Swarming

Viehland L A and Robson R E 1989 Mean energies of ion swarms drifting and diffusing through neutral gases Int. J. Mass Spectrom. Ion Processes 90 167-86... 

In what is called BO MD, the nuclear wavepacket is simulated by a swarm of trajectories. We emphasize here that this does not necessarily mean that the nuclei are being treated classically. The difference is in the chosen initial conditions. A fully classical treatment takes the initial positions and momenta from a classical ensemble. The use of quantum mechanical distributions instead leads to a seraiclassical simulation. The important topic of choosing initial conditions is the subject of Section II.C. 

This picture is often refeired to as swarms of trajectories, and details are given in Appendix B. The nuclear problem is thus reduced to solving Newton s equations of motion for a number of different starting conditions. To connect... 

The big advantage of the Gaussian wavepacket method over the swarm of trajectory approach is that a wave function is being used, which can be easily manipulated to obtain quantum mechanical information such as the spechum, or reaction cross-sections. The initial Gaussian wave packet is chosen so that it... 

Quantum chemical methods, exemplified by CASSCF and other MCSCF methods, have now evolved to an extent where it is possible to routinely treat accurately the excited electronic states of molecules containing a number of atoms. Mixed nuclear dynamics, such as swarm of trajectory based surface hopping or Ehrenfest dynamics, or the Gaussian wavepacket based multiple spawning method, use an approximate representation of the nuclear wavepacket based on classical trajectories. They are thus able to use the infoiination from quantum chemistry calculations required for the propagation of the nuclei in the form of forces. These methods seem able to reproduce, at least qualitatively, the dynamics of non-adiabatic systems. Test calculations have now been run using duect dynamics, and these show that even a small number of trajectories is able to produce useful mechanistic infomiation about the photochemistry of a system. In some cases it is even possible to extract some quantitative information. 

The electrons have a range of kinetic energies and are therefore at different temperatures. Depending on the strength of the applied electric field, some electrons in the swarm will have... 

Gas Handling. The reactants are often gaseous under ambient conditions. To maximize the rate of the catalytic reaction, it is often necessary to minimize the resistance to gas—Uquid mass transfer, and the gases are therefore introduced as swarms of bubbles into a weU-stirred Hquid or into devices such as packed columns that faciHtate gas—Hquid mixing and gas absorption. 

E] Used as an arithmetic couceutratiou difference. Low <3, disperse-phase holdup of drop swarm. 

R Gas huhhle swarm in sparged stirred tank reactor with solids present... 

Mixed liberated particles can be separated from each other by flotation if there are sufficient differences in their wettability. The flotation process operates by preparing a water suspension of a mixture of relatively fine-sized particles (smaller than 150 micrometers) and by contacting the suspension with a swarm of air bubbles of air in a suitably designed process vessel. Particles that are readily wetted by water (hydrcmhiric) tend to remain in suspension, and those particles not wetted by water (hydrophobic) tend to be attached to air bubbles, levitate (float) to the top of the process vessel, and collect in a froth layer. Thus, differences in the surface chemical properties of the solids are the basis for separation by flotation. 

Bubble sizes at formation generally increase with surface tension and orifice diameter. Prediction of sizes in swarms from multiple orifices is difficult. In aqueous solutions of low surface tension, Bubble diameters of the order of 1 mm are common. Bubbles produced by the more complicated techniques of pressure flotation or vacuum flotation are usually smaller, with diameters of the order of 0.1 mm or less. 

Scbwarm, m. swarm, crowd, throng cluster Bact.) colony, -blldung, /. formation of clusters or swarms or (Bact.) colonies, scbwdrmen, v.i. swarm wander, migrate ... 

Swarm is a multi-agent simulation platform for the study of complex adaptive systems. It is currently under development at the Santa Fe Institute ... 

This section is based on the papers An Overview of the Swann simulation system, by 94 Swarm Team, Santa Pe Institute and The Swarm simulation. system and individual-based modeling, by D. Hiebler. 

World-Wide-Web URL link — http //www.saritafe.edu/projects/swarm/. 

Swarm has been intentionally designed to include as few ad-hoc assumptions about the design of a complex system as possible, so as to provide a convenient, reliable and standardized set of software tools that can be tailored by researchers to specific systems. 

Though the prototype has been written using the C programming language, it is object-oriented in style. Future versions of Swarm will be implemented using the Objective-C language. Objective-C is an object-oriented extension of the C language that is widely available as part of the GNU C compiler, and is available on the World-Wide-Web. 

Everything in Swarm is an object with three main characteristics Name, Data and Rules. An object s Name consists of an ID that is used to send messages to the object, a type and a module name. An object s Data consists of whatever local data (i.e. internal state variables) the user wants an agent to possess. The Rules are functions to handle any messages that are sent to the object. The basic unit of Swarm is a swarm a collection of objects with a schedule of event over those objects. Swarm also supplies the user with an interface and analysis tools. 

Hierarchical Structure. In order to be better able to simulate the hierarchical nature of many real-world complex systems, in which agent behavior can itself be best described as being the result of the collective behavior of some swarm of constituent agents. Swarm is designed so that agents themselves can be swarms of other agents. Moreover, Swarm is designed around a time hierarchy, Thus, Swarm is both a nested hierarchy of swarms and a nested hierarchy of schedules. 

Parallel Dynamics. Swarm has been designed to run efficiently on parallel machine architectures. While messages within one swarm schedule execute sequentially, different swarms can execute their schedules in parallel. 

Only one publication on gas-liquid mass transfer in bubble-column slurry reactors has come to the author s attention. However, a relatively large volume of information regarding mass transfer between single bubbles or bubble swarms and pure liquid containing no suspended solids is available, and this information is probably of some relevance to the analysis of systems... 

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