Formation Algorithms and Properties of Binary Quasi-Orthogonal Code Sequence of Modern Satellite Systems

Increased number of threats to user interface of navigation signals, mainly in the form of suppression of navigation signals by jamming as well as navigation signal spoofing by false signals, assumes development of counter measures including improvement of structure security of navigation signals on the basis of stochastic use of code sequences which are ranging codes. This article proves the required number of unique discrete code sequences which can improve structure security of navigation signal in global navigation satellite system upon their stochastic use. Properties of discrete quasi-orthogonal code sequences are estimated which are used and proposed for use in global navigation satellite systems with channel code division, they are compared with optimum values of code balancing, number of element series and lower bounds of maximum lateral peaks of aperiodic auto-correlation function and maximum peaks of aperiodic mutual-correlation function. The experimental results show that the minimum values of the considered correlation functions of discrete quasi-orthogonal code sequences of known global navigation satellite systems exceed the lower bound by 3–6 times. The performances of code balancing and element series of discrete quasi-orthogonal code sequences of the known global navigation satellite systems satisfy in average the allowable intervals. The number of source lines of discrete quasi-orthogonal code sequences of the known global navigation satellite systems is significantly lower than their umber required for improvement of structure security of navigation signal based on their stochastic use. On the basis of the revealed drawbacks of the known discrete quasi-orthogonal code sequences, the necessity to develop new methods is substantiated allowing to obtain their required number together with statistic properties comparable with the best values of discrete quasi-orthogonal code sequences applied as navigation signals in global navigation satellite systems.

A series of dithiocarbamates for americium, curium, and californium

The isolation and characterization of a series of transplutonium coordination complexes provided insight in advancing understanding of how actinide properties change across the 5f-element series.

Evolutionary roots of the conodonts with increased number of elements in the apparatus

ABSTRACTFour kinds of robust elements have been recognised in Amorphognathus quinquiradiatus Moskalenko, 1977 (in Kanygin et al. 1977) from the early Late Ordovician of Siberia, indicating that at least 17 elements were present in the apparatus, one of them similar to the P1 element of the Early Silurian Distomodus. The new generic name Moskalenkodus is proposed for these conodonts with a pterospathodontid-like S series element morphology. This implies that the related Distomodus, Pterospathodus and Gamachignathus lineages had a long cryptic evolutionary history, probably ranging back to the early Ordovician, when they split from the lineage of Icriodella, having a duplicated M location in common. The balognathid Promissum, with a 19-element apparatus, may have shared ancestry with Icriodella in Ordovician high latitudes, with Sagittodontina, Lenodus, Trapezognathus and Phragmodus as possible connecting links. The pattern of the unbalanced contribution of Baltoniodus element types to samples suggests that duplication of M and P2 series elements may have been an early event in the evolution of balognathids. The proposed scenario implies a profound transformation of the mouth region in the evolution of conodonts. The probable original state was a chaetognath-like arrangement of coniform elements; all paired and of relatively uniform morphology. This was modified at the origin of protopanderodontids by the introduction of a medial S0 element, which resulted in the separation of the exposed unit of M and S series elements from the P series elements hidden in the throat. A rotation of the S series elements to an almost horizontal position in early prioniodontids may have promoted duplication of the M element pair. In Gamachignathus, Icriodella and Pterospathodus lineages, these elements are differentiated morphologically. Subsequent anteriorward bending of the P element series caused duplication of the balognathid P2 element pair, but they remained undifferentiated, even in the otherwise elaborate Promissum. The whole clade of conodonts with supernumerary element pairs in the apparatus has its roots in high latitudes of the Ordovician.