The Experts below are selected from a list of 46701 Experts worldwide ranked by ideXlab platform
Yue Zhang - One of the best experts on this subject based on the ideXlab platform.
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kinetically controlled glass transition measurement of organic aerosol thin films using broadband Dielectric Spectroscopy
Atmospheric Measurement Techniques, 2018Co-Authors: Yue Zhang, Shachi Katira, A T Lambe, T B Onasch, Wen Xu, W A Brooks, Manjula R Canagaratna, Andrew Freedman, J T JayneAbstract:Glass transitions from liquid to semi-solid and solid phase states have important implications for reactivity, growth, and cloud forming (cloud condensation nuclei and ice nucleation) capabilities of secondary organic aerosols (SOA). The small size and relatively low mass concentration of SOA in the atmosphere make it difficult to measure atmospheric SOA glass transitions using conventional methods. To circumvent these difficulties, we have adopted a new technique for measuring glass forming properties of atmospherically relevant organic aerosols. Aerosol particles to be studied are deposited in the form of a thin film onto an interdigitated electrode (IDE) using electrostatic precipitation. Dielectric Spectroscopy provides dipole relaxation rates for organic aerosols as a function of temperature (373 to 233 K) that are used to calculate the glass transition temperatures for several cooling rates. IDE-enabled broadband Dielectric Spectroscopy (BDS) was successfully used to measure the kinetically controlled glass transition temperatures of glycerol and citric acid aerosols with selected cooling rates. The glass transition results agree well with available literature data for these two compounds. The results indicate that the IDE-BDS method can provide accurate glass transition data for organic aerosols under atmospheric conditions. The BDS data obtained with the IDE-BDS technique can be used to characterize glass transitions for both simulated and ambient organic aerosols and to model their climate effects.
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kinetically controlled glass transition measurement of organic aerosol thin films using broadband Dielectric Spectroscopy
Atmospheric Measurement Techniques, 2018Co-Authors: Yue Zhang, Shachi Katira, A T Lambe, T B Onasch, W A Brooks, Manjula R Canagaratna, Andrew L Lee, Andrew FreedmanAbstract:Abstract. Glass transitions from liquid to semi-solid and solid phase states have important implications for reactivity, growth, and cloud-forming (cloud condensation nuclei and ice nucleation) capabilities of secondary organic aerosols (SOAs). The small size and relatively low mass concentration of SOAs in the atmosphere make it difficult to measure atmospheric SOA glass transitions using conventional methods. To circumvent these difficulties, we have adapted a new technique for measuring glass-forming properties of atmospherically relevant organic aerosols. Aerosol particles to be studied are deposited in the form of a thin film onto an interdigitated electrode (IDE) using electrostatic precipitation. Dielectric Spectroscopy provides dipole relaxation rates for organic aerosols as a function of temperature (373 to 233 K) that are used to calculate the glass transition temperatures for several cooling or heating rates. IDE-enabled broadband Dielectric Spectroscopy (BDS) was successfully used to measure the kinetically controlled glass transition temperatures of aerosols consisting of glycerol and four other compounds with selected cooling and heating rates. The glass transition results agree well with available literature data for these five compounds. The results indicate that the IDE-BDS method can provide accurate glass transition data for organic aerosols under atmospheric conditions. The BDS data obtained with the IDE-BDS technique can be used to characterize glass transitions for both simulated and ambient organic aerosols and to model their climate effects.
Pedram Mohseni - One of the best experts on this subject based on the ideXlab platform.
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an rf microwave microfluidic sensor based on a 3d capacitive structure with a floating electrode for miniaturized Dielectric Spectroscopy
IEEE Sensors, 2014Co-Authors: Michael A Suster, Brecken Blackburn, Umut A Gurkan, Pedram MohseniAbstract:This paper reports on the design, fabrication and testing of a microfluidic sensor for a miniaturized measurement platform dedicated to Dielectric Spectroscopy at RF/microwave frequencies. The sensor employs a novel, three-dimensional, parallel-plate, capacitive sensing structure with a floating electrode integrated onto a PMMA microfluidic cap used for delivering the material-under-test (MUT) with a 9μL-sample volume. Requiring only an S11 measurement and after a 6-point calibration, complex relative permittivity readings by the sensor in the frequency range of 14MHz to 6.5GHz agree very well with bulk-solution reference measurements conducted with an Agilent 85070E Dielectric probe kit. Using ethanol and ethylene glycol as two different MUTs with the sensor, the rms errors in real and imaginary parts of the complex relative permittivity of ethanol over the full frequency range are 3.5% and 5.6%, respectively. The corresponding numbers for ethylene glycol are 5.4% and 4.5%, respectively. Keywords—Capacitive sensor, Dielectric Spectroscopy, microfluidics, miniaturized platform, RF/microwave sensor
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a broadband sensor interface ic for miniaturized Dielectric Spectroscopy from mhz to ghz
IEEE Journal of Solid-state Circuits, 2014Co-Authors: Mehran Bakhshiani, Michael A Suster, Pedram MohseniAbstract:This paper describes a broadband sensor interface IC as part of a miniaturized measurement platform for MHz-to-GHz Dielectric Spectroscopy. Developed in 0.35 μm 2P/4M RF CMOS, the IC measures frequency-dependent S 21 magnitude and phase of a microfluidic Dielectric sensor fabricated in a thick gold-on-glass microfabrication process and loaded with a material-under-test (MUT). The IC architecture implements a broadband frequency response analysis (bFRA) method by first down-converting the sensor response signal from the RF excitation frequency to an intermediate frequency (IF) of 1 MHz using a low-noise amplifier (LNA) and active mixer, followed by down-converting the IF signal to dc using a coherent detector employing IF amplification stages with programmable gain, a passive mixer driven by in-phase (I) and quadrature-phase (Q) signals and an active-RC low-pass filter (LPF). The sensor interfaced with the IC is fully capable of differentiating among deionized (DI) water, phosphate buffered saline (PBS), ethanol and methanol in tests conducted at four different excitation frequencies of 50 MHz, 500 MHz, 1 GHz and 3 GHz. Further, Dielectric readings of ethanol from the sensor interfaced with the IC at five excitation frequencies in the range of 50 MHz to 2 GHz are in excellent agreement (error <;1%) with those from using a vector network analyzer (VNA) as the sensor readout. A bulk-solution reference measurement by an Agilent 85070E Dielectric probe kit interfaced with a VNA is also performed to verify proof-of-concept feasibility in conducting MHz-to-GHz Dielectric Spectroscopy with a miniaturized measurement platform using μL-sample volumes.
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An RF/microwave microfluidic sensor based on a center-gapped microstrip line for miniaturized Dielectric Spectroscopy
2013 IEEE MTT-S International Microwave Symposium Digest (MTT), 2013Co-Authors: Michael A Suster, Pedram MohseniAbstract:This paper reports on the design, fabrication and testing of a microfluidic sensor as part of a miniaturized measurement platform currently under development for Dielectric Spectroscopy (DS) at RF/microwave frequencies. The sensor employs a microstrip line with a 50-μm gap at the center as a parallel-plate capacitive sensing element and a 3-μL PDMS microfluidic channel on top for delivering the solution-under-test (SUT). Requiring only an S21 measurement and after a 5-point calibration for a Dielectric constant range of 1 to 48, sensor Dielectric readings in the frequency range of 14MHz to 4GHz agree very well with bulk-solution reference measurements conducted with an Agilent Dielectric probe kit. The maximum errors over the full frequency range for ethanol, ethylene glycol and ethyl acetate are -6.9%, -8.4% and -7.4%, respectively. The errors reduce to 1.7%, -4.7% and -7.1%, respectively, for frequencies above 2GHz.
Andrew Freedman - One of the best experts on this subject based on the ideXlab platform.
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kinetically controlled glass transition measurement of organic aerosol thin films using broadband Dielectric Spectroscopy
Atmospheric Measurement Techniques, 2018Co-Authors: Yue Zhang, Shachi Katira, A T Lambe, T B Onasch, Wen Xu, W A Brooks, Manjula R Canagaratna, Andrew Freedman, J T JayneAbstract:Glass transitions from liquid to semi-solid and solid phase states have important implications for reactivity, growth, and cloud forming (cloud condensation nuclei and ice nucleation) capabilities of secondary organic aerosols (SOA). The small size and relatively low mass concentration of SOA in the atmosphere make it difficult to measure atmospheric SOA glass transitions using conventional methods. To circumvent these difficulties, we have adopted a new technique for measuring glass forming properties of atmospherically relevant organic aerosols. Aerosol particles to be studied are deposited in the form of a thin film onto an interdigitated electrode (IDE) using electrostatic precipitation. Dielectric Spectroscopy provides dipole relaxation rates for organic aerosols as a function of temperature (373 to 233 K) that are used to calculate the glass transition temperatures for several cooling rates. IDE-enabled broadband Dielectric Spectroscopy (BDS) was successfully used to measure the kinetically controlled glass transition temperatures of glycerol and citric acid aerosols with selected cooling rates. The glass transition results agree well with available literature data for these two compounds. The results indicate that the IDE-BDS method can provide accurate glass transition data for organic aerosols under atmospheric conditions. The BDS data obtained with the IDE-BDS technique can be used to characterize glass transitions for both simulated and ambient organic aerosols and to model their climate effects.
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kinetically controlled glass transition measurement of organic aerosol thin films using broadband Dielectric Spectroscopy
Atmospheric Measurement Techniques, 2018Co-Authors: Yue Zhang, Shachi Katira, A T Lambe, T B Onasch, W A Brooks, Manjula R Canagaratna, Andrew L Lee, Andrew FreedmanAbstract:Abstract. Glass transitions from liquid to semi-solid and solid phase states have important implications for reactivity, growth, and cloud-forming (cloud condensation nuclei and ice nucleation) capabilities of secondary organic aerosols (SOAs). The small size and relatively low mass concentration of SOAs in the atmosphere make it difficult to measure atmospheric SOA glass transitions using conventional methods. To circumvent these difficulties, we have adapted a new technique for measuring glass-forming properties of atmospherically relevant organic aerosols. Aerosol particles to be studied are deposited in the form of a thin film onto an interdigitated electrode (IDE) using electrostatic precipitation. Dielectric Spectroscopy provides dipole relaxation rates for organic aerosols as a function of temperature (373 to 233 K) that are used to calculate the glass transition temperatures for several cooling or heating rates. IDE-enabled broadband Dielectric Spectroscopy (BDS) was successfully used to measure the kinetically controlled glass transition temperatures of aerosols consisting of glycerol and four other compounds with selected cooling and heating rates. The glass transition results agree well with available literature data for these five compounds. The results indicate that the IDE-BDS method can provide accurate glass transition data for organic aerosols under atmospheric conditions. The BDS data obtained with the IDE-BDS technique can be used to characterize glass transitions for both simulated and ambient organic aerosols and to model their climate effects.
Ulf W. Gedde - One of the best experts on this subject based on the ideXlab platform.
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non destructive condition monitoring of aged ethylene propylene copolymer cable insulation samples using Dielectric Spectroscopy and nmr Spectroscopy
Polymer Testing, 2015Co-Authors: Erik Linde, L. Verardi, Davide Fabiani, Payam Pourmand, Ulf W. GeddeAbstract:Abstract The causes of changes in Dielectric response as a result of thermal and irradiative ageing of cable insulation of ethylene propylene copolymer rubber containing 38 wt.% filler were investigated. Samples were aged in three different combinations of irradiation dose rate and temperature, 0.42 kGy h−1 at 85 °C, and 1.58 kGy h−1 at 55 and 85 °C, and subsequently studied by Dielectric Spectroscopy, NMR Spectroscopy using a portable spectrometer, and tensile testing. The extractable mass fraction and density were determined and related to the imaginary part of the Dielectric permittivity at 100 kHz. The ageing led to an increase in the Dielectric permittivity, stiffness, density and degree of oxidation, together with a decrease in both strain-at-break and relaxation time, as revealed by NMR Spectroscopy. Except for the strain-at-break, the properties changed in a linear fashion with increasing imaginary part of the Dielectric permittivity at 100 kHz, with particularly good agreement with respect to the density. As these properties are affected by the degree of oxidation, the results show that both NMR using a portable spectrometer and Dielectric Spectroscopy can be used as condition monitoring techniques to detect the degree of oxidation in complex systems such as filled copolymers.
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Dielectric Spectroscopy as a condition monitoring technique for cable insulation based on crosslinked polyethylene
Polymer Testing, 2015Co-Authors: Erik Linde, L. Verardi, Davide Fabiani, Ulf W. GeddeAbstract:Dielectric Spectroscopy was evaluated as a condition monitoring technique for aged polyethylene electrical insulation in nuclear power plants. Bare core insulations of crosslinked polyethylene were aged at 55 and 85 °C under exposure to 60Co γ-radiation at different dose rates (0.42, 0.76 and 1.06 kGy h-1) to different total doses. The samples were studied by Dielectric Spectroscopy and tensile testing, and the crystallinity, mass fraction of soluble component and density were determined. The oxidation profiles along the depth of the insulations were assessed by infrared microscopy. The aged samples showed an increase in both the real and imaginary parts of the Dielectric permittivity over the whole frequency range studied, an increase in the mass fraction of soluble component and in the material density, and a decrease in the strain-at-break. The imaginary part of the Dielectric permittivity at 100 kHz increased in a linear fashion with increasing material density, the latter being strictly related to the extent of oxidation of the material according to infrared Spectroscopy and differential scanning calorimetry. The generic relationship between the imaginary part of the permittivity and the density included all the data obtained under different ageing conditions. The results suggest that Dielectric Spectroscopy can be used for in-situ measurements of the degree of oxidation of polyethylene cables, in order to obtain information about the condition of the cable insulation to enable the remaining lifetime to be predicted.
J T Jayne - One of the best experts on this subject based on the ideXlab platform.
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kinetically controlled glass transition measurement of organic aerosol thin films using broadband Dielectric Spectroscopy
Atmospheric Measurement Techniques, 2018Co-Authors: Yue Zhang, Shachi Katira, A T Lambe, T B Onasch, Wen Xu, W A Brooks, Manjula R Canagaratna, Andrew Freedman, J T JayneAbstract:Glass transitions from liquid to semi-solid and solid phase states have important implications for reactivity, growth, and cloud forming (cloud condensation nuclei and ice nucleation) capabilities of secondary organic aerosols (SOA). The small size and relatively low mass concentration of SOA in the atmosphere make it difficult to measure atmospheric SOA glass transitions using conventional methods. To circumvent these difficulties, we have adopted a new technique for measuring glass forming properties of atmospherically relevant organic aerosols. Aerosol particles to be studied are deposited in the form of a thin film onto an interdigitated electrode (IDE) using electrostatic precipitation. Dielectric Spectroscopy provides dipole relaxation rates for organic aerosols as a function of temperature (373 to 233 K) that are used to calculate the glass transition temperatures for several cooling rates. IDE-enabled broadband Dielectric Spectroscopy (BDS) was successfully used to measure the kinetically controlled glass transition temperatures of glycerol and citric acid aerosols with selected cooling rates. The glass transition results agree well with available literature data for these two compounds. The results indicate that the IDE-BDS method can provide accurate glass transition data for organic aerosols under atmospheric conditions. The BDS data obtained with the IDE-BDS technique can be used to characterize glass transitions for both simulated and ambient organic aerosols and to model their climate effects.