Frequency Range Research Articles

Synthesis and study of structural, electric, and dielectric behavior of La0.5Sm0.2Sr0.3Mn1-xFexO3 perovskite

In this study, the synthesized samples La0.5Sm0.2Sr0.3Mn1-xFexO3 (x = 0.05, 0.15 and 0.20) were thoroughly investigated for their crystalline structure, electrical conductivity, and dielectric properties, the samples were prepared using autocombustion method. According to the X-ray diffraction study, the samples crystallized in an orthorhombic symmetry with the Pnma space group. To measure the dielectric characteristics, impedance spectroscopy was conducted over the temperature range of 100–260 K and a frequency range of 100 Hz to 1 MHz. Measurements of AC conductivity are indeed utilized to investigate the transport properties of materials being studied. The results indicated that both temperature and frequency significantly influence the conduction process. Three theoretical hypotheses were proposed to explain the hopping conduction: overlapping large polaron tunneling (OLPT), the non-overlapping small polaron tunneling (NSPT) mechanism, and correlated barrier hopping (CBH). It is also shown that the conductivity diminishes with an increase in Fe content. La0.5Sm0.2Sr0.3Mn1-xFexO3 (x = 0.05, 0.15 and 0.20) can be used in electronic applications because of the high permittivity values confirmed by the dielectric measurements. With the aim of evaluating the distinct impacts of electrodes, grain boundaries, and grains on the complex impedance results, an appropriate alternative electrical circuit was utilized. Analysis of the sample's modulus indicated non-Debye characteristics and electrical relaxation phenomena. The materials exhibit good electrical properties, as well as strong chemical and thermal stability.

Secondary Utilization of Self-Suspending Proppant's Coating Polymer: Enhance Oil Recovery

Fracturing is associated with significant economic costs, and the loss of the utility of the self-suspending proppants’ coating polymer after fracturing appears highly wasteful. To enhance the utilization of the self-suspending proppant's coating polymer, we propose a novel concept: the secondary utilization of coating polymer, enabling the coating polymer to gel-breaking within the reservoir and generate surface-active substances, thereby enhancing the oil recovery efficiency. To realize this concept, this study designed and synthesized a hydrophobic associative polymer, which was combined with ceramic proppant to form self-suspending proppant. Using the surface-active monomer octadecyl dimethyl allyl ammonium chloride (DMDAAC-18), acrylamide (AM), acrylic acid (AA), and 2-acrylamido-2-methylpropane sulfonic acid (AMPS) via aqueous free-radical copolymerization synthesized the PAAAD (Polymer(AM/AA/AMPS/DMDAAC-18)). PAAAD has demonstrated excellent thickening properties, with a viscosity of 240.01 mPa·s at a concentration of 6g/L in shear rate 170s-1. Its solution exhibits high viscoelasticity, and a loss factor (tan δ) < 1 over the frequency range of 0 to 20 Hz at a shear stress of 0.56 Pa indicates that it behaves like a viscoelastic solid with gel-like characteristics, which is beneficial for proppant suspension. The gel-breaking solution of PAAAD reduced surface tension (29.33 mN/m at a PAAAD concentration of 6 g/L), converted oil-wet rocks to water-wet conditions (reducing the contact angle of oil-wet shale to 46.7° and of oil-wet sandstone to 19.9°), and enhanced shale imbibition oil recovery efficiency in 16.5%. The basic properties of self-suspending proppants meet the Chinese Petroleum Industry Standard SY/T 5108-2014 and exhibit good suspension properties, with sedimentation of 1.7mm in 40 minutes at a sand ratio of 15%. This study is the first to propose the secondary utilization of the self-suspending proppant’s coating polymer, significantly enhancing their utilization value.

Frontotemporal lobar degeneration changes neuronal beta-frequency dynamics during the mismatch negativity response

The consequences of frontotemporal lobar degeneration include changes in prefrontal cortical neurophysiology, with abnormalities of neural dynamics reported in the beta frequency range (14–30 Hz) that correlate with functional severity. We examined beta dynamics in two clinical syndromes associated with frontotemporal lobar degeneration: the behavioral variant of frontotemporal dementia (bvFTD) and progressive supranuclear palsy (PSP). Whilst these two syndromes are partially convergent in cognitive effects, they differ in disease mechanisms such as molecular pathologies and prefrontal atrophy. Whether bvFTD and PSP also differ in neurophysiology remains to be fully investigated. We compared magnetoencephalography from 20 controls, 23 people with bvFTD and 21 people with PSP (Richardson’s syndrome) during an auditory roving oddball paradigm. We measured changes in low and high total beta power responses (14–22 and 22–30 Hz respectively) over frontotemporal cortex in the period of the mismatch negativity response (100–250 ms post-stimulus). In controls, we found increased 14–22 Hz beta power following unexpected sensory events (i.e. increased deviant versus standard response), from right prefrontal cortex. Relative to controls, PSP reversed the mismatch response in this time–frequency window, reflecting reduced responses to the deviant stimuli (relative to standard stimuli). Abnormal beta at baseline in PSP could account for the reduced task-modulation of beta. Across bvFTD and PSP groups, the beta response to deviant stimuli (relative to standard stimuli) correlated with clinical severity, but not with atrophy of the prefrontal source region. These findings confirm the proposed importance of higher-order cortical regions, and their beta-power generators, in sensory change detection and context-updating during oddball paradigms. The physiological effects are proposed to result from changes in synaptic density, cortical neurotransmitters and subcortical connections, rather than merely atrophy. Beta-power changes may assist clinical stratification and provide intermediate outcomes for experimental medicine studies of novel therapeutic strategies.

Partially embedded metabarrier to suppress surface waves in granular mediaa).

The gravity-induced depth-dependent elastic properties of a granular half-space result in multiple dispersive surface modes and demand the consideration of material heterogeneity in metabarrier designs to suppress surface waves. Numerous locally resonant metabarrier configurations have been proposed in the literature to suppress Rayleigh surface waves in homogeneous media, with little focus on extending the designs to a heterogeneous half-space. In this work, a metabarrier comprising partially embedded rod-like resonators to suppress the fundamental dispersive surface wave modes in heterogeneous granular media known as first order PSV (PSV1; where P is the longitudinal mode and SV is the shear-vertical mode) and second order PSV (PSV2) is proposed. The unit-cell dispersion analysis, together with an extensive frequency-domain finite element analysis, reveals preferential hybridization of the PSV1 and PSV2 modes with the longitudinal and flexural resonances of the resonators, respectively. The presence of the cutoff frequency for the longitudinal-resonance hybridized mode facilitates straightforward suppression of the PSV1 mode, while PSV2 mode suppression is possible by tailoring the hybridized flexural resonance modes. These PSV1 and PSV2 bandgaps are realized experimentally in a granular testbed comprising glass beads by embedding 3D-printed resonator rods. Also explored are novel graded metabarriers capable of suppressing both PSV1 and PSV2 modes over a broad frequency range for potential applications in vibration control and seismic isolation.

In-Situ Surface Modification of Nickel Mesh for Superior Electromagnetic Interference Shielding

Metal mesh, with its inherent conductivity, transparency, and flexibility, has proven to be an exceptional choice for high-performance reflection-dominated electromagnetic interference (EMI) shielding materials, due to its multifunctionality and wide applicability. However, the development of metal-based absorption-enhanced EMI shielding materials characterized by high absorption and low reflection is crucial but remains challenging. Herein, we introduce a novel surface modification strategy for nickel mesh (NM) aimed at augmenting its surface electromagnetic wave absorption through electrochemical surface microstructure alteration and subsequent wet chemical sulphuration. This approach leverages the multiple reflections within the microporous structure and the impedance matching enhancement provided by the magnetic sulfided nickel layer, resulting in the sulphur-treated porous NM (Ni3S2-PNM) achieving an outstanding average EMI SE of 59.6 dB across a broad frequency range of 4 to 40 GHz. The surface electromagnetic wave absorption rate of Ni3S2-PNM has increased from under 1% for unmodified NM to over 60%, significantly reducing the re-reflection of electromagnetic waves back into free space (the average SER value decreases from about 20 dB to 2.2 dB). Characterized by its simplicity and cost-effectiveness, this in-situ surface modification method on bulk industrial-grade NM, enhancing electromagnetic shielding, presents a promising avenue for wider application in electromagnetic protection.

Design and characteristic analysis of micro multi-core fiber vibration sensor

We proposed and fabricated a miniaturized multi-core fiber grating vibration sensor. The size of the miniaturized vibration sensor is 10mm×10mm×10mm with a mass of only 0.25g. Finite element analysis and experimental tests were carried out to validate the performance of the vibration sensor. The experiment results indicate that the sensor has a sensitivity of 68.72pm/g in the X direction and 64.52pm/g in the Y direction within the operating frequency range of 20 — 240Hz. The cross-interference between the two directions of vibration measurement falls within 4%. The sensor is suitable for measuring mechanical vibrations in the mid-low frequency range, especially in cases where size, quality, and distributed measurement are of particular concern.

In vivo electrical properties of the healthy liver and the hepatic tumor in a mouse model between 1 Hz and 1 MHz during a thermal treatment

Objective: Understansding the changing patterns of in vivo electrical properties for the target tissue is crucial for the accurate temperature monitoring and the treatment efficacy in thermal therapy. Our research aims to investigate the changing patterns and the reversibility of in vivo electrical properties for both healthy livers and liver tumors in a mouse model over a frequency range of 1 Hz to 1 MHz at temperatures between 30 °C to 90 °C. Methods and materials: The mice were anesthetized and the target organ was exposed. An 808-nm near-infrared laser was employed as the heating source to heat the organ in vivo. The four-needle electrode, connected to an impedance analyzer, was utilized to obtain the impedance at varying temperatures, which were monitored by a thermocouple. Results: The findings indicated a gradual decline in impedance with an increase in temperature. Furthermore, the impedance was normalized to that at 30 °C, and the real part of the normalized impedance was defined as the k-values, which range from 0 to 1. The results demonstrated a linear correlation between k-values and temperatures (R2 > 0.9 for livers and R2 > 0.8 for tumors). Significant differences were observed between livers and tumors at 1, 10 and 50 kHz (p < 0.05). Additionally, it was demonstrated that the electrical properties could be reversed when the temperature was below or equal to 45 °C. Conclusion: We believe that these results will contribute to the advancement of radiofrequency ablation systems and the development of techniques for temperature monitoring during liver thermal treatment.

Effect of the chemical substitution on structural parameters and microwave properties of the Co–Ni–Zn spinels

Co0.3Ni0.7-xZn xFe2O4 (where x = 0.00–0.7 with step 0.1) spinels or CNZF with constant Co concentration and varying of the Ni/Zn concentration were obtained by the ceramic method from initial oxides. Based on X-ray diffraction data it was concluded that all samples are single-phase (SG: Fd-3m). Concentration dependences of the lattice constant and unit cell volume correlate well with Vegard's rule and the average value of the Zn2+ and Ni2+ ionic radii. The microwave permeability was measured in the frequency range of 0.1–20 GHz by a coaxial technique. Two resonances on frequency dependences were observed. Analysis of the microwave properties and magnetostatic data showed that low-frequency magnetic peak was caused by a resonance of domain boundaries; high-frequency peak was due to a natural ferrimagnetic resonance. Obtained results opens broad perspectives for practical application of such kind of materials and possibility for microwave parameters control by the external magnetic field.

Breast tumor detection with TR‐DORT based on multilayered Green's function theory

AbstractUltrawideband (UWB) time‐reversal techniques are widely used in microwave imaging systems to detect and localize breast tumors. Measuring the scattering electromagnetic fields from a breast phantom can be time‐reversed and back‐propagated to refocus on a tumor. In this study, a Debye model was applied to the breast phantom. Using the decomposition of the time‐reversal operator (TR‐DORT), images were obtained in the UWB frequency range of 3.1–10.6 GHz. The conventional TR imaging method employs the free‐space Green's function to refocus on the tumor, which degrades refocusing in a lossy and dispersive breast phantom. We propose the use of the cylindrical dyadic Green's function in a three‐layer medium for TR imaging. The excitation system consists of a circular array of spiral antennas. The imaging results of the proposed Green's function in TR‐DORT were subsequently calculated, indicating successful tumor detection in different application scenarios of the lossy and dispersive breast phantom.

The effect of muffler design on reducing the noise pollution of a small two-stroke engine

Designing an efficient muffler for single-cylinder IC engines is not an easy task due to the limitation in designing a large muffler and the possibility of engine suffocation. In this regard, this research aims to experimentally investigate the feasibility of inexpensive muffler modification of a small portable two-stroke engine to reduce noise pollution. In experiments, the default muffler as a control treatment and a modified muffler together with a redesigned muffler have been examined to investigate the effect of muffler internal geometry and muffler design on sound emission characteristics. Based on the obtained results, the sound pressure level (SPL) of the modified and redesigned mufflers decreased by 5.31 and 6.86 percent compared to the default muffler, respectively. Meanwhile, installing the modified and redesigned mufflers increased the transmission loss (TL) equal to 8.62% and 10.08% compared to the default muffler, respectively. Also, the outcome of Discrete Fourier Transform (DFT) revealed that the intensity and amplitude of output frequencies from the redesigned muffler was significantly reduced in the frequency range of 2-6 kHz. As a general conclusion of this study, by installing the redesigned muffler, the maximum working times of the operator increased by 12.1 hours at 5000 rpm.

Microwave reflective properties of amorphous nanogranular composites (CoTaNb)x(MgO)1-x

The most important task of flexible and stretchable electronics is to modify the structure in nanoheterogeneous metal-dielectric media to control the properties of materials and create new small-sized devices based on them. In this paper, we present the results of experimental studies of the structure and microwave reflective properties in the frequency range of 8–12 GHz of amorphous nanogranulated composites (CoTaNb)x(MgO)1−x, 21.73 ≤ x ≤ 73.27 at.% with a thickness of 311–1040 nm. Niobium and tantalum, which are part of the metal alloy, are the most promising metals used in aircraft and rocket engineering, as well as in radio electronics and microprocessor technology, for example, as capacitors. The AFM method revealed a granular structure with a granule size from 70 to 200 nm at a metal alloy content of up to 51.70 at.%. The spectra of the microwave reflectivity as a function of frequency, the dependence of the reflectivity on the metallic phase content and the effective thickness of the composite layer are obtained. It is shown that a significant increase in the microwave reflectivity and its saturation are determined to a greater extent by the metallic phase content than by the effective layer thickness. The results of the experimental effect of magnetic fields with induction up to 0.3 T on the microwave reflectivity of composite films are presented. It is shown that magnetic fields can most effectively change the reflective properties of composites (from 8 % to 29 %) at the extremes of the microwave reflectivity of films with the lowest metallic phase content of 22.61–21.73 at.%. With an increase in the metallic phase content, the maximum change in the microwave reflectivity decreases exponentially.

Simple and Hybrid Metalens with High Polarization Conversion Efficiency for Near-Infrared Spectrum

Thanks to their ability to control light, research on metalenses is developing rapidly. However, it is still quite difficult to design broadband metalenses with high polarization conversion efficiency. In this study, an alternative plasmonic material, aluminum-doped zinc oxide, is presented for metalens operating in near-infrared regime. We propose simple and hybrid metalenses with high polarization conversion efficiency and high transmission values that can focus efficiently in a wide near-infrared bandwidth (700 –1000 nm). We design metalens consisting of subwavelength aluminum-doped zinc oxide nanoblocks based the Pancharatnam-Berry phase method and utilizing the finite-difference time-domain method. The polarization conversion efficiency (minimum 87%) and transmission values (minimum 85%) calculated for the metalens unit cell are higher than those previously obtained over the entire 300 nm bandwidth. In addition, we propose hybrid metalens to focus the incident beam in right and left handed circular polarized states in the studied frequency range. The presented aluminum-doped zinc oxide metalens with high polarization conversion efficiency and transmission values can find a place in the applications of near-infrared nanophotonic systems.

A magnetically switchable demultiplexer via Terfenol-D in phononic crystal

This study introduces a novel approach for developing a controllable demultiplexer by applying a magnetic field to Terfenol-D cylinders within a solid–solid phononic crystal structure. Dynamic controllable demultiplexers are essential devices in acoustic and optical communication networks, yet adjustable elastic demultiplexers are notably lacking in current sound systems and acoustic communication technologies. The proposed phononic crystal-based demultiplexer features a square lattice (12 × 19) composed of tungsten cylinders embedded in a poly methyl methacrylate (PMMA) substrate. The switchable design consists of two identical, symmetrical parts separated by an input waveguide. In addition, each unit includes an output channel, a common input channel, and a square ring resonator, with the output channel side-coupled to the input bus waveguide. Moreover, Terfenol-D, a magnetostrictive material, is utilized in the hollow cylinders of the output channels. Switchability of the elastic demultiplexer outputs is achieved by dynamically altering the Young’s modulus of the Terfenol-D cylinders through the application of a magnetic field. This magnetic influence modifies the Young’s modulus of the Terfenol-D material in the output waveguides, enabling controllability. By varying the magnetic field applied to the demultiplexer, we find two distinct values of Young’s modulus within the structure. These two values facilitate the high transmission of two desirable peaks with narrow bandwidth through the output channels, allowing for switchable functionality based on the magnetic field’s position. The proposed demultiplexer demonstrates an average crosstalk value of −25.34 dB, indicating strong performance, along with a high average quality factor (Q) of 1773.5 and low average insertion losses of 0.85 dB in the MHz frequency range. The solid–solid elastic controllable demultiplexer is simulated using the finite element method, showcasing its potential for practical applications.

Miniaturised ultra‐wideband circular polarised koch fractal crossed dipole array

AbstractUltra‐wideband (UWB) systems utilise a broad frequency spectrum to achieve high data transmission rates and enhanced precision, creating a demand for specialised UWB antennas. Circularly Polarised (CP) antennas are considered essential for maintaining robust performance under varied environmental conditions. Among them, the crossed dipole is effective for UWB CP applications, but its relatively large size could limit its use in various systems. A miniaturised crossed dipole design employing the Koch fractal structure is proposed and the measurement results are presented. The prototype antenna achieved an effective bandwidth covering 88% of the frequency range from 1.4 to 3.6 GHz. Additionally, a 4 × 4 array using this design was tested in the same frequency band, demonstrating beam‐steering capabilities up to 30°. The proposed antenna has demonstrated effective deployment in diverse communication systems and phased array applications within ultra‐wideband (UWB) CP environments.

Geometric Parameter Effects on Bandgap Characteristics of Periodic Pile Barriers in Passive Vibration Isolation

To investigate the impact of the geometric parameters of periodic pile barriers on bandgap characteristics in passive vibration isolation, a two-dimensional, three-component unit cell was developed using the finite element method (FEM). This study analyzed the bandgap properties of periodic pile barriers and validated the effectiveness of the FEM through model testing. The FEM was then methodically applied to evaluate the effects of pipe pile thickness, periodic constant, arrangement pattern, and cross-sectional shape on the bandgap characteristics, culminating in the proposition of a novel H-shaped cross-section for the piles. The results demonstrated that the FEM-calculated bandgap frequency range, featuring steel piles arranged in a square pattern, closely aligned with the attenuation zone in the model tests. The lower band frequency (LBF) was primarily influenced by the pipe pile’s inner radius, while the upper band frequency (UBF) was predominantly affected by its outer radius. As the periodic constant increased, the LBF, UBF, and the width of band gap (WBG) all decreased. Conversely, changing the arrangement pattern from square to hexagonal led to increases in UBF and WBG, while the LBF diminished. Notably, the WBG of the H-section steel piles, possessing the same cross-sectional area, was 1.31 times greater than that of the steel pipe piles, indicating an enhanced vibration isolation performance. Additionally, the impact of transverse and vertical characteristic dimensions of the H-shaped pile on the band gap distribution was assessed, revealing that the transverse characteristic dimensions exerted a more significant influence than the vertical dimensions.

Integrated construction of 0D/1D/2D NiMn-LDH@CNT/MXene with multidimensionally hierarchical architecture towards boosting electromagnetic wave absorption

Constructing MXene-based absorbers with multicomponent and multidimensional hierarchical architecture is crucial but it still remains a formidable challenge to address the serious electromagnetic radiation pollution issue. Herein, a multidimensional 0D/1D/2D NiMn-LDH@CNT/MXene (NCM) hierarchical architecture composed of 0D NiMn-LDH anchored on 1D CNT and then assembled with 2D MXene is rationally constructed for EMW absorption. The EMW absorption performance of the resultant NCM significantly enhances thanks to the coupling effects of multicomponent and multidimensions. The balanced impedance matching, enriched EMW attenuation behaviors and plentiful polarization loss combine to facilitate EMW absorption. The NCM3 realizes an impressive reflection loss as low as −55.7 dB (2.49 mm) and a wide effective absorption bandwidth (EAB) of 5.1 GHz (12.9–18.0 GHz) with a thin matching thickness of 1.51 mm. Moreover, the regulation of matching thickness could enable the EAB to almost cover the entire frequency range. Simulated radar cross section strongly verifies the practical application potential of NCM. This work provides a valuable guidance for the design and construction of EMW absorption materials with hierarchical architecture.

Dielectric properties of Pouteria sapota compounds in terahertz frequency range

The analysis and a mathematical approximation of the dielectric properties of Pouteria sapota (Mamey) pulp compounds in the Terahertz (THz) range are presented. Since THz electromagnetic waves show a high sensitivity to detect water content when interacting with organic materials, this technique was used to determine the effective dielectric function (EDF) of a wet and a dry sample from the THz spectrum data. By fitting the EDF to the Landau-Lifshitz-Looyenga (LLL) dielectric mixture equation, the theoretical dielectric functions of each pulp compounds were approximated. The approach proposed here not only considered dry matter and water content in the Pouteria sapota pulp, as has been reported in the literature for organic samples, but also included the contribution of the volatile components (VC) that allowed a better adjustment to the experimental results. The water and VC content increase the value of the real and imaginary part of the calculated EDF of the wet sample. The use of the non-destructive THz spectroscopy technique allows determining the dielectric properties of fruits that have been dehydrated. Therefore, the methodology proposed here can be used as a method of in situ and ex situ quality control in the agri-food industry.

A primary wideband calibration method for noise hydrophones based on three-transducer spherical wave reciprocity in the frequency domain.

A primary wideband calibration method for noise hydrophones is developed, which can be applied to obtain noise acoustic spectral density sensitivity in the free-field. In this method, a wideband three-transducer spherical wave reciprocity calibration method is proposed in the frequency domain. A lowpass spatial domain filter is utilized to eliminate the reflecting acoustic waves from boundaries and water surface, and the wideband frequency responses of the transducer pair are calculated. Wideband calibrations are performed in a laboratory anechoic water tank, and two hydrophones with different reference sensitivities are calibrated in the frequency range of 250 Hz to 20 kHz using noise signals. The decidecade band sensitivities are obtained by the primary wideband calibration, which is in agreement with the single frequency sensitivities. The expended uncertainty of the primary wideband calibration is analyzed and estimated to be 8.9% (k = 2).

Study on the influencing factors of combined processing of active and passive surface-wave data on dispersion imaging

Active and passive surface-wave methods have garnered significant attention in the near-surface geophysical community for their non-destructive, non-invasive, low-cost, and accurate advantages in delineating subsurface shear (S)-wave velocity structures. They are increasingly being utilized to address numerous engineering and environmental problems. Surface waves obtained from actively excited sources such as a hammer and a harmonic shaker, however, lack low-frequency components, resulting in limited investigation depth. Conversely, passive surface waves such as microseisms (< 0.4 Hz, associated with natural ocean wave activity) and microtremor (>1 Hz, generated by cultural and wind sources) retrieved from ambient seismic noise typically lack high-frequency components, which is not conductive to characterizing fine near-surface structures. To overcome these frequency limitations, we employ a “mixed-source data” strategy, imposing active shot gathers into ambient noise data, to widen the frequency range of dispersion images and depth of investigative capabilities. We simulate both active and passive surface-wave data based on a two-layer model, noting that their dispersion images suffer from a mode kissing phenomenon at lower frequencies. By analyzing influencing factors such as the amplitude intensity, the signal-to-noise ratio and the excitation locations of active shot gathers, as well as the length of passive surface-wave data, we better understand their impacts on dispersion images from mixed-source surface-wave data. Simulation tests demonstrate that processing mixed-source data can effectively distinguish the mode kissing phenomenon. Moreover, the effectiveness of this strategy in enhancing the quality of dispersion image is verified, especially when surface-wave dispersion images perform poorly in either the low- or high-frequency bands. Additionally, a real-world example further demonstrates that processing mixed-source data offers significant advantages in improving the quality of dispersion images. This way provides a convenient and efficient measurement strategy for delineating shear-wave velocity profiles in finer shallow layers and deeper penetration depths.

Detailed structural analyses and viscoelastic properties of nano-fibrillated bacterial celluloses

Nano-fibrillated bacterial cellulose (NFBC) can be prepared by cultivating a cellulose-producing bacterium in a medium containing a dispersant under agitating and aerobic conditions. Although NFBCs have various applications, their detailed structure and physical properties have not been clarified. Therefore, in this study, we performed detailed structural and physical property analyses of NFBCs to advance their potential applications. Atomic force microscopy and image analysis showed that the average fiber length of NFBCs was approximately 17 µm and fiber widths were 10–15 nm; the aspect ratios of NFBCs were > 1000, which are >10-fold higher than that of 2,2,6,6-tetramethylpioeridine-1-oxyl-oxidized cellulose nanofiber. Shear viscosity measurements showed that the NFBCs exhibited shear-thinning flow behavior even at low concentrations (0.01 wt%). Frequency sweep measurements showed that the storage modulus values were greater than the loss modulus values in the measured frequency range, indicating that the NFBCs were in a stable gel state. Thus, the NFBCs exhibited significantly longer fiber lengths, larger aspect ratios, and excellent viscoelastic properties based on these unique structural features. Our findings will help develop novel applications utilizing the ultrahigh aspect ratio unique to NFBC and its viscoelastic properties.