• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 20
  • 19
  • 15
  • 15
  • 7
  • 3
  • 2
  • 2
  • 2
  • 1
  • 1
  • Tagged with
  • 111
  • 17
  • 11
  • 10
  • 9
  • 9
  • 9
  • 9
  • 8
  • 7
  • 6
  • 6
  • 6
  • 6
  • 6
  • 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.
41

Optimal sizing and location of photovoltaic generators on three phase radial distribution feeder

Al-Sabounchi, Ammar M. Munir January 2011 (has links)
The aim of this work is to research the issue of optimal sizing and location of photovoltaic distributed generation (PVDG) units on radial distribution feeders, and develop new procedures by which the optimal location may be determined. The procedures consider the concept that the PVDG production varies independently from changes in feeder load demand. Based on that, the developed procedures deal with two performance curves; the feeder daily load curve driven by the consumer load demand, and the PVDG daily production curve driven by the solar irradiance. Due to the mismatch in the profile of these two curves the PVDG unit might end up producing only part of its capacity at the time the feeder meets its peak load demand. An actual example of that is the summer peak load demand in Abu Dhabi city that occurs at 5:30 pm, which is 5 hours after the time the PV array yields its peak. Consequently, solving the optimization problem for maximum line power loss reduction (∆PPL) is deemed inappropriate for the connection of PVDG units. Accordingly, the procedures have been designed to solve for maximum line energy loss reduction (∆EL). A suitable concept has been developed to rate the ∆EL at one time interval over the day, namely feasible optimization interval (FOI). The concept has been put into effect by rating the ∆EL in terms of line power loss reduction at the FOI (ΔPLFOI). This application is deemed very helpful in running the calculations with no need to repeat the energy-based calculations on hourly basis intervals or even shorter. The procedures developed as part of this work have been applied on actual feeders at the 11kV level of Abu Dhabi distribution network. Two main scenarios have been considered relating to the avoidance and allowance of reverse power flow (RPF). In this course, several applications employing both single and multiple PVDG units have been solved and validated. The optimization procedures are solved iteratively. Hence, effective sub-procedures to help determine the appropriate number of feasible iterative steps have been developed and incorporated successfully. Additionally, the optimization procedures have been designed to deal with a 3-phase feeder under an unbalanced load condition. The line impedances along the feeder are modeled in terms of a phase impedance matrix. At the same time, the modeling of feeder load curves along with the power flow calculations and the resulting losses in the lines are carried out by phase. The resulting benefits from each application have been evaluated and compared in terms of line power loss reduction at the FOI (∆PLFOI) along with voltage and current flow profile.
42

Seasonal Market Trends for Feeder and Stocker and for Slaughter Steers for the Years 1940 through 1948

Embry, J.C. 06 1900 (has links)
Standing on the threshold of a new decade, Texas agriculture is faced with three major problems. The first of these problems is the imperative need for a sound soil and water conservation program. Texas has been struggling with this problem for fifty years and has made some progress toward its solution. During the war, however, it was an all-out production of food regardless of cost, either in terms of dollars or resources. As a result, the conservation problem is more acute today than ever before. The second problem is that farm production is out of balance. Lucrative prices for oil and grain crops, plus the increasing shortage of farm labor, turned thousands of farmers from the more stable diversified farm program which had been built up during the '30s. Now, they are again faced with quotas and acreage allotments. This calls for necessarily early and probably extensive readjustment of the entire agricultural production program. The third major change in the agricultural picture is the rapid industrialization of Texas during and since the war. This increase in urban population in this state means an increased market right at the farmer's door for more livestock, dairy, poultry, fruit, and vegetable production. Fortunately, the solution of these three problems is found in one answer. Pasture grass, forage crops, and legumes provide the best means of soil and water conservation and soil building. Inclusion of these crops in a diversified and balanced cropping program will solve the problem of marketing quotas and acreage allotments. Marketing through livestock will provide the abundance of these foods which is needed to meet the growing demands of Texas markets.
43

Reakce palearktických a nearktických sýkor na sympatrické a alopatrické predátory v krmítkových experimentech: existují regionální rozdíly v rozpoznávání predátorů a hodnocení jejich nebezpečnosti? / Reaction of Palearctic and Nearctic chickadees to sympatric and allopatric predators using feeder experiments: do regional differences in recognition of predators and determination of threat they are posing exist?

Lončík, Lukáš January 2014 (has links)
We have examined wild palearctic and nearctic parids in their ability to recognize and assess a threat level of sympatric and allopatric predators. The study was conducted in Prague, Czech republic, on great tits (Parus major) and blue tits (Parus caeruleus) during the winter of 2013, and the following year in the city of Calgary, Canada, on black-capped chickadees (Poecile atricapillus). Three species of falcons (merlin (Falco columbarius), common kestrel (Falco tinnunculus) and american kestrel (Falco sparverius)), were chosen, two of which were sympatric and one was allopatric to the studied parid species in each area. We have also tested their reaction to nest predators magpies (eurasian magpie (Pica pica), black-billed magpie (Pica hudsonia)). Using two ground feeders in the winter time, we gave parids a choice between a feeder with either one of the three dummies of falcons, or a magpie, and a feeder with a dummy of either a hawk (the most dangerous predator of small birds) or a dove (a harmless bird of the same size as falcons). As a control we have only used sympatric species: eurasian sparrowhawk (Accipiter nisus), Cooper's hawk (Acipiter cooperii), eurasian collared dove (Streptopelia decaocto) and mourning dove (Zenaida macroura). Results from the city of Calgary did not produce any...
44

A survey to describe current feeder calf health and well-being program recommendations made by feedlot veterinary consultants in the United States and Canada

Terrell, Shane Patrick January 1900 (has links)
Master of Science / Department of Clinical Sciences / Daniel Ulan Thomson / Consulting veterinarians (CV; n=23) representing 11,295,000 head of cattle on feed in the United States and Canada participated in a beef cattle health and well-being recommendation survey. Veterinarians were directed to an online survey to answer feeder cattle husbandry, health and preventative medicine recommendation questions. The CV visited their feedyards 1.7 times per month. All CV train employees on cattle handling and pen riding while only 13% of CV speak Spanish. All CV recommend IBR and BVD vaccination for high-risk (HR) calves at processing. Other vaccines were not recommended as frequently by CV. Autogenous bacterins were recommended by 39.1% CV for HR cattle. Metaphylaxis and feed-grade antibiotics were recommended by 95% and 52% of CV, respectively, for HR calves. Banding was more frequently recommended than surgical castration as calf body weight increased. The CV recommended starting HR calves in smaller pens (103 hd/pen) and allowing 13 inches/hd of bunk space. The CV indicated feedlots need to employ one feedlot doctor per 7,083 hd of HR calves and one pen rider per 2,739 hd of HR calves. Ancillary therapy for treating respiratory disease was recommended by 47.8% of CV. Vitamin C was recommended (30.4%) twice as often as any other ancillary therapy. Cattle health risk on arrival, weather patterns and labor availability were most important factors in predicting feedlot morbidity while metaphylactic antibiotic, therapy antibiotic and brand of vaccine were least important. This survey has provided valuable insight into feeder cattle health recommendations by CV and points to needed research areas.
45

Konstruktion av stegmatare för vevstakar / Construction of step feeder for connecting rods

Bergstedt, Pontus, Svemark, Viktor January 2019 (has links)
Detta arbete beskriver förarbete och konstruktion av en stegmatare som sorterar och orienterar vevstakar för en takttid på tio sekunder. Industrier är ofta beroende av materialhanteringsutrustning där olika processer säkerställer någon form av sortering eller orientering, vilket styrker arbetets relevans. Detta har skett genom att dela in maskinen i två huvudfunktioner; trappfunktionen, som försorterar och transporterar vevstakarna vidare till andra huvudfunktionen; orienteringsfunktionen, där orienteringen sker. Genom att tillämpa metoder inom; konstruktion & tillverkning, feleffektsanalys och programvaror för materialdatabashantering, datastödd design, samt numerisk hållfasthetsanalys kunde en konstruktion utformas som speglar de aspekter som kännetecknar en genomtänkt produkt. Sju olika designmetoder användes för att generera och utvärdera idéer i flera itererande steg. Tio undersökande experiment utfördes som ytterligare utvärdering av koncept samt underlag för vidare beräkningar och slutsatser. Utformningen av stegmataren resulterade i en enkelverkande lutande trapp med två rörliga trappsteg och ett statiskt mellan dem för överföring. En enkelmatning efter trappen i form av ett “skovelhjul” säkerställer att vevstakarna levereras en-och-en till orienteringsfunktionen samtidigt som den garanterar takttiden. En orienteringsfunktion bestående av ett “rullband” som med hjälp av friktion och tyngdpunktsförskjutning orienterar vevstakarna med vevänden först. Slutligen studerades tre kritiska områden i konstruktionen för vidare analys med finita element-metoden med godkända resultat. Samtliga mål för projektet uppnåddes, exempelvis har stegmataren färre unika komponenter än befintliga lösningar. Ambitionen var att utforma stegmataren med en låg grad av komplexitet och utan sensorer har genomsyrat hela projektet, vilket även har uppnåtts. / This work describes the preparatory work and construction of a step feeder that sorts and orients connecting rods in a cycle time of ten seconds. Industries are often dependent of different material handling operations which assures a specific material orientation, which validates the importance of this work. This has been done by dividing the machine into two main functions; Stair case-function, which pre-sorts and transports the connecting rods further to the second function, the orientation- function where the orientation is performed. By using methods such as; design for manufacture & assembly, failure mode & effects analysis and softwares for material database handling, computer aided design and numerical strength analysis a construction could be formulated which reflects the aspects that characterize a well-planned product. Seven different design-methods were used in order to generate and evaluate ideas in several iterated steps. Ten investigative experiments were conducted as an additional evaluation of concepts and as a basis for further calculations and conclusions. The formulation of the step feeder resulted in a single-acting stair with two moving stairs and a static between them for transfer. A single-feeder after the staircase in the shape of a “paddle wheel” ensures that the connection rods are delivered one-by-one to the orientation-function while also ensuring the cycle time. An orientation-function consisting of a “conveyor“ that with the aid of friction and an offset of the center of gravity orients the connecting rods with the crankshaft-end first. Lastly were three critical areas in the construction further examined with finite element method with passing results. All objectives for the project were achieved, the step feeder have for instance fewer unique components than existing solutions. The ambition was to design the step feeder with a low grade of complexity and without sensors have permeated throughout the entire project, which also was achieved.
46

Critérios de formatação de funding para projetos em rodovias vicinais no Estado de São Paulo. / Critiria of funding format applied in projects of feeder roads in state of São Paulo.

Falseti, Uirá Watanabe 30 September 2008 (has links)
Este projeto de pesquisa tem como proposta o estudo dos critérios de formatação de funding1 que auxiliem nos projetos de transporte rodoviário no Brasil, em particular as estradas vicinais no Estado de São Paulo. A partir de uma análise crítica da formatação de modelos já existentes para estradas vicinais, no Brasil e no exterior, são estabelecidos processos para o levantamento e formatação de funding para esta classe de negócios. Através da condução de um estudo de caso destinado a avaliar a aplicação destes processos, ao final, esta proposição de critérios é consolidada em um conjunto de diretrizes para a formatação de funding para projetos de estradas vicinais. Desta forma, as empresas do setor de transporte rodoviário e ligadas às atividades do Agronegócio poderão alcançar níveis mais eficientes de planejamento e competitividade, melhorando o suporte às decisões de nível tático, tanto no ambiente da empresa quanto dos empreendimentos de estradas vicinais. / The objective of this research is to study the existing criteria of funding`s models applied in projects of road transportation in Brazil, in particular the feed roads in state of São Paulo. Starting from a critical analysis of existing references and criteria of funding`s models in feeder roads in Brazil and surrounding, processes and database are established to give support to format this type of business. Through study case required to evaluate the application of these processes, at the end, these criteria are consolidated to provide guidelines to format funding applied in feeder roads. So that, the companies of the sector of road transport and agribusiness sector will be able to reach more efficient levels of planning and competitiveness, and improve their support to tactical level decisions, as much in the environment of the company such as the environment of enterprises of feeder roads.
47

Critérios de formatação de funding para projetos em rodovias vicinais no Estado de São Paulo. / Critiria of funding format applied in projects of feeder roads in state of São Paulo.

Uirá Watanabe Falseti 30 September 2008 (has links)
Este projeto de pesquisa tem como proposta o estudo dos critérios de formatação de funding1 que auxiliem nos projetos de transporte rodoviário no Brasil, em particular as estradas vicinais no Estado de São Paulo. A partir de uma análise crítica da formatação de modelos já existentes para estradas vicinais, no Brasil e no exterior, são estabelecidos processos para o levantamento e formatação de funding para esta classe de negócios. Através da condução de um estudo de caso destinado a avaliar a aplicação destes processos, ao final, esta proposição de critérios é consolidada em um conjunto de diretrizes para a formatação de funding para projetos de estradas vicinais. Desta forma, as empresas do setor de transporte rodoviário e ligadas às atividades do Agronegócio poderão alcançar níveis mais eficientes de planejamento e competitividade, melhorando o suporte às decisões de nível tático, tanto no ambiente da empresa quanto dos empreendimentos de estradas vicinais. / The objective of this research is to study the existing criteria of funding`s models applied in projects of road transportation in Brazil, in particular the feed roads in state of São Paulo. Starting from a critical analysis of existing references and criteria of funding`s models in feeder roads in Brazil and surrounding, processes and database are established to give support to format this type of business. Through study case required to evaluate the application of these processes, at the end, these criteria are consolidated to provide guidelines to format funding applied in feeder roads. So that, the companies of the sector of road transport and agribusiness sector will be able to reach more efficient levels of planning and competitiveness, and improve their support to tactical level decisions, as much in the environment of the company such as the environment of enterprises of feeder roads.
48

Diversity of ssDNA Phages Related to the Family <em>Microviridae</em> within the <em>Ciona robusta</em> Gut

Creasy, Alexandria 28 June 2018 (has links)
The gut microbiome is a complex ecosystem of bacteria, viruses, and fungi that strongly influences animal health. The bacterial component, for example, contributes orders of magnitude more gene products to host physiology than the host genome; thus, changes to the composition of these bacterial communities can have profound influences on the health of the animal. By infecting and lysing their hosts, viruses (particularly viruses infecting bacteria or phages) can affect critical functions in these environments, yet the consequences of these infections remain to be fully described. Most studies investigating gut viromes to date have focused on double-stranded DNA (dsDNA) phages and, consequently, little is known about the smaller single-stranded DNA (ssDNA) phages, which also inhabit gut environments. In this study, we investigated ssDNA phages of the Microviridae family within the gut of an invertebrate organism, Ciona robusta, used as a model system to better understand gut microbial interactions. As a filter feeder, Ciona concentrates dissolved organics and microbes as part of its diet, yet maintains a microbiome distinct from the surrounding water column. We identified 258 unique ssDNA phage genomes representing a diversity of Microviridae subgroups including novel members of the established Gokushovirinae subfamily and several proposed phylogenetic groups (Alpavirinae, Aravirinae, Group D, Parabacteroides prophages, and Pequeñovirus). Over 70% of the genomes belonged to the Gokushovirinae; however, 155 of these genomes did not group with previously described sequences. Our results highlight an unprecedented diversity of ssDNA phages from an animal gut. Furthermore, comparative analysis between samples collected from Ciona specimens with full and cleared guts as well as the surrounding water indicated that Ciona retains a unique and highly diverse community of ssDNA phages. The present study significantly expands the known diversity within the Microviridae family and suggests that Ciona is a promising system for studying the role of ssDNA phages within animal guts.
49

Distribution Network Reconfiguration For Loss Reduction By Multi-branch Exchange Method

Galymov, Birzhan 01 September 2012 (has links) (PDF)
As structure and size of electric power distribution systems are getting more complex, distribution automation schemes become more attractive. One of the features that is desirable in an automated system is feeder reconfiguration for loss reduction. Loss reduction can make considerable savings for a utility and results in released system capacity. There is also improved voltage regulation in the system as a result of reduced feeder voltage drop. In this thesis, multi branch exchange algorithm is introduced to solve the network reconfiguration for loss reduction problem. The proposed technique is based on heuristic techniques applied to constraint satisfaction optimization problems. A critical review of earlier methods related with feeder reconfiguration is presented. A computer program was developed using Matlab to simulate this algorithm and results of simulations demonstrate its advantages over single branch exchange method. Moreover, the results show that the final configuration is independent of the initial configuration and give assurance that any solution offered will have a radial configuration with all loads connected.
50

Impact of Distributed Generation on Power Network Operation

Pregelj, Aleksandar 11 December 2003 (has links)
Tools and algorithms are proposed that are useful for planning, designing, and operating a distribution network with a significant penetration of distributed generation (DG). In Task 1, a PV system simulation program is developed, which incorporates the most rigorous models for the calculation of insolation, module temperature, and DC and AC power output of a PV system. The effect of random inverter failures is incorporated in the model of a PV system, and a novel performance-derating coefficient is introduced. Furthermore, a novel inverter control algorithm is presented for systems with multiple inverters. The algorithm is designed to increase overall DC/AC conversion efficiency by selectively shutting down some of the inverters during periods of low insolation, thus forcing the remaining inverters to operate at higher efficiency. In Task 2, a procedure is developed to incorporate the uncertainties imposed by stochastic, renewable DG into the conventional tools for analysis of distribution systems. A clustering algorithm is proposed to reduce large input data sets that result from the interaction of stochastic processes that drive DG output with field measurements of feeder load profiles. In addition, a procedure is proposed to determine the boundary points of the original data set, which yield feeder extreme operating conditions. Finally, a Monte Carlo analysis using a reduced data set is presented, to determine the effects of deploying a large number of renewable DG systems on a distribution feeder. In Task 3, the reliability model of an asymmetric, three--phase, non-radial distribution feeder equipped with capacity-constrained DGs is developed and used to quantify the potential reliability improvements due to the intentional islanded operation of parts of the feeder. A procedure for finding optimal positions for DG and protection devices is presented using a custom-tailored adaptive genetic algorithm.

Page generated in 0.3566 seconds