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Study on impact factors of tracer gas method in investigations of gaseous pollutant transport and building ventilation

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Building Simulation 2023年第3期16卷 413-426页

作者： Naiping Gao Ruge Wang Yan Wu Zhu Wu School of Mechanical Engineering Tongji UniversityShanghai201804China Baoye group co.ltd Zhejiang312000China

Building ventilation is essential to discharge indoor pollutants and improve indoor air quality for occupant *** gas method is an efficient way in the field of building ventilation to measure ventilation rate and to evaluate the ventilation *** shows notable deviation of measured ventilation rate using different tracer *** the present study,CFD simulations are carried out to analyze He-,co_(2)-and SF_(6)-based tracer gas *** effects of tracer gas density and release rate on the concentration distribution and ventilation effectiveness are *** application scenarios of different ventilation rates and airflow distribution forms are *** results show that the deviation of ventilation effectiveness evaluated by different tracer gases can be above 2-4 times,and the error is introduced by non-passive *** tracer gas dispersion is passive or not depends on the relative importance of density difference driven mass transfer to forced convection mass transfer,which is due to the combined effects of density difference,release rate,and indoor airflow velocity,and can be judged by a dimensionless number θ.Under the geometry and ventilation settings in the present study,the critical value of θ is 1.0 for the error range of 5%,and 2.0 for the error range of 10%.When θ is below the critical value,the gas transport is passive and dominated by the indoor ventilation airflow.A release of tracer gas with smaller release rate and smaller density difference into a stronger indoor airflow behaves more *** tracer gas tends to significantly overestimate the performance of upper supply and lower exhaust ventilation,and lighter tracer gas aggravates the overestimation of the performance for lower supply and upper exhaust *** mechanical ventilation rooms with air change rate of 3.0-6.0 h^(−1),a continuous release of tracer gas SF_(6),co_(2) or He with release rate above 8 mg/s or source concentrati

关键词： building ventilation tracer gas method passive dispersion non-passive dispersion ventilation effectiveness

New method to identify optimal discontinuity set number of rock tunnel excavation face orientation based on Fisher mixed evaluation

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Underground Space 2024年第4期17卷 300-319页

作者： Keshen Zhang Wei Wu Min Zhang Yongsheng Liu Yong Huang Baolin Chen college of Civil Engineering Tongji UniversityShanghai 200092China Key Laboratory of Geotechnical and Underground Engineering of Ministry of Education Tongji UniversityShanghai 200092China State Key Laboratory of Disaster Reduction in Civil Engineering Tongji UniversityShanghai 200092China Shudao Investment group co.ltd Chengdu 610095China China Railway Tunnel group co.ltd Guangzhou 511466China China Railway First Survey and Design Institute group co.ltd Xi’an 710043China Zhejiang Institute of communications co.ltd Hangzhou 310012China

Discontinuity is critical for strength,deformability,and permeability of rock *** information is one of the essential discontinuity characteristics and is usually accessed by orientation *** methods of identifying optimal discontinuity set numbers are usually achieved by clustering validity indexes,which mainly relies on the aggregation and dispersion of clusters and leads to the inaccuracy and instability of *** paper proposes a new method of Fisher mixed evaluation(FME)to identify optimal group numbers of rock mass discontinuity *** FME,orientation distribution is regarded as the superposition of Fisher mixed *** grouping results are identified by considering the fitting accuracy of Fisher mixed distributions,the probability monopoly and central location significance of independent Fisher centers.A Halley-Expectation-Maximization(EM)algorithm is derived to achieve an automatic fitting of Fisher mixed *** real rock discontinuity models combined with three orientation clustering algorithms are adopted for discontinuity *** clustering validity indexes are used to automatically identify optimal group numbers for *** results show that FME is more accurate and robust than the other clustering validity indexes in optimal discontinuity group number identification for different rock models and orientation clustering algorithms.

关键词： Rock mass discontinuity Orientation grouping Fisher mixed distribution 3D point cloud Stereo photogrammetry

Research on anti-attack performance of a private cloud safety computer based on the Markov-Percopy dynamic heterogeneous redundancy structure

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Transportation Safety and Environment 2023年第4期5卷 107-116页

作者： Jiakun Wen Zhen Liu Huan Ding CRSC Research&Design Institute group co.ltd Beijing 100070China

With the increasing computing demand of train operation control systems,the application of cloud computing technology on safety computer platforms of train control system has become a research hotspot in recent *** to improve the safety and availability of private cloud safety computers is the key problem when applying cloud computing to train operation control *** the cloud computing platform is in an open network environment,it can face many security loopholes and malicious network ***,it is necessary to change the existing safety computer platform structure to improve the attack resistance of the private cloud safety computer platform,thereby enhancing its safety and ***,a private cloud safety computer platform architecture based on dynamic heterogeneous redundant(DHR)structure is proposed,and a dynamic migration mechanism for heterogeneous executives is ***,a generalized stochastic Petri net(GSPN)model of a private cloud safety computer platform based on DHR is established,and its steady-state probability is solved by using its isomorphism with the continuous-time Markov model(CTMC)to analyse the impact of different system structures and executive migration mechanisms on the system's anti-attack ***,through experimental verifcation,the system structure proposed in this paper can improve the anti-attack capability of the private cloud safety computer platform,thereby improving its safety and reliability.

关键词： Safety computer logical monitoring method continuous time Markov modelling,cloud computing anti-attack analysis

Piezoelectric sensing method for segmental joint contact stress during shield tunnel construction

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Underground Space 2024年第4期17卷 82-99页

作者： Guodong Jiang Minghao Dai Guozhu Zhang Limin Gao Institute of Geotechnical Engineering Southeast UniversityNanjing 211189China Nanjing Metro group co.ltd Nanjing 210000China No.4 construction company of China Petroleum Pipeline Engineering co.ltd Langfang 065000China

The emergence of curved shield tunnels poses a significant construction *** the quality of the segment assembly is not guaranteed,many segment cracks and damage will result from the stress *** the contact stresses between segmental joints is necessary to improve the quality of segments assembled for shield tunnel *** difluoride(PVDF)piezoelectric material was chosen for the sensor because it can convert contact stresses into electrical signals,allowing the state of the segmental joints to be effectively *** matches the working environment between the segmental joints of the shield tunnel,where flexible structures such as rubber gaskets and force transfer pads are *** study proposes a piezoelectric sensing method for segmental joints in shield tunnels and conducts laboratory tests,numerical analyses,and field tests to validate the feasibility of the *** results indicate that the PVDF film sensor can effectively sense the entire compression process of the gasket with different amounts of *** piezoelectric cable sensor can effectively sense the joint offset direction of the *** differently shaped sections,the variation in the force sensed by the piezoelectric cable sensors was different,as verified by numerical *** the field test,it was found that the average contact stress between the segmental joints was in the range of 1.2–1.8 MPa during construction of the curved shield *** location of the segmental joints and the type of segment affect the contact stress *** field monitoring results show that piezoelectric sensing technology can be successfully applied during assembly of the segments for effective sensing of the contact stress.

关键词： Shield tunnel Segmental joint contact stress Piezoelectric sensor

Extrusion process of 304L H-shaped stainless steel used in passive residual heat removal heat exchanger

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Nuclear Science and Techniques 2019年第4期30卷 70-79页

作者： Lei-Feng Tuo Gen-Shu Zhou Zhi-Qiang Yu Xi-Tang Kang Bo-Wen Wang State Key Laboratory for Mechanical Behavior of Materials Xi'an Jiaotong University Stainless Steel Tube Branch company Taiyuan Iron & Steel Group CO.LTD Stainless Steel Tube Branch company Taiyuan Iron & Steel (Group) CO.LTD

304L H-shaped stainless steel is used as the support frame of the passive residual heat removal heat exchanger(PRHR HX) in a nuclear fission reactor. The extrusion process is adopted to manufacture the 304L H-shaped stainless steel. Finite element method simulation is herein used to analyze metal flow characteristics, optimize the extrusion die, and predict the extrusion force at different temperatures and speeds. A Φ400-mm container and Φ388-mm forging billet are selected, and the 304L H-shaped stainless steel is successfully manufactured using a Germany SMS 60 MN horizontal extruder. The mechanical properties and microstructure of the manufactured 304L H-shaped stainless steel meet the requirements of the PRHR HX, and the surfaces of the product pass the dye penetration test. The H-shaped stainless steels are used in Haiyang nuclear power plant in Shandong Province.

关键词： PRHR HX Support frame Extrusion process 304L H-shaped stainless steel

Numerical simulation and experimental investigation of two filling methods in vertical centrifugal casting

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中国有色金属学会会刊：英文版 2006年第5期16卷 1035-1040页

作者：吴士平历长云郭景杰苏彦庆雷修桥傅恒志 School of Materials Science and Engineering Harbin Institute of Technology Foundry co.ltd First Automobile Group Corporation

A mathematical model of the centrifugal filling process was established. The calculated results show that the centrifugal field has an important influence on the filling process. Moreover, the process of liquid flow and the location of free surface in sprue were simulated based on the Solution Algorithm-Volume of Fraction (SOLA-VOF) technique. In order to verify the mathematical model and computational results, hydraulic simulation experiment was carried out. The results of experiments and numerical simulation indicate the accuracy of mathematical model. Two kinds of filling methods were investigated and the results show that the bottom filling is better than the top filling that can achieve stable filling and reduce defects.

关键词：钛合金立式离心铸造水力模拟数值模拟炉顶加料底部加料

Study on enhanced filtration for the 2-methylisoborneol removal in drinking water treatment processes

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Journal of Harbin Institute of Technology(New Series) 2010年第6期17卷 812-818页

作者：郜玉楠李伟光白宇刘水 School of Municipal and Environmental Engineering Harbin Institute of Technology Beijing Drainage group co.ltd

Pilot plant studies on 2-methylisoborneol(2-MIB)removal in drinking water by biological activated carbon-sand filter(BACSF)were conducted in this *** biological activated carbon was chosen from a BAC filter of an advanced treatment plant which has operated for 1 *** results showed that the BACSF worked effectively when high concentrations of MIB in raw water especially in summer *** of the MIB was removed within 450 mm of the top packed media and the removal rate was 75.24%.The biomass on the surface of activated carbon increased to 103 nmolP/g carbon in *** addition to MIB,turbidity,UV254 and DOC consumption value are also effectively removed by *** micro flocculation in combination with BACSF enhanced filtration test provided the evidence that the micro-flocculation made the contaminant in water forming the colloidal matter and it improved the BACSF removal ability of *** optimum PACl dosage was 0.2 mg/L and the PACl contact time was 2-4 min.

关键词： biological activated carbon(BAC) granular activated carbon(GAC) enhanced filtration 2-methylisoborneol(MIB) micro flocculation

Optimal Energy Efficiency Based High-speed Flying control Method for Hydraulic Quadruped Robot

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Journal of Bionic Engineering 2024年第3期21卷 1156-1173页

作者： Qingjun Yang Zhenyang Zhang Rui Zhu Dianxin Wang School of Mechatronics Engineering Harbin Institute of TechnologyHarbin150000China Nanjing Chenguang group co.ltd Nanjing210006China

Herein,a control method based on the optimal energy efficiency of a hydraulic quadruped robot was proposed,which not only realizes the optimal energy efficiency of flying trot gait but also ensures the stability of high-speed ***,the energy consumption per unit distance was adopted as the energy efficiency evaluation index based on the constant pressure oil supply characteristics of the hydraulic system,and the global optimization algorithm was adopted to solve the optimal ***,the gait parameters that affect the energy efficiency of quadruped were analyzed and the mapping relationship between each parameter and energy efficiency was captured,so as to select the optimum combination of energy efficiency parameters,which is significant to improve endurance ***,to ensure the stability of the high-speed flying trot gait motion of the hydraulic quadruped robot,the active compliance control strategy was ***,the proposed method was successfully verified by simulations and *** experimental results reveal that the flying trot gait of the hydraulic quadruped robot can be stably controlled at a speed of 2.2 m/s.

关键词： Hydraulic quadruped robot Flying trot Energy efficiency Active compliance control

Bolt insertion damage and mechanical behaviors investigation of CFRP/CFRP interference fit bolted joints

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Chinese Journal of Aeronautics 2022年第9期35卷 354-365页

作者： Yangjie ZUO Ting YUE Ruisong JIANG Zengqiang CAO Liu YANG School of Aeronautics and Astronautics Sichuan UniversityChengdu 610065China Xi’an Space Engine co.ltd Xi'an 710100China School of Mechanical Engineering Northwestern Polytechnical UniversityXi'an 710072China Xi’an ASN Technology group co.ltd Xi'an 710072China

Interference fit has advantages in improving fatigue behaviors of composite bolted joints,however, interference fit bolt insertion tends to cause damages in laminates weakening joint mechanical properties. Therefore, an experimental study was conducted to investigate bolt insertion damages of Carbon Fiber Reinforced Polymer(CFRP)/CFRP interference fit bolted *** behaviors of joints were also evaluated experimentally under both quasi-static loads and cyclic loads. Scanning Electron Microscope(SEM) and high-resolution X-ray micro-CT scan were used to examine micro damages in laminates. Damage and failure behaviors of joints were characterized. The results demonstrated that the hole entrance in upper laminate and the laminate boundary near the hole wall were the most critical regions for damages during bolt insertions. However, the influence of those damages on quasi-static failure loads and fatigue failure modes of joints was minimal. Delamination and matrix cracking occurred first in laminates following fiber and matrix fracture in quasi-static tensile tests. Interference fit could improve the fatigue resistance of the laminate hole, however, the bolt seemed to suffer a more critical local fatigue loading *** paper can contribute to composite structure designs, especially in understanding damage and failure behaviors of composite bolted joints.

关键词： Bolted joints composite Damage Failure Fatigue life Interference fit