, the 7 eV region corresponds to transitions from O 2p states to unoccupied minority Mn 3d states, whereas the 11 eV band is ascribed to transitions from the O 2p band to the empty Tb 5d band. The broad 2.9 eV band is attributed to the coexistence of on-site Mn 3d-Mn 3d and off-site Mn 3d-Mn' 3d transitions.
Nonmagnetic impurity perturbation to the quasi-two-dimensional quantum helimagnet LiCu2O2
(2010-09-29)
Hsu, H. C.
;
Lin, J. -Y.
;
Lee, W. L.
;
Chu, M. -W.
;
Imai, T.
A complete phase diagram of Zn-substituted quantum quasi-two-dimensional helimagnet LiCu2O2 has been presented. Helical ordering transition temperature (T-h) of the original LiCu2O2 follows finite size scaling for less than similar to 5.5% Zn substitution, which implies the existence of finite helimagnetic domains with domain boundaries formed with nearly isolated spins. Higher Zn substitution >= 5.5% quenches the long-range helical ordering and introduces an intriguing Zn-level-dependent magnetic phase transition with slight thermal hysteresis and a universal quadratic field dependence for T-c(Zn > 0.055, H). The magnetic coupling constants of nearest-neighbor J(1) and next-nearest-neighbor J(2) (alpha = J(2)/J(1)) are extracted from high temperature series expansion fitting and N = 16 finite chain exact diagonalization simulation. We have also provided evidence of direct correlation between long-range helical spin ordering and the magnitude of electric polarization in this spin-driven multiferroic material.
《詩經》愛情篇章的語言技術
(2010-09-29)
吳宏一
;
開放教育推動中心
;
Open Education Office
課程首頁本課程是由交通大學新文藝復興閱讀計畫提供。 96 年 8 月當各大學紛紛摩拳擦掌準備迎接新生的同時，交通大學校長吳重雨則因為一則來自於七月份泰晤士報，有關於英國首相布朗公布其夏日讀書清單的新聞中，看到了他對知識的尊重。在這同時，吳重雨校長也思考著，要如何為學生準備追求知識的環境和激發他們對知識的尊重與喜愛。台積電張忠謀董事長曾陳述他 18 歲進入哈佛那一年，博覽文史哲理工經典群籍，至此奠定了他求知的基礎，並借海明威名言，將其改為「哈佛這一年為人生可帶走的盛宴。」吳重雨校長以張董事長的學習為借鏡，認為學生固然能藉由自我閱讀的方式學習到豐沛的知識，但透過名人、大師親臨現場地介紹經典書籍，更能加深學子們對於書籍的認識與興趣，這也是「新文藝復興閱讀計劃」 ( 以下簡稱 : 「經典名著選讀」 ) 活動展開籌劃的緣由。於是，吳重雨校長便積極敦請「交大通識教育委員會」，接手籌備本計劃的相關活動，而該中心也成為實際施行本計畫的策動、開課以及認證單位。至此，期許交大學子藉由閱讀、聽講來提昇人文素養、開拓視野的「新文藝復興閱讀計劃」，就此展開。
Nonmagnetic impurity perturbation to the quasi-two-dimensional quantum helimagnet LiCu(2)O(2)
(2010-09-29)
Hsu, H. C.
;
Lin, J. -Y.
;
Lee, W. L.
;
Chu, M. -W.
;
Imai, T.
A complete phase diagram of Zn-substituted quantum quasi-two-dimensional helimagnet LiCu(2)O(2) has been presented. Helical ordering transition temperature (T(h)) of the original LiCu(2)O(2) follows finite size scaling for less than similar to 5.5% Zn substitution, which implies the existence of finite helimagnetic domains with domain boundaries formed with nearly isolated spins. Higher Zn substitution >= 5.5% quenches the long-range helical ordering and introduces an intriguing Zn-level-dependent magnetic phase transition with slight thermal hysteresis and a universal quadratic field dependence for T(c)(Zn > 0.055, H). The magnetic coupling constants of nearest-neighbor J(1) and next-nearest-neighbor J(2) (alpha = J(2)/J(1)) are extracted from high temperature series expansion fitting and N = 16 finite chain exact diagonalization simulation. We have also provided evidence of direct correlation between long-range helical spin ordering and the magnitude of electric polarization in this spin-driven multiferroic material.
Temperature dependence of resistance and thermopower of thin indium tin oxide films
(2010-09-30)
Lin, Bo-Tsung
;
Chen, Yi-Fu
;
Lin, Juhn-Jong
;
Wu, Chih-Yuan
;
電子物理學系
We have measured the resistance and thermopower of a series of RF sputtered and annealed indium tin oxide (ITO) thin films from 300 K down to liquid-helium temperatures. Thermal annealing was performed to modulate the levels of disorder (i.e., resistivity) of the samples. The measured resistances are well described by the Bloch-Grilneisen law between 150 and 300 K, suggesting that our thin films are metallic. At lower temperatures, a resistance rise with decreasing temperature was observed, which can be quantitatively ascribed to the two-dimensional electron-electron interaction and weak-localization effects. The thermopowers in all samples are negative and reveal fairly linear temperature dependence over the whole measurement temperature range, strongly indicating free-electron like conduction characteristics in ITO thin films. As a result, the carrier concentration in each film can be reliably determined. This work demonstrates that ITO films as thin as 15 nm thick can already possess high metallic conductivity. (C) 2010 Elsevier B.V. All rights reserved.
High Frequency Flip Chip Package Process of Polymer Substrate and Structure thereof
(2010-09-30)
Chang, Edward-yi
;
Hsu, Li-Han
;
Oil, Chee-Way
;
Wu, Wei-Cheng
;
Wang, Chin-te
In a high frequency flip chip package process of a polymer substrate and a structure thereof, the structure is a one-layer structure packaged by a high frequency flip chip package process to overcome the shortcomings of a conventional two-layer structure packaged by the high frequency flip chip package process. The conventional structure not only incurs additional insertion loss and return loss in its high frequency characteristic, but also brings out a reliability issue. Thus, the manufacturing process of a ceramic substrate in the conventional structure still has the disadvantages of a poor yield rate and a high cost.
Temperature dependence of resistance and thermopower of thin indium tin oxide films
(2010-09-30)
Lin, Bo-Tsung
;
Chen, Yi-Fu
;
Lin, Juhn-Jong
;
Wu, Chih-Yuan
;
電子物理學系
We have measured the resistance and thermopower of a series of RF sputtered and annealed indium tin oxide (ITO) thin films from 300 K down to liquid-helium temperatures. Thermal annealing was performed to modulate the levels of disorder (i.e., resistivity) of the samples. The measured resistances are well described by the Bloch-Grilneisen law between 150 and 300 K, suggesting that our thin films are metallic. At lower temperatures, a resistance rise with decreasing temperature was observed, which can be quantitatively ascribed to the two-dimensional electron-electron interaction and weak-localization effects. The thermopowers in all samples are negative and reveal fairly linear temperature dependence over the whole measurement temperature range, strongly indicating free-electron like conduction characteristics in ITO thin films. As a result, the carrier concentration in each film can be reliably determined. This work demonstrates that ITO films as thin as 15 nm thick can already possess high metallic conductivity. (C) 2010 Elsevier B.V. All rights reserved.
Ultrafast relaxation dynamics of photoexcitations in poly(3-hexylthiophene) for the determination of the defect concentration
(2010-09-30)
Lee, Yu Hsien
;
Yabushita, Atsushi
;
Hsu, Chain Shu
;
Yang, Sheng Hsiung
;
Iwakura, Izumi
Ultrafast pump-probe spectroscopy of poly(3-hexylthiophene) (P3HT) films was performed using a 9-fs laser and a broadband lock-in detection system. The fast geometrical relaxation (GR) time was attributed to the transition from a free exciton (FE) to form a bound polaron pair (BPP), and the time constant was estimated to be tau(GR) = 90 +/- 2 fs. The relaxation time constant of BPP was determined as tau(BPP) = 710 +/- 40 fs. The measurement of pump-power dependence enabled us to distinguish the defect trapping process of BPPs from other parallel decay processes and to determine the defect concentration of a P3HT thin film. (C) 2010 Elsevier B.V. All rights reserved.
Low-power VCO with phase-noise improvement in 0.18 mu m CMOS technology
(2010-09-30)
Liang, C. -P.
;
Huang, T. -J.
;
Rao, P. -Z.
;
Chung, S. -J.
;
傳播研究所
A low-power 5.25 GHz voltage-controlled oscillator ( VCO) with phase-noise improvement is designed in a 0.18 mu m CMOS 1P6M process. Owing to the use of a larger value of parallel capacitor, an additional harmonic-suppressed capacitor, and an appropriate bulk bias voltage of transistor, a good figure of merit of - 190 dBc/Hz can be achieved without extra chip area and CMOS process steps. The fabricated VCO operates from 5.12 to 5.36 GHz with a core power consumption of 1.9 mW and active chip area of 0.15 mm(2). The measured phase noise at 1 MHz offset is about - 119 dBc/Hz.
具電路延遲評估機制之適應性功率控制裝置
(2010-10-01)
謝維致
;
黃威
本發明提供一種具電路延遲評估機制之適應性功率控制裝置，其包含一多模式功率閘網路、一電壓感測器、一可變門檻比較器、一冗餘區間偵測電路以及一雙向位移暫存器，該多模式功率閘網路連接於一電源與一電路模組之間，且該多模式功率閘網路與該電路模組形成一虛擬電壓源，該虛擬電壓源為該電路模組之連接節點，該多模式功率閘網路包含複數個電晶體，其使該多模式功率閘網路依據該冗餘區間偵測電路所判斷之冗餘區間存在狀況而改變該電源輸出至該電路模組之功率。
Authentication and recovery of an image by sharing and lattice-embedding
(2010-10-01)
Lin, Sian-Jheng
;
Lin, Ja-Chen
;
資訊工程學系
;
Department of Computer Science
Based on sharing and lattice-embedding techniques, we present an authentication-recovery method for an image. The recovery data are shared among many shadows, then lattice-embedding is utilized to embed each shadow in the discrete cosine transform domain of an 8x8 block. The proposed method can resist certain content-preserving operations such as JPEG compression, Gaussian noise, and brightness adjustment, up to a tolerance level controlled by a quantization parameter value. The method can also resist certain security attacks such as a cut-and-paste attack, a collage attack, and a vector quantization attack. Compared with previous works, the proposed method has following major advantages and novelty: (1) the method does not require prediction of the tampering trace, and the tampered blocks are always recovered as long as the number of valid blocks reaches a threshold and (2) lattice-embedding yields smaller distortion than does parity-check quantization, and the latter was often used in reported works. (C) 2010 SPIE and IS&T. [DOI: 10.1117/1.3500799]
Structural Effects on Highly Directional Far-Field Emission Patterns of GaN-Based Micro-Cavity Light-Emitting Diodes With Photonic Crystals
(2010-10-01)
Lai, Chun-Feng
;
Kuo, Hao-Chung
;
Chao, Chia-Hsin
;
Yu, Peichen
;
Yeh, Wen-Yung
This study theoretically and experimentally investigates the highly directional far-field emission patterns of GaN photonic crystal (PhC) micro-cavity light-emitting diodes (MCLEDs) depending on varying structural parameters. Angular-spectra-resolved electroluminescence measurements reveals the behavior of guided-mode extraction which is significantly affected by the structural parameters of GaN PhC MCLEDs, where the GaN cavity thickness decides the extracted guided mode numbers, PhC lattice constant influences the distribution of far-field emission, and PhC hole depth affects the interaction with guided modes. The proposed GaN ultrathin MCLED (uMCLED) with PhC lattice constant of 420 nm and deep hole depth of 250 nm exhibited a maximum output light extraction efficiency of 248% under one-watt input power compared to GaN non-PhC uMCLED and produced a directional far-field emission pattern at half intensity near +/- 17 degrees. The present results indicate that highly directional light extraction enhancement could contribute to developments of many applications, especially for etendue-limited applications such as pico-projectors.
Photoresponse of hydrothermally grown lateral ZnO nanowires
(2010-10-01)
Yang, Po-Yu
;
Wang, Jyh-Liang
;
Tsai, Wei-Chih
;
Wang, Shui-Jinn
;
Lin, Jia-Chuan
In this paper, a simple self-assembled lateral growth of ZnO nanowires (NWs) photodetector has been synthesized by a hydrothermal method at a temperature as low as 85 degrees C. The ZnO NWs exhibit single-crystalline wurtzite with elongated c-axis and can be selectively lateral self-assembled around the edges of ZnO seeding layer. The current of ZnO NWs is sensitive to the variation of ambient pressures, i.e. 4.47 mu A was decreased to 1.48 mu A with 5 V-bias as 1.1 x 10(-6) Torr changed to 760 Torr. accordingly. Moreover, the current voltage characteristics of ZnO NWs photodetectors can be evidently distinguished by UV illumination (i.e. lambda = 325 nm). The photocurrent of ZnO NWs with UV illumination is twice larger than dark current while the voltage biased at 5 V. Consequently, this faster photoresponse convinces that the hydrothermally grown lateral ZnO NWs devices have a fairly good for the fabrication of UV photodetectors. (C) 2010 Elsevier B.V. All rights reserved.
高分子基板之高頻覆晶封裝製程及其結構
(2010-10-01)
張翼
;
許立翰
;
胡志偉
;
吳偉誠
;
王景德
本發明係提供一種高分子基板之高頻覆晶封裝製程及其結構，其係利用一階層之高頻覆晶封裝製程所封裝之結構，該結構可有效解決習用經由二階層之高頻覆晶封裝製程所製造之結構，其不僅在高頻特性上會帶來一額外之入射損耗與反射損耗，同時在應用上容易產生一可靠度問題、以及在該習用結構中之一陶瓷基板的製程良率上，仍存在有不佳及成本偏高等缺點。
物件影像偵測方法
(2010-10-01)
韓欽銓
;
陳映濃
本發明揭露一種物件影像偵測方法，其係主要由粗糙至精緻的分析方式以偵測物件影像，此物件影像偵測方法係於採集一影像後，先進行影像的前處理以使得所採集的影像可進行降維與資訊融合，接續，再以已訓練過的過濾器以進行特徵的過濾，最後，則依序利用粗糙層級感知判斷與精緻層級感知判斷以對經過過濾的影像進行進一步類神經網路物件影像偵測以確認此影像之特徵是否符合預先設定之目標物件影像。因此，本發明之物件影像偵測方法係同時利用統計方法、類神經網路方法以及適應性漸進演算法(adaboost)三大主流影像偵測方式來進行物件影像的偵測，以兼顧適應性漸進演算法的快速與類神經網路方法的準確性。