Resonance Peak Research Articles

A Simulation Investigation on the Influence of Bearing Outer Ring Defect on Dynamic Vibration Characteristics of the Axle‐Box System

AbstractIn this paper, a vehicle track coupling dynamic model including bearing outer ring defects is built, the time history of the axle‐box vibration acceleration and the time history of the bearing roller‐outer raceway contact load under the condition of random track irregularity on the Beijing‐Tianjin line are obtained by simulation calculation. The results show that when the outer ring defect of the bearing occurs, the axle box will generate high‐frequency vibration at the resonance peak in the vertical and lateral directions. When the defect on the bearing outer ring is in the small width of 1 mm, the roller only imposes one impact when passing through the defect area. However, when the width exceeds 3 mm, the large defect causes the roller to impose a double impact on the lateral direction of the axle box, due to changes in bearing clearance in the passing‐through process. When the running speed of the train is about 250 km h−1, the width of bearing outer ring defects needs to be limited to within 1 mm, to minimize a series of problems such as structural fatigue caused by the increased bearing roller‐outer raceway contact load caused by bearing outer ring defects.

Terahertz determination of imidacloprid in soil based on a metasurface sensor.

Pesticides in soil are continuously one of the most studied analytes due to their environmental and human health effects. Thus the detection of pesticides in soil is an important means to control and assess soil quality. Here, we theoretically and experimentally present a novel method for the determination of imidacloprid in soil by using a metasurface sensor operating at terahertz frequencies. The metasurface shows a resonance peak at 880 GHz and the electric field at the peak is strongly localized and concentrated in the gap of split I-shaped resonator. The detection of complex refractive index shows that the position and the transmittance of resonance peak are depend on the change in the complex refractive index. The measurement of imidacloprid concentration in soil demonstrates that both the frequency shift and the transmittance change at peak increase almost linearly with the increasing of imidacloprid concentration ranging from 0.25% to 2%. In this case, the frequency shift reaches 97 GHz and the transmittance change at peak is as high as 30.9%. Our work enables the determination of imidacloprid in soil at terahertz frequencies with good reliability and high sensitivity, showing the potential application of terahertz spectroscopy in environmental monitoring.

Phyto-mediated synthesis of silver nanoparticles using flower extract of Erythrina indica and evaluation of their biological activities

The goal of this research was to investigate the antibacterial, cytotoxic and photocatalytic properties of silver nanoparticles synthesized from Erythrina indica flowers (EIF-AgNPs). The green synthesized EIF-AgNPs were characterized by UV–visible spectroscopy, field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HR-TEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FT-IR). The UV–visible spectrum of EIF-AgNPs revealed a 420 nm surface plasmon resonance (SPR) peak. The XRD analysis exhibited that the EIF-AgNPs were crystalline in nature. FT-IR revealed that the flower extract has been stabilized with the EIF-AgNPs by a capping agent. Furthermore, electron microscopy indicated that the EIF-AgNPs were spherical in shape and measured 42.3 nm in diameter. The eco-friendly synthesized EIF-AgNPs show potential antibacterial activity against Staphylococcus aureus and Salmonella typhi in a well-diffusion assay. In addition, in-vitro cytotoxicity tests on MCF-7 cell lines demonstrated that EIF-AgNPs (42.5 µg/mL) have harmful effects. Furthermore, EIF-AgNPs had a high degradation efficiency for reactive orange 16 (RO16), with 90 % elimination after 120 min of sunlight irradiation. Overall, the findings of this study indicate that Erythrina indica flower biosynthesized EIF-AgNPs may have antibacterial, cytotoxic and photocatalytic effects.

An efficient hybrid collocation scheme for vibro-acoustic analysis of the underwater functionally graded structures in the shallow ocean

In this paper, a novel hybrid collocation scheme based on the generalized finite difference method (GFDM) and the Burton–Miller singular boundary method (BMSBM) is developed to study the vibration and acoustic radiation characteristics of an underwater functionally graded (FG) structure immersed in the shallow ocean. By utilizing the individual strengths of both methods, the GFDM is adopted for the vibration analysis of the FG structures, while the BMSBM is applied for the acoustic wave radiation analysis. Numerical examples verify the accuracy and efficiency of the proposed hybrid collocation scheme for the natural frequency and acoustic radiation behavior of the underwater structures consisting of the functionally graded materials (FGMs). The influences of the material parameters, structural geometries and shallow ocean environment on the natural frequencies of the structural vibration and the underwater acoustic wave radiation field are investigated in detail. Numerical study shows that the variation trend of the natural frequencies of the structural vibration is consistent with that of the resonance peak frequencies of the underwater acoustic radiation field. The present results may provide valuable references for the design and application of underwater marine structures consisting of the FGMs.

Design of self-coupled plasmonic hyperbolic metamaterials refractive index sensor based on intensity shift

Achieving efficient, accurate, label-free, and real-time biodetection is urgently required; hence, we propose a miniaturized, easily integrated, high-sensitivity plasmonic metamaterial light intensity refractive index sensor. The main structure of the sensor is layered hyperbolic metamaterial grating comprises eight pairs of Au/Al2O3 thin film, and the highly sensitive bulk plasmon polaritons can be effectively excited inside by the self-coupled effect without external prism or nanograting. The periodic fishnet arrays built in the layered HMM structure can not only be used as nanograting to achieve efficient coupling between incident light and layered HMM, but also increase the volume of the sensing, and the measured substance can get full interaction with the enhancement field to obtain high sensitivity. By detecting the change of reflected optical intensity with the ambient refractive index, the sensor exhibits intensity sensitivity of 36 RIU−1 (refractive index unit) and figure of merit of 403; moreover, the full width at half maximum of resonant peak is low at 5 nm. The sensing performances indicate that the sensor we designed has a significant potential to achieve portable, highly sensitive sensing platforms for precise detection.

Closed-Loop Cavity Shear Layer Control Using Plasma Dielectric Barrier Discharge Actuators

The complex unsteady flow in cavities leads to the formation of large-scale disturbances in the shear layer. Natural closed-loop mechanisms provoke a dramatic increase in pressure pulsations and aerodynamic noise. This paper presents the experimental study of pressure fluctuations in closed-loop control in rectangular cavities using plasma dielectric barrier discharge. The flow velocity was 37 m/s, and the Reynolds number based on a cavity depth was approximately 120,000. The discharge ignition near the leading edge of the cavity provoked the shear layer restructuring. It was found that pressure fluctuations with an amplitude of 120 dB occur at frequencies 480 and 820 Hz. Frequency modulation of the discharge at resonant peaks was carried out by changing the phase shift of the power supply. The peak amplitude was reduced or increased by phase shifts from natural disturbances to forced ones. The optimum energy input was 50 W/m. This was three times less than the power consumption of the open-loop mode. The PIV visualization was organized in the phase-locked mode. The pressure spectrum corresponds to the magnitude of coherent structures in the shear layer of the cavity.

Tightly focused linearly and radially polarized beam effect on the LSPR peak with varying particle size

Interactions of gold and silver spherical nanoparticles (NPs) of a wide range of radius size with tightly focused beams are investigated for a wide range of wavelengths. The scattering of tightly focused beams with a single NP of varying size is examined using a generalized Mie theory and average intensity enhancement in the near-field due to localized surface plasmons is examined for different tightly focused beams. A multipole expansion approach is used to observe the contribution of modes in shaping the scattered light intensity. Influence of particle size and tightly focused beam on intensity enhancement factor is investigated and a shift in localized surface plasmon resonance (LSPR) peak towards higher wavelength is observed with increasing particle size. Maximum intensity enhancement factor due to scattering of different incident beams by a metallic NP is theoretically examined and reported. Gold and silver NP having radius size ranging from 30–60 nm and 1–15 nm respectively showed a maximum intensity enhancement factor in different media. A significant enhancement for the tightly focused radially polarized beam is observed for gold and silver NPs of radius size between 50 nm and 100 nm. Variation towards higher wavelength in LSPR peak due to involvement of higher order of multipoles, and the surrounding medium are also examined in detail.

Seawater Salinity Sensor Based on Dual Resonance Peaks Long-Period Fiber Grating and Back Propagation Neural Network

Seawater Salinity Sensor Based on Dual Resonance Peaks Long-Period Fiber Grating and Back Propagation Neural Network

High-Frequency Harmonic Suppression Strategy and Modified Notch Filter-Based Active Damping for Low-Inductance HPMSM

The voltage inverters have the high-frequency switching characteristic, which will generate massive high-frequency harmonics in the motors. Especially, the inductance of the high-speed permanent magnet synchronous motor (HPMSM) is designed to be small, and the high-frequency harmonic content will be higher than that of ordinary motors, which adversely affects the system. To overcome this problem, this paper proposed a harmonic suppression method based on the LC filter and the adaptive notch filter for HPMSMs. The LC filter is connected between the inverter and the HPMSM to filter out high-frequency harmonics, however, at the cost of the system resonance. Therefore, the adaptive notch filter with the frequency tracking capability is designed to offset specific resonant peaks by constructing an antiresonant peak. The least mean square adaptive algorithm automatically adjusts the filter parameters according to the variation of the input signal to ensure accurate filtering in complex cases. Simulation and experiment results prove the practicability and effectiveness of the proposed scheme. The harmonic contents of HPMSM are significantly reduced, and the dynamic response performance of the control system is improved.

Design, fabrication, and sensing applications of MWCNT/PET terahertz metasurface

In this paper, the periodic rectangular aperture arrays have been etched on a multi-walled carbon nanotube (MWCNT) film prepared by vacuum filtrating to fabricate a terahertz (THz) metasurface on a polyethylene terephthalate (PET) substrate. The transmission properties and the underlying resonance physical mechanism of the metasurface were investigated in detail. An obvious resonant peak located at 0.48 THz can be observed, the results of the scattering powers for various multipole moments show that the enhanced transmission peak is dominated by the radiation contribution of the electric dipole ultimately. To demonstrate the sensing capability, the fabricated metasurface was used to detect different concentrations of 2,4-dichlorophenoxyacetic acid (2,4 - D) solutions. The experimental results reveal that the transmission amplitude decreases linearly as the concentrations increase, and the amplitude sensitivity can achieve 1.69 × 10−2/ppm. This study demonstrates the MWCNT/PET metasurfaces can be applied for trace analytes sensing and improve the sensitivity and accuracy, while the processing technology can also be extended to the preparation and various applications of CNT-based metasurfaces, which provides a beneficial reference for the extended applications of carbon-based metamaterial devices in the THz band.

Synthesis of Silver Oxide Nanoparticles: A Novel Approach for Antimicrobial Properties and Biomedical Performance, Featuring Nodularia haraviana from the Cholistan Desert.

Nanoparticles have emerged as a prominent area of research in recent times, and silver nanoparticles (AgNPs) synthesized via phyco-technology have gained significant attention due to their potential therapeutic applications. Nodularia haraviana, a unique and lesser-explored cyanobacterial strain, holds substantial promise as a novel candidate for synthesizing nanoparticles. This noticeable research gap underscores the novelty and untapped potential of Nodularia haraviana in applied nanotechnology. A range of analytical techniques, including UV-vis spectral analysis, dynamic light scattering spectroscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray powder diffraction, were used to investigate and characterize the AgNPs. Successful synthesis of AgNPs was confirmed through UV-visible spectroscopy, which showed a surface plasmon resonance peak at 428 nm. The crystalline size of AgNPs was 24.1 nm. Dynamic light scattering analysis revealed that silver oxide nanoparticles had 179.3 nm diameters and a negative surface charge of -18 mV. Comprehensive in vitro pharmacogenetic properties revealed that AgNPs have significant therapeutic potential. The antimicrobial properties of AgNPs were evaluated by determining the minimum inhibitory concentration against various microbial strains. Dose-dependent cytotoxicity assays were performed on Leishmanial promastigotes (IC50: 18.71 μgmL-1), amastigotes (IC50: 38.6 μgmL-1), and brine shrimps (IC50: 134.1 μg mL-1) using various concentrations of AgNPs. The findings of this study revealed that AgNPs had significant antioxidant results (DPPH: 57.5%, TRP: 55.4%, TAC: 61%) and enzyme inhibition potential against protein kinase (ZOI: 17.11 mm) and alpha-amylase (25.3%). Furthermore, biocompatibility tests were performed against macrophages (IC50: >395 μg mL-1) and human RBCs (IC50: 2124 μg mL-1). This study showed that phyco-synthesized AgNPs were less toxic and could be used in multiple biological applications, including drug design and in the pharmaceutical and biomedical industries. This study offers valuable insights and paves the way for further advancements in AgNPs research.

Curvature sensor based on D-shape fiber long period fiber grating inscribed and polished by CO2 laser

In this paper, a D-shape fiber long period fiber grating (DLPFG) curvature sensor has been theoretically and experimentally investigated. Different from previous reported long period fiber grating (LPFG) curvature sensor based on D-shape single mode fiber (SMF), the fabrication of DLPFG is divided into two steps: LPFG with a low coupling efficiency is firstly written on a SMF by high-frequency CO2 laser, and then the grating area is subsequently polished to induce deeper resonance peaks and D-shape structure simultaneously. The polishing greatly enhances the fiber asymmetric modulation and thus results in the improvement of curvature sensitivity. Experiments show that the DLPFG has a high curvature sensitivity of 17.6 nm/m−1 and −11.9 nm/m−1 in two opposite directions within the plane perpendicular to CO2 laser-irradiated direction, which has exceeded that of the other reported LPFGs based on D-shape SMF. Besides, the temperature sensitivity is 45 pm/°C in range of −20 °C to 50 °C, and the temperature cross sensitivity is 2.58 × 10-3 m−1/°C. Therefore, this proposed DLPFG sensor with advantages of low-cost, easy-fabrication, high-reproducibility and high-sensitivity is promising for curvature measurement.

A domestic pressure cooker mediated, facile autoclaving method for the synthesis of silver nanoparticles

As an alternative to an expensive hydrothermal reactor, in the current method a domestic pressure was used for the synthesis of silver nanoparticles (Ag NP) using tree gum, kondagogu as dual functional reductant and stabilizer by autoclaving. The formation of Ag NP was evaluated with colour transformation, UV-Visible spectroscopy (UV–Vis) and transmission electron microscopy. The formation of Ag NP by gum confirmed from the developed yellow coloration of the solution and the appearance of surface plasmon resonance peak at 408 nm in the UV–Vis. The produced NP were spherical, polydisperse, particle size ranged from 2.9–17.6 nm and the average particle size was 4.5 ± 3.1 nm. The developed method is useful for demonstration, gaining hands on experience and production of metal and metal oxide NP in resource limited small laboratories, rural colleges, startups etc.•Pressure cooker serves as an easily accessible, durable, inexpensive, electricity independent hydrothermal nanoparticle production vessel.•Autoclaving serves as a facile, ecofriendly, less energy consuming, one pot, green method with dual functional role of in situ nanoparticle synthesis and sterilization.•Production of intrinsically safe and sterile nanoparticles amenable for in vivo and in vitro biomedical applications.

Effect of equilibrium position offset on rotordynamics of a rigid rotor supported by hybrid foil magnetic bearings: Numerical and experimental investigations

This study investigates the influence of equilibrium position offset on the stability of a hybrid foil magnetic bearing (HFMB)-rotor system. Experimental tests and theoretical calculations are conducted using an established setup comprising the HFMB rotor system and a PID control system. The effects of equilibrium position offsets on resonance peaks, 1/2X subsynchronous vibration, and whip are analyzed through waterfall plots, synchronous vibration plots, rotor center orbit, and Fast Fourier transforms. The results reveal that the impact of equilibrium position offset on different vibration components varies due to distinct mechanisms of induced vibration. Surprisingly, the offset does not necessarily decrease system stability. Negative offset of the equilibrium position in the vertical direction mitigates tangential friction and 1/2X subsynchronous vibration. Conversely, positive offset of the equilibrium position in the vertical direction enhances system stiffness and the instability threshold of whip. These findings offer guidance for future PID controller designs for HFMBs and demonstrate the exceptional flexibility and controllability achievable with HFMBs.

MUA/NPAM/ZnO-coated Fiber-Optic surface plasmon resonance sensor for trace Chromium-Ion detection

A transmission fiber-optic surface plasmon resonance (SPR) sensor based on three-core optical fiber (TCF) coated with mercaptoundecanoic acid (MUA)/ nonionic polyacrylamide (NPAM)/zinc oxide (ZnO) composite film for the detection of chromium ions (Cr3+) in water was proposed and fabricated. Multi-mode fiber (MMF) was spliced with both ends of TCF to form the MMF1-TCF-MMF2 sensing structure. The silver (Ag) film was deposited on the surface of TCF cladding, and then a uniform MUA/NPAM/ZnO composite film was coated on the outer surface of the Ag film to adsorb Cr3+, resulting in the wavelength shift of the SPR resonance peak. After adsorption of Cr3+, the refractive index of the sensing film changed and the resonance wavelength shifted about 62 nm. The detection limit of the sensor is about 0.029 μΜ (1.5 ppb), and the minimum detection concentration of Cr3+ is about 0.2 µM (10 ppb), which is far lower than that of the World Health Organization standard (50 ppb). The sensor shows excellent selectivity, high sensitivity and good stability for the trace Cr3+, and has potential application for monitoring Cr3+ in water.

Thermal Hysteresis Effect and Its Compensation on Electro-Mechanical Impedance Monitoring of Concrete Structure Embedded with Piezoelectric Sensor

Piezoelectric (PZT) sensors employed in the electro-mechanical impedance/admittance (EMI/EMA) technique are vulnerable to temperature variations when applied to concrete structural health monitoring (SHM). However, in practice, the ambient temperature transmitted from the air or surface to the concrete inner part is time-dependent during its monitoring process, which inflicts a critical challenge to ensure accurate signal processing for PZT sensors embedded inside the concrete. This paper numerically and experimentally investigated the thermal hysteresis effect on EMA-based concrete structure monitoring via an embedded PZT sensor. In the numerical modeling, a 3D finite element model of a concrete cube embedded with a PZT sensor was generated, where thermal hysteresis in the concrete, adhesive coat, and sensor was fully incorporated by introducing a temperature gradient. In the experiment, an equal-sized concrete cube installed with a cement-embedded PZT (CEP) sensor was cast and heated for 180 min at four temperature regimes for EMA monitoring. Experimental results, as a cogent validation of the simulation, indicated that EMA characteristics were functionally correlated to the dual effect of both heat transfer and the temperature regime. Moreover, a new approach relying on the frequency/magnitude of the maximum resonance peak in the EMA spectrum was proposed to effectively compensate for the thermal hysteresis effect, which could be regarded as a promising alternative for future applications.

Lab-on-a-chip optical biosensor platform: a micro-ring resonator integrated with a near-infrared Fourier transform spectrometer.

In this paper, we demonstrated the design and experimental results of the near-infrared lab-on-a-chip optical biosensor platform that monolithically integrates the MRR and the on-chip spectrometer on the silicon-on-insulator (SOI) wafer, which can eliminate the external optical spectrum analyzer for scanning the wavelength spectrum. The symmetric add-drop MRR biosensor is designed to have a free spectral range (FSR) of ∼19 nm and a bulk sensitivity of ∼73 nm/RIU; then the drop-port output resonance peaks are reconstructed from the integrated spatial-heterodyne Fourier transform spectrometer (SHFTS) with the spectral resolution of ∼3.1 nm and the bandwidth of ∼50 nm, which results in the limit of detection of 0.042 RIU.

Multi-mode detection of iodine based on Au@Ag nanoparticle array with highly sensibility and stability using plasmonic surface lattice resonances

Designing a sensor to rapidly and simply detect iodine (I2) in liquid and gaseous phase with excellent sensitivity, high stability, and low cost at room temperature is highly desirable. Herein, a two-dimensional Au@Ag nanoparticle ordered array was prepared by template method combined with chemical reduction for detecting I2 at room temperature. Due to the ordered structure, a plasmonic surface lattice resonances (PSLR) peak appeared in extinction spectrum of the Au@Ag nanoparticle ordered array. When the ordered array exposed to I2, the Ag shell would react with I2 to form AgI, thus leading to a change in the dielectric medium surrounding the Au nanoparticles. This change would cause a variation of color and a shift of PSLR peak, realizing multi-mode detection of liquid and gaseous I2 at room temperature without any sophisticated instrument. With the increase of I2 concentration, the color of the Au@Ag nanoparticle array changed from red to yellow-green. Meantime, the PSLR peak displayed highly sensitive redshift with a larger offset (about 156 nm) and intense signal strength. Moreover, due to the ordered array structure, the PSLR peak possessed good uniformity and stability. Therefore, the PSLR peak was more suitable for detecting I2 in a large concentration region. Furthermore, the practical application of the present prepared Au@Ag nanoparticle array was explored by detecting gaseous I2 at room temperature. It was found that the Au@Ag nanoparticle array possessed high sensitivity to gaseous I2 with a detection limit reaching to trace level (1 ppb), suggesting tremendous potential for real-world application.

Exploring the Preparation of Calcium-Doped Zinc Aluminate Ceramic Nanoparticles for Microstrip Patch Antenna Fabrication

Zinc aluminate (ZnAl2O4) dielectric materials have proven crucial in microwave applications, particularly in antenna miniaturization. This article presents the characteristics of sol-gel-prepared Ca-doped ZnAl2O4 (ZnAl2O4Ca) ceramic nanoparticles for their application in microstrip patch antenna (MPA). We examined the crystallinity, functional groups, morphology, and elemental properties of ZnAl2O4Ca ceramic nanoparticles using different techniques. Later, a prototype antenna was fabricated and evaluated, which demonstrated the return loss of -23.4 dB and -19.2 dB with voltage standing wave (VSWR) ratios of 1.1 and 1.2 at resonant frequency ( ) values 4.5 and 6.4 GHz, respectively. The presented work demonstrates that the prepared ceramic nanoparticles possess better microwave properties, enabling the fabrication of a patch antenna for c-band communication with two resonant peaks having reasonably good return loss.

Discrimination of Brain Abscess and Necrotic Brain Tumor with Proton MR Spectroscopy and Diffusion-Weighted Imaging

Objective: To compare the efficacy of MR spectroscopy and diffusion-weighted imaging in discriminating between cystic or necrotic tumors and pyogenic brain abscesses.Study Design: A retrospective study design.Place and Duration of Study: The Study was conducted at the Radiology Department of Nishtar Hospital Multan and General Hospital Lahore, Pakistan, from January 2022 to January 2023. Methods: A total ten patients were included in the study. Of 10 patients, 5 had pyogenic abscesses, and 5 had tumors. Tumors were metastases (2 patients), glioblastomas (2 patients), and anaplastic astrocytoma (1 patient). Proton MR spectroscopy and diffusion-weighted imaging were performed in all patients. Results: Results showed that significant resonance lines (creatine/phosphocreatine, N-acetyl aspartate, and choline) observed in normal brain parenchyma were missing in abscesses or necrosis. MR spectroscopy of abscess showed multiple resonance peaks. Diffusion-weighted images showed that all pyogenic abscesses had lower ADC values and were hyperintense compared to normal brains. Conclusion: Diffusion-weighted imaging is more accurate and less time consuming method for discrimination of brain lesions compared to MR spectroscopy.
 How to cite this: Saqib HA, Asghar A, Firdous A, Zahra M, Islam Z, Mushtaq S. Discrimination of Brain Abscess and Necrotic Brain Tumor with Proton MR Spectroscopy and Diffusion Weighted Imaging. Life and Science. 2023; 4(4): 432-437. doi: http://doi.org/10.37185/LnS.1.1.431