Marek Kuczma asked in 1980 whether for every positive integer n, there exists a subsemigroup M of a group G, such that G is equal to the n-fold product M M−1M M−1 . . . M(−1) n−1 , but not to any proper initial subproduct of this product. We answer his question affirmatively, and prove a more general result on representing a certain sort of relation algebra by subsets of a group. We also sketch...

Introduction: Filtering can greatly affect the quality of clinical images. Determining the best filter and the proper degree of smoothing can help to ensure the most accurate diagnosis. Methods: Forty five patient’s data aquired during brain phantom SPECT studies were reconstructed using filtered back-projection technique. The ramp, Shepp-Logan, Cosine, Hamming, Hanning, Butterworth, Metz...

Absfrucf -A universal nearly efficient estimator is proposed for the first order autoregressive (AR) model where the probability distribution of the driving noise is unknown. The proposed estimator has an intuitively appealing relation to universal data compression and to universal tests for randomness. Index Terms -asymptotically efficient estimation, universal estimation, Cramer-Rao bound, Fi...

The purpose of this study is to propose a new outdoor thermal index that simultaneously indicates universal and separate effects. The value indicating universal effect in this index consists of the summation of air temperature and the effective temperature differences by air velocity, longwave radiation, solar radiation, and humidity. This paper describes the theoretical construction of this ne...

The ap index (and derived indices) can be recalibrated by using Mayaud's am index to recover the correct universal time variations. Such variations were artificially removed in the original ap index. A number of tests are performed to show that the corrected index is capable of revealing •he desired variations. These tests include comparisons of the universal time variations on days of opposite...