The perfect sequences are so ideal that all out-of-phase autocorrelation coefficients are zero, and if the sequences are used as the coding modulating signal for the phase-modulated radar, there will be no interferenc...The perfect sequences are so ideal that all out-of-phase autocorrelation coefficients are zero, and if the sequences are used as the coding modulating signal for the phase-modulated radar, there will be no interference of side lobes theoretically. However, it has been proved that there are no binary perfect sequences of period 4 〈 n ≤ 12100. Hence, the almost perfect sequences with all out-of-phase autocorrelation coefficients as zero except one are of great practice in engineering. Currently, the cyclic difference set is one of most effective tools to analyze the binary sequences with perfect periodic autocorrelation function. In this article, two characteristic formulas corresponding to the autocorrelation and symmetric structure of almost perfect sequences are calculated respectively. All almost perfect sequences with period n, which is a multiple of 4, can be figured out by the two formulas. Several almost perfect sequences with different periods have been hunted by the program based on the two formulas and then applied to the simulation program and practical application for ionospheric sounding.展开更多
Let C be a closed bounded convex subset of a uniformaly convex Banach space X with a Frechet differentiable norm, F= {T(t):t ≥0} an asymptotically noncxpansivc semigroup on C, and u:[0,∞)→ C an almost-orbit of F. T...Let C be a closed bounded convex subset of a uniformaly convex Banach space X with a Frechet differentiable norm, F= {T(t):t ≥0} an asymptotically noncxpansivc semigroup on C, and u:[0,∞)→ C an almost-orbit of F. Then we show that {u(t):t ≥ 0} is almost convergent weakly to a common fixed point y of F, that isweak - lim1/tdr - y uniformly in s≥ 0.This implies that {u(t):t≥ 0} converges weakly to y if and onlyif u is weakly asymptotically regular, i.e lim (u(t + s) - u(t) = 0 weakly for all s≥ 0.展开更多
The concept of the binary sequence pair is generalized from a single binary sequence. Binary sequence pairs are applied in many fields of radar, sonar or communication systems, in which signals with optimal periodic c...The concept of the binary sequence pair is generalized from a single binary sequence. Binary sequence pairs are applied in many fields of radar, sonar or communication systems, in which signals with optimal periodic correlation are required. Several types of almost perfect binary sequence pairs of length T = 2q are constructed, where q is an odd number. These almost perfect binary sequence pairs are based on binary ideal sequence or binary ideal two-level correlation sequence pairs by using Chinese remainder theorem. For these almost perfect binary sequence pairs with good balanced property, their corresponding divisible difference set pairs(DDSPs) are also derived.展开更多
基金This poject was supported by the National Natural Science Foundation of China (40474066).
文摘The perfect sequences are so ideal that all out-of-phase autocorrelation coefficients are zero, and if the sequences are used as the coding modulating signal for the phase-modulated radar, there will be no interference of side lobes theoretically. However, it has been proved that there are no binary perfect sequences of period 4 〈 n ≤ 12100. Hence, the almost perfect sequences with all out-of-phase autocorrelation coefficients as zero except one are of great practice in engineering. Currently, the cyclic difference set is one of most effective tools to analyze the binary sequences with perfect periodic autocorrelation function. In this article, two characteristic formulas corresponding to the autocorrelation and symmetric structure of almost perfect sequences are calculated respectively. All almost perfect sequences with period n, which is a multiple of 4, can be figured out by the two formulas. Several almost perfect sequences with different periods have been hunted by the program based on the two formulas and then applied to the simulation program and practical application for ionospheric sounding.
文摘Let C be a closed bounded convex subset of a uniformaly convex Banach space X with a Frechet differentiable norm, F= {T(t):t ≥0} an asymptotically noncxpansivc semigroup on C, and u:[0,∞)→ C an almost-orbit of F. Then we show that {u(t):t ≥ 0} is almost convergent weakly to a common fixed point y of F, that isweak - lim1/tdr - y uniformly in s≥ 0.This implies that {u(t):t≥ 0} converges weakly to y if and onlyif u is weakly asymptotically regular, i.e lim (u(t + s) - u(t) = 0 weakly for all s≥ 0.
基金supported by the National Natural Science Foundation of China(6160140161501395+6 种基金6160139961671402)Natural Science Foundation of Hebei Province(F2015203150F2016203293F2016203312)Natural Science Research Programs of Hebei Educational Committee(QN2016120)the Independent Research Programs for Young Teachers of Yanshan University(15LGB013)
文摘The concept of the binary sequence pair is generalized from a single binary sequence. Binary sequence pairs are applied in many fields of radar, sonar or communication systems, in which signals with optimal periodic correlation are required. Several types of almost perfect binary sequence pairs of length T = 2q are constructed, where q is an odd number. These almost perfect binary sequence pairs are based on binary ideal sequence or binary ideal two-level correlation sequence pairs by using Chinese remainder theorem. For these almost perfect binary sequence pairs with good balanced property, their corresponding divisible difference set pairs(DDSPs) are also derived.
