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A joint algorithm of wavelength domain differential accumulation (WDDA) and local cross-correlation is proposed in an optical frequency domain reflectometry (OFDR) for fast strain measurement along the sensing fiber. Among this, t...
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A joint algorithm of wavelength domain differential accumulation (WDDA) and local cross-correlation is proposed in an optical frequency domain reflectometry (OFDR) for fast strain measurement along the sensing fiber. Among this, the WDDA is used to realize rapid strain positioning first, then the local cross-correlation is operated to the strain region only for fast strain computation. Thus, the processing time is substantially decreased. The mathematical principle of WDDA is theoretically derived and verified by numerical simulation. Meanwhile, the time complexity of WDDA is demonstrated to be reduced from O(
nlogn
) to O(
n
) by theoretical analysis and experimental verification, compared with the traditional whole-region cross correlation. Experiments are carried out to verify the effectiveness of this method. In experiments, we exerted the same strain region over 10.6, 35.0, 63.5, and 113.3 m long fibers. The strain greater than 10 μϵ can be identified by the WDDA. Compared with the traditional cross-correlation method in OFDR, the processing speed is increased by 5.3, 6.1, 6.3 and 6.4 times, respectively.
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This paper presents a novel experimental case study in which tactile sensation is analyzed as 4-dimensional subjective data consisting of stimulus, participant, evaluation term, and temporal components, using a temporal measuremen...
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This paper presents a novel experimental case study in which tactile sensation is analyzed as 4-dimensional subjective data consisting of stimulus, participant, evaluation term, and temporal components, using a temporal measurement approach. Specifically, the skin and lotion interaction was evaluated using the Temporal Check-All-That-Apply (TCATA) method. Two practical analysis examples were conducted to experimentally demonstrate the potential use cases of time-series subjective tactile data. In the first example, stimulus classification accuracy was compared between different sampling periods, including the whole and late periods, with the latter being akin to the conventional Semantic Differential (SD) method condition. The results indicate that the whole and early periods exhibit higher accuracy compared to the latest period, implying that temporal measurements may capture more stimulus characteristics than the conventional approach. In the second example, cluster analysis based on the time-series subjective data was conducted. The results revealed that the participants were classified into two distinct clusters, with the trends of time-series changes being significantly different between the clusters.
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This work presents a novel measurement method to characterize long-term and short-term variations of the LV grid impedance from 20 kHz to 10 MHz with configurable time, frequency and amplitude resolutions. The characterization of ...
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This work presents a novel measurement method to characterize long-term and short-term variations of the LV grid impedance from 20 kHz to 10 MHz with configurable time, frequency and amplitude resolutions. The characterization of the grid access impedance in this frequency range is vital for the design and development of NB-PLC and BB-PLC technologies. The measurement system is valid for in-home, indoor cable networks and for the harsh conditions of the LV distribution grid, where a large input dynamic range and strong protection mechanisms against high-amplitude impulsive noises are required. Its accuracy is evaluated by comparison to a precision impedance meter for a wide set of impedance values, obtaining a maximum deviation within ±8%. First trials of the grid impedance sub-cycle variations caused by commercial appliances and for frequencies assigned to BB-PLC are also presented in this paper. The results demonstrate that the grid impedance is highly time-varying within the mains cycle, both in amplitude and phase. These first outcomes point at the need to evaluate the accumulative effects of sub-cycle variations in the LV distribution grid, so that equalization algorithms in the next BB-PLC technologies could be developed to overcome the impact of these fast variations.
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The dynamic characteristics of a thermal converter for measuring alternating current or voltage are of some importance in a number of applications. The time constant and response time are the characteristics most often required. T...
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The dynamic characteristics of a thermal converter for measuring alternating current or voltage are of some importance in a number of applications. The time constant and response time are the characteristics most often required. The change of emf (electromotive force) of a thermal converter after a step change in heater current is only approximately exponential, so that the definition as well as methods of measuring these quantities must be specified. This investigation of methods of measuring these quantities was undertaken at the request of the AIEE Committee on Indicating and Integrating Instruments.
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Ionospheric refraction is one of the factors limiting the accuracy of radar systems tracking objects in or beyond the ionosphere. In advanced systems it may be desirable to perform accurate corrections for these effects in real ti...
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Ionospheric refraction is one of the factors limiting the accuracy of radar systems tracking objects in or beyond the ionosphere. In advanced systems it may be desirable to perform accurate corrections for these effects in real time, and because of the extreme variability of the ionosphere, this presupposes real time, local ionospheric measurements, e.g., by a modem digital ionosonde. The ionosonde could then be required to monitor the state of the ionosphere, compare it with model conditions, and forecast the radar refraction environment in real time. One component in this problem is the calculation of the radar refraction effects, given the ionospheric electron density profile, the apparent radar range, and look angle. Assuming that the electron density depends on height only, this paper describes such a procedure suitable for use within the Dynasonde or a similar digital ionosonde interfaced to an active radar system.
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Electrochemical Impedance Spectroscopy (EIS) is a non-invasive method to evaluate biological samples. With the use of EIS results, the transepithelial electrical resistance (TEER) can be measured to estimate the condition of e.g. ...
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Electrochemical Impedance Spectroscopy (EIS) is a non-invasive method to evaluate biological samples. With the use of EIS results, the transepithelial electrical resistance (TEER) can be measured to estimate the condition of e.g. in-vitro lung epithelia under various diseases. In this regard, many epithelial samples must be prepared, which is a time consuming task. Parallel measurements with the use of multi-electrode arrays (MEA) increase the throughput of the system. Careful electronic design must be considered to guarantee safe and fast MEA-EIS measurements. Available MEA-EIS systems are mostly limited by either limited frequency and dynamic range or long measurement time. Particularly slow MEA-EIS measurements are disadvantageous for epithelial cells since during the EIS measurements they are kept in a harmful environment. In this work, a fast MEA-EIS system for 24 channels is presented. The designed MEA-EIS system takes less than 20 seconds excitation time for a frequency range of 1 Hz to 100 kHz with the use of parallel recording and multi-tone excitation signals. The proposed system is realized using discrete components on a PCB and its functionality with the designed MEA is successfully verified using biological samples. A matching better than 95% between the extracted TEER values from the designed system and commercially available devices is observed. MEA-EIS measurements are performed in a frequency range from 10 mHz to 100 kHz with minimum and maximum detectable impedances of
$6~\Omega $
and 300
$\text{k}\Omega $
, respectively.
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A method was developed to characterize the coordination of body movements during a prolonged repetitive isodynamic lifting task. Body movements, defined by angles at the hip and knee, were described by hyperbolic tangent models. T...
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A method was developed to characterize the coordination of body movements during a prolonged repetitive isodynamic lifting task. Body movements, defined by angles at the hip and knee, were described by hyperbolic tangent models. The temporal midpoint and the risetime, normalized, by the total duration of the lift, were used to describe the timing of the lift, and differences between the hip and knee midpoints and between the hip and knee risetimes described the relative timing, or coordination, of the hip and knee movements. Control subjects tended to use a lifting pattern in which the two joints finished the movement at the same time, while patients with chronic lower back pain more frequently used a movement pattern in which the two joints finished the lifting movement at different times. The results suggest that the relative movement of the hip and knee may be important to consider when evaluating lifting differences between chronic low back pain patients and control subjects.
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A multichannel dual-mixer time difference (DMTD) system has been developed by the National Institute of Information and Communications Technology (NICT) for a measurement system to generate the UTC(NICT) time scale based on Co-ord...
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A multichannel dual-mixer time difference (DMTD) system has been developed by the National Institute of Information and Communications Technology (NICT) for a measurement system to generate the UTC(NICT) time scale based on Co-ordianted Universal Time (UTC). This system measures time differences between a reference signal and 24 device under test (DUT) signals, simultaneously. We have confirmed that this system has enough accuracy to measure hydrogen maser and cesium clocks at an averaging time of 1 s.
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Wideband near-field (NF) radar cross section (RCS) measurement techniques for improving the far-field RCS prediction accuracies are addressed in this article. Both the data preprocessing and NF-to-far-field transformation (NF2FFT)...
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Wideband near-field (NF) radar cross section (RCS) measurement techniques for improving the far-field RCS prediction accuracies are addressed in this article. Both the data preprocessing and NF-to-far-field transformation (NF2FFT) techniques are used to accurately measure wideband far-field RCSs in a wide azimuthal angle range. By utilizing the calibration set creation and some wideband data preprocessing techniques, including the vector background subtraction, the time-domain calibration and compensation, the time-gating steps, as well as the cylindrical mode expansion or the imaging-based NF2FFT techniques, the accurate wideband far-field RCSs in a wide azimuthal angle range can be obtained with the limited NF measurement range. Both the poor measurement accuracy and dynamic range as well as the main lobe distortion and angular undersampling effects existing in the NF measured raw data can be improved significantly. The proposed techniques are validated with an 8–12-GHz measurement of a 0.5-m-length cone target (in a 3-m measurement range, compared with the at least 30-m far-field range requirement), and the obviously improved RCS patterns and less than 0.5-dB average wideband measurement errors are achieved.
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Time interval (TI) is one of the basic quantities. Its measurement is not included only in the activities running in the time and frequency metrology but also included in the measurement of many other quantities that depend on tim...
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Time interval (TI) is one of the basic quantities. Its measurement is not included only in the activities running in the time and frequency metrology but also included in the measurement of many other quantities that depend on time interval measurement (TIM). This means that improving the accuracy and reducing the measurement uncertainty of TI will reflect also on improving the accuracy and reducing the measurement uncertainty of many other quantities. To do that, we need to decrease or eliminate the effect of the dominant factors that degrade the quality of TIM. One of the major contributors to the measurement uncertainty of TI is the internal error of the time interval counter (TIC) used in the measurement. In this paper we introduce a methodology with which we can estimate precisely the internal error of the counter and eliminate its effect.
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