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In order to mitigate the multipath propagation problems for high rate wlans such as Hiperlan (5 GHz) [2], we study an approach based on electronic beam steering over 360° in azimuth with the help of circular arrays of monopoles [3]. Design simplicity and size constraints intended for potential low-cost applications on the terminals has led us to favor a beam switching topology, using a single feeding-port [4]. Two competing configurations of the microstrip feeding circuit are presented and their principle of operation is experimentally validated through passive circuit configurations. The power distribution is achieved in the first one with the help of a pseudo-divider based on a modified 7-branch star junction, whose specific advantage is its very small size. Unfortunately, this design does not preserve the circular permutation invariance of the radiation patterns. The second circuit bypasses this problem in achieving a power distribution through a virtual point junction, at the cost of an appreciable increase in the circuit size.  相似文献   
2.
We show that intersector correlations may be used as a convenient way to analyze diversity in switched beam antennas, with particular emphasis on the elevation dependence of the received power spectrum. In addition to their experimental characterization, such correlations can be computed from first principles according to the radio environment. The expected diversity performance can then be used as an input to antenna design and optimization.  相似文献   
3.
The results obtained in 151 children who underwent C.T. scan at the Pediatric Department of the University of Padova are reported. The high incidence of negative or aspecific results in the cases of static encephalopathy, in primary generalized epilepsy and in acute diffuse cerebral infectious process is emphasized. C.T. confirmed its high diagnostic value in tuberous sclerosis and cerebral abscess. While non providing the precise diagnosis it may be helpful in some demyelinating diseases. In secondary generalized epilepsy and in partial epilepsy C.T. scan may suggest the prognosis and a possible surgical approach. On the basis of these results and of other published reports a greater selectivity in the use of C.T. is strongly recommended.  相似文献   
4.
The Saint‐Sauveur dam was built in 1992 in the middle section of the Buëch River. Downstream of the dam, a channel incision by several meters was observed. A gravel replenishment operation was planned in order to restore the active channel. An equivalent of two times the mean annual bedload‐transport capacity (43,500 m3) was replenished downstream of the dam in September 2016. The aim of this paper is to quantify morphological change associated with sediment remobilization in order to evaluate the efficiency of the restoration works. The monitoring was based on a combination of (a) change detection using sequential high‐resolution digital elevation models (from airborne LiDAR data), (b) bedload tracing using active ultrahigh‐frequency radio‐frequency identification technology, and (c) complementary field surveys of channel grain‐size distribution and morphology for bedload‐transport computation. Field monitoring allows us to capture a net aggradation along a 2‐km reach after the first post‐replenishment flood. A sediment balance analysis was performed to back‐calculate bedload supply coming from the sluicing operation during the flood. Although the sediment replenishment operation clearly had a positive impact on the morphological conditions of the starved river reach, the effective bedload supply from artificial berms (22,650 m3) was insufficient to initiate substantial channel shifting along the restored reach and a subsequent amplification of the sediment recharge. The combination of high‐resolution topographic resurveys and sediment tracing was successful to evaluate the downstream propagation of sediment replenishment effects.  相似文献   
5.
Osimertinib is currently the preferred first-line therapy in patients with non-small cell lung cancer (NSCLC) with common epidermal growth factor receptor (EGFR) mutation and the standard second-line therapy in T790M-positive patients in progression to previous EGFR tyrosine kinase inhibitor. Osimertinib is a highly effective treatment that shows a high response rate and long-lasting disease control. However, a resistance to the treatment inevitably develops among patients. Understanding the secondary mechanisms of resistance and the possible therapeutic options available is crucial to define the best management of patients in progression to osimertinib. We provide a comprehensive review of the emerging molecular resistance mechanism in EGFR-mutated NSCLC pre-treated with osimertinib and its future treatment applications.  相似文献   
6.
Non-steroidal anti-inflammatory drugs (NSAID's) could be of value in the treatment of liver disease; however, their use in this situation is limited by renal side effects. Therefore, we explored whether naproxen covalently bound to human serum albumin NAP-HSA) was able to reduce toxicity in an acute model of liver disease induced by endotoxin in rats pretreated with Corynebacterium parvum. In the isolated perfused liver of such animals endotoxin induced cholestasis (0.62 +/- 0.05 vs. 0.24 +/- 0.09 microliter.min-1.g liver-1; p < 0.05), increased vascular resistance (11300 +/- 400 vs. 311000 +/- 2000 dyn.s.cm-5; p < 0.05) and alanine aminotransferase release (22 +/- 9 vs. 149 +/- IU/l; p < 0.05). At the highest dose tested (22 mg/kg, corresponding to 6.0 mumoles naproxen), NAP-HSA normalized ALT release (21 +/- 10 IU/l: p < 0.05) while an equimolar amount of non-targeted naproxen was only partially effective (56 +/- 19 IU/l). A conventional dose of naproxen similarly prevented transaminase release. Cholestasis and increased vascular resistance were also prevented by NAP-HSA. Drug targeting by linking drugs to proteins is a potentially useful approach to maximizing drug effect while minimizing adverse events; this could be particularly useful for compounds with potentially serious adverse effects in patients with chronic liver disease such as the nonsteroidal anti-inflammatory agents used in the present study.  相似文献   
7.
The broadband design of a circular array of bent stacked slot antennas (BSSAs) is presented. The angular diversity provided can mitigate multipath propagation and intersymbol interference occurring in indoor wireless communications. Details of the antenna design and experimental results are presented for a fixed sector configuration at 5.2 GHz. Numerical simulation results are consistent with experiments. The 3 dB beamwidth in azimuth and elevation is ~75 and 50°, respectively, and the directivity is 7.7 dBi. Over the whole HIPERLAN bandwidth, a -18 dB return loss is achieved, with only a 3 dB degradation of secondary radiation lobes  相似文献   
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