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161.
经过多年的酝酿,移动WiMAX终于成为一种为网络运营商提供高速数据传输服务的可行方式。近几个月来,一些运营商开始部署这种技术,但是语音服务的欠缺很可能会降低移动WiMAX短期内对客户的吸引力。另外,一些长期性问题依旧悬而未决。例如,运营商将怎样在移动语音技术环境下提供基于移动WiMAX的数据服务?发展 相似文献
162.
163.
Non-treeability for product group actions 总被引:1,自引:0,他引:1
Greg Hjorth 《Israel Journal of Mathematics》2008,163(1):383-409
A product of two lcsc non-compact groups G
1 × G
2 acting freely by measure preserving transformation on a standard Borel probability space gives rise to a non-treeable equivalence
relation unless both groups are amenable.
Partially supported by NSF grant DMS 0140503 相似文献
164.
The compatibility of the switched-capacitor technique with standard digital CMOS processes utilising MOSFET gate capacitance has recently been investigated. Owing to its high voltage-dependence, a technique for enhancing linearity which is suitable for non-delay-free circuits is proposed. The technique was verified by simulation to demonstrate its effectiveness for linearity improvement 相似文献
165.
Corey L. Jones Colan E. Hughes Hamish H.-M. Yeung Alison Paul Kenneth. D. M. Harris Timothy L. Easun 《Chemical science》2021,12(4):1486
The formation processes of metal–organic frameworks are becoming more widely researched using in situ techniques, although there remains a scarcity of NMR studies in this field. In this work, the synthesis of framework MFM-500(Ni) has been investigated using an in situ NMR strategy that provides information on the time-evolution of the reaction and crystallization process. In our in situ NMR study of MFM-500(Ni) formation, liquid-phase 1H NMR data recorded as a function of time at fixed temperatures (between 60 and 100 °C) afford qualitative information on the solution-phase processes and quantitative information on the kinetics of crystallization, allowing the activation energies for nucleation (61.4 ± 9.7 kJ mol−1) and growth (72.9 ± 8.6 kJ mol−1) to be determined. Ex situ small-angle X-ray scattering studies (at 80 °C) provide complementary nanoscale information on the rapid self-assembly prior to MOF crystallization and in situ powder X-ray diffraction confirms that the only crystalline phase present during the reaction (at 90 °C) is phase-pure MFM-500(Ni). This work demonstrates that in situ NMR experiments can shed new light on MOF synthesis, opening up the technique to provide better understanding of how MOFs are formed.A new in situ NMR methodology for studying the formation processes of MOFs is reported, supported by SAXS and PXRD experiments. Synthesis of a phosphonate-based MOF is described, from molecular aggregation through to nucleation and crystallisation. 相似文献
166.
J Deistung D M Forde J P O'Connell K A Proudfoot D Eaton F Willenbrock R O Kingaby B Hughes S Angal C Catterall 《Journal of chromatography. A》1991,539(2):485-492
Recombinant DNA technology has been employed to produce a hybrid gene in which the kringle and serine protease domains of tissue plasminogen activator are linked to the heavy-chain Fd region of a fibrin-specific antibody. The hybrid gene is co-expressed with antibody light chains. This communication describes a purification procedure for the hybrid protein, involving affinity and ion-exchange chromatography. The purified hybrid protein has been used in vivo and in vitro clot lysis experiments and has been shown to be effective at clot dissolution. 相似文献
167.
A new analysis of free riding on the Gnutella network updates data from 2000 and points to an increasing downgrade in the network's overall performance and the emergence of a "metatragedy" of the commons. Individuals who use peer-to-peer (P2P) file-sharing networks such as Gnutella face a social dilemma. They must decide whether to contribute to the common good by sharing files or maximize their personal experience by free riding, downloading files while not contributing any to the network. Individuals gain no personal benefits from uploading files (in fact, it's inconvenient), so it's "rational" for users to free ride. However, significant numbers of free riders degrade the entire system's utility, creating a "tragedy of the digital commons." 相似文献
168.
The modelocking of a Nd:YAG laser using second-harmonic generation in an external cavity as the only pulse shortening process is reported. The output of a long pulse Nd:YAG laser was simultaneously modelocked and Q-switched. The average pulse duration was 30–50 ps and the peak power was in the range 60–160 kW. 相似文献
169.
170.