摘要:

Current injection lasers operating in the blue and blue–green spectral regions have recently been fabricated from II–VI semiconductors. In this paper, the current status of these devices is assessed and the materials developments leading to their production are described.

ISSN:0010-7514    

DOI:10.1080/00107519608217541

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

In the last two decades, space and ground-based observations have revolutionized our understanding of the remnants of stellar evolution, the white dwarf stars. We now have a detailed picture of the evolution of the surface composition of hot white dwarfs, those objects with temperatures above about 20 000 K, as they cool. Significant quantities of heavy elements are supported by radiation pressure against the downward pull of gravity in the very hottest examples (above 40 000 K) but, once the efficiency of the mechanism diminishes below 40 000 K, they fall rapidly out of the atmosphere. However, while the observational results are qualitatively consistent with the predictions of theoretical calculations, the measured element abundances differ substantially from those expected. A viable explanation, supported by good observational evidence, is that the surface composition is further modified through the loss of material in a weak wind. This paper reviews recent developments, made in particular with the International Ultraviolet Explorer, Roentgen Satellit and Extreme Ultraviolet Explorer, setting them in the context of our earlier picture of white dwarf evolution to show the important advances made.

ISSN:0010-7514    

DOI:10.1080/00107519608217542

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Recent theoretical results confirm that quantum theory provides the possibility of new ways of performing efficient calculations. The most striking example is the factoring problem. It has recently been shown that computers that exploit quantum features could factor large composite integers. This task is believed to be out of reach of classical computers as soon as the number of digits in the number to factor exceeds a certain limit. The additional power of quantum computers comes from the possibility of employing a superposition of states, of following many distinct computation paths and of producing a final output that depends on the interference of all of them. This ‘quantum parallelism’ outstrips by far any parallelism that can be thought of in classical computation and is responsible for the ‘exponential’ speed-up of computation.

ISSN:0010-7514    

DOI:10.1080/00107519608217543

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Remote sensing is the popular name for the measurement of physical quantities at a distance, usually by quantitative spectroscopic methods. Its application to the study of the Earth's atmosphere and surface from satellites is a rapidly growing field, with many applications, and new or improved techniques are constantly being developed. In this article we look at some of the basic principles and technical challenges involved, and at the benefits which are accruing in a number of research areas in earth science, with particular emphasis on the use of remote sensing to understand global change.

ISSN:0010-7514    

DOI:10.1080/00107519608217544

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

ISSN:0010-7514    

DOI:10.1080/00107519608217545

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

ISSN:0010-7514    

DOI:10.1080/00107519608217546

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

ISSN:0010-7514    

DOI:10.1080/00107519608217547

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Basic Training in Mathematics: A Fitness Program for Science Students By R. SHANKAR 1995, US$47·50 (hbk), xv+365. Plenum, ISBN 0306450356. Scope: textbook. Level: first and second-year undergraduate.

ISSN:0010-7514    

DOI:10.1080/00107519608217548

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

ISSN:0010-7514    

DOI:10.1080/00107519608217549

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor