Narrow Results

The vehicle scanning method (VSM), an indirect approach for bridge measurement, has attracted intensive attention since it was proposed by Yang and co-workers in 2004. This method is featured by the fact that no vibration sensors need to be mounted on the bridge, but only one or few vibration sensors are required on the test vehicle. Such an idea has been verified by the field tests, and then quickly extended to construction of mode shapes, identification of damping ratios, and detection of damages for bridges, among others. Compared with the conventional direct method that relies fully on the vibration responses recorded by sensors equipped on the bridge, the advantage of the indirect method is obvious: mobility, economy, and efficiency. Over the years, a rapidly growing number of research works have been conducted along the lines of the VSM for bridge measurement. Particularly, extensive lab experiments and field tests have been carried out worldwide to implement the VSM, resulting in numerous new findings. Moreover, while the technique is still flourishing, it is nourished by inclusion of modern devices such as smartphones, vehicular networks, and cloud. In 2018, a review paper was compiled by two of the authors. To reflect the recent rapid growth of research in this area since then, there exists a need to make an expansion to include the huge number of newly published papers (274 papers in total). As an extension of the 2018 paper, this paper represents a state-of-the-art review of the related researches conducted worldwide. Comments and recommendations will be made at proper places, while concluding remarks including future research directions will be presented at the end of the paper.

In 2004, Yang and co-workers proposed the extraction of bridge frequencies from the dynamic response of a moving test vehicle [Y. B. Yang, C. W. Lin and J. D. Yau, Extracting bridge frequencies from the dynamic response of a passing vehicle, J. Sound Vib.272 (2004) 471–493] and verified the technique by a field test [C. W. Lin and Y. B. Yang, Use of a passing vehicle to scan the bridge frequencies — An experimental verification, Eng. Struct.27(13) (2005) 1865–1878]. This technique was extended to construction of mode shapes [Y. B. Yang, Y. C. Li and K. C. Chang, Constructing the mode shapes of a bridge from a passing vehicles: A theoretical study, Smart Struct. Syst.13(5) (2014) 797–819] and damage identification of bridges. It was referred to as the indirect method for bridge measurement because no vibration sensors are needed for installation on the bridge, but it only requires one or few vibration sensors on the test vehicle. When compared with the conventional direct method that relies fully on the response of the bridge fitted with vibration sensors, the advantage of the indirect method is clear: mobility, economy, and efficiency. Over the past years, many research studies were conducted along the lines of the indirect method for bridge measurement. Significant advances have been made on various aspects of application. This paper represents a state-of-the-art review of the related research works conducted worldwide. Comments and recommendations will be made at proper places, while concluding remarks including future research directions will be presented at the end of the paper.

The purpose of this study is to identify and quantify the difference in detections of a subsurface target from a subsurface sensor source between range-independent and range-dependent versions of the same acoustic propagation model. Environmental data were pulled from open source databases to provide an application for the comparison and using novel measures of merit, the authors were able to quantify the difference in detection performance between models. This study suggests that provided multiple types of environments are considered, it is possible to use a range-independent model to give good approximations to the accuracy of detections, one would achieve using a full range-dependent sound propagation model.

The vehicle scanning method (VSM), an indirect approach for bridge measurement, has attracted intensive attention since it was proposed. By this method, a moving test vehicle is employed to detect the “mechanical” properties of the bridge, e.g. frequencies, mode shapes, damages, etc., utilizing the interaction between the two substructures. Compared with the conventional direct approach that requires quite a few sensors and data loggers to be fitted on the bridge, the advantage of the VSM is obvious: mobility, economy, and efficiency. As for railways, the broader vehicle-based techniques have long been used to detect the “geometrical” properties of the track, such as track profiles and rail conditions. Relatively little use has been made of the interaction between the moving vehicle/train and the track/bridge. This paper is a state-of-the-art report of the VSM’s applications to highway bridges and the vehicle-based techniques to railway tracks. It starts with a summary of the pioneering works by Yang and co-workers on the VSM. Then, the applications of the techniques to highway bridges and railway tracks will be separately reviewed. Conclusions will be made, along with future research directions, at the end of the paper.

The development of peroxidase mimics with enhanced peroxidase-like activity is critical to building a convenient and fast glucose colorimetric sensor. Herein, a porphyrin-based conjugated microporous polymer (FePCMP) was synthesized through a Pd-/CuI catalyzed Sonogashira coupling reaction. The FePCMP exhibited specific and superior POD-like activity evaluated by the fast oxidation of 3,3$\prime$,5,5$\prime$-tetramethylbenzidine (a chromogenic substrate, TMB) to form the blue product (oxTMB) in the presence of H₂O₂. The outstanding POD-like activity is mainly ascribed to the Fe-N₄ active sites and the cross-linked porous framework of FePCMP. Furthermore, the FePCMP was applied in selective colorimetric detection of glucose through a glucose oxidase biocatalytic cascade reaction with a low detection limit (LOD) of 0.031 $\mu$M in the linear range of 0.2–5 $\mu$M. This study not only provided a new method for the design and synesis of specific POD-like nanozymes, but also the prepared FePCMP can be used as a POD-like enzyme for the colorimetric detection of other molecules, such as cholesterol, acetylcholine, etc.

Photoelectrochemical (PEC) sensor is an important type of biosensor widely used in glutathione (GSH) sensing. The PEC properties of the photoanode present in the sensor are critical to its sensing performance. Zinc oxide (ZnO) is an excellent semiconductor with a suitable band gap and light absorption ability for photoanode applications. Meanwhile, the interfacial layer is also important in the separation and transportation process of the excitons. In this work, high-quality ZnO nanorods were grown on the indium tin oxide (ITO) substrates. An interfacial layer consisting of reduced graphene oxide (RGO) or MXene (a two-dimensional transition metal carbide)-derived TiO₂ was introduced. Our results show that the introduction of the RGO/TiO₂ hybrid interfacial layer can promote both the high-quality growth of ZnO nanorods and also provides suitable band gap grading for efficient excitons separation and transportation. The GSH sensing performance of the PEC sensor based on the ZnO nanorods grown on the RGO/TiO₂ hybrid layer-coated ITO photoanode can dramatically improve the photocurrent strength and linearity.

We review recent works on optomechanics of optically trapped microspheres and nanoparticles in vacuum, which provide an ideal system for studying macroscopic quantum mechanics and ultrasensitive force detection. An optically trapped particle in vacuum has an ultrahigh mechanical quality factor as it is well-isolated from the thermal environment. Its oscillation frequency can be tuned in real time by changing the power of the trapping laser. Furthermore, an optically trapped particle in vacuum may rotate freely, a unique property that does not exist in clamped mechanical oscillators. In this review, we will introduce the current status of optical trapping of dielectric particles in air and vacuum, Brownian motion of an optically trapped particle at room temperature, Feedback cooling and cavity cooling of the Brownian motion. We will also discuss about using optically trapped dielectric particles for studying macroscopic quantum mechanics and ultrasensitive force detection. Applications range from creating macroscopic Schrödinger's cat state, testing objective collapse models of quantum wavefunctions, measuring Casimir force, searching short-range non-Newtonian gravity, to detect gravitational waves.

The measurement of patients’ dosages of radiation caused by medical diagnostics continues to be challenging. A Cantor sequence photonic crystal structure using porous silicon doped with a polymer of polyvinyl alcohol, carbol fuchsin and crystal violet (DPV) is proposed. The influence rules of geometrical and optical parameters such as the radiation doses, number of periods, porosity of porous layers, incident angle and thickness of layers are investigated using MATLAB based on the transfer matrix method. The transmittance of the Cantor sequence of a defective photonic crystal sensor under different conditions is investigated to select the optimum conditions. The proposed system recorded the accepted sensitivity of 0.265nm/Gy, FoM of 6.5Gy${}^{-1}$, Q of 12,701, RS of $6\times 10^{-3}$ and LoD of $8\times 10^{-3}$ for gamma radiation. The suggested detector has simple design, accurate monitoring efficiency and immense potential for gamma radiation sensing.

Er³⁺ and Yb³⁺ co-doped CaBi₂Ta₂O₉ (CBT)-based bismuth layered-structure oxides were synthesized by a simple solid-state reaction method. Their up-conversion (UC) luminescence, dielectric and ferroelectric properties were investigated. Two strong green emission bands centered at 526 and 547 nm and a weak red emission band centered at 658 nm were obtained under a 980 nm laser excitation at room temperature. These emission bands originated from the radiative relaxation of Er³⁺ from ²H_11/2, ⁴S_3/2, and ⁴F_9/2 levels to the ground state ⁴I_15/2, respectively. At the meantime, the fluorescence intensity ratio (FIR) variation of two green UC emissions at 526 and 547 nm has been studied as a function of temperature in the range of 153–603 K. The maximum sensor sensitivity obtained was 39 × 10^-4 K^-1 at 590 K, which indicated that Er³⁺/Yb³⁺ co-doped CBT ceramic is a promising candidate for applications in optical high temperature sensor.

Driver fatigue can be detected by constructing a discriminant mode using some features obtained from physiological signals. There exist two major challenges of this kind of methods. One is how to collect physiological signals from subjects while they are driving without any interruption. The other is to find features of physiological signals that are of corresponding change with the loss of attention caused by driver fatigue. Driving fatigue is detected based on the study of surface electromyography (EMG) and electrocardiograph (ECG) during the driving period. The noncontact data acquisition system was used to collect physiological signals from the biceps femoris of each subject to tackle the first challenge. Fast independent component analysis (FastICA) and digital filter were utilized to process the original signals. Based on the statistical analysis results given by Kolmogorov–Smirnov Z test, the peak factor of EMG (p < 0.001) and the maximum of the cross-relation curve of EMG and ECG (p < 0.001) were selected as the combined characteristic to detect fatigue of drivers. The discriminant criterion of fatigue was obtained from the training samples by using Mahalanobis distance, and then the average classification accuracy was given by 10-fold cross-validation. The results showed that the method proposed in this paper can give well performance in distinguishing the normal state and fatigue state. The noncontact, onboard vehicle drivers' fatigue detection system was developed to reduce fatigue-related risks.

Visualization is primarily utilized as a training method to enhance athletic movement quality, increase concentration power, and minimize competition stress on the player while building firm confidence. Physical literacy (PL) provides a valuable lens for analyzing physical activity (PA) movement in more significant social and affective learning processes. This paper presents an Interactive Visualization positioning in physical education (IVPPE) to deal with the signal fluctuations and positioning techniques in visualizing Deep Neural Network (DNN). To ensure the success of their game, athletes are always looking for new ways to improve their health and performance. Using sensors to keep tabs on training and recovery has become more popular among athletes. Currently, sports teams are using sensors to track both the players’ internal and external workloads. It illustrates the multilayer localizer (MLL) based on transfer learning to improve the positioning accuracy and physical literacy positioning model (PLPM) as a health determinant. A variety of data augmentation techniques are used to combat signal fluctuations. As a result, the combined effects of motivation-promoting physical activity-based visualization improve the accuracy ratio to 96.7%, prediction ratio to 96.2%, efficiency ratio to 96.8%, and reduce the error rate to 18.7%, stress level (52.8%) compared to other conventional models and have a positive impact on the localizer and positioning, making a difference in physical activity (PA) levels.

Over the past years, we have exploited the bistability features that are commonly found in many individual sensors to develop a network-based [Acebrón et al., 2003; Bulsara et al., 2004; In et al., 2003a; In et al., 2003b; In et al., 2005; In et al., 2006; In et al., 2012; Palacios et al., 2005] approach to modeling, designing, and fabricating extremely sensitive magnetic- and electric-field sensors capable of resolving field changes as low as 150pT and 100fAmps, respectively. Higher sensitivity is achieved by exploiting the symmetry of the network to create infinite-period bifurcations that render the ensuing oscillations highly sensitive to symmetry-breaking effects from external signals. In this paper, we study the effects of noise on the response of a network-based electric-field sensor as well as the effects of parameter mismatch, which appear naturally due to material imperfections and noise. The results show that Signal-to-Noise Ratio (SNR) increases sharply near the onset of the infinite-period bifurcation, and they increase further as the coupling strength in the network increases while passing the threshold that leads to oscillatory behavior. Overall, the SNR indicates that the negative effects of highly contaminated signals are well-mitigated by the sensitivity response of the system. In addition, computer simulations show the network-based system to be robust enough to mismatches in system parameters, while the deviations from the nominal parameter values form regions where the oscillations persist. Noise has a smoothing effect over the boundaries of these regions.

In this paper, we report the preparation and characterization of a sensitive and reusable nonenzymatic glucose (NEG) sensor based on copper nanowires (CuNWs)/polyaniline (PANI)/reduced graphene oxide (rGO) nanocomposite ink. The CuNWs/PANI/rGO nanocomposite ink was prepared by solvothermal mixing of CuNWs, PANI, rGO and binders. The X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), Fourier Transform Infra-Red (FT-IR) spectroscopy techniques were used to assess the structural and morphological parameters of prepared nanocomposite ink. The cyclic voltammetry (CV) technique was used to estimate the electrochemical behavior of prepared NEG sensor. The structural, morphological and spectroscopy results confirmed the change in morphological and oxidation state of CuNWs to CuO nanostructures as a constituent of nanocomposite ink. The CuO nanostructures supported on PANI/rGO demonstrated good electrochemical stability and great electrocatalytic activity toward glucose oxidation. At a glucose oxidation potential of 0.64V, the prepared NEG sensor exhibited great electrocatalytic ability by offering a high sensitivity of 843.06$\mu$AmM${}^{-1}$cm${}^{-2}$ in the linear glucose range 0–4mM with a lower detection limit of 1.6mM. In addition to these outstanding performance characteristics, CuNWs/PANI/rGO nanocomposite ink-based NEG sensor has the advantages of ease of fabrication, low cost and reusability.

Film bulk acoustic wave resonator (FBAR) experienced skyrocketing development in the past 15 years, owing to the explosive development of mobile communication. It stands out in acoustic filters mainly because of high quality factor, which enables low insertion loss and sharp roll off. Except for the massive application in wireless communication, FBARs are also promising sensors because of the high sensitivity and readily integration ability to miniaturize circuits. On the ground of summarizing FBAR’s application in wireless communication as filters and in sensors including electronic nose, bio field, and pressure sensing, this paper review the main challenges of each application faced. The number of filters installed in the mobile phone has being grown explosively, which leads to overcrowded bands and put harsh requirements on component size and power consumption control for each unit. Data flow and rate are becoming increasingly demanding as well. This paper discusses three promising technical strategies addressing these issues. Among which coupled resonator filter is given intense attention because it is able to vigorously reduce the filter size by stacking two or more resonators together, and it is a great technique to increase data flow and rate. Temperature compensation methods are discussed considering their vital influence on frequency stability. Finally, materials improvement and novel materials exploration for band width modulation, tunable band acquisition, and quality factor improvement are discussed. The authors appeal attention of the academic society to bring AlN epitaxial thin film into the FBAR fabrication and have proposed a configuration to implement this idea.

Multi-walled carbon nanotube (MWCNT)-modified MoS₂/BiVO₄ was manufactured and used for the photoelectrochemical (PEC) detection of hydrogen peroxide (H₂O₂) and hypochlorite (ClO⁻). A solvothermal method was used to synthesize an MWCNT/MoS₂/BiVO₄ composite that showed perfect PEC properties because the MWCNTs and MoS₂/BiVO₄ heterostructures increased the composite’s stability against photocorrosion. Compared with the same signal of MWCNT/MoS₂/BiVO₄, the photocurrent signal of other composites was much smaller upon irradiation by visible light. According to this PEC sensor, the linear range of the H₂O₂ concentration was 1–200$\mu$M and 280–1560$\mu$M at $\mathrm{\text{pH}}=7.4$ based on the same pH when detecting ClO⁻ concentrations between 0.5–10$\mu$M and 20–340$\mu$M in a bleach sample. As a result, this sensor can be used to detect reactive oxygen species (ROS) in practical samples.

This study presented an innovative concept to develop a home-made equipment to make a 2D circular-shaped polyvinylidene fluoride (PVDF) fiber piezoelectric sensor. The fibers spun by direct-write near-field electrospinning can be collected orderly to enhance the orientation of dipole moments and the piezoelectric effect. The electrospinning system mainly consists of a high voltage power supply system, a digitally controlled $X$–$Y$ table, a solution injection system, and a rotating flat disc collector system. PVDF piezoelectric fibers were spun for the sensing element of the sensor with a diameter of $\sim$16 $\mu$m under a high electric field ($\sim 1.6\times 10^7$ V/m). The optimal parameters of electrospinning process were investigated and determined by the uniform design (UD) method in terms of the working high voltage, feeding rate, and gap distance between the needle and collector. In addition, a prototype of this newly designed rotating flat disc collector system was utilized to make 2D circular-shaped PVDF piezoelectric fibers. Besides, the newly-designed radial electrodes were used to characterize multi-directional sensing ability. The 2D circular-shaped fibers were then packaged with this radial electrodes and polyethylene terephthalate (PET) film together to measure the dynamic behavior characteristics.

Agriculture catalyzes the economy in developing nations. Malaysian agriculture constitutes 4.06 million hectares, with 80% encompassing industrial crops and agro-food production, boosting the economy through implementing precision agriculture (PA). Precision agriculture gives minimal environmental implications by using an unmanned aerial vehicle (UAV), improving sustainability, productivity, and crop production 30-fold instead of conventional methods. This study aims to review the UAV application based on technical requirements with insights into the potentiality of precision agriculture in UAV agriculture technologies, limitations, and solutions.

This study was based on the hypothesis that spatial–temporal characterization of contaminant-affected redox gradients in a quiescent system could be measured by microbial potentiometric sensor (MPS) arrays incorporated in large, natural biofilm networks. Two experimental chambers, each containing at least 48 equidistantly located MPS electrodes, were fabricated to examine reproducibility of the patterns. The MPS electrodes were exposed to biofilm growth conditions by introducing high dissolved organic carbon (DOC) and dechlorinated tap water at the bottom of the experimental chamber; and the spatial–temporal changes in the MPS array signals were recorded, which showed that signal trends were correlated to the induced changes in DOC. The results indicated that MPS arrays measured the spatial–temporal changes in the aqueous solution caused by an influx of carbon rich water, which could not be detected by conventional oxidation-reduction potential (ORP) electrodes. Interestingly, the experiments conducted over long time periods revealed unusual behaviors like electrical signaling and possible potentiometrically driven communication within the biofilm. These observed behaviors suggest that biofilms may create a large network through which communication signals can be generated and propagated by inducing changes in electric potentials similar to a sophisticated electronic device.

This paper reports the stress and frequency analysis of dynamic silicon diaphragm during the simulation of micro-electro-mechanical-systems (MEMS) based piezoresistive pressure sensor with the help of finite element method (FEM) within the frame work of COMSOL software. Vibrational modes of rectangular diaphragm of piezoresistive pressure sensor have been determined at different frequencies for different pressure ranges. Optimal frequency range for particular applications for any diaphragm is a very important so that MEMS sensors performance should not degrade during the dynamic environment. Therefore, for the MEMS pressure sensor having applications in dynamic environment, the diaphragm frequency of 280 KHz has been optimized for the diaphragm thickness of 50 $\mu$m and hence this frequency can be considered for showing the better piezoresistive effect and high sensitivity. Moreover, the designed pressure sensor shows the high linearity and enhanced sensitivity of the order of ($\sim$0.5066 mV/psi).

It is of great significance to prepare electrochemical glucose sensors with high selectivity and stability via effective and rapid methods. In this work, the self-support electrode with copper and nickel-based oxide is prepared by chemical-etching reaction which occurred under the property of electrochemical potential difference. In this processing, nickel foam is etched selectively by Cu${}^{2+}$ ions and they not only act as self-supporting electrode substrate, but also as nickel ions precursor of NiO. Moreover, the reaction can be completely satisfied on 30 min at room temperature. As a self-supporting electrode nonenzymic glucose electrochemical sensor, the electrode exhibited a wide linear range (0.04–3.00mM), low detection limit (0.02mM) with high sensitivity of 1096$\mu A\cdot {\mathrm{\text{mM}}}^{-1}\cdot {\mathrm{\text{cm}}}^{-2}$ and good selectivity, repeatability and stability. Furthermore, the application of the prepared sensor provides an avenue for the application of the transition metal materials in the field of electrochemical sensing.