Resonant Frequency Band Research Articles

Optical Parameters of Both As2S3 and As2Se3 Thin Films from Ultraviolet to the Near-Infrared via Variable-Angle Spectroscopic Ellipsometer

In the UV-visible-near infrared regions from 245 to 1000 nm, variable-angle spectroscopic ellipsometer (VASE) was used to investigate optical functions of As2S3 and As2Se3 thin films. In the entire measured spectral range, data were analyzed by assembly from several dispersion models. These assemblies comprise individual Tauc–Lorentz supplemented by several Lorentz (TL-group) or single Cody–Lorentz with several Lorentz (CL-group) models. For As2S3 and As2Se3 thin films, the optical parameters were quantified. The model parameters, such as the Lorentz amplitude, resonance frequency, oscillator width, extinction coefficients, refractive indices, and Urbach and optical band energy of both films were obtained. The band gap energy Eg was experimentally determined using the obtained data of CL-group from (αhν)1/2 vs. hν plots. It is found that the band gap energies of As2Se3 and As2S3 were 1.796 and 2.349 eV, respectively. The Eg values for the films were theoretically investigated by the bond statistics of the random covalent network model (CRNM) with the aid of Manca’s relation. Plausible agreement between the experimental and calculated Eg values for both samples was obtained.

Dynamics and nonlinear effects of a compact near-zero frequency vibration isolator with HSLD stiffness and fluid damping enhancement

Aiming to isolate disturbance vibration for heavy payloads with low frequency, a novel hydro-pneumatic near-zero frequency vibration isolator is proposed, which possesses high-static and low-dynamic (HSLD) stiffness. And different from most isolators existing previously, a nonlinear damping strategy realized by fluid damping mechanism is implemented into the device in order to enhance vibration isolation performance. Due to that the natural frequency of isolation system is close to zero and loading capacity can be adjusted by the gas pressure, the proposed device is termed as pneumatic near-zero frequency (NZF) vibration isolator. To obtain the primary resonance response for the harmonically forced nonlinear system, the averaging method is employed first and verified numerically. A direct current (d. c.) term is added in the analytical trial solution, which reflects the asymmetry existed in dynamic response. As a result, multiple steady solutions are observed and the induced amplitude jump appears. Then the stability of periodic response is carried out by using the Jacobin matrix approach. It is concluded that increases of all types damping including linear, square and friction damping are able to shrink the unstable region and further reduce the possibility of occurrence of amplitude sudden-jump in primary resonance. More accurately, the critical border which can separate the jump and none jump zones is found analytically and numerically, and design criterion for avoidance of sudden-jump is developed. After that, equivalent damping analysis gives a new insight into how nonlinearity effects of each damping dominate vibration isolation transmissibility in resonance and effective isolation frequency band. It is shown that the square type damping based on fluid mechanism can suppress the resonance response and transmissibility and does not decrease the effectiveness in isolation band, which will bring the favorable advantage for NZF isolator in practical application.

A low profile miniaturized circular microstrip patch antenna for dual-band application

AbstractA low profile Circular Microstrip Patch Antenna (CMPA) with radius 5 mm has been designed to generate two resonant frequency bands that can be used for WLAN 5.2 (5.15–5.25) GHz, Wi-Fi (5.725–5.850) GHz and Dedicated Short-Range Communications (DSRC) (5.85–5.925) GHz application bands. The designed antenna has been slitted with two slits and a stub has also been attached resulting in an additional resonant band alongside the primary resonant band. Also, primary resonant frequency shifted from 7.22 GHz to 5.87 GHz yielding about 18.7% antenna miniaturization. Frequency bands generated by the designed antenna are (5.15–5.25) GHz and (5.71–6.01) GHz having peak gain 2.3 and 4.9 dB with broadside radiation pattern. A square shape FR4 substrate having dimension 32 × 32 × 3.2 mm3 and very thin copper sheet for radiating patch and ground has been used in the proposed antenna, which can fulfill the requirement of smaller antenna with dual band application. Simulation software HFSS ver.13 has been used to design and analyze the proposed antenna. Very good matching has been obtained between simulated and measured results.

A compact double-band planar printed slot antenna for sub-6 GHz 5G wireless applications

AbstractA planar rectangular slot antenna with dual-band operation and realized higher peak gain is proposed, designed, and fabricated for sub-6 GHz 5G applications. The antenna possesses a rectangular radiating slot with the inverted stub on its upper edge excited simultaneously by a micro-strip feed line having a double folded T-shaped structure. The fabricated design is of compact size with the radiating portion of 0.3 λ0 × 0.17 λ0 (λ0 represents free-space wavelength) and profile of 0.009 λ0. The measured results show the operating frequency bands of 3.29–3.63 GHz and 4.3–5.2 GHz, with a peak gain of around 7.17 dBi. The higher frequency band is generated by the feed patch and the slot whereas lower resonant frequency band is generated by the stub loaded on the slot. The measured results are in a good agreement with the simulated results. The proposed design is suitable for the International Telecommunications Union sub 6 GHz applications.

국내 택배용 딸기의 적정 완충포장 시스템 개발

Due to the rapid increase in cyber shopping mall of agricultural products, the parcel delivery service industry also increased, making it necessary to design an optimum packaging for agricultural products. And Due to the recent increase in strawberry consumption, there is also a need for a packaging system for parcel delivery service. In order to establish the criteria for optimum cushioning packaging design of strawberries, the bioyield strength of strawberries by storage time was measured through the ASABE test standards, and the peak acceleration in the resonance frequency and resonance frequency bands of strawberries was measured through the vibration test regulated in the ASTM test specifications. Tray cup pad and corrugated fiberboard box of delivery strawberries were designed using FEM theoretical analysis of contact stress and resonant frequency. In addition, an optimum packaging system was developed with a cushioning and vibration design considering the impact characteristics when distributing agricultural products. Through the performance evaluation and on-site evaluation of the optimum packaging system of strawberries for parcel delivery service, the random PSD test results of the delivery showed a 74% reduction in the acceleration level, and the actual distribution test of the delivery showed that the damage rate of strawberries was not more than 6.7%, indicating that it was possible to use the optimum packaging of strawberries for delivery.

Recent Advances in QEPAS and QEPTS Based Trace Gas Sensing: A Review

Due to the merits of high quality factor, narrow resonance frequency band, low cost, tiny volume and immune to laser wavelength, QTF is widely used as a sensitive detector in photoacoustic spectroscopy and photothermal spectroscopy based gas sensing. In this invited review paper, the recent progress of QTF based state-of-the-art quartz-enhanced photoacoustic spectroscopy (QEPAS) and quartz-enhanced photothermal spectroscopy (QEPTS) gas sensing techniques in the past 3 years is summarized and discussed. The future development prospect of QEPAS and QEPTS based gas sensing techniques is also presented.

Teager energy spectral kurtosis of wavelet packet transform and its application in locating the sound source of fault bearing of belt conveyor

Kurtogram is widely used in fault diagnosis because it can adaptively identify the resonance frequency band of the fault. However, kurtosis defined in time domain has poor robustness and is very sensitive to noise and non-periodic transient impulse caused by accidental vibration, thus these components easily lead to disturbance in kurtogram algorithm. In this study, a frequency domain statistical index called teager energy spectral kurtosis (TESK) was proposed. This index combines the enhancement of teager energy operator to impulse characteristics and the sensitivity of frequency domain index to periodic characteristics, thus it can easily capture the resonance frequency band of fault characteristics in sound signals of bearing well. Through simulated and experimental analysis, TESK can well represent the sub-band wavelet packet transform, so as to extract the sub-band with relatively concentrated fault information. Further, it is combined with generalized cross-correlation post-processing, and finally the position of fault sound source can be located.

Compound fault identification of rolling element bearing based on adaptive resonant frequency band extraction

The high frequency resonance (HFR) technique is regarded as a powerful tool for fault diagnosis of rolling element bearings. Different from the usage of the HFR in single fault, the determination of multiple resonant frequency bands under the compound faults and extraneous random impulses is still a challenging task. This paper develops a novel compound fault identification method based on adaptive resonant frequency band extraction. The improved redundant second generation wavelet packet transform is first presented to decompose vibration signal into various narrow bands for providing a fine separation of fault signatures. Then the squared envelope spectrum sparsity criteria is designed to quantify fault characteristics buried in narrow frequency bands. Consequently, the squared envelope spectrum sparsogram is constructed to highlight optimal resonant bands, and the compound faults can be well detected by band-pass filtering and envelope analysis. The numerical and experimental results confirm effectiveness and superiority of the proposed method, which is more sensitive to fault-related impulses and robust to extraneous interferences.

Influence of geometric nonlinearity of rectangular plate on vibration reduction performance of nonlinear energy sink

The differences between the vibration reduction of a NES (nonlinear energy sink) on a nonlinear plate and a linear plate are compared, and the effect of NES on the nonlinear plate is mainly analyzed. The nonlinear equations of the plates connected to NES are derived and subsequently solved by the complexification-averaging method and least square method. The amplitude of the first mode of the nonlinear plate is several times higher than that of the linear plate under large excitation when the two plates are attached to identical NES. The amplitudes of the second mode of the two NES equipped plate are similar. However, super-harmonic resonance responses of the two systems are significantly different. The evolution of the higher branch responses in super-harmonic resonance frequency band of the second mode is analyzed, and found to be significantly different with respect to that in the primary resonance frequency band of the first mode.

High-Resolution Dielectric Constant Measurement Using a Sensor Antenna With an Allocated Link for Data Transmission

A dual-band low-profile patch antenna, which operates based on aperture-coupling mechanism, is exploited to measure the permittivity of a sample under test (SUT) in the microwave frequencies and send the measured data simultaneously. The upper resonant frequency, which is considerably affected by changing the permittivity of the SUT, can be utilized for sensing purpose. In contrast, the lower resonant frequency is almost independent of the samples hence can be used as the communication link. The samples are placed on top of the feeding side of the structure. The variation in the sample’s permittivity leads to changes in the input impedance of the sensor antenna. While this change results in having different feedline-dependent resonant frequencies, the cavity-dependent resonant frequency is almost preserved intact for different samples. The sensor antenna is designed using electromagnetic solver and an equivalent circuit is proposed to model its behavior. The effect of varying parameters in the equivalent model is investigated. Moreover, by fabricating the sensor, the measurement results show that by changing the permittivity of samples from 1 to 12.85, the upper band resonant frequency (feedline-dependent) shifts from 12.30 to 11.37 GHz (78 MHz per unit dielectric constant). Nevertheless, the small variation in resonant frequency and radiation characteristics of the antenna in the lower band (cavity-dependent) can provide a stable communication channel with respect to the SUT. This link with a reasonable 2.8% (9.54-9.81 GHz) 10-dB impedance bandwidth can be reserved for sending the measured and pilot data in a wireless sensor system.

Fractal, Scale Free Electromagnetic Resonance of a Single Brain Extracted Microtubule Nanowire, a Single Tubulin Protein and a Single Neuron

Biomaterials are primarily insulators. For nearly a century, electromagnetic resonance and antenna–receiver properties have been measured and extensively theoretically modeled. The dielectric constituents of biomaterials—if arranged in distinct symmetries, then each vibrational symmetry—would lead to a distinct resonance frequency. While the literature is rich with data on the dielectric resonance of proteins, scale-free relationships of vibrational modes are scarce. Here, we report a self-similar triplet of triplet resonance frequency pattern for the four-4 nm-wide tubulin protein, for the 25-nm-wide microtubule nanowire and 1-μm-wide axon initial segment of a neuron. Thus, preserving the symmetry of vibrations was a fundamental integration feature of the three materials. There was no self-similarity in the physical appearance: the size varied by 106 orders, yet, when they vibrated, the ratios of the frequencies changed in such a way that each of the three resonance frequency bands held three more bands inside (triplet of triplet). This suggests that instead of symmetry, self-similarity lies in the principles of symmetry-breaking. This is why three elements, a protein, it’s complex and neuron resonated in 106 orders of different time domains, yet their vibrational frequencies grouped similarly. Our work supports already-existing hypotheses for the scale-free information integration in the brain from molecular scale to the cognition.

Design of Multiband Frequency Reconfigurable Antenna with Defected Ground Structure for Wireless Applications

A novel printed rectangular shape, multi-band frequency reconfigurable antenna with defected ground structure (FRDGS) for multi standard wireless communication systems is designed in this article. The ground plane is modified by embedding U shaped slots with open ends and I shaped slot in short ends to realize the multi band frequency of the antenna and to improve the parameters of the antenna design. The two U shape slots are etched symmetrical to each other to reduce the cross polarization of the antenna. The DGS in the ground plane altered the modeling characteristics of transmission lines with the equivalent values of inductance, capacitance and resistance. Three PIN diodes are inserted in the ground plane to acquire the switching characteristics of multi-resonance frequency. Simulated and measured output clearly depict that the antenna proposed is efficient to change between twelve dissimilar resonant frequency bands centered at 1.36, 1.8, 3.0, 3.9, 5.0, 6.2, 6.4, 7.4, 7.9, 8.2, 8.4, 8.6 GHz through different states of modes over the frequency spectrum from 1.33 to 8.7 GHz. The parameters such as reflection coefficient, VSWR, 2D and 3D radiation pattern, bandwidth, peak gain, peak directivity, gain and directivity are simulated using Ansoft HFSS 17.0v. The proposed antenna finds application in various wireless communication system such as Wi-Fi (5 GHz), WLAN (5 GHz), WI-MAX, UWB (3.1–10.6 GHz) system, fixed mobile and satellite communication systems.

Bistable active spectral tuning of one-dimensional nanophotonic crystal by phase change.

Active spectral tuning of nanophotonic devices offers many fascinating prospects for the realization of novel optical function. Here, switchable spectral response is enabled by the architecture of one-dimensional (1D) photonic crystal (PC) integrated with phase change material of the germanium antimony telluride (GST). Active and precise tuning of the bistable passband and central resonant frequency is demonstrated in the 1D PC composed of alternate SiN and GST nanofilms. An analytical model is derived to specify the tunable spectral features, including the band gap and resonant frequencies. Both the measured and calculated results show distinct red shifts of passband and the resonant minima (or maxima), well confirming theoretical predictions. This work demonstrates a route to construct active photonic devices with the electrically or thermally tunable spectra via 1D PC and potentially extends diverse applications based on the PC platform.

A novel short-frequency slip fault energy distribution-based demodulation technique for gear diagnosis and prognosis

To conduct diagnosis and prognosis of gears, this paper introduces a novel short-frequency slip fault energy distribution-based demodulation method. As an essential step of the method, the resonance-based sparse signal decomposition algorithm is firstly employed to obtain the high-resonance part from the raw gear fault signal. To deal with the difficulty in determining the resonance frequency band, we establish a multi-input signal-output model to describe the signal components acquired from a faulty gear. Based on it, the short-frequency slip fault energy distribution graph is defined to locate the center frequency. Besides, the maximum amplitude in the short-frequency slip fault energy distribution graph can be used as a health indicator for prognosis, which is named as fault-induced resonance energy ratio. The effectiveness of the proposed method is validated with both simulated signal and test data. The positive results achieved in both experiments show the perfect property of the methodology for gear fault detection with high noise, especially when the fault is incipient. In addition, by comparing the fault-induced resonance energy ratio values of faulty gears with different severity, it is proved to be a reliable health indicator for gear prognostic.

An improved higher-order analytical energy operator with adaptive local iterative filtering for early fault diagnosis of bearings

Early fault diagnosis in rolling bearings is crucial to maintenance and safety in industry. To highlight the weak fault features from complex signals combined with multiple interferences and heavy background noise, a novel approach for bearing fault diagnosis based on higher-order analytic energy operator (HO-AEO) and adaptive local iterative filtering (ALIF) is put forward. HO-AEO has better effect in dealing with heavy noise. However, it is subjected to the limitation of mono-components. To solve this limitation, ALIF is adopted firstly to decompose the nonlinear, non-stationary signals into multiple mono-components adaptively. In the next, the resonance frequency band as the optimal intrinsic mode function (IMF) is selected according to the maximum kurtosis. In the following, HO-AEO is utilized to highlight weak fault characteristics of the selected IMF. Finally, the early bearing fault is diagnosed by the energy operator spectrum based on fast Fourier transform (FFT). Comparisons in the simulation indicate that the fourth order HO-AEO shows the best performance in fault diagnosis compared with Teager energy operator (TEO), analytic energy operator (AEO), the second and the third order HO-AEO. The simulated test and experimental results demonstrate that the proposed approach could effectively extract weak fault characteristics from contaminated vibration signals.

On the double resonance activation of electrostatically actuated microbeam based resonators

Electrostatically actuated microelectromechanical system (MEMS) devices have shown prominent potential in various applications. However, despite their low power consumption, they do require high input voltages to be actuated. This is even worse if these devices are driven around their mechanical resonant state. Assuming a double resonance excitation scheme, both electrically and mechanically, activates the system’s mechanical and electrical resonances simultaneously. This double resonance activation was recently verified experimentally to alleviate the problem of high actuating voltage/displacement near the resonant state. Therefore, in this work, an analytical electro-mechanical coupled model for a double-resonance-driven microbeam, assuming a classical nonlinear beam model combined with an RLC electric circuit model is first proposed and then numerically examined. Good match among the numerical simulations and the experimental data when the electrical resonance frequency band is sufficiently high is demonstrated. The suggested model can be used to further optimize certain MEMS designs and therefore fully benefit from this double resonance activation scheme in improving MEMS sensors and actuators.

Novel, compact, circular-sectored antenna for Ultra-Wideband (UWB) communications

ABSTRACTThis article presents a compact circular-sectored microstrip antenna embedded with circular slots and a sectoral ground plane for enhanced bandwidth and applicable for UWB communications exhibiting an equivalent Fractional Bandwidth of 156.04% (2.5–20.25 GHz) and allows a compactness of about 79.15% using Rogers RT-Duroid 5880 as a substrate for lesser surface wave loss and attaining broader bandwidth. The gain of the antenna ranges from 1.85 to 6.10 dBi throughout the resonant frequency band and the results obtained from measurement are validated to justify the applicability of this antenna for various WLAN and Wi-MAX frequency bands.

A 3-D printed square loop frequency selective surface for harmonic radar applications

This paper presents a 3-D printed frequency selective surface (FSS) for harmonic radar applications. The proposed FSS design consists of a square loop printed on the cost-effective acrylonitrile butadiene styrene (ABS) plastic material to pass the signals at 5 GHz resonant frequency band. The proposed FSS is tested for various oblique angles up to 45° and even for different polarization modes. A prototype of the proposed design FSS is fabricated. The results demonstrate a good agreement of simulated results with experimental ones. The 3-D printing technique provides a simple and low-cost method to fabricate FSS and make it suitable for future FSS mass production.

Miniaturized dual‐band slot antenna design for GPS, amateur radio and WLAN applications

In this article, miniaturization of dual-band slot antenna design for GPS, WLAN and amateur radio applications is presented. The proposed dual-band miniaturized antenna is achieved using slits, rectangular split ring and metallic strips fed by 50 Ω microstrip feed. The first resonant frequency is achieved by loading reference antenna with eight slits that is antenna 1 and the second resonant frequency is achieved by loading with one center slits and rectangular split ring that is antenna 2. Dual-band antenna is achieved by loading reference slot antenna with nine slits and rectangular split ring which resonates at frequency of 1.52 and 3.03 GHz respectively. As a result, it is achieved 53.79% reduction in first band resonant frequency with 76.07% improvement in −10 dB bandwidth and 7.90% reduction in second band resonant frequency compared to reference slot antenna. Further, this dual-band antenna is miniaturized by metallic strips which are placed on the bottom of the substrate. This results in 61.39% reduction in first band resonant frequency with 32.07% improvement in −10 dB bandwidth and 26.13% reduction in second band resonant frequency in comparison with reference slot antenna topology.

Bearing Fault Diagnosis Based on Iterative 1.5-Dimensional Spectral Kurtosis

The key step of bearing fault diagnosis is to select a suitable resonance frequency band, so as to filter out interference components to the maximum extent and retain fault information in the resonance band. Kurtogram algorithm can locate the resonance frequency band well, which has been widely researched and applied in recent years, and has produced many derivative algorithms. The statistical indicators used by these methods to identify frequency band features are divided into time domain indicators and frequency domain indicators. Time domain indicators are more sensitive to a single accidental impact components, while frequency domain indicators are easily affected by harmonics in the time domain, that is, single or several frequency extremes in the frequency domain. In order to overcome the impact of non-periodic transient impulse components and modulation harmonic components, this article proposes a new method. This method uses wavelet packet transform (WPT) to divide the frequency band plane, and adopts 3 iterations 1.5-dimensional spectrum (1.5D spectrum) method, which can eliminate the impulse interference that has no coupling relationship in the time domain and frequency domain. Based on the above process, the $\text{K}_{\mathrm {I-1.5D}}$ gram method is constructed, which can realize more accurate positioning of the fault information. Finally, through simulated and experimental analysis, the effectiveness of the proposed method is verified.