Speech Data Rate Reduction Part II: Applicability of Sensitivity and Error Analysis

This paper deals with the application of modern estimation techniques to the problem of speech data rate reduction. It is desirable to adaptively identify and quantitize the parameters of the speech model. These paramaters cannot be identified and quantized exactly; the performance of the predictor is thereby degraded and this could prevent data reduction. In many cases it is desirable to emply a suboptimal predictor in order to simplify the algorithms, and predictor performance is again degraded. This paper develops sensitivity and error analysis as a potential method for determining quantitatively how speech data reduction system performance is degraded by imprecise parameter knowledge or suboptimal filtering. An intended use of the sensitivity and error analysis algorithms is to determine parameter identification and model structure requirements of configuration concepts for adaptive speech digitizers. First, sensitivity and error analysis algorithms are presented that form the basis for the remainder of the work. The algorithms are then used to determine how imprecise knowledge of vocal tract parameters degrades predictor performance in speech. Transversal filters have previously been proposed for this application. The sensitivity analysis algorithms are then used to determine when and by how much the transverse filter is suboptimal to the Kalman filter. In particular, the question of how effectively a higher order of all-pole model approximates a system with zeros is answered, as this question is of considerable importance in speech. Finally, the physical significance of the innovations process in speech data rate reduction is studied.     

Integration of waste processing and biomass production systems as part of the KSC Breadboard project.

After initial emphasis on large-scale baseline crop tests, the Kennedy Space Center (KSC) Breadboard project has begun to evaluate long-term operation of the biomass production system with increasing material closure. Our goal is to define the minimum biological processing necessary to make waste streams compatible with plant growth in hydroponic systems, thereby recycling nutrients into plant biomass and recovering water via atmospheric condensate. Initial small and intermediate-scale studies focused on the recycling of nutrients contained in inedible plant biomass. Studies conducted between 1989-1992 indicated that the majority of nutrients could be rapidly solubilized in water, but the direct use of this crop "leachate" was deleterious to plant growth due to the presence of soluble organic compounds. Subsequent studies at both the intermediate scale and in the large-scale Biomass Production Chamber (BPC) have indicated that aerobic microbiological processing of crop residue prior to incorporation into recirculating hydroponic solutions eliminated any phytotoxic effect, even when the majority of the plant nutrient demand was provided from recycled biomass during long term studies (i.e. up to 418 days). Current and future studies are focused on optimizing biological processing of both plant and human waste streams.     

Peculiarities of biological processes under conditions of microgravity.

The results of experiments aboard spacecraft demonstrated the dependence of the pattern of biological processes on microgravity and on the ability of biological objects to adapt themselves to new environmental conditions. This is of fundamental importance for solving theoretical and practical problems of space biology, or elaborating the theory of organism's behavior in weightlessness, and for elucidating the global mechanisms of the action of microgravity on living systems.     

Yohkoh observations of the solar corona

The Yohkoh soft X-ray telescope obtains several images every 90 minutes. Data from the declining phase of the solar cycle have been used to compare the X-ray signal with other indicators of activity and to study coronal heating. X-ray emission from a north polar coronal hole is found broadly consistent with results of previous EUV observations. In diffuse emission regions, temperature rises to around 2.2 MK and levels off in the height range 1.5 – 1.9 R_O. Such emission underlies streamers and may be the source of the low-speed solar wind. X-ray signatures for Coronal Mass Ejection (CME) events which involve the detection of reduced X-ray intensities in the corona, have been developed with Yohkoh data. CME observations are described     

Organization, selection, and training of crews for extended spaceflight: findings from analogs and implications

Ample research evidence from space analogs points to the crucial role that teamwork plays in the performance of small groups in isolation and confinement. This paper surveys findings about the impacts of group behavior and social interaction on crew morale, coordination, and productivity. Implications for the organization, selection, and training of crews for extended spaceflight are discussed.     

Lunar habitat concept employing the space shuttle external tank

The space shuttle external tank, which consists of a liquid oxygen tank, an intertank structure, and a liquid hydrogen tank, is an expendable structure used for approximately 8.5 min during each launch. A concept for outfitting the liquid oxygen tank-intertank unit for a 12-person lunar habitat is described. The concept utilizes existing structures and openings for both man and equipment access without compromising the structural integrity of the tank. Living quarters, instrumentation, environmental control and life support, thermal control, and propulsion systems are installed at Space Station Freedom. The unmanned habitat is then transported to low lunar orbit and autonomously soft landed on the lunar surface. Design studies indicate that this concept is feasible by the year 2000 with concurrent development of a space transfer vehicle and manned cargo lander for crew changeover and resupply.     

Synthesis Techniques for a Class of SSB-AM-PM Signals

This paper develops synthesis techniques for a particular type of single-sideband sinusoidal carrier which is phase modulated by a subcarrier. Mathematical expressions for signal efficiency, sensitivity of design to parameter variation, and ratio of peak to average power are derived and incorporated in a computer program. Given the desired power ratios for modulated signal components, the program solves for the corresponding modulation parameters and evaluates signal efficiency, design sensitivity, and peak to average power ratio. A sample signal design is presented for clarity.     

Alfven modes of solar coronal magnetic arches: Excitation of ballooning instability and modulation of flare emission

The effect of Alfven-type oscillations in a coronal magnetic arch on modulation of the gyrosynchrotron radiation and development of the ballooning instability in the arch is considered. On the basis of the energy method and the method of normal modes, the expressions are obtained for increments of ballooning instability at its swinging by natural oscillations of the arch. The conclusion is drawn that bending oscillations, which do not actually compress the plasma and, therefore, represent the Alfven-type modes, unlike the radial oscillations, are capable, under solar corona conditions, to effectively swing ballooning instability and, as a consequence, play a part of a trigger for solar flares. The ballooning instability of coronal arches is shown to be capable of causing formation of helmet-shaped structures in the lower solar corona. On the basis of calculations of the intensity modulation depth and the degree of circular polarization of non-thermal gyrosynchrotron radiation, under the assumption of excited Alfven oscillations of a coronal arch, the conclusion is drawn, that microwave observations at a frequency of > 10 GHz can be used for studying the conditions of excitation and propagation of Alfven modes in flare loops. The consequences of obtained results are discussed using the flare on April 15, 2002 as an example.