207,876 research outputs found
Carfentrazone-ethyl Pond Dissipation and Efficacy on Floating Plants
Carfentrazone-ethyl (CE) is a reduced risk herbicide that
is currently being evaluated for the control of aquatic weeds.
Greenhouse trials were conducted to determine efficacy of
CE on water hyacinth (
Eichhornia crassipes
(Mart.) Solms-
Laub.), water lettuce (
Pistia stratiotes
L.), salvinia (
Salvinia
minima
Baker) and landoltia
(Landoltia punctata
(G. Mey.)
Les & D. J. Crawford
)
. CE controlled water lettuce, water hyacinth
and salvinia at rates less than the maximum proposed
use rate of 224 g ha
-1
. Water lettuce was the most susceptible
to CE with an EC
90
of 26.9 and 33.0 g ha
-1
in two separate trials.
Water hyacinth EC
90
values were calculated to be 86.2 to
116.3 g ha
-1
, and salvinia had a similar susceptibility to water
hyacinth with an EC
90
of 79.1 g ha
-1
. Landoltia was not adequately
controlled at the rates evaluated. In addition, CE was
applied to one-half of a 0.08 ha pond located in North Central,
Florida to determine dissipation rates in water and hydrosoil
when applied at an equivalent rate of 224 g ha
-1
. The
half-life of CE plus the primary metabolite, CE-chloropropionic
acid, was calculated to be 83.0 h from the whole pond,
and no residues were detected in water above the limit of
quantification (5 ÎĽg L
-1
) 168 h after treatment. CE dissipated
rapidly from the water column, did not occur in the sediment
above the levels of quantification, and in greenhouse
studies effectively controlled three species of aquatic weeds
at relatively low rates.(PDF contains 6 pages.
Multicast broadcast services support in OFDMA-based WiMAX systems [Advances in mobile multimedia]
Multimedia stream service provided by broadband wireless networks has emerged as an important technology and has attracted much attention. An all-IP network architecture with reliable high-throughput air interface makes orthogonal frequency division multiplexing access (OFDMA)-based mobile worldwide interoperability for microwave access (mobile WiMAX) a viable technology for wireless multimedia services, such as voice over IP (VoIP), mobile TV, and so on. One of the main features in a WiMAX MAC layer is that it can provide'differentiated services among different traffic categories with individual QoS requirements. In this article, we first give an overview of the key aspects of WiMAX and describe multimedia broadcast multicast service (MBMS) architecture of the 3GPP. Then, we propose a multicast and broadcast service (MBS) architecture for WiMAX that is based on MBMS. Moreover, we enhance the MBS architecture for mobile WiMAX to overcome the shortcoming of limited video broadcast performance over the baseline MBS model. We also give examples to demonstrate that the proposed architecture can support better mobility and offer higher power efficiency
A simple element for multilayer beams in NASTRAN thermal stress analysis
In the application of NASTRAN, structural members are usually represented by bar elements with multipoint constraint cards to enforce the interface conditions. While this is a very powerful method in principle, it was found that in practice the process for specification of constraints became tedious and error prone, unless the geometry was simple and the number of grid points low. An alternative approach was found within the framework of the NASTRAN program. This approach made use of the idea that a thermal distortion in a multilayer beam may be similar to a homogeneous beam with a thermal gradient across the cross section. The exact mathematical derivation for the equivalent beam, and all the necessary formulae for the equivalent parameters in NASTRAN analysis are presented. Some numerical examples illustrate the simplicity and ease of this approach for finite element analysis
Adaptive control of CO bending vibration: deciphering field-system dynamics
We combined adaptive closed-loop optimization, phase-shaping with a
restricted search space and imaging to control dynamics and decipher the
optimal pulse. The approach was applied to controlling the amplitude of CO
bending vibration during strong-field Coulomb explosion. The search space was
constrained by expressing the spectral phase as a Taylor series, which
generated pulses with characteristics commensurate with the natural physical
features of this problem. Optimal pulses were obtained that enhanced bending by
up to 56% relative to what is observed with comparably intense, transform
limited pulses. We show that (1) this judicious choice of a reduced parameter
set made unwrapping the dynamics more transparent and (2) the enhancement is
consistent with field-induced structural changes to a bent excited state of
CO, which theoretical simulations have identified as the state from
which the explosion originates.Comment: 4 pages, 3 figures, 1 table, added reference
Delayed fracture of silicon: Silicon sheet growth development for the large area silicon sheet task of the low cost silicon solar array project
Bar specimens were cut from ingots of single crystal silicon, and acid etched prior to testing. Artificial surface flaws were introduced in specimens by indentation with a Knoop hardness tester. The specimens were loaded in four-point bending to 95 percent of the nominal fracture stress, while keeping the surface area, containing the flaw, wet with test liquids. No evidence of delayed fracture, and, therefore stress corrosion, of single crystal silicon was observed for liquid environments including water, acetone, and aqueous solutions of NaCl, NH4OH, and HNO3, when tested with a flaw parallel to a (110) surface. The fracture toughness was calculated
Thermosolutal convection in high-aspect-ratio enclosures
Convection in high-aspect-ratio rectangular enclosures with combined horizontal temperature and concentration gradients is studied experimentally. An electrochemical system is employed to impose the concentration gradients. The solutal buoyancy force either opposes or augments the thermal buoyancy force. Due to a large difference between the thermal and solutal diffusion rates the flow possesses double-diffusive characteristics. Various complex flow patterns are observed with different experimental conditions
Thermal components for 1.8 K space cryogenics
Work of the summer 1986 is summarized in three areas. First, conceptual design of a laboratory system for heat exchanger evaluation in conjunction with the operation of a thermally activated fountain effect pump (FEP) is presented. Second, Knudsen effect evaluation of fine porous media useful for the pressurization plug which forms the main component of the FEP is described. Third, proof-of-principle test of the lab system selected on the basis of the evaluation is summarized
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