Browsing by Issue Date, starting with "1993-10-15"

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POLARON EFFECT ON THE BINDING-ENERGY OF A HYDROGENIC IMPURITY IN A QUANTUM-WELL
(1993-10-15)
HAN, CS
;
PERNG, TM
;
電子物理學系
;
Department of Electrophysics
We have studied the polaron effect on the binding energy of a hydrogenic impurity in a quantum-well structure. The interactions of an electron with both the confined bulk phonon and the interface phonon are taken into account. The competition between these two phonon modes is discussed. We have also extended the calculation for the case of a finite quantum well. It is found that the polaronic correction becomes bigger as the potential barrier gets higher.
CONCURRENT OPERATIONS IN MULTIATTRIBUTE LINEAR HASHING
(1993-10-15)
HO, PC
;
YANG, WP
;
HSU, MC
;
資訊科學與工程研究所
;
Institute of Computer Science and Engineering
Linear hashing is a dynamic hash structure in which the address space may vary dynamically when the database size is changed. Multi-attribute linear hasing is a generalization of linear hashing. It supports operations for associative search and may have wider applicability. This paper presents an algorithm for synchronizing concurrent operations in multi-attribute linear hashing with particular attention paid to the treatment of concurrent partial-match operations. Unlike the previous non-two-phase methods, the algorithm employs the principle of optimistic concurrency control technique, which leads an operation to ''retry'' when interference from concurrent conflicting operations occurs. The method also uses a strictly increasing counter to filter out a significant number of unnecessary retries, thus allowing search, partial-match, insert, and delete operations to proceed concurrently with split and merge operations. The search and partial-match operations do not need to set any lock, and no operations need to set locks on any shared global variables. Therefore, the operations potentially allow a higher degree of concurrency in the system. An argument for the correctness based on the notions of weak consistency and a discussion for the performance of the proposed algorithm are also present.
INVESTIGATION OF INDIUM DOPING IN INGAAS GAAS ALGAAS GRADED-INDEX SEPARATED CONFINEMENT HETEROSTRUCTURE LASERS
(1993-10-15)
TSANG, JS
;
LEE, CP
;
LIU, DC
;
CHEN, HR
;
TSAI, KL
The effect of indium doping in the graded-index regions of the InGaAs/GaAs/AlGaAs graded-index separated confinement heterostructure quantum well laser has been studied. It was found that the threshold current density can be greatly reduced by a proper amount of In doping in the graded AlGaAs region. This result is attributed to an improvement in material quality due to a reduction in group III vacancies. The effect of thermal treatment on laser performance has also been studied. Although high temperature annealing can significantly improve non-In-doped lasers, it has little effect on In-doped lasers.
INFLUENCES OF NOISE ON THE OCCURRENCE OF PERIOD-DOUBLING IN DISTRIBUTED-FEEDBACK LASER-DIODES UNDER DIRECT-CURRENT MODULATION
(1993-10-20)
KAO, YH
;
LIN, HT
;
傳播研究所
;
電信研究中心
;
Institute of Communication Studies
The influences of Langevin noise on period doubling (PD) of a strongly modulated distributed-feedback laser have been investigated. The onset of PD was confirmed to be reduced through the use of the rate equations as a model. The threshold values of PD were examined in terms of driving frequency and rf power and have been compared with the measurements of PD.
STRONG LUMINESCENCE INTENSITIES IN AL0.22GA0.78AS GROWN ON MISORIENTED (111)B GAAS
(1993-10-25)
CHIN, A
;
CHENG, TM
;
PENG, SP
;
OSMAN, Z
;
DAS, U
Strong enhancement in the luminescence intensity is observed in Al0.22Ga0.78As epitaxial layers grown on misoriented (111)B GaAs at 636-degrees-C. For 3-degrees misorientation, the luminescence intensity is almost 10 times that of (100) layers and the luminescence efficiency is an order of magnitude stronger than that of (100). (100) Al0.4Ga0.6As/GaAs quantum well laser diode structures grown under identical conditions with a low threshold current density of 150 A/cm2 are indications of excellent AlGaAs material quality. Electron mobility for 3-degrees misoriented (111) Al0.25Ga0.75As is about 10% higher than that for side-by-side grown (100). The strong luminescence associated with a large red shift of 90 meV, the 10% mobility enhancement, and wirelike structure shown in transmission electron microscopy are indicative of the natural formation of quantized structures.
DUAL-WAVELENGTH BRAGG REFLECTORS USING GAAS/ALAS MULTILAYERS
(1993-10-28)
LEE, CP
;
TSAI, CM
;
TSANG, JS
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Dual-wavelength Bragg reflectors have been demonstrated using GaAs/AlAs multilayer heterostructures. Desired reflection bands can be obtained by adding proper phase shifters in a GaAs/AlAs periodic multilayer structure. The structure is based on the digital representation of the addition of two periodic functions.
RELIABILITY STUDIES OF 0.85 MU-M VERTICAL-CAVITY SURFACE-EMITTING LASERS - 50000-H MTTF AT 25-DEGREES-C
(1993-10-28)
WU, CC
;
TAI, K
;
HAUNG, KF
;
電子物理學系
;
電控工程研究所
Reliability studies of gain-guieded 0.85 mum GaAs/AlGaAs quantum well surface emitting lasers were performed on 45 randomly selected lasers operated at 25, 50 or 90-degrees-C with biased currents up to 15 mA (about four times the threshold values). At 25-degrees-C, no noticeable degradation was seen after 5000 h of operation. A 14% reduction of power was seen at 50-degrees-C after 2700h. A faster degradation on power output was seen at 90-degrees-C, though the lasers are still functional after 1000h. The mean time toward failure (MTTF) of these lasers operated at 25-degrees-C and 15mA is extrapolated to be approximately 5 x 10(4)h.
CONTINUOUS-WAVE VISIBLE INGAP/INGAALP QUANTUM-WELL SURFACE-EMITTING LASER-DIODES
(1993-11-01)
HUANG, KF
;
TAI, K
;
WU, CC
;
WYNN, JD
;
電子物理學系
HIGH-FREQUENCY STABILIZATION AND HIGH-ORDER HARMONIC-GENERATION OF AN EXCITED MORSE OSCILLATOR UNDER INTENSE FIELDS
(1993-11-01)
JIANG, TF
;
電子物理學系
;
物理研究所
;
Department of Electrophysics
;
Institute of Physics
We study the quantum dynamics of a Morse oscillator under an intense field with three different frequencies: (1) one much higher than the dissociation energy from an excited state, (2) one resonant with the dissociation energy from an excited state, and (3) an intermediate one. The calculations were performed by using the momentum-space Fourier-grid Hamiltonian method. The high-frequency stabilization and harmonic-generation spectra are shown. The laser frequencies discussed are currently experimentally available.
PERFORMANCE OF SOME MULTIDESTINATION GBN ARQ PROTOCOLS UNDER UNEQUAL ROUND-TRIP DELAYS
(1993-11-01)
LEE, TH
;
HU, JK
;
交大名義發表
;
電信工程研究所
;
National Chiao Tung University
The performance of various ARQ protocols has recently been analyzed for multidestination environments. In all previous work, the round-trip delays between the transmitter and each of the receivers are assumed (or forced) to be equal to the maximum one, to simplify the analysis and/or the operation. This assumption obviously will sacrifice the system performance. In this paper, we evaluate the throughput efficiencies of three multidestination GBN ARQ protocols under unequal round-trip delays. In the investigated protocols, multiple copies of each data block are (re)transmitted contiguously to the receivers. Tight lower bounds are obtained for the throughput efficiencies of the schemes in which each data block is transmitted with the optimum number of copies. Results show that assuming all the round-trip delays to be equal to the maximum one may sacrifice the performance significantly. We also compare the performances of the three investigated protocols. In general, the performance becomes better as the transmitter utilizes more of the outcomes of previous transmission attempts.
X-WINDOW BASED GROUP COLLABORATIVE EDITING SYSTEM
(1993-11-01)
LEU, WY
;
YUAN, SM
;
交大名義發表
;
資訊工程學系
;
National Chiao Tung University
Group collaborative editing is an activity by which people geographically dispersed can edit the same document simultaneously. It makes use of computers and network communication to provide an interactive and convenient environment, so people can save much of their time and cost. We have developed a group collaborative editing system which not only allows participants to jointly view and process multimedia documents but also provides real-time interactive conversation facilities to let users feel realistic and friendly. This paper describes the concepts of group collaboration and the mechanisms of our system. It also presents the interface design strategy and the synchronization control method.
VLSI IMPLEMENTATION OF AN M-ARRAY IMAGE FILTER BASED ON SHIFT REGISTER ARRAY
(1993-11-01)
LEE, CY
;
TSAI, JM
;
HSU, SC
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
This paper presents a novel VLSI solution for sorting input samples in the transform domain to achieve real-time performance for image/video applications. The sorting is based on a dedicated memory containing so-called bar-chart information. The required value, such as median, can be generated from MSB to LSB sequentially by successively evaluating each bit of the memory content. In the architecture design, the dedicated memory is realized by (1) level control unit and (2) shift register arrays. To speed up the formation of bar-charts, the level control unit provides parallel control signals to the shift register arrays. Moreover, such an architecture can easily be updated when running any order operations are concerned. Our current design can handle at most 25 input samples with word-length of 8 bits, and the resultant IC shows that a 25-MHz clock rate can be achieved and the chip area is 0.69 x 0.56 cm2.
BACKPROPAGATION LEARNS MARR OPERATOR
(1993-11-01)
JOSHI, A
;
LEE, CH
;
資訊工程學系
;
Department of Computer Science
This paper describes a neural network model of the retinal responses to stimuli whose architecture is inspired by neurophysiological data. Suitable assumptions are identified which enable the development of a simple model for an individual X-type ganglion cell using backpropagation. This is then used to make a model of retinal processing. We present here our model of the individual ganglion cells and the underlying assumptions. We show that backpropagation leads to a model which is similar to the mathematical descriptions of retinal processing advanced by Marr. We present the results obtained when our model is used to simulate the effect of retinal processing on images. Empirical results about the speedups obtained when this model is implemented on parallel architectures are also reported.
DEVICE AND CIRCUIT SIMULATION OF ANOMALOUS DX TRAP EFFECTS IN DCFL AND SCFL HEMT INVERTERS
(1993-11-01)
WANG, TH
;
WU, SJ
;
HUANG, CM
;
交大名義發表
;
電子工程學系及電子研究所
An integrated device and circuit analysis has been developed to evaluate the DX trap induced anomalous transient phenomena in DCFL and SCFL AlGaAs/GaAs HEMT inverters. The slow transient effect and the hysteretic characteristics of the input-output voltage transfer function in the inverters are simulated. The result shows that in comparison with the DCFL inverter, the DX trap effects are much improved in the SCFL inverter due to its particular operational principle.
THE BEHAVIOR OF BILATERAL LATCH-UP TRIGGERING IN VLSI ELECTROSTATIC DISCHARGE DAMAGE PROTECTION CIRCUITS
(1993-11-01)
HUANG, HS
;
CHANG, CY
;
HSU, CC
;
CHEN, KL
;
LIN, JK
A new latch-up phenomenon that shows symmetrical diac I-V characteristics has been discovered recently. Electrical measurements show that a diac parasitic semiconductor-controlled-rectifier (SCR) device can exist between two adjacent electro static discharge damage (ESD) protection circuits or output buffers. The SCR consists of two parasitic P-N-P-N paths and can easily induce a localized SCR latch-up between two adjacent input or output terminals. This is not similar to traditional latch-up that creates a parasitic P-N-P-N path between power supply and ground pins, but is a new bilateral latch-up path between two adjacent input and output pins. A new latch-up failure mode due to this diac structure, which creates a bilateral path during temperature humidity bias (THB) testing, is discussed. Some suggestions regarding the improvement of this diac latch-up degradation are proposed. Advanced analyses and modeling are also presented in this paper. The modified diac latch-up lumped element model successfull explains this phenomenon.
MICROTOX BIOASSAY OF PHOTODEGRADATION PRODUCTS FROM PHOTOCATALYTIC OXIDATION OF PESTICIDES
(1993-11-01)
LU, MC
;
ROAM, GD
;
CHEN, JN
;
HUANG, CP
;
環境工程研究所
The mineralization of toxicants and the reduction of toxicity were investigated via the photocatalytic reaction. Dichlorvos (an insecticide), 2,4-D (a herbicide) and propoxur (an insecticide) were used as the model compounds in these experiments. Total organic carbon analyzer was used as a measure of mineralization of toxic compounds to assess the efficiency of photocatalytic mineralization. Microtox bioassay was employed in evaluating the toxicity of solutions treated by photocatalysis. The rate of photocatalytic mineralization is more efficient in acidic than in alkaline solution. The degradation pathway and toxicity of pesticides treated in photocatalytic process are pH dependent. Ultraviolet absorption spectra were also used for showing the different characteristics of the compounds undergoing photocatalytic mineralization.
STUDY OF SCHOTTKY CONTACTS ON N-GA0.51IN0.49P BY LOW-PRESSURE METAL-ORGANIC CHEMICAL-VAPOR-DEPOSITION
(1993-11-01)
CHANG, EY
;
LAI, YL
;
LIN, KC
;
CHANG, CY
;
材料科學與工程學系
A comprehensive study of the Schottky contacts on Ga0.51In0.49P has been made. The Ga0.51In0.49P epitaxial layer was successfully grown on the GaAs substrate by low-pressure metal-organic chemical-vapor deposition to form a lattice-matched heterostructure. Three different types of films, including single-layer metal (Pt, Ni, Pd, Au, Co, Mo, W, Cr, Ti, Al, Ta, and In), metal silicides (WSi2, W5Si3 PtSi, and Pt2Si), and TiW nitrides (TiWN(X)) as the Schottky contacts metals on Ga0.51In0.49P were studied. Due to the high-band-gap nature of Ga0.51In0.49P, the Schottky contacts on Ga0.51In0.49P demonstrate good characteristics. The barrier heights range from 0.79 to 1.19 eV depending on the selection of the metals and the annealing conditions. Among single-metal films, Pt film demonstrates the best thermal stability. A barrier height of 1.09 eV and an ideality factor of 1.06 were obtained even after the Pt Schottky diode was furnace annealed at 500-degrees-C for 30 min. For refractory compounds, the TiWN(X) film with the highest nitrogen content shows the best thermal stability with a barrier height of 1.00 eV and an ideality factor of 1.04 even after high-temperature annealing at 850-degrees-C.
MAGNETOOPTIC HEAD USING SUBSTRATE-MODE GRATING PAIRS FOR POLARIZATION AND LEAKY BEAM SPLITTING
(1993-11-01)
HUANG, YT
;
CHEN, YH
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
A novel substrate-mode grating pair structure for polarization and leaky beam splitting is presented for application to magnetooptic heads. These light weight and compact elements provide better flexibility and easier alignment for system applications. Optimum designs for these two types of beam splitters and theoretical evaluation of the system performance are discussed in detail. Preliminary experimental results are also given to demonstrate the feasibility of application of these substrate-mode grating pairs in a magnetooptic head.
DISTRIBUTED TASK ASSIGNMENT USING CRITICAL PATH ESTIMATE
(1993-11-01)
HSU, CC
;
LEE, PJ
;
資訊科學與工程研究所
;
Institute of Computer Science and Engineering
A very general task assignment scheme for a distributed computing system is presented in this paper. It takes execution time, communication time, and idle time into consideration. All possible task assignments are formed as a state space tree where a path from the root node of the tree to a node represents a partial or total task assignment. We propose an approach called the critical path overestimate for achieving a suboptimal task assignment and pruning most of the nodes of the tree. Combining the above approach with a divide-and-conquer method, we can further reduce the complexity of the problem, and therefore attain a satisfactory solution. Results from a wide range of experiments reveal that the proposed approaches perform well because of their giving close approximation to the actual cost and saving a high percentage of node generations.
STUDY OF LOSS MECHANISMS OF MN-ZN FERRITES IN THE FREQUENCY FROM 1 MHZ TO 10 MHZ
(1993-11-01)
TUNG, MJ
;
CHANG, WC
;
LIU, CS
;
LIU, TY
;
CHEN, CJ
The core loss mechanism of low loss grade Mn-Zn ferrite in the frequency from 1MHz to 10MHz was investigated in order to find out the possibility of developing Mn-Zn ferrites to be used at such high frequency region. under the condition of f;B=25KHz.T, it was found that dielectric loss dominated the core loss at the frequency between 1.1 and 3MHz, while eddy current loss dominated the core loss at the frequency higher than 3MHz. It is suggested that decrease of grain boundary capacitance and increase of grain resistivity of the core mar be the suitable ways for the Mn-Zn ferrites to be used at such frequency region.