基于Langmuir等温吸附的吸附动力学方程

把吸附剂对溶质的吸附看作是吸附剂和溶质之间的化学反应,参照反应动力学方程提出了相应的吸附动力学方程。基于Langmuir等温吸附定义了吸附剂动力学浓度,并导出了它和固液比、Langmuir等温吸附方程参数的关系。吸附动力学微分方程为(1+a)级,对应于吸附剂动力学质量浓度是1级,对应于溶质质量浓度为a级。通过对动力学微分方程求解,分别得到了a=1和a=2时的动力学方程的解析表达式。在a=2时,用提出的动力学方程对文献的吸附数据进行了回归计算,结果表明该动力学模型和实验数据吻合良好,回归的相关系数R^(2)>0.97。

基于Langmuir模型含水率对构造煤吸附CH_(4)/CO_(2)影响试验研究

为探究不同含水率条件下煤样对CH_(4)/CO_(2)单组分气体的吸附特性,以六盘水攀枝花煤矿为研究对象,利用吸附试验(CH_(4)吸附、CO_(2)吸附)结合Langmuir模型对不同含水率状态下的构造煤煤样进行试验,研究结构表明:运用Langmuir拟合对吸附量大小进行研究,其拟合相关系数R^(2)>0.99,在恒温恒压下,随着含水率的增加其CH_(4)吸附与CO_(2)吸附量均减小,且CH_(4)吸附量均小于CO_(2)吸附;对于同一含水率煤样,煤样对气体吸附量随着压力的增大先增大后达到平衡,根据Langmuir拟合得到极限吸附值a,其极限吸附量a值与含水率呈负相关关系,并且CO_(2)的a值均大于CH_(4)的a值。

Study of plasma parameters of coaxial plasma source using triple Langmuir probe and Faraday cup diagnostics

Coaxial plasma guns are a type of plasma source that produces plasma which propagates radially and axially controlled by the shape of the ground electrode, which has attracted much interest in several applications. In this work, a 120° opening angle of CPG nozzle is used as a plasma gun configuration that operates at the energy of 150 J. The ionization of polyethylene insulator between the electrodes of the gun produces a cloud of hydrogen and carbon plasma.The triple Langmuir probe and Faraday cup are used to measure plasma density and plasma temperature. These methods are used to measure the on-axis and off-axis plasma divergence of the coaxial plasma gun. The peak values of ion densities measured at a distance of 25 mm on-axis from the plasma gun are(1.6±0.5)×10^(19)m^(-3)and(2.8±0.6)×10^(19)m^(-3)for hydrogen and carbon plasma respectively and the peak temperature is 3.02±0.5 eV. The mean propagation velocity of plasma is calculated using the transit times of plasma at different distances from the plasma gun and is found to be 4.54±0.25 cm/μs and 1.81±0.18 cm/μs for hydrogen and carbon plasma respectively. The Debye radius is obtained from the measured experimental data that satisfies the thin sheath approximation. The shot-to-shot stability of plasma parameters facilitates the use of plasma guns in laboratory experiments. These types of plasma sources can be used in many applications like plasma opening switches, plasma devices, and as plasma sources.

Performance of physical-informed neural network (PINN) for the key parameter inference in Langmuir turbulence parameterization scheme

The Stokes production coefficient(E_(6))constitutes a critical parameter within the Mellor-Yamada type(MY-type)Langmuir turbulence(LT)parameterization schemes,significantly affecting the simulation of turbulent kinetic energy,turbulent length scale,and vertical diffusivity coefficient for turbulent kinetic energy in the upper ocean.However,the accurate determination of its value remains a pressing scientific challenge.This study adopted an innovative approach by leveraging deep learning technology to address this challenge of inferring the E_(6).Through the integration of the information of the turbulent length scale equation into a physical-informed neural network(PINN),we achieved an accurate and physically meaningful inference of E_(6).Multiple cases were examined to assess the feasibility of PINN in this task,revealing that under optimal settings,the average mean squared error of the E_(6) inference was only 0.01,attesting to the effectiveness of PINN.The optimal hyperparameter combination was identified using the Tanh activation function,along with a spatiotemporal sampling interval of 1 s and 0.1 m.This resulted in a substantial reduction in the average bias of the E_(6) inference,ranging from O(10^(1))to O(10^(2))times compared with other combinations.This study underscores the potential application of PINN in intricate marine environments,offering a novel and efficient method for optimizing MY-type LT parameterization schemes.

Langmuir-Blodgett膜技术的应用研究进展

综述了Langmuir-Blodgett(LB)膜及膜技术的产生及发展过程、表征方法和具有可控堆积密度的成膜特性。分别介绍了LB膜技术在检测传感器、界面纳米结构、化学催化等方面的应用进展,重点阐述了其气体传感器、仿生学传感器、电化学传感器等领域的应用和研究现状,并讨论了应用过程中存在的优缺点,总结了LB膜技术的缺陷,并对膜制备材料与功能性溶剂毒性的问题进行了展望。

A developed dual-site Langmuir model to represent the high-pressure methane adsorption and thermodynamic parameters in shale

Comprehending the mechanism of methane adsorption in shales is a crucial step towards optimizing the development of deep-buried shale gas. This is because the methane adsorbed in shale represents a significant proportion of the subsurface shale gas resource. To properly characterize the methane adsorption on shale, which exhibits diverse mineral compositions and multi-scale pore sizes, it is crucial to capture the energy heterogeneity of the adsorption sites. In this paper, a dual-site Langmuir model is proposed, which accounts for the temperature and pressure dependence of the density of the adsorbed phase. The model is applied to the isothermals of methane adsorption on shale, at pressures of up to 30 MPa and temperatures ranging from 40 to 100 ℃. The results show that the proposed model can describe the adsorption behavior of methane on shale more accurately than conventional models, which assume a constant value for the density of adsorbed phase. Furthermore, the proposed model can be extrapolated to higher temperatures and pressures. Thermodynamic parameters were analyzed using correctly derived equations. The results indicate that the widely used, but incorrect, equation would underestimate the isosteric heat of adsorption. Neglecting the real gas behavior, volume of the adsorbed phase, and energy heterogeneity of the adsorption sites can lead to overestimation of the isosteric heat of adsorption. Furthermore, the isosteric heat evaluated from excess adsorption data can only be used to make a rough estimate of the real isosteric heat at very low pressure.

Influence of the upper mixed layer depth on Langmuir turbulence characteristics

The upper mixed layer depth(h)has a significant seasonal variation in the real ocean and the low-order statistics of Langmuir turbulence are dramatically influenced by the upper mixed layer depth.To explore the influence of the upper mixed layer depth on Langmuir turbulence under the condition of the wind and wave equilibrium,the changes of Langmuir turbulence characteristics with the idealized variation of the upper mixed layer depth from very shallow(h=5 m)to deep enough(h=40 m)are studied using a non-hydrostatic large eddy simulation model.The simulation results show that there is a direct entrainment depth induced by Langmuir turbulence(h_(LT))within the thermocline.The normalized depthaveraged vertical velocity variance is smaller and larger than the downwind velocity variance for the ratio of the upper mixed layer to a direct entrainment depth induced by Langmuir turbulence h/h_(LT)<1 and h/h_(LT)>1,respectively,indicating that turbulence characteristics have the essential change(i.e.,depth-averaged vertical velocity variance(DAVV)DADV for Langmuir turbulence)between h/h_(LT)<1 and h/h_(LT)>1.The rate of change of the normalized depth-averaged low-order statistics for h/h_(LT)<1 is much larger than that for h/h_(LT)>1.The reason is that the downward pressure perturbation induced by Langmuir cells is strongly inhibited by the upward reactive force of the strong stratified thermocline for h/h_(LT)<1 and the eff ect of upward reactive force on the downward pressure perturbation becomes weak for h/h_(LT)>1.Hence,the upper mixed layer depth has significant influences on Langmuir turbulence characteristics.

电解质离子对硬脂酸Langmuir膜稳定性影响机理

利用Langmuir膜实验从微观尺度解释电解质离子对油水界面膜特征的影响规律和机理。通过表面压力-平均分子面积等温曲线研究不同电解质类型与浓度对界面膜强度的影响,从压缩能变化特征角度分析气—液、液—固阶段亥姆赫兹自由能增加速度不同的原因,以黏弹性变化分析油水界面流变特征。研究发现:电解质离子类型对油水界面膜特征有重要影响,影响程度Mg^(2+)>Na^(+)>SO_(4)^(2-),其原因是由于阳离子与硬脂酸阴离子基团—COO^(—)形成金属阳离子-络合物使表面膜结构更加稳定,且阳离子表面电荷密度越高膜强度越高。同时,电解质浓度对油水界面膜特征同样有重要影响,随着电解质离子浓度的增加,硬脂酸在油水界面的排列逐渐紧密,直至临界浓度;继续增加,紧密排列的硬脂酸分子膜逐渐破坏。

Presheath formation and area design limit satellite-based Langmuir probes

In this article,the effect of the finite conductive surface area of a satellite on the use of satellite-based Langmuir probes is reviewed in light of the basic theory of asymmetric double Langmuir probes(ADLPs).Recent theoretical and experimental studies have discussed electron sheath/presheath formation and the electron Bohm criterion along with their implications for satellite-based Langmuir probes.The effects predicted by the latest theory of the electron Bohm criterion were not experimentally observed and the experimental results remain supportive of a critical area ratio(A_(L)/A_(S))_(crit)=(m_(i)/(2.3m_(e)))^(1/2)between the probe area A_(S)and the satellite area A_L as conventionally believed.A satellite-based Langmuir probe must satisfy this criterion to physically act as a single Langmuir probe.However,experimental investigations also found that high-energy electrons adversely affect(A_(L)/A_(S))_(crit)and a Langmuir probe's signal quality by giving additional electron current to A_(L).Based on these results,a number of limitations of the maximum probe area are derived when designing satellite-based Langmuir probes,with consideration of both the aim of the satellite and the plasma where the satellite-based probe works.These proposed measures are expected to only partially alleviate the effect of the inadequate satellite surface area on the application of satellite-based Langmuir probes.Using a larger satellite to carry a Langmuir probe remains the most viable means to obtain precise space plasma parameters.

煤层透气性系数新的测试计算方法

煤层透气性系数是衡量煤层瓦斯流动难易程度的关键参数。现行的煤层透气性系数计算式中,将变压力非线性偏微分方程的系数假定为常数,理论推导结果存在较大缺陷,使得现场测定的透气性系数存在较大偏差。为解决煤层透气性系数测定失准的问题,推导了钻孔径向流量法测试煤层透气性系数的过程,并在推导过程中指出该方法存在的问题。以朗格缪尔式瓦斯含量和达西定律为基础,建立无量纲模型,将模型解算结果进行反演拟合,得到新的煤层透气性系数计算式,并通过现场实测钻孔数据进行验证,修正了现行的煤层透气性系数测试方法,提出准确可靠的计算煤层透气性系数的新方法。结果表明:用抛物线式表示煤层瓦斯含量并将变量煤层瓦斯压力p^(1.5)视为常量推导而来的煤层透气性系数计算式,相当于将瓦斯含量拟合成与压力平方成正比关系,理论与实际测算均存在较大误差。采用朗格缪尔式无量纲模型计算出的无因次瓦斯涌出速度Y’进行反演拟合,可解决现行计算方法的缺陷;当吸附常数b与原始瓦斯压力p_(0)的乘积(无因次原始瓦斯压力)不同时,Y’与无因次时间Fo’的函数曲线明显不同,由此得到了含有无因次原始瓦斯压力的透气性系数计算式;当煤层和钻孔条件一定时,由不同时间测试的瓦斯涌出量计算得到的煤层透气性系数λ值具有良好的再现性。新的煤层透气性系数现场测定方法与现行方法完全相同,不增加额外工作量,但新方法的计算更加精确可靠。

粉煤灰提铝残渣制备4A分子筛及Cu(Ⅱ)吸附研究

4A分子筛由于其优异的阳离子交换能力,成为处理重金属废水优良的吸附材料。为了达到以废治废的目的,以粉煤灰酸法提铝残渣为原料制备地质聚合物,再经水热原位转化合成体型化4A分子筛。采用XRD、FT-IR、SEM、BET、TGA等手段对4A沸石进行表征,探讨吸附时间、Cu(Ⅱ)初始浓度、吸附剂用量及溶液p H对其吸附性能的影响,并结合动力学方程和吸附等温线模型对其吸附过程进行研究。结果表明,所合成的4A分子筛孔隙发达且微孔含量较多,总比表面积为71.85 m^(2)/g,其中微孔比表面积为53.91 m^(2)/g,微孔孔径主要集中在1.3 nm左右。体型化4A分子筛吸附Cu(Ⅱ)的最佳条件为吸附时间为240 min、Cu(Ⅱ)初始质量浓度为100 mg/L、吸附剂用量为2.0 g/L、溶液p H为6~9,此时吸附量为32.97 mg/g,Cu(Ⅱ)的去除率可达65.93%。吸附过程符合准二级动力学模型,以化学吸附为主。Langmuir模型拟合效果较好,表明Cu(Ⅱ)在合成4A沸石上的吸附过程为单分子层吸附,且拟合得到的Cu(Ⅱ)的最大吸附量为37.05 mg/g。

钻井泥浆膨润土与染料示踪剂的吸附性能及机理研究

以新胭脂红(AR)和亚甲基蓝(MB)染料示踪剂作为研究对象,研究其与钻井液中膨润土之间的吸附性能,获得其热力学和动力学作用模型,并探究pH以及矿化度对染料吸附性能的影响。实验结果表明,膨润土对MB具有较强的吸附性能,其吸附量(928 mg/g)远大于膨润土对AR的吸附量(0.73 mg/g);膨润土对示踪剂的吸附过程更加符合伪二级动力学模型和Langmuir等温吸附模型;pH会影响染料示踪剂的紫外吸收,矿化度对染料示踪剂的紫外吸收几乎不产生影响。Zeta电位结果表明,AR主要通过范德华力与膨润土发生作用,因而吸附较弱;MB主要通过静电与膨润土中的Al-O、Si-O键发生作用,因而产生较强吸附。

黑藻吸附Cd^2＋和Cu^2＋的拓展Langmuir模型研究

运用沉水植物修复低浓度重金属污染是一种廉价和清洁的技术。采用摇床振荡试验方法,研究了不同pH条件下,沉水植物——轮叶黑藻鲜样对重金属镉和铜的吸附特征。结果表明,pH值对吸附结果影响较大,黑藻对镉和铜的吸附,最适宜的pH值分别为7.0和5.0。在选用的3个拓展Langmuir模型中,模型A拟合效果最好,模型B大大低估了黑藻对重金属镉和铜的吸附能力,模型C则略偏高,表明沉水植物黑藻对重金属镉和铜的吸附与离子所带电荷关系不大,且没有产生吸附剂-重金属-H+的复合式吸附产物(BMH)。运用模型A的回归参数,绘制的三维吸附网格图清晰阐明了不同H+浓度下,黑藻对重金属镉和铜的吸附曲面特征。拓展Langmuir模型A的计算值与实测值的对比表明:24mg·L-1≤C0≤72mg·L-1时,78%的镉吸附量计算值与实测值偏差控制在22%以内,90%的铜吸附量计算值与实测值偏差控制在10%以内。研究不同pH条件下黑藻对镉和铜的生物吸附特征,将有助于对沉水植物修复低浓度重金属污染技术的理解和规范。

固液相离子吸附体系中吸附剂浓度效应与Langmuir方程的适用性

以蛭石吸附Zn2+和Cd2+为例,探讨Langmuir方程在固液相离子吸附体系中的适用性,结果表明:传统吸附等温线随吸附剂浓度W0增大而下降,吸附量qe不仅仅由液相平衡浓度Ce所决定,而是Ce和W0两个变量的函数;以Langmuir方程的线性形式对实验数据进行拟合,在给定吸附剂浓度水平下的实验数据与Langmuir方程拟合的相关性很好,但方程中的两个参数随吸附剂浓度增大而降低而且差异显著,表明Lang-muir方程仅适用于给定吸附剂浓度的体系,采用单一参数的Langmuir方程难以准确描述试验检测范围内Zn2+和Cd2+的吸附规律.

基于Langmuir理论的平衡吸附量预测模型

为了实现对吸附反应的平衡吸附量的预测,建立了平衡吸附量预测模型.以高岭土、蒙脱土这两种黏土矿物吸附Ca2+为例,验证其等温吸附曲线符合Langmuir吸附方程.在Langmuir吸附等温式的基础上,建立了平衡吸附量预测模型,该模型应用于单组分吸附反应的平衡吸附量的预测.通过实验对该模型进行了验证,模型的计算结果与实验结果可以较好地吻合,证明该模型的可靠性较高.

蛭石的NH_4^+吸附与Langmuir方程

测试检验和理论分析说明在Langmuir方程应用中将平衡吸附量Qe表达为离子起始浓度C0和介质用量W0的函数时,Qe=W0qmC0/(KC+C0),方程式中系数KC不是常数,而是W0的函数并与W0呈线性相关.在蛭石铵离子吸附关系式中,Langmuir方程适用的范围是起始浓度C0较小.

HL-2A 装置边缘湍流与带状流相互作用的实验研究

利用组合静电探针阵列研究了HL-2A装置中湍流与带状流相互作用的动力学过程。实验结果表明,在粒子注入后的等离子体恢复阶段,边界区径向电场剖面逐渐变陡,湍流相干尺度和带状流幅度相应增加,而湍流强度随之降低。这些实验提供了带状流与边缘湍流相互作用的直接实验证据,暗示了能量转移是引起带状流增长的主要原因。

二元混合气体等温吸附实验结果与扩展Langmuir方程预测值的比较

通过实验获得了CH4和N2及其二元混合气体的等温吸附方程,并利用扩展Langmuir方程对二元混合气体的吸附行为进行了预测。结果表明,利用纯CH4气体的等温吸附方程和扩展Langmuir方程对二元混合气体吸附行为的预测结果,均与二元混合气体的等温吸附实验数据存在较大误差。所以,当煤层气中含有一定数量的非甲烷气体时,只有通过混合气体的等温吸附实验,才能获得准确的吸附特性参数。

颗粒物微界面吸附模型的分形修正——朗格缪尔(Langmuir)、弗伦德利希(Freundlich)和表面络合模型

运用分形理论修正了颗粒物微界面吸附模型,建立了朗格缪尔(Langmuir)、弗伦德利希(Freundlich)和表面络合模型的分形吸附等温线方程式.其中,朗格缪尔(Langmuir)吸附等温线的分形表达式为:Γ=ΓmC1 me),指数m与颗粒物表面分维Ds的关系如下:m∝e (bm+C1 maDs 2-10;表面络合模型的分形表达式为:Γ=ΓmC(n x)e (b(x n)+C(n x)0∝rDs-2e),而且lgb=lg(ka kb)+pH,指数x n与颗粒物表面分维Ds的关系如下:x n∝aDs 2-10;相应的弗伦德利希(Freundlich)吸附等温线的分形形式分别为:Γ=(Γm bm)C1 me,Γ=(Γm b(x n))C(n x)e.0∝rDs-2通过对文献中的数据的模拟初步讨论了分形模型的适用性,结果表明,它们具有更接近于实际的描述微界面吸附过程的能力,通过lg(x n)=lgk′+(Ds-2)lgr0计算出土壤颗粒和尾矿砂颗粒的表面分形维数分别为2 42和2 72.

电子束发射诱发航天器充电的数值模拟研究

通过发射电子束测量空间地磁场是一种新的有效的地磁场高精度测量方法,但电子束发射对在轨航天器自身状态和安全存在影响。为了研究这一影响,从同步轨道充电机制出发,基于轨道限制机制和朗缪尔方程研究了航天器发射高能电子束时的诱发充电模型,推导了不同初始电位情况下束流发射的平衡电位公式,并编制程序研究了这一过程中粒子束电流、能量、光照等因素对航天器充电电位的影响,得到了航天器对外发射高能电子束时诱发航天器自身或平台的充电电位随时间变化规律,并通过部分解析解对比验证了模拟结果的正确性。