Browsing by Issue Date, starting with "1996-06-17"

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A four channel polarization and wavelength separation element using substrate-mode stacked holograms
(1996-06-17)
Chang, JT
;
Su, DC
;
Huang, YT
;
電子工程學系及電子研究所
;
光電工程研究所
A four channel polarization and wavelength separation element using substrate-mode stacked holograms is proposed based on the diffraction efficiency characteristics for polarization and the wavelength selectivity of a transmission-type phase volume grating. We fabricated a sample device and measured its polarization selectivity, output spectrum, and insertion loss of each channel to demonstrate its performance. (C) 1996 American Institute of Physics.
A four channel polarization and wavelength separation element using substrate-mode stacked holograms
(1996-06-17)
Chang, JT
;
Su, DC
;
Huang, YT
;
電子工程學系及電子研究所
;
光電工程學系
A four channel polarization and wavelength separation element using substrate-mode stacked holograms is proposed based on the diffraction efficiency characteristics for polarization and the wavelength selectivity of a transmission-type phase volume grating. We fabricated a sample device and measured its polarization selectivity, output spectrum, and insertion loss of each channel to demonstrate its performance. (C) 1996 American Institute of Physics.
Estimates of loss probabilities for delay-sensitive traffic in ATM networks
(1996-06-20)
Lai, KC
;
Lee, TH
;
傳播研究所
;
電控工程研究所
;
Institute of Communication Studies
Simple estimates of loss probabilities for heterogeneous delay-sensitive traffic in ATM networks are presented. Cells of different connections can have different loss priorities. Numerical results show that the estimates, which are derived from the bufferless fluid flow model, are close to the actual cell loss probabilities.
Measurements and modeling of radio propagation in large offices with low metallic partitions
(1996-06-20)
Ju, KM
;
Tarng, JH
;
電信工程研究所
;
Institute of Communications Engineering
A theoretical model is developed to predict the propagation loss of UHF radio waves in large modem offices with low metallic partitions. It is found that in addition to free-space propagation loss the shadowing loss due to the blockage by the low partitions in the out-of-sight situation becomes the dominant one. The shadowing loss can be efficiently formulated by using the theory of single or double knife-edge diffraction. The model has been verified by an experiment conducted at 905 MHz, 1.75 GHz, and 2.44 GHz in large offices. The model shows reasonable accuracy. (C) 1996 John Wiley & Sons, Inc.
Measurements and modeling of radio propagation in large offices with low metallic partitions
(1996-06-20)
Ju, KM
;
Tarng, JH
;
交大名義發表
;
電信工程研究所
;
National Chiao Tung University
A theoretical model is developed to predict the propagation loss of UHF radio waves in large modem offices with low metallic partitions. It is found that in addition to free-space propagation loss the shadowing loss due to the blockage by the low partitions in the out-of-sight situation becomes the dominant one. The shadowing loss can be efficiently formulated by using the theory of single or double knife-edge diffraction. The model has been verified by an experiment conducted at 905 MHz, 1.75 GHz, and 2.44 GHz in large offices. The model shows reasonable accuracy. (C) 1996 John Wiley & Sons, Inc.
The dependence of the electrical characteristics of the GaN epitaxial layer on the thermal treatment of the GaN buffer layer
(1996-06-24)
Lin, CF
;
Chi, GC
;
Feng, MS
;
Guo, JD
;
Tsang, JS
The GaN buffer layer was grown on the sapphire substrate by low-pressure metalorganic chemical vapor deposition (LP-MOCVD) at 525 degrees C. The following 1.3 mu m epitaxial GaN growth was carried out at 1025 degrees C. We varied the ramping rate from 12.5 to 100 degrees C/min to study the quality of the epitaxial GaN. It has been found that the x-ray peak width, photoluminescence (PL) linewidth, Hall mobilities, and carrier concentrations of GaN epitaxial layer strongly depend on the in situ thermal ramping rate. An optimum thermal ramping rate was found to be of 20 degrees C/min. The maximum mobility is 435 cm(2)/V s at carrier concentration of 1.7 x 10(17) cm(-3). The minimum full width at half maximum (FWHM) of x ray and PL were 5.5 min and 12 meV occur at a ramping rate of 20 degrees C/min. The decrease of the mobility at high and low ramping rate can be attributed to the thermal stress and the reevaporation of the GaN buffer layer. (C) 1996 American Institute of Physics.
Reactive compatibilization of the poly(ethylene terephthalate) liquid crystalline polymer blends by solid epoxy resin as a coupling agent
(1996-06-27)
Chin, HC
;
Chiou, KC
;
Chang, FC
;
應用化學系
;
Department of Applied Chemistry
A selected reactive coupling agent can be served as an effective compatibilizer for certain immiscible and incompatible blends should both blend constituents possess the necessary functional groups that can react with the coupling agent at comparable rates. Solid epoxy resin with two epoxide endgroups per molecule was demonstrated to be an efficient reactive compatibilizer for the incompatible blends of poly(ethylene terephthalate) (PET) and co-polyester liquid crystalline polymer (LCP) by functioning as a coupling agent. The main chain structure of the epoxy resin is neither identical nor miscible with PET and LCP and tends to reside at interface during melt mixing. This preferential residence gives the epoxy compatibilizer greater opportunity to react with both PET and LCP simultaneously to produce the in situ-formed epoxy-b-PET-b-LCP mixed copolymer. This in situ-formed mixed copolymer is highly effective in compatibilizing the PET/LCP blends. This reactive epoxy compatibilizer enhances the LCP fibril formation and results in substantial improvements on stiffness and toughness of the PET/LCP blends. (C) 1996 John Wiley & Sons, Inc.
Reactive compatibilization of the poly(ethylene terephthalate) liquid crystalline polymer blends by solid epoxy resin as a coupling agent
(1996-06-27)
Chin, HC
;
Chiou, KC
;
Chang, FC
;
應用化學系
;
Department of Applied Chemistry
A selected reactive coupling agent can be served as an effective compatibilizer for certain immiscible and incompatible blends should both blend constituents possess the necessary functional groups that can react with the coupling agent at comparable rates. Solid epoxy resin with two epoxide endgroups per molecule was demonstrated to be an efficient reactive compatibilizer for the incompatible blends of poly(ethylene terephthalate) (PET) and co-polyester liquid crystalline polymer (LCP) by functioning as a coupling agent. The main chain structure of the epoxy resin is neither identical nor miscible with PET and LCP and tends to reside at interface during melt mixing. This preferential residence gives the epoxy compatibilizer greater opportunity to react with both PET and LCP simultaneously to produce the in situ-formed epoxy-b-PET-b-LCP mixed copolymer. This in situ-formed mixed copolymer is highly effective in compatibilizing the PET/LCP blends. This reactive epoxy compatibilizer enhances the LCP fibril formation and results in substantial improvements on stiffness and toughness of the PET/LCP blends. (C) 1996 John Wiley & Sons, Inc.
Like sign top quark pair production at linear colliders
(1996-06-27)
Hou, WS
;
Lin, GL
;
物理研究所
;
Institute of Physics
In the general two Higgs doublet model with flavor changing neutral Higgs couplings, neutral Higgs bosons may decay dominantly via or <(t)over bar c> final states. At the linear collider, e(+)e(-) --> h(0)A(0) or H(0)A(0) production processes may result in , W+W- t (c) over bar or tt (c) over bar (c) over bar (or (t) over bar (t) over bar cc) final states. The process yy --> h(0), A(0) --> t (c) over bar is also promising, but e(+)e(-) --> (h(0), H-0)Z(0) --> is relatively suppressed. The possibility of observing like sign lepton pairs, usually the hallmark for neutral meson mixing, is quite interesting since T-0 mesons do not even form.
An innovation approach to optimize a Kalman filter with an H-infinity error bound by secant method
(1996-07-01)
Wu, BF
;
Hsu, HH
;
交大名義發表
;
電控工程研究所
;
National Chiao Tung University
Designing a Kalman filter with a constraint on the H-infinity norm of the estimation error was first developed by Bernstein and Haddad in 1989. The main result is a sufficient condition for characterizing the Kalman filter. In this paper, similar to the standard Kalman filter, the properties of orthogonal principles are also shown to be preserved. Furthermore, the uniqueness, as opposed to an H-infinity filter, of the filter is implied by the orthogonal principles. An innovative approach to obtaining the minimum energy with a constraint on the H-infinity norm of the estimation en ol is proposed since the original work of Bernstein and Haddad does not, in general, reach the minimum energy of the estimation error. By means of the Secant method, the energy of the estimation error can be reduced as much as possible, under the condition that the H-infinity error bound is still satisfied.
An improved dynamic model in integral equation methods for the characterization of discontinuities in planar circuits
(1996-07-01)
Sheen, JW
;
Lin, YD
;
電信工程研究所
;
Institute of Communications Engineering
An efficient method to improve the integral equations method is presented in this article. A delta gap source generator and the fundamental mode sampling technique are employed. By employing this modified method, observation of the SWR and the creation of a large matrix in the conventional method employing a delta gap source generator are not necessary. Also, the modeling complexity and the time-consuming computation of the conventional method, which employs the semiinfinite traveling-wave mode, are avoided. In this article we use the coplanar waveguide short-end discontinuity as an example to describe this method in the spectral domain. Moreover, numerical results are compared with our experimental data and they show good agreement. (C) 1996 John Wiley & Sons, Inc.
RWM-cut for color image quantization
(1996-07-01)
Yang, CY
;
Lin, JC
;
資訊工程學系
;
Department of Computer Science
A new simple method for constructing a color palette that uses the radius weighted mean cut (RWM-cut) is proposed. The method is a hierarchically divisive method, and each two-class partition uses the centroid and the RWM only. Experiments show that the RWM-cut algorithm is feasible and visually acceptable. The algorithm can either be used alone or be used to create a good initial palette for the LBG algorithm. Besides the 3-D version, a 1-D version of the RWM-cut algorithm is also included in the paper for realtime color quantization. The quantization error is small and the processing speed is competitive. Dithered images are also provided. Copyright (C) 1996 Elsevier Science Ltd
Detail-preserving smoothing with morphology and fuzzy reasoning
(1996-07-01)
Lee, YG
;
Hsueh, YC
;
交大名義發表
;
資訊工程學系
;
National Chiao Tung University
This study investigates a new approach to removing noise that preserves the fine details which are based on combination of mathematical morphology and fuzzy reasoning. We extract some features from an image using mathematical morphology, then input these features, and the image itself into fuzzy-rule-based systems to produce a more graceful image. (C) 1996 SPIE and IS&T.
Leakage current reduction in chemical-vapor-deposited Ta2O5 films by rapid thermal annealing in N2O
(1996-07-01)
Sun, SC
;
Chen, TF
;
電子工程學系及電子研究所
;
奈米中心
;
Department of Electronics Engineering and Institute of Electronics
This study aims to improve the electrical characteristics and reliability of low-pressure chemical vapor deposited (LPCVD) Ta2O5 films by developing a new postdeposition single-step annealing technique. Experimental results indicate that excited oxygen atoms generated by N2O decomposition can effectively repair the oxygen vacancies in the as-deposited CVD Ta2O5 film, thereby resulting in a remarkable reduction of the film's leakage current. Two other post-deposition annealing conditions are compared: rapid thermal O-2 annealing and furnace dry-O-2 annealing. The comparison reveals that RTN(2)O annealing has the lowest leakage current, superior thermal stability of electrical characteristics and the best time-dependent dielectric breakdown (TDDB) reliability.
Coagulation of colloidal particles in water by chitosan
(1996-07-01)
Huang, CP
;
Chen, Y
;
交大名義發表
;
環境工程研究所
;
National Chiao Tung University
The feasibility of applying chitosan, as prepared from the crab chitin, was assessed in this study for the coagulation of colloidal particles. A series of batch flocculation tests with chitosan under different conditions was also conducted. The results indicate that chitosan is a potent coagulant for bentonite suspension. The relationship between the optimum chitosan dosage and the turbidity of the bentonite suspension is presented as a linear correlation. The evidence infers that an adequate range of the coagulant dosage is the primary consideration in determining the removal efficiency for the turbidity of the source water. It also indicates that the coagulation behavior for kaolinite by chitosan is different from that of bentonite, i.e., chitosan fails to form a good aggregate with kaolinite. Turbid water containing particles which show behavior similar to kaolinite apparently need to have some bentonite particles added as coagulant aid, thereby improving the aggregation of the colloid particles with chitosan. Moreover, the effect of pH on the coagulation efficiency of chitosan is insignificant. The evidence infers that charge neutralization is not a major mechanism controlling the formation of flee for chitosan coagulation.
Passive gain-equalized wide-band erbium-doped fiber amplifier using samarium-doped fiber
(1996-07-01)
Liaw, SK
;
Chen, YK
;
光電工程學系
;
Department of Photonics
A passive gain-equalization technique of erbium-doped fiber amplifier (EDFA) using a samarium-doped fiber to obtain wide-band flattened gain operation is reported, In the wavelength range from 1529-1559-nm, small inter-channel gain variations can be achieved, This simple technique is suitable for multiwavelength wide-band in-line-amplifier cascaded transmission applications.
Deep levels in SnTe-doped GaSb grown on GaAs by molecular beam epitaxy
(1996-07-01)
Chen, JF
;
Chen, NC
;
Liu, HS
;
交大名義發表
;
電子物理學系
A dominant deep level with an activation energy of 0.23-0.26 eV was observed by admittance spectroscopy in SnTe-doped GaSb layers grown directly on GaAs substrates by molecular beam epitaxy (MBE). The Sb-4/Ga Bur ratio was found to affect the Hall mobility and the concentration of the deep level in a similar way, with an optimal beam equivalent pressure ratio of around 7 obtained for GaSb grown at 550 degrees C, which should correspond to the lowest ratio at which a Sb-stabilized surface reconstruction can be maintained. This electron level is commonly detected in n-type (SnTe-, S- and Te-doped) GaSb, but not in undoped p-type GaSb, suggesting that the level is not a simple native defect, but may be connected with the impurity used for n-type doping of GaSb.
Microwave response of superconducting platelet crystals
(1996-07-01)
Wu, CJ
;
Tseng, TY
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
A theoretical study of the microwave response of isotropic and anisotropic superconductors in the Meissner state is presented, We consider a superconducting thin platelet crystal oriented in a parallel field configuration. The linear response analysis is investigated on the basis of modified two-fluid models along with the diffusion equation. The CS coherence effect for conventional superconductors and the anomalous peak in the loss for anisotropic high-T-c. cuprates are considered. The microwave properties are analyzed by the derived dimensionless magnetic permeability. The results show that thin edges have essentially nothing to do with the microwave loss in isotropic superconductors and the simple slab geometry suffices in studying their microwave properties. As for the high-T-c superconductors, the anisotropic effect itself makes the thin edges crucial in determining the microwave loss. The, calculated results qualitatively indicate some good consistence with the reported experimental data. The role of thin edges of the superconducting platelet crystal in the microwave response is therefore evidently clarified.
A methodology for schedule compression
(1996-07-01)
Wu, HH
;
Li, RK
;
交大名義發表
;
工業工程與管理學系
;
National Chiao Tung University
A generated schedule can be improved (especially on due date performance) simply by compressing the current schedule to the left. Additionally, two forms of schedule compression are available, i.e. simple compression and complex compression. In practical considerations, however, knowing exactly where the compression effort should be placed so that the schedule can be improved more efficiently is a relatively difficult task. This decision requires an evaluation methodology, which is the primary objective of this study. The evaluation methodology is based on the priority weight computation for those affected operations. The priority weight computation is an integration of sequence effect weight with time effect weight. The priority weight information provides not only where the compression effort should be placed but also the intelligent information of (1) the operations related to the compression effort and (2) the time that job(s) can be packed to the left. Specifics of the schedule compression concepts and algorithms of the evaluation methodology are also discussed.
A behavior-based classification and retrieval technique for object-oriented specification reuse
(1996-07-01)
Chou, SC
;
Chen, JY
;
Chung, CG
;
資訊工程學系
;
Department of Computer Science
This paper presents a classification and retrieval technique for object-oriented specification reuse, based on the assumption that existing specifications exhibiting behaviors similar to that of the system under development are appropriate for reuse. Existing specifications are classified and retrieved according to the semantic networks abstracted from their behaviors. Since semantic networks attach semantic meanings to certain degrees of detail, our technique is rather precise. Primary behavior is used to classify specifications because it can be obtained in the early phases of system analysis. Therefore, our technique allows early reuse. Moreover, subspecifications and classes of existing specifications are classified independently so that they can be retrieved for reuse separately. Thus, our technique encourages reusing subspecifications as well as classes. Since a subspecification is composed of classes and their relationships, reusing it corresponds to reusing all those classes and relationships, A technique that reuses subspecifications as well as classes is thus expected to save more time than those that reuse only classes.