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Simulated effects of interactions between ocean acidification,marine organism calcification, and organic 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 organisms. 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 organic 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 organic 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 organic 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 organism calcification, and Ca CO3-bound organic carbon

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

System identification and control of the ground operation mode of a hybrid aerial-ground robot

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Control Theory and Technology 2023年第3期21卷 458-468页

作者： Muqing cao Xinhang Xu Kun cao Lihua Xie School of Electrical and Electronic Engineering Nanyang Technological UniversitySingaporeSingapore

This paper presents an in-depth analytical and empirical assessment of the performance of DoubleBee,a novel hybrid aerial-ground ***,the dynamic model of the robot with ground contact is analyzed,and the unknown parameters in the model are *** apply an unscented Kalman filter-based approach and a least square-based approach to estimate the parameters with given measurements and inputs at every time *** data are collected and used to estimate the parameters;test data verify that the values obtained are able to model the rotation of the robot accurately.A gain-scheduled feedback controller is proposed,which leverages the identified model to generate accurate control inputs to drive the system to the desired *** system is proven to track a constant-velocity reference signal with bounded *** and real-world experiments using the proposed controller show improved performance than the PID-based controller in tracking step commands and maintaining attitude under robot movement.

关键词： Modelling Parameter identification Hybrid robots Robot control

Design and numerical analysis of serpentine microchannel integrated with inner-wall ridges for enhanced droplet mixing

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Science China(Technological Sciences) 2023年第2期66卷 560-573页

作者： cao Xiang CHEN YongPing Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education School of Energy and EnvironmentSoutheast UniversityNanjing 210096China Jiangsu Key Laboratory of Micro and Nano Heat Fluid Flow Technology and Energy Application School of Environmental Science and EngineeringSuzhou University of Science and TechnologySuzhou 215009China

A numerical model is developed for three-dimensional droplet mixing in serpentine microchannels with inner-wall ridges(referred to as SMR microchannels).The underlying mechanisms of mixing in SMR microchannels are revealed,and the effects of the ridge width and ridge number on mixing inside droplets of different sizes are *** results indicate that SMR microchannels are capable of enhancing the mixing efficiency by 3.6%–12.5%compared with that in smooth serpentine microchannels,particularly when the droplet length is larger than the microchannel width and the width ratio of the ridge to the microchannel is 0.25–*** above mixing enhancement is determined by two main factors:the combined effects of the vortex pair and reverse flow,and non-horizontal ***,when the width ratio is 1,there is a maximum 16.0%increase in mixing efficiency for small droplets with a length equal to the microchannel ***,for small droplets,mixing in an SMR microchannel is worse than in a smooth serpentine microchannel when the width ratio is less than *** increasing the ridge number,when the width ratio is 0.25,the mixing efficiency is reduced for small droplets but increased for larger droplets.

关键词： droplet mixing serpentine microchannel ridge microfluidics

Stochastic stability of cubature predictive filter

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Science China(Information Sciences) 2016年第9期59卷 107-130页

作者： Lu cao Xiaoqian CHEN The State Key Laboratory of Astronautic Dynamics China Xi'an Satellite Control Center College of Aerospace Science and Engineering National University of Defense Technology

In this paper, the cubature predictive filter(CPF) is derived based on a third-degree spherical-radial cubature rule. It provides a set of cubature-points scaling linearly with the state-vector dimension, which makes it possible to numerically compute multivariate moment integrals encountered in the nonlinear predictive filter(PF). In order to facilitate the new method, the algorithm CPF is given firstly. Then, the theoretical analyses demonstrate that the estimated accuracy of the model error and system for the proposed CPF is higher than that of the traditional PF. Moreover, the authors analyze the stochastic boundedness and the error behavior of CPF for general nonlinear systems in a stochastic framework. In particular, the theoretical results present that the estimation error remains bounded and the covariance keeps stable if the system’s initial estimation error,disturbing noise terms as well as the model error are small enough, which is the core part of the CPF *** of the results have been demonstrated by numerical simulations for a nonlinear example system.

关键词： predictive filter cubature rule nonlinear filter stochastic system

Flat-plate hypersonic boundary-layer ?ow instability and transition prediction considering air dissociation

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Applied Mathematics and Mechanics(English Edition) 2019年第5期40卷 719-736页

作者： Yufeng HAN Wei cao Department of Mechanics Tianjin University

The effects of air dissociation on ?at-plate hypersonic boundary-layer ?ow instability and transition prediction are studied. The air dissociation reactions are assumed to be in the chemical equilibrium. Based on the ?at-plate boundary layer, the ?ow stability is analyzed for the Mach numbers from 8 to 15. The results reveal that the consideration of air dissociation leads to a decrease in the unstable region of the ?rst-mode wave and an increase in the maximum growth rate of the second mode. High frequencies appear earlier in the third mode than in the perfect gas model, and the unstable region moves to a lower frequency region. When the Mach number increases, the second-mode wave dominates the transition process, and the third-mode wave has little effect on the transition. Moreover, when the Mach number increases from 8 to 12, the N-factor envelope becomes higher, and the transition is promoted. However, when the Mach number exceeds 12, the N-factor envelope becomes lower, and the transition is delayed. The N-factor envelope decreases gradually with the increase in the altitude or Mach number.

关键词： air dissociation transition prediction boundary layer

Research of influence of reduced-order boundary on accuracy and solution of interior points

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Applied Mathematics and Mechanics(English Edition) 2017年第1期38卷 111-124页

作者： Yunlong LI Wei cao Department of Mechanics Tianjin UniversityTianjin 300072China

The flow field with a high order scheme is usually calculated so as to solve complex flow problems and describe the flow structure accurately. However, there are two problems, i.e., the reduced-order boundary is inevitable and the order of the scheme at the discontinuous shock wave contained in the flow field as the supersonic flow field is low. It is questionable whether the reduced-order boundary and the low-order scheme at the shock wave have an effect on the numerical solution and accuracy of the flow field inside. In this paper, according to the actual situation of the direct numerical simulation of the flow field, two model equations with the exact solutions are solved, which are steady and unsteady, respectively, to study the question with a high order scheme at the interior of the domain and the reduced-order method at the boundary and center of the domain. Comparing with the exact solutions, it is found that the effect of reduced-order exists and cannot be ignored. In addition, the other two model equations with the exact solutions, which are often used in fluid mechanics, are also studied with the same process for the reduced-order problem.

关键词： reduced-order boundary shock wave accuracy numerical solution high order scheme

Driving forces of continental lithospheric deformation

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Science China Earth Sciences 2024年第12期67卷 3950-3956页

作者： Zebin cao Lijun LIU State Key Laboratory of Lithospheric and Environmental Coevolution Institute of Geology and GeophysicsChinese Academy of SciencesBeijing 100029China

*** The lithosphere is a fundamental component of Earth’s layered structure,and its stress state and deformation mechanisms are critical to understanding Earth’s tectonic evolution(Ghosh and Holt,2012)and managing natural resources(Heidbach et al.,2018).According to the classical theory of plate tectonics,significant lithospheric deformation is expected near active plate boundaries due to the relative motion between tectonic plates.

关键词： tectonic lithospheric Earth

Sensitivity of tropical cyclone damage costs to integrated wind profile

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Journal of Ocean Engineering and Science 2021年第3期6卷 257-264页

作者： cao Wang School of Civil Mining and Environmental EngineeringUniversity of WollongongWollongongNSW 2522Australia

The dramatic tropical cyclone(TC)damages in coastal areas around the world have gained significant attention from asset owners,policy makers and *** estimate of TC damage for a specific region of interest is informative of the preparedness and resilience of the area subjected to TC hazards,and thus should be conducted using a quantitative approach.A reasonable indicator of TC damage should incorporate not only the TC characteristics(e.g.,intensity,frequency and duration)but also the vulnerability of the TC-prone *** this paper,a new indicator is proposed to measure the TC threat,which takes into account both the TC characteristics and the vulnerability of the *** indicator has two forms:the first one considers the maximum wind speed only and the second incorporates the integrated wind speed *** historical damage scenarios along the US East Coast,as well as those in Hong Kong,China,are examined to demonstrate the applicability of the proposed *** show that the proposed indicator is capable of representing the impact of TC wind field profile on the TC damage *** proposed indicator could be further used to project the future TC damages for areas subjected to TC hazards.

关键词： Adaptive potential damage index Damage costs Integrated wind profile Tropical cyclone Wind speed.

Iterative learning based fault diagnosis for discrete linear uncertain systems

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Journal of Systems Engineering and Electronics 2014年第3期25卷 496-501页

作者： Wei cao Ming Sun College of Computer and Control Engineering Qiqihar University

In order to detect and estimate faults in discrete lin-ear time-varying uncertain systems, the discrete iterative learning strategy is applied in fault diagnosis, and a novel fault detection and estimation algorithm is proposed. And the threshold limited technology is adopted in the proposed algorithm. Within the chosen optimal time region, residual signals are used in the proposed algorithm to correct the introduced virtual faults with iterative learning rules, making the virtual faults close to these occurred in practical systems. And the same method is repeated in the rest optimal time regions, thereby reaching the aim of fault diagnosis. The proposed algorithm not only completes fault detection and estimation for discrete linear time-varying uncertain systems, but also improves the reliability of fault detection and decreases the false alarm rate. The final simulation results verify the validity of the proposed algorithm.

关键词： discrete linear uncertain system threshold limited technology iterative learning fault estimation.