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ABSTRACT: The increasing availability of motion data creates unprecedent opportunities to change the paradigm for characterizing movement patterns. While cluster analysis is usually a useful starting point for understanding and exploring data, conventional clustering algorithms are not designed for handling trajectory data. Therefore, in this paper, we propose a direction-based clustering (DEN) method, which aims to group trajectories by moving directions. A key development challenge is how to transform direction information into a data format which is appropriate for traditional clustering algorithms to explore. To this end, we partition the space into grids and turn the movement statistics in a grid into a vector which represents the probabilities of moving directions within the grid. With such data transformation, we are able to develop a grid-level K-means clustering method for direction clustering. We illustrate the use of DEN for showing movement patterns and detecting outliers on real-world data sets.
Information Reuse and Integration (IRI), 2010 IEEE International Conference on; 09/2010
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D-H. Kang,
J.-H. Lee,
J.H. Kong,
D. Ha, J. Yu,
C.Y. Um,
J.H. Park,
F. Yeung,
J.H. Kim,
W.I. Park,
Y.J. Jeon,
M.K. Lee,
Y.J. Song,
J.H. Oh,
G.T. Jeong,
H.S. Jeong
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ABSTRACT: This paper firstly reports key factors which are to be necessarily considered for the successful two-bit (four-level) cell operation in a phase-change random access memory (PRAM). They are: 1) the write-and-verify (WAV) writing of four-level resistance states; and 2) the moderate-quenched (MQ) writing of intermediate resistance levels, 3) the optimization of temporal resistance increase (so-called resistance drift) and 4) of resistance increase after thermal annealing. With taking into account of them, we realized a two-bit cell operation in diode-switch phase change memory cells with 90 nm technology. All of four resistance levels are highly write endurable and immune to write disturbance above 10<sup>8</sup> cycles, respectively. In addition, they are non-destructively readable above 10<sup>7</sup> read pulses at 100 ns and 1 uA.
VLSI Technology, 2008 Symposium on; 07/2008
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D.H. Kang,
J.S. Kim,
Y.R. Kim,
Y.T. Kim,
M.K. Lee,
Y.J. Jun,
J.H. Park,
F. Yeung,
C.W. Jeong, J. Yu, [......],
J.I. Kim,
Y.T. Oh,
K.W. Lee,
S.P. Koh,
S.H. Eun,
N.B. Kim,
G.H. Koh,
G.T. Jeong,
H.S. Jeong,
Kinam Kim
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ABSTRACT: Programming with larger current than optimized one is often preferable to ensure a good resistance distribution of high-resistive reset state in high-density phase-change random access memories because it is very effective to increase the resistance of cells to a target value. In this paper, we firstly report that this larger current writing may conversely degrade the reset distribution by reducing the resistance of normal cells via the partial crystallization of amorphous Ge<sub>2</sub>Sb<sub>2</sub>Te<sub>5</sub> and this degradation can be suppressed by designing a novel cell structure with a heat dissipating layer.
VLSI Technology, 2007 IEEE Symposium on; 07/2007
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J.H. Oh,
J.H. Park,
Y.S. Lim,
H.S. Lim,
Y.T. Oh,
J.S. Kim,
J.M. Shin,
Y.J. Song,
K.C. Ryoo,
D.W. Lim, [......],
J.H. Kim, J. Yu,
F. Yeung,
C.W. Jeong,
J.H. Kong,
D.H. Kang,
G.H. Koh,
G.T. Jeong,
H.S. Jeong,
Kinam Kim
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ABSTRACT: Fully functional 512Mb PRAM with 0.047mum<sup>2</sup> (5.8F<sup>2</sup>) cell size was successfully fabricated using 90nm diode technology in which the authors developed novel process schemes such as vertical diode as cell switch, self-aligned bottom electrode contact scheme, and line-type Ge<sub>2</sub>Sb<sub>2</sub>Te<sub>5</sub>. The 512Mb PRAM showed excellent electrical properties of sufficiently large on-current and stable phase transition behavior. The reliability of the 512Mb chip was also evaluated as a write-endurance over 1E5 cycles and a data retention time over 10 years at 85degC
Electron Devices Meeting, 2006. IEDM '06. International; 01/2007
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ABSTRACT: Super-resolution image reconstruction technique is to restore a high-resolution and high-quality image from multiple degraded low-resolution observations. The POCS method for super-resolution image reconstruction attracts many researchers' attention. This paper proposes to reduce the amount of Gibbs artifacts present on the edges of the high-resolution image estimate obtained by the POCS method. The proposed method weights the blur PSF centered at an edge pixel with an exponential function, so that the modified PSF coefficients decrease in the direction orthogonal to the edge. Experimental results show that the modification effectively reduces the visibility of the artifacts on the edges and obviously improves the quality of the high-resolution reconstructed image
Signal Processing, 2006 8th International Conference on; 02/2006
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ABSTRACT: A unified approach, i.e. the time-averaging equivalent circuit
analysis, is proposed for a class of periodically switching linear
networks. The distinctive feature of the approach is to replace the
pulsewidth modulated switches inside the original network prior to any
further treatment, yielding a structure-invariant linear circuit, which
can thus be analyzed in a conventional manner. The parameters of the
time-averaging equivalent circuit model can easily be determined by the
approach without a prior knowledge of the DC solution for the converter.
The DC analysis and small-signal analysis can then be performed based on
its time-averaging equivalent circuit model
Circuits and Systems, 1988., IEEE International Symposium on; 07/1988
