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Online condition monitoring of winding insulation has been proved to be an effective means to improve the reliability of an inverter-fed machine, but little work has been done on the insulation of line-end coil subjected to much higher transient voltage stress with a higher risk of premature insulation break down. In this paper, the inverter self-excited high-frequency switching oscillations are utilized for the line-end coil insulation condition monitoring. To improve the condition monitoring sensitivity and its robustness to dynamic operating conditions, a switching oscillation mode decomposition (SOMD) method is proposed. Firstly, the condition-sensitive mode, i.e. high-frequency common-mode (HFCM) current is selected and separated by the variation mode decomposition (VMD) algorithm among three dominant modes in switching oscillation current. Then, the amplitude-frequency features of HFCM current are extracted for condition monitoring. Finally, the overall insulation condition of three-phase line-end coils and the degree of asymmetric degradation are quantitatively evaluated by the frequency and amplitude features respectively. Experimental work was carried out and the results demonstrate the good performance of high sensitivity, good robustness, and non-contract safety.

This paper presents a novel configuration of the eddy current speed sensor to measure the rotating speed of iron rods and shafts up to 3000 rpm. The proposed eddy current speed sensor has an axial airgap structure with one excitation coil and two antiserially connected pick up coils. The speed sensor is mounted in the end shaft part region. Different solid iron materials for rotating shaft are considered in the measurements and calculations to evaluate solid iron material effect on the eddy current speed sensor performance. 2D and 3D finite element method is utilized for the performance analysis of the speed sensor. Also, a 2D analytical method is developed for parametric analysis. A copper rod is also used to compare the speed sensor with the rotating iron shaft and copper shaft. Finally, two thin copper discs with different diameters are mounted on the solid iron shaft and their influences on the eddy current speed sensor were evaluated and measured to increase sensitivity and decrease sensor dependency on the permeability of the solid iron shaft. The achieved nonlinearity errors are about 0.2%.

Experiments aimed at searching for variations in the fine-structure constant α are based on spectroscopy of transitions in microscopic bound systems, such as atoms and ions, or resonances in optical cavities. The sensitivities of these systems to variations in α are typically on the order of unity and are fixed for a given system. For heavy atoms, highly charged ions and nuclear transitions, the sensitivity can be increased by benefiting from the relativistic effects and favorable arrangement of quantum states. This article proposes a new method for controlling the sensitivity factor of macroscopic physical systems. Specific concepts of optical cavities with tunable sensitivity to α are described. These systems show qualitatively different properties from those of previous studies of the sensitivity of macroscopic systems to variations in α, in which the sensitivity was found to be fixed and fundamentally limited to an order of unity. Although possible experimental constraints attainable with the specific optical cavity arrangements proposed in this article do not yet exceed the present best constraints on α variations, this work paves the way for developing new approaches to searching for variations in the fundamental constants of physics.

Purpose To predict the change of retinal sensitivity using optical coherence tomography (OCT) parameters in eyes with central serous chorioretinopathy (CSC). Methods Twenty-three eyes of 23 patients with CSC were enrolled. Retinal sensitivity was measured twice with a microperimetry in all examined eyes. OCT measurement was simultaneously conducted. The relationship between retinal sensitivities and the thicknesses of i) retinal nerve fiver layer + ganglion cell layer (RNFL+GCL), ii) inner nuclear layer (INL) iii) outer nuclear layer (ONL) and iV) serous retinal detachment height (SRDH) were investigated in a point-wise manner. We also investigated the association between the change of retinal sensitivity and OCT parameters at baseline. Results The mean age of participants was 49.8 ± 10.7 years. The mean SRDH was significantly lower (p

The equivalent elastic modulus is a parameter for controlling the deformation behavior of fractured rock masses in the equivalent continuum approach. The confining stress, whose effect on the equivalent elastic modulus is of great importance, is the fundamental stress environment of natural rock masses. This paper employs an analytical approach to obtain the equivalent elastic modulus of fractured rock masses containing random discrete fractures (RDFs) or regular fracture sets (RFSs) while considering the confining stress. The proposed analytical solution considers not only the elastic properties of the intact rocks and fractures, but also the geometrical structure of the fractures and the confining stress. The performance of the analytical solution is verified by comparing it with the results of numerical tests obtained using the three-dimensional distinct element code (3DEC), leading to a reasonably good agreement. The analytical solution quantitatively demonstrates that the equivalent elastic modulus increases substantially with an increase in confining stress, i.e. it is characterized by stress-dependency. Further, a sensitivity analysis of the variables in the analytical solution is conducted using a global sensitivity analysis approach, i.e. the extended Fourier amplitude sensitivity test (EFAST). The variations in the sensitivity indices for different ranges and distribution types of the variables are investigated. The results provide an in-depth understanding of the influence of the variables on the equivalent elastic modulus from different perspectives.

Magnetic sensors based on tunneling magnetoresistance (TMR) effect exhibit high sensitivity, small size, and low power consumption. They have gained a lot of attention and have potential applications in various domains. This study first introduces the development history and basic principles of TMR sensors. Then, a comprehensive description of TMR sensors linearization and Wheatstone bridge configuration is presented. Two key performance parameters, the field sensitivity and noise mechanisms, are considered. Finally, the emerging applications of TMR sensors are discussed.

Flexible piezoelectric sensors have attracted much attention due to good dynamic response, high sensitivity, and self-powered sensing advantages. However, piezoelectric outputs are usually affected by temperature variation, thus limit their applications on industrial intelligent equipment. Here, a new flexible piezoelectric sensor with in-situ temperature sensing and piezoelectricity calibration function is developed. The sensor can calibrate the piezoelectric output based on temperature to achieve high-accuracy sensing capability. It consists of a flexible polyimide substrate, S-shaped platinum interdigital electrodes and aligned piezoelectric fibers. The temperature sensor has a high sensitivity of 19.2 /C with good linearity, and keeps good accuracy under bending deformation. And when the working temperature range is 25-60C, the sensor has a good piezoelectricity calibration effect, so that it maintains a stable sensitivity of 244mV/without being affected by temperature. Furthermore, this paper systematically studied the influence of temperature on piezoelectric output, and established a calibration method to improve the accuracy of piezoelectric output under temperature changes. Finally, the flexible integrated sensor was conformably attached on the bearing surface to in-situ sensing temperature and vibration. The structural design and piezoelectricity calibration method can promote the application of flexible piezoelectric sensors in the industrial field.

The traditional remote field eddy current (RFEC) testing is a method widely applied for detecting the corrosion and wall thinning in a ferromagnetic pipe system and shows intrinsic deficiencies in axial defects quantification due to the distinct probe structure. A circumferential alignment probe structure is used to improve the sensitivity to axial defects of pipes. Meanwhile, current approaches typically are incapable of classifying inner diameter (ID) and outer diameter (OD) defects of the pipe, which brings difficulties to the formulation of strategies in pipe repair. An external pulsed RFEC method is proposed to address the issues in this paper. First, we give a thorough analysis of the effects of probe geometry and excitation parameters on the output signal, targeting parameters optimization. Secondly, the finite element model is built and used to analyze the relationships between the defect size and signal features under different excitation types. Finally, the improvements in probe performance and the ability to classify ID and OD defects are validated by measuring the defect depths of the pipe. Results showed the zero-crossing time feature can be used to distinguish ID from OD defects. Thus, the proposed method is an effective complementary measure for the existing RFEC tools.

In electrified railways, pantograph-catenary (PC) arc frequently occurs in the process of train passing through split-zone insulator, which threatens the current collection of PC and operation of electric multiple units (EMUs). So far, there has been few studies on the analysis and modeling of the PC arc on split-zone insulator. It is noting that this research is different from that of split-phase region. This paper firstly analyzes the dynamic variation process of PC distance as EMUs pass the insulator, and deduces the formula which can reflect the PC arc length variation according to the specific mechanical structure of insulator. Then, a black-box arc model of split-zone insulator is proposed. Next, a vehicle-grid model of the EMUs which contains the arc model of split-zone insulator is established to simulate and analyze the characteristics of the PC arc on split-zone insulator. Further, the proposed arc model in this paper is verified by comparing the simulated arc characteristic waveforms with the measured results. Finally, a sensitivity analysis of the arc model under different lifting angles of the contact wire is carried out in order to analyze the suppression of PC arc on split-zone insulator.

The corrosion of steel due to chloride ingress is one of the major causes of deterioration of reinforced concrete structures. In order to ensure a structure achieves the design life specified, predictive modelling is employed. To undertake this modelling, details are required on a number of variables; however, each of these variables has a level of uncertainty which can affect the reliability of the model. To address these issues, this paper reports the analysis of data taken from four distinct elements on a port structure, in Australia, constructed in three phases between 1926 and 1985, using both pre-cast and cast in situ techniques. The cover depth, surface chloride concentration and chloride diffusion coefficient were determined for different elements on the structure, with a total of 244 data points obtained. The data was analysed to identify the statistical distributions and probability density functions produced. A novel analytical model was developed based on the solutions to Fick's equation. The results showed that both surface chloride and the diffusion coefficient were positively skewed with no significant variation in the sensitivity. It was also found that controlling the diffusion coefficient has a more influential effect than increasing the cover.

Quantitative oxygen detection is of great importance in biological fields, complex environments, and chemical process engineering. Due to the high sensitivity and rapid response of long-lived phosp...

Power electronic converter can produce massive voltage stresses on the connected transformer, with great effects on electrical ageing of the insulation. Such effects can be diverse upon different insulation components under different harmonic voltages, which have not been well clarified. This paper aims at enhancing online monitoring of converter transformers from two aspects. First, electrical ageing evaluation models are developed for different types of transformer insulation. It is the first time to clarify the effects related to the component location and the ageing severity under differential-mode and common-mode (CM) voltages. Interlayer (IL) insulation faces a serious ageing threat and the line-lead component is aged with the severest degree. Second, CM voltages are used to build transfer function (TF) measurement for IL insulation monitoring. The key is to identify the optimal monitoring frequency with the highest sensitivity. Based on the analytical case introducing typical parameters, the TF performance is analyzed in different ageing conditions. Online experiments validate that the proposed method is effective and has good application prospect. The contributions lie in that the diverse ageing effects of converter harmonic voltages on different insulation components can be distinguished and online monitoring of IL insulation can be achieved effectively.

KHNP had licensed Dynamic Control rod Reactivity Measurement (DCRM) method using detector current signals of PWRs in 2006. The method has been applied to all PWRs in Korea for about 15 years successfully. However, the original method was inapplicable to PWRs using low-sensitivity integral fission chamber as ex-core detectors because of their pulse pile-up and the nonlinearity of the mean-square voltage at low power region. Therefore, to overcome this disadvantage, a modified method, DCRM-EK, was developed using kinetics behavior after equilibrium condition where the pulse counts maintain the maximum value before pulse pile-up. Overall measurement, analysis procedure, and related computer codes were changed slightly to reflect the site test condition. The new method was applied to a total of 15 control rods of 1000 MWe and 1400 MWe PWRs in Korea with worths in the range of 200 pcm–1200 pcm. The results show the average difference of -0.4% and the maximum difference of 7.1% compared to the design values. Therefore, the new DCRM-EK will be applied to PWRs using low sensitivity integral fission chambers, and also can replace the original DCRM when the evaluation fails by big noises present in current or voltage signals of uncompensated/compensated ion chambers.

This paper presents a bidirectional Thermo-resistive Micro Calorimetric Flow (TMCF) sensor implemented by a 0.18 m CMOS-MEMS technology, while the sensor thickness is thinned to 2.7 m through an in-house developed MEMS fabrication process. For the bidirectional airflow of -6 ~ 6 m/s, the TMCF sensor achieves the highest sensitivity of 453 mV/(m/s), and its highest normalized sensitivity with respect to the signal amplification gain (gain = 250) and the input heating power (1.58 ~ 1.72 mW) is 1150 mV/(m/s)/W. By reducing the heating power to the sub-mW of < 220 W, the TMCF sensor can still give a remarkable sensitivity of 87.4 mV/(m/s). In addition, the developed TMCF sensor has an intrinsic minimum detectable flow velocity (MDFV) of 99 m/s and a response time of 4.8 ms. The performance achieved by this flow sensor enables accurate indoor airflow measurements even when dealing with the extremely low-speed flow (< 0.05 m/s). Furthermore, the high-performance TMCF sensor is applied for remote human motion detection, where different walking speeds and moving patterns of the occupants can be captured. Therefore, this developed CMOS-MEMS sensor will not only be a promising flow sensing node in the HVAC system, but also potentially be used for the non-visible and private occupant counting in buildings/rooms.

Single nanoparticle detection is demanding in fields such as early-stage diagnostics, environmental monitoring and biochemical researches. Microcavities are becoming excellent platforms for ultrasensitive detection due to the extremely strong enhancement of light-matter interactions. However, the analytes to be detected will introduce optical losses, which eventually spoils the detection limit of the optical sensor. The strong light confinement enables optical induced mechanical oscillations that is also sensitive to analyte attachments and can thus be applied as an alternative sensing signal in microcavity sensors. In this work, the mass sensitivities of the mechanical oscillations of a microcavity are theoretically discussed. The sensitivity dependence on different modes, analyte sensing position and microcavity structure are explored via finite-element-method simulations, which are consistent with theoretical predictions. Our results provide an effective guideline for the sensitivity optimization during microcavity design aiming for single nanoparticle mass detection.

Simultaneously and independently measuring two-dimensional (2D) displacement, one-dimensional (1D) for out-of-plane measurement and 1D for in-plane measurement, is important for practical applications. Although extrinsic fiber Fabry-Perot interferometers (EFPIs) have been reported for highly precise out-of-plane displacement measurements for many years, simultaneous measurement of 2D displacement with submicron accuracy has not been realized by a monolithic EFPI as far as we know. In this paper, a monolithic dual-cavity EFPI to realize 2D displacement measurement of a target is reported. By quantitatively analyzing and experimentally calibrating the linear dependences of the in-plane displacement sensitivity and interception on the cavity length, the effect of out-of-plane displacement on the in-plane displacement measurement is removed, which is the basis of the 2D displacement detection. 2D random movement detection and the repeatability of the system are investigated experimentally. Within the range of 10m for in-plane displacement, and 352m-358m for cavity length, demodulation errors better than 96nm are achieved. The 2D displacement measurement system based on the dual-cavity EFPI with the advantages of noncontact, high accuracy and compact size is promising to be applied in the 2D acceleration measurement, 2D rotor vibration measurement, 2D precise positioning in semiconductor manufacture, thermal expansion coefficient measurement, and so on.

In this paper, we propose and theoretically design a highly sensitive refractive index (RI) sensor based on Vernier effect in three coupled micro-ring resonators (CMRR) with identical geometries. When the whispering gallery mode phases of different microresonators match with each other, transmittance of the CMRR increases and the envelope peak wavelength shift of the modulated spectrum could be exploited for wavelength-interrogated RI sensing based on Vernier effect. Further simulation results indicate that RI sensing could be achieved within a wide RI range of 1.33 to 1.43 by adjusting RI of the liquid kept inside the control cavity, and limitless sensitivity could be achieved for some specific RI ranges which are mainly determined by geometric parameters of the resonators and the order of selected envelope peak for sensing, making the sensor available for different sensing requirements. The proposed CMRR provides a compact, flexible and low-cost solution for biochemical sensing applications. And moreover, the proposed RI sensing range extension method as well as limitless sensitivity mechanism pave a new way toward the development of dynamic RI sensing and tunable optoelectronic devices.

Flexible piezoresistive pressure sensors based on a graphene-elastomer composite have gained popularity as electronic wearable sensors due to their simplicity and promising practical application in health monitoring and wearable devices. There is an urgent need to develop pressure sensors that are simplistic in design with good sensitivity and equally capable of production in large volumes. Studies have shown that implementing micro/nanostructures improves the sensitivity of graphene-elastomer pressure sensors. Therefore, in this paper, we fabricated thick nano wrinkles on a graphene-elastomer sandwich structure through a rapid thermal annealing procedure. The wrinkled structure was fabricated by rapid thermal annealing of spin-coated PEDOT:PSS (PH1000) on graphene-PDMS composite to facilitate the generation of wrinkles and optimize the sensitivity of our pressure sensor. We performed analyses on our pressure sensor under various compressive loading ranges. The pressure sensor detected pressure applied at these various ranges within a reasonable response time of 160ms and demonstrated excellent repeatability without hysteresis. In addition, we observed satisfactory sensitivity under tensile strain exhibiting high stretchability. The sensor displayed good sensitivity of 2.83 kPa-1 from compressive loading in the low-pressure range 0 Pa -490 Pa, and from 490 Pa-10 kPa the sensitivity was 0.12k Pa-1. The sensor demonstrated stretchability of up to 50% with a gauge factor of 20.1. We observed that it is highly responsive in the lower pressure range and capable of detecting subtle pressure. Furthermore, we demonstrated pressure detection in human motion monitoring. Overall, the pressure sensor displayed potential applications in human monitoring devices and wearable electronics.

A time-domain free-space technique has been proposed to extract relative permittivity (er) and effective conductivity (σe) of low-loss dielectric samples using their metal- and air-backed calibration-free reflected powers. Numerical computations and 3D electromagnetic simulations were performed to validate the method. A sensitivity analysis was carried out to examine its accuracy. Calibration-free time-domain free-space measurements over 1-12 GHz were conducted by VNA to extract er and σ e of polyethylene and polypropylene low-loss samples.

Optical tunneling is an effect extremely sensitive to wavelength changes. In this article, we use this effect to design a new type of biosensor. The tunneling effect is excited by long range surface plasmon resonance, the energy is concentrated in the sensing medium in the form of standing waves, which lead a very high wavelength sensitivity and quality factor. By using COMSOL for finite element analysis, for the sensor structure of BK7/Cytop /Al2O3/Ag/Al2O3/sensing media/air, a quality factor of 10296 RIU-1 is achieved under angle modulation, a sensitivity of 170,000 nm/ RIU and a quality factor of 11333 RIU-1 are obtained under wavelength modulation. At the same time, the advantage of this structure is that there is no excessive requirement on the refractive index of the material, and a good sensing effect can be achieved even if the material is cheap and easy to prepare. After optimization, this structure is suitable for sensing media with a refractive index of 1.335-1.375, which can be applied to most liquid solutions.

Extremely high sensitivity is the long-time pursing goal for the surface plasmon resonance (SPR) sensor, which means the capability to detect analytes with lower concentrations or interactions for smaller biomolecules. It was suggested that a flat dispersion for the plasmon material enables to enhance the sensitivity dramatically. However, the regulation ability of inherent dispersion in natural materials is limited. With the appearance of hyperbolic metamaterials (HMMs), the management of the plasmon materials dispersion becomes possible. In this paper, the HMMs with metal/dielectric multilayer structure are proposed to construct the SPR sensors. Through numerical simulations and theoretical analysis, we find that the flat dispersion in the HMM structure could significantly benefit the sensitivity improvement for HMM-SPR sensors. As a result, the proposed HMM-SPR sensor obtains an ultrahigh sensitivity of 34.00 m/RIU in the experiment, which is one order higher in magnitude than that of the conventional monolayer metallic SPR sensors. Thus, this research shows insight into understanding the dependence of the HMM-SPR sensitivity on dispersion management and provides a practical methodology to develop extremely high-sensitivity SPR sensors based on artificial plasmon materials.

Uranium and plutonium are required to be accounted in spent fuel head-end and major recovery area in pyro-process for safeguards purpose. The possibility of neutron resonance technique, as a non-destructive analysis, was simulated on isotopic fissile analysis for large scale process. Neutron resonance technique has advantage to distinguish uranium from plutonium directly in mixture. Simulation was performed on U235 and Pu239 assay in spent fuel and for scoping examination of assembly type. The resonance energies were determined for U235 and Pu239. The linearity in the neutron transmission was examined for the selected resonance energies. In addition, the limit for detection was examined by changing sample density, thickness and content for actual application. Several factors were proposed for neutron production and the moderated neutron source was simulated for effective and efficient transmission measurement. From the simulation results, neutron resonance technique is promising to analyze U235 and Pu239 for spent fuel assembly. An accurate fissile assay will contribute to an increased safeguards for the pyro-processing system and international credibility on the reuse of fissile materials in the fuel cycle.

In this paper, we demonstrate the transmission spectral and surrounding refractive index (SRI) sensing performance of long-period fiber gratings (LPFGs) at 2 m waveband. The cladding modes operating at 2 m waveband show higher SRI sensitivity than 1.55 m waveband. The influence of a little off resonance region of grating period, refractive index modulation and duty cycle of gratings are analyzed theoretically. Additionally, the LPFGs of LP08 mode near dispersion turning point operating at 2 m waveband are investigated theoretically and experimentally. Mode splitting brings out with the increasing SRI. After the resonant dip splitting into two dips (dip A and dip A), the SRI sensitivity of dip A are measured to be as high as -8495.2 nm/RIU in the SRI region of 1.445-1.457. The proposed 2-m-waveband LPFG makes it a potential in biochemical and environmental monitoring.

Temperature sensors are indispensable in healthcare, human-machine interface, robotics, and other areas. However, facile and rapid fabrication of flexible temperature sensors with good performance are still required. In this work, a fast-response flexible temperature sensors is fabricated in a facile manner on the basis of laser-reduced graphene oxide(GO) for contactless human-machine interface. The combined effects of the GO concentration and scan line spacing of the laser on the sensitivity of the temperature sensor are investigated systematically. The intrinsic correlation among the two critical process parameters, material properties, and sensor sensitivity is revealed. Results show that the temperature sensor achieves the highest sensitivity of 0.37% °C−1 when the GO concentration is 4 mg/mL and the scan line spacing is 0.12 mm. The temperature sensors fabricated using the optimized process parameter also have a fast response time, good linearity, small hysteresis, good repeatability, and stable performance, and are successfully used to monitor human breathing, blowing, and spatiotemporal temperature variation of a curved surface. The sensors can also detect finger proximity. In addition, a 3 × 3 flexible temperature sensor array is fabricated for contactless unlocking of a code lock. The fabricated array reveals the great potential of the sensors developed in this study for contactless human-machine interface.

In this study, shear resistance of ultra-high-performance fibre-reinforced concrete (UHPFRCs) containing different types (smooth, hooked and twisted fibre), fibre aspect ratios (l/d = 100, 95 and 65) and volume contents (0.0, 0.5 and 1.5 vol.%) of steel fibre was investigated using a new shear test method. Shear resistance of UHPFRCs strongly depended on the fibre type, fibre aspect ratio and fibre volume content. The twisted fibre exhibited the highest resistance in terms of shear strength, shear strain capacity and shear peak toughness, the smooth was the next and the hooked fibres produced the lowest response. The bigger the aspect ratio of fibre added to the mixture, the higher the shear resistance of UHPFRCs can be observed. Besides, the shear resistance of UHPFRCs was significantly enhanced with the increase of fibre volume content. The compressive strength and flowability of all mixtures were also checked. The compressive strength increased from 184 MPa for ultra-high-performance concrete to 210 MPa for UHPFRCs, whereas the flowability of mixtures varied from 203 mm to 250 mm. Finally, a theoretical model to predict the shear resistance of UHPFRC beams without the stirrup bar was proposed and verified.

A biosensor based on the modified Kretschmann configuration is proposed here. The sensitivity of the conventional prism-based sensor using angular interrogation is low. To enhance the sensor's performance, layers of zinc sulfide (ZnS) and graphene have been deposited over the metal layer. The angular interrogation technique is used to analyze the performance of the sensor. The thickness of the Ag metal has been optimized. The thickness of the Ag metal is taken as 50 nm because minimum reflectance has been achieved. With the combinations of the four layers of ZnS and one graphene layer, the maximum sensitivity attained is 305o/RU. Performance parameters such as detection accuracy, FWHM, and quality factor of the sensor have been evaluated as obtained as 0.33 deg-1, 3.05 deg, 100.7 RIU-1, respectively. The proposed sensor has potential application in the field of biochemical and biological analyte detection.

In the field of physical oceanography, the temperature and pressure of seawater are important fundamental parameters. In order to realize the simultaneous measurement of the temperature and pressure in seawater, a reflective optical fiber sensor based on polydimethylsiloxane (PDMS)-sealed optical microfiber coupler combined with a sagnac loop (OMCSL) is proposed. Benefiting from the high thermo-optical coefficient and large elasticity of PDMS, and the large-scale swift field transmission characteristics of optical microfiber coupler (OMC), the sensitivity and structural stability of our sensor is largely improved. The response performance of the sensor is further analyzed by numerical simulation calculations and theoretical modeling. Experimental results show that the temperature and pressure sensitivity of the sensor could reach -2.133 nm/C and 3.416 nm/Mpa, respectively, about one order higher than that of bare fiber OMCSL. Furthermore, via inversely calculating the cross-sensitivity matrix, the temperature and pressure sensing can be demodulated simultaneously, and the average errors of the preliminary experimental settlements are 1.61% and 5.02%, respectively. Due to the merits of compact structure, easy fabrication, high sensitivity, fast response speed and high stability, the basic performance of this dual parametric sensor is comparable to the existing electrical temperature-depth (TD) sensor, which is expected to meet the practical application requirements of marine environmental monitoring and ocean dynamics research.

In this work, we firstly used a new two-dimensional (2D) semiconductor material Bi2O2Se for optical-fiber SPR sensor sensitization, proposed and validated a U-shaped optical-fiber SPR sensor with Au film- Bi2O2Se Sandwich structure. The finite element simulation results illustrate that the electric field strength on the surface is 2.08 times higher than that of the pure Au film, which excites a stronger SPR phenomenon thus leading to a high sensitivity of the sensor. The effect of the Radius on the sensor performance was investigated, and the optimal structural parameters were derived to fabricate the sensing probes. The RI sensitivity of the presented sensor is 6827.41 nm/RIU, 1.98 times superior to that of the pure Au film U-shaped optical SPR sensor. The sensor is insensitive to temperature fluctuations and has good repetitive and environmental stability. The proposed sensor has good potential for future applications in biomass detection, which also indicates that Bi2O2Se has good prospects for future applications in optoelectronic devices.

In the present work, the hydrodynamics behavior of a 3D small-scale cold flow modeling of a gas-solid tapered fluidized bed is evaluated with the Eulerian-Eulerian two-fluid modeling (TFM) approach. The sensitivity of different modeling parameters, including lift and virtual mass forces, viscous force, gas-solid drag force, granular temperature, granular viscosity, granular pressure, particle-wall specularity coefficient, particle-particle restitution coefficient, and particle-wall restitution coefficient, are systematically investigated to optimize the performance of the present numerical model. The results from different sensitivity analyses reveal that the gas-particle drag force is a more important force to resolve the correct time-averaged axial and radial solids holdup profiles of the tapered fluidized bed than the other investigated parameters. The highest accuracy possible from simulations is achieved from the Gibilaro drag model followed by the Arastoopour and EMMS/bubbling models. In contrast, all other drag models over-predict the gas-particle interaction force. The assessment of the lift and virtual mass forces, viscous force, granular temperature, granular viscosity, granular pressure, and particle-wall restitution coefficient results reveal that these parameters are less critical for the numerical simulations of the tapered fluidized bed than the gas-solid drag force. However, the assessment of particle-wall specularity coefficient and particle-particle restitution coefficient reveals that adjusting these parameters in the numerical simulations is helpful to achieve a better agreement between the experimental data and model results. For the higher gas flow rate, the current work shows that a better agreement can be achieved by tuning the parameter values in the standard sub-models than the previously published TFM studies. Meanwhile, for the lower gas flow rate, the accuracy of the present work is slightly lower than the previously published work but acceptable with the experimental measurements. The current work has an advantage over the previously published work in terms of lower computational effort by using the simplified geometry and mean particle diameter assumptions.

We propose and develop a high-sensitivity fiber Bragg grating (FBG) accelerometer based on a flexible hinge for vibration sensing. The proposed method employs a 1 mm FBG that is inscribed pointwise using a femtosecond laser such that the resultant stress concentration at the FBG is improved significantly by reducing the distance between the two bonding points of the FBG structure. Through theoretical calculations and finite element simulations, the relationship between sensitivity and distance was found to be inversely proportional. Using this structure, the sensitivity was enhanced to 804 pm/g at 15 Hz and 30 Hz. The resonant frequency of the proposed accelerometer is 102 Hz, and the working frequency bandwidth is from 10 to 50 Hz. The performance of the accelerometer allows detection of vibrations in seismic explorations with high reliability.

In recent years, high growth in robotics and automation fields, increased the demand of tactile sensors that are designed to detect various information by physical contact, have gained much importance in the development of biomedicine, social assistance, and industry. Piezoelectric tactile sensors fabricated from polyvinylidene difluoride (PVDF) are used to sense vibrations because of their high sensitivity, mechanical flexibility, multi-technology compatibility, and stability and cheaper cost. The analysis of the accepted design of the sensor as two layers of the PVDF and aluminum electrode in between was performed using COMSOL Multiphysics software. The paper aims to study the electrical properties of sandwich structured tactile sensors and validate as use of piezoelectricity of PVDF in sensor design. The obtained results from the simulation as 0.5 V when 42 N/cm2 stress is applied helps to optimize the development of sensors and allow their adjustments by comparing the analytical results of different output signal changes, eigenfrequency, vibration amplitude, and applied pressure to the film.

Developing sensing platforms that simultaneously integrate high sensitivity and accuracy has been a promising but challenging task for the detection of protein biomarkers in clinical samples. Herein, we engineered an Au nanostar-based liquid phase interfacial ratiometric SERS platform with programmable entropy-driven DNA circuits to detect the protein biomarker Mucin 1 (MUC1) in clinical samples.

In the concentrating solar power generation (CSP), the latent heat thermal energy storage system (LHTES) is under the constraint of the outlet threshold temperatures, which caused lower effective utilization rate (Uma) of the phase change material (PCM). The objective of the present work is to improve the performance of the shell-and-tube LHTES which is under the constraint of the outlet threshold temperatures in charging and discharging processes. In this study, a transient, two-dimensional, and axisymmetric model of a shell-and-tube LHTES is established. Based on the model prediction, first, the sensitivity analysis of the geometry parameters to the performance of the LHTES shows that with the increase of the specific surface area and the porosity, the Uma monotonically increases, but the investment cost for LHTES per unit of stored heat (cTES) has a minimum value. Then based on the influence of the number and filling thickness of cascaded PCMs, a design criterion of the cascaded PCMs distribution is proposed for the shell-and-tube LHTES constrained by the outlet threshold temperatures, and the effectiveness of this design criteria is verified. Based on the proposed design criterion, the Uma of the optimal shell-and-tube LHTES with 5-cascaded PCMs can reach 77.6%, which is 3.1 times larger than that of a non-cascaded LHTES. Its cTES is only about 2/5 of a non-cascaded LHTES. The results of optimizing the geometry parameters of the TES device and the distribution of cascaded PCMs can be beneficial to the shell-and-tube LHTES which is under the constraint of outlet threshold temperatures in the real utilization of CSP.

Label-free measurements using impedance sensing could enable microfluidic chip electrophoresis (ME) to be used in point-of-care (POC) diagnostics. However, impedance sensing methods reported in this field need considerable optimisation. GOAL: Develop a novel design process for optimising tetrapolar electrical impedance measurement (TEIM) sensor performance in ME applications through a systematic investigation a) of the impact of a TEIM sensors design parameters on its performance in ME and b) of the relationship between the above parameters with those of the microfluidic channel and the sample to be sensed. METHODS: 3D FEM sensitivity simulations, verified experimentally, were carried out to study the impact of sensor and channel parameters on the measured impedance and their interrelationship. Subsequently, the impact of sensor parameters on sensing a sample band’s conductivity and size was investigated. RESULTS: The impact of channel dimensions on transfer impedance measurements is significant. The non-linearity reported for transfer impedance measurement of volume conductors can be manipulated by appropriate sensor parameter design. The sensor performance can be optimised by designing electrode length and measurement electrode distance in relation to the channel height and sample band length, respectively. The sensor performance is not affected by the injection electrode distance. CONCLUSION: There is a relationship between sensor, channel and band parameters and this warrants establishing a systematic design process of TEIM sensors in ME. SIGNIFICANCE: This paper presents a novel approach to optimising the design of TEIM sensors in ME potentially providing significant performance improvements and thus allowing for label-free POC electrophoresis diagnostics.

We present the modelling, design, and characterization of a novel fiber Bragg grating (FBG) accelerometer based on a bearing. A cantilevered mechanical structure with bearings can effectively decrease energy loss during vibration and enhance sensitivity. The principle of the accelerometer is analysed by a simplified model. The influence of the structural parameters of the proposed sensor on its sensitivity and resonance frequency is further analysed for structural optimization. Meanwhile, its dynamic behaviour and frequency response characteristics are analysed by numerical simulations. In addition, dual-FBG not only enables temperature compensation but also enhances sensitivity. Experimental results indicate that the FBG accelerometer provides a linear response over a broad frequency range from 0.5 Hz to 40 Hz, with a high sensitivity of 575.8 pm/g. This FBG accelerometer with low frequency and high sensitivity provides effective support for the design of sensors of the same type.

The dielectric effects are significant in certain circumstances in hydrocarbon exploration and production. Neglecting these effects can result in an inaccurate description of subsurface structure in terms of resistivity estimation and boundary location. However, almost all existing research has ignored the dielectric effects in the inversion process for ultradeep electromagnetic logging-while-drilling (LWD) measurements. As a complement, this article aims to investigate the impact of the dielectric constant on the inversion performance. In this study, we present the possible causes of the appearance of large dielectric constant in formations and discuss the influence of dielectric constant on one set of measurements via the sensitivity study. Besides, a 2-D pixel-based inversion algorithm is introduced for simultaneous determination of resistivity and dielectric constant. Also, the gradient of measurements with respect to interested parameters using the adjoint method is provided and validated. In addition, the capability of the inversion approach is demonstrated with several numerical examples. It is found that accounting for the dielectric constant in the inversion can help to improve the interpretation of electromagnetic measurements in some scenarios, thus enhancing the understanding of the subsurface structures.

A coupling enhanced surface plasmon resonance (SPR) sensor based on coreless fiber is proposed. Compared with the common fiber, the coreless fiber is easier to perceive the changes of the external medium environment. As one-dimensional material with superior performance, the Au nano biconical particles are used to improve the sensor performance. Based on the finite element method (FEM), the electric field enhancement effect of the coupling between the SPR of the gold film and the Localized surface plasmon resonance (LSPR) of the Au nano biconical particles on the surface of the coreless fiber is analyzed, and the experimental results show that the Au nano biconical particles can improve the sensitivity. The sensitivity of the improved Au nano biconical particle sensor is 3514 nm/RIU, which is 64% higher than that of the traditional gold film SPR sensor, and the quality factor is increased by 24%. The new sensor based on Au nano biconical particles and gold film has a good application prospect in biosensor and chemical measurement.

A series of optical thermometers based on Eu3+/Tb3+ doped Y3Ga5O12 with self-excited GaO6 group phosphors were designed through controllable energy transfer and local crystal field perturbation simulated using the density-functional theory approach and related structures. Color-tunable properties of the phosphors could be achieved through controllable energy transfer. In addition, the thermometers exhibited superb temperature sensitive properties. Over the entire temperature range (298.15–598.15 K), maximum values of the absolute sensitivity and relative sensitivity are 0.028 K−1 and 7.03 %K−1, respectively. Meanwhile, the thermometer has outstanding resolution (ΔT = 0.0043 K) and repeatability (98.37%).

The fluorescence intensity ratio (FIR) technique is widely adopted in thermometric phosphor materials, but the improvement of relative sensitivity is normally limited by the fixed energy gap between two thermally-couped emitting levels of luminescent ions. Herein, LnAl3(BO3)4:Cr3+ (LnAB:Cr3+, Ln = Gd, Y, Lu) phosphors are found to simultaneously show 4T2 and 2E emissions of Cr3+, and their FIR is sensitive to temperature and suitable for fluorescence thermometric applications. Moreover, the energy gap between 4T2 and 2E levels of Cr3+ is tunable and the relative sensitivity can be greatly improved by modifying the host composition. Structural analysis and spectroscopic data confirm that the enhanced crystal-field of Cr3+/Al3+ sites caused by incorporating smaller Ln3+ ions into the host contributes to the improvement of relative sensitivity. The work would provide new insights for the development of novel FIR thermometric materials with high-sensitivity.

It is critical for maintaining the safe operation of turbine blades to inspect the potential structural damages promptly. However, the industry still lacks efficient tools for inspection of the curved surface. In this respect, in this article, a new flexible probe with in-plane differential coils is proposed. With the sophisticated configuration, the probe has four channels, which complement each other in terms of sensitivity to defects of different orientations. The in-plane differential scheme nulls the background signal and reduces the noise resulting in high sensitivity to microdefects. The probe can be bent according to the curved surface due to its flexible configuration. A three-dimensional finite-element method model based on the cluster parallel computation is utilized to study the feasibility and performance of the probe, and a prototype probe is developed and tested by scanning defects on the curved surface of a turbine blade sample. Furthermore, a data fusion method is proposed to obtain a better signal-to-noise ratio so that defects with length*width*depth = 2.5 mm*0.1 mm*0.1 mm can be identified. Based on repeated experiments, it is observed that the probability of detection with the fusion of the multichannels is higher than that of every single channel demonstrating that the data fusion increases the reliability of the inspection.

The dynamic experimental and numerical analysis of cracked beams has been studied with the aim of quantifying the influence of depth crack on the dynamic response of steel beams. Artificial Neural Method ANN has been used where a numerical simulation was improved in Matlab. A finite element model has also been developed by using the Ansys software, and the obtained results were compared with exact crack length. The study takes into account different hidden layer values in order to determine the sensitivity of the predicted crack depth. The results show that the response of the beam (frequencies) is strongly related to the crack depth which significantly affects the beam behavior, especially when the crack is very deep where the ANN allows us to identify the crack in lower computational time. Based on the provided results, we can detect that the effect of hidden layer size can affect the results.