Browsing by Author "Wang, SY"

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A detailed study of non-uniform quantum well infrared photodetectors
(2001-06-01)
Wang, SY
;
Chin, YC
;
Lee, CP
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
A non-uniform quantum well infrared photodetector (NUQWIP) structure is studied. By changing the doping concentration and barrier width of each quantum well, the electric field distribution can be tailored. Different transition types of NUQWIPs were fabricated. Suppressed dark current is obtained for all the NUQWIPs. The NUQWIPs show excellent performance compared with conventional uniform structures. The dark current is about an order of magnitude lower and the background limited temperature increases for 6 degrees. The electric field distribution within the structure is calculated to explain the results and characteristics of the NUQWIPs. The NUQWIP is found to be advantageous for the low cutoff energy detectors using B-C transitions. (C) 2001 Published by Elsevier Science B.V.
A light-induced tunneling state in a submicron double barrier tunneling diode with a center-doped well
(2000-02-01)
Suen, YW
;
Young, CC
;
Chang, CJ
;
Wu, JC
;
Wang, SY
We will present the observation of a light-induced meta-stable impurity state in a submicron center-doped double barrier tunneling diode (DBRTD) manufactured by a novel single-step e-beam lithography process in which no further alignment for the interconnect between the bonding pad and the small active device region is required. We attribute the mete-stable tunneling state, which can be switched by light and high voltage bias, to the light- or field-induced charge redistribution in the active tunneling region. (C) 2000 Elsevier Science B.V. All rights reserved.
A new application of fuzzy set theory to the Black-Scholes option pricing model
(2005-08-01)
Lee, CF
;
Tzeng, GH
;
Wang, SY
;
科技管理研究所
;
資訊管理與財務金融系註：原資管所+財金所
The Black-Scholes Option pricing model (OPM) developed in 1973 has always been taken as the cornerstone of option pricing model. The generic applications of such a model are always restricted by its nature of not being suitable for fuzzy environment since the decision-making problems occurring in the area of option pricing are always with a feature of uncertainty. When an investor faces an option-pricing problem, the outcomes of the primary variables depend on the investor's estimation. It means that a person's deduction and thinking process uses a non-binary logic with fuzziness. Unfortunately, the traditional probabilistic B-S model does not consider fuzziness to deal with the aforementioned problems. The purpose of this study is to adopt the fuzzy decision theory and Bayes' rule as a base for measuring fuzziness in the practice of option analysis. This study also employs 'Fuzzy Decision Space' consisting of four dimensions, i.e. fuzzy state; fuzzy sample information, fuzzy action and evaluation function to describe the decision of investors, which is used to derive a fuzzy B-S OPM under fuzzy environment. Finally, this study finds that the over-estimation exists in the value of risk interest rate, the expected value of variation stock price, and in the value of the call price of in the money and at the money, but under-estimation exists in the value of the call price of out of the money without a consideration of the fuzziness. (C) 2005 Elsevier Ltd. All fights reserved.
A new methodology for easily constructing extensible and high-fidelity TCP/IP network simulators
(2002-10-07)
Wang, SY
;
Kung, HT
;
資訊工程學系
;
Department of Computer Science
This paper proposes a new methodology for easily constructing extensible and high-fidelity TCP/IP network simulators. The methodology uses a kernel-reentering technique to reuse the existing real-life network protocol stacks, real application programs that generate traffic, and real utility programs that configure, monitor, or gather network statistics to the maximum extent. Only an event scheduler and some modifications to the kernel are needed to "glue" these existing components to collectively simulate a network. A simulator constructed this way has many advantages that a traditional network simulator cannot provide. First, reuse of real-life implementation in the simulator can generate more accurate results than a traditional simulator that abstracts a lot of away from the real implementation. Second, it can save much time and effort that would be needed if a high-fidelity simulator is developed from scratch. Third, because real application programs cannot distinguish a simulated network constructed by the simulator from a real one, all existing real-life and future application programs can directly run on any node in a simulated network. (C) 2002 Elsevier Science B.V. All rights reserved.
A practical routing protocol for vehicle-formed mobile ad hoc networks on the roads
(2005)
Wang, SY
;
Lin, CC
;
Hwang, YW
;
Tao, KC
;
Chou, CL
An IVC (Inter-vehicle communication) network is a type of mobile ad hoc networks (MANET) in which high-speed vehicles send, receive, and forward packets via other vehicles on the roads. An IVC network can provide useful applications in future Intelligent Transportation Systems. However, due to frequent network topology changes, a routing path in an IVC network breaks easily. As such, a routing protocol proposed for general MANET (e.g., AODV) performs poorly in IVC networks. To address this problem, we designed and implemented an intelligent flooding-based routing protocol and conducted several field trials to evaluate its performance on the roads. Results obtained from field trials show that (1) our protocol outperforms AODV significantly on IVC networks, and (2) our protocol can make many useful services such as email, ftp, web, video conferencing, and video broadcasting applicable on IVC networks for vehicle users.
A two-dimensional RAKE receiver architecture, with an FFT based matched filtering
(2005-01-01)
Wang, SY
;
Huang, CC
;
Quek, CC
;
交大名義發表
;
National Chiao Tung University
This paper proposes a two-dimensional (2-D) RAKE receiver, which is a spatial-temporal matched filter implemented in the-frequency domain. To form a beam pattern, we calculate the spatial frequency spectra of received signals on the antenna array using fast Fourier transform (FFT). After FFT beamforming, a bank of FFT-based matched filters is used to perform code matching. Afterward, the code-matched signals are summed up with maximal-ratio combining through a spatial-temporal channel-matched filter implemented in the frequency domain. This 2D-DRAKE receiver includes a channel sounder-that is used to estimate the spatial and temporal channel impulse response parameters, such as delays, directions. of arrivals, and complex gains of multipath components. Monte Carlo simulations have been used to evaluate the receiver bit-error rate performance in both static channel and mobile radio channel environments. Simulation results show that the RAKE receiver performs well in both kinds of channels.
Balancing traffic load for multi-node multicast in a wormhole 2-D torus/mesh
(2001)
Wang, SY
;
Tseng, YC
;
Shiu, CS
;
Sheu, JP
;
資訊工程學系
This paper considers the multi-node multicast problem in a wormhole-routed 2-D torus/mesh, where an arbitrary number of source nodes each intends to multicast a message to an arbitrary set of destinations. To resolve the contention and the congestion problems, we propose to partition the network into subnetworks to distribute, and thus balance, the traffic load among all network links. Several ways to partition the network are explored. The network-partitioning idea was used in earlier works for single-node broadcast and single-node multicast. This paper contributes in extending its applicability to multi-node multicast and demonstrating its capability to balance load on torus/mesh. Simulation results show significant improvement over existing results for torus and mesh networks.
Carrier-carrier scattering in GaAs/AlxGa1-xAs quantum wells
(2000-06-15)
Sun, KW
;
Song, TS
;
Sun, CK
;
Wang, JC
;
Kane, MG
We have studied carrier dynamics in highly nonequilibrium two-dimensional (2D) carrier distributions generated with femtosecond laser pulses in p-doped GaAs/Al0.32Ga0.68As quantum wells at photoexcited carrier densities between 10(9) and 10(11) cm(-2). The initially nonthermal carrier distribution is quickly broadened due to inelastic carrier-carrier scattering, with the broadening rate increasing as carrier density is increased. Measurements of the unrelaxed peak height in the hot electron-neutral acceptor luminescence spectra are compared with calculations of the carrier distribution using integration of the 2D dynamically screened Boltzmann equation. Our results indicate that carrier-carrier scattering becomes as significant a scattering mechanism as LO-phonon emission at density of about 10(10) cm(-2).
Carrier-carrier scattering: an experimental comparison of 5 and 3 nm AlxGa1-xAs/GaAs quantum wells
(2000)
Sun, KW
;
Sun, CK
;
Wang, JC
;
Wang, SY
;
Lee, CP
We have studied carrier dynamics among highly nonequilibrium carrier distributions generated with femtosecond laser pulses in Be:AlxGa1-xAs/GaAs quantum wells with different well width at hot carrier densities between 10(9) and 10(11) cm(-2). The spectra, at moderately high densities (greater than or equal to 10(10) cm(-2)) indicate that the initially narrow electron distribution is altered in a time less than or equal to the LO-phonon emission time, as a result of rapid carrier-carrier scattering. At an excitation density of about 10(10) cm(-2), the carrier-carrier scattering rate is faster in narrower quantum wells. By measuring the intensity of the unrelaxed peak, it is possible to determine the relative rates of carrier-carrier scattering and LO-phonon emission. Our results indicate that carrier-carrier scattering becomes as significant as LO-phonon emission at a density of about 1 x 10(10) cm(-2) in the 5 nm quantum wells. (C) 2000 Elsevier Science Ltd. All rights reserved.
Circuit-switched broadcasting in multi-port multi-dimensional torus networks
(2001-11-01)
Wang, SY
;
Tseng, YC
;
Ni, SY
;
Sheu, JP
;
資訊科學與工程研究所
The one-to-all broadcast is the most primary collective communication pattern in a multicomputer network. This paper studies this problem in a circuit-switched torus with alpha -port capability, where a node can simultaneously send and receive alpha messages at one time. This is a generalization of the one-port and all-port models. We show how to efficiently perform broadcast in tori of any dimension, any size, square or nonsquare, using near optimal numbers of steps. The main techniques used are: (i) a "span-by-dimension" approach, which makes our solution scalable to torus dimensions, and (ii) a "squeeze-then-expand" approach, which makes possible solving the difficult cases where tori are non-square. Existing results, as compared to ours, can only solve very restricted sizes or dimensions of tori, or use more numbers of steps.
Designing and implementing a new type of transport-layer socket: the UDTCP socket case
(2004-02-15)
Wang, SY
;
資訊工程學系
;
Department of Computer Science
On most operating systems, the UDP and TCP sockets are the two main types of sockets used to provide transport-layer networking services. However, for several reasons, UDP and TCP sockets are unsuitable for transporting delay-sensitive but error-tolerant streaming data such as the data generated by multimedia streaming applications. In this paper, we create a new type of socket that is suitable for transporting such data and propose a novel and simple implementation for it. We have implemented this new type of socket in Free BSD 4.8 and call it the 'UDTCP socket.' It has both the UDP and TCP socket properties suitable for delay-sensitive but error-tolerant streaming data but not those UDP and TCP socket properties unsuitable for such data. When transporting a stream of such data whose sending rate needs to be regulated by TCP congestion control, our simulation results show that the UDTCP socket can provide a much better delay and delay-jitter performance than the TCP socket. (C) 2003 Elsevier B.V. All rights reserved.
Doping effect on normal incident InGaAs/GaAs long-wavelength quantum well infrared photodetectors
(1997-09-01)
Wang, SY
;
Lee, CP
;
交大名義發表
;
電子工程學系及電子研究所
;
National Chiao Tung University
8-12 mu m InGaAs/GaAs quantum well infrared photodetectors with two different well doping concentrations have been studied. The devices with and without surface gratings are compared for normal incident operation. It is found that the TE to TM absorption ratio depends on the doping density in the quantum wells. A higher doping density increases TE absorption.:A detectivity about 1 x 10(10) cm Hz(1/2)/W and a peak responsivity of 0.23 A/W at 9 mu m have been obtained for the grating-free devices. (C) 1997 American Institute of Physics.
Faithful 1-edge fault tolerant graphs
(1997-02-28)
Wang, SY
;
Hsu, LH
;
Sung, TY
;
資訊工程學系
;
Department of Computer Science
A graph G* is 1-edge fault tolerant with respect to a graph G, denoted by 1-EFT(G), if any graph obtained by removing an edge from G* contains G. A 1-EFT(G) graph is said to be optimal if it contains the minimum number of edges among all 1-EFT(G) graphs. Let G(i)* be 1-EFT(G(i)) for i = 1,2. It can be easily verified that the cartesian product graph G(1)* x G(2)* is 1-edge fault tolerant with respect to the cartesian product graph G(1) x G(2). However, G(1)* x G(2)* may contain too many edges; hence it may nor be optimal for many cases. In this paper, we introduce the concept of faithful graph with respect to a given graph, which is proved to be 1-edge fault tolerant. Based on this concept, we present a construction method of the 1-EFT graph for the cartesian product of several graphs. Applying this construction scheme, we can obtain optimal 1-edge fault tolerant graphs with respect to n-dimensional tori C(m(1), m(2),...,m(n)), where m(i) greater than or equal to 4 are even integers for all 1 less than or equal to i less than or equal to n. (C) 1997 Elsevier Science B.V.
Faithful 1-edge fault tolerant graphs
(1997-02-28)
Wang, SY
;
Hsu, LH
;
Sung, TY
;
資訊工程學系
;
Department of Computer Science
A graph G* is 1-edge fault tolerant with respect to a graph G, denoted by 1-EFT(G), if any graph obtained by removing an edge from G* contains G. A 1-EFT(G) graph is said to be optimal if it contains the minimum number of edges among all 1-EFT(G) graphs. Let G(i)* be 1-EFT(G(i)) for i = 1,2. It can be easily verified that the cartesian product graph G(1)* x G(2)* is 1-edge fault tolerant with respect to the cartesian product graph G(1) x G(2). However, G(1)* x G(2)* may contain too many edges; hence it may nor be optimal for many cases. In this paper, we introduce the concept of faithful graph with respect to a given graph, which is proved to be 1-edge fault tolerant. Based on this concept, we present a construction method of the 1-EFT graph for the cartesian product of several graphs. Applying this construction scheme, we can obtain optimal 1-edge fault tolerant graphs with respect to n-dimensional tori C(m(1), m(2),...,m(n)), where m(i) greater than or equal to 4 are even integers for all 1 less than or equal to i less than or equal to n. (C) 1997 Elsevier Science B.V.
HAWAII: A domain-based approach for supporting mobility in wide-area wireless networks
(2002-06-01)
Ramjee, R
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Varadhan, K
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Salgarelli, L
;
Thuel, SR
;
Wang, SY
Mobile IP is the current standard for supporting macromobility of mobile hosts. However, in the case of micromobility support, there are several competing proposals. In this paper, we present the design, implementation, and performance evaluation of HAWAII, a domain-based approach for supporting mobility. HAWAII uses specialized path setup schemes which install host-based forwarding entries in specific routers to support intra-domain micromobility. These path setup schemes deliver excellent performance by reducing mobility related disruption to user applications. Also, mobile hosts retain their network address while moving within the domain, simplifying quality-of-service (QoS) support. Furthermore, reliability is achieved through maintaining soft-state forwarding entries for the mobile hosts and leveraging fault detection mechanisms built in existing intra-domain routing protocols. HAWAII defaults to using Mobile IP for macromobility, thus providing a comprehensive solution for mobility support in wide-area wireless networks.
High performance InAs/GaAs quantum dot infrared photodetectors with AlGaAs current blocking layer
(2001-06-01)
Wang, SY
;
Lin, SD
;
Wu, HW
;
Lee, CP
;
電子工程學系及電子研究所
Low dark current InAs/GaAs quantum dot infrared photodetector (QDIP) is demonstrated. The dark current reduced for over three orders of magnitude by introducing a thin AlGaAs current blocking layer. This thin AlGaAs can reduce the dark current much more than the response signal. The responsivity at 0.5 V is 0.08 A/W with peak at 6.5 mum and the corresponding detectivity about 2.5 x 10(9) cm Hz(1/2/W1/2). It is the highest detectivity reported for QDIP at 77 K. (C) 2001 Published by Elsevier Science B.V.
Hot-electron relaxation via optical phonon emissions in GaAs/AlxGa1-xAs quantum well structures: dependence upon the alloy composition and barrier width
(2000-12-01)
Sun, KW
;
Chang, HY
;
Wang, CM
;
Wang, SY
;
Lee, CP
We present a systematic investigation of the dependence of the hot-electron-optical-phonon interactions on Al composition and barrier width in GaAs/AlxGa1-xAs MQW structures. Raman scattering measurements at 15 K are presented for samples with different barrier widths and Al composition. The optical phonon energies emitted by the photoexcited electrons in quantum wells were also determined by using hot-electron-neutral acceptor luminescence techniques. It is shown that the relaxation of hot electrons in the quantum wells is dominated by the GaAs LO phonon emission for small x, but by AlAs-like LO phonons for larger Al composition. For samples with larger barriers, the electrons in the GaAs layer relax mostly through the AlAs-like optical phonon emission. However, in samples with smaller barriers, the relaxation of hot electrons is dominated by the GaAs optical phonon emission.
InAs/GaAs quantum dot infrared photodetectors with different growth temperatures
(2003-10-01)
Wang, SY
;
Chen, SC
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Lin, SD
;
Lin, CJ
;
Lee, CP
InAs/GaAs quantum dot infrared photodetectors were fabricated with quantum dots grown at three different temperatures. Large detection wavelength shift (5-14.5 mum) was demonstrated by changing 40 degrees of the epitaxy temperature. The smaller quantum dots grown at lower temperature generate 14.5 mum responses. The detectivity of the normal incident 15 mum QDIP at 77 K is 3 x 10(8) cm Hz(1/2)/W. A three-color detector was also demonstrated with quantum dots grown at medium temperature. The three-color detection comes from two groups of different sizes of dots within one QD layer. This new type of multicolor detector shows unique temperature tuning behavior that was never reported before. (C) 2003 Elsevier B.V. All rights reserved.
Induced Einstein-Kalb-Ramond theory and the black hole
(1996-02-15)
Kao, WF
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Dai, WB
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Wang, SY
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Chyi, TK
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Lin, SY
A four-dimensional induced Einstein-Kalb-Ramond theory with a conformally coupled Kalb-Ramond term is discussed. It is argued that the Kalb-Ramond field is difficult to interpret as an axion field from a dynamical point of view, and hence tends to be unstable. One can, however, apply Routh's method to extract an effective action for the axion field. It is found that the Kalb-Ramond hair will turn the event horizon into a naked singularity. Such an exact solution is found and analyzed carefully.
Induction of apoptosis in MCF-7 human breast cancer cells by phytochemicals from Anoectochilus formosanus
(2004-01-01)
Shyur, LF
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Chen, CH
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Lo, CP
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Wang, SY
;
Kang, PL
The antitumor activity of Anoectochilus formosanus Hayata (Orchidaceae), a popularly used folk medicine in the treatment of cancers in Asia, was investigated in MCF-7 human mammary carcinoma cells. Plant extracts of A. formosanus were observed to induce apoptosis of MCF-7 cells as evidenced by cell-morphological changes, an early redistribution of plasma membrane phosphatidylserine, and DNA content distribution studies. Bioactivity-guided fractionation of A. formosanus extracts produced a specific ethyl acetate (EA)-partitioned fraction in which apoptotic activity was enriched. The chemical profile and candidate index compounds of the active EA fraction were obtained using HPLC and various spectral analyses. Western blot analysis showed that upon treatment of MCF-7 cells with the EA fraction, cleavage of pro-caspases-8, -9, and -7, and poly(ADP-ribose) polymerase as well as significant release of mitochondrial cytochrome c into the cytosol were readily observed. Flow cytometry showed that the Fas ligand protein was overexpressed in EA-treated MCF-7 cells. Functional genomic studies indicated that specific genes related to cytoskeleton rearrangement, apoptotic signal transduction, and various transcription factors were differentially regulated in EA-treated MCF-7 cells. Putative apoptotic signaling pathways of MCF-7 cells in response to the EA extract of A. formosanus are proposed. Copyright (C) 2004 National Science Council, ROC and S. Karger AG, Basel.