2,046 research outputs found
Hybrid collocation perturbation for PDEs with random domains
In this work we consider the problem of approximating the statistics of a
given Quantity of Interest (QoI) that depends on the solution of a linear
elliptic PDE defined over a random domain parameterized by random
variables. The random domain is split into large and small variations
contributions. The large variations are approximated by applying a sparse grid
stochastic collocation method. The small variations are approximated with a
stochastic collocation-perturbation method. Convergence rates for the variance
of the QoI are derived and compared to those obtained in numerical experiments.
Our approach significantly reduces the dimensionality of the stochastic
problem. The computational cost of this method increases at most quadratically
with respect to the number of dimensions of the small variations. Moreover, for
the case that the small and large variations are independent the cost increases
linearly
A Structural Approach to the Analysis of Rock Music
This dissertation situates itself in the middle of an ongoing debate about the applicability of Schenkerian analytical techniques to the analysis of pop and rock music. In particular, it investigates ways in which the standard conceptions of voice leading, harmonic function, and counterpoint may be updated to better apply to this new repertoire. A central claim is that voice-leading structure is intimately related to formal structure such that the two domains are mutually informing.
Part I of the dissertation focuses on harmonic and melodic theory. Chapter 2, Harmonic Syntax, advocates for a conception of harmonic function based on syntax and form rather than the identity of specific chords. In this conception, chords other than V, such as IV, II, flat-VII, or even some versions of I, can often be said to function syntactically as the dominant. Chapter 3, The Melodic-Harmonic Divorce, explores contrapuntal paradigms in which the domains of melody and harmony seem to be operating independently. This chapter outlines three types of melodic-harmonic divorce: hierarchy divorce, rotation divorce, and syntax divorce. Part II of the dissertation aims to devise voice-leading models for full song forms. Chapter 4 focuses on AABA form, Chapter 5 on verse-prechorus-chorus, and Chapter 6 on verse-chorus forms. These chapters demonstrate that these common forms are associated with general voice-leading structures that act in dialog with the specific voice-leading structures of songs that exhibit these forms. This part of the dissertation is largely analytical, and has the secondary goal of demonstrating a Schenkerian analytical methodology applied to rock music
Estudo da ação efetiva do óleo de mamona na ação antiespumante no processo de fermentação alcoólica.
The Cochlear Tuning Curve
The tuning curve of the cochlea measures how large an input is required to
elicit a given output level as a function of the frequency. It is a fundamental
object of auditory theory, for it summarizes how to infer what a sound was on
the basis of the cochlear output. A simple model is presented showing that only
two elements are sufficient for establishing the cochlear tuning curve: a
broadly tuned traveling wave, moving unidirectionally from high to low
frequencies, and a set of mechanosensors poised at the threshold of an
oscillatory (Hopf) instability. These two components suffice to generate the
various frequency-response regimes which are needed for a cochlear tuning curve
with a high slope
Kf evaluation in GFRP composites by thermography
Since the presence of a notch in a mechanical component causes a reduction in the fatigue strength, it is important to know the kf value for a given notch geometry and material. This parameter is fundamental in the fatigue design of aeronautical components that are mainly made of composites. kf is available in the literature for numerous types of notch but only for traditional materials such as metals. This paper presents a new practice, based on thermographic data, for the determination of the fatigue notch coefficient kf in composite notched specimens. The innovative aspect of this study is therefore to propose the application on composite materials of a new thermographic procedure to determine kf for several notch geometries: circular, U and V soft and severe notches. It was calculated, for each type of notch, as the ratio between the fatigue limits obtained on the cold and hot zone corresponding to the smooth and notched specimen, respectively. Consequently, this research activity provides, for the first time, a little database of kf for two particular typologies of composite materials showing a fast way to collect further values for different laminates and notch geometries
Occurrence of antibiotics in mussels and clams from various FAO areas
Filter feeders, like mussels and clams, are suitable bioindicators of environmental pollution. These shellfish, when destined for human consumption, undergo a depuration step that aims to nullify their pathogenic microorganism load and decrease chemical contamination. Nevertheless, the lack of contamination by drugs may not be guaranteed. Antimicrobials are a class of drugs of particular concern due to the increasing phenomenon of antibiotic resistance. Their use in breeding and aquaculture is a major cause of this. We developed a multiclass method for the HPLC\ue2\u80\u93MS/MS analysis of 29 antimicrobials, validated according to the Commission Decision 2002/657/UE guidelines, and applied it to 50 mussel and 50 clam samples derived from various Food and Agricultural Organisation marine zones. The results obtained, indicate a negligible presence of antibiotics. Just one clam sample showed the presence of oxytetracycline at a concentration slightly higher than the European Union Maximum residue limit set for fish
The Economically Important Nitrogen Pathways of Southwest Florida
The global phenomenon of burgeoning coastal population growth has led to
coastal watershed landscape transformation and ecosystem degradation, prompting
policy-makers to set limits on freshwater withdrawals and labile nutrient loads. Important
components of Florida’s economies lie in the state’s expansive coastal zone; the
organisms driving the billion-dollar recreational fishing industry are rooted in coastal
habitats, while the agriculture and real-estate industries sprawl throughout numerous
coastal watersheds. This study aimed to identify the connections between anthropogenic
land use and essential juvenile fish nursery habitats within the coastal zone, which is the
first critical step for sustaining the ecology and related economies of the region.
The need for this study arises from the fact that these economies are
interconnected through nitrogen, and therefore nitrogen management can influence their
prosperity or collapse. Juvenile fish nursery habitats are located in waters that receive
nitrogen from adjacent landscapes. Runoff delivers nitrogen derived from human
nitrogen use and processing within the watersheds to the juvenile fish nursery habitats.
Ecosystem managers must understand that although copious amounts of nitrogen
applied to land may ultimately support nursery habitat foodwebs, overwhelming nitrogen
loads may also create algal blooms that decay and cause lethal hypoxic events leading
to ecosystem degradation. This study aims to pinpoint the specific nitrogen sources that
support primary production and ultimately fish production in watersheds dominated by
agricultural landscapes and residential neighborhoods.
Stable isotopes are versatile tools used to identify these connections. The
nitrogen and carbon compounds that make up the moieties of an ecosystem inherently
carry information on major nitrogen sources, trophic structure as well as the crucial
information concerning dominant nitrogen removal and transformative processes that
occur within sediments. Specifically in this study, the stable isotopes of carbon and
nitrogen of dissolved inorganic nitrogen, primary producers, and fish were used to
identify 1) the connections between urban and agricultural landscapes and the nutrients
that percolate through the foodweb, 2) the primary producers that support fish biomass,
3) the origins of sedimentary organic matter that can provide new nitrogen via recycling,
and 4) the heterogeneous function of fish nursery habitats in polluted systems. This
study was conducted during the region’s wet and dry seasons and in over thirty
watersheds that differ from each other in terms of size and anthropogenic influence.
In agricultural watersheds, nitrogen derived from row crops and tree crops
ultimately supported fish production during the wet season. Convective afternoon
thunderstorms coupled with runoff delivered nitrogen from the landscape to receiving
waters. These nutrients supported phytoplankton which deposited into the sediments
and supported benthic foodwebs. During the dry season, nitrogen derived from row
crops and nitrogen transformation in the sediments ultimately supported fish production.
In this case, irrigation water used for agriculture delivered nitrogen from lands covered
with row crops to the nursery habitats in receiving waters.
The dry season was characterized by the nitrogen transformation process known
as dissimilatory nitrogen reduction to ammonium (DNRA), where biologically available
nitrate is converted to biologically available ammonium. Phytoplankton deposits, most
likely delivered during the wet season, were recycled through the slow burning DNRA
processes, which provided nitrogen for the benthic microalgae that dominated in the dry
season. These organisms in turn supported benthic communities which ultimately
supported dry season fish production.
In small urban watersheds, nitrogen derived from septic tanks, lawn irrigation,
leaky sewage pipes, and atmospheric deposition ultimately supported fish production via
phytoplankton, but unlike the nitrogen sources in agricultural watersheds, these sources
(with the exception of atmospheric deposition) were seasonally consistent because a
mechanisms to deliver nitrogen derived from septic tanks, lawn fertilizer, and leaky
sewage pipes were, at least to some extent, available during both seasons.
In polluted, tidal, fish-nursery habitats, the specific mechanism that
allowed nursery habitats to decrease the ratio of mortality over growth rates of
juvenile fish was not consistent among systems. These mechanisms were likely
dependent on physical-chemical parameters and stream geomorphology. If the
geomorphology or physical-chemical characteristics of nursery habitats are not
adequate to set up an efficient nitrogen transfer process to fish, these habitats
become more of a haven from predators rather than a source of food for fish.
This study has several implications for management. Managers must first
recognize that microalgae are dominant supporters of tidal nursery foodwebs. Managers
must define the relationship between nitrogen loads and fish abundance. If this
relationship is unknown, the results of increasing nitrogen loads on fish production will
remain uncertain; foodwebs in nursery habitats may collapse due to eutrophication, or
fish abundance may increase due to increases in food supply. Connectivity factors
derived from stable isotope mechanistic mass-balance models can be used as
measurable targets for groups of watersheds. The use of wetlands as nitrogen
remediation tools may not be effective at removing nitrogen; nitrogen transformation
processes such as DNRA likely outweigh removal processes in wetland soils
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