To address the limitations of single-source localization methods in complex indoor environments, such as insufficient accuracy and stability, this paper proposes an indoor localization method based on multi-modal information fusion of Wi-Fi channel state information (CSI) fingerprint images and ZigBee received signal strength indication (RSSI). First, Hampel filtering is applied to preprocess CSI signals, and both amplitude and phase information of CSI are combined to form high-resolution image fingerprint data. For RSSI signals, data packets collected by ZigBee sensor networks are processed through outlier removal and matrix transformation to generate corresponding fingerprint data. Inspired by image classification tasks, a lightweight efficient channel attention convolutional neural network (ECA-CNN) is designed to extract and train features from CSI fingerprint images, while a transformer network is utilized to train RSSI fingerprint data. Finally, a soft voting method integrates the fingerprint databases from both models to produce classification outputs. Experimental results demonstrate that this method significantly improves localization accuracy and robustness in indoor environments, effectively overcoming the limitations of single-source localization.
In this paper, CdxZn1−xS thin films were deposited on glass substrates by chemical bath deposition (CBD), and the effects of different concentrations of ammonia water on the morphology, structure and optical properties of the films were studied. CdxZn1−xS thin films have hexagonal crystal structure, the transmittance is above 75
This paper considers the physical layer security (PLS) performance analysis of an unmanned aerial vehicle (UAV)-assisted free-space optical (FSO) communication system over Fisher-Snedecor (F) distributed turbulence fading channel. We consider the combined effects of atmospheric turbulence, pointing error (PE), atmospheric attenuation, and angle-of-arrival (AOA) fluctuations on the channel. The communication between two legitimate peers in the presence of an external eavesdropper is studied from the perspective of communication theory security. Specifically, under two different eavesdropping scenarios where an eavesdropper is located close to the legitimate transmitter or receiver, we derive the exact closed-form expressions of the secrecy outage probability (SOP) and strictly positive secrecy capacity (SPSC), respectively. These analytical results are validated through Monte Carlo simulations. Furthermore, we also analyze the impact of various link parameters for both the main channel and the eavesdropping channel on the system performance.
To address the low accuracy of traditional stereo matching methods in depth-discontinuous and weak-texture regions, we propose an improved algorithm based on dynamic multi-feature fusion and dual-branch adaptive aggregation. A nonlinear weighting function dynamically integrates noise-resistant Re-Census, multi-directional gradient and Lab-color costs. Distinct arm extension rules are applied to weak texture and depth-discontinuous areas, enabling a dual-branch adaptive aggregation that adapts to local scene characteristics. Disparity estimation follows a winner takes all (WTA) strategy. The ultimate disparity map is generated through a region-based disparity optimization module and multiple optimization processes. Experimental results on the Middlebury dataset indicate a 16.1
The laser detection technology based on orbital angular momentum (OAM) beam has been rapidly developed, but it is restricted by many factors from being applied in practice. One of the most significant issues is that it is greatly affected by environmental conditions. When it is applied in the fog environment, the signal-to-noise ratio (SNR) of the echo signal will be seriously reduced due to the interference of environmental noise. A comprehensive study on the forward propagation and backscattering characteristic evolution theory of OAM transmission through the atmospheric fog environment is essential to formulate corresponding strategies to improve its environmental adaptability. In this work, we proposed a light field initialization method based on the acceptance-rejection method (ARM) which can convert the light field to photon flow. By combining this method with the electric Monte-Carlo (EMC), we established a propagation dynamics analysis model of OAM beam in a fog environment to reveal the propagation and evolution process of OAM beam in a complex environment. This work provides the theoretical and technical support for improving the applicability and detection accuracy of OAM laser detection technology in a complex environment. Furthermore, by combining with other models, this model can be updated for analysis of the transmission dynamics of multidimensional modulated light field under more complex environment conditions, such as foggy, smoky, and rainy environments, which can help to improve the performance of free space optical communication, Lidar, and laser energy delivery systems.
This study establishes a coupled fuselage-nozzle-plume model based on thermal-mechanical coupling mechanisms to analyze jet aircraft infrared characteristics. Numerical simulations reveal that skin temperature under non-afterburner flight conditions increases nonlinearly with Mach number and decreases gradiently with altitude, while nozzle thermal disturbance creates jet-like plume temperature attenuation. The 3–5 µm radiation primarily originates from high-temperature nozzle components, whereas 8–14 µm band exhibits stronger sensitivity to skin temperature variations, demonstrating superior omnidirectional detection potential. Information entropy analysis shows long-wave imaging exceeds medium-wave by two orders of magnitude, attributed to enhanced grayscale uniformity. These findings provide critical theoretical support for infrared signature analysis and detection technology development under complex operational conditions.
To address the considerable complexity of the successive cancellation list flip (SCLF) decoding algorithm for polar codes, a partitioned parity check (PC)-aided SCLF decoding algorithm for polar codes based on error distribution of the critical set (CS) (ED-PC-SCLF decoding algorithm) is proposed. The algorithm segments polar codes into several partitions, considering the cumulative likelihood of the initial erroneous occurrence within the CS. For each partition, PC codes are employed to detect and flip the erroneous non-frozen bits. To improve the competitiveness of the correct path, path pruning during decoding is incorporated to only retain the best path per partition, thus the bit-flipping accuracy is enhanced. Additionally, a new partition of the flip set is designed according to re-decoding iterations. The experimental results reveal that the proposed ED-PC-SCLF decoding algorithm is superior to the dynamic SCLF (D-SCLF) decoding algorithm and the SCLF based on distributed parity check codes (DPC-SCLF) decoding algorithm in both the error correction performance and the complexity.
This study proposes the enhanced line-detection adaptive you only look once (ELA-YOLO), an enhanced YOLOv8-based object detection algorithm, to improve the identification and classification of critical power components. By integrating efficient multi-scale attention (EMA) into redesigned cross stage partial feature fusion (C2f) modules (C2f_EMA), the backbone network achieves dynamic multi-scale feature fusion. The neck network is further optimized through asymmetric padding convolution (APConv) in C2f_AP modules, enhancing spatial feature integration. Additionally, the large selective kernel (LSK) attention mechanism strengthens context-aware feature extraction capabilities. Experimental results demonstrate that ELA-YOLO outperforms YOLOv8s with a 2.8
Online monitoring of end-tidal carbon dioxide (EtCO2) concentration held substantial clinical diagnostic value, as it provided insight into a patient’s respiratory and metabolic status. The wavelength modulation spectroscopy (WMS) method, due to real-time capability, high precision, and excellent gas selectivity, was widely used for the measurement of EtCO2 concentration. The Beer-Lambert law was approximated using a first-order Taylor series in traditional WMS methods, resulting in a strong linear relationship between gas concentration and the second harmonic amplitude. However, the measuring errors increased with higher gas sample concentrations, particularly when the concentrations exceeded 10
Silicon substrates were plasma treated before being coated by plasma-polymerized hexamethyldisilazane (pp-HMDSN) thin films. The pretreatments included oxygen (O2), SF6 and argon (Ar) plasmas. The effect of these pretreatments on the properties of deposited thin films was studied, including film thickness, morphology and photoluminescence (PL). The deposition of pp-HMDSN thin films was performed using plasma enhanced chemical vapor deposition (PECVD). It was found that the substrate pretreatment induces an increase of film thickness, and the morphology of the deposited thin film follows that of the treated substrate, while the intensity of PL increases due to change of nanostructure accompanied with roughness and thin film thickness increase.
This paper proposed and demonstrated a scheme to generate frequency-doubled triangular-shaped waveforms based on external modulation and polarization control. After optical carrier suppression (OCS) modulation in a dual-electrode Mach-Zehnder modulator (De-MZM) and optical double sideband (ODSB) modulation in a dual-parallel Mach-Zehnder modulator (DP-MZM), we obtain the optical spectrum with four main sidebands with equal frequency intervals, while maintaining a consistent 9.5 dB amplitude difference between the inner and outer sidebands. Subsequently, polarization control uses an optical interleaver (OI) and a time delay line (TDL) to eliminate the coherent interference of different sidebands. Finally, by applying a 10 GHz radio frequency (RF) signal, a 20 GHz triangular waveform is obtained. The tunability and feasibility of the triangular waveform generation have been also investigated. This proposal provides a feasible method to generate triangular waveform with high repetition rate.
In this paper, an organic-liquid-integrated side-hole microstructured optical fiber (SHMOF) sensor is proposed for high-sensitivity temperature measurement. The air holes of side-hole fibers are infiltrated with quinoline-dimethyl-sulfoxide mixture to excite the resonance coupling between two liquid rods and the solid fiber core. The fundamental core mode in the core region can be coupled into the liquid rod modes at specific wavelengths satisfying the phase matching condition, and the temperature-induced refractive index variation of the infiltrated materials would cause the resonance wavelength shift. By monitoring the resonance wavelength shift, high-sensitivity temperature sensing can be achieved. Further simulation results based on the finite element method are in accordance with the experimentally observed resonance shift behavior in response to the environmental temperature change. Experimental results show that the maximum sensitivity of the fabricated sensor reaches −4.88 nm/°C for the measurement range of 26.1 °C to 62 °C. Our proposed temperature sensing scheme possesses several desirable merits such as high sensitivity, compact structure and low cost, which is anticipated to find applications in various industrial as well as civil engineering areas.
Ge p-i-n resonant-cavity-enhanced photodetectors(RCE-PDs)grown on Si-on-insulator substrate are proposed and optimized at 1 550 nm for high quantum efficiency and bandwidth.A vertical cavity is formed,consisting of a buried oxide layer as the top reflector and Si/SiO2 distributed Bragg reflector(DBR)layers as the bottom reflector,to enhance the light-matter interaction within the Ge p-i-n structure.The results demonstrate the optimized Ge RCE-PDs can achieve the quantum efficiency of 23％for the 346 nm Ge thickness(34％for the 526 nm Ge thickness)and the high bandwidth of 70 GHz(50 GHz)at 1 550 nm with 3 pairs of Si/SiO2 DBRs.These results indicate that the performance of the Ge RCE-PDs surpasses that of Ge PDs without RCE enhancement.
Cu2ZnSn(S,Se)4(CZTSSe)thin films were prepared using the sol-gel method,and the crystal morphology of the CZTSSe films was im-proved by Mg doping.The prepared films were characterized using techniques such as X-ray diffraction(XRD),Raman spectroscopy,scanning electron microscopy(SEM),and ultraviolet-visible-near infrared(UV-Vis-NIR)spectroscopy.The results showed that Mg re-placed Zn in the CZTSSe lattice,forming the Cu2Zn1-xMgxSn(S,Se)4(CMZTSSe)phase.As the Mg doping concentration increased,the grain size initially increased and then decreased.After Mg doping,no additional impurities are produced.When the Mg doping concentra-tion was 0.1,the film exhibited the optimal crystal morphology,the narrowest peak width,the largest grain size,the best light absorption properties,the smoothest and most compact surface,which is favorable for use as an absorber layer in solar cells.
The stimulated Brillouin scattering (SBS) of heavy germania-doped few-mode fiber (HG-FMF) up to 98 mol
To address the difficulty in recognizing subtle differences in facial biomarkers in children with autism,a learnable positional encoding enhancement(LPEE)module was combined with the adaptive token aggregation(ATA)module.The vision transformer with learnable positional encoding and adaptive token aggregation(ViT-LPATA),a predictive model for autism,was proposed.The model leverages the LPEE module to dynamically capture facial geometric deformation features and integrates the ATA module to enhance the feature repre-sentation capability of pathological regions,thereby establishing precise mappings of biomarker differences.Experiments on a publicly available autism facial dataset demonstrated that the ViT-LPATA achieved optimal performance,with 99.2％accuracy and an area under the curve(AUC)value of 0.940.
The implementation of multifunctional metasurfaces through loading diodes has extremely high costs, while increasing the number of channels in the element through polarization multiplexing technology is limited. This paper proposes a dual-band five-channel (DBFC) 1-bit surface, which expands the polarization independent (PD) channels through rotating array. The polarization-independent metasurface element consists of three layers of metal, with the top layer comprising three rectangular patches oriented in the x-direction, the middle layer featuring a Jerusalem cross structure with accompanying resonators, and the bottom layer being a metal ground plane. The middle layer element can easily independently provide the required 1-bit reflection phases for two orthogonal polarizations in every frequency. The rectangular patches in the x-direction on the top layer do not contribute to the phase of y-polarization. By rotating the upper layer dielectric array 90°, the rectangular patches change to the y-direction. Under y-polarized illumination, the current distribution in the middle layer is shielded, providing a fifth set of polarization independent phases. The proposed 1-bit DBFC metasurface array has advantages in terms of structure and cost, while enhancing the utilization rate of the metasurface array. It has high application potential in microwave imaging, wireless power transmission, and other projects.
This paper presents a performance enhancement for a 40 Gbit/s intensity-modulated direct-detected(IM/DD)optical orthogonal fre-quency-division multiplexing(OFDM)system,focusing on minimizing the peak to average power ratio(PAPR)using a selective map-ping(SLM)scheme.The analysis evaluates key performance metrics,including launched power,optical signal to noise ratio(OSNR),propagation length,power spectral density(PSD),and bit error rate(BER).The implementation of the SLM technique significantly re-duces the PAPR from 10.4 dB to 5.55 dB at a complementary cumulative distribution function(CCDF)of 10-3,achieving a 4.85 dB re-duction.These results demonstrate the effectiveness of SLM in mitigating high PAPR in our system,which can improve tolerance to sys-tem nonlinearities while maintaining manageable power efficiency.Furthermore,the analysis suggests that additional PAPR improve-ments are achievable by increasing the number of SLM partition blocks.The SLM method outperforms the partial transmit sequence(PTS)in terms of PAPR reduction,PSD,and BER.
To ensure the stability of the laser communication system under complex dynamic loads, an off-axis dual-mirror optical antenna system was developed. Thermal-mechanical coupling analysis and wavefront aberration evaluation were conducted to predict the aberration under dynamic conditions and verify structural reliability. Based on D’Alembert’s principle, an acceleration-temperature gradient coupling model was constructed, and a mapping between rigid body displacement and wavefront error was established. Simulation results indicate that the maximum deformation under composite loading is 0.065 873 mm, and the root-mean-square (RMS) wavefront error increases from 0.047λ to 0.068λ, remaining within the RMS < 0.1λ design threshold. The initial wavefront RMS measured by the ZYGO interferometer is 0.052λ, deviating from the simulated value of 0.047λ by only 0.005λ. This validates the model’s accuracy and offers theoretical and engineering support for high-precision optical design in space-based laser communication systems.
Versatile switchable terahertz devices have important applications in the field of terahertz technology,but it is currently difficult to imple-ment them in a single device.In order to realize the switching between slow light and absorbing functions,a slow light and absorption switchable terahertz metamaterial based on the phase transition characteristics of vanadium dioxide(VO2)is designed,which is composed of a top layer of aluminum(Al)square ring and a ring resonant unit,a middle layer of SiO2 and a bottom layer of VO2.Based on the elec-tromagnetic field theory,the finite time domain difference(FDTD)method is used to simulate and analyze the optical properties of VO2 in two states.When VO2 is in the insulating state,the metamaterial can achieve a slow light effect with a maximum group delay of 2.85 ps,and when VO2 is in the metallic state,the absorption rate of the metamaterial can reach 88.5％at 0.287 THz and 99.95％at 0.597 THz.We simulate the temperature-controlled phase transition process of VO2 by changing the conductivity of VO2,which can achieve the switching of slow light and absorption functions.In addition,we also found that the material is polarization insensitive.The metamaterial we have designed has some value in the research of terahertz multifunctional devices.
