Search

A low-cost microwave resonator sensor for angular displacement detection is proposed. The sensor uses a strip-loaded dielectric resonator (SLDR) as the key element. The sensor operates in the reflection mode, i.e. by producing a variation in the reflection coefficient (S11) according to the angular position of the SLDR relative to a microstrip transmission line. The primary advantage of the proposed strategy is its fixed-frequency operation enabling the S11 measurement with a low-cost reflectometer, thereby avoiding the costly vector network analyzer (VNA). Design modelling and initial analysis of the sensor are performed with ANSYS HFSS software. To demonstrate proof of concept, a sensor prototype is fabricated and experimentally characterized with a custom-made reflectometer. Results are compared against VNA-based measurements to be in decent agreement. The proposed sensor exhibits 0.43 dB/0 sensitivity over the dynamic range of 00–900. [ABSTRACT FROM AUTHOR]

Copyright of Afyon Kocatepe University Journal of Science & Engineering / Afyon Kocatepe Üniversitesi Fen Ve Mühendislik Bilimleri Dergisi is the property of Afyon Kocatepe University, Faculty of Science & Literature 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.)

In recent years, flexible pressure sensors have garnered significant attention. However, the development of large-area, low-cost, and easily fabricated flexible pressure sensors remains challenging. We designed a flexible fiber optic pressure sensor for contact force detection based on the principle of backward Rayleigh scattering using a single-mode optical fiber as the sensing element and polymer PDMS as the encapsulation material. To enhance the sensor's sensitivity and stability, we optimized its structural design, parameters, and fabrication process and measured the fiber strain using an optical frequency domain reflectometer (OFDR). The results showed that the sensor achieved a high sensitivity of 6.93247 με/kPa with a PDMS concentration ratio of 10:1, a curing time of 2 h, and a substrate thickness of 5 mm. The sensor demonstrated excellent linearity and repeatability in static performance tests and was successfully used to monitor the plantar pressure distribution in real time. This flexible fiber optic pressure sensor can be developed via a simple fabrication process, has a low cost, and has high sensitivity, highlighting its potential applications in smart wearables and medical diagnostics. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Engineering (17264073) is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) 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.)

The design of a time-of-flight neutron reflectometer proposed for the new generation of compact neutron sources is presented. The reflectometer offers the possibility to use spin-polarized neutrons. The reflectometer design presented here takes advantage of a cold neutron source and uses neutrons with wavelengths in the range of 2–15 Å for the unpolarized mode. In general, due to tight spatial restrictions and the need to avoid moving parts inside the beam channel, a multi-channel collimator guide and reflective neutron guide are used for the first section of the instrument. This enables definition of the desired wavelength band and easy selection of one out of three different Q-resolutions. A low background for the collimator system and the reflectometer is ensured by employing a tangential beam channel and an in-channel sapphire filter. The second section is the time-of-flight (TOF) system, which uses a double-disk neutron chopper followed by polarization elements, the sample environment and the neutron detector system. Monte Carlo simulations and neutron beamline intensity measurements are presented. The design considerations are adoptable for neutron sources where space is limited and sections of the instrument are in a high-radiation environment. [ABSTRACT FROM AUTHOR]

JET's frequency-modulated continuous wave (FMCW) reflectometers have been operating well with the current design since 2005, and density profiles have been automatically calculated intershot since then. However, the calculated profiles had long suffered from several shortcomings: poor agreement with other diagnostics, sometimes inappropriately moving radially by several centimeters, elevated levels of radial jitter, and persistent wriggles (strong unphysical oscillations). In this research, several techniques are applied to the reflectometry data analysis, and the shortcomings are significantly improved. Starting with improving the equilibrium reconstruction that estimates the background magnetic field, adding a ripple correction in the reconstructed magnetic field profile, and adding new inner-wall reflection positions estimated through ray-tracing, these changes not only improve the agreement of reconstructed profiles to other diagnostics but also solve density profile wriggles that were present during band transitions. Other smaller but also persistent wriggles were also suppressed by applying a localized correction to the measured beat frequency where persistent oscillations are present. Finally, the burst analysis method, as introduced by Varela et al. [Nucl. Fusion 46 S693 (2006)], has been implemented to extract the beat frequency from stacked spectrograms. Due to the strong suppression of spurious reflections, the radial jitter that sometimes would span several centimeters has been strongly reduced. The stacking of spectrograms has also been shown to be very useful for stacking recurring events, like small gas puff modulations, and extracting transport coefficients that would otherwise be below the noise level. [ABSTRACT FROM AUTHOR]

Fiber-optic sensors for identifying liquids and determining the concentration of solutions have been studied with the possibility of using various types of single-mode optical fibers produced by industry and widely used in optical cables and telecommunications to create sensors for identifying liquids and determining the concentration of solutions. To identify liquids with different refractive indices and determine the concentration of substances dissolved in water, the peak value of the reflectograms of the optical fiber located at the interface between the optical fiber core and the environment can be used as an information parameter. The value of the information parameter depends on the refractive index of the liquid in which one end of the optical fiber is located. The parameters of fiber-optic sensors for identifying liquids and determining the concentration of solutions were studied by optical reflectometry in different wavelength ranges of optical radiation with a duration of reflectometer probe pulses from 25 to 300 ns. It has been established that the fiber-optic sensor can operate at any wavelength of optical radiation corresponding to the transparency windows of the optical loss spectrum of the optical fiber. The influence of the length of the optical fiber between the recording device and the place where the concentration of a liquid solution is determined using a fiber-optic sensor was studied. The possibility of creating a fiber-optic sensor for determining the concentration of the liquid solutions based on optical fibers has been demonstrated.

The need for size and cost-efficient vector network analyzer (VNA) frequency extension modules (VNAX module) is driven by new applications in research and industry. Responding to this potential demand, we present a novel D-band VNAX module based on a single SiGe MMIC. Our work addresses the challenges associated with integrating components on a single chip compared to conventional commercial modules, which typically rely on discrete components. We provide a comprehensive discussion covering the performance of system blocks, such as multiplier chains and receivers, and their impact on the module's performance. In addition, we present extensive measurements of the entire system, including magnitude-and phase stability and dynamic ranges. At a resolution bandwidth (RBW) of 10 Hz, our module shows a system dynamic range (SDR) above 90 dB for the frequency range of 110 GHz to 151 GHz and a maximum SDR close to 100 dB at 122 GHz. The corresponding receiver dynamic range within the D-band ranges from 113 dB to 125 dB, and the Test Port power is between −27 dBm and −16 dBm. In addition, we present and evaluate several measurements of different passive components that verify the calibration capability of our module.

We describe a method for reducing the cost of optical frequency domain reflectometer (OFDR) hardware by replacing two reference channels, including an auxiliary interferometer and a gas cell, with a single channel. To extract useful information, digital signal processing methods were used: digital frequency filtering, as well as empirical mode decomposition. It is shown that the presented method helps to avoid the use of an unnecessary analog-to-digital converter and photodetector, while the OFDR trace is restored by the equal frequency resampling (EFR) algorithm without loss of high resolution and with good measurement repeatability. [ABSTRACT FROM AUTHOR]

The IOWN Global Forum has proposed the Open All-Photonic Network (Open APN) as a network infrastructure that achieves low latency and low power consumption and issued an architecture document entitled "Open All-Photonic Network Functional Architecture," in early 2022. This article introduces the activities carried out since the release of the above architecture document to detail the Open APN architecture and promote its practical application. [ABSTRACT FROM AUTHOR]

The full design of a liquid neutron reflectometer for China spallation neutron source is reported. The horizontal sample geometry enables studies on both solid and liquid samples. A neutron beam with a wavelength range from 1 to 10 Å and neutron flux intensity of 4 × 107 n/cm2/s was optimized for the classical specular reflection. A multi-blade detector with high detection efficiency and a high neutron counting rate was used to ensure the performance of neutron detection. Data acquisition and reduction routines were demonstrated to confirm the reliability of the measurements. The design and algorithms developed in this study pave the way for the future construction of liquid reflectometry for high-performance neutron scattering measurements. [ABSTRACT FROM AUTHOR]

We consider monochromators designed for operation with a point-like soft X-ray laser-plasma radiation source and intended for characterizing mirrors and other X-ray optical elements, including multilayer X-ray optics. Three compact (~0.6 m) high-resolution monochromators are calculated: a Hettrick–Underwood scheme with a plane VLS grating for the range from 110 to 160 Å, a single-element monochromator with a translatable plane VLS grating (120–155 Å), and a single-element monochromator with a classical spherical Rowland grating (110–160 Å). The spectral resolution of the configurations is assessed using numerical ray tracing. The capabilities of these monochromators are compared with the capabilities of monochromators using the three-element Czerny–Turner scheme. The "throughput" factor is used as a comparative criterion (figure of merit), provided that the spectral resolving power is sufficiently high (conventionally λ/δλ ~ 500 or higher). [ABSTRACT FROM AUTHOR]

Imaging using coherent extreme-ultraviolet (EUV) light provides exceptional capabilities for the characterization of the composition and geometry of nanostructures by probing with high spatial resolution and elemental specificity. We present a multi-modal tabletop EUV imaging reflectometer for high-fidelity metrology of nanostructures. The reflectometer is capable of measurements in three distinct modes: intensity reflectometry, scatterometry, and imaging reflectometry, where each mode addresses different nanostructure characterization challenges. We demonstrate the system's unique ability to quantitatively and non-destructively measure the geometry and composition of nanostructures with tens of square microns field of view and sub-nanometer precision. Parameters such as surface and line edge roughness, density, nanostructure linewidth, and profile, as well as depth-resolved composition, can be quantitatively determined. The results highlight the applicability of EUV metrology to address a wide range of semiconductor and materials science challenges. [ABSTRACT FROM AUTHOR]

The main challenges in 3D metrology involve measuring TSVs etched with very high aspect ratios, where the via depth to diameter ratio approaches 10:1–20:1. In this paper, we introduce an innovative approach to enhance our in-house spectroscopic reflectometer module by integrating aperture technology, resulting in a substantial amplification of interference signals. Our system offers the flexibility to conduct measurements on an average number of TSVs, individual TSVs, or specific periodic arrays of TSVs. Additionally, we demonstrate the utility of the spectroscopic reflectometer as a non-destructive, high-speed metrology solution for in-line monitoring of TSV etch uniformity. Through a series of experimental trials in a reactive ion etch (RIE) process, we show that leveraging feedback data from the reflectometer leads to marked improvements in etch depth uniformity. [ABSTRACT FROM AUTHOR]

The important in-field characterization of solar mirror reflectance can be performed by a variety of commercial portable reflectometers. In this study the most common commercially available reflectometers are evaluated in a campaign comparing different reflector materials, covering a wide range of realistic reflectance and specularity values. Where possible, measurements are compared to reference values measured with laboratory equipment. In general, good agreement between measurements is detected for highly specular mirrors (average deviation 0.005±0.004) and methods for improvement are proposed when deviations are detected. Important differences between measurements are found for less specular reflectors, which are caused by the disparity of the measurement parameters of the devices. These differences confirm that detailed knowledge about the device characteristics is important, to be able to correctly interpret and utilize gained results, especially for soiled and degraded mirrors.

The horizontal time-of-flight neutron reflectometer at the reactor of the Delft University of Technology, The Netherlands, has been completely renewed, relocated, and upgraded and allows for the study of air/liquid, solid/liquid, and solid/air interfaces. Innovations in the redesign include (i) a completely flexible double disk chopper system allowing to choose the optimal wavelength resolution with exchangeable neutron guide sections between the chopper disks to increase intensity, (ii) a movable second diaphragm just before the sample position to better control the beam footprint on the sample and effectively decrease counting times, and (iii) guides along the entire flight path of the neutron reflectometer. The performance of the renewed reflectometer is illustrated with measurements of hydrogen sensing materials. [ABSTRACT FROM AUTHOR]

The operating range of a distributed acoustic sensor based on a phase-sensitive optical time-domain reflectometer has been increased using an erbium-doped fiber amplifier with remote forward pumping. It is shown that by incorporating a single segment of erbium-doped fiber at a distance of 70 km and pumping it from the front end by a 500-mW laser at a wavelength of 1480 nm over the sensing fiber, it is possible to increase the operating range of the reflectometer by 45 km and, thereby, obtain the total operating range as large as 120 km along a standard single-mode fiber. [ABSTRACT FROM AUTHOR]

A new architecture of a fiber phase-sensitive optical time-domain reflectometer (φ-OTDR, i.e., a distributed acoustic sensor) suitable for engineering geology application is proposed. The sensor is based on a double-pulse scheme in which a pair of pulses is formed using an unbalanced Michelson interferometer. A symmetrical 3 × 3 coupler built into the Michelson interferometer is used to obtain the phase delay needed for the demodulation of the backscattered light. Using the unbalanced Michelson interferometer in the circuit for dual-pulse probe signal generation, it is possible to reduce the requirements for the degree of coherence of the light source, since the delay line introduced between the dual-pulse parts is compensated in the φ‑OTDR fiber under test. As a result, it is possible to use a laser with a wide spectral line (~1 GHz) and generate short (7-ns-wide) laser pulses by directly modulating the laser-diode injection current. In order to reduce the signal fading in the φ-OTDR and to improve the linearity of its response, responses are averaged over 16 optical frequencies. The efficiency of the proposed distributed acoustic sensor has been demonstrated by detecting a strong impact on a cable that was horizontally buried in the ground as well as by detecting seismic waves using a cable inserted in a well at the sea bottom. [ABSTRACT FROM AUTHOR]

A fiber phase-sensitive optical time-domain reflectometer (a distributed acoustic sensor) with a low-noise output signal in the frequency range of 0.01−1 Hz is proposed for seismology applications. The sensor architecture is based on an unbalanced Mach−Zehnder interferometer, which is used to form a dual-pulse probe signal with required phases of its components and to stabilize the frequency of the laser source in the feedback circuit. The low noise level of the output signal is achieved in the proposed circuit by compensating for the difference in the optical paths of the dual-pulse probe signal fields scattered by different fiber sections. The applicability of the proposed circuit has been experimentally demonstrated by detecting a remote earthquake using a fiber-optic cable located at the bottom of the Black Sea. [ABSTRACT FROM AUTHOR]

The range of applications for distributed fiber-optic sensors is constantly expanding due to both the growing needs of industry and the development of the measurement capabilities of the sensors themselves. In connection with the need to develop methods for interpreting sensor signals, it is extremely important to form sets of test signals for distributed fiber-optic sensors obtained under known conditions and effects on the fiber. In the presence of reliable analytical models of signals from distributed fiber-optic sensors, it is extremely convenient to obtain test signals in the course of numerical experiments. The paper will consider the processes of formation of backscattering signals in Rayleigh reflectometric systems and describe physical and mathematical models that allow calculations of signals under different operating conditions. Two approaches for calculating the resulting backscatter signal are proposed: (1) based on the temporal representation of the probing signal and the impulse response of the sensitive fiber and (2) an alternative approach based on the spectral representation of the probing signal and the transfer function of the fiber. The presented results can be used both for direct simulation of the operation of reflectometric systems using Rayleigh scattering and for the analysis of existing limitations and the specifics of their operation. [ABSTRACT FROM AUTHOR]

Simple measures to improve the signal-to-noise ratio of optical frequency domain reflectometer (OFDR) readings are described. After applying a two-stage optical amplification of the backscattered signal, as well as eliminating the source of spurious reflections, it was possible to increase the signal-to-noise ratio of the frequency domain trace from 8 to 19 dB. This technique can be applied in fiber optic sensors and metrology of fiber optic and integrated optical elements. [ABSTRACT FROM AUTHOR]

The KINX and VENUS codes were used for simulation of the baseline inductive and steady-state scenarios of the ITER tokamak operation. The perturbations of plasma electron density and magnetic field caused by the Alfvén modes were calculated in the flux coordinates for these scenarios. The perturbation fields obtained were converted into the engineering coordinates in order to calculate the propagation of probe electromagnetic radiation of the reflectometer using the two-dimensional full-wave TAMIC RτX code in the expected geometry of the experiment. The calculations performed show that for the baseline inductive scenario, in the case of reflection of the extraordinary wave at the lower cutoff frequency from the high magnetic field side, the electric field relative perturbations of the reflected reflectometer signal correspond to the margin of linear range of the diagnostics operation or even go out of this range. It was found that in a number of scenarios, not only the electron density perturbations, but also the magnetic field perturbations significantly contribute to the total signal perturbations that makes even more difficult the further data interpretation. Another possible problem is the narrow frequency range of probing frequencies where the Alfvén mode can be observed. In addition to simulating the reflection of electromagnetic waves from plasma, it was analyzed also the possibility of measuring the Alfvén modes parameters when the extraordinary wave pass through the plasma in the transparency window between the upper and lower cutoff frequencies of the extraordinary wave (refractometry). It is shown that at the fundamental frequency, the phase perturbations range from 3 to 60 degrees, which makes it impossible to use the amplitude-modulated refractometer for analyzing signals. The "synthetic diagnostics" approach was used, which showed itself well for simulating the operation of reflectometers at plasma facilities. [ABSTRACT FROM AUTHOR]

Plasma Position Reflectometry (PPR) is planned to provide plasma position and shape information for plasma operation in future fusion reactors. Its primary function is to calibrate the drift of the magnetic signals due to the integral nature of magnetic measurement. Here, we attempt to measure plasma position using ordinary mode (O-mode) and extraordinary mode (X-mode) reflectometry systems on two tokamaks. A new physical model based on the phase shift is proposed to deduce the relative movement of the cut-off layer without density inversion. We demonstrate the plasma position measurements by absolute measurement from density profile inversion and relative measurement from phase shift. The combination of X-mode and O-mode reflectometers can minimize the limitations of single polarization reflectometry and further increase the accuracy of plasma position measurement. These results could provide an important technical basis for the further development of a real-time control system based on PPR. [ABSTRACT FROM AUTHOR]

Among the characteristics of the low-temperature plasma often used in semiconductor processes, electron density plays an important role for understanding the plasma physics. Therefore, various studies involving invasive and non-invasive methods have been conducted to measure the electron density. This study aims to verify the possibility of measuring the electron density by simultaneously utilizing the characteristics of both invasive and non-invasive methods using a reflectometer attached to a commercial Wi-Fi antenna on a wafer in the vacuum chamber. The electron density was additionally measured using an interferometer and a single Langmuir probe under the same experimental conditions to assess the reliability of the reflectometer results, and the results were compared. The experiments were performed by increasing the 13.56 MHz radio frequency power applied to generate the plasma discharge in the 300 mm inductively coupled plasma bevel etcher equipment from 200 W to 400 W and 600 W, respectively. The electron densities measured using the three measurement methods (reflectometer/interferometer/single Langmuir probe) were confirmed to be in excellent agreement. Hence, the in-situ reflectometer on the wafer was verified to produce reliable results. [ABSTRACT FROM AUTHOR]

The paper presents the application of a phase-sensitive optical time-domain reflectometer (phi-OTDR) in the field of urban infrastructure monitoring. In particular, the branched structure of the urban network of telecommunication wells. The encountered tasks and difficulties are described. The possibilities of usage are substantiated, and the numerical values of the event quality classification algorithms applied to experimental data are calculated using machine learning methods. Among the considered methods, the best results were shown by convolutional neural networks, with a probability of correct classification as high as 98.55%. [ABSTRACT FROM AUTHOR]

In this paper, a wideband reflectometer based on six-port technology is presented. The designed six-port junction is built by using a modified ring power divider and three identical 90-degree hybrid couplers. The main difference from its initial application as a conventional six-port reflectometer is the addition of a fourth qi point. Here, the four power detectors are used to find the reflection coefficient (4 qi points) and a fifth detector is added as a reference. To simplify the fabrication process and minimize the cost, the six-port circuit is designed on a single-layer PCB. The measured results of the six-port junction reveal high performance over a large frequency band from 2.2 to 3.55 GHz. In order to evaluate its performance for real-time measurements, the proposed six-port reflectometer is then tested by measuring the reflection coefficient of different devices under test (DUTs). The measured results are then corrected by a simplified calibration method to have optimal results. Compared to conventional six-port calibration methods, the proposed calibration process is simple and allows accurate reflection coefficient measurements. After calibration, there is a great improvement in the corrected results of the reflection coefficient compared to the measured results which proves that the calibration process works perfectly from 2.6 to 3.8 GHz. [ABSTRACT FROM AUTHOR]

The study aims to investigate the ability of smart self-sensory carbon roving to detect damaged zones in TRC structures. State of the art monitoring procedures are based on integrative measurements and accordingly are limited in detecting only the occurrence of damage. This study aims to handle this limitation and offers to adopt the Time Domain Reflectometer (TDR) technique. The TDR concept is widely used in Bayonet Nut Coupling (BNC) cables to identify defects along the cable (opens, shorts, etc.). The current study adopts its principle to carbon rovings. To simulate the BNC cable configuration, the study offers to connect two parallel carbon rovings to the TDR Data Acquisition (DAQ) system. The proposed monitoring technique is investigated by loading two textile reinforced MPC beams under uniaxial tensile loading. Results show the potential of the suggested technique to locate damage zones in TRC structures and highlights its limitation. [ABSTRACT FROM AUTHOR]

This pattern recognition method can effectively identify vibration signals collected by a phase-sensitive optical time-domain reflectometer (Φ-OTDR) and improve the accuracy of alarms. An alignment-free end-to-end multi-vibration event detection method based on Φ-OTDR is proposed, effectively detecting different vibration events in different frequency bands. The pulse accumulation and pulse cancellers determine the location of vibration events. The local differential detection method demodulates the vibration event time-domain variation signals. After the extraction of the signal time-frequency features by sliding window, the convolution neural network (CNN) further extracts the signal features. It analyzes the temporal relationship of each group of signal features using a bidirectional long short-term memory network (Bi-LSTM). Finally, the connectionist temporal classification (CTC) is used to label the unsegmented sequence data to achieve single detection of multiple vibration targets. Experiments show that using this method to process the collected 8563 data, containing 5 different frequency bands of multi-vibration acoustic sensing signal, the system F1 score is 99.49% with a single detection time of 2.2 ms. The highest frequency response is 1 kHz. It is available to quickly and efficiently identify multiple vibration signals when a single demodulated acoustic sensing signal contains multiple vibration events. [ABSTRACT FROM AUTHOR]

In the present study, we aimed to evaluate the total directional hemispherical reflectance (THR) in expired and unexpired effervescent tablets. Expired tablets were stored in ambient conditions. The THR was measured using a SOC-410 Directional Hemispherical Reflectometer (Surface Optics Corporation, San Diego, CA, USA) in seven wavelength bands from ultraviolet, through visible, to near-infrared light. Significantly higher values of THR for the ranges of 700–1100 nm and 1700–2500 nm were observed for expired tablets than for unexpired tablets (p < 0.001). The measurement of THR may be a rapid method to detect adverse physicochemical changes in effervescent tablets and can be used for a further detailed evaluation of active pharmaceutical ingredients (APIs) and related degradation products. [ABSTRACT FROM AUTHOR]

In the present study, we aimed to determine whether the shelf life of effervescent tablets may be assessed during storage using total directional hemispherical reflectance (THR). We also analyzed selected pharmacopeial parameters of the tablets and used X-ray microtomography to assess the internal structure of the tablets. Two types of effervescent tablets of one commercial product containing magnesium and vitamin B6 (expired and unexpired) were analyzed. In addition, randomly selected unexpired and expired tablets were dried in a vacuum oven for 24 h at 50 °C. The expired effervescent tablets disintegrated in a significantly shorter time than the unexpired tablets (68 s vs. 83 s, p = 0.016). The remaining pharmacopeial parameters did not differ between the two types of tablets. We observed that expired effervescent tablets showed lower mean values of THR in five spectral ranges, which indicates that a greater amount of radiation beam was transmitted into their inner structure than for unexpired tablets. The density of the inner structure assessed on the microtomographic scans differed significantly between all the analyzed tablets (p < 0.001). The highest mean density was observed in the case of the unexpired tablets dried in a vacuum oven (1.273 g/cm3), while the lowest density was observed in the case of the expired tablets (1.261 g/cm3). The expired tablets had a larger pore diameter compared to the unexpired tablets (0.095 mm vs. 0.074 mm, respectively; p = 0.007). Additionally, the percentage of porosity was higher in the expired tablets compared to the unexpired tablets (p < 0.001). [ABSTRACT FROM AUTHOR]

The Spatz neutron beam instrument is the second time‐of‐flight neutron reflectometer to be installed at the OPAL research reactor. The instrument was formerly the V18 BioRef reflectometer at the BER‐II reactor in Berlin and was transferred to Australia in 2016. Subsequently the instrument was re‐installed in the neutron guide hall of the OPAL reactor at the end position of the CG2B cold‐neutron guide and recommissioned. The instrument performance has not been compromised by the move, with reflectivity achieved down to 10−7 and good counting statistics within a reasonable time frame using a wavelength range of 2–20 Å. Several different samples at the solid–air interface and the solid–liquid interface have been measured to demonstrate the instrument's capabilities. [ABSTRACT FROM AUTHOR]

By using optical frequency domain reflectometer(OFDR), a high-precision laboratory test of backfill was carried out, and the internal strain evolution law and distribution characteristics of the backfill during the early hardening process with different cement content was obtained. The results show that the internal strain evolution of the backfill is affected by the combined action of the physical sedimentation of solid particles and the chemical hydration reaction, which can be divided into four stages: physical sedimentation and stretching, hydration exothermic expansion, chemical autogenous shrinkage and basically stablestage. The internal strain distribution of the backfill mainly presents an upward convex curve in the early stage, and with the increase of curing time, it presents a multi-peak curve characteristic; OFDR technology can be used to realize high-precision distributed measurement of the internal strain of backfill and analyze the evolution characteristics of internal strain of backfill. [ABSTRACT FROM AUTHOR]

In order to improve the real-time performance of a phase-sensitive optical-time-domain reflectometer (Φ-OTDR), a fully digital phase processing system is demonstrated. Using digital down-conversion and field programmable gate array (FPGA) hardware calculation, the phase of the Rayleigh scattering light can be demodulated in real-time. Benefiting from the pipeline calculation in the FPGA, the real-time performance of this system is not affected by the interrogation rate and fiber sensing distance. Experiments show that this real-time detection system has the same vibration detection performance as an offline data process and has good stability. The dynamic strain sensing with a sensing distance of 50 km, an interrogation rate of 1 kHz, and a spatial sampling interval of 1 m is experimentally demonstrated. The obtained results indicate that the fully digital signal processing system can ensure the real-time detection of Φ-OTDR under the condition of long distance and high resolution. [ABSTRACT FROM AUTHOR]

The Quite Intense Kinetics Reflectometer (QIKR) will be a general-purpose, horizontal-sample-surface neutron reflectometer. Reflectometers measure the proportion of an incident probe beam reflected from a surface as a function of wavevector (momentum) transfer to infer the distribution and composition of matter near an interface. The unique scattering properties of neutrons make this technique especially useful in the study of soft matter, biomaterials, and materials used in energy storage. Exploiting the increased brilliance of the Spallation Neutron Source Second Target Station, QIKR will collect specular and off-specular reflectivity data faster than the best existing such machines. It will often be possible to collect complete specular reflectivity curves using a single instrument setting, enabling "cinematic" operation, wherein the user turns on the instrument and "films" the sample. Samples in time-dependent environments (e.g., temperature, electrochemical, or undergoing chemical alteration) will be observed in real time, in favorable cases with frame rates as fast as 1 Hz. Cinematic data acquisition promises to make time-dependent measurements routine, with time resolution specified during post-experiment data analysis. This capability will be deployed to observe such processes as in situ polymer diffusion, battery electrode charge–discharge cycles, hysteresis loops, and membrane protein insertion into lipid layers. [ABSTRACT FROM AUTHOR]

A Ku-band (12–18 GHz) multichannel Doppler reflectometer (DR) has been developed in the GAMMA 10/potential control and divertor simulating experiment (PDX) tandem mirror device to improve the applicability of DR measurement for simultaneous monitoring of velocity of electron density turbulence at different locations. Our previous single-channel DR circuit has been replaced by the multichannel microwave system using a nonlinear transmission line based comb generator with heterodyne technique. The multichannel DR system has been installed in the central cell of GAMMA 10/PDX. Initial results of application to GAMMA 10/PDX plasma are presented, showing Doppler frequency shifts during an additional ion cyclotron resonance frequency heating and gas-puffing experiment. [ABSTRACT FROM AUTHOR]

• Significant compression occurs in box tunnel crown and wall near adjacent jacking tunnel. • Layout scheme of "W" shaped optical fiber can evaluate tunnel misalignment and rotation. • Earlier constructed tunnel rotates by adjacent box jacking with a spacing of < 1· B (box width). • Twin tunnels interaction (misalignment and rotation) diminishes with a spacing of > 1· B. Field tunnel monitoring of stresses and strains is of critical importance for understanding the interaction behavior of twin tunnels, but it is rarely done for projects of twin box jacking tunnels. In this study, the optical frequency domain reflectometer (OFDR) sensing technique was employed to conduct field monitoring for a project of twin box jacking tunnels with a small spacing (5.4 m), a shallow minimum cover depth (4.39 m), a large cross-section (9.8 m × 5.9 m), and a long jacking distance (215.9 m) crossing the Beijing-Hangzhou Grand Canal. A scheme of laying circumferential and axial "W" shaped optical fibers was proposed to monitor the accumulated vertical misalignment and rotation of tunnel. Results indicate that small spacing could cause more significant compressive strains in the earlier constructed tunnel, and the maximum compression positions were in the crown and the wall near the second tunnel. In addition, the rotation angle decreased with the increment of tunnel spacing, when the spacing was lower than one times the box width. In the end, an axial monitoring scheme was discussed to evaluate the tunnel opening, and a horizontal misalignment scheme was derived to accomplish the full monitoring of tunnel misalignment in three directions. [ABSTRACT FROM AUTHOR]

This paper presents the first six-port reflectometer, which is insensitive to power detectors’ impedance mismatch. It exhibits optimum measurement conditions and provides low measurement error regardless the reflection coefficient of the used power detectors. Simultaneously, the developed six-port is of low complexity, comparable to other solutions. A theoretical analysis reveals that by application of identical power detectors the impact of their impedance mismatch on the six-port’s measurement performance is completely eliminated. To validate this concept experimentally two six-port reflectometers are developed i.e., the proposed one and a reference six-port, which for ideally matched power detectors provides theoretically identical power distribution. Both reflectometers are calibrated and applied to measure reflection coefficients over the frequency range from 5.7 GHz to 5.9 GHz with both well-matched and highly reflective power detectors. The obtained results clearly show that the proposed six-port provides low measurement errors for both types of power detectors, whereas the reference six-port cannot operate properly with highly reflective power detectors.

The proper classification of the origins of food products is a crucial issue all over the world nowadays. In this paper, the authors present a device—a multispectral portable fibre-optic reflectometer and signal processing patch—together with a machine-learning algorithm for the classification of the origins of chicken eggshells in the case of Mycoplasma synoviae infection. The sensor device was developed based on previous studies with a continuous spectrum in transmittance and selected spectral lines in reflectance. In the described case, the sensor is based on the integration of reflected spectral data from short spectral bands from the VIS and NIR region, which are produced by single-colour LEDs and introduced to the sample via a fibre bundle. The measurement is carried out in a sequence, and the reflected signal is pre-processed to be put in the machine learning algorithm. The support vector machine algorithm is used together with three different types of data normalization. The obtained results of the F-score factor for classification of the origins of samples show that the percentages of eggs coming from Mycoplasma synoviae infected hens are up to 87% for white and 96% for brown eggshells. [ABSTRACT FROM AUTHOR]

Optical fiber links are customarily monitored by Optical Time Domain Reflectometer (OTDR), an optoelectronic instrument that measures the scattered or reflected light along the fiber and returns a signal, namely the OTDR trace. OTDR traces are typically analyzed by experts in laboratories or by hand-crafted algorithms running in embedded systems to localize critical events occurring along the fiber. In this work, we address the problem of automatically detecting optical events in OTDR traces through a deep learning model that can be deployed in embedded systems. In particular, we take inspiration from Faster R-CNN and present the first 1D object-detection neural network for OTDR traces. Thanks to an ad-hoc preprocessing pipeline for OTDR traces, we can also identify unknown events, namely events that are not represented in training data but that might indicate rare and unforeseen situations that need to be reported. The resulting network brings several advantages with respect to existing solutions, as these typically classify fixed-size windows of OTDR traces, thus are less accurate in the localization. Moreover, existing solutions do not report events that cannot be safely associated to any label in the training set. Our experiments, performed on real OTDR traces, show very promising performance, and can be directly executed on embedded OTDR devices. [ABSTRACT FROM AUTHOR]

Sequential equivalent time sampling (ETS) has been extensively used in data acquisition instruments (e.g., sampling oscilloscopes and time domain reflectometers). A novel step delay method is proposed based on the frequency difference to obtain a higher sampling rate in sequential ETS. It is different from the classic step delay methods and is capable of increasing the sampling rate. The sampling clock and the repetitive signal are taken as examples in this study. The time–frequency conversion relationship indicates that a fine step delay will be generated in the time domain if there is a frequency difference between the two in the frequency domain. The core of the proposed method is the selection of the appropriate frequency difference (step delay) according to the desired equivalent sampling rate. Two experiments were performed to verify the proposed method. The feasibility of the proposed method is verified using a digital storage oscilloscope. Four cases are examined in the experiment, and the final equivalent sampling rate is obtained as 5 PS/s for the equivalent sampling of a 4.999 995 GHz (or higher) signal. A data acquisition system with a 10 MS/s real-time sampling rate is designed to verify the feasibility of the proposed method, obtaining a theoretical equivalent sampling rate of 585 GS/s. The theoretical equivalent sampling rate and the examined equivalent sampling rate are consistent. The equivalent sampling waveform and real-time sampling waveform of a 1 GHz signal are compared, and the comparison result suggests that the proposed method can acquire more waveform information. The proposed method obtains a high equivalent sampling rate for repetitive signals, and techniques (e.g., oversampling) are given to obtain higher vertical resolution. The proposed method, combined with a sample-and-hold amplifier, can also achieve a higher analog bandwidth. [ABSTRACT FROM AUTHOR]

Measuring the time variation of the wavenumber spectrum of turbulence is important for understanding the characteristics of high-temperature plasmas, and the application of a Doppler reflectometer with simultaneous multi-frequency sources is expected. To implement this diagnostic in future fusion devices, the use of a phased array antenna (PAA) that can scan microwave beams without moving antennas is recommended. Since the frequency-scanning waveguide leaky-wave antenna-type PAA has a complex structure, we have investigated its characteristics by modeling it with 3D metal powder additive manufacturing (AM). First, a single waveguide is fabricated to understand the characteristics of 3D AM techniques, and it is clear that there are differences in performance depending on the direction of manufacture and surface treatment. Then, a PAA is made, and it is confirmed that the beam can be emitted in any direction by frequency scanning. The plasma flow velocity can be measured by applying the 3D manufacturing PAA to plasma measurement. [ABSTRACT FROM AUTHOR]

System-on-chip millimeter wave integrated circuit technology is used on the two-dimensional millimeter-wave imaging reflectometer (MIR) upgrade for density fluctuation imaging on the DIII-D tokamak fusion plasma. Customized CMOS chips have been successfully developed for the transmitter module and receiver module array, covering the 55–75 GHz working band. The transmitter module has the capability of simultaneously launching eight tunable probe frequencies (>0 dBm output power each). The receiver enclosure contains 12 receiver modules in two vertical lines. The quasi-optical local oscillator coupling of previous MIR systems has been replaced with an internal active frequency multiplier chain for improved local oscillator power delivery and flexible installation in a narrow space together with improved shielding against electromagnetic interference. The 55–75 GHz low noise amplifier, used between the receiver antenna and the first-stage mixer, significantly improves module sensitivity and suppresses electronics noise. The receiver module has a 20 dB gain improvement compared with the mini-lens approach and better than −75 dBm sensitivity, and its electronics noise temperature has been reduced from 55 000 K down to 11 200 K. The V-band MIR system is developed for co-located multi-field investigation of MHD-scale fluctuations in the pedestal region with W-band electron cyclotron emission imaging on DIII-D tokamak. [ABSTRACT FROM AUTHOR]

Early detection of fault in underground cables (UC) reduces abnormal degradation. Fault detection is vital to sustain the availability of service to consumers in order to avoid line disruptions or irregularities of supply. This paper presents the methodology of detecting and correcting of aging mechanism known as partial discharge (PD) in underground cables. The methodology of detecting and correcting partial discharge in underground cables necessitates developing a reliable and efficient method of detection when the cable is near failure before resulting to catastrophic failure. For this paper, the Time Domain Reflectometer (TDR) device, offline, online methods were adopted for review, detection and compared by exploring their peculiarities and shortcomings. In conclusion, one method out of the three is chosen after examination and recommended for use to significantly reduce irregularities along the supply line of transmission. [ABSTRACT FROM AUTHOR]

M-STAR is a next generation polarized neutron reflectometer with advanced capabilities. A new focusing guide concept is optimized for samples with dimensions down to a millimeter range. A proposed hybrid pulse-skipping chopper will enable experiments at constant geometry at one incident angle in a broad range of wavevector transfer Q up to 0.3 A−1 for specular, off-specular, and GISANS measurements. M-STAR will empower nanoscience and spintronics studies routinely on small samples (∼2 × 2 mm2) and of atomic-scale thickness using versatile experimental conditions of magnetic and/or electric fields, light, and temperature applied in situ to novel complex device-like nanosystems with multiple buried interfaces. M-STAR will enable improved grazing incidence diffraction measurements, as a surface-sensitive depth-resolved probe of, e.g., the out-of-plane component of atomic magnetic moments in ferromagnetic, antiferromagnetic, and more complex structures as well as in-plane atomic-scale structures inaccessible with contemporary diffractometry and reflectometry. New horizons will be opened by the development of an option to probe near-surface dynamics with inelastic grazing incidence scattering in the time-of-flight mode. These novel options in combination with ideally matched parameters of the second target station will place M-STAR in the world's leading position for high resolution polarized reflectometry. [ABSTRACT FROM AUTHOR]

Copyright of Study on Optical Communications / Guangtongxin Yanjiu is the property of Study on Optical Communications 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.)