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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
651

The Effect of Hose Type and Cleanout Procedure on Crop Injury due to Herbicide Residues

Cundiff, Gary Thomas 07 May 2016 (has links)
Field and greenhouse experiments were conducted to determine the effect of auxin injury on soybean and cotton due to spray hose material, formulation and cleanout procedures on auxin equipment cleanout. Visual estimations of injury (VEOI) in wheat, height reduction, and yield reduction due to rimsulfuron and glyphosate titration was higher when compared to rimsulfuron only treatments with respect to 1/2X through the 1/256X treatments. Sequestration of 2,4-D within agricultural hose types did differ due to hose type and is confirmed by analytical testing, but field observation of wheat did not show differences among treatments due to VEOI, height reduction or yield reduction. Using soybean as a bio-indicator, differences did occur with respect to dicamba sequestration in agricultural hose types with respect to VEOI, height reduction, node reduction, yield reduction and ppm analyte retained. Results indicate chemical makeup of hose type in determination of ppm analyte dicamba retained. Cleaning procedures of water or ammonia do not prove to be different with respect to VEOI, height reduction, yield reduction or ppm analyte retained. Sequestration of 2,4-D within valved manifold systems and using water or ammonia as cleanout procedures in conjunction with rinse procedures did not show differences with respect to VEOI, height reduction, nodes above cracked boll (NACB), yield reduction or ppm analyte retained. It was not until standard 2,4-D applications were applied in field experiments when differences were observed. Deactivation of dicamba and 2,4-D using the Fenton procedure within various rates, showed an interaction with respect to VEOI, height reduction, node reduction, yield reduction and ppm analyte. Using soybean as a bio-indicator showed differences with the Fenton procedure deactivating the dicamba analyte in the 1/16X, 1/64X and 1/256X rate with respect to VEOI, height reduction, node reduction, yield reduction and ppm analyte retained. Using cotton as a bio-indicator showed differences with the Fenton procedure deactivating the 2,4-D analyte in every rate with respect to VEOI, height reduction, yield reduction and ppm analyte.
652

Dispersal and Management of Invasive Aquatic Plants in Mississippi Waterways

Fernandez, Amanda Louise 14 December 2013 (has links)
To understand the flow of water as a factor that influences aquatic vegetation communities and aquatic plant dispersal, custom-made Global Positioning System (GPS) drones were used to monitor the movement of water in Aliceville Lake, Columbus Lake, and Ross Barnett Reservoir, MS. In each reservoir, the drones drifted in the wind-generated surface current. Analysis of wind speeds suggests that a certain wind speed may be necessary to overcome gradient flow. Wind direction and wind speed should be incorporated in future spatial simulation models for aquatic plant dispersal and distribution. An herbicide evaluation on Cuban bulrush (Oxycaryum cubenese) was conducted to determine what herbicides would effectively control the invasive species. Applications made prelowering were more successful than postlowering applications for all herbicides tested with glyphosate, 2,4-D, triclopyr, diquat, imazamox, and imazapyr resulting in 100% mean biomass reduction. For postlowering applications, glyphosate, triclopyr, and diquat are recommended.
653

Generell modell för anpassningsbara journalsystem / General model for adaptable journal systems

Wikzén, Erik, Olsson, Andreas January 2021 (has links)
Det finns ett behov av användarvänliga, anpassningsbara och tillgängliga journalsystem inom en variation av branscher. Befintliga system har visat sig vara bristfälliga inom dessa tre aspekter. Bristerna bottnar i att systemen sällan är anpassade för det specifika ändamålet, vilket i många fall grundar sig i att slutanvändarna inte varit med i utvecklingsprocessen. När användare har implementerat befintliga journalsystem inom sina verksamheter har även bristfälligheter gällande tillgänglighet påvisats. På den utvecklade journalsystemprototypen som arbetet resulterade i, utfördes ett antal tester av uppdragsgivarens anställda. Dessa tester påvisade att prototypens användarvänlighet, anpassningsbarhet och tillgänglighet uppnådde de krav som företaget hade på ett journalsystem. Prototypen har, trots det positiva resultatet, fortfarande utvecklingspotential och områden att förbättra. / There is a need for user-friendly, customizable and accessible record systems in a variety of industries. Existing systems have proven to be deficient in these three aspects. The shortcomings are due to the fact that the systems are seldom adapted for the specific purpose, which in many cases is a consequence of the end users not being involved in the development process. When users have implemented existing journal systems within their operations, deficiencies regarding accessibility have also been identified. On the developed record system prototype that the work resulted in, a number of tests were performed by the client's employees. These tests showed that the user-friendliness, adaptability and availability of the prototype met the requirements of the company for a record system. Despite the positive result, the prototype still has development potential and areas for improvement.
654

Towards Fairness-Aware Online Machine Learning from Imbalanced Data Streams

Sadeghi, Farnaz 10 August 2023 (has links)
Online supervised learning from fast-evolving imbalanced data streams has applications in many areas. That is, the development of techniques that are able to handle highly skewed class distributions (or 'class imbalance') is an important area of research in domains such as manufacturing, the environment, and health. Solutions should be able to analyze large repositories in near real-time and provide accurate models to describe rare classes that may appear infrequently or in bursts while continuously accommodating new instances. Although numerous online learning methods have been proposed to handle binary class imbalance, solutions suitable for multi-class streams with varying degrees of imbalance in evolving streams have received limited attention. To address this knowledge gap, the first contribution of this thesis introduces the Online Learning from Imbalanced Multi-Class Streams through Dynamic Sampling (DynaQ) algorithm for learning in such multi-class imbalanced settings. Our approach utilizes a queue-based learning method that dynamically creates an instance queue for each class. The number of instances is balanced by maintaining a queue threshold and removing older samples during training. In addition, new and rare classes are dynamically added to the training process as they appear. Our experimental results confirm a noticeable improvement in minority-class detection and classification performance. A comparative evaluation shows that the DynaQ algorithm outperforms the state-of-the-art approaches. Our second contribution in this thesis focuses on fairness-aware learning from imbalanced streams. Our work is motivated by the observation that the decisions made by online learning algorithms may negatively impact individuals or communities. Indeed, the development of approaches to handle these concerns is an active area of research in the machine learning community. However, most existing methods process the data in offline settings and are not directly suitable for online learning from evolving data streams. Further, these techniques fail to take the effects of class imbalance, on fairness-aware supervised learning into account. In addition, recent fairness-aware online learning supervised learning approaches focus on one sensitive attribute only, which may lead to subgroup discrimination. In a fair classification, the equality of fairness metrics across multiple overlapping groups must be considered simultaneously. In our second contribution, we thus address the combined problem of fairness-aware online learning from imbalanced evolving streams, while considering multiple sensitive attributes. To this end, we introduce the Multi-Sensitive Queue-based Online Fair Learning (MQ-OFL) algorithm, an online fairness-aware approach, which maintains valid and fair models over evolving streams. MQ-OFL changes the training distribution in an online fashion based on both stream imbalance and discriminatory behavior of the model evaluated over the historical stream. We compare our MQ-OFL method with state-of-art studies on real-world datasets and present comparative insights on the performance. Our final contribution focuses on explainability and interpretability in fairness-aware online learning. This research is guided by the concerns raised due to the black-box nature of models, concealing internal logic from users. This lack of transparency poses practical and ethical challenges, particularly when these algorithms make decisions in finance, healthcare, and marketing domains. These systems may introduce biases and prejudices during the learning phase by utilizing complex machine learning algorithms and sensitive data. Consequently, decision models trained on such data may make unfair decisions and it is important to realize such issues before deploying the models. To address this issue, we introduce techniques for interpreting the outcomes of fairness-aware online learning. Through a case study predicting income based on features such as ethnicity, biological sex, age, and education level, we demonstrate how our fairness-aware learning process (MQ-OFL) maintains a balance between accuracy and discrimination trade-off using global and local surrogate models.
655

Cosmic Ray Instrumentation and Simulations

McBride, Keith William 29 September 2021 (has links)
No description available.
656

Dual-stage Thermally Actuated Surface-Micromachined Nanopositioners

Hubbard, Neal B. 17 March 2005 (has links) (PDF)
Nanopositioners have been developed with electrostatic, piezoelectric, magnetic, thermal, and electrochemical actuators. They move with as many as six degrees of freedom; some are composed of multiple stages that stack together. Both macro-scale and micro-scale nanopositioners have been fabricated. A summary of recent research in micropositioning and nanopositioning is presented to set the background for this work. This research project demonstrates that a dual-stage nanopositioner can be created with microelectromechanical systems technology such that the two stages are integrated on a single silicon chip. A nanopositioner is presented that has two stages, one for coarse motion and one for fine motion; both are fabricated by surface micromachining. The nanopositioner has one translational degree of freedom. Thermal microactuators operate both stages. The first stage includes a bistable mechanism: it travels 52 micrometers between two discrete positions. The second stage is mounted on the first stage and moves continuously through an additional 8 micrometers in the same direction as the first stage. Two approaches to the control of the second stage are evaluated: first, an electrical input is transmitted to an actuator that moves with the first stage; second, a mechanical input is applied to an amplifier mechanism mounted on the first stage after completing the coarse motion. Four devices were designed and fabricated to test these approaches; the one that performed best was selected to fulfill the objective of this work. Thermal analysis of the actuators was performed with previously developed tools. Pseudo-rigid-body models and finite element models were created to analyze the mechanical behavior of the devices. The nanopositioners were surface micromachined in a two-layer polysilicon process. Experiments were performed to characterize the resolution, repeatability, hysteresis, and drift of the second stages of the nanopositioners with open-loop control. Position measurements were obtained from scanning electron micrographs by a numerical procedure, which is described in detail. The selected nanopositioner demonstrated 170-nanometer resolution and repeatability within 37 nanometers. The hysteresis of the second stage was 6% of its full range. The nanopositioner drifted 25 nanometers in the first 60 minutes of operation with a time constant of about 6 minutes. The dual-stage nanopositioner may be useful for applications such as variable optical attenuators or wavelength-specific add--drop devices.
657

Managing Mission Drift In Social Business Hybrids : An Exploratory Study On Strategies That Employees Of Social Business Hybrids Apply To Mitigate The Risk Of Mission Drift

Bussian, Kim Naike, Goettert, Janina January 2022 (has links)
Background: Rising global uncertainty and volatility have changed how businesses envision themselves and their future. Particularly Social Business Hybrids emphasize the importance of purpose beyond profit. Their aim is to develop a more inclusive and green economy by pursuing and creating both financial and social value. This aim, however, comes with the risk of mission drift, meaning that the organization could prioritize one value at the expense of the other. As this is an emergent strategic dilemma in the field of social entrepreneurship, it is prudent to find ways to manage the risk of mission drift. In this context, considerable attention has to be given to the question of how employees of Social Business Hybrids manage the risk of mission drift, as their viewpoint has mostly been neglected by prior scholarship. Purpose: The purpose of the present study is to provide an understanding of why the management of mission drift is relevant for Social Business Hybrids and to give new insights into perspectives that employees of Social Business Hybrids have towards tactics and strategies that support successful management of mission drift. By researching the critical role that employees play as stakeholders in the context of mission drift management, we aim to enrich current literature by deriving new insights into strategies that can help Social Business Hybrids successfully balance their dual objectives. Method: This study is based on: Qualitative, inductive research; Ontology – Relativism; Epistemology – Social Constructionism; Methodology – Grounded Theory; Data Collection – 12 semi-structured in-depth Interviews; Sampling – Purposive, Snowball; Data Analysis – Grounded Analysis  Conclusion: In our findings, we ascertained distinct sources that anticipate a risk for mission drift. Further, we identified detailed tactics that can significantly support the management of mission drift. Finally, resulting from the findings, a framework was developed, that proposes five distinctive overarching strategies, which are enabled by two underlying mechanisms that employees in Social Business Hybrids apply to manage mission drift.
658

Kan trämaterialet DDW ersätta stål vid konstruktion av framtida gång- och cykel broar : Jämförelse utifrån LCC / Can the wood material DDW replace steel in the construction of future pedestrian and bicycle bridges : Comparison based on LCC

Ashna, Emran, Dashti, Amir January 2018 (has links)
I detta examensarbete behandlas en jämförelse mellan två olika material utifrån LCC för GC-broar. Dessa är stål och Delignified Densified Wood (DDW). Samhället är i behov av att utvecklas inom ett mer hållbart- och anpassad till klimatkraven. Detta innebär att det ställs krav på Trafikverket. Dessa krav innebär bland annat att byggnadsmaterial behöver utvecklas. Sverige har god tillgång till skog och träframtagning. Trafikverket bör nyttja mer av träets potential. Denna studie har därför gjorts för att bedöma DDW som är ett träbaserat material utifrån intervjuer och livscykelkostnadsanalys (LCC-analys). LCC är ett tillvägagångsätt för att få en totalbild över en produkts samtliga kostnader under dess livslängd. Det vill säga att för en bro bedöms kostnaderna från projektering till rivning. Syftet med LCC-analys är att hitta den mest lönsamma investeringskostnad som uppfyller dagens samhällskrav. DDW är framtagen av Forskare vid Marylands Universitet. Forskningen har observerat att obehandlat trä går att få lika starkt som stål. Processen innebär att ligninet avlägsnas och träet placeras i tryck under värme på cirka 100 C°. Detta leder till att cellulosafibrerna pressas samman och blir hårdare. Det resulterar förenklat sagt att träet blir mycket hårdare, tåligare och starkare och går att forma och böja. Resultatet av examensarbetet tyder på att DDW inte är lämpligt just nu som konstruktionsmaterial i utomhusklimat och inte är ekonomiskt lönsamt. DDW är vetenskapligt intressant och bör forskas vidare. I dagsläget rekommenderas inte DDW som GC-bromaterial. Trafikverket bör bygga mer GC- broar av trä som passar väl som GC-bromaterial. / n this thesis a comparison is made between two different construction materials based on LCC for pedestrian and cycle bridges. These materials are steel and Delignified Densified Wood (DDW). Today ́s society needs to develop with more sustainable and climate-friendly construction. This need imposes demands on the Swedish transport administration, e.g. that building materials need to be developed. One viable material for Sweden, since it has good access to forestry and wood production, is wood. The Swedish transport administration should use more of the potential of wood. This study therefore assesses DDW, which is a wood-based material, based on interviews and life cycle cost analysis (LCC-analysis). LCC is a way of getting a complete picture of a product's entire costs during its lifespan. In the case of a bridge, the costs are estimated from planning to demolition. The purpose of LCC analysis is to find the most profitable investment cost that meets today's social requirements. DDW is developed by researchers at Maryland University. Researchers have observed that natural wood can be as strong as steel. The process involves removing lignin and placing it under pressure at a temperature of about 100 ° C. This causes the cellulosic fibers to compress and become harder. This simply means that the wood becomes much harder, more durable and stronger, and can also shape and bend. The result of the thesis suggests that DDW is not suitable at present as construction material in outdoor climate and is not economically profitable. DDW is scientifically interesting and should be researched further.
659

Effects of Column Stiffness on Seismic Behavior of Steel Plate Shear Walls

Guo, Xuhua 01 November 2011 (has links) (PDF)
Steel plate shear walls (SPSWs) are a lateral force resisting system consisting of thin infill steel plates surrounded by boundary frame members. The infill steel plates are allowed to buckle in shear and subsequently form diagonal tension field actions during earthquake events. Hysteretic energy dissipation of this system is primarily achieved through yielding of the infill plates. Conceptually, in a SPSW system with ideally rigid columns pinned to ground, the infill plates at different stories will yield simultaneously as a result of the lateral loads. However, when the columns become flexible, infill plate yielding may initially occur at one story and progressively spread into the other stories with increasing roof displacement. This research investigates the effect of column stiffness on infill plate yielding sequence and distribution along the height of steel plate shear walls subjected to earthquake forces. Analytical models are derived and validated for two-story SPSWs. Based on the derived model, probabilistic simulations are conducted to calculate the probability of achieving infill plate yielding in both stories before occurrence of a premature failure caused by excessive inter story drift at the initially yielded story. A total of three simulation methods including the Monte-Carlo method, the Latin Hypercube sampling method, and the Rosenblueth’s 2K+1 point estimate method were considered to account for the uncertain infill plate thickness and lateral force distributions in the system.The investigation is also extended to multi-story SPSWs. Three example six-story SPSWs are evaluated using the Rosenblueth's 2K+1 point estimation method which is identified to be most efficient from the simulation on two-story SPSWs. Moreover, the effectiveness of the column minimum moment of inertia required in the current code for achieving infill plate yielding at every story of SPSWs is evaluated.
660

An assessment of steering drift during braking: a comparison between finite-element and rigid body analyses

Klaps, J., Day, Andrew J., Hussain, Khalid, Mirza, N. January 2010 (has links)
No / A vehicle that deviates laterally from its intended path of travel when the brakes are applied is considered to demonstrate ‘instability’ in the form of an unexpected and undesirable response to the driver input. Even where the magnitude of lateral displacement of the vehicle is small (i.e. ‘drift’ rather than ‘pull’) such a condition would be considered unacceptable by manufacturers and customers. Steering ‘drift’ during braking can be caused by several factors, some of which relate to vehicle design and others to external influences such as road conditions. The study presented here examines the causes and effects of steering drift during straight-line braking. A comparative analysis is made between two types of vehicle model: one built with rigid suspension components and the other with flexible components. In both the cases, the vehicle behaviour is simulated during braking in a straight line, and responses including lateral acceleration, yaw rate, and lateral displacement of the vehicle are predicted and analysed under fixed steering control. Suspension/steering geometry characteristics, namely toe steer and caster angle, have been studied to understand how the effect of variations in these parameters differs in models with rigid or flexible components drift during straight-line braking. Results from both vehicle models show that differences between rigid and flexible components can affect the predicted steering drift propensity. The differences between the two models have emphasized the importance of using flexible (compliant) components in vehicle handling simulations to achieve better correlation between prediction and experiment.

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