Relative positioning of multiple moving platforms using GPS

To obtain subdecimeter level accuracy in relative kinematic positioning, the use of double differenced GPS carrier phase measurement with carrier phase ambiguities fixed to their correct integer values must be adopted. If multiple platforms are available in the configuration, the redundancy provided by the multiplicity of platforms can speed up the time to integer ambiguity fixing while at the same time improve the reliability of the solution. An approach to effectively construct ambiguity constraints through the multiplicity of platforms is presented herein. The use of these ambiguity constraints to position multiple moving platforms with respect to each other is then discussed. A series of simulations and field tests are designed and conducted to investigate the effects of different system parameters on this approach, with a configuration of up to 10 moving platforms. The test results show that the use of ambiguity constraints can improve the time to integer ambiguity fixing by up to 67%, relative to the case when no constraints are used. In addition, the use of ambiguity constraints is found to enhance the ability of the multiple platform system to detect wrong ambiguity fixes.     

Automated video protection, monitoring & detection

The latest generation of computer vision technology is revolutionizing concepts, applications, and products in video surveillance and CCTV. This is of prime relevance to security for large outdoor facilities such as commercial airfields, refineries, power plants, and office/industrial campuses. Most airfields, for example, have open (unfenced) perimeters, high volume heterogeneous traffic, are easily accessed on foot or by water, and exist in areas where regulations providing a safety buffer are difficult to legislate or enforce. And all airfields require 24/7 outdoor monitoring - snow, fog, rain, or shine. Likewise, most high-value facilities appealing to criminals and terrorists are in close proximity to public areas (roads, residences, city, etc.). The appeal of automated real-time surveillance is obvious $maximizing efficiency and effectiveness of security personnel and resources while increasing the probability of preventing a serious security breach. Computer vision based solutions have the potential for very discriminating detection and very low false alarms. The bottom line is that applied computer vision has the potential for the greatest return on investment (ROI), both short-term and long-term.     

Limits in tracking with extended Kalman filters

The classical linearized conversion of measurements from polar or spherical coordinates to Cartesian ones generates a bias restricting the use of this conversion to cases where the bias can be neglected. In this work, the validity limits for the classical 2D transformation from polar to Cartesian coordinates, as derived in previous work, are shown to be too restrictive and the limits for the 3D transformation from spherical to Cartesian coordinates are introduced. Furthermore, quantitative measures for the performance degradation of the commonly used extended Kalman filter (EKF) in comparison with the best linear unbiased estimation (BLUE) filter are obtained by simulating typical tracking scenarios.     

Structure of the Venusian atmosphere from surface up to 100 km

The goal of this paper is to summarize the experimental data on the atmosphere of Venus obtained after 1985, when the VIRA (Venus International Reference Atmosphere) or COSPAR model was published. Among the most important results that have appeared since then are the following: measurements of the vertical temperature profile by the VEGA spacecraft with high precision and high altitude resolution; measurements made with balloons of the VEGA spacecraft; radio occultation measurements of Magellan, Venera-15, and Venera-16; and temperature profiles derived from the data of infrared spectrometry obtained by Venera-15. The new result as compared to VIRA is the creation of a model of the atmosphere in the altitude range 55 to 100 km dependent on local time. This model is presented in our paper in tabulated form.     

Measuring the matter distribution within z = 0.2 cluster lenses with XMM-Newton

We present an analysis of seven clusters observed by XMM-Newton as part of our survey of 17 most X-ray luminous clusters of galaxies at z  0.2 selected for a comprehensive and unbiased study of the mass distribution in massive clusters. Using the public software FTOOLS and XMMSAS we have set up an automated pipeline to reduce the EPIC MOS and pn spectro-imaging data, optimized for extended sources analysis. We also developped a code to perform intensive spectral and imaging analysis particularly focussing on proper background estimate and removal. XMM-Newton deep spectro-imaging of these clusters allowed us to fit a standard β-model to their gas emission profiles as well as a standard MEKAL emission model to their extracted spectra, and test their inferred characteristics against already calibrated relations.     

Tapped-inductor filter assisted soft-switching PWM DC-DC power converter

A novel high-frequency transformer linked full-bridge type soft-switching phase-shift pulsewidth modulated (PWM) controlled dc-dc power converter is presented, which can be used as a power conditioner for small-scale photovoltaic and fuel cell power generation systems as well as isolated boost dc-dc power converter for automotive ac power supply. In these applications with low-voltage large-current sources, the full-bridge circuit is the most attractive topology due to the possibility of using low-voltage high-performance metal-oxide-semiconductor field-effect transistor (MOSFET) and achieving high efficiency of the dc-dc power converter. A tapped-inductor filter including the freewheeling diode is newly implemented in the output stage of the full-bridge phase-shift PWM dc-dc converter to achieve soft-switching operation for the wide load variation range. Moreover, in the proposed converter circuit, the circulating current is effectively minimized without using additional resonant circuit and auxiliary power switching devices. The practical effectiveness of the proposed soft-switching dc-dc power converter was verified in laboratory level experiment with 1 kW 100 kHz breadboard setup using power MOSFETs. Actual efficiency of 94-97% was obtained for the wide duty cycle and load variation ranges.     

Forecasting the 23 and 24 solar cycles on the basis of MGM spectrum

A new method of nonlinear spectral analysis (called the method of global minimum: MGM), based on the best presentation (in sense of minimal squares) of a given time data set as a sum of sinusoids whose frequencies, amplitudes and phases are to be determined, has been used to find periodicities in annual Wolf sunspot numbers (W) during the period 1700–1995. The possible future behaviour of the 11-year solar cycle (based on an extrapolation of the calculated model) is also presented. The main characteristics of the 23^rd solar cycle are as follows: the W maximum occurs about 2004, with a peak of nearly 220. An unusually large value of W will occur during the 23^rd cycle, which should be characterised by the longest maximum, specifically, W will be greater than 100 during the 11-year period from 1997 to 2007. The first sharp rise will occur during the period 1996–1998, the second sharp during 2002–2004. The main features of the 24 year cycle are as follows: the next minimum in W, associated with the 24^th solar cycle, should occur in the year 2008 and the maximum in 2014. W is expected to peak at about 180. The minimum value for the 25^th year cycle is expected to occur in the year 2019. It is shown that the accuracy of these predictions depends, first of all, on the extrapolation of the hyperlong harmonic of the calculated polyharmonic model fit of observed annual sunspot numbers during the period 1700–1995. The error bars in the definition of the maximum and minimum epochs can be as large as two years.     

Reconfigurable NDI controller using inertial sensor failuredetection & isolation

A modified derivation of nonlinear dynamic inversion provides the theoretical underpinnings for a reconfigurable control law for aircraft that have suffered combinations of actuator failures, missing effector surfaces, and aerodynamic changes. The approach makes use of acceleration feedback to extract information pertaining to any aerodynamic change and thus does not require a complete aerodynamic model of the aircraft. The control law does require feedback of effector positions to accommodate actuator dynamics. Both accelerometer and rate gyro failure detection and isolation (FDI) systems are implemented, allowing up to three independent failures for each FDI system as long as they are in different axes. Nonlinear simulation results show that the FDI systems improve the robustness to accelerometer/rate gyro uncertainties. An advanced tailless aircraft model is used to demonstrate the concepts. The simulation includes accelerometer and rate gyro noise and bias, failures due to accelerometers, rate gyros, and actuators, and modeled missing surfaces that cause airplane aerodynamic changes