Browsing by Issue Date, starting with "2011-05-01"

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A Delegation Framework for Task-Role Based Access Control in WFMS
(2011-05-01)
Hsu, Hwai-Jung
;
Wang, Feng-Jian
;
資訊工程學系
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Department of Computer Science
Access control is important for protecting information integrity in workflow management system (WfMS). Compared to conventional access control technology such as discretionary, mandatory, and role-based access control models, task-role-based access control (TRBAC) model, an access control model based on both tasks and roles, meets more requirements for modern enterprise environments. However, few discussions on delegation mechanisms for TRBAC are made. In this paper, a framework considering temporal constraints to improve delegation and help automatic delegation in TRBAC is presented. In the framework, the methodology for delegations requested from both users and WfMS is discussed. The constraints for delegatee selection such as delegation loop and separation of duty (SOD) are addressed. With the framework, a sequence of algorithms for delegation and revocation of tasks are constructed gradually. Finally, a comparison is made between our approach and the representative related works.
Microstructures and electrical properties of lead-based PBZNZT and lead-free BNKT piezoelectric ceramics using microwave sintering
(2011-05-01)
Chen, P. Y.
;
Chen, C. S.
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Chou, C. C.
;
Tseng, T. Y.
;
Chen, H. D.
This paper is a comparative study involving sintering conditions (different sintering temperatures and time), process (conventional and microwave sintering), microstructures, and electrical measurements to investigate the mechanism of microwave absorption, and the difference in the microstructural characteristics and electrical properties of lead-based and lead-free ceramics. The lead-based piezoelectric ceramics are x(0.94PbZn(1/3)Nb(2/3)O(3) + 0.06BaTiO(3)) + (1 - x) PbZr(y)Ti(1) (y)O(3) where x = 0.5, y = 0.52 (abbreviated as PBZNZT) and the lead-free ceramics are (Bi(0.5)(Na(1-x)K(x))(0.5))TiO(3) where x = 0.18 (abbreviated as BNKT), all sintered by microwave heating. Experimental results indicate that PBZNZT and BNKT specimens have different microwave absorption efficiencies. Compared with BNKT samples, PBZNZT samples absorb microwave radiation more efficiently in MWS process. This might be attributed to the contribution of the dielectric constant and dipole loss which might dominate the absorption of microwave energy for ferroelectric and piezoelectric materials. HRTEM and energy dispersive spectroscopic investigations show that the grain boundaries of MWS samples exhibit less PbO and ZnO segregation than those of CS samples form PBZNZT specimens. On the other hand, BNKT specimens exhibit no compositional segregation at the grain boundaries after the CS and MWS processes. In addition, the MWS process can achieve a more uniform composition and crystallization in PBZNZT and BNKT ceramics, thus improving the electrical properties. (C) 2011 Elsevier B.V. All rights reserved.
Enhanced light harvesting with pi-conjugated cyclic aromatic hydrocarbons for porphyrin-sensitized solar cells
(2011-05-01)
Wang, Chin-Li
;
Chang, Yu-Cheng
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Lan, Chi-Ming
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Lo, Chen-Fu
;
Diau, Eric Wei-Guang
Zinc porphyrins in a series bearing a phenylethynyl, naphthalenylethynyl, anthracenylethynyl, phenanthrenylethynyl or pyrenylethynyl substituent, denoted LD1, LD2, LD3a, LD3p or LD4, respectively, were prepared as photosensitizers for dye-sensitized solar cells. The overall efficiencies of the corresponding devices show a trend LD4 > LD3p > LD2 > LD3a > LD1. Significantly, LD4 features J(SC)/mA cm(-2) 19.627, V(OC)/V = 0.711, and FF = 0.721, giving an efficiency eta = 10.06% of power conversion. This value is superior to that of a N719-based solar cell fabricated under similar experimental conditions. The remarkable performance of the LD4 cell is rationalized to be due to the broader and more red-shifted spectral feature that makes the IPCE spectrum to cover broadly across the entire visible region, 400-800 nm.
微波退火提升有機電子元件特性之方法
(2011-05-01)
陳方中
;
葛祖榮
;
林義凱
本發明為一種微波退火提升有機電子元件特性之方法，包括下列步驟：提供有機電子元件；以及微波退火有機電子元件。因為微波退火具有非接觸式、退火標的具選擇性、以及退火時間短等特性，且可以僅針對有機電子元件的有機主動層(Organic active layer)退火，使得有機主動層內的有機分子在短時間內重新排列以提高有機分子的排列程度，進而增加光電轉換效率，並提升有機電子元件的特性。
Design and performance analysis on adaptive reservation-assisted collision resolution protocol for WLANs
(2011-05-01)
Lin, Jia-Shi
;
Feng, Kai-Ten
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電機工程學系
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Department of Electrical and Computer Engineering
In conventional IEEE 802.11 medium access control protocol, the distributed coordination function is designed for the wireless stations (WSs) to perform channel contention within the wireless local area networks (WLANs). Packet collision is considered one of the major issues within this type of contention-based scheme, which can severely degrade network performance for the WLANs. Research work has been conducted to modify the random backoff mechanism in order to alleviate the packet collision problem while the WSs are contending for channel access. However, most of the existing work can only provide limited throughput enhancement under specific number of WSs within the network. In this paper, an adaptive reservation-assisted collision resolution (ARCR) protocol is proposed to improve packet collision resulting from the random access schemes. With its adaptable reservation period, the contention-based channel access can be adaptively transformed into a reservation-based system if there are pending packets required to be transmitted between the WSs and the access point. Analytical model is derived for the proposed ARCR scheme in order to evaluate and validate its throughput performance. It can be observed from both analytical and simulation results that the proposed protocol outperforms existing schemes with enhanced channel utilization and network throughput.
搜救犬引導員袁明桂
(2011-05-01)
黃萱如
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Department of Communication and Technology
;
傳播與科技學系
轉個彎進到馴養中心後面的房舍，一聲聲響亮的狗吠此起彼落，大約五、六隻德國狼犬從鐵欄杆裡探出頭，朝闖入者發出警告。「安靜！」威嚴的喝斥聲來自一個身穿著深藍色的工作制服的人，他手持著水管沖洗著狗舍，且毫不在意被沾濕的褲腳，他，是袁明桂，一位搜救犬的資深引導員。
用於磁振造影之磁性奈米粒子
(2011-05-01)
王雲銘
;
陳亭蓉
本發明提供一種用於磁振造影之磁性奈米粒子，包含一個具有一表面且由超順磁性氧化鐵奈米粒子所構成之核，及多數個與核之表面共價偶合且由下式(I)所示之矽氧烷基團：式(I)之各個取代基及n、m及p的意義如說明書及申請專利範圍所界定。本發明之磁性奈米粒子可用作為磁振造影對比劑。
Analytical Solutions of Multilevel Space-Vector PWM for Multiphase Voltage Source Inverters
(2011-05-01)
Hu, Jwu-Sheng
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Chen, Keng-Yuan
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Shen, Te-Yang
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Tang, Chi-Him
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電機工程學系
This study systematically analyzes multilevel space-vector pulse width modulation for a multiphase voltage source inverter (VSI). The instantaneous output voltages of the VSI, which are called space vectors, can be classified according to the switching states of the VSI. By applying the eigenspace decomposition of the system matrix, the n-phase VSI control problem can be solved analytically. This analysis leads to a switching strategy that uses the fewest space vectors and minimum total conduction time. This yields a minimum switching number and efficient dc supply utilization. Further, the switching strategy of a multilevel multiphase VSI system can be solved based on the switching strategy of a two-level multiphase VSI. Simulations and experimental results confirm the effectiveness of the proposed algorithm.
Radiative recombination of indirect exciton in type-II ZnSeTe/ZnSe multiple quantum wells
(2011-05-01)
Chia, Chin-Hau
;
Fan, Wen-Chung
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Lin, Yen-Chen
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Chou, Wu-Ching
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電子物理學系
The tunability of the emission energy, oscillator strength and photoluminescence (PL) efficiency by varying the well thickness and excitation density was demonstrated in the ZnSe(0.8)Te(0.2)/ZnSe multiple quantum wells. A significant blueshift about 260 meV of the PL peak energy was observed as the well width decreased from 5 to 1 nm. An extraordinary long lifetime (300 ns) of the recombination for the widest sample was detected. The binding energy of the indirect excitons is determined as 12 meV for the thinnest sample. The reduction of PL efficiency by thermal energy is greatly suppressed by employing a high excitation power. Crown Copyright (C) 2011 Published by Elsevier B.V. All rights reserved.
光電裝置
(2011-05-01)
范士岡
;
邱誠樸
本發明提供一種光電裝置，包含一流體、一導體，及一設置在該導體與該流體之間並與該導體及該流體連接的介電層，使得該介電層的一區域是受該流體所覆蓋，該介電層包含一基體及限制於該基體內之液晶；藉此，當對該光電裝置施加一電壓時，該流體及該導體之間形成一電場並通過該介電層之該區域，使得該流體的狀態及位於該介電層之該區域內之液晶的指向同時被改變。本發明之光電裝置可有效控制流體之狀態以及可發揮電光效應。
Efficient Tool Replacement Procedure Based on Yield Evaluation
(2011-05-01)
Lin, Chen-ju
;
Pearn, W. L.
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工業工程與管理學系
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Department of Industrial Engineering and Management
Tool wear is an inevitable problem in many machining processes. The problem constitutes an inseparable component of variation and can be considered as a systematic assignable cause of process variability. Tool replacement should be initiated when the yield drops below a certain level. Determining the best time for tool replacement is essential to balance between production quality and tool utilization. The yield index, S(pk), has been effectively applied to assess the yield of processes. However, its ordinary measure is inaccurate when data is contaminated by inseparable nonrandom variation. Yield evaluation becomes imprecise when a process is subjected to the tool wear problem. Thus, this paper presents an efficient procedure that determines the best time to replace tools under an extremely low fraction of defectives. The variation from assignable causes is removed by using the linear regression technique. A modified estimator of the S(pk) index with its distribution is proposed to evaluate the processes with the tool wear problem.
An inverted method for culturing dissociated mouse hippocampal neurons
(2011-05-01)
Chen, Wen-Shin
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Yueh, Chao-Yen
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Huang, Yung-An
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Hwang, Eric
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生物科技學系
Dissociated hippocampal neuron culture has long been the model system of choice for many neuroscientists. The ability to culture dissociated hippocampal neurons from genetically modified mice provides an invaluable tool for studying many neuronal processes. In this study, we established a novel method to culture dissociated hippocampal neurons from embryonic and neonatal mice. Dissociated neurons were cultured in a microchamber between the glass coverslip and the plastic cell container without the use of glial feeder cells. Our method significantly simplifies the preparation while produces healthy and long-lived neuronal cultures that are difficult to achieve without the use of feeder cells. (C) 2011 Elsevier Ireland Ltd and the Japan Neuroscience Society. All rights reserved.
以自然為師　詹武龍
(2011-05-01)
張宇翔
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Department of Communication and Technology
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傳播與科技學系
可以算的上是秀明自然農法資深農夫的詹武龍，投入此農法的種植行列有四年的時間，雖然只是竹北璞玉田裡三分、四分（一分地等於０.１公頃）的土地，卻讓他成功的號召了不遠千里的同好和許多重視親子關係的家庭，一同投入了以自然為師的行列。
Improved Bound on Approximating Jug Measuring Problem
(2011-05-01)
Shieh, Min-Zheng
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Tsai, Shi-Chun
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資訊工程學系
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Department of Computer Science
In this note, we investigate the hardness of approximating the optimal jug measuring problem, which studies how to use jugs with certain capacities to measure a given quantity in minimum steps. Based on a recent related development, we prove that it is NP-hard to approximate this problem within n(c/loglog n) for some constant c > 0. This improves previous known result significantly.
Modified Single-Loop Current Sensorless Control for Single-Phase Boost-Type SMR With Distorted Input Voltage
(2011-05-01)
Chen, Hung-Chi
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Lin, Chih-Chieh
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Liao, Jhen-Yu
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電機工程學系
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Department of Electrical and Computer Engineering
The first single-loop current sensorless control (SLCSC) for single-phase boost-type switching-mode-rectifier (SMR) had been proposed in the prior paper. SLCSC with sinusoidal input voltage possesses good performance, but its performance with distorted input voltage should be improved. In this paper, a modified SLCSC is proposed and implemented in a field-programmable gate array (FPGA)-based system to obtain better performance than SLCSC. Instead of the phase-shift signal in SLCSC, the inductor voltage amplitude signal becomes the output of proportional-plus-integral (PI)-type voltage controller in the modified SLCSC. The provided simulation and experiment results demonstrate the modified SLCSC.
Design to suppress return-back leakage current of charge pump circuit in low-voltage CMOS process
(2011-05-01)
Weng, Yi-Hsin
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Tsai, Hui-Wen
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Ker, Ming-Dou
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電機學院
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College of Electrical and Computer Engineering
A new charge pump circuit has been proposed to suppress the return-back leakage current without suffering the gate-oxide reliability problem in low-voltage CMOS process. The four-phase clocks were used to control the charge-transfer devices turning on and turning off alternately to suppress the return-back leakage current. A test chip has been implemented in a 65-nm CMOS process to verify the proposed charge pump circuit with four pumping stages. The measured output voltage is around 8.8 V with 1.8-V supply voltage to drive a capacitive output load, which is better than the conventional charge pump circuit with the same pumping stages. By reducing the return-back leakage current and without suffering gate-oxide overstress problem, the new proposed charge pump circuit is suitable for applications in low-voltage CMOS IC products. (C) 2011 Elsevier Ltd. All rights reserved.
The elusive excited states of bithiophene: a CASPT2 detective story
(2011-05-01)
Andrzejak, Marcin
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Witek, Henryk A.
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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
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Department of Applied Chemistry
A systematic multi-reference perturbation theory investigation of the excitation energies and oscillator strengths for the lowest excited states of 2,2'-bithiophene unequivocally shows that its optical spectrum is produced by two (1) B (u) states separated from each other by approximately 1 eV. This picture is confirmed by additional calculations with alternative quantum chemical methods. Our findings are in strong contrast with the previous CASPT2 results of Rubio et al. [J Chem Phys 102:3580 (1995) and Chem Phys Chem 4:1308 (2003)], who predicted that the two lowest (1) B (u) states are quasi-degenerate. The methodological reasons responsible for the previous seemingly erroneous assignment of the optical spectrum of bithiophene are identified and explained in terms of unusually large coupling between the (1) B (u) states introduced by dynamical correlation effects. A general discussion of applicable computational techniques is offered aiming at avoiding similar problems for other molecular systems.
殺子兇手　我原諒你
(2011-05-01)
張瑜庭
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Department of Communication and Technology
;
傳播與科技學系
「每個人都有祕密瞞著她，包括她最最親愛的孩子。」
勇於挑戰　不一樣的七年級
(2011-05-01)
潘珮瑄
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Department of Communication and Technology
;
傳播與科技學系
老一輩的人，總愛說著七年級生抗壓性低，重玩樂不重成就，而在校園中，仍舊有著一些學生，用著勇氣與專業，在挑戰「學生」的極限。
Integrated semiconductor optoelectronic devices for real-time and indicator-free detection of aqueous nitric oxide
(2011-05-01)
Chao, Yu-Chiang
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Yeh, Shih-De
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Zan, Hsiao-Wen
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Chang, Gao-Fong
;
Meng, Hsin-Fei
A real-time and indicator-free sensor specific to nitric oxide (NO) is realized for the first time by integrating a sensing hydrogel film, a top-emitting polymer light-emitting diode (PLED), and a silicon photodetector. The top-emitting PLED is utilized to excite the sensing film specific to NO, and the photoluminescence of the sensing film is transformed into electric signal by the photodetector. The influence of the excitation light on the out-put photocurrent of the photodetector is diminished by two delicately selected organic filters based on their absorption spectra. Lead phthalocyanine is deposited on a top-emitting PLED as a filter for generating an excitation light without overlapping the emission maximum of the sensing hydrogel film. Poly(3-hexylthiophene) is placed in front of the photodetector as another filter to remove the excitation light. This sensor demonstrated a fast photocurrent response to NO with response time within 5 min. (C) 2011 Elsevier B.V. All rights reserved.