化学反应速率对爆轰特性的影响研究—基于离散Boltzmann模型

基于我们课题组以前提出的高速可压LBGK模型[Gan, Xu, Zhang, Yang, EPL 103 (2013) 24003],发展了一个适用于模拟爆轰问题的离散Boltzmann模型。化学反应率模型采用只保留增长项的Lee模型。基于新构建的模型,模拟了不同反应速率的爆轰情形,找到了一个临界反应速率。当反应速率等于临界反应速率时,模拟的结果与CJ理论值符合较好。当反应速率低于临界反应速率时,爆轰波的波结构中会出现von-Neumann峰,之后从峰值点过渡到稳态,稳态为CJ爆轰状态。当反应速率高于临界反应速率时,爆轰波会以高于CJ爆轰波速的速度向前传播,稳态为弱爆轰状态。

爆轰问题的一个高效二维离散玻尔兹曼模型

本文构建了多松弛时间离散玻尔兹曼模型,并使用该模型模拟爆轰现象。相对于我们之前的一个模型[Xu A., Lin C., Zhang G., Li Y., Phys. Rev. E 91 (2015) 043306],本模型在模拟有化学反应或无化学反应流体系统时的计算效率更高。这是因为前者使用了24个离散速度,而本模型只使用16个。在模拟部分高马赫物理系统时,本模型表现出更高的数值稳定性。使用该模型,本文分四种情况模拟了爆轰波激发的Richtmyer-Meshkov不稳定性问题。当爆轰波由反应物传向另一种较轻的不反应的物质时,由于突然失去能量补充,温度急剧下降,在物质界附近将会出现一层高密区域。

Nonequilibrium kinetics effects in Richtmyer–Meshkov instability and reshock processes

Kinetic effects in the inertial confinement fusion ignition process are far from clear.In this work,we study the Richtmyer-Meshkov instability and reshock processes by using a two-fluid discrete Boltzmann method.The work begins by interpreting the experiment conducted by Collins and Jacobs(2002,J.Fluid Mech.464,113-136).It shows that the shock wave causes substances in close proximity to the substance interface to deviate more significantly from their thermodynamic equilibrium state.The thermodynamic non-equilibrium(TNE)quantities exhibit complex but inspiring kinetic effects in the shock process and behind the shock front.The kinetic effects are detected by two sets of TNE quantities.The first set includes∣Δ_(2)^(*)∣,∣Δ_(3,1)^(*),∣Δ_(3)^(*)∣,and∣Δ_(4,2)^(*)∣,which correspond to the intensities of the non-organized momentum Flux(NOMF),Non-Organized Energy Flux(NOEF),the flux of NOMF and the flux of NOEF.All four TNE measures abruptly increase in the shock process.The second set of TNE quantities includes■_(NOMF),■_(NOEF)and■_(sum),which denote the entropy production rates due to NOMF,NOEF and their summation,respectively.The mixing zone is the primary contributor to■_(NOEF),while the flow field region outside of the mixing zone is the primary contributor to■_(NOMF).Additionally,each substance exhibits different behaviors in terms of entropy production rate,and the lighter fluid has a higher entropy production rate than the heavier fluid.

Ensemble learning system to identify nutritional risk and malnutrition in cancer patients without weight loss information

Dear Editor,Malnutrition is a prevalent disease in oncology practice(Arends et al.,2017).With its cancer-specific prevalence ranging from 21%–72%,malnutrition is responsible for 10%–20% cancer deaths(Yin et al.,2021b).However,malnutrition is often underestimated,misclassified,or left untreated in cancer care(Hébuterne et al.,2014).

论商住两用房的法律属性和政策困扰

一、引言:问题的提出。“商住两用”是日常生活中常用的一个词语。房地产经济学的术语,称为“商改住”,也就是商业用地改作住房用途;法律规范文件和司法判例中,偶尔会出现“商住两用”的概念,但是在正式法律文本里,“商住两用”不成其为一个法律术语,并没有专门的法律规范予以调整。从房地产经济学和民商法学的角度看,“商住两用房”都是一个小众的现象,在房地产经济中备受打压,在法律世界里为人所漠视。

Complex fields in heterogeneous materials under shock:modeling, simulation and analysis

In this mini-review we summarize the progress of modeling, simulation and analysis of shock responses of heterogeneous materials in our group in recent years. The basic methodology is as below. We first decompose the problem into different scales. Construct/Choose a model according to the scale and main mechanisms working at that scale. Perform numerical simulations using the relatively mature schemes. The physical information is transferred between neighboring scales in such a way: The statistical information of results in smaller scale contributes to establishing the constitutive equation in larger one. Except for the microscopic Molecular Dynamics(MD) model, both the mesoscopic and macroscopic models can be further classified into two categories,solidic and fluidic models, respectively. The basic ideas and key techniques of the MD, material point method and discrete Boltzmann method are briefly reviewed. Among various schemes used in analyzing the complex fields and structures, the morphological analysis and the home-built software, GISO, are briefly introduced. New observations are summarized for scales from the larger to the smaller.

Serum macrophage migration inhibitory factor as a potential biomarker to evaluate therapeutic response in patients with allergic asthma:an exploratory study

Background:Previous studies have shown that macrophage migration inhibitory factor(MIF)is involved in the pathogenesis of asthma.This study aimed to investigate whether serum MIF reflects a therapeutic response in allergic asthma.Methods:We enrolled 30 asthmatic patients with mild-to-moderate exacerbations and 20 healthy controls,analyzing the parameter levels of serum MIF,serum total immunoglobulin E(tIgE),peripheral blood eosinophil percentage(EOS%),and fractional exhaled nitric oxide(FeNO).Lung function indices were used to identify disease severity and therapeutic response.Results:Our study showed that all measured parameters in patients were at higher levels than those of controls.After one week of treatment,most parameter levels decreased significantly except for serum tIgE.Furthermore,we found that serum MIF positively correlated with EOS%as well as FeNO,but negatively correlated with lung function indices.Receiver operator characteristic(ROC)curve analysis indicated that among the parameters,serum MIF exhibited a higher capacity to evaluate therapeutic response.The area under the curve(AUC)of MIF was 0.931,with a sensitivity of 0.967 and a specificity of 0.800.Conclusions:Our results suggested that serum MIF may serve as a potential biomarker for evaluating therapeutic response in allergic asthma with mild-to-moderate exacerbations.

Effects of the initial perturbations on the Rayleigh–Taylor–Kelvin–Helmholtz instability system

The effects of initial perturbations on the Rayleigh–Taylor instability (RTI), Kelvin–Helmholtz instability (KHI), and the coupled Rayleigh–Taylor–Kelvin–Helmholtz instability (RTKHI) systems are investigated using a multiple-relaxation-time discrete Boltzmann model. Six different perturbation interfaces are designed to study the effects of the initial perturbations on the instability systems. It is found that the initial perturbation has a significant influence on the evolution of RTI. The sharper the interface, the faster the growth of bubble or spike. While the influence of initial interface shape on KHI evolution can be ignored. Based on the mean heat flux strength D3,1, the effects of initial interfaces on the coupled RTKHI are examined in detail. The research is focused on two aspects: (i) the main mechanism in the early stage of the RTKHI, (ii) the transition point from KHI-like to RTI-like for the case where the KHI dominates at earlier time and the RTI dominates at later time. It is found that the early main mechanism is related to the shape of the initial interface, which is represented by both the bilateral contact angle θ_(1) and the middle contact angle θ_(2). The increase of θ_(1) and the decrease of θ_(2) have opposite effects on the critical velocity. When θ_(2) remains roughly unchanged at 90 degrees, if θ_(1) is greater than 90 degrees (such as the parabolic interface), the critical shear velocity increases with the increase of θ_(1), and the ellipse perturbation is its limiting case;If θ_(1) is less than 90 degrees (such as the inverted parabolic and the inverted ellipse disturbances), the critical shear velocities are basically the same, which is less than that of the sinusoidal and sawtooth disturbances. The influence of inverted parabolic and inverted ellipse perturbations on the transition point of the RTKHI system is greater than that of other interfaces: (i) For the same amplitude, the smaller the contact angle θ_(1), the later the transition point appears;(ii) For the same interface morphology, the disturbance amplitude increases, resulting in a shorter duration of the linear growth stage, so the transition point is greatly advanced.

Rayleigh-Taylor instability under multimode perturbation:Discrete Boltzmann modeling with tracers

The two-dimensional Rayleigh-Taylor Instability(RTI)under multi-mode perturbation in compressible flow is probed via the Discrete Boltzmann Modeling(DBM)with tracers.The distribution of tracers provides clear boundaries between light and heavy fluids in the position space.Besides,the position-velocity phase space offers a new perspective for understanding the flow behavior of RTI with intuitive geometrical correspondence.The effects of viscosity,acceleration,compressibility,and Atwood number on the mixing of material and momentum and the mean nonequilibrium strength at the interfaces are investigated separately based on both the mixedness defined by the tracers and the non-equilibrium strength defined by the DBM.The mixedness increases with viscosity during early stage but decreases with viscosity at the later stage.Acceleration,compressibility,and Atwood number show enhancement effects on mixing based on different mechanisms.After the system relaxes from the initial state,the mean non-equilibrium strength at the interfaces presents an initially increasing and then declining trend,which is jointly determined by the interface length and the macroscopic physical quantity gradient.We conclude that the four factors investigated all significantly affect early evolution behavior of an RTI system,such as the competition between interface length and macroscopic physical quantity gradient.The results contribute to the understanding of the multi-mode RTI evolutionary mechanism and the accompanied kinetic effects.