21,130 research outputs found
Nitrogen fluxes and plant production in forest and agro ecosystems at Sorø, Denmark - part of the SOROFLUX project
Worship in small churches
The article advocates and elaborates a theological point of view with respect to worship that is in the interest of the small church and that the small church is in a unique position to advocate. Specific rubrical proposals are made. \u27The means of grace, i.e., the Word and Sacraments, are the central and only indispensable elements in worship. The smaller amount of human resources available to small churches can lead them to focus on these means of grace. This focus is an outstanding strength\u27
Evolution of weak disturbances in inert binary mixtures
The evolution of weak disturbances in inert binary mixtures is determined for the one-dimensional piston problem. The interaction of the dissipative and nonlinear mechanisms is described by Burgers' equation. The binary mixture diffusion mechanisms enter as an additive term in an effective diffusivity. Results for the impulsive motion of a piston moving into an ambient medium and the sinusoidally oscillating piston are used to illustrate the results and elucidate the incorrect behavior pertaining to the associated linear theory
Acoustic disturbances produced by an unsteady spherical diffusion flame
The disturbances produced by a moving spherical diffusion flame are investigated within the framework of a linearized theory. After the flame position and species concentrations are determined, the problem of determining the associated density, pressure, temperature, and velocity fields is delineated. Explicit results for certain limiting situations are discussed
Field weed population models: a review of approaches and application domains
We evaluated models of weed population dynamics based on an analysis of their assumptions, biological rationale, flexibility, documentation, accessibility, demand for parameter estimation and documented validity. We arrived at general recommendations regarding which modelling approach should be applied in order to address different application domains
An integrated aerodynamic/propulsion study for generic aero-space planes based on waverider concepts
The design of a unified aero-space plane based on waverider technology is analyzed. The overall aerodynamic design and performance of an aero-space plane are discussed in terms of the forebody, scramjet, and afterbody. Other subjects considered in the study are combustion/nozzle optimization, the idealized tip-to-tail waverider model, and the two-dimensional minimum length nozzle. Charts and graphs are provided to show the results of the preliminary investigations
Fusion, collapse, and stationary bound states of incoherently coupled waves in bulk cubic media
We study the interaction between two localized waves that propagate in a bulk (two transverse dimensions) Kerr medium, while being incoherently coupled through cross-phase modulation. The different types of stationary solitary wave solutions are found and their stability is discussed. The results of numerical simulations suggest that the solitary waves are unstable. We derive sufficient conditions for when the wave function is bound to collapse or spread out, and we develop a theory to describe the regions of different dynamical behavior. For localized waves with the same center we confirm these sufficient conditions numerically and show that only when the equations and the initial conditions are symmetric are they also close to being necessary conditions. Using Gaussian initial conditions we predict and confirm numerically the power-dependent characteristic initial separations that divide the phase space into collapsing and diffracting solutions, and further divide each of these regions into subregions of coupled (fusion) and uncoupled dynamics. Finally we illustrate how, close to the threshold of collapse, the waves can cross several times before eventually collapsing or diffracting
Hamiltonian Reduction of -theories at the Level of Correlators
Since the work of Bershadsky and Ooguri and Feigin and Frenkel it is well
known that correlators of current algebra for admissible
representations should reduce to correlators for conformal minimal models. A
precise proposal for this relation has been given at the level of correlators:
When primary fields are expressed as with being
a variable to keep track of the representation multiplet (possibly
infinitely dimensional for admissible representations), then the minimal model
correlator is supposed to be obtained simply by putting all . Although
strong support for this has been presented, to the best of our understanding a
direct, simple proof seems to be missing so in this paper we present one based
on the free field Wakimoto construction and our previous study of that in the
present context. We further verify that the explicit correlators we
have published in a recent preprint reduce in the above way, up to a constant
which we also calculate. We further discuss the relation to more standard
formulations of hamiltonian reduction.Comment: 13 pages, LaTe
Computational analysis of hypersonic flows past elliptic-cone waveriders
A comprehensive study for the inviscid numerical calculation of the hypersonic flow past a class of elliptic-cone derived waveriders is presented. The theoretical background associated with hypersonic small-disturbance theory (HSDT) is reviewed. Several approximation formulas for the waverider compression surface are established. A CFD algorithm is used to calculate flow fields for the on-design case and a variety of off-design cases. The results are compared with HSDT, experiment, and other available CFD results. For the waverider shape used in previous investigations, the bow shock for the on-design condition stands off from the leading-edge tip of the waverider. It was found that this occurs because the tip was too thick according to the approximating shape formula that was used to describe the compression surface. When this was corrected, the bow shock became closer to attached as it should be. At Mach numbers greater than the design condition, a lambda-shock configuration develops near the tip of the compression surface. At negative angles of attack, other complicated shock patterns occur near the leading-edge tip. These heretofore unknown flow patterns show the power and utility of CFD for investigating novel hypersonic configurations such as waveriders
Suggesting Cooking Recipes Through Simulation and Bayesian Optimization
Cooking typically involves a plethora of decisions about ingredients and
tools that need to be chosen in order to write a good cooking recipe. Cooking
can be modelled in an optimization framework, as it involves a search space of
ingredients, kitchen tools, cooking times or temperatures. If we model as an
objective function the quality of the recipe, several problems arise. No
analytical expression can model all the recipes, so no gradients are available.
The objective function is subjective, in other words, it contains noise.
Moreover, evaluations are expensive both in time and human resources. Bayesian
Optimization (BO) emerges as an ideal methodology to tackle problems with these
characteristics. In this paper, we propose a methodology to suggest recipe
recommendations based on a Machine Learning (ML) model that fits real and
simulated data and BO. We provide empirical evidence with two experiments that
support the adequacy of the methodology
- …