Current Measurement Methods Research Articles

Laser-induced surface acoustic waves for measurement of elastic constants based on mode conversion

The measurement of elastic constants is very important to the study of materials. Laser ultrasonic technology has been widely concerned for its unique advantages and used to measure elastic constants, but the current measurement methods have their limitations. In general, traditional measurement methods require the use of a fatigue tester or measurement of all modal waves during the experiment. It is found that cracks can transform the mode of ultrasonic wave, in other words, the surface acoustic waves can be transformed into shear waves by mode conversion. So, we proposed a new method of measuring elastic constants of materials by laser ultrasound based on mode conversion. Surface acoustic waves are induced by laser ultrasound system, the reflection and mode conversion of surface acoustic waves can be realized by cracks. Therefore, direct waves, reflected waves and mode converted waves are included in the collected surface wave signals, then the wave velocity of surface waves and shear waves are calculated by the surface acoustic waves, and the elastic constants of materials are obtained by the acoustic elasticity equation. Since the experiment and processing are all based on surface acoustic waves, multiple waveform acquisition and processing are avoided. After calculation, the error is kept below 3% compared with the standard measurement value. In order to further confirm the application range of the method, cracks of different depths are used in the experiment, it is further proved that this method has nothing to do with the crack size. The research results of this paper can extend the application range of laser ultrasound. It also provides a new approach to the characterization of materials.

Wireless intravesical device for real-time bladder pressure measurement: Study of consecutive voiding in awake minipigs.

Traditional urodynamics have poor correlation with urological symptoms. Ambulatory urodynamics may improve this correlation but the need for a transurethral catheter and the time-consuming nature of this examination limits its use. Therefore, the objective of this study was to develop a wireless real-time bladder pressure measurement device for repeated and prolonged-term measurement of bladder behavior in awake pigs. The Bladder Pill is an intravesical device with a pressure microsensor and a 3-dimensional inductive coupling coil for energy supply. A corresponding external coil provides wireless power transmission and real-time communication of bladder pressure data. To test the correlation between the pressure data measured by the device and by standard methods, we compared static water column pressures with this device and water-filled urodynamic catheter systems. In vivo assessment of awake voiding by the pill was done by introducing the bladder pill into the bladder of Göttingen minipigs. An air-charged urodynamic catheter was introduced transurethrally as control for pressure measurements. The optimal physical configuration of the pill was investigated to maximize the containment in the bladder. We used two versions of external signal receivers (one waistband and one rectangular frame) to test the optimal external signal capture. Next to that, we performed short-term and medium-term comparative pressure studies. The in vitro static pressure measurement demonstrated a mean difference of less than 1 cm H2O between the methods. The optimal design of the pill for maximal retainment in the bladder proved to be a pigtail configuration. The bending of the device during bladder contractions caused offset of 2.7 +/- 1.4 cm H2O (mean +/- SD) on the pressure measurements. The rectangular frame performed signal capture during 5 consecutive voids with a good correlation of the pressure measurements. The device can be inserted through the urethra and is retrieved using string or endoscopic extraction. In conclusion, wireless long-term measurement of bladder pressure is demonstrated and yields comparable results to current available catheter methods of measurement in a pig model.

A Novel Method for Wide Range Electric Current Measurement in Gas-Insulated Switchgears With Shielded Magnetic Measurements

Magnetic field (MF) sensing and interpretation remains an active area of research for source current reconstruction and measurement applications. One such area is large current measurement for power system components with contact less MF sensing. The output of recently made available magnetic sensors is favorable for large current measurement applications. This stimulates development of a noncontact magnetic sensor-based large electric current measurement system for fixed conductors to be employed in power systems. However, the presence of strong magnetic noise from near equipment imposes restriction on the use of sensitive magnetic sensor in open air where magnetic noise sources operating at the same frequency may distort the sensor output. The novelty of this paper is the application of MF sensor inside magnetic shielding layers for large current measurement. High-permeability Mu-metal is employed and arranged in three arc-shaped layers for designing a semicircular special shielding arrangement. The application of the method and design is demonstrated for large current carrying conductor arranged inside a gas-insulated switchgear. The measurement system is first validated by the finite-element analysis method and then tested with a comprehensive experimental setup in the presence of strong magnetic noise stimulus of 0.28 T generated by a strong neodymium magnet. The resultant apparatus is tested for current of up to 1000 A with a resolution of 0.01% and error less than 3% in the worst case scenario. The prototype demonstrated excellent linearity during experimental validation of current measurement of 100–1000 A in the presence of magnetic noise stimuli at different positions where the standard deviation between slopes value for sensor response to input current (100–1000 A) curve for six different test cases remains only 0.83%.

Self-Oscillating Mode of a Probe with Increased Secondary Emission for Nonequilibrium Plasma Diagnostics

A method of ion saturation current measurement in a nonequilibrium plasma by a self-oscillating voltage sweep on the probe is described. The generation of voltage pulses is possible if a high secondary electron emission from the probe surface is ensured, significantly exceeding unity at a moderate negative potential. The theoretical basis of the self-oscillating probe method has been considered, which made it possible to describe the ways for controlling the repetition rate and pulse amplitude and the effect of plasma parameters on the shape of current and voltage signals. It is shown that the features of the phase trajectory of the signal from the probe on the (U, I) plane allow one to determine the reference points of instantaneous probe characteristic, in particular, the ion saturation current. The results of experiments on testing the self-oscillating probe technique, which were carried out using the PR-2 plasma-beam facility, are presented.

A new method for mining information of co-expression network based on multi-cancers integrated data

BackgroundGene co-expression network is a favorable method to reveal the nature of disease. With the development of cancer, the way to build gene co-expression networks based on cancer data has been become a hot spot. However, there are still a limited number of current node measurement methods and node mining strategies for multi-cancers network construction.MethodsIn this paper, we introduce a new method for mining information of co-expression network based on multi-cancers integrated data, named PMN. We construct the network by combining the different types of relevant measures (linear and nonlinear rules) for different nodes based on integrated gene expression data of multi-cancers from The Cancer Genome Atlas (TCGA). For mining genes, we combine different properties (local and global characteristics) of the nodes.ResultsWe uncover more suspicious abnormally expressed genes and shared pathways of different cancers. And we have also found some proven genes and pathways; of course, there are some suspicious factors and molecules that need clinical validation.ConclusionsThe results demonstrate that our method is very effective in excavating gene co-expression genes of multi-cancers.

Improved Flow Awareness Among Edge Nodes by Learning-Based Sampling in Software Defined Networks

To improve the specific quality of service, internal network management and security analysis in the future mobile network, accurate flow-awareness in the global network through packet sampling has been a viable solution. However, the current traffic measurement method with the five tuples cannot recognize the deep information of flows, and the Deep Packet Inspection (DPI) deployed at the gateways or access points is lack of traffic going through the internal nodes(e.g., base station, edge server). In this paper, by means of Deep Q-Network (DQN) and Software-Defined Networking (SDN) technique, we propose a flow-level sampling framework for edge devices in the Mobile Edge Computing (MEC) system. In the framework, an original learning-based sampling strategy considering the iterative influences of nodes is used for maximizing the long-term sampling accuracy of both mice and elephant flows. We present an approach to effectively collect traffic packets generated from base stations and edge servers in two steps: 1) adaptive node selection, and 2) dynamic sampling duration allocation by Deep Q-Learning. The results show that the approach can improve the sampling accuracy, especially for mice flows.

Effect of surface conduction-induced electromigration on current monitoring method for electroosmotic flow measurement.

Current monitoring method for measurement of EOF in microchannels involves measurement of time-varying current while an electrolyte displaces another electrolyte having different conductivity due to EOF. The basic premise of the current monitoring method is that an axial gradient in conductivity of a binary electrolyte in a microchannel advects only due to EOF. In the current work, using theory and experiments, we show that this assumption is not valid for low concentration electrolytes and narrow microchannels wherein surface conduction is comparable with bulk conduction. We show that in presence of surface conduction, a gradient in conductivity of binary electrolyte not only advects with EOF but also undergoes electromigration. This electromigration phenomenon is nonlinear and is characterized by propagation of shock and rarefaction waves in ion concentrations. Consequently, in presence of surface conduction, the current-time relationships for forward and reverse displacement in the current monitoring method are asymmetric and the displacement time is also direction dependent. To quantify the effect of surface conduction, we present analytical expressions for current-time relationship in the regime when surface conduction is comparable to bulk conduction. We validate these relations with experimental data by performing a series of current monitoring experiments in a glass microfluidic chip at low electrolyte concentrations. The experimentally validated analytical expressions for current-time relationships presented in this work can be used to correctly estimate EOF using the current monitoring method when surface conduction is not negligible.

USE OF SENSOR TECHNOLOGY TO MAP THE SOCIAL NETWORKS OF PEOPLE LIVING WITH DEMENTIA: A FEASIBILITY STUDY

For older adults living with dementia, social network quality influences health outcomes. However, current social network measurement methods are time consuming and mentally draining for people living with dementia. This study aimed to accurately measure social networks using sensor technology. Bluetooth and radio-frequency identification (RFID) sensors were used to collect social network data in a simulation of a falling nursing home resident living with dementia. Participants wore sensors on their clothing, and video recordings were compared to sensor data. Bluetooth data reflected general direction of movement and instances of idling but were neither precise or accurate. RFID data was accurate after applying data filters. Both systems detected multiple sensors simultaneously. The Bluetooth system is not feasible for clinical use, but the RFID system shows potential for clinical application and accurate measurement of social network factors as interaction frequency and duration.

Novel Wood Resistance Measurement Method Reducing the Initial Transient Instabilities Arising in DC Methods Due to Polarization Effects

A novel method for measuring the electrical resistance in wood is presented. It is based on applying an Alternating Current (AC) to two electrodes rammed into the wood. The method reduces the transient time for value stabilization. In case of Direct Current (DC) resistance measurement methods, typically used in wood measurement, an initial transient exists, invalidating the measured value during an initial transient period. This measurement method uses an electronic circuit based on a relaxation oscillator where the wood automatically sets the oscillation frequency depending on its electrical resistance. Compared to other AC methods, this circuit greatly simplifies the measurement process, not requiring any previous analysis for wood AC frequency estimation. Experimental results for four different wood species showed that, in all cases, the transient response of the measured wood resistance is improved when compared to the DC resistance method, reducing the stabilization time from 10–12 min in DC measurements to almost zero for the novel measurement method. The deviation between the initial wood resistance measurement and the stable value resulted in a range between 0.2% and 5% with the proposed method, while a range between 6% and 10% was obtained when using the DC method. Moreover, the proposed circuit is able to detect changes in wood resistance produced by small variations in temperature and environmental relative humidity during continuous long term measurements. For repeatability analysis, it was verified that similar ambient conditions of temperature and relative humidity (variations lower than 1 °C and 1%, respectively) in different moments provided variations lower than 1.5%. The method can also be applied to other fiber materials affectd by polarization effects when an electrical current is applied into them.

Direct Evaluation of Unsymmetrical Dimethylhydrazine with Wide Concentration Range in Wastewater by Ion Chromatography

Current methods for measurement of unsymmetrical dimethylhydrazine (UDMH) in wastewater suffer from a small detection range and complex pretreatment. In this study, ion chromatography (IC) with conductivity detection was used to directly analyze UDMH in wastewater, without any derivatization pretreatment, and the measurement range was as wide as 0.5–1000 μg·mL⁻¹. The effects of column temperature and sample pH on the detection were investigated. Furthermore, the chromatography conditions were optimized by combining the effects of different combinations of nitric acid, 2,6-pyridinedicarboxylic acid (PDCA), and methanesulfonic acid (MSA) on the analysis of mixed samples of UDMH and alkali metal ions. The linearity of the detected peak height (H) and peak area (A) versus UDMH concentration was studied at low, medium, and high concentrations. A good linear relationship was observed in the range of 0.5–1000 μg·mL⁻¹, especially for A, the relative standard deviation (RSD) and correlation coefficient (R²) of which were 0.077–1.653% and 0.9998–1.0000, respectively. In addition, the method showed good sensitivity with a limit of detection (LOD) of 0.05 μg·mL⁻¹ and a limit of quantitation (LOQ) of 0.16 μg mL⁻¹. The precision and accuracy (expressed by recovery) were verified, where the RSD were less than 1.49% and 3.17%. Interference between hydrazines and alkali metal ions was discussed. Finally, actual UDMH samples were determined, confirming the applicability of the developed method for analyzing UDMH in wastewater during the degradation process.

Surface Diffusion in Gaseous Monolayers of an Insoluble Surfactant.

Surface diffusion is an important mass transfer mechanism of surfactant molecules within adsorbed layers, which has to be taken into account in many fluid dynamics problems. Although considerable research has been devoted to studying the thermodynamic and rheological properties of surface films, rather less attention has been paid to surface diffusivity measurements. Current measurement methods, which are based on marking part of surfactant molecules in uniform motionless layers with the radiotracer or fluorescence technique, are well suited for use in quite condensed layers, but they do not work in rarefied layers due to increasing contribution of density fluctuations at an interface. In this study, we propose a method for measuring the surface diffusion coefficient in gaseous monolayers of an insoluble surfactant under dynamic conditions, i.e., in the presence of a flow at an interface. Our approach is based on measuring the velocity of thermocapillary flow on the water surface, which contains molecules of an insoluble surfactant. We show that under conditions of the balance between thermo- and solutocapillary tangential stresses the convective motion exists at an interface, which is caused by a blurring of the surface concentration gradient of surfactant molecules due to the surface diffusion mechanism. For calculations of the surface diffusion coefficient, we use the equation proposed earlier in the theoretical study [ Homsy , G. M. ; et al. J. Fluid Mech. 1984 139 , 443 - 459 ]. The surface diffusion coefficient measured by us in gaseous layers is 2-3 orders of magnitude larger than the results for liquid-expanded and liquid-condensed layers obtained by other researchers. Finally, we compare the obtained results with the known measurements of surface diffusion and discuss the limitations of the proposed method.

Validation study of an automated algorithm to calculate the aortic angulations based on the analysis of tortuosity

The aortic angulations are associated with the risk of endoleak after EVAR. All the current methods of measurement of the angulations are based on a two- dimensional visual analysis. However, aortic reconstructions from CT acquisitions allow three-dimensional analysis of data. The aim of this study was to show that it is possible to automatically identify the significant points of curvature of the central line (CL) using an algorithm.

Design of a Portable Orthogonal Surface Acoustic Wave Sensor System for Simultaneous Sensing and Removal of Nonspecifically Bound Proteins.

One challenge for current surface acoustic wave (SAW) biosensors is reducing nonspecific adsorption. A device propagating Rayleigh and shear horizontal surface acoustic waves in orthogonal directions fabricated in ST quartz has the capability of achieving simultaneous detection and nonspecific binding (NSB) protein removal. Current measurement methods for a SAW sensor system based on this device require large-size and expensive equipment such as a vector network analyzer (VNA), signal generator, and frequency counter, which are not suitable for portable, especially point-of-care, applications. In this work, a portable platform based on a direct digital synthesizer (DDS) is investigated for the orthogonal SAW sensor, integrating signal synthesis, gain control, phase/amplitude measurement, and data processing in a small, portable electronic system. This prototype was verified for both stability and repeatability, and the results matched very well with VNA measurements. Finally, system performance in real-time sensing and NSB removal was evaluated.

Laboratory assessment of alternative stream velocity measurement methods.

Understanding streamflow in montane watersheds on regional scales is often incomplete due to a lack of data for small-order streams that link precipitation and snowmelt processes to main stem discharge. This data deficiency is attributed to the prohibitive cost of conventional streamflow measurement methods and the remote location of many small streams. Expedient and low-cost streamflow measurement methods used by resource professionals or citizen scientists can provide scientifically useful solutions to this data deficiency. To this end, four current velocity measurement methods were evaluated in a laboratory flume: the surface float, rising body, velocity head rod, and rising air bubble methods. The methods were tested under a range of stream velocities, cross-sectional depths, and streambed substrates. The resulting measurements provide estimates of precision and bias of each method, as well as method-specific insight and calibration formulas. The mean values of the coefficient of variation, a measure of precision, were 10% for the surface float, 10% for the velocity head rod, 14% for the rising body, and 9% for the air bubble method. The values of scaled mean error, a measure of bias, were -8% for the surface float, -4% for the velocity head rod, -1% for the rising body, and 4% for the air bubble. The velocity head rod and surface float methods were the easiest methods to use, providing greater precision at large (> = 0.6 m/s) and small (<0.6 m/s) velocities, respectively. However, the reliance on a velocity ratio for each of these methods can generate inaccuracy in their results. The rising body method is more challenging to execute and of lower precision than the former two methods but provides low bias measurements. The rising air bubble method has a complex instrument assembly that is considered impractical for potential field user groups.

Why Are Signature Strengths and Well-Being Related? Tests of Multiple Hypotheses

The study of character strengths stems from positive psychology’s quest to understand positive personality traits that foster positive functioning and flourishing. Signature strengths are character strengths that are considered particularly relevant to the identity of the individual. These have been related to subjective well-being (SWB) in both cross-sectional and intervention studies. However, contributors to this relationship remain unclear. The present study examined the following possible explanations for the relationship between signature strengths and SWB: the perceived ability to use signature strengths, recognition of signature strengths by others, and valuing of signature strengths by one’s school, workplace, and country. Also, existing approaches to identifying signature strengths do not accurately reflect the construct as it was originally conceived. To address these issues, this study used the Signature Strengths Survey (McGrath in Technical report: the VIA assessment suite for adults: development and initial evaluation, rev ed. VIA Institute on Character, Cincinnati, 2019), which was developed to address inadequacies in current measurement methods, allowing the respondent to set the number of signature strengths. In a sample of 2875 adults recruited online, results revealed that signature strengths being perceived as valued and recognized by others, rather than identification with and enactment of particular strengths, best predicted SWB. Results merit replication, but suggest that focus on signature strengths valued by others in one’s environment can be particularly contributory to SWB.

Structural displacement monitoring using deep learning-based full field optical flow methods

Current vision-based displacement measurement methods have limitations such as being in need of manual targets and parameter adjustment, and significant user involvement to reach the desired result. This study proposes a novel structural displacement measurement method using deep learning-based full field optical flow methods. The performance of the proposed method is verified via a laboratory experiment conducted on a grandstand structure with a comparative study, where the same data samples are analysed with a commonly used vision-based method, and a displacement sensor measurement is used as the ground truth. Statistical analysis of the comparative results show that the proposed method gives higher accuracy than the traditional optical flow algorithm and shows consistent results in compliance with displacement sensor measurements. Image collection, tracking, and non-uniform sampling are investigated in the experimental data and suggestions are made to obtain more accurate displacement measurements. A field-validation on a footbridge showed that the measurement error induced by the camera motion is mitigated by a camera motion subtraction procedure. The proposed method has good potential to be applied by structural engineers, who have little or no experience in computer vision and image processing, to do vision-based displacement measurements.

Analysis of contemporary tools for the measurement of enophthalmos: a PRISMA-driven systematic review

Enophthalmos has many causes, and serious post-traumatic cases indicate the need for operation. Such diagnoses should be made objectively, and a robust method for quantifying the degree to which the globe has been displaced is key. Current methods of measurement, however, have long been considered unreliable and inconsistent, in particular with regard to interobserver variability. The aim of this paper therefore was to review all these methods systematically, to analyse their reliability, and to compare them with others. The paper also includes a proposed protocol for the accurate and reliable measurement of protrusion of an eye, which aims to standardise the assessment of patients and to create a uniform approach that will enable the selection of those who are most likely to benefit from surgical treatment. Analysis of the data showed that computed tomographic (CT) exophthalmometry is the most reliable, followed by the Mourits’ exophthalmometer, which performed better than the other clinical methods. In the acute phase of orbital blowout fractures, the measurement of herniated tissue through a fracture defect may give a good prediction of the degree of enophthalmos that is likely to occur without surgical correction. Measurement of the herniated volume and CT exophthalmometry should be the foundation for diagnosis and the planning of treatment. Three-dimensional imaging or Mourits’ exophthalmometers (which are reliable non-radiological methods) could be used in a follow-up protocol.

Eddy-current loss measurement of permanent magnetic material at different frequency

Based on a closed-circuit testing equipment, eddy current loss measurement method of the permanent magnetic material is proposed and studied in this paper. The tested material sample is NdFeB, which has been widely used in electrical machines. The NdFeB is usually coated with corrosion-resistant me tal, such as highly conductive zinc and copper to resist corrosion in practical use. The coating material may influence the eddy current loss of the permanent magnet. In this situation, eddy current losses of the NdFeB sample with and without coating are measured and compared with sinusoidal excitation at different frequencies. The experimental results provide very important reference in electrical machine design.

A fiber optic current sensor on tunnel boring machine for current measurement application in tunnel geological prediction

A fiber optic current sensor (FOCS) used for current measurement application on tunnel boring machine (TBM) in tunnel geological prediction is proposed in this paper. Compared with the FOCS designed for power gird, the sensor developed in this paper is especially suitable for measuring the current which flows in a large diameter conductor, such as TBM. Aiming at solving the signal fading problem and sensitivity drift induced by the harsh working environment, the proposed FOCS utilizes a technique which is based on rotatable half-wave retarder and alternated current measurement. Verified by mathematical analysis and laboratory test, the rotatable half-wave retarder technique has been proved to be effective in solving the signal fading. The alternated current measurement method has been employed by a TBM which works for a water-diversion tunnel project, and the measurement record of field test suggests that the method reduces the sensitivity drift in long time measurement. Comparing with direct measurement, the coefficient of variance of the measuring result has been reduced significantly.

Post-processing method for extracting the resistivity of Rare-Earth Barium Copper Oxide (REBCO) coated conductors in over-critical current conditions from ultra-fast V-I pulsed current measurements

This paper presents a simple but rigorous method to extract correctly the resistivity of the superconducting Rare-Earth Barium Copper Oxide (REBCO) layer of High Temperature Superconductor coated conductors, when the latter are characterized in over-critical current conditions using ultrafast V-I pulsed current measurements. The pulsed current measurement method is used to reduce the amount of heat generated by the strong current flowing in the sample, but it cannot prevent it completely at current levels well above the critical current. In order to estimate accurately the temperature rise, we developed the so-called “Uniform Current” (UC) model, which consists in a static current sharing model coupled with a 2D thermal solver. The model assumes that the electric field is uniform over the sample cross section. It has been shown that this hypothesis works fine at high currents, but for lower current levels, although still higher than the critical current, one must wait until the magnetic relaxation effects disappear before using the outputs of the UC model. We also derived a theoretical bound for the error related to magnetic relaxation, which can be estimated experimentally by using a rectangular pick-up coil located just above the sample surface. After applying the UC model on an experimental set of data, one obtains a whole set of data points defining the resistivity ρ(J,T) of the REBCO superconductor being characterized.