Browsing by Issue Date, starting with "2011-09-15"

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Numerical ranges of weighted shifts
(2011-09-15)
Wang, Kuo-Zhong
;
Wu, Pei Yuan
;
應用數學系
;
Department of Applied Mathematics
Let A be a unilateral (resp., bilateral) weighted shift with weights w(n), n >= 0 (resp., -infinity < n < infinity). Eckstein and Racz showed before that A has its numerical range W (A) contained in the closed unit disc if and only if there is a sequence {a(n)}(n=0)(infinity) (resp., {a(n))(n=-infinity)(infinity)) in [-1,1] such that |w(n)|(2) = (1 - a(n))(1 + a(n+1)) for all n. In terms of such a(n)'s, we obtain a necessary and sufficient condition for W (A) to be open. If the w(n)'s are periodic, we show that the a(n)'s can also be chosen to be periodic. As a result, we give an alternative proof for the openness of W (A) for an A with periodic weights, which was first proven by Stout. More generally, a conjecture of his on the openness of W (A) for A with split periodic weights is also confirmed. (C) 2011 Elsevier Inc. All rights reserved.
Social trend tracking by time series based social tagging clustering
(2011-09-15)
Chen, Shihn-Yuarn
;
Tseng, Tzu-Ting
;
Ke, Hao-Ren
;
Sun, Chuen-Tsai
;
資訊工程學系
Social tagging is widely practiced in the Web 2.0 era. Users can annotate useful or interesting Web resources with keywords for future reference. Social tagging also facilitates sharing of Web resources. This study reviews the chronological variation of social tagging data and tracks social trends by clustering tag time series. The data corpus in this study is collected from Hemidemi.com. A tag is represented in a time series form according to its annotating Web pages. Then time series clustering is applied to group tag time series with similar patterns and trends in the same time period. Finally, the similarities between clusters in different time periods are calculated to determine which clusters have similar themes, and the trend variation of a specific tag in different time periods is also analyzed. The evaluation shows the recommendation accuracy of the proposed approach is about 75%. Besides, the case discussion also proves the proposed approach can track the social trends. (C) 2011 Elsevier Ltd. All rights reserved.
Two distinct ballistic processes in graphene at the Dirac point
(2011-09-15)
Lewkowicz, M.
;
Rosenstein, B.
;
Nghiem, D.
;
電子物理學系
;
Department of Electrophysics
The dynamical approach is applied to ballistic transport in mesoscopic graphene samples of length L and contact potential U. At times shorter than both relevant time scales, the flight time t(L) = L/v(g) (v(g) is Fermi velocity) and t(U) = (h) over bar /U, the major effect of the electric field is to create electron-hole pairs, i.e., causing interband transitions. In linear response, this leads (for width W >> L) to conductivity sigma(2) = pi/2 e(2)/h. On the other hand, at times lager than the two scales, the mechanism and value are different. It is shown that the conductivity approaches its intraband value, equal to the one obtained within the Landauer-Butticker approach resulting from evanescent waves. It is equal to sigma(1) = 4/pi e(2)/h for W >> L and t(U) << t(L). The interband transitions, within linear response, are unimportant in this limit. Between these extremes there is a crossover behavior dependent on the ratio between the two time scales t(L)/t(U). At strong electric fields (beyond linear response) the interband process dominates. The electron-hole mechanism is universal, namely, does not depend on geometry (aspect ratio, topology of boundary conditions, properties of leads), while the evanescent modes mechanism depends on all of them. On basis of the results we determine that while in absorption measurements and in dc transport in suspended graphene sigma(2) was measured, sigma(1) would appear in experiments on small ballistic graphene flakes on substrate.
Creating the aspired intelligent assessment systems for teaching materials
(2011-09-15)
Chen, Cheng-Hsiung
;
Tzeng, Gwo-Hshiung
;
科技管理研究所
;
Institute of Management of Technology
The core objective of the Nine-Year Integrated Curriculum for primary schools is to "enable students to demonstrate their talents instead of just scoring high on exams" around the world. The determining factor in education reform is to declare the competence indicators of necessary educational behavior in primary and junior high school. In the reform process, for all domains, the enriched rate of competence indicators for educational materials and methods is very meaningful. Because educational materials and methods in different domains have their own style, we should evaluate these teaching materials separately. Thus, in this research we propose a novel MCDM (Multiple Criteria Decision Making) framework for evaluating, comparing, and improving the effectiveness of competence indicators in the various publications for teaching materials in primary school based on different viewpoints. The ANP (Analysis Network Process) weights are based on the DEMATEL technique with the MCDM method for resolving the problems of dependence and feedback among criteria. Then, a VIKOR technique with ANP weights is proposed for addressing and reducing the performance gaps for each criterion, thus hopefully improving, re-configuring and selecting the aspired Intelligent Assessment Systems (IAS) for teaching materials. An empirical study of Mandarin Chinese based on this system design of three publishers is illustrated to verify the effectiveness of the proposed method. The results can improve the efficiency and quality of the authored Mandarin Chinese teaching materials and may extend to other Learning Areas. (C) 2011 Elsevier Ltd. All rights reserved.
Curcumin enhances the mitomycin C-induced cytotoxicity via downregulation of MKK1/2-ERK1/2-mediated Rad51 expression in non-small cell lung cancer cells
(2011-09-15)
Ko, Jen-Chung
;
Tsai, Min-Shao
;
Weng, Shao-Hsing
;
Kuo, Ya-Hsun
;
Chiu, Yu-Fan
Curcumin (diferuloylmethane), a major active component of turmeric (Curcuma longa), has been reported to suppress the proliferation of a wide variety of tumor cells. Rad51 is a key protein in the homologous recombination (HR) pathway of DNA double-strand break repair, and HR represents a novel target for cancer therapy. A high expression of Rad51 has been reported in chemo- or radio-resistant carcinomas. Therefore, in the current study, we will examine whether curcumin could enhance the effects of mitomycin C (MMC), a DNA interstrand cross-linking agent, to induce cytotoxicity by decreasing Rad51 expression. Exposure of two human non-small lung cancer (NSCLC) cell lines (A549 and H1975) to curcumin could suppress MMC-induced MKK1/2-ERK1/2 signal activation and Rad51 protein expression. Enhancement of ERK1/2 activation by constitutively active MKK1/2 (MKK1/2-CA) increased Rad51 protein levels in curcumin and MMC co-treated human lung cells. Moreover, the synergistic cytotoxic effect induced by curcumin combined with MMC was decreased by MKK1-CA-mediated enhancement of ERK1/2 activation by a significant degree. In contrast, MKK1/2 inhibitor, U0126 was shown to augment the cytotoxicity of curcumin and MMC through downregulation of ERK1/2 activation and Rad51 expression. Depletion of endogenous Rad51 expression by siRad51 RNA transfection significantly enhanced MMC and/or curcumin induced cell death and cell growth inhibition. In contrast, an overexpression of Rad51 protected lung cancer cells from synergistic cytotoxic effects induced by curcumin and MMC. We concluded that Rad51 inhibition may be an additional action mechanism for enhancing the chemosensitization of MMC by curcumin in NSCLC. (C) 2011 Elsevier Inc. All rights reserved.
Conversion Efficiency Enhancement of GaN/In0.11Ga0.89N Solar Cells With Nano Patterned Sapphire and Biomimetic Surface Antireflection Process
(2011-09-15)
Wang, H. W.
;
Chen, H. C.
;
Chang, Y. A.
;
Lin, C. C.
;
Han, H. W.
In this study, p-i-n double-heterojunction GaN/In0.11Ga0.89N solar cells grown by metal-organic chemical vapor deposition on pattern sapphire substrate are presented. The solar cell with standard process has a conversion efficiency of 3.1%, which corresponds to a fill factor of 58%, short circuit current density of 2.86 mA/cm(2), and open circuit voltage of 1.87 V under AM1.5G illumination. To further improve the conversion efficiency of the GaN/In0.11Ga0.89N solar cells, two-dimensional polystyrene nanospheres were deposited and self-organized as mask in the anisotropic inductively coupled plasma reactive ion etching process to form a biomimetic surface roughing texture. The surface morphology of the solar cell shows a periodically hexagonal bead pattern and the beads are formed in a diameter of 160 nm with a period of 250 nm. An increase of 15% in short circuit current density is found, thus improving the conversion efficiency to 3.87%. If we optimize the structure for 180 nm of the height and 375 nm of the period, a 10% gain can be expected when compared to the current structure.
MULTIPLEXED BI-DIRECTIONAL CIRCULATOR
(2011-09-15)
Chang Rong-Yuan
;
Chen Fu-Chiarng
In the present invention, a novel multi-port microwave circuit, also known as a multiple bi-directional circulator, is designed based upon the basis of the EBG characteristic of the meta-materials. Firstly, the concept of the traditional single-layered mushroom structure is extended with the suspending microstrip line to the multi-layered structure. In this way, the multi-layered structure can reveal multi-band EBG characteristic and achieve miniaturization. Moreover, we use three sets of proposed dual-band EBG circuit to be series-connected in a ring-type structure. By using proper impedance matching, the design of the multiple bi-directional circulator is accomplished. It combines the capabilities of the diplexer, the duplexer and the circulator. The triplex bi-directional circulator can integrate three kinds of communication systems with each other, which operates at frequencies comprising GSM 1800 MHz, WiFi 2.45 GHz, and WiMAX 3.5 GHz, respectively. It is suitable for the information integration of multi-band and multi-system communication applications.
Electrical conduction processes in ZnO in a wide temperature range 20-500 K
(2011-09-15)
Lien, Chien-Chi
;
Wu, Chih-Yuan
;
Li, Zhi-Qing
;
Lin, Juhn-Jong
;
電子物理學系
We have investigated the electrical conduction processes in as-grown and thermally cycled ZnO single crystal as well as as-grown ZnO polycrystalline films over the wide temperature range 20-500 K. In the case of ZnO single crystal between 110 and 500 K, two types of thermal activation conduction processes are observed. This is explained in terms of the existence of both shallow donors and intermediately deep donors that are consecutively excited to the conduction band as the temperature increases. By measuring the resistivity rho(T) of a given single crystal after repeated thermal cycling in vacuum, we demonstrate that oxygen vacancies play an important role in governing the shallow donor concentrations but leave the activation energy (similar or equal to 27 +/- 2 meV) largely intact. In the case of polycrystalline films, two types of thermal activation conduction processes are also observed between similar to 150 and 500 K. Below similar to 150 K, we found an additional conductionprocess due to the nearest-neighbor-hopping conduction mechanism, which takes place in the shallow impurity band. As the temperature further decreases below similar to 80 K, a crossover to the Mott variable-range-hopping conduction process is observed. Taken together with our previous measurements on rho(T) of ZnO polycrystalline films in the temperature range 2-100 K [Y. L. Huang et al., J. Appl. Phys. 107, 063715 (2010)], this work establishes a quite complete picture of the overall electrical conduction mechanisms in the ZnO material from liquid-helium temperatures up to 500 K. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3638120]
Fluctuation-induced tunneling conduction through RuO(2) nanowire contacts
(2011-09-15)
Lin, Yong-Han
;
Lin, Juhn-Jong
;
電子物理學系
;
物理研究所
;
Department of Electrophysics
A good understanding of the electronic conduction processes through nanocontacts is a crucial step for the implementation of functional nanoelectronic devices. We have studied the current-voltage (I-V) characteristics of nanocontacts between single metallic RuO(2) nanowires and contacting Au electrodes, which were pre-patterned by simple photolithography. Both the temperature behavior of contact resistance in the low-bias voltage ohmic regime and the I-V curves in the high-bias voltage non-ohmic regime have been investigated. We found that the electronic conduction processes in the wide temperature interval 1-300 K can be well described by the fluctuation-induced tunneling (FIT) conduction theory. Taken together with our previous work [Lin et al., Nanotechnology 19, 365201 (2008)], where the nanocontacts were fabricated by delicate electron-beam lithography, our study demonstrates the general validity of the FIT model in characterizing electronic nanocontacts. (C) 2011 American Institute of Physics. [doi:10.1063/1.3638707]
Conversion Efficiency Enhancement of GaN/In(0.11)Ga(0.89)N Solar Cells With Nano Patterned Sapphire and Biomimetic Surface Antireflection Process
(2011-09-15)
Wang, H. W.
;
Chen, H. C.
;
Chang, Y. A.
;
Lin, C. C.
;
Han, H. W.
In this study, p-i-n double-heterojunction GaN/In(0.11)Ga(0.89)N solar cells grown by metal-organic chemical vapor deposition on pattern sapphire substrate are presented. The solar cell with standard process has a conversion efficiency of 3.1%, which corresponds to a fill factor of 58%, short circuit current density of 2.86 mA/cm(2), and open circuit voltage of 1.87 V under AM1.5G illumination. To further improve the conversion efficiency of the GaN/In(0.11)Ga(0.89)N solar cells, two-dimensional polystyrene nanospheres were deposited and self-organized as mask in the anisotropic inductively coupled plasma reactive ion etching process to form a biomimetic surface roughing texture. The surface morphology of the solar cell shows a periodically hexagonal bead pattern and the beads are formed in a diameter of 160 nm with a period of 250 nm. An increase of 15% in short circuit current density is found, thus improving the conversion efficiency to 3.87%. If we optimize the structure for 180 nm of the height and 375 nm of the period, a 10% gain can be expected when compared to the current structure.
Charge Pump
(2011-09-15)
WU Chun-Yi
;
HSIEH Wei-Chih
;
CHANG Ming-Hung
;
HWANG Wei
A charge pump is disclosed for amplifying an input voltage received at an input end and outputting the amplified voltage at an output end as an output voltage. The charge pump includes a plurality of source/drain coupling transistors for serving as charging capacitors, and a plurality of cascode-connected transistors being symmetrically connected to between the input end and the output end. The charge pump further includes a plurality of diode-connected transistors to protect the source/drain coupling transistors against breakdown during the course of charge transfer and to speed up the charge transfer.
DEVICE AND METHOD FOR FABRICATING MICRO ARTICLES
(2011-09-15)
FAN SHIH-KANG
;
LIN TING-HSU
;
LIN JING-WEI
;
WU CHIH-MING
A device for fabricating micro articles, which includes a first electrode plate, a second electrode plate, and a spacing component. The first electrode plate has a forming electrode, where the forming electrode correspondingly matches a cross-section of the micro article. The spacing component is disposed in between the first electrode plate and the second electrode plate, with the thickness corresponds to the thickness of the micro article. Thereby, the device is able to store the solidifiable liquid therein, where the solidifiable liquid is controlled for shaping according to the forming electrode. After the solidifiable liquid has shaped and solidified, the finished product of the micro article is attained. The present disclosure also provides a method for fabricating micro articles.
Fine Tuning of HOMO Energy Levels for Low-Band-Gap Photovoltaic Copolymers Containing Cyclopentadithienopyrrole and Bithiazole Units
(2011-09-15)
Patra, Dhananjaya
;
Sahu, Duryodhan
;
Padhy, Harihara
;
Kekuda, Dhananjay
;
Chu, Chih-Wei
Five conjugated LBG polymers P1-P5 consisting of a DTP unit as an electron donor and various bithiazole units as electron acceptors are designed and synthesized for photovoltaic applications. The effects of the electron-deficient bithiazole derivatives on the thermal, optical, electrochemical, and photovoltaic properties are investigated. The molecular structures are confirmed and characterized. The resulting polymers have high thermal stabilities and broad absorption bands with low optical bandgaps. The hole and electron mobilities are calculated. PSC devices are fabricated utilizing the polymers as electron donors and PCBM as an electron acceptor. The PSC device with an active layer of P4:PCBM (1:1 by weight) exhibits the best power-conversion efficiency.
Investigation of Emission Polarization and Strain in InGaN-GaN Multiple Quantum Wells on Nanorod Epitaxially Lateral Overgrowth Templates
(2011-09-15)
Huang, Huei-Min
;
Lu, Tien-Chang
;
Chang, Chiao-Yun
;
Ling, Shih-Chun
;
Chan, Wei-Wen
Non-polar (a-plane) InGaN-GaN multiple quantum wells (MQWs) on the GaN nanorod epitaxially lateral overgrowth templates with different nanorod height have been fabricated. The average in-plane strain in the InGaN MQWs has been determined from 2.73 x 10(-2) to 2.58 x 10(-2) while the nanorod height in templates increases from 0 to 1.7 mu m. The polarization ratio of the emission from InGaN MQWs varies from 85% to 53% along with the increase of the GaN nanorod height. The reduction of polarization ratio has been attributed to the partial strain relaxation within the epitaxial structures as a result of growth on the GaN nanorod templates and the micro-size air-voids observed in the nanorod templates.
The Application of the Sawtooth Photonic Crystal on Producing Polarized Light
(2011-09-15)
Pei, Ting-Hang
;
Chen, Wei-Chou
;
Yang, Kei-Hsiung
;
光電學院
;
College of Photonics
We have proposed a sawtooth photonic crystal formed by Si-SiO(2) periodic layers designed on a planar medium as a polarizer. The polarizer can produce H-polarized light very efficiently because the frequency of E-polarized light is chosen at the photonic band gap but that of H-polarized light at the photonic conduction band. The best polarization ratio is as high as 2.56 x 10(5) : 1 when the normalized frequency a/lambda is 0.24 and the incident angle is about 13 degrees. Highly polarized light can be produced in a normalized frequency range from 0.23 to 0.25, and this can possibly be applied to an LED with a certain bandwidth.
Complex symmetric stabilizing solution of the matrix equation X plus A(T)X(-1)A = Q
(2011-09-15)
Guo, Chun-Hua
;
Kuo, Yueh-Cheng
;
Lin, Wen-Wei
;
數學建模與科學計算所(含中心)
;
Graduate Program of Mathematical Modeling and Scientific Computing, Department of Applied Mathematics
We study the matrix equation X + A(T)X(-1)A = Q, where A is a complex square matrix and Q is complex symmetric. Special cases of this equation appear in Green's function calculation in nano research and also in the vibration analysis of fast trains. In those applications, the existence of a unique complex symmetric stabilizing solution has been proved using advanced results on linear operators. The stabilizing solution is the solution of practical interest. In this paper we provide an elementary proof of the existence for the general matrix equation, under an assumption that is satisfied for the two special applications. Moreover, our new approach here reveals that the unique complex symmetric stabilizing solution has a positive definite imaginary part. The unique stabilizing solution can be computed efficiently by the doubling algorithm. (C) 2011 Elsevier Inc. All rights reserved.
Effects of Cr doping on physical properties of amorphous In-Ga-Zn-O films
(2011-09-15)
Liu, Shiu-Jen
;
Su, Shih-Hao
;
Fang, Hau-Wei
;
Hsieh, Jang-Hsing
;
Juang, Jenh-Yih
Amorphous thin films of InGaZnO(4) (a-IGZO) doped with Cr have been fabricated by using pulsed-laser deposition (PLD). The electrical, optical and magnetic properties of Cr-doped a-IGZO films grown at 25 degrees C and 150 degrees C were investigated. The conductivity, optical transmission and band gap of films are remarkably enhanced by increasing the growth temperature. Conductivity, carrier concentration and mobility decrease with increasing the Cr content. However, the optical transmission and band gap are not significantly affected by Cr doping. Moreover, all Cr-doped films exhibit room-temperature ferromagnetism. (C) 2011 Elsevier B.V. All rights reserved.
Fluctuation-induced tunneling conduction through RuO2 nanowire contacts
(2011-09-15)
Lin, Yong-Han
;
Lin, Juhn-Jong
;
電子物理學系
;
物理研究所
;
Department of Electrophysics
A good understanding of the electronic conduction processes through nanocontacts is a crucial step for the implementation of functional nanoelectronic devices. We have studied the current-voltage (I-V) characteristics of nanocontacts between single metallic RuO2 nanowires and contacting Au electrodes, which were pre-patterned by simple photolithography. Both the temperature behavior of contact resistance in the low-bias voltage ohmic regime and the I-V curves in the high-bias voltage non-ohmic regime have been investigated. We found that the electronic conduction processes in the wide temperature interval 1-300 K can be well described by the fluctuation-induced tunneling (FIT) conduction theory. Taken together with our previous work [Lin et al., Nanotechnology 19, 365201 (2008)], where the nanocontacts were fabricated by delicate electron-beam lithography, our study demonstrates the general validity of the FIT model in characterizing electronic nanocontacts. (C) 2011 American Institute of Physics. [doi:10.1063/1.3638707]
多頻雙工環路器
(2011-09-16)
張榮原
;
陳富強
本發明為一種新型微波電路之設計，此微波電路稱為三頻雙工環路器，其亦基於後設材料之電磁帶隙性質所建構出。首先，將傳統單層蕈狀結構結合懸置微帶線之理論，推廣至多層結構，使其擁有多頻電磁帶隙特性，達到電路縮小化效果。接著將三組所設計的雙頻電磁帶隙電路作環形串聯，並經過妥善的阻抗匹配，進而完成三頻雙工環路器之設計，它結合了雙工器與環路器之功能，其可使GSM 1800MHz、WiFi 2.45GHz和WiMAX 3.5GHz系統之間，作多頻段與多通道的資料整合。
用於多階衝擊器之多微孔噴嘴板及其製造方法
(2011-09-16)
蔡春進
;
陳聖傑
;
陳宏達
一種用於多階衝擊器之多微孔噴嘴板，由半導體製程之微影、蝕刻及電鑄方法所製成，此一多微孔噴嘴板包含有一板體以及多數微孔，微孔形成於該板體且貫穿該板體之頂底兩側，其內徑由噴嘴板之底側朝上逐漸擴大，且內表面平滑，而可避免微粒於其內部堆積而導致阻塞。