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Flexural rigidity of honeycomb consisting of hexagonal cells

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Acta Mechanica Sinica 2011年第5期27卷 840-844页

作者： dai-Heng Chen Department of Mechanical Engineering Tokyo University of Science1-3 Kagurazaka Shinjuku-kuTokyo 162-8601 Japan

In this study,the flexural rigidity of a honeycomb consisting of regular hexagonal cells is *** is found that the honeycomb bending can not be evaluated by using the equivalent elastic moduli obtained from the in-plane deformation because the moments acting on the inclined cell wall are different for in-plane deformation and bending *** on the fact that the inclined wall is twisted under the condition of the rotation angle in both connection edges being zero,a theoretical technique for calculating the flexural rigidity of honeycombs is proposed,and the validity of the present analysis is demonstrated by numerical results obtained by BFM.

关键词： Honeycomb · Flexural rigidity · Equivalent elastic modulus · Bending · Elasticity

Energy-efficient Approach to Minimizing the Energy Consumption in An Extended Job-shop Scheduling Problem

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Chinese Journal of Mechanical Engineering 2015年第5期28卷 1048-1055页

作者： TANG Dunbing dai Min College of Mechanical and Electrical Engineering Nanjing University of Aeronautics & Astronautics Jiangsu Key Laboratory of Precision and Micro-manufacturing Technology Nanjing University of Aeronautics & Astronautics

The traditional production planning and scheduling problems consider performance indicators like time, cost and quality as optimization objectives in manufacturing processes. However, environmentally-friendly factors like energy consumption of production have not been completely taken into consideration. Against this background, this paper addresses an approach to modify a given schedule generated by a production plarming and scheduling system in a job shop floor, where machine tools can work at different cutting speeds. It can adjust the cutting speeds of the operations while keeping the original assignment and processing sequence of operations of each job fixed in order to obtain energy savings. First, the proposed approach, based on a mixed integer programming mathematical model, changes the total idle time of the given schedule to minimize energy consumption in the job shop floor while accepting the optimal solution of the scheduling objective, makespan. Then, a genetic-simulated annealing algorithm is used to explore the optimal solution due to the fact that the problem is strongly NP-hard. Finally, the effectiveness of the approach is performed small- and large-size instances, respectively. The experimental results show that the approach can save 5%-10% of the average energy consumption while accepting the optimal solution of the makespan in small-size instances. In addition, the average maximum energy saving ratio can reach to 13%. And it can save approximately 1%-4% of the average energy consumption and approximately 2.4% of the average maximum energy while accepting the near-optimal solution of the makespan in large-size instances. The proposed research provides an interesting point to explore an energy-aware schedule optimization for a traditional production planning and scheduling problem.

关键词： energy consumption makespan production planning and scheduling job-shop floor different cutting speeds

Single Image Dehazing Based on Combining Dark Channel Prior and Scene Radiance Constraint

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Chinese Journal of Electronics 2016年第6期25卷 1114-1120页

作者： ZENG Liang dai Yongzhen College of Computer National University of Defense Technology

Images captured in foggy or hazy weather conditions often suffer from poor visibility. The dark channel prior method has well solved the single image dehazing problem in nature, but it is invalid when the scene objects are inherently similar to the atmospheric light and no shadow is cast on them. We propose an efficient regularization method by adding a scene radiance constraint and combing the dark channel prior to remove hazes from a single input image. The experiments show that this improved algorithm can deal with various levels of foggy weather conditions, as well as greatly enhance the image's visibility and details. In addition, the recovered haze-free image has little or no halo artifacts.

关键词： Image dehazing Scene radiance constraint Dark channel prior Visibility enhancement Detail augment

Inhibition of ammonia-oxidizing bacteria promotes the growth of ammonia-oxidizing archaea in ammonium-rich alkaline soils

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Pedosphere 2022年第4期32卷 532-542页

作者： Chang YIN Xiaoping FAN Hao CHEN Mujun YE Guochao YAN Tingqiang LI Hongyun PENG shengzhe E Zongxian CHE Steven AWAKELIN Yongchao LIANG Key Laboratory of Environment Remediation and Ecological Health Ministry of EducationCollege of Environmental&Resource SciencesZhejiang UniversityHangzhou 310058China Institute of Soil and Fertilizer and Water-Saving Agriculture Gansu Academy of Agricultural SciencesLanzhou 730070China Scion Research P.O.Box 29237Christchurch 8011New Zealand

Disparities in the substrate affinity and tolerance threshold for ammonia have been believed to play a key role in driving niche differentiation between ammonia-oxidizing archaea (AOA) and bacteria (AOB);however, recent surveys argue that direct competition between AOA and AOB is also important in this phenomenon. Accordingly, it is reasonable to predict that diverse AOA lineages would grow in ammonium (NH_(4)^(+))-rich alkaline arable soils if AOB growth is suppressed. To test this hypothesis, a microcosm study was established using three different types of alkaline arable soils, in which a high NH_(4)^(+) concentration (200 μg N g^(-1) dry soil) was maintained by routinely replenishing urea and the activities of AOB were selectively inhibited by 1-octyne or 3,4-dimethylpyrazole phosphate (DMPP). Compared with amendment with urea alone, 1-octyne partially retarded AOB growth, while DMPP completely inhibited AOB. Both inhibitors accelerated the growth of AOA, with significantly higher ratios of abundance of AOA to AOB observed with DMPP amendment across soils. Nonmetric multidimensional scaling analysis (NMDS) indicated that different treatments significantly altered the community structures of both AOA and AOB and AOA OTUs enriched by high-NH_(4)^(+) amendment were taxonomically constrained across the soils tested and closely related to Nitrososphaera viennensis EN76 and N. garnensis. Given that these representative strains have been demonstrated to be sensitive to high ammonia concentrations, our results suggest that it is the competitiveness for ammonia, rather than disparities in substrate affinity and tolerance threshold for ammonia, that drives niche differentiation between these phylotypes and AOB in NH_(4)^(+)-rich alkaline soils.

关键词： community structure 3,4-dimethylpyrazole phosphate niche differentiation 1-octyne substrate affinity tolerance threshold

Characterization and catalytic performance of CeO_2-Co/SiO_2 catalyst for Fischer-Tropsch synthesis using nitrogen-diluted synthesis gas over a laboratory scale fixed-bed reactor

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Journal of Natural Gas Chemistry 2008年第1期17卷 17-23页

作者： Xiaoping dai Changchun Yu The Key Laboratory of Catalysis China National Petroleum Corporation China University of Petroleum Beijing 102249 China

The surface species of CO hydrogenation on CeO2-Co/SiO2 catalyst were investigated using the techniques of temperature programmed reaction and transient response method. The results indicated that the formation of H2O and CO2 was the competitive reaction for the surface oxygen species, CH4 was produced via the hydrogenation of carbon species step by step, and C2 products were formed by the polymerization of surface-active carbon species （-CH2-）. Hydrogen assisted the dissociation of CO. The hydrogenation of surface carbon species was the rate-limiting step in the hydrogenation of CO over CeO2-Co/SiO2 catalyst. The investigation of total pressure, gas hourly space velocity （GHSV）, and product distribution using nitrogen-rich synthesis gas as feedstock over a laboratory scale fixed-bed reactor indicated that total pressure and GHSV had a significant effect on the catalytic performance of CeO2-Co/SiO2 catalyst. The removal of heat and control of the reaction temperature were extremely critical steps, which required lower GHSV and appropriate CO conversion to avoid the deactivation of the catalyst. The feedstock of nitrogen-rich synthesis gas was favorable to increase the conversion of CO, but there was a shift of product distribution toward the light hydrocarbon. The nitrogen-rich synthesis gas was feasible for F-T synthesis for the utilization of remote natural gas.

关键词： CeO2-Co/SiO2 catalyst Fischer-Tropsch synthesis surface species reaction condition nitrogen-rich synthesis gas product distribution

Methods and advances in the study of aeroelasticity with uncertainties

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Chinese Journal of Aeronautics 2014年第3期27卷 461-474页

作者： dai Yuting Yang Chao School of Aeronautic Science and Engineering Beihang University

Uncertainties denote the operators which describe data error, numerical error and model error in the mathematical methods. The study of aeroelasticity with uncertainty embedded in the subsystems, such as the uncertainty in the modeling of structures and aerodynamics, has been a hot topic in the last decades. In this paper, advances of the analysis and design in aeroelasticity with uncertainty are summarized in detail. According to the non-probabilistic or probabilistic uncer- tainty, the developments of theories, methods and experiments with application to both robust and probabilistic aeroelasticity analysis are presented, respectively. In addition, the advances in aeroelastic design considering either probabilistic or non-probabilistic uncertainties are introduced along with aeroelastic analysis. This review focuses on the robust aeroelasticity study based on the structured singular value method, namely the ~t method. It covers the numerical calculation algo- rithm of the structured singular value, uncertainty model construction, robust aeroelastic stability analysis algorithms, uncertainty level verification, and robust flutter boundary prediction in the flight test, etc. The key results and conclusions are explored. Finally, several promising problems on aeroelasticity with uncertainty are proposed for future investigation.

关键词： Polynomial chaos expansion Probabilisticity Robustness Structured singular value Uncertainty

Subduction and retreating of the western Pacific plate resulted in lithospheric mantle replacement and coupled basin-mountain respond in the North China Craton

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Science China Earth Sciences 2018年第4期61卷 406-424页

作者： Jianping ZHENG Hongkun dai School of Earth Sciences State Key Laboratory of Geological Processes and Mineral Resources China University of GeosciencesWuhan

The North China Craton(NCC) witnessed Mesozoic vigorous tectono-thermal activities and transition in the nature of deep lithosphere. These processes took place in three periods:(1) Late Paleozoic to Early Jurassic(~170 Ma);(2) Middle Jurassic to Early Cretaceous(160-140 Ma);(3) Early Cretaceous to Cenozoic(140 Ma to present). The last two stages saw the lithospheric mantle replacement and coupled basin-mountain response within the North China Craton due to subduction and retreating of the Paleo-Pacific plate, and is the emphasis in this paper. In the first period,the subduction and closure of the PaleoAsian Ocean triggered the back-arc extension, syn-collisional compression and then post-collisional extension accompanied by ubiquitous magmatism along the northern margin of the NCC. Similar processes happened in the southern margin of the craton as the subduction of the Paleo-Tethys ocean and collision with the South China Block. These processes had caused the chemical modification and mechanical destruction of the cratonic margins. The margins could serve as conduits for the asthenosphere upwelling and had the priority for magmatism and deformation. The second period saw the closure of the Mongol-Okhotsk ocean and the shear deformation and magmatism induced by the drifting of the Paleo-Pacific slab. The former led to two pulse of N-S trending compression(Episodes A and B of the Yanshan Movement) and thus the pre-existing continental marginal basins were disintegrated into sporadically basin and range pro vince by the Mesozoic magmatic plutons and NE-SW trending *** the anticlockwise rotation of the Paleo-Pacific moving direction, the subduction-related magmatism migrated into the inner part of the craton and the Tanlu fault became normal fault from a sinistral one. The NCC thus turned into a back-arc extension setting at the end of this period. In the third period, the refractory subcontinental lithospheric mantle(SCLM) was firstly remarkably eroded and thin

关键词： Paleo-Pacific slab Subduction and retreating Mantle replacement Mountain-basin coupling North China Craton Deep processes and shallow response Yanshan Movement

Numerical simulation of flow and heat transfer in a random packed bed

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Particuology 2010年第3期8卷 293-299页

作者： Xueyan Guo Ren dai School of Energy and Power Engineering University of Shanghai for Science and Technology S 16Jun Gong Road Shanghai 200093 China

Random packed beds have more complex interior structure than structured beds and are widely used in industry and engineering. CFD simulation was carried out to investigate and analyze the local flow and heat transfer in a 120-sphere random packed bed. 3D Navier-Stokes equation was solved with a finite volume formulation based on the Chimera meshing technique. Investigation was focused on low Reynolds number flow （Re=4.6-56.2）, which typically occurs in packed bed reactors in bio-chemical fields. Detailed temperature field information was obtained. Inhomogeneity of flow and heat transfer due to the non-uniform distribution of void fraction was discussed and analyzed.

关键词： Packed bed Heat transfer Chimera grid Numerical simulation Low Reynolds number

PRECONDITIONING BLOCK LANCZOS ALGORITHM FOR SOLVING SYMMETRIC EIGENVALUE PROBLEMS

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Journal of Computational Mathematics 2000年第4期18卷 365-374页

作者： Hua dai Peter Lancaster Nanjing University of Aeronautics and Astronautics Naming210018China University of Calgary CalgaryCanada

A preconditioned iterative method for computing a few eigenpairs of large sparse symmetric matrices is presented in this paper. The proposed method which combines the preconditioning techniques with the efficiency of block Lanczos algorithm is suitable for determination of the extreme eigenvalues as well as their multiplicities. The global convergence and the asymptotically quadratic convergence of the new method are also demonstrated. [ABSTRACT FROM AUTHOR]

关键词： eigenvalue eigenvector sparse matrices Lanczos method preconditioning