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1.
We consider a packet switched wireless network where each cell's communication channel is shared among packet voice sources. In this paper, we present a method for the design and analysis of wireless cells using a reservation random access (RRA) scheme for packet access control. This scheme is integrated with a call admission control procedure. We model the state process of a single cell as a vector Markov chain. We compute the steady state distribution of the Markov chain. This result is used to calculate the packet dropping probability and the call blocking probability. By setting limits on maximum permissible levels for the call blocking probability and the packet dropping probability, we obtain the Erlang capacity of a single cell, with and without hand-off traffic. For an illustrative RRA scheme, the Erlang capacity of a single cell is shown to be about twice that attained by a comparable fixed assigned TDMA scheme. We show that a cellular network using this RRA scheme and which applies can be no blocking of hand-off calls, exhibits similar call capacity levels.This work is supported by a University of California MICRO and Pacific-Bell Grant No. 94-107. 相似文献
2.
Vera Sheinman Christiane Fellbaum Isaac Julien Peter Schulam Takenobu Tokunaga 《Language Resources and Evaluation》2013,47(3):797-816
We propose a new semantic relation for gradable adjectives in WordNet, which enriches the present, vague, similar relation with information on the degree or intensity with which different adjectives express a shared attribute. Using lexical-semantic patterns, we mine the Web for evidence of the relative strength of adjectives like “large”, “huge” and “gigantic” with respect to their attribute (“size”). The pairwise orderings we derive allow us to construct scales on which the adjectives are located. To represent the intensity relation among gradable adjectives in WordNet, we combine ordered scales with the current WordNet dumbbells based on the relation between a pair of central adjectives and a group of undifferentiated semantically similar adjectives. A new intensity relation links the adjectives in the dumbbells and their concurrent representation on scales. Besides capturing the semantics of gradable adjectives in a way that is both intuitively clear as well as consistent with corpus data, the introduction of an intensity relation would potentially result in several specific benefits for NLP. 相似文献
3.
The effect of laser surface texturing on transitions in lubrication regimes during unidirectional sliding contact 总被引:13,自引:0,他引:13
Andriy Kovalchenko Oyelayo Ajayi Ali Erdemir George Fenske Izhak Etsion 《Tribology International》2005,38(3):219-225
Laser surface texturing (LST) is an emerging effective method for improving the tribological performance of friction units lubricated with oil. In LST technology, a pulsating laser beam is used to create thousands of arranged microdimples on a surface by a material ablation process. These dimples generate hydrodynamic pressure between oil-lubricated parallel sliding surfaces. The impact of LST on lubricating-regime transitions was investigated in this study. Tribological experiments were conducted with a pin-on-disk apparatus at sliding speeds in the range of 0.015–0.75 m/s and nominal contact pressures that ranged from 0.16 to 1.6 MPa. Two oils with different viscosities (54.8 and 124.7 cSt at 40 °C) were used as lubricants. The test results showed that laser texturing expanded the contact parameters in terms of load and speed for hydrodynamic lubrication, as indicated by friction transitions on the Stribeck curve. The beneficial effects of laser surface texturing are more pronounced at higher speeds and loads and with higher viscosity oil. 相似文献
4.
E. L. Sheinman 《Metal Science and Heat Treatment》1999,41(10):460-462
Conclusions
Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 10, pp. 37–39, October, 1999. 相似文献
1. | The elevated content of silicon in high-carbon, chromium-manganese alloys increases the wear resistance only if the content of carbon and manganese in them is sufficiently high and the structure is oriented. |
2. | The introduction of about 4% Si into high-carbon chromium-manganese alloys increases their wear resistance by 60% or doubles it with respect to the most expensive alloy sormite-1 |
5.
Severe splenomegaly and anemia developed in a 5-year-old girl with diffuse lymphangiomatosis of the upper part of the body. Radioisotope scanning and celiac angiography demonstrated lymphangiomatosis of the spleen, a rare but diagnosable condition. Intractable infection in areas of ulcerated skin led to her death from overwhelming sepsis. 相似文献
6.
Bilenca A. Lasri J. Sheinman B. Eisenstein G. Ritter D. 《Lightwave Technology, Journal of》2001,19(9):1340-1351
This paper describes the use of an InGaAs-InP photoheterojunction bipolar transistor (photo-HBT) for millimeter-wave generation and digital modulation. Optical mixing of two coherent signals generates the carrier, and a digital drive signal to the base is used for the modulation. We describe an advanced large signal model of the photo-HBT that takes into account distributed effects at high frequencies and all noise sources, including optical amplifier noise and noise correlations due to the high operation frequency and the nonlinear mixing processes. The model enables one to predict carrier-to-noise ratio dependence on frequency, optical power, and the transistor operating point. Frequency- and time-domain responses of the modulated millimeter- wave carrier and bit error rates are also calculated. Experiments at 10 and 45 GHz with modulation rates ranging between 50 Mb/s and 2.5 Gb/s were performed, and a superb fit to the calculated responses is found 相似文献
7.
8.
E. L. Sheinman 《Metal Science and Heat Treatment》1997,39(3):120-122
Properties of eutectic alloys are studied mainly in the presence of eutectic structures. An interesting study concerns the
wear resistance of alloys with a phase composition characteristic for conglomerate structures.
Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 3, pp. 31–32, March, 1997. 相似文献
9.
10.
Izhak Tamir Yigal Rappaport 《International Journal of Satellite Communications and Networking》1987,5(1):49-56
A generalized model for the satellite link that includes non-linear effects is presented. The transponder is handled as a black box with nominal gain gs. At a specific operating point each signal in the transponder has its own gain, gsci, that may be different from gs. The parameter gsci depends on the operating point of the transponder, the power of the signal and the distribution of the residual transponder power among the other carriers. The intermodulation between the carriers and between them and the up-link noise is included in the model as well. The generalized model is represented by the conventional traditional equation, modified with correction factors which account for the nonlinear effects. Application of the model to typical transmission plans is given and comparison of the results to field experiments and transponder analysis program is included. Emphasis is placed on the use of the transponder with mixed TV and SCPC operation. 相似文献