953 resultados para Input saturation


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The goal of the Puget Sound Nearshore Ecosystem Restoration Project (PSNERP) is to improve system-wide functionality of nearshorei ecosystem processes. To achieve that goal, PSNERP plans to strategically restore nearshore sites throughout Puget Sound. PSNERP scientists are assessing changes to the nearshore, and will recommend an environmentally strategic restoration portfolio. Yet, PSNERP also needs stakeholder input to design a socially strategic portfolio. This research investigates the values and preferences of stakeholders in the Whidbey Sub-Basin of Puget Sound to help PSNERP be both socially and environmentally strategic. This investigation may be repeated in the six other Puget Sound Sub-Basins. The results will guide restoration portfolio design and future stakeholder involvement activities. This study examines four areas of stakeholder values and preferences: 1) beliefs about the causes, solutions, and severity of nearshore problems; 2) priorities for nearshore features, shoreforms, developments, and restoration objectives; 3) thoughts about ecosystem servicesiii and trade-offs among them; and 4) visions of a future, restored Puget Sound nearshore and the role of science in attaining this vision. The study is framed by two hypotheses from the Advocacy Coalition Framework (ACF), which suggests that groups of policy advocates form around shared “policy core beliefs” which can transcend traditional categories of stakeholders.(PDF contains 3 pages)

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Standard earthquake analyses of civil engineering structures use uniform ground motions even though considerable variations in both amplitude and phase can occur along the foundation interface for long-span bridges and large dams. The objective of this thesis is to quantify the effect that these nonuniformities have on the structural response.

The nonuniform, free-field motions of the foundation interface are assumed to be caused by incident plane body waves. The medium in which these waves travel is a linear, elastic half-space containing a canyon of uniform cross section in which the structure is placed. The solutions for the free-field motions that are due to incident SH, P and SV waves are calculated using the boundary element method.

An analysis of Pacoima (arch) dam located near Los Angeles, California, is performed for both uniform and nonuniform excitations. The important effect of nonuniformities in the free-field motions, sometimes leading to a decrease in the dam response and sometimes to an increase, is quantified.

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Red-shift conical emission (CE) is observed by femtosecond laser pulse propagating in BK7 at a low input power (compared to those input powers for generation of blue-shift CE). With the increasing input power the blue-shift CE begins to appear whereas the red-shift CE ring (902 nm in our experiment) disappears accompanied by the augment of the central white spot size synchronously. The disappearing of red-shift CE in our experiment is explained such that the increase of axial intensity is much higher than that of ring emission and the augment of the central white spot size with the increasing input laser power.

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A description is given of experimental work on the damping of a second order electron plasma wave echo due to velocity space diffusion in a low temperature magnetoplasma. Sufficient precision was obtained to verify the theoretically predicted cubic rather than quadratic or quartic dependence of the damping on exciter separation. Compared to the damping predicted for Coulomb collisions in a thermal plasma in an infinite magnetic field, the magnitude of the damping was approximately as predicted, while the velocity dependence of the damping was weaker than predicted. The discrepancy is consistent with the actual non-Maxwellian electron distribution of the plasma.

In conjunction with the damping work, echo amplitude saturation was measured as a function of the velocity of the electrons contributing to the echo. Good agreement was obtained with the predicted J1 Bessel function amplitude dependence, as well as a demonstration that saturation did not influence the damping results.

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SECTION I

Section I is concerned with a partial sequence analysis conducted on 5S RNA from HeLa cells. Analysis of the oligonucleotide pattern after pancreatic ribonuclease digestion of a highly-purified preparation of 5S RNA gave results which were in general agreement with those published for KB cells, both with respect to the identity and the frequency of the partial sequences. However, the presence of a trinucleotide not found in the KB 5S pattern, together with the reproducibly much lower than expected molar yield of the larger oligonucleotides strongly suggested the occurrence of alternate sequences at various sites in the 5S molecules of human cells. The presence of ppGp and pppGp at the 5'-terminus of HeLa 5S RNA was clearly demonstrated. The implications of this finding with regard to the origin of 5S RNA are discussed.

SECTION II

In Section II the proportion of the HeLa cell genome complementary to tRNA was investigated by using RNA- DNA hybridization. The value for saturation of the HeLa DNA by tRNA was found to be 1.1 x 10-5, which corresponds to about 4900 sites for tRNA per HeLa cell in an exponentially growing culture. Analysis of the nucleotide composition of the hybridized tRNA revealed significant differences from the nucleotide composition of the input tRNA, with the purine to pyrimidine ratio indicating, however, that these differences were not produced by excessive RNase attack of the hybrid. The size of the hybridized tRNA was only moderately smaller than that of the input RNA; the average S value in formaldehyde was 2.7 (corresponding to a length of about 65 nucleotides), suggesting that a relatively small portion near the ends of the hybridized 4S chains had been removed by RNase.

SECTION III

The proportion of the HeLa cell genome complementary to 5S RNA was investigated by using RNA-DNA hybridization. The value for saturation of the HeLa DNA by 5S RNA was found to be 2.3 x 10-5, which corresponds to about 7,000 sites for 5S RNA per HeLa cell in an exponentially growing culture. Analysis of the nucleotide composition of the hybridized 5S RNA revealed no significant difference from the nucleotide composition of the input RNA. At the RNA to DNA input ratio of 1:1000, the average S value in formaldehyde of the hybridized 5S RNA corresponded to a polynucleotide chain about two-thirds the size of the input RNA.

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Theoretical and experimental studies of a gas laser amplifier are presented, assuming the amplifier is operating with a saturating optical frequency signal. The analysis is primarily concerned with the effects of the gas pressure and the presence of an axial magnetic field on the characteristics of the amplifying medium. Semiclassical radiation theory is used, along with a density matrix description of the atomic medium which relates the motion of single atoms to the macroscopic observables. A two-level description of the atom, using phenomenological source rates and decay rates, forms the basis of our analysis of the gas laser medium. Pressure effects are taken into account to a large extent through suitable choices of decay rate parameters.

Two methods for calculating the induced polarization of the atomic medium are used. The first method utilizes a perturbation expansion which is valid for signal intensities which barely reach saturation strength, and it is quite general in applicability. The second method is valid for arbitrarily strong signals, but it yields tractable solutions only for zero magnetic field or for axial magnetic fields large enough such that the Zeeman splitting is much larger than the power broadened homogeneous linewidth of the laser transition. The effects of pressure broadening of the homogeneous spectral linewidth are included in both the weak-signal and strong-signal theories; however the effects of Zeeman sublevel-mixing collisions are taken into account only in the weak-signal theory.

The behavior of a He-Ne gas laser amplifier in the presence of an axial magnetic field has been studied experimentally by measuring gain and Faraday rotation of linearly polarized resonant laser signals for various values of input signal intensity, and by measuring nonlinearity - induced anisotropy for elliptically polarized resonant laser signals of various input intensities. Two high-gain transitions in the 3.39-μ region were used for study: a J = 1 to J = 2 (3s2 → 3p4) transition and a J = 1 to J = 1 (3s2 → 3p2) transition. The input signals were tuned to the centers of their respective resonant gain lines.

The experimental results agree quite well with corresponding theoretical expressions which have been developed to include the nonlinear effects of saturation strength signals. The experimental results clearly show saturation of Faraday rotation, and for the J = 1 t o J = 1 transition a Faraday rotation reversal and a traveling wave gain dip are seen for small values of axial magnetic field. The nonlinearity induced anisotropy shows a marked dependence on the gas pressure in the amplifier tube for the J = 1 to J = 2 transition; this dependence agrees with the predictions of the general perturbational or weak signal theory when allowances are made for the effects of Zeeman sublevel-mixing collisions. The results provide a method for measuring the upper (neon 3s2) level quadrupole moment decay rate, the dipole moment decay rates for the 3s2 → 3p4 and 3s2 → 3p2 transitions, and the effects of various types of collision processes on these decay rates.

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A decade-long time series recorded in southern Monterey Bay, California demonstrates that the shallow, near-shore environment (17 m depth) is regularly inundated with pulses of cold, hypoxic and low pH water. During these episodes, oxygen can drop to biologically threatening levels, and pH levels were lower than expected. Weekly water chemistry monitoring revealed that the saturation state of aragonite (the more soluble form of calcium carbonate) was often below saturation and had a moderate positive relationship with pH, however, analytical and human error could be high. Pulses of hypoxia and low pH water with the greatest intensity arise at the onset of the spring upwelling season, and fluctuations are strongly semidurnal (tidal) and diurnal. Arrival of cold, hypoxic water on the inner shelf typically occurs 3 days after the arrival of a strong upwelling event and appears to be driven by upwelling modulated by internal tidal fluctuations. I found no relationship between the timing of low-oxygen events and the diel solar cycle nor with terrestrial nutrient input. These observations are consistent with advection of hypoxic water from the deep, offshore environment where water masses experience a general decline of temperature, oxygen and pH with depth, and inconsistent with biochemical forcing. Comparisons with concurrent temperature and oxygen time series taken ~20 km away at the head of the Monterey Canyon show similar patterns but even more intense hypoxic events due to stronger semidiurnal forcing there. Analysis of the durations of exposure to low oxygen levels establishes a framework for assessing the ecological relevance of these events. Increasing oceanic hypoxia and acidification of both surface and deep waters may increase the number, intensity, duration and spatial extent of future intrusions along the Pacific coast. Evaluation of the resiliency of nearshore ecosystems such as kelp forests, rocky reefs and sandy habitats, will require consideration of these events.