Ensemble Simulation of Land Evapotranspiration in China Based on a Multi-Forcing and Multi-Model Approach

In order to reduce the uncertainty of offline land surface model （LSM） simulations of land evapotranspiration （ET）, we used ensemble simulations based on three meteorological forcing datasets [Princeton, ITPCAS （Institute of Tibetan Plateau Research, Chinese Academy of Sciences）, Qian] and four LSMs （BATS, VIC, CLM3.0 and CLM3.5）, to explore the trends and spatiotemporal characteristics of ET, as well as the spatiotemporal pattern of ET in response to climate factors over China's Mainland during 1982-2007. The results showed that various simulations of each member and their arithmetic mean （EnsAVlean） could capture the spatial distribution and seasonal pattern of ET sufficiently well, where they exhibited more significant spatial and seasonal variation in the ET compared with observation-based ET estimates （Obs_MTE）. For the mean annual ET, we found that the BATS forced by Princeton forcing overestimated the annual mean ET compared with Obs_MTE for most of the basins in China, whereas the VIC forced by Princeton forcing showed underestimations. By contrast, the Ens_Mean was closer to Obs_MTE, although the results were underestimated over Southeast China. Furthermore, both the Obs_MTE and Ens_Mean exhibited a significant increasing trend during 1982-98; whereas after 1998, when the last big EI Nifio event occurred, the Ens_Mean tended to decrease significantly between 1999 and 2007, although the change was not significant for Obs_MTE. Changes in air temperature and shortwave radiation played key roles in the long-term variation in ET over the humid area of China, but precipitation mainly controlled the long-term variation in ET in arid and semi-arid areas of China.

Kinetic Model and Simulation Analysis for Toluene Disproportionation and C9-Aromatics Transalkylation

A new kinetic model for commercial unit of toluene disproportionation and C9-armatiocs transalkylation is developed based on the reported reaction scheme.A time based catalyst deactivation function taking weight hourly space velocity(WHSV)into account is incorporated into the model,which reasonably accounts for the loss in activity because of coke deposition on the surface of catalyst during long-term operation.The kinetic parameters are benchmarked with several sets of balanced plant data and estimated by the differential variable metric optimiza- tion method.Sets of plant data at different operating conditions are applied to make sure validation of the model and the results show a good agreement between the model predictions and plant observations.The simulation analysis of key variables such as temperature and WHSV affecting process performance is discussed in detail,giv- ing the guidance to select suitable operating conditions.

A simulation study of water property changes using geometrical alteration in SPC/E

We present a systematic investigation of the impact of changing the geometry structure of the SPC/E water model by performing a series of molecular dynamic simulations at 1 bar （1 bar = 105 Pa） and 298.15 K. The geometric modification includes altering the H-O-H angle range from 90° to 115° and modifying the O-H length range from 0.90 A to 1.10 A in the SPC/E model. The former is achieved by keeping the dipole moment constant by modifying the O-H length, while in the latter only the O-H length is changed. With the larger bond length and angle, we find that the liquid shows a strong quadrupole interaction and high tetrahedral structure order parameter, resulting in the enhancement of the network structure of the liquid. When the bond length or angle is reduced, the hydrogen bond lifetime and self-diffusion constant decrease due to the weakening of the intermolecular interaction. We find that modifying the water molecular bond length leading to the variation of the intermolecular interaction strength is more intensive than changing the bond angle. Through calculating the average reduced density gradient and thermal fluctuation index, it is found that the scope of vdW interaction with neighbouring water molecules is inversely proportional to the change of the bond length and angle. The effect is mainly due to a significant change of the hydrogen bond network. To study the effect of water models as a solvent whose geometry has been modified, the solutions of ions in different solvent environments are examined by introducing NaCI. During the dissolving process, NaCI ions are ideally dissolved in SPC/E water and bond with natural water more easily than with other solvent models.

生物科学与技术虚拟仿真实验教学中心的建设与应用

生物科学与技术虚拟仿真实验教学中心通过优秀科研项目转化以及与高新技术企业合作开发,建设了一批高质量的生物类虚拟仿真实验教学资源。多层次、多元化的资源为学生前沿科学知识学习、综合性科研训练和生物下游产业技术训练提供有利环境,有效地实现教学模式的转变以及学科交叉知识的学习和延伸。全天候开放共享虚拟仿真实验教学平台,实现虚拟仿真实验教学软件、实验标准化视频、教学课件和测试题库等线上教学资源的有机整合,满足随时随地实验教学需求,支持了一系列的混合式线上线下实验教学课程开展。生物科学与技术虚拟仿真实验教学中心与国家级生物科学实验教学示范中心形成了“双中心”融合发展的创新人才培养实验教学体系,“虚实结合”的实验教学模式,提升了学生的综合科研能力与教师的业务水平,培养了满足社会需求的生物技术创新实践人才。

微振动模拟与主被动隔振一体化实验平台

针对遥感卫星地面微振动实验的复杂要求,设计了一种同时具备微振动模拟与主被动隔振功能的一体化微振动实验平台,并对该平台的主、被动隔振性能以及微振动模拟效果分别进行了仿真分析和实验测试。其中,被动隔振由气浮支撑实现,主动隔振采用主动阻尼方法抑制共振峰,微振动模拟采用基于线性系统频响函数的控制策略。实验结果表明,平台前六阶的模态频率分布均小于10 Hz,被动隔振系统能大幅抑制10~200 Hz频段内的地面微振动;主动隔振能够实现14 dB的隔振系统共振峰衰减效果。微振动模拟功能能够有效产生接近星上的单频和多频真实扰动线谱,在特定频谱的扰动模拟实验中,幅值最大误差为5.9%,在误差允许范围内。该多功能一体化实验平台的各项功能均能满足地面模拟实验需求。

数字图像处理及应用虚拟仿真实验平台设计

针对数字图像处理及应用实验教学的需要,结合当下图像处理技术的热点应用,利用虚拟仿真技术、交互操作等信息化手段进行实验教学,设计并开发了数字图像处理及应用虚拟仿真实验教学平台。实验教学平台包含交通标志数字图像处理、图像分类、图像识别、视频处理、自动驾驶应用等5个虚拟仿真实验教学资源,共13个交互实验步骤。该平台特色显著、虚实结合,达到了良好的教学效果,为“新工科”背景下的虚拟仿真实验教学提供有益的参考。

加强油源岩沉积成岩成油模拟实验研究

干酪根热降解生油学说源于油页岩高温热解生成“人造石油”的生产实践,其理论内涵是凡富含干酪根的岩石,经高温热解后其所含的干酪根都可以生成“人造石油”。应用该学说的高温热解实验方法,可以评价油页岩的品质及其热解生成“人造石油”的潜力,因此仅适用于油页岩的评价研究。但该学说的倡导者却认为油页岩和油源岩都是能生成石油的岩石,如果埋藏较浅时就称为油页岩,如果埋藏较深时就是油源岩,因此干酪根热降解生油学说同样适用于油源岩。这种观点并没有被美欧等国家所认可,但遗憾的是,在改革开放之初不甚了解国外同行对该学说如何评价的情况下,中国的石油地质家不仅全盘接受了该学说,而且推广应用了40多年。为彻底改变这种被动局面,唯一可行的就是通过油源岩沉积成岩成油模拟实验,研究油源岩中可溶有机质的生油问题和评价方法。

微缝吸声板吸声性能探讨

为了研究微缝吸声板的几何参数对其吸声性能的影响,以微孔吸声板理论为基础,设计制作了微缝吸声板,对微缝吸声板进行阻抗管试验并与仿真模拟结果进行对比分析,仿真结果与试验结果基本一致。通过仿真不同几何参数下微缝吸声板的相对声阻抗,计算得出吸声系数进行对比,结果表明,当缝宽和膜厚相对增加时,微缝吸声板的吸声峰值和吸声带宽均略有减小。

一种多飞行器协同的GNC系统飞行模拟平台设计

空间站在轨组装和长期运营阶段涉及到多飞行器独立飞行、飞行器间交会对接、多飞行器组合体融合控制、多飞行器分离过程控制和飞行器返回再入等复杂飞行任务,完整、真实的飞行模拟是必需且至关重要的.基于时间同步、实时数据交换的分布式一体化仿真架构,设计了一种多飞行器协同的通用半物理制导、导航与控制(guidance,navigation and control,GNC)系统飞行模拟平台,可很好地满足复杂系统的飞行模拟需要.平台由若干灵活、可扩展的通用模拟器构成,单个模拟器通过配置可以实现任一飞行器的功能,能够独立对指定飞行器的全任务过程进行仿真.平台通过靶场仪器组B时间码(inter-range instramentation group-B,IRIG-B)信号进行时间同步,利用1553B总线完成动力学仿真数据实时交换,并在多模拟器之间通过协调机制实现热并网后进行协同仿真.该模拟平台成功应用于空间站飞行控制演练.

铝型材静电粉末喷涂模型的研究与应用

针对实际生产中企业为实现铝型材表面均匀涂层而耗费巨大人力物力的问题,提出了一种适用于生产实际的变高斯分布模型。通过对铝型材静电粉末喷涂影响因素的分析,使用控制变量法进行定点和连续喷涂实验,获得涂层厚度实验数据,基于高斯分布对定点实验数据进行拟合,对于拟合模型存在的远离中心截面偏差问题,采用变峰值宽度的方式对模型进行优化修正,进一步提高了模型与实验数据的拟合程度,在此基础上,通过实验数据分析了静电电压、粉末流量、喷涂速度对膜厚分布的影响,建立了不同参数下静电粉末喷涂涂层的变高斯分布模型。最后进行了喷涂实验,铝型材成品的膜厚分布情况符合模型仿真预测的结果,表明该模型能准确预测不同参数下铝型材的膜厚分布情况,在生产实际中,模型的应用可以为均匀涂层提供可靠的仿真参考和生产指导,有效减少企业调试参数的次数,提高了企业的生产效率。

基于InVEST和PLUS模型下的土地利用变化及生境质量演变分析:以汉中盆地为例

汉中盆地是中国南水北调工程中的重要源头区,分析区内土地利用及生境质量,能提高对该地区演变规律的认识,进一步保护下游研究区的自然资源和生态环境安全。笔者基于2000~2020年20年内共3期土地利用数据,建立了研究区多类型土地利用数据库和生境质量评估体系,从土地利用转移矩阵、景观格局指数、生境质量等多个方面对研究区内的土地利用的时空变化进行研究,并利用PLUS模型进行土地利用扩张和预测分析。结果表明:2000~2020年,土地利用类型变化较大,变化转移主要发生在水田和农村居民点用地、城镇用地之间;蔓延度指数逐年减少,景观破碎化程度较高;生境质量结果呈逐年下降趋势,高值面积减少并向南部扩展,低值面积增多并以城镇为中心向外辐射扩散,高等级的生态质量景观由水域和林草为主,主要沿汉江流域分布。

基于粒子群算法的瞬变电磁检测小车结构优化

利用瞬变电磁法进行管道移动检测的过程中,经常由于检测设备抖动造成检测信号的误差或检测失败。为此,设计了一款可搭载瞬变电磁检测设备的自动检测小车。基于检测小车和埋地管道检测的工作要求,进行可变线圈搭载平台和减震机构设计,并利用解析法对弹簧阻尼器的刚度系数和阻尼系数进行优化。基于ANSYS Workbench软件对上摆臂和车轮连接件进行拓扑优化。基于减震机构的关键零件下摆臂对整体性能的影响,利用CCD中心组合试验法,进行仿真试验设计取得数据,并利用响应面法得出最大应力和质量与下摆臂设计参数的映射关系。采用粒子群算法对映射关系进行优化设计,获得最大应力和质量最小时的下摆臂参数。优化结果表明:采用Adams对优化后的检测小车进行运动学仿真,小车平台质心在竖直方向上位移和速度的峰值分别降低约55.7%和26.5%,均值分别降低约67.9%和24.2%,波动的次数也明显减少,检测小车性能显著增强。所得结论可为检测小车设计提供理论参考,对管道缺陷检测领域具有一定的工程意义。

一种大口径平面镜支撑结构的仿真与实验

为提高600 mm大口径立式平面镜沿光轴旋转90°后的表面面型测量精度,对多孔支撑结构下5种不同材料的平面镜重力变形进行有限元仿真分析,并通过实验测量探究旋转后的静置时间对面型精度的影响等问题。结果表明,该多孔支撑结构下的平面镜表面由重力导致的轴向变形量不超过14 nm,满足精度要求。该多孔结构支撑的平面镜沿光轴旋转90°静置1 h后达到稳定状态,与静置2 h后的面型结果PV值仅相差0.337 nm,RMS值相差0.081 nm,实验探究了静置时间对面型结果的影响。研究发现,在至多去除6%外口径的条件下可以大幅降低平面镜表面面型PV值,PV值降低超过50 nm,由此提出一种制造大口径平面镜时通过设置支撑结构缓冲区以提高面型精度的方法,可以有效提高大口径平面镜的面型精度。

干燥机非稳态运行模拟分析——定量分析

根据计算模型,分析了蒸汽回转干燥机和流化床干燥机在进料含水率、进料温度和加热蒸汽压力三个失稳后的运行状况。结果表明,进料含水率从2%升高至4%,回转干燥机的产能降低39%、蒸汽单耗增加63%;流化床干燥机的产能降低43%、蒸汽单耗增加75%。进料温度从15℃升高至75℃,回转干燥机的产能增加67%、蒸汽单耗减少45%;流化床干燥机产能增加97%,蒸汽单耗减少57%。加热蒸汽压力从0.4 MPa(G)升高到1.6 MPa(G),回转干燥机的产能提升77%,流化床干燥机产能提升74%。

大跨度悬挑钢结构施工技术优化过程模拟与实测对比

针对悬挑钢结构单一结构复杂,施工难度较大,施工阶段的受力状态与设计阶段、结构最终受力状态完全不一致等问题。运用有限元仿真软件MIDAS CIVIL对挑空连廊钢结构施工过程进行模拟分析,拆撑后钢桁架竖向位移不满足规范要求,钢桁架施工时应设置预拱度。对钢桁架重要部位进行应力及位移监测,对比分析拆除临时支撑后钢结构竖向位移的实测值与仿真值,两者基本相符,施工阶段均处于安全施工状态。结果表明,采用有限元软件可以模拟分析获得大跨度连廊及悬挑钢结构施工阶段受力、变形状态,为大跨度连廊及悬挑钢结构现场安全施工提供指导。

基于索-梁结构的斜拉桥非线性振动仿真研究

本文建立了索-梁结构的有限元模型,对斜拉桥线性和非线性振动问题进行研究.首先对结构进行模态分析,发现结构振动表现出全局模态,局部模态以及混合模态,且索梁两者之间固有频率相互影响,对低阶频率影响较大,对高阶频率影响较小.其次,应用有限元软件对索-梁结构的自由振动和强迫振动进行仿真研究.结果表明:整个自由振动过程中频率有先增大后减小的趋势,且最终小于真实频率;在强迫振动中,观察到了丰富的非线性振动现象,包括索的亚谐波共振和内共振,与以往的实验和理论研究结果定性上得到验证;为斜拉桥全桥非线性动力学分析提供参考.

10万t/a混合C5生产1,4-丁二醇工艺中氧化反应器的模拟与优化

针对10万t/a顺酐法生产1,4-丁二醇工艺受原料影响较大的缺陷,结合我国混合C5烃的市场情况,采用C5原料生产1,4-丁二醇,针对该工艺的关键设备-正戊烷氧化反应器,采用Aspen Plus软件对影响顺酐和苯酐产率和选择性的关键参数进行了灵敏度分析,优化了反应参数,提高了顺酐和苯酐的产率和选择性。在优化条件下,正戊烷的转化率以及苯酐和顺酐的产量大大提高。在单耗不变的情况下,顺酐的产率和选择性由原来的34.1%和6.9%分别增加到45.1%和32.1%,苯酐的产率从15.7%降低到13.5%,苯酐的选择性从3.2%升高到9.6%,而一氧化碳的产率和选择性由原来的43.1%和8.7%分别降低到32.0%和2.7%。优化后的反应条件提高了顺酐的产率和选择性,有利于正戊烷氧化生成顺酐的反应。

Electromagnetic interaction between local surface plasmon polaritons and an atmospheric surface wave plasma jet

We analyze the electromagnetic interaction between local surface plasmon polaritons （SPPs） and an atmospheric surface wave plasma jet （ASWPJ） in combination with our designed discharge device. Before discharge, the excitation of the SPPs and the spatial distribution of the enhanced electric field are analyzed. During discharge, the critical breakdown electric field of the gases at atmospheric gas pressure and the surface wave of the SPPs converted into electron plasma waves at resonant points are studied. After discharge, the ionization development process of the ASWPJ is simulated using a two- dimensional fluid model. Our results suggest that the local enhanced electric field of SPPs is merely the precondition of gas breakdown, and the key mechanism in maintaining the discharge development of a low-power ASWPJ is the wave-mode conversion of the local enhanced electric field at the resonant point.

Phase transition and chemical decomposition of liquid carbon dioxide and nitrogen mixture under extreme conditions

Thermodynamic and chemical properties of liquid carbon dioxide and nitrogen（CO_（2~–）N_2） mixture under the conditions of extremely high densities and temperatures are studied by using quantum molecular dynamic（QMD） simulations based on density functional theory including dispersion corrections（DFT-D）. We present equilibrium properties of liquid mixture for 112 separate density and temperature points, by selecting densities ranging from ρ = 1.80 g/cm^3 to 3.40 g/cm^3 and temperatures from T = 500 K to 8000 K. In the range of our study, the liquid CO_（2~–）N_2 mixture undergoes a continuous transition from molecular to atomic fluid state and liquid polymerization inferred from pair correlation functions（PCFs）and the distribution of various molecular components. The insulator–metal transition is demonstrated by means of the electronic density of states（DOS）.

A study on the surface overpressure distribution and formation of a double curvature liner under a two-point initiation

The formation mechanism of an EFP(explosively formed projectile)using a double curvature liner under the overpressure effect generated by a regular oblique reflection was investigated in this paper.Based on the detonation wave propagation theory,the change of the incident angle of the detonation wave collision at different positions and the distribution area of the overpressure on the surface of the liner were calculated.Three dimensional numerical simulations of the formation process of the EFP with tail.as well as the ability to penetrate 45#steel were performed using LS-DYNA software,and the EFP ve locity,the penetration ability,and the forming were assessed via experiments and x_ray photographs.The experimental results coincides with those of the simulations.Results indicate that the collision of the detonation wave was controlled to be a regular oblique reflection acting on the liner by setting the di-mensions of the unit charge and maintai ning the pressure at the collision point region at more than 2.4 times the CJ detonation when the incident angle approached the cnitical angle.The distance from the liner midline to the boundary of the area within which the pressure ratio of the regular oblique reflection pressure to the qJ detonation pressure was greater than 2.5,2,and 15was approximately 0.66 mm,132 mm,and 3.3 mm,respectively.Itis noted that pressure gradient caused the liner to turn inside out in the middle to form the head of the EFP and close the two tails of the EFP at approximately 120μs.The penetration depth of the EFP into a 45#steel target exceeded 30 mm,and there was radial expansion between the head and tail of the EFP,increasing the penetration resistance of the EFP.Therefore,the structural size of the unit charge and the liner can be further optimized to reduce resist ance to increase the penetration ability of the EFP.