Iztok Lebar Bajec

Organized flight in birds

The organized flight of birds is one of the most easily observed, yet challenging to study, phenomena in biology. Birds that fly in organized groups generally do so in one of two fashions: Line formations and Cluster formations. The former groups are typical of large birds such as waterfowl, where birds fly arranged in single lines, often joined together. The scientific questions about these groups usually involve potential adaptive functions, such as why geese fly in a V. Cluster formations are typically made up of large numbers of smaller birds such as pigeons or starlings flying in more irregular arrangements that have a strong three-dimensional character. The groups are defined by synchronized and apparently simultaneous rapid changes in direction. Scientific questions about these groups are usually concerned with mechanism such as how synchrony is achieved. Although field observations about the phenomenon date to the origins of natural history, experimental studies did not begin until the 1970s. Early experimenters and theoreticians were primarily biologists, but more recently aeronautical engineers, mathematicians, computer scientists and, currently, physicists have been attracted to the study of organized flight. Computer modelling has recently generated striking visual representations of organized flight and a number of hypotheses about its functions and mechanisms, but the ability to test these hypotheses lags behind the capacity to generate them. We suggest that a multi disciplinary approach to the phenomenon will be necessary to resolve apparently conflicting current hypotheses.

Fuzzy cellular automata: from theory to applications

In this paper we present a fuzzified cellular automata structure called fuzzy cellular automata. We begin our paper with a fuzzified entity called fuzzy automaton, then we present basics of cellular automata and finally we define fuzzy cellular automata. At the end we present some simulation results from the field of fire spread in homogeneous nature environment.

Solving the ternary QCA logic gate problem by means of adiabatic switching

This paper demonstrates that with the introduction of adiabatic switching one can successfully solve the ternary quantum-dot cellular automata (QCA) problem of the basic geometry that implements the AND and OR logic functions. It is shown that in that case the geometry can perform both the binary majority logic function as well as ternary AND and OR logic functions.

Solving the Ternary Quantum-Dot Cellular Automata Logic Gate Problem by Means of Adiabatic Switching

Quantum-dot cellular automata (QCA) are one of the most promising alternative platforms of the future. Recent years have witnessed the development of basic logic structures as well as more complex processing structures, however most in the realm of binary logic. On the grounds that future platforms should not disregard the advantages of multi-valued logic, Lebar Bajec et al. were the first to show that quantum-dot cellular automata can be used for the implementation of ternary logic as well. In their study the ternary AND and OR logic functions proved to be the most troublesome primitive to implement. This research presents a revised solution that is based on adiabatic switching.

Fuzzifying the thoughts of animats

In this article we present a fuzzy logic based method for the construction of thoughts of artificial animals (animats). Due to the substantial increase of the processing power of personal computers in the last decade there was a notable progress in the field of animat construction and simulation. Regardless of the achieved results, the coding of the animats behaviour is very inaccurate and can, to someone not familiar with common physics variables like speed, acceleration, banking, etc., seem like pure black magic. Our leading hypothesis is, that by using linguistic programming based on common sense, unclear and even partially contradictory knowledge of dynamics, we can achieve comparable, if not better, simulation results. We begin the article with the basics of animats, continue with their fuzzyfication and end with the presentation and comparison of simulation results.

Quantum-Dot Cellular Automata Serial Comparator

The quantum-dot cellular automata (QCA) are one of the few alternative computing platforms that meet most of the criteria desired for computing platforms of the future. One of the basic concepts that has popularized the QCA platform to computer designers is adiabatic pipelining, which implicitly assures the correct data flow and in this view simplifies digital design. When designing QCA devices this should be taken advantage of instead of copying digital device designs that were optimized for the CMOS technology. One of the basic digital devices and probably a vital part of many modern computing platforms is the comparator. We here present a novel approach to comparator design, which takes advantage of adiabatic pipelining. Our analysis was based on the QCADesigner tool.

Two-layer synchronized ternary quantum-dot cellular automata wire crossings

AbstractQuantum-dot cellular automata are an interesting nanoscale computing paradigm. The introduction of the ternary quantum-dot cell enabled ternary computing, and with the recent development of a ternary functionally complete set of elementary logic primitives and the ternary memorizing cell design of complex processing structures is becoming feasible. The specific nature of the ternary quantum-dot cell makes wire crossings one of the most problematic areas of ternary quantum-dot cellular automata circuit design. We hereby present a two-layer wire crossing that uses a specific clocking scheme, which ensures the crossed wires have the same effective delay.

The Ternary Quantum-dot Cellular Automata Memorizing Cell

Quantum-dot Cellular Automata (QCA) were demonstrated to be a possible candidate for the implementation of a future multi-valued processing platform. Recent papers show that the introduction of adiabatic switching and the elegant application of the adiabatic pipelining concept in the QCA logic design can be used to efficiently solve the issues of the elementary ternary QCA logic primitives. The architectures of the resulting ternary QCAs become similar to their binary counterparts and thus the design rules for large circuit design remain similar to those developed for the binary QCA domain. In spite of this the design of the binary QCA SR memorizing cell cannot be directly transferred to the ternary domain, mostly because the control logic cannot properly handle the third value. We here propose a ternary QCA memorizing cell that efficiently exploits the pipelining mechanism at a wire level. It is centered on the circulating memory model (i.e. the memory in motion concept), which proved to be an efficient concept in memorizing cell design in the binary QCA domain. The proposed memorizing cell is capable of serving as one trit (ternary digit) of memory and represents a step forward to the ternary register, one of the basic building blocks of a ternary processor.

Quantum-dot Field Programmable Gate Array: enhanced routing

FPGA (field programmable gate array) architecture contains configurable logic blocks (CLB) and programmable interconnects. CLB is used to implement most of the logic in FPGA. A hierarchy of programmable interconnects called programmable switch matrix (PSM) allows the logic blocks of FPGA to be interconnected as needed by the system designer. Logic blocks and interconnects can be programmed after the manufacturing process by the customer/designer so that FPGA can perform whatever logical function is needed. Wherever a vertical and a horizontal line intersect there is a switch matrix interconnect point. In this article FPGA based on quantum-dot cellular automata (QCA) technology is presented. The research is dedicated mostly to PSM.

Simulated predator attacks on flocks: A comparison of tactics

It is not exactly known why birds aggregate in coordinated flocks. The most common hypothesis proposes that the reason is protection from predators. Most of the currently developed examples of individual-based predator-prey models assume predators are attracted to the center of a highly coordinated flock. This proposed attraction of a predator to a flock would appear to be contradictory to an alternate hypothesis that flocks evolved as a protection against predation. In an attempt to resolve this apparent conflict, in this article we use a fuzzy individual-based model to study three attack tactics (attack center, attack nearest, attack isolated) and analyze the success of predation on two types of prey (social and individualistic). Our simulations revealed that social flocking (as opposed to individualistic behavior) is the optimal anti-predatory response to predators attacking mainly isolated individuals.