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A semantic segmentation-based underwater acoustic image transmission framework for cooperative SLAM

Defence Technology（防务技术） 2024年第3期33卷 339-351页

作者： Jiaxu Li Guangyao Han Shuai Chang Xiaomei Fu School of Marine Science and Technology Tianjin UniversityTianjin 300072China

With the development of underwater sonar detection technology,simultaneous localization and mapping(SLAM)approach has attracted much attention in underwater navigation field in recent *** the weak detection ability of a single vehicle limits the SLAM performance in wide ***,cooperative SLAM using multiple vehicles has become an important research *** key factor of cooperative SLAM is timely and efficient sonar image transmission among underwater ***,the limited bandwidth of underwater acoustic channels contradicts a large amount of sonar image *** is essential to compress the images before ***,deep neural networks have great value in image compression by virtue of the powerful learning ability of neural networks,but the existing sonar image compression methods based on neural network usually focus on the pixel-level information without the semantic-level *** this paper,we propose a novel underwater acoustic transmission scheme called UAT-SSIC that includes semantic segmentation-based sonar image compression(SSIC)framework and the joint source-channel codec,to improve the accuracy of the semantic information of the reconstructed sonar image at the *** SSIC framework consists of Auto-Encoder structure-based sonar image compression network,which is measured by a semantic segmentation network's *** that sonar images have the characteristics of blurred target edges,the semantic segmentation network used a special dilated convolution neural network(DiCNN)to enhance segmentation accuracy by expanding the range of receptive *** joint source-channel codec with unequal error protection is proposed that adjusts the power level of the transmitted data,which deal with sonar image transmission error caused by the serious underwater acoustic *** results demonstrate that our method preserves more semantic information,with advantages over existing methods at the sa

关键词： Semantic segmentation Sonar image transmission Learning-based compression

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Optimal synthesis of heat-integrated distillation configurations using the two-column superstructure

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Chinese Journal of Chemical Engineering 2024年第2期66卷 238-249页

作者： Xiaodong Zhang Lu Jin Jinsheng Sun School of Chemical Engineering and Technology Tianjin UniversityTianjin 300072China

In the realm of the synthesis of heat-integrated distillation configurations,the conventional approach for exploring more heat integration possibilities typically entails the splitting of a single column into a twocolumn ***,this approach frequently necessitates tedious enumeration procedures,resulting in a considerable computational *** surmount this formidable challenge,the present study introduces an innovative remedy:The proposition of a superstructure that encompasses both single-column and multiple two-column ***,a simultaneous optimization algorithm is applied to optimize both the process parameters and heat integration structures of the twocolumn *** effectiveness of this approach is demonstrated through a case study focusing on industrial organosilicon *** results underscore that the superstructure methodology not only substantially mitigates computational time compared to exhaustive enumeration but also furnishes solutions that exhibit comparable performance.

关键词： Superstructure Process synthesis Heat integration Simulation-based optimization Industrial organosilicon separation

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Optical manipulation of ratio-designable Janus microspheres

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Photonics Research 2024年第6期12卷 1239-1249页

作者： YULU CHEN CONG ZHAI XIAOQING GAO HAN WANG ZUZENG LIN XIAOWEI ZHOU CHUNGUANG HU State Key Laboratory of Precision Measuring Technology and Instruments Tianjin UniversityTianjin 300072China

Angular optical trapping based on Janus microspheres has been proven to be a novel method to achieve controllable *** contrast to natural birefringent crystals,Janus microspheres are chemically synthesized of two compositions with different refractive ***,their structures can be artificially regulated,which brings excellent potential for fine and multi-degree-of-freedom manipulation in the optical ***,it is a considerable challenge to model the interaction of heterogeneous particles with the optical field,and there has also been no experimental study on the optical manipulation of microspheres with such designable refractive index *** the specific structure affects the kinematic properties of Janus microspheres remains ***,we report systematic research on the optical trapping and rotating of various ratio-designable Janus *** employ an efficient T-matrix method to rapidly calculate the optical force and torque on Janus microspheres to obtain their trapped postures and rotational characteristics in the optical *** have developed a robust microfluidic-based scheme to prepare Janus *** experimental results demonstrate that within a specific ratio range,the rotation radii of microspheres vary linearly and the orientations of microsphere are always aligned with the light polarization *** is of great importance in guiding the design of Janus *** their orientations flip at a particular ratio,all consistent with the *** work provides a reliable theoretical analysis and experimental strategy for studying the interaction of heterogeneous particles with the optical field and further expands the diverse manipulation capabilities of optical tweezers.

关键词： polarization ratio refractive

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Research progress on simulation of multiscale mass transfer processes in gas-solid system by computational mass transfer

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Particuology 2024年第7期90卷 478-492页

作者： Xu Li Yaohui Wang Leifu Li Runye Zhang Hailun Ren Wenbin Li Zhongli Tang Donghui Zhang The Research Center of Chemical Engineering School of Chemical Engineering and TechnologyTianjin UniversityTianjin 300072China The Department of Chemical Engineering Tianjin Renai CollegeTianjin 301636China Collaborative Innovation Center of Chemical Science and Engineering(tianjin) School of Chemical Engineering and TechnologyTianjin UniversityTianjin 300072China

Particle-fluid system is one of the most popular systems in chemical *** to complex interface structure and high-velocity turbulence,the momentum and mass transfer exhibit nonlinear characteristics,which pose a great challenge for further study and *** solve this problem,computational mass transfer(CMT)emerged and has been proved to be effective in deeply exploring the mass transfer behavior of particle-fluid ***,this paper reviews recent gas-solid numerical studies of turbulence issues from empirical to theoretical,then discusses interphase mass transfer rate models and the interfacial interaction ***,the present study particularly reviews researches on mass transfer process of fixed and fluidized regime by CMT,providing reliable analysis of turbulent anisotropy diffusivity as well as multiscale structure and presenting theoretical instruction for the industrial optimization of mass transfer processes in chemical engineering.

关键词： Fixed bed Fluidized bed Computational mass transfer Turbulent mass diffusion Multiscale Anisotropy

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Enhanced picosecond terahertz wave generation based on cascade effects in a terahertz parametric generator

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Chinese Physics B 2024年第8期33卷 271-275页

作者：张敬喜王与烨徐炳烽陈锴刘紫鲲马鸿儒徐德刚姚建铨 School of Precision Instruments and Optoelectronics Engineering Tianjin UniversityTianjin 300072China Key Laboratory of Optoelectronic Information Technology(Ministry of Education) Tianjin UniversityTianjin 300072China

Enhanced terahertz wave generation via a Stokes cascade process has been demonstrated using picosecond pulse pumped terahertz parametric generation at 1 kHz repetition *** cascade saturation of terahertz output was observed,and the corresponding cascade-Stokes spectra were *** maximum terahertz wave average power was 22μW under a pump power of 30 W,whereas the maximum power conversion efficiency was 8×10^(-7)under a pump power of 21 *** THz power fluctuation was measured to be about 1%in 20 *** THz parametric source with a relatively stable output is suitable for a variety of practical applications.

关键词： terahertz parametric generation stimulated polariton cascade effect CLN crystal

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Elucidation of the last steps of photo-ammonification:analytical method development and mechanism elucidation

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Frontiers of Environmental Science & Engineering 2024年第8期18卷 101-106页

作者： Yingjing Miao Hui Wang Chunpeng Yang Ruochun Zhang Hao Zhang Peizhe Sun School of Environmental Science and Engineering Tianjin UniversityTianjin 300072China SINOPEC Research Institute of Petroleum Processing Co. Ltd.Beijing 100083China School of Earth System Science Tianjin UniversityTianjin 300072China

The mechanisms underlying the photo-ammonification of nitrogenous organic compounds(NOCs)remain unclear,partly due to the analytical challenges of small NOC *** study introduced a simple methodology for accurately and simultaneously quantifying multiple small NOCs during ammonification *** developed method employed phenyl isothiocyanate as derivatization reagents,followed by high-performance liquid chromatography analysis to measure primary and secondary amines,amides,as well as NH4+over variable photo-ammonification *** our experimental setup,vacuum ultraviolet(VUV)irradiation serves as the controlled reaction environment to simulate harsh photo-ammonification *** NOCs,including pyridine,N,N-dimethylformamide,and acrylonitrile,were chosen due to their structural diversity and environmental relevance as model *** method was able to achieve excellent nitrogen mass balance,and revealed that the last steps of photo-ammonification involved oxidation of nitrogen-adjacent carbon to amide followed by the cleavage of N-C *** novel method may also help quantitative investigation of nitrogen transformations in different environmental contexts.

关键词： Ammonification NOCs Amines Nitrogen mass balance

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Effective Activation of Melamine for Synchronous Synthesis of Catalytically Active Nanosheets and Fluorescence-Responsive Quantum Dots

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Transactions of tianjin University 2024年第3期30卷 284-296页

作者： Jie Xuan Guijian Guan Ming-Yong Han Institute of Molecular Plus Tianjin UniversityTianjin 300072China

Because of the low reactivity of cyclic nitrides,liquid-phase synthesis of carbon nitride introduces challenges despite its favorable potential for energy-efficient preparation and superior *** this study,we demonstrate a strong interaction between citric acid and melamine through experimental observation and theoretical simulation,which eff ectively activates melamine-condensation activity and produces carbon-rich carbon nitride nanosheets(CCN NSs)during hydrothermal *** a large specific surface area and increased light absorption,these CCN NSs demonstrate significantly enhanced photocatalytic activity in CO_(2) reduction,increasing the CO production rate by approximately tenfold compared with hexagonal melamine(h-Me).Moreover,the product selectivity of CCN NSs reaches up to 93.5%to generate CO from CO_(2).Furthermore,the annealed CCN NSs exhibit a CO conversion rate of up to 95.30μmol/(g h),which indicates an 18-fold increase compared with traditional carbon *** the CCN NS synthesis,nitrogen-doped carbon quantum dots(NDC QDs)are simultaneously produced and remain suspended in the supernatant after *** QDs disperse well in water and exhibit excellent luminescent properties(QY=67.2%),allowing their application in the design of selective and sensitive sensors to detect pollutants such as pesticide 2,4-dichlorophenol with a detection limit of as low as 0.04μmol/***,the simultaneous synthesis of CCN NSs and NDC QDs provides a cost-eff ective and highly efficient process,yielding products with superior capabilities for catalytic conversion of CO_(2) and pollutant detection,respectively.

关键词： Carbon nitride Hydrothermal reaction Photocatalysis Carbon dioxide Quantum dots

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High adsorption selectivity of activated carbon and carbon molecular sieve boosting CO_(2)/N_(2) and CH_(4)/N_(2) separation

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Chinese Journal of Chemical Engineering 2024年第3期67卷 282-297页

作者： Siang Chen Wenling Wu Zhaoyang Niu Deqi Kong Wenbin Li Zhongli Tang Donghui Zhang The Research Center of Chemical Engineering School of Chemical Engineering and TechnologyTianjin UniversityTianjin 300072China

Flue gas and coal bed methane are two important sources of greenhouse *** swing adsorption process has a wide range of application in the field of gas separation,and the selection of adsorbent is *** this regard,in order to assess the better adsorbent for separating CO_(2) from flue gas and CH_(4) from coal bed methane,adsorption isotherms of CO_(2),CH_(4) and N_(2) on activated carbon and carbon molecular sieve are measured at 303.15,318.15 and 333.15 K,and up to 250 *** experimental data fit better with Langmuir 2 compared to Langmuir 3 and Langmuir-Freundlich models,and Clausius-Clapeyron equation was used to calculate the isosteric *** the order of the adsorbed amount and the adsorption heat on the two adsorbents are CO_(2)>CH_(4)>N_(2).The adsorption kinetics are calculated by the pseudo-first kinetic model,and the order of adsorption rates on activated carbon is N_(2)-CH_(4)>CO_(2),while on carbon molecular sieve,it is CO_(2)-N_(2)>CH_(4).It is shown that relative molecular mass and adsorption heat are the primary effect on kinetics for activated carbon,while kinetic diameter is the main resistance factor for carbon molecular ***,the adsorption selectivity of CH_(4)/N_(2) and CO_(2)/N_(2) were estimated with the ideal adsorption solution theory,and carbon molecular sieve performed best at 318.15 K for both CO_(2) and CH_(4) *** study suggested that activated carbon is a better choice for separating flue gas and carbon molecular sieve can be a strong candidate for separating coal bed methane.

关键词： Activated carbon Carbon molecular sieve Adsorbent evaluation Adsorption equilibrium and kinetics Heat of adsorption Selectivity

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Experimental Study on Towing Characteristics of Composite Bucket Wellhead Platform

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China Ocean Engineering 2024年第3期38卷 531-542页

作者： ZHANG Pu-yang LIU Ying-fei LE Cong-huan DING Hong-yan BAI Yu State Key Laboratory of Hydraulic Engineering Intelligent Construction and Operation Tianjin UniversityTianjin 300072China

With the rapid development of large-scale development of marginal oilfields in China,simple wellhead platforms that are simple in structure and easy to install have become an inevitable choice in the process of oilfield ***,traditional simple wellhead platforms are often discarded after a single *** pursuit of a more costeffective approach to developing marginal oilfields,this paper proposes a new offshore oil field development facility—an integrated bucket foundation for wellhead *** verify the safety of its towing behavior and obtain the dynamic response characteristics of the structure,this paper takes a bucket integrated bucket foundation for wellhead platform with a diameter of 40 m as the research *** combining physical model tests and numerical simulations,it analyzes the static stability and dynamic response characteristics of the structure during towing,complete with the effects of the draft,wave height,wave period,and towing point height,which produce the dynamic responses of the structure under different influence factors,such as roll angle,pitch angle,heave acceleration and towing force as well as the sensibility to transport *** results show that the integrated bucket foundation for wellhead platform is capable of self-floating towing,and its movement is affected by the local environment,which will provide a reference for actual projects.

关键词： composite bucket foundation wellhead platform air flotation towing model test

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Control of Virtual Synchronous Generator for Frequency Regulation Using a Coordinated Self-adaptive Method

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CSEE Journal of Power and Energy Systems 2024年第1期10卷 175-184页

作者： Hongwei Fang Zhiwei Yu School of Electrical and Information Engineering and Key Laboratory of tianjin Electric Power System Simulation and Control Tianjin UniversityTianjin 300072China

Power inverter adopting virtual synchronous generator(VSG)control can provide inertia support for distributed generation ***,it cannot take into account the dynamic regulation characteristics of ***,when the system encounters a sudden change in load or disturbance,the dynamic process of frequency regulation will be greatly *** view of this issue,an improved VSG control strategy based on a coordinated self-adaptive(CSA)method is *** time domain analysis method is used to study the influences of virtual inertia and damping parameter perturbation on the system steady and dynamic ***,in order to make the control strategy suitable for large load changes and suppress frequency variations beyond the limit,the secondary frequency modulation is introduced into the control *** the coordinated adaptive control of virtual inertia,virtual damping and frequency modulation,the dynamic performance of vSG frequency regulation can be obviously *** and experiment results have verified the effectiveness of the proposed CSA control strategy.

关键词： Coordinated self-adaptive method frequency regulation time domain analysis virtual synchronous generator

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