Search

Here, we report the first successful exfoliation of two-dimensional Ti3C2Tx MXene through selective etching of silicon from titanium silicon carbide (Ti3SiC2) MAX. The successful etching and exfoliation of MXene are confirmed through the shifting of all (00l) peaks to lower angles along with the increase in the c-lattice parameter as determined by X-ray diffraction to detail the material structure. The c-lattice parameter of multilayered MXene was found to be 19.34 A which was increased to 26.22 A after the delamination process indicating the successful intercalation of TMA+ ions within the MXene Sheets. The scanning electron microscopy (SEM) images show the formation of a 2D layered structure. The magnetic measurement of the etched MXene sample was measured using a superconducting quantum interference device (SQUID: Quantum Design). The magnetization versus magnetic (M − H) curves indicate the ferromagnetic-dominant hysteresis loops at low-temperature as well as at room temperature along with the presence of a small silicon carbide (SiC) diamagnetic phase. The presence of the SiC phase is confirmed through XRD and Raman spectra that show the vibrational modes of SiC within the 2D MXene structure. The present work shows the co-existence of ferromagnetic and diamagnetic phases, making it suitable for 2D material for future spintronics devices.

Two-dimensional (2D) semiconductors, such as transition-metal dichalcogenides (TMDs), have attracted immense interest due to their excellent electronic and optical properties. The combination of single and multilayered 2D TMDs coupled with either Si or II-VI semiconductors can result in robust and reliable photodetectors. In this paper, we report the deposition process of MoSe2-layered films using pulsed laser deposition (PLD) over areas of 20 cm2 with a tunable band gap. Raman and X-ray diffraction indicates crystalline and highly oriented layered MoSe2. X-ray photoelectron spectroscopy shows Mo and Se present in the first few layers of the film. Rutherford backscattering demonstrates the effect of O and C on the surface and film/substrate interface of the deposited films. Ultraviolet-visible spectroscopy, Kelvin probe, photoelectron spectroscopy, and electrical measurements are used to investigate the band diagram and electrical property dependence as a function of MoSe2 layers/thickness. As the MoSe2 thickness increases from 3.5 to 11.4 nm, the band gap decreases from 1.98 to 1.75 eV, the work function increases from 4.52 to 4.72 eV, the ionization energy increases from 5.71 to 5.77 eV, the sheet resistance decreases from 541 to 56.0 kΩ, the contact resistance decreases from 187 to 54.6 Ω·cm2, and the transfer length increases from 2.27 to 61.9 nm. Transmission electron microscopy (TEM) cross-sectional images demonstrate the layered structure of the MoSe2 with an average interlayer spacing of 0.68 nm. The fabricated MoSe2-Si photodiodes demonstrate a current on/off ratio of ∼2 × 104 orders of magnification and photocurrent generation with a 22.5 ns rise time and a 190.8 ns decay time, respectively.

Resumen Context: Due to the low emissions of CO2 generated by electric systems, those solutions have been receiving attention from industries and academia. However, the electrical storage systems required for a large amount of applications must have high energy and power densities. Method: To meet those requirements, this paper proposes an active hybrid energy storage system formed by a battery, i.e. a device with a high energy density, and a capacitor, i.e. a device with a high power capability. The proposed solution also protects the battery by limiting the current derivative. Results: Two sliding-mode controllers are designed to regulate both the battery current and the load voltage. The design process guarantees global stability and safe battery operation. Conclusions: The controller avoids battery degradation caused by the high-frequency current components since the capacitor assumes those components as demanded by the load profile. Resumen Contexto: Gracias a las bajas emisiones de CO2 de los sistemas eléctricos, estos han ganado mucha atención por parte de la industria y la academia. Sin embargo, los sistemas de almacenamiento de energía requeridos en un sin número de aplicaciones deben garantizar ser de alta densidad de energía y potencia. Método: Para satisfacer estos requerimientos, este trabajo propone un controlador no-linear para asegurar la estabilidad de un sistema de almacenamiento de energía híbrido activo, el cual es formado por una batería como dispositivo de alta densidad de energía y un capacitor como el dispositivo de alta densidad de potencia. Asimismo, la solución propuesta protege la batería a través de la limitación de la derivada de la corriente. Resultados: Se diseñan dos controladores por modos deslizantes, uno para la corriente de la batería y otro para regular el voltaje en la carga. El proceso de diseño garantiza la estabilidad global del sistema y una operación segura de la batería. Conclusiones: El controlador de corriente evita la degradación de la batería causada por los componentes de alta frecuencia de la corriente demandados por la carga. Estos componentes de alta frecuencia son asumidos por el capacitor.

Molybdenum trioxide (MoO

Solid-state electrolytes have attracted significant attention in rechargeable battery and solid-state device research due to the added benefits over the liquid electrolytic counterpart owing to their solid nature. Here, we demonstrated centimeter-scale growth of MoS 2 thin film, a promising two-dimensional (2D) material for transistor and energy storage, on Li-ion solid electrolyte substrate by sulfurization of Molybdenum thin film. The sulfurized film was characterized using a combination of spectroscopic and microscopic analyses, including optical microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and Raman spectroscopy. The film was further characterized by electrical probing to measure the film quality and underlying transport mechanism.

Regulation of DC‐bus voltages is important for the stable operation of different applications, like microgrids and electric vehicles, and it is usually performed by charging/discharging (C/D) batteries. Such C/D system is formed by a power converter and a control system, and it is aimed at guaranteeing the system stability and extending the battery life. To extend the battery life, it is important to reduce the battery current ripples, which is usually performed with interleaved converters and nonlinear controllers; however, most of those controllers do not provide the design procedure nor guarantee the system stability. This paper proposes a nonlinear control strategy to regulate the voltage in a DC‐bus by C/D a battery through a two‐branch interleaved Boost converter. The proposed control strategy is formed by two sliding mode controllers (SMCs), where the first one regulates the DC‐bus voltage by acting on the first converter branch and the second SMC controls the current in the second branch. The reference of the second SMC is generated from the delayed current of the first branch, in order to coordinate the controllers and to reduce the ripples in the battery current. The paper includes a procedure to design the two SMCs as well as simulation and experimental results to validate the proposed solution and to illustrate its performance. The results prove the system stability and its dynamic performance according to the design.

The development of silicon semiconductor technology has produced breakthroughs in electronics—from the microprocessor in the late 1960s to early 1970s, to automation, computers and smartphones—by downscaling the physical size of devices and wires to the nanometre regime. Now, graphene and related two-dimensional (2D) materials offer prospects of unprecedented advances in device performance at the atomic limit, and a synergistic combination of 2D materials with silicon chips promises a heterogeneous platform to deliver massively enhanced potential based on silicon technology. Integration is achieved via three-dimensional monolithic construction of multifunctional high-rise 2D silicon chips, enabling enhanced performance by exploiting the vertical direction and the functional diversification of the silicon platform for applications in opto-electronics and sensing. Here we review the opportunities, progress and challenges of integrating atomically thin materials with silicon-based nanosystems, and also consider the prospects for computational and non-computational applications. Progress in integrating atomically thin two-dimensional materials with silicon-based technology is reviewed, together with the associated opportunities and challenges, and a roadmap for future applications is presented.

Influenza A viruses are responsible for seasonal epidemics, and pandemics can arise from the transmission of novel zoonotic influenza A viruses to humans1,2. Influenza A viruses contain a segmented negative-sense RNA genome, which is transcribed and replicated by the viral-RNA-dependent RNA polymerase (FluPolA) composed of PB1, PB2 and PA subunits3,4,5. Although the high-resolution crystal structure of FluPolA of bat influenza A virus has previously been reported6, there are no complete structures available for human and avian FluPolA. Furthermore, the molecular mechanisms of genomic viral RNA (vRNA) replication—which proceeds through a complementary RNA (cRNA) replicative intermediate, and requires oligomerization of the polymerase7,8,9,10—remain largely unknown. Here, using crystallography and cryo-electron microscopy, we determine the structures of FluPolA from human influenza A/NT/60/1968 (H3N2) and avian influenza A/duck/Fujian/01/2002 (H5N1) viruses at a resolution of 3.0–4.3 Å, in the presence or absence of a cRNA or vRNA template. In solution, FluPolA forms dimers of heterotrimers through the C-terminal domain of the PA subunit, the thumb subdomain of PB1 and the N1 subdomain of PB2. The cryo-electron microscopy structure of monomeric FluPolA bound to the cRNA template reveals a binding site for the 3′ cRNA at the dimer interface. We use a combination of cell-based and in vitro assays to show that the interface of the FluPolA dimer is required for vRNA synthesis during replication of the viral genome. We also show that a nanobody (a single-domain antibody) that interferes with FluPolA dimerization inhibits the synthesis of vRNA and, consequently, inhibits virus replication in infected cells. Our study provides high-resolution structures of medically relevant FluPolA, as well as insights into the replication mechanisms of the viral RNA genome. In addition, our work identifies sites in FluPolA that could be targeted in the development of antiviral drugs.

In this work, 2D Nb2C MXene, synthesized from the wet-chemical etching route, is used as direct electrode material for electrochemical hydrazine sensing. Also, the Erbium (Er)adsorbed Nb2C MXene was prepared using the hydrothermal process in a weight-percentage ratio of 2.5%, 5%, 7.5% and 10%. The X-ray diffraction of Nb2C and Er-doped Nb2C samples confirmed the existence of 2D MXene structure with c-lattice parameter increase from 13.83 A to 22.7 A and successful adsorption of Er into MXene, respectively. The scanning electron microscopy (SEM) shows the layered structure morphology of all the samples with clear sheet separation. The sample with the highest surface area, determined by Brunauer–Emmett–Teller (BET) technique, was used for hydrazine sensing using cyclic voltammetry and linear sweep voltammetry techniques. The sensitivity for MXene and Er-doped sample was observed to be 169µA m−1 M−1 cm−2 and 276µA m−1 M−1 cm−2, respectively which shows that the Er-doped MXene is much more sensitive than the unmodified one. Our results provide hydrazine sensing ability for 2D Nb2C MXene as well as Er-doped Nb2C which will help explore their potential for future sensor applications.

Resumen Este trabajo presenta la metodología de diseño de un control digital para reducir el rizado en la corriente que se inyecta a la batería por medio de los convertidores que procesan la energía de carga y descarga, el cual es uno de los parámetros indicados en la literatura que disminuyen el tiempo de vida de las baterías. Este trabajo tiene como alcance mostrar el procedimiento de diseño e implementación de la estrategia propuesta sobre un convertidor entrelazado. La metodología implementada se presenta por medio de cuatro etapas (i) modelado del sistema batería-convertidor-carga, (ii) diseño de control digital basado en el modelo, (iii) diseño de la plataforma práctica donde se presenta la etapa de instrumentación e implementación utilizando un dispositivo embebido y (iv) la validación práctica del funcionamiento de la estrategia presentada y la disminución del rizado inyectado en la batería. Por medio de la metodología presentada se logra evidenciar el correcto desempeño del control digital cumpliendo los parámetros de diseño para diferentes modos de operación de carga de la batería y reduciendo el rizado de corriente en la batería entre un 50 % a 65 %. Esta reducción protege la vida útil de la batería y de las fuentes o cargas conectadas al sistema. Adicionalmente, permite que los algoritmos de estimación de estado de carga y estado de salud incrementen su precisión, lo que conlleva a una mejora en los protocolos de mantenimiento y planificación de reemplazo de los elementos. Abstract According to the literature, battery ripple current is one of the phenomena that most significantly affect the state of health of batteries. Therefore, this paper presents a methodology to design a digital control in order to reduce such ripple current, which is injected by means of converters that process the charge and discharge energy. The strategy was designed for and implemented in an interlaced converter. The implemented methodology is presented in four stages: (i) modelling the battery-converter-charge system; (ii) designing the digital control based on the model; (iii) designing the practical implementation, where the instrumentation and implementation stage is presented using an embedded device; and (iv) practical validation of the operation of the strategy and the reduction of battery ripple current. The methodology presented here produced a correct performance of the digital control, fulfilling the design parameters of different operation modes and reducing the ripple current in the battery between 50 and 65%. This reduction protects the battery’s useful life and the sources or loads connected to the system. Additionally, it allows the state-of-charge and health estimation algorithms to increase their accuracy, which leads to an improvement in maintenance protocols and the planning of element replacement.

Two-dimensional materials such as graphene and MoS2 have been the main focus of intense research efforts over the past few years. The most common method of exfoliating these materials, although efficient for lab-scale experiments, is not acceptable for large area and practical applications. Here, we report the deposition of MoS2 layered films on amorphous (SiO2) and crystalline substrates (sapphire) using a pulsed laser deposition (PLD) method. Increased substrate temperature (∼700 °C) and laser energy density (>530 mJ /cm2) promotes crystalline MoS2 films < 20 nm, as demonstrated by fast Fourier transform (FFT) and transmission electron microscopy (TEM). The method reported here opens the possibility for large area layered MoS2 films by using a laser ablation processes. (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Processing electrical energy is one of the most important research fields in our society. So far, tremendous efforts have been made to improve the efficiency of each step in electrical systems: generation systems have been enhanced by introducing renewable energy sources and new control systems for conventional generators, losses have been reduced, the power quality of distribution and transmission systems has been increased, the life-time and state-of-health of energy storage devices have been extended, and sections of the power grid have been isolated for intelligent energy management.

Negative-sense RNA viruses, such as influenza, encode large, multidomain RNA-dependent RNA polymerases that can both transcribe and replicate the viral RNA genome1. In influenza virus, the polymerase (FluPol) is composed of three polypeptides: PB1, PB2 and PA/P3. PB1 houses the polymerase active site, whereas PB2 and PA/P3 contain, respectively, cap-binding and endonuclease domains required for transcription initiation by cap-snatching2. Replication occurs through de novo initiation and involves a complementary RNA intermediate. Currently available structures of the influenza A and B virus polymerases include promoter RNA (the 5′ and 3′ termini of viral genome segments), showing FluPol in transcription pre-initiation states3,4. Here we report the structure of apo-FluPol from an influenza C virus, solved by X-ray crystallography to 3.9 Å, revealing a new ‘closed’ conformation. The apo-FluPol forms a compact particle with PB1 at its centre, capped on one face by PB2 and clamped between the two globular domains of P3. Notably, this structure is radically different from those of promoter-bound FluPols3,4. The endonuclease domain of P3 and the domains within the carboxy-terminal two-thirds of PB2 are completely rearranged. The cap-binding site is occluded by PB2, resulting in a conformation that is incompatible with transcription initiation. Thus, our structure captures FluPol in a closed, transcription pre-activation state. This reveals the conformation of newly made apo-FluPol in an infected cell, but may also apply to FluPol in the context of a non-transcribing ribonucleoprotein complex. Comparison of the apo-FluPol structure with those of promoter-bound FluPols allows us to propose a mechanism for FluPol activation. Our study demonstrates the remarkable flexibility of influenza virus RNA polymerase, and aids our understanding of the mechanisms controlling transcription and genome replication.

We report a simple and selective solution method to prepare Molybdenum Disulfide (MoS2) thin films for functional thin film transistors (TFTs). The selective area solution-processed MoS2 grows on top and around the gold (Au) source and drain electrodes and in the channel area of the TFT. MoS2 thicknesses in the channel area are in the order of 11 nm. A mechanism for the selective growth is also proposed. The Au electrodes act not only as contact, but also as a catalytic surface for the hydrazine hydrate used in the reaction, which induces the selective growth of MoS2 on the Au surface and into the channel region. This one step process demonstrates functional TFTs with a carrier mobility of ∼0.4 cm2 V−1 s−1.

This paper deals with the optimization of maximum power point tracking when a photovoltaic panel is modelled as two diodes. The adopted control is implemented using a sliding mode control (SMC) and the optimization is implemented using an improved Pattern Search Method. Thus, the problem of maximum power point tracking is reduced to an optimization problem whose solution is implemented by Pattern Search Techniques, inheriting their convergence properties. Simulation examples show the effectiveness of the proposed technique in practice, being able to deal with different radiations. In addition, improved pattern search method (IPSM) is compared with other techniques such as perturb & observe and Particle Swarm optimization, after which IPSM presents lower energy losses in comparison with the other two algorithms, with the advantage of ensuring the location of the optimal power point in all cases.

El diseño de convertidores conmutados en gran parte de la literatura científica está realizado desde el modelo promediado, debido a la facilidad de obtener las funciones de transferencia lineales. Asimismo, la conmutación en los convertidores de potencia causa un rizado en las variables de estado que no es considerado en el modelo promediado. El componente de frecuencia de una de las variables de estado está compuesto por un espectro de potencia con un único pico de nivel DC (valor promedio), un único pico a la frecuencia de conmutación (componente de rizado) y en un número finito de picos en cada sub-armónico (inestabilidades). El método de Filippov es utilizado para la predicción de inestabilidades debidas a las dinámicas rápidas, este método predice el rango de los parámetros que evitan la primera bifurcación en las dinámicas rápidas. En el presente artículo se presenta una predicción de un espacio de parámetros estables para el controlador PI (Kp , Ti), estimados por el método de Filippov para un convertidor buck de dos fases con regulación de voltaje. Finalmente, los resultados presentados son validados mediante simulaciones de Matlab y Psim. In many papers, the averaged model of power switching converters is used to design the control system due to its simple manipulation, which can be approximated by linear transfer functions. Therefore, the power converter commutation causes a state variable ripple that is not considered on the averaged model. The component frequency of the state variables is composed by a power spectrum with a unique peak at the DC level (average variable), a unique peak at the switching frequency (ripple component) and a finite number of peaks in each sub-harmonic (instabilities). The Filippov method is used for instability predictions due to fast dynamics, this method predicts the parameters range that avoids the first bifurcation of the fast dynamics. In this paper a stable space of parameters (Kp , Ti) for a PI controller is presented, it estimated with the Filippov method, for a buck converter with voltage regulation. Finally, the presented results are validated using both Matlab and Psim simulations.

In this study, we describe a new coordination mechanism for non-atomic congestion games that leads to a (selfish) social cost which is arbitrarily close to the non-selfish optimal. This mechanism incurs no additional cost, in contrast to tolls that typically differ from the social cost as expressed in terms of delays. © 2017 The Korean Institute of Communications Information Sciences

The complete mitochondrial genome of a freshwater planorbid snail, Planorbella duryi (Mollusca, Gastropoda) was recovered from de novo assembly of genomic sequences generated with the Illumina NextSeq500 platform. The P. duryi mitogenome (14,217 base pairs) is AT rich (72.69%) and comprises 13 protein-coding genes, two ribosomal subunit genes, and 22 transfer RNAs. The gene order is identical to that of Biomphalaria glabrata and other snail species in the family Planorbidae. This is the first full characterization of a mitochondrial genome of the genus Planorbella.

The implementation of energy policies to reduce CO2 emissions poses specific challenges, especially to public authorities, who should define specific objectives, and evaluate the adequacy and impact of energy actions proposed. Nevertheless, an appropriate analysis is highly time-consuming due to the lack of tools. In this process, the first step is to establish the baseline energy status of the area of study. Only with this knowledge, in particular of the residential sector (main CO2 emissions contributor in cities), is it possible to plan for a low carbon economy. In this context, the ENERGIS tool will support energy planners by mapping energy demand of the residential sector at different scales, as a first step towards CO2 emissions calculation. To do so, a nationally validated Energy Performance Certification (EPC) tool has been automated, its results at building level mapped and aggregated at different scales. By basing the proposed platform on EPC calculation methodologies supported by the Energy Performance Directive of Buildings (EPBD 2010/31/EU), the ENERGIS platform achieves two main goals: it aids in the implementation of energy directives and energy actions by offering an easy to use tool to identify areas in need and, secondly, it promotes the EPBD, by making use of one of its main instruments to measure energy performance: the EPCs.

In this study, an approach to identify and control stable, unstable and integrating systems with unknown delays, framed on the generalized Pattern Search Method is presented. The proposed method inherits the global convergence properties of the generalized Pattern Search Method, allowing us to make a stability analysis of the proposed approach and delay identification capabilities. The proposed approach identifies the delay and guarantees closed-loop stability, which could be a difficult task since in unstable and integrating cases, open-loop experiments are not feasible. Simulation examples show the usefulness of the proposed strategy proving that the scheme is capable of identifying the delay and stabilizing the system even with long delay.

Resumen Las celdas de combustible son alternativas tecnológicas para producir energía renovable, sin embargo, los altos costos hacen a estas una opción poco rentable. Este artículo analiza el impacto de los incentivos del Gobierno de Colombia en la rentabilidad de la generación de energía eléctrica a partir de celdas de combustible. El análisis está basado en los costos totales de la operación de las celdas de combustible en tres escenarios representativos: una residencia, una oficina y un elevador de un edificio. La viabilidad económica de la generación con celdas de combustible en estos tres casos es contrastada con soluciones clásicas como generación a partir de diésel y la red eléctrica convencional. Los resultados permiten identificar que los incentivos del Gobierno de Colombia son muy efectivos para quienes generen a partir de energía renovable, como celdas de combustible, en contraste con otras opciones menos amigables con el medio ambiente, como los generadores diésel. Finalmente, nuevos incentivos son propuestos sobre la base de subsidios ofrecidos por otros países con alta penetración de las celdas de combustible en su mercado eléctrico. Todos los análisis están soportados en simulaciones realizadas con modelos matemáticos parametrizados que consideran las características de los dispositivos comerciales. Abstract Fuel cells are a technological alternative to produce green energy, however, high costs make fuel cell a non-profitable option. This paper analyses the impact of the Colombian government incentives in the profitability of fuel cells. The analysis is based on the total operation cost of the fuel cell in three representative applications: residential, office and building elevator. The economic viability of fuel cell generation in those cases is contrasted with classical solutions like diesel generators and standard grid to provide a reference framework. Such results enable to evaluate the effectiveness of the Colombian government incentives in promoting the use of fuel cells over other less environmental-friendly options such as diesel generators. Finally, new incentives are proposed by subsidies offered by other countries with higher fuel cell penetration into their electric market. All the analyses are supported in simulations performed with a mathematical model parameterized using the characteristics of commercial devices.

A scalable and catalyst-free method to deposit stoichiometric molybdenum disulfide (MoS2) films over large areas is reported, with the maximum area limited by the size of the substrate holder. The method allows deposition of MoS2 layers on a wide range of substrates without any additional surface preparation, including single-crystal (sapphire and quartz), polycrystalline (HfO2), and amorphous (SiO2) substrates. The films are deposited using carefully designed MoS2 targets fabricated with excess sulfur and variable MoS2 and sulfur particle size. Uniform and layered MoS2 films as thin as two monolayers, with an electrical resistivity of 1.54 × 10(4) Ω cm(-1), were achieved. The MoS2 stoichiometry was confirmed by high-resolution Rutherford backscattering spectrometry. With the method reported here, in situ graded MoS2 films ranging from ∼1 to 10 monolayers can be deposited.

In the multi-criteria optimization approach to IMRT planning, a given dose distribution is evaluated by a number of convex objective functions that measure tumor coverage and sparing of the different organs at risk. Within this context optimizing the intensity profiles for any fixed set of beams yields a convex Pareto set in the objective space. However, if the number of beam directions and irradiation angles are included as free parameters in the formulation of the optimization problem, the resulting Pareto set becomes more intricate. In this work, a method is presented that allows for the comparison of two convex Pareto sets emerging from two distinct beam configuration choices. For the two competing beam settings, the non-dominated and the dominated points of the corresponding Pareto sets are identified and the distance between the two sets in the objective space is calculated and subsequently plotted. The obtained information enables the planner to decide if, for a given compromise, the current beam setup is optimal. He may then re-adjust his choice accordingly during navigation. The method is applied to an artificial case and two clinical head neck cases. In all cases no configuration is dominating its competitor over the whole Pareto set. For example, in one of the head neck cases a seven-beam configuration turns out to be superior to a nine-beam configuration if the highest priority is the sparing of the spinal cord. The presented method of comparing Pareto sets is not restricted to comparing different beam angle configurations, but will allow for more comprehensive comparisons of competing treatment techniques (e.g., photons versus protons) than with the classical method of comparing single treatment plans.

Background Malignant melanoma risk factors have been studied in different geographical area populations. However, no study has focused on risk factors which are more frequently associated to the over 60's age group. Methods A case-control study was performed that included 160 patients age ≥ 60 years diagnosed of cutaneous melanoma and 318 controls matched for age and sex. Both groups were assessed, by personal interview and physical examination, for different phenotype characteristics (hair and eye color, phototype), the presence of other cutaneous lesions (solar lentigines, actinic keratoses and nevi), degree and type of solar exposure and personal and family past history of cutaneous or non-cutaneous cancer. Differences were evaluated by contingency tables and univariate and multivariate logistic regression. Results Of 17 factors, those risk factors with a strong effect on the development of melanoma in the elderly were: fair eyes, severe sunburns, years of occupational sun exposure, smoking, > 50 melanocytic nevi and personal history of NMSC and other non-cutaneous neoplasias. Conclusions Tobacco smoking is an independent risk factor for cutaneous melanoma in the elderly. Intense (both acute and chronic) sun exposure and constitutional features, such as tumor susceptibility (NMSC, non-cutaneous neoplasias, and multiple nevi) are also associated with melanoma risk. All these factors should help to better design educational campaigns in older people.

A recent approach to mitigate the adverse effects of photovoltaic (PV) arrays operating under mismatching conditions is the dynamic electrical reconfiguration of the PV panels. This paper introduces a procedure to determine the best configuration of a PV array connected in a series-parallel structure without using complex mathematical models. Such a procedure uses the experimental current vs. voltage curves of the PV panels, which are composed of multiple PV modules, to construct the power vs. voltage curves of all of the possible configurations to identify the optimal one. The main advantage of this method is the low computational effort required to reconstruct the power vs. voltage curves of the array. This characteristic enables one to implement the proposed solution using inexpensive embedded devices, which are widely adopted in industrial applications. The proposed method, and its embedded implementation, were tested using a hardware-in-the-loop simulation of the PV system. Finally, the real-time operation and benefits of the proposed solution are illustrated using a practical example based on commercial devices.

El diseño de convertidores conmutados en gran parte de la literatura científica está realizado desde el modelo promediado, debido a la facilidad de obtener las funciones de transferencia lineales. Asimismo, la conmutación en los convertidores de potencia causa un rizado en las variables de estado que no es considerado en el modelo promediado. El componente de frecuencia de una de las variables de estado está compuesto por un espectro de potencia con un único pico de nivel DC (valor promedio), un único pico a la frecuencia de conmutación (componente de rizado) y en un número finito de picos en cada sub-armónico (inestabilidades). El método de Filippov es utilizado para la predicción de inestabilidades debidas a las dinámicas rápidas, este método predice el rango de los parámetros que evitan la primera bifurcación en las dinámicas rápidas. En el presente artículo se presenta una predicción de un espacio de parámetros estables para el controlador PI (), estimados por el método de Filippov para un convertidor buck de dos fases con regulación de voltaje. Finalmente, los resultados presentados son validados mediante simulaciones de Matlab y Psim.

A previous article has presented the members of the asymmetrical interleaved dc/dc switching converters family as very appropriate candidates to interface between photovoltaic or fuel cell generators and their loads because of their reduced ripple and increased current processing capabilities. After a review of the main modeling methods suitable for high-order converters operating, as the asymmetrical interleaved converters (AIC) ones, in discontinuous current conduction mode a full-order averaged model has been adapted and improved to describe the dynamic behavior of AIC. The excellent agreement between the mathematical model predictions, the switched simulations and the experimental results has allowed for satisfactory design of a linear-quadratic regulator (LQR) in a fuel-cell application example, which demonstrates the usefulness of the improved control-oriented modeling approach when the switching converters operate in discontinuous conduction mode.

This paper proposes an active postfilter based on two Buck converters, connected in parallel, operating in complementary interleaving. In such a configuration the ripple in the load current could be virtually eliminated to improve the power quality in comparison with classical Point-Of-Load (POL) regulators based on a single Buck converter. The postfilter is designed to isolate the load from the main Buck regulator, leading to the proposed three-converter structure named BuckPS. The correct operation of the postfilter is ensured by means of a sliding-mode controller. Finally, the proposed solution significantly reduces the current harmonics injected into the load, and at the same time, it improves the overall electrical efficiency. Such characteristics are demonstrated by means of analytical results and illustrated using numerical results.

Este articulo presenta un modelo para sistemas de generación fotovoltaica orientado a evaluar el desempeño de algoritmos distribuidos de búsqueda del punto de máxima potencia. El modelo considera la conexión en serie de n conjuntos módulo-convertidor que pueden ser dimensionados dependiendo de la aplicación en particular. Dicho modelo está compuesto por un conjunto de ecuaciones que pueden ser implementadas en cualquier software de cálculo matemático o en un lenguaje de programación que soluciones este tipo de ecuaciones. El modelo incluye el comportamiento estático del módulo fotovoltaico a partir de una ecuación que estima su relación voltaje-corriente, además, incluye el modelo del convertidor elevador de potencia con pérdidas en el inductor, esto con el fin de aproximar el modelo general a una solución realística de la aplicación. El modelo final es validado mediante simulaciones y comparado con una implementación del mismo en un software de simulación electrónica tradicional.