Browsing by Issue Date, starting with "1998-02-02"

Now showing 1 - 20 of 82359

Alterable temperature-dependent wavelength shifts in (InP)(2)/(GaP)(2) quantum wells
(1998-02-02)
Cheng, YC
;
Tai, K
;
Chou, ST
;
Huang, KF
;
Tu, SL
Alterable temperature-dependent emission wavelength shifts were observed from (InP)(2)/(GaP)(2) short-period superlattices (SPSs) quantum wells grown with different interruption periods. Photoluminescence spectra showed that the peak energy of the SPS samples is inversely proportional to the interruption time conducted between the two consecutive binary growth sequences in the SPS regions. It is believed that a lateral composition modulation occurred during the interruption period which resulted in periodic In-rich and Ga-rich regions in the SPS quantum wells along the growth plane. With the lateral compositional variation, temperature variation can induce a multiaxial strain effect which can either amplify or reduce the temperature-dependent wavelength shift of the SPS quantum wells with different interruption periods. (C) 1998 American Institute of Physics.
Low power parallel Huffman decoding
(1998-02-05)
Lin, CH
;
Jen, CW
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
A low power design technique for a parallel Huffman decoder is presented. According to the length of the incoming Huffman codeword, the proposed strategy makes the barrel shifter in the parallel Huffman decoder turn off the unnecessary shifting bits to reduce power dissipation. The result of a SPICE simulation indicates that up to 50 percent power reduction in the barrel shifter may be achieved with the proposed technique.
Double degeneracy and chaos in a rate gyro with feedback control
(1998-02-05)
Ge, ZM
;
Chen, HH
;
機械工程學系
;
Department of Mechanical Engineering
The analysis of a single-axis rate gyro subjected to feedback control mounted on a space vehicle that is spinning with uncertain angular velocity omega(2) about its spin of the gyro is presented. For the autonomous case in which omega(2) is steady, we examine the dynamics of the resulting system on the center manifold near the double-zero degenerate point by using center manifold and normal form methods. There exist a few kinds of bifurcations in the autonomous case such as pitchfork and Hopf bifurcations for local bifurcation analyses, and a saddle-connection bifurcation for global analyses. As singular velocity omega(2) of the space vehicle is harmonic, the Melnikov technique was used to give criteria for the existence of chaos in the gyro motion. The numerical simulations are performed to verify the analytical results in the form of phase portraits, bifurcation diagrams and Lyapunov exponents. In addition, chaotic motions of this system can be changed into regular motions by a small parametric perturbation with Lyapunov exponent calculations. (C) 1998 Academic Press Limited.
Optimal 1-Hamiltonian graphs
(1998-02-13)
Wang, JJ
;
Hung, CN
;
Hsu, LH
;
資訊工程學系
;
Department of Computer Science
In this paper, we present a family of 3-regular, planar, and hamiltonian graphs. Any graph in this family remains hamiltonian if any node or any edge is deleted. Moreover, the diameter of any graph in this family is O(root p) where p is the number of nodes. (C) 1998 Elsevier Science B.V.
週末讀詩會「管管說詩」
(1998-02-14)
余亮
Ordering reduction in In0.5Ga0.5P grown by solid source molecular beam epitaxy
(1998-02-15)
Cheng, YC
;
Tai, KC
;
Chou, ST
;
Huang, KF
;
Tu, SL
In0.5Ga0.5P grown on GaAs substrates with different tilting angles by solid source molecular beam epitaxy (SSMBE) is studied. The results showed that a weak ordering effect still exists in SSMBE grown epilayers with tilted substrates. However, the ordering effect can be drastically reduced by growing In0.5Ga0.5P on a 15 degrees tilted substrate with an InAlP/InGaP superlattices (SL) buffer layer. The In0.5Ga0.5P epilayer grown by this method showed a peak photoluminescence (PL) energy of similar to 1.91 eV at room temperature, which is similar to the reported value for a fully disordered sample. The intensity of the ordering effect is characterized by polarized PL spectroscopy, and the reduction in the ordering intensity is attributed to the elimination of initial surface strain by the SL buffer layer.
Electrical characteristics of CO2-sensitive diode based on WO3 and IrO2 for microsensor applications
(1998-02-15)
Chao, SC
;
電子物理學系
;
Department of Electrophysics
Devices based on the contact of sputtered WO3 and IrO2 that are covered by an HCO3--containing polymer exhibit reversible and reproducible CO2-dependent, diodelike current rectification at 1 atm and room temperature. The gain or loss of current in the forward direction as a function of CO2 concentration is found to be tunable by controlling the thickness ratio of the WO3 and IrO2 films. The rectification mechanism is uniquely governed by the thermodynamic free energies; this is the key to the durability previously not attainable using conventional diodes in microsensor applications. These diodes are useful as a basis of construction for durable microsensors operating in gases or liquids.
Effects of N2O-annealed sacrificial oxide on the short-channel effects of nMOSFETs
(1998-02-19)
Jong, FC
;
Huang, TY
;
Chao, TS
;
Lin, HC
;
Wang, MF
The authors report the effects of N2O-annealed sacrificial oxide on nMOSFETs. It is demonstrated that by adding an N2O-annealing step to the sacrificial. oxide which was stripped off before growing the final gate oxide, the reverse short-channel effects (RSCE) can still be effectively suppressed.
Effects of 3 '-phosphoadenosine 5 '-phosphate on the activity and folding of phenol sulfotransferase
(1998-02-20)
Yang, YS
;
Tsai, SW
;
Lin, ES
;
生物科技學系
;
Department of Biological Science and Technology
Known spectroscopic and kinetic data are used to formulate pathways of the physiological and transfer reactions and the substrate inhibition of phenol sulfotransferase. Kinetic mechanisms indicate that release of PAP from enzyme complex is required for the physiological reaction but not for the transfer reaction. The pathways explain rate difference between the physiological and transfer reactions since the release of PAP is the rate-limiting step of the former reaction. Two enzyme species of phenol sulfotransferase which distinguish the physiological and transfer reaction were found to involve the binding of PAP. Differences between two forms of phenol sulfotransferase, alpha and beta, indicate that they assemble through different folding process. It is demonstrated that only alpha enzyme renatures in the presence of PAP and beta enzyme renatures only ir. the absence of PAP in vitro. In the over-expressed system, formation of alpha and beta phenol sulfotransferase is also dependent on the availability of PAP in Escherichia coli. It is concluded that folding of phenol sulfotransferase is assisted by PAP to form alpha enzyme. In the absence of PAT, beta form of phenol sulfotransferase is produced. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.
Quantum dynamics of a diatomic molecule under chirped laser pulses
(1998-02-28)
Lin, JT
;
Lai, TL
;
Chuu, DS
;
Jiang, TF
;
電子物理學系
The photodissociation probability of a diatomic molecule is usually very small even under a strong field due to its anharmonicity. However, the progress in laser technology provides a chirped laser pulse to lower the threshold of the dissociation intensity. We investigate the quantum dynamics of a diatomic molecule under such a kind of pulse. It is found that there is a significant dissociation probability at moderate intensity for a diatomic molecule under a chirped pulse. The quantum dissociation probability is found to be suppressed with respect to the classical one for intensities above the dissociation threshold. Therefore the chirped pulse can efficiently dissociate a diatomic molecule.
Solving facility-layout optimization problems with clustering constraints
(1998-03-01)
Li, HL
;
Hsieh, MC
;
資訊管理與財務金融系註：原資管所+財金所
;
Department of Information Management and Finance
Most facility-layout problems are at present solved by heuristic methods, which are not suitable for treating layout problems if some facilities need to be placed together. In this paper we add the constraints of clustering facilities and thus propose an optimization model for facility-layout problems. The advantages of introducing clustering constraints are: first, they fit the more practical rationale of facility layouts; second, they can help improve the computational efficiency owing to the reduction in nonoverlapping constraints among the facilities.
Bound water content and water binding strength on sludge flocs
(1998-03-01)
Wu, CC
;
Huang, CP
;
Lee, DJ
;
環境工程研究所
;
Institute of Environmental Engineering
On the basis of the thermodynamic hypothesis and using the thermodynamic approach, a binding strength was calculated to define the physical meaning of bound water content of sludge as measured by dilatometer. The sludge samples considered in this study included kaolin, alum and biological sludge. The binding strength of bound water at -20 degrees C was calculated as 24.5 kJ/kg, which is close to that of the normal physico-adsorption process. Most of the frozen moisture in st dilatometric measurement should be interstitial water or vicinal water. Results also indicated that moisture with a lower binding strength easily became free water. The release of interstitial water from sludge flocs would cause less bound water. When solid concentration is higher, the expelling strength induced by the compacting action of sludge flocs is increased over the binding strength, thereby forcing out the interstitial water. Lower bound water contents are attained. Accurate measurement of bubble volumes with the calculated stem on the top of the dilatometer could improve the precision of expansion coefficient and bound water content measurement. (C) 1998 Elsevier Science Ltd. All rights reserved.
Improvements on Sloan's algorithm for constructing Delaunay triangulations
(1998-03-01)
Huang, CW
;
Shih, TY
;
土木工程學系
;
Department of Civil Engineering
Similarity retrieval by 2D C-trees matching in image databases
(1998-03-01)
Hsu, FJ
;
Lee, SY
;
Lin, BS
;
資訊科學與工程研究所
;
Institute of Computer Science and Engineering
The image retrieval based on spatial content is an attracting task in many image database applications. The 2D strings provide a natural way of constructing spatial indexing for images and support effective picture query. Nevertheless, the 2D string is deficient in describing the spatial knowledge of nonzero sized objects with overlapping. In this paper, we use an ordered labeled tree, a 2D C-tree, to be the spatial representation for images and propose the tree-matching algorithm for similarity retrieval. The distance between 2D C-trees is used to measure the similarity of images. The proposed tree comparison algorithm is also modified to compute the partial tree distance for subpicture query. Experimental results for verifying the effectiveness of similarity retrieval by 2D C-trees matching are presented. (C) 1998 Academic Press.
GMNF-DVMRP: An enhanced version of distance vector multicast routing protocol
(1998-03-01)
Lai, YC
;
Lin, YD
;
Yu, WC
;
資訊工程學系
;
Department of Computer Science
In this paper we propose an enhancement to the Distance Vector Multicast Routing Protocol (DVMRP), called 'Group Membership Near First DVMRP' (GMNF-DVMRP), to decrease the network cost (NC) of the multicast tree formed by DVMRP. A simulation is implemented to compare our enhanced version and the original DVMRP. We find that our method saves about 5%-7% of NC of the multicast tree formed by DVMRP. (C) 1998 John Wiley & Sons, Ltd.
High-performance capillary electrophoretic analysis of synthetic food colorants
(1998-03-01)
Kuo, KL
;
Huang, HY
;
Hsieh, YZ
;
應用化學系
;
Department of Applied Chemistry
A high-performance capillary electrophoresis method with diode-array detection has been developed for analysis of synthetic food colorants. The influence of buffer composition on the separation of the food colorants was examined, as were the effects of alpha-, beta- and gamma-cyclodextrins on analyte migration behavior. Eight food colorants were completely separated within 10 min using pH 9.5 borax - NaOH buffer containing 5 mM beta-cyclodextrin. Experimental results indicate that the relative standard deviations of analyte migration times were < 0.88% under the optimized separation condition. Correlation coefficients of the linear calibration plots of the analytes exceeded 0.998. The method was suitable for determination of the quantities of synthetic food colorants in ice cream bars and fruit soda drinks.
Computerized tooth profile generation and undercut analysis of noncircular gears manufactured with shaper cutters
(1998-03-01)
Chang, SL
;
Tsay, CB
;
機械工程學系
;
Department of Mechanical Engineering
Pitch curves of a conjugate noncircular gear pair are derived based on kinematic considerations. A method for considering the inverse mechanism relationship and the equation of meshing, is proposed here to derive a complete mathematical model of noncircular gears manufactured with involute-shaped shaper-cutters. The proposed method is similar to the contact line method and the envelope method but is easier to apply to the determination of tooth profiles. A computer program is developed for generation the tooth profile with backlashes. Undercutting analysis is also investigated by considering the relative velocity and equation of meshing. Finally modified elliptical gears are presented to illustrate the tooth profile generation when the proposed mathematical model is applied and to investigate the phenomenon of tooth undercutting.
New imidazoles as probes of the active site topology and potent inhibitors of beta-glucosidase
(1998-03-01)
Li, YK
;
Hsu, HS
;
Chang, LF
;
Chen, G
;
應用化學系
Series of 4-arylimidazoles, omega-N-acylhistamines and 4-(omega-phenylalkyl) imidazoles were synthesized in order to probe the active site topology of sweet almond beta-glucosidase. These imidazole derivatives were shown to be very powerful competitive inhibitors. Among the 20 tested compounds, omega-N-benzoylhistamine and 4-(3'-phenylpropyl)imidazole are the most potent inhibitors of the enzyme, with pH-independent K-i values of 0.06 and 0.07 mu M, respectively, The inhibition of 4-(omega-phenylalkyl)imidazoles exhibited an interesting trend as to K-i values: 4-phenylimidazole (6.6 mu M)>4-benzylimidazole (1.4 mu M)>4-(2'-phenylethyl)imidazole (0.82 mu M)>4-(3'-phenylpropyl)imidazole (0.07 mu M)<4-(4'-phenylbutyl)imidazole (0.13 mu M)<4-(5'-phenylpentyl)imidazole (0.3 mu M), This revealed that the imidazole and aryl binding sites (which result from favorable interactions within the corresponding glycone and aglycone binding subsites) are separated by the optimal distance equivalent to the length of a -CH2-CH2-CH2-group, Substitutions of the phenyl moieties of 4-phenylimidazole and 4-benzoylhistamine result in weaker inhibition, These classes of imidazoles are particularly powerful inhibitors of sweet almond beta-glucosidase.
Robot control optimization using reinforcement learning
(1998-03-01)
Song, KT
;
Sun, WY
;
電控工程研究所
;
Institute of Electrical and Control Engineering
Conventional robot control schemes are basically model-based methods. However, exact modeling of robot dynamics poses considerable problems and faces various uncertainties in task execution. This paper proposes a reinforcement learning control approach for overcoming such drawbacks. An artificial neural network (ANN) serves as the learning structure, and an applied stochastic real-valued (SRV) unit as the learning method. Initially, force tracking control of a two-link robot arm is simulated to verify the control design. The simulation results confirm that even without information related to the robot dynamic model and environment states, operation rules for simultaneous controlling force and velocity are achievable by repetitive exploration. Hitherto, however, an acceptable performance has demanded many learning iterations and the learning speed proved too slow for practical applications. The approach herein, therefore, improves the tracking performance by combining a conventional controller with a reinforcement learning strategy. Experimental results demonstrate improved trajectory tracking performance of a two-link direct-drive robot manipulator using the proposed method.
Broadcasting secrets in communication networks
(1998-03-01)
Chang, CC
;
Wu, TC
;
Yeh, YS
;
資訊科學與工程研究所
;
Institute of Computer Science and Engineering
One property of a broadcast channel is that a single message broadcasted from an originator may be received simultaneously by several recipients in communication links. Based on the Chinese remainder theorem (CRT), we propose a new secure broadcasting scheme to distribute different secrets in one single broadcasting transaction such that each of the secrets is dedicated to different authorized recipients. On receiving the ciphertext broadcasted by the originator, only authorized recipients can obtain and authenticate their dedicated secrets individually, while no secret is revealed to unauthorized recipients. In a single broadcasting transaction, each authorized recipient cannot know who are the other intended recipients for this transaction. Furthermore, the processes for decryption and authentication of the dedicated secret are performed through simple arithmetic computation, i.e., modular operations, hence it is suitable for the applications that the recipient has less computing power. We also show that the proposed scheme can withstand the attack on replaying a previously intercepted broadcasting message.