Browsing by Issue Date, starting with "2003-05-01"

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Integrating mobile IP with ad hoc networks
(2003-05-01)
Tseng, YC
;
Shen, CC
;
Chen, WT
;
交大名義發表
;
National Chiao Tung University
The Internet Engineering Task Force's mobile Internet protocol uses mobile agents to support. seamless handoffs, making it possible for mobile hosts to roam from subnet to subnet without changing IP addresses. Another emerging wireless architecture, mobile ad hoc networks (Manets), can be flexibly deployed in most environments without the need for infrastructure base stations. Integrating these two architectures will facilitate the current trend of moving to an all-IP wireless environment. By supporting greater roaming flexibility, the authors propose integrating mobile IP with Manets to realize the dream of broadband wireless Internet access.
Enhanced negative substrate bias degradation in nMOSFETs with ultrathin plasma nitrided oxide
(2003-05-01)
Perng, TH
;
Chien, CH
;
Chen, CW
;
Lin, HC
;
Chang, CY
The degradation induced by substrate hot electron (SHE) injection in 0.13-mum nMOSFETs with ultrathin (similar to2.0 - nm) plasma nitrided gate dielectric was studied. Compared to the conventional thermal oxide, the ultrathin nitrided gate dielectric is found to be more vulnerable to SHE stress, resulting in enhanced threshold voltage (V-t) shift and transconductance (G(m)) reduction. The severity of the enhanced degradation increases with increasing nitrogen content in gate dielectric with prolonged nitridation time. While the SHE-induced degradation is found to be strongly related to the injected electron energy for both conventional oxide [1], [2]and plasma-nitrided oxide, dramatic degradation in threshold voltage shift for nitrided oxide is found to occur at a lower substrate bias magnitude (- - 1 V), compared to thermal oxide (similar to -1.5 V). This enhanced degradation by negative substrate bias in nMOSFETs with plasma-nitrided gate dielectric is attributed to a higher concentration of paramagnetic electron trap precursors introduced during plasma nitridation [3].
Oscillations of magnetoconductance in semiconductor-superconductor junctions with a laterally potential barrier isolator inside semiconductor region
(2003-05-01)
Yang, TJ
;
Hsue, YC
;
Gu, BY
;
電子物理學系
;
Department of Electrophysics
Magnetoconductance (MC) injunctions of a superconductor and a semiconductor (Sm) consisting of two parallel quantum waveguides (QW) coupled through a potential barrier under a perpendicular applied magnetic field in the semiconductor region is studied theoretically. The results of MC showing a series of oscillations with stepwise platform and spikes may be understood well within the phenomenological argument similar to Y. Asano (Phys. Rev. B 61 (2000) 1732) proposed. The oscillatory peaks of the MC in the dual QW are found essentially due to the variation of the number of the propagation modes. (C) 2003 Elsevier Science B.V. All rights reserved.
Calculations of the inter-subband scattering rates of electrons in GaAs/AlGaAs quantum wells
(2003-05-01)
Lee, HC
;
Sun, KW
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
In this presentation, we report the calculated results on hot electron relaxation through inter- and intra-subband scatterings with LO phonons in quantum well structures. The scattering rates were calculated for electrons excited both in the gamma valley and L valleys. The types of optical phonons adapted in our model are determined based on the dielectric continuum model. We have also studied the dependence of the scatterings on the structure parameters of the quantum well. (C) 2003 Elsevier Science Ltd. All rights reserved.
Correlation between dewatering index and dewatering performance of three mechanical dewatering devices
(2003-05-01)
Pan, JRS
;
Huang, CP
;
Cherng, MY
;
Li, KC
;
Lin, CF
Efficient sludge conditioning can improve sludge dewatering characteristics and promote the separation of flocs from the liquid phase to achieve a high solid content. To optimize this process, a reliable dewatering index must be established. Although numerous researches investigated sludge conditioning, few are devoted to the correlation between the conditioning index and the dewatering efficiency. In this study, sludges were conditioned with both synthetic and natural polymers, and their dewatering characteristics after three different mechanical dewatering devices, the filter press, belt press, and the centrifuge, were compared. The result shows that the traditionally used dewatering index may not reflect sludge conditioning properly. Correlation between sludge conditioning indices and dewaterability depends upon both the type of sludge and the means of sludge conditioning and dewatering. It is therefore concluded that dewatering index must be properly chosen for optimum sludge conditioning. (C) 2002 Elsevier Science Ltd. All rights reserved.
Adaptive approaches to relieving broadcast storms in a wireless multihop mobile ad hoc network
(2003-05-01)
Tseng, YC
;
Ni, SY
;
Shih, EY
;
資訊工程學系
;
Department of Computer Science
In a multihop mobile ad hoc network, broadcasting is an elementary operation to support many applications. In [15], it is shown that naively broadcasting by flooding may cause serious redundancy, contention, and collision in the network, which we refer to as the broadcast storm problem. Several threshold-based schemes are shown to perform better than flooding in that work. However, how to choose thresholds also poses a dilemma between reachability and efficiency under different host densities. In this paper, we propose several adaptive schemes, which can dynamically adjust thresholds based on local connectivity information. Simulation results show that these adaptive schemes can offer better reachability as well as efficiency as compared to the results in [15].
Peculiar hole doping by Ca substitution in cuprate superconductors
(2003-05-01)
Lin, JY
;
Chung, PC
;
Liu, SJ
;
Hsiang, CC
;
Lin, PH
The doping effect of Ca substitution in Y0.7Ca0.3Ba2Cu3Oy has been studied for y=6.9 and 6 by the x-ray absorption near edge spectroscopy (XANES). While Ca doping leads to an obvious increase in hole concentration in the CuO2 planes in Y0.7Ca0.3Ba2Cu3O6.9, XANES indicates absence of this doping effect in Y0.7Ca6.3Ba2Cu3O6. These two contradict results suggest that the doping effect by Ca substitution could be sensitive to the oxygen content when y similar to6.0. Comparisons with others' works are made.
An iterative maximum SINR receiver for multicarrier CDMA systems over a multipath fading channel with frequency offset
(2003-05-01)
Deng, JH
;
Lee, TS
;
電信工程研究所
;
友訊交大聯合研發中心
;
Institute of Communications Engineering
A robust iterative multicarrier code-division multiple-access (MC-CDMA) receiver with adaptive multiple-access interference (MAI) suppression is proposed for a pilot symbols assisted system over a multipath fading channel with frequency offset. The design of the receiver involves a two-stage procedure. First, an adaptive filter based on the generalized sidelobe canceller (GSC) technique is constructed at each finger to perform despreading and suppression of MAI. Second, pilot symbols assisted frequency offset estimation, channel estimation and a RAKE combining give the estimate of signal symbols. In order to enhance the convergence behavior of the GSC adaptive filters, a decisions-aided scheme is proposed, in which the signal waveform is first reconstructed and then subtracted from the input data of the adaptive filters. With signal subtraction, the proposed MC-CDMA receiver can achieve nearly the performance of the ideal maximum signal-to-interference-plus noise ratio receiver assuming perfect channel and frequency offset information. Finally, a low-complexity partially adaptive (PA) realization of the GSC adaptive filters is presented as an alternative to the conventional multiuser detectors. The new PA receiver is shown to be robust to multiuser channel estimation errors and offer nearly the same performance of the fully adaptive receiver.
Bipolar photogenerated terahertz radiation in biased photoconductive switches
(2003-05-01)
Lin, PI
;
Luo, CW
;
Liu, HS
;
Wu, KH
;
Juang, JY
The characteristics of optically induced bipolar THz radiation in biased photoconductive switches were investigated systematically by using free-space electro-optic sampling technique. The emitted radiation shows nearly symmetrical waveform with broadband frequency spectrum spanning over 0.1-3 THz. It was observed that the bipolar nature and the emitted frequency spectrum distribution remained unchanged on varying the optical excitation fluence, strength of biased field and the emitter gap spacing. The dynamics of emitted THz transient are in agreement with the optically induced ultrafast charge transport process driven by the biased field. (C) 2003 Elsevier Science B.V. All rights reserved.
Planar mode converter used in printed microwave integrated circuits
(2003-05-01)
Lee, Cheng-Jung
;
Tzsuang, Ching-Kuang
A planar mode converter includes a rectangular waveguide, a microstrip feed-in circuit, and a microstrip feed-out circuit. The rectangular waveguide is filled with dielectric layers and surrounded with metal materials. The lowermost dielectric layer has usually largest thickness and dielectric constant. Except for the lowermost dielectric layer, each of the dielectric layers has a rectangular aperture at its front-end and back-end, respectively. The microstrip feed-in circuit is constituted by first, second and third metal strips, and a feed-in metal ground plane. The first metal strip and the feed-in metal ground plane form a feed-in signal line. The first, second and third metal strips are adhered to the top surface of the lowermost dielectric layer, and the feed-in metal ground plane is adhered to the bottom surface of the lowermost dielectric layer. The microstrip feed-out circuit is constituted of fourth, fifth and sixth metal strips, and a feed-out metal ground plane. The sixth metal strip and the feed-out metal strip form a feed-out signal line.
Highly reliable nickel silicide formation with a Zr capping layer
(2003-05-01)
Lee, TL
;
Lee, JW
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Lee, MC
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Lei, TF
;
Lee, CL
Zr is proposed to be the capping layer for nickel silicide to obtain a stable low resistance contact system even at an annealing temperature as high as 850degreesC. A NiSi monolayer is the only phase observed in those samples annealed from 500 to 850degreesC. Experimental results from transmission electron microscopy and X-ray diffractometry analysis show that the agglomeration and precipitate of nickel silicide problems which are usually encountered in the NiSi system are eliminated. (C) 2003 The Electrochemical Society.
A stochastic modeling approach to real-time prediction of queue overflows (vol 37, pg 97, 2003)
(2003-05-01)
Sheu, JB
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運輸與物流管理系註：原交通所+運管所
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Department of Transportation and Logistics Management
Queue overflow is a critical issue in developing queue prediction technologies for applications in Advanced Transportation Management System (ATMS). Conventional queue prediction methods, however are limited to incident-free queue length prediction where traffic arrivals can be readily obtained using detectors. Despite the problems posed by queue overflow, studies addressing queue-overflow issues, or for predicting queue overflows beyond detectors, appear inadequate. This paper describes an advanced methodology which uses a stochastic system modeling approach and random processes for predicting queue lengths beyond detectors in real time. Lane changing is taken into account in developing the queue-overflow prediction model because lane changing accompanies queue overflow in most cases. A discrete-time, nonlinear stochastic system is specified for modeling the queues and lane changes beyond detectors during queue-overflow occurrence. The noise terms of the recursive equations of the model account for the effects of queues and a variety of arriving volumes on vehicular lane-changing maneuvers during queue-overflow occurrence. The unknown traffic arrivals beyond detectors a-re predicted employing random processes. In addition, a recursive estimation algorithm for predicting real-time queue overflows is developed utilizing the extended Kalman filtering technique. Preliminary test results indicate that the proposed methodology is promising for real-time prediction of queue overflows. The predicted queue overflows can be used not only in understanding the phenomenon of lane traffic patterns during queue-overflow occurrence, but also in developing related advanced technologies such as real-time road traffic congestion control and management systems.
Numerical investigation of heat transfer of a heated channel with an oscillating cylinder
(2003-05-01)
Fu, WS
;
Tong, BH
;
機械工程學系
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Department of Mechanical Engineering
A numerical simulation is performed to study the influence on the heat transfer rate of the heated wall in the channel with an oscillating cylinder. An arbitrary Lagrangian-Eulerian kinematic description method is adopted to describe the flow and thermal fields. A penalty consistent finite-element formulation is applied to solve the governing equations. The effects of Reynolds number, oscillating amplitude, oscillating frequency, eccentric ratio, and blockage on the heat transfer characteristics of the heated wall are examined. The results show that not only the region relating to heat transfer is enlarged substantially, but also that the heat transfer rate of this region is enhanced remarkably.
Investigation of Cu/TaN metal gate for metal-oxide-silicon devices (vol 150, pg G22, 2003)
(2003-05-01)
Tsui, BY
;
Huang, CF
;
電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
Superconducting behaviors of copper-germanium alloys
(2003-05-01)
Hsu, SY
;
Chen, JY
;
電子物理學系
;
Department of Electrophysics
We have observed superconducting properties in three dimensional CuxGe100-x samples with 38 less than or equal to x less than or equal to 67. Transition temperature T-c is about 0.4 K. Upper critical magnetic field H-c2 has been measured in these samples confirming that they are indeed superconductors. Near the zero field T-co, H-c2 depends linearly on temperature. Our results show robust superconducting properties present in CuGe samples with weakly disorder. (C) 2003 Elsevier Science B.V. All rights reserved.
A low-complexity adaptive multi-beam space-time receiver for CCI/ISI cancellation over frequency selective multipath channels
(2003-05-01)
Ho, CL
;
Lee, TS
;
電信工程研究所
;
友訊交大聯合研發中心
;
Institute of Communications Engineering
A space-time (ST) receiver is proposed for combating the cochannel interference (CCI) and intersymbol interference (ISI) in a frequency-selective multipath environment. The scheme involves two stages. First, a set of adaptive beamformers pointed at a prescribed angular sector in space is constructed on an oversampled antenna array, each providing effective suppression of CCI and reception of desired signals. Second, a fractionally-spaced decision feedback equalizer (DFE) follows to eliminate the ISI left in beamformer outputs. In particular, both the beamformers and DFE can be realized in the form of a generalized sidelobe canceller (GSC) with the aid of channel estimation, and partial adaptivity is incorporated for reduced complexity processing and improved convergence. The proposed ST receiver can be employed as a multi-beam smart antenna system which is suitable for cellular communications. Computer simulations demonstrate that it can achieve nearly the same performance as the optimal ST minimum mean square error (MMSE) DFE with a much lower implementation complexity.
Superpolishing for planarizing copper damascene interconnects
(2003-05-01)
Chang, SC
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Shieh, JM
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Dai, BT
;
Feng, MS
;
Li, YH
We demonstrate a superpolishing electrolyte, which consists of acid additives in conventional Cu polishing electrolytes (H3PO4), for efficiently planarizing Cu damascene features. The significant additive concentration gradient in features, resulting in a selective Cu dissolution rate within features, is explored as a major mechanism that yields such electrolytes with high planarization efficiency. Moreover, another additive, polyethylene glycol as a suppressor, is also employed to reduce oxygen bubbling on polished films. Consequently, a smooth surface with a complete step height elimination is obtained in a 70 mm trench after electropolishing. (C) 2003 The Electrochemical Society.
Metal drift induced electrical instability of porous low dielectric constant film
(2003-05-01)
Fang, KL
;
Tsui, BY
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Nano-porous carbon doped oxide (CDO) is one of the potential low dielectric constant (low-k) materials that can achieve a dielectric constant as low as 2.2 and is expected to be suitable for the next generation multilevel interconnection. However, the electrical stability of CDO in contact with metal has not been addressed. In this work, metal ions' drift into nano-porous CDO is investigated. It is observed that both the Al and Cu ions can be driven into porous CDO film easily by applying electric field or thermal treatment. This results in a severe flat band voltage shift of the metal/CDO/Si capacitor structure. It is hypothesized that the lacking formation of self-limited aluminum oxide between Al and CDO film make Al ions drift into CDO. The adhesion of Al and Cu to CDO is also very poor. A physical model, combining weak dielectric polarization and metal ions drift, was proposed to explain the observed electrical instability. The inconsistent results regarding the Al/porous low-k/Si structure reported in the previous literatures can also be explained with this proposed model. Fortunately, TaN, as a common diffusion barrier material for Cu interconnect structure, is proved to have good adhesion to CDO. Negligible metal ions would drift in CDO during electrical stress. It is concluded that with a suitable diffusion barrier, such as TaN, CDO is still a very promising material for next generation Cu-interconnect technology. (C) 2003 American Institute of Physics.
Locating faults on cables by applying the principle of the transmission line oscillator
(2003-05-01)
Liu, WC
;
Lu, MH
;
光電工程學系
;
Department of Photonics
A new method for locating the break point of a cable has been developed. It operates by application of the principle of the transmission line oscillator. Coaxial cables of four different lengths (1.5 m, 5 m, 10 m, 20 m) were measured in accordance with this method. The results show high precision (deviation <0.5 cm) and accuracy (error &LE;3 cm).
Photoexcited carrier relaxation in a-axis oriented YBa2Cu3O7-delta thin films measured by femtosecond time-resolved spectroscopy
(2003-05-01)
Luo, CW
;
Chen, MH
;
Wu, KH
;
Lin, JY
;
Juang, JY
The photoexcited carrier relaxation dynamics in a-axis oriented YBa2Cu3O7-delta (YBCO) thin films has been investigated by femtosecond time-resolved spectroscopy. Distinct responses along b-axis (CuO3 chain) and c-axis of YBCO have been separated by the polarization-dependent femtosecond pump-probe measurements. It is found that the transient reflectivity (DeltaR/R) curves for the electric field E of the polarized light parallel to the b- or c-axes of the a-axis oriented YBCO film (Eparallel tob or Eparallel toc) are significantly different. The opening of superconducting gap in CuO3 chain was obviously observed from the measurements of the DeltaR/R curves for Eparallel tob at temperatures below T-c. However, the DeltaR/R curves for Eparallel toc did not exhibit the similar characteristics. (C) 2003 Elsevier Science B.V. All rights reserved.