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Microimage strain sensing (MISS) is a novel piston‐type sensor based on microscopic vision. In this study, optical disc slice is used as information carriers to improve MISS. There are multiple pits on the surface of an optical disc. By using machine vision algorithms, the pits can be converted into digital information, making them scales for recording displacements. By this means, we proposed a sensing method that combines high resolution, wide range, and strong robustness. The study measured displacement under different conditions. To address inevitable factors such as pixel drift, and manufacturing errors, corresponding compensation methods were provided. The results show that the measurements closely match those of the linear variable differential transformer, with a resolution of up to 20 nm and a range approaching the sensor size. Despite the sensor's dependence on machine vision, it demonstrates strong resistance to environmental factors such as brightness and angle. Combining compensation methods for pixel drift, and manufacturing errors, this sensor can be well‐applied in various working conditions. [ABSTRACT FROM AUTHOR]

Background: There are a limited number of commercially available sensors for monitoring the deformation of materials in-situ during harsh environment applications, such as those found in the nuclear and aerospace industries. Such sensing devices, including weldable strain gauges, extensometers, and linear variable differential transformers, can be destructive to material surfaces being investigated and typically require relatively large surface areas to attach (> 10 mm in length). Digital image correlation (DIC) is a viable, non-contact alternative to in-situ strain deformation. However, it often requires implementing artificial patterns using splattering techniques, which are difficult to reproduce. Objective: Additive manufacturing capabilities offer consistent patterns using programmable fabrication methods. Methods: In this work, a variety of small-scale periodic patterns with different geometries were printed directly on structural nuclear materials (i.e., stainless steel and aluminum tensile specimens) using an aerosol jet printer (AJP). Unlike other additive manufacturing techniques, AJP offers the advantage of materials selection. DIC was used to track and correlate strain to alternative measurement methods during cyclic loading, and tensile tests (up to 1100 µɛ) at room temperature. Results: The results confirmed AJP has better control of pattern parameters for small fields of view and facilitate the ability of DIC algorithms to adequately process patterns with periodicity. More specifically, the printed 100 μm spaced dot and 150 μm spaced line patterns provided accurate measurements with a maximum error of less than 2% and 4% on aluminum samples when compared to an extensometer and commercially available strain gauges. Conclusion: Our results highlight a new pattern fabrication technique that is form factor friendly for digital image correlation in nuclear applications. [ABSTRACT FROM AUTHOR]

The piles are structural elements in a foundation that transfer weight from the superstructure to the soil. The behaviour of pile foundations under lateral loading is critical. The pile needs to have enhanced tensile strength and ductility by adding supplementary material to withstand the lateral loads. There were many research studies done to improve these properties in concrete, and the addition of fibre to the concrete is one among them. Fibre-reinforced concrete is classified into numerous categories depending on the type of fibre used. This study is to use the combination of Basalt and E-glass fibre i.e., hybrid in the full-scale pile foundation under combined axial and lateral cyclic loadings. The experimental investigation was conducted on the full-scaled Conventional Concrete (CC) and Hybrid Fibre Reinforced Concrete (HFRC) piles to understand the behaviour under static and cyclic lateral loads. The lateral displacement on the piles was measured at each level of loadings using a Linear Variable Differential Transformer (LVDT). The load–displacement behaviour of CC and HFRC piles was compared under different loading conditions. The HFRC pile exhibits a 40% reduction in displacement and a 10% increase in ultimate carrying capacity compared to the CC pile. HFRC piles tend to have more load-carrying capacity than the CC piles under all types of loadings. [ABSTRACT FROM AUTHOR]

In steel structures, cover plate joints are mainly used with normal round holes, but slotted holes, where the slot is oriented perpendicular to the direction of the bearing force, make it possible to release displacements in selected directions and thus better control the complex state of stresses in the connected plates. This study investigates the initial stiffness of a cover plate with a single slotted hole. The aim of this paper is to propose an analytical model that predicts the initial stiffness of slotted holes with respect to experimental results obtained on a panel of different geometries. This approach makes it possible to evaluate the effects of the end distances on the bending of the plate compared to the bearing under the bolt. A large panel of geometries is tested to quantify the experimental value of initial stiffness using Digital Image Correlation (DIC) technique compared to Linear Variable Differential Transformer (LVDT) sensors. To evaluate the initial stiffness, a method of processing experimental data is developed that allows a reproducible determination of stiffnesses. An analytical model is then proposed based on the improvement of existing models available in the literature. It is validated for different specimen geometries considering the contribution to the initial stiffness due to bending, shearing and support of the steel plate under the bolt. The comparisons show that the proposed analytical model can predict the initial stiffness of different geometries of tested specimens with slotted holes. [ABSTRACT FROM AUTHOR]

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The article presents the effect of the addition of short straight steel fibers on the behavior of high-strength concrete (HSC) under compression (σ–ε curves). Deformations of cylindrical samples were measured simultaneously with the use of linear variable differential transformers (LVDT), strain gauges and the method of digital image correlation (DIC). The study showed that as the content of short straight steel fibers increases, both the composite compressive strength (fc) and strains (ε0), which correspond to the stress equal to the compressive strength, increase as well. To a lesser extent, the effect of short straight fibers on the descending part of the σ–ε curve was observed. An increase in the density and toughness ratio of the compressive strength of high-strength concrete with fibers compared to concrete without fibers was also observed. Moreover, compressive strength of the composite was estimated using the ultrasonic method. Based on the obtained results, a statistical analysis and an estimation of parameters fc and ε0 were carried out, and an analytical model was proposed to describe σ–ε relationship for HSC reinforced with short straight fibers under compressive loading. The results obtained for compressed fiber-reinforced concrete were compared with data available in literature. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to propose a novel technique for extracting the position signal from an inductive displacement transducer named a linear variable differential transformer (LVDT). In general, the movement of the LVDT core causes its primary inductance change in linear form. The primary winding of the LVDT is used as a time-dependent element for the triangular and square wave generator, which can be called self-oscillation, to generate frequency. The advantage of the proposed technique is that it can measure the displacement using the LVDT without an external oscillator. The change in primary inductance causes the frequency deviation generated by the oscillator. The deviated frequency is captured and converted into a voltage signal using the principle of the phase-locked loop. All the components used in this study are commercially available. The merits of this proposed technique are simple configuration, small size, and low cost. Moreover, the operating range of the LVDT can be extended without the limitation of the nonlinear transfer characteristic. The performance of the proposed technique is discussed in detail and confirmed by experimental implementation. Experimental results show that the maximum error from the proposed technique is about 0.42% and the operating range of the LVDT can be extended to more than 200%. It can be seen that the proposed technique is suitable for embedded measurement in small or micro robots. [ABSTRACT FROM AUTHOR]

In experimental investigations, conventional measuring instruments such as dial gauges, linear variable differential transformers, and extensometers are used to measure the displacement at a specific gauge length (i.e., global deformation). They are contact-based instruments which are not able to evaluate the displacements within the gauge length (i.e., localized deformations). The image analysis techniques are able to evaluate the displacements at each point within the gauge length. In the present study, the applicability and effectiveness of the image analysis technique are assessed for four different materials, i.e., concrete, steel, wood, and geomembrane which are widely used in the field of geotechnical engineering as construction material for geo-structures. For this, four different tests, i.e., compression testing of the concrete cube, tensile testing of the steel plate and wooden strip, and wide-width tensile testing of the geomembrane are performed in a systematic manner. The image analysis technique is used to evaluate the displacement fields for each material under given loading conditions. The results obtained from the image analysis technique are compared with those of conventional measuring instruments to emphasize the applicability and effectiveness of the image analysis technique for different materials having different properties. [ABSTRACT FROM AUTHOR]

Abstract The phase‐locked loop (PLL) is a critical control module applied in the control system of renewable energy sources (RESs) to synchronize with the grid voltage. When a fault occurs, the dynamic response process of the PLL will generate a phase locking error, resulting in a mass of harmonic components in the fault current of the PV inverter, which further poses challenges to transformer differential protection. To address the challenges posed by the phase locking error in practical engineering applications, this paper proposes an improved scheme that uses a digital computer algorithm to record and store the pre‐fault voltage and introduces the limiting coefficient. Firstly, the memory voltage is used to eliminate the phase locking error of the PLL, thereby mitigating harmonic distortion in the fault current of the RESs and ensuring the reliability of the transformer differential protection. In addition, the limiting coefficient is introduced to eliminate the effect of the increased amplitude of the fault current caused by the memory voltage. The voltage reference value of the inverter is multiplied by an appropriate limiting coefficient k and then output to the physical system. Finally, the effectiveness of the proposed scheme is verified by MATLAB/Simulink simulation.

Accurate determination of thermo‐mechanical properties in precipitation hardenable materials using an electro‐thermal mechanical testing (ETMT) system is a well‐established challenge. The non‐uniform distribution of temperature resulting from heating based on the joule effect (i.e., resistivity heating) leads to heterogeneous deformation along the gauge length, owing to the temperature dependency of mechanical properties, which makes their direct measurements complicated. This study presents an evaluation of four different miniaturised sample geometries that were tested to achieve an optimised sample with acceptable uniform strain and temperature distributions in the gauge volume. In‐situ displacement mapping, using digital image correlation (DIC), was utilised to calibrate the optimised sample dimensions with the aim of forcing the deformation to the hottest region of the gauge lengths during the tests. Tests were carried out on Inconel 718 (IN718) at 720°C, an optimal temperature for the precipitation of γ″, the primary strengthening particle in this alloy. The results showed that only in the case of the geometry proposed in this study (i.e., a sample with a short gauge length [~2 mm]) did the deformation acceptably localise at the centre, compared to other geometries. A correction methodology is developed that equates the strain measured using DIC over the 2 mm gauge length of the modified sample geometry with the strain measured using the linear variable differential transformer (LVDT) integrated to the ETMT, making future tests on IN718, and other precipitation hardenable materials, possible without the need for the use of a DIC system. [ABSTRACT FROM AUTHOR]

A miniature pneumatic bellows device was designed for in-situ testing inside the scanning electron microscope. The device uses a pneumatic actuator to load the specimen and displacement is directly monitored with a linear variable differential transformer sensor. Its application allowed the direct monitoring of microstructural and defect evolution in materials at the micro scale. The data produced by this testing device, in combination with measurements from micro digital image correlation, were successfully used to model the crystal plasticity of a martensitic/bainitic steel at the microstructural length scale. [ABSTRACT FROM AUTHOR]

The phase‐locked loop (PLL) is a critical control module applied in the control system of renewable energy sources (RESs) to synchronize with the grid voltage. When a fault occurs, the dynamic response process of the PLL will generate a phase locking error, resulting in a mass of harmonic components in the fault current of the PV inverter, which further poses challenges to transformer differential protection. To address the challenges posed by the phase locking error in practical engineering applications, this paper proposes an improved scheme that uses a digital computer algorithm to record and store the pre‐fault voltage and introduces the limiting coefficient. Firstly, the memory voltage is used to eliminate the phase locking error of the PLL, thereby mitigating harmonic distortion in the fault current of the RESs and ensuring the reliability of the transformer differential protection. In addition, the limiting coefficient is introduced to eliminate the effect of the increased amplitude of the fault current caused by the memory voltage. The voltage reference value of the inverter is multiplied by an appropriate limiting coefficient k and then output to the physical system. Finally, the effectiveness of the proposed scheme is verified by MATLAB/Simulink simulation. [ABSTRACT FROM AUTHOR]

Cracks pose a significant issue in rigid pavement, leading to substantial damage. The manual mixing and casting of road pavement concrete underscore the importance of concrete quality as a critical parameter. This study investigates crack behavior by varying concrete quality. Loading is performed statically using line loads, shedding light on the impact of concrete quality on crack development. The concrete to be used has a quality fc′ of 15 MPa, 25 MPa, and 35 MPa. The fine aggregate used in this study was Lumajang black sand, while the coarse aggregate used was machine crushed stone, and Portland Composite Cement (PCC) was used in all concrete mixes. The reinforcing steel used had a quality fy of 480 MPa, with a reinforcement ratio of ρ = 0.010, which was converted to 5-D16 reinforcement. The subgrade density used to support the specimens had a CBR value of 10 %. Specimen dimensions were 2×0.6×0.2 m for length, width, and thickness. Pavement plates, 30 cm thick, were placed on leveled subgrade soil in a steel box set to achieve a 6 % CBR reading. Hydraulic jacks, monitored by a load cell, applied monotonic static loading with 2 kN intervals, reaching a maximum load of 200 kN. Steel tension and plate settlement were measured using a tension sensor and Linear Variable Differential Transformer (LVDT), respectively. A data logger recorded readings, and crack widths were captured by a digital microscope with 0.01 mm accuracy. Experimental results show that low concrete compressive strength values result in larger crack widths, and vice versa. Cracks also occur at earlier loading of concrete quality fc′ 15 MPa. In addition, experiments show that the reinforcement stress value has a significant influence on crack width in specimens with low concrete quality. [ABSTRACT FROM AUTHOR]

The objective of this study is to develop a monitoring algorithm that measures the displacement of concrete structures using light detection and ranging (LiDAR). The suggested method is based on non-contact measurements providing 3D point clouds of the scanning area with high resolution. This overcomes the limitation of traditional contact-type and point-based measurement methods such as linear variable differential transformer (LVDT) and strain gauge. The developed algorithm enables one to track the boundaries of a concrete specimen and measures the vertical or lateral displacement. To demonstrate that displacement in the horizontal and vertical direction can be measured irrespective of the field of view (FOV), two different concrete specimens were constructed where gradually increasing vertical or lateral loads were applied. Then, the displacements were monitored using the set of LVDT and LiDAR for the correlation analysis. The results demonstrated a high accuracy of 98~99% correlation in comparison between LVDT and LiDAR. [ABSTRACT FROM AUTHOR]

This paper presents the optimization of an inductive displacement transducer or linear variable differential transformer (LVDT). The method integrates design software (SolidWorks 2023), simulation tools (COMSOL Multiphysics), and MATLAB. The optimization phase utilizes the non-dominated sorting genetic algorithm (NSGA)-II and -III to fine-tune the geometry configuration by adjusting six inner parameters corresponding to the dimension of the interior components of the LVDT, thus aiming to improve the overall performance of the device. The outcomes of this study reveal a significant achievement in LVDT enhancement. By employing the proposed methodology, the operational range of the LVDT was effectively doubled, extending it from its initial 8 (mm) to 16 (mm). This expansion in the operational range was achieved without compromising measurement accuracy, as all error values for the working range of 0–16 (mm) (NSGA-II with a maximum final relative error of 2.22% and NSGA-III with 2.44%) remained below the imposed 3% limit. This research introduces a new concept in LVDT optimization, capitalizing on the combined power of NSGA-II and NSGA-III algorithms. The integration of these advanced algorithms, along with the interconnection between design, simulation, and programming tools, distinguishes this work from conventional approaches. This study fulfilled its initial objectives and generated quantifiable results. It introduced novel internal configurations that substantially improved the LVDT's performance. These achievements underscore the validity and potential of the proposed methodology in advancing LVDT technology, with promising implications for a wide range of engineering applications. [ABSTRACT FROM AUTHOR]

This work deals with modeling and controlling the oscillations of a horizontally-supported car under the effect of a nonlinear spring, a damper, and a harmonic excitation external force. The proposed controller is the integral resonant controller (IRC) which is a first order oscillator coupled the car via a linear variable differential transformer (LVDT) and a servo-controlled linear actuator (SCLA). The multiple scales perturbation method is used to obtain an approximate solution and stability analyses are carried out. Based on the stability analysis, the optimum values of the controller parameters are recommended in this work for a better control operation. Several response curves are plotted for clarifying the concept of the proposed integral resonant control algorithm. A numerical simulation of the car’s motion is achieved by numerically integrating the model equations with the 4th order Rung-Kutta algorithm. The applied controller can treat the severe jumps in the oscillation amplitude where it is suppressed at different conditions of forward and backward sweeping of the amplitude and frequency of the external excitation force. [ABSTRACT FROM AUTHOR]

The High Sensitivity Terahertz Detection Module (HSTDM) is one of the scientific payloads of the Chinese Space Survey Telescope. The core of the HSTDM is the NbN superconducting SIS (Superconductor Insulator Superconductor) mixer, operating around 10 K. The installation structure of the SIS mixer needs to be specially designed to cope with the mechanical vibration during the launch phase and the thermal insulation requirements during the operation phase. Material thermal expansion characteristics investigation based on low-temperature LVDT (Linear Variable Differential Transformer) measurement and scratch marking measurement were carried out to confirm the validity of the thermal expansion lock mechanism design. The two methods are cross verified. The LVDT experimental measurement results show that the shrinkage rate of Teflon changes with temperature and meets the theoretical model. At the same time, we verified the LVDT results with scratch marking method. Consistently, the shrinkage rate of the material is 1.86 % at 80 K, so the Teflon front-end lock mechanism of the SIS mixer can achieve effective separation after cooling down. [ABSTRACT FROM AUTHOR]

Measuring the structure's displacement plays a very important role in ensuring the safe operation of railway bridges in general and urban railway bridges in particular. In Vietnam, traditional methods using high-precision mechanical gauges have been used to measure the displacement of railway bridges. However, these methods need a lot of effort in installation and traffic control during implementation. These methods are based on the static principle: The test loads are placed on the bridge structure, and then the structure's displacement is observed. The safety assessment and analysis results are guaranteed by multiplying the dynamic coefficients, leading to some assessments that may not be close to the actual exploitation of the bridge structure. Therefore, the current study presents a new solution for measuring the displacement of railway bridge structures. This method uses Linear Variable Differential Transformer (LVDT) sensors to record the continuous displacement of the structure during the time the train passes over the bridge. Through field measurements combined with a finite element analysis model, the research focuses on developing and applying LVDT sensors in urban railway bridge structure health monitoring. At the same time, the potential of developing this method in Vietnam in the future is evaluated. [ABSTRACT FROM AUTHOR]

Bangladesh is connected through bridges and many of them are experiencing damages due to the aging of concrete, weathering effect, or excessive loading. Repair and retrofitting of those bridges are becoming inevitable to make them operational. In this study, the damages of a concrete bridge have been investigated through non‐destructive tests and numerical methods. A repair and retrofitting strategy for the damaged girders has been developed using epoxy injection, shrinkage‐compensated micro mortar, and externally bonded Carbon Fiber Reinforced Polymer (CFRP) sheets. The micro mortars are injected inside the large cracks and damaged portions of the girders. The flexural zones of the girders were strengthened using U‐shaped CFRP sheets. Field load tests are also conducted to determine the achieved improvement from the repair strengthening work. Dynamic accelerometers, digital probes, and linear variable differential transformers (LVDT) were attached to determine the actual deflections of the girder before and under loading. Finite Element models (FEM) are developed to validate the field data and determine the shear and flexural resistance of the retrofitted girders. The outcomes show that the retrofitted bridge satisfies the design requirements of the AASHTO‐LRFD guidelines. [ABSTRACT FROM AUTHOR]

Strain measurements have a significant role in evaluating the condition of various structural types and have become an essential component in the area of structural health monitoring. However, there are some limitations in the current means of strain measurement, and this study aims to improve these methods. We have designed a novel strain measurement method based on template matching algorithms and microscopic vision techniques, developed a new sliding strain sensor, and paired it with a new microscope to realize strain measurement. The method has the function of remote wireless acquisition with a cell phone, which is more widely applicable. In the laboratory performance testing, the zero drift of the sensor is mainly concentrated in the fluctuation range of ±2 με, and the effective range reaches nearly 40,000 με. In the comparison experiments with the linear variable differential transformer, the maximum error of the static loading is only 5 με, and the maximum error rate of the dynamic loading is less than 1%, which proves that it has a relatively high accuracy. Finally, the short-term real-time monitoring of the local structure of the footbridge was accomplished, and the strain changes on the surface of the structure were captured instantly, stably, and efficiently in the actual measurements. The proposed strain measurement system has the advantages of high accuracy, a low cost, convenient measurement, and wide applicability, and it provides a novel alternative means for strain measurement in the field of structural health monitoring. [ABSTRACT FROM AUTHOR]

Predicting stock prices has long been the holy grail for providing guidance to investors. Extracting effective information from Limit Order Books (LOBs) is a key point in high-frequency trading based on stock-movement forecasting. LOBs offer many details, but at the same time, they are very noisy. This paper proposes a differential transformer neural network model, dubbed DTNN, to predict stock movement according to LOB data. The model utilizes a temporal attention-augmented bilinear layer (TABL) and a temporal convolutional network (TCN) to denoise the data. In addition, a prediction transformer module captures the dependency between time series. A differential layer is proposed and incorporated into the model to extract information from the messy and chaotic high-frequency LOB time series. This layer can identify the fine distinction between adjacent slices in the series. We evaluate the proposed model on several datasets. On the open LOB benchmark FI-2010, our model outperforms other comparative state-of-the-art methods in accuracy and F1 score. In the experiments using actual stock data, our model also shows great stock-movement forecasting capability and generalization performance. [ABSTRACT FROM AUTHOR]

The differential transformer is an important component in the front-end electronics of high-precision capacitive position sensing circuits, which are widely employed in space inertial sensors and electrostatic accelerometers. The position sensing offset, one of the space inertial sensors' most critical error sources in the performance range, is dominated by the differential transformer asymmetry and requires a high-precision evaluation. This paper proposes a method to assess differential transformers' asymmetry and realize a prototype circuit to test a transformer sample. The results show that the asymmetry measurement precision can achieve 0.6 ppm for the transformer with an asymmetry level of about −278.2 ppm. [ABSTRACT FROM AUTHOR]

An analog circuit technique to realize an inverse transfer characteristic of a linear variable differential transformer (LVDT) is presented in this paper. Practically, the structure of the LVDT causes a narrow linear operating range compared with its full stroke range. However, a large linear operating range requires a huge structure for the LVDT, making it unsuitable for a small or compact measurement system. The proposed technique can be used in a commercial LVDT to extend the linear operating range to its full stroke range. The technique utilizes an inherent behavior of an operational transconductance amplifier (OTA) to emulate the LVDT transfer characteristic. The LVDT transfer characteristic generated by the OTA is used as a feedback path of the inverting amplifier formed by an operational amplifier (opamp) to realize the inverse transfer characteristic. The residual error due to the OTA behavior is very small and can be neglected without adversely affecting the performance of the proposed technique. All devices used in the proposed scheme are commercially available. The attractive features of the proposed technique are its simple configuration, small size, low cost, and high accuracy. The performance of the proposed technique is discussed in detail and confirmed by its experimental implementation. Measurement results demonstrate that the linear operating range of the commercial LVDT used in this study can be extended by a factor of more than 2.4, and a fullscale percentage error of about 0.068% was obtained. [ABSTRACT FROM AUTHOR]

Safe drilling and effective fracturing are constant challenges for shale formations. One of the most important influencing factors is the accurate characterization of the deformation and damage caused by inherent lamination and natural fractures. Furthermore, shale formations exhibit fine-scale heterogeneity, which conventional laboratory methods (linear variable differential transformer (LVDT), strain gauges, etc.) cannot distinguish. To overcome these constraints, this research aims to investigate the damage and deformation characteristics of shale samples using three-dimensional digital image correlation (3D-DIC). Under uniaxial and diametrical compression, samples of Wolfcamp, Mancos, and Eagle Ford shale with distinct lamination and natural fractures are evaluated. The 3D-DIC system is utilized for image processing, visualization, and analysis of the shale damage process under varying loads. DIC made quantitative full-field strain maps with load (tension, compression, and shear), showing all the damage process steps and strain localization zones (SLZs). DIC maps are used to quantify damage variables in order to investigate sample damage. Damage variables are used to categorize the damage evolution process of shale specimens into four stages: initial damage, linear elastic, elastic–plastic, and plastic damage. Characterizing shale damage evolution with a strain localization line is more effective because there is more damage there than in the whole sample. Damage variables based on major strain and its standard deviation from the DIC strain map for all tested shale samples follow a similar trend, though diametrical compression variables are greater than uniaxial compression. In both uniaxial and diametrical compression, the Wolfcamp shale was reported to have the highest damage variable, which was measured at 0.37, while the Eagle Ford shale was reported to have the lowest damage variable. This image-based technique is more effective not only for understanding the laminated and naturally fractured rocks but also for predicting the hydraulic fractures that will occur during the stimulation process. [ABSTRACT FROM AUTHOR]

Brittle failure of rock is characterized by the initiation, propagation and coalescence of micro- and macro-cracks. To study the macro-crack evolution of rocks, a parallel long strain gauge measurement apparatus was developed, which was composed of multiple long axial strain gauges and linear variable differential transformers (LVDTs). Using the developed strain measurement apparatus, conventional triaxial compression (CTC) tests were carried out on Linghai granite specimens. The results showed that a) using the radial strain of rock specimens monitored by LVDT as the servo feedback signal, the strain gauges can obtain the local complete stress–strain curves of the specimen. b) Macro-cracks often formed in the areas with large pre-peak axial strain (ε1) values, but not in the areas with small pre-peak ε1 values. c) There were three typical cracking patterns in Linghai granite: rapid tensile cracking, slow tensile cracking, and rapid shear cracking, among which rapid tensile cracking was the most common. d) The macro-crack evolution process can be deduced through the fracture sequence of the strain gauges and the failure pattern of the specimen. In addition, the typical crack propagation velocity of Linghai granite under a confining pressure of 80 MPa was approximately 667 m/s. [ABSTRACT FROM AUTHOR]

The interstory drift ratio (IDR) is a key engineering parameter utilized by several codes and standards to quantify structural performance and correlate with potential structural damage following a seismic event. A number of methods have been explored for measuring building interstory drift, including approaches that rely on accelerometers, linear variable differential transformers (LVDTs), global position systems, combinations of cameras and optical sensors, and, most recently, on machine learning surrogate models. Nevertheless, limitations related to accuracy, cost, and challenges associated with data processing and interpretation still hinder the broad utilization of such methods for rapid post-event damage assessment. This paper presents a recently developed optical sensor, termed a biaxial discrete diode position sensor (2DDPS), which is able to directly measure earthquake transient and residual interstory drift in the two horizontal directions and transmit structure observables to offsite locations in near real-time. The sensor performance is herein evaluated through a series of shake-table tests carried out on the single 2DDPS to provide a statistical basis for sensor performance evaluations and on the 2DDPS installed on a 3D two-story frame subject to realistic earthquake biaxial excitation to evaluate system performance under realistic deployment conditions. The experimental campaign design and execution has been supported by advanced computational models. Results of the investigation demonstrate that the 2DDPS can reliably measure transient and residual bidirectional interstory drifts with an accuracy of the order of a millimeter. A critical review of the observed error and strategies to reduce it are also provided. Evidence from the presented study demonstrates that the 2DDPS has the potential to be utilized as a key tool for rapid, postevent decision-making and field inspection prioritization. [ABSTRACT FROM AUTHOR]

Linear variable differential transformer (LVDT) is a commonly used linear displacement sensor because of its good measurement characteristics. When using laminated ferromagnetic cores in LVDTs, it is very important to take eddy currents into the account during design phase of the sensor. Particularity of the open-type core means that the eddy currents induced by the stray magnetic flux that flow in large loops tangential to the lamination surfaces take on significant values. Due to the open-type core a typical LVDT has, depending on the core material, it is, therefore, very important to take eddy currents into the account when designing the sensor. This paper's goal is to present a methodology for calculating LVDT eddy current losses that can be applied to LVDT design in order to optimize the dimensions and help with selection of materials of the LVDTs, in order to achieve the highest measurement accuracy. Presented approach using an A τ A -formulation with elimination of redundant degrees of freedom exhibits rapid convergence. In order to calculate the relationship between eddy current losses and core displacement, frequency, and material characteristics, a number of 3D finite element method (FEM) simulations was performed. Analysis of the obtained results using presented methodology for eddy current losses calculation in LVDTs enables the designer optimize the design of the LVDT. [ABSTRACT FROM AUTHOR]

Percussion driven earth anchors (PDEAs) are driven into soils using an installation steel hammer rod. PDEAs are relatively easy to install and have gained wide applications recently. The Texas Department of Transportation (TxDOT) planned to use these anchors for slope stability mitigation along the Clear Fork Trinity River at Interstate Highway 20 (IH-20) in Benbrook, Texas. However, there are no straightforward design and construction guidelines for these systems. In addition, the pull-out capacity and failure mechanisms of PDEAs in clayey soils have not been thoroughly studied. In this study, three PDEAs, Duckbill model 138 II (DB-138 II), were installed and tested on the proposed west channel bank slope to acquire the ultimate pull-out capacity. The anchors were embedded to an average depth of 10 feet into the slope bank, predominantly consisting of sandy lean clay (CL) soil. The slope was graded at an average 2:1 to 2.5:1 configuration. After installation, the anchors were subjected to an upward pull-out force using a hydraulic jack system to measure their pull-out capacity. The pull-out load, displacement, and strains were continuously recorded with a load cell, a linear variable differential transformer (LVDT), and a strain gauge, respectively. Pull-out load versus displacement curves were produced and analyzed to determine the behavior of the anchors. An empirical estimation method was then chosen to estimate pull-out capacity based on undrained shear strengths obtained either from laboratory tests or in situ Texas cone penetration (TCP) data. The comparison between estimated and field-obtained pull-out capacities showed that the pull capacity estimated using TCP data resulted in reasonably good agreement with the field-obtained capacity. The field experiment results help us to understand the relationship between the calculated and actual field pull-out resistance when PDEAs are used in clayey soil slopes. [ABSTRACT FROM AUTHOR]

Gaze behavior is important and non-invasive human–computer interaction information that plays an important role in many fields—including skills transfer, psychology, and human–computer interaction. Recently, improving the performance of appearance-based gaze estimation, using deep learning techniques, has attracted increasing attention: however, several key problems in these deep-learning-based gaze estimation methods remain. Firstly, the feature fusion stage is not fully considered: existing methods simply concatenate the different obtained features into one feature, without considering their internal relationship. Secondly, dynamic features can be difficult to learn, because of the unstable extraction process of ambiguously defined dynamic features. In this study, we propose a novel method to consider feature fusion and dynamic feature extraction problems. We propose the static transformer module (STM), which uses a multi-head self-attention mechanism to fuse fine-grained eye features and coarse-grained facial features. Additionally, we propose an innovative recurrent neural network (RNN) cell—that is, the temporal differential module (TDM)—which can be used to extract dynamic features. We integrated the STM and the TDM into the static transformer with a temporal differential network (STTDN). We evaluated the STTDN performance, using two publicly available datasets (MPIIFaceGaze and Eyediap), and demonstrated the effectiveness of the STM and the TDM. Our results show that the proposed STTDN outperformed state-of-the-art methods, including that of Eyediap (by 2.9%). [ABSTRACT FROM AUTHOR]

The article deals with DIC (Digital Image Correlation) tests on steel plates used in the automotive and railway industries, as well as in the construction industry. The most critical part of DIC tests is the quality of proper surface preparation, painting, and random patterns. The paint mediates the deformation of the optical systems, and its quality is paramount. The authors' goal in this research is to determine the optimal dye–cleaning–drying time parameters for DIC studies. Commercially available surface preparation and cleaning agents were tested alongside commercially available spray paints. Standard and specific qualification procedures were applied for the measurements. Once the appropriate parameters were determined, the results were validated and qualified by GOM ARAMIS tests. Based on the results, DIC measurements can be performed with higher accuracy and safety in laboratorial and industrial conditions, compared to the traditional deformation measurements executed by dial gauges or linear variable differential transformers. [ABSTRACT FROM AUTHOR]

In recent times, Electro-Mechanical Actuator (EMA) is widely employed in various aerospace applications because of its compactness, ease of maintenance, and cost efficiency. It attracts most of the researcher for simulation and performance analysis. It is very much important to study its control system behaviour. In general, EMA requires, three loop cascade control, but for aerospace application two loop cascade control is used for speed and position controls due to dynamic load changing requirement. Most research efforts on EMA system has used a transfer function model of all its subsystems. Nevertheless, this technique does not yield complete outcomes for analysing its performance. To analyse its performance and characteristics in dynamic condition, an experimental model is essential. In addition, this model needs to cater for analysing performance of different capacity EMA. The primary goal of this work is to simulate unique EMA model with position control using a practical data and analyse its performance. In this design, EMA is modelled by three-phase Brushless Direct Current (BLDC) motor, six-step commutation logic, a speed sensor (Tacho) and a position sensor using Linear Variable Differential Transformer (LVDT). Position and speed controls are handled by Proportional (P) and Proportional plus Integral (PI) controllers respectively. The process reaction curve method is used to tune the controllers. This tuning approach is adequate to enable accurate and robust speed and position control. This paper focus on the simulation and performance analysis of a practical EMA system with position and speed controls in matlab-simulink. The performance analysis results shows that simulated model characteristic is close to physical system and reliable. [ABSTRACT FROM AUTHOR]

Differential protection normally detects short circuits and ground faults in the windings of a power transformer and its terminals. Inter-turn faults refer to flashovers among the electrodes that arise only in a similar type of physical winding. Inter-turn faults can be examined when the adequate sum of turns is served as short-circuited. In electrical protection, it is difficult to detect inter-turn faults. An inter-turn fault of small magnitude is based on the limited number of turns that resultantly provide a large quantity of current. Due to this reason, protection that comes from the differential scenario possesses a higher degree of sensitivity without causing unwanted operations during external faults. In this paper, a protection-based stability method is proposed whereby external voltages are applied at the low-voltage (LV) side of the transformer while keeping the high-voltage (HV) side short-circuited. This was conducted using a three-phase power transformer (rating: 100 MVA, 380 kV/13.8 kV) at SWCC Shoaiba Power Plant, Saudi Arabia. In this work, differential protection (87T) and high-impedance differential protection for HV-restricted earth faults (REFs) were verified by creating In-Zone and Out-Zone fault conditions to ensure current transformer (CT) circuits and tripping logic. All of the IEDs, protection, and control schemes involved were designed by ABB. This method verifies protection stability for power transformers by implementing differential protection (87T) and high-impedance restricted earth fault (64HV) schemes through creating In-Zone and Out-Zone fault conditions. [ABSTRACT FROM AUTHOR]

Objective: Since composites still face a critical problem called polymerization shrinkage and bulk‐fill composites have reported acceptable results for this issue, this study aims to assess the polymerization shrinkage of a new bulk‐fill flowable composite (G‐aenial bulk injectable [GBI]) and compare it to other bulk‐fill and conventional composites. Materials and Methods: In this in vitro study, 25 composite discs were fabricated using three bulk‐fill and two conventional composites. They were bonded to a microscopic slide and were covered by a coverslip. This assembly was transferred to a linear variable differential transformer and composite samples were cured from underneath the slides. Dimensional changes formed in composite samples were recorded. Data were analyzed using analysis of variance followed by post hoc Tukey's and Dunnett's tests. Results: The groups were significantly different regarding polymerization shrinkage. G‐aenial bulk injectable and G‐aenial universal flo showed significantly higher polymerization shrinkage than other composites at 30, 60, and 1800 s after light irradiation, while X‐tra fil and Filtek Z250 showed the lowest polymerization shrinkage at the aforementioned time points. Conclusion: According to the results, the new composite had polymerization shrinkage similar to the conventional one. Bulk‐fill composites reported similar or lower shrinkage to conventional composites. Clinical significance: Polymerization shrinkage can lead to treatment failure by causing secondary caries, enamel cracks, posttreatment pain, and pulpitis. Since the type of material has a role in the amount of this shrinkage, using composites with lower polymerization shrinkage causes restorations with increased longevity. [ABSTRACT FROM AUTHOR]

This paper presents a unique study to reveal the effect of the mounting system of the linear variable differential transformer (LVDT) on the mechanical property tests of timber materials. This effect has been overlooked in the past but proven to be significant enough that will distort the measurements completely if the displacement is relatively small. The reason for causing this error is because the LVDT is not directly measuring targeting points on a sample, instead, the LVDT is measuring the distance between one point on the stop-end (where the tip rested on) and the holder. The wrong common sense hopes that this point on the stop-end and holder reliably following the movement of the sample points. But this study reveals that it is not always the case with the aid from the photogrammetry method. The messages of this paper are simple but alertly useful and, important: (1) the mounting system and the method of installation of the LVDTs have a significant impact on the actual displacement measurement in a mechanical properties test of timber materials. It should be carefully designed and validated before the actual test; (2) the displacement distribution is not uniform across the timber sample. This should be taken into account when selecting the mounting points of the LVDTs. Testing standards should consider this effect when recommending displacement transducers to be used in a timber-related test. [ABSTRACT FROM AUTHOR]

A novel method for structural health monitoring (SHM) by using RGB+D data has been recently proposed. RGB+D data are created by fusing image and laser scan data, where the D channel represents the distance, interpolated from laser scanner data. RGB channel represents image data obtained by an image sensor integrated in robotic total station (RTS) telescope, or on top of the telescope i.e., image assisted total station (IATS). Images can also be obtained by conventional cameras, or cameras integrated with RTS (different kind of prototypes). RGB+D image combines the advantages of the two measuring methods. Laser scans are used for distance changes in the line of sight and image data are used for displacements determination in two axes perpendicular to the viewing direction of the camera. Image feature detection and matching algorithms detect and match discrete points within RGB+D images obtained from different epochs. These way 3D coordinates of the points can be easily calculated from RGB+D images. In this study, the implementation of this method was proposed for measuring displacements and monitoring the behavior of structural elements under constant load in field conditions. For the precision analysis of the proposed method, displacements obtained from a numerical model in combination with measurements from a high precision linear variable differential transformer (LVDT) sensor was used as a reference for the analysis of determined displacements from RGB+D images. Based on the achieved results, we calculated that in this study, the precision of the image matching and fusion part of the RGB+D is ±1 mm while using the ORB algorithm. The ORB algorithm was determined as the optimal algorithm for this study, with good computing performance, lowest processing times and the highest number of usable features detected. The calculated achievable precision for determining height displacement while monitoring the behavior of structural element wooden beam under different loads is ±2.7 mm. [ABSTRACT FROM AUTHOR]

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

Long‐span bridges are susceptible to vortex‐induced vibration (VIV), which affects the serviceability and safety of bridges when the vibration amplitude is too large and lasts for a long time. Traditional contact‐type sensing technologies (i.e., accelerometers and linear variable differential transformer) are inconvenient and dangerous to be installed on long‐span bridges for monitoring VIV events. To address this limitation, this article focuses on the VIV measurement of a long‐span suspension bridge through noncontact sensing strategies. The contribution of this article lies in (1) noncontact sensing technologies including microwave radar, optical camera and video equipment were employed to measure multiple‐point displacements of the studied bridge under VIV events; (2) dynamic properties of the bridge (i.e., natural frequency, damping ratio, mode shapes) and characteristics of the VIV event (i.e., single‐mode vibration and dominant vibration mode switch) were identified by analyzing monitoring data; (3) an early warning framework for VIV event of long‐span suspension bridges was proposed based on monitored dynamic responses and wind fields; specifically, two indicators, the dominant vibration frequency and the similarity between bridge shape and vibration mode shape, were proposed to identify the VIV event, and then the root mean square (RMS) of measured response was further calculated to determine whether there is a need to trigger the warning system or not. The proposed noncontact VIV measurement strategy has the advantage of rapid measurement of vibration magnitude, rapid identification of dynamic properties of the studied bridge and characteristics of the VIV event, which are helpful for the government and bridge owners to make decisions on vibration mitigation measures and to avoid safety issues. [ABSTRACT FROM AUTHOR]

This paper is the first result of an experimental study of manufacturing deformation monitoring equipment using a position sensor, an efficient solution for contractors in bridge monitoring during either process of construction or operation in the context of the increasing number of large bridges. The object of the research is bridgework. And the work is aimed at achieving two tasks, which include meeting the need of the surveyors in real-time monitoring and warning during the construction process with a suitable price and reducing the reliance on manufacturers in supplying and operating monitoring systems. The study used a KTR position sensor, a Linear Variable Differential Transformer, and an Arduino board for embedded coding. Data from the KTR sensor are acquired, processed, and controlled by a program written in Python. The results of the study are compared to the true observations from a Mitutoyo Palmer which has 0.01 mm accuracy in a laboratory. The initial results from the laboratory show prospects for applications in reality, and accuracy is suitable for technical measurements. This is also a good choice for surveyors in acquiring continuously monitoring data at high accuracy for bridge monitoring in general and structure in particular. The study is fundamental to expanding the number of channels from 1 to 8 or 16 for monitoring a full cross-section. At the same time, cable connection mode will be developed to Wi-Fi or Bluetooth mode for online observation. The results of the study confirm the scientificity, and feasibility of the solution. This solution can be applied for either bridge monitoring or other monitoring fields and can be produced by contractors. The cost of monitoring projects will be significantly reduced and there will be no more disruption of monitoring projects after suppliers leave as a new system will be quickly added or replaced. [ABSTRACT FROM AUTHOR]

The unconfined compressive strength (UCS) and modulus of elasticity characteristics for stabilized soil are required in many geotechnical applications. This work aimed to investigate the potential of Fly ash (FA) and Rice Husk ash (RHA) as cement replacement in soil stabilization of the lateritic soil for materials used in pavement applications. The specimens were compacted under modified Proctor at optimum water content. The cement content was varied from 1 to 3%, the percentage of ash replacement was varied from 10 to 30%. A series of UCS tests are carried out after 28 days of curing. To investigate deformation response, the Local Deformation Transducer (LDT) and the Linear Variable Differential Transformer (LVDT) were used to measure the deformation of the specimens. By considering the UCS value, the amount of RHA at 10-30% replaced effectively to the 1-2% cement mixed lateritic soil without reducing the mixing strength. Satisfactory performance of FA was observed at only 1% cement mixture. The modulus measured by both the LVDT and LDT has linear relations with the strength. The empirical expressions for predicting the strength of cement and cement-ash treated are used to characterize the influences of mixing ratio on the strength of cementash treated lateritic soil. The efficiency factor and effective void ratio concepts are reasonable to predict the strength of cement-ash treated lateritic. [ABSTRACT FROM AUTHOR]

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

Wind tunnel tests often require deformation and displacement measures to determine the behavior of structures to evaluate their response to wind excitation. However, common measurement techniques make it possible to measure these quantities only at a few specific points. Moreover, these kinds of measurements, such as Linear Variable Differential Transformer LVDTs or fiber optics, usually influence the downstream and upstream air fluxes and the structure under test. In order to characterize the displacement of the structure not just at a few points, but for the entire structure, in this article, the application of 3D cameras during a wind tunnel test is presented. In order to validate this measurement technique in this application field, a wind tunnel test was executed. Three Kinect V2 depth sensors were used for a 3D displacement measurement of a test structure that did not present any optical marker or feature. The results highlighted that by using a low-cost and user-friendly measurement system, it is possible to obtain 3D measurements in a volume of several cubic meters (4 m × 4 m × 4 m wind tunnel chamber), without significant disturbance of wind flux and by means of a simple calibration of sensors, executed directly inside the wind tunnel. The obtained results highlighted a displacement directed to the internal part of the structure for the side most exposed to wind, while the sides, parallel to the wind flux, were more subjected to vibrations and with an outwards average displacement. These results are compliant with the expected behavior of the structure. [ABSTRACT FROM AUTHOR]

Cell expansion and contraction are major concerns for battery pack and module developers. This work is an effort to understand the behavior of cell expansion due to formation, lithiation and cycling, with measurements made by a system that uses a Linear Variable Differential Transformer (LVDT) sensor. For a NCM622-Silicon cell, impact of factors such as initial compression pressure and calendaring of electrodes on cell expansion were explored. Reversible expansion during charge/discharge in a cycle is a function of cell capacity and reversible expansion can be reduced with increasing initial compression. Irreversible expansion during cycling grows linearly with the number of cycles and can also be reduced with initial compression of the cell. With initial compression of 45 psi, measurements showed 3% cell expansion during formation, 4% reversible expansion in a charge/discharge cycle with C/5 rate, and 12% irreversible expansion over 220 cycles. From the data, a hypothesis was developed suggesting that SEI growth and plastic deformation of the silicon particles could be the main causes for irreversible expansion of the cells with silicon electrodes, with the assumption that cells show less than 20% capacity fade over life. [ABSTRACT FROM AUTHOR]

The deflection of railroad bridges under in‐service loads is an important indicator of the structure's health. Over the past decade, an increasing number of studies have demonstrated the efficacy of using vision‐based approaches for displacement tracking of civil infrastructure. These studies have relied primarily on external processing of manually recorded videos of a structure's motion to estimate displacements. To date, vision‐based techniques applied to long‐term structural health monitoring have yet to be proven effective as an alternative to the traditional displacement measurement methods, such as linear variable differential transformers. This paper proposes a wireless SmartVision system (WSVS) that uses edge computing to directly output bridge displacements that can be sent to the end user. The system estimates displacements using both target‐free and target‐based approaches. A synchronized sensing framework is developed for multipoint displacement estimation using several wireless vision‐based nodes for full‐scale displacement‐based modal analysis of structures. Pose estimation using an AprilTag, a fiducial marker, is employed with a modified algorithm for improved displacement tracking of targets installed on a bridge, yielding subpixel accuracy. The robustness of the results in field conditions is enhanced by linking a tracking quality factor to each timestamp to handle vision‐related uncertainties. To meet the need for precise error metrics evaluation, an inexpensive cyber‐physical setup using a synthetic testing environment is also developed in this study. Following laboratory validation, field tests on a cable‐stayed pedestrian bridge were performed to demonstrate the efficacy of the proposed WSVS. [ABSTRACT FROM AUTHOR]

This paper presents a study on the electromagnetic effects of a main fuel control system under the action of a strong electromagnetic pulse. It assesses the electromagnetic sensitivity of a speed sensor and a linear variable differential transformer (LVDT) sensor. This assessment focuses on the control system's electromagnetic effects and the sensors' coupling signals. The effects and signals were determined using radiation and pulse current injection tests. Analysis of the signal at the system power port shows that it is the same as those for the two test methods. Based on analysis of the working mechanism and terminal signals of the sensors, the electromagnetic sensitivity of the system is different under the different electromagnetic pulse conditions. The electromagnetic sensitivity characteristics of the sensors were verified, and the electromagnetic effects of the main fuel regulation control system were analyzed. Meanwhile, the degree of sensor coupling mechanism caused by the electromagnetic coupling effects of the main fuel regulation control system under strong electromagnetic pulses were studied. These findings have clear practical implications for electromagnetic pulse protection of aero-engine control systems. [ABSTRACT FROM AUTHOR]

In this research, a model-free control strategy for vibration suppression of base-isolated structures, which are excited by an earthquake, is investigated. For this purpose, the semi-active base isolated system including a magnetorheological (MR) damper is utilized. In this way, the displacement of the base isolator is measured by a linear variable differential transformer (LVDT). Accordingly, an adaptive fuzzy sliding mode observer is implemented to estimate the vector of state tracking error. This estimated vector is then employed by an adaptive fuzzy sliding mode control scheme to calculate the input voltage of the MR damper. The efficiency of the implemented model-free control strategy is studied by some numerical simulations. The advantages of the proposed controller can be summarized as its flexibility and robustness against disturbance rejection and model uncertainty. • The dynamics of the superstructure is considered as an unknown external disturbance on the base isolator dynamics. • The control objective is recast to asymptotically stabilize the base isolator. • Since, obtaining an accurate model for the base-isolated building is impossible,an adaptive fuzzy sliding mode controller (AFSMC), which is a model-free control strategy, is then implemented. • Since the state vector of the plant cannot be measured easily, a model-free adaptive fuzzy sliding mode observer is applied. • The same controller can be implemented for every building and earthquake. [ABSTRACT FROM AUTHOR]