Preprocessing Scheme Research Articles

Penalty computations for the set partitioning problem

The computation of penalties associated with the continuous relaxation of integer programming problems can be useful to derive conditional and relational tests which allow to fix some variables at their optimal value or to generate new constraints (cuts). We study in this paper the computation and the use of penalties as a tool to improve the efficiency of algorithms for solving set partitioning problems. This leads to a preprocessing scheme which can be embedded within any exact or approximate algorithm. The strength of these penalties is illustrated through computational results on some real-world set partitioning problems.

Two-dimensional angle-of-arrival estimation in the presence of finite distance sources

When sources are a finite distance away from an array system, most high-resolution bearing estimation techniques exhibit unsatisfactory performance due to the invalidity of the planar wavefront assumption. This problem has been addressed by a far-field approximation (FFA) method based on a preprocessing scheme. By exploiting favorable characteristics of a uniform linear array, the method constructs a FFA covariance matrix, which is Toeplitz and approximates to the far-field data covariance matrix, from the observed data covariance matrix. Then eigenstructure methods can be applied to perform bearing estimation without revising the planar wavefront assumption. This method is extended to the problem of two-dimensional angle-of-arrival (AOA) estimation using a uniform planar array in the presence of finite distance sources. A procedure is derived for reconstructing the 2-D FFA covariance matrix with block-Toeplitz structure. Using the 2-D FFA covariance matrix, eigenstructure methods can be applied in conjunction with a 2-D AOA search to solve the problem. Simulation results confirm the theoretical work. >

The resolution of modal Doppler shifts in a dispersive oceanic waveguide

In this paper, a method for estimating the source velocity from the acoustic signal field propagating in a dispersive oceanic waveguide is presented. The signal is observed at an omnidirectional receiver in the presence of additive white noise. The source transmits a continuous wave (cw) signal, and the source motion is assumed to be uniform (unaccelerated). The ocean is modeled as a waveguide that is horizontally stratified with an arbitrary sound-speed profile in the vertical. The acoustic field generated by a moving point source in terms of normal modes predicts that each mode has a different Doppler shift, which contrasts with a single Doppler shift in a homogeneous unbounded medium. The modes are considered to remain phase locked with each other, i.e., coherent. The source velocity, including the number of modes involved, can be estimated through resolving modal Doppler shifts. The method is a time-domain interpretation of a recently developed eigenstructure technique for a multitarget direction finding with passive antenna arrays, in conjunction with a smoothing preprocessing scheme to deal with coherent modes [Shan et al., IEEE Trans. Acoust. Speech Signal Process. ASSP-33, 806–811 (1985)]. Simulation results that illustrate the performance of the method are presented.

The resolution of modal Doppler shifts in an acoustic waveguide

A method for estimating the source velocity from the acoustic signal field propagating in a dispersive oceanic waveguide is presented. The signal is observed at an omnidirectional receiver in the presence of additive white noise. The source transmits a continuous‐wave (cw) signal, and the source motion is assumed to be uniform (unaccelerated). The ocean is modeled as a waveguide that is horizontally stratified with an arbitrary sound‐speed profile in the vertical. The acoustic field generated by a moving point source in terms of normal modes predicts that each mode has a different Doppler shift, which contrasts with a single Doppler shift in a homogeneous unbounded medium. The modes are considered to remain phase locked with each other, i.e., coherent. The source velocity, including the number of modes involved, can be estimated through resolving Doppler shifts. The method is a time‐domain interpretation of a recently developed eigenstructure technique for multitarget direction finding with passive antenna arrays, in conjunction with smoothing preprocessing scheme to deal with coherent modes [Shan et al., IEEE Trans. Acoust. Speech Signal Process. ASSP‐33 (4) (1985)]. Simulation results that illustrate the performance of the method are presented.

Design of tactile sensing systems for dextrous manipulators

Preliminary work aimed at understanding the general issues and tradeoffs governing the design of extended tactile sensing systems is reviewed. General methods for estimating the bandwidths of line-addressed and matrix-addressed systems are presented. The proposed tactile sensing system incorporates four subsystems that permit the high-speed access of tactile data: (1) a transduction scheme; (2) a preprocessing scheme; (3) a multiplexing and transmission subsystem; and (4) tactile data selection techniques. Designs for implementation at each of these levels are presented. The designs emphasize practical necessities such as simplicity, reliability, and economy, along with plans to incorporate a tactile system into the Utah/MIT dextrous hand. >