Search Results (389)

The increasing demand for sustainable disease management in aquaculture has intensified interest in plant-based therapeutics. This study evaluated the formulation and efficacy of andrographolide-loaded nanostructured lipid carriers (AND-NLCs) in Nile tilapia (Oreochromis niloticus) challenged with Streptococcus agalactiae ENC06. AND-NLCs were prepared by the phase-inversion technique and characterized by dynamic light scattering, transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR), and in vitro release profiling. Antibacterial activity was assessed by measuring inhibition zone diameters, minimum inhibitory concentration (MIC), and minimum bactericidal concentration (MBC). Growth performance, feed utilization, hepatosomatic index (HSI), and disease resistance were evaluated over a 60-day feeding trial. The AND-NLCs exhibited an optimal particle size (189.6 nm), high encapsulation efficiency (90.58%), sustained release, and structural stability. Compared to the free AND and control group, AND-NLC supplementation significantly improved growth, feed efficiency, HSI, and positive allometric growth. It also enhanced survival (73.3%) and relative percent survival (RPS = 65.6%) following S. agalactiae ENC06 infection. Antibacterial efficacy and physiological responses showed positive correlations with nanoparticle characteristics. These findings suggest that AND-NLCs enhance bioavailability and therapeutic efficacy, supporting their potential as a functional dietary additive to promote growth and improve disease resistance in tilapia aquaculture. Full article

High-frequency (HF) communication is critical for applications such as over-the-horizon positioning and ionospheric detection. However, precise time-delay estimation in complex HF channels faces significant challenges from multipath fading, Doppler shifts, and noise. This paper proposes a Modulation Signal-based Adaptive Time-Delay Estimation (MATE) algorithm, which effectively decouples carrier and modulation signals and integrates phase-locked loop (PLL) and delay-locked loop (DLL) techniques. By leveraging the autocorrelation properties of 8PSK (Eight-Phase Shift Keying) signals, MATE compensates for carrier frequency deviations and mitigates multipath interference. Simulation results based on the Watterson channel model demonstrate that MATE achieves an average time-delay estimation error of approximately 0.01 ms with a standard deviation of approximately 0.01 ms, representing a 94.12% reduction in mean error and a 96.43% reduction in standard deviation compared to the traditional Generalized Cross-Correlation (GCC) method. Validation with actual measurement data further confirms the robustness of MATE against channel variations. MATE offers a high-precision, low-complexity solution for HF time-delay estimation, significantly benefiting applications in HF communication systems. This advancement is particularly valuable for enhancing the accuracy and reliability of time-of-arrival (TOA) detection in HF-based sensor networks and remote sensing systems. Full article

To address the issue of reduced observer accuracy under low carrier–frequency ratio (CFR) conditions in the sensorless control of high-speed motors, which limits system performance, this paper proposes a discrete mathematical modeling method for surface-mounted permanent magnet synchronous motors (SPMSMs). Based on this established accurate discrete motor model, the influence of low CFR on the phase estimation error of back electromotive force (EMF) is analyzed. Building on this foundation, an accurate discrete Luenberger observer (ALO) is designed, and a corresponding phase compensation control method is proposed. A motor drive control system comprising hardware, software, and experimental test setups is constructed. The experimental results demonstrate that, compared to the Euler model, the discrete mathematical model established by this method significantly improves position observation accuracy under low CFR conditions. Furthermore, compared to the traditional Luenberger observer (TLO), the estimation error of the proposed observer under a low CFR is reduced by approximately 85%. This approach exhibits high application value in the sensorless control of high-speed and high-frequency motors. Full article

Traditional villages (TVs) and intangible cultural heritage (ICH) serve as dual carriers for the living transmission of agrarian civilization, with their spatial compatibility being crucial for the sustainable development of cultural ecosystems. Existing research shows deficiencies in quantitative analysis, multidimensional driving mechanism interpretation, and spatial heterogeneity identification. This study establishes a three-phase framework (“spatial pattern identification–spatial relationship analysis–impact mechanism assessment”) using nationwide data encompassing 8155 TVs and 3587 ICH elements. Through the comprehensive application of the spatial mismatch index, Optimal-Parameter Geographic Detector (OPGD), and multiscale geographically weighted regression (MGWR) model, we systematically reveal their spatial differentiation patterns and driving mechanisms. Key findings: First, TVs exhibit a “three-primary-core and two-secondary-core” strong agglomeration pattern, while ICH shows multi-center balanced distribution. Significant positive spatial correlation coexists with prevalent mismatch: 65% of China’s territory displays positive mismatch (ICH dominance) and 35% displays negative mismatch (TV dominance). Second, the spatial mismatch mechanism follows a “weakened natural foundation with dual drivers of socio-economic dynamics and cultural policy momentum”, where the GDP, tertiary industry ratio, general public budget expenditure, number of ICH inheritors, museums, and key cultural relic protection units emerge as dominant factors. Third, core drivers demonstrate significant spatial heterogeneity, with economic factors showing differentiated regulation while cultural policy elements exhibit distinct regional dependency. The proposed “economy–culture” dual governance approach, featuring cross-scale analysis methods and three-dimensional indicator system innovation, holds practical value for optimizing cultural heritage spatial governance paradigms. Full article

Hydrogen possesses distinctive characteristics that position it as a potential energy carrier to substitute fossil fuels. Nonetheless, there is still an essential need to create secure and effective storage solutions prior to its broad application. The use of hydride-forming metals (HFMs) for hydrogen storage is a method that has been researched thoroughly over the past several decades. This study investigates the structural and chemical modifications in titanium (Ti) and zirconium (Zr) thin coatings over aluminum hydroxide (AlO₃) granules before and after hydrogenation. The materials were subjected to hydrogenation at 400 °C and 5 atm of hydrogen pressure for 2 h, with a hydrogen flow rate of 0.8 L/min. The SEM analysis revealed significant morphological changes, including surface roughening, a grain boundary separation, and microcrack formations, indicating the formation of metal hydrides. The EDS analysis showed a reduction in Ti and Zr contents post-hydrogenation, likely due to the formation of hydrides. The presence of hydride phases, with shifts in diffraction peaks indicating structural modifications due to hydrogen absorption, is confirmed by the XRD analysis. The FTIR analysis revealed dihydroxylation, with the removal of surface hydroxyl groups and the formation of new metal–hydride bonds, further corroborating the structural changes. The formation of metal hydrides was confirmed by the emergence of new peaks within the 1100–1200 cm⁻¹ range, suggesting the incorporation of hydrogen. Mathematical modeling based on the experimental parameters was conducted to assess the hydride formation and the rate of hydrogen penetration. The hydride conversion rate for Ti- and Zr-coated AlO₃ granules was determined to be 3.5% and 1.6%, respectively. While, the hydrogen penetration depth for Ti- and Zr-coated AlO₃ granules over a time of 2 h was found to be 1200 nm and 850 nm approximately. The findings had a good agreement with the experimental results. These results highlight the impact of hydrogenation on the microstructure and chemical composition of Ti- and Zr-coated AlO₃, shedding light on potential applications in hydrogen storage and related fields. Full article

This paper presents an uncertainty quantification analysis of the first fix in a time-differenced carrier phase (TDCP) observation model. TDCP is a widely used method in GNSS-based odometry for precise positioning and displacement estimation. A key point in the TDCP modeling is the assumption that the GNSS receiver’s initial position is perfectly known, which is never exactly the case in real-world applications. This study assesses the impact of initial position errors on estimated displacement by formulating a correct TDCP model and a misspecified one, where the first position is not correct. Theoretical derivations provide a generic framework of estimation under the misspecified model and its associated mean squared error (MSE), as well as estimation performance bounds through the misspecified Cramer Rao bound (MCRB) for the considered case. These theoretical considerations are then used to build an estimator of the receiver’s displacement, with comparisons to the MCRB for performance evaluation. Extensive simulations using realistic GNSS geometry assess the influence of a first-fix error under various conditions, including different time intervals, first-fix error norms, and first-fix error direction. As an example, it is shown that for the considered geometry, if a TDCP of $t_2-t_1=1$ s is built with an initial first fix error norm $\parallel \mathsf{\Delta }{\mathit{r}}_1\parallel =10 \mathrm{m}$, then it introduces an estimation of the displacement, with an error of norm equal to $1.3 \mathrm{m}\mathrm{m}$, at most. The results indicate that the displacement estimation error is linearly related to the initial position error and the time interval between observations, highlighting the importance of accurate first-fix estimation for reliable TDCP-based odometry. The findings contribute to highlighting the order of magnitude of errors on solutions as a function of the error on parameters. Full article

High-frequency injection (HFI) is widely adopted for the sensorless control of permanent magnet synchronous motors (PMSMs) at low speeds. However, conventional HFI strategies relying on fixed-frequency carrier modulation and square-wave injection concentrate current harmonic energy within narrow spectral bands, thereby inducing pronounced high-frequency motor vibrations and noise. To mitigate this issue, this paper proposes a noise suppression strategy based on synchronized periodic frequency modulation (PFM) of both the carrier and high-frequency square-wave signals. By innovatively synchronizing the periodic modulation of the triangular carrier in space vector pulse width modulation (SVPWM) with the injected high-frequency square wave, harmonic energy dispersion and noise reduction are achieved, substantially lowering peak acoustic emissions. First, the harmonic characteristics of the voltage-source inverter output under symmetric triangular carrier SVPWM are analyzed within a sawtooth-wave PFM framework. Concurrently, a harmonic current model is developed for the high-frequency square-wave injection method, enabling the precise derivation of harmonic components. A frequency-synchronized modulation strategy between the carrier and injection signals is proposed, with a rigorous analysis of its harmonic suppression mechanism. The rotor position is then estimated via high-frequency signal extraction and a normalized phase-locked loop (PLL). Comparative simulations and experiments confirm significant noise peak attenuation compared to conventional methods, while position estimation accuracy remains unaffected. This work provides both theoretical and practical advancements for noise-sensitive sensorless motor control applications. Full article

The combination of GNSS RTK and INS offers complementary advantages but faces significant challenges in urban canyons. Frequent cycle slips in carrier phase measurements and ambiguity resolution algorithms increase computational burden without improving positioning accuracy. Additionally, environmental interference introduces noise into observations, potentially leading to complete signal loss. To address these issues, this paper proposes a factor graph optimization (FGO) positioning algorithm incorporating predictive observation factors. First, a penalized spline (P-spline) is constructed to predict and smooth Doppler measurements. The predicted Doppler is then fused with the dynamics model predictions to enhance robustness. Using predictive Doppler, carrier phase and pseudorange observations are reconstructed, generating predictive constraint factors to improve positioning accuracy. Real-world tests conducted in urban canyons, including Shanghai, demonstrate that the proposed method maintains stable positioning performance even under short-term signal outages, effectively mitigating cumulative positioning errors caused by data loss. Compared to traditional methods that rely solely on available observations, the proposed algorithm improves northward and dynamic positioning accuracy by 35% and 29%, respectively, providing a highly robust navigation solution for complex urban environments. Full article

The increase in biogas production has caused a simultaneous increase in the production of digestate, which is a valuable carrier of nutrients in crop plant production. Digestate-derived nitrogen ensures the optimal nutritional status of winter oilseed plants at critical stages of yield formation. This hypothesis was verified in field experiments with winter oilseed rape (WOSR) conducted in the 2015/2016, 2016/2017, and 2017/2018 growing seasons. The experiment consisted of three nitrogen fertilization systems (FSs)—mineral ammonium nitrate (AN) (AN-FS), digestate-based (D-FS), and ²/₃ digestate + ¹/₃ AN (DAN-FS)—and five N_f doses: 0, 80, 120, 160, and 240 kg N ha⁻¹. Plants fertilized with digestate had higher yields than those fertilized with AN. The highest seed yield (SY) was recorded in the DAN-FS, which was 0.56 t ha⁻¹ higher than that in the M-FS. The nitrogen fertilizer replacement value (NFRV), averaged over N doses, was 104% for the D-FS and reached 111% for the mixed DAN-FS system. The N content in WOSR leaves, which was within the range of 41–48 g kg⁻¹ DM at the rosette stage and within 34–44 g kg⁻¹ DM at the beginning of flowering, ensured optimal plant growth and seed yield. In WOSR plants fertilized with digestate, the nitrogen (N) content was significantly lower compared to that in plants fertilized with AN, but this difference did not have a negative impact on the seed yield (SY). The observed positive effect of the digestate on plant growth in the pre-flowering period of WOSR growth and on SY resulted from the impact of Mg, which effectively controlled Ca, especially in the third growing season (which was dry). Mg had a significant effect on the biomass of rosettes and on SY, but only when its content in leaves exceeded 2.0 g kg⁻¹ DM. It is necessary to emphasize the specific role of the digestate, which significantly reduced the Ca content in the indicator WOSR organs. Increased Ca content during the vegetative period of WOSR growth reduced leaf N and Zn contents, which ultimately led to a decrease in SY. Therefore, the rosette phase of WOSR growth should be considered a reliable diagnostic phase for both the correction of plants’ nutritional status and the prediction of SY. It can be concluded that the fertilization value of digestate-derived N was the same as that of ammonium nitrate. This means that the mineral fertilizer can be replaced by digestate in WOSR production. Full article

Non-stoichiometric skinnerite Cu_3+mSbS₃ (−0.04 ≤ m ≤ 0.04) was synthesized via mechanical alloying and hot pressing. A phase analysis, microstructural characterization, and thermoelectric property evaluation were conducted to investigate the effects of Cu deficiency and excess. An X-ray diffraction of the mechanically alloyed powders confirmed the formation of cubic skinnerite, while the hot-pressed Cu-rich samples contained a secondary phase, identified as cubic tetrahedrite (Cu₁₂Sb₄S₁₃). The lattice constant decreased within the range of 1.0341–1.0347 nm for the non-stoichiometric compositions. The microstructural analysis revealed a skinnerite matrix with tetrahedrite inclusions in the Cu-excess samples. The differential scanning calorimetry showed a single endothermic peak at 876 K for the stoichiometric skinnerite, corresponding to its melting point, whereas the non-stoichiometric samples exhibited additional phase transitions at 814–818 K, and a melting reaction at 873–874 K. The electrical conductivity increased with the temperature, indicating non-degenerate semiconductor behavior. Between 323 and 423 K, the electrical conductivity varied depending on the Cu deficiency or excess, but above 423 K, all the non-stoichiometric samples exhibited higher electrical conductivity than the stoichiometric skinnerite. A positive Seebeck coefficient confirmed p-type conduction in all the samples, while Cu deficiency led to a decrease in the Seebeck coefficient but enhanced the power factor, due to increased electrical conductivity. The Cu_2.98SbS₃ sample exhibited the highest power factor of 0.85 mWm⁻¹K⁻² at 623 K. Although Cu deficiency resulted in increased thermal conductivity due to a higher carrier concentration, the significant enhancement in the power factor led to a maximum dimensionless figure of merit (ZT) of 0.59 at 623 K for Cu_2.98SbS₃, surpassing the ZT of 0.51 for the stoichiometric Cu₃SbS₃. Full article

The low-symmetry Weyl semimetallic Td-phase WTe₂ exhibits both a distinct out-of-plane damping torque (${\tau }_{\mathrm{DL}}$) and exceptional charge–spin interconversion efficiency enabled by strong spin-orbit coupling, positioning it as a prime candidate for spin–orbit torque (SOT) applications in two-dimensional transition metal dichalcogenides. Herein, we report on thickness-dependent unconventional out-of-plane ${\tau }_{\mathrm{DL}}$ in chemically vapor-deposited (CVD) polycrystalline Td-WTe₂ (t)/Ni₈₀Fe₂₀/MgO/Ti (Td-WTN-t) heterostructures. Angle-resolved spin-torque ferromagnetic resonance measurements on the Td-WTN-12 structure showed significant spin Hall conductivities of σ_SH,y = 4.93 × 10³ (ℏ/2e) Ω⁻¹m⁻¹ and σ_SH,z = 0.81 × 10³ (ℏ/2e) Ω⁻¹m⁻¹, highlighting its potential for wafer-scale spin–orbit torque device applications. Additionally, a detailed examination of magnetotransport properties in polycrystalline few-layer Td-WTe₂ films as a function of thickness revealed a marked amplification of the out-of-plane magnetoresistance, which can be ascribed to the anisotropic nature of charge carrier scattering mechanisms within the material. Spin pumping measurements in Td-WTN-t heterostructures further revealed thickness-dependent spin transport properties of Td-WTe₂, with damping analysis yielding an out-of-plane spin diffusion length of λ_SD ≈ 14 nm. Full article

Global navigation satellite system (GNSS) real-time kinematic (RTK) has been widely applied in landslide monitoring and warning, since it can provide real-time and high-precision three-dimensional deformation information in all weather and all the time. The Kalman filter is often adopted for parameter estimation in GNSS RTK positioning since it can effectively suppress the observational noise and improve the positioning accuracy and reliability. However, the discrepancy between the empirical state model in the Kalman filter and the actual state of the monitoring object could lead to large positioning errors or even the divergence of the Kalman filter. In this contribution, we propose a novel rapid deformation identification and adaptive filtering approach with GNSS time-differenced carrier phase (TDCP) under different scenarios for landslide monitoring. We first present the methodology of the proposed TDCP-based rapid deformation identification and adaptive filtering approach for GNSS RTK positioning. The effectiveness of the proposed approach is then validated with a simulated displacement experiment with a customized three-dimensional displacement platform. The experimental results demonstrate that the proposed approach can accurately and promptly identify the rapid between-epoch deformation of more than approximately 1.5 cm and 3.0 cm for the horizontal and vertical components for the monitoring object under a complex observational environment. Meanwhile, it can effectively suppress the observational noise and thus maintain mm-to-cm-level monitoring accuracy. The proposed approach can provide high-precision and reliable three-dimensional deformation information for GNSS landslide monitoring and early warning. Full article

Assessing the quality of a received signal is of fundamental importance to predict the performance of the receiver. In general, the signal to noise ratio (SNR) or the carrier to noise density $C/N_0$ ratio is used as an indicator to describe the signal quality of most receivers. For the medium-frequency (MF) R-Mode, a terrestrial positioning navigation and timing (PNT) system, the knowledge of the SNR or $C/N_0$ is important for monitoring purposes, helping the service operator to assess the healthiness of the transmitted signals, as well as for the users to optimize the receiver algorithms and performance. In this paper, we present how the $C/N_0$ can be estimated from the output of the discrete Fourier transform (DFT). The DFT is already used in the receiver to perform the phase estimation; hence, the receiver computational load is reduced. Theory is first presented and discussed, followed by the definition of the estimator, which is tested with Monte Carlo simulation as well as with real data to validate the approach. The results show good agreement between theory, simulation, and in-field measurements, which proves that the estimated $C/N_0$ is a good indicator to measure the received signal quality under optimal propagation condition. Full article

Conventional methods for train positioning and integrity monitoring are limited by their dependence on trackside infrastructure. This reliance on fixed equipment has prompted the investigation of global navigation satellite systems (GNSSs) as a more efficient alternative. The track-constrained algorithm based on the ‘train head (TH) and train tail (TT)’ double-difference (DD) baseline model (Single DD algorithm) has been applied for positioning and train length monitoring. It has been observed that the coefficient matrix can cause the inflation of the odometer corrections when the difference in track slope at both ends of the train is small. This inflation problem reduces the train positioning accuracy. A dual DD baseline fusion algorithm (Dual DD algorithm) with minimized sensitivity on the difference in track slope is thereby introduced. Furthermore, to validate the status of reference stations, a cross-checking function is utilized. The simulation results demonstrate that with a noise setting of 0.0067 m in carrier phase measurement, the Dual DD algorithm enhances the accuracy of train location estimation by up to 10 times compared to the Single DD algorithm. Meanwhile, the simulation result of train length difference validates the feasibility of the cross-checking function. Full article

Maghemite (γ-Fe₂O₃) nanoparticles have attracted considerable interest for electronic applications due to their tunable electrical properties. Doping strategies offer an effective way to optimize their resistive behavior for use in electronic devices. In this study, cobalt (Co) was incorporated into γ-Fe₂O₃ to enhance its resistive properties. X-ray diffraction (XRD) confirmed the retention of the cubic P4₃32 phase, with Co doping inducing subtle lattice distortions due to ionic substitution. Scanning and transmission electron microscopy (SEM/TEM) revealed morphological changes, where Co incorporation influenced particle shape and size distribution. Electrical conductivity analysis demonstrated a decrease in both AC and DC conductivity with the increase in Co content, indicating enhanced resistive behavior. The increase in activation energy suggests a reduction in charge carrier mobility, leading to higher resistivity. Impedance spectroscopy further confirmed increased real and imaginary impedance values, reinforcing the role of Co in suppressing charge transport. These results position cobalt-doped maghemite as a promising material for electronic resistive devices, such as tunable resistors and negative temperature coefficient (NTC) thermistors, where controlled conductivity and stable resistive behavior are essential. Full article