1,721,163 research outputs found
Radiation from narrow circumferential slots on a conducting circular cylinder
No full textRadiation from narrow circumferential slots on a conducting circular cylinder is analyzed. The incident TM01 mode is assumed to propagate along a thick conducting cylinder multiply slotted in the axial direction. The Fourier transform and mode matching are utilized to obtain a set of simultaneous equations for the discrete modal coefficients. Simple, fast convergent series solutions are presented using residue calculus. The radiation, transmission, and reflection characteristics are investigated in terms of the operating frequency and slot geometry. Our numerical results agree favorably with other existing data as well as measurements at X-band
Estimation of dielectric slab permittivity using a flared coaxial line
No full text[1] Estimation of dielectric slab permittivity is considered by using a flared coaxial line. A problem of reflection from a flared coaxial line that radiates into a dielectric slab with a flange is solved. A flared coaxial line is modeled with multiply stepped coaxial lines with different inner and outer conductors. A set of simultaneous equations for the modal coefficients is constituted based on the boundary conditions. Computations are performed to illustrate the reflection behavior in terms of the coaxial line geometry, frequency, and permittivity of a dielectric slab. Nomograms are developed to estimate the permittivity from the measured reflection coefficients. The utility of a flared coaxial line for the determination of slab permittivity is discussed
EXPLICIT PATH TRACKING BY AUTONOMOUS VEHICLES
No full textWe have suggested a novel approach to autonomously navigate a full sized autonomous vehicle that separately treats vehicle control and obstacle detection. In this paper we discuss the vehicle control that has enabled our autonomous vehicle to travel at speeds upto 20 mph. We point out the limitations of existing schemes that restrict their consideration to kinematic models and show that it is possible to obtain an increase in performance through the use of approximate dynamical models that capture first-order effects. Our approach combines such a modeling philosophy with accurate feedback in world coordinates from sensors that have only recently become available. Experimental results of our implementation on NavLab, a modified van at CMU, are presented
Deformation behavior of powder-metallurgy processed high-strain-rate superplastic 20%SiCp/2124 Al composite in a wide range of temperature
No full textDeformation behavior of high-strain-rate superplastic PM 20%SiCp/2124 Al composite was investigated over a wide range of temperature from 643 to 838 K. The entire temperature range of investigation was separated into two regions where grain boundary sliding (high-temperature range from 748 to 838 K: region I) and dislocation climb creep (low-temperature range from 643 to 693 K: region II) dominate the plastic flow, respectively. Determination of true activation energy at a constant value of modulus-compensated effective stress reveals that the energy for region I is considerably higher than that for lattice diffusion in aluminum, Q(L), while the energy for region II is close to Q(L). The composite was shown to be stronger in region II than the unreinforced PM 2124 Al alloy but weaker in region I. The threshold-stress behavior was investigated as a function of temperature. Different behavior was observed between region I and region II. (C) 1999 Elsevier Science S.A. All rights reserved.Korea Science and
Engineering foundation (KOSEF 1999.
Audio fingerprinting scheme by temporal filtering for audio identification immune to channel-distortion
No full textChannel-distortion in real-environment is at issue in music information retrieval system by content-based audio identification technique. As a matter of fact, audio signal is commonly distorted by channel and background noise in case of that it is recorded under real-situation. Recently, Philips published a robust and efficient audio fingerprinting system for audio identification. To extract a robust and efficient audio fingerprint, Philips applied the first derivative (differential) to the frequency-time sequence of perceptual filter-bank energies. In practice, however, it is not sufficient to remove the undesired perturbations. This paper introduces an extension method of the audio fingerprint extraction scheme of Philips that is more immune to channel-distortion. The channel-normalization techniques for temporal filtering are used to lessen the channel effects of real-environment
Low-power dynamic termination scheme using NMOS diode clamping
No full textAn NMOS diode clamped termination (NDCT) with NMOS threshold voltage (V-th) of around 0 V is proposed as a dynamic termination for a high-speed/low-power chip-to-chip interconnection scheme. Both simulation and experimental results for several benchmark circuits show that, compared with open termination, the magnitudes of both overshoot and undershoot for nanosecond-range input pulses are typically less than similar to 15% of supply voltage (V-cc = 3.3 V) with the same order of magnitude in pou er saving, Last, the NDCT is found to be very immune to electrostatic discharge, guaranteeing more than 3000 V for a human body model, Our results demonstrate the potentiality of NDCT as the high-speed interconnection scheme.The authors wish to acknowledge the useful comments from
the reviewers on the potential problems due to the nonideality
of the NMOS diode
A full-wave analysis of a coaxial waveguide slot bridge using the Fourier transform technique
No full textElectromagnetic wave scattering from a coaxial waveguide slot bridge is theoretically investigated. The Fourier transform/series technique is utilized to constitute a set of simultaneous equations for the discrete modal coefficients. The residue calculus is applied to transform the scattered-field integral representations into fast-converging series forms. Numerical computations illustrate the behavior of scattering in terms of the slot geometry, the incident mode, and the operating frequency
Evaluation of polychlorinated dibenzo-p-dioxin/dibenzofuran (PCDD/F) emission in municipal solid waste incinerators
No full textThis paper summarizes an engineering approach taken for 10 commercial MSW incinerators to formulate a basis for PCDD/F emission reduction schemes and to interpret the measurement results before and after the plant modifications of moderate scale. Control strategy of PCDD/F emission from the operating incinerators can be established on the basis of the interpretation of reliable measurements as well as understanding of the formation/destruction processes. The fate of PCDD/F is known to be influenced by the flue gas subprocesses: the initial formation/oxidation in the combustion chamber, reformation through synthesis, removal by adsorption, and catalytic destruction. A simplified model is proposed for PCDD/F level at various stages of the flue gas, basically integrating the reaction kinetic rates at the corresponding state. Since the kinetic rate is dependent on temperature, time-temperature history of the flue gas is considered as the important input data. Using the plant design and operating conditions, this global prediction model calculates the PCDD/F level not only at the stack but also at the process midstream. The model predictions are discussed along with measurement results from the different design of incinerator plants.Energy and Environment Research Center of KAIST, Institute of Environmental and Energy Technology of POSTECH
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