Inverse analysis of coupled carbon-nitrogen cycles against multiple datasets at ambient and elevated CO_(2)

Aims Carbon(C)sequestration in terrestrial ecosystems is strongly regulated by nitrogen(N)processes.However,key parameters that determine the degree of N regulation on terrestrial C sequestration have not been well quantified.Methods Here,we used a Bayesian probabilistic inversion approach to estimate 14 target parameters related to ecosystem C and N interactions from 19 datasets obtained from Duke Forests under ambient and elevated carbon dioxide(CO_(2)).Important FindingsOur results indicated that 8 of the 14 target parameters,such as C:N ratios in most ecosystem compartments,plant N uptake and external N input,were well constrained by available datasets whereas the others,such as N allocation coefficients,N loss and the initial value of mineral N pool were poorly constrained.Our analysis showed that elevated CO_(2)led to the increases in C:N ratios in foliage,fine roots and litter.Moreover,elevated CO_(2)stimulated plant N uptake and increased ecosystem N capital in Duke Forests by 25.2 and 8.5%,respectively.In addition,elevated CO_(2)resulted in the decrease of C exit rates(i.e.increases in C residence times)in foliage,woody biomass,structural litter and passive soil organic matter,but the increase of C exit rate in fine roots.Our results demonstrated that CO_(2)enrichment substantially altered key parameters in determining terrestrial C and N interactions,which have profound implications for model improvement and predictions of future C sequestration in terrestrial ecosystems in response to global change.

Effect of dry-wet cycles on dynamic properties and microstructures of sandstone:Experiments and modelling

Underground pumped storage power plant(UPSP)is an innovative concept for space recycling of abandoned mines.Its realization requires better understanding of the dynamic performance and durability of reservoir rock.This paper conducted ultrasonic detection,split Hopkinson pressure bar(SHPB)impact,mercury intrusion porosimetry(MIP),and backscatter electron observation(BSE)tests to investigate the dynamical behaviour and microstructure of sandstone with cyclical dry-wet damage.A coupling FEM-DEM model was constructed for reappearing mesoscopic structure damage.The results show that dry-wet cycles decrease the dynamic compressive strength(DCS)with a maximum reduction of 39.40%,the elastic limit strength is reduced from 41.75 to 25.62 MPa.The sieved fragments obtain the highest crack growth rate during the 23rd dry-wet cycle with a predictable life of 25 cycles for each rock particle.The pore fractal features of the macropores and micro-meso pores show great differences between the early and late cycles,which verifies the computational statistics analysis of particle deterioration.The numerical results show that the failure patterns are governed by the strain in pre-peak stage and the shear cracks are dominant.The dry-wet cycles reduce the energy transfer efficiency and lead to the discretization of force chain and crack fields.

Sensitivity of Nonlinearity on the ENSO Cycle in a Simple Air-Sea Coupled Model

In this paper,the influence of the El NioSouthern Oscillation (ENSO) cycle on the sensitivity of nonlinear factors in the numerical simulation is investigated by conducting numerical experiments in a simple air-sea coupled model for ENSO prediction.Two sets of experiments are conducted in which zonal nonlinear factors,meridional nonlinear factors,or both are incorporated into the governing equations for the atmosphere or ocean.The results suggest that the ENSO cycle is very sensitive to the nonlinear factor of the governing equation for the atmosphere or ocean.Thus,incorporating nonlinearity into air-sea coupled models is of exclusive importance for improving ENSO simulation.

Economy, environmental assessment and energy conservation for separation of isopropanol/diisopropyl ether/water multi-azeotropes via extractive distillation coupled pervaporation process

This wok proposed the extraction distillation coupled pervaporation(ED+PV) technology process using two different solvents to separate isopropanol(IPA) and diisopropyl ether(DIPE) from DIPE/IPA/H_(2)O ternary heterogeneous azeotropes in industrial wastewater from the synthesis of isopropanol in this study.Based on strict design specifications, simulation and sequential iteration methods are used for process design and optimization. Compared to the ethylene glycol(EG)-EG+H_(2)O process and the 1,3-propanediol(PDO)-IPA+H_(2)O process, the total annual cost(TAC) of the EG-IPA+H_(2)O process decreased by 20.76% and 7.86%(PDO). Compared to the EG-EG+H_(2)O process, the TAC of the PDO-IPA+H_(2)O process reduced 14%, but the global warming potential(GWP) and human toxicity of the PDO-IPA+H_(2)O process increased 11.3% and 4.07% respectively. Compared to the PDO-IPA+H_(2)O process, the EG-IPA+H_(2)O process saves 7.86%(TAC), 9.78%(GWP) and 9.85%(human toxicity). The ED+PV process with EG is superior to PDO in factors of TAC, energy consumption, human toxicity and environment. The EG-IPA+H_(2)O process changed the separation order of the products of the multi-azeotropic system, reduced the cost and energy conservation of the system, and enhanced the environmental protection evaluation of the process, is the best process through life cycle assessment for analyzing the economy, energy conservation, environmental assessment and human toxicity, designing cleaner products, controlling waste discharge, and promoting the chemical purification industry. This work provides a new process design and optimized separation ideas, will have a good guiding significance for the research and application separation of multi-azeotropic mixture with mixed solvents in organic wastewater from the cleaner chemical production, has been up to standard wastewater discharge process, and realized the development goal of carbon peak and carbon neutrality in the sustainable development of chemical clean industry.

Concrete Damage and Neutralization under Coupling Effect of Carbonation and Freeze-thaw Cycles

Simulating the coupling effect brought by freeze-thaw and carbonation environment, we experimentally investigated concrete durability, the variation characteristics of both concrete dynamic elastic modulus, and its neutralization depth. The influences imposed by carbonation on the freeze-thaw damage of concrete was studied as well and vise versa so as to shed light on the influencing mechanism together with the mutual interaction between them. The experimental results show that the damage caused by the coupling effect of freeze-thaw and carbonation on concrete is severer than any single effect of them two could bring. This provides certain theoretical references and paves down foundations for the further study in concrete durability related by the coupling environmental effect.

Coupling Mechanism of Saturated Concrete Subjected to Simultaneous Fatigue Loading and Freeze-thaw Cycles

The coupling mechanism of saturated concrete subjected to simultaneous 4-point fatigue loading and freeze-thaw cycles was, for the first time, experimentally studied by strain technology. The coupling strain, temperature strain and fatigue strain of concrete specimens were measured at the same time from one sample with stain analysis method and the relationship among these three kinds of strains was studied by fitting data to present coupling mechanism at macro level. The results showed that there was no interaction between fatigue strain and temperature strain and the coupling strain could be written by linear superposition of temperature strain and fatigue strain.

Annual Cycle and Interannual Variability in the Tropical Pacific as Simulated by Three Versions of FGOALS

The seasonal cycle and interannual variability in the tropical oceans simulated by three versions of the Flexible Ocean-Atmosphere-Land System （FGOALS） model （FGOALS-gl.0, FGOALS-g2 and FGOALS- s2）, which have participated in phases 3 and 5 of the Coupled Model Intercomparison Project （CMIP3 and CMIP5）, are presented in this paper. The seasonal cycle of SST in the tropical Pacific is realistically reproduced by FGOALS-g2 and FGOALS- s2, while it is poorly simulated in FGOALS-gl.0. Three feedback mechanisms responsible for the SST annual cycle in the eastern Pacific are evaluated. The ocean-atmosphere dynamic feedback, which is successfully re- produced by both FGOALS-g2 and FGOALS-s2, plays a key role in determining the SST annual cycle, while the overestimated stratus cloud-SST feedback amplifies the annual cycle in FGOALS-s2. Because of the seri- ous warm bias existing in FGOALS-gl.0, the ocean-atmosphere dynamic feedback is greatly underestimated in FGOALS-gl.0, in which the SST annual cycle is mainly driven by surface solar radiation. FGOALS-gl.0 simulates much stronger ENSO events than observed, whereas FGOALS-g2 and FGOALS- s2 successfully simulate the observed ENSO amplitude and period and positive asymmetry, but with less strength. Further ENSO feedback analyses suggest that surface solar radiation feedback is principally re- sponsible for the overestimated ENSO amplitude in FGOALS-gl.0. Both FGOALS-gl.0 and FGOALS-s2 can simulate two different types of E1 Nifio events -- with maximum SST anomalies in the eastern Pacific （EP） or in the central Pacific （CP） -- but FGOALS-g2 is only able to simulate EP E1 Nifio, because the negative cloud shortwave forcing feedback by FGOALS-g2 is much stronger than observed in the central Pacific.

Coupled modeling of land hydrology-regional climate including human carbon emission and water exploitation

碳排出物和水使用是人的活动的二种主要类型。揭示这二项活动是否能在中国修改水文学周期和气候系统，我们用地区性的气候模型 RegCM4 进行了数字实验的二个集合。在过去常学习气候的回答到人的碳排出物的第一个实验，因为碳排出物的影响能越过整个国家被检测，模型在全部中国上被设置。从第一个实验的结果揭示了温度可以显著地以超过 0.1 的率从 2007 ～ 2059 增加的那近表面的表情 ? 漠 ? 偉 ??? 猠散慮楲獯※ ?? 潬杮眠瑩 ? 楲楳杮琠浥数慲畴敲 ? 景吗？

Observed Solar Cycle Variation of the Stratospheric QBO Generated in the Mesosphere and Amplified by Upward Propagating Waves

With an analysis of zonal wind observations over 40 years, Salby and Callaghan [1] showed that the Quasi-biennial Oscillation (QBO) at 20 km is modulated by 11-year solar cycle (SC) variations from about 12 to 20 m/s (Figure 2). The observations are reproduced qualitatively in a study with the 3D Numerical Spectral Model, which shows that the SC effect of the stratospheric QBO is produced by dynamical downward coupling originating in the mesosphere. In this modeling study, the SC period is taken to be 10 years, and a realistic heat source is applied varying exponentially with altitude: 0.2%, surface;2%, 50 km;20%, 100 km and above. The numerical results show that the variable solar radiation in the mesosphere around 65 km generates a hemispheric symmetric Equatorial Annual Oscillation (EAO), which is modulated by relatively large SC variations. Under the influence of wave mean flow interactions, the EAO propagates into the lower atmosphere and is the dynamical source or pacemaker for the large SC modulation of the QBO. The numerical results show that the upward propagating small-scale gravity waves from the troposphere amplify the SC modulations of the QBO and EAO in the stratosphere, part of the SC mechanism. The zonal winds of the equatorial QBO and EAO produce through the meridional circulation measurable SC variations in the temperature of the stratosphere and troposphere at high latitudes. Analysis of NCEP temperature and zonal wind data (1958 to 2006) provides observational evidence of the EAO with SC variations around 11 years.

Synchronization transition of limit-cycle system with homogeneous phase shifts

The behaviors of coupled oscillators, each of which has periodic motion with random natural frequency in the absence of coupling, are investigated when phase shifts are considered. In the system of coupled oscillators, phase shifts are the same between different oscillators. Synchronization and synchronization transition are revealed with different phase shifts. Phase shifts play an important role for this kind of system. When the phase shift α〈 0.5π, the synchronization state can be attained by increasing the coupling, and the system cannot reach the synchronization state while α≥ 0.5π. A clear scaling between complete synchronization critical coupling strength Kpc and α - 0.5π is found.

Study on damage-stress loss coupling model of rock and prestressed anchor cable in dry-wet environment

The loss of anchoring force is one of the problems to be solved urgently.The anchorage loss is a key factor causing the failure of anchoring engineering,so it is crucial to study the time-dependent variation of anchoring force.Alternating dry and wet(D-W)conditions have a significant effect on deformation of rock.The anchoring system is composed of anchoring components and rock mass,and thus rock deformation has a significant impact on the loss of anchoring force.Quantifying rock deformation under the effects of D-W cycles is a prerequisite to understanding the factors that influence loss of anchoring force in anchor bolts.In this study,we designed an anchoring device that enabled real-time monitoring of the variation in strain during D-W periods and rock testing.Nuclear magnetic resonance(NMR)measurements showed that under D-W conditions,the increment in porosity was smaller for prestressed rock than unstressed rock.The trends of prestress loss and strain variation are consistent,which can be divided into three characteristic intervals:rapid attenuation stage,slow attenuation stage and relatively stable stage.At the same stress level,the rate of stress loss and strain for the soaking specimen was the highest,while that of the dried specimen was the lowest.In the same D-W cycling conditions,the greater the prestress,the smaller the strain loss rate of the rock,especially under soaking conditions.The characteristics of pore structure and physical mechanical parameters indicated that prestress could effectively suppress damage caused by erosion related to D-W cycles.The study reveals the fluctuation behavior of rock strain and prestress loss under D-W conditions,providing a reference for effectively controlling anchoring loss and ideas for inventing new anchoring components.

Variability of Air-Sea CO_(2) Fluxes and Dissolved Inorganic Carbon Distribution in the Atlantic Basin:A Coupled Model Analysis

The biogeochemical dynamics of carbon in the ocean is a subject of fundamental interest to environmental studies. In this context, we have implemented a ten year run of the Brazilian Earth System Coupled Ocean-Atmosphere Model (BESM-OA2.3) integrated with TOPAZ biogeochemical model for the Atlantic basin. The modeled ΔpCO2 for the tropical Atlantic shows very clearly a high dominance of positive fluxes, that is, the CO2 fluxes are sea-to-air throughout the tropical region and for both winter and summer periods. In the mid-latitudes regions negatives fluxes (air-to-sea) were observed for both seasons. An exception to this pattern is an extensive negative tongue on the latitude 10N. The occurrence of this negative ΔpCO2 tongue region in the Tropical Atlantic is highly correlated to negative Evaporation-Precipitation values during this season. In the northern hemisphere (NH) summer the negative values of ΔpCO2 in the tropical Atlantic region are concentrated in the adjacent zone of the Amazon river mouth due to the North Equatorial Counter Current intensification. This process favors the formation of a carbon sink in the adjacent region of the Amazon river mouth. Model results show lowest values of dissolved inorganic carbon (DIC) in a surface layer (100 - 150 m). Highest DIC values are observed in deeper layers and concentrated in an equatorial band. The chlorophyll bloom in equatorial zones was well represented by the model. These blooms are the result of equatorial upwelling that brings the high concentration tongues of DIC present in the equatorial band towards the euphotic zone. This is the first published paper about the BESM-OA2.3 integrated with TOPAZ. The presented results suggest that this modeling system is able to reproduce the main regional carbon dynamics features of the mid-latitude/tropical Atlantic.

森林植被不同尺度的碳水过程及耦合机制研究进展

[目的]陆地生态系统中的碳循环和水循环是陆地生态系统物质和能量循环的核心,也是连接地圈、生物圈和大气层的纽带。森林植被是陆地生态系统的重要组成部分,是表征陆地碳-水循环的重要变量,在维持生物圈和大气圈的动态平衡中发挥着重要作用。目前,对陆地生态系统中碳-水循环的耦合关系和机制缺乏系统的分析和总结。[方法]从森林植被碳与水过程及其相互作用、植被水分利用和耦合机制的角度,综述了森林植被碳与水循环过程及其相互作用的研究与进展,以及不同空间尺度(叶片到区域/全球尺度)碳-水耦合的定义、方法、进展和展望。[结果]新兴的技术和方法实现了不同尺度碳水过程的高频观测,WUE等耦合指标体系推动了碳水耦合机制的研究和发展。[结论]通过系统阐述植被碳水耦合关系的多尺度整合和碳水耦合机理,为系统认识森林碳水耦合机理和水资源管理提供了理论基础,对未来植被经营管理决策具有重要的科学支撑意义。

校地双循环耦合视阈下地方高校区域特色人才培养研究

区域特色人才是充分掌握、适应特定区域所具有的特殊条件、状态和特性,并以此为基础形成某种知识素质能力的特质,能够在区域内有效就业创业,促进区域经济社会发展的人才。培养区域特色人才,要使高校人才培养的内循环、小循环与地方经济社会发展的外循环、大循环在质态、性质、特点、规模、方向等方面互相适应、支撑和耦合。当前,区域特色人才培养存在社会契合度、社会支撑度和政府政策力度不足等问题。优化区域特色人才培养,需要纵深推进地方经济循环和地方高校人才培养循环的利益、过程、人才、制度耦合,强化人才培养的驱动力量、根本基础、主体力量和制度保障。

基于陆气耦合模式的降雨径流模拟研究进展

基于陆气耦合模式的降雨径流模拟是变化环境下水文循环过程研究的重要内容之一。围绕陆气耦合降雨径流模拟,分析基于陆气耦合模式的降雨径流模拟框架,对比基础输入资料、天气模式和陆面水文模型各方面的优缺点,回顾基于该框架的发展历程,从集合预报、数据驱动、陆面水文模型与天气模式3个方面介绍了陆气耦合降雨径流模拟技术的发展,提出多尺度转换、双向耦合、不确定性问题及误差修正4个热点关键技术问题,并对未来研究进行展望,以期为推进基于陆气耦合模式的降雨径流模拟研究提供参考。

陆地高分辨率水文—生物地球化学过程CNMM-DNDC三维模型的研发及应用进展

CNMM-DNDC模型是本文作者团队研发的陆地高分辨率水文—生物地球化学过程三维模型。本文系统介绍了建模背景和理念、核心过程和模型特点、模拟功能和观测验证、多尺度区域或流域初步应用以及未来发展展望。自2018年刊发首个版本以来,该模型经过了多方面科学过程改进和模拟功能扩展,在元素化学反应、物质相变和机械迁移等基本物理、化学、生物过程层面,完成了对陆地表层系统碳氮磷水循环全耦合的精细刻画。迄今开展的观测验证表明,CNMM-DNDC模型基本普适于不同生物气候带(从热带到寒区多年冻土地带)的流域或区域长时间序列“三高”(时间、空间和过程高分辨率)综合模拟,实现对陆地生态系统的碳、氮、磷、水三维运移、水土流失、水力驱动溶解态和颗粒态碳氮磷横向迁移、碳氮温室气体和污染气体排放、生态系统生产力、水分蒸散发和水分能量平衡等众多可持续发展目标表征变量的预测。该模型广泛推广应用于多尺度区域或流域的复杂过程虚拟科学试验研究和服务于面向生态环境建设与减污降碳的优化调控决策,可望为协同落实联合国多个可持续发展目标提供先进的数值模拟技术支撑。

基于生命周期理论的《物流综合实训》课程改革研究

产品生命周期理论凭借将产品分成不同策略阶段的优点而得到市场的认可,将产品生命周期理论运用到课程教学中便产生了课程教学生命周期理论。由于传统的《物流综合实训》课程教学内聚过强、耦合性不足,生命周期特性不足和智慧特性不足等问题,这些问题严重制约了课程教学的质量和效益。基于此,文章以传统《物流综合实训》课程教学模式为研究对象,结合生命周期理论,将课程教学看作是一种产品,并将产品生命周期理论运用到课程教学中,提出相应的课程改革策略。同时,文章还对生命周期理论与课程建设的研究趋势进行了探讨,以期对课程教学改革提供实践性支持。

热、振及热振耦合作用下IGBT模块失效分析

针对功率器件IGBT模块在多场载荷作用下的焊层失效问题,设计并构建了IGBT模型,基于有限元仿真软件对IGBT模块进行热循环、随机振动以及热振耦合试验,并对三种载荷条件下失效位置的分布规律以及失效模式进行对比分析。结果表明,在热循环载荷条件下,应力集中在DBC焊接层下表面中心位置,最大应力值为226.84 MPa;在随机振动载荷条件下,应力集中在DBC焊接层下表面周边边角位置,最大应力值约为0.0023 MPa;在热振耦合条件下,应力集中在DBC焊接层上表面靠近中心及周边边角位置,最大应力值为377 MPa。热振耦合条件下的焊料层力学行为表现有所变化。研究结果对多种不同载荷下功率器件IGBT模块的响应特性分析提供参考,同时为模块结构的设计提供理论依据。

基于循环工况的电动汽车双电机驱动系统协同优化设计

双电机优化设计需要考虑双电机系统的耦合运行,在传统优化方法中多采用估计效率Map的方法得到双电机系统最优的转矩分配系数。然而在高效电机优化设计中无法忽视估计法带来的误差。此外不同工况下电机的控制策略也不同。为了提高双电机驱动系统全工况运行效率,本文基于两种循环工况,系统地提出了一种电动汽车双电机协同优化设计方法。首先通过参数匹配获得了初代电机参数,接着提出了基于半解析模型的电机效率Map计算方法。基于此方法研究了不同工况下双电机系统的最优转矩分配和控制策略。然后基于粒子群算法,考虑电机不同工况下的控制策略对双电机本体参数进行了全工况优化。最后搭建了半实物实验平台,仿真和实验结果表明,所提优化方法能够提高双电机驱动系统的运行效率。

硫酸盐侵蚀和干湿、冻融循环下混凝土单轴受压损伤对比

为研究宁夏典型服役环境下混凝土材料的损伤特点,本文在硫酸钠侵蚀和干湿、冻融循环三因素的共同作用和耦合作用下研究混凝土棱柱体试样的不同单轴受压应力-应变特点。改变硫酸钠溶液浓度和腐蚀次数,测量试样的质量损失率、相对动弹性模量以及应力-应变曲线。结果表明:随着腐蚀次数的增加,耦合作用下质量损失率和相对动弹模均先增大后减小,共同作用下则均逐渐减小;随着硫酸钠溶液浓度的增大,两种腐蚀制度下试样的应力-应变曲线上升段斜率和峰值应力均逐渐减小,且共同作用比耦合作用劣化效果更明显;随着腐蚀次数的增加,两种腐蚀制度下试样的应力-应变曲线上升段斜率均逐渐减小,耦合作用下峰值应力先增大后减小,共同作用下则逐渐减小,两种腐蚀制度下峰值应变均逐渐增大,共同作用比耦合作用劣化更大。本文提出的两种腐蚀制度下的混凝土应力-应变曲线预测模型可为宁夏服役环境下的混凝土结构寿命预测提供依据。