Browsing by Issue Date, starting with "2002-03-01"

Now showing 1 - 20 of 74889

Polarized blue emission based on a side chain liquid crystalline polyacrylate containing bis-tolane side groups
(2002-03-01)
Chang, SW
;
Li, AK
;
Liao, CW
;
Hsu, CS
;
應用化學系
A novel side chain liquid crystalline (LC) polyacrylate (1P) containing highly conjugated bis-tolane side groups was synthesized and used for polymer light emitting diodes application. Polymer 1P shows a nematic phase at room temperature. It exhibits a UV absorption peak at 330 run and emits a blue light at 425 inn. Polyimide (PI), polyaniline (PA) and poly(3,4-diethylenedioxythiophene) (PEDOT) were used as alignment materials for polymer 1P. The photoluminescence dichroic ratios of 1P on rubbed PI, PA and PEDOT films are 10.4, 8.3 and 7.3, respectively. The electroluminescence dichroic ratio of IP aligned on a PEDOT film is 6.1.
Effective strategy for porous organosilicate to suppress oxygen ashing damage
(2002-03-01)
Liu, PT
;
Chang, TC
;
Mor, YS
;
Chen, CW
;
Tsai, TM
Photoresist stripping with oxygen plasma ashing destroys numerous functional groups in porous organosilicate glasses (OSGs), This impact makes the porous OSG relatively hydrophilic and causes low-k dielectric degradation, To mitigate these issues, various strategies are investigated to enhance oxygen plasma resistance of the porous OSG. These include physical and chemical procedures. Both structural and electrical analyses are used to determine their efficiency. In addition, an optimum prescription that consists of H, plasma and chemical trimethylchlorosilane treatment is developed in this work. The enhancement of oxygen plasma resistance can provide the porous OSG for practical application in the multilevel interconnection. (C) 2002 The Electrochemical Society.
Design and fabrication of fiberlenses for optical recording applications
(2002-03-01)
Tien, CH
;
Lai, YC
;
Milster, TD
;
Shieh, HPD
;
光電工程學系
The novel design and fabrication of a microlens on the front end of a single-mode fiber is described. The beam quality and spot size for optical recording applications are analyzed. A hyperbolic-shaped microlens on a single-mode fiber with focused spot of 1/e(2) = 0.82 mum (x-direction) and 0.89 mum (y-direction) at similar to 145 mum working distance was achieved by a simple fabrication procedure.
A release combined scheduling scheme for non-uniform dependence loops
(2002-03-01)
Pean, DL
;
Chua, HT
;
Chen, C
;
資訊工程學系
;
Department of Computer Science
In general, synchronization mechanisms can be used to preserve dependence constraints in any nested loop, and can be combined with a loop scheduling scheme to form a uniform framework to obtain the correct execution order and balance workload distribution. Most current scheduling mechanisms cannot handle non-uniform dependence loops. In this paper, we propose a new combined scheduling scheme called Release Combined Scheduling for Non-uniform Dependence Loops (RCS) to schedule non-uniform dependence doubly-nested loops in multiprocessor systems. It combines both static and dynamic scheduling mechanisms in order to optimize the system performance. In our approach, initialisation of a set of scheduling information is based on the concept of the minimum dependence distance. During runtime, scheduling information is used to adjust the number of parallelizable iterations. Our method is able to discover more parallelism from a given non-uniform dependence doubly-nested loop than is possible with previous approaches. The experimental results show that the RCS method reliably exploits parallelism and outperforms most of the existing non-uniform dependence loop scheduling schemes by 20.29%, on average.
Group testing in bipartite graphs
(2002-03-01)
Juan, ST
;
Chang, GJ
;
應用數學系
;
Department of Applied Mathematics
This paper investigates the group testing problem in graphs as follows. Given a graph G = (V, E), determine the minimum number t(G) such that t(G) tests are sufficient to identify an unknown edge e with each test specifies a subset X subset of or equal to V and answers whether the unknown edge e is in G[X] or not. Damaschke proved that [log(2) e(G)] less than or equal to t(G) less than or equal to [log(2) e(G)] + 1 for any graph G, where e(G) is the number of edges of G. While there are infinitely many complete graphs that attain the upper bound, it was conjectured by Chang and Hwang that the lower bound is attained by all bipartite graphs. This paper verifies the conjecture for bipartite graphs G with e(G) less than or equal to 2(4) or 2(k-1) < e(G) less than or equal to 2(k-1) + 2(k-3) + 2(k-6) + 19(.)2(k-7/2) -1 for k greater than or equal to 5.
An electro-thermally driven microactuator with two dimensional motion
(2002-03-01)
Wu, CT
;
Hsu, W
;
機械工程學系
;
Department of Mechanical Engineering
In previous literatures, most of the microactuators were designed to deflect in one dimension only. Here, an electro-thermally driven microactuator with out-of-plane and in-plane two dimensional motion is designed, fabricated and tested. This microactuator comprised of a series of bimorph beams, a moving plate, a lateral driven unit, and contact pads. The out-of-plane motion is produced due to the bimorph effect and residual stress between the layers of Au and polysilicon when they are heated. The in-plane motion is obtained by heating the lateral driven unit which consists of two adjacent beams with different cross sections but the same length, then the asymmetrical thermal expansions in two adjacent beams lead to lateral deflection. The microactuator proposed here is fabricated by surface micromaching technique. A twostep releasing method is used here to free the microactuator successfully. The testing results show that the lateral driven unit can produce 10 mum lateral displacements at input voltages of 5 V, and bimorph structures at the same voltage can produce about 12 mum downward displacement. It is also found that this two dimensional motion can be controlled almost independently.
Diamond deposition on Si (111) and carbon face 6H-SiC (0001) substrates by positively biased pretreatment
(2002-03-01)
Chang, TF
;
Chang, L
;
材料科學與工程學系
;
Department of Materials Science and Engineering
The growth of textured diamond films on Si (111) and carbon face 6H-SiC (0001) has been achieved by positive bias-enhanced-nucleation in microwave plasma chemical vapor deposition. A bias voltage of + 100 to +300 V, 3% CH4 concentration in bias step, and 0.33% CH4 concentration in growth step were used to synthesize diamond films on Si and carbon face 6H-SiC. Highly oriented diamond films were observed by scanning electron microscopy and X-ray diffraction patterns. Cross-sectional transmission electron microscopy showed that the interface between diamond and Si substrate was smooth, while it was rough between diamond and SiC. It also showed that diamond films were directly grown on both substrates. (C) 2002 Elsevier Science B.V. All lights reserved.
The removal selectivity of titanium and aluminum in chemical mechanical planarization
(2002-03-01)
Hsu, JW
;
Chiu, SY
;
Wang, YL
;
Dai, BT
;
Tsai, MS
The removal selectivity control of aluminum and titanium metal barrier during aluminum chemical mechanical polishing in the Damascene process is known to be critical for surface planarity without metal dishing and dielectric erosion. Unfortunately, the electrochemical behaviors of aluminum and titanium are dissimilar, as one may expect. In this study, in situ electrochemical impedance spectroscopy was carried out to investigate the influences of H(2)O(2) concentration, slurry pH, and metal oxide formation through the passivation on aluminum and titanium. As H(2)O(2) concentration increases, the measured impedance of aluminum and titanium decreases, or the oxidation rates of these two metals are enhanced upon increasing the oxidizer concentration. As the slurry pH increases, the removal rate of polished titanium increases, but it decreases for polished aluminum. The removal rate of titanium was limited to its oxidation rate and aluminum was limited to its oxide dissolution rate. (C) 2002 The Electrochemical Society.
Spatial disorder of cellular neural networks with biased term
(2002-03-01)
Ban, JC
;
Lin, SS
;
Hsu, CH
;
應用數學系
;
Department of Applied Mathematics
This study describes the spatial disorder of one-dimensional Cellular Neural Networks (CNN) with a biased term by applying the iteration map method. Under certain parameters, the map is one-dimensional and the spatial entropy of stable stationary solutions can be obtained explicitly as a staircase function.
Fuzzy modeling employing fuzzy polyploidy genetic algorithms
(2002-03-01)
Wu, MD
;
Sun, CT
;
資訊工程學系
;
Department of Computer Science
Fuzzy modeling generally comprises structure identification and parameter identification. The former determines the structure of a rule-base, whereas the latter determines the contents of each rule. Applying neural networks or genetic algorithms to identify the parameter sets and structures of a fuzzy system is increasingly popular owing to their ability to learn and adapt. However, most conventional approaches cannot integrate structure identification and parameter identification efficiently. This work presents a general approach to fuzzy modeling, i.e. fuzzy polyploidy genetic algorithms which integrate structure identification and parameter identification in a single evolution process. Capable of simulating the structural adaptation process of natural evolution, the proposed model is a generalized model for simultaneously optimizing both structure and parameters of fuzzy rule-bases. The structural adaptation proposed herein provides complete structural operations to simulate structural variation process and simple to complex life form of natural evolution. Illustrative examples involving typical FLCs, such as Mamdani and TSK models, demonstrate the effectiveness of applying the polyploidy scheme.
Effect of annealing on electron dephasing in three-dimensional polycrystalline metals
(2002-03-01)
Lin, JJ
;
Zhong, YL
;
Li, TJ
;
電子物理學系
;
物理研究所
We have studied the effect of thermal annealing on electron dephasing times in three-dimensional polycrystalline metals. Measurements are performed on as-sputtered and annealed AuPd and Sb thick films, using the weak-localization method. In all samples, we find that possesses an extremely weak temperature dependence as T --> 0. Our results show that the effect of annealing is non-universal, and it depends strongly on the amount of disorder quenched in the microstructures during deposition. The observed saturation behavior of cannot be easily explained by magnetic scattering. We suggest that the issue of saturation can be better addressed in three-dimensional, rather than lower-dimensional, structures.
Adaptive-feedrate interpolation for parametric curves with a confined chord error
(2002-03-01)
Yeh, SS
;
Hsu, PL
;
電控工程研究所
;
Institute of Electrical and Control Engineering
Recently, modern manufacturing systems have been designed which can machine arbitrary parametric curves while greatly reducing data communication between CAD/CAM and CNC systems. However, a constant feedrate and chord accuracy between two interpolated points along parametric curves are generally difficult to achieve due to the non-uniform map between curves and parameters. A speed-con trolled interpolation algorithm with an adaptive feedrate is proposed in this paper. Since the chord error in interpolation depends on the curve speed and the radius of curvature, the feedrate in the proposed algorithm is automatically adjusted so that a specified limit on the chord error is met. Both simulation and experimental results for non-uniform rational B-spline (NURBS) examples are provided to verify the feasibility and precision of the proposed interpolation algorithm. (C) 2001 Elsevier Science Ltd. All rights reserved.
Developing the e-Delphi system: a web-based forecasting tool for educational research
(2002-03-01)
Chou, C
;
教育研究所
;
Institute of Education
On the distribution of the estimated process yield index S-pk
(2002-03-01)
Lee, JC
;
Hung, HN
;
Pearn, WL
;
Kueng, TL
;
統計學研究所
This paper considers an asymptotic distribution for an estimate (S) over cap (pk) of the process yield index S-pk proposed by Boyles (1994). The asymptotic distribution of (S) over cap (pk) is useful in statistical inferences for S-pk. An illustrative example is given for hypothesis testing and for interval estimation on the yield index S-pk. Copyright (C) 2002 John Wiley Sons, Ltd.
Two-phase minislot scheduling algorithm for HFC QoS services provisioning
(2002-03-01)
Yin, WM
;
Wu, CJ
;
Lin, YD
;
資訊工程學系
;
Department of Computer Science
Data-Over-Cable Service Interface Specifications v1.1 (DOCSIS v1.1 ), developed for data transmissions over Hybrid Fiber Coaxial (HFC networks. defines five upstream services for supporting per-flow Quality of Services QoS). The cable modern termination system (CMTS) must periodically grant upstream transmission opportunities to the QoS flows based on their QoS parameters. However, packets may violate QoS requirements when several flows demand the same interval for transmission. This study proposes a two-phase, i.e.. the scheduling sequence determination phase and the minislot assignment phase. minislot scheduling algorithm to reduce the QoS violation rate. In the scheduling sequence determination phase, the flow whose packets are most unlikely to violate QoS is scheduled first. Then. in the minislot assignment phase, the scheduler allocates to a flow the available interval where the likelihood of packet violation is minimum. Simulation results demonstrate that our scheduling algorithm can reduce the QoS violation rate by 80-35% over that of the first-come-first-serve-random-selection algorithm. It increases the utilization by 25% as well, The two-phase minislot scheduling algorithm can work within the DOCSIS v1.1 framework.
Characterization of Si/SiGe heterostructures on Si formed by solid phase reaction
(2002-03-01)
Huang, CH
;
Chin, A
;
Chen, WJ
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
We have characterized the Si/Si(0.6)Ge(0.4) heterostructure formed by two-step solid-phase reaction. Single crystalline behavior is evidenced by X-ray diffraction. In sharp contrast to conventional strain-relaxed SiGe, an extremely smooth surface close to the Si substrate is measured by cross-sectional transmission electron microscopy and atomic force microscopy. Good material quality is further evidenced from the near identical current-voltage characteristics for thermal oxide grown on Si/Si(0.6)Ge(0.4) and on the Si control sample. (C) 2002 The Electrochemical Society.
Study of carbon nanoemitters using CO2-CH4 gas mixtures in triode-type field emission arrays
(2002-03-01)
Chen, CF
;
Tsai, CL
;
Lin, CL
;
材料科學與工程學系
;
Department of Materials Science and Engineering
In this study. we used methane/carbon dioxide gas mixtures to deposit nanoemitters on the gate-structured metal-insulator-semiconductor (MIS) diodes. Due to the nanoemitters growing in a high carbon concentration gas source of CH4/CO2, the growth rate is better than conventional mixtures by using hydrocarbons diluted in hydrogen. Moreover, the bias also promotes the growth rate in the CH4/CO2 gas mixtures. In addition, selected area deposition (SAD) of emitters was successfully achieved by using the Pt layer as inhibitor in the bias assisted microwave plasma chemical vapor deposition (BAMPCVD). The field emission. current and the current density of nanoemitters on field emission arrays (FEAs) are 154 LA and 490 mA cm(-2), respectively. This may be due to the following reasons: (I) short gate-emitter spacing; (II) small gate aperture; and (III) emitter with a sharp feature. (C) 2002 Elsevier Science B.V. All rights reserved.
A classification of noncircular attribute grammars based on the look-ahead behavior
(2002-03-01)
Yang, W
;
資訊工程學系
;
Department of Computer Science
We propose a family of static evaluators for subclasses of the well-defined (i.e., noncircular) attribute grammars. These evaluators augment the evaluator for the absolutely noncircular attribute grammars with look-ahead behaviors. Because this family covers exactly the set of all well-defined attribute grammars, well-defined attribute grammars may be classified into a hierarchy, called the NC hierarchy, according to their evaluators in the family. The location of a noncircular attribute grammar in the NC hierarchy is an intrinsic property of the grammar. The NC hierarchy confirms a result of Riis and Skyum, which says that all well-defined attribute grammars allow a (static) pure multivisit evaluator by actually constructing such an evaluator. We also show that, for any finite m, an NC(m) attribute grammar can be transformed to an equivalent NC(0) grammar.
Growth mechanism and properties of the large area well-aligned carbon nano-structures deposited by microwave plasma electron cyclotron resonance chemical vapor deposition
(2002-03-01)
Lin, CH
;
Chang, HL
;
Tsai, MH
;
Kuo, CT
;
材料科學與工程學系
Large area (4-inch diameter) well-aligned carbon nano-structures on Si substrate were successfully synthesized by using a catalyst-assisted microwave plasma electron cyclotron resonance chemical vapor deposition (ECR-CVD) system with CH4 as source gas. The catalysts include Fe, Co and Ni. The catalysts and the deposited nano-structures were characterized by scanning electron microscopy (SEM) transmission electron microscopy (TEM), Raman and field emission I-V measurements. Effects of process parameters on morphologies, structures and properties of the nano-structures were examined. The results show that the deposited nano-structures can include normal nano-tubes, split catalyst nano-tubes, seaweed-like nano-sheets and carbon film, depending mainly on substrate temperature and bias, catalyst materials and their application methods. Deposition mechanisms for different nano-structures, especially, the unique split catalyst nano-tubes and seaweed-like nano-sheets, were proposed. The differences in oxidation resistance and field emission proper-ties between different nano-structures will be compared and discussed. (C) 2002 Elsevier Science B.V. All rights reserved.
Implantation induced defects in the retrograde well with a buried layer
(2002-03-01)
Hsu, WC
;
Liang, MS
;
Chen, MC
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
This work investigates the implantation induced extended defects in the retrograde p- and n-well with/without a buried layer after postimplantation thermal annealing at 950degreesC in N(2) ambient. A preferential etchant of CrO(3)/HF mixed solution was used to delineate the defects induced by high-energy ion implantation. It is found that the extended defects elongated to the top surface of the retrograde well with a buried layer, which was implanted with high-energy boron ion at 1500 keV to a dose of 3x10(13) cm(-2), resulting in the etching pits of extended defects at a density of about 10(5) cm(-2). (C) 2002 The Electrochemical Society.