检索结果-南通市图书馆

Lateral Flight Stability of Two Hovering Model Insects

在线全文

学校读者我要写书评

暂无评论

Journal of Bionic Engineering 2014年第3期11卷 439-448页

作者： na xu Mao Sun Ministry-of-Education Key Laboratory of Fluid Mechanics Beihang University Beijing 100191 P. R. China

The longitudinal disturbance motion of different insects at hovering flight has the same modal structure. Here, we consider the case of lateral motion. The lateral dynamic flight stability of two model insects, hoverfly and honeybee, at hovering flight is studied. The method of computational fluid dynamics is applied to compute the stability derivatives. The techniques of eigenvalue and eigenvector analysis are used to solve the equations of motion. Results show that the lateral disturbance motion of the hoverfly has three natural modes of motion： an unstable divergence mode, a stable oscillatory mode and a stable subsidence mode, and the flight is unstable; while the honeybee has a different modal structure （a stable slow subsidence mode, a stable fast subsidence mode, and a nearly neutrally stable oscillatory mode） and the flight is nearly neutrally stable. The change in modal structure between the two insects is due to their roll-moment/side-velocity derivative having different sign, and the sign difference is because that the hoverfly has a relatively small, but the honeybee has a relatively large, distance between the wing roots and the center of mass. Thus, unlike the case of longitudinal motion, for lateral motion, some insects have different modal structures and stability properties from others.

关键词： insect hovering flight dynamic flight stability modal structure

Improved scheme with cooperative diversity based on distributed space-time block coding

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Systems Engineering and Electronics 2009年第3期20卷 463-469页

作者： Du na xu Dazhuan Coll. of Information Science & Technology Nanjing Univ. of Aeronautics and Astronautics Nanjing 210016 P. R. China

An improved scheme with cooperative diversity based on distributed space-time block coding （WCD- DSTBC） is proposed, which effectively achieves diversity gains and improves the performance of the system by sharing some single-antenna users＇ antennas to form a virtual antenna array and combining with distributed spacetime block coding （DSTBC） mode. Then the relation between the system BER and the interuser BER for WCDDSTBC scheme is theoretically derived and the closed-form expression of BER for WCD-DSTBC system is obtained. The simulation results show that the proposed WCD-DSTBC scheme achieves distinct gains over the non-cooperative multi-carrier CDMA （MC-CDMA） system. When system BER is le-3 and interuser BER is le-3, about 2.5 dB gain can be gotten. When interuser channel state information （CSI） outgoes the users＇ individual CSI, about 3 dB gain is also achieved.

关键词： multiple input multiple output cooperative diversity distributed space-time block coding multicarrier CDMA.

Isoparametric Hypersurfaces Induced by navigation in Lorentz Finsler Geometry

在线全文

学校读者我要写书评

暂无评论

Acta Mathematica Sinica,English Series 2023年第8期39卷 1547-1564页

作者： Ming xu Ju TAN na xu School of Mathematical Sciences Capital Normal UniversityBeijing 100048P.R.China School of Microelectronics and Data Science Anhui University of TechnologyMaanshan 243032P.R.China

Using a navigation process with the datum(F,V),in which F is a Finsler metric and the smooth tangent vector field V satisfies F(−V(x))>1 everywhere,a Lorentz Finsler metric F˜can be *** functions and isoparametric hypersurfaces with or without involving a smooth measure can be defined for F˜.When the vector field V in the navigation datum is homothetic,we prove the local correspondences between isoparametric functions and isoparametric hypersurfaces before and after this navigation *** these correspondences,we provide some examples of isoparametric functions and isoparametric hypersurfaces on a Funk space of Lorentz Randers type.

关键词： Finsler metric homothetic vector field isoparametric function isoparametric hypersurface Lorentz Finsler metric Zermelo navigation

Multi-Attribute Preferences Mining Method for Group Users with the Process of Noise Reduction

在线全文

学校读者我要写书评

暂无评论

Journal of Computer Science & Technology 2021年第4期36卷 944-960页

作者： Qing-Mei Tan xu-na Wang College of Economic and Management Nanjing University of Aeronautics and AstronauticsNanjing 211106China Research Base for Civilian-Military Integration Development in Jiangsu Province Nanjing 211106China

Traditional researches on user preferences mining mainly explore the user’s overall preferences on the project,but ignore that the fundamental motivation of user preferences comes from their attitudes on some attributes of the *** addition,traditional researches seldom consider the typical preferences combination of group users,which may have influence on the personalized service for group *** solve this problem,a method with noise reduction for group user preferences mining is proposed,which focuses on mining the multi-attribute preference tendency of group ***,both the availability of data and the noise interference on preferences mining are considered in the algorithm *** the process of generating group user preferences,a new path is used to generate preference keywords so as to reduce the noise ***,the Gibbs sampling algorithm is used to estimate the parameters of the ***,using the user comment data of several online shopping websites as experimental objects,the method is used to mine the multi-attribute preferences of different *** proposed method is compared with other methods from three aspects of predictive ability,preference mining ability and preference topic *** results show that the method is significantly better thap other existing methods.

关键词： preferences mining group user multi-attribute noise reduction noise interference

Comparative analysis of the microbiome of sympatric wintering Bean Geese,Domestic Ducks,humans,and soil at Shengjin Lake of China reveals potential public risk to human health

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Avian Research 2024年第2期15卷 279-286页

作者： Gang Liu na xu Chongyang Yu College of Life Sciences Anhui Medical UniversityHefei 230032China

The gut microbiota of migratory waterbirds is affected by various complex factors,including cross-species transmission,which increases the risk of pathogen spreading among sympatric animals and poses a potential public health risk to *** this study,we investigated the microbial communities of wintering Bean Geese(Anser fabalis),Domestic Ducks(*** domesticus),humans,and soil using high-throughput sequencing of the 16S rRna gene region in Shengjin Lake,*** total,6,046,677 clean reads were obtained,representing 41,119 operational taxonomic units(OTUs)across the four *** dominant microbial phyla were the Proteobacteria,Firmicutes,Bacteroidota,and *** Sorensen similarity index and alpha and beta diversity results showed that the gut microbial communities of Bean Geese and Domestic Ducks were more similar to those of the other *** analysis revealed that Faecalibacterium prausnitzii,Pseudomonas fragi,and Bradyrhizobium elkanii were hubs of the three major *** common microbiomes were iden-tified in Bean Geese,Domestic Ducks,humans,and soil in Shengjin Lake.A total of 96 potential pathogens were identified among the four groups,with 20 specific potentially pathogenic microbiomes found in the gut of Bean *** of these pathogens are responsible for significant financial losses in the poultry industry and pose risks to human *** pneumoniae,Morganella morganii,Escherichia coli,and Ralstonia insidiosa are potential core pathogens found in the four groups at Shengjin Lake that can cause diseases in humans and an-imals and facilitate cross-species transmission through various ***,humans are at risk of con-tracting these pathogens from migratory birds because of their frequent contact with domestic ***,further studies are required to explore the potential pathogenic species and transmission pathways among sympatric wintering Bean Geese,Domestic Ducks,humans,and soil.

关键词： Microbiome Migratory waterbird Pathogens Poultry Sympatric species

Adult neurogenesis in the primate hippocampus

在线全文

学校读者我要写书评

暂无评论

Zoological Research 2023年第2期44卷 315-322页

作者： Ye Li na-na xu Zhao-Zhe Hao Sheng Liu State Key Laboratory of Ophthalmology Zhongshan Ophthalmic CenterSun Yat-sen UniversityGuangdong Provincial Key Laboratory of Ophthalmology and Visual ScienceGuangzhouGuangdong 510060China Guangdong Province Key Laboratory of Brain Function and Disease GuangzhouGuangdong 510080China

Adult hippocampal neurogenesis(AHN) is crucial for learning,memory,and *** of AHN may lead to reduced cognitive abilities and neurodegenerative disorders,such as Alzheimer’s *** studies on rodent AHN have clarified the developmental and maturation processes of adult neural stem/progenitor ***,to what extent these findings apply to primates remains *** advances in next-generation sequencing technologies have enabled in-depth investigation of the transcriptome of AHN-related populations at single-cell ***,we summarize studies of AHN in *** suggest that neurogenesis is largely shared across species,but substantial differences also *** gene expression patterns in primates differ from those of *** with rodents,the primate hippocampus has a higher proportion of immature dentate granule cells and a longer maturation period of newly generated granule *** research on species divergence may deepen our understanding of the mechanisms underlying adult neurogenesis in primates.

关键词： Neural precursor cells Immature granule cells Sc-Rna-seq

Mass transfer mechanism and relationship of gas–liquid annular flow in a microfluidic cross-junction device

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Chemical Engineering 2023年第12期64卷 37-48页

作者： Xin xu na xu Wei Zhang Junwen Wang Yao Li Chen Yang Shanxi Key Laboratory of Chemical Product Engineering College of Chemical Engineering and TechnologyTaiyuan University of TechnologyTaiyuan 030024China Shanxi Coking Coal in Yuncheng Salt Refco Group Ltd. Yuncheng 044000China

Mass transfer performance of gas–liquid two-phase flow at microscale is the basis of application of microreactor in gas–liquid reaction *** present,few researches on the mass transfer property of annular flow have been ***,the mass transfer mechanism and relationship of gas–liquid annular flow in a microfluidic cross-junction device are studied in the present *** find that the main factors,i.e.,flow pattern,liquid film thickness,liquid hydraulic retention time,phase interface fluctuation,and gas flow vorticity,which influence the flow mass transfer property,are directly affected both by gas and liquid flow *** the influences of gas and liquid velocities on different mass transfer influencing factors are ***,the fitting relationships between gas and liquid flow velocities and mass transfer influencing factors are *** comparing the results from calculations using fitting equations and simulations,it shows that the fitting equations have relatively high degrees of ***,the Pareto front,namely the Pareto optimal solution set,of gas and liquid velocity conditions for the best flow mass transfer property is obtained using the method of multi-objective particle swarm *** is proved that the mass transfer property of the gas–liquid two-phase flow can be obviously enhanced under the guidance of the obtained Pareto optimal solution set through experimental verification.

关键词： Gas-liquid microreactor Annular flow Mass transfer mechanism Mass transfer relationship Multi-objective particle swarm optimization

Fluid-based Slotting Optimization for Automated Order Picking System with Multiple Dispenser Types

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Mechanical Engineering 2011年第4期24卷 529-538页

作者： LIU Peng WU Yaohua ZHOU Chen xu na School of Control Science andEngineering Shandong University Jinan 250061 China School of Industrial and Systems Engineering Georgia Institute of Technology Atlanta GA 30332 USA Business School Shandong Jianzhu University Jinan 250101 China

Slotting strategy heavily influences the throughput and operational cost of automated order picking system with multiple dispenser types, which is called the complex automated order picking system （CAOPS）. Existing research either focuses on one aspect of the slotting optimization problem or only considers one part of CAOPS, such as the Low-volume Dispensers, to develop corresponding slotting strategies. In order to provide a comprehensive and systemic approach, a fluid-based slotting strategy is proposed in this paper. The configuration of CAOPS is presented with specific reference to its fast-picking and restocking subsystems. Based on extended fluid model, a nonlinear mathematical programming model is developed to determine the optimal volume allotted to each stock keeping unit （SKU） in a certain mode by minimize the restocking cost of that mode. Conclusion from the allocation model is specified for the storage modules of high-volume dispensers and low-volume dispensers. Optimal allocation of storage resources in the fast-picking area of CAOPS is then discussed with the aim of identifying the optimal space of each picking mode. The SKU assignment problem referring to the total restocking cost of CAOPS is analyzed and a greedy heuristic with low time complexity is developed according to the characteristics of CAOPS. Real life application from the tobacco industry is presented in order to exemplify the proposed slotting strategy and assess the effectiveness of the developed methodology. Entry-item-quantity （EIQ） based experiential solutions and proposed-model-based near-optimal solutions are compared. The comparison results show that the proposed strategy generates a savings of over 18% referring to the total restocking cost over one-year period. The strategy proposed in this paper, which can handle the multiple dispenser types, provides a practical quantitative slotting method for CAOPS and can help picking-system-designers make slotting decisions efficiently and

关键词： slotting complex automated order picking system restocking cost dispenser

Water Vapor Retrievals from Near-infrared Channels of the Advanced Medium Resolution Spectral Imager Instrument onboard the Fengyun-3D Satellite

在线全文

学校读者我要写书评

暂无评论

Advances in Atmospheric Sciences 2021年第8期38卷 1351-1366页

作者： Ling WANG Xiuqing HU na xu Lin CHEN Key Laboratory of Radiometric Calibration and Validation for Environmental Satellites China Meteorological AdministrationBeijing 100081China national Satellite Meteorological Center China Meteorological AdministrationBeijing 100081China

Water vapor plays a key role in weather, climate and environmental research on local and global scales. Knowledge about atmospheric water vapor and its spatiotemporal variability is essential for climate and weather research. Because of the advantage of a unique temporal and spatial resolution, satellite observations provide global or regional water vapor distributions. The advanced Medium Resolution Spectral Imager (MERSI) instrument-that is, MERSI-II-onboard the Fengyun-3D (FY-3D) meteorological satellite, has been one of the major satellite sensors routinely providing precipitable water vapor (PWV) products to the community using near-infrared (NIR) measurements since June 2018. In this paper, the major updates related to the production of the NIR PWV products of MERSI-II are discussed for the first time. In addition, the water vapor retrieval algorithm based on the MERSI-II NIR channels is introduced and derivations are made over clear land areas, clouds, and sun-glint areas over the ocean. Finally, the status and samples of the MERSI-II PWV products are presented. The accuracy of MERSI-II PWV products is validated using ground-based GPS measurements. The results show that the accuracies of the water vapor products based on the updated MERSI-II instrument are significantly improved compared with those of MERSI, because MERSI-II provides a better channel setting and new calibration method. The root- mean-square error and relative bias of MERSI-II PWV products are typically 1.8-5.5 mm and −3.0% to −14.3%, respectively, and thus comparable with those of other global remote sensing products of the same type.

关键词： precipitable water vapor FY-3D MERSI GPS