Analytical Design and Stability Analysis of the Universal Integral Regulator Applied in Flight Control

Yohan Díaz-Méndez,Marcelo S. de Sousa,Guilherme Gomes,Sebastião Cunha,Alexandre Ramos 제어·로봇·시스템학회 2019 International Journal of Control, Automation, and Vol.17 No.2

This paper considers the analytical design and stability analysis of an output feedback flight controlproblem for a rigid fighter aircraft which has a highly nonlinear dynamic. In this paper, a robust technique knownas Universal Integral Regulator (UIR) has been chosen to solve the tracking problem due to the possibility todemonstrate the stability of the system and analytically compute the control parameters. The UIR is a combinationof Continuous Sliding Mode Control (CSMC) and a Conditional Integrator (CI) which provides integral actiononly inside the boundary layer, enhancing the transient response of the system and providing an equilibrium pointwhere the tracking error is zero. The general procedure consists firstly of rewriting the aircraft dynamics in thecontrol-affine form, then the relative degree of the system is computed and the system is transformed to normalform. An output feedback controller using a CSMC controller is proposed, and a sliding surface considering a CIis designed. The controller parameters are designed analytically, taking into account two approaches. The firstapproach does not consider uncertain parameters and the second one treats a stability derivative as a parametricuncertainty. Simulations were performed in order to validate the design procedure of the control technique andto demonstrate the robustness of the UIR. Detailed step by step information about the computing of the controllerparameters was done and an analytical analysis of stability was developed to demonstrate the convergence of thesliding surface, conditional integrator and tracking error dynamics.

Nanoscale aggregation phenomena at the contact line of air-drying pure water droplets on silicon revealed by atomic force microscopy

A. Méndez-Vilas,A.B. Jódar-Reyes,J. Díaz,M.L. González-Martín 한국물리학회 2009 Current Applied Physics Vol.9 No.1

In the present work, silicon wafer surfaces were studied during a pure water dewetting process in ambient conditions by intermittentcontact atomic force microscopy (AFM). With an acid-free surface cleaning, large network structures of tens of microns in extension but only a few nanometers in height were observed, being stable for days. Fractal-like assemblies have been previously reported in a variety of different scenarios, for example, when an aqueous solution of carbon-based species, especially carbon nanotubes, is left to evaporate on a solid substrate, provided that no complete wetting was produced. Chemical mapping of silicon wafer surfaces, while unable to provide a spatial resolution comparable to that of the AFM, clearly showed the initially formed contact line to be enriched in carbon. Therefore, hydrophobic and/or non-soluble (or slightly soluble) substances which are present on every surface exposed to air are expected to be responsible for the observed fractal structures. Reactions of the network structures toward changing environmental conditions were analyzed. When increasing the ambient humidity, the structures grew only slightly, which is indicative of their highly (but not totally) hydrophobic nature. Heating the sample above 100 ℃ for about 10 h led to an almost complete disappearance of these nanostructures. Due to the lateral extension of these stable network heterogeneities, they are expected to affect contact angle measurements in wetting studies, especially at the micro- and nanoscale. When acid-cleaned wafers are used as substrate, deposited water extends as a film over the silicon surface without droplet formation. No fractal structures are then observed. In the present work, silicon wafer surfaces were studied during a pure water dewetting process in ambient conditions by intermittentcontact atomic force microscopy (AFM). With an acid-free surface cleaning, large network structures of tens of microns in extension but only a few nanometers in height were observed, being stable for days. Fractal-like assemblies have been previously reported in a variety of different scenarios, for example, when an aqueous solution of carbon-based species, especially carbon nanotubes, is left to evaporate on a solid substrate, provided that no complete wetting was produced. Chemical mapping of silicon wafer surfaces, while unable to provide a spatial resolution comparable to that of the AFM, clearly showed the initially formed contact line to be enriched in carbon. Therefore, hydrophobic and/or non-soluble (or slightly soluble) substances which are present on every surface exposed to air are expected to be responsible for the observed fractal structures. Reactions of the network structures toward changing environmental conditions were analyzed. When increasing the ambient humidity, the structures grew only slightly, which is indicative of their highly (but not totally) hydrophobic nature. Heating the sample above 100 ℃ for about 10 h led to an almost complete disappearance of these nanostructures. Due to the lateral extension of these stable network heterogeneities, they are expected to affect contact angle measurements in wetting studies, especially at the micro- and nanoscale. When acid-cleaned wafers are used as substrate, deposited water extends as a film over the silicon surface without droplet formation. No fractal structures are then observed.

Zinc doping effects on the microstructural, electrical and optical properties of nanostructured ZnxBi2-xS3 (0≤x≤0.09) thin films grown by ultrasonic spray pyrolysis

Bouachri M.,Oubakalla M.,El-Habib A.,Guerra Carlos Díaz,Shaili H.,Fernández Paloma,Zimou J.,Nouneh K.,Fahoume M. 한국물리학회 2023 Current Applied Physics Vol.54 No.-

Zinc-doped bismuth sulfide (Bi2-xZnxS3) nanocrystalline thin films were deposited on glass substrates by using an ultrasonic spray pyrolysis (USP) technique and their structural, morphological, electrical and optical properties experimentally addressed. X-ray diffraction (XRD) and micro-Raman spectroscopy have confirmed the generation of a single-phase polycrystalline orthorhombic material. The crystallite size and micro-deformation of the films was found to depend on the dopant concentration. The surface appears condensed and dense with a uniform spatial grain distribution, as revealed by scanning electron microscopy (SEM) images. Energy dispersive X-ray spectroscopy (EDS) studies revealed a certain Bi deficiency in both undoped and Zn-doped films. When the nominal Zn doping concentration increases from x = 0 to x = 0.09, the crystallite size decreases from 30 to 21 nm. The optical band gap of the films increased from 1.62 to 1.65 eV with Zn content increasing up to x = 0.06, then reducing to 1.58 eV for the maximum Zn content. Optical measurements showed a high absorption coefficient (α > 104 cm−1) in the visible and near-infrared ranges. The Urbach energy followed a similar behavior as a function of doping concentration. The electrical conductivity as well as the sheet carrier mobility of the Bi2-xZnxS3 films increase sharply by increasing the Zn content up to x = 0.06. For this doping concentration, mobility reaches 1.37 × 105 cm2/Vs while keeping carrier concentration above 1017 cm−3. Our experimental results provide strong evidence that Zn-doping is a suitable method to increase Bi2S3 light-harvesting efficiency in solar cell devices.

A general exergy-based environmental impact index

Sósimo E. Díaz-Méndez,José María Rodríguez-Lelis,Abel Hernández-Guerrero 대한기계학회 2011 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.25 No.8

An ecosystem is a complex system in which biotic and abiotic factors interact and influence each other both directly and indirectly. Each of these factors has to comply with a specific function in the different processes that occur inside the ecosystem, whether transporting or transforming energy or both. When anthropogenic emissions are produced, part of the useful energy of the ecosystem is used to assimilate or absorb those emissions, and the energy spent, loses its function and becomes lost work in accordance with the Gouy-Stodola theorem. Thus, the work that an ecosystem can carry out varies as a function of the lost work produced by anthropogenic sources. The permanency or loss of the ecosystem depends on how many irreversibilities it can support. The second law of thermodynamics through a systematic use of the exergy and lost work is the basis of this paper where a general environmental impact index, based on exergy, is proposed. For the purpose of this work, the ecosystem is divided in subsystems--water, soil, atmosphere, organisms and society--all of them inter-related. The ideal work variation can be obtained from each subsystem within the selected ecosystem, and a global index can be determined by adding the partial lost work of each subsystem. This global index is then used to determine the trend followed by the ecosystem from its pristine, original or environmental line base state. This environmental impact index applicability is presented for a simple combustion example.

Preparation of a Porous Scaffold Based on Polypropylene Grafted with Monomethylitaconate as Potential Bone Graft

A. Neira-Carrillo,M. S. Fernández,J. L. Arias,S. Navarrete G,M. Paz Díaz,M. Yazdani-Pedram 한국고분자학회 2011 Macromolecular Research Vol.19 No.11

Based on polypropylene (PP) grafted with different percentages of maleic anhydride (PP-g-MA) or monomethylitaconate (PP-g-MMI) a new porous scaffold was prepared with porosities in the range of 50-200 μm. The swelling capacity was analyzed, and morphological, mechanical, and elemental analyses of these scaffolds were carried out. In vitro swelling in the simulated body fluid (SBF), chitosan (CHI) of low (70 kDa) and high (350 kDa)molecular weight, and chitosan-hydroxyapatite solutions were assayed at 37 ℃ from 24 h to 4 weeks. The swelling degree (SD) of these scaffolds was in the range of 25%-125%. The highest SD value was found in the low-molecular weight (LMW) chitosan solution. The PP-g-MMI and PP-g-MA with 0.7% and 1% of grafting, respectively, showed the highest SD values in the CHI solution. The in vitro treatment of the scaffold was performed by immersion in LMW chitosan and/or the double ionic diffusion (DID) method. The pore structure of the scaffolds was unaltered after these treatments, as revealed by scanning electron microscopy (SEM). Mechanical properties, that is, fracture resistance and deformation of the porous scaffolds depended on the percentage of grafting. Scaffolds with a smaller pore size showed higher mechanical properties. Energy Dispersive Spectroscopy (EDS) measurements of PP-g-MMI with 0.7% of grafting after in vitro treatment revealed the formation of hydroxyapatite (HA) crystals with different morphologies on the porous scaffold. It was concluded that the porous scaffold based on PP-g-MMI could be used as a potential prototype bone graft.

New metal-free nanolubricants based on carbon-dots with outstanding antiwear performance

C. Chimeno-Trinchet,M.E. Pacheco,A. Fernández-González,M.E. Díaz-García,R. Badía-Laíño 한국공업화학회 2020 Journal of Industrial and Engineering Chemistry Vol.87 No.-

Nanoparticles have already demonstrated a good performance in improving the wear and/or coefficientof friction when used as nanolubricants. Nevertheless, they show two main drawbacks: most of them aremetal-based and, therefore, eco-unfriendly, and they are mostly hydrophilic and, consequently, unstablein organic media, whichfinally drives to aggregation/sedimentation and the loose of the good properties. In this work, we carry out the synthesis of carbon-based nanoparticles for additives in lubricants fromtwo different approaches: either using ionic liquids as carbons source, or using glutathione as carbonsource and decorating the so-obtained carbon dots with the big organic cations of the ionic liquid. Thefinal materials (diameters between 2.2 and 3.5 nm) were characterized by TEM, FTIR, XPS, andluminescent methodologies,finding long-term stability of the suspensions in organic media ( 15 days). Carbon dots obtained directly from the ionic liquids, in particular from methyltrioctylammoniumchloride (MTOACDs) have demonstrated to be the best candidate as additive in different base oils (0.1%,w/v) and lubrication regimes, reducing the coefficient of friction about 30% and wear scar in more than60% in the most extreme of the tested conditions (120 N). Additionally, nanolubricants are metal-free andtherefore, more eco-friendly than classic additives.

Dye-Perfused Human Placenta for Simulation in a Microsurgery Laboratory for Plastic Surgeons

Zambrano-Jerez Laura C.,Díaz-Santamaría Karen D.,Rodríguez-Santos María A.,Alarcón-Ariza Diego F.,Meléndez-Flórez Genny L.,Ramírez-Blanco Mónica A. 대한성형외과학회 2023 Archives of Plastic Surgery Vol.50 No.6

In recent decades, a number of simulation models for microsurgical training have been published. The human placenta has received extensive validation in microneurosurgery and is a useful instrument to facilitate learning in microvascular repair techniques as an alternative to using live animals. This study uses a straightforward, step-by-step procedure for instructing the creation of simulators with dynamic flow to characterize the placental vascular tree and assess its relevance for plastic surgery departments. Measurements of the placental vasculature and morphological characterization of 18 placentas were made. After the model was used in a basic microsurgery training laboratory session, a survey was given to nine plastic surgery residents, two microsurgeons, and one hand surgeon. In all divisions, venous diameters were larger than arterial diameters, with minimum diameters of 0.8 and 0.6 mm, respectively. The majority of the participants considered that the model faithfully reproduces a real microsurgical scenario; the consistency of the vessels and their dissection are similar in in vivo tissue. Furthermore, all the participants considered that this model could improve their surgical technique and would propose it for microsurgical training. As some of the model's disadvantages, an abundantly thick adventitia, a thin tunica media, and higher adherence to the underlying tissue were identified. The color-perfused placenta is an excellent tool for microsurgical training in plastic surgery. It can faithfully reproduce a microsurgical scenario, offering an abundance of vasculature with varying sizes similar to tissue in vivo, enhancing technical proficiency, and lowering patient error.

Crystal structure and second harmonic generation in Bi₂TeO₅: An X-N study from synchrotron and neutron diffraction data

Ló,pez, C.A.,Bâ,ati, E.,Ferná,ndez-Dí,az, M.T.,Saouma, F.O.,Jang, J.I.,Alonso, J.A. Academic Press 2019 Journal of solid state chemistry Vol.276 No.-

<P><B>Abstract</B></P> <P>Bi<SUB>2</SUB>TeO<SUB>5</SUB> has been obtained in polycrystalline form via solid state reaction and structurally characterized from both synchrotron and neutron powder diffraction data, enabling the precise determination of the atomic positions. The crystal structure is defined in the acentric <I>Amb</I>2 space group, containing three crystallographically unequivalent Bi atoms. The position of the stereochemically active electron lone pairs of both Bi<SUP>3+</SUP> and Te<SUP>4+</SUP> ions is inferred to be opposite to the strongly covalent BiO and TeO chemical bonds; the global electron polarization arises from the non-compensated Bi<SUP>3+</SUP> lone electron pairs. Additionally, from difference Fourier maps between synchrotron and neutron diffraction data (X-N technique) it was possible to observe experimental evidence of the lone electron pair for Bi<SUP>3+</SUP>. Nonlinear optical measurements display highly active second harmonic generation response, comparable to that of reference AgGaSe<SUB>2</SUB>.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The crystal structure is defined in the non-centrosymmetric <I>Amb</I>2 space group. </LI> <LI> Fourier maps between synchrotron and neutron diffraction data (X-N technique). </LI> <LI> Experimental evidence of Bi<SUP>3+</SUP>lone electron pair from X-N study. </LI> <LI> Nonlinear optical measurements display highly active SHG response. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>