The influence of natural enemies and plant apparency in
determining the abundance of the cabbage aphid Brevicoryne brassicae L.
and the imported cabbageworm Pieris rapae L. was examined on collards
grown in a collard monoculture and in a collard-alfalfa biculture.
This design was used to examine the factors affecting collardherbivore...
In recent years, red raspberry production in Washington and British Columbia has been severely limited by a newly emerged virus complex that causes symptoms of crumbly fruit. The complex is comprised of three viruses: Raspberry bushy dwarf virus (RBDV), Raspberry leaf mottle virus (RLMV) and Raspberry latent virus (RpLV). Both...
Modeling and analyzing the combined effects of disease and population dynamics
is important in understanding the effects of mechanisms such as pathogen transmission
and direct competition between host species on the distribution and abundance of different
species in an ecological community. Mathematical analysis of such models in a
spatially explicit...
The work in this thesis solves the problem of restoring a power
system to its operating stable equilibrium point, following a transient
disturbance, in minimum time without any oscillation. The idealized
power system considered consists of cylindrical rotor generator connected
to an infinite busbar with the following cases of control:...
Greenhouse and growth chamber experiments were conducted with
the following objectives: (a) to study the effects of N-1-naphthylphthalamic
acid (naptalam) on shoot and tuber production, rhizome transformation,
and growth of yellow nutsedge (Cyperus esculentus L.) plants;
(b) to study the effects of N-phosphonomethyl glycine (glyphosate) on
nutsedge plants at different...
As a significant class of nonlinear systems, bilinear systems (BLS) are extensively developed in the past years. In addition to their advantages over linear systems which are often not adequate to represent accurately many control processes, the BLS are particularly appealing in modeling biological systems in which parametric controls are...
A new approximation technique to a certain class of nonlinear
filtering problems is considered in this dissertation. The method is
based on an approximation of nonlinear, partially-observable systems
by a stochastic control problem with fully observable state. The
filter development proceeds from the assumption that the
unobservables are conditionally Gaussian...
Control issues are investigated for a parafoil and payload system with left and right parafoil brakes used as the control mechanism. It is shown through dynamic modeling and simulation that parafoil and payload systems can exhibit two basic modes of lateral control, namely, roll and skid steering. Using a small...
The feasibility of managing codling moth, Cydia pomonella (L.), with mixtures
of Bacillus thuringiensis-based microbial and selected chemical insecticides was
studied under laboratory and field conditions. Joint actions (synergism, additivity and
antagonism) of these mixtures were determined for both egg and larval stages. Higher
rates of microbial control agents (MCAs),...
This dissertation studies the microeconomics of forest fire suppression programs. It starts with an inquiry into the causes of increasing shares of public land management budgets devoted to wildland fire suppression in lieu of hazardous fuel reduction or other pre-fire risk mitigation programs. The first two chapters consider competing economic...
This paper describes a learning control system which is capable
of controlling a linear plant subjected to periodic inputs, providing
that an upper limit for the order of the plant is known. Otherwise the
characteristics of the plant and the inputs are unknown. Only one
system variable is measured. The...
The present investigation was designed to test two major hypotheses
and five sub-hypotheses. The two major hypotheses were:
(1) Parental models influence the shaping of children's responses to
frustration, and (2) There is a positive relation between parental
consistency in responses to frustration and children's imitation of
parental responses. Three...
Elodea densa Planch. was exposed to diquat (6, 7 dihydrodipyrido [1,2-a: 2', 1'-c] pyrazinediium dibromide), alone and in combination
with disodium endothall (disodium salt of 7-oxabicyclo [2.2.1]
heptane-2, 3-dicarboxyclic acid), and copper sulfate pentahydrate.
Studies were conducted in coastal lakes of Oregon infested with E.
densa. Dichlobenil (2, 6 dichlorobenzonitrile)...
The amounts of residual dichlobenil (2,6-dichlorobenzonitrile)
in water and hydrosoil were compared periodically following application
of the wettable powder and granular formulations of the
herbicide to separate ponds at ten pounds of active ingredient per
surface acre {0.6 ppmw (parts per million by weight) }. Dichlobenil
was measured by electroncapture...
This report is concerned with the analysis of the effect of
finite wordlength, channel capacity and source rate in digital feedback
control of linear systems. The cases considered are (1) finite
wordlength A/D conversion, no feedback delay, ideal ROM (read
only memory) controller; (2) finite A/D wordlength (source rate),
state...
Tansy ragwort (Senecio jacobaea L. ) is a poisonous weed which
infests alfalfa fields in western Oregon. Studies were conducted to
evaluate the effectiveness of asulam (methyl sulfanilylcarbamate)for
control of tansy ragwort in alfalfa and to elucidate factors responsible
for its selectivity. In seven replicated field trials in 1973 and...