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931.
S.G. Ungar S.N. Goward 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1983,3(2):291-295
Improvements in crop discrimination can be realized by using mid-IR bands (1.55–1.75 μm and 2.08–2.35 μm) which are sensitive to canopy moisture content. Analyses of data from two growing seasons in Webster County, Iowa clearly indicate that corn and soybeans are highly separable in the mid-IR from early season through harvest. This contrasts sharply with visible and near-IR bands where corn and soybeans are confused throughout much of the growing season. The mid-IR temporal reflectance behavior appears to result from differences between C4 monocot and C3 dicot internal leaf structure. If this hypothesis holds, mid-IR observations should improve discrimination in other instances where similar differences in internal leaf structure are present. 相似文献
932.
Mahle C.E. Geller B.D. Potukuchi J.R. Hyde G. 《Aerospace and Electronic Systems Magazine, IEEE》1988,3(11):3-10
Technology drivers for commercial communications satellites are examined based on the efficient use of spacecraft mass which is to be accomplished by increasing the efficiency of the microwave power amplifiers and antenna feed systems used for communications satellites, such as the INTELSAT series. The history of the INTELSAT series of satellites, the late 1980s market and available technology, and future directions of development are considered. Emphasis is on multibeam solid-state antennas, microwave switch matrices, solid-state power amplifiers, and the use of several filter modes in one physical cavity. By using quasimonolithic solid state techniques in a class B amplification mode they have achieved 40-60% efficiencies, compared with 20% for the conventional travelling wavetube amplifiers. It is concluded that technology directed towards improving the economics of satellite communications will continue to be a major driver of future communications satellite payloads. Through their use and their extension, the authors foresee more than doubling the telephone channels per satellite from the current 80000 to perhaps 200000 by the turn of the century 相似文献
933.
T.M. Bauer G. Paschmann R.A. Treumann W. Baumjohann N. Sckopke 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1997,19(12):1947-1950
For a rotational MHD discontinuity the bulk flow is Alfvénic in the de Hoffmann-Teller frame. Using AMPTE/IRM data, we present ion distribution functions during three crossings of the dayside low-latitude magnetopause. For these crossings a well defined de Hoffmann-Teller frame can be found, but the field-aligned bulk flow is always slower than the Alfvén speed. Nevertheless, we find signatures in the distribution functions that provide clear evidence for magnetic reconnection: solar wind ions reflected off the magnetopause, “D-shaped” solar wind ion distributions in the boundary layer, and counterstreaming of solar wind ions and ionospheric ions in the boundary layer. 相似文献
934.
N. F. Blagoveshchenskaya T. D. Borisova O. V. Kolosov V. A. Kornienko 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1995,15(12):111-114
Results of experimental studies of the ionospheric effects produced by CRRES barium releases are considered. The experimental observations of HF spectral characteristics by Doppler method are made by a network of long distance radio paths intersecting the L-shell of releases. The time dependence of their occurrence relative to the moment of release and the character of changes of spectral parameters produces signal effects (SE) which may be classified as: the unique burst, the quasiperiodic group of bursts, the regular changes of spectral parameters and wave processes. Observed types of SE are analogous to those seen when the releases were produced at the heights from 140 to 160 km. The result of experimental observations testify that there are special geophysical phenomena produced by barium releases. 相似文献
935.
David N. Schramm 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1984,3(10-12)
To illustrate the interaction of Grand Unified Theories (GUTs), supersymmetry (SUSY), and cosmology, a worked example is carried out. This example is the dark matter problem, or “What is the dominant matter of the Universe?” It is shown that if GUTs are assumed then the primordial perturbations are probably adiabatic, if inflation is assumed then Ω = 1 and GUTs first name is probably SUSY. If Ω = 1, big bang nucleosynthesis tells us that the bulk of the matter is non-baryonic. SUSY-GUTs gives us some possible candidate inos to which massive neutrinos, axion or planetary mass black holes can be added. These candidates can be classified hot (or warm) or cold types of dark matter. It is shown that hot gives Ω = 1 and naturally gives large scale structure but does not give small scale structure or galaxy formation times, whereas cold gives small scale structure and formation times but cannot easily yield Ω = 1. It is concluded that either a hybrid of both hot and cold or non-random phases for the perturbations may be needed. 相似文献
936.
F. Bonde-Petersen M. Suzuki N.J. Christensen 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1984,4(12):31-33
The purpose was to combine bicycle exercise and LBNP as a model to investigate the mechanisms regulating circulation during gravitatiobal stresses. METHODS: Cardiac Output (CO) by acetylene-, argon-, oxygen rebreathing; Heart Rate (HR) from ECG; Mean Arterial Pressure (MAP) by arm cuff; Plasma Nor-Epinephrine (NE), Epinephrine (E), and Lactate (HLa) by isotope and enzymatic techniques respectively. Total Peripheral Resistance (TPR)=MAP/CO and stroke volume (SV)=CO/HR. Six subjects exercised at 180–200 Watts in the upright position on a mechanically braked computer controlled small bicycle ergometer placed in a LBNP box. The above parameters were measured at rest and at 5 and 9 min of exercise without and with LBNP at −30 or −40 mmHg (depending on LBNP tolerance). RESULTS AND CONCLUSIONS: In the face of an increased sympathetic nervous activity (Ne+E, TPR, and HR increased) during exercise in LBNP, there was a decrease in CO and SV indicating that the venous return was insufficient. However, HLa was unchanged demonstrating that the blood flow to the working muscles did not suffer. 相似文献
937.
938.
D. Spänkuch W. von Hoyningen-Huene 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1982,2(5):131-134
In a previous paper the authors showed that the aerosol size distribution can be estimated with reasonable accuracy from spectral extinction measurements in a limited spectral region (λ ≤ 1 μm) only. Using the same method it will be discussed if the anticipated WMO turbidity network with four spectral channels has the potential of estimating the aerosol size distribution. 相似文献
939.
G. Stanev M. Petrunova D. Teodosiev I. Kutiev K. Serafimov S. Chapkunov V. Chmyrev N. Isaev P. Puschaev I. Pimenov S. Bilichanko 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1982,2(7):43-47
The instrument IESP-IPMP represents the complex unit measuring the vector of the DC electric field, the vectors of the electric and magnetic field in the frequency range of 0.2 – 6.5 Hz (wave form), autocorrelation functions of waves with frequencies of 0.1 – 5 kHz, and wave amplitudes in 8 bandpass channels. Some results are shown and compared in the various frequency ranges. 相似文献
940.
K. Frieler N. Phlippovich R. Stickler W. Bathke 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1981,1(5):117-120
Experiments of vacuum brazing under both microgravity and 1-g conditions show the effect of hydrostatic pressure on ga-filling. The absence of buoyancy forces under microgravity affects the microstructure of the solidified braze in the joint. 相似文献