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ABSTRACT: The integrity of the electric power cables is vital to the safety of an entire electrical system. To ensure the health of the cables, a technique is needed for both detecting/locating defects, and predicting hard defects before they occur. The theory and limitations of the classical wiring diagnostic techniques time domain reflectometry (TDR) and frequency domain reflectometry (FDR) are discussed. This study then introduces joint time-frequency domain reflectometry (JTFDR) as a unique solution for the cable diagnostics and prognostics. By employing an interrogating incident signal and advanced post-processing of the reflected signals, JTFDR is shown to be capable of overcoming those limitations. JTFDR is experimentally proven to be successful for detecting and locating both hard and incipient defects. The prognostic capabilities of JTFDR are also demonstrated via accelerated ageing tests of an electric power cable. By utilising the incident/reflected signal information in the time and frequency domains simultaneously, JTFDR is proven to be a more effective diagnostic technique than the classical TDR and FDR. JTFDR can also be used to monitor incipient defects and better predict hard defects before they occur.
IET Signal Processing 09/2010; · 0.56 Impact Factor
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F. Gatta,
R. Gomez, Y.J. Shin,
T. Hayashi,
Hanli Zou,
J.Y.C. Chang,
L. Dauphinee,
Jianhong Xiao,
D.S.-H. Chang,
Tai-Hong Chih, [......],
M. Introini,
G. Cusmai,
E. Zencir,
F. Singor,
H. Eberhart,
L.K. Tan,
B. Currivan,
Lin He,
P. Cangiane,
P. Vorenkamp
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ABSTRACT: An embedded CMOS digital dual tuner for DOCSIS 3.0 and set-top box applications is presented. The dual tuner down-converts a total of ten 6 MHz Annex B channels or eight 8 MHz Annex A channels, for a maximum data rate of 320 Mb/s in Annex B and 400 Mb/s in Annex A mode. The dual tuner exceeds all the stringent SCTE 40 specifications over the 48-1004 MHz bandwidth, without using any external components or SAW filters. Enabling technologies are a harmonic rejection front-end, a low-noise high-frequency resolution phase-locked loop (PLL) and digital image rejection. To our knowledge this is the first reported multi-channel Broadband Tuner embedded in a DOCSIS 3.0 System on a Chip implemented in a 65 nm pure digital CMOS technology.
IEEE Journal of Solid-State Circuits 01/2010; · 3.23 Impact Factor
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J.-S. Kang,
S.S. Lee,
H.J. Lee,
G. Kim,
D.H. Kim,
H.K. Song, Y.J. Shin,
M.C. Jung,
H.J. Shin,
J.E. Lee,
B.I. Min
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ABSTRACT: The electronic structures of AgNi<sub>1-x</sub>Co<sub>x</sub>O<sub>2</sub> (0 les x les 1) delafossite oxides have been investigated by employing photoemission spectroscopy (PES) and X-ray absorption spectroscopy (XAS) in the soft X-ray regime of synchrotron radiation. The Ag 3d core-level PES spectra shift toward the higher binding energy with increasing x, in agreement with the metallic nature for low values of x and the insulating nature for high values of x in AgNi<sub>1-x</sub>Co<sub>x</sub>O<sub>2</sub> . Further, the Ag 3d core-level PES spectra become more asymmetric with decreasing x, which reflects the larger number of electron-hole pairs in the Ni-rich regime. Valence-band PES spectra reveal that the band width of the occupied Ni 3d states is broader than that of the Co 3d states, implying the larger Ni 3d-O 2p hybridization than the Co 3d-O 2p hybridization. The Co and Ni 2p XAS spectra show that Co ions are in the low-spin Co<sup>3+</sup> states for all x, while Ni ions are in the Ni<sup>2+</sup>-Ni<sup>3+</sup> mixed-valent states. The Ni<sup>3+</sup> component increases with x.
IEEE Transactions on Magnetics 07/2009; · 1.36 Impact Factor
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ABSTRACT: Per-flow congestion control helps endpoints fairly and efficiently share network resources. Better utilization of network resources can be achieved, however, if congestion management algorithms can determine when two different flows share a congested link. Such knowledge can be used to implement cooperative congestion control or improve the overlay topology of a P2P system. Previous techniques to detect shared congestion either assume a common source or destination node, drop-tail queueing, or a single point of congestion. We propose in this paper a novel technique, applicable to any pair of paths on the Internet, without such limitations. Our technique employs a signal processing method, wavelet denoising , to separate queueing delay caused by network congestion from various other delay variations. Our wavelet-based technique is evaluated through both simulations and Internet experiments. We show that, when detecting shared congestion of paths with a common endpoint, our technique provides faster convergence and higher accuracy while using fewer packets than previous techniques, and that it also accurately determines when there is no shared congestion. Furthermore, we show that our technique is robust and accurate for paths without a common endpoint or synchronized clocks; more specifically, it can tolerate a synchronization offset of up to one second between two packet flows.
IEEE/ACM Transactions on Networking 09/2008; · 2.03 Impact Factor
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J.-S. Kang,
S. S. Lee,
G. Kim,
H. J. Lee,
H. K. Song, Y. J. Shin,
S. W. Han,
C. Hwang,
M. C. Jung,
H. J. Shin,
B. H. Kim,
S. K. Kwon,
B. I. Min
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ABSTRACT: Electronic structures of delafossite oxides AgNi1−xCoxO2 and the frustrated Jahn-Teller (JT) system ANiO2 (A=Li,Na) have been investigated by employing soft x-ray absorption spectroscopy and photoemission spectroscopy (PES). It is found that Ni ions are in the Ni2+-Ni3+ mixed-valent states and that the low-spin (LS) Ni3+ component increases from LiNiO2 to AgNiO2 and NaNiO2, in agreement with the presence of the JT transition in NaNiO2 and the absence of the JT transition in LiNiO2 and AgNiO2. In AgNi1−xCoxO2, the Ni3+ component increases with x, while Co ions are in the LS Co3+ states for all x, which is consistent with the metallic nature for low values of x. A good agreement is found between the measured PES spectra and the calculated local spin density approximation (LSDA) electronic structures of AgNiO2 and AgCoO2, but the pseudogap feature in PES of AgNiO2 is not described by the LSDA.
Physical Review B 11/2007; 76(19). · 3.69 Impact Factor
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ABSTRACT: In order to design the power apparatus such as bus bar or power
cable, the current carrying capacity (or ampacity) should be determined
exactly since it is limited by maximum operating temperature. The
temperature rise in the power apparatus is due to Joule's loss in the
current carrying conductor and due to the induced eddy current in the
tank. This paper presents a new technique that can be used to estimate
the temperature rise in the extra high voltage bus bar. In this paper,
the power losses are calculated from the magnetic field analysis for
various materials when ac current flows into the single- and three-phase
bus bar and are used as the input data to predict temperature rise for
the thermal analysis. However, it is not easy to apply the heat transfer
coefficient on the boundaries correctly, because the coefficient is not
a constant, but depends on temperature as well as model geometry, etc.
The heat transfer coefficient is calculated according to the model
geometry and varying temperature and is coupled with the finite element
method. The temperature distribution in the bus bar by proposed method
shows good agreement with the experimental data, compared to that of the
analytic method using fixed coefficient
IEEE Transactions on Magnetics 04/2002; · 1.36 Impact Factor
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ABSTRACT: The electronic structures of the AgTO2 delafossites (T = Fe, Co, Ni) have been investigated using photoemission spectroscopy. T 2p spectra exhibit satellite structures around 6 eV below main peaks, reflecting the strong on-site 3d Coulomb interaction. T 2p spectra of AgTO2 (T=Fe, Co, Ni) are similar to those of α-Fe2O3, CoO, and NiO, respectively, suggesting the strong covalent bonding in AgTO2. The valence-band spectrum of Ag0.75CoO2 shows negligible spectral weight near EF, consistent with its semiconducting behavior. The extracted Ag 4d and Co 3d partial spectral weight (PSW) distributions of Ag0.75CoO2 reveal a small overlap between these two states, while the O 2p PSW shows a significant overlap with the Co 3d PSW. Such trends in the PSWs are consistent with those in the calculated partial densities of states of AgCoO2.
Phys. Rev. B. 61(16).
