78,256 research outputs found
Kaleidoscopic light feedback for television systems
Technique generates special effects for broadcast television to study effects of light feedback on television systems. Signals are produced for tape recording, broadcasting, or displaying on black-and-white or color monitors. The patterns have from three to eight sides and expand, contract, or rotate at various speeds
First Record of \u3ci\u3eAphis Helianthi\u3c/i\u3e (Homoptera: Aphididae) as a Pest of Celery
In 1989, the aphid Aphis helianthi severely damaged five of 10 scouted celery fields in west central Michigan. In 1990 and in 1991, A. helianthi again was a problem. reaching pestiferous levels in three of 10 and two of 10 scouted fields. respectively. This insect has not been reported previously as a pest of celery or any other commercial crop. Insecticide efficacy studies showed that some of the most commonly used insecticides are ineffective against A. helianthi. Resistance or tolerance to insecticides may explain its new status as a pest
Thermocapillary flows and their stability: Effects of surface layers and combination
The theoretical analysis of the fluid mechanics and heat transfer of motions driven by surface tension gradients (Marangoni convection) was researched. Convection accompanying the process of growing high quality single crystals from the melt in a micro-g environment was examined. The geometries considered include two dimensional liquid filled slots and axisymmetric float-zone configurations
The development of a pseudo-nyquist analysis technique for hybrid sampled-data control systems
The stability characteristics of a launch vehicle, as a function of gain and phase variations at the thrust vector controller, cannot be obtained using classical sampled-data control theory if the launch vehicle attitude control system contains both sampled-data and continuous feedback control loops. A method was developed which can be used to generate a sampled-data pseudo-Nyquist plot for gain and phase variations at the controller. This method was developed and used to determine the stability characteristics of the Saturn 1B launch vehicle in the backup guidance mode
Effects of heat input rates on T-1 and T-1A steel welds
Technology of T-1 and T-1A steels is emphasized in investigation of their weld-fabrication. Welding heat input rate, production weldment circumstances, and standards of welding control are considered
ASCA observations of massive medium-distant clusters of galaxies. II
We have selected seven medium-distant clusters of galaxies (z ~ 0.1 - 0.3)
for multi-wavelength observations with the goal of investigating their
dynamical state. Following Paper I (Pierre et al. 1999) which reported the ASCA
results about two of them, we present here the analysis of the ASCA
observations of the other five clusters; RXJ1023.8-2715 (A3444),
RXJ1031.6-2607, RXJ1050.5-0236 (A1111), RXJ1203.2-2131(A1451), and
RXJ1314.5-2517. Except for RXJ1031.6, whose X-ray emission turned out to be
dominated by an AGN, the ASCA spectra are well fitted by a one-temperature thin
thermal plasma model. We compare the temperature-luminosity relation of our
clusters with that of nearby ones (z<0.1). Two clusters, RXJ1050.5 and
RXJ1023.8, show larger luminosities than the bulk of clusters at similar
temperatures, which suggests the presence of a cooling flow. The temperature
vs. iron-abundance relationship of our sample is consistent with that of nearby
clusters.Comment: 9 pages, 20 figures, A&AS in pres
Unusual conductance of polyyne-based molecular wires
We report a full self-consistent ab initio calculation of the current-voltage
curve and the conductance of thiolate capped polyynes in contact with gold
electrodes. We find the conductance of polyynes an order of magnitude larger
compared with other conjugated oligomers. The reason lies in the position of
the Fermi level deep in the HOMO related resonance. With the conductance weakly
dependent on the applied bias and almost independent of the length of the
molecular chain, polyynes appear as nearly perfect molecular wires.Comment: 4 pages, 5 figures, 3 table
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