轧制+增材TC4合金电子束焊接接头组织与性能

研究了一种电子束焊接规范对轧制+增材TC4钛合金焊接接头组织影响,分析了焊后钛合金力学性能.结果表明,轧制侧热影响区合金组织变化较大,离焊缝中心距离越近,β转变组织含量增加,晶粒逐渐转变为等轴晶组织,等轴晶内有集束状马氏体α′相析出,越靠近焊缝等轴晶尺寸越大;增材侧热影响区组织形态变化较小,β晶粒形态保持柱状晶形态,无等轴晶区产生,晶内组织转变为马氏体α′相.焊缝两侧热影响区显微硬度变化趋势相同,均为越靠近焊缝中心,显微硬度越高,焊接重熔区硬度最高,达400HV左右.焊接接头力学性能与TC4钛合金锻件相当,且断裂位置均位于激光沉积母材区域.

不同陆地生态系统碳通量对GEOS-Chem模型模拟全球CO2浓度的影响

大气中CO2含量的增加速率已经超过了自然界所能吸收的速度,并逐步影响到全球气候变暖。利用模型模拟分析已经成为一个重要的工具用以深入对碳循环的理解。本文使用2008~2010年的生物模型SiB3(Simple Biosphere version 3)与优化后的CT2016(Carbon Tracker 2016)陆地生态系统碳通量驱动GEOS-Chem大气化学传输模型模拟全球CO2浓度。通过分析模拟CO2浓度的空间分布与季节变化,加深对全球碳源汇分布特点的理解,探究陆地生态系统碳通量不确定性对模拟结果的影响,进而认识陆地生态系统碳通量反演精度提升的重要性。SiB3与优化后的CT2016陆地生态系统碳通量都具有明显的季节变化,但在欧洲地区碳源汇的表现相反,其全球总量与空间分布也存在极大的不确定性。模拟CO2浓度结果表明:在人为活动较少地区,陆地生态系统碳通量对近地面CO2浓度空间分布起主导作用,尤其在南半球和欧洲地区模拟浓度有明显差异,且两种模拟结果的季节差异依赖于陆地生态系统碳通量的季节变化。将模拟结果与9个观测站点资料进行对比,以期选用合适的陆地生态系统碳通量来提升GEOS-Chem模拟CO2浓度的精度。实验结果表明:两种模拟结果均能较好的模拟CO2浓度的季节变化及其峰谷值,但CT2016模拟的CO2浓度在多数站点处更接近观测资料,模拟准确性更高。

锂离子动力电池组热失控扩展防护研究进展

随着新能源汽车行业的迅猛发展,电动汽车锂离子动力电池的安全问题成为重要的研究方向。而锂离子动力电池组安全性的一个核心点就是锂离子动力电池组热失控扩展。综述国内外锂离子动力电池组关于热失控扩展的研究进展,分析热失控扩展的方式及影响因素,阐述几种有代表性的热失控扩展防护措施。

常压蒸馏塔塔顶空冷器腐蚀原因分析及防护

针对中国石油辽阳石化分公司3.5Mt/a常压蒸馏塔塔顶空冷器频繁发生腐蚀泄漏的现状,分析其腐蚀泄漏原因,并采取相应措施后,脱后原油的盐含量(以NaCl计)低于3mg/L的控制指标,且投用后6台常顶空冷器未出现过泄漏,达到了预期的效果。

The impacts of modeling global CO2 concentrations with GEOS-Chem using different ocean carbon fluxes

人类活动引起大气CO2浓度升高导致全球气候变化,给人们生存和发展带来巨大的威胁。本研究对有年际变化的海洋碳通量与气候态的海洋碳通量的分布特征进行对比分析,加深对于碳源汇分布特征的理解。使用有年际变化的海洋碳通量与气候态的海洋碳通量分别驱动大气化学传输模型GEOS-Chem模拟2008至2010年间全球CO2浓度,并将模拟值与9个观测站点CO2浓度比较,以探究海洋碳通量的年际变化对模型模拟CO2浓度的影响。结果表明两种模拟结果在全年的南半球差异较大,而在四个季节中秋季的差异最大。与观测对比得到有年际变化的海洋碳通量模拟的CO2浓度更接近观测资料,模拟准确性更高。

Application of multigrid NLS-4DVar in radar radial velocity data assimilation with WRF-ARW

非线性最小二乘法的集合四维变分同化方法是一种结合了集合卡尔曼滤波和四维变分同化优势的混合同化方法。引入多重网格策略的NLS-4DVar方法不仅可以避免使用伴随模式,而且可以从大尺度到小尺度依次修正误差得到精度更高的分析场。本文将高效的多重网格策略的NLS-4DVar方法应用于雷达径向风数据同化中。通过一组基于ARW-WRF模式的观测系统模拟试验检验该方法对雷达径向风的同化能力和同化效率。试验结果显示,同化雷达径向风数据后,初始场得到明显改进且24小时累计降水预报精度有大幅度提高。与此同时,多重网格策略的NLS-4DVar方法还减少了计算代价,明显提高了计算效率。

基于WEAP水资源模型的西部矿区最优发展规划研究

水资源短缺严重影响着西部矿区煤炭开采的可持续发展。为了从水资源角度指导矿区发展规划的制定,使西部矿区综合效益达到最大,以西部某矿区为例,根据该矿区可能的发展方向,综合考虑人口增长、矿山开采规模、节水力度、绿化强度4个因素,以2015年数据为基准,制定矿山发展至2035年的8个预案。采用WEAP模型对不同预案下矿区需水量、缺水量、缺水率等的变化进行模拟。基于模拟结果,建立矿区经济、社会、生态环境多目标函数,最终选出最优预案。结果表明,使矿区综合效益值能够达到最大的预案是“强力开采强力节水适度绿化”预案,综合评价值为0.6856。以该预案作为矿区制定下一步发展规划的参考,矿区水资源承载力得到了提升,实现了矿区的综合效益最大化。

增材制造钛合金凝固晶粒调控研究进展

钛合金由于比强度高、耐腐蚀好、高温性能好等优异的性能而广泛应用于航空航天、船舶、核电等领域。增材制造技术为大型整体关键钛合金构件的短周期、低成本制造提供了变革性途径,但增材制造产生的粗大柱状晶组织导致了构件的各向异性,限制了合金性能的充分发挥。进行晶粒调控以消除各向异性、提高力学性能成为近些年的研究热点。本文综述了增材制造钛合金构件典型晶粒形貌及形成机制,阐述了国内外在增材制造钛合金晶粒调控方面的研究进展,包括工艺参数优化、微合金化改性与新合金成分设计、外加能量场、后续热处理、新型增材制造工艺和多种方法复合等,总结了各类方法的调控机制和调控效果,对增材制造钛合金凝固晶粒调控的未来发展提出了思考与展望。

上肢康复机器人联合健宁膏膏摩疗法治疗脑梗死后上肢运动功能障碍的效果

目的分析上肢康复机器人联合健宁膏膏摩疗法治疗脑梗死后上肢运动功能障碍的临床效果.方法选取2021年2月—2022年8月我院收治的脑梗死后上肢运动功能障碍患者90例,采用随机数字表法分为三组,每组30例.患者均接受脑梗死二级预防治疗及常规康复运动治疗,在此基础上,膏摩组采用自制健宁膏膏摩疗法治疗,上肢机器人组采用上肢康复机器人康复治疗,联合组采用上肢康复机器人联合健宁膏膏摩疗法治疗,均治疗4周.比较三组患者的上肢运动功能、患肢粗大及精细动作情况、日常生活能力及治疗效果.结果治疗后,联合组的简化Fugl-Meyer运动功能量表上肢部分评分、上肢动作研究量表评分、改良Barthel指数评分均高于膏摩组及上肢机器人组,组间差异有统计学意义(P<0.05).联合组的治疗总有效率为100.00%,高于膏摩组的76.67%及上肢机器人组的80.00%,组间差异有统计学意义(P<0.05).结论采用上肢康复机器人联合健宁膏膏摩疗法治疗脑梗死后上肢运动功能障碍患者的效果良好,可改善上肢运动功能及手精细运动功能,提升其日常生活活动能力,值得临床推广使用.

基于多源卫星遥感的高分辨率全球碳同化系统研究进展

大气中CO2浓度上升是全球气候变暖的重要原因,陆地生态系统碳汇显著减缓了大气中CO2浓度上升和全球变暖的速度,但具有明显的时空变异性。全球碳同化系统是精确监测全球不同地区陆地生态系统碳汇的有效技术手段。本文将介绍全球碳同化系统的发展动态,国家重点研发计划项目“基于多源卫星遥感的高分辨率全球碳同化系统研究”的目标和主要研究内容,以及已经取得的主要进展,并展望了未来应用前景。

TiC添加量对激光增材制造MC碳化物增强Inconel625复合材料组织及性能的影响

利用激光增材制造技术制备了MC碳化物增强Inconel625复合材料,研究了TiC添加量对复合材料显微组织、显微硬度和摩擦磨损性能的影响。结果表明,添加TiC的复合材料的显微组织由枝晶状γ基体与枝晶间呈弥散分布的增强体组成。随着TiC添加量的增大,复合材料中一次枝晶间距逐渐减小,而枝晶间碳化物含量和显微硬度逐渐增大,抗磨损性能比Inconel625合金提高80%以上。当TiC的质量分数为1%时,复合材料的屈服强度和抗拉强度比Inconel625合金分别提高了21.9%和27.5%,但延伸率减小。

基于TOPSIS法的西部矿区水资源承载力综合评价

水资源短缺严重制约我国西部矿区煤炭资源的开发。基于我国西部矿区煤炭和水资源之间的供需现状,分别从水资源状况、生态环境以及社会经济3方面选取指标构建评价指标体系,通过熵权法计算指标权重,并采用改进的TOPSIS评价方法对矿区水资源承载力进行定量评价,为相关部门制定合理的水资源管控措施提供参考依据。为保证评价结果的准确性、客观性以及时效性,从权重计算到评价模型建立都充分利用了原始数据。利用该模型对西部某矿区近10a的水资源承载力进行评价,结果表明该矿区水资源承载力有所提升,从参与的评价指标来看,此现象得益于该矿区不断兴建水库。但是截止到2018年水资源承载力仍然处于临界超载状态,距离可载状态仍有较大差距,说明该矿区水资源短缺问题依然严峻,相关部门应该加大管理力度,合理调控以维持水资源供需平衡。

热处理对复合制造AerMet100超高强度钢组织均匀性与拉伸性能的影响

研究了不同热处理工艺下复合制造AerMet100超高强度钢试样的组织均匀性,测试了其室温拉伸性能,并分析了其断裂机制。结果表明,沉积态复合制造AerMet100钢的显微组织很不均匀,包括激光沉积区、锻件区以及锻件热影响区;经正火+高温回火+最终热处理后,激光沉积区的晶粒由柱状晶转变为等轴晶,激光沉积区、锻件区以及锻件热影响区的显微组织基本一致,均为回火马氏体,但激光沉积区的枝晶元素偏析仍然存在;增加1200℃均匀化处理后,激光沉积区的元素偏析基本消除,复合制造AerMet100钢试样的显微组织变得非常均匀,室温拉伸性能最优,且与锻件区试样相当,拉伸试样断在了激光沉积区一侧,微观断裂机制为韧性断裂。

A land surface soil moisture data assimilation framework in consideration of the model subgrid-scale heterogeneity and soil water thawing and freezing

The Ensemble Kalman Filter (EnKF) is well known and widely used in land data assimilation for its high precision and simple operation. The land surface models used as the forecast operator in a land data assimilation system are usually designed to consider the model subgrid-heterogeneity and soil water thawing and freezing. To neglect their effects could lead to some errors in soil moisture assimilation. The dual EnKF method is employed in soil moisture data assimilation to build a soil moisture data as- similation framework based on the NCAR Community Land Model version 2.0 (CLM 2.0) in considera- tion of the effects of the model subgrid-heterogeneity and soil water thawing and freezing: Liquid volumetric soil moisture content in a given fraction is assimilated through the state filter process, while solid volumetric soil moisture content in the same fraction and solid/liquid volumetric soil moisture in the other fractions are optimized by the parameter filter. Preliminary experiments show that this dual EnKF-based assimilation framework can assimilate soil moisture more effectively and precisely than the usual EnKF-based assimilation framework without considering the model subgrid-scale heteroge- neity and soil water thawing and freezing. With the improvement of soil moisture simulation, the soil temperature-simulated precision can be also improved to some extent.

激光增材制造DD98M高温合金组织及稳定性研究

采用激光增材制造技术制备了DD98M镍基高温合金管状试样,研究了其沉积态、固溶时效态和长期时效态微观组织变化,对比分析了沉积态和固溶时效态试样中γ’相尺寸分布及在1000℃长期时效时γ’相的演化规律。结果表明:沉积态组织主要由外延生长的微细柱晶组成,枝晶间无γ-γ’共晶组织析出,试样中γ’相体积分数约为70%。合金中元素微偏析造成了枝晶干和枝晶间γ’相尺寸差异,其中枝晶干处为210 nm,枝晶间为560 nm。经固溶时效处理后,γ’相(约370 nm)均匀分布在γ基体上,其尺寸分布符合LSW模型。经1000℃长期时效500 h后,合金组织中无TCP相(拓扑密排相)生成,γ’相仍保持立方形貌,其尺寸几乎保持不变。固溶时效处理后,合金显微硬度从沉积态时的4420 MPa增加至4870 MPa,长期时效能降低合金硬度,降幅约5.9%。

A soil water and heat transfer model including changes in soil frost and thaw fronts

Freeze-thaw processes in soils,including changes in frost and thaw fronts(FTFs),are important physical processes.The movement of FTFs affects soil hydrothermal characteristics,as well as energy and water exchanges between the land surface and the atmosphere and hydrothermal processes in the land surface.This paper reduces the issue of soil freezing and thawing to a multiple moving-boundary problem and develops a soil water and heat transfer model which considers the effects of FTF on soil hydrothermal processes.A local adaptive variable-grid method is used to discretize the model.Sensitivity tests based on the hierarchical structure of the Community Land Model(CLM)show that multiple FTFs can be continuously tracked,which overcomes the difficulties of isotherms that cannot simultaneously simulate multiple FTFs in the same soil layer.The local adaptive variable-grid method is stable and offers computational efficiency several times greater than the high-resolution case.The simulated FTF depths,soil temperatures,and soil moisture values fit well with the observed data,which further demonstrates the potential application of this simulation to the land-surface process model.

An explicit four-dimensional variational data assimilation method based on the proper orthogonal decomposition: Theoretics and evaluation

The proper orthogonal decomposition (POD) method is used to construct a set of basis functions for spanning the ensemble of data in a certain least squares optimal sense. Compared with the singular value decomposition (SVD), the POD basis functions can capture more energy in the forecast ensemble space and can represent its spatial structure and temporal evolution more effectively. After the analysis variables are expressed by a truncated expansion of the POD basis vectors in the ensemble space, the control variables appear explicitly in the cost function, so that the adjoint model, which is used to de-rive the gradient of the cost function with respect to the control variables, is no longer needed. The application of this new technique significantly simplifies the data assimilation process. Several as-similation experiments show that this POD-based explicit four-dimensional variational data assimila-tion method performs much better than the usual ensemble Kalman filter method on both enhancing the assimilation precision and reducing the computation cost. It is also better than the SVD-based ex-plicit four-dimensional assimilation method, especially when the forecast model is not perfect and the forecast error comes from both the noise of the initial filed and the uncertainty of the forecast model.

GRACE terrestrial water storage data assimilation based on the ensemble four-dimensional variational method PODEn4DVar:Method and validation

Seasonal and interannual changes in the Earth's gravity field are mainly due to mass exchange among the atmosphere,ocean,and continental water sources.The terrestrial water storage changes,detected as gravity changes by the Gravity Recovery and Climate Experiment(GRACE) satellites,are mainly caused by precipitation,evapotranspiration,river transportation and downward infiltration processes.In this study,a land data assimilation system LDAS-G was developed to assimilate the GRACE terrestrial water storage(TWS) data into the Community Land Model(CLM3.5) using the POD-based ensemble four-dimensional variational assimilation method PODEn4 DVar,disaggregating the GRACE large-scale terrestrial water storage changes vertically and in time,and placing constraints on the simulation of vertical hydrological variables to improve land surface hydrological simulations.The ideal experiments conducted at a single point and assimilation experiments carried out over China by the LDAS-G data assimilation system showed that the system developed in this study improved the simulation of land surface hydrological variables,indicating the potential of GRACE data assimilation in large-scale land surface hydrological research and applications.

A new approach for Bayesian model averaging

Bayesian model averaging(BMA) is a recently proposed statistical method for calibrating forecast ensembles from numerical weather models.However,successful implementation of BMA requires accurate estimates of the weights and variances of the individual competing models in the ensemble.Two methods,namely the Expectation-Maximization(EM) and the Markov Chain Monte Carlo(MCMC) algorithms,are widely used for BMA model training.Both methods have their own respective strengths and weaknesses.In this paper,we first modify the BMA log-likelihood function with the aim of removing the addi-tional limitation that requires that the BMA weights add to one,and then use a limited memory quasi-Newtonian algorithm for solving the nonlinear optimization problem,thereby formulating a new approach for BMA(referred to as BMA-BFGS).Several groups of multi-model soil moisture simulation experiments from three land surface models show that the performance of BMA-BFGS is similar to the MCMC method in terms of simulation accuracy,and that both are superior to the EM algo-rithm.On the other hand,the computational cost of the BMA-BFGS algorithm is substantially less than for MCMC and is al-most equivalent to that for EM.

Effects of sample density on the assimilation performance of an explicit four-dimensional variational data assimilation method

The concepts of sample sphere radius and sample density are proposed in this paper to help illustrate that different vector transformations result in diverse sample density with the same sample ensemble, which finally affects their assimilation performance. Several numerical experiments using a onedimensional (1-D) soil water equation and synthetic observations are conducted to evaluate this new theory in land data assimilation.