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The optical absorption of water-containing bio-fuel is investigated as a parameter to determine the gasoline content of this fuel. Optical measurements reveal that gasoline shows an interesting and useful spectrum with typical absorption behavior in the UV range between 230 and 300 nm. This result indicates that significant information can be obtained to determine the gasoline concentration in bio-fuel by UV absorption spectroscopy. A concept for a low-cost measurement system in the fuel line is presented, by implementing a LVOF in combination with a wide-band light source and detector arrays. [ABSTRACT FROM AUTHOR]

The design of a metamaterial-based absorber for use in a mid-IR microspectrometer-based gas sensor is reported. The microspectrometer consists of a linear variable optical filter (LVOF) that is aligned with an array of thermopile detectors, which is fabricated on a SiN membrane and covered with the absorber. Special emphasis was put on the CMOS compatible fabrication, which resulted in an absorber design based on aluminium disk resonators and an aluminium background plane that are separated by a SiO 2 layer. The fabrication process is described, and the challenges are discussed. [ABSTRACT FROM AUTHOR]

The design and CMOS-compatible fabrication of stacked dielectric membranes are presented. The structures are intended for use as airgap-based interference filters operating in the UV-visible spectrum. In optical filters, maximizing the fill-factor, i.e. the ratio of the active area to the total area of the filter, is essential, which calls for minimum dimensions of the anchoring pillars and the openings that are required for the fabrication of the structures. This requirement necessitates the fabrication of large area free- standing membranes. Maintaining flatness over such a large area (> 1000μ m 2 ) membrane, as required by the optical application (deformation< λ/10), is challenging. While the thickness of the free-standing membrane is defined by the optical specification, the residual stress is the main force acting on the structure. Although an overall tensile residual stress can effectively stretch the membrane, the presence of a residual stress gradient causes the membrane to deform. Furthermore, a high residual stress results in the rupture of the membrane. These challenges in the fabrication of airgap-dielectric Bragg gratings are discussed. Higher-order optical designs were investigated to simultaneously satisfy both the mechanical and optical requirements. Bragg reflectors with one and two periods have been fabricated and characterized. The preliminary results are presented. [ABSTRACT FROM AUTHOR]

Y 2 O 3 nanopowders were synthesized by the hydrothermal treatment of Y(NO 3 ) 3 ·6H 2 O and citric acid (CA) as Y +3 and the capping agent, respectively. The effect of different CA:Y +3 mol ratios, heat treatment time, and calcination temperature was investigated in order to determine their influence on the morphology, particle size and phase of Y 2 O 3 nanopowders. The narrow size distribution of particles was obtained with CA:Y +3 mol ratio=1.6, heat treatment time of 6 h, and a calcination temperature at 900 °C for 90 min. Then, the synthesized Y 2 O 3 nanopowder was consolidated by the spark plasma sintering technique at 1500 °C with a heating rate of 100 °C/min and held for 8 min before turning off the power. As a result, the ceramic prepared with 3 mm thickness got the highest transmission of 80% at 2.5–6 µm wavelength. The highest density and the grain size of yttria ceramic were 99.58% and 1–1.2 µm at 1500 °C, respectively. [ABSTRACT FROM AUTHOR]

The design and CMOS-compatible fabrication of airgap-based optical filters in a surface micromachining process with sacrificial release using thevapour phase is presented. An airgap-dielectric layer combination offers a higher refractive index contrast, as compared to the conventional all-dielectriclayer based filters, which results in a higher peak reflectance and a wider bandwidth in a distributed Bragg reflector (DBR). Several DBRs and Fabry-Perot filters with multiple (low-n) airgap layers separating a stack of (high-n) layers of a dielectric material were designed for operation in the UV-visible spectrum. The fabrication was based on an Al 2 O 3 and SiO 2 system. The lateral design includes a set of anchor points and access holes. Finally, a vapour phase HF etching was used to remove the SiO 2 layers and release the Al 2 O 3 membranes. This method prevents the stiction of the membranes and provides a higher control and uniformity over the filter area. [ABSTRACT FROM AUTHOR]

The design, fabrication and characterization of a highly integrated optical gas sensor is presented. The gas cell takes up most of the space in a microspectrometer and is the only component that has so far not been miniaturized. Using the tapered resonator cavity of a linear variable optical filter as a gas cell enables ultimate miniaturization, while maintaining robustness without any moving parts. Multiple reflections from highly reflective mirrors allow a 24-25.5 μm long resonator cavity to also act as a gas cell with an equivalent optical absorption path length of 6 mm. [ABSTRACT FROM AUTHOR]

In this paper, a 200 kW horizontal axis wind turbine (HAWT) blade is designed using an efficient iterative algorithm based on the blade element momentum theory (BEM) on aerodynamic of wind turbines. The effects of off-design variations of wind speed are investigated on the blade performance parameters according to constant rotational speed of the rotor. The performance parameters considered are power coefficient, axial and angular induction factors, lift and drag coefficients on the blade, angle of attack and angle of relative wind. At higher or lower wind speeds than the designed rated speed, the power coefficient is reduced due to considerable changes in the angle of attacks. Therefore, proper pitch control angles were calculated to extract maximum possible power at various off-design speeds. The results showed a considerable improvement in power coefficient for the pitch controlled blade as compared with the baseline design in whole operating range. The present approach can be equally employed for determining pitch angles to design pitch control system of medium and large-scale wind turbines. [ABSTRACT FROM AUTHOR]

This paper presents the design, fabrication and characterization of two Fabry Perot type optical filters (415 nm and 540 nm) for enabling Narrow Band Imaging (NBI) in medical devices (MD). The two-colour illumination should satisfy a highly specific optical design, which is composed of a thin-film optical filter stack of titanium dioxide (TiO2) and silicon dioxide (SiO2) thin-films and commercially available light-emitting diodes (LEDs). The short-wavelength design is the most critical and simulations show a maximum relative optical output of 21% at 415 nm with Full-Width-Half-Maximum (FWHM) of 13 nm for a blue LED with the designed optical filter, which is confirmed by experiment. The green light simulations show a maximum relative optical output of 34% with FWHM 36 nm at 540 nm. The TiO2 and SiO2 thin films were fully characterized. [ABSTRACT FROM AUTHOR]

In CMOS-compatible optical filter designs, SiO2 is often used as the low-index material, limiting the optical contrast (nHi/nLo) to about 2. Using the air as low-index material improves the optical contrast by about 50%, thus increasing the reflectivity and bandwidth at a given design complexity. The design and fabrication of a 4-layered air-dielectric distributed Bragg reflector (DBR) centered at 400 nm using surface micromachining techniques, is presented here. Fabrication is based on the deposition of poly-Si thin films and subsequent thermal oxidation. Selectively removing the Si layers, produces an air/SiO2 filter stack according to the optical design. The width of the air-gaps needed in this application is typically smaller as compared to conventional MEMS devices. The number of layers is also higher, while no electrical contact is required. The concept, the fabrication of 4-layer DBRs and preliminary measurement results are discussed in this paper. [ABSTRACT FROM AUTHOR]

A set-up for optical gas composition measurement based on absorption spectroscopy is composed of a white light source, a gas cell and a spectrometer. The Fabry-Perot optical filter is suitable for miniaturization of this system, as it is composed of only two reflectors with a transparent layer in-between. Varying the width of this optical resonator to cover the wavelength range in which the components to be analyzed have specific features, gives the absorption spectrum. The gas cell remains a separate unit in the conventional microsystem and a MEMS is the implementation of the microspectrometer. The ultimate miniaturization requires the monolithic integration of all these components. In the lossy Fabry-Perot filter that is presented in this paper, the gas cell and the microspectrometer are functionally integrated, using a gas-filled resonator in which the optical path is determined by multiple reflections in the resonator cavity itself. [ABSTRACT FROM AUTHOR]

The resistive particulate matter sensor is a simple device that transduces the presence of soot through impedance change across inter-digital electrodes (IDEs). We investigate the information provided by impedance spectroscopy over the frequency range from 100 Hz to 10 kHz for two purposes. The first is to investigate the opportunities for an improved sensor response to particulate matter (PM), based on the additional information provided by the measurement of both the in-phase (resistive) and out-of-phase (capacitive) components of the change in impedance over this frequency range as compared to DC resistance measurement only. Secondly, the origin of the capacitive response of the device is investigated from the perspective that soot on the device is in the form of bendable dendrites that grow in three dimensions. An IDE structure with the housing acting as an additional suspended electrode for introducing a controllable vertical electric field component has been used for this purpose. The formation of dipoles, due to bending of the charged dendrites, is found to be the source of the capacitive response. Simulation of electrostatic soot deposition reinforces dendritic self-assembly mechanisms, driven by charged particle trajectories along electric field lines. Optical microscopy confirms that dendrites growing out of the substrate plane are sensitive to electric and flow forces, bending when force balances are appropriate. We also apply impedance spectroscopy under varying electric field strengths, showing that capacitive response is only observed when conditions are conducive to dendrite bending in response to the applied AC electric fields. • Impedance spectroscopy in the 100 Hz to 10 kHz frequency range is applied to an IDE. • The change in capacitance of the IDE is more gradual with PM deposit as resistance. • A model for soot dendrite growth is validated by spectral permittivity measurement. • Electrophoresis results in preferred soot deposition at IDE surface irregularities. • A vertical electric field component results in vertical growth of soot dendrites. [ABSTRACT FROM AUTHOR]

A generic method to reduce the in-line flow dependence of thermal conductivity detectors (TCDs) is presented. The principle is based on a dual-MEMS device configuration. Two thin-film sensors on membranes in parallel in the gas stream on the same chip are differentially operated. Both micro-TCDs are designed to be identical in terms of contact with the main gas flow, however a different depth of the detection chamber results in a different response to the thermal conductivity of the sample gas. Static and dynamic simulations have been performed to characterize the design of the fabricated structures. Devices have been fabricated in a MEMS process using a combined surface- and bulk micromachining process. The devices have been characterized statically and dynamically. Measurements on prototypes show that depending on the range of gases, device size and flow range device the effect of flow on the thermal conductivity can be reduced by a factor 4–15. [ABSTRACT FROM AUTHOR]

Measuring the ethanol/water ratio in biofuel of high ethanol content, such as E85, is important when used in a flex-fuel engine. A capacitive probe is generally used for measuring the ethanol/gasoline ratio. However, the water content in E85 biofuel cannot be disregarded or considered constant and full composition measurement of biofuel is required. Electric impedance spectroscopy with a customized coaxial probe operating in the 10 kHz to 1 MHz frequency range was investigated. An in-depth investigation of the electrical impedance domain has led to the conclusion that additional information is required to unambiguously determine the composition of the ternary biofuel mixture. Among the different options of measurement domains and techniques, optical absorption spectroscopy in the UV spectral range between 230 and 300 nm was found to be the most appropriate. The typical absorbance in the UV range is highly dominated by gasoline, while ethanol and water are almost transparent. This approach is experimentally validated using actual fuels. [ABSTRACT FROM AUTHOR]

• Proposing a dipole plasma antenna in VHF band with kinetic method to analyze the plasma environment. • The radial charge distribution as a zeroth-order Bessel function of the first type investigated in a plasma tube with DC and AC excitations. • Finite-difference time-domain (FDTD) numerical method is used to solve transactions. • Fluid method and CST Microwave Studio software are used to validate the results. In this paper, a dipole plasma antenna element in the VHF band with DC or AC excitation is investigated using kinetic method. The finite-difference time-domain (FDTD) numerical method is employed to solve the equations. To validate the results, the parameters obtained for the antenna parameters including S 11, input impedance and radiation pattern are compared with the results obtained from CST software as well as the fluid method. The S 11 of the antenna is presented for the frequency range of 150 to 300 MHz, with −10 dB bandwidth of 95 MHz It is observed that at central frequency of 210 MHz, S 11 is equal to −34 dB and the antenna input impedance has only real part equal to 160 Ω. In addition, the radiation pattern of the antenna is calculated and it is observed that the orientation of the directivity of the antenna is equal to 2.09 dB. [ABSTRACT FROM AUTHOR]

In this paper, a high-performance epoxy nanocomposite with dual active/barrier protection ability based on calcium zinc phosphate (CZP) nanopigment was fabricated. Then chemistry, morphology, and anti-corrosion ability of the commercial zinc phosphate (ZP) and CZP pigments were studied. By electrochemical techniques, the inhibition potency of the CZP nanopigment was examined in a NaCl solution on mild steel (MS) substance and compared with that of ZP. Results revealed a higher corrosion inhibition degree of the CZP compared to the ZP. The growth of a protective layer on the metal coupons exposed to the CZP extract was illustrated by X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FE-SEM), and Fourier transform infrared (FT-IR) spectroscopy. The reinforcement effects of CZP and ZP pigments on the epoxy composites' corrosion resistance were proved by electrochemical impedance spectroscopy (EIS) and salt spray test results. The better protection properties of the CZP loaded coating (23,600 MΩ cm2) compared with the unfilled coating (0.014 MΩ cm2) and the one loaded with ZP (0.26 MΩ cm2) were understood from the EIS test results. [Display omitted] • Calcium zinc phosphate (CZP) nanopigment was synthesized and characterized. • Inhibitive power of CZP nanopigment was studied in details. • The CZP extract behaves as a mixed-type inhibitor in 3.5% NaCl solution. • Dual active/barrier inhibition performance was proved through electrochemical methods. [ABSTRACT FROM AUTHOR]

This article describes the fabrication of MgF 2 and MgO thin-film-based optical filters and compares the optical transmission of the filters over UV. The MgF 2 thin-films were deposited by use of an e-beam technique and their optical properties were characterised by ellipsometry. The effect of substrate temperature on the optical properties was studied. The MgF 2 optimum refractive indices were obtained with a substrate temperature between 200 °C and 300 °C. Optical simulations were performed to compare the performance of MgF 2 and MgO in the fabrication of near-UV narrow bandpass optical filters. While MgO-based optical filters result in a higher transmittance peak intensity, especially at 350 nm, the MgF 2 optical filters are narrower, present lower values of FWHM, a mean value of 20 nm. This feature could be especially relevant for specific applications on fluorescent optical sensors. Finally, a Fabry-Perot based on a MgF 2 /TiO 2 optical filter was deposited, using an e-beam technique for the MgF 2 thin-films and RF-sputtering technique for the TiO 2 thin-films. The MgF 2 /TiO 2 optical filter peak transmittance is approximately 70% close to 400 nm, as expected. The results are discussed with focus on applications in fluorescent optical sensors for peaks at 350, 370, 380 and 400 nm, respectively. • MgF 2 /TiO 2 UV optical filter fabrication. • Comparison between MgO/TiO 2 and MgF 2 /TiO 2 UV optical filters. • The MgF 2 /TiO 2 UV optical filter was optically; morphologically and chemically characterized. • The recipe for fabrication of MgF 2 is presented with most updated results in comparison with the references. [ABSTRACT FROM AUTHOR]