Room temperature synthesis of high purity 2D ZnO nanoneedles

E. J. A. Campo,A. C. Caballero,M. Villegas,J. E. Rodríguez-Páez,M. Peiteado 한양대학교 세라믹연구소 2009 Journal of Ceramic Processing Research Vol.10 No.4

Current technological requirements demand ZnO particles of controlled morphology, distribution and size. The achievement of such specific conditions cannot be guaranteed with conventional synthesis routes and new techniques should be applied to attain this goal. In the present contribution we prove that the controlled precipitation method (CPM) could be successfully applied to obtain high purity 2D zinc oxide nanoparticles with needle-type morphology. By using the appropriate precursors and washing medium, the synthesis could be achieved at room temperature without any additional thermal treatment required. Current technological requirements demand ZnO particles of controlled morphology, distribution and size. The achievement of such specific conditions cannot be guaranteed with conventional synthesis routes and new techniques should be applied to attain this goal. In the present contribution we prove that the controlled precipitation method (CPM) could be successfully applied to obtain high purity 2D zinc oxide nanoparticles with needle-type morphology. By using the appropriate precursors and washing medium, the synthesis could be achieved at room temperature without any additional thermal treatment required.

A nonlinear controller based on saturation functions with variable parameters to stabilize an AUV

Campos, E.,Monroy, J.,Abundis, H.,Chemori, A.,Creuze, V.,Torres, J. The Society of Naval Architects of Korea 2019 International Journal of Naval Architecture and Oc Vol.11 No.1

This paper deals with a nonlinear controller based on saturation functions with variable parameters for set-point regulation and trajectory tracking control of an Autonomous Underwater Vehicle (AUV). In many cases, saturation functions with constant parameters are used to limit the input signals generated by a classical PD (Proportional-Derivative) controller to avoid damaging the actuators; however this abrupt bounded harms the performance of the controller. We, therefore, propose to replace the conventional saturation function, with constant parameters, by a saturation function with variable parameters to limit the signals of a PD controller, which is the base of the nonlinear PD with gravitational/buoyancy compensation and the nonlinear PD + controllers that we propose in this paper. Consequently, the mathematical model is obtained, considering the featuring operation of the underwater vehicle LIRMIA 2, to do the stability analysis of the closed-loop system with the proposed nonlinear controllers using the Lyapunov arguments. The experimental results show the performance of an AUV (LIRMIA 2) for the depth control problems in the case of set-point regulation and trajectory tracking control.

A nonlinear controller based on saturation functions with variable parameters to stabilize an AUV

E. Campos,J. Monroy,H. Abundis,A. Chemori,V. Creuze,J. Torres 대한조선학회 2019 International Journal of Naval Architecture and Oc Vol.11 No.1

This paper deals with a nonlinear controller based on saturation functions with variable parameters for set-point regulation and trajectory tracking control of an Autonomous Underwater Vehicle (AUV). In many cases, saturation functions with constant parameters are used to limit the input signals generated by a classical PD (Proportional-Derivative) controller to avoid damaging the actuators; however this abrupt bounded harms the performance of the controller. We, therefore, propose to replace the conventional saturation function, with constant parameters, by a saturation function with variable parameters to limit the signals of a PD controller, which is the base of the nonlinear PD with gravitational/ buoyancy compensation and the nonlinear PD þ controllers that we propose in this paper. Consequently, the mathematical model is obtained, considering the featuring operation of the underwater vehicle LIRMIA 2, to do the stability analysis of the closed-loop system with the proposed nonlinear controllers using the Lyapunov arguments. The experimental results show the performance of an AUV (LIRMIA 2) for the depth control problems in the case of set-point regulation and trajectory tracking control.

Health Monitoring System (HMS) for structural assessment

e Matos, Jose Campos,Garcia, Oscar,Henriques, Antonio Abel,Casas, Joan Ramon,Vehi, Josep Techno-Press 2009 Smart Structures and Systems, An International Jou Vol.5 No.3

As in any engineering application, the problem of structural assessment should face the different uncertainties present in real world. The main source of uncertainty in Health Monitoring System (HMS) applications are those related to the sensor accuracy, the theoretical models and the variability in structural parameters and applied loads. In present work, two methodologies have been developed to deal with these uncertainties in order to adopt reliable decisions related to the presence of damage. A simple example, a steel beam analysis, is considered in order to establish a liable comparison between them. Also, such methodologies are used with a developed structural assessment algorithm that consists in a direct and consistent comparison between sensor data and numerical model results, both affected by uncertainty. Such algorithm is applied to a simple concrete laboratory beam, tested till rupture, to show it feasibility and operational process. From these applications several conclusions are derived with a high value, regarding the final objective of the work, which is the implementation of this algorithm within a HMS, developed and applied into a prototype structure.

Health Monitoring System (HMS) for structural assessment

José Campos e Matos,Oscar Garcia,António Abel Henriques,Josep Vehí,Joan Ramon Casas 국제구조공학회 2009 Smart Structures and Systems, An International Jou Vol.5 No.3

As in any engineering application, the problem of structural assessment should face the different uncertainties present in real world. The main source of uncertainty in Health Monitoring System (HMS) applications are those related to the sensor accuracy, the theoretical models and the variability in structural parameters and applied loads. In present work, two methodologies have been developed to deal with these uncertainties in order to adopt reliable decisions related to the presence of damage. A simple example, a steel beam analysis, is considered in order to establish a liable comparison between them. Also, such methodologies are used with a developed structural assessment algorithm that consists in a direct and consistent comparison between sensor data and numerical model results, both affected by uncertainty. Such algorithm is applied to a simple concrete laboratory beam, tested till rupture, to show it feasibility and operational process. From these applications several conclusions are derived with a high value, regarding the final objective of the work, which is the implementation of this algorithm within a HMS, developed and applied into a prototype structure.

Effect of mechanical alloying on the microstructural evolution of a ferritic ODS steel with (Y-Ti-Al-Zr) addition processed by Spark Plasma Sintering (SPS)

Macia, E.,Garcia-Junceda, A.,Serrano, M.,Hong, S.J.,Campos, M. Korean Nuclear Society 2021 Nuclear Engineering and Technology Vol.53 No.8

The high-energy milling is one of the most extended techniques to produce Oxide dispersion strengthened (ODS) powder steels for nuclear applications. The consequences of the high energy mill process on the final powders can be measured by means of deformation level, size, morphology and alloying degree. In this work, an ODS ferritic steel, Fe-14Cr-5Al-3W-0.4Ti-0.25Y₂O₃-0.6Zr, was fabricated using two different mechanical alloying (MA) conditions (M_std and M_act) and subsequently consolidated by Spark Plasma Sintering (SPS). Milling conditions were set to evidence the effectivity of milling by changing the revolutions per minute (rpm) and dwell milling time. Differences on the particle size distribution as well as on the stored plastic deformation were observed, determining the consolidation ability of the material and the achieved microstructure. Since recrystallization depends on the plastic deformation degree, the composition of each particle and the promoted oxide dispersion, a dual grain size distribution was attained after SPS consolidation. M_act showed the highest areas of ultrafine regions when the material is consolidated at 1100 ℃. Microhardness and small punch tests were used to evaluate the material under room temperature and up to 500 ℃. The produced materials have attained remarkable mechanical properties under high temperature conditions.

Static and Fatigue Test on Real Steel Bridge Components Deteriorated by Corrosion

Martin Macho,Pavel Ryjáček,José Campos e Matos 한국강구조학회 2019 International Journal of Steel Structures Vol.19 No.1

The combined eff ects of corrosion and fatigue have become a topic issue in recent times. Decades-old steel bridges that are still in service need to be reassessed. However, there is no relevant background information that can be used in assessment of this phenomenon. There are no recommendations for civil engineers how to take into account the corrosion weakening for the assessment of bearing capacity and fatigue strength of riveted members. For this reason the aim of the research presented in this paper was preparation and execution of laboratory tests on real bridge components that were deteriorated by corrosion. Two types of tests were performed to fi nd out how corrosion weakening aff ects the statics and the fatigue strength of members. The evaluation of the tests indicates that the service life of members may be signifi cantly reduced due to fatigue. In addition, the bearing capacity is reduced while, in particular, the local stress rises. All of this is strongly dependent on the level of corrosion and the surface irregularities. Our paper ends with recommendations on how the loss of material due to corrosion could be taken into account for an assessment of the load capacity and the residual lifetime of members.

Corrosion resistance assessment of nickel-titanium endodontic files with and without heat treatment

Costa Tatiana Dias,Silva Elison da Fonseca e,Caetano Paula Liparini,Campos Marcio José da Silva,Resende Leandro Marques,Machado André Guimarães,do Carmo Antônio Márcio Resende 대한치과보존학회 2021 Restorative Dentistry & Endodontics Vol.46 No.1

Objectives: The aim of this study was to evaluate the corrosion resistance of heat-treated (Reciproc and WaveOne) and non-heat-treated (ProTaper and Mtwo) superelastic nickel-titanium endodontic files when immersed in a 5.25% sodium hypochlorite solution. Materials and Methods: Anodic polarization curves were obtained with potential sweeps that began at the open circuit potential or corrosion potential (Ecorr). The pitting potential (Epit) was identified on the anodic polarization curve as the potential at which a sudden increase in current was observed. The micromorphology of the 28 tested files was analyzed before and after the electrochemical assay using scanning electron microscope (SEM). The data were analyzed using 1-way analysis of variance with the post hoc Bonferroni test (for Ecorr) and the Student t-test for independent samples (for Epit). Results: The mean Ecorr values were 0.506 V for ProTaper, 0.348 V for Mtwo, 0.542 V for Reciproc, and 0.321 V for WaveOne files. Only WaveOne and Protaper files exhibited pitting corrosion, with Epit values of 0.879 V and 0.904 V, respectively. On the SEM images of the ProTaper and WaveOne files, cavities suggestive of pitting corrosion were detected. Conclusions: Signs of corrosion were observed in both heat-treated and non-heat-treated files. Of the evaluated files, WaveOne (a heat-treated file) and ProTaper (a non-heat-treated file) exhibited the lowest corrosion resistance.

High-performance circular sawing of AISI 1045 steel with cermet and tungsten carbide inserts

A. M. Abrão,M. C. Moreira,P. E. Faria,J. C. Campos Rubio 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.10

This work investigated the influence of cutting speed and feed rate on cutting forces, surface roughness, and slot width circular sawingof AISI 1045 steel. The effects of tool material (cermet and tungsten carbide) and geometry (chip breaker flute and pre-cutting/postcuttingteeth) were also investigated. Thrust and radial forces generally tended to decrease as the cutting speed increased and tended toincrease with the feed rate. The lowest values of thrust and radial forces were obtained using a tungsten carbide saw ground with precuttingand post-cutting teeth. With regard to the quality of the machined wall, the lowest surface roughness was obtained by applying thehighest cutting speed and lowest feed rate and employing a cermet brazed saw. Under this condition, roughness values comparable toface turning and parting off operations were obtained. The cermet brazed saw was responsible for producing the narrowest slot widths.

Nutrient requirements and evaluation of equations to predict chemical body composition of dairy crossbred steers

Silva Flavia Adriane de Sales,Valadares Filho Sebastião de Campos,Costa e Silva Luiz Fernando,Fernandes Jaqueline Gonçalves,Lage Bruno Corrêa,Chizzotti Mario Luiz,Felix Tara Louise 아세아·태평양축산학회 2021 Animal Bioscience Vol.34 No.4

Objective Objectives were to estimate energy and protein requirements of dairy crossbred steers, as well as to evaluate equations previously described in the literature (HH46 and CS16) to predict the carcass and empty body chemical composition of crossbred dairy cattle. Methods Thirty-three Holstein×Zebu steers, aged 19±1 months old, with an initial shrunk body weight (BW) of 324±7.7 kg, were randomly divided into three groups: reference group (n = 5), maintenance level (1.17% BW; n = 4), and the remaining 24 steers were randomly allocated to 1 of 4 treatments. Treatments were: intake restricted to 85% of ad libitum feed intake for either 0, 28, 42, or 84 d of an 84-d finishing period. Results The net energy and the metabolizable protein requirements for maintenance were 0.083 Mcal/EBW0.75/d and 4.40 g/EBW0.75, respectively. The net energy (NEG) and protein (NPG) requirements for growth can be estimated with the following equations: NEG (Mcal/kg EBG) = 0.2973(±0.1212) ×EBW0.4336(±0.1002) and NPG (g/d) = 183.6(±22.5333)×EBG−2.0693(±4.7254)×RE, where EBW, empty BW; EBG, empty body gain; and RE, retained energy. Crude protein (CP) and ether extract (EE) chemical contents in carcass, and all the chemical components in the empty body were precisely and accurately estimated by CS16 equations. However, water content in carcass was better predicted by HH46 equation. Conclusion The equations proposed in this study can be used for estimating the energy and protein requirements of crossbred dairy steers. The CS16 equations were the best estimator for CP and EE chemical contents in carcass, and all chemical components in the empty body of crossbred dairy steers, whereas water in carcass was better estimated using the HH46 equations. Objective: Objectives were to estimate energy and protein requirements of dairy crossbred steers, as well as to evaluate equations previously described in the literature (HH46 and CS16) to predict the carcass and empty body chemical composition of crossbred dairy cattle.Methods: Thirty-three Holstein × Zebu steers, aged 19 ± 1 months old, with an initial shrunk body weight of 324 ± 7.7 kg, were randomly divided into three groups: reference group (n = 5), maintenance level (1.17% BW; n = 4), and the remaining 24 steers were randomly allocated to 1 of 4 treatments. Treatments were: intake restricted to 85% of <i>ad libitum</i> feed intake for either 0, 28, 42, or 84 d of an 84-d finishing period.Results: The net energy and the metabolizable protein requirements for maintenance were 0.083 Mcal/EBW^0.75/d and 4.40 g/EBW^0.75, respectively. The net energy (NE_G) and protein (NP_G) requirements for growth can be estimated with the following equations: NE_G (Mcal/kg EBG) = 0.2973_{(± 0.1212)} × <i>EBW</i>^{0.4336(± 0.1002)} and NP_G (g/d) = 183.6_{(± 22.5333)} × EBG – 2.0693_{(± 4.7254)} × RE, where EBW = empty body weight, EBG = empty body gain, and RE = retained energy. Crude protein (CP) and ether extract (EE) chemical contents in carcass, and all the chemical components in the empty body were precisely and accurately estimated by CS16 equations. However, water content in carcass was better predicted by HH46 equation.Conclusion: The equations proposed in this study can be used for estimating the energy and protein requirements of crossbred dairy steers. The CS16 equations were the best estimator for CP and EE chemical contents in carcass, and all chemical components in the empty body of crossbred dairy steers, whereas water in carcass was better estimated using the HH46 equations.