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131.
132.
Peter Nijkamp 《突发事故与危机管理杂志》1994,2(1):1-9
This paper gives an overview of social science challenges in global environmental research. After a sketch of backgrounds, the ‘social dilemma’ is introduced as a major research question. It is asserted that current uncertainties over global environmental change provoke innovative studies on risk behaviour and management of long-range, largely unpredictable, phenomena. Various illustrations of new research initiatives and directions are given. 相似文献
133.
EuLisp has an integrated object system with reflective capabilities. We discuss some example applications which use these facilities to experiment with some advanced and powerful concepts, namely, finalization, virtual shared memory and persistence. A secondary goal is to attempt to illustrate the additional possibilities of metaobject programming over non-metalevel techniques. 相似文献
134.
G. É. Tsyrlin N. P. Korneeva V. N. Demidov N. K. Polyakov V. N. Petrov N. N. Ledentsova 《Semiconductors》1997,31(10):1057-1059
A specially developed detection system and an analysis of RHEED diffraction patterns were used to investigate the dynamics
of transition from two-dimensional to three-dimensional growth mechanism in the heteroepitaxial InAs/GaAs system. An analysis
of the dynamics of the diffraction patterns was used for the first time to investigate the dynamics of formation of quantum
dots. A time shift in the dynamic behavior of the diffracted intensity for diffraction patterns recorded at different angles
was found. This shift is explained in terms of the size differences in the three-dimensional islands at the initial stage
of decay of the pseudomorphic layer. InAs/GaAs quantum dots grown under certain conditions produce reflections at 45° relative
to the principal reflections. This is evidence for the ordering of islands in the [001] and [010] crystallographic directions.
Fiz. Tekh. Poluprovodn. 31, 1230–1232 (October 1997) 相似文献
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138.
Peter J. McAlindon 《Computers & Industrial Engineering》1992,23(1-4):205-207
Enhancing the way people use computers to perform tasks has become a very important issue in interface design and human-computer interactions. When the concept of human-computer interaction first began to emerge it was commonly understood as the hardware and software through which a human and computer could effectively communicate (Laurel, 1990). This effective communication is also know as user-friendliness. The concept of user friendliness has recently been expanded to include various attributes and cognitive aspects of the user's needs and experiences. Focus should be on the user's experiences, expectations, preferences, and cognitive aspects in developing efficient and effective computer interface designs. It is the basic premise of this paper to emphasize using a user-centered design in developing computer interfaces. 相似文献
139.
When using a conventional demodulator, a sufficient condition to maintain ODS-CDMA codeword orthogonality is constant relative channel amplitude over the codeword duration. When transmitted over a memoryless, AM/PM nonlinearity channel, the chip-to-chip fluctuating amplitude of a composite ODS-CDMA QPSK waveform produces a chip-to-chip fluctuating phase that deorthogonalizes the ODS-CDMA codewords, resulting in an additional multiple access self-interference similar to that found in asynchronous DS-CDMA. For ODS-CDMA QPSK in an AM/PM nonlinearity channel, we utilize the Central Limit Theorem, derive, and evaluate: (i) an expression for the signal-to-distortion ratio at the demodulator output, (ii) an expression for the uncoded bit error probability, and (iii) an upper bound on the convolutionally-coded bit error probability. We find that the degradation to BER depends on both the AM/PM nonlinearity slope and the ODS-CDMA channel loading. 相似文献
140.
John K. Montgomery Peter L. Drzal Kenneth R. Shull K. T. Faber 《Journal of the American Ceramic Society》2002,85(5):1164-1168
A new ceramic processing method, thermoreversible gelcasting (TRG), has been developed. The method uses a gelation process that can be reversed multiple times. Two Al2 O3 systems have been explored with the use of a specific triblock copolymer to form a binding gel network. The mixture becomes a free-flowing liquid on heating above 60°C. However, on cooling below 60°C, the slurry instantaneously transforms to a physical gel. This process can be reversed easily (essentially with an infinite processing time window) while the solvent is present in the system, which is advantageous when trying to produce high-quality dense pieces if initial casting irregularities occur. Near-theoretically dense specimens have been produced with properties consistent with reported values of high-density Al2 O3 . 相似文献