Browsing by Issue Date, starting with "2010-10-11"

Now showing 1 - 20 of 45066

Abnormal polarization switching phenomenon in a-plane Al(x)Ga(1-x)N
(2010-10-11)
Huang, Huei-Min
;
Huang, Hung-Hsun
;
Wu, Yuh-Renn
;
Lu, Tien-Chang
;
光電工程學系
The optical polarization properties of a-plane Al(x)Ga(1-x)N films have been investigated by polarization-dependent photoluminescence (PL). The degree of polarization decreased with increasing the Al composition, and the main optical polarization direction switched from epsilon perpendicular to c to epsilon // c at about x = 0.07 due to the valence band switching, representing that the optical transition energy of epsilon // c is surpassing that of epsilon perpendicular to c. However, with the Al composition larger than x = 0.1, the higher energy optical transitions of epsilon // c exhibited the stronger PL intensity, opposite to the normal situations that higher energy states commonly have weaker PL intensity than the lower energy states. We utilized the 6 x 6 k.p model and the lambertian-like radiation pattern assumption to explain this abnormal optical polarization switching behavior in the a-plane Al(x)Ga(1-x)N layers and obtained good agreement with the experimental results. (C) 2010 Optical Society of America
Abnormal polarization switching phenomenon in a-plane AlxGa1-xN
(2010-10-11)
Huang, Huei-Min
;
Huang, Hung-Hsun
;
Wu, Yuh-Renn
;
Lu, Tien-Chang
;
照明與能源光電研究所
The optical polarization properties of a-plane AlxGa1-xN films have been investigated by polarization-dependent photoluminescence (PL). The degree of polarization decreased with increasing the Al composition, and the main optical polarization direction switched from epsilon perpendicular to c to epsilon // c at about x = 0.07 due to the valence band switching, representing that the optical transition energy of epsilon // c is surpassing that of epsilon perpendicular to c. However, with the Al composition larger than x = 0.1, the higher energy optical transitions of epsilon // c exhibited the stronger PL intensity, opposite to the normal situations that higher energy states commonly have weaker PL intensity than the lower energy states. We utilized the 6 x 6 k.p model and the lambertian-like radiation pattern assumption to explain this abnormal optical polarization switching behavior in the a-plane AlxGa1-xN layers and obtained good agreement with the experimental results. (C) 2010 Optical Society of America
Temporal contrast enhancement of femtosecond pulses by a self-diffraction process in a bulk Kerr medium
(2010-10-11)
Liu, Jun
;
Okamura, Kotaro
;
Kida, Yuichiro
;
Kobayashi, Takayoshi
;
電子物理學系
We demonstrated for the first time the application of a self-diffraction (SD) process in a bulk Kerr medium to improve the temporal, spectral, and spatial qualities of femtosecond laser pulses. A proof-of-principle experiment succeeded in improving the temporal contrast of a femtosecond pulse by four orders of magnitude even in the picosecond region using a 0.5-mm-thick fused silica glass plate by this technique. The energy conversion efficiency from the incident pulses to the two first-order SD signals is about 12%. By the SD process, a laser pulse with smoother spectral shape, higher beam quality, and shorter pulse duration than those of the input pulse was generated. This technique is expected to be used to design background-free petawatt laser system in the future. (C) 2010 Optical Society of America
Cholesteric liquid crystal devices with nanoparticle aggregation
(2010-10-11)
Jeng, Shie-Chang
;
Hwang, Shug-June
;
Hung, Yu-Hsiang
;
Chen, Sheng-Chieh
;
影像與生醫光電研究所
A broadband cholesteric liquid crystal (CLC) device with a multi-domain structure is demonstrated by using an aggregation of polyhedral oligomeric silsesquioxane (POSS) nanoparticles in the CLC layer. The aggregation pattern of the self-assembled POSS nanoparticles depends on the concentration of POSS doped in the mixture of POSS/CLC and the cooling rate of the mixture from a temperature higher than the clear point. POSS-induced changes in the bulk and surface properties of the cholesteric cells, such as a promotion of homeotropic alignment, help to form a cholesteric structure with a broadband reflection of light; the latter can be used for improvement of bistable CLC devices. A higher POSS concentration and a higher cooling rate both improve the appearance of the black-white CLC device. (C) 2010 Optical Society of America
Strain-driven phase transitions and associated dielectric/piezoelectric anomalies in BiFeO(3) thin films
(2010-10-11)
Huang, C. W.
;
Chu, Y. H.
;
Chen, Z. H.
;
Wang, Junling
;
Sritharan, T.
Strain-driven phase transitions and related intrinsic polarization, dielectric, and piezoelectric properties for single-domain films were studied for BiFeO(3) using phenomenological Landau-Devonshire theory. A stable and mixed structure between tetragonal and rhombohedral-like (monoclinic) phases is predicted at a compressive misfit strain of u(m)=-0.0382 without an energy barrier. For a tensile misfit strain of u(m)=0.0272, another phase transition between the monoclinic and orthorhombic phases was predicted with sharply high dielectric and piezoelectric responses. (c) 2010 American Institute of Physics. [doi:10.1063/1.3499658]
Cholesteric liquid crystal devices with nanoparticle aggregation
(2010-10-11)
Jeng, Shie-Chang
;
Hwang, Shug-June
;
Hung, Yu-Hsiang
;
Chen, Sheng-Chieh
;
影像與生醫光電研究所
A broadband cholesteric liquid crystal (CLC) device with a multi-domain structure is demonstrated by using an aggregation of polyhedral oligomeric silsesquioxane (POSS) nanoparticles in the CLC layer. The aggregation pattern of the self-assembled POSS nanoparticles depends on the concentration of POSS doped in the mixture of POSS/CLC and the cooling rate of the mixture from a temperature higher than the clear point. POSS-induced changes in the bulk and surface properties of the cholesteric cells, such as a promotion of homeotropic alignment, help to form a cholesteric structure with a broadband reflection of light; the latter can be used for improvement of bistable CLC devices. A higher POSS concentration and a higher cooling rate both improve the appearance of the black-white CLC device. (C) 2010 Optical Society of America
Strain-driven phase transitions and associated dielectric/piezoelectric anomalies in BiFeO3 thin films
(2010-10-11)
Huang, C. W.
;
Chu, Y. H.
;
Chen, Z. H.
;
Wang, Junling
;
Sritharan, T.
Strain-driven phase transitions and related intrinsic polarization, dielectric, and piezoelectric properties for single-domain films were studied for BiFeO3 using phenomenological Landau-Devonshire theory. A stable and mixed structure between tetragonal and rhombohedral-like (monoclinic) phases is predicted at a compressive misfit strain of u(m)=-0.0382 without an energy barrier. For a tensile misfit strain of u(m)=0.0272, another phase transition between the monoclinic and orthorhombic phases was predicted with sharply high dielectric and piezoelectric responses. (c) 2010 American Institute of Physics. [doi:10.1063/1.3499658]
《正義論》的「正義」探索
(2010-10-13)
錢永祥
;
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。
Morphological study on pentacene thin-film transistors: the influence of grain boundary on the electrical properties
(2010-10-13)
Chen, Fang-Chung
;
Chen, Ying-Pin
;
Huang, Yu-Jen
;
Chien, Shang-Chieh
;
光電工程學系
We have prepared organic thin-film transistors (OTFTs) featuring pentacene molecules deposited at various substrate temperatures onto either hexamethyldisilazane (HMDS)- or poly(alpha-methylsyrene) (P alpha MS)-treated SiO(2) surfaces. As a result, we obtained different grain boundary densities in the conducting channel. Since the surface-modified devices featured similar grain boundary densities in their active layers, but displayed different electrical performances, we suspected that different trap states probably existed at the grain boundaries for the two different kinds of OTFTs. In addition, the surface morphologies of the initial layers featured grain boundaries that were rather blurred for the thin films prepared on the P alpha MS-treated substrates, whereas shallow boundaries appeared for the pentacene layers on the HMDS-treated surfaces. Therefore, we deduced that the different surface treatment processes resulted in different Schwoebel (step-edge) barriers, and hence, different morphologies. These results suggested that different trap states existed at the grain boundaries of the two types of surface-treated devices, leading to variations in the electrical performance, even though the grain boundary densities were similar.
Morphological study on pentacene thin-film transistors: the influence of grain boundary on the electrical properties
(2010-10-13)
Chen, Fang-Chung
;
Chen, Ying-Pin
;
Huang, Yu-Jen
;
Chien, Shang-Chieh
;
光電工程學系
We have prepared organic thin-film transistors (OTFTs) featuring pentacene molecules deposited at various substrate temperatures onto either hexamethyldisilazane (HMDS)- or poly(alpha-methylsyrene) (P alpha MS)-treated SiO(2) surfaces. As a result, we obtained different grain boundary densities in the conducting channel. Since the surface-modified devices featured similar grain boundary densities in their active layers, but displayed different electrical performances, we suspected that different trap states probably existed at the grain boundaries for the two different kinds of OTFTs. In addition, the surface morphologies of the initial layers featured grain boundaries that were rather blurred for the thin films prepared on the P alpha MS-treated substrates, whereas shallow boundaries appeared for the pentacene layers on the HMDS-treated surfaces. Therefore, we deduced that the different surface treatment processes resulted in different Schwoebel (step-edge) barriers, and hence, different morphologies. These results suggested that different trap states existed at the grain boundaries of the two types of surface-treated devices, leading to variations in the electrical performance, even though the grain boundary densities were similar.
NANOSTRUCTURED THIN-FILM FORMED BY UTILIZING OBLIQUE-ANGLE DEPOSITION AND METHOD OF THE SAME
(2010-10-14)
Chang, Chia-Hua
;
Yang, Chin-Sheng
;
Chiu, Ching-Hua
;
Yu, Pei-Chen
;
Kuo, Hao-Chung
The present invention discloses a transparent conductive nanostructured thin-film by oblique-angle deposition and method of the same. An electron beam system is utilized to evaporate the target source. Evaporation substrate is disposed on a plurality of adjustable sample stage. Multiple gas control valve and heat source is provided to control the gas flow and temperature within the process chamber. An annealing process is performed after the evaporation to improve the thin-film structure and optoelectronic properties.
ROUTING METHOD AND ROUTING PATH RECOVERY MECHANISM IN WIRELESS SENSOR NETWORK ENVIRONMENT
(2010-10-14)
LAI, Jun-Yu
;
Huang, Kuei-Li
;
Wang, Jui-Tang
;
Tseng, Chien-Chao
;
Wu, Chao-Nan
The present invention discloses an asymmetric routing method and routing path recovery mechanism. The wireless sensor network environment includes at least a management unit, at least a gateway, and mobile nodes. When joining, each mobile node obtains an unique ID code and, additionally, a depth as the gradient to the management unit. Accordingly, a mobile node sends an uplink packet via a nearby node with lower depth to the management unit; while the management unit transmits a downlink packet to a mobile node by utilizing the source route method. When the parent node of a mobile node is damaged or moves to another position or said mobile node with its sub-tree descendants changes their position together, the uplink routing path is recovered via selecting a nearby node of the sub-tree as relay node and the downlink routing path is recovered via sending a control message to the management unit.
CHANNEL ESTIMATION TECHNIQUE FOR MULTI-CARRIER SYSTEM
(2010-10-14)
Hung, Kun-Chien
;
Lin, David W.
The present invention relates to a channel estimation technique for multi-carrier system which uses pilot signal to first obtain pilot subcarrier channel responses, then estimate the mean delay and the root-mean-square delay spread of the channel, and then uses interpolation to obtain the channel responses of arbitrary subcarriers. The present invention is able to perform channel estimation and to accurately estimate various channel delay parameters (such as the initial delay, the mean delay, and the root-mean-square delay spread) with very low quantity of pilot signal and with low computational complexity. In addition, the present invention has broad applicability, as it does not require the channel power-delay profile to be of certain specific types and it can operate in systems where pilot subcarriers have an irregular configuration.
COLLINEAR VOLUME HOLOGRAPHIC OPTICAL STORAGE SYSTEM AND INFORMATION STORAGE STRUCTURE THEREOF
(2010-10-14)
SUN, Ching-Cherng
;
Yu, Yeh-Wei
;
Hsieh, Shu-Ching
A collinear volume holographic optical storage system records a plurality pages of holographic data on the storage material, where the intensity distribution of the saved recorded holographic data of each page is in a “+” format. It is possible to incur the inter-page cross talk between two adjacent pages of holographic data along the storage track or between two adjacent storage tracks. An rotation angle between the direction of the distribution of the volume grating and the direction of the storage track can be used to increase the descendent of data storage intensity along storage track, so the effect of the inter-page cross talk is decreased; or the distance between reading centers of two pages of holographic data is shorten to increase the storage density of the storage material.
Detection and Alignment of 3D Domain Swapping Proteins Using Angle-Distance Image-Based Secondary Structural Matching Techniques
(2010-10-14)
Chu, Chia-Han
;
Lo, Wei-Cheng
;
Wang, Hsin-Wei
;
Hsu, Yen-Chu
;
Hwang, Jenn-Kang
This work presents a novel detection method for three-dimensional domain swapping (DS), a mechanism for forming protein quaternary structures that can be visualized as if monomers had "opened'' their "closed'' structures and exchanged the opened portion to form intertwined oligomers. Since the first report of DS in the mid 1990s, an increasing number of identified cases has led to the postulation that DS might occur in a protein with an unconstrained terminus under appropriate conditions. DS may play important roles in the molecular evolution and functional regulation of proteins and the formation of depositions in Alzheimer's and prion diseases. Moreover, it is promising for designing auto-assembling biomaterials. Despite the increasing interest in DS, related bioinformatics methods are rarely available. Owing to a dramatic conformational difference between the monomeric/closed and oligomeric/open forms, conventional structural comparison methods are inadequate for detecting DS. Hence, there is also a lack of comprehensive datasets for studying DS. Based on angle-distance (A-D) image transformations of secondary structural elements (SSEs), specific patterns within A-D images can be recognized and classified for structural similarities. In this work, a matching algorithm to extract corresponding SSE pairs from A-D images and a novel DS score have been designed and demonstrated to be applicable to the detection of DS relationships. The Matthews correlation coefficient (MCC) and sensitivity of the proposed DS-detecting method were higher than 0.81 even when the sequence identities of the proteins examined were lower than 10%. On average, the alignment percentage and root-mean-square distance (RMSD) computed by the proposed method were 90% and 1.8 angstrom for a set of 1,211 DS-related pairs of proteins. The performances of structural alignments remain high and stable for DS-related homologs with less than 10% sequence identities. In addition, the quality of its hinge loop determination is comparable to that of manual inspection. This method has been implemented as a web-based tool, which requires two protein structures as the input and then the type and/or existence of DS relationships between the input structures are determined according to the A-D image-based structural alignments and the DS score. The proposed method is expected to trigger large-scale studies of this interesting structural phenomenon and facilitate related applications.
Optical power equalization for upstream traffic with injection-locked Fabry-Perot lasers in TDM-PON
(2010-10-15)
Huang, Ting-Tsan
;
Sheu, Lih-Gen
;
Chi, Sien
;
光電工程學系
;
Department of Photonics
An optical power equalization of upstream traffic in time-division-multiplexed passive optical network (TDM-PON) based on injection-locked Fabry-Perot lasers has been experimentally investigated. The upstream transmitters with stable spectrum are achieved by using an external injection light source in the optical line terminal (OLT). The different upstream powers can be equalized by injection locking a Fabry-Perot laser diode (FP-LD) biased below threshold current in OLT. The dynamic upstream power range from -8.5 to -19.5 db m is reduced to a 1.6 dB maximal power variation, when the uplink signal is directly modulated at 1.25 Gb/s. (C) 2010 Elsevier B.V. All rights reserved.
Preparation and characterization of high-durability zwitterionic crosslinked proton exchange membranes
(2010-10-15)
Ye, Yun-Sheng
;
Chen, Wen-Yi
;
Huang, Yao-Jheng
;
Cheng, Ming-Yao
;
Yen, Ying-Chieh
The present present paper describes the development of a novel proton exchange membrane comprising a poly (styrene sulfonic acid-co-4-vinylpyridine) copolymer that was crosslinked with a haloalkyl crosslinker through the formation of ionic bonding linkages The nucleophilic substitution of these crosslinked membranes as well as a model reaction between pyridine and 1-bromobutane was confirmed by nuclear magnetic resonance (NMR) Tough and flexible membranes of a high mechanical strength were prepared. They demonstrated very elevated thermal, hydrolytic and oxidative stabilities as compared to other sulfonated polymers. The crosslinked membrane composed of zwitterionic molecules with a crosslinking fraction of 90.3, denoted SP-1, exhibited a proton conductivity of ca 7 1 x 10(-2) S cm(-1) at 30 degrees C under 90% relative humidity; a value comparable to that of Nafion 117 Moreover, the crosslinked SP-1 membrane possessed the highest selectivity for methanol fuel cells (3 38 x 10(5) S cm(-3) s), approximately five times that of Nafion 117. thus implying its potential for practical use in high-energy-density devices (C) 2010 Elsevier B.V All rights reserved.
ALM: An adaptive location management scheme for approximate location queries in wireless sensor networks
(2010-10-15)
Yeh, Lo-Yao
;
Huang, Chen-Che
;
Wu, Cheng-En
;
Huang, Jiun-Long
;
資訊工程學系
Location management is an important issue for object tracking applications of wireless sensor networks. Since locations obtained by most positioning techniques are inherently imprecise, users may send approximate location queries with precision constraints to trade for energy consumption of sensor nodes. Therefore, we propose an Adaptive Location Management scheme called ALM to process approximate location queries. ALM employs a two-tier storage architecture (i.e., centric storage node and local storage node) to facilitate approximate query resolving and to reduce the energy consumption of sensor nodes. We propose a storage node relocation and replication mechanism, which can create, remove replicas of storage nodes and adjust the positions of storage nodes according to the location queries and updates. As such, the number of forwarding location update and query messages is reduced by the proposed storage node relocation and replication mechanism, thereby conserving more energy. The experimental results show that compared with EASE (Xu et al. (2008) [18]), ALM is able to reduce the number of transmission messages and the energy consumption of sensor network, and prolong the network lifetime. (C) 2010 Elsevier B.V. All rights reserved.
Growth and optical properties of high-density InN nanodots
(2010-10-15)
Ke, W. C.
;
Lee, S. J.
;
Kao, C. Y.
;
Chen, W. K.
;
Chou, W. C.
High density InN/GaN nanodots were grown by pulsed mode (PM) metal-organic chemical vapor deposition (MOCVD). InN nanodots density of up to similar to 5 x 10(10) cm(-2) at a growth temperature of 550 degrees C was achieved. The high diffusion activation energy of 2.65 eV due to high NH(3) flow rate generated more reactive nitrogen adatoms on the growth surface, and is believed to be the main reason for the growth of high density InN nanodots. In addition, an anomalous temperature dependence of the PL peak energy was observed for high density InN nanodots. The high carrier concentration, due to high In vacancy (V(ln)) in the InN nanodots, thermally agitated to the conduction band. As the measurement temperature increased, the increase of Fermi energy resulted in blue-shifted PL peak energy. From the Arrhenius plot of integrated PL intensity, the thermal activation energy for the PM grown InN nanodots was estimated to be E(a)similar to 51 meV, indicating strong localization of carriers in the high density InN nanodots. (C) 2010 Elsevier B.V. All rights reserved.
Long-Cavity Fabry-Perot Laser Amplifier Transmitter With Enhanced Injection-Locking Bandwidth for WDM-PON Application
(2010-10-15)
Lin, Gong-Ru
;
Liao, Yu-Sheng
;
Chi, Yu-Chieh
;
Kuo, Hao-Chung
;
Lin, Gong-Cheng
We simulate the injection-locking performance of a 1% antireflection coated Fabry-Perot laser amplifier (AR-FPLA) and demonstrate the 2.5-Gbit/s DWDM-PON application with the directly modulated AR-FPLA based ONU transmitter under side-mode injection-locking condition. The effect of the AR-FPLA front-facet reflectivity on the injection locking range detuning and the Q-factor are interpreted from theoretical simulations and are experimentally characterized. A 25-channel locking capacity is reported for such a side-mode injection-locked AR-FPLA with corresponding wavelength locking range of 30 nm, the minimal requested power of -7 dBm and gain extinction ratio of < 7 dB by reducing its front-facet reflectivity to 1%. At bit rate of 2.5 Gbit/s, the BER of 10(-12) is achievable for the nearest 17 channels of AR-FPLA at receiving power of -21 dBm, and all of the 25 injection-locked channels with SMSR of > 35 dB can guarantee the BER of < 10(-9) with their worst receiving sensitivity degrading to -19 dBm.