Volumetric lattice Boltzmann method for pore-scale mass diffusionadvection process in geopolymer porous structures

Porous materials present significant advantages for absorbing radioactive isotopes in nuclear waste streams.To improve absorption efficiency in nuclear waste treatment,a thorough understanding of the diffusion-advection process within porous structures is essential for material design.In this study,we present advancements in the volumetric lattice Boltzmann method(VLBM)for modeling and simulating pore-scale diffusion-advection of radioactive isotopes within geopolymer porous structures.These structures are created using the phase field method(PFM)to precisely control pore architectures.In our VLBM approach,we introduce a concentration field of an isotope seamlessly coupled with the velocity field and solve it by the time evolution of its particle population function.To address the computational intensity inherent in the coupled lattice Boltzmann equations for velocity and concentration fields,we implement graphics processing unit(GPU)parallelization.Validation of the developed model involves examining the flow and diffusion fields in porous structures.Remarkably,good agreement is observed for both the velocity field from VLBM and multiphysics object-oriented simulation environment(MOOSE),and the concentration field from VLBM and the finite difference method(FDM).Furthermore,we investigate the effects of background flow,species diffusivity,and porosity on the diffusion-advection behavior by varying the background flow velocity,diffusion coefficient,and pore volume fraction,respectively.Notably,all three parameters exert an influence on the diffusion-advection process.Increased background flow and diffusivity markedly accelerate the process due to increased advection intensity and enhanced diffusion capability,respectively.Conversely,increasing the porosity has a less significant effect,causing a slight slowdown of the diffusion-advection process due to the expanded pore volume.This comprehensive parametric study provides valuable insights into the kinetics of isotope uptake in porous structures,facilitating the development of porous materials for nuclear waste treatment applications.

Evaluation of natural gas hydrate resources in the South China Sea by combining volumetric and trend-analysis methods

Natural gas hydrate(NGH),considered as a type of premium energy alternative to conventional hydrocarbons,has been broadly studied.The estimate of the total NGH resources in the world has decreased by more than 90%since the first evaluation in 1973.Geographic and geophysical conditions of the South China Sea(SCS)are favorable for the formation of NGH,which has been proved by drilling results up to date.The recoverability of the NGH in the SCS has been confirmed by the production tests using both vertical and horizontal wells.Since 2001,35 estimates of NGH resources in the SCS have been made,with relatively stable results varying between 600 and 900×109 ton oil equivalent.In these estimations,the volumetric method was commonly adopted,but the geological conditions,the migration-accumulation mechanisms of NGH,and the practical recoverability were not considered.These estimates cannot be regarded as evaluated resources according to the international resource evaluation standards,but are at most about prospective gas content of NGH,thus inefficient for guiding explorations and developments.To solve these problems,this study divides the past NGH surveys in the SCS into seven stages,acquires key geological parameters of every stage based on previous studies and analogy with other areas,evaluates the NGH resources of these seven stages by using the volumetric method,then adopts a new trend-analysis method to simulate the downward trend of these estimates,and finally predicts the NGH resources in the SCS at 2025 and 2030.The downward trend is because of the continuous improvement of NGH understanding over time,which is consistent with the trend of global NGH estimates.At the present stage(from 2019 to 2021),the average technically recoverable resource(ATRR)is 7.0×10^(12)m^(3),and the estimates of 2025 and 2030 ATRR are 6.46×10^(12)m^(3) and 4.01×10^(12)m^(3)respectively,with a difference of less than 40%.Therefore,it can be inferred that the ATRR of NGH in the SCS is between 4.0 and 6.5×10^(12)m^(3),with an average of 5.25×10^(12)m^(3).

Chemical Analysis Method for Carbon Bearing Refractory Products——Determination of Magnesium Oxide Content by CyDTA Volumetric Method

This standard specifies the method summary, reagents, apparatus, sampling, procedure, test results calculation and permissible tolerance of the determination of magnesium oxide by CyDTA volumetric method.

Comparison of Direct Pore-Scale and Volume-Averaging Methods for the Performance Evaluation of Porous Volumetric Solar Receiver

Direct pore-scale and volume-averaging numerical simulations are two methods for investigating the performance of porous volumetric solar receivers.To clarify the difference in the prediction of heat transfer processes,a direct comparison between these two methods was conducted at both steady state and transient state.The numerical models were established based on X-ray computed tomography scans and a local thermal non-equilibrium model,respectively.The empirical parameters,which are indispensable to the volume-averaging simulation,were determined by Monte Carlo ray tracing and direct pore-scale numerical simulations.The predicted outlet air temperature of the receiver by the volume-averaging simulation method corresponded satisfactorily to that in the direct pore-scale simulation.The largest discrepancies were observed when the receiver's working temperature was elevated,with differences of 5.5%and 3.68%for the steady state and transient state simulations,respectively.However,the volume-averaging method is incapable of capturing the local temperature information of the air and porous skeleton.It underestimates the inlet temperature of the receiver,leading to an overestimation of the receiver's thermal efficiency,with the largest difference being 6.51%.The comparison results show that the volume-averaging model is a good approximation to the pore-scale model when the empirical parameters are carefully selected.

A novel twice-interpolation finite element method for solid mechanics problems

Formulation and numerical evaluation of a novel twice-interpolation finite element method （TFEM） is presented for solid mechanics problems. In this method, the trial function for Galerkin weak form is constructed through two stages of consecutive interpolation. The primary interpolation follows exactly the same procedure of standard FEM and is further reproduced according to both nodal values and averaged nodal gradients obtained from primary interpolation. The trial functions thus constructed have continuous nodal gradients and contain higher order polynomial without increasing total freedoms. Several benchmark examples and a real dam problem are used to examine the TFEM in terms of accuracy and convergence. Compared with standard FEM, TFEM can achieve significantly better accuracy and higher convergence rate, and the continuous nodal stress can be obtained without any smoothing operation. It is also found that TFEM is insensitive to the quality of the elemental mesh. In addition, the present TFEM can treat the incompressible material without any modification.

A modified discrete element method for concave granular materials based on energy-conserving contact model

The development of a general discrete element method for irregularly shaped particles is the core issue of the simulation of the dynamic behavior of granular materials.The general energy-conserving contact theory is used to establish a universal discrete element method suitable for particle contact of arbitrary shape.In this study,three dimentional(3D)modeling and scanning techniques are used to obtain a triangular mesh representation of the true particles containing typical concave particles.The contact volumebased energy-conserving model is used to realize the contact detection between irregularly shaped particles,and the contact force model is refined and modified to describe the contact under real conditions.The inelastic collision processes between the particles and boundaries are simulated to verify the robustness of the modified contact force model and its applicability to the multi-point contact mode.In addition,the packing process and the flow process of a large number of irregular particles are simulated with the modified discrete element method(DEM)to illustrate the applicability of the method of complex problems.

Vibration Fatigue Probabilistic Life Prediction Model and Method for Blade

Vibration fatigue is one of the main failure modes of blade.The vibration fatigue life of blade is scattered caused by manufacture error,material property dispersion and external excitation randomness.A new vibration fatigue probabilistic life prediction model(VFPLPM)and a prediction method are proposed in this paper.Firstly,as one-dimensional volumetric method(ODVM)only considers the principle calculation direction,a three-dimensional space vector volumetric method(TSVVM)is proposed to improve fatigue life prediction accuracy for actual threedimensional engineering structure.Secondly,based on the two volumetric methods(ODVM and TSVVM),the material C-P-S-N fatigue curve model(CFCM)and the maximum entropy quantile function model(MEQFM),VFPLPM is established to predict the vibration fatigue probabilistic life of blade.The VFPLPM is combined with maximum stress method(MSM),ODVM and TSVVM to estimate vibration fatigue probabilistic life of blade simulator by finite element simulation,and is verified by vibration fatigue test.The results show that all of the three methods can predict the vibration fatigue probabilistic life of blade simulator well.VFPLPM &TSVVM method has the highest computational accuracy for considering stress gradient effect not only in the principle calculation direction but also in other space vector directions.

A study of laboratory testing and calculation methods for coal sorption isotherms

Measurement of the volume of gas adsorbed per unit mass of coal with increasing pressure at a constant temperature produces an isotherm that describes the gas storage capacity of this type of coal. The accurate testing and interpretation of coal sorption isotherm plays an important role in the areas of coal mine methane drainage, coalbed methane （CBM） reservoir resource assessment, enhanced coalbed methane （ECBM） recovery, as well as the carbon dioxide （CO2） sequestration in deep coal seams or similar geological formations. Different coal sorption isotherm testing apparatus and associated calculation methods are critically reviewed and presented in this paper. These include both volumetric and gravimetric based methods, as well as experimental sorption tests with confining stress and direction sorption methods. The volumetric techniques utilise experimental apparatus with sample cell and injection pump and that with both sample cell and reference cell. Whilst the gravimetric approachesinclude methods with sample cell and suspension magnetic balance and that with both sample cell and reference cell. Different testing methods are compared and discussed in this study. A unique in-house-built coal sorption isotherm testing apparatus at the University of Wollongong was presented together with the calculation method, procedures and experimental results. The isotherm results can be calculated by both Soave-Redlich-Kwong （SRK） equation and calibration cure methods which can be used directly to convert the volume of adsorbed gas in different test conditions to standard condition （NTP）.

煤焦油衍生模板碳孔隙重整及高体积电容性能

各类储能器件中,超级电容器因其功率密度高、充放电速度超快、循环寿命长等优点,是电化学储能技术的重要发展方向。其中,多孔碳电极是超级电容的核心材料。然而,传统多孔碳电极材料重点关注高孔隙率和高比面积的实现,从而导致疏松的碳骨架结构,使材料密度降低,进一步限制了超级电容器的体积性能。因此,具有合理孔隙结构和致密骨架的碳电极材料是提升双电层电容器体积性能的关键。以低成本煤焦油为碳源,对基于相转变过程制备的不同模板材料进行包覆后碳化,获得具有致密多孔结构的碳纳米片PCS。该材料中优化的分级孔结构降低了多余的中/大孔占比,使其具有高堆积密度(0.64 g/cm^(3)),可同时实现优异的质量和体积比电容性能。在水系双电层电容器中,制备的PCS电极在低质量负载2 mg/cm^(2)时可以获得277 F/cm^(3)的高体积比电容;在高质量负载8 mg/cm^(2)时,体积比电容仍保持244 F/cm^(3),且最大体积能量密度和功率密度分别为8.46 Wh/L和10.9 kW/L。此外,双电层对称电容器也表现出优异的循环稳定性(超过4万次循环),证明了PCS在双电层电容器高密度储能方面的应用潜力。

基于容积法和水文模型法的海绵设施效能评估研究

为了提升海绵设施布设的科学性和合理性,充分发挥海绵设施的效能,提出了基于容积法和水文模型法的海绵设施效能评估方法.以迁安市某海绵型建筑小区为例,借助容积法量化海绵设计方案,利用水文模型设置海绵设施控制雨水的优选路径,分别选用2、5、10 a的短历时(2 h)设计降雨情景对海绵设施建设效能进行评估,结果表明:1)与排水口演算和不透水区演算模式相比,透水区演算模式更契合海绵城市建设理念;2)在2、5、10 a的短历时(2h)设计降雨情景下,相对于海绵设施布设前,布设后场地雨水径流总量削减率分别为86.9%、82.4%、79.6%,径流峰值流量平均削减为94.57%、87.89%、86.45%,雨水管道中最大充满度80%以上的管道长度分别降低了86.55%、85.27%、64.48%;3)在10 a一遇设计降雨重现期下,溢流节点J31在海绵设施布设后,井内最高水位降低了1.332 m,且其他9个溢流风险节点其水位也明显降低.上述研究表明,在低重现期短历时(2h)设计降雨情景下,海绵设施对场地径流总量、峰值流量有很好的削减作用,对雨水管道排水压力有显著减轻作用,对节点溢流风险有很好的控制效果,为今后开展海绵城市源头减排设施的布设提供了有价值的参考.

自动化学滴定仪在冶金分析中的应用

介绍了一种自动化学滴定仪的分析原理和实验方法。以重铬酸钾滴定分析铁矿石中全铁含量为例,通过与传统化学容量法比较,得出该自动化学滴定仪在冶金分析中具有精密度和准确度高、滴定速度可控及滴定分析误差小等优点。

混合型饲料添加剂中胆汁酸含量测定方法比较研究

本试验采用高效液相色谱-示差折光(HPLC⁃RID)和高效液相色谱-荧光(HPLC⁃FLD)法,研究建立混合型饲料添加剂中猪胆酸、猪去氧胆酸、鹅去氧胆酸含量的高效液相色谱测定方法,并对2种高效液相色谱法、重量法、容量法胆汁酸含量测定结果进行比较分析。HPLC⁃RID法:试样用甲醇-乙腈-水溶液提取,C18柱分离,HPLC⁃RID测定,3种胆汁酸的定量限为10.0~20.0 mg/g,平均回收率为82.54%~108.50%,相对标准偏差(RSD)为2.90%~7.61%;HPLC⁃FLD法:试样用甲醇提取,氢氧化钾甲醇溶液皂化,以1,4,7,10,13,16-六氧杂环十八烷乙腈液和4-溴甲基-7-甲氧基香豆素乙腈液衍生,C18柱分离,HPLC⁃FLD测定,3种胆汁酸的定量限为2.0~3.0 mg/g,平均回收率为70.43%~84.31%,RSD为4.82%~9.80%。结果表明:HPLC⁃RID法、HPLC⁃FLD法均可测定混合型饲料添加剂中的3种胆汁酸含量,但由于HPLC⁃FLD法胆汁酸需要衍生,易受样品基质影响,胆汁酸含量测定结果重现性、稳定性差;重量法、容量法测定的是混合型饲料添加剂中所有胆汁酸的总含量,但由于方法特性所限,容量法测定结果不能准确反映产品所有胆汁酸的总含量。本研究建立的HPLC⁃RID法重现性、稳定性、可信度高,适用于混合型饲料添加剂中猪胆酸、猪去氧胆酸和鹅去氧胆酸含量的测定;重量法适用于混合型饲料添加剂中胆汁酸总含量的测定。

油藏型储气库库容影响因素及其变化规律研究

针对目前中、低含水饱和度对自由气库容量影响的研究较少的问题,开展室内实验模拟了多次注气-焖井-采气实验,并根据相似原理,利用实验数据建立了自由气库容量与初始含水饱和度、注采次数的量化表征模型。结果表明,自由气库容量随注采次数的增多而增大,但单次注采后的增幅快速降低;含水饱和度(初始含水饱和大于50%)的提高有利于油藏改建储气库,但是建库初期的注采能力和库容提高相对缓慢;当初始含水饱和度由50%提高到85%时,经过6次注采后,含气饱和度降低幅度约9.27%,而当注采次数分别增至20、30、50时,自由气库容量增加幅度分别为0.51%、3.34%、6.61%。研究结果可为油藏型储气库的注采能力及库容评价提供借鉴。

Numerical investigation on the flow and thermal behaviors of the volumetric solar receivers with different morphologies

Morphologies of the porous materials influence the processes of solar radiation transport, flow, and thermal behaviors within volumetric solar receivers. A comprehensive comparative study is conducted by applying pore scale numerical simulations on volumetric solar receivers featuring various morphologies, including Kelvin, Weaire-Phelan, and foam configurations. The idealized unit cell and X-ray computed tomography scan approaches are employed to reconstruct pore scale porous models.Monte Carlo ray tracing and pore scale numerical simulations are implemented to elucidate the radiative, flow, and thermal behaviors of distinct receivers exposed to varying thermal boundary conditions and real irradiation situations. The findings demonstrate that the foam structure exhibits greater solar radiation absorptivity, while Kelvin and Weaire-Phelan structures enhance the penetration depth under non-perpendicular solar irradiation. In comparison with Kelvin and Weaire-Phelan configurations, the foam structure presents efficient convective heat transfer, with the Weaire-Phelan structure showing pronounced thermal non-equilibrium phenomena. The variance in convective heat transfer coefficient between Kelvin and Weaire-Phelan configurations is approximately 8.4%. The foam structure exhibits higher thermal efficiency and flow resistance under nonperpendicular irradiation compared to Kelvin and Weaire-Phelan structures, attributed to its smaller pore size and intricate flow channels. An increase of 1.3% in thermal efficiency is observed with a substantial rise in pressure drop of 32.2%.

Geological reservoir and resource potential(10^(13)m^(3))of gas hydrates in the South China Sea

A detailed understanding of the distribution and potential of natural gas hydrate(NGHs)resources is crucial to fostering the industrialization of those resources in the South China Sea,where NGHs are abundant.In this study,this study analyzed the applicability of resource evaluation methods,including the volumetric,genesis,and analogy methods,and estimated NGHs resource potential in the South China Sea by using scientific resource evaluation methods based on the factors controlling the geological accumulation and the reservoir characteristics of NGHs.Furthermore,this study compared the evaluation results of NGHs resource evaluations in representative worldwise sea areas via rational analysis.The results of this study are as follows:(1)The gas hydrate accumulation in the South China Sea is characterized by multiple sources of gas supply,multi-channel migration,and extensive accumulation,which are significantly different from those of oil and gas and other unconventional resources.(2)The evaluation of gas hydrate resources in the South China Sea is a highly targeted,stratified,and multidisciplinary evaluation of geological resources under the framework of a multi-type gas hydrate resource evaluation system and focuses on the comprehensive utilization of multi-source heterogeneous data.(3)Global NGHs resources is n×10^(15)m^(3),while the NGHs resources in the South China Sea are estimated to be 10^(13)m^(3),which is comparable to the abundance of typical marine NGHs deposits in other parts of the world.In the South China Sea,the NGHs resources have a broad prospect and provide a substantial resource base for production tests and industrialization of NGHs.

基于容量法测量钒系产品中钒含量的不确定度对比分析

针对目前钒产品中钒含量测定的两种主流容量法(高锰酸钾氧化法和过硫酸铵氧化法),试验通过比较分析二者测量钒时的合成不确定度大小,分析在测定过程中影响不确定度的各因素,包括标准溶液、滴定过程、测量重复性等,对这些因素的不确定度进行评定,并计算测量的合成标准不确定度和扩展不确定度。通过比较发现:采用高锰酸钾氧化测量数据比过硫酸铵氧化测量数据稳定,尤其是测量高含量钒时更为明显;当取置信水平为95%,包含因子取2时,采用高锰酸钾氧化法和过硫酸铵氧化法分别测量3种钒产品中钒含量时,扩展不确定度分别为:五氧化二钒(0.28%和0.29%)、钒氮合金(0.21%和0.26%)、钒铁(0.12%和0.13%)。

EDTA滴定法和原子吸收光谱法相结合准确测定石灰岩中的钙镁含量

传统的EDTA滴定法在测定氧化镁含量较低的石灰岩矿物时存在一定弊端,本文提出一种改进方法:EDTA滴定钙镁合量,再利用原子吸收测定氧化镁含量,二者相减得到氧化钙含量。经验证,本方法测定钙镁含量误差低于3%,具有良好的准确性,且操作简单,流程较短,能够满足石灰岩矿物样品中钙镁含量特别是低镁含量灰岩的分析测定需求。

矿石体重的测量方法研究

矿石体重,是估算矿石量的主要参数,是评价勘查成果的重要参数,也是生产经营决策常用的重要参数。通常利用体积和重量计算体重,而不能直接测量体重。由于利用符合精度的设备可直接测量重量,但一般不能直接测量体积,故体重测量的关键在于体积测量。结合生产实践介绍五种大体重的测量方法及其优适用范围,并侧重介绍体积测量。

磷矿石中氧化锰含量的测定分光光度法和容量法的比较

在磷矿石中测定氧化锰含量时,分光光度法和容量法各有优缺点。分光光度法基于吸收光谱特性测定浓度,具有高准确性和良好重复性,但操作较为复杂,对仪器和技术要求高;适用于低浓度锰样品,但需解决其他物质干扰。而容量法通过滴定确定浓度,操作简便,适用于实验室条件,尤其是碘量法在控制下准确度高,适用范围广,能有效排除一些干扰物如三价铁离子。其重复性依赖于滴定精度。因此,选择方法时应考虑样品特性、准确性要求和操作便利性,并针对具体情况进行方法验证和优化,以确保结果的可靠性。

二异丙基醚中总酚含量的测定方法研究

采用溴化容量法测定二异丙基醚中的总酚含量时,二异丙基醚会对测量产生干扰,严重影响测量结果的准确性。可先利用氢氧化钠溶液与二异丙基醚中的酚反应生成酚钠,再用水浴加热的方式将二异丙基醚蒸发,消除干扰物质二异丙基醚,然后冷却样品,并调节其pH值至中性后,再采用溴化容量法即可准确测定二异丙基醚中的总酚含量。将该方法进行加标试验,测得回收率在96.4%~102.2%,相对标准偏差小于3%。