Browsing by Issue Date, starting with "2002-11-22"

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Aqueous two-phase extraction as an effective tool for isolation of geniposide from gardenia fruit
(2002-11-22)
Pan, IH
;
Chiu, HH
;
Lu, CH
;
Lee, LT
;
Li, YK
Natural products are normally obtained by organic solvent extraction and many subsequent chromatographic separations. Compounds of interest are often isolated with very low yield and limited purity. An aqueous two-phase extraction process combined with a simple ethanol treatment, for removing excess inorganic salt, has been developed for preparation of geniposide from gardenia. The system was comprised of PE62, a random copolymer composed of 20% ethylene oxide and 80% propylene oxide, KH2PO4 and ethanol. To find optimal conditions, the partition behavior of geniposide under an aqueous two-phase system was investigated. Various factors were considered, including the concentration of salt, the concentration of polymer, the sample loading, and the addition of ethanol. The experimental results demonstrated that increasing salt concentration or decreasing PE62 concentration results in enhancement of the geniposide partition in the salt-rich phase. The addition of ethanol and higher sample loading also promoted the partition efficiency of geniposide. Based on this study, an optimized system containing 5% PE62, 7.5% KH2PO4, and 10% ethanol was tested on a large-scale extraction. A 39.0-g aliquot of final product (in powder form) with 77% purity of geniposide can be effectively extracted from 500 g of gardenia fruit. This process is proved to be useful for industrial application of geniposide preparation. (C) 2002 Elsevier Science B.V. All rights reserved.
Observation of the wave function of a quantum billiard from the transverse patterns of vertical cavity surface emitting lasers
(2002-11-25)
Huang, KF
;
Chen, YF
;
Lai, HC
;
Lan, YP
;
電子物理學系
We demonstrate experimentally that the near-field and far-field transverse patterns of a large aperture vertical cavity surface emitting laser (VCSEL) can be successfully interpreted as a two-dimensional (2D) billiard system. It is found that the near-field and far-field transverse patterns of a large aperture VCSEL evidently represent the coordinate-space and momentum-space wave functions of a 2D quantum billiard, respectively. The result of this paper suggests that large aperture VCSELs are potentially appropriate physical systems for the wave-function study in quantum problems.
Genetic algorithm-based neural fuzzy decision tree for mixed scheduling in ATM networks
(2002-12-01)
Lin, CT
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Chung, IF
;
Pu, HC
;
Lee, TH
;
Chang, JY
Future broad-band integrated services networks based on the asynchronous transfer mode (ATM), technology are expected to support multiple types of multimedia information with diverse statistical characteristics and quality of service (QoS) requirements. To meet these requirements, efficient scheduling methods are important for traffic control in the ATM networks. Among the general scheduling schemes, the rate monotonic algorithm is simple enough to be used in high-speed networks, but it does not attain as high a system utilization as the deadline driven algorithm does. However, the deadline driven scheme is computationally complex and hard to implement in hardware. The mixed scheduling algorithm is the combination of the rate monotonic algorithm and the deadline driven algorithm; thus it can provide most of the benefits of these two algorithms. In this paper, we use the mixed scheduling algorithm to achieve high system utilization under the hardware constraint. Because there is no analytic method for the schedulability test of the mixed scheduling, we propose a genetic algorithm-based neural fuzzy decision tree (GANFDT) to realize it in a real-time environment. The GANFDT combines the GA and a neural fuzzy network into a binary classification tree. This approach also exploits the power of the classification tree. Simulation results show that the GANFDT provides an efficient way to carry out the mixed scheduling in the ATM networks.
Transformation mechanism of different chemically precipitated apatitic precursors into beta-tricalcium phosphate upon calcination
(2002-12-01)
Liou, SC
;
Chen, SY
;
材料科學與工程學系
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Department of Materials Science and Engineering
The Ca-deficient apatite (CDHA) was prepared from the precursors of (CH3COO)(2)Ca - xH(2)O, Ca(NO3)(2).4H(2)O and H3PO4, (NH4)H2PO4 to investigate the transformation mechanism of beta-tricalcium phosphate (beta-TCP). X-ray diffraction analysis shows that the development of beta-TCP is not via direct reaction between Ca and P for all the different combinations between Ca and P precursors. The activation energy of beta-TCP formation with (NH4)H2PO4 as precursor was higher than that with H3PO4. Following the Johnson-Mehl-Avrami equation, the reaction kinetics of beta-TCP phase formation is found one-dimension growth with interface-controlled and diffusion controlled growth depending on the annealing temperature. There exists a transition between 750 degreesC and 825 degreesC, and the transition rate from interface-controlled to diffusion-controlled growth is precursor-dependent. (C) 2002 Elsevier Science Ltd. All rights reserved.
An adaptive sniff schedliling scheme for power saving in Bluetooth
(2002-12-01)
Lin, TY
;
Tseng, YC
;
資訊工程學系
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Department of Computer Science
Bluetooth is expected to be an important basic constructing component of smart homes. In a smart home environment, many devices will be portable and battery-operated, making power saving an essential issue. In this article we study the problem of managing the low-power sniff mode in Bluetooth, where a slave is allowed to be awake only periodically. One challenging problem is how to schedule each slave's sniffing period in a piconet so as to resolve the trade-off between traffic and power-saving requirements, to which we refer as the sniff-scheduling problem. We propose an adaptive protocol to dynamically adjust each slave's sniff parameters, with a goal of catching the varying, and even asymmetric, traffic patterns among the master and slaves. Compared to existing works, our work is unique. First, our scheduling considers multiple slaves simultaneously. Existing work only considers one slave, and different slaves are treated independently. Second, our scheduling is more accurate and dynamic in determining the sniff-related parameters based on slaves' traffic patterns. Most work is restricted to a naive exponential adjustment in sniff interval/sniff-attempt window. Third, our proposal includes the placement of sniff-attempt periods of sniffed slaves on the time axis when multiple slaves are involved. This issue is ignored by earlier work. Extensive simulation results are presented. Among many observations, one interesting result is that with proper settings, our protocol can save significant power while achieving higher network throughput than a naive always active round-robin scheme.
Engineering phosphors for improved brightness
(2002-12-01)
Lin, CH
;
Chiou, BS
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Lin, JD
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
Factors affecting the cathodoluminescent (CL) efficiency of phosphors include: morphology, size, stoichiometry, composition, and surface of the phosphors. In the design of phosphors for low-voltage operations, processes such as surface etching are used to enhance phosphor efficiency. In this study, zinc-activated ZnO phosphors were subjected to three processes: acid etching, ball milling, and/or ultrasonic vibration, and the effect of each process on the CL efficiency studied. It is found that the brightness of phosphors increases 40% after ultrasonic vibration followed by etching twice with 0.005 M HNO3. (C) 2002 Kluwer Academic Publishers.
RPIM-SM: extending PIM-SM for RP relocation
(2002-12-01)
Lin, YD
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Hsu, NB
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Hwang, RH
;
資訊工程學系
;
Department of Computer Science
The protocol independent multicast-sparse mode (PIM-SM) protocol establishes core-base tree to forward multicast datagrams in a network. In PIM-SM, the core or rendezvous point (RP) of a group is determined at each multicast router by hashing a group address, i.e. a class-D IP address, to one of the candidate RPs. The hash function is characterized by its ability to evenly and uniquely choose the core for a group and remains insensitive to the geographic distribution of the group members and the sources. However, it may result in a multicast tree with high cost. This study presents a relocation mechanism, which is extension to PIM-SM, in which RP could be relocated periodically. When a new RP is found, the original RP informs all members to re-join to the new RP. Simulation results indicate that the extended version, RPIM-SM, reduces about 20% tree cost than PIM-SIM when the group size is medium. Moreover, comparing RPIM-SM with the optimal core-based tree reveals that they have less than 5% difference in tree cost. Furthermore, an increase of the number of candidate RPs brings RPIM-SM even closer to the optimal core-based tree. Results in this study demonstrate that relocation improve the performance of PIM-SM. (C) 2002 Published by Elsevier Science B.V.
Minimizing weighted earliness and tardiness penalties in single-machine scheduling with idle time permitted
(2002-12-01)
Chen, JY
;
Lin, SF
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電控工程研究所
;
Institute of Electrical and Control Engineering
In this paper, a single-machine scheduling problem with weighted earliness and tardiness penalties is considered. Idle time between two adjacent jobs is permitted and due dates of jobs could be unequal. The dominance rules are utilized to develop a relationship matrix, which allows a branch-and-bound algorithm to eliminate a high percentage of infeasible solutions. After combining this matrix with a branching strategy, a procedure to solve the problem is proposed. (C) 2002 Wiley Periodicals, Inc.
Unloading law for a LEO spacecraft with two-gimbals solar array
(2002-12-01)
Jan, YW
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Chiou, JC
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電控工程研究所
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Institute of Electrical and Control Engineering
The purpose of this paper is to present a modified cross-product unloading law that can be used to provide an open-loop compensation control design to counteract the predominant effects of the gravity gradient torque. The modified cross-product unloading law, is successfully applied to a three-axis stabilized, nadir-pointed LEO spacecraft with two-gimbals solar array. The variation of the two solar array orientations can significantly change the spacecraft's moment of inertia during the nominal operation mode, which can produce significant momentum accumulation in the roll-yaw body plane and cause large yaw pointing error. A rigorous study of momentum management performance capability has been conducted by using a high-fidelity performance simulation software that contains models of four environmental disturbance torque (gravity gradient, aerodynamic, solar, and magnetic). The simulation results show that the proposed momentum unloading control law has enabled a substantial reduction in the maximum accumulated roll momentum, which results in improving the pointing accuracy of the LEO spacecraft enormously. (C) 2002 Published by Elsevier Science Ltd.
Effects of surfactant addition on dewatering of alum sludges
(2002-12-01)
Huang, C
;
Pan, JR
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Fu, CG
;
Wu, CC
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環境工程研究所
In Taiwan, surfactants are frequently used in the flotation process to aid in solid/liquid separation. Their effect on the dewatering of alum sludge was investigated. Various amounts of cationic and anionic surfactants were added to sludge samples, and the dewatering characteristics of the sludge and the water content of sludge cakes were evaluated. Both surfactants improved the dewatering of the sludge by lowering the specific resistance to filtration, decreasing the bound water content, and increasing the dewatering rate of the sludge. Different combinations of anionic and cationic surfactants and polyelectrolytes were also experimented on to study the effect of surfactant addition on the dewatering characteristics of polyelectrolyte-conditioned sludge. Experimental results indicated that both cationic and anionic surfactants adversely affected the dewatening of the conditioned sludge. The addition of surfactant to the oppositely charged polyelectrolyte proved to be most detrimental to sludge dewatering due to the precipitation between surfactant and polyelectrolyte. The addition of cationic surfactant to the cationic polyelectrolyte-conditioned sludge had the least effect.
缸
(2002-12-01)
管管
A learnable cellular neural network structure with ratio memory for image processing
(2002-12-01)
Wu, CY
;
Cheng, CH
;
電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
In this paper, a learnable cellular neural network (CNN) with space-variant templates and ratio memory (RM) called the RMCNN, is proposed and analyzed. By incorporating both modified Hebbian learning rule and RM into CNN architecture, the RMCNN as the associative memory can generate the absolute weights and then transform them into the ratioed A-template weights as the ratio memories for recognition of noisy input patterns. It is found from simulation results that due to the feature enhancement effect of RM, the RMCNN under constant leakage on template coefficients can store and recognize more patterns than the CNN associative memories without RM, but with the same learning rule and the same constant leakage on space-variant template coefficients. For 9 x 9 (18 x 18) RMCNNs, three (five) patterns can be learned, stored and recognized. Based upon the RMCNN architecture, an experimental chip of CMOS 9 x 9 RMCNN is designed and fabricated by using 0.35 mum CMOS technology. The measurement results have successfully verified the correct functions of RMCNN.
Fuzzy multiple-criteria decision-making approach for industrial green engineering
(2002-12-01)
Chiou, HK
;
Tzeng, GH
;
運輸與物流管理系註：原交通所+運管所
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科技管理研究所
;
Department of Transportation and Logistics Management
This paper describes a fuzzy hierarchical analytic approach to determine the weighting of subjective judgments. In addition, it presents a nonadditive fuzzy integral technique to evaluate a green engineering industry case as a fuzzy multicriteria decision-making (FMCDM) problem. When the investment strategies are evaluated from various aspects, such as economic effectiveness, technical feasibility, and environmental regulation, it can be regarded as an FMCDM problem. Since stakeholders cannot clearly estimate each considered criterion in terms of numerical values for the anticipated alternatives/strategies, fuzziness is considered to be applicable. Consequently, this paper uses triangular fuzzy numbers to establish weights and anticipated achievement values. By ranking fuzzy weights and fuzzy synthetic utility values, we can determine the relative importance of criteria and decide the best strategies. This paper applies what is called a X fuzzy measure and nonadditive fuzzy integral technique to evaluate the synthetic performance of green engineering strategies for aquatic products processors in Taiwan. In addition, we demonstrate that the nonadditive fuzzy integral is an effective evaluation and appears to be appropriate, especially when the criteria are not independent.
Colour image retrieval based on primitives of colour moments
(2002-12-01)
Shih, JL
;
Chen, LH
;
資訊工程學系
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Department of Computer Science
A colour image retrieval method based on the primitives of colour moments is proposed. First, an image is divided into several blocks. Then, the colour moments of all blocks are extracted and clustered into several classes. The mean moments of each class are considered as a primitive of the image. All primitives are used as features. Since two different images may have different numbers of features, a new similarity measure is then proposed. To demonstrate the effectiveness of the proposed method, two test databases from Corel are used to compare the performances of the proposed method with other existing ones. The experimental results show that the proposed method is usually better than the others. Furthermore, since for a few special types of images, other methods may have better results occasionally, a relevance feedback algorithm is also provided to automatically determine the best method according to the user's response.
缸
(2002-12-01)
管管
Quantum manifestations of classical periodic orbits in a square billiard: Formation of vortex lattices
(2002-12-01)
Chen, YF
;
Huang, KF
;
Lan, YP
;
電子物理學系
;
光電工程研究所
We extend the presentation of the SU(2) coherent states to analytically construct the wave function concentrated on high-order classical periodic orbits in a square billiard. With the constructed wave function, the localization of the wave pattern is found to be very efficient. We also analyze the vortices arising from the singular points of the quantum phase for the constructed coherent states. It is found that the wave interference gives rise to the appearance of vortex lattices in the probability current density associated with the high-order periodic orbits. Moreover, the topological charge of the vortex is in general nonintegral except for the periodic orbits with the same winding number to the sides of the square.
缸
(2002-12-01)
管管
GaAs metal-semiconductor-metal photodetectors with low dark current and high responsivity at 850 nm
(2002-12-01)
Lin, SD
;
Lee, CP
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
In this paper, we report on the fabrication a GaAs metal-semiconductor-metal photodetector with both low dark current and high responsivity at 850 nm. By using the Schottky contacts modified by a thin, n(+)-doped layer on the surface of the devices, the lowest dark current density of about 4.5 x 10(-7) cm(-2) was achieved. Besides, in the same devices, the responsivity resulting from a newly designed resonant-cavity-enhanced structure with a superlattice distributed Bragg reflector was about 0.34 A W-1 at 850 nm. The equivalent external quantum efficiency of the devices with equal finger spacing and finger width was about 48%. Our design is relatively easy and reproducible for both the sample growth and the device process.
Sortability of multi-partitions
(2002-12-01)
Hwang, FK
;
Wang, YM
;
Lee, JS
;
應用數學系
;
Department of Applied Mathematics
Recently, the theory of sortability of partition property has been shown to be an effective tool to prove the existence of an optimal partition with that property. In this paper, we extend the theory to multi-partition where the partition is on t types of components. We apply our results to settle an optimal assignment problem whose proof was incomplete as given in the literature.
A note on the interval estimation of C-pk with asymmetric tolerances
(2002-12-01)
Lin, GH
;
Pearn, WL
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工業工程與管理學系
;
Department of Industrial Engineering and Management
Pearn and Chen (1998) proposed a generalization of the widely used process capability index (PCI) C-pk to handle processes with asymmetric tolerances. They investigated the sampling distribution and obtained the exact formulae for the expected value and variance of its natural estimator. Recently, Pearn and Lin (2000) considered a different estimator under different process condition, and investigated the statistical properties of the new estimator. However, their efforts focused on the small sample properties under the normality assumption. In this paper, we investigate the large sample properties of its natural estimator under the general condition. Based on the limiting distribution of the new estimator, we provide an approximate 100(1 - alpha)% confidence interval of the considered PCI. The obtained confidence interval provides great benefit to quality engineers on monitoring the process and assessing process performance.