Use of MOBITEX wireless wide area networks as a solution toland-based positioning and navigation

The emergence of land-based positioning and navigation systems is the direct result of advancements in technologies relating to geographic information, wireless data communication, and navigation. The increasing demand for these systems has stimulated their rapid development. This paper identifies the wide variety of land-based positioning and navigation systems and classifies them into five groups. The basic system elements that are required in all land-based positioning and navigation systems are also discussed. A proposed system infrastructure that supports the five types of land-based positioning and navigation systems is described. The specific technologies integrated in this proposed infrastructure include the Global Positioning System (GPS), differential GPS, and the MOBITEX wireless wide area packet data networks. Real-time wireless mobile data communication is a key component of any land-based positioning and navigation system. Finally, the evaluation criteria necessary for field testing a pilot land-based positioning and navigation system are presented. This pilot system is used to determine the feasibility and effectiveness of the proposed system design     

Experimental evaluation of the processes resulting from the introduction of the transgenic microorganism Escherichia coli Z905/pPHL7 (lux+) into aquatic microcosms.

The processes resulting from the introduction of the tranagenic microorganism (TM) E. coli Z905/pPHL7 into aquatic microcosms have been modeled experimentally. It has been shown that the TM E. coli is able to adapt to a long co-existence with indigenous heterotrophic microflora in variously structured microcosms. In more complex microcosms the numerical dynamics of the introduced E. coli Z905/pPHL7 population is more stable. In the TM populations staying in the microcosms for a prolonged time, changes are recorded in the phenotypic expression of plasmid genes (ampicillin resistance and the luminescence level) and chromosome genes (morphological and physiological traits). However, in our study microcosms, the recombinant plasmid persisted in the TM cells for 6 years after the introduction, and as the population adapts to the conditions of the microcosms, the efficiency of the cloned gene expression in the cells is restored. In the microcosms with high microalgal counts (10(7) cells/ml), cells with a high threshold of sensitivity to ampicillin dominate in the population of the TM E. coli Z905/pPHL7.     

Use of service history for certification credit for COTS [avionic software]

Much has been written in the last ten years about how the use of commercial-off-the-shelf (COTS) components would revolutionize the aerospace industry avionics, communication, navigation, surveillance/air traffic management (CNS/ATM) as well as global air traffic management (GATM). Civil aviation authorities around the world have been faced with numerous requests to certify aircraft containing increasing percentages of COTS components, much of it never designed or intended for use in the safety critical environment of an aircraft. Product service history is one method for demonstrating that such software is acceptable for use. In theory, product service history would seem to be a fairly simple concept, both to understand and to apply. However, in practice, such use has proven extremely problematic, as questions of how to measure the historic performance and the relevance of the provided data have surfaced. This paper elaborates a research effort funded by the United States Federal Aviation Administration to collect, analyze, and synthesize what is known and understood about applying product service history. The effort is limited to the topic of software product service history as applied in the certification of airborne systems and equipment.     

International HARM precision navigation upgrade - a GPS/INS missile upgrade that improves effectiveness and minimizes friendly-fire accidents

The high speed anti-radiation missile (HARM) is an air-to-surface tactical missile designed to seek and destroy enemy radar-equipped air defense systems. Unfortunately, the HARM is "no respecter of persons," and it has been known, most notably during the Gulf War, to attack "friendly" targets. The international HARM upgrade project is a tri-national missile technology project sponsored by the United States, Italian, and German governments. The HARM precision navigation upgrade (PNU) program has as its goal, the development and installation of a PNU into the HARM that will improve the weapon's effectiveness, while nearly eliminating the likelihood of fratricide. The precision navigation system consists of a modern selective availability anti-spoofing module (SAASM) based Global Positioning System (GPS) receiver, and an inertial measurement unit (IMU), consisting of state-of-the-art fiber optic gyros and a modern micro-machined accelerometer triad.     

Analysis of a PWM-resonant converter

When a parallel resonant tank is excited by a bipolar current pulse train a sinusoidal voltage develops across the tank whose amplitude depends on the duty cycle of the pulse train. An isolated secondary can be derived by applying the tank voltage to an isolation transformer whose magnetizing inductance acts as the resonant inductor of the tank circuit. A dc output voltage is obtained after rectification and filtering of the sinusoidal secondary voltage and regulation is achieved by controlling the duty cycle of the pulse train. The sinusoidal nature of the voltage across the isolation transformer alleviates some of the noise problem associated with parasitic capacitances of an isolation transformer when operated with square voltage waveform. In this work the dc and small-signal analysis of the converter is given and an equivalent small-signal circuit model is derived. Experimental results which confirm the validity of the model are presented.     

Growth and development in higher plants under simulated microgravity conditions on a 3-dimensional clinostat.

Growth and development of etiolated pea (Pisum sativum L. cv. Alaska) and maize (Zea mays L. cv. Golden Cross Bantam) seedlings grown under simulated microgravity conditions were intensively studied using a 3-dimensional clinostat as a simulator of weightlessness. Epicotyls of etiolated pea seedlings grown on the clinostat were the most oriented toward the direction far from cotyledons. Mesocotyls of etiolated maize seedlings grew at random and coleoptiles curved slightly during clinostat rotation. Clinostat rotation promoted the emergence of the 3rd internodes in etiolated pea seedlings, while it significantly inhibited the growth of the 1st internodes. In maize seedlings, the growth of coleoptiles was little affected by clinostat rotation, but that of mesocotyls was suppressed, and therefore, the emergence of the leaf out of coleoptile was promoted. Clinostat rotation reduced the osmotic concentration in the 1st internodes of pea seedlings, although it has little effect on the 2nd and the 3rd internodes. Clinostat rotation also reduced the osmotic concentrations in both coleoptiles and mesocotyls of maize seedlings. Cell-wall extensibilities of the 1st and the 3rd internodes of pea seedlings grown on the clinostat were significantly lower and higher as compared with those on 1 g conditions, respectively. Cell-wall extensibility of mesocotyls in seedlings grown on the clinostat also decreased. Changes in cell wall properties seem to be well correlated to the growth of each organ in pea and maize seedlings. These results suggest that the growth and development of plants is controlled under gravity on earth, and that the growth responses of higher plants to microgravity conditions are regulated by both cell-wall mechanical properties and osmotic properties of stem cells.     

High resolution 3D “snapshot” ISAR imaging and featureextraction

We have developed a new formulation for three dimensional (3D) radar imaging of inverse synthetic aperture radar (ISAR) data based on recent developments in high resolution spectral estimation theory. Typically for non real-time applications, image formation is a two step process consisting of motion determination and image generation. The technique presented focuses on this latter process, and assumes the motion of the target is known. The new technique offers several advantages over conventional techniques which are based on the correlation imaging function. In particular, the technique provides for a direct 3D estimate (versus back projection to a 3D target grid matrix) of the locations of the dominant scattering centers using only a minimum set of independent 2D range-Doppler ISAR “snapshots” of the target. Because of the snapshot nature of the technique, it is particularly applicable to 3D imaging of sectors of sparse-angle data, for which the sidelobes of the correlation imaging integral become high. Furthermore, the technique provides for an estimate of amplitude and phase of each scattering center as a function of aspect angle to the target, for those aspect angles which encompass the set of 2D range-Doppler snapshots. Results illustrating the technique developed are presented for both simulated and static range data     

Compact equipment for on-board communications subsystem supervisoryand control system

Onboard equipment for the communications subsystem supervisory and control (CSC) system of a next-generation multibeam high-capacity communications satellite is discussed. In order to keep the equipment as compact, lightweight, and low in power consumption as possible, an onboard data bus system using four kinds of LSIs was developed. It will be carried on-board the Japanese Engineering Test Satellite VI for launch in 1993. Configuration and functions of the CSC equipment, design philosophy of the LSIs, and characteristics of the LSIs developed are discussed     

Fallacies in computational testing of matrix positivedefiniteness/semidefiniteness

The status of computational tests for establishing matrix positive semidefiniteness and positive definiteness is reviewed. Two pervasive real-time tests that have been used for many years in varied applications to ensure that computed covariances encountered in Kalman filter applications are positive definite and discussed. Structural representations of covariance matrices are reviewed as a prelude to constructing a counterexample and demonstrating that it refutes these real-time tests. It is maintained that the latter are bogus approaches despite the fact that they are pervasive. It is suggested that such bogus tests arose as an attempt to fill the need for a quick check (over the entire mission time) of the massive number of matrices computationally encountered in real-time applications     

Organic solids produced from simple C/H/O/N ices by charged particles: applications to the outer solar system.

CH4, CO, and CO2 are all potential one-carbon molecular repositories in primitive icy objects. These molecules are all found in the Comet Halley coma, and are probable but, (except for CH4 detected on Triton and Pluto) undetected subsurface constituents in icy outer solar system objects. We have investigated the effects of charged particle irradiation by cold plasma discharge upon surfaces of H2O:CH4 clathrate having a 200:1 ratio, as well as upon ices composed of H2O plus C2H6 or C2H2 (sometimes plus NH3) which are also plausible constituents. These materials color and darken noticeably after a dose 10(9) - 10(10) erg cm-2, which is deposited rapidly (< or = 10(4) yr.) in solar system environments. The chromophore is a yellowish to tan organic material (a tholin) which we have studied by UV-VIS reflection and transmission, and IR transmission spectroscopy. Its yield, -1 C keV-1, implies substantial production of organic solids by the action of cosmic rays and radionuclides in cometary crusts and interiors, as well as rapid production in satellite surfaces. This material shows alkane bands which Chyba and Sagan have shown to well match the Halley infrared emission spectrum near 3.4 microns, and also bands due to aldehyde, alcohol and perhaps alkene/aromatic functional groups. We compare the IR spectral properties of these tholins with the spectra of others produced by irradiation of gases and ices containing simple hydrocarbons.