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731.
732.
Gerlach K. Kretschmer F.F. Jr. 《IEEE transactions on aerospace and electronic systems》1991,27(4):646-654
Digitally coded radar waveforms can be used to obtain large time-bandwidth products (pulse compression ratios). It is demonstrated that periodic radar waveforms with zero sidelobes or almost zero sidelobes can be defined. A perfect periodic code is a periodic code whose autocorrelation function has zero sidelobes and whose amplitude is uniform (maximum power efficiency=1). An asymptotically perfect periodic code has the property that as the number of elements in the code goes to infinity the autocorrelation function of the code has zero sidelobes and its power efficiency is one. The authors introduce a class of radar waveforms that are either perfect or asymptotically perfect codes. These are called reciprocal codes because they can be derived through a linear transformation of known codes. The aperiodic performance of the reciprocal code is examined 相似文献
733.
It has been suggested that under hypokinesia (reduced number of steps/day) and intensive physical exercise, the intensification of fluid excretion in men is apparently caused as a result of the inability of the body to retain optimum amounts of water. Thus, to evaluate this hypothesis, studies were performed with the use of fluid and sodium chloride (NaCl) supplements on 12 highly trained physically healthy male volunteers aged 19-24 years under 364 days of hypokinesis (HK) and a set of intensive physical exercises (PE). They were divided into two groups with 6 volunteers per group. The first group of subjects were submitted to HK and took daily fluid and salt supplements in very small doses and the second group of volunteers were subjected to intensive PE and fluid-salt supplements. For the simulation of the hypokinetic effect, both groups of subjects were kept under an average of 4000 steps/day. During the prehypokinetic period of 60 days and under the hypokinetic period of 364 days water consumed and eliminated in urine by the men, water content in blood, plasma volume, rate of glomerular filtration, renal blood flow, osmotic concentration of urine and blood were measured. Under HK, the rate of renal excretion of water increased considerably in both groups. The additional fluid and salt intake failed to normalize water balance adequately under HK and PE. It was concluded that negative water balance evidently resulted not from shortage of water in the diet but from the inability of the body to retain optimum amounts of fluid under HK and a set of intensive PEs. 相似文献
734.
A. Urban K.M. Torkar J. Bjordal J.A˚. Lundblad F. Søraas B. Grandal L.G. Smith J.C. Ulwick R.P. Vancour 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1982,2(10):77-80
Measurements of the precipitation of electrons and positive ions (in the keV to MeV range) detected aboard eight rockets launched from Northern Scandinavia are reported together with corresponding satellite data. The downgoing integral fluxes indicate the temporal fluctuations during each flight. Height profiles of the energy deposition into the atmosphere at different levels of geomagnetic disturbance are given. 相似文献
735.
V.M. Balebanov O.L. Vaisberg E.M. Vasiliev G.N. Zastenker V.P. Evdokimov E.G. Eroshenko L.V. Pesotski V.F. Babkin S. Fisher Z. Nemechek Ya. Shafrankova 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1982,2(7):75-79
This paper deals with the principal methods of achieving high-time resolution measurements for the study of fine structure of shocks and other discontinuities in space plasmas. In the measurements of ion energy spectra, we have obtained the time resolution about 1s.In the Soviet-Czechoslovak INTERSHOCK project we will obtain temporal resolution better than 0.1s in the measurement of the main plasma parameters. This will be obtained with the multichannel energy spectrometer and the on-board data acquisition and processing system triggered by the shock signature. This system controls the data sampling rate from some scientific instruments and switches on a high-sampling rate near the shock. The method implies detecting a shock by means of on-board processing of magnetic field and plasma parameters. The algorithm for this detection uses both parameters separately as well as in combinations. 相似文献
736.
Magnetic field experiment for Voyagers 1 and 2 总被引:1,自引:1,他引:0
K. W. Behannon M. H. Acuna L. F. Burlaga R. P. Lepping N. F. Ness F. M. Neubauer 《Space Science Reviews》1977,21(3):235-257
The magnetic field experiment to be carried on the Voyager 1 and 2 missions consists of dual low field (LFM) and high field magnetometer (HFM) systems. The dual systems provide greater reliability and, in the case of the LFM's, permit the separation of spacecraft magnetic fields from the ambient fields. Additional reliability is achieved through electronics redundancy. The wide dynamic ranges of ± 0.5 G for the LFM's and ± 20 G for the HFM's, low quantization uncertainty of ± 0.002 ( = 10–5 G) in the most sensitive (± 8 ) LFM range, low sensor RMS noise level of 0.006 , and use of data compaction schemes to optimize the experiment information rate all combine to permit the study of a broad spectrum of phenomena during the mission. Objectives include the study of planetary fields at Jupiter, Saturn, and possibly Uranus; satellites of these planets; solar wind and satellite interactions with the planetary fields; and the large-scale structure and microscale characteristics of the interplanetary magnetic, field. The interstellar field may also be measured. 相似文献
737.
Results are reported on the attempt to define a pseudotransfer funtion of a circuit composed of a 2-pulse canceler and hard limiter. 相似文献
738.
L. Koch-Miramond R. Rocchia J. Davelaar F. A. Jansen R. H. Becker R. Braun 《Space Science Reviews》1985,40(3-4):521-526
The X-ray properties of the supernova remnant G 29.7-0.3 are discussed based on spectral data from the EXOSAT satellite. In the 2 to 10 keV range a featureless power-law spectrum is obtained, the best-fit parameters being: energy spectral index =-0.77, hydrogen column density on the line of sight NH=2.3.1022 cm–2. The incident X-ray flux from the source is (3.6±0.1) 1011 erg cm–2 s–1 in the 2 to 10 keV range corresponding to an intrinsic luminosity of about 2. 1036 erg s–1 for a distance of 19 kpc. The source was not seen with the imaging instrument thus constraining the hydrogen column density to be NH=(3.3 ±0.3) 1022 cm–2 and the energy spectral index =1.0±0.15. This new observation is consistent with emission by a synchroton nebula presumably fed by an active pulsar. An upper limit of 1.5% for the pulsed fraction in the range of periods 32ms to 104 s has been obtained. 相似文献
739.
Lee F.C.Y. Wilson T.G. Feng S.Y.M. 《IEEE transactions on aerospace and electronic systems》1973,(4):571-584
A familiar two-transistor saturable-core parallel inverter is modeled as a nonlinear negative resistance in parallel with energy-storage elements. The techniques of singular-point analysis are combined with piecewise linear techniques to permit determination of solution trajectories on the phase plane. Clear insight is provided, not only into steady-state oscillation, but also into transient behavior of the circuit. Experimental results confirming the analytical model are included. 相似文献
740.
A system is developed to detect tracks crossing two-dimensional noise fields. This is accomplished by filtering and integration of signal power in the frequency domain of a new class of generalized transforms which include the FFT and FBT as limiting forms. If the track is essentially parallel to a transform axis and if filters are derived from hard-limited linear approximations to tracks, the FBT offers considerable hardware economy over the FFT in the mechanization algorithm. 相似文献