Application and Research of Data Interface Synchronization on Web Maintenance

To adapt to the changing requirement of task data interface under the situation of far distance, multiple segment, multiple circle, multiple satellite and multi-station visibility for satellite misson in transfer orbit segment, the web incremental maintenance system based on materialized view was achieved through applying incremental maintenance principle, database technology, synchronization mechanism and maintenance proxy, and realizing the synchronization and consistency of data interface about the distributed experiment information surveillance software system. The result shows that web incremental maintenance system can ensure the real-time and consistency of data processing and transmission.

Initial Orbit Determination Using Single Frequency GPS Measurements of Launch Vehicle

Orbit determination by using GPS measurements of a launch vehicle is an important option for the initial orbit determination of the vehicle's payload, and its accuracy is higher than the results generated by radar measurements. However, only broadcast GPS ephemeris and clock products are used in the current GPS measurements processing method, and Klobuchar model is directly used. The paper proposes to use precise ephemeris and clock products, and adopts an improved ionospheric model based on altitude factor for GPS measurements processing. The dynamic smoothing method is further used. The numerical results show that the proposed method can improve the early orbit satellites orbit segment to determine accuracy.

Continuation-Based Numerical Detection of After-Depolarization and Spike-Adding Thresholds

The changes in neuronal firing pattern are signatures of brain function, and it is of interest to understand how such changes evolve as a function of neuronal biophysical properties. We address this important problem by the analysis and numerical investigation of a class of mechanistic mathematical models. We focus on a hippocampal pyramidal neuron model and study the occurrence of bursting related to the after-depolarization (ADP) that follows a brief current injection. This type of burst is a transient phenomenon that is not amenable to the classical bifurcation analysis done, for example, for periodic bursting oscillators. In this letter, we show how to formulate such transient behavior as a two-point boundary value problem (2PBVP), which can be solved using well-known continuation methods. The 2PBVP is formulated such that the transient response is represented by a finite orbit segment for which onsets of ADP and additional spikes in a burst can be detected as bifurcations during a one-parameter continuation. This in turn provides us with a direct method to approximate the boundaries of regions in a two-parameter plane where certain model behavior of interest occurs. More precisely, we use two-parameter continuation of the detected onset points to identify the boundaries between regions with and without ADP and bursts with different numbers of spikes. Our 2PBVP formulation is a novel approach to parameter sensitivity analysis that can be applied to a wide range of problems.

Non-integrability of cylindric billiards and transitive Lie group actions

A conjecture is formulated and discussed which provides a necessary and sufficient condition for the ergodicity of cylindric billiards (this conjecture improves a previous one of the second author). This condition requires that the action of a Lie-subgroup ${\cal G}$ of the orthogonal group $SO(d)$ ($d$ being the dimension of the billiard in question) be transitive on the unit sphere $S^{d-1}$. If $C_1, \dots, C_k$ are the cylindric scatterers of the billiard, then ${\cal G}$ is generated by the embedded Lie subgroups ${\cal G}_i$ of $SO(d)$, where ${\cal G}_i$ consists of all transformations $g\in SO(d)$ of ${\Bbb R}^d$ that leave the points of the generator subspace of $C_i$ fixed ($1 \le i \le k$). In this paper we can prove the necessity of our conjecture and we also formulate some notions related to transitivity. For hard ball systems, we can also show that the transitivity holds in general: for an arbitrary number $N\ge 2$ of balls, arbitrary masses $m_1, \dots, m_N$ and in arbitrary dimension $\nu \ge 2$. This result implies that our conjecture is stronger than the Boltzmann–Sinai ergodic hypothesis for hard ball systems. We also note a somewhat surprising characterization of the positive subspace of the second fundamental form for the evolution of a special orthogonal manifold (wavefront), namely for the parallel beam of light. Thus we obtain a new characterization of sufficiency of an orbit segment.