多航天器并行测试综合显示平台的设计与实现

为解决载人航天器并行测试遥测数据集中判读和关联分析问题,提出一种支持多航天器并行测试的综合显示平台设计方法。对多航天器并行测试方案进行研究,对综合显示平台总体架构进行设计。平台采用插件式程序架构便于功能扩展,采用脚本引擎技术提高平台可配置性,采用MVC设计模式增加页面编辑的可维护性,采用多线程技术和定时器策略实现海量数据的实时显示。平台具备图形页面、列表页面、曲线页面显示功能,可以实现常规数值显示、报警监视及源码、序列显示,同时,支持测试数据本地保存与回放判读。综合显示平台已应用于载人航天器全阶段地面测试和某型号航天器在轨交会对接任务中,应用效果良好。     

Analysis of the Possibility of Creating a Stable Satellite of the Asteroid Apophis as a Homogeneous Triaxial Ellipsoid

Doklady Physics - The problem of creating a stable satellite orbit about the asteroid Apophis as a homogeneous triaxial ellipsoid is investigated. The motion of the spacecraft around the asteroid...     

Low-thrust trajectory optimization of asteroid sample return mission with multiple revolutions and moon gravity assists

Near-Earth asteroids have gained a lot of interest and the development in low-thrust propulsion technology makes complex deep space exploration missions possible. A mission from low-Earth orbit using low-thrust electric propulsion system to rendezvous with near-Earth asteroid and bring sample back is investigated. By dividing the mission into five segments, the complex mission is solved separately. Then different methods are used to find optimal trajectories for every segment. Multiple revolutions around the Earth and multiple Moon gravity assists are used to decrease the fuel consumption to escape from the Earth. To avoid possible numerical difficulty of indirect methods, a direct method to parameterize the switching moment and direction of thrust vector is proposed. To maximize the mass of sample, optimal control theory and homotopic approach are applied to find the optimal trajectory. Direct methods of finding proper time to brake the spacecraft using Moon gravity assist are also proposed. Practical techniques including both direct and indirect methods are investigated to optimize trajectories for different segments and they can be easily extended to other missions and more precise dynamic model.     

Duality Theorems in Ergodic Transport

We analyze several problems of Optimal Transport Theory in the setting of Ergodic Theory. In a certain class of problems we consider questions in Ergodic Transport which are generalizations of the ones in Ergodic Optimization. Another class of problems is the following: suppose ?? is the shift acting on Bernoulli space X={1,2,??,d}^?, and, consider a fixed continuous cost function c:X×X???. Denote by ?? the set of all Borel probabilities ?? on X×X, such that, both its x and y marginals are ??-invariant probabilities. We are interested in the optimal plan ?? which minimizes ??c? d?? among the probabilities in ??. We show, among other things, the analogous Kantorovich Duality Theorem. We also analyze uniqueness of the optimal plan under generic assumptions on c. We investigate the existence of a dual pair of Lipschitz functions which realizes the present dual Kantorovich problem under the assumption that the cost is Lipschitz continuous. For continuous costs c the corresponding results in the Classical Transport Theory and in Ergodic Transport Theory can be, eventually, different. We also consider the problem of approximating the optimal plan ?? by convex combinations of plans such that the support projects in periodic orbits.     

脉冲激光烧蚀推进技术的航天应用进展

脉冲激光烧蚀推进技术具有比冲高和推力可精确控制的特点,既可用于发射有效载荷也可用于星载动力,甚至可用小行星表面物质作为推进剂使其偏转轨道,因此,在航天领域得到越来越多关注。围绕激光单级入轨发射、同步轨道和火星轨道运输;激光微推力器用于航天器姿轨控,以及激光与电组合推进;激光烧蚀操控cm级空间碎片的轨道,以及激光烧蚀操控较大尺寸碎片的姿态;激光烧蚀偏转小行星轨道等方面,对脉冲激光烧蚀推进技术在航天领域研究现状和进展,进行了系统全面地归纳和总结,并对激光平均功率、波长、脉宽和推进剂选材等关键问题,进行了详细分析。     

Optimization approaches of aircraft flight path reducing noise: Comparison of modeling methods

An optimization model of flight paths is designed for minimizing aircraft noise at reception points around airports. It is stated as a nonconvex and nonlinear control problem governed by ordinary differential equations using a jet noise model. The vertical plan and the space cases have been solved using two approaches, one direct and one indirect. The objective was initially to apply these two methods, then to carry out comparisons, and finally to retain the method which would be applied for the general case including engine and airframe sources. Results showed that the direct method is adapted for solving the problem and can be implemented with moderate computing times. It is sufficient to analyze the constrained flight path optimization of commercial aircraft reducing noise levels. The three-segment approach procedure has been obtained as an optimized flight path which can substantially reduce noise levels. This modified approach procedure has been examined and could benefit both airlines and communities.     

Charting the invisible in phase space (Abstract only)

One challenge in particle physics is that not all the momenta relevant to many processes are observable. Some particles are nearly invisible (neutrinos and hypothetical neutralinos), others escape undetected down the beam pipes of colliders. One faces the task of extracting the maximum information (e.g. on the mass of the unobserved particles) from a set of more unknowns than constraining energy?Cmomentum conservation equations. We study the simplest realistic case of current interest: single-W production at a hadron collider, followed by its leptonic decay. We derive and discuss the statistically-optimal ??singularity variable?? relevant to the measurement of the W mass. In spite of its simplicity, this process is fairly non-trivial and constitutes a good ??training?? example for the scrutiny of phenomena involving invisible objects. Our graphical analysis of the phase space is akin to that of a Dalitz plot, extended to such processes.     

Exponential smoothing weighted correlations

In many practical applications, correlation matrices might be affected by the ??curse of dimensionality?? and by an excessive sensitiveness to outliers and remote observations. These shortcomings can cause problems of statistical robustness especially accentuated when a system of dynamic correlations over a running window is concerned. These drawbacks can be partially mitigated by assigning a structure of weights to observational events. In this paper, we discuss Pearson??s ?? and Kendall??s ?? correlation matrices, weighted with an exponential smoothing, computed on moving windows using a data-set of daily returns for 300 NYSE highly capitalized companies in the period between 2001 and 2003. Criteria for jointly determining optimal weights together with the optimal length of the running window are proposed. We find that the exponential smoothing can provide more robust and reliable dynamic measures and we discuss that a careful choice of the parameters can reduce the autocorrelation of dynamic correlations whilst keeping significance and robustness of the measure. Weighted correlations are found to be smoother and recovering faster from market turbulence than their unweighted counterparts, helping also to discriminate more effectively genuine from spurious correlations.     

Ideal gas/liquid transition as a generalization of the problem of “partitio numerorum”

It is shown that the Boltzmann-Maxwell distribution is not applicable to the generalized notion of ideal gas and corresponds to this ideal gas at low density only. The behavior of an ideal gas and its transition to liquid is studied as a result of a kind of generalization of the problem of ??partitio numerorum??. The reflection of particles of the ideal gas from the walls of the vessel walls is taken into account (as a kind of ??trap?? for the Bose gas). Two constants are additionally introduced, namely, the constant ?? inversely proportional to the mass and the heat g of the phase transition as T ?? 0 (the constant of the Clausius-Clapeyron relation), and also the experimental value of the critical compressibility factor for the given gas and the experimental value of the pressure at the triple point, from which one can find the value of the constant ??.     

Linear and nonlinear liftings of states of quantum systems

In this paper, we study the representability of an arbitrary quantum state ?? ?? ??(H) as the reduction of a vector state r ?? ??(H) of the extended system. We extend the operation of lifting from the set of states ?? _n (H) to the set of generalized states ??(H). A method of constructing the Hilbert space H and the affine linear lifting ??(H) ?? ??(H) is studied. The construction of individual expansion H _?? of the space H for which the state ?? is a reduction of a vector state H _?? is of special interest.     

Potential in the “Clearance” of torus: Development on spherical functions

The method of solution of the Dirichlet problem for potentials of volume bodies with torus topology when the boundary conditions are set in the form of a series on spherical harmonics on pieces of two spherical surfaces is developed. The problem representation of an exterior potential homogeneous gravitating (or charged by static electric charge) circular torus out of a substance in a special (??intermediate??) spherical zone is presented and solved. The solution is received in the form of a combination of the Laplace series on even positive and odd negative degrees of the radius-vector of a test point. Coefficients of this series are received in a final analytical form. The general member of the series at the limit of big n tends to zero so the series converges fast and the radius of convergence are defined by torus geometry. The specified solution meets a gap in the theory, connecting together earlier discovered by us, two expansions in the Laplace series of a torus potential in ??interior?? and ??exterior?? spherical space zones. Thus, it is proved that it is possible to present the torus potential by power rows in all free space from the substance. For control of results by means of the obtained series, equipotential surfaces of the torus were calculated.     

Improvement of the orbit of the <Emphasis Type="Italic">Spektr-R</Emphasis> spacecraft in the <Emphasis Type="Italic">RadioAstron</Emphasis> mission and required conditions for improvement using a Kalman filter

This paper is concerned with improvement of the state vector of the Spektr-R spacecraft of the RadioAstron mission. The state vector includes three coordinates of the position of the spacecraft and three components of its velocity in the Geocentric Celestial Reference System. Improvement of the orbit of the spacecraft is understood as improvement of the state vector. The results are compared with the original orbits determined at the Keldysh Institute of Applied Mathematics (IAM). The paper considers both using the Kalman filter based on a single set of radio-range and Doppler data from ground-based stations and the analysis of conditions that will lead to improvement of the orbit. It has been shown that using three ground-based stations that perform simultaneous measurements the problem is solved completely, even when a poor initial approximation is used. Based on the results, a list of requirements is obtained that will provide more accurate information on the orbit of the Spektr-R spacecraft.     

The Dirac particle in a one-dimensional “hydrogen atom”

Specific features of the behavior of the spectrum of steady states of the Dirac particle in a regularized ??Coulomb?? potential V??(z) = ?q/(|z| + ??) as a function of the cutting parameter of ?? in 1 + 1 D are investigated. It is shown that in such a one-dimensional relativistic ??hydrogen atom?? at ?? ? 1, the discrete spectrum becomes a quasi-periodic function of ??; this effect depends on the bonding constant analytically and has no nonrelativistic analog. This property of the Dirac spectral problem clearly demonstrates the presence of a physically containable energy spectrum at arbitrary small ?? > 0 and simultaneously the absence of the regular limiting transition to ?? ?? 0. Thus, the necessity of extension of a definition for the Dirac Hamiltonian with irregularized potential in 1 + 1 D is confirmed at all nonzero values of the bonding constant q. It is also noted that the three-dimensional Coulomb problem possesses a similar property at q = Z?? > 1, i.e., when the selfconsistent extension is required for the Dirac Hamiltonian with an irregularized potential.     

PASP Plus solar array parasitic current collection flight results

Exposed positive potential surfaces of spacecraft solar cells (interconnects and cell sides) collect electrons from the surrounding plasma. In low-Earth-orbit, this current is a drain on the array power that can be significant for high-power arrays, and this current influences the floating potential of the spacecraft. One objective of the Air Force PASP Plus (Photovoltaic Array Space Power Plus Diagnostics) experiment is an improved understanding of parasitic current collection. We examined the flight data for the arrays facing the ram direction. Overall, the effective current collection area rises about two orders of magnitude as the applied bias rises one order of magnitude, as is typical when snapover plays a role. The collecting area has a weak dependence on plasma density, with larger collecting areas corresponding to lower densities (longer debye length). This dependence on plasma density is stronger for lower densities and weaker for higher densities. There is a large amount of scatter in the measurements, with the current collected under similar conditions varying by up to a factor ten. Further laboratory and flight experiments are needed to determine the cause of the scatter. Even with this ambiguity, PASP Plus results can be used to quantify this effect by spacecraft designers and have already been used to validate an analytic model of this process     

A class of discontinuous Petrov–Galerkin methods. Part IV: The optimal test norm and time-harmonic wave propagation in 1D

The phase error, or the pollution effect in the finite element solution of wave propagation problems, is a well known phenomenon that must be confronted when solving problems in the high-frequency range. This paper presents a new method with no phase errors for one-dimensional (1D) time-harmonic wave propagation problems using new ideas that hold promise for the multidimensional case. The method is constructed within the framework of the discontinuous Petrov–Galerkin (DPG) method with optimal test functions. We have previously shown that such methods select solutions that are the best possible approximations in an energy norm dual to any selected test space norm. In this paper, we advance by asking what is the optimal test space norm that achieves error reduction in a given energy norm. This is answered in the specific case of the Helmholtz equation with L²-norm as the energy norm. We obtain uniform stability with respect to the wave number. We illustrate the method with a number of 1D numerical experiments, using discontinuous piecewise polynomial hp spaces for the trial space and its corresponding optimal test functions computed approximately and locally. A 1D theoretical stability analysis is also developed.     

Global wolf numbers

A new (global) series of Wolf numbers (W _G ), which takes all the sunspots on the Sun??s surface, including the spots that are invisible from the Earth, into account, is proposed for consideration with the aim of obtaining a more complete characteristic of solar activity. The optimum configuration of spacecraft for this purpose is examined.     

Towards a quantum field theory of primitive string fields

We denote generating functions of massless even higher-spin fields ??primitive string fields?? (PSF??s). In an introduction we present the necessary definitions and derive propagators and currents of these PDF??s on flat space. Their off-shell cubic interaction can be derived after all off-shell cubic interactions of triplets of higher-spin fields have become known. Then we discuss four-point functions of any quartet of PSF??s. In subsequent sections we exploit the fact that higher-spin field theories in AdS _d+1 are determined by AdS/CFT correspondence from universality classes of critical systems in d-dimensional flat spaces. The O(N) invariant sectors of the O(N) vector models for 1 ?? N ??? play for us the role of ??standard models??, for varying N, they contain, e.g., the Ising model for N = 1 and the spherical model for N = ??. A formula for the masses squared that break gauge symmetry for these O(N) classes is presented for d = 3. For the PSF on AdS space it is shown that it can be derived by lifting the PSF on flat space by a simple kernel which contains the sum over all spins. Finally we use an algorithm to derive all symmetric tensor higher-spin fields. They arise from monomials of scalar fields by derivation and selection of conformal (quasiprimary) fields. Typically one monomial produces a multiplet of spin s conformal higher-spin fields for all s ?? 4, they are distinguished by their anomalous dimensions (in CFT ₃) or by theirmass (in AdS ₄). We sum over these multiplets and the spins to obtain ??string type fields??, one for each such monomial.     

On a microscopic representation of space-time

We start from a noncompact Lie algebra isomorphic to the Dirac algebra and relate this Lie algebra in a brief review to low-energy hadron physics described by the compact group SU(4). This step permits an overall physical identification of the operator actions. Then we discuss the geometrical origin of this noncompact Lie algebra and ??reduce?? the geometry in order to introduce in each of these steps coordinate definitions which can be related to an algebraic representation in terms of the spontaneous symmetry breakdown along the Lie algebra chain su*(4) ?? usp(4) ?? su(2) × u(1). Standard techniques of Lie algebra decomposition(s) as well as the (physical) operator identification give rise to interesting physical aspects and lead to a rank-1 Riemannian space which provides an analytic representation and leads to a 5-dimensional hyperbolic space H ₅ with SO(5, 1) isometries. The action of the (compact) symplectic group decomposes this (globally) hyperbolic space into H ₂ ?? H ₃ with SO(2, 1) and SO(3, 1) isometries, respectively, which we relate to electromagnetic (dynamically broken SU(2) isospin) and Lorentz transformations. Last not least, we attribute this symmetry pattern to the algebraic representation of a projective geometry over the division algebra H and subsequent coordinate restrictions.     

The Modified Bell Inequality and Its Physical Implications in the ESR Model

The extended semantic realism (ESR) model proposes a theoretical perspective which reinterprets quantum probabilities as conditional on detection rather than absolute and embodies the mathematical formalism of standard (Hilbert space) quantum mechanics (QM) in a noncontextual, hence local, framework. The assumptions needed to prove the Bell inequality therefore hold in the ESR model, but we show that the Bell inequality must be substituted in it by the modified Bell inequality and that the standard quantum expectation values, when reinterpreted as proposed by the ESR model, do not violate the latter inequality. Hence the long-standing conflict between ??local realism?? and QM is settled in the ESR model. Finally we provide an elementary example of a prediction that might be used to check whether the ESR model is correct.