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排序方式: 共有485条查询结果,搜索用时 31 毫秒
1.
Mobile positioning using wireless networks: possibilities and fundamental limitations based on available wireless network measurements 总被引:5,自引:0,他引:5
Positioning in wireless networks is mainly used for safety, gaming, and commercial services. It is expected to increase in popularity when emergency call services become mandatory as well as with the advent of more advanced location-based services and mobile gaming. In this article, we discuss and illustrate the possibilities and fundamental limitations associated with mobile positioning based on available wireless network measurements. The possibilities include a sensor fusion approach and model-based filtering, while the fundamental limitations provide hard bounds on the accuracy of position estimates, given the information in the measurements in the most favorable situation. The focus of this article is to illustrate the relation between performance requirements, such as those stated by the Federal Communications Commission (FCC), and the available measurements. Specific issues on accuracy limitation in each measurement, such as synchronization and multipath problems, are briefly commented upon. A geometrical example, as well as a realistic example adopted from a cell planning tool, are used for illustration. 相似文献
2.
The class II trans-activator (CIITA) is a bi- or multi-functional domain protein which plays a critical role in the expression of MHC class II genes. We report that removal of the N-terminal 151 amino acids, encompassing all of the acidic domain but leaving intact the proline/serine/threonine-rich domain, results in a mutant protein with potent suppressive properties for MHC class II expression. HeLa cells stably or transiently transfected with mutant CIITA constructs showed up to 99% suppression of MHC class II antigen induction by IFN-gamma and marked suppression of HLA-DRA mRNA expression. Transient transfection of a B lymphoma line resulted in up to 89% reduction of constitutive MHC class II expression within 5 days and suppression of HLA-DRA mRNA synthesis. 相似文献
3.
R Albrecht TC Awes C Baktash P Beckmann F Berger R Bock G Claesson G Clewing L Dragon A Eklund RL Ferguson A Franz S Garpman R Glasow HA Gustafsson HH Gutbrod J Idh P Jacobs K Kampert BW Kolb P Kristiansson IY Lee H Loehner I Lund FE Obenshain A Oskarsson I Otterlund T Peitzmann S Persson F Plasil AM Poskanzer M Purschke H Ritter S Saini R Santo HR Schmidt T Siemiarczuk SP Sorensen E Stenlund ML Tincknell GR Young 《Canadian Metallurgical Quarterly》1991,44(6):2736-2752
4.
B Brismar JE Akerlund S Sj?stedt C Johansson A T?rnqvist B B?ckstrand H B?ng L And?ker PO Gustafsson N Darle M Anger?s A Falk G Tunevall B Kasholm-Tengve T Skau PO Nystr?m T Gasslander A Hagelb?ck B Olsson-Liljequist AE Eklund CE Nord 《Canadian Metallurgical Quarterly》1996,28(5):507-512
The objective of this study is to describe usual medical management and costs associated with recurrent respiratory infections in subjects with chronic obstructive bronchitis in France. A prospective survey was performed in Autumn 1994 on a national sample of private practice pulmonologists (N = 71). Two hundred forty-four patients, presenting at least one infection of the lower respiratory tract, were included. Bronchitis was the most frequent acute exacerbation observed (94%). Pneumonia concerned 9% of the patients. Biological tests, X-rays and pulmonary function tests were prescribed for, respectively, 59, 65 and 45% of the patients. Following the visit, 15 patients were hospitalized (6%). The direct medical cost per acute exacerbation was estimated 3,289 francs (1994 value) of which 60% were hospital-related. An average 10.4 day sick-leave was prescribed to 21% of patients in employment. For those patients, this sick-leave was associated to an extra-cost of 1,264-1,876 francs for Social Security and of 0-2,553 francs out of pocket per episode varying according to their Benefit Regimen. 相似文献
5.
6.
Due to the growing importance of width control in strip and plate mills, edge rolling is currently an im-portant process in
hot rolling mills. Research in edge rolling has been carried out, and in the present ar-ticle, models for roll force, torque,
and lever arm coefficient are derived using the upper bound method. A simple, kinematically admissible deformation zone and
velocity field, independent of friction in the roll gap, is proposed, and the energy dissipation rate is derived. The formula
for energy dissipation rate has, in practice, no limitation because all edge rolling geometries are safely in the area where
the formula is valid. Roll force and torque are derived by means of two independent integrals. Thus, the lever arm coef-ficient
is evaluated from the expressions for roll force and torque using conventional rolling theory. Roll-ing trials report good
agreement with theory. Measured roll forces are similar to calculated forces. Furthermore, the shape of the dogbone that arises
during edge rolling is in fairly good agreement with the calculated dogbone shape. Deviations are due to the deviation from
ideally plastic material in the ex-periments. Also, the strain distribution over the dogbone is similar to the proposed deformation
zone. Thus, a new formula has been developed to a stage that it can be implemented in width control systems for edge rolling
stands in hot strip and plate mills. 相似文献
7.
Six distillation column models have been used in studies of the usefulness of the Inverse Nyquist Array (INA) method for design of dual composition control for distillation. Five of the column models are experimental, one describing an industrial column, the others four pilot plants. One column model is obtained by modeling from first principles.
The control strategies investigated and compared are multiloop SISO, 2-way decoupling and l-way decoupling. The control variables are the standard ones, i.e. reflux flow and boilup.
In most of the cases INA has been found to be a useful tool for design of the loops and for comparison of the different control approaches. INA has also been found to be useful for simultaneous tuning of the decouplers and the feedback controllers.
For 2-way decoupling the criterion to minimize interaction at the critical frequency for each primary feedback loop has been found useful in most, but not all, cases. The scheme can be designed by pure gains in the decouplers and there is no reason to introduce dynamics into the decouplers—the systems studied are already sufficiently rich in dynamics.
INA has been found to be a suitable vehicle for the choice between the two possible l-way decoupling schemes.
With the design approach taken, l-way decoupling has been found to provide considerably better control quality than 2-way decoupling in two of the six systems, the differences in control quality being small in the other cases.
The effect of model mismatching on the results, caused e.g. by process nonlinearities, is discussed and simple rules to decrease the parameter sensitivity for 2-way decoupling schemes are given. When model mismatching is considered, the advantage of l-way decoupling over 2-way decoupling seems to increase.
One deficiency of the INA design as used in this paper is that it does not single out the design which is to be preferred on the grounds of robustness. 相似文献
The control strategies investigated and compared are multiloop SISO, 2-way decoupling and l-way decoupling. The control variables are the standard ones, i.e. reflux flow and boilup.
In most of the cases INA has been found to be a useful tool for design of the loops and for comparison of the different control approaches. INA has also been found to be useful for simultaneous tuning of the decouplers and the feedback controllers.
For 2-way decoupling the criterion to minimize interaction at the critical frequency for each primary feedback loop has been found useful in most, but not all, cases. The scheme can be designed by pure gains in the decouplers and there is no reason to introduce dynamics into the decouplers—the systems studied are already sufficiently rich in dynamics.
INA has been found to be a suitable vehicle for the choice between the two possible l-way decoupling schemes.
With the design approach taken, l-way decoupling has been found to provide considerably better control quality than 2-way decoupling in two of the six systems, the differences in control quality being small in the other cases.
The effect of model mismatching on the results, caused e.g. by process nonlinearities, is discussed and simple rules to decrease the parameter sensitivity for 2-way decoupling schemes are given. When model mismatching is considered, the advantage of l-way decoupling over 2-way decoupling seems to increase.
One deficiency of the INA design as used in this paper is that it does not single out the design which is to be preferred on the grounds of robustness. 相似文献
8.
H. Tatsuno W. B. Doriese D. A. Bennett C. Curceanu J. W. Fowler J. Gard F. P. Gustafsson T. Hashimoto R. S. Hayano J. P. Hays-Wehle G. C. Hilton M. Iliescu S. Ishimoto K. Itahashi M. Iwasaki K. Kuwabara Y. Ma J. Marton H. Noda G. C. O’Neil S. Okada H. Outa C. D. Reintsema M. Sato D. R. Schmidt H. Shi K. Suzuki T. Suzuki J. Uhlig J. N. Ullom E. Widmann S. Yamada J. Zmeskal D. S. Swetz 《Journal of Low Temperature Physics》2016,184(3-4):930-937
9.
The aim of this study was to investigate whether there are differences in technique between young adults with and without musculoskeletal symptoms when using a mobile phone for texting and whether there are differences in muscle activity and kinematics between different texting techniques. A total of 56 young adults performed a standardised texting task on a mobile phone. Their texting techniques were registered using an observation protocol. The muscular activity in six muscles in the right forearm/hand and both shoulders were registered by surface electromyography and the thumb abduction/adduction and flexion/extension were registered using a biaxial electrogoniometer. Differences in texting techniques were found between the symptomatic and the asymptomatic group, with a higher proportion of sitting with back support and forearm support and with a neutral head position in the asymptomatic group. Differences in muscle activity and kinematics were also found between different texting techniques. The differences in texting technique between symptomatic and asymptomatic subjects cannot be explained by them having symptoms but may be a possible contribution to their symptoms. STATEMENT OF RELEVANCE: There has been a dramatically increased use of mobile phones for texting especially among young people during the last years. A better understanding of the physical exposure associated with the intensive use is important in order to prevent the development of musculoskeletal disorders and decreased work ability related to this use. 相似文献
10.
Electromagnetic wave propagation close to a material discontinuity is simulated by using summation by part operators of second, fourth and sixth order accuracy. The interface conditions at the discontinuity are imposed by the simultaneous approximation term procedure. Stability is shown and the order of accuracy is verified numerically. 相似文献