LCR Meter Research Articles

Investigation of Structural, Dielectric, Magnetic and Impedance Spectroscopy of MgO/CuFe2O4 Nanocomposites

This study investigates the properties of (MgO)x/(CuFe2O4)1-x x= 10–50 wt.% nanocomposites (NCPs) prepared by physical mixing of both materials. The crystal structure, phase identification and morphology were analyzed by x-ray Diffraction (XRD) and Scanning Electron Microscope (SEM). The investigation revealed the formation of required phases which are in nanometer dimension (22–54 nm) computed by Debye-Sherrer’s formula. Both the real and imaginary parts of dielectric constant (ε/ & ε//), a.c. conductivity (σac), and impedance were measured in the frequency range of 1kHz to 2MHz by LCR meter. The ε/ and ε// revealed a decreasing trend with frequency, while MgO weight fractions in NCPs enhance the permittivity values. The real and imaginary parts of impedance (Z/ & Z//) demonstrate a decreasing trend with frequency which is ascribed to increase in σac. The complex impedance spectroscopy (CIS) analysis shows semicircular arcs at higher frequency, which are due to electrical transport properties of conducting grains. The effect of MgO contents on magnetic properties were analyzed by measuring M-H loops at room temperature through vibrating sample magnetometer (VSM). Both the saturation magnetization (Ms) and coercivity (Hc) values show a decreasing profile with MgO fractions, which are due to increase in nonmagnetic contents and decrease in surface anisotropy respectively.

Fragility assessment of sea-crossing cable-stayed bridge subjected to multi-hazard action via TKC and R-vine copula

Seismic fragility analysis methods commonly used for assessing structural components and systems have certain limitations. This paper introduces a new semi-parametric approach for structural component fragility analysis, the TKC method. This method is based on log-transformed kernel density estimation (log-TKDE) and copula functions, which establish the joint probability distribution (JPD) of a structural response value (d) and a disaster-inducing factor strength parameter (α) using log-TKDE and match the marginal cumulative distributions (MCDs) of d and a via bivariate copula functions. A novel method for evaluating structural system fragility is also proposed based on the R-vine copula function. This approach accounts for the intricate correlations among different components, providing a precise estimation of the multidimensional JPD. The reliability and accuracy of the proposed methods are demonstrated through a seismic fragility analysis of a sea-crossing cable-stayed bridge under earthquake load. Furthermore, a multi-hazard fragility analysis of bridge components and systems is conducted considering hazards such as earthquake, wind, and wave loads. A comparison is made with the seismic fragility of bridges subjected to earthquake loads alone. The results show that the median and 95% confidence of the damage probability of structural components calculated by the TKC method and Monte Carlo simulation (MCS) closely match, which validates the proposed method. The TKC method is also more accurate and computationally efficient than the MCS method with the same Bootstrap sample size and confidence level (95%). The proposed structural system fragility assessment method based on the R-vine copula accounts for complex correlations between components and yields more accurate results than the first-order boundary method. Load spectrum characteristics, structural component characteristics, and other factors cause the multi-hazard fragility of bridge components and systems to differ substantially from their seismic fragility. The difference rate of system damage probability can reach 28.82%. In evaluating the anti-disaster performance of sea-crossing bridges, it is necessary to incorporate the marine environmental load and consider the dynamic response coupling effect of the bridge excited by seafloor ground motions with extreme wind and wave loads. This approach can guide the optimization of bridge designs and facilitate multi-hazard fragility analysis in accordance with real damage probabilities.

Deep spatiotemporal fusion network for vision-based robotic inspection of structures

The convolutional neural networks commonly deployed for semantic understanding of visual inspection data can, in general, learn robust spatial features. However, they lack the ability to capture temporal dependencies that characterize the video data collected by various robotic inspection systems. As a result, they are found lacking in dealing with various challenges arising from cross-view illumination variation, perspective difference, scale change, background clutter, and occlusion. Their performance is further deteriorated by motion blur and other distortions induced by rapid camera movement. This study aims to address this challenge by extending the task of visual scene understanding from the still image domain to the video domain by incorporating cross-frame information fusion. A deep end-to-end network is developed by integrating an encoder–decoder-based convolutional neural network with a long short-term memory-based recurrent neural network for pixel-level semantic labeling of sequential visual inspection data. The proposed multishot architecture can jointly learn discriminative fusion features leading to a rich understanding of the complex spatiotemporal dynamics. The proposed approach is validated with two case studies involving automatic structural element segmentation in robotic building and bridge inspection videos. Two different multishot fusion techniques are suggested leveraging sequence-to-one and sequence-to-sequence architectures. Additionally, two different fusion schemes based on the sum-of-scores and Bayesian updating rules are examined to aggregate multiple label maps produced at each time step by an overlapping sliding window-based inference scheme. A comprehensive performance evaluation indicated that multishot fusion could enhance the intersection over union (IoU) score by 4.6% and 13.3% for building and bridge component segmentation tasks, respectively, compared to a baseline single-shot approach.

Stress and temperature sensing in self-sensing flexible felt composite based on carbon fibers

Self-sensing composites based on carbon fibers (CFs) offer a wide range of remarkable properties, making them suitable for various significant industrial and engineering applications. In this study, the wet-laid method was employed to prepare flexible short carbon fiber felts (CFFs). The microstructure analysis was performed using scanning electron microscopy (SEM), X-ray diffraction (XRD), and Raman spectroscopy. To exclude contact capacitance, the relative permittivity was measured using an LCR meter. The resistivity was measured through the four-probe method and a multimeter. We investigated the relationship between stress, temperature, and the dielectric and conduction behavior while also analyzing the underlying mechanisms behind the self-sensing phenomenon. The results indicate that for an areal density of 52.6 g/m2, the CFF exhibits a relative permittivity of 400, which is significantly lower than that of pitch-based carbon fiber. This disparity suggests that smaller crystallite sizes promote AC polarization. Additionally, both permittivity and conductivity increase with rising compressive stress and temperature, implying that compression and heating strengthen the dielectric and conduction behavior. The increase in polarization during compression is attributed to the enhanced polarization continuity, whereas the rise in conduction is attributed to the improved conduction connectivity. The rise in charged carriers induced by thermal energy leads to positive pyropermittivity and negative pyroresistivity. Notably, self-sensing in terms of permittivity is more pronounced compared to resistivity, suggesting that polarization is more sensitive to stress and temperature changes than conduction.

Tuning the optical, and dielectric properties of PVC/PEO/NiMoO4/MWCNTs/x wt %PANI blended polymers for optoelectronic applications

Nanoparticles of nickel molybdate (NiMoO4) have attracted significant interest for their application as electrode materials. Here, new hybrid blended polymers, poly (vinyl chloride)/polyethylene oxide/nickel molybdate/multi-walled carbon nanotubes/polyaniline (PVC/PEO/NiMoO4/MWCNTs/x wt %PANI) were prepared. Several techniques, including X-ray diffraction (XRD), scanning electron microscopy (SEM), diffused reflectance, fluorescence and LCR meter were used to investigate the impact of the different fillers on the structure, electrical and optical features of the PVC/PEO blend. The structures of NiMoO4 and different blends were explored using XRD technique. The linear and nonlinear optical properties and the emitted colors of host blend are found to be affected by NiMoO4, MWCNTs and different amounts of PANI fillers. The T values of PVC/PEO were reduced as it loaded with NiMoO4/MWCNTs/x wt %PANI and it reached its minimum value (21–37% in the visible range) in NiMoO4/MWCNTs/x 0.4 %PANI blend. The minimum direct and indirect optical band gap values (4.09, 4.9) eV and (1.92, 3.47, 3.94) eV, respectively, were obtained as the amount of PANI became 0.4 wt % in the doped blend. The doped PVC/PEO blend with NiMoO4 has the highest refractive index value (2.11) at 600 nm. The highest nonlinear optical parameters were acquired exclusively in the visible spectrum when PVC/PEO was doped with NiMoO4.The maximum energy density value (6.03 × 10−3 J/m3) was obtained when the host blend loaded with NiMoO4/MWCNTs. Thus, PVC/PEO/NiMoO4/MWCNTs/x wt %PANI blends are recognized as a good prospect for UV blocking, solar cell, optoelectronic, nonlinear optical devices and energy storage innovation.

Biopolymer blend composite films based on polyvinyl alcohol/ chitosan/ grape seed extract via green approach for flexible optoelectronic devices

The flourishing environmental concerns have grabbed the attention of researchers developing environmentally supportive materials in various fields. A green approach was used to create biopolymer blend composites based on polyvinyl alcohol (PVA) and chitosan (CS) doped with various concentrations of grape seed (GS). Various analytical techniques, such as Fourier-transform infrared spectroscopy (FTIR), UV–visible (UV) spectra, field emission scanning electron microscope (FE-SEM) and differential scanning calorimetry (DSC) were used to evaluate the optical, structural and thermal properties of the prepared blend composites. The optical properties of blend composites were determined by UV spectroscopy and the findings revealed that absorption intensity increased with increasing GS, while bandgap energy decreased from 4.18 eV for pure blend to 2.91 eV for blend/15 wt% GS. The homogeneous distribution of GS particles in the biopolymer blend was identified with FE-SEM images. DSC results showed that increasing the GS content increased the glass transition temperature of the blend composites. The AC conductivity and dielectric constant were measured using the LCR meter. The conductivity rises with increasing frequency and dosage of GS, with the greatest conductivity obtained at 15 wt% loading. In comparison to a pure blend, it was discovered that the inclusion of 15 wt% GS enhanced the tensile strength by 50%, hardness by 17% and the reduction in elongation at break by 19 %. As a consequence, environmentally friendly PVA/CS/GS biopolymer blend composites with excellent mechanical, thermal, electrical, and dielectric parameters might be a viable green option for flexible electronic, electrochemical and energy storage devices.

Temperature-dependent heterojunction ternary nanocomposite: Assessing photocatalytic and antibacterial applications

Heterojunction nanocomposites (ZnO:NiO:CuO) were synthesized via a hydrothermal method and annealed at three different temperatures (400 °C, 600 °C, and 800 °C). The structural, optical, and electrical properties were examined by employing XRD, SEM, UV–Vis, FTIR, and LCR meter techniques to investigate the effects of annealing. Increasing the annealing temperature resulted in the nanocomposites (NCPs) exhibiting enhanced crystallinity, purity, optical properties, and improved electrical and dielectric behavior. The calculated crystalline sizes (Debye-Scherrer method) of the NCPs were determined to be 21, 26 and 34 nm for annealing temperature 400 °C, 600 °C, and 800 °C, respectively. The calculated bandgaps of synthesized samples were found in the range of 2.92-2.55 eV. This temperature-dependent annealing process notably influenced particle size, morphology, band-gap characteristics, and photocatalytic efficiency. EDX analysis affirmed the sample purity, with elemental peaks of Zn, Cu, Ni, and O. These NCPs demonstrated exceptional photocatalytic activity against various dyes solutions (Methyl orange (MO), Methylene Blue (MB), and mixed solution of dyes) under sunlight and also showed good antibacterial properties assessed by the disc diffusion method. Notably, the nanocomposite annealed at 400 °C exhibited a particularly high degradation efficiency by degrading 96% MB and 91% MO in just 90 min under sunlight.

Experimental verification and rapid estimation of uncalibrated cable force via video-based and vibration-based measurements.

The stayed-cable is an important component of cable-stayed bridges, with cable force being a focal point during construction and bridge operation. The advancement of camera and image processing technology has facilitated the integration of computer vision technology in structural inspection and monitoring. This paper focuses on enhancing cable force measurement methods and addressing the limitations of traditional testing techniques by conducting experimental research on cable force estimation using video recording. The proposed approach involves capturing video footage of the target on the cable with a smartphone. Subsequently, a combination of techniques such as the background subtraction method, image morphology processing, and Hough transform image processing technology are employed to detect the precise center coordinates and ultimately obtain the accurate displacement-time curve of the cable's vibration. In addition, the graphic Circularity Coefficient (CC) has been introduced to assess its effectiveness in post-motion-blur image processing for circular targets. The fundamental frequency of the cable is determined by the fast Fourier transformation, and the relationship between the cable force and the fundamental frequency is used to estimate the cable force. The experimental results are compared with data from accelerometers and force gauges, demonstrating that the frequency measurement error is below 1.2% and the cable force test error is less than 3%. In the process of acquiring the cable's fundamental frequency, the test directly employs the pixel as the displacement unit, eliminating the need for image calibration. The innovative use of the CC in processing motion-blurred targets ensured accurate recognition of target coordinates. The experimental findings highlight the method's simplicity, speed, and accuracy.

Quantifying landscape fragmentation and forest carbon dynamics over 35 years in the Brazilian Atlantic Forest

The Brazilian Atlantic Forest (AF) covers 13% of Brazil but retains only 26% of its original forest area. Utilizing a Morphological Spatial Pattern Analysis (MSPA), we generated 30 m spatial resolution fragmentation maps for old-growth and secondary forests across the AF. We quantified landscape fragmentation patterns and carbon (C) dynamics over 35 years using MapBiomas data between the years 1985 and 2020. We found that from 1985 to 2020 the forest suffered continuous fragmentation, losing core (nuclei forest fragments) and bridge (areas that connect different core areas) components of the landscape. About 87.5% (290 468.4 km2) of the remaining forest lacked core areas, with bridges (38.0%) and islets (small, isolated fragments) (35.4%) being predominant. Secondary forests (1986–2020) accounted for 99 450.5 km2 and played a significant role in fragmentation pattern, constituting 44.9% of the areas affected by edge effects (perforation, edge, bridge, and loop), 53.7% of islets, and comprising only 1.4% of core forest. Additionally, regeneration by secondary forests contributed to all fragmentation classes in 2020. Even with the regrowth of forests, the total forested area in the biome did not increase between 1985 and 2020. Deforestation emissions reached 818 Tg CO2, closely paralleled by edge effects emissions at 810 Tg CO2, highlighting a remarkable parity in C emissions between the two processes. Despite slow changes, AF biome continues to lose its C stocks. We estimated that around 1.96 million hectares (19 600 km2) of regenerated forest would be required to offset the historical C emissions over the analysed period. Hence, MSPA can support landscape monitoring, optimizing natural or active forest regeneration to reduce fragmentation and enhance C stocks. Our study’s findings are critical for guiding land-use policies focusing on minimizing emissions, promoting forest regrowth, and monitoring its permanence. This study offers biome scale, spatially explicit information, critical for AF conservation and management.

Manufacturing of soft capacitive strain sensor based on dielectric elastomer material for an elastic element of a jaw coupling

In this work, we present a procedure for manufacturing a soft capacitive strain sensor in the form of a multi-layer electrical capacitor for further integration into the elastic gear rim of a jaw coupling. The dielectric elastomer sensor (DES) is based on an elastomeric substrate with alternating layers of conductive carbon black based ink as electrode layers and elastomeric film as a dielectric and electrical insulation. A variety of thin multi-layer sensors were produced to evaluate the manufacturing process. Additionally, using an LCR meter and a tensile test machine, the equivalent electrical capacitance (C) at the two sensor contacts and the applied force are measured, respectively. It is shown that C varies depending on the amount of sample strain caused by the applied force. By testing two versions of DES, a maximum change in capacitance of ΔC = 1.55 pF was achieved. The obtained characteristics show that the presented manufacturing process for the DES can be used as a soft strain sensor to measure the strain caused by the force applied to the elastic element between the jaw couplings.

Assessing the feasibility of laser ablation coating removal (LACR) on legacy bridge steel: Coating removal and adhesion, and effects on mechanical properties

The application of protective organic coatings is one of the most effective and commonly used corrosion mitigation strategies. To maintain the protective nature of coatings on long-term-exposed surfaces such as steel bridge components, coatings must be periodically removed and reapplied. A relatively new method called laser ablation coating removal (LACR), which incorporates a high energy nanosecond pulsed laser beam in combination with a high efficiency filtration system, allows for safe and effective removal of coatings and contamination from metal surfaces. In this study, LACR cleaning is tested on legacy bridge steel components to investigate the effect on substrate cleanliness and steel mechanical properties. These bridge sections were never blasted and contain a 20–100 μm thick mill-scale layer (iron oxide) below several coating layers (including lead-rich coatings). The top micron of the oxide layer is melted by LACR and also thermally insulates the underlying steel and prevents any melting within the metallic substrate. The resulting surfaces are analyzed using microscopy, hardness testing, tensile, and fatigue testing, and it is shown that LACR does not cause any measurable detrimental effects to the bulk mechanical properties of the bridge steel, as well as effectively removes all paint coatings. Furthermore, adhesion testing on LACR-cleaned substrates shows excellent adhesion, qualifying above adhesion requirements for coated steel.

Effect of alloying elements on microstructural and electrical property in Sn–Cu–Bi lead-free solder alloys

Sn–0.7Cu eutectic alloy is a low-cost alloy with moderate melting point and wetting that appears to be adequate for some applications. Lead-free Sn–0.7Cu joint solders on copper substrate were investigated in this study. To enhance the performance of the alloy, many previous studies verified the importance of adding bismuth to the eutectic alloy. (84.3Sn–0.7Cu–15Bi) ternary alloy is regarded as a potential substitute for hazardous Sn–Pb solders, possessing a melting point of 206 °C. The effects of incorporating selenium, zinc, or indium on the electrical characteristics, crystal structure and microstructure of the tin copper-bismuth alloy were examined. Phase identification of the base solder and various newly developed alloys was performed by X-ray diffraction tests and an LCR meter was used to measure the electrical resistance of the prepared samples. The unit cell volume, and lattice parameters of the tetragonal Sn base were altered, along with the electrical characteristics of the base solder alloy. According to the test results, the best addition was by indium since it reduced the grain size of the base solder alloy. Smaller grain size improves the mechanical properties of the solder. Furthermore, indium addition increased the electrical conductivity of the base solder alloy compared to other alloying additions.

Configuring Taiwan’s highway bridge performance indicator: a semi-quantitative risk assessment approach

The Taiwan Bridge Management System (TBMS) calculates the condition index (CI) of every highway bridge in its inventory using the latest findings from biennial routine inspections. However, the computational approach for CI can yield skewed results and make a bridge appear healthier than it actually is. To address this issue, a highway bridge performance indicator called the bridge risk index (RI) is presented. The RI is determined by combining the risks associated with the failure of each bridge component, which are evaluated using a semi-quantitative risk assessment approach. This evaluation considers the probability and consequence of a bridge component’s failure as a function of a component's deterioration state and criticality to the bridge’s overall structural safety and serviceability, respectively. To validate the effectiveness of the RI, inspection data from a sample of seven highway bridges were extracted from the TBMS and used to compare the RI with the CI. The results showed that the RI and its associated parameters can mitigate the inherent issues observed with the CI. Hence, the RI has the potential to be a valuable decision-support tool for transport agencies that rely on similar routine inspection processes to enhance their bridge management systems.

Analysis and Determination of Self-Inductance through Direct and Indirect Measurements Methods

Practicum is an activity that helps students to understand an abstract concept. One of the concepts in physics that requires practicum is the concept of electricity. Inductance is an electrical quantity studied in high and vocational high schools. This study aims to determine the inductor's inductance value using several methods and analyze the most suitable method for determining the inductor inductance value. The inductor used is a commercial inductor with a color band code with an inductance value of 2.7 mH and a tolerance of 10%. Inductor inductance measurements were carried out using a benchtop LCR meter, handheld LCR meter, series RLC method, and LC resonance method. Each measuring instrument requires a frequency setting: refer to the manual for benchtop and handheld LCR meters, the resonant frequency for the serial RLC method, and adjusting the AFG (arbitrary function generator) frequency. Hence, a clear oscillation pattern is visible on the oscilloscope. The results of this study indicate that measurements using benchtop LCR meters, handheld LCR meters, and LC resonance methods produce inductance values within the inductance tolerance limits.

Toward the response of coastal bridges with updated RC shear key properties under the multi-hazard action of earthquakes and tsunamis

Coastal bridges are significantly endangered by the combined effects of earthquakes and tsunamis. The accurate prediction of bridge responses in such scenarios is vital to ensure their security. Reinforced concrete (RC) shear keys, which serve as sacrificial bridge components, can effectively mitigate inertial loads from superstructures, and thus safeguard pier columns. Previous research has shown that their mechanical properties can differ considerably under cyclic and persistent impacts. Therefore, this study focused on the seismic-tsunami responses of a simple-support coastal bridge equipped with RC shear keys. A horizontal failure shear key was incorporated because of its distinct performance observed previously. The OpenSees platform was employed to conduct the numerical work, with an updated material framework developed to modify the shear key behavior before the tsunami analysis. Natural ground motion records were selected to demonstrate the dynamic analysis, and the records were scaled using spectral accelerations (Sa) to account for the various damage states of shear keys resulting from superstructure collisions. The tsunami wave impact was modeled using the second-order solitary wave theory, with different wave conditions employed to consider the immersed conditions. The calculation results were compared for the bridges with and without updated shear key properties, showing distinctions in terms of time-history and maximum responses at certain seismic levels. Based on the analysis results, this study is expected to provide a reliable estimation of the seismic-tsunami responses of coastal bridges.

Effect of Water Absorption on Electric Properties of Temperature-Resistant Polymers.

The effects of water absorption on the electric resistivity and dielectric constant of polyimide (PI) and poly(ethylene terephthalate) (PET) were investigated, and the mechanism of deterioration in electrical insulation properties was discussed. The polyimides are poly(oxydianiline pyromellitimide) (PMDA-ODA) and poly(para-phenylene diamine biphenyltetracarboxydiimide) (BPDA-PDA). These polymer films were immersed in pure water for various immersion times at room temperature, and the water absorption ratio was evaluated. The electric resistance for these films was measured at room temperature using a high-resistance meter, and the dielectric constant at room temperature was measured using an LCR meter in a frequency range of 200 kHz to 2 MHz. The absorption ratios at equilibrium absorption for PMDA-ODA, BPDA-PDA, and PET were 2.7, 2.5, and 0.5%, respectively. The critical volume fraction of the percolation threshold of electric conductivity due to water absorption was 0.034 for both PMDA-ODA and BPDA-PDA. On the other hand, PET did not show a significant decrease in the resistivity. For both PIs and PET, the dielectric constant observed could be explained by a series model of the respective capacitances of pure water and polymer. Actually, the resistivity of samples cut from the edges of the film after water absorption was almost the same value as that in the dry state. These results suggest that the absorbed water molecules are not uniformly dispersed in the film but are localized at the edges of the film even after the absorption equilibrium has been reached.

An investigation of cracks caused by concrete shrinkage and temperature difference in common reinforced concrete bridge structures.

Cracking phenomena commonly occur in reinforced concrete structures of bridge and culvert components. While some bridge design standards, such as the AASHTO LRFD standard from America, allow for the presence of cracks, they do not provide direct quantitative limits on permissible crack widths. This research analyzes the crack formation mechanism of reinforced concrete structures under the influence of shrinkage and temperature loading, using the "tension-chord" model from the fib MODEL CODE. The research findings demonstrate that despite the steel reinforcement adequately arranged to resist shrinkage and temperature, as per American bridge design standards, cracks frequently occur with widths that may exceed the allowable limits specified in the fib MODEL CODE. The main reason is the inadequate control of concrete construction temperature, especially for large-sized concrete structures. Other findings are: with the same steel ratio, using small diameter reinforcement can significantly reduce the crack width compared to larger ones; Increasing the steel ratio can reduce the crack width but increases the susceptibility to cracking; Crack does not occur immediately after maintenance completion but after a period ranging from several days to several months; Crack width due to concrete shrinkage and temperature changes is typically 0.3mm but may reaches to 0.7mm due to high hydration heat of large sizes structures.

Dynamic Receptance Analysis Combined with Hybrid FE-SEA Method to Predict Structural Noise from Long-Span Cable-Stayed Bridge in Urban Rail Transit

In this study, dynamic receptance analysis (DRA) is proposed and combined with hybrid finite element (FE)-statistical energy analysis (SEA) method to accurately predict structural noise from long-span cable-stayed bridge (LSCB) with steel box composite girder (SBCG) in urban rail transit (URT). To begin with, a vertical vehicle–track coupling model in frequency domain is established based on DRA, in which the rail is represented by an infinite Timoshenko beam supported by a series of fasteners that are regarded as springs with complex stiffness. The floating slab is regarded as the Euler beam with both ends free supported by steel springs. Using this model, the spectrums of the wheel–rail force and the forces transferred to the bridge can be efficiently obtained by taking rail roughness as the excitation. Due to the low modal density of the concrete deck, the hybrid FE-SEA method is introduced to establish the noise prediction model, in which the discontinuity caused by using distinct models for different frequency bands is avoided. Then the on-site noise tests of a LSCB with SBCG in URT are carried out to verify of the proposed method. Finally, based on the prediction method, the acoustic contributions of the bridge components are analyzed in detail. The force transfer characteristics as well as the noise reduction effects of different track structures are thoroughly investigated, so as to provide reference for the future research on bridge-borne noise control.

Studies of the Properties of New Electrospun Based on PVA-PEG Polymer Systems Electrolytes for Energy Storage Devices

Solid polymer electrolytes (SPEs) have been considerably investigated due to various electrochemical device applications. Most of the SPEs comprise polymer as a host material to provide strength and good mechanical stability and salt that transfers charge carriers to cause conductivity. Nanocomposite solid polymer electrolyte membranes based on poly(vinyl alcohol) (PVA)-poly(ethylene glycol) (PEG) blend complexed with LiClO4 and nanofillers Al2O3 at different weight percent ratios have been obtained by using electrospinning method. The conductivity and structural properties of the different systems have been characterized by using various experimental approaches such as X-ray diffraction (XRD) and Fourier transform infrared FTIR spectroscopy. The ionic conductivity of the systems has been measured by using an LCR meter in a temperature ranging from 298 to 353 K. Maximum ionic conductivity of 1.58 × 10-4 S cm-1 at room temperature has been observed for the system of PVA-PEG-LiClO4-Al2O3 (50-25-15-10) with 15 wt% weight percent of LiClO4 salt in PVA-PEG blend matrix. The ac conductivity report indicates that the ionic conductivity of the PVA-PEG-LiClO4-Al2O3 complex is influenced by the concentration of LiClO4. The effect of temperature on the ionic conductivity of polymer electrolyte complexes has been estimated by changing the temperature ranging from 298 to 353 K. However, the conductivity of the nanofiber polymer electrolyte systems increases with the rise of temperature, and the maximum conductivity of 1.58 × 10-2 S cm-1 has been recorded at 353 K. The temperature-dependent conductivity follows the Arrhenius behavior.

Failure investigation of a propped cantilever truss bridge

Propped cantilever truss is not a common bridge construction technique. The performance of such bridges under operational and extreme loading is not reported in the literature either. In this paper, failure mechanisms in a propped cantilever truss bridge are reported using field investigation. The field observations are supplemented by numerical analysis to identify the causes of failure. A a systematic account of damage mechanisms in bridge components is also reported. The failure of the Lamgadi Bridge over the Seti River in Nepal is used as a case study example. The loading and construction protocols are detailed, and numerical analysis results are juxtaposed with the field observations to explain the failure mechanisms. Field observations and numerical results show that lack in adequate design is the most likely cause of the bridge collapse. Numerical results also indicate that the roller support at the propped end, unlike the hinged pot bearing used in the as constructed bridge would have been a safer choice. The failure could have been easily prevented with proper numerical simulation of the bridge response during the design phase.