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834 KiB

Open AccessArticle

Synthesis of Cascadable DDCC-Based Universal Filter Using NAM

by Huu-Duy Tran, Hung-Yu Wang, Min-Chuan Lin and Quoc-Minh Nguyen

Appl. Sci. 2015, 5(3), 320-343; https://doi.org/10.3390/app5030320 - 11 Aug 2015

Cited by 9 | Viewed by 4932

Abstract

A novel systematic approach for synthesizing DDCC-based voltage-mode biquadratic universal filters is proposed. The DDCCs are described by infinity-variables’ models of nullor-mirror elements which can be used in the nodal admittance matrix expansion process. Applying the proposed method, the obtained 12 equivalent filters [...] Read more.

A novel systematic approach for synthesizing DDCC-based voltage-mode biquadratic universal filters is proposed. The DDCCs are described by infinity-variables’ models of nullor-mirror elements which can be used in the nodal admittance matrix expansion process. Applying the proposed method, the obtained 12 equivalent filters offer the following features: multi-input and two outputs, realization of all five standard filter functions, namely lowpass, bandpass, highpass, notch and allpass, high-input impedance, employing only grounded capacitors and resistors, orthogonal controllability between pole frequency and quality factor, and cascadable, low active and passive sensitivities. The workability of some synthesized filters is verified by HSPICE simulations to demonstrate the feasibility of the proposed method. Full article

(This article belongs to the Special Issue Feature Papers)

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1067 KiB

Open AccessArticle

Excess Phase Noise Characterization in Multifrequency Remote Clock Distribution Based on Femtosecond Frequency Combs

by Changjun Hu, Ravi P. Gollapalli, Lin Yang and Lingze Duan

Appl. Sci. 2015, 5(2), 77-87; https://doi.org/10.3390/app5020077 - 7 May 2015

Cited by 5 | Viewed by 5982

Abstract

Remote distribution of optical frequency references, based on multifrequency sources such as femtosecond frequency combs, holds many advantages over its single-frequency counterpart. However, characterizing the excess noise caused by the transmission links or external perturbations in a multifrequency scheme posts new challenges. We [...] Read more.

Remote distribution of optical frequency references, based on multifrequency sources such as femtosecond frequency combs, holds many advantages over its single-frequency counterpart. However, characterizing the excess noise caused by the transmission links or external perturbations in a multifrequency scheme posts new challenges. We have experimentally demonstrated direct measurement of excess phase noise spectrum in both free-space and fiber-optic transfer of a frequency comb using a multiheterodyne technique. In fiber-optic distribution, we focused on the excess phase noise under a single-tone acoustic perturbation. Increased overall noise power and a change of phase noise spectrum have been observed. In free-space distribution, a fractional instability of 3 × 10⁻¹⁴ at 1 s was observed for a 60 m outdoor atmospheric transmission, and large phase modulation due to air fluctuations causes a sizable line broadening. Full article

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1650 KiB

Open AccessArticle

Numerical Models for Exact Description of in-situ Digital In-Line Holography Experiments with Irregularly-Shaped Arbitrarily-Located Particles

by Marc Brunel, Wisuttida Wichitwong, Sébastien Coetmellec, Adrien Masselot, Denis Lebrun, Gérard Gréhan and Guillaume Edouard

Appl. Sci. 2015, 5(2), 62-76; https://doi.org/10.3390/app5020062 - 22 Apr 2015

Cited by 6 | Viewed by 5184

Abstract

We present the development of a numerical simulator for digital in-line holography applications. In-line holograms of arbitrarily shaped and arbitrarily located objects are calculated using generalized Huygens-Fresnel integrals. The objects are 2D opaque or phase objects. The optical set-up is described by its [...] Read more.

We present the development of a numerical simulator for digital in-line holography applications. In-line holograms of arbitrarily shaped and arbitrarily located objects are calculated using generalized Huygens-Fresnel integrals. The objects are 2D opaque or phase objects. The optical set-up is described by its optical transfer matrix. A wide variety of optical systems, involving windows, spherical or cylindrical lenses, can thus be taken into account. It makes the simulator applicable for design and description of in situ experiments. We discuss future applications of this simulator for detection of nanoparticles in droplets, or calibration of airborne instruments that detect and measure ice crystals in the atmosphere. Full article

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489 KiB

Open AccessArticle

Derivation of Oscillators from Biquadratic Band Pass Filters Using Circuit Transformations

by Hung-Yu Wang, Huu-Duy Tran, Quoc-Minh Nguyen, Li-Te Yin and Chih-Yi Liu

Appl. Sci. 2014, 4(4), 482-492; https://doi.org/10.3390/app4040482 - 29 Sep 2014

Cited by 9 | Viewed by 7052

Abstract

Network transformations are the techniques to obtain new functional schemes from available circuits. They are systematic methodologies, since each transformation technique can be applied to many circuits to obtain the desired functions or characteristics. A convenient network transformation method, exploiting different circuit transformations, [...] Read more.

Network transformations are the techniques to obtain new functional schemes from available circuits. They are systematic methodologies, since each transformation technique can be applied to many circuits to obtain the desired functions or characteristics. A convenient network transformation method, exploiting different circuit transformations, for deriving linear sinusoidal oscillators from biquadratic band pass filters is proposed. This method with generality can be applied to any band pass filter. The oscillation frequency of the new obtained oscillator is identical to the center frequency of the original band pass filter, and the useful properties of the selected band pass filter can be retained. Two examples are illustrated to confirm the feasibility of the proposed approach. The workability of the obtained oscillators is verified with PSPICE simulations. Full article

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1895 KiB

Open AccessArticle

Effect of RhOx/CeO₂ Calcination on Metal-Support Interaction and Catalytic Activity for N₂O Decomposition

by Verónica Rico-Pérez and Agustin Bueno-López

Appl. Sci. 2014, 4(3), 468-481; https://doi.org/10.3390/app4030468 - 22 Sep 2014

Cited by 15 | Viewed by 7391

Abstract

The effect of the calcination conditions on the catalytic activity for N₂O decomposition of 2.5% RhOx/CeO₂ catalysts has been investigated. Ramp and flash calcinations have been studied (starting calcinations at 25 or 250/350 °C, respectively) both for cerium nitrate and [...] Read more.

The effect of the calcination conditions on the catalytic activity for N₂O decomposition of 2.5% RhOx/CeO₂ catalysts has been investigated. Ramp and flash calcinations have been studied (starting calcinations at 25 or 250/350 °C, respectively) both for cerium nitrate and ceria-impregnated rhodium nitrate decomposition. The cerium nitrate calcination ramp has neither an effect on the physico-chemical properties of ceria, observed by XRD, Raman spectroscopy and N₂ adsorption, nor an effect on the catalysts performance for N₂O decomposition. On the contrary, flash calcination of rhodium nitrate improved the catalytic activity for N₂O decomposition. This is attributed to the smaller size of RhOx nanoparticles obtained (smaller than 1 nm) which allow a higher rhodium oxide-ceria interface, favoring the reducibility of the ceria surface and stabilizing the RhOx species under reaction conditions. Full article

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371 KiB

Open AccessArticle

Comparisons of Halogenated β-Nitrostyrenes as Antimicrobial Agents

by Hugh Cornell, Thu Nguyen, Gina Nicoletti, Neale Jackson and Helmut Hügel

Appl. Sci. 2014, 4(3), 380-389; https://doi.org/10.3390/app4030380 - 29 Aug 2014

Cited by 16 | Viewed by 7116

Abstract

The influence of three types of halogen-substituted E-β-methyl-β-nitrostyrenes (such as Compounds B, D, H) to overcome bacterial activity that is currently a significant health threat was studied. The evaluations of their bio-potency was measured and related to their structure [...] Read more.

The influence of three types of halogen-substituted E-β-methyl-β-nitrostyrenes (such as Compounds B, D, H) to overcome bacterial activity that is currently a significant health threat was studied. The evaluations of their bio-potency was measured and related to their structure and activity relationships for the purposes of serving to inhibit and overcoming resistant microorganisms. In particular, fluorine-containing β-nitrostyrenes were found to be highly active antimicrobial agents. The addition of the β-bromo group enhanced the antibacterial activity significantly. Our work has illustrated that halogen substituents at both the 4-position in the aromatic ring and also at the β-position on the alkene side chain of nitropropenyl arenes enhanced the antimicrobial activity of these compounds. Full article

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2580 KiB

Open AccessArticle

Selection of a Visible-Light vs. Thermal Infrared Sensor in Dynamic Environments Based on Confidence Measures

by Juan Serrano-Cuerda, Antonio Fernández-Caballero and María T. López

Appl. Sci. 2014, 4(3), 331-350; https://doi.org/10.3390/app4030331 - 8 Aug 2014

Cited by 19 | Viewed by 5808

Abstract

This paper introduces a confidence measure scheme in a bimodal camera setup for automatically selecting visible-light or a thermal infrared in response to natural environmental changes. The purpose of the setup is to robustly detect people in dynamic outdoor scenarios under very different [...] Read more.

This paper introduces a confidence measure scheme in a bimodal camera setup for automatically selecting visible-light or a thermal infrared in response to natural environmental changes. The purpose of the setup is to robustly detect people in dynamic outdoor scenarios under very different conditions. For this purpose, two efficient segmentation algorithms, one dedicated to the visible-light spectrum and another one to the thermal infrared spectrum, are implemented. The segmentation algorithms are applied to five different video sequences recorded under very different environmental conditions. The results of the segmentation in both spectra allow one to establish the best-suited confidence interval thresholds and to validate the overall approach. Indeed, the confidence measures take linguistic values LOW, MEDIUM and HIGH, depending on the reliability of the results obtained in visible-light, as well as in thermal infrared video. Full article

(This article belongs to the Special Issue Feature Papers)

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826 KiB

Open AccessArticle

Determination of Morphological Parameters of Supported Gold Nanoparticles: Comparison of AFM Combined with Optical Spectroscopy and Theoretical Modeling versus TEM

by Frank Hubenthal, David Blázquez Sánchez and Frank Träger

Appl. Sci. 2012, 2(3), 566-583; https://doi.org/10.3390/app2030566 - 2 Jul 2012

Cited by 10 | Viewed by 9376

Abstract

The morphology of small gold particles prepared by Volmer–Weber growth on sapphire substrates have been investigated by two different characterization techniques. First, by non-extensive atomic force microscopy (AFM) in combination with optical spectroscopy and modeling of the optical properties using a theoretical model, [...] Read more.

The morphology of small gold particles prepared by Volmer–Weber growth on sapphire substrates have been investigated by two different characterization techniques. First, by non-extensive atomic force microscopy (AFM) in combination with optical spectroscopy and modeling of the optical properties using a theoretical model, recently developed in our group. Second, by extensive transmission electron microscopy (TEM). Comparing the results obtained with both techniques demonstrate that for small gold nanoparticles within the quasistatic limit, the morphological properties can be precisely determined by an appropriate theoretical modeling of the optical properties in combination with simple AFM measurements. The apparent mean axial ratio of the nanoparticles, i.e., the axial ratio that corresponds to the center frequency of the ensemble plasmon resonance, is obtained easily from the extinction spectrum. The mean size is determined by the nanoparticle number density and the amount of deposited material, measured by AFM and a quartz micro balance, respectively. To extract the most probable axial ratio of the nanoparticle ensemble, i.e., the axial ratio that corresponds to the most probable nanoparticle size in the ensemble, we apply the new theoretical model, which allows to extract the functional dependence of the nanoparticle shape on its size. The morphological parameters obtained with this procedure will be afterwards compared to extensive TEM measurements. The results obtained with both techniques yield excellent agreement. For example, the lateral dimensions of the nanoparticles after deposition of 15.2 × 10¹⁵ atoms/cm² of gold has been compared. While a mean lateral diameter of (13 ± 2) nm has been extracted from AFM, optical spectroscopy and modeling, a value of (12 ± 2) nm is derived from TEM. The consistency of the results demonstrate the precision of our new model. Moreover, since our theoretical model allows to extract the functional dependence of the nanoparticle size and shape, a relatively simple analysis is sufficient for a full characterization of small noble metal nanoparticles. Full article

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309 KiB

Open AccessArticle

Effects of Nonlinear Chirp on the Self-Phase Modulation of Ultrashort Optical Pulses

by Akira Suda and Takanori Takeda

Appl. Sci. 2012, 2(2), 549-557; https://doi.org/10.3390/app2020549 - 4 Jun 2012

Cited by 24 | Viewed by 7909

Abstract

In this article, we analytically investigate the spectral broadening by self-phase modulation of strongly chirped optical pulses. The dispersion due to the nonlinear optical process is expressed as functions of a linear and a nonlinear initial chirp. As a result, it is found [...] Read more.

In this article, we analytically investigate the spectral broadening by self-phase modulation of strongly chirped optical pulses. The dispersion due to the nonlinear optical process is expressed as functions of a linear and a nonlinear initial chirp. As a result, it is found that the third-order dispersion strongly depends on the initial linear chirp and the nonlinearity for self-phase modulation. Full article

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561 KiB

Open AccessArticle

High Performance Shape Memory Polyurethane Synthesized with High Molecular Weight Polyol as the Soft Segment

by Manzoor Ahmad, Bin Xu, Hendra Purnawali, Yongqing Fu, Weimin Huang, Mohsen Miraftab and Jikui Luo

Appl. Sci. 2012, 2(2), 535-548; https://doi.org/10.3390/app2020535 - 31 May 2012

Cited by 58 | Viewed by 11026

Abstract

Shape memory polyurethanes (SMPUs) are typically synthesized using polyols of low molecular weight (M_W~2,000 g/mol) as it is believed that the high density of cross-links in these low molecular weight polyols are essential for high mechanical strength and good shape memory [...] Read more.

Shape memory polyurethanes (SMPUs) are typically synthesized using polyols of low molecular weight (M_W~2,000 g/mol) as it is believed that the high density of cross-links in these low molecular weight polyols are essential for high mechanical strength and good shape memory effect. In this study, polyethylene glycol (PEG-6000) with M_W~6000 g/mol as the soft segment and diisocyanate as the hard segment were used to synthesize SMPUs, and the results were compared with the SMPUs with polycaprolactone PCL-2000. The study revealed that although the PEG-6000-based SMPUs have lower maximum elongations at break (425%) and recovery stresses than those of PCL-based SMPUs, they have much better recovery ratios (up to 98%) and shape fixity (up to 95%), hence better shape memory effect. Furthermore, PEG-based SMPUs showed a much shorter actuation time of < 10 s for up to 90% shape recovery compared to typical actuation times of tens of seconds to a few minutes for common SMPUs, demonstrated their great potential for applications in microsystems and other engineering components. Full article

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1094 KiB

Open AccessArticle

Electrically Small Resonators for Planar Metamaterial, Microwave Circuit and Antenna Design: A Comparative Analysis

by Miguel Durán-Sindreu, Jordi Naqui, Ferran Paredes, Jordi Bonache and Ferran Martín

Appl. Sci. 2012, 2(2), 375-395; https://doi.org/10.3390/app2020375 - 20 Apr 2012

Cited by 60 | Viewed by 17770

Abstract

Planar metamaterials and many microwave circuits and antennas are designed by means of resonators with dimensions much smaller than the wavelength at their resonance frequency. There are many types of such electrically small resonators, and the main purpose of this paper is to [...] Read more.

Planar metamaterials and many microwave circuits and antennas are designed by means of resonators with dimensions much smaller than the wavelength at their resonance frequency. There are many types of such electrically small resonators, and the main purpose of this paper is to compare them as building blocks for the implementation of microwave components. Aspects such as resonator size, bandwidth, their circuit models when they are coupled to transmission lines (as is usually required), as well as key applications, will be considered. Full article

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539 KiB

Open AccessArticle

Reduction and Immobilization of Potassium Permanganate on Iron Oxide Catalyst by Fluidized-Bed Crystallization Technology

by Guang-Xia Li, Yao-Hui Huaug, Teng-Chien Chen, Yu-Jen Shih and Hui Zhang

Appl. Sci. 2012, 2(1), 166-174; https://doi.org/10.3390/app2010166 - 1 Mar 2012

Cited by 10 | Viewed by 9729

Abstract

A manganese immobilization technology in a fluidized-bed reactor (FBR) was developed by using a waste iron oxide (i.e., BT-3) as catalyst which is a by-product from the fluidized-bed Fenton reaction (FBR-Fenton). It was found that BT-3 could easily reduce potassium permanganate [...] Read more.

A manganese immobilization technology in a fluidized-bed reactor (FBR) was developed by using a waste iron oxide (i.e., BT-3) as catalyst which is a by-product from the fluidized-bed Fenton reaction (FBR-Fenton). It was found that BT-3 could easily reduce potassium permanganate (KMnO₄) to MnO₂. Furthermore, MnO₂ could accumulate on the surface of BT-3 catalyst to form a new Fe-Mn oxide. Laboratory experiments were carried out to investigate the KMnO₄-reduction mechanism, including the effect of KMnO₄ concentration, BT-3 dosage, and operational solution pH. The results showed that the pH solution was a significant factor in the reduction of KMnO₄. At the optimum level, pH_f 6, KMnO₄ was virtually reduced in 10 min. A pseudo-first order reaction was employed to describe the reduction rate of KMnO₄. Full article

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285 KiB

Open AccessArticle

Scaling Law for Photon Transmission through Optically Turbid Slabs Based on Random Walk Theory

by Xuesong Li and Lin Ma

Appl. Sci. 2012, 2(1), 160-165; https://doi.org/10.3390/app2010160 - 1 Mar 2012

Cited by 8 | Viewed by 6564

Abstract

Past work has demonstrated the value of a random walk theory (RWT) to solve multiple-scattering problems arising in numerous contexts. This paper’s goal is to investigate the application range of the RWT using Monte Carlo simulations and extending it to anisotropic media using [...] Read more.

Past work has demonstrated the value of a random walk theory (RWT) to solve multiple-scattering problems arising in numerous contexts. This paper’s goal is to investigate the application range of the RWT using Monte Carlo simulations and extending it to anisotropic media using scaling laws. Meanwhile, this paper also reiterates rules for converting RWT formulas to real physical dimensions, and corrects some errors which appear in an earlier publication. The RWT theory, validated by the Monte Carlo simulations and combined with the scaling law, is expected to be useful to study multiple scattering and to greatly reduce the computation cost. Full article

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103 KiB

Open AccessArticle

Surface Sampling of a Dry Aerosol Deposited Ricin

by Jason M. Edmonds, Patricia J. Collett, Rebecca L. Brown and Kishna Mangaya

Appl. Sci. 2012, 2(1), 13-23; https://doi.org/10.3390/app2010013 - 13 Jan 2012

Cited by 1 | Viewed by 6693

Abstract

Sampling of small molecules from both porous and non-porous surfaces poses a significant challenge across biological agents. Particle sizes of toxins are smaller than living organisms and can be extremely toxic at low level concentrations. A small number of studies evaluating sampling efficiencies [...] Read more.

Sampling of small molecules from both porous and non-porous surfaces poses a significant challenge across biological agents. Particle sizes of toxins are smaller than living organisms and can be extremely toxic at low level concentrations. A small number of studies evaluating sampling efficiencies of commercial off the shelf (COTS) materials have been performed with toxins and proteins. However, they have been limited to non-ricin stimulants with drastically different physical properties than their native counterparts. We have identified a commercially available non-toxic recombinant ricin, complete with both A and B subunits present, which can be recognized by antibodies commonly used to assay native ricin. In evaluating recovery efficiency, we deposited the recombinant ricin by both liquid deposition, and as a dry aerosol. Our studies demonstrated a significant difference in recovery efficiencies from liquid deposited ricin, ranging between 30% and 70%, than from an aerosol generated deposition ranging from below detectable levels to 22%, depending on the contaminated surface and swab material being used. This study demonstrates the necessity for accurate dissemination techniques of sampling technologies for the consideration of use in an environment where suspected toxin contamination is being evaluated. Full article

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270 KiB

Open AccessCommunication

Chiral β-Amino Alcohols as Ligands for the Ruthenium-Catalyzed Asymmetric Transfer Hydrogenation of N-Phosphinyl Ketimines

by Óscar Pablo, David Guijarro and Miguel Yus

Appl. Sci. 2012, 2(1), 1-12; https://doi.org/10.3390/app2010001 - 9 Jan 2012

Cited by 8 | Viewed by 7561

Abstract

Some chiral β-amino alcohols have been evaluated as potential ligands for the ruthenium-catalyzed asymmetric transfer hydrogenation (ATH) of N-phosphinyl ketimines in isopropyl alcohol. The ruthenium complex prepared from [RuCl₂(p-cymene)]₂ and (1S,2R)-1-amino-2-indanol has shown [...] Read more.

Some chiral β-amino alcohols have been evaluated as potential ligands for the ruthenium-catalyzed asymmetric transfer hydrogenation (ATH) of N-phosphinyl ketimines in isopropyl alcohol. The ruthenium complex prepared from [RuCl₂(p-cymene)]₂ and (1S,2R)-1-amino-2-indanol has shown to be an efficient catalyst for the ATH of several N-(diphenylphosphinyl)imines, affording the reduction products in very good isolated yields and enantiomeric excesses up to 82%. The inherent rigidity of the indane ring system present in the ligand seems to be very important to achieve good enantioselectivities. Full article

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Review

Jump to: Research

2260 KiB

Open AccessReview

New Trends in Dental Biomechanics with Photonics Technologies

by Lídia Carvalho, Paulo Roriz, José Simões and Orlando Frazão

Appl. Sci. 2015, 5(4), 1350-1378; https://doi.org/10.3390/app5041350 - 24 Nov 2015

Cited by 13 | Viewed by 8762

Abstract

Engineering techniques used to evaluate strain-stress fields, materials’ mechanical properties, and load transfer mechanisms, among others, are useful tools in the study of biomechanical applications. These engineering tools, as experimental and numerical ones, were imported to biomechanics, in particular in dental biomechanics, a [...] Read more.

Engineering techniques used to evaluate strain-stress fields, materials’ mechanical properties, and load transfer mechanisms, among others, are useful tools in the study of biomechanical applications. These engineering tools, as experimental and numerical ones, were imported to biomechanics, in particular in dental biomechanics, a few decades ago. Several experimental techniques have been used in dental biomechanics, like photoelasticity, ESPI (Electronic Speckle Pattern Interferometry), strain gages, and other kinds of transducers. However, these techniques have some limitations. For instance, photoelasticity and ESPI give the overall field pattern of the strain, showing the stress-strain concentration points. These methods cannot give an accurate measurement at all points. On the contrary, strain gages can be used to perform local measurements. However, as they use electrical resistances, their use is limited to perform in vivo measurements. Optical fiber sensors have already been used in dentistry, for diagnostic and therapeutic purposes, and in dental biomechanics studies. Lasers have also been used in clinical dentistry for a few decades. Other optical technologies, like optical coherence tomography (OCT), became suitable for dental practice and nowadays it is perhaps one that has had more development in dentristry, along with lasers. Full article

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538 KiB

Open AccessReview

A Review on the Role of Color and Light in Affective Computing

by Marina V. Sokolova and Antonio Fernández-Caballero

Appl. Sci. 2015, 5(3), 275-293; https://doi.org/10.3390/app5030275 - 5 Aug 2015

Cited by 48 | Viewed by 11322

Abstract

Light and color are ubiquitous environmental factors which have an influence on the human being. Hence, light and color issues have to be considered especially significant in human-computer interaction (HCI) and fundamental in affective computing. Affective computing is an interdisciplinary research field which [...] Read more.

Light and color are ubiquitous environmental factors which have an influence on the human being. Hence, light and color issues have to be considered especially significant in human-computer interaction (HCI) and fundamental in affective computing. Affective computing is an interdisciplinary research field which aims to integrate issues dealing with emotions and computers. As a consequence, it seems important to provide an updated review on the significance of light and color in affective computing. With this purpose, the relationship between HCI/affective computing and the emotions affected by light and color are introduced in first place. So far, there is a considerable number of studies and experiments that offer empirical results on the topic. In addition, the color models generally used in affective computing are briefly described. The review on the usage of color and light in affective computing includes a detailed study of the characteristics of methods and the most recent research trends. The paper is complemented with the study of the importance of light and color from demographic, gender and cultural perspectives. Full article

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2636 KiB

Open AccessReview

by Jordi Naqui, Lijuan Su, Javier Mata and Ferran Martín

Appl. Sci. 2015, 5(2), 88-113; https://doi.org/10.3390/app5020088 - 18 May 2015

Cited by 2 | Viewed by 7583

Abstract

This paper reviews the recent progress in the analysis and applications of the symmetry-related electromagnetic properties of transmission lines loaded with symmetric configurations of resonant elements. It will be shown that the transmission characteristics of these reactively loaded lines can be controlled by [...] Read more.

This paper reviews the recent progress in the analysis and applications of the symmetry-related electromagnetic properties of transmission lines loaded with symmetric configurations of resonant elements. It will be shown that the transmission characteristics of these reactively loaded lines can be controlled by the relative orientation between the line and the resonant elements. Two main types of loaded lines are considered: (i) resonance-based structures; and (ii) frequency-splitting structures. In resonance-based transmission lines, a line is loaded with a single resonant (and symmetric) element. For a perfectly symmetric structure, the line is transparent if the line and resonator exhibit symmetry planes of different electromagnetic nature (electric or magnetic wall), whereas the line exhibits a notch (resonance) in the transmission coefficient if the symmetry planes behave as either electric or magnetic walls (symmetric configuration), or if symmetry is broken. In frequency-splitting lines, paired resonators are typically loaded to the transmission line; the structure exhibits a single notch for the symmetric configuration, whereas generally two split notches appear when symmetry is disrupted. Applications of these structures include microwave sensors (e.g., contactless sensors of spatial variables), selective mode suppressors (of application in common-mode suppressed differential lines, for instance) and spectral signature barcodes, among others. Full article

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444 KiB

Open AccessReview

Fluorinated and Non-Fluorinated Electro-Optic Copolymers: Determination of the Time and Temperature Stability of the Induced Electro-Optic Coefficient

by Alessandro Belardini

Appl. Sci. 2012, 2(4), 682-708; https://doi.org/10.3390/app2040682 - 9 Oct 2012

Cited by 4 | Viewed by 7521

Abstract

Organic fluorinated materials demonstrate their excellent electro-optic properties and versatility for technological applications. The partial substitution of hydrogen with fluorine in carbon-halides bounds allows the reduction of absorption losses at the telecommunication wavelengths. In these interesting compounds, the electro-optic coefficient was typically induced [...] Read more.

Organic fluorinated materials demonstrate their excellent electro-optic properties and versatility for technological applications. The partial substitution of hydrogen with fluorine in carbon-halides bounds allows the reduction of absorption losses at the telecommunication wavelengths. In these interesting compounds, the electro-optic coefficient was typically induced by a poling procedure. The magnitude and the time stability of the coefficient is an important issue to be investigated in order to compare copolymer species. Here, a review of different measurement techniques (such as nonlinear ellipsometry, second harmonic generation, temperature scanning and isothermal relaxation) was shown and applied to a variety of fluorinated and non-fluorinated electro-optic compounds. Full article

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1103 KiB

Open AccessReview

Optical Current Sensors for High Power Systems: A Review

by Ricardo M. Silva, Hugo Martins, Ivo Nascimento, José M. Baptista, António Lobo Ribeiro, José L. Santos, Pedro Jorge and Orlando Frazão

Appl. Sci. 2012, 2(3), 602-628; https://doi.org/10.3390/app2030602 - 2 Jul 2012

Cited by 147 | Viewed by 24179

Abstract

The intrinsic advantages of optical sensor technology are very appealing for high voltage applications and can become a valuable asset in a new generation of smart grids. In this paper the authors present a review of optical sensors technologies for electrical current metering [...] Read more.

The intrinsic advantages of optical sensor technology are very appealing for high voltage applications and can become a valuable asset in a new generation of smart grids. In this paper the authors present a review of optical sensors technologies for electrical current metering in high voltage applications. A brief historical overview is given together with a more detailed focus on recent developments. Technologies addressed include all fiber sensors, bulk magneto-optical sensors, piezoelectric transducers, magnetic force sensors and hybrid sensors. The physical principles and main advantages and disadvantages are discussed. Configurations and strategies to overcome common problems, such as interference from external currents and magnetic fields induced linear birefringence and others are discussed. The state-of-the-art is presented including commercial available systems. Full article

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