Browsing by Issue Date, starting with "1997-07-21"

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Electro-optical properties of aligned polymer dispersed liquid crystal films
(1997-07-21)
Wu, JJ
;
Wang, CM
;
光電工程學系
;
Department of Photonics
We study the electro-optical properties of polymer dispersed liquid crystal (PDLC) films with various kinds of alignment. These films are transparent in the electric field-on state and opaque in the field-off slate. Experimental data show that the contrast ratio of these aligned films can be higher than that of a usual type PDLC film. The relationship between the field-off state transmittance of such a PDLC film and the polarization of the incident light is discussed. The optical properties of such aligned films can be described by a theory based on Beer's law. (C) 1997 Published by Elsevier Science B.V.
Reactive compatibilization of PET and PPE blends by epoxy couplers
(1997-07-25)
Lo, DW
;
Chiang, CR
;
Chang, FC
;
應用化學系
;
Department of Applied Chemistry
A commercially available tetrafunctional epoxy monomer was demonstrated to be an effective reactive compatibilizer for blends of poly( ethylene terephthalate) (PET) and polyphenylene ether (PPE). It requires about 10-20% by weight of a conventional reactive compatibilizer to achieve the same level of compatibilization in terms of domain size reduction and mechanical property improvement. This epoxy monomer is able to contact and react with PET and PPE simultaneously during high shear extruder blending to form the desirable PET-epoxy-PPE mixed copolymer. This mixed copolymer contains PET and PPE segments that tend to anchor at the interface to act as an efficient compatibilizer of the PET and PPE blends. (C) 1997 John Wiley & Sons, Inc.
Precrack hysteresis energy in determining polycarbonate ductile-brittle transition .4. Effect of strain rate
(1997-07-25)
Chiou, KC
;
Hsu, HC
;
Chang, FC
;
應用化學系
;
Department of Applied Chemistry
Effect of deformation rate on the ductile-brittle transition behavior for polycarbonate (PC) with different molar mass, notch radius, and rubber content has been investigated. PC with higher molar mass, notch radius, or rubber-modification possesses a higher critical strain rate when the ductile-brittle transition occurs. Whether a notched specimen will fail in a ductile mode or a brittle mode is already decided before the onset of the crack initiation. If size of the precrack plastic zone exceeds a critical level prior to onset of crack initiation, the crack extension developed later will propagate within the plastic zone and result in a ductile mode fracture. The precrack elastic storage energy, the input energy subtracting the hysteresis energy, is the main driving force to strain the crack tip for crack initiation. The precrack hysteresis energy (directly related to the precrack plasticity) increases with the decrease of the applied strain rate. Therefore, the strain rate is also closely related to the size of the precrack plastic zone. If the strain rate is lower than the critical strain rate, the specimen is able to grow a precrack plastic zone exceeding the critical plastic zone and results in a ductile mode fracture. (C) 1997 John Wiley & Sons, Inc.
Precrack hysteresis energy in determining polycarbonate ductile-brittle transition .4. Effect of strain rate
(1997-07-25)
Chiou, KC
;
Hsu, HC
;
Chang, FC
;
應用化學系
;
Department of Applied Chemistry
Effect of deformation rate on the ductile-brittle transition behavior for polycarbonate (PC) with different molar mass, notch radius, and rubber content has been investigated. PC with higher molar mass, notch radius, or rubber-modification possesses a higher critical strain rate when the ductile-brittle transition occurs. Whether a notched specimen will fail in a ductile mode or a brittle mode is already decided before the onset of the crack initiation. If size of the precrack plastic zone exceeds a critical level prior to onset of crack initiation, the crack extension developed later will propagate within the plastic zone and result in a ductile mode fracture. The precrack elastic storage energy, the input energy subtracting the hysteresis energy, is the main driving force to strain the crack tip for crack initiation. The precrack hysteresis energy (directly related to the precrack plasticity) increases with the decrease of the applied strain rate. Therefore, the strain rate is also closely related to the size of the precrack plastic zone. If the strain rate is lower than the critical strain rate, the specimen is able to grow a precrack plastic zone exceeding the critical plastic zone and results in a ductile mode fracture. (C) 1997 John Wiley & Sons, Inc.
Growth of CdMnS films by pulsed laser evaporation
(1997-07-30)
Chuu, DS
;
Chang, YC
;
Hsieh, CY
;
電子物理學系
;
Department of Electrophysics
High orientation CdMnS thin films were grown on glass substrate by the pulsed laser evaporation (PLE) technique. Pulsed Nd:Yag laser was used as the evaporation source. During the deposition, various pulsed laser powers, substrate temperatures and different ratios of high purity CdS and MnS powder were used. X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive analysis of X-rays (EDAX) were employed to study the crystal structure, surface morphology and the Mn concentration of the as-deposited films. Absorption spectra were used to investigate the band gap of CdMnS films. It was found that the deviation of the band gap of CdMnS films from that of bulk CdS at room temperature depends on the concentration of Mn, The Raman spectra of our samples showed that the mixed mode behavior of transversal (longitudinal) frequency omega(T) (omega(L)) might exist in the CdMnS thin films. (C) 1997 Elsevier Science S.A.
A real-time poling approach for preparing second-order nonlinear optical polymer thin films
(1997-07-30)
Jou, JH
;
Wu, HS
;
Chiou, JF
;
Yang, PK
;
Huang, JY
A new real-time poling approach for preparing second-order nonlinear optical (NLO) polymer thin films is presented. The presented method may be conveniently applied to many polymer thin film systems without going through the complicated conventional synthesis and poling procedures. This method, which is proven in this work to be feasible experimentally, is done by simultaneously co-depositing a NLO active dye, disperse red 1 and two polyamide thin film forming monomers on a gold electrodes pre-patterned glass substrate while concurrently applying an electrical field for poling. A second harmonic generation (SHG) signal is detected from the resultant thin films at a very low poring field ranging from 0.01 to 0.1 MV/cm which increases in intensity as the poling field increases. (C) 1997 Elsevier Science S.A.
A real-time poling approach for preparing second-order nonlinear optical polymer thin films
(1997-07-30)
Jou, JH
;
Wu, HS
;
Chiou, JF
;
Yang, PK
;
Huang, JY
A new real-time poling approach for preparing second-order nonlinear optical (NLO) polymer thin films is presented. The presented method may be conveniently applied to many polymer thin film systems without going through the complicated conventional synthesis and poling procedures. This method, which is proven in this work to be feasible experimentally, is done by simultaneously co-depositing a NLO active dye, disperse red 1 and two polyamide thin film forming monomers on a gold electrodes pre-patterned glass substrate while concurrently applying an electrical field for poling. A second harmonic generation (SHG) signal is detected from the resultant thin films at a very low poring field ranging from 0.01 to 0.1 MV/cm which increases in intensity as the poling field increases. (C) 1997 Elsevier Science S.A.
Growth rate control of fumarase (fumA) gene expression in Escherichia coli
(1997-07-31)
Tseng, CP
;
Yu, CC
;
Hwang, SM
;
交大名義發表
;
National Chiao Tung University
Reactions of phenol sulfotransferase with nucleotides
(1997-07-31)
Yang, YS
;
Lin, ES
;
生物科技學系
;
Department of Biological Science and Technology
Reactions of phenol sulfotransferase with nucleotides
(1997-07-31)
Yang, YS
;
Lin, ES
;
生物科技學系
;
Department of Biological Science and Technology
A multicasting solution for ATM video applications
(1997-08-01)
Tsai, JM
;
Fang, HH
;
Lee, CY
;
交大名義發表
;
電子工程學系及電子研究所
This paper presents a multicasting solution for shared-buffer ATM switch, The cell duplicating function is performed by a one-to-many modified demur circuit, A shared multicast server is used to translate input multicast cells to find destination ports and corresponding routing information, By using link-list based ring structure, the multicast server can provide high speed (5 ns to search entry in 256-entry block in 0.8-mu m CMOS process) and cascadable multicast translating function, In addition, the channel complexity of multipoint-to-multipoint multicast applications can be reduced to N channels per N users. The shared-buffer controller is modified by adding controlling and scheduling functions for multicasting queues to process the multicast feature. Finally with the aid of the quality of service (QoS) management, this proposed solution provides multi-QoS for multicast cells to meet the needs of various video applications.
Thickness dependence of magnetic force acting on a magnetic dipole over a type-II superconducting thin film
(1997-08-01)
Yang, TJ
;
Wei, JC
;
Chen, JL
;
Horng, L
;
電子物理學系
The thickness dependence of the magnetic force acting on a point magnetic dipole over a superconducting thin film in the mixed state with a single vortex line is calculated by London theory. The magnetic force is decomposed into two parts, vertical and lateral components. Both vertical and lateral force components approach to the saturated value with increasing thickness when the thickness is much larger than the London penetration depth. A single vortex created in the thin film by the field of the magnetic dipole is also considered. The thickness dependence of the critical position of the point dipole for creating the first vortex line in the thin film is exploited and derived.
The design of a hybrid filter bank for the psychoacoustic model in ISO/MPEG phases 1,2 audio encoder
(1997-08-01)
Liu, CM
;
Lee, WC
;
資訊工程學系
;
Department of Computer Science
The ISO/MPEG phases 1 and 2 audio compression are receiving a wide range of applications. In the encoding process of MPEG, the psychoacoustic model exploits audio irrelevancy which is the key role to achieve high compression ratio without losing audio quality. However, the Fourier transform (FT) which has been used by the two psychoacoustic models suggested in standard draft requires high computational complexity, and hence leads to high hardware and software cost for real-time applications. This paper presents a new design named the hybrid filter bank to replace the FT. The hybrid filter bank can be integrated with the psychoacoustic models and provides a much lower complexity than the FT. Also, this paper shows that the hybrid filter is more suitable for the stereo coding and hence can provide a better quality for the intensity stereo coding, which is the key technology for the MPEG 1 to achieve near transparent quality lower than 96x2 kbits for two stereo channels.
Objective image quality measure for block-based DCT coding
(1997-08-01)
Liu, CM
;
Lin, JY
;
Wu, KG
;
Wang, CN
;
交大名義發表
The block-based discrete cosine transform (DCT) coding has been widely adopted in image or video compression standards, such as JPEG and MPEG. Such type of coding will produce a noticeable artifact known as the blocking effect at very low bit rate applications. In the literature, there have been various postprocessing methods proposed to reduce the blacking effect. However, there is no suitable objective criterion evaluating the effectiveness of these various methods. This paper presents a new objective measure evaluating the postprocessing methods. The proposed measure also provides an analytical result on the underlying sources of artifacts.
Stability and chaotic dynamics of a rate gyro with feedback control
(1997-08-01)
Ge, ZM
;
Chen, HH
;
機械工程學系
;
Department of Mechanical Engineering
An analysis is presented of a single-axis rate gyro subjected to linear feedback control mounted on a space vehicle that is spinning with uncertain angular velocity w(Z)(t) about its spin of the gyro. The stability of the nonlinear nonautonomous system is investigated by Liapunov stability and instability theorems. Bs the electrical Dime constant is much smaller than the mechanical time constant, the full singularly perturbed system is obtained. We study the stability of the system by forming a Liapunov function candidate as a linear combination of the Liapunov functions for the reduced and boundary-layer systems. When the perturbation near angular velocity w(Z)(t) of the space vehicle is harmonic, the feedback control system reduces to a planar system of parametrical excitation by the singular perturbation theory. Using the Melnikov technique, we can give criteria for the existence of chaos in the gyro motion. The numerical results, in which the existence of chaos is demonstrated, are presented in the form of phase plane, Poincare maps, bifurcation diagrams and Lyapunov exponents.
Three-dimensional finite element analysis of sheet-metal bending with complex die geometry
(1997-08-01)
Chou, IN
;
Hung, CH
;
機械工程學系
;
Department of Mechanical Engineering
The purpose of this research was to and manufacturing processing conditions that would prevent the occurrence of fractures in a sheet-metal bending product. The finite element code ABAQUS was used to analyze the tensile strain at the particular point where fractures frequently occur. First an optimal combination of factors was sought using the method of controlling parameters. The analysis showed that the three factors, r(2), r(4), and the coefficient of friction, which are typical controlling factors, cannot be used to reduce the tensile strain at the critical point efficiently. A preform design was then applied to solve the problem of fracturing. By using a two-step bending operation, we successfully moved the highest tensile strain away from the critical point and also reduced the magnitude of this strain.
The application of Petri nets to failure analysis
(1997-08-01)
Liu, TS
;
Chiou, SB
;
交大名義發表
;
機械工程學系
;
National Chiao Tung University
Unlike the technique of fault tree analysis that has been widely applied to system failure analysis in reliability engineering, this study presents a Petri net approach to failure analysis. It is essentially a graphical method for describing relations between conditions and events. The use of Petri nets in failure analysis enables to replace logic gate functions in fault trees, efficiently obtain minimal cut sets, and absorb models. It is demonstrated that for failure analysis Petri nets are more efficient than fault trees. In addition, this study devises an alternative; namely, a trapezoidal graph method in order to account for failure scenarios. Examples validate this novel method in dealing with failure analysis. (C) 1997 Elsevier Science Limited.
Internetting connectionless data networks with a wide area public ATM network
(1997-08-01)
Tsai, IF
;
Jan, RH
;
資訊工程學系
;
Department of Computer Science
Connectionless data services on ATM-based B-ISDN can be realized directly by means of the connectionless service function which is provided in connectionless servers. In this paper, we consider how to locate a certain amount of connectionless servers among the switching nodes in a public ATM network for the internetworking of connectionless data networks. The problem is formulated as a network optimization problem which is similar to the p-median problem. Two algorithms, one based on the greedy method and the other using branch-and-bound strategy, are presented to determine the locations of connectionless servers. By finding the optimal locations of connectionless servers, an optimal virtual overlay network which has minimized total transport costs for the connectionless data traffics can be constructed. (C) Elsevier Science B.V.
Hybrid-damped resolved-acceleration control for manipulators
(1997-08-01)
Wu, SL
;
Lin, SK
;
交大名義發表
;
電控工程研究所
;
National Chiao Tung University
The singularity problem of the resolved-acceleration control scheme can be solved by the damped least-squares method. This approach, however, does suffer from one serious drawback: oscillations of the end-effector when the target is outside the workspace and self-motion of the manipulator when it is at the orientation degeneracy. In this paper, we present a hybrid-damped resolved-acceleration control scheme (HDRAC), which is capable of damping both the accelerations and the velocities to overcome this drawback. The main advantage of the present approach is that the control system need not plan the path to avoid the infeasible region of the manipulator, since the controller will automatically command the end-effector to move along the boundary of the workspace with a minimum trajectory error. Thus this approach renders the resolved-acceleration control scheme a much more practical control for the industry. The stability of the proposed control scheme is also proved in this paper. Incorporated with the concept of the degenerated-direction damped least-squares method (DDDLSM), this new control scheme can also apply only to the degenerated directions, which scheme is simulated on the PUMA 560 manipulator to verify its usefulness. (C) 1997 John Wiley & Sons, Inc.
Study of the acoustic feedback problem of active noise control by using the l(1) and l(2) vector space optimization approaches
(1997-08-01)
Bai, MSR
;
Wu, TY
;
交大名義發表
;
機械工程學系
;
National Chiao Tung University
This study attempts to explore the acoustic feedback problem that is frequently encountered in feedforward active noise control (ANC) structure from the standpoint of control theories. The analysis is carried out on the basis of the Youla's parametrization and the l(1)-norm and l(2)-norm vector space optimization. The ANC problem is formulated as a model matching procedure and is solved via linear programming in the dual vector space. These methods alleviate the problems caused by the nonminimum phase (NMP) zeros of the cancellation path. The ANC algorithms are implemented by using a digital signal processor. Various types of noises were chosen for validating the developed algorithms. The proposed methods are also compared with the well-known filtered-u least-mean square (FULMS) method, The experimental results show that the acoustic feedback problem significantly degrades the performance and stability of the ANC system regardless which method is used. Insights into the difficulties due to acoustic feedback are addressed along the line of control theories. (C) 1997 Acoustical Society of America.