检索结果-南通市图书馆

Isotopic characteristics and source analysis of atmospheric ammonia during agricultural periods in the Xichuan area of the Danjiangkou Reservoir

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 Environmental Sciences 2024年第2期136卷 460-469页

作者： xiaoshu chen Tongqian Zhao Chunyan xiao xiaoming Guo Feihong chen Institute of Resources and Environment Henan Polytechnic UniversityJiaozuo 454000China

Nitrogen deposition is an important means of exogenous nitrogen input in reservoir water.Agricultural activities around the reservoir lead to a sharp increase in the concentration of ammonia in the atmosphere,which poses a threat to the reservoir water body.Clarifying the contribution of agricultural ammonia release to atmospheric NH_(x)(gaseous NH_(3)and particulate NH_(4)^(+)),in the reservoir area can provide a theoretical foundation for local reactive nitrogen control.We collected atmospheric NH_(3)and NH_(4)^(+)samples during the agricultural periods and analyzed the isotopic characteristics of atmospheric NH_(x)and the contribution rates of different ammonia sources in the Xichuan area of the Danjiangkou Reservoir.The results showed that the initialδ~(15)N values of NH_(3)(-30.0‰to–7.2‰)and particulate NH_(4)^(+)(–33‰to+4.9‰for finer and coarser particles,respectively)are different,and their contribution ratios from dissimilar ammonia sources are also different,among which NH_(4)^(+)is more susceptible to meteorological factors.However,since the atmospheric NH_(x)in the Xichuan area is mainly gaseous NH_(3),the final sources of atmospheric ammonia nitrogen source depend on gaseous NH_(3).Agricultural sources(59%-74%)were the main NH_(3)sources in this area.Among them,the fertilizer use emission was dominant;it had the highest contribution rate in summer during the agricultural period and a more prominent impact in areas with less human interference.Reasonable regulation of the application of high-ammonia releasing fertilizer,especially during the agricultural period in summer,is an effective way to reduce the threat of atmospheric ammonia to water health.

关键词： Danjiangkou reservoir Atmospheric ammonia nitrogen Isotope Ammonia source analysis Agricultural sources

Neuronomodulation of Excitable Neurons

在线全文

学校读者我要写书评

暂无评论

Neuroscience Bulletin 2024年第1期40卷 103-112页

作者： Yizhang chen Lin xiao Jian Qiu Institute of Neuroscience Second Military Medical UniversityShanghai 200433China Institute for Brain Research and Rehabilitation Key Laboratory of BrainCognition and Education Sciences of Ministry of EducationSouth China Normal UniversityGuangzhou 510631China Department of Chemical Physiology and Biochemistry Oregon Health and Science UniversityPortlandOR 97239USA

Neuronomodulation refers to the modulation of neural conduction and synaptic transmission(i.e.,the conduction process involved in synaptic transmission)of excitable neurons via changes in the membrane potential in response to chemical substances,from spillover neuro-transmitters to paracrine or endocrine hormones circulating in the blood.Neuronomodulation can be direct or indirect,depending on the transduction pathways from the ligand binding site to the ion pore,either on the same molecule,i.***.the ion channel,or through an intermediate step on different molecules.The major players in direct neurono-modulation are ligand-gated or voltage-gated ion channels.The key process of direct neuronomodulation is the binding and chemoactivation of ligand-gated or voltage-gated ion channels,either orthosterically or allosterically,by various ligands.Indirect neuronomodulation involves metabotropic receptor-mediated slow potentials,where steroid hormones,cytokines,and chemokines can implement these actions.Elucidating neuronomodulation is of great significance for understanding the physiological mechanisms of brain function,and the occurrence and treatment of diseases.

关键词： Neuron Membrane potential Excitability Chemoactivation Neuronomodulation

A Fluctuation Test for Structural Change Detection in Heterogeneous Panel Data Models

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 Science & Complexity 2024年第3期37卷 1184-1208页

作者： LI Fuxiao xiao Yanting chen Zhanshou Department of Applied Mathematics Xi'an University of TechnologyXi'an 710048China School of Mathematics and Statistics Qinghai Normal UniversityXining 810008China Academy of Plateau Science and Sustainability Xining 810008China

Structural change in panel data is a widespread phenomena. This paper proposes a fluctuation test to detect a structural change at an unknown date in heterogeneous panel data models with or without common correlated effects. The asymptotic properties of the fluctuation statistics in two cases are developed under the null and local alternative hypothesis. Furthermore, the consistency of the change point estimator is proven. Monte Carlo simulation shows that the fluctuation test can control the probability of type I error in most cases, and the empirical power is high in case of small and moderate sample sizes. An application of the procedure to a real data is presented.

关键词： Common correlated effects fuctuation test heterogeneous panel data models structural change detection

Experimental and numerical investigation of the impacts of rotor tip-rake on excitation forces of pump-jet propulsors

在线全文

学校读者我要写书评

暂无评论

Journal of Hydrodynamics 2024年第1期36卷 142-157页

作者： Xue-qin Ji xiao-song Zhang chen-jun Yang xiao-qian Dong State Key Laboratory of Ocean Engineering Marine Numerical Experiment CentreSchool of Naval ArchitectureOcean and Civil EngineeringShanghai Jiao Tong UniversityShanghai200240China CSSC Shanghai Marine Energy Saving Technology Co. Ltd.Shanghai200011China China Ship Scientific Research Center Shanghai Branch Shanghai200011China

The tip-clearance flow in a pump-jet propulsor exerts great impacts on the fluctuating pressures and resultant unsteady forces,which are important sources of structural vibrations and radiated noise underwater.The blade geometry close to the tip is an important factor determining the vortex strength in the tip-clearance flow.In the open-water condition,the effects of raking the rotor tips on the duct-surface fluctuating pressures and the resultant unsteady forces acting on different components of the propulsor are investigated via physical model experiments and the numerical solution of Reynolds-averaged Navier-Stokes(RANS)equations coupled with the SST k-ωturbulence model.The measured and simulated results of hydrodynamic pressures are consistent to each other,and the simulated flows help better understand why the fluctuating pressures change with the tip geometry.The strong fluctuations of duct-surface pressures are caused by intensive tip separation vortices.The duct-surface pressure fluctuations are effectively reduced by using the rake distribution near the tip towards blade back side and,for the combination of the five-bladed rotor and the seven-bladed stator,the resultant unsteady horizontal(and vertical)forces acting on the duct and stator are also reduced;while increasing rake leads to negative effect on pressure fluctuations and unsteady horizontal(and vertical)forces acting on all the components of the propulsor.

关键词： Pump-jet tip-clearance tip-rake fluctuating pressures excitation forces

Metal-organic frameworks on 3D interconnected macroporous sponge foams for large-scale water decontamination:A mini review

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

Chinese Chemical Letters 2024年第5期35卷 77-84页

作者： xiao-Hong Yi Chong-chen Wang Beijing Key Laboratory of Functional Materials for Building Structure and Environment Remediation School of Environment and Energy EngineeringBeijing University of Civil Engineering and ArchitectureBeijing 100044China

Water pollution caused by global population growth,urban expansion and industrialization development is one of the urgent issues that need to be addressed in the 21st century.Up to now,it was challenging for metal-organic frameworks(MOFs)to be used in the actual water treatment due to that the powder MOFs suffered from difficult reuse,poor water stability and easy corrosion.It is an effective strategy to immobilize MOFs powder onto porous sponge foam carriers for accomplishing large flux,facile recycling,easy processing water treatment setups.In this review article,the fabrication approaches and applications of different MOFs/sponge composites were highlighted,in which the fluorescence detection of pollutants,adsorption and separation of pollutants,catalytic reduction and oxidation of pollutants were included.Finally,the future challenges and opportunities of MOF/sponge for water treatment are proposed,aiming to provide in-depth guidance for the future design and manufacture of the immobilized MOFs onto sponge foams.

关键词： Metal-organic frameworks Sponge foam Water decontamination Adsorption Catalysis

Price Masking Strategy of Cross-Border E-Commerce Platform Financing

在线全文

学校读者我要写书评

暂无评论

Journal of Systems Science & Complexity 2024年第2期37卷 668-691页

作者： LI Jianbin HANG Zhouxin chen Zhiyuan xiao Shan School of Management Huazhong University of Science and TechnologyWuhan 430074China School of Economics and Management Wuhan UniversityWuhan 430072China

E-commerce platform financing is a new service pattern of supply chain finance.However,this pattern may bring some new issues when considering the problem of cash flow shortage and financing difficulties of small and medium-sized enterprises.When enterprises use this service,they worry about the leakage of preferential wholesale price when applying the full loan amount and providing the true transaction information.Based on the model consisting of a supplier,a retailer and a cross-border e-commerce platform,the authors design a price masking strategy to prevent the retailer’s preferential wholesale price information from leakage.The authors analyze the profit of the retailer and the platform before and after adopting the price masking strategy.The authors find that the price masking strategy always benefits the retailer.Besides,the optimal profit of the retailer and the platform are both affected by the loan interest rate.Moreover,there exists a range of loan interest rates that can benefit both the retailer and the platform if the price masking strategy is adopted.The research emphasizes that platform can expand the total business volume by allowing retailers to use price masking strategy.In other words,there will be more and more retailers attracted by the strategy,which benefits the long-term growth of cross-border e-commerce platform financing.

关键词： Cross-border e-commerce e-commerce platform financing price masking supply chain finance

Cnoidal waves and their soliton limits in single mode fiber lasers

在线全文

学校读者我要写书评

暂无评论

Photonics Research 2024年第3期12卷 543-551页

作者： xiao HU TUPEI chen SEONGWOO YOO DINGYUAN TANG Julong College Shenzhen Technology UniversityShenzhen 518118China School of Electrical and Electronic Engineering Nanyang Technological UniversitySingapore 639798Singapore

Cnoidal waves are a type of nonlinear periodic wave solutions of the nonlinear dynamic equations.They are well known in fluid dynamics,but it is not the case in optics.In this paper we show both experimentally and numerically that cnoidal waves could be formed in a fiber laser either in the net normal or net anomalous cavity dispersion regime,especially because,as the pump power is increased,the formed cnoidal waves could eventually evolve into a train of bright(in the net anomalous cavity dispersion regime)or dark(in the net normal cavity dispersion regime)solitons.Numerical simulations of the laser operation based on the extended nonlinear Schrödinger equation(NLSE)have well reproduced the experimental observations.The result not only explains why solitons can still be formed in a fiber laser even without mode locking but also suggests a new effective way of automatic stable periodic pulse train generation in lasers with a nonlinear cavity.

关键词： fiber pump mode

Structure-Preserving Recurrent Neural Networks for a Class of Birkhoffian Systems

在线全文

学校读者我要写书评

暂无评论

Journal of Systems Science & Complexity 2024年第2期37卷 441-462页

作者： xiao Shanshan chen Mengyi ZHANG Ruili TANG Yifa LSEC ICMSECAcademy of Mathematics and Systems ScienceChinese Academy of SciencesBeijing 100190China School of Mathematical Sciences University of Chinese Academy of SciencesBeijing 100049China School of Mathematics and Statistics Beijing Jiaotong UniversityBeijing 100044China

In this paper,the authors propose a neural network architecture designed specifically for a class of Birkhoffian systems—The Newtonian system.The proposed model utilizes recurrent neural networks(RNNs)and is based on a mathematical framework that ensures the preservation of the Birkhoffian structure.The authors demonstrate the effectiveness of the proposed model on a variety of problems for which preserving the Birkhoffian structure is important,including the linear damped oscillator,the Van der Pol equation,and a high-dimensional example.Compared with the unstructured baseline models,the Newtonian neural network(NNN)is more data efficient,and exhibits superior generalization ability.

关键词： Birkhoffian system k(z,t)-symplectic neural networks recurrent neural network

Identification of high oxygen-consuming substances in stormwater drainage systems illicitly connected with sewage system

在线全文

学校读者我要写书评

暂无评论

Journal of Environmental Sciences 2024年第4期138卷 132-140页

作者： chen Xu Zuxin Xu Wenhai Chu Shanshan Wu Rong xiao Lei Su State Key Laboratory of Pollution Control and Resource Reuse College of Environmental Science and EngineeringTongji UniversityShanghai 200092China Ministry of Education Key Laboratory of Yangtze River Water Environment Tongji UniversityShanghai 200092China Guangzhou Resource Environmental Protection Technology Co. Ltd.Guangzhou 510030China

The dissolved oxygen content in water is an important indicator for assessing the quality of the water environment,and maintaining a certain amount of dissolved oxygen is essential for the healthy development of the ecological environment.When a water body is anoxic,the activity of anaerobic microorganisms increases and organic matter is decomposed to produce a large number of blackening and odorizing substances,resulting in black and odorous water bodies,which is a very common and typical phenomenon in China.Presently,there is still a relatively universal occurrence of illicitly connected stormwater and sewage pipes in the urban drainage pipe network in China,which makes oxygen-consuming substances be directly discharged into rivers through stormwater pipes and consume the dissolved oxygen in the water bodies,resulting in an oxygen deficiency of the water.This induces seasonal or year-round black and stink phenomena in urban rivers.Hence,identifying high oxygen-consuming substances,which lays the foundation for the subsequent removal of oxygen-consuming substances,is essential.Through a series of comparisons of water quality indicators and analysis of organic characteristics,it was found that the oxygen consumption capacity of domestic sewage was higher than that of industrial wastewater in the selected area of this study,and the oxygen-consuming substances of domestic sewage were small molecular amino acids.By comparing 20 conventional free amino acids,it was found that seven of them consumed oxygen easily,and compared with chemical oxygen consumption,biological oxygen consumption was in a leading position.

关键词： Urban drainage system Oxygen-consuming substances Domestic sewage Amino acid