VARIABLE METHOD OF SYNTHESIS OF THE ELEMENTAL SIGNAL WITH MINIMUM ENERGY OUTSIDE OF WORKING FREQUENCY

It is shown in the paper that the synthesis of a signal of the optimum form is an extreme problem, the variational nature of which allows for its solution to apply the ideas and methods of functional analysis. Variational calculus was applied to study the extreme properties of the functional. An expression describing the form of the elementary signal of finite duration with minimum energy outside the working frequency band was obtained.

Multiscale Adaptive Gabor Expansion (MAGE): Improved Detection of Transient Oscillatory Burst Amplitude and Phase

Since Denis Gabor’s pioneering paper on the discrete Gabor Expansion (Gabor, 1946), time-frequency signal analysis has proven to be an important tool for many fields. In neurophysiology, time-frequency analysis has often been used to characterize and describe transient bursts in local field potential data. However, these transient bursts have a wide range of variable durations, suggesting that a time-frequency-scale dictionary composed of elementary signal “atoms” may prove useful to more accurately match recorded bursts. While overcomplete multiscale dictionaries are useful, generating a sparse code over such dictionaries is a difficult computational problem. Existing adaptive algorithms for discovering a sparse description are slow and computationally intensive. Here we describe the Multiscale Adaptive Gabor Expansion (MAGE), which uses an implicit dictionary of parametric time-frequency-scale Gabor atoms to perform fast parameter reassignment to accelerate discovery of a sparse decomposition. Using analytic expressions together with numerical computation, MAGE is a greedy pursuit algorithm similar to Matching Pursuit, restricted to a dictionary of multiscale Gaussian-envelope Gabor atoms. MAGE parameter reassignment is robust in the presence of moderate noise. By expressing a unknown signal as a weighted sum of Gabor atoms, MAGE permits a more accurate estimate of the amplitude and phase of transient bursts than existing methods.

Optimization of LDPC Coded IDMA System

The issue of optimization of LDPC Coded IDMA system is studied. The iterative decoding process of LDPC code is called inner iteration, and the iterative process between LDPC code and elementary signal estimator (ESE) is called outer iteration. The performance of the system is shown by BER and the complexity is indicated by iteration number. Check matrix is constructed randomly based on the obtained degree profile and simulations are made. The results show that performance of the system improves as the iteration number increases, either inner or outer iteration number. On the other hand, the performance gain of the system decreases with the increase of iteration number. Besides, the performance can be improved by reasonable setting of iteration number with the same complexity.

Fatigue-Seismic Ratcheting Interactions in Pressurized Elbows

Three dynamic tests on pressurized elbows involving fatigue-ratcheting as the major failure mode are investigated. The fatigue analysis is carried out with two approaches: the first is global and consists of Markl’s equation; the second is local and is based on local fatigue criteria combined with a suggestion by Coffin to take ratcheting into account. The implementation of these approaches required some elementary signal processing to separate the cyclic part of the strain from ratcheting. Results on narrow-band processes were used to assess cumulative damage. Finite element computations extended the data into uninstrumented locations. The great sensitivity of the implemented criteria to their arguments is discussed and exemplified. Despite the complexities of the issue, computed results match well with the experimental data.