A Unified Approach to Model-Reference Adaptive Systems Part II: Application of Conventional Design Techniques

The use of linearized error equations in the design of model-reference adaptive systems developed by Part I is illustrated. Using standard control specifications on the system error (e.g., percent overshoot, rise time, etc.), a set of desired root locations on the root loci can be obtained. Then constants in the adaptive scheme can be chosen to obtain the desired root locations. Simulation results are given to illustrate the validity of the linearized error characteristic equation design procedure.     

Current views and future programs in cardiovascular physiology in space.

The volume shift of 2000 cm3 from the lower to the upper part of the human body during weightlessness gave rise to theoretical and practical questions which are addressed in this communication. The analysis revealed that the mobilized fluid reduced the interstitial fluid of the lower extremities by 40%. Applying the current ideas in the field of interstitial tissue physiology to these problems, one must conclude that the fluid displacement can only be brought about by a change of the interstitial tissue compliance. Based on the observations made by the astronauts and on our working hypothesis, a method was proposed to follow the fluid migration and to measure the tissue compliance in man. Results are reported from experiments under terrestrial conditions. They show that the tissue compliance indeed can be modulated. Applying the method in space can eventually help to clarify several concepts in terrestrial physiology.     

Properties of the mesosphere and lower thermosphere

The variability and systematic variations of the properties of the upper mesosphere and lower thermosphere are probably the least well known aspects of the terrestrial atmosphere. Satellite measurements of this region are very limited and rocket and remote sounding techniques do not provide comprehensive coverage. Progress is being made in theoretical studies of this region, primarily with regard to tidal effects, and some progress is being made in analyzing the relatively sparse experimental data that are available. Turbulence dynamics of the region has been studied by analyzing structure measurements at Kwajalein, wind data from Natal and systematic variations of the turbopause altitude determined from measurements of the diffusive separation of argon. One question that is being raised at this time, and it is appropriate at a time near solar maximum, is the extent of solar activity control of the properties of this region of the atmosphere. The occurrence rates and magnitudes of the turbulent diffusivity in the 70 to 90 km altitude region appear to correlate with solar activity with a time lag, as do also the incidence of aurora and the atomic oxygen green line intensity. Solar cycle dependence has been identified in mean zonal wind speeds in the 65 to 110 km altitude region above Saskatoon and in lower thermosphere temperatures measured at Heiss Island and at St. Santin. Millstone Hill data show that the mean meridional wind changes during a solar cycle. Solar cycle variations have also been detected in the stratosphere and troposphere.     

Comprehensive investigation of the basic parameters of the upper atmosphere at the time of the flight of the geophysical rocket “vertical-6”

Ion temperature and total ion concentration measured on 25th October 1977 during the flight of the geophysical rocket “Vertical-6” are analyzed. The solar EUV fluxes determined in five wave-length bands with a photoelectron analyzer are also given. The observed anomalous variation of ion temperature between 700 and 900 km and the measured ion concentration can be explained, if the charge exchange reactions H⁺ ? O⁺ and diffusion are taken into account.     

Solar maximum mission experiment: Early results from the soft X-ray polychromator experiment

The X-Ray Polychromator experiment has been in operation on the SMM satellite for over three months. It is observing flares and active regions in the wavelength range 1Å to 23Å using a number of different modes. These include polychromatic imaging, high resolution line profiles, high dispersion spectra, and light curves with high time-resolution. Data are described together with some of the preliminary analysis and interpretation.     

Photosynthesis and respiration of a wheat stand at reduced atmospheric pressure and reduced oxygen.

A 34-day functional test was conducted in Johnson Space Center's Variable Pressure Growth Chamber (VPGC) to determine responses of a wheat stand to reduced pressure (70 kPa) and modified partial pressures of carbon dioxide and oxygen. Reduced pressure episodes were generally six to seven hours in duration, were conducted at reduced ppO2 (14.7 kPa), and were interrupted with longer durations of ambient pressure (101 kPa). Daily measurements of stand net photosynthesis (Pn) and dark respiration (DR) were made at both pressures using a ppCO2 of 121 Pa. Corrections derived from leakage tests were applied to reduced pressure measurements. Rates of Pn at reduced pressure averaged over the complete test were 14.6% higher than at ambient pressure, but rates of DR were unaffected. Further reductions in ppO2 were achieved with a molecular sieve and were used to determine if Pn was enhanced by lowered O2 or by lowered pressure. Decreased ppO2 resulted in enhanced rates of Pn, regardless of pressure, but the actual response was dependent on the ratio of ppO2/ppCO2. Over the range of ppO2/ppCO2 of 80 to 200, the rate of Pn declined linearly. Rate of DR was unaffected over the same range and by dissolved O2 levels down to 3.1 ppm, suggesting that normal rhizosphere and canopy respiration occur at atmospheric ppO2 levels as low as 11 kPa. Partial separation of effects attributable to oxygen and those related to reduced pressure (e.g. enhanced diffusion of CO2) was achieved from analysis of a CO2 drawdown experiment. Results will be used for design and implementation of studies involving complete crop growth tests at reduced pressure.     

Jikiken(EXOS-B) observation of siple transmissions

A Japanese magnetospheric satellite Jikiken (EXOS-B) was used to observe Siple transmissions and VLF emissions triggered by the Siple signals. Energetic particle fluxes were also observed at the same time. The first experiments were made during July, August and September in 1979 and the second experiments were made during December in 1979 and January in 1980. The Siple triggered emissions were observed in August. This report reviews the preliminary results.     

Propagation of upstream protons in the near-earth solar wind

The propagation of energetic protons (35–1600 keV) from the Earth's magnetosphere to the ISEE-3 spacecraft located about 240 earth radii (R_E) upstream in the solar wind is used as a tool to study the interaction between these protons and the solar wind. In this preliminary study we present proton pitch angle distributions seen at different times during the development of upstream events that occur in relatively quiet interplanetary conditions. In general a highly anisotropic sunward flow is seen at the beginning of the events. During the course of the events pitch angle distributions may vary between streaming along the field lines (peaked around 0° pitch angle), a uniform intensity between 0° and 90°, and a peaked distribution around a preferred pitch angle that is often near 90°.