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Copyright of Earthquake (1000-3274) is the property of Editorial Office of Earthquake Journal and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Time-resolved microwave conductivity (TRMC) is a contactless technique utilized for the investigation of carrier density, transport properties, trapping phenomena, and recombination parameters in charge transport materials. Traditional TRMC methods rely on resonant cavities or resonators, which impose limitations on the frequency range and accuracy of measurements. In this study, we introduce an innovative approach that employs a non-resonant coplanar transmission line and a microwave interferometric detection scheme to investigate the phase-dependent complex microwave conductivity. Additionally, we demonstrate unique calibration techniques for determining the absolute complex microwave conductivity by combining transient photoconductivity (TPC) and electron spin resonance (ESR) as complementary methods. By utilizing a phase-sensitive microwave interferometer, our detection scheme significantly enhances measurement sensitivity and eliminates the need for a resonant cavity. This broadband detection system enables direct measurement of phase-dependent changes in film conductivity (Δσ). Moreover, it allows us to measure subtle variations in sample photoconductivity upon optical excitation and accommodates greatly restricted volumes (∼nL) consistent with typical device sizes. Here we demonstrate the utility of this technique on a series of poly(3-hexylthiophene) (P3HT) and the electron acceptor [6,6]-phenylC61-butyric acid methyl ester (PCBM) thin films with varying concentrations of PCBM and film thickness.

Dynamic processes in catalysis are gaining increased attention and could very well be one of the next frontiers in surface science. One way to study such processes is to induce chemical changes on the surface for example by periodically adjusting the (electro)chemical potential in situ and identify the resulting spectral changes. Often this is referred to as Modulation Excitation Spectroscopy (MES). Using Ambient Pressure Photoelectron Spectroscopy data, we here discuss and compare the analysis of MES data using both Phase Sensitive Detection (PSD) and Fourier analysis. We discuss that PSD determines the component magnitude at a user-defined phase value while Fourier analysis provides the maximum oscillation amplitude and respective phase value of oscillating spectral features. We discuss advantages and disadvantages of the different analysis schemes and explore how the full time-evolution can be obtained. [Display omitted] • Phase Sensitive Detection and Fourier analysis are compared for the first time • Pros and cons and limitations of the PSD and Fourier analysis are discussed in detail • Fourier analysis enables on-the-fly detection of oscillating minority species in situ • For the special case of APXPS this enables structure-activity correlation • We hope our work will inspire many future studies of oscillating surface structures [ABSTRACT FROM AUTHOR]

A system was developed that allows different acoustic parameters to be measured inside the frequency audio range and that can be used in different propagation mediums. A simple configuration of fiber optic sensors based on multimodal interference (MMI) is used, due to the advantages they provide. To perform a spatial and frequency filtering according to the characteristics of the source of interest, a beamformer is applied to the data obtained and then phase sensitive detection is used to obtain the resulting signal. The simulations were made by replicating the existing conditions in the experiments subsequently made in the laboratory. The system showed that the combination of the proposed techniques increases the signal-to-noise ratio even in cases where the ambient noise exceeds the signal of interest several times. [ABSTRACT FROM AUTHOR]

Copyright of Experimental Technology & Management is the property of Experimental Technology & Management Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A radar system has been developed to predict global warming by measuring ice-shelf thicknesses. This system uses a frequencymodulated continuous-wave(FMCW) waveform and phase-sensitive method through the so-called Vernier-like process, which measures the target range by adding the fine range from the phase information to the rough range from the frequency. However, the continuous waves require a large dynamic range of the receiver because short-range and long-range reflection signals are received simultaneously. To improve this, we propose a frequency-modulated interrupted continuous wave(FMICW) method and demonstrate its performance through simulation. Although the proposed method reduces the signal-to-noise ratio(SNR) based on the same peak power, the gain can be adjusted according to the range, and the minimum detection range can be controlled. [ABSTRACT FROM AUTHOR]

Phase-sensitive surface plasmon resonance biosensors are known for their high sensitivity. One of the technology bottle-necks of such sensors is that the phase sensorgram, when measured at fixed angle set-up, can lead to low reproducibility as the signal conveys multiple data. Leveraging the sensitivity, while securing satisfying reproducibility, is therefore is an underdiscussed key issue. One potential solution is to map the phase sensorgram into refractive index unit by the use of sensor calibration data, via a simple non-linear fit. However, basic fitting functions poorly portray the asymmetric phase curve. On the other hand, multi-layer reflectivity calculation based on the Fresnel coefficient can be employed for a precise mapping function. This numerical approach however lacks the explicit mathematical formulation to be used in an optimization process. To this end, we aim to provide a first methodology for the issue, where mapping functions are constructed from Bayesian optimized multi-layer model of the experimental data. The challenge of using multi-layer model as optimization trial function is addressed by meta-modeling via segmented polynomial approximation. A visualization approach is proposed for assessment of the goodness-of-the-fit on the optimized model. Using metastatic cancer exosome sensing, we demonstrate how the present work paves the way toward better plasmonic sensors.

This paper presents the quadrature sinusoidal oscillators for a phase sensitive detection (PSD) system. The proposed oscillators are design by using the commercially available ICs (LT1228). The core oscillator consists of three LT1228s: two grounded capacitors and one resistor. By adding four resistors without the requirement of additional active devices, the amplitudes of two quadrature waveforms become adjustable. The quadrature output nodes are of low impedance, which can be connected to the impedance sensor or other circuits in a phase sensitive detection system without the need of buffer devices. The amplitudes of the quadrature waveform are equal during the frequency of oscillation (FO) tuning. The frequency of oscillation is electronically and linearly controlled by bias current or voltage without affecting the condition of oscillation (CO). Furthermore, the condition of oscillation is electronically controlled without affecting the frequency of oscillation. The performances of the proposed oscillators are experimentally tested with ±5 voltage power supplies. The frequency of the proposed sinusoidal oscillator can be tuned from 8.21 kHz to 1117.51 kHz. The relative frequency error is lower than 3.12% and the relative phase error is lower than 2.96%. The total harmonic distortion is lower than −38 dB (1.259%). The voltage gain of the quadrature waveforms can be tuned from 1.97 to 15.92. The measurement results demonstrate that the proposed oscillators work in a wide frequency range and it is a suitable choice for an instrument-off-the-shelf device

Copyright of China Sciencepaper is the property of China Sciencepaper and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A new, non-contact, planar spiral coil-based inductive displacement sensor is presented in this paper. The proposed sensor employs a fixed planar coil and a movable $U$ -shaped magnetic core. The sensor is designed such a way that the shape of inductance versus displacement x$ is sinusoidal. Due to this feature, the value of x$ is obtained easily from the inductance measured without the need of a look-up table, which is not the case for most of the planar coil-based sensors. The proposed sensor has very low sensitivity to vertical misalignment of the core. A phase-sensitive detector-based measurement scheme is employed to measure the inductance. The inductance characteristic of the proposed sensor is symmetric with respect to the center of the coil. A simple capacitive detection scheme to distinguish the position of the core between the two halves of the coil is proposed in this paper. This method enables to extend the sensor range with multiple coils connected in series. A prototype of the proposed sensor has been developed and tested. The sensor has a worst case error of 0.6%. A modified sensor using two coil sets has been developed. The modified sensor has high sensitivity over its entire range, unlike the first prototype. It has a worst case error of 0.2% and a resolution of 6.5 . The low-cost sensor developed will be useful for many industrial linear position sensing applications. [ABSTRACT FROM PUBLISHER]

This paper presents a low-power fully integrated quadrature signal generator for system-on-chip (SoC) impedance spectroscopy applications. It has been designed in a 0.18 μm-1.8 V CMOS technology as a self-contained oscillator, without the need for an external reference clock. The frequency can be digitally tuned from 10 to 345 kHz with 12-bit accuracy and a relative mean error below 1.7%, thus supporting a wide range of impedance sensing applications. The proposal is experimentally validated in two impedance spectrometry examples, achieving good magnitude and phase recovery results compared to the results obtained using a commercial LCR-meter. Besides the wide frequency tuning range, the proposed programmable oscillator features a total power consumption lower than 0.77 mW and an active area of 0.129 mm2, thus constituting a highly suitable choice as stimulation module for instrument-on-a-chip devices.

This paper presents a simple and efficient interfacing scheme for passive LC sensors, connected to the measurement unit through a magnetically coupled readout and sensor coils. The proposed scheme always measures at or near the parallel resonant frequency fp of the system. The scheme first converts the capacitance of the sensor into a phase angle ( \phi ) between the excitation voltage ( V_{\textrm {in}} ) and the current I_{1} through the readout coil. The final output is given by tan( \phi ), but easily realized using a phase sensitive detector (PSD). The inputs to the PSD are V_{\textrm {in}} and a signal proportional to the I_{1} . This new approach gives the following advantages: 1) it realizes a simple, hardware optimized measurement system, which draws the minimum current from V\textrm {in} as the measurement is at fp ; 2) the time taken for the measurement is much less, compared with the frequency sweep approach; 3) the output is linear; and 4) the output is insensitive to the variations in the coupling coefficient ( k ), for a wide range of $k$ . In addition, a new, but simple method is employed to calibrate the system from the readout coil side. This enables the output to be less sensitive to the variation in the quality factor, coupling coefficient, and resistance of the coil. A prototype of the proposed readout system has been developed and tested for a range of ±5 pF. The output of the interfacing scheme showed a high sensitivity of 5.5°/pF. The worst case linearity noted was 0.52% and the worst case error observed in the test was less than 0.67%. [ABSTRACT FROM PUBLISHER]

We demonstrate a self-heterodyne terahertz (THz) frequency-domain spectrometer in which commercially available uni-traveling-carrier photodiodes (UTC-PDs) are used as opticalto-electrical (O/E) converter and optoelectronic mixer (OEM). The optical intensity beat generated by mixing two frequency-detuned free-running 1.55 μm laser diodes (LDs) is used as a source for the photomixing at the O/E converter, and as an optical local oscillator (LO) signal for the OEM. The frequency of the optical LO signal is coherently shifted with an electrooptic frequency shifter so that the heterodyne detection is realized using free-running LDs for the beat source. We investigate the sensitivity characteristics of the spectrometer as functions of diode bias voltage and optical LO level. The maximum signal-to-noise ratio of 47 dB for the RF power of -16 dBm is achieved at 300 GHz with the lock-in time constant of 23.4 ms. The standard deviation of the phase measurement is 0.73°, where the amplitude noise limited standard deviation is 0.25°. We measure the system response ranging from 200 to 1450 GHz and find that it fits well the response which is calculated using the frequency characteristics of the output power of the UTC-PDs. Our results show that UTC-PDs are promising candidates not only for the high-power terahertz wave generator, but also for the wideband THz-OEM. Integration of UTC-PDs with free-running LDs on the same substrate with the same process steps would significantly reduce the cost and size of the present spectrometer. [ABSTRACT FROM PUBLISHER]

Dual-phase lock-in amplifiers (LIAs) are designed to extract information (amplitude and phase) from signals buried in high noise levels. In spite of their popularity, their use has been traditionally limited to input sinusoidal waves with symmetric power supplies. This paper presents an algorithm that enables single-supply analog LIAs to properly process input square waves. Formed by linear equations, its computational implementation is much simpler than that of the traditional sinusoidal algorithm. Moreover, applied to battery-operated microcontrolled systems where square signals can be generated by the embedded microcontroller, it presents intrinsic advantages such as simplicity, versatility, and reduction in power and size. Experimental results validate the proposed algorithm, confirming its enormous possibilities in sensing applications. [ABSTRACT FROM PUBLISHER]

We propose and demonstrate a technique for phase change measurement of a continuous terahertz (THz) wave, based on 1.55-\mum photonic techniques. The generation of the THz wave is based on photomixing using a uni-traveling-carrier photodiode. The detection of the THz wave is based on heterodyne mixing of the THz wave, using a low-temperature-grown GaAs photoconductor with frequency-shifted photonic local oscillator signal. The measurement of a phase shift induced by a single sheet of paper with 85-\mum thickness has been demonstrated at 300 GHz. [ABSTRACT FROM PUBLISHER]

Abstract: A new type of differential surface plasmon (SPR) sensor integrated with a microfluidic system is presented. The working principle of the microfluidic device is based on hydrodynamic modulation of two laminar streams inside a microchannel to provide periodic changes of the environment on the SPR sensor. The modulated reflectance is then demodulated using a lock-in amplifier. The presented sensor provides sensitivities of index of refraction about 4×10−8 RIU together with a 4 orders of magnitude dynamic range. This method demonstrates a sensitive detection scheme which could be used for label-free detection. [Copyright &y& Elsevier]

In Photoacoustic experiments and low frequency Photodiode applications, Phase sensitive detection is one of the basic operations performed by a lock-in amplifier. Regrettably, it is common to use only basic functions of those devices, in spite of their high cost. The objective of this research is to show the results that were obtained from the development and design of a basic phase shift sensitive device using reconfigurable hardware, which allows a reduction in experimental costs while generating the possibility to apply the developed device in different research fields. [ABSTRACT FROM AUTHOR]

Abstract: Using finite-difference time-domain method, we investigate phase and amplitude reflective properties of a metallic photonic crystal slab comprising a two-dimensional array of gold disks placed on top of a thin gold film resting on a dielectric substrate. Photonic crystal slab overcladding is a gaseous analyte. Throughout the paper we discuss prospectives of application of such photonic crystal slabs to sensing of changes in the gas refractive index. We start by studying the field distributions and spectral positions of two types of surface plasmons supported by such PhCs as a function of the photonic crystal lattice period, the gold film thickness, and the gold disk size. First, we find that the spectral positions of plasmon peaks depend almost linearly on the photonic crystal lattice constant, which is a manifestation of the delocalized nature of a plasmon extending over the PhC lattice. This is possible due to connectivity between metallic disks via an underlying thin metallic film. Second, we find that the width of plasmonic peaks is highly sensitive to the relative size of the metallic disks compared to the lattice period. This can be well explained via interaction between the localized plasmons situated at the disc edges in the adjacent unit cells. We therefore find that plasmons in the metallic PhC slabs featuring metallic discs connected by a metallic film exhibit both strong local and non-local properties. Third, we find that, generally, there are two types of plasmons supported by such metallic PhCs. One type is a plasmon with a large fraction of its field located in the gas overcladding, which is most suitable for sensing. In contrast, another plasmon type has its field concentrated at the interface between a thin metal film and a substrate; such plasmons are only weakly sensitive to the refractive index of the sensor overcladding, and, therefore, can serve as convenient references for the sensor measurements. Finally, we report sensor sensitivities to changes in the real part of the gas refractive index when using amplitude and phase-based detection strategies. We start by demonstrating that when measured in the sensor far field, the phase sensitive detection provides much lower detection limit ( RIU) compared to that of the amplitude-based detection ( RIU). We then find that sensor phase and amplitude sensitivities can be considerably enhanced when performing measurements using point detectors placed in the near field of a sensor. Particularly, we have established that both phase and amplitude sensitivities are maximal when measured in the sensor near field along the normal to the sensor surface going through the point of the highest symmetry of a photonic crystal unit cell ( point). Sensor resolution as high as RIU for the phase-based detection and RIU) for the amplitude-based detection are found, with the most dramatic enhancement observed for the phase detection approach. We believe that experimental verification of the sensor sensitivity enhancement using phase detection in the sensor near field can be accomplished by using scanning near-field optical microscopy. [Copyright &y& Elsevier]

We analyze the properties of InAs-GaAs quantum-dot semiconductor optical amplifiers operating around 1300 nm. Using radiofrequency current modulation and phase sensitive detection, we characterize the phase-amplitude coupling (alpha-factor) as a function of injection current density. We obtain values for a up to 39 when the ground state is heavily saturated, and demonstrate large-signal phase modulator operation of the device. [ABSTRACT FROM PUBLISHER]

Abstract: We determine the linewidth of the hyperfine structure a 10 component of R(56) 32-0 transition of 127I2 at 532nm using the dependence of the peak amplitude of the third-derivative signal on the modulation width. We also use the same method to investigate pressure broadening and power broadening of the a 10 component. [Copyright &y& Elsevier]

Modulation spectroscopy can be an adequate tool to separate a weak system response from a huge background absorption, provided the process under consideration enables a periodic external stimulation. Phase sensitive detection (PSD) is then used to demodulate the periodic system response. We introduce a new method of PSD that can be used in modulated excitation (ME)-FTIR spectroscopy without the need of a lock-in amplifier or spectrometer build-in hardware. An advantage of this method is that only standard procedures included in all FTIR instruments, such as the measurement of time-resolved spectra, are required. The principal mathematical formalism of the used PSD is described.As an example we show phase-resolved spectra of the amid I′ region obtained from temperature modulated FTIR spectroscopic experiments of RNase A. The advantage of the ME compared to a relaxation process is shown by the power of separation of overlapping absorption bands. [Copyright &y& Elsevier]

To detect the flaws of bearing steel ball and sort its quality on-line, a kind of online quality detecting and sorting system for bearing steel ball is developed, which based on the eddy current inspection theory. The design of scheme, circuit and mechanical structure of the system is described in detail. PSD(Phase Sensitive Detection) is applied to pick up the signal of cracks and restrain interferential signal. The flaws will be quantificational analysed based on the X-R orthogonal decomposition technology which include the size and depth information of flaws. By analysing and processing the amplitude and phase of the defect signal, the flaws can be found with high accuracy and low error-detected ratio. ARM and MCU Processor ensures the real-time ability of discriminating algorithm. The CPLD is used for generating reference signal which can be easy to get synchronous with the source signal. It has good properties of real-time to detect the quality of bearing steel ball.

Phase-sensitive surface plasmon resonance biosensors are known for their high sensitivity. One of the technology bottle-necks of such sensors is that the phase sensorgram, when measured at fixed angle set-up, can lead to low reproducibility as the signal conveys multiple data. Leveraging the sensitivity, while securing satisfying reproducibility, is therefore is an underdiscussed key issue. One potential solution is to map the phase sensorgram into refractive index unit by the use of sensor calibration data, via a simple non-linear fit. However, basic fitting functions poorly portray the asymmetric phase curve. On the other hand, multi-layer reflectivity calculation based on the Fresnel coefficient can be employed for a precise mapping function. This numerical approach however lacks the explicit mathematical formulation to be used in an optimization process. To this end, we aim to provide a first methodology for the issue, where mapping functions are constructed from Bayesian optimized multi-layer model of the experimental data. The challenge of using multi-layer model as optimization trial function is addressed by meta-modeling via segmented polynomial approximation. A visualization approach is proposed for assessment of the goodness-of-the-fit on the optimized model. Using metastatic cancer exosome sensing, we demonstrate how the present work paves the way toward better plasmonic sensors. [ABSTRACT FROM AUTHOR]

Infrared spectroscopy is typically not used to establish the oxidation state of metal-based catalysts. In this work, we show that the baseline of spectra collected in diffuse reflectance mode of a series of Pd/Al2O3 samples of increasing Pd content varies significantly and reversibly under alternate pulses of CO or H2 and O2. Moreover, these baseline changes are proportional to the Pd content in Pd/Al2O3 samples exhibiting comparable Pd particle size. Similar measurements by X-ray absorption spectroscopy on a different 2 wt.% Pd/Al2O3 confirm that the baseline changes reflect the reversible reduction-oxidation of Pd. Hence, we demonstrate that changes in oxidation state of metal-based catalysts can be determined using diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and that this behavior is part of the spectral changes that are returned by experiments under operando conditions. [ABSTRACT FROM AUTHOR]

Methane is a well-established fuel molecule whose production from CO 2 through methanation garners increasing interest as an energy storage solution. While often produced with Ni based catalysts, other metals are of interest thanks to higher robustness and activity-selectivity numbers. The Rh/CeO 2 catalyst has shown appreciable properties for CO 2 methanation and its structural dynamics has been studied in situ. However, the reaction pathway is unknown. Here, we present infrared modulation excitation spectroscopy measurements with phase sensitive detection of a Rh/CeO 2 catalyst adsorbate composition during H 2 pulsing (0–2 vol.%) to a constant CO 2 (0.5 vol.%) feed. Various carbonyl (CO) and carbonate (b-CO 3 /p-CO 3 ) ad-species clearly respond to the hydrogen stimulus, making them potential reaction intermediates. The different CO ad-species are likely intermediates for product CO and CH 4 but their individual contributions to the respective formations are not unambiguously ascertained. As for the carbonate dynamics, it might be linked to the reduction/oxidation of the CeO 2 surface upon H 2 pulsing. Formate (HCOO) ad-species are clearly visible but appear to be, if not spectators, linked to slow side reactions possibly also affected by CeO 2 redox processes. [ABSTRACT FROM AUTHOR]

This paper presents the quadrature sinusoidal oscillators for a phase sensitive detection (PSD) system. The proposed oscillators are design by using the commercially available ICs (LT1228). The core oscillator consists of three LT1228s: two grounded capacitors and one resistor. By adding four resistors without the requirement of additional active devices, the amplitudes of two quadrature waveforms become adjustable. The quadrature output nodes are of low impedance, which can be connected to the impedance sensor or other circuits in a phase sensitive detection system without the need of buffer devices. The amplitudes of the quadrature waveform are equal during the frequency of oscillation (FO) tuning. The frequency of oscillation is electronically and linearly controlled by bias current or voltage without affecting the condition of oscillation (CO). Furthermore, the condition of oscillation is electronically controlled without affecting the frequency of oscillation. The performances of the proposed oscillators are experimentally tested with ±5 voltage power supplies. The frequency of the proposed sinusoidal oscillator can be tuned from 8.21 kHz to 1117.51 kHz. The relative frequency error is lower than 3.12% and the relative phase error is lower than 2.96%. The total harmonic distortion is lower than −38 dB (1.259%). The voltage gain of the quadrature waveforms can be tuned from 1.97 to 15.92. The measurement results demonstrate that the proposed oscillators work in a wide frequency range and it is a suitable choice for an instrument-off-the-shelf device [ABSTRACT FROM AUTHOR]

Light Detection and Ranging (LIDAR) is a remote sensing technique that measures properties of backscattered light in order to obtain information of a distant target. This work presents a method to improve the signal-to-noise ratio by 8 dB with respect to the direct detection of the backscattered signal of a LIDAR system. This method consists of the measurement of the Fourier coefficients of the LIDAR signal, which is possible thanks to the novel coupling of a sequential equivalent time base sampling (SETS) circuit and a conventional lock-in amplifier that allows to measure the Fourier coefficients of the LIDAR signal, the results are comparable to noise elimination using Empirical Mode Decomposition. The feasibility of the proposal is demonstrated experimentally with mist. The method can be used to different applications of elastic-scattering LIDAR under the conditions of the devices for applied the phase sensitive detection. [ABSTRACT FROM AUTHOR]

The excess noise due to impact ionization has been measured explicitly for the first time in In0.53Ga0.47As. By using a phase sensitive detection technique, the noise due to avalanche current was determined even in the presence of high tunneling currents. The excess noise due to pure electron injection measured on a series of thick In0.53Ga0.47As p+-i-n+ diodes suggests large electron to hole ionization coefficient ratio between 3.7 at electric field of 310 kV·cm-1 to 5.3 at 260 kV·cm-1. Excess noise was also measured at fields as low as 155 kV·cm-1 suggesting that significant impact ionization occurs at these low fields. The multiplication and excess noise calculated using published ionization coefficients and ignoring dead space effects, gave good agreement with the experimental data for mixed and pure electron injection. [ABSTRACT FROM PUBLISHER]