They wrote " History, as Hegel said, moves upward in a spiral of negations ," and that " punctuated equilibria is a model for discontinuous tempos of change ( in ) the process of speciation and the deployment of species in geological time.

Actual deflation was prevented because supply shocks are not the only cause of inflation ; in terms of the modern triangle model of inflation, supply-driven deflation was counteracted by demand-pull inflation and built-in inflation resulting from adaptive expectations and the price / wage spiral.

There are four main media influence theories: hypodermic needle model ( 1930s behaviorism ), two-step flow model ( Katz and Lazarsfeld, 1955 ), limited effects ( Klapper, 1960 ), and the spiral of silence ( Noelle-Neumann, 1984 ).

According to this model, the two stars in a binary slowly spiral towards each other due to the release of energy via gravitational radiation until the neutron stars suddenly rip each other apart due to tidal forces and collapse into a single black hole.

After descending a narrow spiral stone stairwell of 19 metres to the darkness and silence broken only by the gurgling of a hidden aqueduct channelling local springs away from the area, and after passing through a long ( about 1. 5 km ) and twisting hallway of mortared stone, visitors find themselves before a sculpture that existed from a time before this part of the mines became an ossuary, a model of France's Port-Mahon fortress created by a former Quarry Inspector.

The spiral model is a software development process combining elements of both design and prototyping-in-stages, in an effort to combine advantages of top-down and bottom-up concepts.

Also known as the spiral lifecycle model ( or spiral development ), it is a systems development method ( SDM ) used in information technology ( IT ).

The spiral model is intended for large, expensive and complicated projects.

The spiral model was defined by Barry Boehm in his 1986 article " A Spiral Model of Software Development and Enhancement ".

The spiral model also explicitly includes risk management within software development.

The spiral model is based on continuous refinement of key products for requirements definition and analysis, system and software design, and implementation ( the code ).

The spiral lifecycle model allows for elements of the product to be added in when they become available or known.

Another positive aspect is that the spiral model forces early user involvement in the system development effort.

The spiral model is mostly used in large projects.

The military had adopted the spiral model for its Future Combat Systems program.

The spiral model thus may suit small ( up to $ 3 million ) software applications and not a complicated ($ 3 billion ) distributed, interoperable, system of systems.

Also it is reasonable to use the spiral model in projects where business goals are unstable but the architecture must be realized well enough to provide high loading and stress ability.

For example, the Spiral Architecture Driven Development is the spiral based Software Development Life Cycle ( SDLC ) which shows one possible way how to reduce the risk of non-effective architecture with the help of a spiral model in conjunction with the best practices from other models.

The organized peasant and indigenous based agrarian movements ( i. e. the Via Campesina ) consider that only by changing the export-led, free-trade based, industrial agriculture model of large farms can the downward spiral of poverty, low wages, rural-urban migration, hunger and environmental degradation be halted.

A more refined model also includes a series inductance, to represent the effects of its lead inductance ( resistors constructed as a spiral have more significant inductance ).

Edison's early patents show that he also considered the idea that sound could be recorded as a spiral onto a disc, but Edison concentrated his efforts on cylinders, since the groove on the outside of a rotating cylinder provides a constant velocity to the stylus in the groove, which Edison considered more " scientifically correct ".

This notion was an underpinning for his concept of the spiral curriculum which posited the idea that a curriculum should revisit basic ideas, building on them until the student had grasped the full formal concept.

Some of the criticism focused on the idea that the building overshadows the artworks displayed inside, and that it is difficult to properly hang paintings in the shallow, windowless, concave exhibition niches that surround the central spiral.

He realized that the idea of stars arranged permanently in a spiral shape was untenable.

Mr. Reum came up with the idea as he was playing with different techniques to produce a spiral hose for watering plants.

Tests were performed on Schauberger's specially designed copper pipes, which had a conical, spiral, rifled shape, with apparent success confirming Schauberger's idea.

In the fourth of his Norton lectures of 1958 – 59, titled " Repetition in Music " ( Chávez 1961, 55 – 84 ), he described a mode of composition already observable in many of his compositions since the 1920s, in which " The idea of repetition and variation can be replaced by the notion of constant rebirth, of true derivation: a stream that never comes back to its source ; a stream in eternal development, like a spiral …" ( Chávez 1961, 84 ).

The idea behind this scheme was that drivers were supposed to enter the clockwise only roundabout, go to the center and then, about two exits before their chosen exits get into a lane that would spiral them off.

The spiral idea failed, as many drivers ignored the lane markings, while those who followed the spiral tended to accelerate as they went round.

In 2008, Lake Superior State University included " X is the new Y " on their annual " Banished Words List ", stating, " The idea behind such comparisons was originally good, but we've all watched them spiral out of reasonable uses into ludicrous ones and it's now time to banish them from use.

Having just read Fred Hoyle's book The Nature of the Universe, he had the idea that Longman's design resembled a spiral galaxy.

… this approach, the ultimate capability delivered to the user is divided into two or more blocks, with increasing increments of capability ... software development shall follow an iterative spiral development process in which continually expanding software versions are based on learning from earlier development.

A spiral drawn with an iterative turtle-graphics algorithm

… this approach, the ultimate capability delivered to the user is divided into two or more blocks, with increasing increments of capability ... software development shall follow an iterative spiral development process in which continually expanding software versions are based on learning from earlier development.

Dr. Richard Spademan saw 150 spiral fractures pass through his emergency department near Squaw Valley in three days, an event that led to the development of the Spademan binding.

Yet development costs were allowed to spiral out of control, almost forcing Fokker out of business in 1987.

Beginning in the fifth week of development, the auditory vesicle also gives rise to the cochlear duct, which contains the spiral organ of Corti and the endolymph that accumulates in the membranous labyrinth.

Early in the development of the Compact Disc, engineers realized that the perfection of the spiral of bits was critical to playback fidelity.

Boehm also created the spiral model of software development, in which the phases of development are repeatedly revisited.

Currently, a spiral curriculum is promoted as allowing students to revisit a subject matter's content at the different levels of development of the subject matter being studied.

An interpretation of social and psychological development that could also be considered a theory of spiritual evolution is spiral dynamics, based on the work of Clare W. Graves.

To manage this level of complexity, a number of SDLC models or methodologies have been created, such as " waterfall "; " spiral "; " Agile software development "; " rapid prototyping "; " incremental "; and " synchronize and stabilize ".

A number of system development life cycle ( SDLC ) models have been created: waterfall, fountain, spiral, build and fix, rapid prototyping, incremental, and synchronize and stabilize.