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THE EFFECT OF RECLAMATION IN AREAS BETWEEN ISLANDS IN A COMPLEX TIDAL ESTUARY ON THE HYDRODYNAMIC SEDIMENT ENVIRONMENT

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Journal of Hydrodynamics 2010年第3期22卷 338-350页

作者： LI meng-guo Key Laboratory of Engineering Sediment of Ministry of Transport Tianjin Research Institute of Water Transport Engineering Tianjin 300456 China

The Oujiang Estuary is a very complex tidal estuary with many islands, which is located in Zhejiang Province, China. Reclamation of areas between islands will create a great amount of land. In this article, the feasibility of reclamation of areas between Lingkun Island and Niyu is studied from the angle of its impacts on the hydrodynamic sediment environment. First, the natural hydrodynamic and sediment conditions and the seabed evolution are analyzed according to in-situ data. Second, numerical models of tidal current and sediment movement under the combined action of wave and current are set up with irregular triangular grid to carry out numerical simulations. The following conclusions are drawn from the study. （1） The areas between Linkun Island and Niyu are not a tidal passage. Wenzhou Shoal has been aggraded gradually, a condition favorable for reclamation. （2） The reclamation is feasible as far as its effect on surrounding hydrodynamic sediment environment is concerned. （3） The reclamation has great favorable socio-economic impacts.

关键词： the Oujiang Estuary tidal current numerical model numerical simulation Wenzhou Shoal reclamation

Influence of Charging Oil Condition on Torque Converter Cavitation Characteristics

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Chinese Journal of Mechanical Engineering 2022年第3期35卷 236-249页

作者： Cheng Liu meng guo Qingdong Yan Wei Wei School of Mechanical Engineering Beijing Institute of TechnologyBeijing 100081China Chongqing Innovation Center Beijing Institute of TechnologyChongqing 401122China Advanced Technology Research Institute Beijing Institute of TechnologyJinan 250307China

Cavitation inside a torque converter induces noise,vibration and even failure,and these effects have been disregarded in previous torque converter design ***,modern torque converter applications require attention to this issue because of its high-speed and high-capacity ***,this study investigated the cavitation effect on a torque converter using both numerical and experimental methods with an emphasis on the influence of the charging oil feed location and charge *** fluid dynamics(CFD)models were established to simulate the transient cavitation behaviour in the torque converter using different charging oil pressures and inlet arrangements and testing against a base case to validate the *** CFD results suggested that cavitating bubbles mainly takes place in the stator of the torque *** transient cavitation CFD model yielded good agreement with the experimental data,with an error of 7.6%in the capacity constant and 7.4%in the torque *** the experimental and numerical studies showed that cavitation induced severe capacity degradation,and that the charge pressure and charging oil configuration significantly affects both the overall hydrodynamic performance and the fluid behaviour inside the torque converter because of *** the charge pressure and charging the oil from the turbine-stator clearance were found to suppress cavitation development and reduce performance degradation,especially in terms of the capacity *** study revealed the fluid field mechanism behind the influence of charging oil conditions on torque converter cavitation behaviour,providing practical guidelines for suppressing cavitation in torque converter.

关键词： Torque converter Cavitation CFD Transient flow

Effect of Dy substitution on the microstructure and magnetic properties of nanograin Nd-Fe-B single-phase alloys

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International Journal of Minerals,Metallurgy and Materials 2010年第3期17卷 335-339页

作者： Zhi-an Chen Ji Luo Zhi-meng guo School of Materials Science and Engineering University of Science and Technology Beijing Beijing 100083 China

Nanocrystalline single-phase alloys with the nominal compositions （at%） of Nd12.3-xDyxFe79.7Zr0.8Nb0.8Cu0.4B6.0 （x=0, 0.5, 1.5, and 2.5） were prepared by melt-spinning and subsequent annealing. X-ray diffraction analysis shows that the as-spun ribbons were mainly com- posed of the amorphous phase. A slight content of Dy stabilizes the amorphous phase during annealing treatment. The grain size becomes smaller and the coercivity of the annealed ribbon is gradually improved with the increase of Dy content. Excessive Dy is harmful to the remanence. It is found that no intergramtlar phase exists between the grains by high-resolution transmission electron microscopy, and the grain boundaries are crystallographically coherent in the optimally annealed sample. The optimum magnetic properties of remanence （Jr=1.09 T）, coercivity （Hei=1048 kA/m）, and maximum magnetic energy product （（BH）m=169.5 kJ/m3） are obtained from the x=0.5 ribbon in a post heat-treated state （700℃, 10 min）.

关键词： NdFeB magnets dysprosium nanocrystalline amorphous grain size magnetic properties

Fast and Adaptive Multi-Agent Planning under Collaborative Temporal Logic Tasks via Poset Products

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Research 2024年第2期2024卷 81-94页

作者： Zesen Liu meng guo Weimin Bao Zhongkui Li Deparment of Mechanics and Engineering Science College of EngineeringPeking UniversityBejing 0081 China Science and Technology Commission of China Aerospace Science and Technology Corporation Beijing 100048China

Efficient coordination and planning is essential for large-scale multi-agent systems that collaborate in a shared dynamic environment. Heuristic search methods or learning-based approaches often lack the guarantee on correctness and performance. Moreover, when the collaborative tasks contain both spatial and temporal requirements, e.g., as linear temporal logic (LTL) formulas, formal methods provide a verifiable framework for task planning. However, since the planning complexity grows exponentially with the number of agents and the length of the task formula, existing studies are mostly limited to small artificial cases. To address this issue, a new planning paradigm is proposed in this work for system-wide temporal task formulas that are released online and continually. It avoids two common bottlenecks in the traditional methods, i.e., (a) the direct translation of the complete task formula to the associated B點hi automaton and (b) the synchronized product between the B點hi automaton and the transition models of all agents. Instead, an adaptive planning algorithm is proposed, which computes the product of relaxed partially ordered sets (R-posets) on-the-fly and assigns these subtasks to the agents subject to the ordering constraints. It is shown that the first valid plan can be derived with a polynomial time and memory complexity with respect to the system size and the formula length. Our method can take into account task formulas with a length of more than 400 and a fleet with more than 400 agents, while most existing methods fail at the formula length of 25 within a reasonable duration. The proposed method is validated on large fleets of service robots in both simulation and hardware experiments.

关键词： hardware service system

Study on the cohesion and adhesion of hot-poured crack sealants

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Frontiers of Structural and Civil Engineering 2017年第3期11卷 353-359页

作者： meng guo Yiqiu TAN Xuesong DU Zhaofeng LV National Center for Materials Service Safety University of Science and Technology Beijing Beijing China School of Transportation Science and Engineering Harbin Institute of Technology Harbin China Northeast Electric Power Design Institute Co. Ltd. of China Power Engineering Consulting Group Chang Chun China Heilongjiang Zhongda Road & Bridge Group Co. Ltd. Harbin China

Filling crack sealant is a main method to repair cracking of pavement. The cohesion and adhesion of crack sealant directly determine its service performance and durability. However, the competitive mechanism of cohesion and adhesion failure modes is not clear currently. This research proposed two methods to evaluate cohesion and adhesion of crack sealant, and analyzed the influence of temperature on cohesion and adhesion. The effect of moisture on low- temperature performance of crack sealant was also be evaluated by conducting a soaking test. Results show that with the decrease of temperature, the cohesion force of crack sealant increases significantly, while the adhesion force changes little. There is a critical temperature at which the cohesion force equals the adhesion force. When the temperature is higher, the adhesion force will be greater than cohesion force, and the cohesion failure will happen more easily. In contrast, the adhesion failure will happen more easily when the temperature is lower than the critical value. Soaking in 25 ℃ water for 24-48 hours will slightly improve the low-temperature tension performance of crack sealant. However, soaking in 60 ℃ water for 24 hours will decrease the failure energy of low-temperature tension and damage the durability of crack sealant.

关键词： crack sealant concrete pavement cohesion adhesion moisture damage

A state-of-the-art review on interfacial behavior between asphalt binder and mineral aggregate

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Frontiers of Structural and Civil Engineering 2018年第2期12卷 248-259页

作者： meng guo Yiqiu TAN Linbing WANG Yue HOU National CenterJor Materials Service Sa[ety University of Science and Technology Beijing Beijing 100083 China School of Transportation Science and Engineering Harbin Institute of Technology Harbin 150090 China Joint USTB-Virginia Teeh Lab on Multifunctional Materials University of Science and Technology Beijing Beijing 100083 China Virginia Tech Blacksburg VA 24061 USA

The interface between asphalt binder and mineral aggregate directly affects the service life of pavement because the defects and stress concentration occur more easily there. The interaction between asphalt binder and mineral aggregate is the main cause of forming the interface. This paper presents an extensive review on the test technologies and analysis methods of interfacial interaction, including molecular dynamics simulation, phase field approach, absorption tests, rheological methods and macro mechanical tests. All of the studies conducted on this topic clearly indicated that the interfacial interaction between asphalt binder and mineral aggregate is a physical-chemical process, and can be qualitatively characterized by microscopical technique （such as SEM and AFM）, and also can be quantitatively evaluated by rheological methods and interfacial mechanical tests. Molecular dynamics simulation and phase field approach were also demonstrated to be effective methods to study the interfacial behavior and its mechanism.

关键词： Asphalt binder Mineral aggregate Interfacial behavior Multiscale

Influence of mechanical alloying time on the properties of Fe_3Al intermetallics prepared by spark plasma sintering

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Journal of University of Science and Technology Beijing 2007年第4期14卷 331-334页

作者： Chengchang Jia Qing He Jie meng Lina guo Materials Science and Engineering School University of Science and Technology Beijing Beijing 100083 China

The Fe3Al-based intermetallics were prepared by mechanical alloying and spark plasma sintering （SPS）, and the influence of milling time on the properties of materials was investigated. The phase identification was investigated by X-ray, and the surface morphology and fractography were observed by scanning electron microscope （SEM）. The mechanical properties such as bending strength, strain, and microhardness were tested. The results show that Fe reacts with Al completely to form Fe3Al during short SPS processing time. The relative densities of the sintered samples were nearly 100%. The mechanical properties of the sintered samples can be improved along with the milling time. The representative values are the bend strength of 1327 MPa and the microhardness of 434.

关键词： Fe3A1 intermetallics mechanical properties mechanical alloying and milling powder metallurgy

Modelling the dead fuel moisture content in a grassland of Ergun City,China

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Journal of Arid Land 2023年第6期15卷 710-723页

作者： CHANG Chang CHANG Yu guo meng HU Yuanman CAS Key Laboratory of Forest Ecology and Management Institute of Applied EcologyChinese Academy of SciencesShenyang 110016China University of Chinese Academy of Sciences Beijing 100049China School of Geographical Sciences Northeast Normal UniversityChangchun 130024China E'erguna Wetland Ecosystem National Research Station Hulunbuir 022250China

The dead fuel moisture content(DFMC)is the key driver leading to fire *** estimating the DFMC could help identify locations facing fire risks,prioritise areas for fire monitoring,and facilitate timely deployment of fire-suppression *** this study,the DFMC and environmental variables,including air temperature,relative humidity,wind speed,solar radiation,rainfall,atmospheric pressure,soil temperature,and soil humidity,were simultaneously measured in a grassland of Ergun City,Inner Mongolia Autonomous Region of China in *** chose three regression models,i.e.,random forest(RF)model,extreme gradient boosting(XGB)model,and boosted regression tree(BRT)model,to model the seasonal DFMC according to the data *** ensure accuracy,we added time-lag variables of 3 d to the *** results showed that the RF model had the best fitting effect with an R2value of 0.847 and a prediction accuracy with a mean absolute error score of 4.764%among the three *** accuracies of the models in spring and autumn were higher than those in the other two *** addition,different seasons had different key influencing factors,and the degree of influence of these factors on the DFMC changed with time ***,time-lag variables within 44 h clearly improved the fitting effect and prediction accuracy,indicating that environmental conditions within approximately 48 h greatly influence the *** study highlights the importance of considering 48 h time-lagged variables when predicting the DFMC of grassland fuels and mapping grassland fire risks based on the DFMC to help locate high-priority areas for grassland fire monitoring and prevention.

关键词： dead fuel moisture content(DFMC) random forest(RF)model extreme gradient boosting(XGB)model boosted regression tree(BRT)model grassland Ergun City

Forest succession trajectories after fi res in valleys and on slopes in the Greater Khingan Mountains,China

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Journal of Forestry Research 2023年第3期34卷 623-640页

作者： Chao Zhong meng guo Fenfen Zhou Jianuo Li Fangbing Yu Futao guo Wenshan Li Key Laboratory of Geographical Processes and Ecological Security in Changbai Mountains Ministry of EducationSchool of Geographical SciencesNortheast Normal UniversityChangchun 130024People’s Republic of China College of Forestry Fujian Agriculture and Forestry UniversityFuzhou 350002People’s Republic of China Huzhong Nature Reserve Administration of Heilongjiang Province Huzhong 165033People’s Republic of China

Accurate assessment of postfire vegetation recovery is important for forest management and the conservation of species *** is an important factor aff ecting vegetation recovery but whether species composition varies with diff erent recovery stages and between valleys and slopes is *** fi eld data and a space-for-time substitution method,we quantifi ed species richness and diversity to obtain the successional trajectories of valleys and *** surveyed the species of 10 burned areas from 1986 to 2010 in the Greater Khingan Mountains in northeastern China,and found that with increasing postfi re recovery time,species richness in both valleys and slopes gradually ***,species richness in valleys was relatively *** recovered rapidly in the valleys,and species diversity maximized approximately 11 years after fi ***,it maximized 17–18 years after fi re on the *** shade-tolerant species were present in the valleys 11 years after fi re but not until after 18 years on *** appeared earlier than 11 years after fi re and its recovery was slow in the valleys but appeared quickly on slopes and established dominance *** study provides some new insights into vegetation succession after fi re at local *** fi re,the vegetation recovery processes diff er with topography and it aff ects the initial rate of recovery and species composition at diff erent successional stages.

关键词： Vegetation recovery Valleys and slopes Space-for-time substitution Species richness/diversity/composition Greater Khingan Mountains