Search Results (1,246)

This paper presents an experimental longitudinal mode control approach for a biomimetic underwater robot. Input–output models for surge velocity and pitch angle were derived through experiments, considering the fish robot body with servo motors and control pins as a single system to solve the problem of fish robots, which are complex and nonlinear, and also contain uncertainty. Closed-loop control systems were designed using PID controllers based on these models, and their performance was verified through simulations and experiments. Surge velocity and pitch angle response models were developed for nominal surge velocities of 0.2 m/s and 0.4 m/s. The surge velocity response models exhibited high agreement rates of 75.25% and 81.23% between the identified linear models and experimental results at 0.2 m/s and 0.4 m/s, respectively. In contrast, the pitch angle response model showed lower agreement rates of 68.02% and 34.24% between the identified linear model and experimental results at 0.2 m/s and 0.4 m/s, respectively. The gain margin and phase margin of the surge controller were 28.7 dB and 116°, and 37.2 dB and 70.6°, respectively. For the pitch response model, the low-frequency gain of the transfer function was very small at −31 dB when the nominal surge velocity was 0.2 m/s; this gain increased to −8 dB when the nominal surge velocity was increased to 0.4 m/s. It was observed that the initial value responses of the pitch angle converged to 0° with some oscillations in both the simulations and experiments. Therefore, it is believed that by identifying a linear model and subsequently designing a controller based on it, the surge velocity of the fish robot can be effectively controlled while stabilizing its pitch angle. Full article

Ship-radiated noise (SRN) recognition is vital for underwater acoustics, with applications in both military and civilian fields. Traditional manual recognition by sonar operators is inefficient and error-prone, motivating the development of automated recognition systems. However, most existing deep learning approaches demand high computational resources, limiting their deployment on resource-constrained edge devices. To overcome this challenge, we propose LW-MS-LFTFNet, a lightweight model informed by time-frequency analysis of SRN that highlights the critical role of low-frequency components. The network integrates a multi-scale depthwise separable convolutional backbone with CBAM attention for efficient spectral representation, along with two LSTM-based modules to capture temporal dependencies in low-frequency bands. Experiments on the DeepShip dataset show that LW-MS-LFTFNet achieves 75.04% accuracy with only 0.85 M parameters, 0.38 GMACs, and 3.27 MB of storage, outperforming representative lightweight architectures. Ablation studies further confirm that low-frequency temporal modules contribute complementary gains, improving accuracy by 2.64% with minimal overhead. Guided by domain-specific priors derived from time-frequency pattern analysis, LW-MS-LFTFNet achieves efficient and accurate SRN recognition with strong potential for edge deployment. Full article

To meet the requirements of integrated accelerometers for a high-precision reference voltage under wide supply voltage range, high current drive capability, and low power consumption, this paper presents a bandgap reference operational amplifier (op-amp) circuit implemented in CMOS/BiCMOS technology. The proposed design employs a folded-cascode input stage, a push–pull Class-AB output stage, an adaptive output switching mechanism, and a composite frequency compensation scheme. In addition, overcurrent protection and low-frequency noise suppression techniques are incorporated to balance low static power consumption with high load-driving capability. Simulation results show that, under the typical process corner (TT), with VDD = 3 V and T = 25 °C, the op-amp achieves an output swing of 0.2 V~2.8 V, a low-frequency gain of 102~118 dB, a PSRR of 90 dB at 60 Hz, overcurrent protection of ±25 mA, and a phase margin exceeding 48.8° with a 10 μF capacitive load. Across the entire supply voltage range, the static current remains below 150 μA, while maintaining a line regulation better than 150 μV/V and a load regulation better than 150 μV/mA. These results verify the feasibility of achieving both high drive capability and high stability under stringent power constraints, making the proposed design well-suited as a bandgap reference buffer stage for integrated accelerometers, with strong engineering practicality and potential for broad application. Full article

In radio frequency (RF) systems, the mixer is a critical component for achieving frequency conversion in electromagnetic sensor backends. This paper proposes a mixer design methodology aimed at improving noise figure and conversion gain specifically for sensor signal processing applications. This design employs a process incorporating high-quality bipolar junction transistors (BJTs) and adopts a mixer-first architecture instead of a conventional low noise amplifier (LNA). By optimizing the layout and symmetry of the BJTs, the input impedance can be flexibly adjusted, thereby simplifying the receiver front-end while simultaneously improving local oscillator (LO) feedthrough. Design and simulation were completed using Advanced Design System (ADS) 2020 software. Simulation results demonstrate that the proposed mixer exhibits significant advantages in suppressing noise and interference while enhancing conversion gain, making it particularly suitable for electromagnetic sensor backend applications. Full article

This paper presents the development of a 224-channel radio frequency (RF) receiver operating in the 0.6–1.8 GHz band, intended for a wide-field phased array radio telescope. The system employs a cost-effective architecture that combines the flexibility of phased array feeds with the low-cost characteristics of reflector systems, enabling high gain, rapid scanning, and multi-beam observation. The receiver achieves low-noise amplification, dynamic gain control, and filtering through a modular design. The system provides a total gain of 80–85 dB with a noise temperature of less than 35.1 K. Full article

This paper presents a wideband multi-linear polarization reconfigurable antenna featuring five linear polarization states. We use the semi-ellipsoidal dipoles as the main radiators to broaden the operating bandwidth; the states of linear polarizations are switched by controlling the ON/OFF of PIN diodes between feeding pads and dipoles to excite a specific pair of dipoles. A 7 × 7 AMC array is added below the antenna to obtain a small height of 0.14 λ₀ (λ₀ is the free space wavelength at the operating frequency). Prototypes of the designed antenna are fabricated, and experimental results illustrate that the proposed antenna yields an impedance bandwidth of 50% (from 2.25 GHz to 3.75 GHz) for all polarization states, stable radiation patterns, and low cross-polarization within the operating band. In addition, the maximum gain reaches 8.1 dBi. The proposed five linear-polarized switching antenna with wide band and low-profile features can be applied in reconfigurable conformal array antennas, thus flexibly realizing linear polarization reconfiguration of conformal arrays in radar and military platforms. Full article

Background/Objectives: Binaural beat audio has gained popularity as a non-invasive tool to promote relaxation and enhance cognitive performance, though empirical support has been inconsistent. We developed a novel algorithm integrating real-time electroencephalography (EEG) feedback to dynamically tailor binaural beats to induce relaxed brain states. This study aimed to examine the efficacy and feasibility of this algorithm in a clinical trial. Methods: In a randomized, double-blinded, sham-controlled crossover trial, 25 healthy adults completed two 30 min sessions (EEG-guided intervention versus sham). EEG (Fp1) was recorded using a consumer-grade single-electrode headset, with auditory stimulation adjusted in real time based on EEG data. Outcomes included EEG frequency profiles, stop signal reaction time (SSRT), and novelty encoding task performance. Results: The intervention rapidly reduced dominant EEG frequency in all participants, with 100% achieving <8 Hz and 96% achieving <4 Hz within median 7.4 and 9.0 min, respectively. Compared to the sham, the intervention was associated with an faster novelty encoding reaction time (p = 0.039, dz = −0.225) and trends towards improved SSRT (p = 0.098, dz = −0.209), increased boundary separation in stop trials (p = 0.065, dz = 0.350), and improved inhibitory drift rate (p = 0.067, dz = 0.452) within the limits of the exploratory nature of these findings. Twenty-four (96%) participants reached a target level of <4 Hz with the intervention, while none reached this level with the sham. Conclusions: Real-time EEG-guided binaural beats may rapidly induce low-frequency brain states while potentially preserving or enhancing aspects of executive function. These findings support the feasibility of personalized, closed-loop auditory entrainment for promoting “relaxed alertness.” The results are preliminary and hypothesis-generating, warranting larger, multi-channel EEG studies in ecologically valid contexts. Full article

Background/Objectives: Horizontal alveolar ridge deficiency is a common clinical challenge in dental implant placement. The osseodensification (OD) technique has been proposed as a minimally invasive alternative to conventional osteotomy. This study aimed to compare the outcomes of OD and conventionally performed ridge-split procedures in terms of implant stability and horizontal bone gain. Methods: In this retrospective study, 65 patients (a total of 268 implants) who underwent simultaneous implant placement with ridge-split procedures were evaluated. Cases were divided into two groups: OD burs (n = 133 implants) and the conventional Esset kit (n = 135 implants). Ridge width was measured at coronal and apical levels using cone-beam computed tomography (CBCT) preoperatively and four months postoperatively. Implant stability was assessed at the time of placement (primary stability) and at four months (secondary stability) using resonance frequency analysis (RFA). Results: Both techniques achieved comparable horizontal bone gain (1.1–1.6 mm; p > 0.05). In the maxilla, the OD group demonstrated a tendency toward higher primary and secondary stability values (p < 0.01). A similar trend was observed for secondary stability in the mandibular posterior region (p < 0.01). The mean Implant Stability Quotient (ISQ) values in the OD group generally exceeded the threshold of 65, considered sufficient for prosthetic loading. Conclusions: The findings suggest that the OD technique may have a favorable effect on implant stability, particularly in regions with low-to-moderate bone density, while providing comparable horizontal bone gain to the conventional method. These results indicate that OD could serve as a potentially useful alternative in the management of horizontal ridge deficiencies; however, its long-term efficacy should be further evaluated in larger, prospective clinical studies. Full article

Oxidative stress plays an important role in the progression of neurodegenerative diseases (NDDs), and N-acetylcysteine (NAC) has gained attention as a potential agent due to its antioxidant capabilities. This study investigated the synergistic neuroprotective effects of combining NAC with non-contact, high-frequency, low-intensity pulsed electric field (H-LIPEF) stimulation on SH-SY5Y human neuronal cells subjected to hydrogen peroxide (H₂O₂)-induced oxidative damage. It was found that after SH-SY5Y cells were pretreated with NAC and exposed to H-LIPEF stimulation, the oxidative stress of cells was reduced in the subsequent treatment with H₂O₂. The results showed that the combined NAC and H-LIPEF treatment significantly improved cell viability and more effectively reduced mitochondrial apoptosis. Mechanistic analyses revealed that the combination substantially decreased levels of superoxide and intracellular H₂O₂, which was associated with enhanced activation of the phosphorylated Akt (p-Akt)/nuclear factor erythroid 2-related factor 2 (Nrf2)/superoxide dismutase type 2 (SOD2) signaling pathway. Furthermore, the treatment reduced the accumulation of 8-oxo-2′-deoxyguanosine triphosphate (8-oxo-dG) accumulation and elevated MutT homolog 1 (MTH1) expression, indicating a protective effect against oxidative DNA damage. These results suggest that H-LIPEF enhances the neuroprotective efficacy of low-dose NAC, highlighting the potential of this combination approach as a new therapeutic strategy for the treatment of NDDs. Full article

A high-gain microstrip antenna array is proposed. The dual-frequency and dual-polarization characteristics of the array allow a satellite communication system to transmit and receive signals with a single antenna. To avoid high losses in microstrip feed lines for large apertures, the array is divided into subarrays, each fed by a low-loss separate feed network. The dual-frequency dual-polarization function is realized by utilizing two orthogonal modes of a corner-fed rectangular patch in a single-layer substrate. Moreover, to minimize losses in the separate feed network, semi-ridged coaxial lines and five four-way radial power dividers are employed. The power divider, composed of a cylindrical cavity and five SMA connectors, features very low insertion loss. Finally, to validate the design concept, a prototype of the proposed 32 × 32-element array operating at 12.5 GHz and 14.25 GHz is fabricated and measured. The measured results are in good agreement with the simulated ones. The −10 dB return loss frequency bands for the two operating frequencies are 12.04 GHz–12.69 GHz and 13.82 GHz–14.66 GHz, respectively. The measured gains at the two operating bands are 34.5 dBi and 35.2 dBi, respectively. Full article

Reactive jamming remains a critical threat to low-latency telemetry of Unmanned Aerial Vehicles (UAVs) using Orthogonal Frequency Division Multiplexing (OFDM). In this paper, a Bi-scale Mahalanobis approach is proposed to detect and classify reactive jamming attacks on UAVs; it jointly exploits window-level energy and the Sevcik fractal dimension and employs self-adapting thresholds to detect any drift in additive white Gaussian noise (AWGN), fading effects, or Radio Frequency (RF) gain. The simulations were conducted on 5000 frames of OFDM signals, which were distorted by Rayleigh fading, a ±10 kHz frequency drift, and log-normal power shadowing. The simulation results achieved a precision of 99.4%, a recall of 100%, an F1 score of 99.7%, an area under the receiver operating characteristic curve (AUC) of 0.9997, and a mean alarm latency of 80 μs. The method used reinforces jam resilience in low-power commercial UAVs, yet it needs no extra RF hardware and avoids heavy deep learning computation. Full article

Background: Chronic constipation lacks effective long-term treatments. Non-digestible oligosaccharides (NDOs) are short-chain carbohydrates that resist digestion and may improve bowel function. This systematic review and meta-analysis examines the effect of NDOs on constipation-related outcomes in humans. Methods: We searched Ovid MEDLINE, Embase, and Web of Science (2010–May 2025) for randomized controlled trials (RCTs) comparing NDOs with placebo, reporting stool frequency, stool consistency, fecal pH, or short-chain fatty acids (SCFAs). Data were pooled using random-effects meta-analysis. All effect estimates are reported as standardized mean differences (SMDs) with 95% confidence intervals (CIs). Subgroups were analyzed based on baseline constipation status and treatment duration. Results: We included 20 RCTs (1786 participants) evaluating seven NDO types. NDO supplementation significantly increased stool frequency overall, with larger effects in constipated individuals (SMD 0.99, 95% CI 0.58–1.28) than in non-constipated population (SMD 0.30, 95% CI 0.10–0.51). By duration, shorter interventions (≤3 weeks) yielded greater frequency gains (SMD 0.89, 95% CI 0.40–1.38) than longer ones (SMD 0.24, 95% CI 0.09–0.38). While the overall effect on stool consistency was non-significant, constipated patients (SMD 0.46, 95% CI 0.19–0.74) and short-term trials (SMD 0.20, 95% CI 0.03–0.37) showed modest improvements. NDOs also lowered fecal pH (SMD −1.02, 95% CI −1.25–−0.79). Data on SCFAs were inconclusive and based on very limited studies. Conclusions: NDOs modestly increase stool frequency and lower fecal pH, with greater effects in constipated individuals and short-term interventions. However, evidence certainty remains low due to heterogeneity and study limitations. Further studies are needed to establish clinical utility. Full article

This study presents a transmitarray antenna design operating at a center frequency of 9 GHz, addressing the need for high-gain and broad bandwidth antennas in modern data communication. The proposed design is structured as a quad-layer configuration using FR-4 dielectric substrates. The transmitarray’s phase profile is tailored to deliver a wideband flat response with low Side Lobe Level (SLL) and stable aperture efficiency across the operating band. It achieves a 1-dB gain bandwidth of 12.12% (from 8.56 GHz to 9.67 GHz) and a 3-dB gain bandwidth of 49.43% (from 8.45 GHz to 13.46 GHz) with an aperture efficiency of 21.3%. A prototype of the proposed design with 11 × 11 elements was fabricated and measured, and its measurement results closely aligned with simulation results, validating its performance. The proposed simple design realizes reduced complexity and fabrication costs while expanding operational gain bandwidth, thereby demonstrating substantial promise for next-generation X-band communication systems. Full article

For orthogonal time–frequency space (OTFS) systems in high-mobility scenarios, traditional signal detection algorithms face challenges due to their reliance on channel state information (CSI), requiring excessive pilot overhead. Meanwhile, based on convolutional neural network (CNN) detection suffer from insufficient signal feature extraction, the message passing (MP) algorithm exhibits low efficiency in iterative signal updates. This paper proposes a signal detection method for an OTFS system based on feature fusion and a CNN (MP-WCNN), which employs wavelet decomposition to extract multi-scale signal features, combining MP enhancement for feature fusion and constructing high-dimensional feature tensors through channel-wise concatenation as CNN input to achieve signal detection. Experimental results demonstrate that the proposed MP-WCNN method achieves approximately 9 dB signal-to-noise ratio (SNR) gain compared to the MP algorithm at the same bit error rate (BER). Furthermore, the proposed method operates without requiring pilot assistance for CSI acquisition. Full article

Accurate reconstruction of pressure fields using phase-only acoustic holograms is critical for applications requiring high spatial precision, such as targeted ultrasound therapies. In this study, we investigate the effect of excitation frequency on reconstruction accuracy by performing a controlled sweep from 0.75 to 4.0 MHz, while keeping all other parameters such as aperture size, simulation grid, target patterns, and optimization settings constant. To evaluate performance, we employ five quantitative metrics: Mean Squared Error (MSE), Peak Signal-to-Noise Ratio (PSNR), Cross-Correlation, Uniformity, and Efficiency. The results show that reconstruction fidelity improves as frequency increases, particularly in the low-to-mid range, where finer spatial features become resolvable due to the shorter wavelengths. However, beyond a certain point, the gains begin to taper, and in some cases, high frequencies introduce subtle artifacts such as edge ringing or increased variance. Moreover, higher frequencies are associated with increased acoustic attenuation and imposing stricter fabrication demands on holographic elements. These findings suggest that frequency selection in acoustic holography must be application-specific, as both low and high frequencies offer distinct advantages depending on the target characteristics and system constraints. Full article