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排序方式: 共有662条查询结果,搜索用时 15 毫秒
71.
Robust wireless location over fading channels 总被引:4,自引:0,他引:4
Yousef N.R. Sayed A.H. Jalloul L.M.A. 《Vehicular Technology, IEEE Transactions on》2003,52(1):117-126
This paper develops an estimation algorithm for the time and amplitude of arrival of a known transmitted sequence over a single-path fading channel. The algorithm is optimized to enhance robustness to fast channel fading and low signal-to-noise ratio (SNR) conditions, which are common in wireless location applications. The paper also presents a noise and fading bias correction technique for amplitude of arrival estimation that improves the estimation accuracy significantly. The proposed algorithm is then applied to the case of code-division multiple-access (CDMA) wireless location finding for which the paper gives simulation results that demonstrate significant estimation accuracy improvement over known algorithms. 相似文献
72.
Shared memory is a simple yet powerful paradigm for structuring systems. Recently, there has been an interest in extending this paradigm to non-shared memory architectures as well. For example, the virtual address spaces for all objects in a distributed object-based system could be viewed as constituting a global distributed shared memory. We propose a set of primitives for managing distributed shared memory. We present an implementation of these primitives in the context of an object-based operating system as well as on top of Unix. 相似文献
73.
A continuous release of cesium-134 and strontium-85 into a simulated river system was maintained for more than 3 weeks for the purpose of evaluating the influence of photosynthetic oxygen production on cesium and strontium uptake. The flow rates and radioisotope concentration were maintained at a constant input throughout the experiment.The flow through time in the model river system was 6 h. Samples were taken from various stations every 4 h over a 36 h time interval. Temperature, dissolved oxygen, as well as other routine measurements were made. Samples were processed for plankton count and radioactivity in both the suspended phytoplankton and the water.The uptake of 134Cs by phytoplankton was related to diurnal photosynthetic production of oxygen and a linear relationship exists between rate of change in 134Cs concentration and the rate of net photosynthetic oxygen production. 相似文献
74.
B Sammak B Yousef M Abd El Bagi M Al Karawi A Mohamed M Gali M Al Shahed 《Canadian Metallurgical Quarterly》1998,45(22):1097-1099
We report two cases of needle track seeding in the subcutaneous tissue and intercostal muscles following percutaneous ethanol injection for the treatment of hepatocellular carcinoma. In one patient, tumor seeding was observed 11 months after a total of 12 alcohol injections, and in the other patient, tumor seeding was observed 30 months after a total of 18 alcohol injections. The cases reported in the literature are discussed. 相似文献
75.
The aim of this study was to determine the impact of the broadening of fuel specifications on the performance of a gas turbine combustor, particularly on soot formation and oxidation, and flame tube durability. Tests were conducted with a fully-developed combustor system, the main measurements comprising total radiation, exhaust smoke and temperatures at different locations. Five fuels were used: kerosine, as aviation fuel; gas oil, as the current industrial gas turbine fuel and possible future aviation fuel; R25 (where 25 is the volume percentage of residual fuel oil in the blend with gas oil), as equivalent to crude oil now in use in many utility gas turbines; and also R50 and R70 to represent future heavier fuels. Combustor pressures were 0.3, 0.7 and 1.0 MPa. Inlet air temperatures were 313, 390 and 460 K. Primary zone air/fuel mass ratios were 12, 15 and 25. Total air/fuel ratios were 60 and 120. Attempts were made to develop a mathematical model of the soot formation-oxidation processes that occur in the system, and to include in the model some parameters to represent the change in fuel properties. In this paper, comparison of the soot formation predictions of the model with the experimental data is seen to be favourable, particularly at full power conditions. 相似文献
76.
Abou-Zeid A. Abou-Zeid Abd-El-Sadek A. Yousef 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1976,26(1):454-458
Mitomycins were fermentatively produced using certain agricultural raw by-products by Streptomyces caespitosus NRRL 2564. The excreted antibiotics were thoroughly extracted with ethyl acetate at pH 6.0–8.0. The ethyl acetate extract was extensively purified by paper and thin-layer chromatographic techniques. The most efficient solvent systems in the complete separation of mitomycins were water-benzene-methanol (2:1:1 by vol.) in the case of paper chromatography, while acetone-ligroin-n-octanol (5:5:2 by vol.) was suitable for silical gel and alumina thin-layer plates. Pure samples of mitomycins A, B and C were obtained by preparative thin-layer chromatography using the solvent system composed of acetone-ligroin-n-octanol (5:5:2 by vol.). The active principles of mitomycins A, B and C, when biologically assayed on Bacillus subtilis ATCC 6622, were 980, 955 and 1000 μg/mg respectively. Mitomycin A can be converted into mitomycin C by exposing thin-layer chromatograms to concentrated ammonia vapour for 20 min. 相似文献
77.
Shriram Bagrodia Yousef Mohajer Garth L. Wilkes Robson F. Storey Joseph P. Kennedy 《Polymer Bulletin》1983,9(4-5):174-180
Mechanical properties of tri-arm polyisobutylene based ionomers have been investigated. Number average molecular weights (¯Mn's) of the polymers were varied from 8,300 to 34,000. The ionomer of lowest ¯Mn (8,300) exhibits very low extension at break (~ 150%) while the others with ¯Mn's of 11,000, 14,000 and 34,000 show very high extensions, often exceeding 1,000%, and display relatively low permanent set and low hysteresis behavior. Since the ionic bonding is located exclusively at the chain ends, end-linked pseudo networks are formed due to coulombic attractions.At higher temperatures the coulombic interactions are weakened and the networks can be compression molded (~150°C). 相似文献
78.
Antifungal activity of Lactobacillus paracasei ssp. tolerans isolated from a sourdough bread culture 总被引:2,自引:0,他引:2
Lactic acid bacteria were isolated from four different sourdough bread cultures previously investigated for antifungal activity. A total of 116 isolates were obtained and screened for antifungal activity against a battery of molds. The most inhibitory isolate obtained was identified by API 50 CHL and 16s ribosomal RNA genotyping and found to be Lactobacillus paracasei ssp. tolerans. This isolate completely inhibited the growth of Fusarium proliferatum M 5689, M 5991 and Fusarium graminearum R 4053 compared to controls in a dual agar plate assay. 相似文献
79.
Prediction of Egg Freshness and Albumen Quality Using Visible/Near Infrared Spectroscopy 总被引:1,自引:0,他引:1
Nicolas Abdel-Nour Michael Ngadi Shiv Prasher Yousef Karimi 《Food and Bioprocess Technology》2011,4(5):731-736
Important changes occur in egg during storage leading to loss of quality. Prediction of these changes is critical in order
to monitor egg quality and freshness. The aim of this research was to evaluate application of visible (VIS) and near infrared
(NIR) spectroscopy as a rapid and non-destructive technique for egg quality assessment. Three hundred and sixty intact white-shelled
eggs freshly laid by the same flock of hens fed with a standard feed were obtained. They were put under controlled conditions
of temperature and humidity (T = 18 °C and RH = 55%) for 16 days of storage. Forty eggs were analyzed at day 0, 2, 4, 6, 8, 10, 12, 14, and 16. Transmission
spectral data was obtained in the range from 350 to 2,500 nm. The non-destructive spectral data was compared to egg sample’s
Haugh unit (HU) and albumen pH in terms of quality and to the number of storage days in terms of freshness. A partial least
squares predictive model was developed and used to link the destructive assessment methods and the number of storage days
with the spectral data. The correlation coefficient between the measured and predicted values of HU, albumen pH, and number
of storage days were up to 0.94, R
2 was up to 0.90 and the root mean square error values for the validation were 5.05, 0.06, and 1.65, respectively. These results
showed that VIS/NIR transmission spectroscopy is a good tool for assessment of egg freshness and albumen pH and can be used
as a non-destructive method for the prediction of HU, albumen pH, and number of storage days. In addition, the relevant information
about these parameters was in the VIS and NIR ranging from 411 to 1,729 nm. 相似文献
80.
Elzohiery Mohamed Fan Deqiu Mohassab Yousef Sohn H. Y. 《Metallurgical and Materials Transactions B》2020,51(3):1003-1015
Metallurgical and Materials Transactions B - An experimental investigation of the reduction of magnetite concentrate particles was conducted in a laboratory-scale flash reactor representing a novel... 相似文献