摘要:

This article deals with the way in which vertebrate, and in particular primate, visual systems are organized for the detection of spatially distributed light stimuli, i.e. for form perception. The principles of this organization are of concern to physicists who design and employ pattern recognition machines for various purposes, as well as to those who are directly concerned with psychophysical studies of visual perception. A brief description of the anatomy and histology of the retina and the central visual pathways is given. The electrical responses of the nerve cells (neurones) which make up the neural networks of the visual system are then examined in two particular cases, namely, the frog and the primate. Maturana and his colleagues have shown that in the frog, the retinal ganglion cells are selectively responsive to a small number of geometric features of the retinal image, and that the responses of tho different clssses of ganglion cell are relayed to different layers of neurones in the mid-brain. ‘Feature extraction’ also appears to occur in primate vision, but in this case it is observed primarily in the responses of cortical neurones.

ISSN:0010-7514    

DOI:10.1080/00107517508210817

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

Any assessment of resources naturally depends on the definition of the word: one man's meat is another's poison: Britain as a society cries out for all kinds of materials and sources of energy while the ordinary Afghan can exist reasonably well on a bountiful supply of water and fertiliser. With the world population increasing, and with a shift toward a more egalitarian usage of resources, it is to be expected that a serious shortage of most things may occur by the year 2000. Such a situation requires a re-thinking of Man's needs and sources of supply. One inevitable solution has been the ‘cornucopia’ of the sea: the marine environment, so the argument runs, can provide most of the energy requirements through the vast submarine deposits of the fossil fuels (oil, gas and coal) and by harnessing the tides, while a wide range of minerals (send and gravel, tin, diamonds, manganese, copper, etc.) seem to exist to serve material needs. But is this fact or fancy? Undoubtedly, a resource wealth does exist within and beneath the sea, but in exploration and exploitation present technologies will be strained to the limits. And in so doing will another resource—the environment itself—be destroyed?

ISSN:0010-7514    

DOI:10.1080/00107517508210818

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

The magnetic impurity problem is that transition metal impurities are magnetic in some, but not all, simple metal solvents. There is a whole spectrum of anomalous effects associated with the occurrence of magnetism (as defined in Section 2), particularly in the temperature variation of the low temperature resistivity, the size of the thermo power, and a drastic effect on the superconductivity of the solvent. The magnetic impurity problem became the Kondo problem when Kondo in 1964 explained these anomalies in terms of repeated spin flip scattering between the impurity and the host conduction electrons. It was soon realized that the presence or absence of magnetism was itself intimately tied up with the multiple spin scattering, and that the division between magnetic and non-magnetic is not as sharp as had been thought. The problem has now achieved a certain unity, largely because careful experiments have shown that physically these systems are always well-behaved, but its rigorous theoretical resolution still remains as a difficult task.

ISSN:0010-7514    

DOI:10.1080/00107517508210819

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

Within the last 25 years, the precision with which many physical measurements can be made has increased dramatically. The place of measurement in establishing physical ideas is considered and examples of the use of very precise measurements in fundamental studies are given. Modern engineering is largely dependent on accurate, convenient measurements in design, construction and communication, and modern measurements depend on quantum standards of frequency, wavelength, voltage and others. The very precise measurements that these techniques make possible have many applications; examples arc taken from the study of the structure of matter, from geophysics and astronomy.

ISSN:0010-7514    

DOI:10.1080/00107517508210820

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

Course on the Stationary and Quasi-Stationary Toroidal Reactors. (Commission of the European Community, Luxembourg, 1973.) [Pp. 489.] B.Fr. 500 (approx. £5.75).

ISSN:0010-7514    

DOI:10.1080/00107517508210821

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

ISSN:0010-7514    

DOI:10.1080/00107517508210822

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor