Effects of errors on decoupled control systems

Various error sources in a decoupled control system are considered in connection with longitudinal control on a simulated externally blown jet-flap STOL aircraft. The system employed the throttle, horizontal tail, and flaps to decouple the forward velocity, pitch angle, and flight-path angle. The errors considered were: (1) imperfect knowledge of airplane aerodynamic and control characteristics; (2) imperfect measurements of airplane state variables; (3) change in flight conditions, and (4) lag in the airplane controls and in engine response. The effects of the various errors on the decoupling process were generally minor. Significant coupling in flight-path angle was caused by control lag during speed-command maneuvers. However, this coupling could be eliminated by including the control lag in the design of the decoupled system. Other error sources affected primarily the commanded response quantity

Milling characteristics and distribution of phytic acid and zind in long-, medium- and short-grain rice

Milling and polishing are important operations during the production of white rice. The degree of milling and polishing has a significant effect on the nutritional aspects of white rice, especially on minerals, due to a non-uniform distribution of nutrients in the kernel. Information on the distribution of nutrients in rice will greatly help in understanding the effect of milling and aid in designing procedures that improve technological and sensory properties of rice while retaining its essential nutrients as much as possible. In this study, three kernel shapes (short-, medium- and long-grain) of rice were selected for the study of milling characteristics and distribution of zinc (Zn) and phytic acid using abrasive milling and X-ray fluorescent microscope imaging approaches. Milling characteristics differed with kernel shapes and cultivars. Mass loss (y, %) correlated well with milling duration (x, s) and was fitted using a polynomial equation of y=ax2+bx+c (R2=0.99). Different kernel shapes of rice resulted in different patterns. Breakage in milling increased with longer duration of milling. The relation between breakage (y, %) and milling duration (x, s) fitted the exponential equation y=aebx. Levels of phytic acid, as well as Zn, decreased with prolonged milling. Phytic acid decreased at a higher rate than Zn. The analysis of different milling runs showed that the concentration of phytic acid decreased from the surface region inward, whereas X-ray fluorescent images indicated that the highest concentration of phosphorus was at the interface of the embryo and perisperm. Our results help in understanding the milling characteristics of different rice cultivars. Understanding these characteristics offers opportunities to optimize milling procedures for maximum phytate removal at minimum mineral losses and yield los

Effects of model error on control of large flexible space antenna with comparisons of decoupled and linear quadratic regulator control procedures

An analysis was performed to determine the effects of model error on the control of a large flexible space antenna. Control was achieved by employing two three-axis control-moment gyros (CMG's) located on the antenna column. State variables were estimated by including an observer in the control loop that used attitude and attitude-rate sensors on the column. Errors were assumed to exist in the individual model parameters: modal frequency, modal damping, mode slope (control-influence coefficients), and moment of inertia. Their effects on control-system performance were analyzed either for (1) nulling initial disturbances in the rigid-body modes, or (2) nulling initial disturbances in the first three flexible modes. The study includes the effects on stability, time to null, and control requirements (defined as maximum torque and total momentum), as well as on the accuracy of obtaining initial estimates of the disturbances. The effects on the transients of the undisturbed modes are also included. The results, which are compared for decoupled and linear quadratic regulator (LQR) control procedures, are shown in tabular form, parametric plots, and as sample time histories of modal-amplitude and control responses. Results of the analysis showed that the effects of model errors on the control-system performance were generally comparable for both control procedures. The effect of mode-slope error was the most serious of all model errors

Decoupled control of a long flexible beam in orbit

Control involved commanding changes in pitch attitude as well as nulling initial disturbances in the pitch and flexible modes. Control force requirements were analyzed. Also, the effects of parameter uncertainties on the decoupling process were analyzed and were found to be small. Two methods were investigated: the system was completely coupled and certain actuators were then eliminated, one by one, which resulted in some or all modes not fully controlled; specified modes of the system were excluded from the decoupling control law by employing viewer control actuators than modes in the model. In both methods, adjustments were made in the feedback gains to include the uncontrolled modes in the overall control of the system

Rainfall but not selective logging affect changes in abundance of tropical forest butterfly in Sabah, Borneo

We investigated the effects of rainfall on the distribution and abundance of the satyrine butterfly Ragadia makuta in selectively logged and unlogged forest on Borneo. In 1997-98, there was a severe El Nino-Southern Oscillation (ENSO) drought, and annual surveys over a 4-y period showed that abundance of R. makuta was greatly reduced during the drought, but that populations quickly recovered after it. Monthly surveys over a 12-mo period of typical rainfall showed that high rainfall in the month preceding surveys significantly reduced butterfly abundance. Butterfly abundance and distribution did not differ between selectively logged and unlogged areas in either monthly or annual surveys and there was no difference between selectively logged and unlogged areas in the pattern of post-drought recovery. These results indicate that the abundance of R. makuta was significantly reduced both after high rainfall and during severe drought, but that these impacts were short-lived and were not affected by habitat disturbance. ENSO droughts on Borneo naturally often lead to widespread forest fires and thus impacts of ENSO events for butterflies are more likely to be due to indirect effects of habitat loss, rather than direct effects of drought on butterfly population dynamics

Decoupled and linear quadratic regulator control of a large, flexible space antenna with an observer in the control loop

An analysis is performed to compare decoupled and linear quadratic regulator (LQR) procedures for the control of a large, flexible space antenna. Control objectives involve: (1) commanding changes in the rigid-body modes, (2) nulling initial disturbances in the rigid-body modes, or (3) nulling initial disturbances in the first three flexible modes. Control is achieved with two three-axis control-moment gyros located on the antenna column. Results are presented to illustrate various effects on control requirements for the two procedures. These effects include errors in the initial estimates of state variables, variations in the type, number, and location of sensors, and deletions of state-variable estimates for certain flexible modes after control activation. The advantages of incorporating a time lag in the control feedback are also illustrated. In addition, the effects of inoperative-control situations are analyzed with regard to control requirements and resultant modal responses. Comparisons are included which show the effects of perfect state feedback with no residual modes (ideal case). Time-history responses are presented to illustrate the various effects on the control procedures

The bacterial transposon Tn7 causes premature polyadenylation of mRNA in eukaryotic organisms: TAGKO mutagenesis in filamentous fungi

TAGKO is a Tn7-based transposition system for genome wide mutagenesis in filamentous fungi. The effects of transposon insertion on the expression of TAGKO alleles were examined in Magnaporthe grisea and Mycosphaerella graminicola. Northern analysis showed that stable, truncated transcripts were expressed in the TAGKO mutants. Mapping of the 3′-ends of TAGKO cDNAs revealed that they all contain Tn7 end sequences, regardless of the transposon orientation. Polyadenylation signals characteristic of eukaryotic genes, preceded by stop codons in all frames, are located in both ends of the bacterial transposon. Thus, TAGKO transcripts are prematurely polyadenylated, and truncated proteins are predicted to be translated in the fungal mutants. Depending on the extent of protein truncation, TAGKO mutations in HPD4 (encoding p-hydroxyphenylpyruvate dioxygenase) resulted in tyrosine sensitivity in the two fungi. Similarly, a particular M.grisea CBS1 (encoding cystathionine β-synthase) TAGKO cDNA failed to complement cysteine auxotrophy in a yeast CBS mutant. TAGKO, therefore, represents a useful tool for in vivo study of truncated gene products in filamentous fungi.postprin

Temporal variation in abundance and diversity of butterflies in Bornean rain forests: opposite impacts of logging recorded in different seasons

We used traps baited with fruit to examine how the temporal variation of butterflies within primary forest in Sabah, Borneo differed between species. In addition, we compared patterns of temporal variation in primary and selectively logged forest, and we tested the hypothesis that selective logging has different recorded impacts on species diversity of adults during the wet monsoon period and the drier remaining half of the year. Species of Satyrinae and Morphinae had significantly less-restricted flight periods than did species of Nymphalinae and Charaxinae, which were sampled mainly during the drier season. especially in primary forest. Species diversity of adults was significantly higher during the drier season in primary forest, but did not differ between seasons in logged forest. As a consequence, logging had opposite recorded impacts on diversity during wetter and drier seasons: primary forest had significantly higher diversity than logged forest during the drier season but significantly lower diversity than logged forest during the wetter monsoon season. The results of this study have important implications for the assessment of biodiversity in tropical rain forests, particularly in relation to habitat disturbance: short-term assessments that do not take account of seasonal variation in abundance are likely to produce misleading results, even in regions where the seasonal variation in rainfall is not that great

Density Matrix Renormalisation Group Approach to the Massive Schwinger Model

The massive Schwinger model is studied, using a density matrix renormalisation group approach to the staggered lattice Hamiltonian version of the model. Lattice sizes up to 256 sites are calculated, and the estimates in the continuum limit are almost two orders of magnitude more accurate than previous calculations. Coleman's picture of `half-asymptotic' particles at background field theta = pi is confirmed. The predicted phase transition at finite fermion mass (m/g) is accurately located, and demonstrated to belong in the 2D Ising universality class.Comment: 38 pages, 18 figures, submitted to PR

Path Integral Monte Carlo Approach to the U(1) Lattice Gauge Theory in (2+1) Dimensions

Path Integral Monte Carlo simulations have been performed for U(1) lattice gauge theory in (2+1) dimensions on anisotropic lattices. We extractthe static quark potential, the string tension and the low-lying "glueball" spectrum.The Euclidean string tension and mass gap decrease exponentially at weakcoupling in excellent agreement with the predictions of Polyakov and G{\" o}pfert and Mack, but their magnitudes are five times bigger than predicted. Extrapolations are made to the extreme anisotropic or Hamiltonian limit, and comparisons are made with previous estimates obtained in the Hamiltonian formulation.Comment: 12 pages, 16 figure