Tobacco (<i>Nicotiana tabacum</i> L.) leaf initiation stops when floral induction is completed. Floral induction (an internal biochemical change which signals development of flowers) can occur prematurely, during the pre- and/or post-transplant environment. Plants which flower prematurely have few leaves and low yields. Removal of the influorescence on these plants will break apical dominance and allow production of additional leaves from axillary bud. This practice requires additional labor and increases production costs. Objectives of this study were to 1) determine how application timing, rate, localization, and on-plant duration of ethephon (2-chloroethylphosphonic acid) influences growth and flowering of flue-cured ‘NC 82’ tobacco; 2) examine the relationship between temperatures in the seedling environment and premature flowering and determine how time of plant bed cover removal affects premature flowering; and 3) quantify the ethylene released from buds, leaves, stems, and roots of tobacco seedlings at various days after application of ethephon. Ethephon applied to flue-cured tobacco seedlings before the completion of floral induction significantly reduced premature flowering and increased days to flower, number of leaf nodes per plant, and yield. Multiple applications and increased rates of ethephon did not increase the number of leaf nodes beyond the level obtained from a single application of 960 mg L⁻¹ ethephon solution applied at the rate of 44 mL m⁻² of plant bed. In wash-off studies, maximum benefit was obtained when ethephon remained on the seedlings one to two hours after application. In localization studies, increases in number of leaf nodes per plant were not different when 0.09 and 0.51 mg of ethephon was applied to the bud and largest leaf, respectively. Ethylene released from ethephon-treated greenhouse seedlings remained detectable four weeks after treatment. On-farm test locations with the two highest percentages of premature flowering had the lowest average daily minimum temperatures during the pretransplant period. Premature flowering was significantly increased at two of seven locations by removal of the perforated plastic plant bed covers two weeks compared to one week before transplanting. Floral induction of tobacco seedlings in controlled pretransplant environments was obtained by continuous 15°C temperature and 8 h photoperiods for 3 weeks. / Ph. D.

Master of Agribusiness / Department of Agricultural Economics / Vincent R. Amanor-Boadu / Over the last few years there have been many changes to the container export industry. There are a variety of reasons for these changes including exchange rate fluctuations, fuel and energy price fluctuations and their effects on bulk freight rates. The pressure to enhance and remain competitive has also increased amid these rapid changes. An effective strategy is for companies to focus attentions on costs they can control. In the container freight industry, one of these costs is reducing the “paper” aspects of operations and increasing its “electronic” aspects. This thesis focuses specifically on evaluating FileBound®, document management software, for the purpose of going “paperless” in a Container Freight, Non-Vessel Operating Common Carrier (NVOCC) and freight forwarding company. Going paperless has many advantages: increased efficiency, paper and printing cost savings, time savings, storage cost savings, environmental benefits, efficient file retrieval, and enhanced customer service. By adopting the FileBound® technology, the case study company hopes to achieve most of these benefits, allowing it to reduce overall costs, and especially, reduce the number of employees managing physical documents and move people into sales and marketing. The critical assumption of the study was that the electronic processes contributed to time savings and it is from these time savings that most of the other benefits emanated. Therefore, a time study was conducted to determine the time savings resulting from using FileBound® in comparison to the current method in the file completion process. The data collected was analyzed using regression analysis to determine the factors that influenced time savings, if any, and their statistical significance. There are three specific activities involved with the process of completing a transaction in the container freight business: booking, instruction and bill of lading. The analysis was conducted for each of these steps in the process. The results show that the different methods, FileBound® or manual, were not statistically significant on determining the time it took to complete the file. That being said, this thesis recommends that a mixture of both the FileBound® and manual method be used to take advantage of the potential cost savings.

Bacterial adhesion is the first step of biofilm formation and in the focus of research interest since several decades. Biofilms cause many problems, sometimes dramatic, for example in health, food packing or waste water purification. Despite of high interest, bacterial adhesion process is only poorly understood yet. In this work, bacterial adhesion was investigated on well-organized and structured model surfaces with various chemistries at molecular scale. For that purpose a characterization methodology was developed to sufficiently analyze monolayers on silicon wafers, and controlled mixed monolayers surfaces with different densities of NH 2 backfilled with CH3 were developed and optimized. These controlled surfaces with different densities of 0 % NH2 up to 100% NH2 were eventually used as tool to study bacterial adhesion in batch and real time conditions. The results demonstrate a significant impact on bacterial adhesion of weak difference in the surface chemistry at molecular scale. In the batch experiments, two so-called "plateaus" zones were determined, in which bacterial adhesion is not significantly different despite the change of the amine concentration on the surface. On the contrary, one transition zone exists between the "plateaus" in which a slight chunge.in the amine concentration leads to a significant increase / decrease of the bacterial adhesion. The same trend of bacteria behavior was observed for different bacterial strains.

A solution to the vehicle state estimation problem is given using the Kalman filtering and the Particle filtering theories. Vehicle states are necessary for an active or a semi-active suspension control system, which is intended to enhance ride comfort, road handling and stability of the vehicle. Due to a lack of information on road disturbances, conventional estimation techniques fail to provide accurate estimates of all the required states. The proposed estimation algorithm, named Supervisory Kalman Filter (SKF), consists of a Kalman filter with an extra update step which is inspired by the particle filtering technique. The extra step, called a supervisory layer, operates on the portion of the state vector that cannot be estimated by the Kalman filter. First, it produces N randomly generated state vectors, the particles, which are distributed based on the Kalman filter’s last updated estimate. Then, a resampling stage is implemented to collect the particles with higher probability. The effectiveness of the SKF is demonstrated by comparing its estimation results with that of the Kalman filter and the particle filter when a test vehicle is passing over a bump. The estimation results confirm that the SKF precisely estimates those states of the vehicle that cannot be estimated by either the Kalman filter or the particle filter, without any direct measurement of the road disturbance inputs. Once the vehicle states are provided, a suspension control law, the Skyhook strategy, processes the current states and adjusts the damping forces accordingly to provide a better and safer ride for the vehicle passengers. This thesis presents a novel systematic and practical methodology for the design and implementation of the Skyhook control strategy for vehicle’s semi-active suspension systems. Typically, the semi-active control strategies (including the Skyhook strategy) have switching natures. This makes the design process difficult and highly dependent on extensive trial and error. The proposed methodology maps the discontinuous control system model to a continuous linear region, where all the time/frequency design techniques, established in the conventional control system theory, can be applied. If the semiactive control law is designed to satisfy ride and stability requirements, an inverse mapping offers the ultimate control law. The effectiveness of the proposed methodology in the design of a semi-active suspension control system for a Cadillac SRX 2005 is demonstrated by real-time road tests. The road tests results verify that the use of the newly developed systematic design methodology reduces the required time and effort in real industrial problems.

A solution to the vehicle state estimation problem is given using the Kalman filtering and the Particle filtering theories. Vehicle states are necessary for an active or a semi-active suspension control system, which is intended to enhance ride comfort, road handling and stability of the vehicle. Due to a lack of information on road disturbances, conventional estimation techniques fail to provide accurate estimates of all the required states. The proposed estimation algorithm, named Supervisory Kalman Filter (SKF), consists of a Kalman filter with an extra update step which is inspired by the particle filtering technique. The extra step, called a supervisory layer, operates on the portion of the state vector that cannot be estimated by the Kalman filter. First, it produces N randomly generated state vectors, the particles, which are distributed based on the Kalman filter’s last updated estimate. Then, a resampling stage is implemented to collect the particles with higher probability. The effectiveness of the SKF is demonstrated by comparing its estimation results with that of the Kalman filter and the particle filter when a test vehicle is passing over a bump. The estimation results confirm that the SKF precisely estimates those states of the vehicle that cannot be estimated by either the Kalman filter or the particle filter, without any direct measurement of the road disturbance inputs. Once the vehicle states are provided, a suspension control law, the Skyhook strategy, processes the current states and adjusts the damping forces accordingly to provide a better and safer ride for the vehicle passengers. This thesis presents a novel systematic and practical methodology for the design and implementation of the Skyhook control strategy for vehicle’s semi-active suspension systems. Typically, the semi-active control strategies (including the Skyhook strategy) have switching natures. This makes the design process difficult and highly dependent on extensive trial and error. The proposed methodology maps the discontinuous control system model to a continuous linear region, where all the time/frequency design techniques, established in the conventional control system theory, can be applied. If the semiactive control law is designed to satisfy ride and stability requirements, an inverse mapping offers the ultimate control law. The effectiveness of the proposed methodology in the design of a semi-active suspension control system for a Cadillac SRX 2005 is demonstrated by real-time road tests. The road tests results verify that the use of the newly developed systematic design methodology reduces the required time and effort in real industrial problems.

L'adhésion bactérienne est la première étape du processus de formation d'un biofilm et est un enjeu majeur de la recherche depuis plusieurs dizaines d'années. Les biofilms ont des conséquences parfois dramatiques dans des domaines comme la santé, l'agroalimentaire ou la purification des eaux usées. Toutefois, l'adhésion bactérienne reste un phénomène mal compris. Dans cette thèse, l'adhésion bactérienne est étudiée sur des surfaces modèles très bien organisées et structurées, de chimie de surface variable à l'échelle moléculaire. Une méthodologie de caractérisation adaptée aux monocouches déposées sur wafers de silicium est proposée. Des surfaces modèles composées de monocouches mixtes auto-assemblées de densités variables de NH2 dans un continuum de CH, sont développées et optimisées. Ces surfaces contrôlées, de densités de 0% NH2 à 100% NH2 dans CH3, sont utilisées comme outil pour étudier l'adhésion bactérienne en conditions de culture « batch »et « temps réel ». Les résultats montrent un impact significatif sur l'adhésion bactérienne de faibles différences chimiques à l'échelle moléculaire. Les résultats des expériences menées en conditions « batch » permettent de déterminer deux zones « plateau » dans lesquelles l'adhésion bactérienne ne varie pas significativement malgré des variations importantes de la concentration en groupements amine sur la surface. Une zone de transition entre les zones « plateau » est mise en évidence, dans laquelle une faible modification de la concentration en groupement amine mène à l'augmentation / diminution significative du nombre de bactéries adhérées. Cette tendance est montrée pour deux souches différentes de bactérie. / Bacterial adhesion is the first step of biofilm formation and in the focus of research interest since several decades. Biofilms cause many problems, sometimes dramatic, for example in health, food packing or waste water purification. Despite of high interest, bacterial adhesion process is only poorly understood yet. In this work, bacterial adhesion was investigated on well-organized and structured model surfaces with various chemistries at molecular scale. For that purpose a characterization methodology was developed to sufficiently analyze monolayers on silicon wafers, and controlled mixed monolayers surfaces with different densities of NH 2 backfilled with CH3 were developed and optimized. These controlled surfaces with different densities of 0 % NH2 up to 100% NH2 were eventually used as tool to study bacterial adhesion in batch and real time conditions. The results demonstrate a significant impact on bacterial adhesion of weak difference in the surface chemistry at molecular scale. In the batch experiments, two so-called "plateaus" zones were determined, in which bacterial adhesion is not significantly different despite the change of the amine concentration on the surface. On the contrary, one transition zone exists between the "plateaus" in which a slight chunge.in the amine concentration leads to a significant increase / decrease of the bacterial adhesion. The same trend of bacteria behavior was observed for different bacterial strains.