Optimization of Artificial Viscosity in Production Codes Based on Gaussian Regression Surrogate Models

To accurately model flows with shock waves using staggered-grid Lagrangian hydrodynamics, the artificial viscosity has to be introduced to convert kinetic energy into internal energy, thereby increasing the entropy across shocks. Determining the appropriate strength of the artificial viscosity is an art and strongly depends on the particular problem and experience of the researcher. The objective of this study is to pose the problem of finding the appropriate strength of the artificial viscosity as an optimization problem and solve this problem using machine learning (ML) tools, specifically using surrogate models based on Gaussian Process regression (GPR) and Bayesian analysis. We describe the optimization method and discuss various practical details of its implementation. The shock-containing problems for which we apply this method all have been implemented in the LANL code FLAG (Burton in Connectivity structures and differencing techniques for staggered-grid free-Lagrange hydrodynamics, Tech. Rep. UCRL-JC-110555, Lawrence Livermore National Laboratory, Livermore, CA, 1992, 1992, in Consistent finite-volume discretization of hydrodynamic conservation laws for unstructured grids, Tech. Rep. CRL-JC-118788, Lawrence Livermore National Laboratory, Livermore, CA, 1992, 1994, Multidimensional discretization of conservation laws for unstructured polyhedral grids, Tech. Rep. UCRL-JC-118306, Lawrence Livermore National Laboratory, Livermore, CA, 1992, 1994, in FLAG, a multi-dimensional, multiple mesh, adaptive free-Lagrange, hydrodynamics code. In: NECDC, 1992). First, we apply ML to find optimal values to isolated shock problems of different strengths. Second, we apply ML to optimize the viscosity for a one-dimensional (1D) propagating detonation problem based on Zel’dovich-von Neumann-Doring (ZND) (Fickett and Davis in Detonation: theory and experiment. Dover books on physics. Dover Publications, Mineola, 2000) detonation theory using a reactive burn model. We compare results for default (currently used values in FLAG) and optimized values of the artificial viscosity for these problems demonstrating the potential for significant improvement in the accuracy of computations.

Optimization of Ceramic Paste Viscosity Use for the Elaboration of Tubular Membrane Support by Extrusion and Its Application

The objective of this work was to determine the optimum size and amount of raw materials which influence the viscosity of ceramic paste using the experimental design for the production of tubular support by the extrusion technique and its application in microfiltration. The Box Behnken design was used to optimize the viscosity of the ceramic paste. ANOVA was used to model the system represented by independent parameters and dependent output response and to optimize the system by estimating the statistical parameters. A three-factor and three-level design was used generating thus 15 experiments. The independent factors were the amount of porogen, size of porogen and amount of binder and dependent factor the viscosity of the ceramic paste. The minimum (−1), intermediate (0) and maximum (+1) level of the amount of porogen, size of porogen and amount of binder used were 20 g, 30 g and 40 g, 50 μm, 100 μm and 150 μm, and 2 g, 3.5 g and 5 g respectively. The statistical analyses showed that the values of the answers would adapt to a second degree polynomial model. The R-square value obtained was greater than 95%, the Biais factor was equal to the unit and the Absolute Average Deviation (AAD) equal to the zero thus validating the model. The optimal size of raw material was found to be 100 μm for an amount of clay of 66 g, amount of porogen of 30 g and amount of binder of 4 g. The optimum viscosity of the ceramic paste was found to be 26.7 Pa∙s which is close to the viscosity of the clay paste only found to be 28.5 Pa∙s, thus good for shaping by the extrusion technique. The ceramic paste showed a pseudo-plastic behavior. The tubular porous support was sintered at 950°C and the dimensions, such as outer and inner diameters and length of the tube were 4 cm, 2 cm, and 19 cm, respectively. The sintered membrane possesses a porosity of 43.5%, water permeability of 244.9 L/h∙m2 bar, an average pore size of 2.4 μm and mechanical strength of 9.2 MPa with very good corrosion resistance in acidic and basic conditions. The membrane was subjected to microfiltration of synthetic clay suspension at various combinations of applied pressures (0.5 - 2 bar) with a feed concentration of 100 NTU. An increase in the applied pressure leads to an increase in the flow rate and retention rate. The flow rate decreases steadily with time. The highest retention was obtained at 2 bar with permeability of 184.69 L/h∙m2 bar and a retention of 96% decreasing the turbidity to about 3.5 NTU which is below the acceptable value of 5 NTU.

COMPUTER OPTIMIZATION OF DENSITY AND VISCOSITY FOR BINARY METALLIC MELTS

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Effects of fluid flow rate and viscosity on gravel-pack plugging and the optimization of sand-control wells production

Series of experiments were performed to simulate the invasion of formation sand into and the plugging process of gravel-pack at different viscosities and flowing rates of fluid.Two types of formation sands with the medium size of 0.10 mm and 0.16 mm and the quartz sand and ceramsite of 0.6-1.2 mm were used in the experiments.A new viscosity-velocity index(the product of fluid viscosity and velocity)was put forward to characterize the influencing mechanism and law of physical property and flow condition of formation fluid on gravel-pack plugging,and a new method to optimize the production rate of wells controlling sand production with gravel-packing was proposed.The results show that the permeability of formation sand invaded zone and final permeability of plugged gravel-pack have negative correlations with viscosity and flow velocity of fluid,the higher the flow velocity and viscosity,the lower the permeability of formation sand invaded zone and final permeability of plugged gravel-pack will be.The flow velocity and viscosity of fluid are key factors affecting plugging degree of the gravel zone.The viscosity-velocity index(v-v index)can reflect the flow characteristics of fluid very well and make it easier to analyze the plugging mechanism of gravel zone.For different combinations of fluid viscosity and flow velocity,if the v-v index is the same or close,their impact on the final gravel permeability would be the same or close.With the increase of the v-v index,the permeability of plugged gravel zone decreases first,then the reduction rate slows down till the permeability stabilizes.By optimizing production and increasing production step by step,the optimal working scheme for sand-control well can reduce the damage to gravel-pack zone permeability caused by sand-carrying fluid effectively,and increase well productivity and extend the sand control life.

WEAK SOLUTIONS OF MONGE-AMPRE TYPE EQUATIONS IN OPTIMAL TRANSPORTATION

This paper concerns the weak solutions of some Monge-Amp^re type equa- tions in the optimal transportation theory. The relationship between the Aleksandrov solutions and the viscosity solutions of the Monge-Ampere type equations is discussed. A uniform estimate for solution of the Dirichlet problem with homogeneous boundary value is obtained.

UNIQUENESS OF VISCOSITY SOLUTIONS OF STOCHASTIC HAMILTON-JACOBI EQUATIONS

This article is devoted to the study of fully nonlinear stochastic Hamilton-Jacobi (HJ) equations for the optimal stochastic control problem of ordinary differential equations with random coefficients. Under the standard Lipschitz continuity assumptions on the coefficients, the value function is proved to be the unique viscosity solution of the associated stochastic HJ equation.

A NOTE ON STOCHASTIC OPTIMAL CONTROL OF REFLECTED DIFFUSIONS WITH JUMPS

Stochastic optimal control problems for a class of reflected diffusion with Poisson jumps in a half-space are considered. The nonlinear Nisio' s semigroup for such optimal control problems was constructed. A Hamilton-Jacobi-Bellman equation with the Neumann boundary condition associated with this semigroup was obtained. Then, viscosity solutions of this equation were defined and discussed, and various uniqueness of this equation was also considered. Finally, the value function was such optimal control problems is shown to be a viscosity solution of this equation.

Optimal Switching Control for Nonlinear Systems in A Finite Duration

This paper proposes a optimal control problem for a general nonlinear systems with finitely many admissible control settings and with costs assigned to switching of controls. With dynamic programming and viscosity solution theory we show that the switching lower-value function is a viscosity solution of the appropriate systems of quasi-variational inequalities（the appropriate generalization of the Hamilton-Jacobi equation in this context） and that the minimal such switching-storage function is equal to the continuous switching lower-value for the game. With the lower value function a optimal switching control is designed for minimizing the cost of running the systems.

黏温黏压下径向柱塞泵滑靴副温度分布与泄漏量分析

针对高压大排量径向柱塞泵滑靴副摩擦失效和泄漏问题,以XDP1000型径向柱塞泵为例,对滑靴副温度分布与泄漏量进行了流场仿真和数值计算。首先,根据滑靴柱塞组件运动学特性分析,求解了滑靴偏转角变化规律,并通过建立滑靴副不同通道流量计算公式的方式,建立了滑靴副静压支承特性方程;然后,建立了滑靴副泄漏功率损失和摩擦功率损失模型,求解了滑靴副最佳油膜厚度,并分析了最佳油膜厚度的变化规律;最后,在考虑了油液黏温黏压特性的基础上,通过流场数值计算的方式,研究了滑靴副温度分布与泄漏量随径向柱塞泵工况参数的变化规律。研究结果表明:额定工况下,滑靴副最佳油膜厚度值约为14μm,滑靴副最佳油膜厚度值随着转子转角的增大而增大,随着工作压力和温度的增大而减小;滑靴运动方向侧油膜温度较另一侧高13 K,滑靴副温度值基本不受工作压力的影响,而随着转速的增大而升高;滑靴副阻尼孔泄漏量较滑靴边界泄漏量大0.02 kg/s,而且泄漏量随着压力、转速和油液温度的增大而增大。该研究结论可为高压大排量径向柱塞泵滑靴副设计及优化提供参考。

顶侧吹双炉连续炼铜渣型优化

利用FactSage软件研究了赤峰双炉连续炼铜过程中不同渣系和造渣剂添加量对熔渣熔点、黏度的热力学影响规律。结果表明:熔炼渣熔点是随CaO、SiO_(2)、MgO以及Al_(2)O_(3)添加量增加而增大的。当吹炼渣中CaO含量超过15%时,吹炼渣的熔点迅速升高。熔炼渣黏度随CaO、SiO_(2)和MgO添加量的增加而降低,随Al_(2)O_(3)添加量增加而增大。结合生产实际得出:随着熔炼温度从1200℃升高至1350℃,熔体黏度由0.3 Pa·s降低至0.128 Pa·s。吹炼渣黏度比熔炼渣黏度小,随CaO和SiO_(2)添加量增加而减小,说明适当升高温度和造渣剂添加量有助于提高渣的流动性。在1340℃熔炼时,最优熔炼渣型组成为CaO 2.5%~3%,SiO_(2)20%~22%,MgO 1.5%,Al_(2)O_(3)4%~4.5%,铁硅比为1.9~2.0。在1280℃吹炼时,最优熔炼渣型组成为CaO 8.5%~9.5%,SiO_(2)1.5%~2.5%,铁含量在30%左右,铁钙比为3.4左右。

Relationship Between General MP and DPP for the Stochastic Recursive Optimal Control Problem with Jumps

This paper is concerned with the relationship between general maximum principle and dynamic programming principle for the stochastic recursive optimal control problem with jumps,where the control domain is not necessarily convex.Relations among the adjoint processes,the generalized Hamiltonian function and the value function are proven,under the assumption of a smooth value function and within the framework of viscosity solutions,respectively.Some examples are given to illustrate the theoretical results.

玉米淀粉黏合剂的强度相关性研究

以玉米淀粉为主要原料、硼砂为交联剂、氢氧化钠为氧化剂、十八水硫酸铝为防水剂、聚乙烯醇改性脲醛树脂为黏合强度增强剂、水为溶剂,制备了一种具有黏合强度强的瓦楞纸箱用玉米淀粉黏合剂,并对瓦楞纸箱用玉米淀粉黏合剂的配方进行优化研究。采用单因素变量法分别研究玉米淀粉、硼砂、氢氧化钠、十八水硫酸铝、聚乙烯醇改性脲醛树脂、水用量等因素对黏度和黏合强度的影响。同时使用响应面试验分析法中的中心组合设计(Box-Behnken Design),以黏合强度和黏度为指标,研究配方中影响较大的组分对玉米淀粉黏合剂黏合强度的影响,并结合实际生产筛选出较优配方。研究结果表明:较佳配方(质量比)为玉米淀粉12.5%、氢氧化钠溶液3.7%、硼砂0.42%、十八水硫酸铝0.15%、聚乙烯醇改性脲醛树脂1.75%、水量81.48%。该制备工艺稳定可靠,制备成本较低,具有一定的实用价值。

基于改进鲸鱼算法优化极限学习机的无氟保护渣黏度预测

针对结晶器无氟保护渣黏度值预测复杂、预测精度低的问题,提出了一种基于改进鲸鱼优化算法的极限学习机模型并用于无氟保护渣黏度值预测。首先,构建无氟保护渣成分数据集,并对保护渣中成分与黏度值进行相关性分析;然后,利用改进Tent混沌映射和反向学习策略初始化鲸鱼优化算法的种群,融合非线性收敛因子和自适应t分布变异策略提高算法对极限学习机中超参数的寻优能力;最后,对无氟保护渣数据集进行黏度值预测对比实验,验证了改进算法的有效性。结果表明:与反向传播神经网络(back propagation neural network, BPNN)、极限学习机(extreme learning machine, ELM)模型相比,平均绝对百分比误差平均降低了29.50%,在寻优精度、预测精度和稳定性方面取得较大提升。

裂化催化剂级配优化后对加氢尾油影响分析

中国石化海南炼油化工有限公司(以下简称海南炼化)加氢裂化装置于2017年大检修期间对原催化剂FF-46与FC-16B采用器外再生后重新装入反应器并补充新的精制剂FF-66与裂化剂FC-80。通过FRIPP对催化剂的级配作优化调整后,根据裂化剂FC-80具有良好的环状烃开环与优异的的芳烃加氢饱和特性,加裂尾油的黏度指数提高了20,尾油中BMCI值(芳烃指数)降低8,但加氢后的尾油凝点提高10℃,作为润滑油基础油。下游装置的进一步的临氢异构脱蜡后产品的凝点在-20℃以下,加氢后的产品性能满足要求。

Influence and optimization of parameters of prepreg viscosity during placement

This paper tested the viscosity of prepreg in the automatic placement process, and conducted the probe and placement-90° peel tests through the test systems. The law of variation of prepreg viscosity during the laying process was studied through these tests under different conditions by taking the peel force to intuitively and quantitatively characterise the viscosity of the prepreg.The results show that this viscosity is inversely proportional to the laying rate, proportional to the laying pressure, and quadratic to the laying temperature. Then, peel tests were simulated to validate both the correctness of the peel test and that of the probe test data fitting the two-line cohesion model. On this basis, a response surface test for laying and peeling was designed. Taking viscous peel force as the response target, the laying process parameters were optimised and the significance of their influence was further studied. The error between the test value and the predicted value of the maximum viscous peel force is 3.03%.

甘油水溶液提取米糠多酚绿色工艺优化及多酚种类鉴定

为探究甘油作为绿色溶剂提取米糠多酚的可行性,该文选取提取温度、甘油体积分数、液料比和提取时间4个因素,采用单因素结合响应面试验进行米糠多酚提取工艺优化。同时,分析了甘油提取液的黏度特性,并利用超高效液相色谱串联三重四级杆飞行时间质谱(UPLC-Triple-TOF/MS)方法进行多酚鉴定。结果表明,甘油提取米糠多酚最优条件为提取温度67℃,甘油体积分数19%,液料比33 mL/g,提取时间固定为80 min,获得的最大多酚得率为700.35 mg/(100 g)。甘油对米糠多酚的提取效率和甘油的黏度有显著的负相关性。此外,UPLC-Triple-TOF/MS分析表明,最优条件下甘油提取得到13种米糠多酚,其中酚酸质量分数如下:对羟基苯甲酸48.53μg/g,香草酸69.64μg/g,丁香酸33.63μg/g,4-香豆酸361.18μg/g,阿魏酸392.17μg/g,水杨酸34.67μg/g。研究结果表明,甘油可以作为从米糠中提取多酚的绿色溶剂。

大港油田高凝高粘原油特性

通过大量室内试验分析了大港油田高凝高粘原油粘温关系及在不同含水条件下的粘度变化。结果表明：在不同含水率下，随着温度的升高，高凝高粘原油粘度都有不同程度的降低，表现出明显的粘温特性；在同一温度下，原油的粘度随着含水率的变化是一个先增加后减小的过程，峰值区间为含水率20％～40％；原油平均析蜡温度为60％；凝固点随着含蜡量的增加而升高；若降粘剂发挥作用，则含水率最低为10％；添加剂的浓度对原油粘度的峰值区间有影响，最佳添加剂浓度为3‰～7‰。

铜渣组分含量对渣锍高温沉降分离效果的影响

本文利用高温沉降实验对FeO-SiO2-Fe3O4-CaO-Al2O3-MgO系中不同组分含量以及温度对铜渣、铜锍分离效果的影响进行研究,同时利用热力学计算软件FactSage结合含固相熔渣的黏度、密度计算公式,对不同渣型炉渣的黏度和密度进行计算,进而研究其对渣锍分离效果的影响。结果表明,当炉渣黏度大于0.5 Pa·s时,黏度升高对渣锍分离有着十分不利的影响。当炉渣各组分控制在SiO2/Fe比(w(SiO2)/w(Fe))0.82%~0.97%、w(CaO)0~6.2%、w(Al2O3)2%~7%、w(MgO)0~1.25%和w(Fe3O4)0~10%,且沉降温度在1230℃以上时,熔渣具有良好的流动性,其密度也在理想的范围内,沉降后渣中的含铜量低于1%。由沉降后渣的矿相分析表明,难以沉降的铜物相主要为呈点状分布的微米级黄铜矿和少量大粒径的辉铜矿。

单硝酸异山梨酯定时脉冲释放片的制备及体外溶出度研究

目的 研制单硝酸异山梨酯 (5 ISMN)定时脉冲释放片 ,并考察体外溶出的影响因素。方法 采用压制包衣技术制备 5 ISMN定时脉冲释放片 ,以崩解时间和膨胀率为指标 ,筛选了崩解剂类型和用量 ;采用反相高效液相色谱法测定体外溶出度 ,以释药时滞为指标 ,经均匀设计实验 ,筛选优化外包衣层处方组成。结果 片芯选用羧甲基淀粉钠为崩解剂 ,用量 2 0 %即能达到设计要求。固定硬度 ,调整亲疏水性成分的比例 ,确定了时滞为 3,4 ,5h的 3个基本处方。硬度、亲疏水性物质比、溶出介质黏度对时滞影响显著。结论 单硝酸异山梨酯压制包衣片能实现体外定时脉冲释药 ,并可通过调整处方和工艺因素实现不同时滞的控释效果。

航天器用超低黏度齿轮泵轻量化设计

为追求航天器用超低黏度介质齿轮泵较好的容积率和较低的发射成本,该文在创建容积率和新重合度公式的基础上,采用最优化设计方法,通过泵的单位排量体积或单位排量质量最小化,实现了90%的最小容积率和质量最轻化,分析了结构参数对优化结果的影响。结果表明:采用齿顶重合度优化设计后的根切重合度为–0.3429,不能保证连续传动要求;压力角、轴半径、齿条刀具齿顶圆角半径和过渡区起始角对优化结果,分别有6.07%、7.8%、2.9%和6.4%的影响,总体上影响不大;径向、轴向间隙的影响很大,并具有0.04、0.07 mm的影响转折点,该转折点为径向、轴向间隙的取值上限提供了依据。初次针对航天用齿轮泵的优化设计尝试,阐明了超低黏度介质同样适用于齿轮泵。该研究可为提高其他行业用超低黏度液压泵的研发提供参考。