Wednesday, May 28, 2008


The term ecosystem was coined in 1930 by Roy Clapham, to denote the physical and biological components of an environment considered in relation to each other as a unit. British ecologist Arthur Tansley later refined the term, describing it as the interactive system established between biocoenosis (a group of living creatures) and their biotope (the environment in which they live).

Central to the ecosystem concept is the idea that living organisms are continually engaged in a set of relationships with every other element constituting the environment in which they exist. The human ecosystem concept is then grounded in the deconstruction of the human/nature dichotomy, and the emergent premise that all species are ecologically integrated with each other, as well as with the abiotic constituents of their biotope.

Tuesday, May 20, 2008

Ecological Systems Theory

Ecological Systems Theory, also called "Development in Context" or "Human Ecology" theory, specifies four types of nested environmental systems, with bi-directional influences within and between the systems. The theory was developed by Urie Bronfenbrenner, generally regarded as one of the world's leading scholars in the field of developmental psychology. Later a fifth system was added:

* Microsystem: Immediate environments (family, school, peer group, neighborhood, and childcare environments)
* Mesosystem: A system comprised of connections between immediate environments (i.e., a child’s home and school)
* Exosystem: External environmental settings which only indirectly affect development (such as parent's workplace)
* Macrosystem: The larger cultural context (Eastern vs. Western culture, national economy, political culture, subculture)
* Chronosystem: The patterning of environmental events and transitions over the course of life.

The person's own biology may be considered part of the microsystem; thus the theory has recently sometimes been called "Bio-Ecological Systems Theory." Each system contains roles, norms, and rules that can powerfully shape development.

Tuesday, May 13, 2008

Evolutionary robotics

Evolutionary Robotics (ER) is a methodology that uses evolutionary computation to develop controllers for autonomous robots. Algorithms in ER frequently operate on populations of candidate controllers, initially selected from some distribution. This population is then repeatedly modified according to a fitness function. In the case of genetic algorithms (or "GAs"), a common method in evolutionary computation, the population of candidate controllers is repeatedly grown according to crossover, mutation and other GA operators and then culled according to the fitness function. The candidate controllers used in ER applications may be drawn from some subset of the set of artificial neural networks, although some applications (including SAMUEL, developed at the Naval Center for Applied Research in Artificial Intelligence) use collections of "IF THEN ELSE" rules as the constituent parts of an individual controller. It is theoretically possible to use any set of symbolic formulations of a control laws (sometimes called a policies in the machine learning community) as the space of possible candidate controllers. It is worth noting that artificial neural networks can also be used for robot learning outside of the context of evolutionary robotics. In particular, other forms of reinforcement learning can be used for learning robot controllers.

Wednesday, May 07, 2008


Although having its origins in the late 1780s or earlier, the global standardisation of containers and container handling equipment was one of the important innovations in 20th century logistics.

By the 1830s, railroads on several continents were carrying containers that could be transferred to trucks or ships, but these containers were invariably small by today's standards. Originally used for shipping coal on and off barges, 'loose boxes' were used to containerize coal from the late 1780s, on places like the Bridgewater Canal. By the 1840's, iron boxes were in use as well as wooden ones. The early 1900s saw the adoption of closed container boxes designed for movement between road and rail.