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Simulated effects of interactions between ocean acidification,marine orga.ism calcification, and orga.ic carbon export on ocean carbon and oxygen cycles

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Science China Earth Sciences 2018年第6期61卷 804-822页

作者： Han ZHANG long CAO Department of Atmospheric Sciences School of Earth Sciences Zhejiang University

Ocean acidification caused by oceanic uptake of anthropogenic carbon dioxide(CO_2) tends to suppress the calcification of some marine orga.isms. This reduced calcification then enhances surface ocean alkalinity and increases oceanic CO_2 uptake, a process that is termed calcification feedback. On the other hand, decreased calcification also reduces the export flux of calcium carbonate(Ca CO_3), potentially reducing Ca CO_3-bound orga.ic carbon export flux and CO_2 uptake, a process that is termed ballast feedback. In this study, we incorporate a range of different parameterizations of the links between orga.ic carbon export, calcification, and ocean acidification into an Earth system model, in order to quantify the long-term effects on oceanic CO_2 uptake that result from calcification and ballast feedbacks. We utilize an intensive CO_2 emission scenario to drive the model in which an estimated fossil fuel resource of 5000 Pg C is burnt out over the course of just a few centuries. Simulated results show that, in the absence of both calcification and ballast feedbacks, by year 3500, accumulated oceanic CO_2 uptake is2041 Pg C. Inclusion of calcification feedback alone increases the simulated uptake by 629 Pg C(31%), while the inclusion of both calcification and ballast feedbacks increase simulated uptake by 449–498 Pg C(22–24%), depending on the parameter values used in the ballast feedback scheme. These results indicate that ballast effect counteracts calcification effect in oceanic CO_2 uptake. Ballast effect causes more orga.ic carbon to accumulate and decompose in the upper ocean, which in turn leads to decreased oxygen concentration in the upper ocean and increased oxygen at depths. By year 2600, the inclusion of ballast effect would decrease oxygen concentration by 11% at depth of ca. 200 m in tropics. Our study highlights the potentially critical effects of interactions between ocean acidification, marine orga.ism calcification, and Ca CO3-bound orga.ic carbon

关键词： Ocean carbon cycle Ocean acidification Carbon cycle modeling Carbon cycle-climate feedback

New Method to Improve Dynamic Stiffness of Electro-hydraulic Servo Systems

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Chinese Journal of Mechanical Engineering 2013年第5期26卷 997-1005页

作者： BAI Yanhong QUAN long Key Laboratory of Advanced Transducers and Intelligent Control System of Ministry of Education Taiyuan University of Technology School of Electronics Information Engineering Taiyuan University of Science and Technology

Most current researches working on improving stiffness focus on the application of control *** controller in closed-loop hydraulic control system takes effect only after the controlled position is deviated,so the control action is *** dynamic performance aga.nst force disturbance and dynamic load stiffness can’t be improved evidently by advanced control *** this paper,the elementary principle of maintaining piston position unchanged under sudden external force load change by charging additional oil is *** this basis,the conception of raising dynamic stiffness of electro hydraulic position servo system by flow feedforward compensation is put *** a scheme using double servo valves to realize flow feedforward compensation is presented,in which another fast response servo valve is added to the regular electro hydraulic servo system and specially utilized to compensate the compressed oil volume caused by load impact in *** two valves are arranged in parallel to control the cylinder ***,the model of flow compensation is derived,by which the product of the amplitude and width of the valve’s pulse command signal can be *** determination rules of the amplitude and width of pulse signal are concluded by analysis and *** the proposed scheme,simulations and experiments at different positions with different force changes are *** simulation and experimental results show that the system dynamic performance aga.nst load force impact is largely improved with decreased maximal dynamic position deviation and shortened settling *** is,system dynamic load stiffness is evidently *** paper proposes a new method which can effectively improve the dynamic stiffness of electro-hydraulic servo systems.

关键词： electro-hydraulic servo system flow feedforward compensation dynamic load stiffness double-valve actuation

Structural controllability of multi-agent systems with absolute protocol under fixed and switching topologies

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Science China(Information Sciences) 2017年第9期60卷 226-240页

作者： Yongqiang GUAN long WANG Center for Complex Systems School of Mechano-Electronic EngineeringXidian University Center for Systems and Control College of Engineering Peking University

The paper investiga.es the structural controllability of leader-follower multi-agent systems under fixed and switching topologies. Three models of agents: double-integrator, high-order integrator and generallinear dynamics are analyzed. Necessary and sufficient graphical conditions are provided for structural controllability based on communication topology of the system. In particular, a linear neighbor-based control protocol is designed for generic linear agents under which structural controllability is proved to be uniquely determined by communication topology structure. The role that leaders play in the structural controllability of multi-agent system is characterized, and a method is developed to realize structural controllability under single leader. The results clearly indicate the role of leaders and the effect of communication topology on structural controllability.

关键词： multi-agent systems structural controllability absolute protocol leader-follower connectedness switching topology

An Additive-Multiplicative Cox-Aalen Subdistribution Hazard Model for Competing Risks Data

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Journal of Systems Science & Complexity 2019年第6期32卷 1727-1746页

作者： LI Wanxing long Yonghong Department of Statistics School of Mathematics and Information ScienceShaanxi Normal UniversityXi'an 710119China School of Mathematics Renmin University of ChinaBeijing 100872China

This paper proposes a flexible additive-multiplicative Cox-Aalen hazard model which allows time-varying covariate effects for the subdistribution in a competing risks *** ted estimating equation approaches under an covariates-dependent adjusted weight by fitting the Cox proportional hazard model for the censoring distribution are established for inference on the model parametric and nonparametric *** addition,large number properties are presented and the finite sample behavior of the proposed estimators is evaluated through simulation studies,estimators from the proposed method perform satisfactorily on reduction of the *** authors apply our model to a competing risks data set from a tamoxifen trail for breast cancer study.

关键词： Aalen's additive model competing risks cumulative incidence function estimating equation inverse probability of censoring weight proportional hazard function time-varying effects

Multi‑level autonomous integrity monitoring method for multi‑source PNT resilient fusion naviga.ion

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Satellite Naviga.ion 2023年第3期4卷 210-226页

作者： Rui Chen long Zhao School of Automation Science and Electrical Engineering Beihang UniversityBeijing 100191China

For the integrity monitoring of a multi-source PNT(Positioning,Naviga.ion,and Timing)resilient fusion naviga.ion system,a theoretical framework of multi-level autonomous integrity monitoring is *** to the mode of multi-source fusion naviga.ion,the framework adopts the top-down logic structure and establishes the naviga.ion source fault detection model based on the multi-combination separation residual method to detect and isolate the fault source at the system level and subsystem *** isolated non-redundant naviga.ion sources,the system level recovery verification model is *** the isolated multi-redundant naviga.ion sources,the sensor fault detection model optimized with the dimension-expanding matrix is used to detect and isolate the fault sensors,and the isolated fault sensors are verified in ***,according to the fault detection and verification results at each level,the observed information in the fusion naviga.ion solution is dynamically *** this basis,the integrity risk dynamic monitoring tree is established to calculate the Protection Level(PL)and evaluate the integrity of the multi-source integrated naviga.ion *** autonomous integrity monitoring method proposed in this paper is tested using a multi-source naviga.ion system integrated with Inertial Naviga.ion System(INS),Global Naviga.ion Satellite System(GNSS),long Baseline Location(LBL),and Ultra Short Baseline Location(USBL).The test results show that the proposed method can effectively isolate the fault source within 5 s,and can quickly detect multiple faulty sensors,ensuring that the positioning accuracy of the fusion naviga.ion system is within 5 m,effectively improving the resilience and reliability of the multi-source fusion naviga.ion system.

关键词： Autonomous integrity monitoring Fault detection and isolation Multi-source PNT resilient fusion naviga.ion Protection level

Mathematical Model of Hydrodynamic Torque Converter and Analytic Description of Streamline

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Chinese Journal of Mechanical Engineering 2009年第1期22卷 70-77页

作者： LIU Shiping QUAN long Institute of Mechatronics Engineering Taiyuan University of Technology Taiyuan 030024 China

The mathematical model of a 3-element centripetal-turbine hydrodynamic torque converter and analytic description of fluid flow inside the hydrodynamic torque converter are investiga.ed. A new torus coordinate system is proposed so as to quantitatively describe fluid movement inside the hydrodynamic torque converter. The particle movement inside the hydrodynamic torque converter is decomposed into meridional component movement and torus component movement, and a universal meridional streamline equation is derived. According to the relationship between the converter wheel velocity polygon and its blade angle, a torus streamline differential equation is established. The universal meridional streamline equation is approximated with square polynomials. The approximation error curve is given and the percentage error is not greater than 0.86%. Considered as a function of polar angle, the blade angle cotangent of each converter wheel varies linearly with polar angle. By using integral calculus, torus streamline equations are obtained. As a result, the problem of difficult flow description of the hydrodynamic torque converter is solved and a new analytic research system is established.

关键词： hydrodynamic torque converter toms coordinate system analytic description meridional streamline equation toms streamline equation

Invalidity of Geometrical Interpretation of F-Spin Structure of Nuclear Rotations by Otsuka’s View

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Chinese Physics Letters 1995年第6期12卷 342-343页

作者： long Guilu Department of Physics Tsinghua UniversityBeijing 100084

In Otsuka's view of nuclear rotations neutrons and protons are not rotating around a common axis,but rather around separate *** this letter,we pointed out that this invalidates the geometrical interpretation of F-spin structure of the neutron-proton interacting boson model,where the angle between the axis of symmetries of neutron ellipsoid and proton ellipsoid is used to determine whether a state is F-spin symmetric or mixed symmetric.

关键词： symmetric validity rotating

Entrance Effect on Load Capacity of Orifice Compensated Aerostatic Bearing with Feeding Pocket

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Chinese Journal of Mechanical Engineering 2010年第4期23卷 451-459页

作者： long Wei BAO ga.g School of Mechatronics Engineering Harbin Institute of Technology Harbin 150001 China

The current research of the aerostatic thrust bearing mainly focuses on the porous material bearing and inherent compensated air bearing, which aims at obtaining small physical dimension and large load capacity. Although porous material bearing appears larger load capacity, materials anisotropy itself and void content distortion caused in heat-treating, and machining processes add greater complexity to internal flow transfer process. Inherent compensated air bearing has the advantages of simple structure and good stability, but its load capacity and static stiffness is not worth somewhat. In this paper, based on hydrostatic lubrication theory, finite volume method is presented for taking entrance effects into account in computing pressure distribution, load capacity and mass flow rates of circular aerostatic thrust bearings. Technical analysis, numerical simulations and laboratory demonstration tests of influence of pocket diameter and pocket depth on loading capacity of aerostatic thrust bearing are carried out on simple orifice compensated air bearings with feeding pockets. The static parameters, such as air consumption and pressure distributions, are measured as a function of supply pressure and air ga. height for several different orifices and pockets size. Entrance effects are described in term of typical throttling types, and the effect of pocket diameter and pocket depth on load capacity is systematically described respectively. The proposed research results uncover the causation of throttling action of the orifice compensated air bearing with feed pocket and further develop and improve the design theory of air bearing.

关键词： aerostatic thrust bearing feeding pocket entrance effects

Characterization of condensed phase nitric acid particles formed in the ga. phase

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Journal of Environmental Sciences 2011年第3期23卷 412-418页

作者： long Jia Yongfu Xu State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100029 China Graduate University of Chinese Academy of Sciences Beijing 100049 China

The formation of nitric acid hydrates has been observed in a chamber during the dark reaction of NO2 with O3 in the presence of air. The size of condensed phase nitric acid was measured to be 40-100 nm and 20-65 nm at relative humidity （RH） ≤ 5% and RH = 67% under our experimental conditions, respectively. The nitric acid particles were collected on the glass fiber membrane and their chemical compositions were analyzed by infrared spectrum. The main components of nitric acid hydrates in particles are HNO3.3H2O and NO3-.xH2O （x≥ 4） at low RH, whereas at high RH HNO3.H2O, HNO3-2H2O, HNO3.3H2O and NO3--xH20 （x≥ 4） all exist in the condensed phase. At high RH ***2O （x ≤3） collected on the glass fiber membrane is greatly increased, while NO3-.xH2O （x ≥ 4） decreased, compared with low RH. To the best of our knowledge, this is the first time to report that condensed phase nitric acid can be generated in the ga. phase at room temperature.

关键词： nitric acid particles relative humidity chamber