Technology is the practical use of science, including the making, modification or improvement, applied activity or behavior, use and knowledge of tools, machines, techniques, crafts, systems, methods of organization, or environmental modifications or arrangement in order to solve a problem, improve a preexisting solution to a problem, achieve a goal or perform a specific function. It can also refer to the collection of such tools, machinery, modifications, environmental arrangement and procedures. Technologies significantly affect human as well as other animal species' ability to control and adapt to their natural environments. The word technology comes from Greek τεχνολογία (technología); from τέχνη (téchnē), meaning "art, skill, craft", and -λογία (-logía), meaning "study of-". The term can be applied either generally or to many specific areas, examples of which include construction technology, medical technology and information technology.
The human species' use of technology began with the conversion of natural resources into simple tools. The prehistorical discovery of the ability to control fire increased the available sources of food and the invention of the wheel helped humans in travelling in and controlling their environment. Recent technological developments, including the printing press, the telephone, and the Internet, have lessened physical barriers to communication and allowed humans to interact freely on a global scale. However, not all technology has been used for peaceful purposes; the development of weapons of ever-increasing destructive power has progressed throughout history, from clubs to nuclear weapons.
Technology has affected society and its surroundings in a number of ways. In many societies, technology has helped develop more advanced economies (including today's global economy) and has allowed the rise of a leisure class. Many technological processes produce unwanted by-products, known as pollution, and deplete natural resources, to the detriment of the Earth and its environment. Various implementations of technology influence the values of a society and new technology often raises new ethical questions. Examples include the rise of the notion of efficiency in terms of human productivity, a term originally applied only to machines, and the challenge of traditional norms.
Philosophical debates have arisen over the present and future use of technology in society, with disagreements over whether technology improves the human condition or worsens it. Neo-Luddism, anarcho-primitivism, and similar movements criticise the pervasiveness of technology in the modern world, opining that it harms the environment and alienates people; proponents of ideologies such as transhumanism and techno-progressivism view continued technological progress as beneficial to society and the human condition. Indeed, until recently, it was believed that the development of technology was restricted only to human beings, but recent scientific studies indicate that other primates and certain dolphin communities have developed simple tools and learned to pass their knowledge to other generations.
A mechanical filter
is a signal processing filter
usually used in place of an electronic filter
at radio frequencies
to allow a range of signal frequencies to pass, but to block others. The filter acts on mechanical vibrations. Transducers
at the input and output of the filter convert the electrical signal into, and then back from, these mechanical vibrations. The mechanical elements obey mathematical functions which are identical to their corresponding electrical elements. Electrical theory has developed a large library of mathematical forms that produce useful filter frequency responses
for use in the design of mechanical filters. Steel
alloys are common materials for mechanical filter components. Resonators in the filter made from these materials need to be machined to precisely adjust their resonance frequency
prior to final assembly. The high "quality factor", Q
, that mechanical resonators can attain, far higher than that of an all-electrical LC circuit
, made possible the construction of mechanical filters with excellent selectivity
. Good selectivity, being important in radio receivers
, made such filters highly attractive. Contemporary researchers are working on microelectromechanical filters, the mechanical devices corresponding to electronic integrated circuits.
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Otto Julius Zobel
(1887–1970) was a design engineer who worked for the American Telephone & Telegraph Company (AT&T)
in the early part of the 20th century. Zobel's work on filter design was revolutionary and led, in conjunction with the work of John R. Carson
, to significant commercial advances for AT&T in the field of frequency division multiplex
(FDM) telephone transmissions. Although much of Zobel's work has been superseded by more modern filter designs, it remains the basis of filter theory and his papers are still referenced today. Zobel invented the m-derived filter
and the constant-resistance filter
, which remains in use. Zobel and Carson helped to establish the nature of noise in electric circuits, concluding that—contrary to mainstream belief—it is not even theoretically possible to filter out noise entirely and that noise will always be a limiting factor in what it is possible to transmit. Thus, they anticipated the later work of Claude Shannon
, who showed how the theoretical information rate of a channel is related to the noise of the channel.
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