494 research outputs found
Apparatus and method for control of a solid fueled rocket vehicle Patent
Solid propellant rocket vehicle thrust control method and apparatu
Exact Solution of Two-Species Ballistic Annihilation with General Pair-Reaction Probability
The reaction process is modelled for ballistic reactants on an
infinite line with particle velocities and and initially
segregated conditions, i.e. all A particles to the left and all B particles to
the right of the origin. Previous, models of ballistic annihilation have
particles that always react on contact, i.e. pair-reaction probability .
The evolution of such systems are wholly determined by the initial distribution
of particles and therefore do not have a stochastic dynamics. However, in this
paper the generalisation is made to , allowing particles to pass through
each other without necessarily reacting. In this way, the A and B particle
domains overlap to form a fluctuating, finite-sized reaction zone where the
product C is created. Fluctuations are also included in the currents of A and B
particles entering the overlap region, thereby inducing a stochastic motion of
the reaction zone as a whole. These two types of fluctuations, in the reactions
and particle currents, are characterised by the `intrinsic reaction rate', seen
in a single system, and the `extrinsic reaction rate', seen in an average over
many systems. The intrinsic and extrinsic behaviours are examined and compared
to the case of isotropically diffusing reactants.Comment: 22 pages, 2 figures, typos correcte
Glyphosate and saflufenacil: elucidating their combined action on the control of glyphosate-resistant conyza bonariensis.
Synergic efects of glyphosate and saflufenacil have been reported to control Conyza spp. However, the mechanism of this synergic combination is unknown. The objectives of this study were to investigate the efects of the combination of glyphosate and saflufenacil on the control and resistance status of glyphosate-resistant (GR) C. bonariensis, as well as on oxidative stress and lipidic peroxidation. Glyphosate-resistant and glyphosate-sensitive (GS) biotypes were treated with diferent rates of saflufenacil, glyphosate, and glyphosate combined with saflufenacil. The combination of glyphosate (1480 g ae haf1) and saflufenacil (f15 g haf1) presented the best control of GR plants compared with their individual efects. It also reduced the resistance factor from 19.6 to 4.6 (4.3-fold) and represents a good alternative for resistance management. The combination of glyphosate and saflufenacil resulted in higher oxidative stress and lipidic peroxidation compared with the efects of either herbicide alone. The oxidative stress and lipid peroxidation promoted by the combination of the herbicides occurred earlier after treatment and remained at higher levels over a longer period (12?192 h) compared with their individual results. The combined oxidative stress and lipid peroxidation at high levels over a long time is likely to be one reason that the combination of glyphosate and saflufenacil efectively controls GR C. bonariensis
Kinetics and scaling in ballistic annihilation
We study the simplest irreversible ballistically-controlled reaction, whereby
particles having an initial continuous velocity distribution annihilate upon
colliding. In the framework of the Boltzmann equation, expressions for the
exponents characterizing the density and typical velocity decay are explicitly
worked out in arbitrary dimension. These predictions are in excellent agreement
with the complementary results of extensive Monte Carlo and Molecular Dynamics
simulations. We finally discuss the definition of universality classes indexed
by a continuous parameter for this far from equilibrium dynamics with no
conservation laws
Model of Enterpreneurship and Social-cultural and Market Orientation of Small Business Owners in Poland
In the development of SMEs in Poland crucial meaning is legislation, steadily adapted to EU regulations, especially to the European Charter for Small Enterprises. Research conducted in Poland by many authors provide data for doing so, to confirm the hypothesis that among small businesses a vital role in shaping their work situation did not continue to play the market mechanisms and orientations, but mainly socio-cultural factors.W rozwoju MŚP w Polsce podstawowe znaczenie mają również uregulowania prawne, systematycznie dostosowywane do regulacji unijnych, zwłaszcza zaś do Europejskiej Karty Małych Przedsiębiorstw. Badania prowadzone w Polsce przez wielu autorów dostarczają danych ku temu, by potwierdzić tezę, że wśród drobnych przedsiębiorców decydującą rolę w kształtowaniu ich sytuacji pracy odgrywają nadal nie mechanizmy i orientacje rynkowe, ale przede wszystkim czynniki społeczno-kulturowe
Ballistic Annihilation
Ballistic annihilation with continuous initial velocity distributions is
investigated in the framework of Boltzmann equation. The particle density and
the rms velocity decay as and , with the
exponents depending on the initial velocity distribution and the spatial
dimension. For instance, in one dimension for the uniform initial velocity
distribution we find . We also solve the Boltzmann equation
for Maxwell particles and very hard particles in arbitrary spatial dimension.
These solvable cases provide bounds for the decay exponents of the hard sphere
gas.Comment: 4 RevTeX pages and 1 Eps figure; submitted to Phys. Rev. Let
Deterministic Soluble Model of Coarsening
We investigate a 3-phase deterministic one-dimensional phase ordering model
in which interfaces move ballistically and annihilate upon colliding. We
determine analytically the autocorrelation function A(t). This is done by
computing generalized first-passage type probabilities P_n(t) which measure the
fraction of space crossed by exactly n interfaces during the time interval
(0,t), and then expressing the autocorrelation function via P_n's. We further
reveal the spatial structure of the system by analyzing the domain size
distribution.Comment: 5 pages, RevTeX fil
Microscopic Derivation of Non-Markovian Thermalization of a Brownian Particle
In this paper, the first microscopic approach to the Brownian motion is
developed in the case where the mass density of the suspending bath is of the
same order of magnitude as that of the Brownian (B) particle. Starting from an
extended Boltzmann equation, which describes correctly the interaction with the
fluid, we derive systematicaly via the multiple time-scale analysis a reduced
equation controlling the thermalization of the B particle, i.e. the relaxation
towards the Maxwell distribution in velocity space. In contradistinction to the
Fokker-Planck equation, the derived new evolution equation is non-local both in
time and in velocity space, owing to correlated recollision events between the
fluid and particle B. In the long-time limit, it describes a non-markovian
generalized Ornstein-Uhlenbeck process. However, in spite of this complex
dynamical behaviour, the Stokes-Einstein law relating the friction and
diffusion coefficients is shown to remain valid. A microscopic expression for
the friction coefficient is derived, which acquires the form of the Stokes law
in the limit where the mean-free in the gas is small compared to the radius of
particle B.Comment: 28 pages, no figure, submitted to Journal of Statistical Physic
Control of Italian ryegrass and Alexandergrass in corn using different corn sowing date, pre- and post-emergent herbicides.
Glyphosate-resistant (GR) Italian ryegrass (LOLMU) and Alexandergrass (URPLA) are troublesome weeds in corn cropping systems in Southern Brazil. The emergence pattern of those weeds is not uniform and may change according to the season?s environmental characteristics. Also, herbicide resistance has been diminishing the success of the weed control programs. The objectives of this study were to evaluate the influence of corn-sowing date on LOLMU and URPLA densities and their control provided by pre- and post-emergent herbicides. Field trials were conducted in two crop seasons in Southern Brazil consisting of three corn sowing date (August, September, and October) and the application of atrazine + S-metolachlor (residual) in corn pre-emergence in different post-emergence weed control programs with glyphosate, ammonium-glufosinate, nicosulfuron, and atrazine. The results indicated that the sowing date had a significant influence on LOLMU and URPLA densities. Corn sown in the earliest period was exposed to a higher LOLMU density, whereas corn sown in the latest period had a higher density of URPLA. Also, the application of residual herbicide at corn pre-emergence reduced both weed species densities and decreased the pressure for the control of glyphosate-resistant LOLMU for the post-emergence herbicides. The use of residual herbicides in corn pre-emergence is an efficient strategy to be considered in the LOLMU and URPLA control programs, followed by post-emergence application of glyphosate, ammonium-glufosinate, atrazine, and nicosulfuron
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