Large-signal stability analysis of solar array power system

A large-signal stability analysis of the solar array regulator system is performed to facilitate the design and analysis of a low-earth-orbit (LEO) satellite power system. The effective load characteristics of various control methods in the solar array regulator system, such as the constant power load, variable power load, constant voltage load, constant current load, and constant resistive load, are classified to analyze the large-signal stability. Then, using the state plane analysis technique, the large-signal behavior of the solar array system is portrayed and the stability of various equilibrium points is analyzed. Thus, this approach can be contributed to organize the optimal controller structure of the system by representing the relationship between the control method of the solar array regulator and the large-signal stability. For the verification of the proposed large-signal analysis, a solar array regulator system that consists of two 100 W parallel module buck converters has been built and tested using a real 200 W solar array.     

Reactions to receipt of a message from extraterrestrial intelligence: a cross-cultural empirical study

If we ever receive a message from extraterrestrial intelligence (ETI), the societal impact may be significant. To date, several authors have speculated on factors that may predict people’s reactions, but there have been no systematic empirical studies on the range of responses. One obstacle to conducting such studies is that there has been no questionnaire to assess such reactions. In the current study we have designed a psychometrically sound set of scales to assess six beliefs: (1) that extraterrestrial life exists, (2) that ETI would be benevolent and that we should respond to a message, (3) that ETI would be malevolent, (4) that message receipt would be unsettling, (5) that message receipt would be religiously significant and (6) that experts should determine the content of a reply. We report on the construction and use of these new scales, drawing on data gathered from American and Chinese undergraduate students. Respondents also completed measures of alienation, optimism, anthropocentrism and religiosity. This allowed us to predict beliefs about ETI based on personal characteristics and beliefs of the respondents.     

Current distribution control for parallel connected converters. II

For pt.I, see ibid., vol.28, no.3, p.829-840 (1992). In the central-limit control (CLC), the multiloop controls are employed to regulate the output voltage and track the central weighted current, thus equalizing the output current of each converter module (CM). The current distribution error (CDE) between the output current of each CM is used as a criterion in judging system performance. The prediction and simulation results of this control scheme are illustrated. When incorporated with the maximum current limit, the proposed control method can determine the number of required converters in the active state for each load condition. As a result, the efficiency of a system can be increased significantly. A comparison between the performances of the system under master-slave control (MSC) and CLC is given     

Observations of Stratosphere-Troposphere Coupling During Major Solar Eclipses from FORMOSAT-3/COSMIC Constellation

Sudden tropospheric cooling and induced stratospheric warming were found during the 22 July 2009 total solar eclipse. Can the 22 July 2009 hallmark also be seen in other major solar eclipses? Here we hypothesize that the tropospheric cooling and the stratospheric warming can be predicted to occur during a major solar eclipse event. In this work we use the FORMOSAT-3/COSMIC (F3C) Global Positioning System (GPS) radio occultation (RO) data to construct eclipse-time temperature profiles before, during, and after the passages of major solar eclipses for the years 2006–2010. We use four times a day of meteorological analysis from the European Centre for Medium Range Weather Forecast (ECMWF) global meteorological analysis to construct non-eclipse effect temperature profiles for the same eclipse passages. The eclipse effects were calculated based on the difference between F3C and ECMWF profiles. A?total of five eclipse cases and thirteen non-eclipse cases were analyzed and compared. We found that eclipses cause direct thermal cooling in the troposphere and indirect dynamic warming in the stratosphere. These results are statistically significant. Our results show ?0.6 to ?1.2°C cooling in the troposphere and 0.4 to 1.3°C warming in the middle to lower stratosphere during the eclipses. This characteristic stratosphere-troposphere coupling in temperature profiles represent a distinctive atmospheric responses to the solar eclipses.     

Optimal Design Strategy of Switching Converters Employing Current in jected Control

This paper analyzes a buck/boost regulator employing current-injected control (CIC). It reveals the complex interactions between the dc loop and the current-injected loop and underlines the fundamental principle that governs the loop gain determination. Three commonly used compensation techniques are compared. The integral and lead/lag compensation are shown to be most desirable for performance optimization and stability.     

The Improvement of a Low-Cost Inertial Navigator Through Conditional Feedback

A concept for providing an accurate low-cost inertial reference was presented in a previous paper. Low-cost platform gyros, poor in terms of their drift rates, furnish the space-fixed reference frame. A single high-accuracy gyro, mounted on the platform, monitors the performance of the platform gyros. Consequently, drift rates are estimated, predicted, and applied as signals to correct the platform for gyro uncertainties. This paper features new estimation and predictive techniques.     

Stochastic Acceleration of Energetic Particles in the Heliosphere

In this paper we assess possible roles of stochastic acceleration by random electric field and plasma motion in the production and transport of energetic particles in the heliosphere. Stochastic acceleration can occur in the presence of multiple small-scale magnetohydrodynamic waves propagating in different directions. Usually, this type of stochastic acceleration is closely related to particle pitch angle scattering or parallel diffusion. Given the values of the parallel diffusion coefficient inferred from the observations of cosmic ray modulation or other energetic particle phenomena in the heliosphere, stochastic acceleration by small-scale waves is much slower than acceleration by shock waves and it is also much slower than adiabatic cooling by the expansion of the solar wind; thus it is considered as inefficient for producing heliospheric energetic particles or for the modulation of cosmic rays. Another type of stochastic acceleration occurs when particles go through random compressions or expansions due to large-scale plasma motion. This acceleration mechanism could be very fast when the correlation time of the fluctuations in plasma compression is short compared to the diffusion time. Particle acceleration by an ensemble of small shock waves or intermittent long wavelength compressible turbulence belongs to this category. It tends to establish an asymptotic p ^?3 universal distribution function quickly if there is no or little large-scale adiabatic cooling. Such a particle distribution will contain an infinite amount of pressure. Back reaction from the pressure is expected to modify the amplitude of plasma waves to an equilibrium state. At that point, the pressure of accelerated particles must remain finite and the accelerated particles could approach a p ^?5 distribution function.     

Process of establishing design requirements and selecting alternative configurations for conceptual design of a VLA

In this study, a process for establishing design requirements and selecting alternative con-figurations for the conceptual phase of aircraft design has been proposed. The proposed process uses system-engineering-based requirement-analysis techniques such as objective tree, analytic hier-archy process, and quality function deployment to establish logical and quantitative standards. Moreover, in order to perform a logical selection of alternative aircraft configurations, it uses advanced decision-making methods such as morphological matrix and technique for order prefer-ence by similarity to the ideal solution. In addition, a preliminary sizing tool has been developed to check the feasibility of the established performance requirements and to evaluate the flight perfor-mance of the selected configurations. The present process has been applied for a two-seater very light aircraft (VLA), resulting in a set of tentative design requirements and two families of VLA configurations: a high-wing configuration and a low-wing configuration. The resulting set of design requirements consists of three categories: customer requirements, certification requirements, and performance requirements. The performance requirements include two mission requirements for the flight range and the endurance by reflecting the customer requirements. The flight performances of the two configuration families were evaluated using the sizing tool developed and the low-wing configuration with conventional tails was selected as the best baseline configuration for the VLA.