High-Sensitivity Acquisition of Ultrahigh Dynamic Direct Sequence Spread Spectrum Signals in Space Communications

According to the requirements of the high-sensitivity acquisition of Direct Sequence Spread Spectrum(DSSS) signals under ultrahigh dynamic environments in space communications, a three-dimensional joint search of the phase of Pseudo-Noise-code(PN-code),Doppler frequency and its rate-of-change is presented to achieve high sensitivity in sensing high-frequency dynamics. By eliminating the correlation peak loss caused by ultrahigh Doppler frequency and its rate-of-change offset,the proposed method improves the acquisition sensitivity by increasing the non-coherent accumulation time. The validity of the algorithm is proved by theoretical analysis and simulation results. It is shown that signals with a carrier- to-noise ratio as low as 39 dBHz can be captured with high performance when the Doppler frequency is up to ±1 MHz and its rate-of-change is up to ±200 kHz/s.

Research on Estimator and Testing Acquisition Schemes in Direct Sequence Spectrum Spreading Systems

Serveral methods for the pararrel acquisition of a PN sequence in a baseband direct sequence spread spectrum system are investigated. Four different kinds of schemes are considered: the optimal estimation scheme, the locally optimal estimation scheme, the optimal testing searches and the locally optimal testing scheme. In the four kinds of parallel acquisition schemes, the expressions for the probability of error are given and compared with the actual error probabilities obtained via Monte Carlo simulation. We also outline a technique that can be suboptimal because of a large amount of hardware and computation when using the parallel acquisition schemes.

New Acquisition Algorithm for Direct Sequence Spread Spectrum Signals

Aiming at improving acquisition performance for direct sequence spread spectrum （DSSS） signals, a new acquisition algorithm based on fast Fourier transform （FFT） is proposed. The code phases are parallel searched throughout the Doppler frequency domain. Since the influence of Doppler frequency errors on peak-to- average ratios of correlation power shows a pattern similar to the sinc function, it is our belief that by judging on peak-to-average ratios for different Doppler frequency errors false alarm probabilities should be lowered. Analyses have supported the underlying principle of this new algorithm. Simulation results have also indicated that the new algorithm can effectively improve the acquisition performance for DSSS signals.

A Study of Morpheme Order of Acquisition Through Obligatory Accasion Anlysis

Much consideration has been given to the study of certain grammatical morphemes by researchers.The study of learners' use of morphemes through obligatory analysis has important implications for both second language acquisition and the second language teaching.It suggests that some linguistic features,particularly grammatical features,are inherently easier to learn than others.For example,in this study,the fact that learners master article before 3rd person singular suggests that article in some sense easier to learn.

SOME EULER SPACES OF DIFFERENCE SEQUENCES OF ORDER m

Kizmaz [13] studied the difference sequence spaces ∞（A）, c（A）, and co（A）. Several article dealt with the sets of sequences of m-th order difference of which are bounded, convergent, or convergent to zero. Altay and Basar [5] and Altay, Basar, and Mursaleen [7] introduced the Euler sequence spaces e0^r, ec^r, and e∞^r, respectively. The main purpose of this article is to introduce the spaces e0^r△^（m））, ec^r△^（m））, and e∞^r△^（m））consisting of all sequences whose mth order differences are in the Euler spaces e0^r, ec^r, and e∞^r, respectively. Moreover, the authors give some topological properties and inclusion relations, and determine the α-, β-, and γ-duals of the spaces e0^r△^（m））, ec^r△^（m））, and e∞^r△^（m））, and the Schauder basis of the spaces e0^r△^（m））, ec^r△^（m））. The last section of the article is devoted to the characterization of some matrix mappings on the sequence space ec^r△^（m））.

CHARACTERIZATIONS OF COMPACT OPERATORS ON SOME EULER SPACES OF DIFFERENCE SEQUENCES OF ORDER m

In the past, several authors studied spaces of m-th order difference sequences, among them, H.Polat and F.Basar （[17]） defined the Euler spaces of m-th order difference sequences e r 0 （△ （ m ） ）, e r c （△ （ m ） ） and e r ∞ （△ （ m ） ） and characterized some classes of matrix transformations on them. In our paper, we add a new supplementary aspect to their research by characterizing classes of compact operators on those spaces. For that purpose, the spaces are treated as the matrix domains of a triangle in the classical sequence spaces c 0 , c and ∞ . The main tool for our characterizations is the Hausdorff measure of noncompactness.

Sedimentary Facies Architectures of Third-Order Sequences from Early to Middle Triassic in Nanpanjiang Basin

There are complex and regular changes on sedimentary facies from the Early to the Middle Triassic in the Nanpanjiang basin. After the obvious drowned event of carbonate platforms in the transitional period between Permian and Triassic, carbonate platforms have evolved into the ramp type from the rimmed shelf type. The differentiation of sedimentary facies becomes clearer in space, which are marked by the changes from an attached platform to a turbidity basin and several isolated platforms in the basin. The striking characteristics are the development of oolitic banks on isolated platforms in Nanning and Jingxi and the reef and bank limestones in the margin of the attached platform in the Early Triassic. Despite the difference of the time span and the architecture of facies succession of third order sedimentary sequences, the process of the third order relative sea level changes reflected by the sedimentary facies succession of the third order sequences is generally synchronous. Therefore, six third order sequences could be discerned in the strata from the Early to the Middle Triassic in the Nanpanjiang basin. Using two types of facies changing surfaces and two types of diachronisms in stratigraphic records as the key elements, the sedimentary facies architectures of the third order sequences that represent sequence stratigraphic frameworks from the Early to the Middle Triassic in the Nanpanjiang basin could be constructed.

Ordered Generalized Sequence Spaces and their Duals

The main result of this paper is the identification of the sequential order dual [∧(X)]so containing sequentially order continuous linear functionals on the ordered generalized sequence space ∧(X) with its generalized Kothe dual ∧x(Xso), defined corresponding to the dual pair <X, Xso>.

The asymptotic relation between the first crossing point and the last exit time of Gaussian order statistics sequences

In this paper,we study the asymptotic relation between the first crossing point and the last exit time for Gaussian order statistics which are generated by stationary weakly and strongly dependent Gaussian sequences.It is shown that the first crossing point and the last exit time are asymptotically independent and dependent for weakly and strongly dependent cases,respectively.The asymptotic relations between the first crossing point and the last exit time for stationary weakly and strongly dependent Gaussian sequences are also obtained.

Two Sequences of Operator Monotone Functions and Strictly Chaotic Order

In this paper we introduce two sequences of operator functions and their dualfunctions： fk（t） = （flogt）k-（t-1）k/log^k＋2t （k = 1,2,...）, gk（t） = （t-1）k-logkt /log^k＋1t （k = 1,2,...） and fk（t）tklog^k＋1t/（tlogt）k-（t-1）^k（k=1,2…）,gk（t）=t^klog^k＋1t/（t-1）^k-log^kt（k=1,2…）defined onWe find that they are all operator monotone functions with respect to the strictly chaoticorder and some ordinary orders among positive invertible operators. Indeed, we extend theresults of the operator monotone function tlogt-t＋1/log^2t which is widely used in the theory of heat transfer of the heat engineering and fluid mechanics[1].

Type division and controlling factor analysis of 3rd-order sequences in marine carbonate rocks

Type division and controlling factor analysis of 3rd-order sequence are of practical significance to tec-tonic analysis, sedimentary environment identification, and other geological researches. Based on the comprehensive analysis of carbon and oxygen isotope trends, paleobathymetry and spectral-frequency of representative well logs, 3rd-order sequences can be divided into 3 types： （a） global sea level （GSL） sequence mainly controlled by GSL change;（b） tectonic sequence mainly controlled by regional tectonic activity;and （c） composite sequence jointly controlled by GSL change and regional tectonic activity. This study aims to identify the controlling factors of 3rd-order sequences and to illustrate a new method for classification of 3rd-order sequences of the middle Permian strata in the Sichuan Basin, China. The middle Permian strata in the Sichuan Basin consist of 3 basin-contrastive 3rd-order sequences, i.e., PSQ1, PSQ2 and PSQ3. Of these, PSQ1 is a GSL sequence while PSQ2 and PSQ3 are composite sequences. The results suggest that the depositional environment was stable during the deposition of PSQ1, but was activated by tectonic activity during the deposition of the middle Permian Maokou Formation.

Generating functions for powers of second-order recurrence sequences

For the sequences satisfying the recurrence relation of the second order,the generating functions for the products of the powers of these sequences are established.This study was from Carlita and Riordan who began a study on closed form of generating functions for powers of second-order recurrence sequences.This investigation was completed by Stnica.Inspired by the recent work of Istva＇n about the non-closed generating functions of the products of the powers of the second-order sequences,the authors give several extensions of Istva＇n＇s results in this paper.

ON THE NATURAL ORDER OF ACQUISITION OF LANGUAGE

How do children acquire their mother tongue? Are the process in acquiring L1 (first language) and L2 (second language) the same? These questions always arouse the interests of the linguists. For many years, linguists have made a lot of research on first language acquisiton. They have put forward several

Development characteristics of the third-order sequence of Upper Devonian–Lower Carboniferous shore-mixed shelf in Tarim Basin, NW China

Based on the study of stratigraphic sedimentary facies of the prototype sedimentary basin formed in the Late Devonian to Permian Period in the Tarim Basin, the prototype sedimentary basin are divided into five order sequences according to the theory of sequence stratigraphy. It is considered that the Upper Devonian–Lower Carboniferous shore-mixing shelf in the lower part of the prototype sedimentary basin is a typical third-order sequence and a sequence development model is established. The third-order sequence is actually a transgression systems tract and highstand systems tract cycle assemblage, and the type I sequence(no lowstand systems tract) is a typical developmental mode of the third order sequence, and the identification mark is the existence of huge mudstone and limestone wedges from sea to land. The fifth-order parasequence is the basic sequence, which is a single cycle sequence. The thin layer limestone isochronous sediments, which are easy to be identified in the mixed shelf areas, are the isochronous sediments of the largest or secondary marine-flooding surface. The mixed shelf area belongs to the equilibrium sedimentary profile of internal and external sediments, and there is no condensed section. The inclined deposition phenomenon of extraneous source sediments in the sea area weakens or disappears in the mixed shelf area. The paleogeomorphology at the bottom of the third-order sequence is a terrace-slope break zone. This paleogeomorphological feature is not only the main reason for the sedimentary diachronism of Donghe sandstone, but also the main reason for the formation of the transgression-highstand fourth-order cyclic sequences of the Donghe sandstone section and its upper gravel-bearing sandstone section.

MULTIPLE RECIPROCITY METHOD WITH TWO SERIES OF SEQUENCES OF HIGH-ORDER FUNDAMENTAL SOLUTION FOR THIN PLATE BENDING

The boundary value problem of plate bending problem on two_parameter foundation was discussed.Using two series of the high_order fundamental solution sequences, namely, the fundamental solution sequences for the multi_harmonic operator and Laplace operator, applying the multiple reciprocity method(MRM), the MRM boundary integral equation for plate bending problem was constructed. It proves that the boundary integral equation derived from MRM is essentially identical to the conventional boundary integral equation. Hence the convergence analysis of MRM for plate bending problem can be obtained by the error estimation for the conventional boundary integral equation. In addition, this method can extend to the case of more series of the high_order fundamental solution sequences.

RELIABILITY ANALYSIS OF FRP LAMINATED PLATES WITH CONSIDERATION OF BOTH INITIAL IMPERFECTION AND FAILURE SEQUENCE

A probabilistic progressive failure analyzing method is applied to estimating the reliability of a simply supported laminated composite plate with an initial imperfection under bi-axial compression load. The initial imperfection and the strength parameters are considered as random variables. Ply-level failure probability is evaluated by the first order reliability method (FORM) together with the Tsai-Wu strength criterion and Tan criterion. Current stresses in the laminated structure are calculated by the classical lamination theory with the stiffness modified based on the last step ply failure. Probabilistically dominant ply-level failure sequences leading to overall system failure are identified, based on which the system failure probability is estimated. A numerical example is presented to demonstrate the methodology proposed. Through parameter studies it is shown that the deviation of the initial imperfection and some of the strength parameters largely influence the system reliability.

Study on Fast Acquisition of Hybrid DS/FHSS

In hybrid Direct Sequence/Frequency Hopping Spread Spectrum （DS/FH SS） system, the fast acquisition is a key technique. A combined fast scanning and waiting method for FH acquisition is introduced, and a neural network for DS acquisition is presented also. Using these two methods, the fast acquisition of the hybrid DS/FH SS system can be realized.

New acquisition decision algorithm for multiple access interference suppression in DSSS system

For decreasing the multiple access interference of weaker signal acquisition in direct sequence spread spectrum（DSSS） systems,a new single decision algorithm is presented.The maximum value of correlation results is conventionally detected.However,there may be not only one strong peak among correlation results when the cross-correlation noise is strong enough to affect the correlation results.The proposed algorithm decreases the false alarm probability through the decision of the ratio of the maximum value and the second maximum value of the correlation results.Theoretical analysis and simulation results indicate that the proposed algorithm effectively suppresses the acquisition problem of multiple access interference in DSSS system.

A Climatic Sequence Stratigraphic Model in the Terrestrial Lacustrine Basin:A Case Study of Green River Formation,Uinta Basin,USA

In recent years, with the development of terrestrial sequence stratigraphy, more attention has been focused on the study of the terrestrial lacustrine sequence stratigraphic model globally. Different viewpoints are preferred by researchers. Under the guidance of the theory of sequence stratigraphy, the findings of this paper indicate that climate is a major factor controlling the formation of the fourth-order sequence, based upon the study of the sequence stratigraphy in the Green River Formation of the Uinta basin in the USA. It also divides the fourth-order sequence in the terrestrial lacustrine basin into two system tracts： the wet （rising） half-cycle and the dry （falling） half- cycle, establishing a new-style fourth-order sequence stratigraphic model for the terrestrial lacustrine basin, that is, the climate-genetic sequence stratigraphic model. As a result, the theory of sequence stratigraphy is greatly enriched.

The Acquisition of English Negatives by a Portuguese Boy

this study provided the strong evidence that L2 learner's development patterns in syntactic structure is very similar to the pattern of L1 learners.L2 and L1 learner pass the similar gradual route to get the TL negative structure.But L2 learners' acquisitional sequences are not completely rigid.Individual learners may be interfered by other social or psychological factors en route and they may take longer than two years and some never travel the whole distance.