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Some analytical results have been developed for the analysis and design of a packet-voice receiver in previous work [1], namely, the delay suffered by packets because of the reassembly mechanism is described in terms of the overall delay probability density function (pdf)w(t) . This basic analytical result is used here in order to obtain the pdfb(t) of the time spent by packets in the receiver buffer. In this way, the previous work [1] is extended to analysis of the delay distribution of the receiver buffer where arriving talkspurts are delayed to compensate for the variable network delay of all packets within a talkspurt. The tools developed here facilitate a choice of the buffer size at the prescribed level of packet-loss probability. 相似文献
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Carvalho Lucila Martinez-Maldonado Roberto Goodyear Peter 《International Journal of Computer-Supported Collaborative Learning》2019,14(1):77-107
International Journal of Computer-Supported Collaborative Learning - The theory of Instrumental Genesis (IG) accounts for the mutual evolution of artefacts and their uses, for specific purposes in... 相似文献
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Suitability for Ready‐to‐Eat Processing and Preservation of Six Green and Red Baby Leaves Cultivars and Evaluation of Their Antioxidant Value during Storage and after the Expiration Date 下载免费PDF全文
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Nora S. Fígoli Juan P. Barberis Pablo C. L'Argentire 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1996,67(1):72-76
The selective hydrogenation of cyclopentadiene to cyclopentene has been studied in the liquid phase using Pd and Pd Me/Al2O3 bimetallic catalysts (Me = Mn, Ni, Co, W). The highest activity was obtained with Pd Co and Pd W/Al2O3. For these catalysts, no hydrogen or CO chemisorption was detected although Pd could be seen by XPS at 335·8 eV; it is considered that new species, more active for the selective hydrogenation of cyclopentadiene, appeared at the catalyst surface. The sulfur resistance towards thiophene has also been studied. It was observed that the highest sulfur resistance is coincident with the highest activity. XPS analysis shows that the poisoning species is thiophene adsorbed on the catalyst surface. 相似文献
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Phosphorus sorption in relation to soil properties in some cultivated Swedish soils 总被引:10,自引:0,他引:10
Katarina Börling Erasmus Otabbong Elisabetta Barberis 《Nutrient Cycling in Agroecosystems》2001,59(1):39-46
Phosphorus (P) sorption properties are poorly documented for Swedish soils. In this study, P sorption capacity and its relation to soil properties were determined and evaluated in 10 representative Swedish topsoils depleted in available P. P sorption indices were estimated from sorption isotherms using Langmuir and Freundlich equations (Xm and aF, respectively) and P buffering capacity (PBC). Xm ranged from 6.0 to 12.2 mmol kg–1. All indices obtained from sorption isotherms were significantly correlated with each other (r=0.96*** to r=0.99***). Two single-point sorption indices (PSI1 and PSI2) were also determined, with additions of 19.4 and 50 mmol P kg–1 soil, respectively. Both PSI indices were well correlated with Xm (r0.98***), with PSI1 giving the highest correlation. As isotherms for determining P sorption capacities involve laborious analytical operations, PSI1 would be preferable for routine analyses. Xm was significantly correlated with Fe extracted by sodium pyrophosphate and ammonium oxalate, to Al extracted by ammonium oxalate and dithionite-citrate-bicarbonate and to organic c. Xm was also significantly correlated with the sum of Fe and Al extracted by ammonium oxalate. The best prediction of Xm through multiple regression was obtained when Fe extracted in ammonium oxalate and Al extracted in dithionite-citrate-bicarbonate were used. Based on the results obtained, both PSI1 and oxalate-extractable Fe plus Al can be used for predicting P sorption capacity in Swedish soils. 相似文献
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Detection of postharvest changes of ascorbic acid in fresh-cut melon, kiwi, and pineapple, by using a low cost telemetric system 总被引:1,自引:0,他引:1
The present paper deals with a novel telemetric device combined with a carbon amperometric sensor system to determine postharvest changes of ascorbic acid (AA) in fresh-cut fruits, without displacing products out of the storage rooms. The investigation was performed on kiwi, pineapple and melon, subjected to minimal processing, packaging, cold storage, and simulated shelf life. Results demonstrated that AA content of fresh-cut fruits of all species declines differently during storage. Cold storage notably reduced the degradation rate of AA in comparison with samples stored at 20°C. The cold-chain interruption resulted in a sharp AA content reduction when the optimal storage condition was not rapidly replaced. Unpredicted results showed a high activity of oxidative enzymes, which prevented AA detection in melon samples. Our sensor system allowed us to demonstrate that both ascorbate peroxidase and ascorbate oxidase affected the oxidative stability and the nutritional quality of fresh cut melon fruits. 相似文献
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