Browsing by Issue Date, starting with "1993-01-15"

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TRANSMISSION ELECTRON-MICROSCOPY STUDY OF HEAVILY DELTA-DOPED GAAS GROWN BY MOLECULAR-BEAM EPITAXY
(1993-01-15)
LIU, DG
;
FAN, JC
;
LEE, CP
;
CHANG, KH
;
LIOU, DC
N-type and p-type delta-doped GaAs grown by molecular beam epitaxy with rather significantly high doses of Si and Be have been investigated by transmission electron microscopy (TEM). The amount of doses ranged from half a monolayer to two monolayers. The microscopic structures of the delta-doped regions and the adjacent epilayers were directly observed by TEM. The effect of impurity spreading on the heterointerfaces and superlattices was also studied. Si atoms present in Si delta-doped samples were confined to within a few atomic layers. The Be atoms present in Be delta-doped samples, however, spread over a quite wide region and caused rough heterointerfaces and wavy superlattices to form. Spreading of Be was attributed to segregation and diffusion which occurred during growth. Stacking faults were found in the delta-doped samples when they were grown at low temperatures. They could be attributed to local strain caused by heavy doping.
風流即事
(1993-01-15)
管管
風流即事
(1993-01-15)
管管
GRAIN-BOUNDARY PRECIPITATION IN AN FE-8.0AL-31.5MN-1.05C ALLOY
(1993-01-15)
HWANG, CN
;
CHAO, CY
;
LIU, TF
;
交大名義發表
;
材料科學與工程學系
風流即事
(1993-01-15)
管管
COBALT ORDERING IN LAYERED BI2SR2COO6+DELTA-SINGLE CRYSTAL
(1993-01-15)
SHI, JB
;
HO, JC
;
LEE, TJ
;
CHIOU, BS
;
KU, HC
Insulating Bi2Sr2CoO6+delta is nearly isomorphic with the Bi(2201)-type high-T(c) superconductors. Magnetic and calorimetric studies were carried out on single crystal samples of this layered compound. Based on magnetic measurements, the cobalt ions undergo a canted antiferromapetic ordering at T(N) = 159 K. A low-temperature neutron diffraction study of the magnetic structure is in progress. The molar magnetic susceptibility chi(ab)(H perpendicular-to c) above 200 K can be well fitted by the Curie-Weiss form chi(ab)(T) = chi0+C/(T-theta(p)), with chi0 = 0.56 cm3K/mol, Curie constant C = 3.2 x 10(-2) cm3K/mol and Curie-Weiss intercept theta(p) = 159 K. There is no magnetic specific heat peak, however, prevailing around T(N). This anomalous calorimetric behavior is attributed to the two-dimensional quantum spin fluctuation of Co spins above T(N) in the layered compound as previously observed for Cu spins in (Gd1.85Ce0.15)CuO4-delta and La2CuO4-delta.
風流即事
(1993-01-15)
管管
HYBRID TRANSMISSIVE OPTICAL STAR COUPLERS WITH GAIN USING FIBER AMPLIFIERS
(1993-02-01)
CHEN, YK
;
CHI, S
;
LIAW, JW
;
光電工程學系
;
電信研究中心
A hybrid transmissive star coupler incorporating fiber amplifiers for WDM/FDM networks is proposed. It is found that the total fiber length and conduit length required for this hybrid star coupler/network can be reduced tremendously as comparing with either the centralized or the distributed cases. Furthermore, this coupler is easier to construct and more cost-effective.
HIGH-SPEED OPTICAL RECEIVER WITH SOFT DECISION ISI CANCELLATION
(1993-02-01)
CHIANG, PY
;
KAO, MS
;
電信工程研究所
;
電信研究中心
;
Institute of Communications Engineering
Due to the stimulating success in developing optical amplifiers, intersymbol interference (ISI) will become the dominant limit on both bit rate and transmission distance in long-haul optical fiber communication systems. Here we present a receiver with ''Soft Decision ISI Cancellation'' (SDIC) to deal with ISI in high-speed lightwave systems. The analytical and simulation results show that the transmission distance can be doubled with SDIC. In addition, the receiver with SDIC allows the ISI cancellation circuit operating with processing and propagation delay much longer than 1-b period. Therefore, it is very promising in very high bit rate optical systems.
DYE-DEPENDENCE OF THE 830NM AND 1.16-MU-M EMISSIONS IN SODIUM VAPOR PUMPED NEAR THE 3S-4D 2-PHOTON RESONANCE
(1993-02-01)
LIU, YM
;
LU, MH
;
交大名義發表
;
光電工程學系
;
National Chiao Tung University
The 830 nm and 1.16 mum emissions in sodium vapor which is pumped near 3S-4D two-photon resonance have been observed. It has been found that these two emissions are induced by the spontaneous emission of the dye R590, that provides the emissions near 584 nm, which as idle photons are coupled to the 830 nm and 1.16 mum emissions in the axially phase-matched six-wave mixing processes. This conclusion is based on the fact that the observed 830 nm and 1.16 mum emissions will almost disappear if the spontaneous emission of the dye R590 in the 584 nm wavelength range is blocked. As a result, the fluctuation and band-like structure in the emission spectra of the 830 nm and 1.16 mum lines can be understood to be due to the broad band and fluctuating in the spontaneous emission of the dye R590, and also due to the amplification in these generation processes that makes many unstable peaks in their spectra.
SYNTHESIS AND CHARACTERIZATION OF LIQUID-CRYSTALLINE COPOLYSILOXANES CONTAINING AZOBENZENE DYES AND 1,3-DIOXANE BASED MESOGENIC SIDE GROUPS
(1993-02-01)
HSIUE, GH
;
WEN, JS
;
HSU, CS
;
應用化學系
;
Department of Applied Chemistry
The synthesis and characterization of nine side-chain liquid crystalline copolysiloxanes containing trans-5-(n-undecanyl)-2-(4-cyanophenyl)-1,3-dioxane and 4-(alkanyloxyphenylazo)benzonitrile side groups are presented. The azobenzene dye contents in the copolymers range from about 5 to 20 wt.-%. The nature of the mesophase exhibited by the copolysiloxanes depends very much on the dye concentration. Three copolysiloxanes which contain about 5 wt.-% azobenzene dye, display a smectic A phase while the other six copolysiloxanes which contain more then 10 wt.-% azobenzene dye, exhibit a nematic phase. All the obtained copolysiloxanes show a very low glass transition temperature and a very wide temperature range of mesophase.
K-BAND QUASI-PLANAR TAPPED COMBLINE FILTER AND DIPLEXER
(1993-02-01)
LO, WT
;
TZUANG, CKC
;
交大名義發表
;
電信工程研究所
;
National Chiao Tung University
The quasi-planar realizations of combline bandpass filter and diplexer using multiple coupled suspended substrate striplines (MCSSS's) have demonstrated good performance at K-band without any tuning. The N MCSSS's excite N zero-cutoff-frequency quasi-TEM modes. A new computer-aided filter design approach employing rigorous SDA (spectral-domain-approach) and 2N-port microwave circuit theory accounts for the effects of the N quasi-TEM modes, the couplings through non-adjacent MCSSS's, and cover height. Two 19.5-to-20.5 GHz MCSSS's combline filters with different cover heights are built and tested to compare their filter characteristics. The reduction in cover height decreases the amount of non-adjacent couplings through MCSSS's and results in better filter stopband performance. Another 18.5-to-19 GHz and 20-to-20.5 GHz MCSSS's diplexer is also presented. All the measured results for the combline filters and diplexer agree well with the theoretic calculations.
ANOMALIES OF MOMENT OF INERTIA IN OS-170-180
(1993-02-01)
CHIANG, HC
;
HSIEH, ST
;
YEN, MMK
;
CHUU, DS
;
電子物理學系
The anomalies of moment of inertia in 170-180Os are analysed in the interacting-boson-plus-fermion-pair model. The angular momentum-angular momentum interaction term (L.L) in the boson Hamiltonian is renormalized by a (1 + fL.L)- 1 factor. It was found that the renormalization facilitates the interaction parameter searching and all boson-boson and boson-fermion interaction parameters for the isotope chain can be unified. Energy levels can be reproduced quite well. The general features in the moment of inertia anomalies can be reproduced. The transition quadrupole moments are calculated and compared with other estimates.
ALGORITHMIC ASPECTS OF NEIGHBORHOOD NUMBERS
(1993-02-01)
CHANG, GJ
;
FARBER, M
;
TUZA, Z
;
應用數學系
;
Department of Applied Mathematics
In a graph G = (V, E), E[v] denotes the set of edges in the subgraph induced by N[v] = {v} or {u is-an-element-of V: uv is-an-element-of E}. The neighborhood-covering problem is to find the minimum cardinality of a set C of vertices such that E = or {E[v]: v is-an-element-of C}. The neighborhood-independence problem is to find the maximum cardinality of a set of edges in which there are no two distinct edges belonging to the same E[v] for any v is-an-element-of V. Two other related problems are the clique-transversal problem and the clique-independence problem. It is shown that these four problems are NP-complete in split graphs with degree constraints and linear time algorithms for them are given in a strongly chordal graph when a strong elimination order is given.
A HYBRID NEURAL NETWORK MODEL FOR SOLVING OPTIMIZATION PROBLEMS
(1993-02-01)
SUN, KT
;
FU, HC
;
資訊工程學系
;
Department of Computer Science
In this paper, we propose a hybrid neural network model for solving optimization problems. We first derive an energy function, which contains the constraints and cost criteria of an optimization problem, and we then use the proposed neural network to find the global minimum (or maximum) of the energy function, which corresponds to a solution of the optimization problem. The proposed neural network contains two subnets: a Constraint network and a Goal network. The Constraint network models the constraints of an optimization problem and computes the gradient (updating) value of each neuron such that the energy function monotonically converges to satisfy all constraints of the problem. The Goal network points out the direction of convergence for finding an optimal value for the cost criteria. These two subnets ensure that our neural network finds feasible as well as optimal (or near-optimal) solutions. We use two well-known optimization problems-the Traveling Salesman Problem and the Hamiltonian Cycle Problem-to demonstrate our method. Our hybrid neural network successfully finds 100 % of the feasible and near-optimal solutions for the Traveling Salesman Problem and also successfully discovers solutions to the Hamiltonian Cycle Problem with connection rates of 40% and 50%.
EVENT-DRIVEN INCREMENTAL TIMING FAULT SIMULATOR
(1993-02-01)
JOU, SJ
;
CHIOU, SH
;
TAO, YS
;
SHEN, WZ
;
電控工程研究所
An efficient simulator of multiple sets of multiple faults, with electrical timing information for an MOS IC. is presented. The physical faults in a real circuit are modelled more realistically by the node-short, line-open and threshold voltage degradation faults at the transistor level. On using event-driven, selective trace and mixed incremental-in-space. signal and time simulation techniques. the simulation results show that it is superior to other approaches in speed, extra memory used, and precision. Moreover, this simulator is suitable for parallel simulation in a multiprocessor system.
PRODUCTS OF DIAGONAL OPERATORS
(1993-02-01)
WU, PY
;
HOU, JC
;
GAO, MC
;
ZHANG, XL
;
交大名義發表
ON THE MANUFACTURING TOLERANCE OF DISK CAM PROFILE
(1993-02-01)
WANG, WH
;
TSENG, CH
;
TSAY, CB
;
LING, SF
;
機械工程學系
For a given rocker-roller cam system, the mathematical expression of the cam profile was first derived from the desired displacement function utilizing theory of gearing and differential geometry. Furthermore, the variance in the cam profile due to cutting tolerance was modelled using the Monte-Carlo method as set of normally-distributed random numbers. Based on these models, the deviation from the desired motion resulting from manufacturing imprecision can be calculated by reversing the procedure. An optimization scheme was then employed to identify the optimal configuration which minimizes the motion deviation. It is found that the kinematic error of the mechanism can be minimized if the pressure angle of the mechanism remains small. Also the usefulness of the methodology developed for designing a rocker-roller cam mechanism taking the fabricating error of the cam profiles into consideration is demonstrated.
ESTIMATION OF MULTIPLE SINUSOIDAL FREQUENCIES USING TRUNCATED LEAST-SQUARES METHODS
(1993-02-01)
HSIEH, SF
;
LIU, KJR
;
YAO, K
;
電信工程研究所
;
Institute of Communications Engineering
Various SVD-based methods have been shown effective for resolving closely spaced frequencies. However, the massive computations required by SVD makes it unsuitable for real-time applications. To reduce the computational complexity, three truncated QR methods are proposed: 1) truncated QR without column pivoting (TQR); 2) truncated QR with reordered columns (TQRR); and 3) truncated QR with column pivoting (TQRP). It is demonstrated that many of the benefits of the SVD-based methods are achievable under the truncated QR methods with much lower computational cost. Based on the forward-backward linear prediction model, computer simulations and comparisons are provided for different truncation methods under various SNR's. Comparisons of asymptotic performance with large data samples are also given.
A CONFERENCE KEY DISTRIBUTION-SYSTEM BASED ON CROSS-PRODUCT
(1993-02-01)
WU, TC
;
YEH, YS
;
交大名義發表
;
資訊科學與工程研究所
;
National Chiao Tung University
Extended from the Diffie-Hellman public key distribution system (PKDS), we propose a conference key distribution system (CKDS) based on the cross-product operations on row vectors over a Galois field GF(P), where P is a prime number. In our CKDS, the chairperson computes a conference key CK and then embeds it to some public interpolating polynomials to let only the legal intended principals recover CK, while the illegal intended principals can not. From the public parameters, an intruder or any intended principal in the network does not know how many and who are the legal intended principals in the conference. Furthermore, since the construction of the CK does not interfere with the secret keys of the intended principals, any intended principals in the network has no useful information for revealing any other principals' secret keys. Besides, our CKDS can be implemented practically.