Browsing by Author "Huang, JM"

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A high speed circuit scheme for driving field emission array
(1996)
Lu, CW
;
Lee, CL
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Huang, JM
;
交大名義發表
;
電子工程學系及電子研究所
The field emission array (FEA), when used as a display device, requires a scanning driving circuit. Due to the large FEA capacitance (typically 5 pF for one pixel), the driving circuit is usually slow. In this work, a new driving circuit, which employs the voltage controlled current source (VCCS), overcomes the above-mentioned problem, thus can reach a high driving speed. In addition, the circuit has the advantages of a uniform current driving, the gray level control and the low power consumption.
A new and efficient hybrid model for estimating space diversity in indoor environment
(2000-03-01)
Tarng, JH
;
Chang, RS
;
Huang, JM
;
Tu, YM
;
電信工程研究所
This study presents a novel hybrid model based on a two-dimensional (2-D) site-specific model and a statistical model to investigate space diversity in indoor environments. The statistical model describes the field scattered by rough surface boundaries and randomly positioned scatterers, which may be important when one or both of the receiving and transmitting antennas are close to the boundaries of the scatterers. Comparing the computed spatial correlation with the measured one with the transmitting frequency at 2.44 GHz at many different sites demonstrates the effectiveness of the hybrid model. In addition to accurately predicting field strength, the hybrid model can quantify the relative mean contribution of diffused scattering in an indoor environment with a factor r. The factor is equal to the ratio of ensemble average of a randomly scattered envelope to the spatially averaged envelope. Its optimum value is in a narrow range from 0.3 to 0.5 when the intensity fluctuation at the measurement sites is in or close to saturation regions, where a large number of micromultipaths are generated. This finding confirms the relative ease in applying the hybrid model. Experimental results suggest that choosing r = 0.4 in a saturation allows the hybrid model to yield a satisfactory performance, as confirmed by a blind test. Moreover, good diversity gains can be obtained with an antenna spacing greater than or equal to one wavelength. Our results further demonstrate that the diversity gain of horizontally spaced antennas exceeds that of vertically spaced antennas.
A novel and efficient hybrid model of radio multipath-fading channels in indoor environments
(2003-03-01)
Tarng, JH
;
Liu, WS
;
Huang, YF
;
Huang, JM
;
電信工程研究所
This paper presents a novel and efficient hybrid model combining a two-dimensional (2-D) site-specific model and a statistical model to characterize multipath fading in indoor environments. The site-specific, model describes the propagation effects of interior walls and building walls. The latter model characterizes the effect of scattering due to rough surface boundaries and/or randomly positioned scatterers such as furniture and personnel, which significantly affects small-scale fading. The hybrid model is computationally efficient since only the 2-D site-specific model is needed. In addition to Accurately predicting mean field strength, the model can effectively quantify the relative mean contribution of diffused scattering with a factor r. The factor is also an effective index to quantify the cluttering strength of the propagation environment: 1) light-cluttering situation r less than or equal to 0.35 and 2) heavy-cluttering situation r greater than or equal to 0.65. Some blind tests validate the effectiveness of the model. A large amount of experimental data for 2.44-GHz radio at many different sites shows that a Nakagami distribution describes the fading distribution well.
A novel concept for finding proper orthogonal wavelets effectively to solve a large object scattering problem
(2003-04-18)
Chen, CM
;
Tarng, JH
;
Huang, JM
;
電信工程研究所
;
友訊交大聯合研發中心
[1] A novel concept of "visible energy" is proposed, and its magnitude is shown to be valuable information for determining whether the chosen orthogonal wavelet is proper in solving a large object scattering problem. With the properly chosen wavelets for the targeting problem the ( transformed) wavelet-domain impedance matrix can be sparsified effectively for solving electromagnetic integral problems. Visible energy is defined as the energy of all dilations of a single mother wavelet for an arbitrary translation in the spectral domain over the entire "visible region." It is found that for large matrix sizes, using wavelets with smaller visible energy will lead to a greater sparsification of the matrix. Numerical examples considering various scatterers with different shapes such as a circular cylinder, an L-shaped scatterer, and a duct show the validity of our findings.
A SPICE simulation model for field emission triode
(1996)
Lu, CW
;
Lee, CL
;
Huang, JM
;
交大名義發表
;
電子工程學系及電子研究所
In this work, a simple but accurate circuit model, which can be incorporated into circuit simulation programs such as SPICE, for field emission triode (FET) is developed. The model is based on the Fowler-Nordheim (F-N) J-E relationship but takes into account the charge distribution on the surface of the tip of the device. A procedure is also developed to extract the parameters of the model.
Application of mix-phase wavelets to sparsify impedance matrices
(1999-10-01)
Huang, JM
;
Leou, JL
;
Jeng, SK
;
Tarng, JH
;
電信工程研究所
Effective wavelets to solve electromagnetic integral equations are proposed. It is based on the same construction procedure as Daubechies wavelets but with mix-phase to obtain maximum sparsity of moment matrix. These new wavelets are proved to have excellent performance in non-zero elements reduction in comparison with minimum-phase wavelet transform (WT). If further sparsity is concerned, wavelet packet (WP) transform can be applied but increases the computational complexity. In some eases, the capability of non-zero elements reduction by this nsw wavelets even better than WP with minimum-phase wavelets and with less computational efforts. Numerical experiments demonstrate the validity and effectiveness of the neu; wavelets.
Application of wavelets to scattering problems of inhomogeneous dielectric slabs
(1999-10-01)
Leou, JL
;
Huang, JM
;
Jeng, SK
;
Li, HJ
;
電信工程研究所
In this paper, we apply the discrete wavelet transform (DWT) and the discrete wavelet packet transform (DWPT) with the Daubechies wavelet of order 16 to effectively solve for the electromagnetic scattering from a one-dimensional inhomogeneous slab. Methods based on the excitation vector and the [Z] matrix are utilized to sparsify an MoM matrix. As we observed, there are no much high frequency components of the field in the dielectric region, hence the wavelet coefficients of the small scales components (high frequency components) are very small and negligible. This is different from the case of two-dimensional scattering from perfect conducting objects. In the excitation-vector-based method, a modified excitation vector is introduced to extract dominant terms and achieve a better compression ratio of the matrix. However, a smaller compression ratio and a tiny relative error are not obtained simultaneously owing to their deletion of interaction between different scales. Hence, it is inferior to the [Z]-matrix-based methods. For the [Z]-marix-based methods, our numerical results show the column-tree-based DWPT method is a better choice to sparsify the MoM matrix than DWT-based and other DWPT-based methods. The cost of a matrix-vector multiplication for the wavelet-domain sparse matrix is reduced by a factor of 10, compared with that of the original dense matrix.
Blends of poly(propylene) and polyacetal compatibilized by ethylene vinyl alcohol copolymers
(2003-08-08)
Huang, JM
;
Cheng, HJ
;
Wu, JS
;
Chang, FC
;
應用化學系
Polymer blends of poly(propylene) (PP) and polyacetal (polyoxymethylene, POM) with ethylene vinyl alcohol (EVOH) copolymers were investigated by differential scanning calorimetry (DSC), rheological, tensile, and impact measurements, Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The PP-POM-EVOH blends were extruded with a co-rotating twin-screw extruder. The ethylene group in the EVOH is partially miscible with PP, whereas the hydroxyl group in the EVOH can form hydrogen bonding with POM. The EVOH tends to reside along the interface, acting as a surfactant to reduce the interfacial tension and to increase the interfacial adhesion between the blends. Results from SEM and mechanical tests indicate that a small quantity of the EVOH copolymer or a smaller vinyl alcohol content in the EVOH copolymer results in a better compatibilized blend in terms of finer phase domains and better mechanical properties. (C) 2003 Wiley Periodicals, Inc.
Conformational changes and molecular motion of poly(ethylene terephthalate) annealed above glass transition temperature
(2000-03-01)
Huang, JM
;
Chu, PP
;
Chang, FC
;
應用化學系
;
Department of Applied Chemistry
Conformational conversion and molecular dynamics of the amorphous poly(ethylene terephthalate) (PET) annealed above T-g were investigated by C-13 high-resolution solid-state NMR and differential scanning calorimetry (DSC). Rapid increase in the PET trans content and crystallinity were observed near the onset crystallization temperature (congruent to 120 degrees C). By comparing both changes in conformation and crystallinity during thermal annealing, we found that the trans conformer increases continuously while the degree of crystallinity levels off during the later stage of annealing. The H-1 spin-lattice relaxation time in the rotating frame (T-1 rho(H)) correlates linearly with PET crystallinity but less well with the trans content. A three-domain model containing crystalline (all trans), constrained noncrystalline (trans rich) and amorphous (gauche rich) phases satisfactorily explains the relationship among the PET conformation, crystallinity and annealing conditions. This study complements the prior study of molecular motion by T-1 rho(C), and illustrates the importance of the trans conformer to induce PET crystallization. (C) 1999 Elsevier Science Ltd. All rights reserved.
Construction of complex-valued wavelets and its applications to scattering problems
(2000-06-01)
Leou, JL
;
Huang, JM
;
Jeng, SK
;
Li, HJ
;
電信工程研究所
This paper introduces the construction of a Family of complex-valued scaling functions and wavelets with symmetry/antisymmetry, compact support, and orthogonality from the Daubechies polynomial, and applies them to solve electromagnetic scattering problems. For simplicity, only two extreme cases in the family, maximum-localized complex-valued wavelets and minimum-localized complex-valued wavelets are investigated. Regularity of root location of the Daubechies polynomial in spectral Factorization are also presented to construct these two extreme genus of complex-valued wavelets. When wavelets are used as basis functions to solve electromagnetic scattering problems by the method of moment (MoM), they often lead to sparse matrix equations. We will compare the sparsity of MoM matrices by the real-valued Daubechies wavelets, minimum-localized complex-valued Daubechies and maximum-localized complex-valued Daubechies wavelets. Our research summarized in this paper shows that the wavelets with smaller signal width will result in a more sparse MoM matrix, especially when the scatterer is with many corners.
Crystal polymorphism of poly(butylene-2,6-naphthalate) prepared by thermal treatments
(2002-03-01)
Ju, MY
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Huang, JM
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Chang, FC
;
應用化學系
;
Department of Applied Chemistry
The crystal polymorphisms of the poly(butylene-2,6-naphthalate) (PBN) prepared by various thermal treatments in bulk state were investigated. Crystalline forms obtained from different thermal treatments were characterized using wide-angle X-ray diffraction (WAXD) measurements. The a-form crystal is obtained by annealing the quenched PBN sample in the solid state or by crystallizing from the static melt at a relatively lower temperature (T-C < 205 degreesC). On the other hand, an exclusive beta-form crystal is generated through unique thermal treatment by non-isothermal crystallization at a cooling rate of 0.1 degreesC min(-1) from 280 to 25 degreesC. Additionally, both alpha- and beta-form crystals appear in the sample melt-crystallized at a relatively higher temperature, and the relative ratio of the a- and P-forms depends on the predetermined crystallization temperature. In this study, it was found that the crystalline form transition never occurs in the solid state. Optical microscopic observations indicate that the a-form crystal exhibits a typical spherulite morphology, while the P-form crystal displays a dendritic spherulite morphology due to the extremely slow spherulite growth rate. Fourier transform infrared spectroscopy was used to examine the crystal structures of both a- and P-forms of the PBN. It is proposed that the main difference between these two crystal structures of PBN prepared by different thermal treatments lies in the packing efficiency of the crystal chains, rather than in the conformation change of the glycol residue, with the beta-form possessing tighter packing efficiency than the alpha-form. (C) 2002 Elsevier Science Ltd. All rights reserved.
Crystallization and melting behaviors of poly(trimethylene terephthalate)
(1999-10-01)
Huang, JM
;
Ju, MY
;
Chu, PP
;
Chang, FC
;
應用化學系
The crystallization and melting behaviors of poly(trimethylene terephthalate) (PTT) have been studied by differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD), and solid-state NMR. At certain crystallization temperatures (T-c) for a given time, the isothermally crystallized PTT exhibits two melting endotherms, which is similar to that of PBT and PBT. At higher crystallization temperature (T-c = 210 degrees C), the low-temperature endotherm is related to the melting of the original crystals, while the high-temperature endotherm is associated with the melting of crystals recrystallized during the hearing. The peak temperatures of these double-melting endotherms depend on crystallization temperature, crystallization time, and cooling rate from the melt as well as the subsequent heating rate. At a low cooling rate (0.2 degrees C/min) or a high heating rate (40 degrees C/min), these two endotherms tend to coalesce into a single endotherm, which is considered as complete melting without reorganization. WAXD results confirm that only one crystal structure exists in the PTT sample regardless of the crystallization conditions even with the appearance of double melting endotherms. The results of NMR reveal that the annealing treatment increases proton spin lattice relaxation time in the rotation frame, T-1 rho(H), of the PTT. This phenomenon suggests that the mobility of the PTT molecules decreases after the annealing process. The equilibrium melting temperature (T(m)degrees) determined by the Hoffman-Weeks plot is 248 degrees C.
Crystallization kinetics of poly(trimethylene terephthalate)
(2000-04-01)
Huang, JM
;
Chang, FC
;
應用化學系
;
Department of Applied Chemistry
The isothermal crystallization kinetics of poly(trimethylene terephthalate) (PTT) have been investigated using differential scanning calorimetry (DSC) and polarized light microscopy (PLM). Enthalpy data of exotherm from isothermal crystallization were analyzed using the Avrami theory. The average value of the Avrami exponent, n, is about 2.8. From the melt, PTT crystallizes according to a spherulite morphology. The spherulite growth rate and the overall crystallization rate depend on crystallization temperature. The increase in the spherulitic radius was examined by polarized light microscopy. Using values of transport parameters common to many polymers (U* = 1500 cal/mol, T-infinity = T-g - 30 degrees C) together with experimentally determined values of T-m(0) (248 degrees C) and T-g (44 degrees C), the nucleation parameter, k(g), for PTT was determined. On the basis of secondary nucleation analyses, a transition between regimes III and II was found in the vicinity of 194 degrees C (Delta T congruent to 54 K). The ratio of k(g) of these two regimes is 2.1, which is very close to 2.0 as predicted by the Lauritzen-Hoffman theory. The lateral surface-free energy, sigma = 10.89 erg/cm(2) and the fold surface-free energy, sigma(e) = 56.64 erg/cm(2) were determined. The latter leads to a work of chain-folding, q = 4.80 kcal/mol folds, which is comparable to PET and PET previously reported. (C) 2000 John Wiley & Sons, Inc.
Electromagnetic absorption in human brains by using fast wavelet transform methods
(2001)
Chen, CM
;
Tarng, JH
;
Huang, JM
;
電信工程研究所
;
Institute of Communications Engineering
An application of fast wavelet transform methods including discrete wavelet transform (DWT) and discrete wavelet packet (DWP) methods to the electromagnetic absorption in the human brains is presented. The total induced electric field inside the brain determined from the tensor integral-equation (TIE) is solved by the method of moments (MoM), DWT and DWP, respectively. It is found that using the wavelet transform methods especially using the DWP method in the targeted problems will lead to very sparsely moment matrices and relatively reduced computational complexities and memory requirements. Numerical examples are given to show the validity and effectiveness of the method.
Fault diagnosis of rotating machinery using an intelligent order tracking system
(2005-02-23)
Bai, MS
;
Huang, JM
;
Hong, MH
;
Su, FC
;
機械工程學系
This research focuses on the development of an intelligent diagnostic system for rotating machinery. The system is composed of a signal processing module and a state inference module. In the signal processing module, the recursive least square (RLS) algorithm and the Kalman filter are exploited to extract the order amplitudes of vibration signals, followed by fault classification using the fuzzy state inference module. The RLS algorithm and Kalman filter provide advantages in order tracking over conventional Fourier-based techniques in that they are insensitive to smearing problems arising from closely spaced orders or crossing orders. On the basis of thus obtained order features, the potential fault types are then deduced with the aid of a state inference engine. Human diagnostic rules are fuzzified for various common faults, including the single fault and double fault situations. This system is implemented on the platform of a floating point digital signal processor, where a photo switch and an accelerometer supply the shaft speed and acceleration signals, respectively. Experiments were carried out for a rotor kit and a practical four-cylinder engine to show the effectiveness of the proposed system in tracking the rotating order with precise inference. (C) 2003 Elsevier Ltd. All rights reserved.
Finding proper orthogonal wavelets to solve electromagnetic scattering problems
(2001)
Chen, CM
;
Tarng, JH
;
Huang, JM
;
電信工程研究所
;
Institute of Communications Engineering
A novel concept of "visible energy" is proposed and its magnitude is valuable information for determining whether the chosen orthogonal wavelet is proper in solving a electromagnetic scattering problem. With the properly chosen wavelets for the targeting problem, the (transformed) wavelet-domain impedance matrix can be sparsified effectively for solving electromagnetic integral problems. It is found that for the large matrix size using the wavelets with smaller visible energy will lead to a greater sparsification of the matrix. A simple scattering problem of circular cylinder is considered to show the validity of our findings.
Impedance matrix compression using an effective quadrature filter
(2000-08-01)
Huang, JM
;
Leou, JL
;
Jeng, SK
;
Tarng, JH
;
電信工程研究所
An effective quadrature mirror filter (QMF) proposed by Vaidyanathan has been used to solve 2D scattering problems. QMF has been popular for some time in digital signal processing, under the names of multirate sampling, wavelets, etc. In this work, the impulse response coefficients of QMF were used to construct the wavelet transform matrix. Using the matrix to transform the impedance matrices of 2D scatterers produces highly sparse moment matrices that can be solved efficiently. Such a presentation provides better sparsity than the celebrated and widely used Daubechies wavelets. These QMF coefficients are dependent on the filter parameters such as transition bandwidth and filter length. It was found that the sharper the transition bandwidth, the greater the reduction in nonzero elements of the impedance matrix. It also can be applied in the wavelet packet algorithm to further sparsify the impedance matrix. Numerical examples are given to demonstrate the effectiveness and validity of our finding.
In situ compatibilized SAN/LCP blends through reactive copolymers
(2001-12-20)
Huang, JM
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You, MF
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Chang, FC
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應用化學系
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Department of Applied Chemistry
Styrene-acrylonitrile-glycidyl methacrylate (SAG) copolymers with various contents of glycidyl methacrylate (GMA) were used to compatibilize the incompatible blends of styrene-acrylonitrile (SAN) and a liquid crystalline polymer (LCP). These SAG copolymers contain reactive glycidyl groups that are able to react with the carboxylic acid and/or hydroxyl end groups of the LCP to form the SAG-g-LCP copolymers during melt processing. The in situ-formed graft copolymers tend to reside along the interface to reduce the interfacial tension and to increase the interface adhesion. The morphologies of the SAN/LCP blends were examined by using scanning electron microscopy (SEM), where the compatibilized SAN/LCP blends were observed with greater numbers and finer fibrils than those of the corresponding uncompatibilized blends. The mechanical properties of the blends increased after compatibilization. The presence of a small amount (200 ppm) of ethyl triphenylphosphonium bromide (ETPB) catalyst further promotes the graft reaction and improves the compatibilization. (C) 2001 John Wiley & Sons, Inc.
Low-dielectric, nanoporous polyimide films prepared from PEO-POSS nanoparticles
(2005-11-14)
Lee, YJ
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Huang, JM
;
Kuo, SW
;
Chang, FC
;
應用化學系
Dielectric insulator materials that have low dielectric constants (k < 2.5) are required as inter-level dielectrics to replace silicon dioxide (SiO2) in future semiconductor devices. In this paper, we describe a novel method for preparing nanoporous polyimide films through the use of a hybrid PEO-POSS template. We generated these nanoporous foams are generated by blending polyimide as the major phase with a minor phase consisting of the thermally labile PEO-POSS nanoparticles. The labile PEO-POSS nanoparticles would undergoes oxidative thermolysis to releases small molecules as byproducts that diffuse out of the matrix to leave voids into the polymer matrix. We achieved significant reductions in dielectric constant (from k = 3.25 to 2.25) for the porous PI hybrid films, which had pore sizes in the range of 1040 nm. (c) 2005 Elsevier Ltd. All rights reserved.
Miscibility, melting, and crystallization of poly(trimethylene terephthalate)/poly(ether imide) blends
(2002-04-25)
Huang, JM
;
Chang, FC
;
應用化學系
;
Department of Applied Chemistry
Miscibility, melting, and crystallization behaviors of solution-blended poly trimethylene terephthalate) (PTT)/poly(ether imide) (PEI) blends ha,e been investigated using thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and polarized light microscopy (PLM). These blends show a single and composition-dependent glass transition temperatures over the entire composition range, implying that these blends are fully miscible in the amorphous region. The enthalpy of the middle endotherm melting of the primary crystallization decreases with increasing PEI content in the blend. Recrystallization of PTT during heating scan in DSC is either retarded or fully inhibited by the presence of PEI. In nonisothermal crystallization, the depression of crystallization temperature of PTT also depends on the blend composition and cooling rate; the presence of PEI decreases the PTT segments migrating to the crystallite-melt interface, The effects of temperature and PEI content on the spherulite growth rate of PTT were evaluated by PLM. The spherulite growth rate decreases with the, increase of the PEI content, implying that it is a thermodynamically dominant process. Both thermodynamic and kinetic factors cause total inhibition of PTT crystallization at higher PEI content in the blend. (C) 2002 John Wiley Sons, Inc.