Effects of CO2 concentration and light intensity on photosynthesis of a rootless submerged plant, Ceratophyllum demersum L., used for aquatic food production in bioregenerative life support systems.

In addition to green microalgae, aquatic higher plants are likely to play an important role in aquatic food production modules in bioregenerative systems for producing feed for fish, converting CO2 to O2 and remedying water quality. In the present study, the effects of culture conditions on the net photosynthetic rate of a rootless submerged plant, Ceratophyllum demersum L., was investigated to determine the optimum culture conditions for maximal function of plants in food production modules including both aquatic plant culture and fish culture systems. The net photosynthetic rate in plants was determined by the increase in dissolved O2 concentrations in a closed vessel containing a plantlet and water. The water in the vessel was aerated sufficiently with a gas containing a known concentration of CO2 gas mixed with N2 gas before closing the vessel. The CO2 concentrations in the aerating gas ranged from 0.3 to 10 mmol mol-1. Photosynthetic photon flux density (PPFD) in the vessel ranged from 0 (dark) to 1.0 mmol m-2 s-1, which was controlled with a metal halide lamp. Temperature was kept at 28 degrees C. The net photosynthetic rate increased with increasing PPFD levels and was saturated at 0.2 and 0.5 mmol m-2 s-1 PPFD under CO2 levels of 1.0 and 3.0 mmol mol-1, respectively. The net photosynthetic rate increased with increasing CO2 levels from 0.3 to 3.0 mmol mol-1 showing the maximum value, 75 nmol O2 gDW-1 s-1, at 2-3 mmol mol-1 CO2 and gradually decreased with increasing CO2 levels from 3.0 to 10 mmol mol-1. The results demonstrate that C. demersum could be an efficient CO2 to O2 converter under a 2.0 mmol mol-1 CO2 level and relatively low PPFD levels in aquatic food production modules.     

Correlation between horizontal and vertical monopulse measurements

Many radar systems use the monopulse ratio to extract angle of arrival (AOA) measurements in both azimuth and elevation angles. The accuracies of each such measurement are reasonably well known: each measurement is, conditioned on the sum-signal return, Gaussian-distributed with calculable bias (relative to the true AOA), and variance. However, we note that the two monopulse ratios are functions of basic radar measurements that are not entirely independent, specifically in that the sum signal is common to both. The effect of this is that the monopulse ratios are dependent, and a simple explicit expression is given for their correlation; this is of considerable interest when the measurements are supplied to a tracking algorithm that requires a measurement covariance matrix. The system performance improvement when this is taken into account is quantified: while it makes little difference for a tracking radar with small pointing errors, there are more substantial gains when a target is allowed to stray within the beam, as with a rotating (track-while-scan) radar or when a single radar dwell interrogates two or more targets at different ranges. But in any case, the correct covariance expression is so simple that there is little reason not to use it. We additionally derive the Cramer-Rao lower bound (CRLB) on joint azimuth/elevation angle estimation and discover that it differs only slightly from the covariance matrix corresponding to the individual monopulse ratios. Hence, using the individual monopulse ratios and their simple joint accuracy expression is an adequate and quick approximation of the optimal maximum likelihood procedure for single resolved targets.     

Fast data association using multidimensional assignment withclustering

We present a fast data association technique based on clustering and multidimensional assignment algorithms for multisensor-multitarget tracking Assignment-based methods have been shown to be very effective for data association. Multidimensional assignment for data association is an NP-hard problem and various near-optimal modifications with (pseudo-)polynomial complexity have been proposed. In multidimensional assignment, candidate assignment tree building consumes about 95% of the time. We present the development of a fast data association algorithm, which partitions the problem into smaller sub-problems. A clustering approach, which attempts to group measurements before forming the candidate tree, is developed for various target-sensor configurations. Simulation results show significant computational savings over the standard multidimensional assignment approach without clustering     

Sequential localization of a radiating source by Doppler-shiftedfrequency measurements

For a single omnidirectional sensor in contact with a constant velocity source that radiates a constant frequency tone, the measurements of the Doppler-shifted frequencies over time do not provide sufficient information to localize the source. Instead, only the parameters of source rest frequency, speed, and range relative to a sensor can be determined. However, if over time three or more sensors sequentially come in contact with the source, the source trajectory can then be specified. This is termed sequential localization. A two-dimensional grid search technique to find the Doppler parameters from measurements taken by a single sensor alone is presented. From these parameters, it is next shown how sequential localization is accomplished. Two simulation examples are provided to verify the development. The localization root mean squared errors (RMSEs) are found to be very close to the Cramer-Rao bound     

A PC based test system for an on-board computer

This paper presents a robust method of testing a processor based on-board computer used in the Indian remote sensing satellite (IRS-1C). The novelty of this scheme lies in a judicious mix of software and hardware approaches adopted to realise this PC-based system. All the electrical interfaces (like telemetry, Telecommand, timer and star sensor) are simulated. They are fabricated as add-on cards to PC-AT (ISAbus). The on-board computer controls two star sensors apart from handling three telemetry streams and accepting more than one hundred Telecommands     

A payload for the study of electric fields and electron density in the equatorial region

A rocket borne payload for simultaneous measurement of the electric field along and perpendicular to the rocket spin axis and the electron density in the medium was developed and flown from Thumba (8° 31′N, 0° 47′S dip) onboard two Centaure rockets for the study of plasma dynamcis in the equatorial E-region. The arrangement of sensors in this payload allows near continuous measurements of some of these parameters to be made.     

Radar measurement extraction in the presence of sea-surface multipath

In the presence of sea-surface multipath monopulse radar signals from a low elevation target have three alternative paths in addition to the direct (radar-to-target) path due to reflections from the sea surface. The specular reflection causes significant signal fading. The diffuse reflection causes an approximately constant bias to the in-phase component of the monopulse ratio, which is the standard extractor of the direction of arrival (DOA) in the monopulse processing. The diffuse reflection also causes higher standard deviation to the in-phase component of the monopulse ratio. We propose a maximum likelihood (ML) angle extraction technique for low elevation targets of known average signal strength having a Rayleigh fluctuation. The results show that this method reduces the error of the estimated angle compared with the conventional monopulse ratio estimator. Subsequently, the ML angle extractor is modified for the unknown average signal strength case. This modified angle extractor has only a small performance degradation compared with the known average signal strength case, but it performs much better than the monopulse ratio based estimator. An algorithm to calculate the accuracy of the estimated angle (or height) is also presented. This angle extractor reduces the root-mean-square error (RMSE) by more than 50% in the signal processing stage when used in a low flying target tracking scenario. The same algorithm can be used to track sea skimmers.     

A Controllable and Observable Protein Cystallization Facility.

A Controllable and Observable Protein Crystallization Facility (ACOP) was developed in 1999 for space experiment in the Get Away Special canister of Space Shuttle. To regulate the vapor diffusion rate, in a crystallization chamber, five cells each containing precipitant solution of different concentrations, exposed to one protein cell in turn. Five layers of chambers were overlapped coaxially. The crystallization process was observed and recorded by digital cameras. Structure of facility and result of image sequence were given.     

Mutagenic effects of heavy ion radiation in plants.

Genetic and developmental effects of heavy ions in maize and rice were investigated. Heavy particles with various charges and energies were accelerated at the BEVALAC. The frequency of occurrence of white-yellow stripes on leaves of plants developed from irradiated maize seeds increased linearly with dose, and high-LET heavy charged particles, e.g., neon, argon, and iron, were 2-12 times as effective as gamma rays in inducing this type of mutation. The effectiveness of high-LET heavy ion in (1) inhibiting rice seedling growth, (2) reducing plant fertility, (3) inducing chromosome aberration and micronuclei in root tip cells and pollen mother cells of the first generation plants developed from exposed seeds, and (4) inducing mutation in the second generation, were greater than that of low-LET gamma rays. All effects observed were dose-dependent; however, there appeared to be an optimal range of doses for inducing certain types of mutation, for example, for argon ions (400 MeV/u) at 90-100 Gy, several valuable mutant lines with favorable characters, such as semidwarf, early maturity and high yield ability, were obtained. Experimental results suggest that the potential application of heavy ions in crop improvement is promising. RFLP analysis of two semidwarf mutants induced by argon particles revealed that large DNA alterations might be involved in these mutants.