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This work proposes the application of a slot in the ground plane, Defected Ground Structure (DGS), of a microstrip patch antenna. The application of this technique aims to attenuate higher-order excited modes without deteriorating the antenna parameters in the fundamental mode. The methodology for the design of the slot in H-format is presented, based on the physical dimensions of the microstrip patch antenna. The positioning of the DGS concerning the feed line was determined from a detailed parametric analysis. The antenna was designed for the fundamental mode at 2.45 GHz frequency. Two antenna prototypes were built, with and without DGS, and measurements of reflection coefficient, gain, and radiation pattern were performed. The measured results show that the application of DGS considerably attenuated higher-order excited modes. A good agreement between simulated and measured results is achieved.

Conventional flexible and wearable antennas are currently fabricated with substrates which are neither biodegradable. Another negative point is the use of ecounfriendly processes to produce these circuits thus generating e-waste and causing environment contamination. In this paper, an eco-friendly metamaterial antenna for 2.4 GHz WLAN applications is presented. The rectangular patch antenna is composed of two copper tape layers, one as the radiating element and the other as the modified ground plane with Complementary Split Ring Resonators (CSRR). The substrate that separates these two layers is a mixture of polybutylene adipate-co-terephthalate (PBAT) and polyhydroxybutyrate (PHB) polymers, both biodegradable. The electrical characterizations of the mixture were performed using the probe method and the antenna simulations were performed using the commercial software ANSYSO Electronics Desktop. Convergent results were obtained with simulated and measured prototypes, with a measured resonant frequency in 2.44 GHz and bandwidth of 360 MHz, simulated gain of 4.01 dBi and half power beam width of $4\mathrm {S}.2^{\mathrm {o}}$, which shows great potential for WLAN applications.

This paper describes by the first time, at least of the authors’ knowledge, a frequency selective surface, FSS, based on the Matryoshka geometry, with dual-band band-pass frequency response, keeping the interesting features previously outlined: angular stability and polarization independence. Moreover, it is a single layer FSS and the reduction of the resonant frequencies, a characteristic of the Matryoshka geometry, was maintained. Initial design equations are proposed, providing good results, making easy the design of the FSS for other resonant frequencies and specific applications. Two FSS were designed, fabricated and characterized, verifying a good agreement between numerical and experimental results. The resonant frequencies remain almost constant for different incident angles, from 0° to 45°, confirming the angular stability.

In this article, the applicability of an UHF circular printed monopole antenna with slotted ground plane was evaluated in order to detect partial discharges in power transformers. To verify the applicability of the antenna, two measurement batteries were performed: reflection coefficient (bandwidth) and gain in an anechoic chamber, to avoid external interference; and PD sensitivity tests from the comparison with the conventional method of IEC 60270, using for this purpose an oil cell with immersed flat-tip electrodes. These analyzes were performed for the design of an antenna with optimized performance. The obtained values for the antenna's bandwidth, size, gain and PD detection sensitivity make it possible to classify the antenna as efficient in detecting partial discharges in power transformers.

Herein we report the total syntheses of communesin F and putative members of the communesin family of polycyclic bis-aminal alkaloids. The successful strategy featured a novel organocatalytic reaction between two oxindole subunits to cast, after extensive optimization, the all-carbon vicinal quaternary stereocenters of the target molecule with high enantiocontrol. The resulting bis-oxindole intermediate further underwent a Ti(OiPr)4-mediated dehydrative skeletal rearrangement to furnish the communesin core structure. Consider the ready availability and low-cost of unsubstituted isatin, and the inferior organocatalytic reaction employing a bromo-substituted substrate, a Pd(OAc)2-catalyzed and oxalamide-directed aryl CH-alkenylation reaction was implemented to assemble the complete skeletal backbone of the target molecule. Collectively, the synthetic technologies disclosed herein constitute the first asymmetric organocatalytic approach to the communesins, together with a highly effective late-stage CH-funct...

Here we report asymmetric total syntheses of communesin F and a putative member of the communesin family of bis-aminal alkaloid natural products. The successful strategy featured the invention of an asymmetric organocatalytic reaction to unify two oxindole subunits, a Ti(OiPr)4-mediated dehydrative skeletal rearrangement, and a late-stage Pd(OAc)2-catalyzed directed CH-alkenylation reaction. Collectively, the synthetic technologies disclosed herein enabled the preparation of a late-stage polycyclic intermediate catered for the synthesis of both naturally occurring and designed communesins. More importantly, speculated and yet to be discovered member(s) of the communesin family can now be accessed to facilitate a better understanding of the communesin biosynthetic network.

In this paper is developed a transparent antenna, bioinspired in ingae edulis mart plants, build in Indio Tin Oxide film, and flexible transparent dielectric of low cost (cellulose acetate), generated by Gielis formula, for wireless local area network application in 5 GHz (5.15–5.85 GHz). The measured bioinspired transparent antenna presented bandwidth of 4.11 GHz (4.50-8.66 GHz), covering the WLAN band, with maximum gain of 5.44 dBi, and half power beamwidth of 126° at resonance frequency.

For fatigue life estimation as well as for fatigue testing analysis of welded structures by local stresses approaches, the stress concentration factor (SCF) at the weld must be known. Full penetration butt welded joints are extensively used in steel structures. Some empirical formulas to estimate SCFs are available in the literature, but their ranges of application are not always clearly defined, as well as the hypotheses on their local geometry. In this study, notch SCFs at steel butt welded joints under uniaxial tension are investigated by means of 2D plane strain linear elastic finite element analysis. The weld profile is modeled with splines. A detailed definition of the geometry is given. The influence of parameters such as the plate thickness, the weld reinforcement, the flank angle, the weld toe radius, the weld length and the presence of linear misalignment is assessed. Finally new parametric equations to estimate the SCFs at steel butt welded joints are proposed.

We formulate supersymmetric non-Hermitian quantum field theories with PT symmetry, starting with free chiral boson/fermion models and then including trilinear superpotential interactions. We consider models with both Dirac and Majorana fermions, analyzing them in terms of superfields and at the component level. We also discuss the relation between the equations of motion, the (non)invariance of the Lagrangian and the (non)conservation of the supercurrents in the two models. We exhibit a similarity transformation that maps the free-field supersymmetric PT-symmetric Dirac model to a supersymmetric Hermitian theory, but there is, in general, no corresponding similarity transformation for the Majorana model. In this model, we find generically a mass splitting between bosons and fermions, even though its construction is explicitly supersymmetric, offering a novel non-Hermitian mechanism for soft supersymmetry breaking. We formulate supersymmetric non-Hermitian quantum field theories with PT symmetry, starting with free chiral boson/fermion models and then including trilinear superpotential interactions. We consider models with both Dirac and Majorana fermions, analyzing them in terms of superfields and at the component level. We also discuss the relation between the equations of motion, the (non-)invariance of the Lagrangian and the (non-)conservation of the supercurrents in the two models. We exhibit a similarity transformation that maps the free-field supersymmetric PT-symmetric Dirac model to a supersymmetric Hermitian theory, but there is, in general, no corresponding similarity transformation for the Majorana model. In this model, we find generically a mass splitting between bosons and fermions, even though its construction is explicitly supersymmetric, offering a novel non-Hermitian mechanism for soft supersymmetry breaking.

International audience; In this paper is described the competition and transition between hydrogen bonding and protonation of alkynes connected, on one side, to various aromatic rings and to chiral amino ester appendages on the other side. While the first mode of activation induced the cyclization into pyrrolidines, the protonation of the alkyne led preferentially to tetrahydropyridines due to the higher level of the highest occupied molecular orbital (HOMO) of the considered arylogous ynolethers and ynamines. The transition between H-bonding and protonation was observed with the alkyne substituted with 2-methoxyphenyl, for which the cyclization delivered either five- or six-membered rings depending on the temperature of the experiment. From there, the cyclization of dialkoxy- and trialkoxyphenyl-substituted alkynes into six-membered rings, i.e., tetrahydropyridines, was developed. When next applied to alkynylindoles, the same pattern of cyclization provided six-membered rings as an illustration of the reactivity of arylogous ynamines. Thanks to the high reactivity of the intermediate cationic species, weak nucleophiles such as NH-oxazolidinone participated efficiently in the hydroamination reaction of alkynylindoles. Pyrrolidines, tetrahydropyridines, and piperidines decorated with various aromatics and substituents were thus prepared in enantio- and stereoselective manner. Capitalizing on the enamine moiety of the azaheterocycles, the molecular diversity was extended through stereoselective oxidation and ring contraction processes.

In this paper, we propose a flexible passive RFID tag using a Complementary Split Ring Resonator (CSRR) structure for antenna gain enhancement. The tag is based on a folded dipole antenna and 8 CSRR cells in the same layer, on a polyamide substrate. Simulation results performed in the ANSYS Electronics Desktop software are presented. It has been shown that with the insertion of the metamaterial structure there is a considerable improvement in some parameters of the antenna, such as directivity, efficiency and, consequently, gain. The gain of the antenna increased, approximately, from −6.8 dB to 5.3 dB. In addition, a read range of approximately 24.21 m was obtained at the operating frequency (915 MHz) with the metamaterial-based antenna.

In this article, the applicability of an UHF circular microstrip antenna with slotted ground plane in the detection of partial discharges in power transformers was analyzed. Dimensional parametric analyzes were carried out for the design of an antenna with optimized performance. The values of bandwidth, size, gain and directivity obtained allow to classify the designed antennas applicable in the detection of partial discharges in power transformers.

The RFID technology has been widely used in wireless body-area applications lately because of its capability of sensing and signal processing in addition to the low cost feature. Even so, the RFID tag's performance in terms of resonant frequency, gain and reading range, for example, is usually degraded when close to the human body tissues, being important to ensure a way of compensating this problem. This paper presents the design of a flexible RFID tag operating in the American UHF frequency of 915 MHz with two pairs of metamaterial circular CSRR (Complementary Split Ring Resonators) applied to its ground plane which promoted an increase of the tag reading range in about 37%.

Radio-frequency identification (RFID) is a constantly evolving technology, used more and more in the most diverse applications, which demands a continuous improvement of its basic components, e.g., tags, antennas and readers. An optimized low-cost circular polarized antenna, for the US standard UHF RFID application working frequency (902–928 MHz), is proposed in this paper. An initial work was developed and obtained 5.76 dB of gain, 48 dB of return loss (S 11 ) and axial ratio of 1.87 dB at 915 MHz in simulation results. However, in order to achieve these results, an airgap was introduced between two plates of FR4 substrate, which caused a great sensibility in the antenna results. So, in this work the airgap was replaced for a polyethylene foam layer, which has similar proprieties to the air, with a relative permittivity (er) of 1.2348 and a loss tangent of 0.0053. With this new substrate configuration, not only the S 11 sensibility of the antenna was decreased, but also the fabrication process was simplified and the antenna structure became more stable. The antenna was optimized using the ANSYS® HFSS software and it was obtained a slightly higher gain of 6 dB, a return loss of 15 dB and an axial ratio of 0.04 dB at 915 MHz. The antenna was manufactured and its S 11 was measured to compare with the simulation results.

The adulteration of gasoline has become a common practice in the process of its transportation, distribution and commercialization. Using non-compliant gasoline has many negative consequences for society including financial and health problems like gasoline overconsuming, decreasing engine performance, spontaneous combustion and increasing of pollutants emission. Therefore, several methods of complete gasoline analysis are available in the market, but many of these methods are only feasible in laboratories, requiring specialized people to gauge the quality of the product. Furthermore, non-invasive methods are not yet widely used to perform gasoline quality measurement, which is a further aggravation of gasoline handling throughout the entire testing and analysis process. Hence, considering that standard gasoline is a dielectric liquid mixture with about 30 different hydrocarbons, the present paper proposes a noninvasive method applied to gasoline quality measurement. This method is based on the variation of electrical parameters of the mixture, utilizing as the sensor a microwave resonator, once that varying dielectric parameters alter the power transmission in specific structures.

In this work, the evaluation of the metamaterial application in the gain improvement of a circular microfita antenna developed for the detection of partial discharges is presented. For this, a rectangular Split Ring Resonator was combined with Capacitive Load Strip for the development of the proposed metamaterial unit cell. The designed metamaterial was individually simulated for the evaluation of its double negativity features (e

In this work, the applicability of a circular microstrip antenna with U-slot and L probe in the detection of partial discharges in power transformers was analyzed. Dimensional parametric analyzes were carried out for the design of an antenna with optimized performance. The joint application of both bandwidth enhancement techniques proved to be more efficient in terms of bandwidth and gain than their respective individual applications. In addition, the values of bandwidth, size, gain and directivity obtained allow to classify the designed antenna as applicable in the detection of partial discharges in power transformers.

In this paper is presented a rectangular Koch pre-fractal patch antenna until three iterations on wearable flexible polyamide dielectric operating in the ultrahigh frequency band for medical wireless applications. The antennas were implemented by MATLAB, with generated images simulated in commercial software ANSYS. The polyamide presents characteristics of mechanical and thermal resistance suitable for wearable applications that require high-temperature resistance and constant movement. The use of Koch pre-fractal geometries from square patch antenna provides a decrease of 20.3 % in resonance frequency, and 30° in half-power beamwidth, making it more directional (first iteration). The wearable patch antenna with Koch pre-fractal for the third iteration shows maximum a gain at the resonance frequency of 5.57 dBi, and a current density of 41 A/m2.

In this paper, the design and development of a bio-inspired UHF sensor for partial discharge detection in power transformers is presented. The UHF sensor was developed for external use in dielectric windows of power transformers. For this purpose, a microstrip antenna was designed with a radiating element shape based on the leaf of the Jatropha mollissima (Pohl) Baill plant. Then, an epoxy coating and an aluminium enclosure were developed to protect the antenna against corrosion and to provide mechanical support, external noise immunity, and a lifetime compatibility with power transformers. In order to verify the electrical parameters of the developed sensor, measurements of the gain and the reflection coefficient were performed in an anechoic chamber. Lastly, the antenna sensitivity for denominated partial discharge (PD) detection was compared with the IEC 60270 standard method. For this purpose, simultaneous tests were carried out in a partial discharge generator setup, composed of an oil cell with needle-plane electrodes. The experimental tests demonstrated the effectiveness of the sensor for detecting PD signals with apparent charge values higher than 35 pC.

International audience; Benzyltrimethylammonium hydroxide act as an efficient metal-free catalyst for the intramolecular hydroalkoxylation of alkynes. Notably, the use of microwave irradiation allowed reaction to operate in only two minutes. Under optimized reaction conditions, linear alkynes bearing aryl and heteroaryl substituents were successfully cyclized with good level of stereoselectivity.

Wearable antennas present flexible dielectric and microstrip antenna normally used in Wireless Body Area Network systems with medical and no-medical applications. This article presents a new wearable printed monopole antenna for second generation (2G), third generation (3G), and fourth generation (4G) systems on textile material and laminate cooper to flat cable. The bioinspired geometry of a gynkgo biloba leaf was generated by Gielis formula. The proposed antenna presents a bandwidth of 2.70 GHz, covering the ranges of 2G, 3G, and 4G systems, with an omnidirectional radiation pattern, 3.10 dBi gain, and a HPBW of 102°. Measurements were performed with the antenna nearly on the head, on hand and in the pocket of trousers. The biggest difference, in the resonance frequency, was observed with the antenna on hand, and the antenna nearly on head, showed greater difference in bandwidth. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:2818–2823, 2016

Due to the increasing production of volatile new renewable energies as solar and wind, storage hydropower plants have to operate under harsh operation conditions in order to stabilize the electricity grid. As a result, highly transient water pressures occur in pressure tunnels and shafts more frequently. Non-intrusive monitoring techniques are therefore of special interest for these critical infrastructures. The propagation of a pressure wave generated actively by a cavitation bubble was experimentally investigated in a steel test pipe divided in several reaches. A local wall stiffness drop was simulated by replacing steel pipe reaches with less stiff materials as aluminum and PVC. Through the analysis of the pressure wave reflections due to the cavitation bubble explosion, recorded by two hydrophones placed at the extremities of the test pipe, the location of the weak reaches could be detected. An underwater spark generator was developed to produce cavitation bubbles in the pipe resulting in very steep shock waves. This allowed identifying very precisely the wave front and correspondingly the wave speed and the weak reach location. Compared to the wave analysis from water-hammer signals, the active cavitation bubble generation in the pipe is an innovative method that significantly increased the effectiveness of the detection of wall stiffness drops. (C) 2016 Elsevier Ltd. All rights reserved.

In this paper, a biologically inspired design methodology to develop directional leaf-shaped printed monopole antennas (PMA) for applications in the fourth-generation (4G) of mobile telecommunications technology is presented. Bio-inspired in the leaf shapes of a sugar cane plant, compact directional PMA are designed (with partial ground planes and flat rectangular reflectors) to cover the Brazilian 4G 700 MHz regulated band (698–806 MHz), with broadside radiation patterns and maximum directive gain up to 7.7 dBi. Simulated and measured results are presented for the proposed leaf-shaped antenna prototypes, and obtained results are compared with a square PMA. The use of bio-inspired leaf-shaped radiators and flat reflectors provides a fine tuning of ultra-wideband commonly presented by a conventional PMA, and the lowest resonant mode can be adjusted to cover the 700 MHz band. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:1529–1533, 2016