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Quantifying the effects of temperature on dormancy change and germination in orchardgrass (<i>Dactylis glomerata</i> L.) and western wheatgrass (<i>Pascopyrum smithii</i> [Rydb.] L.)Qiu, Jie 14 June 2005
Orchardgrass (<i>Dactylis glomerata</i> L.) and western wheatgrass (<i>Pascopyrum smithii </i>(Rydb.) L.) seeds have different degrees of dormancy that result in non-uniform seedling emergence in the field. Seed dormancy of the two species, in part, causes disagreement between germination tests in the laboratory and seedling emergence in the field. Experiments were conducted over two years in the laboratory and in the field to determine the effects of alternating temperatures on changes in seed dormancy and germination of orchardgrass and western wheatgrass. The two western wheatgrass cultivars (Walsh and LC9078a) had deeper dormancy than the two orchardgrass cultivars (Arctic and Lineta). Dormancy of both species was broken by temperatures with 10oC amplitude; this temperature variation was similar to that which occurred at a 1 cm depth in the soil. Optimal temperatures for germination of orchardgrass (10-25oC) were broader than those for western wheatgrass (15-20oC). Seedling emergence of orchardgrass was less sensitive to seeding date in the spring than western wheatgrass; seedling emergence of western wheatgrass increased as seeding date was delayed from early to late May if soil water was not limiting. The rate of seedling emergence increased with increasing temperature in both species, therefore, faster and more uniform seedling emergence can be expected from late spring seeding dates. Seeds were often exposed to light during germination tests in the laboratory while planting seeds in the soil usually prevented exposure of seeds to light. Seedling emergence of orchardgrass in the field was usually less than the germination percentage obtained in the laboratory because of light exposure during germination tests could break dormancy in orchardgrass seeds and the small seeds of orchardgrass had limited energy reserves for pre-emergence seedling growth. On the other hand, germination of western wheatgrass seeds was reduced by exposure to light during germination and seeds were larger than those of orchardgrass. Therefore, seedling emergence of western wheatgrass in the field was usually greater than germination tests would predict. The use of thermal time models to study seed dormancy changes and germination revealed the dual effects of temperature on these processes. The modified thermal time model takes the difference between germination and seedling emergence into account and can accurately predict seedling emergence in the field (R2=0.88 to 0.99). Thermal time models for predicting seedling emergence in the field can also be developed for other forages, however, cultivar- and species-specific parameters must be developed for the models.
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The role of BDNF in the injured/regenerating sensory neuronGeremia, Nicole Marie 22 December 2005
Peripheral nerve injury induces a robust regenerative state in sensory neurons that includes elevated expression of injury/regeneration-associated genes. The molecular signal(s) underlying the transition to the regenerating state are largely unknown. Brain-derived neurotrophic factor (BDNF) is the sole identified neurotrophin that is upregulated in sensory neurons following peripheral nerve injury. As members of the neurotrophin family exert a profound influence on the intact phenotype of sensory neurons, I hypothesize that injury-associated alterations in BDNF expression play a similar role in the injured/regenerating response. Antagonizing endogenous BDNF with a function-blocking antibody prevented increases in injury/regeneration-associated gene expression and decreased the growth capabilities of the injured sensory neurons. However, BDNF was not important for maintaining this cell body response in injured neurons. The elevation of BDNF expression in injured sensory neurons either through intrathecal infusion or electrical stimulation was associated with increased injury/regeneration-associated gene expression in a dose dependent manner and the latter corresponded to increased sensory axonal regeneration. Though BDNF was able to induce and enhance the intrinsic cell body response of injured sensory neurons, exogenous BDNF was not sufficient to induce an injury phenotype in intact sensory neurons. Thus, additional signals are likely induced by the injury response. In conclusion, BDNF plays a critical role in inducing the regenerative state in sensory neurons following injury and strategies aimed at elevating levels of BDNF available to the injured sensory neuron during the inductive phase improve the cell body response.
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Finite element based rotor design optimization for the brushless doubly-fed machineSalim, Mohamed Ali, 1968- 13 April 1993 (has links)
Brushless Doubly-Fed Machines have potential benefits in variable speed
generation and adjustable speed drive applications by combining a robust machine
structure with a reduced power converter rating. While recent work has demonstrated
feasibility, steady-state performance has not been optimized. The nature of doubly-fed
operation causes rotor currents of varying, relatively high frequency. Moreover, the rotor
structure deviates from conventional squirrel cages. Consequently, induction machine
rotor bar geometries need to be carefully examined and refined for applicability in the
doubly-fed system.
The present thesis uses finite element analysis to investigate alternative rotor bar
design. Two-dimensional finite element analysis is used to investigate basic rotor bar
characteristics. Interface with a detailed simulation program enables investigation of
assembled rotors, otherwise a three-dimensional analysis problem.
Rotor bar geometries for a high speed alternator are investigated. Bar shapes are
kept simple to allow manufacturing of the rotor in the absence of the-casting equipment.
Rotor prototypes are constructed using custom, laser-cut laminations and experimental
results for the alternator verify improved line-to-shaft efficiencies over conventional rotor
geometries as well as off-the-shelf alternators. / Graduation date: 1994
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A low cost AC motor drive for battery powered applicationsWiley, Brian 19 August 1993 (has links)
Environmental concerns have renewed the interest in electric vehicles. To gain
widespread use, electric vehicles will also have to offer good performance and be
reasonably priced. AC drive systems using modern semiconductors can provide
efficient operation at the required power levels, but their cost at present is still too
high. This paper discusses the development of an AC induction motor drive system
which potentially lowers cost by using a digital controller. The controller is shown to
implement a high performance field-oriented control, while keeping a low parts count
by maximizing use of interface circuits which are integrated onto the microprocessor
chip. Cost is further reduced by designing the system to reuse motor control
components for battery charging and eliminate the need for external circuits.
Experimental results are presented for a low power prototype system. / Graduation date: 1994
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Recovering Data with Group Sparsity by Alternating Direction MethodsDeng, Wei 06 September 2012 (has links)
Group sparsity reveals underlying sparsity patterns and contains rich structural information in data. Hence, exploiting group sparsity will facilitate more efficient techniques for recovering large and complicated data in applications such as compressive sensing, statistics, signal and image processing, machine learning and computer vision. This thesis develops efficient algorithms for solving a class of optimization problems with group sparse solutions, where arbitrary group configurations are allowed and the mixed L21-regularization is used to promote group sparsity. Such optimization problems can be quite challenging to solve due to the mixed-norm structure and possible grouping irregularities. We derive algorithms based on a variable splitting strategy and the alternating direction methodology. Extensive numerical results are presented to demonstrate the efficiency, stability and robustness of these algorithms, in comparison with the previously known state-of-the-art algorithms. We also extend the existing global convergence theory to allow more generality.
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Quantifying the effects of temperature on dormancy change and germination in orchardgrass (<i>Dactylis glomerata</i> L.) and western wheatgrass (<i>Pascopyrum smithii</i> [Rydb.] L.)Qiu, Jie 14 June 2005 (has links)
Orchardgrass (<i>Dactylis glomerata</i> L.) and western wheatgrass (<i>Pascopyrum smithii </i>(Rydb.) L.) seeds have different degrees of dormancy that result in non-uniform seedling emergence in the field. Seed dormancy of the two species, in part, causes disagreement between germination tests in the laboratory and seedling emergence in the field. Experiments were conducted over two years in the laboratory and in the field to determine the effects of alternating temperatures on changes in seed dormancy and germination of orchardgrass and western wheatgrass. The two western wheatgrass cultivars (Walsh and LC9078a) had deeper dormancy than the two orchardgrass cultivars (Arctic and Lineta). Dormancy of both species was broken by temperatures with 10oC amplitude; this temperature variation was similar to that which occurred at a 1 cm depth in the soil. Optimal temperatures for germination of orchardgrass (10-25oC) were broader than those for western wheatgrass (15-20oC). Seedling emergence of orchardgrass was less sensitive to seeding date in the spring than western wheatgrass; seedling emergence of western wheatgrass increased as seeding date was delayed from early to late May if soil water was not limiting. The rate of seedling emergence increased with increasing temperature in both species, therefore, faster and more uniform seedling emergence can be expected from late spring seeding dates. Seeds were often exposed to light during germination tests in the laboratory while planting seeds in the soil usually prevented exposure of seeds to light. Seedling emergence of orchardgrass in the field was usually less than the germination percentage obtained in the laboratory because of light exposure during germination tests could break dormancy in orchardgrass seeds and the small seeds of orchardgrass had limited energy reserves for pre-emergence seedling growth. On the other hand, germination of western wheatgrass seeds was reduced by exposure to light during germination and seeds were larger than those of orchardgrass. Therefore, seedling emergence of western wheatgrass in the field was usually greater than germination tests would predict. The use of thermal time models to study seed dormancy changes and germination revealed the dual effects of temperature on these processes. The modified thermal time model takes the difference between germination and seedling emergence into account and can accurately predict seedling emergence in the field (R2=0.88 to 0.99). Thermal time models for predicting seedling emergence in the field can also be developed for other forages, however, cultivar- and species-specific parameters must be developed for the models.
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The role of BDNF in the injured/regenerating sensory neuronGeremia, Nicole Marie 22 December 2005 (has links)
Peripheral nerve injury induces a robust regenerative state in sensory neurons that includes elevated expression of injury/regeneration-associated genes. The molecular signal(s) underlying the transition to the regenerating state are largely unknown. Brain-derived neurotrophic factor (BDNF) is the sole identified neurotrophin that is upregulated in sensory neurons following peripheral nerve injury. As members of the neurotrophin family exert a profound influence on the intact phenotype of sensory neurons, I hypothesize that injury-associated alterations in BDNF expression play a similar role in the injured/regenerating response. Antagonizing endogenous BDNF with a function-blocking antibody prevented increases in injury/regeneration-associated gene expression and decreased the growth capabilities of the injured sensory neurons. However, BDNF was not important for maintaining this cell body response in injured neurons. The elevation of BDNF expression in injured sensory neurons either through intrathecal infusion or electrical stimulation was associated with increased injury/regeneration-associated gene expression in a dose dependent manner and the latter corresponded to increased sensory axonal regeneration. Though BDNF was able to induce and enhance the intrinsic cell body response of injured sensory neurons, exogenous BDNF was not sufficient to induce an injury phenotype in intact sensory neurons. Thus, additional signals are likely induced by the injury response. In conclusion, BDNF plays a critical role in inducing the regenerative state in sensory neurons following injury and strategies aimed at elevating levels of BDNF available to the injured sensory neuron during the inductive phase improve the cell body response.
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Synthesis and Characterization of Low Bandgap Copolymer based on Thiophene DerivativeJhuang, Syun-Fong 08 July 2011 (has links)
Since the discovery of the photovoltaic effect in bulk heterojunction
devices¡Mthe considerable publications in PSCs have been reported¡OPSCs
based on the concept of bulk heterojunction (BHJ) configuration where
active layer comprises of a p-type donor (conjugated polymer) and a n-type
acceptor (fullerene derivative) materials¡Mrepresents the most useful strategy
to maximize the internal donor-acceptor interface area allowing for efficient
charge separation¡OTo further enhance the power conversion efficiency
from solar cells made of poly(3-hexylthiophene)/[6,6]-phenyl C61 butyric
acid methyl ester (P3HT/PCBM) ¡M a new conducting polymer with
optimized band energy levels are demonstrated to be one of the key
properties¡OIn this study¡MI synthesized a soluble and strongly visible-light
absorbing alternating conducting polymer using Suzuki coupling
polymerization method¡OThe UV-Vis absorption spectra of copolymer contains an intramolecular charge transfer (ICT) transition band¡Mwhich
leads to absorption extending to near-infrared region and optical band gaps
is 1.55 eV¡OThe photo-electron spectroscopy in air(PESA) measurements
show that the HOMO level of the polymer is ~5.0eV which is lower than
P3HT¡O
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Application of the ADI-FDTD Method to Planar CircuitsFan, Yang-Xing 01 July 2004 (has links)
The Finite-Difference Time Domain (FDTD) method is a very useful numerical simulation technique for solving problems related to electromagnetism. However, as the traditional FDTD method is based on an explicit finite-difference algorithm, the Courant-Friedrich-Levy(CFL) stability condition must be satisfied when this method is used. Therefore, a maximum time-step size is limited by minimum cell size in a computational domain, which means that if an object of analysis has fine scale dimensions, a small time-step size creates a significant increase in calculation time.
Alternating-Direction Implicit (ADI) method is based on an implicit finite-difference algorithm. Since this method is unconditionally stable, it can improve calculation time by choosing time-step arbitrarily. The ADI-FDTD is based on an Alternating direction implicit technique and the traditional FDTD algorithm. The new method can circumvent the stability constraint. In this thesis, we incorporate Lumped Element and Equivalent Current Source method into the ADI-FDTD. By using them to simulate active or passive device, the application of method will be more widely.
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A three-phase hybrid dc-ac inverter system utilizing hysteresis control /White, Terence H. January 2004 (has links) (PDF)
Thesis (M.S. in Electrical Engineering)--Naval Postgraduate School, June 2004. / Thesis advisor(s): Robert Ashton. Includes bibliographical references (p. 73-74). Also available online.
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