This study focuses on the teaching reform of the communication application development course based on the core requirements of engineering education accreditation.To address key challenges such as the disconnection b...This study focuses on the teaching reform of the communication application development course based on the core requirements of engineering education accreditation.To address key challenges such as the disconnection between software and hardware teaching and insufficient practical skills among students,a project-driven“learning-practiceapplication”teaching model is proposed.By optimizing course content,innovating teaching methods,and introducing university-industry collaboration mechanisms,the reform aligns the curriculum more closely with engineering education standards and industry demands.The approach significantly enhances students’comprehensive skills,practical abilities,and employability.This study provides theoretical foundations and practical strategies for the teaching reform of courses in communication engineering.展开更多
The GaN-based heterostructures are widely used in optoelectronic devices,but the complex surface reconstructions and lattice mismatch greatly limit the applications.The stacking of two-dimensional transition metal dic...The GaN-based heterostructures are widely used in optoelectronic devices,but the complex surface reconstructions and lattice mismatch greatly limit the applications.The stacking of two-dimensional transition metal dichalcogenide(TMD=MoS_(2),MoSSe and MoSe_(2))monolayers on reconstructed GaN surface not only effectively overcomes the larger mismatch,but also brings about novel electronic and optical properties.By adopting the reconstructed GaN(0001)surface with adatoms(N-ter GaN and Ga-ter GaN),the influences of complicated surface conditions on the electronic properties of heterostructures have been investigated.The passivated N-ter and Ga-ter GaN surfaces push the mid-gap states to the valence bands,giving rise to small bandgaps in heterostructures.The charge transfer between Ga-ter GaN surface and TMD monolayers occurs much easier than that across the TMD/N-ter GaN interfaces,which induces stronger interfacial interaction and larger valence band offset(VBO).The band alignment can be switched between type-I and type-II by assembling different TMD monolayers,that is,MoS_(2)/N-ter GaN and MoS_(2)/Ga-ter GaN are type-II,and the others are type-I.The absorption of visible light is enhanced in all considered TMD/reconstructed GaN heterostructures.Additionally,MoSe_(2)/Ga-ter GaN and MoSSe/N-ter GaN have larger conductor band offset(CBO)of 1.32 eV and 1.29 eV,respectively,extending the range from deep ultraviolet to infrared regime.Our results revel that the TMD/reconstructed GaN heterostructures may be used for high-performance broadband photoelectronic devices.展开更多
The prospect ofα-Ga2O3 in optical and electrical devices application is fascinating.In order to obtain better performance,Ge and F elements with similar electronegativity and atomic size are selected as dopants.Based...The prospect ofα-Ga2O3 in optical and electrical devices application is fascinating.In order to obtain better performance,Ge and F elements with similar electronegativity and atomic size are selected as dopants.Based on density functional theory(DFT),we systematically research the electronic structure and optical properties of dopedα-Ga2O3 by GGA+U calculation method.The results show that Ge atoms and F atoms are effective n-type dopants.For Ge-dopedα-Ga2O3,it is probably obtained under O-poor conditions.However,for F-dopedα-Ga2O3,it is probably obtained under O-rich conditions.The doping system of F element is more stable due to the lower formation energy.In this investigation,it is found that two kinds of doping can reduce theα-Ga2O3 band gap and improve the conductivity.What is more,it is observed that the absorption edge after doping has a blue shift and causes certain absorption effect on the visible region.Through the whole scale of comparison,Ge doping is more suitable for the application of transmittance materials,yet F doping is more appropriate for the application of deep ultraviolet devices.We expect that our research can provide guidance and reference for preparation ofα-Ga2O3 thin films and photoelectric devices.展开更多
Based on the region model of lambda bipolar transistor ( LBT), a dividing region theory model of PLBT is set up,simulated and verified. Firstly, the principal operations of different kinds of photoelectronic lambda bi...Based on the region model of lambda bipolar transistor ( LBT), a dividing region theory model of PLBT is set up,simulated and verified. Firstly, the principal operations of different kinds of photoelectronic lambda bipolar transistor ( PLBT) are characterized by a simple circuit model. Through mathematical analysis of the equivalent circuit, the typical characteristics curve is divided into positive resistance, peak, negative resistance and cutoff regions. Secondly, by analyzing and simulating this model, the ratio of MOSFET width to channel length, threshold voltage and common emitter gain are discovered as the main structure parameters that determine the characteristic curves of PLBT. And peak region width, peak current value, negative resistance value and valley voltage value of PLBT can be changed conveniently according to the actual demands by modifying these parameters. Finally comparisons of the characteristics of the fabricated devices and the simu- lation results are made, which show that the analytical results are in agreement with the observed devices characteristics.展开更多
Two-dimensional(2D)materials offer novel platforms to meet the increasing demands of next-generation miniaturized electronics.Among them,the recently emerged 2D Bi_(2)O_(2)Se with unique non-van der Waals interlayer i...Two-dimensional(2D)materials offer novel platforms to meet the increasing demands of next-generation miniaturized electronics.Among them,the recently emerged 2D Bi_(2)O_(2)Se with unique non-van der Waals interlayer interaction,high mobility,sizeable bandgap,and capability to fabricate homologous heterojunction,is of particular interest.In this Review,we introduce recent progress in preparation,transfer,mechanical and electrical properties,and electronic applications of 2D Bi_(2)O_(2)Se.First,we summarize methodologies to synthesize and massively produce 2D Bi_(2)O_(2)Se,as well as recent advances in transferring them from growth substrate to arbitrary substrates.Then,we review current understandings on the intrinsic mechanical properties of Bi_(2)O_(2)Se at 2D thickness limit,and its in-plane and out-of-plane electrical properties.Electronic devices including field-effect transistors,memristors,and sensors based on 2D Bi_(2)O_(2)Se for neuromorphic computing,memory,logic,and integrated circuits are discussed.Finally,challenges and prospects for the development of 2D Bi_(2)O_(2)Se are proposed.展开更多
The fiber optic sensing technology provides data support in structural health monitoring of the macro facilities,including design,construction,and maintenance of bridges,tunnels,ports and other infrastructures.In this...The fiber optic sensing technology provides data support in structural health monitoring of the macro facilities,including design,construction,and maintenance of bridges,tunnels,ports and other infrastructures.In this paper,a distributed vibration sensing system is proved to be responsive to a single touch over a 1.8-m-long equivalent fiber segment,covering a vibration frequency from 5 Hz to 25 kHz.The sensing fiber was arranged as an S type layout on the bridge to recognize the standing state,windblown disturbance,and walking vibration.Moreover,the knocking and climbing events are recognized fiber laying spinning lines and hanging on the fences,respectively.The demonstration shows an accurate positioning and sensitive vibration monitoring applied on the automated three-dimensional(3D) printed bridge,which is applicable to all kinds of 3D printed facilities as intelligent sensory neuro-networks.展开更多
This work proposes a computational algorithm to improve the determination of the timing of the respiratory phases.The algorithm was developed using a database of breathing sound signals acquired through properly posit...This work proposes a computational algorithm to improve the determination of the timing of the respiratory phases.The algorithm was developed using a database of breathing sound signals acquired through properly positioned face masks and electret microphones.Most of the proposed works use the frequency domain and decimation in time to detect the respiratory period and phases,as well as some specific pathology.In this work the processing applied is only in time without applying decimation,thus improving the detection of a greater number of respiratory periods.The segmentation is very important since it allows the isolation of phases of the signal to later detect some pathology or to estimate the volume of inspired and exhaled air.The proposed algorithm involves the extraction of signal envelopes with the use of high selectivity filters without decimation and adaptive normalization processes that aim to achieve an adequate detection.In the validation process,the algorithm detection results were compared with the timing of respiratory periods and phases marked by visual inspection.The results show a maximum error of 4.36%for the respiratory period and 3.23%and 3.09%for the expiration and inspiration times,respectively.展开更多
The detection of surface defects in concrete bridges using deep learning is of significant importance for reducing operational risks,saving maintenance costs,and driving the intelligent transformation of bridge defect...The detection of surface defects in concrete bridges using deep learning is of significant importance for reducing operational risks,saving maintenance costs,and driving the intelligent transformation of bridge defect detection.In contrast to the subjective and inefficient manual visual inspection,deep learning-based algorithms for concrete defect detection exhibit remarkable advantages,emerging as a focal point in recent research.This paper comprehensively analyzes the research progress of deep learning algorithms in the field of surface defect detection in concrete bridges in recent years.It introduces the early detection methods for surface defects in concrete bridges and the development of deep learning.Subsequently,it provides an overview of deep learning-based concrete bridge surface defect detection research from three aspects:image classification,object detection,and semantic segmentation.The paper summarizes the strengths and weaknesses of existing methods and the challenges they face.Additionally,it analyzes and prospects the development trends of surface defect detection in concrete bridges.展开更多
This paper proposes a novel method for the automatic diagnosis of keratitis using feature vector quantization and self-attention mechanisms(ADK_FVQSAM).First,high-level features are extracted using the DenseNet121 bac...This paper proposes a novel method for the automatic diagnosis of keratitis using feature vector quantization and self-attention mechanisms(ADK_FVQSAM).First,high-level features are extracted using the DenseNet121 backbone network,followed by adaptive average pooling to scale the features to a fixed length.Subsequently,product quantization with residuals(PQR)is applied to convert continuous feature vectors into discrete features representations,preserving essential information insensitive to image quality variations.The quantized and original features are concatenated and fed into a self-attention mechanism to capture keratitis-related features.Finally,these enhanced features are classified through a fully connected layer.Experiments on clinical low-quality(LQ)images show that ADK_FVQSAM achieves accuracies of 87.7%,81.9%,and 89.3% for keratitis,other corneal abnormalities,and normal corneas,respectively.Compared to DenseNet121,Swin transformer,and InceptionResNet,ADK_FVQSAM improves average accuracy by 3.1%,11.3%,and 15.3%,respectively.These results demonstrate that ADK_FVQSAM significantly enhances the recognition performance of keratitis based on LQ slit-lamp images,offering a practical approach for clinical application.展开更多
The rapid evolution of Fifth-Generation(5G)networks and the strategic development of Sixth-Generation(6G)technologies have significantly advanced the implementation of air-ground integrated networks with seamless cove...The rapid evolution of Fifth-Generation(5G)networks and the strategic development of Sixth-Generation(6G)technologies have significantly advanced the implementation of air-ground integrated networks with seamless coverage.Unmanned Aerial Vehicles(UAVs),serving as high-mobility aerial platforms,are extensively utilized to enhance coverage in long-distance emergency communication scenarios.The resource-constrained communication environments in emergencies by classifying UAVs into swarm UAVs and relay UAVs as aerial communication nodes is inversitgated.A horizontal deployment strategy for swarm UAVs is formulated through K-means clustering algorithm optimization,while a vertical deployment scheme is established using convex optimization methods.The minimum-path trajectory planning for relay UAVs is optimized via the Particle Swarm Optimization(PSO)algorithm,enhancing communication reliability between UAV swarms and terrestrial base stations.A three-dimensional heterogeneous network architecture is realized by modeling spatial multi-hop relay links.Experimental results demonstrate that the proposed joint UAV relay optimization framework outperforms conventional algorithms in both coverage performance and relay capability during video stream transmission,achieving significant improvements in coverage enhancement and relay efficiency.This work provides technical foundations for constructing high-reliability air-ground cooperative systems in emergency communications.展开更多
Traffic datasets exhibit complex spatiotemporal characteristics,including significant fluctuations in traffic volume and intricate periodical patterns,which pose substantial challenges for the accurate forecasting and...Traffic datasets exhibit complex spatiotemporal characteristics,including significant fluctuations in traffic volume and intricate periodical patterns,which pose substantial challenges for the accurate forecasting and effective management of traffic conditions.Traditional forecasting models often struggle to adequately capture these complexities,leading to suboptimal predictive performance.While neural networks excel at modeling intricate and nonlinear data structures,they are also highly susceptible to overfitting,resulting in inefficient use of computational resources and decreased model generalization.This paper introduces a novel heuristic feature extraction method that synergistically combines the strengths of non-neural network algorithms with neural networks to enhance the identification and representation of relevant features from traffic data.We begin by evaluating the significance of various temporal characteristics using three distinct assessment strategies grounded in non-neural methodologies.These evaluated features are then aggregated through a weighted fusion mechanism to create heuristic features,which are subsequently integrated into neural network models for more accurate and robust traffic prediction.Experimental results derived from four real-world datasets,collected from diverse urban environments,show that the proposed method significantly improves the accuracy of long-term traffic forecasting without compromising performance.Additionally,the approach helps streamline neural network architectures,leading to a considerable reduction in computational overhead.By addressing both prediction accuracy and computational efficiency,this study not only presents an innovative and effective method for traffic condition forecasting but also offers valuable insights that can inform the future development of data-driven traffic management systems and transportation strategies.展开更多
High-selectivity common-mode(CM)and differential-mode(DM)reflectionless balanced bandpass filters(BBPFs)are proposed in this article.By loading absorption networks at single/both ends of the basic ring resonator,input...High-selectivity common-mode(CM)and differential-mode(DM)reflectionless balanced bandpass filters(BBPFs)are proposed in this article.By loading absorption networks at single/both ends of the basic ring resonator,input-/two-port wideband CM and DM reflectionless performance,wideband filtering performance and all-stop CM suppression are obtained.The absorption network composed of K-sections of coupled-lines(CLs)terminated with grounded resistors can not only extend the filtering performance to high order,but also realize wideband absorption of CM noise and out-of-band DM signals.Absorptive stubs are loaded at ports to increase the design flexibility and enhance the absorption.As for the input-reflectionless type,multiple independently controlled transmission zeros(TZs)are obtained by the TZ control network to improves the selectivity and out-of-band rejection.A set of 2 GHz micro-strip BBPFs are designed and measured,which shows simultaneous CM and DM absorption performance.展开更多
A wideband low-profile aperture-coupled antenna based on a novel dual-mode-composite scheme is presented.The mode-composite scheme where the TM10 cavity mode and the TE121 dielec-tric resonator(DR)mode are combined of...A wideband low-profile aperture-coupled antenna based on a novel dual-mode-composite scheme is presented.The mode-composite scheme where the TM10 cavity mode and the TE121 dielec-tric resonator(DR)mode are combined offers an ap-proach to obtain a wide bandwidth accompanied by stable unidirectional radiation and high efficiency.The use of a lengthened coupling aperture that supports the one-wavelength resonance in the band of interest is an effective feed method of simultaneously excit-ing the two composite modes without compromising the increased complexity of the antenna geometry.An impedance bandwidth of 49%for|S_(11)|of less than-10 dB,a maximum gain of 10.8 dBi,and stable radiation patterns with low cross-polarization are realized ex-perimentally by a fabricated prototype.Considering the simplicity of the geometry,the wide bandwidth that can cover n77,n78,and n79 bands for the fifth generation(5G)mobile communications and the sat-isfying radiation performance,the proposed antenna would be a promising candidate for advanced wireless applications.展开更多
Graph computing has become pervasive in many applications due to its capacity to represent complex relationships among different objects in the big data era.However,general-purpose architectures are computationally in...Graph computing has become pervasive in many applications due to its capacity to represent complex relationships among different objects in the big data era.However,general-purpose architectures are computationally inefficient for graph algorithms,and dedicated architectures can provide high efficiency,but lack flexibility.To address these challenges,this paper proposes ParaGraph,a reduced instruction set computing-five(RISC-V)-based software-hardware co-designed graph computing accelerator that can process graph algorithms in parallel,and also establishes a performance evaluation model to assess the efficiency of co-acceleration.ParaGraph handles parallel processing of typical graph algorithms on the hardware side,while performing overall functional control on the software side with custom designed instructions.ParaGraph is verified on the XCVU440 field-programmable gate array(FPGA)board with E203,a RISC-V processor.Compared with current mainstream graph computing accelerators,ParaGraph consumes 7.94%less block RAM(BRAM)resources than ThunderGP.Its power consumption is reduced by 86.90%,24.90%,and 76.38%compared with ThunderGP,HitGraph,and GraphS,respectively.The power efficiency of connected components(CC)and degree centrality(DC)algorithms is improved by an average of 6.50 times over ThunderGP,2.51 times over HitGraph,and 3.99 times over GraphS.The software-hardware co-design acceleration performance indicators H/W.Cap for CC and DC are 13.02 and 14.02,respectively.展开更多
Fiber optic temperature sensors stand out in a variety of applications due to their small size,chemical resistance,and resistance to electromagnetic interference.The traditional optical fiber temperature sensor direct...Fiber optic temperature sensors stand out in a variety of applications due to their small size,chemical resistance,and resistance to electromagnetic interference.The traditional optical fiber temperature sensor directly places the sensing structure in the temperature to be measured,and uses the thermo-optical effect and thermal expansion effect of the SiO_(2)material that constitutes the sensing structure to achieve measurement,while the thermo-optical coefficient and thermal expansion coefficient of SiO_(2) are very small,which limits the high sensitivity response characteristics of the optical fiber temperature sensing structure.In order to solve the problem of low sensitivity of traditional optical fiber temperature sensors,a Mach-Zehnder interferometric temperature sensor with a liquid-encapsulated tapered microfiber is developed.The sensor converts the temperature change into a change in the refractive index of the liquid material and thus realizes the measurement of temperature.In the range of 25~50℃,as the temperature increases,the wavelength of the transmission spectrum shifts towards shorter wavelengths.Experimental results show that the sensitivity of the liquid encapsulated microfiber interferometric temperature sensor can reach-57.91 nk·nm^(-1).This sensor has great potential for applications in marine environmental monitoring,biomedical diagnosis,and aerospace.展开更多
Developing highly efficient and recyclable photocatalysts has been regarded as an attractive strategy to solve antibiotic contaminants.Herein,we designed and fabricated Cy-C_(3) N_(4)/TiO_(2) S-scheme heterojunction f...Developing highly efficient and recyclable photocatalysts has been regarded as an attractive strategy to solve antibiotic contaminants.Herein,we designed and fabricated Cy-C_(3) N_(4)/TiO_(2) S-scheme heterojunction film with boosted charge transfer and a highly hydrophilic surface.The as-prepared heterojunction exhibited outstanding removal efficiency on tetracyclines and fluoroquinolone antibiotics(more than 80% within 90 min).The removal rate of 300-Cy-C_(3) N_(4)/TiO_(2) on norfloxacin(NOR)was 2.12,and 1.59 times higher than that of pristine TiO_(2),C_(3) N_(4)/TiO_(2),respectively.The excellent photocatalytic performance of 300-Cy-C_(3) N_(4)/TiO_(2) was attributed to the highly hydrophilic surface and effective transfer and separation of carriers.Moreover,the NOR degradation pathways were proposed based on the results of density functional theory(DFT),and liquid chromatography-mass spectrometry.The toxicity assessment indicated the toxicity of intermediates can be remarkably alleviated.The DFT calculation and selective photo-deposition experiment demonstrated that an internal electric field was formed at the heterojunction interface,and the charge carriers migrated between Cy-C_(3) N_(4) and TiO_(2) following an S-scheme transfer pathway.This research not only provides a promising method for tracking charge distribution on thin-film heterojunction photocatalysts but also helps us to design high-efficiency,and recyclable heterojunctions to solve antibiotic contaminants.展开更多
Microalgae are one of the promising feedstocks for biorefinery,contributing significantly to net-zero emissions through carbon capture and utilization.However,the disposal of microalgal byproducts from the manufacturi...Microalgae are one of the promising feedstocks for biorefinery,contributing significantly to net-zero emissions through carbon capture and utilization.However,the disposal of microalgal byproducts from the manufacturing process causes additional environmental pollution,thus,a new application strategy is required.In this study,the Tetraselmis suecica byproduct from the carotenoid extraction process was carbonized and converted into biochar.The converted biochar was proved to be nitrogen-doped biochar(NDB),up to 4.69%,with a specific surface area of 206.59m^(2)/g andwas used as an electrode for a supercapacitor.The NDB electrode(NDB-E)in half-cell showed a maximum specific capacitance of 191 F/g.In a full-cell test,the NDB-E exhibited a high energy density of 7.396 Wh/kg and a high-power density of 18,100 W/kg,and maintained specific capacity of 95.5%after charge and discharge of 10,000 cycles.In conclusion,our study demonstrated that the carotenoid-extracted microalgal byproducts are a useful resource for the supercapacitor production.This approach is the first to convert T.suecica into active materials for supercapacitors.展开更多
In this study,a comprehensive analysis of microstructural features,morphology,crystal structures,and interface structures of long-period stacking ordered(LPSO)structures in a non-equilibrium Mg_(97)Zn_(1)Y_(16)Ca_(0.4...In this study,a comprehensive analysis of microstructural features,morphology,crystal structures,and interface structures of long-period stacking ordered(LPSO)structures in a non-equilibrium Mg_(97)Zn_(1)Y_(16)Ca_(0.4)alloy cast in a steel mold was carried out.The addition of Ca element plays an important role in the refinement of LPSO structure.The result reveals new poly-types including 20H F2F2F4,60R(F2F3F3)_(3),and 66H F2F3F3F2(F6)_(4)featuring a 6-Mg structure,alongside the prevalent 18R and 14H LPSO structures.The incoherent interface between 20H and the Mg matrix is split into two dislocation arrays,leading to the formation of a segment of 60R_(1).Moreover,the superstructure 116L,designated as(F2)_(18)F4,is formed through the ordered distribution of F4 stacking faults in 18R.展开更多
The dung beetle optimizer(DBO)is a metaheuristic algorithm with fast convergence and powerful search capabilities,which has shown excellent performance in solving various optimization problems.However,it suffers from ...The dung beetle optimizer(DBO)is a metaheuristic algorithm with fast convergence and powerful search capabilities,which has shown excellent performance in solving various optimization problems.However,it suffers from the problems of easily falling into local optimal solutions and poor convergence accuracy when dealing with large-scale complex optimization problems.Therefore,we propose an adaptive DBO(ADBO)based on an elastic annealing mechanism to address these issues.First,the convergence factor is adjusted in a nonlinear decreasing manner to balance the requirements of global exploration and local exploitation,thus improving the convergence speed and search quality.Second,a greedy difference optimization strategy is introduced to increase population diversity,improve the global search capability,and avoid premature convergence.Finally,the elastic annealing mechanism is used to perturb the randomly selected individuals,helping the algorithm escape local optima and thereby improve solution quality and algorithm stability.The experimental results on the CEC 2017 and CEC 2022 benchmark function sets and MCNC benchmark circuits verify the effectiveness,superiority,and universality of ADBO.展开更多
The construction of bifurcated tunnels is essential to advancing urban infrastructure systems,as they conserve land,reduce carbon emissions,and optimize traffic.However,the bifurcation structure of the parallel conflu...The construction of bifurcated tunnels is essential to advancing urban infrastructure systems,as they conserve land,reduce carbon emissions,and optimize traffic.However,the bifurcation structure of the parallel confluence section of such tunnels poses significant challenges in the design and operation of the tunnel ventilation system,in terms of both the internal and external environment.In this work,the flow and loss characteristics of parallel confluence sections are studied with numerical simulations and model experiments.The influences of the confluence ratio q and the confluence angle O on the flow characteristics and loss mechanisms of the parallel confluence section are revealed theoretically.The results indicate that when q is small,the high-velocity airflow from the mainline entrains the low-speed airflow from the ramp,leading to flow separation at the upper connection between the parallel section and the gradual transition section;when q is large,the high-velocity airflow from the ramp entrains the low-speed airflow from the mainline,resulting in flow separation on the side of the confluence section adjacent to the mainline.Additionally,the mismatch between the airflow ratio Q and cross-sectional area ratio of the mainline tunnel and the ramp prior to confluence enhances the jet entrainment effect,increases the curvature of the streamline,expands the range of the flow separation area,and generates higher confluence loss coefficients|K_(13)|and|K_(23)|of the mainline and the ramp.For small q,|K_(13)|,and|K_(23)|,remain relatively constant with respect toθ,whereas for large q,both|K_(13)|and|K_(23)|decrease asθincreases.Finally,a semi-empirical formula is proposed to predict the loss coefficients for parallel bifurcated tunnels with confluence angles ranging from 5°to 15°.This study provides insights into the aerodynamic behaviour and loss mechanisms in bifurcated tunnels,offering guidelines for enhancing the efficiency of tunnel ventilation systems in tunnel-like underground infrastructure.展开更多
基金Quality Engineering Project of Higher Education Institutions in Anhui Province(2023aqnujyxm26,2023sx060,2023zyxwjxalk124)Natural Science Key Research Project for Higher Education Institutions of Anhui Province(2024AH051117,2024AH051126)+1 种基金Excellent Young Backbone Teachers’Domestic and Foreign Visiting and Training Program in Universities(gxgnfx20220262022)Research and Industrialization Project of High Precision Positioning System for Intelligent Connected Vehicles。
文摘This study focuses on the teaching reform of the communication application development course based on the core requirements of engineering education accreditation.To address key challenges such as the disconnection between software and hardware teaching and insufficient practical skills among students,a project-driven“learning-practiceapplication”teaching model is proposed.By optimizing course content,innovating teaching methods,and introducing university-industry collaboration mechanisms,the reform aligns the curriculum more closely with engineering education standards and industry demands.The approach significantly enhances students’comprehensive skills,practical abilities,and employability.This study provides theoretical foundations and practical strategies for the teaching reform of courses in communication engineering.
基金Project supported by the Science Challenge Project(Grant No.TZ2018004)the Natural Science Basic Research Program of Shaanxi Province,China(Grant No.2021JQ-697)+2 种基金the National Natural Science Foundation of China(Grant Nos.11874097,91961204,and 12004303)XinLiaoYingCai Project of Liaoning Province,China(Grant No.XLYC1905014)Key Research and Development Project of Liaoning Province,China(Grant No.2020JH2/10500003)。
文摘The GaN-based heterostructures are widely used in optoelectronic devices,but the complex surface reconstructions and lattice mismatch greatly limit the applications.The stacking of two-dimensional transition metal dichalcogenide(TMD=MoS_(2),MoSSe and MoSe_(2))monolayers on reconstructed GaN surface not only effectively overcomes the larger mismatch,but also brings about novel electronic and optical properties.By adopting the reconstructed GaN(0001)surface with adatoms(N-ter GaN and Ga-ter GaN),the influences of complicated surface conditions on the electronic properties of heterostructures have been investigated.The passivated N-ter and Ga-ter GaN surfaces push the mid-gap states to the valence bands,giving rise to small bandgaps in heterostructures.The charge transfer between Ga-ter GaN surface and TMD monolayers occurs much easier than that across the TMD/N-ter GaN interfaces,which induces stronger interfacial interaction and larger valence band offset(VBO).The band alignment can be switched between type-I and type-II by assembling different TMD monolayers,that is,MoS_(2)/N-ter GaN and MoS_(2)/Ga-ter GaN are type-II,and the others are type-I.The absorption of visible light is enhanced in all considered TMD/reconstructed GaN heterostructures.Additionally,MoSe_(2)/Ga-ter GaN and MoSSe/N-ter GaN have larger conductor band offset(CBO)of 1.32 eV and 1.29 eV,respectively,extending the range from deep ultraviolet to infrared regime.Our results revel that the TMD/reconstructed GaN heterostructures may be used for high-performance broadband photoelectronic devices.
基金Project supported by the National Natural Science Foundation of China(Grant No.51302215)the Natural Science Basic Research Program of Shaanxi Province,China(Grant Nos.2018JQ6084 and 2019JQ-860).
文摘The prospect ofα-Ga2O3 in optical and electrical devices application is fascinating.In order to obtain better performance,Ge and F elements with similar electronegativity and atomic size are selected as dopants.Based on density functional theory(DFT),we systematically research the electronic structure and optical properties of dopedα-Ga2O3 by GGA+U calculation method.The results show that Ge atoms and F atoms are effective n-type dopants.For Ge-dopedα-Ga2O3,it is probably obtained under O-poor conditions.However,for F-dopedα-Ga2O3,it is probably obtained under O-rich conditions.The doping system of F element is more stable due to the lower formation energy.In this investigation,it is found that two kinds of doping can reduce theα-Ga2O3 band gap and improve the conductivity.What is more,it is observed that the absorption edge after doping has a blue shift and causes certain absorption effect on the visible region.Through the whole scale of comparison,Ge doping is more suitable for the application of transmittance materials,yet F doping is more appropriate for the application of deep ultraviolet devices.We expect that our research can provide guidance and reference for preparation ofα-Ga2O3 thin films and photoelectric devices.
基金Supported by "973" National Key Basic Research Program ( No. 2002CB311905).
文摘Based on the region model of lambda bipolar transistor ( LBT), a dividing region theory model of PLBT is set up,simulated and verified. Firstly, the principal operations of different kinds of photoelectronic lambda bipolar transistor ( PLBT) are characterized by a simple circuit model. Through mathematical analysis of the equivalent circuit, the typical characteristics curve is divided into positive resistance, peak, negative resistance and cutoff regions. Secondly, by analyzing and simulating this model, the ratio of MOSFET width to channel length, threshold voltage and common emitter gain are discovered as the main structure parameters that determine the characteristic curves of PLBT. And peak region width, peak current value, negative resistance value and valley voltage value of PLBT can be changed conveniently according to the actual demands by modifying these parameters. Finally comparisons of the characteristics of the fabricated devices and the simu- lation results are made, which show that the analytical results are in agreement with the observed devices characteristics.
基金We acknowledge support from the Guangdong Basic and Applied Basic Research Foundation(No.2021A1515110980)the National Natural Science Foundation of China(Nos.51991343,51991340,52188101,and 52102179)+3 种基金the National Science Fund for Distinguished Young Scholars(No.52125309)Guangdong Innovative and Entrepreneurial Research Team Program(No.2017ZT07C341)the Bureau of Industry and Information Technology of Shenzhen for the“2017 Graphene Manufacturing Innovation Center Project”(No.201901171523)the Shenzhen Basic Research Program(No.JCYJ20200109144616617)。
文摘Two-dimensional(2D)materials offer novel platforms to meet the increasing demands of next-generation miniaturized electronics.Among them,the recently emerged 2D Bi_(2)O_(2)Se with unique non-van der Waals interlayer interaction,high mobility,sizeable bandgap,and capability to fabricate homologous heterojunction,is of particular interest.In this Review,we introduce recent progress in preparation,transfer,mechanical and electrical properties,and electronic applications of 2D Bi_(2)O_(2)Se.First,we summarize methodologies to synthesize and massively produce 2D Bi_(2)O_(2)Se,as well as recent advances in transferring them from growth substrate to arbitrary substrates.Then,we review current understandings on the intrinsic mechanical properties of Bi_(2)O_(2)Se at 2D thickness limit,and its in-plane and out-of-plane electrical properties.Electronic devices including field-effect transistors,memristors,and sensors based on 2D Bi_(2)O_(2)Se for neuromorphic computing,memory,logic,and integrated circuits are discussed.Finally,challenges and prospects for the development of 2D Bi_(2)O_(2)Se are proposed.
基金supported by the National Natural Science Foundation of China (No.6210031560)the Natural Science Foundation of Hebei Province (No.A2020202013)the Natural Science Foundation of Tianjin City (No.21JCQNJC00780)。
文摘The fiber optic sensing technology provides data support in structural health monitoring of the macro facilities,including design,construction,and maintenance of bridges,tunnels,ports and other infrastructures.In this paper,a distributed vibration sensing system is proved to be responsive to a single touch over a 1.8-m-long equivalent fiber segment,covering a vibration frequency from 5 Hz to 25 kHz.The sensing fiber was arranged as an S type layout on the bridge to recognize the standing state,windblown disturbance,and walking vibration.Moreover,the knocking and climbing events are recognized fiber laying spinning lines and hanging on the fences,respectively.The demonstration shows an accurate positioning and sensitive vibration monitoring applied on the automated three-dimensional(3D) printed bridge,which is applicable to all kinds of 3D printed facilities as intelligent sensory neuro-networks.
基金Dirección de Investigación of Universidad Peruana de Ciencias Aplicadas,Lima,Peru,for funding(No.UPC-DExpost-2021)and logistical support.
文摘This work proposes a computational algorithm to improve the determination of the timing of the respiratory phases.The algorithm was developed using a database of breathing sound signals acquired through properly positioned face masks and electret microphones.Most of the proposed works use the frequency domain and decimation in time to detect the respiratory period and phases,as well as some specific pathology.In this work the processing applied is only in time without applying decimation,thus improving the detection of a greater number of respiratory periods.The segmentation is very important since it allows the isolation of phases of the signal to later detect some pathology or to estimate the volume of inspired and exhaled air.The proposed algorithm involves the extraction of signal envelopes with the use of high selectivity filters without decimation and adaptive normalization processes that aim to achieve an adequate detection.In the validation process,the algorithm detection results were compared with the timing of respiratory periods and phases marked by visual inspection.The results show a maximum error of 4.36%for the respiratory period and 3.23%and 3.09%for the expiration and inspiration times,respectively.
基金supported by the Key Research and Development Program of Shaanxi Province-International Science and Technology Cooperation Program Project (No.2020KW-001)the Contract for Xi'an Municipal Science and Technology Plan Project-Xi'an City Strong Foundation Innovation Plan (No.21XJZZ0074)the Key Project of Graduate Student Innovation Fund at Xi'an University of Posts and Telecommunications (No.CXJJZL2023013)。
文摘The detection of surface defects in concrete bridges using deep learning is of significant importance for reducing operational risks,saving maintenance costs,and driving the intelligent transformation of bridge defect detection.In contrast to the subjective and inefficient manual visual inspection,deep learning-based algorithms for concrete defect detection exhibit remarkable advantages,emerging as a focal point in recent research.This paper comprehensively analyzes the research progress of deep learning algorithms in the field of surface defect detection in concrete bridges in recent years.It introduces the early detection methods for surface defects in concrete bridges and the development of deep learning.Subsequently,it provides an overview of deep learning-based concrete bridge surface defect detection research from three aspects:image classification,object detection,and semantic segmentation.The paper summarizes the strengths and weaknesses of existing methods and the challenges they face.Additionally,it analyzes and prospects the development trends of surface defect detection in concrete bridges.
基金supported by the National Natural Science Foundation of China(Nos.62276210,82201148 and 62376215)the Key Research and Development Project of Shaanxi Province(No.2025CY-YBXM-044)+3 种基金the Natural Science Foundation of Zhejiang Province(No.LQ22H120002)the Medical Health Science and Technology Project of Zhejiang Province(Nos.2022RC069 and 2023KY1140)the Natural Science Foundation of Ningbo(No.2023J390)the Ningbo Top Medical and Health Research Program(No.2023030716).
文摘This paper proposes a novel method for the automatic diagnosis of keratitis using feature vector quantization and self-attention mechanisms(ADK_FVQSAM).First,high-level features are extracted using the DenseNet121 backbone network,followed by adaptive average pooling to scale the features to a fixed length.Subsequently,product quantization with residuals(PQR)is applied to convert continuous feature vectors into discrete features representations,preserving essential information insensitive to image quality variations.The quantized and original features are concatenated and fed into a self-attention mechanism to capture keratitis-related features.Finally,these enhanced features are classified through a fully connected layer.Experiments on clinical low-quality(LQ)images show that ADK_FVQSAM achieves accuracies of 87.7%,81.9%,and 89.3% for keratitis,other corneal abnormalities,and normal corneas,respectively.Compared to DenseNet121,Swin transformer,and InceptionResNet,ADK_FVQSAM improves average accuracy by 3.1%,11.3%,and 15.3%,respectively.These results demonstrate that ADK_FVQSAM significantly enhances the recognition performance of keratitis based on LQ slit-lamp images,offering a practical approach for clinical application.
文摘The rapid evolution of Fifth-Generation(5G)networks and the strategic development of Sixth-Generation(6G)technologies have significantly advanced the implementation of air-ground integrated networks with seamless coverage.Unmanned Aerial Vehicles(UAVs),serving as high-mobility aerial platforms,are extensively utilized to enhance coverage in long-distance emergency communication scenarios.The resource-constrained communication environments in emergencies by classifying UAVs into swarm UAVs and relay UAVs as aerial communication nodes is inversitgated.A horizontal deployment strategy for swarm UAVs is formulated through K-means clustering algorithm optimization,while a vertical deployment scheme is established using convex optimization methods.The minimum-path trajectory planning for relay UAVs is optimized via the Particle Swarm Optimization(PSO)algorithm,enhancing communication reliability between UAV swarms and terrestrial base stations.A three-dimensional heterogeneous network architecture is realized by modeling spatial multi-hop relay links.Experimental results demonstrate that the proposed joint UAV relay optimization framework outperforms conventional algorithms in both coverage performance and relay capability during video stream transmission,achieving significant improvements in coverage enhancement and relay efficiency.This work provides technical foundations for constructing high-reliability air-ground cooperative systems in emergency communications.
基金supported by the Shandong Province Higher Education Young Innovative Talents Cultivation Programme Project:TJY2114Jinan City-School Integration Development Strategy Project:JNSX2023015the Natural Science Foundation of Shandong Province:ZR2021M F074.
文摘Traffic datasets exhibit complex spatiotemporal characteristics,including significant fluctuations in traffic volume and intricate periodical patterns,which pose substantial challenges for the accurate forecasting and effective management of traffic conditions.Traditional forecasting models often struggle to adequately capture these complexities,leading to suboptimal predictive performance.While neural networks excel at modeling intricate and nonlinear data structures,they are also highly susceptible to overfitting,resulting in inefficient use of computational resources and decreased model generalization.This paper introduces a novel heuristic feature extraction method that synergistically combines the strengths of non-neural network algorithms with neural networks to enhance the identification and representation of relevant features from traffic data.We begin by evaluating the significance of various temporal characteristics using three distinct assessment strategies grounded in non-neural methodologies.These evaluated features are then aggregated through a weighted fusion mechanism to create heuristic features,which are subsequently integrated into neural network models for more accurate and robust traffic prediction.Experimental results derived from four real-world datasets,collected from diverse urban environments,show that the proposed method significantly improves the accuracy of long-term traffic forecasting without compromising performance.Additionally,the approach helps streamline neural network architectures,leading to a considerable reduction in computational overhead.By addressing both prediction accuracy and computational efficiency,this study not only presents an innovative and effective method for traffic condition forecasting but also offers valuable insights that can inform the future development of data-driven traffic management systems and transportation strategies.
文摘High-selectivity common-mode(CM)and differential-mode(DM)reflectionless balanced bandpass filters(BBPFs)are proposed in this article.By loading absorption networks at single/both ends of the basic ring resonator,input-/two-port wideband CM and DM reflectionless performance,wideband filtering performance and all-stop CM suppression are obtained.The absorption network composed of K-sections of coupled-lines(CLs)terminated with grounded resistors can not only extend the filtering performance to high order,but also realize wideband absorption of CM noise and out-of-band DM signals.Absorptive stubs are loaded at ports to increase the design flexibility and enhance the absorption.As for the input-reflectionless type,multiple independently controlled transmission zeros(TZs)are obtained by the TZ control network to improves the selectivity and out-of-band rejection.A set of 2 GHz micro-strip BBPFs are designed and measured,which shows simultaneous CM and DM absorption performance.
基金supported in part by the Beijing Natural Science Foundation No.JQ22011the National Science Foundation of China for Distinguished Young Scholars under Grant No.62325102+1 种基金the National Natural Science Foundation of China under Grant No.62031004the Fundamental Research Funds for the Central Universities No.2023YJS160.
文摘A wideband low-profile aperture-coupled antenna based on a novel dual-mode-composite scheme is presented.The mode-composite scheme where the TM10 cavity mode and the TE121 dielec-tric resonator(DR)mode are combined offers an ap-proach to obtain a wide bandwidth accompanied by stable unidirectional radiation and high efficiency.The use of a lengthened coupling aperture that supports the one-wavelength resonance in the band of interest is an effective feed method of simultaneously excit-ing the two composite modes without compromising the increased complexity of the antenna geometry.An impedance bandwidth of 49%for|S_(11)|of less than-10 dB,a maximum gain of 10.8 dBi,and stable radiation patterns with low cross-polarization are realized ex-perimentally by a fabricated prototype.Considering the simplicity of the geometry,the wide bandwidth that can cover n77,n78,and n79 bands for the fifth generation(5G)mobile communications and the sat-isfying radiation performance,the proposed antenna would be a promising candidate for advanced wireless applications.
基金Supported by the National Key R&D Program of China(No.2022ZD0119001)the National Natural Science Foundation of China(No.61834005)+1 种基金the Shaanxi Province Key R&D Plan(No.2022GY-027,2021GY-029)the Key Scientific Research Project of Shaanxi Department of Education(No.22JY060).
文摘Graph computing has become pervasive in many applications due to its capacity to represent complex relationships among different objects in the big data era.However,general-purpose architectures are computationally inefficient for graph algorithms,and dedicated architectures can provide high efficiency,but lack flexibility.To address these challenges,this paper proposes ParaGraph,a reduced instruction set computing-five(RISC-V)-based software-hardware co-designed graph computing accelerator that can process graph algorithms in parallel,and also establishes a performance evaluation model to assess the efficiency of co-acceleration.ParaGraph handles parallel processing of typical graph algorithms on the hardware side,while performing overall functional control on the software side with custom designed instructions.ParaGraph is verified on the XCVU440 field-programmable gate array(FPGA)board with E203,a RISC-V processor.Compared with current mainstream graph computing accelerators,ParaGraph consumes 7.94%less block RAM(BRAM)resources than ThunderGP.Its power consumption is reduced by 86.90%,24.90%,and 76.38%compared with ThunderGP,HitGraph,and GraphS,respectively.The power efficiency of connected components(CC)and degree centrality(DC)algorithms is improved by an average of 6.50 times over ThunderGP,2.51 times over HitGraph,and 3.99 times over GraphS.The software-hardware co-design acceleration performance indicators H/W.Cap for CC and DC are 13.02 and 14.02,respectively.
文摘Fiber optic temperature sensors stand out in a variety of applications due to their small size,chemical resistance,and resistance to electromagnetic interference.The traditional optical fiber temperature sensor directly places the sensing structure in the temperature to be measured,and uses the thermo-optical effect and thermal expansion effect of the SiO_(2)material that constitutes the sensing structure to achieve measurement,while the thermo-optical coefficient and thermal expansion coefficient of SiO_(2) are very small,which limits the high sensitivity response characteristics of the optical fiber temperature sensing structure.In order to solve the problem of low sensitivity of traditional optical fiber temperature sensors,a Mach-Zehnder interferometric temperature sensor with a liquid-encapsulated tapered microfiber is developed.The sensor converts the temperature change into a change in the refractive index of the liquid material and thus realizes the measurement of temperature.In the range of 25~50℃,as the temperature increases,the wavelength of the transmission spectrum shifts towards shorter wavelengths.Experimental results show that the sensitivity of the liquid encapsulated microfiber interferometric temperature sensor can reach-57.91 nk·nm^(-1).This sensor has great potential for applications in marine environmental monitoring,biomedical diagnosis,and aerospace.
基金funded by the National Natural Science Foundation of China(Nos.51772003 and 51701001)the Excellent Research and Innovation Team Project of Anhui Province(No.2023AH010077)the Key Research and Development Projects in Anhui Province(No.202004b11020021).
文摘Developing highly efficient and recyclable photocatalysts has been regarded as an attractive strategy to solve antibiotic contaminants.Herein,we designed and fabricated Cy-C_(3) N_(4)/TiO_(2) S-scheme heterojunction film with boosted charge transfer and a highly hydrophilic surface.The as-prepared heterojunction exhibited outstanding removal efficiency on tetracyclines and fluoroquinolone antibiotics(more than 80% within 90 min).The removal rate of 300-Cy-C_(3) N_(4)/TiO_(2) on norfloxacin(NOR)was 2.12,and 1.59 times higher than that of pristine TiO_(2),C_(3) N_(4)/TiO_(2),respectively.The excellent photocatalytic performance of 300-Cy-C_(3) N_(4)/TiO_(2) was attributed to the highly hydrophilic surface and effective transfer and separation of carriers.Moreover,the NOR degradation pathways were proposed based on the results of density functional theory(DFT),and liquid chromatography-mass spectrometry.The toxicity assessment indicated the toxicity of intermediates can be remarkably alleviated.The DFT calculation and selective photo-deposition experiment demonstrated that an internal electric field was formed at the heterojunction interface,and the charge carriers migrated between Cy-C_(3) N_(4) and TiO_(2) following an S-scheme transfer pathway.This research not only provides a promising method for tracking charge distribution on thin-film heterojunction photocatalysts but also helps us to design high-efficiency,and recyclable heterojunctions to solve antibiotic contaminants.
基金supported by the National Research Foundation of Korea(NRF)grant funded by Ministry of Science,ICT(Nos.2018M3A7B4070990,2020R1A2C2103137,2020R1F1A1076359,and 2022R1C1C2011696)the Education(Nos.2020R1A2C2103137 and 2020R1F1A1076359)Materials,Components&Equipment Research Program funded by the Gyeonggi Province。
文摘Microalgae are one of the promising feedstocks for biorefinery,contributing significantly to net-zero emissions through carbon capture and utilization.However,the disposal of microalgal byproducts from the manufacturing process causes additional environmental pollution,thus,a new application strategy is required.In this study,the Tetraselmis suecica byproduct from the carotenoid extraction process was carbonized and converted into biochar.The converted biochar was proved to be nitrogen-doped biochar(NDB),up to 4.69%,with a specific surface area of 206.59m^(2)/g andwas used as an electrode for a supercapacitor.The NDB electrode(NDB-E)in half-cell showed a maximum specific capacitance of 191 F/g.In a full-cell test,the NDB-E exhibited a high energy density of 7.396 Wh/kg and a high-power density of 18,100 W/kg,and maintained specific capacity of 95.5%after charge and discharge of 10,000 cycles.In conclusion,our study demonstrated that the carotenoid-extracted microalgal byproducts are a useful resource for the supercapacitor production.This approach is the first to convert T.suecica into active materials for supercapacitors.
基金supported by the open research fund of Songshan Lake Materials Laboratory(No.2022SLABFN08)Guangxi Science and Technology Base and Talents Special Project(Nos.Guike AD20297034 and AD21220053)+2 种基金the National Natural Science Foundation of China(No.51801214 and 52171021)the Research Start-up Funding from Guangxi University of Science and Technology(No.03200150)the Middle-aged and Young Teachers’Basic Ability Promotion Project of Guangxi(No.2022KY0329)。
文摘In this study,a comprehensive analysis of microstructural features,morphology,crystal structures,and interface structures of long-period stacking ordered(LPSO)structures in a non-equilibrium Mg_(97)Zn_(1)Y_(16)Ca_(0.4)alloy cast in a steel mold was carried out.The addition of Ca element plays an important role in the refinement of LPSO structure.The result reveals new poly-types including 20H F2F2F4,60R(F2F3F3)_(3),and 66H F2F3F3F2(F6)_(4)featuring a 6-Mg structure,alongside the prevalent 18R and 14H LPSO structures.The incoherent interface between 20H and the Mg matrix is split into two dislocation arrays,leading to the formation of a segment of 60R_(1).Moreover,the superstructure 116L,designated as(F2)_(18)F4,is formed through the ordered distribution of F4 stacking faults in 18R.
基金Project supported by the National Natural Science Foundation of China(No.62102130)the Central Government Guides Local Science and Technology Development Fund Project of China(No.226Z0201G)+4 种基金the Natural Science Foundation of Hebei Province of China(Nos.F2020204003 and F2024204001)the Hebei Youth Talents Support Project of China(No.BJ2019008)the Science and Technology Research Projects of Higher Education Institutions in Hebei Province of China(No.QN2024138)the Basic Scientific Research Funds Research Project of Hebei Provincial Colleges and Universities of China(No.KY2022073)the Hebei Province Higher Education Institution Scientific Research Project of China(No.QN2025192)。
文摘The dung beetle optimizer(DBO)is a metaheuristic algorithm with fast convergence and powerful search capabilities,which has shown excellent performance in solving various optimization problems.However,it suffers from the problems of easily falling into local optimal solutions and poor convergence accuracy when dealing with large-scale complex optimization problems.Therefore,we propose an adaptive DBO(ADBO)based on an elastic annealing mechanism to address these issues.First,the convergence factor is adjusted in a nonlinear decreasing manner to balance the requirements of global exploration and local exploitation,thus improving the convergence speed and search quality.Second,a greedy difference optimization strategy is introduced to increase population diversity,improve the global search capability,and avoid premature convergence.Finally,the elastic annealing mechanism is used to perturb the randomly selected individuals,helping the algorithm escape local optima and thereby improve solution quality and algorithm stability.The experimental results on the CEC 2017 and CEC 2022 benchmark function sets and MCNC benchmark circuits verify the effectiveness,superiority,and universality of ADBO.
基金supported by the National Natural Science Foundation of China(Nos.52408439 and 52478422)the Natural Science Basic Research Program of Shaanxi(No.2023-JC-YB-378),China+3 种基金the Young Talent Fund of Xi'an Association for Science and Technology(No.0959202513050),Chinathe Fundamental Research Funds for the Zhejiang Provincial Universities(No.226-2024-00099),Chinathe Postdoctoral Fellowship Program of China Postdoctoral Science Foundation(No.GZC20241518)the Xi'an Shiyou University Graduate Student Innovation Fund Program(No.YCX2512041),China.
文摘The construction of bifurcated tunnels is essential to advancing urban infrastructure systems,as they conserve land,reduce carbon emissions,and optimize traffic.However,the bifurcation structure of the parallel confluence section of such tunnels poses significant challenges in the design and operation of the tunnel ventilation system,in terms of both the internal and external environment.In this work,the flow and loss characteristics of parallel confluence sections are studied with numerical simulations and model experiments.The influences of the confluence ratio q and the confluence angle O on the flow characteristics and loss mechanisms of the parallel confluence section are revealed theoretically.The results indicate that when q is small,the high-velocity airflow from the mainline entrains the low-speed airflow from the ramp,leading to flow separation at the upper connection between the parallel section and the gradual transition section;when q is large,the high-velocity airflow from the ramp entrains the low-speed airflow from the mainline,resulting in flow separation on the side of the confluence section adjacent to the mainline.Additionally,the mismatch between the airflow ratio Q and cross-sectional area ratio of the mainline tunnel and the ramp prior to confluence enhances the jet entrainment effect,increases the curvature of the streamline,expands the range of the flow separation area,and generates higher confluence loss coefficients|K_(13)|and|K_(23)|of the mainline and the ramp.For small q,|K_(13)|,and|K_(23)|,remain relatively constant with respect toθ,whereas for large q,both|K_(13)|and|K_(23)|decrease asθincreases.Finally,a semi-empirical formula is proposed to predict the loss coefficients for parallel bifurcated tunnels with confluence angles ranging from 5°to 15°.This study provides insights into the aerodynamic behaviour and loss mechanisms in bifurcated tunnels,offering guidelines for enhancing the efficiency of tunnel ventilation systems in tunnel-like underground infrastructure.
