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101.
102.
S. A. J. Upton A. R. Holt G. J. G. Upton 《International Journal of Satellite Communications and Networking》1987,5(3):249-260
Over one hundred hours of British Telecom's half-second event data from the OTS and ATS-6 satellites has been analysed with respect to short-term frequency scaling of attenuation. The ratio of attenuation at two frequencies is particularly vulnerable to system effects and noise. Data analysis techniques are discussed and it is shown that a least-squares analysis is not suitable when the time period is short. Appreciable variation occurred in the mean value of the short-term ratio from one event to another. Only on a few occasions did significant changes occur during an event. Simultaneous data from other equipment gives confidence that these changes are due to propagation effects. 相似文献
103.
The error rate in active sonar is given for binary non-coherent frequency shift keying (FSK) in slow and non-selective Rayleigh fading (multipath) and additive non-Gaussian reverberation noise. The improvement achieved by using time-diversity is derived from the expression for the probability of error. It is shown that for error probabilities of the order of 10?5 the improvement factor is 10 dB. 相似文献
104.
First SIR-C ScanSAR results 总被引:1,自引:0,他引:1
Chang C.Y. Jin M.Y. Yun-Ling Lou Holt B. 《Geoscience and Remote Sensing, IEEE Transactions on》1996,34(5):1278-1281
During the two space shuttle missions in 1994, the Space-borne Imaging Radar-C (SIR-C) acquired several experimental datatakes: using the ScanSAR mode. Same of these ScanSAR data have been processed into images of swath wider than 200 km. Example images are shown. These early results demonstrate that ScanSAR operation is not only feasible, but also represents a potentially useful tool for regional and global scale imaging by the future SAR missions 相似文献
105.
This paper examines the outage probabilities of BPSK and BPSK/DFE radio modems with omnidirectional and six-sector antennas. The effects of room size, data rate, transmitted power and sector antenna patterns on the performance of the systems are analyzed. A 2-D ray tracing algorithm is used to model the radio propagation in a typical indoor environment used for wireless LAN applications. The parameters of the radio propagation model are adjusted to fit the results of simulations to the results of empirical measurements with omnidirectional antenna. It is shown that in a line-of-sight (LOS) environment, a six-sector antenna is more effective than a DFE with an omnidirectional antenna at eliminating the effects of multipath. For an obstructed-line-of-sight (OLOS) environment where at least one wall exists between the transmitter and the receiver, the DFE is more effective than the six-sector antenna. It is shown that a BPSK/DFE modem with a six-sector antenna can support data rates close to 20 Mbps 相似文献
106.
107.
M. A. Forbes J. N. Holt A. M. Watts 《The Journal of the Operational Research Society》1994,45(2):143-150
In this paper, a network transportation model is developed for determining the minimum cost recontouring of the surface of a spoil pile created in open cut coal mining operations to achieve a prespecified target surface. A fast algorithm for the resulting large-scale, highly dense transportation problem is presented. Computational experience on test data is presented and practical application to real data is illustrated. 相似文献
108.
Bulten HJ Anthony PL Arnold RG Arrington J Beise EJ Belz E van Bibber K Bosted PE van den Brand JF Chapman MS Coulter KP Dietrich FS Ent R Epstein M Filippone BW Gao H Gearhart RA Geesaman DF Hansen J Holt RJ Jackson HE Jones CE Keppel CE Kinney E Kuhn SE Lee K Lorenzon W Lung A Makins NC Margaziotis DJ McKeown RD Milner RG Mueller B Napolitano J Nelson J O'Neill TG Papavassiliou V Petratos GG Potterveld DH Rock SE Spengos M Szalata ZM Tao LH White JL Zeidman B 《Physical review letters》1995,74(24):4775-4778
109.
Feili Lai Nan Chen Xiaobin Ye Guanjie He Wei Zong Katherine B. Holt Bicai Pan Ivan P. Parkin Tianxi Liu Renjie Chen 《Advanced functional materials》2020,30(11)
Electrocatalytic nitrogen reduction reaction (NRR) and hydrogen evolution reaction (HER) are intriguing approaches to nitrogen fixation and hydrogen production under ambient conditions, given the need to discover efficient and stable catalysts to light up the “green chemistry” future. However, bottlenecks are often found during N2/H2O activation, the very first step of NRR/HER, due to energetic electron injection from the surface of electrocatalysts. It is reported that the bottlenecks for both NRR and HER can be tackled by engineering the energy level via low‐valent transition‐metal doping, simultaneously, where rhenium disulfide (ReS2) is employed as a model platform to prove the concept. The doped low‐valent transition‐metal domains (e.g., Fe, Co, Ni, Cu, Zn) in ReS2 provide more active sites for N2/H2O chemisorption and electron transfer, not only weakening the N?N/O? H bonds for easier dissociation through proton coupling, but also elevating d‐band center toward the Fermi level with more electron energy for N2/H2O reduction. As a result, it is found that iron‐doped ReS2 nanosheets wrapped nitrogen‐doped carbon nanofiber (Fe‐ReS2@N‐CNF) catalyst exhibits superior electrochemical activity with eightfold higher ammonia production yield of 80.4 µg h?1 mg?1cat., and lower onset overpotential of 146 mV and Tafel slope of 63 mV dec?1, when comparing with the pristine ReS2. 相似文献