Error Analysis of Space-Stable Inertial Navigation Systems

The error equations for a space-stable inertial navigation system are derived. This is done by directly perturbing the mechanization equations in the inertial frame and then transforming in open-loop fashion to the local-level frame. A rotating inertial platform and velocity and altitude damping are considered. The relations between errors in space-stable and local-level systems are noted. Numerical results are presented for certain random error sources.     

Altitude Damping of Space-Stable Inertial Navigation Systems

In order to stabilize the altitude calculation in an inertial navigation system, an altimeter is commonly used. In a conventional local-level mechanization, this is generally accomplished by correcting the vertical channel integrators with the difference between the inertial system and altimeter indication of vertical position. However, in a space-stable system the procedure is not as clear since a vertical channel is not physically present. Three altitude damping mechanizations for a space-stable inertial navigation system are proposed. The equivalent local-level mechanizations are then found by comparing error propagation equations in a common coordinate frame.     

Validation of the stratospheric sounding unit

The Stratospheric Sounding Unit (SSU) is part of the TOVS (TIROS Operational Vertical Sounder) on NOAA operational meteorological satellites. SSU measurements can be validated by comparison with temperature measurements from colocated rocket sondes. Systematic differences are found which vary with rocket station and sonde and are a function of height. However, these measurements are not adequate to define the performance of individual SSUs to a precision which would allow the observations from different SSUs to be combined in the study of diurnal and semidiurnal tides and of long term trends in stratospheric temperature. Instead this is achieved by detailed radiometric and spectroscopic investigation of each individual SSU, both prior to launch and during its operational life. Using the techniques descirbed, it is demonstrated that measurements from different SSUs can be combined with a relative error of less than 0.2K in equivalent brightness temperature.     

Effect of Vertical Deflections and Ocean Currents on a Maneuvering Ship

Vertical deflections and ocean currents introduce errors into ship's inertial navigation systems (SINS). In the absence of exact knowledge, these quantities may be treated as distance-dependent stationary random processes. However, these distance-dependent random processes enter SINS as time-dependent error sources. The autocorrelation functions of these time functions depend on the manner in which the ship maneuvers. An equation relating the time-dependent autocorrelation function to the distance-dependent autocorrelation function is derived. The time-dependent autocorrelation function is obtained for four different situations. The first two examples are ships steaming at constant heading and constant, but not necessarily known, velocity. The third example involves a ship tracking back and forth over the same path. The last example describes a ship that steams at a constant speed but changes heading in a random manner.     

对“三育人”的几点思考

“三育人”是具有中国特色的一种教育模式，它对整个教育过程都会产生深远的影响。然而现实中却时常出现一些误区，其中主要是思想认识问题。这些问题或是简单的理解，或是片面的追求，或是死抱着过时的东西不放。其结果必然损害育人质量。我们必须以邓小平教育思想为指导，以服务国家和社会为前提，纠正不正确观念，使育人质量和育人水平不断提高。     

Comparison of Error Propagation in Local-Level and Space-Stable Inertial Systems

A comparison of the error propagation in a local-level reference frame is derived for two inertial navigation systems; one has a local-level configuration, and the other has a space-stable configuration. The error propagation is shown to be equivalent for the two cases considered. This equivalence is demonstrated by starting with the error propagation equations for the space-stable system and transforming them to a local-level reference frame. The transformed equations are then compared with the classical local-level error equations, and the equivalence is noted. The specific implementation used in each case considers velocity damping but not altitude damping.     

Doppler Radar Error Equations for Damped Inertial Navigation System Analysis

The use of Doppler radar measurements to provide velocity damping for an aircraft inertial navigation system is considered. Three different Doppler antenna configurations are examined: two-axis stabilized, azimuth stabilized, and data stabilized antennas. A general reference velocity error equation is presented and appropriately evaluated for each of the Doppler configurations. Specific elements of the error equations are examined and physically interpreted for both local-level and space-stable inertial systems. Detailed examination of the interaction of Doppler radar and inertial navigation velocity error mechanisms is provided.     

Molecular diversity of cyanobacteria inhabiting coniform structures and surrounding mat in a Yellowstone hot spring

Lithified coniform structures are common within cyanobacterial mats in Yellowstone National Park hot springs. It is unknown whether these structures and the mats from which they develop are inhabited by the same cyanobacterial populations. Denaturing gradient gel electrophoresis and sequencing and phylogenetic analysis of 16S rDNA was used to determine whether (1) three different morphological types of lithified coniform structures are inhabited by different cyanobacterial species, (2) these species are partitioned along a vertical gradient of these structures, and (3) lithified and non-lithified sections of mat are inhabited by different cyanobacterial species. Our results, based on multiple samplings, indicate that the cyanobacterial community compositions in the three lithified morphological types were identical and lacked any vertical differentiation. However, lithified and non-lithified portions of the same mat were inhabited by distinct and different populations of cyanobacteria. Cyanobacteria inhabiting lithified structures included at least one undefined Oscillatorialean taxon, which may represent the dominant cyanobacteria genus in lithified coniform stromatolites, Phormidium, three Synechococcus-like species, and two unknown cyanobacterial taxa. In contrast, the surrounding mats contained four closely related Synechococcus-like species. Our results indicate that the distribution of lithified coniform stromatolites may be dependent on the presence of one or more microorganisms, which are phylogenetically different from those inhabiting surrounding non-lithified mats.     

关于普通高校体育教学的思考

通过对高校体育教学中的教学模式、内容设制、考核形式几方面的分析、探讨，提出了高校体育教学应以未来社会人才的需要为出发点，使体育教学从根本上摆脱传统教学观念的束缚，从单纯培养“知识型”、“技能型”人才向培养“创造性”、“综合性”、“应用性”人才转变。     

浅析提高投篮命中率的技术因素

本文分析了影响投篮命中率的各种技术因素,并提出了相应的提高命中率的方法,为篮球教学工作提供有益的参考。