NetWork
Experimental design for intelligent traffic sign detection in rainy and foggy weather based on YOLOv8
YUE Xiaoquan;YU Jun;HUANG Hainan;XU Jinqiang;[Objective] Current traffic engineering laboratory exercises often lack sufficient integration of cutting-edge technologies， have limited experimental design diversity， and result in unequal development of practical skills among students. To address these issues， this experiment was designed for intelligent traffic sign detection within an autonomous driving application. Using the TT100K dataset as a base， the experiment incorporates data augmentation techniques， specifically sign replacement and fog/rain simulation algorithms. Based on the YOLOv8 object detection framework， the experiment guides students through targeted optimizations to better suit traffic sign detection tasks. The effectiveness of the optimized algorithm is validated through ablation studies. [Methods] This experiment focuses on building and optimizing a traffic sign detection model using the YOLOv8 architecture. The TT100K dataset was enhanced via data augmentation strategies to improve model robustness in adverse weather. Three key algorithmic improvements were implemented: 1) structural modifications to the C2f module for enhanced feature representation; 2) incorporation of a P2 feature pyramid layer to improve detection performance for small traffic signs; and 3) optimization of the complete intersection over union–based loss function. Ablation experiments were conducted to evaluate the individual and combined contributions of these improvements. Model performance was measured using the mean average precision (mAP) at the intersection over union (IoU) threshold of 0.5 (mAP@0.5) and across IoU thresholds from 0.5 to 0.95 (mAP@0.5:0.95). [Results] Experimental results on the TT100K dataset demonstrated that the mAP@0.5 score increased from 86.40% to 90.90%， and the mAP@0.5:0.95 score improved from 67.60% to 71.00%. These quantitative results confirm the effectiveness of the proposed optimizations. Furthermore， the experimental design successfully cultivated students' practical abilities in image data processing， detection algorithm construction， and model optimization. [Conclusions] This laboratory experiment effectively enhances students' understanding of the working principles and application scenarios of sign detection within intelligent transportation systems. By engaging students in a complete pipeline from data augmentation to model optimization and evaluation， the exercise markedly improved their skills in solving real-world engineering problems. The design successfully integrates contemporary research trends into the curriculum， addresses the limitations of single-method experiments， and promotes the equitable development of practical competencies among students.
based on mechanism surrogate modeling
ZHOU Yu;LIN Zhisong;HUANG Jie;[Objective] Under the background of the New Energy Vehicle Industry Development Plan， higher education faces the critical task of cultivating high-level interdisciplinary engineering talents. Power batteries are the core components of new energy vehicles， which involve complex electrochemical–thermal coupling mechanisms. However， traditional teaching practices encounter several challenges: the abstract nature of electrochemical models makes it difficult for students to understand their internal mechanisms; safety risks and equipment limitations restrict high-rate charging and discharging experiments in the classroom; and the fragmented teaching of modeling， parameter identification， and experimental verification lacks a systematic closed-loop perspective. Therefore， this study aims to develop a reproducible and integrated multiphysics simulation teaching case. By focusing on Blade batteries， the research explores an integrated design of mechanism modeling， cosimulation， and parameter identification， aiming to transform abstract theoretical models into intuitive cognitive experiences and improve students’ abilities to solve complex engineering problems. [Methods] This study implements a simulation teaching scheme based on the synergy of mechanism models and surrogate acceleration. First， a multiphysics coupling model of a commercial Blade battery is established. The electrochemical behavior is characterized by a pseudo-two-dimensional model based on the Doyle–Fuller–Newman framework， describing lithium-ion distribution and dynamics. This is bidirectionally coupled with a three-dimensional solid heat transfer model in COMSOL Multiphysics， where electrochemical heat sources (including reversible entropy heat， ohmic heat， and polarization heat) drive temperature evolution， while the temperature field simultaneously adjusts the electrochemical parameters such as diffusion coefficients and exchange current densities. Second， a coordinated MATLAB–COMSOL simulation environment is developed for parameter identification. To overcome the high computational cost of high-fidelity simulations， a surrogate-assisted Teaching–Learning-Based Optimization (TLBO) framework is introduced. The identification process is decoupled into two sequential stages: the first stage identifies 21 electrochemical parameters using the terminal voltage response， and the second stage identifies 8 thermal parameters based on multipoint temperature data. A Kriging surrogate model is constructed to approximate the expensive objective function， and a lower confidence bound acquisition function is employed to balance exploration and exploitation. This strategy triggers high-fidelity simulation feedback only for the most promising candidates， significantly reducing the number of model calls while maintaining high identification accuracy. [Results] The simulation teaching case was validated through experimental data collected from a high-precision battery test platform. Under the 1 C constant-current discharge condition， the simulation terminal voltage curves were highly consistent with the experimental measurements， accurately reproducing the local fluctuation characteristics of the discharge platform. The identified electrochemical parameters yielded a root mean square error (RMSE) of 0.046 699 V. Regarding the temperature field， the model successfully reconstructed the spatial temperature distribution， showing that the high-temperature region was concentrated near the positive tab and diffused toward the center. The average temperature RMSE remained at 1.021 926 K. To evaluate the generalization capability， the identified parameters were extrapolated to a 1.5 C discharge condition without recalibration. The model accurately captured the downward shift of the voltage platform and the accelerated temperature rise caused by the increased rate， maintaining a high determination coefficient. Crucially， compared to the traditional optimization method without surrogate assistance， the proposed strategy reduced the number of high-fidelity model calls from 9 600 to 349， achieving a 96.4% improvement in computational efficiency. Furthermore， sensitivity analysis revealed that voltage prediction is dominated by geometric and mass transfer parameters， while temperature prediction is primarily governed by boundary convection and thermal conductivities. [Conclusions] This research provides a systematic and efficient pathway for the teaching of power battery simulation. By integrating mechanism modeling with surrogate-assisted optimization， the proposed teaching mode effectively resolves the conflict between simulation accuracy and computational time in the classroom setting. The visualization of multiphysics fields helps students bridge the gap between abstract mathematical equations and physical phenomena. The quantitative sensitivity analysis and cross-rate validation further cultivate students' rigorous engineering thinking and abilities to interpret complex system behaviors. This case study serves as a valuable reference for the construction of virtual simulation laboratories and the reform of courses related to new energy vehicle engineering.
Establishment of the QuEChERS–LC–MS/MS method for high-throughput detection of 12 quinolone residues in chicken
GUO Zhaobin;CHEN Liye;SHI Xixiong;CHEN Cheng;MA Guoyuan;[Objective] Quinolones (QNs) are a class of antibiotics widely used in livestock and poultry breeding owing to their wide range of antibacterial spectrum and strong antibacterial activity. They are widely used for the prevention and treatment of infectious diseases in animals. However， in practice， issues such as overuse， misuse， and failure to follow withdrawal periods are frequently encountered. This leads to excessive QN residues and their metabolites in animal tissues. Long-term consumption of animal-based foods containing QN residues may lead to the development of pathogen resistance， increase the risk of allergic reactions， and disrupt the gut microbiota， posing a serious threat to human health. Therefore， the issue of QN residues warrants increasing attention. Chicken， a widely consumed meat product in China， makes the monitoring of QN residues particularly important. Establishing an efficient and sensitive detection method for monitoring QN residues in livestock and poultry products is critical. [Methods] Efficient and reliable pretreatment techniques are crucial for achieving accurate and stable liquid chromatography–tandem mass spectrometry (LC–MS/MS) analysis. In this study， a high-throughput detection method based on QuEChERS pretreatment combined with LC–MS/MS is established for the simultaneous determination of 12 QN residues in chicken products. The established QuEChERS–LC–MS/MS method provides a rapid， efficient， sensitive， and reliable analytical approach for routine monitoring， risk assessment， and scientific research on various QN residues in chicken， considerably enhancing detection efficiency. At the same time， a comprehensive validation of the established method is conducted. In accordance with international standards， key parameters such as the linear range， sensitivity， accuracy， precision， and specificity are verified to prove its reliability. [Results] The results show that this method can complete the analysis of 12 QN within 9 minutes. At the 9-minute time point， the standard sample exhibits excellent separation， with symmetrical and sharp chromatographic peaks and no corresponding interference peaks observed near the retention times of the standard sample. The methodological evaluation revealed that the correlation coefficients of the calibration curves were all above 0.9970， the limits of detection value ranged from 0.01 to 0.07 μg/kg， and the limits of quantification value ranged from 0.04 to 0.21 μg/kg. The precision determination results showed that the relative standard deviations (RSDs) of retention times for different concentration standard solutions ranged from 0.03% to 0.27%， whereas the RSDs of peak areas ranged from 1.13% to 4.93%， indicating good instrument precision. The matrix addition experiment showed that the recovery rates of the 12 QN after addition ranged from 91.90% to 108.60%. The higher recovery rate indicates that this method complies with the relevant regulations of the national poultry product quality inspection methods. [Conclusions] This study adopts the advanced QuEChERS sample preparation technique and establishes a rapid determination method for QN residues in chicken， replacing the traditional solid-phase extraction procedure. The method offers fast analysis speed， high sensitivity， good recovery rate， and improved lipid removal efficiency. This simple， rapid， and cost-effective feature can provide guidance for large-scale residue detection experiments， offer strong technical support for poultry meat safety supervision work， and safeguard food safety and human health.
Design of a real-time gas-kick monitoring and early-warning system for deep-water drilling
YIN Xiaokang;ZHANG Ziheng;LI Wei;ZHOU Langfei;ZHANG Shuhang;SUN Chaoqiang;[Objective] During deep-water oil and gas exploration， gas kicks can easily evolve into major safety accidents such as blowouts. Therefore， timely online monitoring and accurate early-warning identification of gas kick conditions are critical to ensuring operational safety. Safety Engineering Informatization is a course that cultivates students’ safety supervision awareness and engineering practice capabilities. The course currently uses theoretical lectures and case analyses to explain deep-water drilling gas kick monitoring without practical training support. Consequently， students often struggle to systematically master the core skills required for gas kick monitoring， including sensor signal acquisition， data transmission link establishment， and debugging of signal-processing and gas-kick identification algorithms. To address these teaching shortcomings and improve practical training quality， this study proposes the development of a teaching and experimental system for real-time gas kick monitoring and early warning in deep-water drilling based on the ultrasonic Doppler effect， thereby providing an integrated training platform that is demonstrable， reproducible， and scalable for teaching purposes. [Methods] The system adopts a modular design and consists of independent units， including ultrasonic Doppler sensors， an integrated temperature–pressure sensor， a monitoring instrument， and host computer teaching software. Each unit has clearly defined functions and can be easily disassembled for instructional demonstration. After acquiring and decoding multisource sensor data， the monitoring instrument transmits the data to the upper computer stably via the RS-485 communication protocol. The upper-computer teaching software enables real-time display and dynamic updating of key parameters such as frequency shift， temperature， and pressure. In addition， the software incorporates a gas-kick identification and early-warning algorithm， enabling rapid discrimination and alarm prompting of gas-kick events. It also supports data storage， historical review， and experimental process replay. [Results] Using the deep-water drilling gas-kick simulation experimental setup as the test platform， representative operating conditions with a liquid-phase flow rate of 120 m3/h and a maximum injected gas content of 5% were selected to evaluate monitoring system performance. The system achieves continuous and stable online acquisition and real-time visualization of key parameters， including frequency shift， temperature， and pressure. Meanwhile， during the gas injection stage， the frequency-shift signal exhibits clear and highly repeatable abnormal responses. The built-in gas-kick identification algorithm can suppress alarm triggering when the frequency-shift signal first exceeds the warning threshold and the threshold crossing is determined to be a transient fluctuation induced by pump start-up; however， when the frequency-shift signal continues to exceed the threshold in the absence of manual pump on/off commands， the algorithm can rapidly identify a gas kick and trigger an alarm， without generating redundant alarms after pump shut-down. [Conclusions] Based on the ultrasonic Doppler effect， this research developed a teaching and experimental system for accurate real-time gas-kick monitoring and early warning. Its modular architecture not only improves scalability and maintainability but also facilitates students’ component cognition， principle exploration， and secondary development practices. This system fills the experimental gap in relevant teaching activities and provides students with a full-process hands-on training platform covering sensor application， data transmission， and algorithm verification， demonstrating clear value for experimental teaching as well as potential for further translation into field-deployable equipment development.
Prototype test study on external pressure-bearing capacity of large-diameter steel-reinforced concrete drainage pipe
LIN Chao;SONG Shaojing;MA Huabing;ZHAO Huanle;HAN Chi;CUI Guangyao;[Objective] The reinforced concrete drainage pipe with a steel cylinder features a novel structure， yet its load-bearing characteristics remain unclear. To promote its application and ensure safety during the construction and operational phases， this study investigates its performance. [Methods] To achieve these objectives， a full-scale experimental investigation was conceived and executed. The study was strategically located within the context of a major municipal drainage infrastructure project in the Xiong'an New Area， thereby ensuring the direct relevance of the research to real-world engineering applications. A meticulously designed external pressure prototype test was used as the core methodology. This test was engineered to simulate realistic burial conditions and loading scenarios. By applying incrementally increasing external pressure to a representative large-diameter pipe specimen and employing a comprehensive array of strain gauges and displacement sensors， the research aimed to capture and quantify the intricate structural strain response. The experimental setup allowed for detailed monitoring of stress redistribution， compatibility of deformation between the steel cylinder， reinforcement， and concrete， and the progression of damage from initial elastic behavior to ultimate failure. [Results] The experimental findings yielded a detailed and multistage characterization of the structural performance of the pipe. First， a consistent positive correlation was observed between the applied external pressure and the induced strain across all monitored structural components throughout the testing sequence. Notably， the deformation patterns of the inner and outer layers of reinforcement exhibited substantial compatibility with the surrounding concrete in their respective layers during the initial loading phases， indicating effective composite action. The strain distribution under load revealed distinct stress states， with the steel cylinder demonstrating tensile stresses at its crown， invert， and springline. The inner concrete layer and its associated reinforcement were subjected to tension at the crown and invert but transitioned to compression at the mid-section (springline). Conversely， the outer concrete and reinforcement exhibited compression at the crown and invert and tension at the springline. The structural stiffness of the pipe was not constant but evolved with the applied load. Initially， under external pressures below 131 kN， the pipe operated within the elastic stage. Strain increased linearly across all sections， with the inner and outer concrete shells functioning as the primary load-bearing components and the steel and reinforcement elements serving a secondary role. As the load increased from 131 to 276 kN， the onset of visible microcracking on the concrete surfaces indicated the transition into the plastic stage. During this phase， the internal stress was considerably redistributed. The uncracked concrete， in conjunction with the reinforcement network that had become more actively engaged， became the principal elements resisting the applied load， thereby demonstrating the ductility of the structure. Upon exceeding 276 kN， the pipe progressed into the cracking and failure stage. The concrete in the tensile zones effectively ceased to contribute to load-bearing capacity owing to extensive cracking. At this final stage， the structural integrity predominantly relied on the integrated system comprising the steel cylinder， reinforcement cages， and confined concrete matrix between them. Together， these elements formed a final load-carrying mechanism until ultimate collapse. [Conclusion] This study successfully designed and implemented a definitive external pressure prototype testing method for a novel class of large-diameter reinforced concrete drainage pipes with an integrated steel cylinder. The study has systematically elucidated the complete spectrum of their external load-bearing characteristics from the initial elastic response through plastic deformation and culminating in failure. The results provide critical insights into the complex interaction among the constituent materials—concrete， steel， and cylinder—under load. By mapping the strain distributions， identifying key load thresholds for stage transitions (131 kN for the elastic limit and 276 kN for severe cracking) and clarifying the shifting roles of different components during each phase， this study delivers robust technical support for the large-scale and confidence-driven application of this pipe technology. Furthermore， the findings provide scientifically grounded reference guidelines and valuable empirical data for the future structural optimization design， performance-based specification， and safe engineering implementation of large-diameter reinforced steel-cased concrete drainage pipes in critical infrastructure projects.
Design of a visible light communication system for underwater wireless data transmission of UUVs
WANG Zijian;SHAN Mingguang;[Objective] Unmanned underwater vehicles (UUVs) are widely used in marine environmental monitoring， underwater resource exploration， inspection， and cooperative operation. These applications require short-range underwater links with high transmission rates， high reliability， and strong anti-interference capability. In practical underwater systems， wireless charging and data transmission are often integrated on the same platform. Under this condition， conventional electromagnetic communication is easily affected by interference generated by wireless power transfer equipment， which limits transmission stability. By contrast， underwater wireless optical communication based on visible light offers advantages such as high bandwidth， low latency， and strong immunity to electromagnetic interference， making it suitable for short-range underwater transmission. However， in compact bidirectional underwater systems， local transmitting light sources may introduce backscatter self-interference， whereas the co-existence of communication and wireless charging modules may further cause electromagnetic coupling interference. To address these problems， this study proposes a visible light communication system for underwater wireless data transmission in UUVs under the co-existence of wireless charging and communication. [Methods] An underwater optical communication channel model is first established to analyze light propagation in water， with emphasis on scattering effects and backscatter self-interference in short-range transmission. Based on the channel characteristics， a combined interference suppression method is proposed. In the optical path， wavelength division is used to reduce mutual interference between transmitting and receiving channels， and narrowband optical filters are employed at the receiver to suppress undesired spectral components and weaken optical scattering interference. In the circuit and structural design， electromagnetic shielding is adopted to reduce the electromagnetic coupling interference introduced by the wireless charging system and surrounding electronic modules. On this basis， a miniaturized low-power bidirectional underwater visible light communication experimental system is implemented. The system employs an LED array as the optical transmitter and adopts a field-programmable gate array(FPGA) as the core digital processing platform for communication control and data processing. In addition， a packet loss retransmission mechanism based on the User Datagram Protocol(UDP) protocol is introduced to improve transmission reliability in practical applications. Finally， experiments are carried out to evaluate the performance of the proposed system under the co-existence of underwater wireless charging and visible light communication. [Results] The experimental results show that the proposed system can achieve stable short-range underwater wireless data transmission for UUVs in a complex interference environment. The combined optical-electrical interference suppression method effectively reduces the influence of optical backscatter and electromagnetic coupling interference， thereby improving the stability of signal reception and data recovery. Within a communication distance of 20 cm， the system achieves stable bidirectional transmission at a rate of 2 Mb/s， and the measured bit error rate is only 8.07×10-7. The system maintains high transmission quality under the co-existence of wireless charging and communication. In addition， the UDP-based packet loss retransmission mechanism enhances the reliability of data transmission in practical applications. The experimental prototype also verifies the feasibility of miniaturized and low-power implementation， which is favorable for integration into compact underwater platforms. [Conclusions] By combining underwater channel analysis， wavelength-division light source design， narrowband optical filtering， electromagnetic shielding， and UDP-based packet retransmission， the proposed system improves communication reliability under wireless charging and data trabsmission. This study provides a practical reference for short-range high-speed underwater communication and energy-information collaborative transmission in UUV platforms.
Construction and Practice of the "Four Inspections and One Supervision" Laboratory Safety Inspection System
FANG Yongzhi;SHANG Lei;WANG Haijie;SONG Bin;ZHOU Weiyu;[Objective] University laboratories are essential spaces for experimental teaching， scientific research and technological innovation， but they also concentrate multiple types of safety risks， such as hazardous chemicals， special equipment， biological materials， radiation sources， electrical facilities and laboratory waste. In many universities， laboratory safety inspection has long been regarded as an important management tool; however， practical problems remain prominent， including insufficient integration of different inspection forces， weak linkage between inspection and rectification， limited professional support for high-risk hazards， and inadequate digital traceability. These problems make it difficult to transform inspection results into continuous risk control. In response to the requirements of laboratory safety governance and the dual-prevention mechanism of risk grading control and hidden-danger investigation， this study aims to construct a systematic， collaborative and closed-loop laboratory safety inspection system named “Four Inspections and One Supervision”， and to explore its operational logic and practical value in university laboratory safety management. [Methods] A problem-oriented design approach was adopted. On the basis of national policy requirements， laboratory safety standards and the actual needs of university laboratories， the study first analyzed the limitations of conventional inspection practices， especially the separation of hazard identification， rectification assignment， process tracking and final verification. It then designed a micro-grid-based responsibility structure in which laboratory rooms， personnel， hazardous sources and management roles are linked to specific responsibility units. Supported by a PC- and mobile-end laboratory safety inspection system， the inspection process was digitized from task creation and automatic notification to on-site recording， rectification dispatch， progress tracking， review and closure. The “Four Inspections” include self-inspection， mutual inspection， specialized inspection and comprehensive inspection， while “One Supervision” refers to safety supervision focusing on external professional diagnosis and rectification implementation. Self-inspection emphasizes routine responsibility at college and laboratory levels; mutual inspection introduces cross-unit perspectives and promotes experience sharing; specialized inspection targets professional and high-risk fields; comprehensive inspection strengthens hierarchical and risk-based oversight; and safety supervision ensures that hidden dangers are corrected through a closed-loop mechanism. In addition， institutional， organizational， team-building， technological and safety-culture safeguards were established to support the stable operation of the system. [Results] The proposed system changed laboratory safety inspection from a relatively fragmented activity into an integrated governance process. First， the micro-grid structure clarified the relationship between inspection tasks and responsibility subjects， enabling hidden dangers to be assigned to specific personnel and followed up until completion. Second， the combination of routine self-inspection， cross-unit mutual inspection， specialized inspection and comprehensive inspection improved the coverage and depth of hazard identification. It allowed common risks to be detected through daily management， while professional and concealed risks were examined through targeted expert-supported inspections. Third， the information platform improved the efficiency， transparency and traceability of the inspection process. Inspection records， rectification requirements， responsible persons， deadlines， review results and closure status could be managed online， which reduced the possibility of unresolved or repeatedly neglected hazards. Fourth， the supervision mechanism strengthened accountability by connecting inspection findings with rectification verification， notification， interview and assessment measures. In practical application， the system promoted the formation of a coordinated pattern in which university-level management departments， colleges， laboratories， experts and frontline users participate in safety governance according to their respective roles. [Conclusions] The “Four Inspections and One Supervision” system provides a practical framework for improving laboratory safety inspection in universities. Its core value lies not simply in adding more inspection forms， but in integrating multiple inspection methods， grid-based responsibility transmission， professional support and information-based closed-loop management into one governance mechanism. The system helps address the common problem of “emphasizing inspection while neglecting rectification”， strengthens the connection between risk identification and rectification implementation， and supports the transformation of laboratory safety management from passive response and fragmented control to proactive prevention and systematic governance. This practice may provide a reference for universities seeking to build a normalized， traceable and sustainable laboratory safety inspection and hidden-danger rectification mechanism.
Suppression jamming experimental platform based on low-cost software-defined radio
CHEN Lei;XU Rui;FANG Bo;WU Xiangzong;XIONG Zhi;[Objective] This study aims to develop and evaluate a low-cost suppression jamming experimental platform using software-defined radio (SDR) technology. The platform’s ability to generate multiple types of suppression jamming signals in a controlled wired-loop environment was assessed. The proposed platform provides a flexible， configurable， and cost-effective solution for evaluating GNSS receiver anti-jamming performance， while avoiding the complexity and high cost of commercial jamming equipment. [Methods] A suppression jamming experimental platform was designed and implemented using GNU Radio and HackRF hardware. It features a modular architecture comprising parameter configuration， jamming signal generation， signal selection， waveform monitoring， and radio frequency (RF) transmission modules. Four representative suppression jamming waveforms were generated: continuous wave， frequency-swept， pulse， and band-limited Gaussian noise jamming. Jamming parameters such as center frequency， sweep characteristics， pulse repetition pattern， and output power could be configured via software interfaces. To verify signal generation accuracy， a spectrum analyzer and oscilloscope were used to evaluate the frequency-domain characteristics and pulse-modulation timing performance of the generated signals. The platform was further integrated into a wired-loop test environment， enabling direct injection of jamming signals into the RF input of GNSS receivers. This configuration provides a repeatable and controllable testing environment， eliminating uncertainties caused by wireless propagation. To assess jamming effectiveness， comparative experiments were conducted between the proposed low-cost SDR platform and a commercial high-cost jammer under identical test conditions. The carrier-to-noise density ratio (C/N?) variation and attenuation characteristics of the receiver were selected as the primary evaluation metrics. In addition， dynamic interference experiments were performed to investigate platform performance under motion conditions and evaluate its capabilities in continuous jamming signal generation. [Results] Experimental verification demonstrated that the generated suppression jamming signals exhibit spectral characteristics and temporal behaviors consistent with theoretical design expectations. Measured center frequencies， bandwidths， sweep patterns， and pulse timing parameters showed good agreement with configured values， confirming the accuracy of signal generation and modulation processes. Comparative testing indicated that the proposed SDR platform and the commercial jammer produced similar interference effects on GNSS receivers. Within the GPS L1 frequency band and over a jammer-to-signal ratio range of 30–60 dB， both systems resulted in nearly identical trends of receiver C/N? degradation. As interference intensity increased， both platforms progressively deteriorated signal quality， eventually leading to receiver tracking failure and signal loss-of-lock. The observed attenuation characteristics and loss-of-lock thresholds exhibited strong consistency between the two jamming sources. Dynamic experiments further demonstrated that the proposed platform can continuously generate stable suppression jamming signals during motion without considerable frequency drift or power fluctuation. The platform effectively degraded receiver tracking performance and maintained stable interference throughout the test. These results verify the reliability and practicality of the proposed system for dynamic anti-jamming experiments. [Conclusions] A low-cost SDR-based suppression jamming experimental platform was successfully developed and validated. Experimental results demonstrate that the proposed platform accurately generates multiple suppression jamming waveforms， achieving interference effects comparable to commercial high-cost jammers in the GPS L1 band. The platform offers several advantages， including low implementation cost， flexible architecture， convenient software configuration， and strong scalability. By supporting various suppression jamming modes and providing stable operation in both static and dynamic environments， it serves as an effective experimental tool for evaluating GNSS receiver anti-jamming performance， analyzing interference mechanisms， and other applications in navigation research.
Development of similar material and model experimental design based on the strength reduction method
AN Baixin;KONG Chao;QIU Wenge;ZHANG Jiezhen;[Objective] The rapid development of rail transit has led to increasingly complex tunnel spatial layouts， substantially elevating construction and operational risks. The strength reduction method has been widely applied in tunnel engineering; however， existing studies have predominantly relied on numerical analysis， whereas field evidence and experimental validation remain limited. To address these issues， we developed a rock–soil analog material in which shear strength parameters can be quantitatively reduced through controlled heating. By integrating laboratory-scale physical model tests with numerical simulations， we investigated the potential failure modes of tunnel groups under surrounding-rock strength degradation as well as the associated displacement–stress evolution. Taking the Hongyancun tunnel group in Chongqing， China， as an engineering background example， we aimed to provide targeted guidance for the design and risk management of tunnel groups. [Methods] The analog material was prepared using paraffin wax as the binder and quartz sand together with 400-mesh barite powder as aggregates. Temperature was introduced as an external control variable， enabling controlled reductions in the material’s shear strength parameters through heating. The mechanical properties of the analog material were characterized using a ZJ-type strain-controlled direct shear apparatus and a universal testing machine， based on which the mass ratio of paraffin wax:quartz sand:barite powder was determined as 6:56.4:37.6. To achieve stable and precise control while heating the physical model， an in-house intelligent temperature-control device was developed for accurate heating and temperature regulation. Numerical simulations and laboratory excavation–heating tests on a tunnel group were conducted to analyze the failure patterns and the evolution of displacement and stress fields following quantitative reductions in the surrounding-rock strength. During the tests， displacement transducers and embedded strain blocks were installed to monitor displacement and stress responses throughout excavation and heating. [Results] Based on the strength-reduction concept， an analog material was successfully developed in which cohesion and internal friction angle decrease proportionally with increasing temperature， allowing the mechanical behavior of Grade III–V surrounding rock to be effectively reproduced. The developed intelligent temperature-control device enabled accurate heating and stable temperature regulation of the model material. The tunnel-group heating tests indicated that the sustained development of damage in the pillar rock (intervening rock mass) was the primary factor triggering collapse of the tunnel group. By contrast， even when localized failure occurred in noncritical regions， it typically did not directly lead to overall instability of the tunnel group. [Conclusions] Herein， we propose and validate a temperature-controlled physical modeling approach for quantitatively understanding reductions in the rock strength surrounding tunnels. The developed analog material and temperature-control system effectively capture potential failure zones and instability modes of tunnel groups under strength degradation during excavation and operation. The findings provide experimental evidence and practical references for optimizing the spatial configuration of complex tunnel groups， identifying critical locations， and managing risks throughout the construction–operation lifecycle.
A Virtual Simulation Platform for Resilience Enhancement in New Distribution Systems
QIN Chao;WANG Yongxue;YU Hao;SONG Guanyu;[Objective] In recent years， extreme disaster events have exhibited a trend of higher frequency， wider impact， and stronger intensity. This has imposed stringent requirements on the secure and reliable operation of distribution systems. Concurrently， the large-scale integration of distributed generation (DG) enhances operational flexibility but substantially complicates post-fault behaviors. The most notable of these post-fault behaviors involve the distribution of fault currents and the consequent decisions on fault isolation and service restoration， particularly when multiple concurrent faults and dynamically changing network topologies are present. Despite the prevalence of the term “distribution system resilience” in academic discourse， which characterizes the ability to prevent， withstand， respond to， and recover from extreme disturbances， the existing curriculum in electrical engineering remains predominantly focused on conventional subjects such as power flow， short-circuit calculation， and relay protection. There is a conspicuous absence of an integrated training environment that would link resilience theory to engineering actions. Therefore， the objective of this study is to develop a virtual simulation experimental platform that enables students to comprehend the full-chain and multi-stage process of resilience and to practice designing strategies for resilience enhancement in a scenario-driven and operable manner. [Methods] The proposed platform is constructed by integrating full-chain resilience concepts (i.e.， prevention， mitigation， response， and recovery) with distribution system operational models. It also involves the organization of learning tasks according to the staged evolution of system performance under extreme events. To comprehensively address the resilience workflow， four progressive experimental modules have been implemented: (1) A pre-event preventive proactive islanding simulation is employed， wherein network reconfiguration using remotely controlled switches and manual switches is applied to pre-partition the system into supply islands， with the objective of protecting critical loads from external faults. (2) A fault-current distribution simulation is conducted based on a virtual network-flow representation， which unifies the description of fault-current existence and propagation paths under multi-source， multi-fault conditions and changing switch states. (3) A fault propagation and faulted-section identification module is developed， which explicitly models how automatic tripping of protective switching devices changes topological connectivity and hence delineates the fault influence region. (4) A multi-stage service restoration module formulates post-event isolation and restoration as coordinated topology reconfiguration and supply reachability with multiple switch types， while enforcing that restoration actions must not expand the fault-affected area. The platform facilitates interactive simulation with customizable networks and fault scenarios， providing visualized outputs to ensure the traceability and interpretability of the resilience response process for learners. [Results] The developed platform operationalizes the abstract resilience concept into a coherent sequence of experiments spanning preparation， degradation analysis， and staged recovery. This enables systematic “process-level” learning rather than isolated topic exercises. Module 1 utilizes comparative topology settings to demonstrate how proactive islanding prior to an event can substantially compress the affected region and enhance the continuity of critical-load supply without altering the fault location. Module 2 demonstrates the efficacy of virtual network-flow modeling in representing fault-current distribution at the topological level. It expedites the generation of lucid results concerning propagation paths and associated influence regions in complex DG/multi-fault scenarios. This approach mitigates the modeling and reasoning burden when compared with exhaustive path enumeration， thereby directly supporting subsequent localization， isolation， and restoration reasoning. Module 3 employs a visual approach to illustrate the causal chain from protective-device tripping logic to the emergence of clearly delineated fault impact regions. This module serves to reinforce students’ comprehension of how switching operations influence fault transfer and faulted-section localization. Module 4 delineates multi-stage restoration as an executable sequence of switching operations and resource coordination. The sequence initiates with the “compression” and isolation of the fault region， followed by a stepwise expansion of the restored supply. This approach enables learners to observe the impact of diverse action sequences on restoration scale and tempo. [Conclusions] The integration of full-chain resilience theory with operable distribution system models， embedded within four progressively linked simulation modules， establishes a nexus between theoretical instruction and engineering practice for resilience-oriented education under extreme events and high DG penetration.