Chaos theory and radio emission

The application of chaos theory has become popular to understand the nature of various features of solar activity because most of them are far from regular. The usual approach, however, that is based on finding low-dimensional structures of the underlying processes seems to be successful only in a few exceptional cases, such as in rather coherent phenomena as coronal pulsations. It is important to note that most phenomena in solar radio emission are more complex. We present two kinds of techniques from nonlinear dynamics which can be useful to analyse such phenomena:

1. Fragmentation processes observed in solar spike events are studied by means of symbolic dynamics methods. Different measures of complexity calculated from such observations reveal that there is some order in this fragmentation.
2. Bursts are a typical transient phenomenon. To study energization processes causing impulsive microwave bursts, the wavelet analysis is applied. It exhibits structural differences of the pre- and post-impulsive phase in cases where the power spectra of both are not distinct.

     

跨声速流自发凝结水滴的测量

应用基于多波长消光法原理发展的光学探针,测量了跨声速风洞中不同马赫数湿空气流自发凝结形成的水滴尺寸及浓度,并给出了实验结果     

Fuel mass penalty due to generators and fuel cells as energy source of the all-electric aircraft

The paper presents the results of an assessment of the fuel mass penalty due to generators and fuel cell systems. Based on the simulation tool SysFuel, fuel mass penalties for different mission ranges and fuel cell architectures are calculated and compared to a conventional reference architecture. Different fuel cell architectures using ram air or cabin exhaust air and different options of energy recovery are considered. As a result of the studies, target values are presented for the mass to power ratio of fuel cell systems to achieve fuel mass reductions compared to conventional generator and auxiliary power unit systems.     

DLR-TUBSAT, qualification of high precision attitude control in orbit

DLR-TUBSAT is a joint project of the DLR Institute of Space Sensor Technology and the Institute of Aeronautics and Astronautics at the Technical University of Berlin. Based on the experience gained with TUBSAT-A and TUBSAT-B an attitude control unit of minimal dimensions has been developed for the DLR-TUBSAT microsatellite. The DLR-TUBSAT microsatellite is mainly used to carry out tests involving exact three axes attitude control and to qualify the different subsystems with regard to their tasks in target pointing and high-resolution earth observation.