Integrated dynamic analysis simulation of space stations with controllable solar array

A methodology is formulated and presented for the integrated structural dynamic analysis of space stations with controllable solar arrays and non-controllable appendages. The structural system flexibility characteristics are considered in the dynamic analysis by a synthesis technique whereby free-free space station modal coordinates and cantilever appendage coordinates are inertially coupled. A digital simulation of this analysis method is described and verified by comparison of interaction load solutions with other methods of solution. Motion equations are simulated for both the zero gravity and artificial gravity (spinning) orbital conditions. Closed loop controlling dynamics for both orientation control of the arrays and attitude control of the space station are provided in the simulation by various generic types of controlling systems. The capability of the simulation as a design tool is demonstrated by utilizing typical space station and solar array structural representations and a specific structural perturbing force. Response and interaction load solutions are presented for this structural configuration and indicate the importance of using an integrated type analysis for the predictions of structural interactions

Absence of localization in a disordered one-dimensional ring threaded by an Aharonov-Bohm flux

Absence of localization is demonstrated analytically to leading order in weak disorder in a one-dimensional Anderson model of a ring threaded by an Aharonov-Bohm (A-B) flux. The result follows from adapting an earlier perturbation treatment of disorder in a superconducting ring subjected to an imaginary vector potential proportional to a depinning field for flux lines bound to random columnar defects parallel to the axis of the ring. The absence of localization in the ring threaded by an A-B flux for sufficiently weak disorder is compatible with large free electron type persistent current obtained in recent studies of the above model

Transmission, reflection and localization in a random medium with absorption or gain

We study reflection and transmission of waves in a random tight-binding system with absorption or gain for weak disorder, using a scattering matrix formalism. Our aim is to discuss analytically the effects of absorption or gain on the statistics of wave transport. Treating the effects of absorption or gain exactly in the limit of no disorder, allows us to identify short- and long lengths regimes relative to absorption- or gain lengths, where the effects of absorption/gain on statistical properties are essentially different. In the long-lengths regime we find that a weak absorption or a weak gain induce identical statistical corrections in the inverse localization length, but lead to different corrections in the mean reflection coefficient. In contrast, a strong absorption or a strong gain strongly suppress the effect of disorder in identical ways (to leading order), both in the localization length and in the mean reflection coefficient.Comment: Important revisions and expansion caused by a crucial property of $\hat Q

Enhanced Transmission Through Disordered Potential Barrier

Effect of weak disorder on tunneling through a potential barrier is studied analytically. A diagrammatic approach based on the specific behavior of subbarrier wave functions is developed. The problem is shown to be equivalent to that of tunneling through rectangular barriers with Gaussian distributed heights. The distribution function for the transmission coefficient $T$ is derived, and statistical moments \left are calculated. The surprising result is that in average disorder increases both tunneling conductance and resistance.Comment: 10 pages, REVTeX 3.0, 2 figures available upon reques

Integrated dynamic analysis simulation of space stations with controllable solar arrays (supplemental data and analyses)

Space station and solar array data and the analyses which were performed in support of the integrated dynamic analysis study. The analysis methods and the formulated digital simulation were developed. Control systems for space station altitude control and solar array orientation control include generic type control systems. These systems have been digitally coded and included in the simulation

Susceptibility of the sod webworm \u3ci\u3ePediasia trisecta\u3c/i\u3e to biological control agents

Homeowners in Tennessee have observed complete destruction of their lawns by the sod webworm a few months after applying an insecticide to control sod webworms or white grubs. The reason for this increase rather than a decrease in the webworm population is not perfectly understood. We believe, however, that the natural enemies of the webworm may be reduced to such low population levels that they exert very little control on the webworm. Thus, once the natural enemies are destroyed in a lawn, it may require several months or even years for them to increase to a population level necessary to exert a satisfactory control on the webworms. In the absence of their natural enemies, which serve to control their population, the webworms, because of their high reproductive potential, increase rapidly and lawn destruction follows. Insecticides which cause an increase of webworm numbers are the chlorinated hydrocarbons such as dieldrin and chlordane. These are excellent insecticides for the control of soil insects such as white grubs which feed on grass roots but have not been satisfactory in webworm control in Tennessee. Insecticides that are recommended by the Institute of Agriculture for webworm control (Sevin and Diazinon) have not been implicated in causing webworm increases, but they probably do have an adverse effect on the natural enemy population. There is also a possibility that webworms may develop resistance to these chemieaIs. In addition, these chemicals have the disadvantage of having to be applied every 3 weeks during the summer because of their short activity period. Because of the above-mentioned disadvantages of chemicals, we are searching for new means of sod webworm control. Biological control, which involves the dissemination of large numbers of parasites, predators, and/or insect pathogens, may offer promise in sod webworm control. We have conducted preliminary studies utilizing biological control agents which are non-toxic to humans, birds, wildlife, and fish. Some of these agents are so specific as to insects attacked that certain ones can be selected that destroy the target insect pest but leave unharmed other insects and mites which are predators and parasites. Biological control agents cause no phytotoxicity at high rates as some insecticides do. Insect pathogens, which were the subject of this study, are manufactured in various formulations such as wettable powders, dusts, baits, and aqueous suspensions, and can be applied with the same equipment as insecticides. Costs for those whi

Influence of external magnetic fields on growth of alloy nanoclusters

Kinetic Monte Carlo simulations are performed to study the influence of external magnetic fields on the growth of magnetic fcc binary alloy nanoclusters with perpendicular magnetic anisotropy. The underlying kinetic model is designed to describe essential structural and magnetic properties of CoPt_3-type clusters grown on a weakly interacting substrate through molecular beam epitaxy. The results suggest that perpendicular magnetic anisotropy can be enhanced when the field is applied during growth. For equilibrium bulk systems a significant shift of the onset temperature for L1_2 ordering is found, in agreement with predictions from Landau theory. Stronger field induced effects can be expected for magnetic fcc-alloys undergoing L1_0 ordering.Comment: 10 pages, 3 figure

Exact transmission moments in one-dimensional weak localization and single-parameter scaling

We obtain for the first time the expressions for the mean and the variance of the transmission coefficient for an Anderson chain in the weak localization regime, using exact expansions of the complex transmission- and reflection coefficients to fourth order in the weakly disordered site energies. These results confirm the validity of single-parameter scaling theory in a domain where the higher transmission cumulants may be neglected. We compare our results with earlier results for transmission cumulants in the weak localization domain based on the phase randomization hypothesis

Nitrogênio e potássio na produtividade da bananeira cultivar thap maeo.

O experimento foi realizado em Latossolo Amarelo distrófico da Amazônia Central e teve por objetivo verificar o efeito de doses nitrogênio e de potássio (K2O) sobre a produtividade e a e estado nutricional da bananeira cultivar Thap Maeo (Musa spp. - AAB). O delineamento experimental utilizado foi o de blocos casualizados em esquema fatorial (3 x 4), com os seguintes tratamentos: três doses de N (0, 267 e 534 kg ha-1 ciclo - fonte: uréia) e quatro doses de K2O (200, 800, 1600 e 2400 kg ha-1 ciclo ? fonte: cloreto de potássio), com três repetições e dois ciclos. Os resultados mostraram que o aumento das doses de N até 534 kg ha-1 reduziu a produtividade. No segundo ciclo houve interação significativa entre as doses de N e de K2O, sendo a maior produção obtida com aplicação de 1600 kg ha-1 de K2O

Concentrate levels and \u3cem\u3eSaccharomyces cerevisiae\u3c/em\u3e affect rumen fluid-associated bacteria numbers in dairy heifers

Total viable rumenbacteria counts through the use of colony-unit forming assays lack accuracy because they only include culturable bacteria capable of initiating cell division. Thus, bacterial counts can be underestimated. The use of fluorescent characteristics of cell membranes allows flow cytometry to enumerate and distinguish dead from live bacteria cells. The objective of this experiment was to investigate the viable and total ruminal bacteria counts when 3 levels of forage:concentrate in diets were fed at restricted levels with the addition of Saccharomycescerevisiae (YC). Three cannulated post-pubertal Holstein heifers (age 18 ± 1.0 months) were fed corn silage (CS)-based diets in a 3-period (35 d) Latin square design. Heifers were fed the diets for 21 d with no yeast addition, followed by 14 d where yeast culture (YC) was added (1 g/kg as-fed basis); (Yea-Sacc1026, Alltech, Inc., Nicholasville, KY). A low concentrate (LC) TMR (80% CS, 20% concentrate; 12.4% CP, 35% NDF), a medium concentrate (MC) TMR (60% CS, 40% concentrate; 12.3% CP. 28% NDF), and a high concentrate (HC) TMR (40% CS, 60% concentrate; 12.6% CP, 25% NDF), were fed once per day. Rumenfluid was sampled − 2, 0, 2, 4, 6, 8, 10, 12 h after feeding. Samples were immediately stained with fluorescent dyes using the BacLight kit (Molecular Probes Inc., Eugene, OR) and analyzed with a Coulter XL-MCL single laser flow cytometer. Mean rumen viable bacteria counts linearly increased among treatments (4.96, 4.78, 6.73 × 1011 ± 0.53 × 1011 cells/ml; P = 0.02) for LC, MC and HC respectively, and YC addition increased number of viable bacteria cells (P \u3c 0.01). Total and viable bacteria counts decreased for the first 2 h after feeding then increased 4 h post-feeding. Dietary concentratelevel and YC can alter rumenbacteria counts as measured by this method