多向不规则波浪的确定性模拟

波浪波动时间过程及波列的模拟,对于开展实际波浪对于工程建筑物的作用具有重要的意义。本文采用线性叠加的单叠加模型,建立了多向不规则波浪的确定性模拟方法。基于理论模拟的规则波、单向不规则波和多向不规则波,验证了波浪确定性模拟方法的有效性。定性地对比分析了模拟波列和已知波列的一致性;定量地研究了模拟波浪在空间范围rr/Ls的误差分布情况(rr表示指定位置与给定位置的空间距离,Ls为有效波长)。并且建议,采用本文方法进行波浪确定性模拟时,最佳的浪高仪间距应小于0.12Ls。

基于陆面水文耦合模式CLHMS的淮河流域水文过程的模拟评估及其不确定性分析

利用最新的CFSR（Climate Forecast System Reanalysis）再分析及观测的降水和地表气温资料驱动陆面水文耦合模式CLHMS（Coupled Landsurface and Hydrologic Model System），对淮河流域1980-2003年共24年的水文水循环过程进行了模拟，系统评估了CLHMS对淮河流域水文过程的模拟能力及其不确定性。分析结果表明，CLHMS模式对淮河流域水文过程具有良好的模拟能力，模式尤其对湿润年份流域的水量平衡以及河道流量的季节、年际变化具有很强的模拟能力，而对降水偏少的干旱年份，模式模拟的河道流量通常会高于观测实况，与实况间存在着一定的偏差，而这也是导致CLHMS对流域水文过程模拟能力存在显著年代际差异的主要原因。基于三组不同降水强迫的流域水文过程模拟结果比较表明，降水驱动资料准确与否是陆面水文模拟最主要的不确定性来源之一，正是由于CFSR再分析降水与观测降水之间存在较大的差异，从而导致CFSR降水驱动下模式模拟的淮河流域河道流量与观测存在较大的偏差，其模拟性能相对较差。进一步分析还表明，可以保持较强降水日变化的时间解集方法，也是保证合理模拟流域水文过程的重要因素。

融合AR模型和MCMC方法的水文模拟不确定性分析

为提高水文模型参数识别的可靠性,融合自回归模型与马尔可夫链-蒙特卡洛方法(auto regressive model based modified Markov Chain-Monte Carlo,AR-MCMC),利用自回归模型刻画残差序列的自相关性,修正MCMC方法中的残差协方差矩阵。通过新疆提孜那甫河流域融雪径流模型(SRM)的案例分析发现:融雪径流模拟的残差序列具有显著的自相关性;修正残差协方差矩阵后,边缘似然值更大;综合考虑多项评价指标,AR-MCMC方法在识别期与验证期推求的预测区间均优于MCMC方法;对比2种方法在识别期与验证期的纳什系数,采用AR-MCMC方法依次为0.86、0.89,而采用MCMC方法依次为0.84、0.87,即AR-MCMC方法获取的模型拟合效果更好。分析结果表明,相对于传统的MCMC方法,AR-MCMC方法能够更好地对研究区融雪径流过程进行模拟预测。

草原生态系统模式中参数不确定性导致的模拟结果不确定性研究

基于五变量草原生态系统理论模式,应用与参数有关的条件非线性最优扰动(CNOP-P)方法,探讨了由参数不确定性导致的草原生态系统模式模拟结果的不确定性问题。参数的不确定性可能来源于观测和(或)对物理过程描述等的不确定性。选取了五变量草原生态系统模式中具有物理意义的32个模式参数进行数值试验。试验结果表明,对所考察的32个模式参数,在一定的不确定性和给定的优化时刻范围内,单独优化每个参数所得CNOP-Ps的联合模态与同时优化32个参数所得CNOP-P的模态并不相同。比较了上述两类参数误差以及随机参数误差对草原生态系统模拟的差异。随机参数误差与上述优化方法所得参数误差的不确定性范围大小相同。数值结果表明,同时优化32个参数所得CNOP-P类型参数误差使得草原生态系统模拟的不确定性程度最大。这种影响表现在使得草原生态系统转变为沙漠生态系统,或者使得草原生态系统转变为具有更多生草量的草原生态系统。上述数值结果不依赖于优化时间和参数不确定性程度的大小。这些数值结果建议我们应当考虑多参数的非线性相互作用来研究草原生态系统模式模拟的不确定性问题,并且揭示出CNOP-P方法是讨论上述问题的一个有用的工具。

金属凝固微观组织数值模拟研究现状

通过对凝固微观组织的模拟,能很好地预测材料的性能,对实际应用具有重要意义。对微观组织模拟中的3个主要模型(确定性模型、随机性模型和相场模型)及它们的应用现状进行了阐述,并分析了它们的优缺点。随着计算机技术的发展,新的计算模型的出现将使金属凝固微观组织的数值模拟向着高精度、高效率和高速度的方向发展。

铸造合金凝固组织的计算机模拟与预测

数值模拟技术与计算机技术的迅速发展,使凝固过程的数值模拟正在由宏观向微观转变。微观模拟不仅可以得到材料的凝固组织,而且还能为宏观模拟提供准确的潜热释放信息。对宏观和微观现象的完整耦合可以使我们对铸造凝固过程作出更加准确的模拟预测。针对目前微观组织模拟的研究现状,介绍了几种主要的模拟研究方法,如确定性模拟方法、随机性模拟方法和相场方法等,阐述了其主要特征和模拟微观组织时存在的优缺点,并给出了各种模拟方法的计算实例。由于凝固组织数值模拟的复杂性,对其进行深入的研究是必要的,也是未来计算材料科学的重要发展方向。最后对微观模拟中的问题及发展方向作了分析。

铸件微观组织数值模拟的研究进展

针对目前微观组织模拟的最新研究现状,简述了几种主要的研究方法,如确定性模拟方法、随机性模拟方法和相场方法等,探讨了其主要特征和模拟微观组织时的局限性,同时展望了凝固组织模拟的发展方向。

半固态合金组织模拟方法

随着半固态成形技术的发展,半固态成形机理和理论研究成为人们关注的热点问题,也是推动半固态成形技术发展的关键。目前在这一领域的模拟工作和机理研究主要集中在宏观尺度上的温度场模拟,从而定性解释成形工艺并试图使模具设计趋于合理,而对微观组织的定量模拟工作则较少。综合评述了近年来材料计算领域中关于材料相变模拟方法及研究进展,介绍了几种主要的微观组织模拟方法,如确定性模拟方法、随机性模拟方法和相场方法等,阐述了各种方法的主要特点,提出了与宏观尺度耦合计算进行半固态成形过程模拟的多尺度模拟方法,从而定量、直观地模拟和分析成形条件与微观组织演化的关系,对成形过程的定量预测和控制具有重要意义。

基于GP14.3运动学混合震源模型和SPECFEM 3D谱元法的宽频地震动模拟

基于确定性物理模型的全过程地震动模拟是现代地震工程的重要发展方向.然而受限于合理震源模型和计算资源需求,目前模拟的有效频率还多处于低频范围,难以满足工程结构敏感频带(5~10 Hz或更高)需求.本文即借助运动学混合震源模型能激发宽频地震波和谱元法空间高精度及计算收敛快的优势,首先将确定性的凹凸体震源模型与GP14.3随机震源模型结合得到有限断层运动学混合震源模型,进而将上述混合震源模型开发到SPECFEM 3D谱元法开源代码中,实现了基于谱元法和运动学混合震源模型的全过程宽频带地震动模拟.将方法首先应用于一维波速结构模型0~10 Hz地震动模拟,通过与频率波数域(FK)方法结果进行比较,验证了方法的精度;进而应用于2021年5月21日云南漾濞6.4级地震0.1~5 Hz地震动模拟,通过与4个台站的时程记录和相应反应谱的比较,以及与NGA-West2地震动衰减方程在频率0.1~5 Hz的反应谱的比较,检验了方法的适用性;最后给出了漾濞地区的地震动峰值加速度(PGA)和峰值速度(PGV)云图,分析了漾濞地震下近场强地面运动的空间分布特征.结果显示,震中PGA接近400 cm·s-2,PGV达到45 cm·s^(-1),烈度达到Ⅸ度,且受局部地形起伏影响,大理以及洱海西侧位置出现高烈度异常区.

旋流排螺装置中水螺运动数值模拟

本文在对旋流排螺装置中水流运动三维数值模拟的基础上,采用拉格朗日法初步构建钉螺运动的数学模型,对钉螺运动进行确定性模拟和随机性模拟。结果表明,旋流排螺装置中钉螺的运动与钉螺粒径、装置进口流量有关,进口流量越小,钉螺粒径越大,其通过底出水口排出的趋势越明显;钉螺粒径越小,运动的随机性越大。

CMIP6火山强迫的气候响应模拟比较计划（VolMIP）概况与评述

为揭示造成火山强迫气候响应模拟不确定性的原因,第六次国际耦合模式比较计划(CMIP6)设立了火山强迫的气候响应模拟比较计划(VolMIP)。该计划由基于历史火山爆发的理想火山扰动试验组成,包括三组主要的试验:第一组关注短期(季节至年际)大气动力响应;第二组关注海气耦合系统的长期(年际至年代际)响应;第三组关注气候系统对火山群的响应。VolMIP旨在通过给定相同的辐射强迫并进行多成员集合模拟,揭示模式对外强迫响应的不确定性,通过设定不同的背景气候态,阐明内部变率和外强迫对气候响应的相对贡献。

基于改进Newmark模型的同震滑坡易发性研究

Newmark模型被广泛应用于同震滑坡快速评估,然而传统模型受限于参数(如黏聚力、内摩擦角)的不确定性.本文从概率建模的角度,基于蒙特卡罗方法提出改进Newmark模型,该模型从特定分布(如高斯分布)中抽取随机样本以解释参数不确定性.以2017年九寨沟地震为例阐述了改进Newmark模型在同震滑坡易发性快速评估中的应用,并与不同采样策略下3种机器学习模型相对比.结果表明:改进Newmark模型极高易发区面积占比为5%,包含滑坡数量占比为59.6%,频率比值为128.4,不同采样策略下模型平均AUC值为0.70,表明改进Newmark模型在同震滑坡易发性评估中取得较好效果.本文所提出的模型由特定参数驱动,与数据驱动方法的区别在于不依赖历史滑坡数据,其成果可应用于震后滑坡快速评估,或在给定地震情境下模拟区域滑坡失稳概率以服务于工程早期选址.

一种随机竞争学习矢量量化图像编码算法

本文分析了确定性模拟退火技术、竞争学习算法在图像编码中的压缩机理 ,提出了一种新的随机竞争学习矢量量化算法 .该算法将竞争过程与代价函数最小化结合起来 ,在学习过程中引入模拟退火 ,并针对矢量量化图像编码的特点 ,提出了新的参数选取策略 ,具有对初始码书依赖性小 ,不会局部最小 ,收敛速度快 ,码书性能好等优点 .文中还通过计算机实践对该方法进行了性能分析 ,验证了算法的有效性和鲁棒性 .

Characterizing uncertainty in pavement performance prediction

Taking variability and uncertainty involved in performance prediction into account, in order to make the prediction reliable and meaningful, a distribution-based method is developed to predict future PSI. This method, which is based on the AASHTO pavement performance model, treats predictor variables as random variables with certain probability distributions and obtains the distribution of future PSI through the method of Monte-Carlo simulation. A computer program PERFORM using Monte Carlo simulation is developed to implement the numerical computation. Simulation results based on pavement and traffic parameters show that traffic, surface layer material property, and initial pavement performance are the most significant factors affecting pavement performance. Once the distribution of future PSI is determined, statistics such as the mean and the variance of future PSI are readily available.

现代技术的采用问题

美国公司正在寻找提高近20年丧失的竞争力、市场份额和产品信誉的途径。它们的努力旨在通过增加业务灵活性来减少对消费者迅速变化的需求和爱好作出反应的时间．使质量达到日本的水平，降低费用。为达到这些目标，必须在制造业中进行革命。工程、生产、市场和其他职能应当联结到一个计算机系统中去．在其中进行信息流的计算，以便作出关于发展生产、加工、改型和市场反应的最佳决策。为此．应当用其他方法对传统的投资分析方法进行补充．如优化法和模拟法。作者们提出了决策支持等级系统，它包括以下子系统：把费用同活动类别联系起来；确定应当进行投资的机器数量的可数程序；劳动和生产设备消耗量；计算不确定性模拟。作者认为，这种方法的优点是可以考虑到费用来制定各种方案并从中选出最佳方案。

Regional Climate Change and Uncertainty Analysis based on Four Regional Climate Model Simulations over China

Four sets of climate change simulations at grid spacing of 50 km were conducted over East Asia with two regional climate models driven at the lateral bounda- ries by two global models for the period 1981-2050. The locus of the study was on the ensemble projection of cli- mate change in the mid-21st century （2031-50） over China. Validation of each simulation and the ensemble average showed good performances of the models overall, as well as advantages of the ensemble in reproducing present day （1981 2000） December-February （DJF）, June-August （JJA）, and annual （ANN） mean temperature and precipitation. Significant wanning was projected for the mid-21st century, with larger values of temperature increase found in the northern part of China and in the cold seasons. The ensemble average changes of precipitation in DJF, JJA, and ANN were determined, and the uncertainties of the projected changes analyzed based on the consistencies of the simulations. It was concluded that the largest uncertainties in precipitation projection are in eastern China during the summer season （monsoon pre-cipitation）.

Uncertainty in Dust Budget over East Asia Simulated by WRF/Chem with Six Different Dust Emission Schemes

In this study, the dependence of dust budgets on dust emission schemes is investigated through the simulation of dust storm events, which occurred during 14–25 March 2002, over East Asia, by the Weather Research and Forecasting with Chemistry(WRF/Chem) model coupled with six dust emission schemes. Generally, this model can reasonably reproduce the spatial distribution of surface dust concentration; however, the simulated total dust budget differs significantly with different emission schemes. Moreover, uncertainties in the simulated dust budget vary among regions. It is suggested that the dust emission scheme affects the regional dust budget directly through its impact on the total emitted dust amount; however, the inflow and outflow of dust aerosols simulated by different schemes within a region also depend on the geographical location of the dust emission region. Furthermore, the size distribution of dust particles for a specific dust emission scheme has proven to be important for dust budget calculation due to the dependence of dust deposition amount on dust size distribution.

Effect of Uncertainty of Grid DEM on TOPMODEL:Evaluation and Analysis

TOPMODEL,a semi-distributed hydrological model,has been widely used.In the process of simulation of the model,Digital Elevation Model(DEM) is used to provide the input data,such as topographic index and distance to the drainage outlet;thus DEM plays an important role in TOPMODEL.This study aims at examining the impacts of DEM uncertainty on the simulation results of TOPMODEL.In this paper,the effects were evaluated mainly from quantitative and qualitative aspects.Firstly,DEM uncertainty was simulated by using the Monte Carlo method,and for every DEM realization,the topographic index and distance to the drainage outlet were extracted.Secondly,the obtained topographic index and the distance to the drainage outlet were input to the TOPMODEL to simulate seven rain-storm-flood events,and four evaluation indices,such as Nash and Sutcliffe efficiency criterion(EFF),sum of squared residuals over all time steps(SSE),sum of squared log residuals over all time steps(SLE) and sum of absolute errors over all time steps(SAE) were recorded.Thirdly,these four evaluation indices were analyzed in statistical manner(minimum,maximum,range,standard deviation and mean value),and effect of DEM uncertainty on TOPMODEL was quantitatively analyzed.Finally,the simulated hydrographs from TOPMODEL using the original DEM and realizations of DEM were qualitatively evaluated under each flood cases.Results show that the effect of DEM uncertainty on TOPMODEL is inconsiderable and could be ignored in the model’s application.This can be explained by:1) TOPMODEL is not sensitive to the distribution of topographic index and distance to the drainage outlet;2) the distri-bution of topographic index and distance to the drainage outlet are slightly affected by DEM uncertainty.

Significance of Rare Mineral Resources to Strategic Emerging Industries

As non-renewable natural resources, rare minerals＇ are extensively used as important raw materials in strategic emerging industries. As global consumption continues to increase over recent years, international competition in the area of rare mineral minerals has been escalating. On the basis＇ of the identification of 22 rare mineral resources of six categories and analysis of their applications in strategic emerging industries, this paper has adopted a three-factor analytical framework and designed nine indicators from the three dimensions of supply risks, environmental impacts and economic impacts of restricted supply to conduct a quantitative evaluation of the strategic significance of rare mineral resources. The result indicates that the strategic significance of platinum-group metals is the highest and the strategic significance of cesium is the lowest. In order to further increase the reliability of evaluation results, this paper has employed the Monte Carlo simulation for uncertainty analysis＇. Simulation result demonstrates that after the impacts＂ of individual indicators have been taken into account, the results＇ of this paper＇s evaluation of 22 rare mineral resources remain valid. Given the growing significance of rare mineral resources to strategic emerging industries, China should formulate a national strategy on rare mineral resources＇, strive to inerease the supply security of key raw materials for strategic emerging industries and achieve the sustainable development and utilization of rare mineral resources for national security of natural resources.

Study on the Cause and Dynamics of Seawater Intrusion in Laizhou Bay

In this paper, we conduct research on the cause and dynamics of seawater intrusion in the Laizhou bay. To consider modelling the Laizhou bay, we should then take the listed tools into consideration. In actual engineering, wave is a complicated stochastic process. If the numerical value of wave model is a little too large, the wave attenuation should be considered sufficiently, such as wave refraction caused by terrain change, wave attenuation due to submarine friction, wave into the very shallow waters of the broken and small wind area. We integrate the current conition of the Laizhou bay and the further model the seawater intrusion steps. The uncertainty research of ground water solute migration is at present a ground water research area quite popular topic, but the seawater intrusion is the variable density class solute migration issue, applies the uncertainty analysis of seawater intrusion simulation also to have certain difficulty the existing research results. In the future, more simulation will be down to verify the effectiveness.