24,463 research outputs found
Within-Generation Morality of the Jack Pine Tip Beetle, \u3ci\u3eConophthorus Banksianae\u3c/i\u3e McPherson, in Michigan
(excerpt)
The jack pine tip beetle (Conophthorus banksianae McPherson) is a shoot-infesting scolytid hat primarily attacks jack pine (Pinus banksiana Lamb.) in Michigan. The insect was previously thought to be a variant of C. resinosae Hopkins, which attacks cones and shoot tips of red pine. McPherson described C. banksianae as a new species, following life cycle and behavioral studies (McPherson, Wilson, and Stehr 1970; McPherson, Stehr, and Wilson 1970). Separating them by morphological features has been unsuccessful (Herdy 1963)
Ecosystem-based Management for Protected Species in the North Pacific Fisheries
In the North Pacific Ocean, an ecosystem-based fishery management approach has been adopted. A significant objective of this approach is to reduce interactions between fishery-related activities and protected species. We review management measures developed by the North Pacific Fishery Management Council and the National Marine Fisheries Service to reduce effects of the groundfish fisheries off Alaska on marine mammals and seabirds, while continuing to provide economic opportunities for fishery participants. Direct measures have been taken to mitigate known fishery impacts, and precautionary measures have been taken for species with potential (but no documented) interactions with the groundfish fisheries. Area closures limit disturbance to marine mammals at rookeries and haulouts, protect sensitive benthic habitat, and reduce potential competition for prey resources. Temporal and spatial dispersion of catches reduce the localized impact of fishery removals. Seabird avoidance measures have been implemented through collaboration with fishery participants and have been highly successful in reducing seabird bycatch. Finally, a comprehensive observer monitoring program provides data on the location and extent of bycatch of marine mammals and seabirds. These measures provide managers with the flexibility to adapt to changes in the status of protected species and evolving conditions in the fisheries. This review should be useful to fishery managers as an example of an ecosystem-based approach to protected species management that is adaptive and accounts for multiple objectives
Connecting physical resonant amplitudes and lattice QCD
We present a determination of the isovector, -wave scattering
phase shift obtained by extrapolating recent lattice QCD results from the
Hadron Spectrum Collaboration using MeV. The finite volume spectra
are described using extensions of L\"uscher's method to determine the infinite
volume Unitarized Chiral Perturbation Theory scattering amplitude. We exploit
the pion mass dependence of this effective theory to obtain the scattering
amplitude at MeV. The scattering phase shift is found to be in
good agreement with experiment up to center of mass energies of 1.2 GeV. The
analytic continuation of the scattering amplitude to the complex plane yields a
-resonance pole at .
The techniques presented illustrate a possible pathway towards connecting
lattice QCD observables of few-body, strongly interacting systems to
experimentally accessible quantities.Comment: 8 pages, 6 figures, equivalent to published version, added two
appendices and a figur
Carbon Brainprint Case Study: optimising defouling schedules for oil- refinerypreheat trains
In an oil refinery, crude oil is heated to 360-370°C before entering a
distillation columnoperating at atmospheric pressure where the gas fraction and
several liquid fractions withdifferent boiling points (e.g. gasoline, kerosene,
diesel, gas oil, heavy gas oil) are separated off.The crude oil is heated in two
stages. The preheat train - a series of heat exchangers - heats itfrom ambient
temperature to about 270°C when it enters the furnace, known as the coil
inlettemperature. The furnace then heats the oil to the temperature required for
distillation.The purpose of the preheat train is to recover heat from the liquid
products extracted in thedistillation column. Without this, 2-3% of the crude
oil throughput would be used for heating thefurnace; with the preheat train up
to 70% of the required heat is recovered. It also serves tocool the refined
products: further cooling normally uses air or water.
Over time, fouling reduces the performance of the heat exchangers, increasing
the amount ofenergy that has to be supplied. It is possible to bypass units to
allow them to be cleaned, withan associated cost and temporary loss of
performance. The cleaning schedule thus has animpact on the overall efficiency,
cost of operation and emissions.
The group at the Department of Chemical Engineering and Biotechnology at
Cambridgedeveloped a scheduling algorithm for this non-linear optimisation
problem. It yields a good,though not-necessarily optimal, schedule and can
handle additional constraints, such as thepresence of desalters with specific
temperature requirements within the preheat train. This isnow being developed
into a commercial software product.
Data from two refineries - one operated by Repsol YPF in Argentina and the Esso
FawleyRefinery in the UK - were used to model the systems and test the
algorithm.
For the Repsol YPF refinery, when compared with current practice and including a
constrainton the desalter inlet temperature, the most conservative estimate of
the emissions reductionwas 773 t CO2/year. This assumed a furnace efficiency of
90%. The emissions reductionincreased to 927 t CO2/year at 75% efficiency and
1730 t CO2/year at 40%. These were basedon a stoichiometric estimate of the
emissions from the furnace. Using a standard emissionfactor increased them by
7.4%.
For Esso Fawley, the estimated emission reduction compared to no maintenance
was1435 t CO2/year at 90% furnace efficiency. This increased to 1725 t CO2/year
at 75% and3225 t CO2/year at 40% efficien
Isoscalar scattering and the mesons from QCD
We present the first lattice QCD study of coupled isoscalar
- and -wave scattering extracted from
discrete finite-volume spectra computed on lattices which have a value of the
quark mass corresponding to MeV. In the sector we find
analogues of the experimental and states, where the
appears as a stable bound-state below threshold, and, similar
to what is seen in experiment, the manifests itself as a dip in the
cross section in the vicinity of the threshold. For
we find two states resembling the and ,
observed as narrow peaks, with the lighter state dominantly decaying to
and the heavier state to . The presence of all these
states is determined rigorously by finding the pole singularity content of
scattering amplitudes, and their couplings to decay channels are established
using the residues of the poles
Tailoring Systems Engineering for Rapid Acquisition
The use of Systems Engineering (SE) is mandated by the Department of Defense and United States Air Force (USAF) policy and is to be considered under the purview of the Program Manager. A normal SE program can consist of multiple processes from user requirement generation to the verification and validation of the system under design. The SE process encompasses the entire acquisition program and can take multiple years to conduct with completion only being achieved when the program is disposed of at the end of its life. Rapid acquisition programs such as a Joint Urgent Operational Need can have timelines that are compressed to less than 24 months. This compressed timeline often necessitates the truncation or removal of tasks. This research examines the literature on how the USAF completes rapid acquisitions and compares it to the responses of twelve members of the acquisition community with experience in rapid acquisition. The data is categorized to allow for the main points to be collected explaining how the USAF tailors the acquisition and SE processes. The results showed that while some programs do follow prescribed instructions most use an ad-hoc execution process and the Systems Engineering Technical Management Processes were underutilized
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