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561.
The effects of frequency multiplication circuits on the short-term stability of an oscillator system are analyzed. The short-term stability of real components such as varactor multipliers are compared to the short-term stability of an ?ideal? frequency multiplier which maintains the stability of the basic oscillator. In addition, it is shown that positive feedback like that used in a synchronized oscillator, while useful for tracking, degrades short-term stability. 相似文献
562.
Ch. I. Chaban R. T. Ripetskyj E. L. Kordyum N. A. Kit 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1999,23(12):2011-2016
Under gravistimulation, dark-grown protonemata of Pottia intermedia revealed negative gravitropism with a growth rate of approximately 28 μm·h−1 at room temperature (20 °C). In 7 days, the protonema formed a bundle of vertically oriented filaments. At an elevated temperature (30 °C), bundles of vertically growing filaments were also formed. However, both filament growth rate and amplitude of the gravicurvature were reduced. Red light (RL) irradiation induced a positive phototropism of most apical protonemal cells at 20 °C. In a following period of darkness, approximately two-thirds of such cells began to grow upward again, recovering their negative gravitropism. RL irradiation at the elevated temperature caused a partial increase in the number of protonemal cells with negative phototropism, but the protonemata did not exhibit negative gravitropism after transfer to darkness. The negative gravitropic reaction was renewed only when protonemata were placed at 20 °C. A dramatic decrease in starch amount in protonemal apical cells, which are sensitive to both gravity and light, occurred at the higher temperature. Such a decrease may be one of the reasons for the inhibition of the protonemal gravireaction at the higher temperature. The observation has a bearing on the starch-statolith theory. 相似文献
563.
Active Spacecraft Potential Control Investigation 总被引:1,自引:0,他引:1
K. Torkar R. Nakamura M. Tajmar C. Scharlemann H. Jeszenszky G. Laky G. Fremuth C. P. Escoubet K. Svenes 《Space Science Reviews》2016,199(1-4):515-544
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566.
567.
Pulsone N.B. Raghavan R.S. 《IEEE transactions on aerospace and electronic systems》1999,35(3):903-916
Coherent signal detection in non-Gaussian interference is presently of interest in adaptive array applications. Conventional array detection algorithms inherently model the interference with a multivariate Gaussian random vector. However, non-Gaussian interference models are also under investigation for applications where the Gaussian assumption may not be appropriate. We analyze the performance of an adaptive array receiver for signal detection in interference modeled with a non-Gaussian distribution referred to as a spherically invariant random vector (SIRV). We first motivate this interference model with results from radar clutter measurements collected in the Mountain Top Program. Then we develop analytical expressions for the probability of false alarm and the probability of detection for the adaptive array receiver. Our analysis shows that the receiver has constant false alarm rate (CFAR) performance with respect to all the interference parameters. Some illustrative examples are included that compare the detection performance of this CFAR receiver with a receiver that has prior knowledge of the interference parameters 相似文献
568.
Large-scale Coronal Heating, Clustering of Coronal Bright Points, and Concentration of Magnetic Flux
By combining quiet-region Fe XII coronal images from SOHO/EIT with magnetograms from NSO/Kitt Peak and from SOHO/MDI, we show
that the population of network coronal bright points and the magnetic flux content of the network are both markedly greater
under the bright half of the large-scale quiet corona than under the dim half. These results (1) support the view that the
heating of the entire corona in quiet regions and coronal holes is driven by fine-scale magnetic activity (microflares, explosive
events, spicules) seated low in the magnetic network, and (2) suggest that this large-scale modulation of the magnetic flux
and coronal heating is a signature of giant convection cells.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
569.
T. Aramaki S.E. Boggs W.W. Craig H. Fuke F. Gahbauer C.J. Hailey J.E. Koglin N. Madden K. Mori R.A. Ong T. Yoshida 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2010
The General AntiParticle Spectrometer (GAPS) is a novel approach for indirect dark matter searches that exploits cosmic antideuterons. GAPS complements existing and planned direct dark matter searches as well as other indirect techniques, probing a different and unique region of parameter space in a variety of proposed dark matter models. The GAPS method involves capturing antiparticles into a target material with the subsequent formation of an excited exotic atom. The exotic atom decays with the emission of atomic X-rays and pions from the nuclear annihilation, which uniquely identifies the captured antiparticle. This technique has been verified through the accelerator testing at KEK in 2004 and 2005. The prototype flight is scheduled from Hokkaido, Japan in 2011, preparatory for a long duration balloon flight from the Antarctic in 2014. 相似文献
570.
A. N. Kusyumov E. V. Romanova A. S. Batrakov R. R. Nurmukhametov G. N. Barakos 《Russian Aeronautics (Iz VUZ)》2012,55(3):263-268
We consider a problem of a stationary incompressible viscous fluid flow around a flat circular cylinder. In the vicinity of the critical Reynolds number Re cr a stepwise drop of the cylinder drag takes place, which is called the drag crisis. 相似文献