Browsing by Issue Date, starting with "1997-02-01"

Now showing 1 - 20 of 84069

On the complexity of point-in-polygon algorithms
(1997-02-01)
Huang, CW
;
Shih, TY
;
土木工程學系
;
Department of Civil Engineering
Point-in-polygon is one of the fundamental operations of Geographic Information Systems. A number of algorithms can be applied. Different algorithms lead to different running efficiencies. In the study, the complexities of eight point-in-polygon algorithms were analyzed. General and specific examples are studied. In the general example, an unlimited number of nodes are assumed; whereas in the second example, eight nodes are specified. For convex polygons, the sum of area method, the sign of offset method, and the orientation method is well suited for a single point query. For possibly concave polygons, the ray intersection method and the swath method should be selected. For eight node polygons, the ray intersection method with bounding rectangles is faster. (C) 1997 Elsevier Science Ltd.
Modeling techniques for large-scale PCS networks
(1997-02-01)
Lin, YB
;
資訊工程學系
;
Department of Computer Science
Over the past few years there has been rapid growth in the demand for mobile communications that has led to intensive research and development of complex PCS (personal communication services) networks. Capacity planning and performance modeling are necessary to maintain a high quality of service to the PCS subscriber while minimizing costs. Effective and practical performance models for large-scale PCS networks are currently available. Two new performance models are presented in this article which can be solved using analytical techniques. The first is the so-called portable population model, based on the flow equivalent assumption (the rate of portables into a cell equals the rate of portables out of the cell). The model provides the steady-state portable population distribution in a cell that is independent of the portable residual time distribution, which can be used by simulations to reduce the necessary execution time by reaching the steady state more rapidly. Additionally, this model can be used to study the blocking probability of a low (portable) mobility PCS network and the performance of portable deregistration strategies. The second model is the so-called portable movement model which can be used to study location tracking and handoff algorithms. The model assumes that the arriving calls to a portable form a Poisson process, and portable residual times have a general distribution. This model can be used to study location-tracking algorithms and handoff algorithms. it is shown that under some assumptions, the analytic techniques are consistent with the simulation model.
Unsteady vortex roll structures in a mixed convective air flow through a horizontal plane channel: A numerical study
(1997-02-01)
Yu, CH
;
Chang, MY
;
Huang, CC
;
Lin, TF
;
機械工程學系
A three-dimensional unsteady numerical simulation was conducted to investigate the buoyancy induced vortex how structures in a forced air flow through a bottom heated horizontal plane channel. In particular, a third-order upwind finite difference scheme was chosen to solve the Navier-Stokes and energy equations. In the ranges of the Reynolds number Re from 20 to 50 and Rayleigh number Ra up to 31 000, several roll structures were predicted. In the steady flow at high Re and low Ra after the initial transient the longitudinal rolls possess spanwise symmetry and grow regularly to a fully developed state as it proceeds downstream. While in the time periodic flow at low Re and high Ra the rolls may tilt towards the right side wall and the flow is asymmetric or they may tilt to both sides and are symmetric, depending on the particular case studied. This roll tilting causes the rolls to terminate as they encounter the side walls. Meanwhile, new space is provided in the region near the other side of the duct or near the central vertical plane for the generation of new cells. It is also noted that the rolls are wavy in axial direction. Moreover, the rolls change their sizes during moving downstream and no fully developed state can be discerned. Based on the present data, correlating equations for the onset of convection and Hopf bifurcation were proposed. Copyright (C) 1996 Elsevier Science Ltd.
Resist-related damage on ultrathin gate oxide during plasma ashing
(1997-02-01)
Chien, CH
;
Chang, CY
;
Lin, HC
;
Chang, TF
;
Chiou, SG
This paper presents an important observation of plasma-induced damage on ultrathin oxides during O-2 plasma ashing by metal ''antenna'' structures with photoresist on top of the electrodes, It is found that for MOS capacitors without overlying photoresist during plasma ashing, only minor damage occurs on thin oxides, even for oxide thickness down to 4.2 nm and an area ratio as large as 10(4), In contrast, oxides thinner than 6 nm with resist overlayer suffer significant degradation from plasma charging, This phenomenon is contrary to most previous reports, It suggests that the presence of photoresist will substantially affect the plasma charging during ashing process, especially for devices with ultrathin gate oxides.
Chemical transformations of 4,6-dimethyl-2 beta-hydroxy-8-oxo-3,5,7-trioxatetracyclo[7.2.1.0(4,11).0(6,10)]dodecane
(1997-02-01)
Chem, JH
;
Wu, HJ
;
交大名義發表
;
應用化學系
;
National Chiao Tung University
Reactions of 4,6-dimethyl-2 beta-hydroxy-8-oxo-3,5,7-trioxatetracyclo-[7.2.1.0(4,11).0(6,10)] dodecane 1 with nucleophiles have been studied. Reaction of 1 with alcohols, triethylsilane, allyltrimethylsilane,and methylthiotrirnethylsilane in CH2Cl2 in the presence of TiCl4 gave the substitution products 2, 7a, 7b, and 7c in 80-90% yields. The substitution reaction took place chemoselectively on the hemiacetal group of 1. Reaction of 1 with cyanotrimethylsilane in CH2Cl2 in the presence of TiCl4 gave compound 8 and the rearranged product 9. The structure of 9 was proven by X-ray analysis.
The design of a 3-V 900-MHz CMOS bandpass amplifier
(1997-02-01)
Wu, CY
;
Hsiao, SY
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
A new bandpass amplifier which performs both functions of low-noise amplifier (LNA) and bandpass filter (BPF) is proposed for the application of 900-MHz RF front-end in wireless receivers, In the proposed amplifier, the positive-feedback Q-enhancement technique is used to overcome the low-gain low-Q characteristics of the CMOS tuned amplifier, The Miller capacitance tuning scheme is used to compensate for the process variations of center frequency, Using the high-Q bandpass amplifier in the receivers, the conventional bulky off-chip filter is not required, An experimental chip fabricated by 0.8-mu m N-well double-poly-double-metal CMOS technology occupies 2.6 x 2.0 mm(2) chip area, Under a 3 V supply voltage, the measured quality factor is tunable between 2.2 and 44. When the quality factor is tuned at Q = 30, the measured center frequency of the amplifier is tunable between 869-893 MHz with power gain 17 dB, noise figure 6.0 dB, output 1 dB compression point at -30 dBm, third-order input intercept point at -14 dBm, and power dissipation 78 mW.
Characterization of an isozyme of beta-glucosidase from sweet almond
(1997-02-01)
Li, YK
;
Chang, LF
;
Shu, HH
;
Chir, J
;
交大名義發表
A sweet almond beta-glucosidase (EC 3.2.1.21) isozyme was purified from commercial crude product. The process of purification consisted of a Protein-Pak Q anion exchange chromatography following by a Superdex 75 HR gel filtration separation. The purified enzyme is a monomeric glycoprotein with molecular weight of 58 kDa and pI = 4.55 which is distinguished from reported isozymes. The enzyme has a pH optimum in the range of 5.2-5.6 when p-nitrophenyl-beta-D-glycopyranosides are used as substrate and is stable up to 50 degrees C at that pH range. The purified protein also exhibits profound beta-galactosidase and alpha-L-arabinosidase activity. The study of substrate specificity revealed that lacking of hydroxymethyl group at C-5 of glycosides resulted in higher affinity for substrate binding to enzyme, whereas the chemical step of hydrolysis (k(cat)) was prevented significantly. The pH activity profile displayed a bell-shaped curve for all measured p-nitrophenyl-beta-D-glycopyranosides with apparent pK(1) and pK(2) values of 4.4-4.7 and 6.2-6.4, respectively. This isozyme was strongly inhibited by delta-gluconolactone (K-i = 160 mu M) and 4-phenylimidazole (K-i = 17.8 mu M) reversibly at pH 6.2. Among the tested glycoses, the binding affinity of N-acetyl-beta-D-glucosamine to the enzyme (K-i = 52 mM) was 6 times stronger than that of glucose and its epimers.
Moment-based image normalization with high noise-tolerance
(1997-02-01)
Gruber, M
;
Hsu, KY
;
交大名義發表
;
National Chiao Tung University
In this paper the effects of noise with nonzero mean on existing moment-based image normalization methods are studied. Several modifications to reduce noise sensitivity are presented and tested. They involve nonlinear mapping and fractional- and negative-order moments.
Intelligent video smoother for multimedia communications
(1997-02-01)
Yuang, MC
;
Tien, PL
;
Liang, ST
;
交大名義發表
;
資訊工程學系
Multimedia communications often require intramedia synchronization for video data to prevent potential playout discontinuity resulting from network delay variation (jitter) while still achieving satisfactory playout throughput. In this paper, we propose a neural network (NN) based intravideo synchronization mechanism, called the intelligent video smoother (IVS), operating at the application layer of the receiving end system. The IVS is composed of an NN traffic predictor, an NN window determinator, and a window-based play out smoothing algorithm, The NN traffic predictor employs an on-line-trained back-propagation neural network (BPNN) to periodically predict the characteristics of traffic modeled by a generic interrupted Bernoulli process (IBP) over a future fixed time period. With the predicted traffic characteristics, the NN window determinator determines the corresponding optimal window by means of an off-line-trained BPNN in an effort to achieve a maximum of the playout quality (Q) value. The window-based playout smoothing algorithm then dynamically adopts various playout rates according to the window and the number of packets in the buffer, Finally, we show that via simulation results and live video scenes, compared to two other playout approaches, IVS achieves high-throughput and low-discontinuity playout under a mixture of IBP arrivals.
Accurate calculation of collision integrals using adaptive methods
(1997-02-01)
Gau, YT
;
Guo, SF
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
In this work, we have developed accurate and efficient methods for calculating the scattering angle, time integral and electronic energy loss for binary collisions in matter. In contrast to the conventional integration and the hard sphere approximations, our new time integral is obtained by calculating the difference between the distance to the target atom and the ion path length. To compute the scattering angle and time integral accurately and efficiently, an adaptive Simpson quadrature using a smoother integrand is adopted. The energy loss arising from the local electron-concentration-dependent electronic stopping power is obtained by tracing the ion trajectory. To reduce the computation time, a second-order differential equation for the ion motion using an adaptive Runge-Kutta-Fehlberg algorithm is developed.
Dynamic scheduling for GSM data services
(1997-02-01)
Jeng, JY
;
Lin, CW
;
Lin, YB
;
交大名義發表
;
National Chiao Tung University
A new GSM data protocol called high speed circuit switched data (HSCSD) have been developed by European Telecommunications Standards Institute (ETSI) for high speed file transfer and mobile video applications. HSCSD increases data rate by using multiple TDMA time slots (up to 8) instead of one time slot in the current GSM implementation. The problem of multiple time slot assignment is that the blocking rate of the system will increase. This problem can be solved by flexible resource assignment where the service specifies the maximum and the minimum capacity. Based on the current available capacity of a base station, a user will be assigned any rate between the maximum and the minimum capacities. This article describes HSCSD protocol and presents four radio resource allocation strategies for HSCSD: always allocates maximum, always allocates minimum, allocates maximum unless available resources are not enough, and allocates resources according to the current blocking statistics of the base station. A simulation model is proposed to investigate the performance of these algorithms. The blocking probability, the call completion probability, and the quality of service are used to evaluate the effects of algorithms in different system behaviors.
Effects of bromine-methanol and hydrogen chloride pretreatments on Pt/Al/n-InP diodes
(1997-02-01)
Huang, WC
;
Lei, TF
;
Lee, CL
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
This paper reports the passivation effects of bromine-methanol (Br/M) and hydrogen chloride (HCl) treatments on the n-InP surface to form Pt/Al/n-InP diodes. It was found that Br/M and HCl passivated the n-InP surface. The Br/M-dipped and the HCl-dipped Pt/Al/n-InP diodes exhibited a barrier height of 0.83 and 0.86 eV, respectively, and a low reverse leakage current of 7.07 x 10(-7) and 1.10 x 10(-7) A/cm(2) at -3 V, respectively. The secondary ion mass spectroscopy and electron spectroscopy for chemical analysis showed that the Br/M or HCl treatment made formation of bromides and chlorides on the n-InP surface, respectively. They also revealed the existence of Al2O3, which is believed to be formed with the native In2O3 during the Al evaporation. This, which made the diodes be of the metal-insulator-semiconductor structure, in conjunction with the passivation effect of bromides and chlorides, improved the diode characteristics and produced the high barrier heights.
Spread spectrum CDMA systems for subband image transmission
(1997-02-01)
Chang, PR
;
交大名義發表
;
電信工程研究所
;
National Chiao Tung University
;
Institute of Communications Engineering
This paper investigates the application of spread spectrum code-division multiple access (SS-CDMA) techniques to subband image transmission over a bandlimited radio channel. For the transmission of images over SS-CDMA AWGN channels, a subband coding scheme that divides the image information into a number of independent data streams using an analysis filter bank, each of which Is multiplied by its unique signature PN code, enables the transmission of these data streams via multiple parallel virtual channels created by their corresponding PN codes. With a sufficiently large number of streams, the total signal is able to fit within the narrow radio channel bandwidth even though the total bandwidth of all the signals may exceed the channel bandwidth. At receiver, each received signal is separately recovered at the decoder by multiplying its PN code and integrating over the code length in order to obtain the desired subband. All the recovered subbands are then reassembled by a synthesis filter bank into a close reproduction to the original image. Additionally, for color subband image transmission, color images are first transferred to luminance (Y) and two chrominance components (I, Q). Each component is then decomposed independently into several subbands for SS-CDMA transmission. Therefore, a number of additional PN codes are required to support the transmission of the chrominance signals over the CDMA channels whereas the luminance signal was treated in the same manner as monochrome pictures. Moreover, SS-CDMA allows more than one image to he transmitted and be accessed simultaneously at the same limited channel bandwidth, If all the product signals for different images are transmitted over the SS-CDMA AWGN channel with perfect power control, the performance is the same as if the data were transmitted in a single stream. However, the quality of the farther received images would he degraded when the near-far problem occurs. In this paper, the image quality of both the monochrome and color subband image transmission via SS-CDMA AWGN channels is evaluated For both perfect and imperfect power control cases.
Shape representation using a generalized potential field model
(1997-02-01)
Ahuja, N
;
Chuang, JH
;
資訊工程學系
;
Department of Computer Science
This paper is concerned with efficient derivation of the medial axis transform of a two-dimensional polygonal region. Instead of using the shortest distance to the region border, a potential field model is used for computational efficiency. The region border is assumed to be charged and the valleys of the resulting potential field are used to estimate the axes for the medial axis transform. The potential valleys are found by following force field, thus, avoiding two-dimensional search. The potential field is computed in closed form using the equations of the border segments. The simple Newtonian potential is shown to be inadequate for this purpose. A higher order potential is defined which decays faster with distance than as inverse of distance. It is shown that as the potential order becomes arbitrarily large, the axes approach those computed using the shortest distance to the border. Algorithms are given for the computation of axes, which can run in linear parallel time for part of the axes having initial guesses. Experimental results are presented for a number of examples.
Coplanar waveguide-fed uniplanar bow-tie antenna
(1997-02-01)
Lin, YD
;
Tsai, SN
;
電信工程研究所
;
Institute of Communications Engineering
The design of coplanar waveguide (CPW)-fed bow-tie antenna for the 2.4-GHz ISM band is described in this letter. A coplanar waveguide-to-coplanar strips (CPW-to-CPS) balun is used to obtain the balanced feed line for the printed bow tie. Analysis method based on the mixed potential integral equation method is used to characterize the input characteristics of the bow-tie antenna. Obtained numerical results are in good agreement with experimental data. Through experiments with bow-tie antennas of various extended angles, the bow-tie antenna with a 90 degrees extended angle exhibits the widest bandwidth in the desired frequency band which has a bandwidth of 17% for VSWR <1.5:1.
Reducing location update cost in a PCS network
(1997-02-01)
Lin, YB
;
交大名義發表
;
資訊工程學系
;
National Chiao Tung University
;
Department of Computer Science
Location tracking operations in a personal communications services (PCS's) network are expensive. Several strategies have been proposed to reduce the location update cost, This paper studies a special case of a location tracking algorithm called the alternative location algorithm, This special case is referred to as the two location algorithm (TLA), An analytical model is proposed to compare the performance of TLA and the IS-41 protocol. Our study indicates that the performance of TLA is significantly affected by the user moving patterns and the call traffic. If the user mobility is higher than the call frequency or the user tends to move back to the previously visited registration areas, then TLA may significantly outperform IS-41, We also observe that the variance of the portable residence times in registration areas has impact on the performance of TLA (i.e., better performance is expected for larger variance).
Resist-related damage on ultrathin gate oxide during plasma ashing
(1997-02-01)
Chien, CH
;
Chang, CY
;
Lin, HC
;
Chang, TF
;
Chiou, SG
This paper presents an important observation of plasma-induced damage on ultrathin oxides during O-2 plasma ashing by metal ''antenna'' structures with photoresist on top of the electrodes, It is found that for MOS capacitors without overlying photoresist during plasma ashing, only minor damage occurs on thin oxides, even for oxide thickness down to 4.2 nm and an area ratio as large as 10(4), In contrast, oxides thinner than 6 nm with resist overlayer suffer significant degradation from plasma charging, This phenomenon is contrary to most previous reports, It suggests that the presence of photoresist will substantially affect the plasma charging during ashing process, especially for devices with ultrathin gate oxides.
On-line signature verification using LPC cepstrum and neural networks
(1997-02-01)
Wu, QZ
;
Jou, IC
;
Lee, SY
;
資訊工程學系
;
Department of Computer Science
In this paper, an on-line signature verification scheme based on Linear Prediction Coding (LPC) cepstrum and neural networks is proposed. Cepstral coefficients derived from linear predictor coefficients of the writing trajectories are calculated as the features of the signatures. These coefficients are used as inputs to the neural networks. A number of single-output multilayer perceptrons (MLP's), as many as the number of words in the signature, are equipped for each registered person to verify the input signature. If the summation of output values of all MLP's is larger than verification threshold, the input signature is regarded as a genuine signature; otherwise, the input signature is a forgery. Simulations show that this scheme can detect the genuineness of the input signatures from our test database with an error rate as low as 4%.
Mathematical model of spiral bevel and hypoid gears manufactured by the modified roll method
(1997-02-01)
Lin, CY
;
Tsay, CB
;
Fong, ZH
;
機械工程學系
;
Department of Mechanical Engineering
Based on grinding mechanism and machine-tool settings of the Gleason modified roll hypoid grinder, a mathematical model for the tooth geometry of spiral bevel and hypoid gears is developed. Since all the machine-tool settings and machine constants are involved in the proposed mathematical model, excellent correlation between the mathematical model and actual manufacturing machines can be obtained. An example is given to illustrate the application of the proposed mathematical model. Surface deviation between a real cut spiral bevel gear surface and the model surface is investigated. Bearing contacts and kinematic errors in the spiral bevel gear set are also studied. Copyright (C) 1996 Elsevier Science Ltd.
Characterization of an isozyme of beta-glucosidase from sweet almond
(1997-02-01)
Li, YK
;
Chang, LF
;
Shu, HH
;
Chir, J
;
應用化學系
A sweet almond beta-glucosidase (EC 3.2.1.21) isozyme was purified from commercial crude product. The process of purification consisted of a Protein-Pak Q anion exchange chromatography following by a Superdex 75 HR gel filtration separation. The purified enzyme is a monomeric glycoprotein with molecular weight of 58 kDa and pI = 4.55 which is distinguished from reported isozymes. The enzyme has a pH optimum in the range of 5.2-5.6 when p-nitrophenyl-beta-D-glycopyranosides are used as substrate and is stable up to 50 degrees C at that pH range. The purified protein also exhibits profound beta-galactosidase and alpha-L-arabinosidase activity. The study of substrate specificity revealed that lacking of hydroxymethyl group at C-5 of glycosides resulted in higher affinity for substrate binding to enzyme, whereas the chemical step of hydrolysis (k(cat)) was prevented significantly. The pH activity profile displayed a bell-shaped curve for all measured p-nitrophenyl-beta-D-glycopyranosides with apparent pK(1) and pK(2) values of 4.4-4.7 and 6.2-6.4, respectively. This isozyme was strongly inhibited by delta-gluconolactone (K-i = 160 mu M) and 4-phenylimidazole (K-i = 17.8 mu M) reversibly at pH 6.2. Among the tested glycoses, the binding affinity of N-acetyl-beta-D-glucosamine to the enzyme (K-i = 52 mM) was 6 times stronger than that of glucose and its epimers.