16,371 research outputs found
A fuzzy k-modes algorithm for clustering categorical data
This correspondence describes extensions to the fuzzy k-means algorithm for clustering categorical data. By using a simple matching dissimilarity measure for categorical objects and modes instead of means for clusters, a new approach is developed, which allows the use of the k-means paradigm to efficiently cluster large categorical data sets. A fuzzy k-modes algorithm is presented and the effectiveness of the algorithm is demonstrated with experimental results.published_or_final_versio
Testing Cluster Structure of Graphs
We study the problem of recognizing the cluster structure of a graph in the
framework of property testing in the bounded degree model. Given a parameter
, a -bounded degree graph is defined to be -clusterable, if it can be partitioned into no more than parts, such
that the (inner) conductance of the induced subgraph on each part is at least
and the (outer) conductance of each part is at most
, where depends only on . Our main
result is a sublinear algorithm with the running time
that takes as
input a graph with maximum degree bounded by , parameters , ,
, and with probability at least , accepts the graph if it
is -clusterable and rejects the graph if it is -far from
-clusterable for , where depends only on . By the lower
bound of on the number of queries needed for testing graph
expansion, which corresponds to in our problem, our algorithm is
asymptotically optimal up to polylogarithmic factors.Comment: Full version of STOC 201
An ultrafast 1 x M all-optical WDM packet-switched router based on the PPM header address
This paper presents an all-optical 1 x M WDM router architecture for packet routing at multiple wavelengths simultaneously, with no wavelength conversion modules. The packet header address adopted is based on the pulse position modulation (PPM) format, thus enabling the use of only a singlebitwise optical AND gate for fast header address correlation. It offers multicast as well as broadcast capabilities. It is shown that a high speed packet routing at 160 Gb/s can be achieved with a low channel crosstalk (CXT) of ~ -27 dB at a channel spacing of greater than 0.4 THz and a demultiplexer bandwidth of 500 GHz
Space-charge effects of the proposed high-intensity Fermilab booster
Space-charge effects on beam stabilities are studied for the proposed two-ring high-intensity Fermilab booster destined for the muon collider. This includes microwave instabilities and rf potential-well distortions. For the first ring, ferrite insertion is suggested to cancel the space-charge distortion of the rf wave form. To control the inductance of the ferrite during ramping and to minimize resistive loss, perpendicular biasing to saturation is proposed
Optimal multi-user MISO solution with application to multi-user orthogonal space division multiplexing
In this paper, we shall show that for a nT-element base station (BS) communicating with M(≤ nT) single-element mobile stations (MS) (or multi-user MISO) orthogonally in the spatial domain, the optimization problem is equivalent to the least squares (LS) problem for an underdetermined linear system. We then prove that the optimal BS antenna weights can be expressed as the pseudo-inverse of the multi-user channel matrix. This solution decomposes the multi-user system into many single-user systems with maximal resultant channel responses. The average of the squared channel response (defined as channel gain) and the inverse of the normalized variance of the squared channel response (defined as diversity order) are derived for performance analysis. It is found that every individual user of the resulting system behaves like a single-user system with nT-M+1 reception diversity. Finally, by applying the solution on a multi-user MIMO antenna system (i.e., with multiple antennas at the MS as well), an iterative approach is proposed to perform multi-user orthogonal space division multiplexing (OSDM) in the downlink.published_or_final_versio
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