Relevant bibliographies by topics / Load Flow Methods

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  2. Dissertations / Theses
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Academic literature on the topic 'Load Flow Methods'

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Published: 6 September 2023

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Journal articles on the topic "Load Flow Methods"

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Seng, Chieng Kai, Tay Lea Tien, and Syafrudin Masri. "Load Flow Analysis Using Second-Order Load Flow Methods and its Variations." Applied Mechanics and Materials 785 (August 2015): 73–77. http://dx.doi.org/10.4028/www.scientific.net/amm.785.73.

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The load flow or power flow computer program is the basic tool for investigating the steady-state conditions of power system. This paper introduces improved algorithms based on the basic Second-order Load Flow method for a wide range of electrical bus system sizes. It is attractive for accurate or approximate off- and on-line calculations for routine and contingency purposes. Tests of 4 different variations based on the basic Second-order Load Flow method are run on 6 different standard bus systems and the results are discussed in this paper.
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Ekwue, A. O., and J. F. Macqueen. "Comparison of load flow solution methods." Electric Power Systems Research 22, no. 3 (December 1991): 213–22. http://dx.doi.org/10.1016/0378-7796(91)90008-b.

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Xiao-Ping Zhang. "Fast three phase load flow methods." IEEE Transactions on Power Systems 11, no. 3 (1996): 1547–54. http://dx.doi.org/10.1109/59.535696.

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Baldwin, T. L., and S. A. Lewis. "Distribution Load Flow Methods for Shipboard Power Systems." IEEE Transactions on Industry Applications 40, no. 5 (September 2004): 1183–90. http://dx.doi.org/10.1109/tia.2004.834128.

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Srivastava, L., S. C. Srivastava, and L. P. Singh. "Fast decoupled load flow methods in rectangular coordinates." International Journal of Electrical Power & Energy Systems 13, no. 3 (June 1991): 160–66. http://dx.doi.org/10.1016/0142-0615(91)90005-g.

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Shahriari, Amidaddin, Hazlie Mokhlis, and Ab Bakar. "Critical Reviews of Load Flow Methods for Well, Ill and Unsolvable Condition." Journal of Electrical Engineering 63, no. 3 (May 1, 2012): 144–52. http://dx.doi.org/10.2478/v10187-012-0022-x.

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Critical Reviews of Load Flow Methods for Well, Ill and Unsolvable ConditionThis paper presents a critical review of Load flow methods in well, ill and unsolvable conditioned systems. The comparison studies deals with multiple load flow solution (MLFS), second-order load-flow (SOLF) and continuation load flow (CLF). The ability of theses method to return from unsolvable solution to a solvable solution in load flow analysis is analyzed and discuss thoroughly. Special attention is given to the problems and techniques to provide optimal recommendations of the parameters that are used in these load flow methods. A part of the reviews, this paper also presents the comparison of numerical result using different type of aforesaid load flow methods for well and ill-conditioned systems.
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Zhu, Linbo, Yongsheng Zhu, and Yuping Yan. "Methods to test and generate the wear load spectrum of journal bearing in concrete pump." Advances in Mechanical Engineering 13, no. 4 (April 2021): 168781402110077. http://dx.doi.org/10.1177/16878140211007716.

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Load spectrum is the basis of wear analysis and life prediction in journal bearing. This paper proposed a method to generate the wear load spectrum from the measured loads that avoiding the errors introduced by the assumptions of traditional constant load. An axle pin load sensor that can recognize the load value and its orientation is developed to test the original wear loads of journal bearing in a concrete pump under working conditions. The interactive influence of perpendicular components in the measured loads is involved by introducing two effect coefficients. Subsequently, the amplitude distribution of the wear load and its lasting time are extracted from the measured complex load-time history using the rain-flow counting method and Weibull distribution. The wear load spectrum is generated by dividing the continuous load into eight load steps. The validity of the approach is supported by finite element analysis on the wear simulation of journal bearing using the generated load spectrum and the measured load. In addition, the effects of load types and load sequence on the wear are discussed based on the proposed method and the FE model. This study provides guidelines to efficiently generate the wear load spectrum for journal bearing, and enhances its reliability of wear prediction in the experimental tests and theoretical analysis.
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Kayser, K., S. Kunst, G. Fehr, and H. Voermanek. "Nitrification in reed beds - capacity and potential control methods." Water Science and Technology 46, no. 6-7 (September 1, 2002): 363–70. http://dx.doi.org/10.2166/wst.2002.0701.

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Vertical-flow reed beds (VFBs) are known to be very effective regarding nitrification. However, a generally accepted design formula for dimensioning reed beds for a controlled nitrification process has still not been found. Especially for the purpose of nitrification a vertical-flow reed bed (VFB) has been installed following an existing unaerated pond-system. The paper presents the results concerning the limits of the VFB's performance as well as the main factors influencing the nitrification process gained by balancing the conversion rates under different loads. Even under high loads the VFB provides an excellent nitrification performance, which is mainly influenced by the wastewater temperature. The ammonia oxidation rate is about 90% at temperatures over 10°C; at temperatures below 5°C the average nitrification rate is still approximately 50%. The hydraulic load and the TKN load have almost no impact on this efficiency (the maximum load has been: 180 mm/d, 7.1 g TKN/(m2*d)). The redox potenial, which is continuously measured in the effluent of the reed bed, proved to be dependent on the current nitrification performance and the oxygen supply of the VFB, and therefore appears to be a suitable control parameter for the operation of VFBs.
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Wang, An, and Qinghua Zeng. "Load Characteristics and Modeling Methods for the Flow Regulator of a Solid Ducted Rocket." International Journal of Aerospace Engineering 2019 (November 18, 2019): 1–10. http://dx.doi.org/10.1155/2019/8031290.

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The load characteristics for the flow regulator of a solid ducted rocket are discussed in this paper. The mechanism and the influence factor of the load in the flow regulator were studied both theoretically and experimentally, and the system load and the working load were divided according to the mechanism. Additionally, the load influence on the working quality of the flow regulator and the ducted rocket were analyzed. System modeling of the flow regulator was carried out based on the working mechanism of the gas generator and the Stribeck friction model, and models of the actuator, gas generator, and load were built. Furthermore, considering the identification of the model parameters and the inapplicability of the conventional Stribeck identification method to the flow regulator, a new Stribeck model parameter identification method was proposed. A sine wave was used as the signal source, and specially designed devices were used to accomplish the switch of the working condition. Through the use of the genetic algorithm, the rotational inertia and parameters of the system load and working load were identified by stages. Finally, the validation of the identification method was carried out with a simulation.
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Quintana, V. H., and N. Müller. "Studies of load flow methods in polar and rectangular coordinates." Electric Power Systems Research 20, no. 3 (March 1991): 225–35. http://dx.doi.org/10.1016/0378-7796(91)90067-w.

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Dissertations / Theses on the topic "Load Flow Methods"

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Joubert, Adriaan Wolfgang. "Parallel methods for systems of nonlinear equations applied to load flow analysis." Thesis, Queen Mary, University of London, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.362721.

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Trussell, Larry V. "Segflow: a new object-oriented load flow which uses trace methods and affiliation objects." Diss., Virginia Tech, 1994. http://hdl.handle.net/10919/40082.

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Borquez, Caballero Rodrigo Edgardo. "Calculating the Distance to the Saddle-Node Bifurcation Set." Thesis, KTH, Elektriska energisystem, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-119236.

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A power system will experience voltage collapse when the loads increase up to a certain critical limit, where the system physically cannot support the amount of connected load. This point identified as a Saddle- Node Bifurcation (SNB), corresponds to a generic instability of parameterized differential equation models and represents the intersection point where different branches of equilibria meet. At this point the jacobian matrix of the system is singular and the system loses stability bringing the typical scenario of voltage collapse. To prevent voltage instability and collapse, the computation of the closest distance from a present operating point to the saddle-node bifurcation set can be used as a loadability index useful in power system operation and planning. The power margin is determined by applying the iterative or direct method described in [16]. Numerical examples of both methods applied to IEEE 9-bus system and IEEE 39-bus system shows that the iterative method is more reliable although it requires a longer computation time. The stability of the system is negatively affected in two ways when generators reach their reactive power limits: the voltage stability margin is deteriorated, or immediate voltage instability and collapse is produced.
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Gupta, Nitin. "HOLOMORPHIC EMBEDDED LOAD-FLOW METHOD'S APPLICATION ON THREE-PHASE DISTRIBUTION SYSTEM WITH UNBALANCED WYE-CONNECTED LOADS." Cleveland State University / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=csu1624146858767491.

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Garbelini, Enio. "Proposição de uma técnica de parametrização geométrica para o fluxo de carga continuado /." Ilha Solteira : [s.n.], 2008. http://hdl.handle.net/11449/100326.

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Orientador: Dílson Amâncio Alves
Banca: Carlos Roberto Minussi
Banca: Francisco Villarreal Alvarado
Banca: Vivaldo Fernando da Costa
Banca: Walmir de Freitas Filho
Resumo: O fluxo de carga convencional é considerado inadequado para a obtenção do ponto de máximo carregamento devido a singularidade da matriz Jacobiana. Os métodos da continuação são ferramentas eficientes para a solução deste tipo de problema, e diferentes parametrizações são utilizadas para evitar a singularidade da matriz. Neste trabalho apresentase uma técnica de parametrização geométrica que possibilita o traçado completo das curvas PV sem os problemas de mal condicionamento. A técnica proposta associa a robustez com a simplicidade e a facilidade de compreensão. A singularidade da matriz Jacobiana é eliminada pela adição da equação de uma reta que passa por um ponto no plano formado pelas variáveis perdas de potência ativa totais e o fator de carregamento, dois parâmetros físicos de fácil compreensão. A técnica, aplicada aos sistemas do IEEE (14, 30, 57, 118 e 300 barras) e ao sistema brasileiro sul-sudeste (638 e 787 barras), mostra que as características do fluxo de carga não só são preservadas, mas também melhoradas. Diversos testes são realizados para proporcionar a comparação do desempenho do esquema de parametrização proposto para o método do fluxo de carga continuado.
Abstract: The conventional Newton's method has been considered inadequate to obtain the maximum loading point of power systems due to the Jacobian matrix singularity. Continuation methods are efficient tools for solving this kind of problem, and different parameterizations are used to avoid the matrix singularity. This paper presents a new geometric parameterization scheme that allows the complete tracing of the PV curves without ill-conditioning problems. The proposed technique associates the robustness to the simplicity and easy understanding. The Jacobian matrix singularity is overcome by the addition of a line equation, which passes through a point in the plane, determined by the real power losses and loading factor variables, two parameters with clear physical meaning. The application of this new technique to the IEEE systems (14, 30, 57, 118 and 300 buses) and to the Brazilian systems south-southeast (638 and 787 buses) shows that the characteristics of the conventional Newton's method are not only preserved but also improved. Several tests are carried out to compare the performance of the proposed parameterization scheme for the continuation power flow method.
Doutor
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Guedes, Renato Braga de Lima. "Cálculo das soluções de baixa tensão das equações de fluxo de carga através de sistemas dinâmicos auxiliares e função energia estendida com modelo ZIP para análise de colapso de tensão." Universidade de São Paulo, 2004. http://www.teses.usp.br/teses/disponiveis/18/18133/tde-19052017-154844/.

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Este trabalho está dividido em duas partes distintas que constituem contribuições inéditas ao estudo da estabilidade em sistemas elétricos de potência. A primeira parte do trabalho é a mais importante e trata do problema da identificação das soluções de baixa tensão críticas do fluxo de carga. Esta parte do trabalho se presta a análise de estabilidade de tensão a pequenas perturbações. Os últimos capítulos deste trabalho apresentam também uma proposta de função energia estendida que modela as cargas dependentes da tensão segundo o modelo ZIP de carga, considerando a estrutura da rede preservada. Assim, a função energia proposta pode ser utilizada para analisar tanto a estabilidade de tensão como a estabilidade de ângulo em sistemas de potência. Esta proposta também é inédita na literatura. Embora a função energia proposta tenha sido aplicada apenas a sistemas de dimensão reduzidas, os resultados apresentados neste trabalho nos levam a acreditar que essa mesma função energia pode ser utilizada na análise de estabilidade de sistemas de potência de grandes dimensões. Já o método proposto para identificação das soluções de baixa tensão das equações de fluxo de carga se utiliza de um sistema dinâmico auxiliar das equações de fluxo de carga. O sistema dinâmico auxiliar utilizado não tem significado físico, mas pode ser escolhido de tal forma que a solução usual das equações de fluxo de carga seja um ponto de equilíbrio estável do sistema dinâmico auxiliar, eque as soluções de baixa tensão do fluxo de carga sejam pontos de equilíbrio instáveis do sistema dinâmico auxiliar. Dessa forma, é possível calcular as soluções de baixa tensão do fluxo de carga, calculando-se os pontos de equilíbrio instáveis do sistema dinâmico auxiliar. Assim, é possível utilizar partes da teoria de sistemas dinâmicos para estudar as soluções das equações de fluxo de carga. Baseado nestes princípios, foi desenvolvido um programa para calcular trajetórias do sistema dinâmico auxiliar, que se iniciam e se mantêm nas vizinhanças da fronteira da área de atração do ponto de equilíbrio estável do SEP. Dessa forma é possível afirmar que a trajetória calculada tende a convergir para a solução crítica das equações de fluxo de carga. O programa foi inicialmente concebido para calcular as soluções de baixa tensão de sistemas elétricos sem perdas. Em seguida o programa desenvolvido foi adaptado para calcular as soluções de baixa tensão de sistemas de potência completos, incluindo também as resistências das linhas de transmissão. Esta última versão do programa foi testada para os sistemas IEEE 39 e IEEE 118 barras, e os resultados obtidos se mostraram bastante satisfatórios. Assim, o método proposto é uma ferramenta original e eficaz para a solução do problema de calcular a solução crítica das equações de fluxo de carga de sistemas elétricos de potência.
This work may be divided into two distinct parts. Both of them are new contributions to stability analysis of power systems. In the first part it is proposed a new method to calculate the critical load flow low voltage solutions, and it is the main part of this work. Meanwhile, the last two chapters of this work presents a proposed extended energy function that consider the common load ZIP models. It allows the analysis of angle and voltage stability for power systems subjected to large disturbances. This work proposes a method to calculate the low voltage solutions (LVS) of the load flow equations of an electrical power system. The proposed method identifies the LVS involved in the saddle-node bifurcation leading the power system to a voltage collapse. This solution is known as the critical low voltage solution. In order to perform the proposed calculation, an auxiliary dynamical gradient system is used. It is shown that the equilibrium points of that associated auxiliary dynamical gradient system are the solutions of the load flow equations. In such manner, the paper proposes identifying the critical LVS calculating the equilibrium points of an auxiliary dynamical gradient system. The proposed method was tested on the Stagg 5-bus, on the IEEE 39-bus and on IEEE 118-bus test systems, and the results are presented at the end of the text.
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Bodin, Hristina. "Wastewater treatment in constructed wetlands : Effects of vegetation, hydraulics and data analysis methods." Doctoral thesis, Linköpings universitet, Biologi, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-91402.

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Degradation of water resources has become one of the most pressing global concerns currently facing mankind. Constructed Wetlands (CWs) represent a concept to combat deterioration of water resources by acting as buffers between wastewater and receiving water bodies. Still, constructing wetlands for the sole purpose of wastewater treatment is a challenging task. To contribute to this research area, the fundamental question raised in this doctorate thesis was: how do factors such as vegetation and residing water movements (hydraulics) influence wastewater treatment in CWs? Also, effects of different data analysis methods for results of CW hydraulics and wastewater treatment were investigated. Research was focused on  phosphorus (P), ammonium-nitrogen (NH4+-N) and solids (TSS) in wastewater and o n P in macrophyte biomass. Studies were performed in pilot-scale free water surface (FWS) CW systems in Kenya (Chemelil) and Sweden (Halmstad) and as computer simulations. Results from the Chemelil CWs demonstrated that meeting effluent concentration standards simultaneously for all water quality parameters in one CW was difficult. Vegetation harvest, and thus nutrient uptake by young growing macrophytes, was important for maintaining low effluents of NH4+-N and P, especially during dry seasons. On the other hand, mature and dense vegetation growing for at least 4 months secured meeting TSS standards. Phosphorus in above-ground green biomass accounted for almost 1/3 of the total P mass removal, demonstrating high potential for P removal through macrophyte harvest in CWs. Also, results suggested that harvest should be species-specific to achieve high P removal by macrophytes and overall acceptable wastewater treatment in CWs. Still, different methods to estimate evapotranspiration (ET) from the Chemelil CWs showed that water balance calculations greatly impacted estimations of wastewater treatment results. Hydraulic tracer studies performed in the Chemelil and Halmstad CWs showed that mature and dense emergent vegetation in CWs could reduce effective treatment volumes (e-values), which emphasized the importance of regulating this type of vegetation. Also, it was shown that hydraulic tracer studies with lithium chloride performed in CWs with dense emergent vegetation had problems with low tracer recoveries. This problem could be reduced by promoting the distribution of incoming tracer solution into the CW using a barrier near the CW inlet pipe. Computer simulation results showed that the choice of tracer data analysis method greatly influenced quantifications of CW hydraulics and pollutant removal. The e-value could be 50% higher and the pollutant removal 13% higher depending upon used method. Moreover, unrealistic evalues (above 100%) in published literature could to some extent be explained by tracer data analysis method. Hence, to obtain more reliable hydraulic data and wastewater treatment results from CWs, more attention should be paid to the choice of tracer data analysis method.
Konstruerade våtmarker representerar ett koncept för möjligheten att nå en hållbar vattenresurshantering genom att agera som ”filter” mellan föroreningskälla och viktiga vattenresurser såsom sjöar och hav. Mycket kunskap saknas däremot om hur man konstruerar våtmarker med en optimal och pålitlig vattenreningskapacitet. Den här avhandlingen undersöker därför hur vegetation och vattnets väg genom våtmarken (hydrauliken) påverkar avloppsvattenrening i våtmarker. Dessutom undersöktes hur valet av dataanalysmetod av insamlad data påverkar resultaten. Studier genomfördes i Kenya och Sverige i experimentvåtmarker (ca. 40-60 m2) och inkluderadedatainsamling av vattenkvalité, hydraulik (spårämnesexperiment) samt biomassa och fosfor i biomassan av två olika våtmarksväxter. Dessutom genomfördes datorsimuleringar. Resultaten från Kenya visade att växtskörd och efterföljande näringsupptag av nyskördade växter var viktig för att uppnå låga utgående koncentrationer av fosfor och ammonium i en tropisk våtmark, speciellt under torrsäsongen. Däremot var en välutvecklad och tät vegetation viktig för reningen av partiklar. Fosfor i grön växtbiomassa representerade cirka 1/3 av våtmarkernas totala fosforrening, vilket påvisade potentialen i att genom skörd ta bort fosfor från avloppsvatten m.h.a. konstruerade våtmarker. Resultaten pekade också på att skörden bör vara art-specifik för att uppnå en hög fosforrening och generellt bra vattenreningsresultat. Dock visade olika beräkningsmetoder att vattenbalansen i en tropisk våtmark markant kan påverka vattenreningsresultaten. Resultaten från spårämnesexperimenten demonstrerade att den effektiva våtmarksvolymen för vattenrening blev mindre vid hög täthet av övervattensväxter. Detta pekade på att regelbunden växtskörd var viktig för att uppnå god vattenrening i våtmarker. Experiment med spårämnet litium visade att man kan få felaktiga resultat p.g.a. att en del spårämne fasthålls på botten i våtmarken om denna har mycket övervattensväxter. Därför bör spridningen av spårämnet i sådana våtmarker underlättas m.h.a. en spridningsbarriär nära inloppsröret. Simuleringar visade också att valet av dataanalysmetod av spårämnesdata starkt kan påverka resultaten och därmed också vår tolkning av en våtmarks hydraulik och reningskapacitet. Den effektiva volymen kunde vara 50% högre och reningseffekten 13% högre beroende på vilken metod som användes. Likaså kan valet av dataanalysmetod ha bidragit till överskattade och orealistiska effektiva volymer (över 100%) i artiklar publicerade de senaste 25 åren. Genom att fokusera mer på valet av dataanalysmetod och t.ex. jämföra resultaten från två olika metoder kan man minimera risken för bristfälliga resultat och därmed felaktiga slutsatser om en våtmarks vattenreningskapacitet.
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Oke, Oluwabukola A. "Enhanced unscented transform method for probabilistic load flow studies." Thesis, University of Nottingham, 2013. http://eprints.nottingham.ac.uk/14040/.

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The advent of deregulated electricity and the call for sustainable energy practices are major drivers for the continued increase of renewable energy systems within the modern day power network. Dominant among them is the wind energy system whose output is uncertain because of its dependence on the prevailing climatic conditions. This increases the level of uncertainty witnessed within the power system as such, as the penetration of renewable energy systems continue to increase, their effects cannot be trivialised. Probabilistic load flow (PLF) is employed by power system analysts to account for the effect of uncertainty within the power network. The common technique which is based on Monte Carlo Simulation (MCS), though accurate is very time consuming and for large systems it becomes unwieldy. Alternative approaches with the advantages of the MCS method but with reduced computational burden are required. A viable alternative method should therefore require minimum computational time and burden, be able to accurately model various network uncertainties, be applicable to practical small and large systems, be able to account for the effect of dependency among network variables and possess good overall accuracy. This thesis proposes a novel approximate approach referred to as the enhanced unscented transform method to meet the requirements of PLF. The method combines the Gaussian quadrature method and the Stieljes procedure with dimension reduction technique in deciding estimation points while the Cholesky decomposition is incorporated to account for the effect of dependency. The performance of the proposed technique is demonstrated using modified IEEE 6, 14, and 118 test systems and a practical distribution test system all incorporating wind farms. Results obtained for numerous scenarios show a good match between the proposed method and the MCS method but with significant computational burden saving. The performance of the method is also shown to compare favourably with other existing PLF methods.
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Ellis, Mikle Val. "The ladder load-flow method extended to distribution networks." Diss., Virginia Tech, 1994. http://hdl.handle.net/10919/39138.

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The rigorous load-flow analysis of Distribution Networks requires the modeling of mutual coupling, multiphase possibilities and unbalanced loading. The Ladder Load-Flow Method meets these requirements, but is limited to radial systems. The Switch Compensation Method presented here, extends the Ladder Load-Flow Method to solve Distribution Networks. A network analysis program has been developed using the Electric Power Research Distribution Engineering Workstation (DEWorkstation). The program uses the pointers provided by the DEWorkstation to represent the connectivity of the system. The use of these pointers increases the speed of execution while naturally handling the sparsity of the system. The user is also provided with "on line" attribute and topological data maintenance. The extension technique is based on Thevenin's Theorem. This approach allows the accurate determination of the equivalent impedance for networks which contain series and shunt elements. The equivalent impedance can be changed during the iterative solution process. This allows the algorithm to simulate the operation of control devices which significantly alter the impedance of the network. A transformer model for the forward and reverse trace of the Ladder Method is also presented.
Ph. D.
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CASTRO, ANDRE MILHORANCE DE. "PROBABILISTIC LOAD FLOW VIA MONTE CARLO SIMULATION AND CROSS-ENTROPY METHOD." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2017. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=36794@1.

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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO
CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
Em planejamento e operação de sistemas de energia elétrica, é necessário realizar diversas avaliações utilizando o algoritmo de fluxo de potência, para obter e monitorar o ponto de operação da rede em estudo. Em sua utilização determinística, devem ser especificados valores de geração e níveis de carga por barra, bem como considerar uma configuração especifica da rede elétrica. Existe, porém, uma restrição evidente em se trabalhar com algoritmo de fluxo de potência determinístico: não há qualquer percepção do impacto gerado por incertezas nas variáveis de entrada que o algoritmo utiliza. O algoritmo de fluxo de potência probabilístico (FPP) visa extrapolar as limitações impostas pelo uso da ferramenta convencional determinística, permitindo a consideração das incertezas de entrada. Obtém-se maior sensibilidade na avaliação dos resultados, visto que possíveis regiões de operação são mais claramente examinadas. Consequentemente, estima-se o risco do sistema funcionar fora de suas condições operativas nominais. Essa dissertação propõe uma metodologia baseada na simulação Monte Carlo (SMC) utilizando técnicas de amostragem por importância via o método de entropia cruzada. Índices de risco para eventos selecionados (e.g., sobrecargas em equipamentos de transmissão) são avaliados, mantendo-se a precisão e flexibilidade permitidas pela SMC convencional, porém em tempo computacional muito reduzido. Ao contrário das técnicas analíticas concebidas para solução do FPP, que visam primordialmente à elaboração de curvas de densidade de probabilidade para as variáveis de saída (fluxos, etc.) e sempre necessitam ter a precisão obtida comparada à SMC, o método proposto avalia somente as áreas das caudas dessas densidades, obtendo resultados com maior exatidão nas regiões de interesse do ponto de vista do risco operativo. O método proposto é aplicado nos sistemas IEEE 14 barras, IEEE RTS e IEEE 118 barras, sendo os resultados obtidos amplamente discutidos. Em todos os casos, há claros ganhos de desempenho computacional, mantendo-se a precisão, quando comparados à SMC convencional. As possíveis aplicações do método e suas derivações futuras também fazem parte da dissertação.
In planning and operation of electric energy systems, it is necessary to perform several evaluations using the power flow algorithm to obtain and monitor the operating point of the network under study. Bearing in mind its deterministic use, generation values and load levels per bus must be specified, as well as a specific configuration of the power network. There is, however, an obvious constraint in running a deterministic power flow tool: there is no perception of the impact produced by uncertainties on the input variables used by the conventional algorithm. The probabilistic power flow (PLF) algorithm aims to solve the limitations imposed by the use of the deterministic conventional tool, allowing the consideration of input uncertainties. Superior sensitivity is obtained in the evaluation of results, as possible regions of operation are more clearly examined. Consequently, the risk of the system operating outside its nominal conditions is duly estimated. This dissertation proposes a methodology based on Monte Carlo simulation (MCS) using importance sampling techniques via the cross-entropy method. Risk indices for selected events (e.g., overloads on transmission equipment) are evaluated, keeping the same accuracy and flexibility tolerable by the conventional MCS, but in much less computational time. Unlike the FPP solution obtained by analytical techniques, which primarily aim at assessing probability density curves for the output variables (flows, etc.) and always need to have the accuracy compared to MCS, the proposed method evaluates only the tail areas of these densities, obtaining results with greater accuracy in the regions of interest from the operational risk point of view. The proposed method is applied to IEEE 14, IEEE RTS and IEEE 118 bus systems, and the results are widely discussed. In all cases, there are clear gains in computational performance, maintaining accuracy when compared to conventional SMC. The possible applications of the method and future developments are also part of the dissertation.
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Books on the topic "Load Flow Methods"

1

Orchard, Richard D. New method for measuring water seepage through salmon spawning gravel. Portland, Or: U.S. Dept. of Agriculture, Pacific Northwest Research Station, 1988.

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Waldman, W. An improved computational procedure for the unsteady doublet lattice method. Melbourne, Australia: Aeronautical Research Laboratories, 1986.

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Askari, Abid Hasan. Finite element prediction of bin loads. Edmonton, Alta., Canada: Dept. of Civil Engineering, University of Alberta, 1986.

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Grubbs, J. W. Application of acoustical methods for estimating water flow and constituent loads in Perdido Bay, Florida. Tallahassee, Fla: U.S. Department of the Interior, U.S. Geological Survey ; Denver, CO, 1997.

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M, Arnold S., Iyer Saiganesh K, and Lewis Research Center, eds. Flow/damage surfaces for fiber-reinforced metals having different periodic microstructures. [Cleveland, Ohio]: National Aeronautics and Space Administration, Lewis Research Center, 1998.

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Hsing-jen, Chang, and Langley Research Center, eds. H-P adaptive methods for finite element analysis of aerothermal loads in high-speed flows. Hampton, Va: National Aeronautics and Space Administration, Langley Research Center, 1993.

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Xingren, Zhang, and Langley Research Center, eds. H-P adaptive methods for finite element analysis of aerothermal loads in high-speed flows. Hampton, Va: National Aeronautics and Space Administration, Langley Research Center, 1993.

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Hsing-jen, Chang, and Langley Research Center, eds. H-P adaptive methods for finite element analysis of aerothermal loads in high-speed flows. Hampton, Va: National Aeronautics and Space Administration, Langley Research Center, 1993.

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Sibikin, Yuriy. Power supply. ru: INFRA-M Academic Publishing LLC., 2022. http://dx.doi.org/10.12737/1863101.

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The textbook discusses methods for calculating electrical loads, issues of the quality of electrical energy and reactive power compensation, power supply schemes of objects; describes the methodology for determining losses in elements of power supply systems, provides material related to the operation and calculation of electrical networks associated with the process of electric current flow in the wires of external and internal power supply of objects. It is intended for students of training areas and specialties "Electric power engineering and electrical engineering", "Power stations, networks and systems", "Power supply", "Automatic control of electric power systems", "Relay protection and automation of electric power systems" and other electric power training areas and specialties of universities and institutions of secondary vocational education.
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Trias, Antonio. The Holomorphic Embedding Load-Flow Method: Foundations and Implementations. Now Publishers, 2018.

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Book chapters on the topic "Load Flow Methods"

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Soman, S. A., S. A. Khaparde, and Shubha Pandit. "Load Flow Analysis." In Computational Methods for Large Sparse Power Systems Analysis, 147–78. Boston, MA: Springer US, 2002. http://dx.doi.org/10.1007/978-1-4615-0823-6_8.

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Hubana, Tarik, Sidik Hodzic, Emir Alihodzic, and Ajdin Mulaosmanovic. "The Valuation of Kron Reduction Application in Load Flow Methods." In Advanced Technologies, Systems, and Applications III, 70–85. Cham: Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-030-02574-8_7.

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Lahaye, Domenico, and Kees Vuik. "Globalized Newton–Krylov–Schwarz AC Load Flow Methods for Future Power Systems." In Intelligent Integrated Energy Systems, 79–98. Cham: Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-030-00057-8_4.

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Ponter, A. R. S. "Limit Load Theorems for the Drucker-Prager Yield Condition with a Non-associated Flow Rule." In Advances in Direct Methods for Materials and Structures, 1–11. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-59810-9_1.

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George-Williams, Hindolo, T. V. Santhosh, and Edoardo Patelli. "Simulation Methods for the Analysis of Complex Systems." In Uncertainty in Engineering, 95–113. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-83640-5_7.

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AbstractEveryday systems like communication, transportation, energy and industrial systems are an indispensable part of our daily lives. Several methods have been developed for their reliability assessment—while analytical methods are computationally more efficient and often yield exact solutions, they are unable to account for the structural and functional complexities of these systems. These complexities often require the analyst to make unrealistic assumptions, sometimes at the expense of accuracy. Simulation-based methods, on the other hand, can account for these realistic operational attributes but are computationally intensive and usually system-specific. This chapter introduces two novel simulation methods: load flow simulation and survival signature simulation which together address the limitations of the existing analytical and simulation methods for the reliability analysis of large systems.
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Ekhlakov, Roman. "Modern Methods of Traffic Flow Modeling: A Graph Load Calculation Model Based on Real-Time Data." In Intelligent Decision Technologies, 302–9. Singapore: Springer Nature Singapore, 2023. http://dx.doi.org/10.1007/978-981-99-2969-6_27.

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Sambaiah, Kola Sampangi, and T. Jayabarathi. "A Survey on Load/Power Flow Methods and DG Allocation Using Grasshopper Optimization Algorithm in Distribution Networks." In Advances in Intelligent Systems and Computing, 621–30. Singapore: Springer Singapore, 2019. http://dx.doi.org/10.1007/978-981-15-0184-5_53.

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Heinze, Tassilo, Hans-Joachim Koriath, and Alexander Pavlovich Kuznetsov. "Thermal Growth of Motor Spindle Units." In Lecture Notes in Production Engineering, 219–39. Cham: Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-031-34486-2_17.

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AbstractThe paper deals with strategies for numerical compensation of thermo-mechanical deformation of machine tool spindles and the TCP, respectively. Methods for digital modelling and simulating the temperatures and thermo-elastic deformation are presented. This is done by considering the geometry, material data, drive signals and temperature values. The topic of compensating thermo-elastic effects in spindle units is an important topic in manufacturing. Analytical equation and function block methods for measuring and predicting thermal spindle growth are compared. The heat flow model converts variable spindle load, speed, coolant and ambient temperature into local temperatures followed by elastic deformations of the spindle unit. The simulation results were verified for different types of motor spindles by experiments on a spindle test rig at SPL GmbH. A thermal stiffness value [W/µm] is characterized by the energy losses of the spindle, which result in thermal growth. Different strategies for digital reduction of a thermal spindle growth were developed.
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Kłos, Andrzej. "Current-Based Method of Load Flow Solution." In Mathematical Models of Electrical Network Systems, 97–105. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-52178-7_15.

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Kamal Kumar, U., and Varaprasad Janamala. "Comparative Analysis of Load Flows and Voltage-Dependent Load Modeling Methods of Distribution Networks." In Advances in Intelligent Systems and Computing, 467–83. Singapore: Springer Singapore, 2021. http://dx.doi.org/10.1007/978-981-33-6984-9_38.

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Conference papers on the topic "Load Flow Methods"

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Murty, V. V. S. N., B. Ravi Teja, and Ashwani Kumar. "A contribution to load flow in radial distribution system and comparison of different load flow methods." In 2014 International Conference on Power Signals Control and Computations (EPSCICON). IEEE, 2014. http://dx.doi.org/10.1109/epscicon.2014.6887494.

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Melhorn, Alexander C., and Aleksandar Dimitrovski. "Correlation between EVs and Other Loads in Probabilistic Load Flow for Distribution Systems." In 2018 IEEE International Conference on Probabilistic Methods Applied to Power Systems (PMAPS). IEEE, 2018. http://dx.doi.org/10.1109/pmaps.2018.8440435.

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Chihota, Munyaradzi J., and Charles T. Gaunt. "Impact of Input Model Accuracy on Probabilistic Load Flow Outputs." In 2018 IEEE International Conference on Probabilistic Methods Applied to Power Systems (PMAPS). IEEE, 2018. http://dx.doi.org/10.1109/pmaps.2018.8440208.

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Li, Gan, and Xiao-Ping Zhang. "Comparison between two probabilistic load flow methods for reliability assessment." In Energy Society General Meeting (PES). IEEE, 2009. http://dx.doi.org/10.1109/pes.2009.5275534.

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Stalewski, Wieńczysław, and Janusz Sznajder. "LOAD CONTROL OF NATURAL-LAMINAR-FLOW WING VIA BOUNDARY LAYER CONTROL." In VII European Congress on Computational Methods in Applied Sciences and Engineering. Athens: Institute of Structural Analysis and Antiseismic Research School of Civil Engineering National Technical University of Athens (NTUA) Greece, 2016. http://dx.doi.org/10.7712/100016.2271.15624.

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Trakas, D. N., E. M. Voumvoulakis, and N. D. Hatziargyriou. "Decentralized control of power system zones based on probabilistic constrained load flow." In 2014 International Conference on Probabilistic Methods Applied to Power Systems (PMAPS). IEEE, 2014. http://dx.doi.org/10.1109/pmaps.2014.6960652.

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Melhorn, Alexander C., Aleksandar Dimitrovski, and Andrew Keane. "Probabilistic load flow: A business park analysis, utilizing real world meter data." In 2016 International Conference on Probabilistic Methods Applied to Power Systems (PMAPS). IEEE, 2016. http://dx.doi.org/10.1109/pmaps.2016.7763932.

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Amid, Pouya, and Curran Crawford. "Cumulant-based probabilistic load flow analysis of wind power and electric vehicles." In 2016 International Conference on Probabilistic Methods Applied to Power Systems (PMAPS). IEEE, 2016. http://dx.doi.org/10.1109/pmaps.2016.7764136.

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Ramirez, Ulises Tovar, and Jose Horacio Tovar Hernandez. "Efficiency analysis of load flow methods for balanced radial distribution systems." In 2013 IEEE International Autumn Meeting on Power, Electronics and Computing (ROPEC). IEEE, 2013. http://dx.doi.org/10.1109/ropec.2013.6702756.

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Bhalla, Sonia, Sanjeev Kumar, and Sanjeev Kumar Aggarwal. "Comparative Analysis of Newton’s Higher Order Methods for Load Flow Problem." In 2019 Amity International Conference on Artificial Intelligence (AICAI). IEEE, 2019. http://dx.doi.org/10.1109/aicai.2019.8701346.

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Reports on the topic "Load Flow Methods"

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Leis and Brust. L51604 Ductile Fracture Properties of Selected Line Pipe Steels. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), January 1990. http://dx.doi.org/10.55274/r0010213.

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The objective of this report is to present the ductile fracture properties needed to assess stable flaw growth. These properties are presented following a brief discussion of the analysis method being developed to provide the gas industry with an accurate and validated model for predicting growth of a flaw due to the effects of a hydrostatic test or hydrostatic retesting. The end product will be a validated model that predicts crack extension during the load and hold portion of a hydrotest, and subsequent operation. Test methods to develop these properties are presented along with discussion of data analysis. Results are presented for three line-pipe steels for the LT (through-wall axial flaw) orientation, for three levels of prestrain.
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Bruce. L52282 State-of-the-Art Assessment of Alternative Casing Repair Methods. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), July 2007. http://dx.doi.org/10.55274/r0010195.

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Many natural gas storage wells suffer damage during normal storage operations. Storage operators spend upwards of $100 million per year recovering lost deliverability. Damage to casings in gas storage wells is largely the result of localized loss of metal from corrosion; however, other types of damage do occur. Individual corrosion pits can be found either on the inside or outside of the casing wall. Repair methods that are currently used for natural gas storage well casings include patches, plugs, liners, etc. While currently-used repair methods can be a cost-effective means of repairing damaged casings as compared to the cost of running an entirely new casing, there is a need to identify and develop alternative casing repair methods that are more economical and/or do not have inherent operational disadvantages. Many of the current repair methods are proprietary, and as a result, are relatively costly to perform. In addition, many of these repair methods (e.g., tube and packer system repairs) result in a decreased cross-sectional area, which creates operational limitations due to flow restrictions and reduces the ability to perform well logging operations. The objective of this project was to review current state-of-the-art casing repair technologies to identify more cost effective alternatives. The most prominent form of underground U.S. gas storage is depleted reservoirs. American Petroleum Institute specification 5CT contains the industry standard design guidance for new casings; however, there are no industry standard repair procedures and each state has their own. The most common state required repair integrity test is pressure testing. Casings must withstand tensile, burst, and collapse loads. Most state repair procedures do not specify a target mechanical property that defines repair success. It is therefore easy to assume that a repair should return a casing back to its original integrity level; however, it may not be necessary. The major types of damage mechanisms are corrosion, threaded connection separation, sealant leaks, split casings, and drill bit damage. While a literature search indicated that the most commonly used types of cost effective repair processes are squeezes, liners, and plating, industry feedback indicated that liner repair is the most commonly used repair process. Adhesively bonded, helically-wound, steel strip repair and magnetic pulse welding are the most promising alternative repair technologies identified, mainly because both are applicable for a broad range of damage types and as an alternative to both traditional casing liner and expandable tubular repair technologies.
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Lehotay, Steven J., and Aviv Amirav. Fast, practical, and effective approach for the analysis of hazardous chemicals in the food supply. United States Department of Agriculture, April 2007. http://dx.doi.org/10.32747/2007.7695587.bard.

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Background to the topic: For food safety and security reasons, hundreds of pesticides, veterinary drugs, and environmental pollutants should be monitored in the food supply, but current methods are too time-consuming, laborious, and expensive. As a result, only a tiny fraction of the food is tested for a limited number of contaminants. Original proposal objectives: Our main original goal was to develop fast, practical, and effective new approaches for the analysis of hazardous chemicals in the food supply. We proposed to extend the QuEChERS approach to more pesticides, veterinary drugs and pollutants, further develop GC-MS and LC-MS with SMB and combine QuEChERS with GC-SMB-MS and LC-SMB-EI-MS to provide the “ultimate” approach for the analysis of hazardous chemicals in food. Major conclusions, solutions and achievements: The original QuEChERS method was validated for more than 200 pesticide residues in a variety of food crops. For the few basic pesticides for which the method gave lower recoveries, an extensive solvent suitability study was conducted, and a buffering modification was made to improve results for difficult analytes. Furthermore, evaluation of the QuEChERS approach for fatty matrices, including olives and its oil, was performed. The QuEChERS concept was also extended to acrylamide analysis in foods. Other advanced techniques to improve speed, ease, and effectiveness of chemical residue analysis were also successfully developed and/or evaluated, which include: a simple and inexpensive solvent-in-silicone-tube extraction approach for highly sensitive detection of nonpolar pesticides in GC; ruggedness testing of low-pressure GC-MS for 3-fold faster separations; optimization and extensive evaluation of analyte protectants in GC-MS; and use of prototypical commercial automated direct sample introduction devices for GC-MS. GC-MS with SMB was further developed and combined with the Varian 1200 GCMS/ MS system, resulting in a new type of GC-MS with advanced capabilities. Careful attention was given to the subject of GC-MS sensitivity and its LOD for difficult to analyze samples such as thermally labile pesticides or those with weak or no molecular ions, and record low LOD were demonstrated and discussed. The new approach of electron ionization LC-MS with SMB was developed, its key components of sample vaporization nozzle and flythrough ion source were improved and was evaluated with a range of samples, including carbamate pesticides. A new method and software based on IAA were developed and tested on a range of pesticides in agricultural matrices. This IAA method and software in combination with GC-MS and SMB provide extremely high confidence in sample identification. A new type of comprehensive GCxGC (based on flow modulation) was uniquely combined with GC-MS with SMB, and we demonstrated improved pesticide separation and identification in complex agricultural matrices using this novel approach. An improved device for aroma sample collection and introduction (SnifProbe) was further developed and favorably compared with SPME for coffee aroma sampling. Implications, both scientific and agricultural: We succeeded in achieving significant improvements in the analysis of hazardous chemicals in the food supply, from easy sample preparation approaches, through sample analysis by advanced new types of GC-MS and LCMS techniques, all the way to improved data analysis by lowering LOD and providing greater confidence in chemical identification. As a result, the combination of the QuEChERS approach, new and superior instrumentation, and the novel monitoring methods that were developed will enable vastly reduced time and cost of analysis, increased analytical scope, and a higher monitoring rate. This provides better enforcement, an added impetus for farmers to use good agricultural practices, improved food safety and security, increased trade, and greater consumer confidence in the food supply.
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Brosh, Arieh, David Robertshaw, Yoav Aharoni, Zvi Holzer, Mario Gutman, and Amichai Arieli. Estimation of Energy Expenditure of Free Living and Growing Domesticated Ruminants by Heart Rate Measurement. United States Department of Agriculture, April 2002. http://dx.doi.org/10.32747/2002.7580685.bard.

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Research objectives were: 1) To study the effect of diet energy density, level of exercise, thermal conditions and reproductive state on cardiovascular function as it relates to oxygen (O2) mobilization. 2) To validate the use of heart rate (HR) to predict energy expenditure (EE) of ruminants, by measuring and calculating the energy balance components at different productive and reproductive states. 3) To validate the use of HR to identify changes in the metabolizable energy (ME) and ME intake (MEI) of grazing ruminants. Background: The development of an effective method for the measurement of EE is essential for understanding the management of both grazing and confined feedlot animals. The use of HR as a method of estimating EE in free-ranging large ruminants has been limited by the availability of suitable field monitoring equipment and by the absence of empirical understanding of the relationship between cardiac function and metabolic rate. Recent developments in microelectronics provide a good opportunity to use small HR devices to monitor free-range animals. The estimation of O2 uptake (VO2) of animals from their HR has to be based upon a consistent relationship between HR and VO2. The question as to whether, or to what extent, feeding level, environmental conditions and reproductive state affect such a relationship is still unanswered. Studies on the basic physiology of O2 mobilization (in USA) and field and feedlot-based investigations (in Israel) covered a , variety of conditions in order to investigate the possibilities of using HR to estimate EE. In USA the physiological studies conducted using animals with implanted flow probes, show that: I) although stroke volume decreases during intense exercise, VO2 per one heart beat per kgBW0.75 (O2 Pulse, O2P) actually increases and measurement of EE by HR and constant O2P may underestimate VO2unless the slope of the regression relating to heart rate and VO2 is also determined, 2) alterations in VO2 associated with the level of feeding and the effects of feeding itself have no effect on O2P, 3) both pregnancy and lactation may increase blood volume, especially lactation; but they have no effect on O2P, 4) ambient temperature in the range of 15 to 25°C in the resting animal has no effect on O2P, and 5) severe heat stress, induced by exercise, elevates body temperature to a sufficient extent that 14% of cardiac output may be required to dissipate the heat generated by exercise rather than for O2 transport. However, this is an unusual situation and its affect on EE estimation in a freely grazing animal, especially when heart rate is monitored over several days, is minor. In Israel three experiments were carried out in the hot summer to define changes in O2P attributable to changes in the time of day or In the heat load. The animals used were lambs and young calves in the growing phase and highly yielding dairy cows. In the growing animals the time of day, or the heat load, affected HR and VO2, but had no effect on O2P. On the other hand, the O2P measured in lactating cows was affected by the heat load; this is similar to the finding in the USA study of sheep. Energy balance trials were conducted to compare MEI recovery by the retained energy (RE) and by EE as measured by HR and O2P. The trial hypothesis was that if HR reliably estimated EE, the MEI proportion to (EE+RE) would not be significantly different from 1.0. Beef cows along a year of their reproductive cycle and growing lambs were used. The MEI recoveries of both trials were not significantly different from 1.0, 1.062+0.026 and 0.957+0.024 respectively. The cows' reproductive state did not affect the O2P, which is similar to the finding in the USA study. Pasture ME content and animal variables such as HR, VO2, O2P and EE of cows on grazing and in confinement were measured throughout three years under twenty-nine combinations of herbage quality and cows' reproductive state. In twelve grazing states, individual faecal output (FO) was measured and MEI was calculated. Regression analyses of the EE and RE dependent on MEI were highly significant (P<0.001). The predicted values of EE at zero intake (78 kcal/kgBW0.75), were similar to those estimated by NRC (1984). The EE at maintenance condition of the grazing cows (EE=MEI, 125 kcal/kgBW0.75) which are in the range of 96.1 to 125.5 as presented by NRC (1996 pp 6-7) for beef cows. Average daily HR and EE were significantly increased by lactation, P<0.001 and P<0.02 respectively. Grazing ME significantly increased HR and EE, P<0.001 and P<0.00l respectively. In contradiction to the finding in confined ewes and cows, the O2P of the grazing cows was significantly affected by the combined treatments (P<0.00l ); this effect was significantly related to the diet ME (P<0.00l ) and consequently to the MEI (P<0.03). Grazing significantly increased O2P compared to confinement. So, when EE of grazing animals during a certain season of the year is estimated using the HR method, the O2P must be re measured whenever grazing ME changes. A high correlation (R2>0.96) of group average EE and of HR dependency on MEI was also found in confined cows, which were fed six different diets and in growing lambs on three diets. In conclusion, the studies conducted in USA and in Israel investigated in depth the physiological mechanisms of cardiovascular and O2 mobilization, and went on to investigate a wide variety of ruminant species, ages, reproductive states, diets ME, time of intake and time of day, and compared these variables under grazing and confinement conditions. From these combined studies we can conclude that EE can be determined from HR measurements during several days, multiplied by O2P measured over a short period of time (10-15 min). The study showed that RE could be determined during the growing phase without slaughtering. In the near future the development microelectronic devices will enable wide use of the HR method to determine EE and energy balance. It will open new scopes of physiological and agricultural research with minimizes strain on animals. The method also has a high potential as a tool for herd management.
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Shmulevich, Itzhak, Shrini Upadhyaya, Dror Rubinstein, Zvika Asaf, and Jeffrey P. Mitchell. Developing Simulation Tool for the Prediction of Cohesive Behavior Agricultural Materials Using Discrete Element Modeling. United States Department of Agriculture, October 2011. http://dx.doi.org/10.32747/2011.7697108.bard.

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The underlying similarity between soils, grains, fertilizers, concentrated animal feed, pellets, and mixtures is that they are all granular materials used in agriculture. Modeling such materials is a complex process due to the spatial variability of such media, the origin of the material (natural or biological), the nonlinearity of these materials, the contact phenomenon and flow that occur at the interface zone and between these granular materials, as well as the dynamic effect of the interaction process. The lack of a tool for studying such materials has limited the understanding of the phenomena relevant to them, which in turn has led to energy loss and poor quality products. The objective of this study was to develop a reliable prediction simulation tool for cohesive agricultural particle materials using Discrete Element Modeling (DEM). The specific objectives of this study were (1) to develop and verify a 3D cohesionless agricultural soil-tillage tool interaction model that enables the prediction of displacement and flow in the soil media, as well as forces acting on various tillage tools, using the discrete element method; (2) to develop a micro model for the DEM formulation by creating a cohesive contact model based on liquid bridge forces for various agriculture materials; (3) to extend the model to include both plastic and cohesive behavior of various materials, such as grain and soil structures (e.g., compaction level), textures (e.g., clay, loam, several grains), and moisture contents; (4) to develop a method to obtain the parameters for the cohesion contact model to represent specific materials. A DEM model was developed that can represent both plastic and cohesive behavior of soil. Soil cohesive behavior was achieved by considering tensile force between elements. The developed DEM model well represented the effect of wedge shape on soil behavior and reaction force. Laboratory test results showed that wedge penetration resistance in highly compacted soil was two times greater than that in low compacted soil, whereas DEM simulation with parameters obtained from the test of low compacted soil could not simply be extended to that of high compacted soil. The modified model took into account soil failure strength that could be changed with soil compaction. A three dimensional representation composed of normal displacement, shear failure strength and tensile failure strength was proposed to design mechanical properties between elements. The model based on the liquid bridge theory. An inter particle tension force measurement tool was developed and calibrated A comprehensive study of the parameters of the contact model for the DEM taking into account the cohesive/water-bridge was performed on various agricultural grains using this measurement tool. The modified DEM model was compared and validated against the test results. With the newly developed model and procedure for determination of DEM parameters, we could reproduce the high compacted soil behavior and reaction forces both qualitatively and quantitatively for the soil conditions and wedge shapes used in this study. Moreover, the effect of wedge shape on soil behavior and reaction force was well represented with the same parameters. During the research we made use of the commercial PFC3D to analyze soil tillage implements. An investigation was made of three different head drillers. A comparison of three commonly used soil tillage systems was completed, such as moldboard plow, disc plow and chisel plow. It can be concluded that the soil condition after plowing by the specific implement can be predicted by the DEM model. The chisel plow is the most economic tool for increasing soil porosity. The moldboard is the best tool for soil manipulation. It can be concluded that the discrete element simulation can be used as a reliable engineering tool for soil-implement interaction quantitatively and qualitatively.
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6

Application of acoustical methods for estimating water flow and constituent loads in Perdido Bay, Florida. US Geological Survey, 1997. http://dx.doi.org/10.3133/wri974101.

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7

POWER FLOW ANALYSIS OF BRIDGE U-RIB STIFFENED PLATES BASED ON THE CONCEPT OF STRUCTURAL INTENSITY. The Hong Kong Institute of Steel Construction, August 2022. http://dx.doi.org/10.18057/icass2020.p.061.

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Due to its advantages of good mechanical properties, simple appearance and strong adaptability, the steel box girder is being widely utilized in urban bridges. The noise radiated by steel box girders subjected to vehicle impacts has the characteristics of wide-spectrum, high-magnitude and control difficulty. U-rib stiffened roof, as a part of the steel box girder, directly bears the input load, which is the basis of studying the vibration of the steel box girder. Currently, the investigation on the vibro-acoustic performance of U-rib plates is very limited. With this regard, this paper introduces the concept of Structural Intensity (SI). The SI vector is calculated by the Finite Element (FE) method. The power flow is visualized by the self-programming post-processing code. The global and local vibration energy transmission characters of a U-rib stiffened plate under a harmonic nodal force are analyzed. Further, the influence of plate thickness is investigated. The optimum design is carried out based on the engineering standard dimensions. The research results indicate that increasing the thickness ratio of the U-rib to the baseplate is beneficial to reducing the vibration.
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