Geocenter motion (GCM) is one important topic for constructing and maintaining the terrestrial reference frame and its applications.
GCM is studied from CHAMP with the multi-step approach in this paper. Geometric orbits of CHAMP in 2001–2006 are precisely
determined with the kinematic method only from the satellite-borne GPS zero-difference data. Then a GCM time series is estimated
from the precise kinematic orbits based on the theory of satellite dynamics to fit the CHAMP’s real geometric orbits. We compare
the series with the geocenter series used in ITRF2005. Then the GCM series are analyzed with Fourier transform and wavelet
transformation. The mean motions within 6 years in TX, TY and TZ directions are respectively 0.8 mm, 2.2 mm, and 7.9 mm. The trends of GCM in the three directions are 0.495 mm/a, −0.004
mm/a, and 1.309 mm/a, respectively. The long-term movement (2001–2006) indicates that the crustal figure is changing. The
seasonal variations are the main component which may be excitated by the mass redistribution of Earth’s fluid layer, e.g.
ocean, atmosphere and continental water. The inter-annual variations are also found in the GCM series measured with CHAMP.
Supported by the International S&T Cooperation Program of China (Grant No. 2006DFA21980), the National Hi-tech R&D Program
of China (Grant No. 2006AA12z303), the National Natural Science Foundation of China (Grant No. 40774009), and the Natural
Science Foundation of Shandong Province, China (Grant No. Y2003E01) 相似文献
Let XP be a variety (respectively an open subset of an analytic submanifold) and let xX be a point where all integer valued differential invariants are locally constant. We show that if the projective second fundamental form of X at x is isomorphic to the second fundamental form of a point of a Segre P× P, n,m2, a Grassmaniann G(2,n+2), n4, or the Cayley plane OP2, then X is the corresponding homogeneous variety (resp. an open subset of the corresponding homogeneous variety). The case of the Segre P2×P2 had been conjectured by Griffiths and Harris in [GH]. If the projective second fundamental form of X at x is isomorphic to the second fundamental form of a point of a Veronese v2(P) and the Fubini cubic form of X at x is zero, then X=v2 (P) (resp. an open subset of v2(P)). All these results are valid in the real or complex analytic categories and locally in the C category if one assumes the hypotheses hold in a neighborhood of any point x. As a byproduct, we show that the systems of quadrics I2(P P) S2C, I2(P1× P) S2C and I2(S5) S2C16 are stable in the sense that if A S* is an analytic family such that for t0,AA, then A0A. We also make some observations related to the Fulton–:Hansen connectedness theorem. 相似文献
The optimal attitude control problem of spacecraft during its solar arrays stretching process is discussed in the present
paper. By using the theory of wavelet analysis in control algorithm, the discrete orthonormal wavelet function is introduced
into the optimal control problem, the method of wavelet expansion is substituted for the classical Fourier basic function.
An optimal control algorithm based on wavelet analysis is proposed. The effectiveness of the wavelet expansion approach is
shown by numerical simulation.
This work is supported by the National Natural Science Foundation of China. 相似文献
In the early 1960s of the 20th century de Broglie was able to explain the cosmological observable red shift, without ad hoc assumptions. Starting from basic quantum considerations he developed his tired light model for the photon. This model explains in a single and beautiful causal way the cosmological redshift without need of assuming the Big Bang and consequently a beginning for the universe. Evidence coming from Earth sciences seems also to confirm these ideas and furthermore concrete proposal of laboratorial scale experiments that can test the model are reviewed. 相似文献
Starting from any two compactly supported refinable functions in L2(R)
with dilation factor d,we show that it is always possible to construct 2d wavelet functions
with compact support such that they generate a pair of dual d-wavelet frames in L2(R).
Moreover, the number of vanishing moments of each of these wavelet frames is equal
to the approximation order of the dual MRA; this is the highest possible. In particular,
when we consider symmetric refinable functions, the constructed dual wavelets are also
symmetric or antisymmetric. As a consequence, for any compactly supported refinable
function in L2(R), it is possible to construct, explicitly and easily, wavelets that are
finite linear combinations of translates (d · – k), and that generate a wavelet frame with
an arbitrarily preassigned number of vanishing moments.We illustrate the general theory
by examples of such pairs of dual wavelet frames derived from B-spline functions. 相似文献
This paper is concerned with tight closure in a commutative Noetherian ring of prime characteristic , and is motivated by an argument of K. E. Smith and I. Swanson that shows that, if the sequence of Frobenius powers of a proper ideal of has linear growth of primary decompositions, then tight closure (of ) `commutes with localization at the powers of a single element'. It is shown in this paper that, provided has a weak test element, linear growth of primary decompositions for other sequences of ideals of that approximate, in a certain sense, the sequence of Frobenius powers of would not only be just as good in this context, but, in the presence of a certain additional finiteness property, would actually imply that tight closure (of ) commutes with localization at an arbitrary multiplicatively closed subset of .
Work of M. Katzman on the localization problem for tight closure raised the question as to whether the union of the associated primes of the tight closures of the Frobenius powers of has only finitely many maximal members. This paper develops, through a careful analysis of the ideal theory of the perfect closure of , strategies for showing that tight closure (of a specified ideal of ) commutes with localization at an arbitrary multiplicatively closed subset of and for showing that the union of the associated primes of the tight closures of the Frobenius powers of is actually a finite set. Several applications of the strategies are presented; in most of them it was already known that tight closure commutes with localization, but the resulting affirmative answers to Katzman's question in the various situations considered are believed to be new.
We study the action of translation operators on wavelet subspaces. This action gives rise to an equivalence relation on the
set of all wavelets. We show by explicit construction that each of the associated equivalence classes is non-empty. 相似文献
When a cardinal B-spline of order greater than 1 is used as the scaling function to generate a multiresolution approximation of L2=L2(R) with dilation integer factor M2, the standard matrix extension approach for constructing compactly supported tight frames has the limitation that at least one of the tight frame generators does not annihilate any polynomial except the constant. The notion of vanishing moment recovery (VMR) was introduced in our earlier work (and independently by Daubechies et al.) for dilation M=2 to increase the order of vanishing moments. This present paper extends the tight frame results in the above mentioned papers from dilation M=2 to arbitrary integer M2 for any compactly supported M-dilation scaling functions. It is shown, in particular, that M compactly supported tight frame generators suffice, but not M–1 in general. A complete characterization of the M-dilation polynomial symbol is derived for the existence of M–1 such frame generators. Linear spline examples are given for M=3,4 to demonstrate our constructive approach. 相似文献