检索结果-南通市图书馆

Control Theory and Technology 2021年第1期19卷 127-141页

作者： Jeisson E.Otero-Leal John Cortes-Romero Efredy delgado Aguilera Felipe Galarza-Jimenez Alexander Jimenez-Triana departamento de Eléctricay Electrónica Facultad de IngeníeraUniversidad Nacional de ColombiaBogotáD.C..Colombia department of Control Engineering Universidad Distrital Francisco Joséde CaldasBogotáColombia

An adaptation of the active disturbance rejection control(AD RC)approach is applied to a fractional-order system with a flat *** the rather scarce information about the system,the conditions to establish an ultimate bound for a specific configuration of the system are found and compiled in a guideline for the tuning of the observer implemented in the ADRC.

关键词： ADRC Fractional-order system Ultimate bound Final value theorem

Average Current Control with Internal Model Control and Real-time Frequency decoupling for Hybrid Energy Storage Systems in Microgrids

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Modern Power Systems and Clean Energy 2023年第2期11卷 511-522页

作者： Alejandro Latorre Wilmar Martinez Camilo A.Cortes EMC-UN Research Group Universidad Nacional de ColombiaBogotaColombia KU Leuven Campus DiepenbeekEnergy Ville 1-GenkBelgiumDiepenbeekBelgium

Among hybrid energy storage systems(HESSs),battery-ultracapacitor systems in active topology use DC/DC power converters for their *** are part of the solutions designed to improve the operation of power systems in different *** the residential microgrid applications,a multilevel control system is required to manage the available energy and interactions among the microgrid *** this purpose,a rule-based power management system is designed,whose operation is validated in the simulation,and the performances of different controllers are compared to select the best strategy for the DC/DC *** average current control with internal model control and real-time frequency decoupling is proposed as the most suitable controller according to the contemplated performance parameters,allowing voltage regulation values close to 1%.The results are validated using real-time hardware-in-the-loop(HIL).These systems can be easily adjusted for other applications such as electric vehicles.

关键词： Internal model control energy management system(EMS) hybrid energy storage system(HESS) microgrids real-time frequency decoupling

Universal deformation Rings of Modules over Self-injective Cluster-Tilted Algebras Are Trivial

在线全文

学校读者我要写书评

暂无评论

Algebra Colloquium 2021年第2期28卷 269-280页

作者： I.D.M.Gaviria JoséA.Vélez-Marulanda Peng Shan universidad nacional de colombia Bogota D.C.Colombia department of Mathematics Valdosta State UniversityValdostaGAUSA 不详

Let k be a fixed algebraically closed field of arbitrary characteristic,let Λ be a finite dimensional self-injective k-algebra,and let ∨ be an indecomposable non-projective left Λ-module with finite dimension over *** prove that if τΛ∨ is the Auslander-Reiten translation of ∨,then the versal deformation rings R(Λ,∨)and R(Λ,τΛ∨)(in the sense of *** and the second author)are *** use this to prove that if Λ is further a cluster-tilted k-algebra,then R(Λ,∨)is universal and isomorphic to k.

关键词： self-injective cluster tilted algebras Frobenius algebras (uni)versal deformation rings

Some Open Problems in the Context of Skew PBW Extensions and Semi-graded Rings

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Communications in Mathematics and Statistics 2021年第3期9卷 347-378页

作者： Oswaldo Lezama Seminario deÁlgebra Constructiva-SAC2 Departamento de MatemáticasUniversidad Nacional de ColombiaSede BogotáBogotáColombia

In this paper,we discuss some open problems of non-commutative algebra and noncommutative algebraic geometry from the approach of skew PBW extensions and semi-graded *** exactly,we will analyze the isomorphism arising in the investigation of the Gelfand–Kirillov conjecture about the commutation between the center and the total ring of fractions of an Ore *** Serre’s conjecture will be discussed for a particular class of skew PBW *** questions about the Noetherianity and the Zariski cancellation property of Artin–Schelter regular algebras will be reformulated for semi-graded *** for the solution of some of the problems are included.

关键词： Gelfand–Kirillov conjecture Serre’s conjecture Artin–Schelter regular algebras Zariski cancellation problem Skew PBW extensions Semi-graded rings

Exploring the reproductive ecology of the tropical semifossorial snake Ninia atrata

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Zoological Research 2020年第2期41卷 157-171页

作者： Teddy Angarita-Sierra Cesar Alejandro Lopez-Hurtado Tropical Organism Biology Research Group Universidad Nacional de ColombiaBogota111321Colombia Yoluka ONG Fundacion de Investigacion en Biodiversidad y ConservacionBogota110931Colombia Vicerrectoria de Investigacion Universidad Manuela BeltranBogota110231Colombia

Based on histological analyses and field studies,this research describes the reproductive ecology of a population of Ninia atrata snakes inhabiting an oil palm ***,through a multivariate approach,we explored the main drivers of reproductive output in *** showed that prey abundance and food intake were crucial variables contributing to reproductive *** linear regression models showed that neonates had high sensitivity(R2=55.29%)to extreme changes in climate,which was strongly related to slug and snail abundance variability and microhabitat *** cycles were markedly different between the sexes,being continuous in males and cyclical in *** this variation,reproductive cycles at the population level were seasonal *** recruitment of neonates all year,multiple clutches,high mating frequency,and continuous sperm production characterized the reproductive phenology of *** addition,a significant number of previtellogenic females presented oviductal sperm as well as uterine scars,suggesting a high precocity in the *** main drivers of reproductive output also differed between the *** females,clutch size and secondary follicle variability were highly related to stomach bolus volume,fat body area,and body *** males,height of piles of palm leaves and body mass,rather than intrinsic reproductive traits,were the main drivers of sperm ***,in both cases,the relationship between body mass,prey abundance,and food intake suggests that *** follows the income breeding strategy to compensate for reproductive costs and to maximize fitness.

关键词： Continuous male reproduction Clutch mass Income breeding Iteroparity Spermatogenesis Oogenesis Reproductive effort El Nino-Southern Oscillation(ENSO)

Multiscale Finite ElementMethods for Flows on Rough Surfaces

在线全文

学校读者我要写书评

暂无评论

Communications in Computational Physics 2013年第9期14卷 979-1000页

作者： Yalchin Efendiev Juan Galvis M.Sebastian Pauletti department of Mathematics TAMUCollege StationTX 77843-3368USA departamento de Matematicas Universidad Nacional de ColombiaBogotaColombia

In this paper,we present the Multiscale Finite Element Method(MsFEM)for problems on rough heterogeneous *** consider the diffusion equation on oscillatory *** objective is to represent small-scale features of the solution via multiscale basis functions described on a coarse *** problem arises in many applications where processes occur on surfaces or thin *** present a unified multiscale finite element framework that entails the use of transformations that map the reference surface to the deformed *** main ingredients of MsFEM are(1)the construction of multiscale basis functions and(2)a global coupling of these basis *** the construction of multiscale basis functions,our approach uses the transformation of the reference surface to a deformed *** the deformed surface,multiscale basis functions are defined where reduced(1D)problems are solved along the edges of coarse-grid blocks to calculate nodalmultiscale basis ***,these basis functions are transformed back to the reference *** discuss the use of appropriate transformation operators that improve the accuracy of the *** method has an optimal convergence if the transformed surface is smooth and the image of the coarse partition in the reference configuration forms a quasiuniform *** this paper,we consider such transformations based on harmonic coordinates(following *** and ***[*** and Applied Math.,LX(2007),pp.675-723])and discuss gridding issues in the reference *** results are presented where we compare the MsFEM when two types of deformations are used formultiscale basis *** first deformation employs local information and the second deformation employs a global *** numerical results showthat one can improve the accuracy of the simulations when a global information is used.

关键词： Multiscale finite elements on surfaces Laplace Beltrami resonance error harmonic maps

Kinetics and mechanisms of the catalytic thermal cracking of asphaltenes adsorbed on supported nanoparticles

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Petroleum Science 2016年第3期13卷 561-571页

作者： Tatiana Montoya Blanca L.Argel Nashaat N.Nassar Camilo A.Franco Farid B.Cortés department of Chemical and Petroleum Engineering University of Calgary 2500 University Drive NW CalgaryAB Canada Grupo de Investigacion Fenomenos de Superficie-Michael Polanyi Facultad de Minas Universidad Nacional de Colombia Sede Medellin Medellin Colombia Grupo de Investigacion en Yacimientos de Hidrocarburos Facultad de Minas Universidad Nacional de Colombia Sede Medellfn Kra 80 No. 65-223 Medellfn Colombia

The production of heavy and extra-heavy oil is challenging because of the rheological properties that crude oil presents due to its high asphaltene *** upgrading and recovery processes of these unconventional oils are typically water and energy intensive,which makes such processes costly and environmentally *** catalysts could be used to enhance the upgrading and recovery of heavy oil under both in situ and ex situ *** this study,the effect of the Ni-Pd nanocatalysts supported on fumed silica nanoparticles on post-adsorption catalytic thermal cracking of n-C_7 asphaltenes was investigated using a thermogravimetric analyzer coupled with *** performance of catalytic thermal cracking of n-C_7asphaltenes in the presence of NiO and PdO supported on fumed silica nanoparticles was better than on the fumed silica support *** a fixed amount of adsorbed n-C_7asphaltenes（0.2 mg/m～2）,bimetallic nanoparticles showed better catalytic behavior than monometallic nanoparticles,confirming their synergistic *** corrected OzawaFlynn-Wall equation（OFW） was used to estimate the effective activation energies of the catalytic *** mechanism function,kinetic parameters,and transition state thermodynamic functions for the thermal cracking process of n-C_7 asphaltenes in the presence and absence of nanoparticles are investigated.

关键词： Catalytic thermal cracking Adsorption Nanoparticles SHS n-C7 asphaltene

Comparison of lipid extraction methods for the microalgae Acutodesmus obliquus

在线全文

学校读者我要写书评

暂无评论

International Journal of Agricultural and Biological Engineering 2018年第5期11卷 211-217页

作者： Diana Ximena Hurtado Claudia Lorena Garzón-Castro Jhon Cortés-Romero Edisson Tello Camacho Bioprospecting and CAPSAB Research Groups Faculty of EngineeringUniversidad de La SabanaCundinamarca 53753Colombia Biosciences Doctoral Program Faculty of EngineeringUniversidad de La SabanaCundinamarca 53753Colombia department of Electrical and Electronic Engineering Universidad Nacional de ColombiaBogotá53753Colombia

Microalgae are widely used in the pharmaceutical and energy industries,therefore the conditions for their cultivation and extraction methods play an important role in the profiling and acquisition of *** efficiency of lipid extraction from microalgae has attracted great interest from industry because of the wide variety of lipids and amounts that can be *** obliquus(Scenedesmus obliquus UTEX 393)was used in this *** was cultivated in Bold 3N medium modified with 75%nitrogen at 25℃,pH 6.8,125 r/min and a photoperiod of 18/6 h and illuminated with white light provided by a Light-Emitting Diode Surface Mount device extensions(LED SMD)with an intensity of 1200μE/(m^(2)·s).The cells were stained with the Red Nile(RN)technique to indicate lipid *** extraction methods were compared,classical,microwave(MW),Soxhlet,and ultrasound(US),using the same solvent proportions(hexane:chloroform:methanol=1:2:3).All samples were analyzed with Fourier Transform Infrared Spectroscopy(FTIR)and Gas Chromatography coupled to Mass Spectrometry(GC-MS).The results showed:1)lipid production detected by RN was consistent with microalgal growth;2)the MW technique was the best extraction method,according to the statistical analysis through Randomized Complete Block(RCB)design and performance of 4.6%;and 3)the presence of saturated and unsaturated acids was indicated by FTIR ***-MS was able to identify palmitic and linoleic acids as the likely major constituents of the sample.

关键词： Acutodesmus obliquus lipid extraction trans-esterification Red Nile(RN)

Hot corrosion mechanism of yttria-stabilized zirconia powder in the presence of molten Na_(2)SO_(4)+V_(2)O_(5) salts

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Rare Metals 2021年第5期40卷 1307-1316页

作者： Jhonattan de la Roche Juan Manuel Alvarado-Orozco Alejandro Toro Tribology and Surfaces Group Universidad Nacional de ColombiaMedellin 050041Colombia Centro de Ingeniena y desarrollo Industrial-CIdeSI Queretaro 76125Mexico Consorcio de Manufactura Aditiva-CONMAD Queretaro 76125Mexico

The hot corrosion behavior of yttria-stabilized zirconia(YSZ)powder specimens exposed to Na_(2)SO_(4)/V_(2)O_(5) salts mixtures at high temperature was *** tests were carried out at 1000℃ for 10 h,the salt concentrations varied from 0.1 wt%to 1.00 wt%,and the Na_(2)SO_(4)/V_(2)O_(5) mass ratios were between 0.20 and 0.44 following a factorial design 22.X-ray diffraction(XRD)analyses of the tested samples showed with a confidence of95%that the mixture composed of 32 wt%Na_(2)SO_(4)+68 wt%V_(2)O_(5),and 1.00 wt% salt concentration led to high destabilization of the t’-YSZ phase and formation of YVO_(4) products.A second set of experiments were conducted to assess the influence of temperature on the hot corrosion response of the YSZ in the range between 490 and 1100℃.Thermogravimetric analysis(TGA)experiments and Rietveld adjustments of XRD patterns showed that the mass loss of the samples varied with testing temperature and also that the major destabilization of tetragonal phase occurred at 900℃.

关键词： Hot corrosion Molten salts Yttria-stabilized zirconia Thermal barrier coatings

Data-driven disturbance observer-based control: an active disturbance rejection approach

在线全文

学校读者我要写书评

暂无评论

Control Theory and Technology 2021年第1期19卷 80-93页

作者： Harvey Rojas-Cubides John Cortés-Romero Jaime Arcos-Legarda deparameno de Ingeniera Elétricay Electrónica Universidad Nacional de ColombiaAv.K30 No.45-03 Edif.453 Of.222BogoiáColombia department of Mechatromies Engineering Universidad de San BuenaventuraBogotá.Colombia

In this paper,a data-driven method for disturbance estimation and rejection is *** proposed approach is divided into two stages:an inner stabilization loop,to set the desired reference model,together with an outer loop for disturbance estimation and *** by the active disturbance rejection control framework,the exogenous and endogenous disturbances are lumped into a lotal disturbance *** signal is estimaed using an on-line algorithm based on a data-driven predictor scheme,whose parameters are chosen Io salisfy high robustnessperformance *** above process is presented as a novel enhancement lo design a disturbance observer,w hich constitutes the main contribution of the *** addition,the control strategy is completely presented in discrete time,avoiding the use of discretization methods for its digital *** a case study,the voltage control of a DC-DC synchronous buck converter aflected by disturbances in the input voltage and the load is ***,experimental results that validate the proposed stralegy and some comparisons with the classical disturbance observer-based control are presented.

关键词： Active disturbance rejection control Data-driven disturbance observer Disturbance observer-based control Signal prediction