Discrete formulation of mixed finite element methods for vapor deposition chemical reaction equations

The vapor deposition chemical reaction processes, which are of extremely extensive applications, can be classified as a mathematical model by the following governing nonlinear partial differential equations containing velocity vector, temperature field, pressure field, and gas mass field. The mixed finite element （MFE） method is employed to study the system of equations for the vapor deposition chemical reaction processes. The semidiscrete and fully discrete MFE formulations are derived. And the existence and convergence （error estimate） of the semidiscrete and fully discrete MFE solutions are demonstrated. By employing MFE method to treat the system of equations for the vapor deposition chemical reaction processes, the numerical solutions of the velocity vector, the temperature field, the pressure field, and the gas mass field can be found out simultaneously. Thus, these researches are not only of important theoretical means, but also of extremely extensive applied vistas.

Simultaneous effects of chemical reaction and Ohmic heating with heat and mass transfer over a stretching surface: A numerical study

In this article, we have considered the simultaneous influence of ohmic heating and chemical reaction on heat and mass transfer over a stretching sheet. The effects of applied magnetic field are also taken into consideration while the induced magnetic field is not considered due to very small magnetics Reynolds number. The governing flow problem comprises of momentum, continuity, thermal energy and concentration equation which are transformed into highly nonlinear coupled ordinary differential equations by means of similarity transforms, which are then, solved numerically with the help of Successive Linearization method(SLM) and Chebyshev Spectral collocation method. Numerical values of skin friction coefficient, local Nusselt number, and Sherwood number are also taken into account with the help of tables. The physical influence of the involved parameters of flow velocity, temperature and concentration distribution is discussed and demonstrated graphically. The numerical comparison is also presented with the existing published results and found that the present results are in excellent agreement which also confirms the validity of the present methodology.

Chemical reaction effects on unsteady MHD flow past semi-infinite vertical porous plate with viscous dissipation

The chemical reaction effect on an unsteady magnetohydrodynamic （MHD） flow past a semi-infinite vertical porous plate with viscous dissipation is analyzed. The governing equations of motion, energy, and species are transformed into ordinary differential equations （ODEs） using the time dependent similarity parameter. The resultant ODEs are then solved numerically by a finite element method. The effects of various parameters on the velocity, temperature, and concentration profiles are presented graphically, and the values of the skin-friction, Nusselt number, and Sherwood number for various values of physical parameters are presented through tables.

Magneto Hydrodynamics Stagnation Point Flow of a Nano Fluid over an Exponentially Stretching Sheet with an Effect of Chemical Reaction, Heat Source and Suction/Injunction

A numerical investigation is carried out on the effects of heat source suction and viscous dissipation on Magneto hydrodynamics boundary layer flow of a viscous, steady and incompressible fluid. The flow is assumed to be over on exponentially stretching sheet. The governing system of partial differential equations has been transformed into ordinary differential equation using similarity transformation. Keller box method is simulated on the dimensionless system of differential equations. The skin friction coefficient and the heat and mass transfer rates are very significant parameters that are computed, analysed discussed in detail.

Extracting Human Reaction Time from Observations in the Method of Constant Stimuli

We consider the psychophysical experiments in which the test subject’s binary reaction is determined by the prescribed exposure duration to a stimulus and a random variable subjective threshold. For example, when a subject is exposed to a millimeter wave beam for a prescribed duration, the occurrence of flight action is binary (yes or no). In experiments, in addition to the binary outcome, the actuation time of flight action is also recorded if it occurs;the delay from the initiation time to the actuation time of flight action is the human reaction time, which is not measurable. In this study, we model the random subjective threshold as a Weibull distribution and formulate an inference method for estimating the human reaction time, from data of prescribed exposure durations, binary outcomes and actuation times of flight action collected in a sequence of tests. Numerical simulations demonstrate that the inference of human reaction time based on the Weibull distribution converges to the correct value even when the underlying true model deviates from the inference model. This robustness of the inference method makes it applicable to real experimental data where the underlying true model is unknown.

Investigation of the ^(121)Sb(α,γ)^(125)I reaction cross-section calculations at astrophysical energies

Proton-rich nuclei are synthesized via photodisintegration and reverse reactions.To examine this mechanism and reproduce the observed p-nucleus abundances,it is crucial to know the reaction rates and thereby the reaction cross sections of many isotopes.Given that the number of experiments on the reactions in astrophysical energy regions is very rare,the reaction cross sections are determined by theoretical methods whose accuracy should be tested.In this study,given that ^(121)Sb is a stable seed isotope located in the region of medium-mass p-nuclei,we investigated the cross sections and reaction rates of the ^(121)Sb(α,γ)^(125)I reaction using the TALYS computer code with 432 different combinations of input parameters(OMP,LDM,and SFM).The optimal model combinations were determined using the threshold logic unit method.The theoretical reaction cross-sectional results were compared with the experimental results reported in the literature.The reaction rates were determined using the two input parameter sets most compatible with the measurements,and they were compared with the reaction rate databases:STARLIB and REACLIB.

民族高校化学反应工程课程的“信息化+多学科融合”教学改革

为了响应“西部大开发形成新格局”的国家战略,培养适应西部地区未来发展的新工科技术人才,西南民族大学化学与环境学院联合西北民族大学、北方民族大学等民族院校开展了“信息化+多学科融合”跨区域多专业协同教学改革。西南民族大学化学反应工程课程团队基于课程目标要求、授课特点和民族院校基本学情,从2014年起充分利用现代设计方法和信息技术,转变教学理念,创新教学内容和方法,依托学科竞赛提高课程教学质量和人才培养质量,面向区域新经济为西部地区培养高素质化工技术人才。

新工科教学化学反应工程课改基本思路

本文宗旨阐述以复杂系统理论基础为指导,对《化学反应工程》学科研究的“对象、方法”进行讨论。研究对象的确定从划定框架范围开始,在子一级或更小的界定范畴,明确要研究什么。研究方法是建立模型,把模型化思想方法作为解决问题的普遍化方法。以三种理想反应器特征分析建立物料衡算式的不同结果分析为例及教学效果,实践了如何培养学生构筑坚固理论基础,为学生厚积薄发打好基础,把新工科建设落实到实处。

5933例更年期泌尿生殖系统综合征女性阴道微生态情况分析

目的分析更年期泌尿生殖系统综合征(GSM)女性阴道微生态情况,为临床诊疗提供实验室依据。方法回顾性分析2020年6月至2023年7月该院门诊就诊的绝经后患有GSM的5933例女性的临床资料。按照年龄分为≤50岁组(2138例)、>50~60岁组(3043例)、>60~70岁组(614例)、>70岁组(138例)。采用湿片镜检进行阴道分泌物形态学检测(包括鳞状上皮细胞、基底旁上皮细胞、白细胞、红细胞、假菌丝、芽生孢子、滴虫、乳酸杆菌、球菌、线索细胞)并评定阴道清洁度,采用化学反应法进行干化学功能指标检测[包括pH值、白细胞酯酶(LE)、过氧化氢(H_(2)O_(2))、唾液酸苷酶(SNA)、脯氨酸氨基肽酶(PIP)、乙酰氨基葡萄糖苷酶(NAG)]。结果4组鳞状上皮细胞、基底旁上皮细胞、白细胞、乳酸杆菌、球菌、芽生孢子、红细胞、线索细胞分布情况及阴道清洁度比较,差异均有统计学意义(P<0.05)。4组滴虫、假菌丝分布情况比较,差异均无统计学意义(P>0.05)。4组pH值、LE、NAG水平比较,差异均有统计学意义(P<0.05)。4组H_(2)O_(2)、SNA、PIP水平比较,差异均无统计学意义(P>0.05)。结论GSM患者在妇科门诊绝经后女性中发生率较高,且不同年龄段GSM患者阴道微生态状况存在差异,对不同年龄段GSM患者进行微生态分析,能够指导临床医生精准治疗,减少反复感染发生,提高患者的生活质量。

Transient analysis of diffusive chemical reactive species for couple stress fluid flow over vertical cylinder

The unsteady natural convective couple stress fluid flow over a semi-infinite vertical cylinder is analyzed for the homogeneous first-order chemical reaction effect. The couple stress fluid flow model introduces the length dependent effect based on the material constant and dynamic viscosity. Also, it introduces the biharmonic operator in the Navier-Stokes equations, which is absent in the case of Newtonian fluids. The solution to the time-dependent non-linear and coupled governing equations is carried out with an unconditionally stable Crank-Nicolson type of numerical schemes. Numerical results for the transient flow variables, the average wall shear stress, the Nusselt number, and the Sherwood number are shown graphically for both generative and destructive reactions. The time to reach the temporal maximum increases as the reaction constant K increases. The average values of the wall shear stress and the heat transfer rate decrease as K increases, while increase with the increase in the Sherwood number.

Balancing Chemical Equations by Systems of Linear Equations

In this paper, a formal and systematic method for balancing chemical reaction equations was presented. The results satisfy the law of conservation of matter, and confirm that there is no contradiction to the existing way(s) of balancing chemical equations. A chemical reaction which possesses atoms with fractional oxidation numbers that have unique coefficients was studied. In this paper, the chemical equations were balanced by representing the chemical equation into systems of linear equations. Particularly, the Gauss elimination method was used to solve the mathematical problem with this method, it was possible to handle any chemical reaction with given reactants and products.

Investigation of Synthesis of Functionally Substituted Endiines and Their Chemical and Microbiological Conversion

The methods of preparation of endiine and endiallene diols by interaction of cis-1,4-dibrombutene and cis-1,4-dichlor-rbutene with monosubstituted acetylene alcohols in presence of the catalytic systems consisting of one-iodide copper, triethylamine and K2СО3 in a medium of dimethylformamide have been developed. It has been shown that unlike 1,4-dibrombutene, the nucleophilic substitution reaction with 1,4-dichlorbutene proceeds by acetylene-allene isomerization with formation of endiallene diols. It has been established that the endiine diols can be used in thin organic synthesis (in the reactions of oxidation, splitting, dehydration, epoxidation, hydrolysis, 1,2-cycloaddition and hypochlorination) with the aim of preparation of practically useful substances. It has been revealed during hydrolysis of epoxide compounds by the chemical and microbiological methods that in the course of microbiological hydrolysis (Aspеrgillus niger), the optically active trans-structured diols are formed.

Numerical Investigation of Unsteady Free Convection on a Vertical Cylinder with Variable Heat and Mass Flux in the Presence of Chemically Reactive Species

A mathematical model is presented to study the effect of chemical reaction on unsteady natural convection boundary layer flow over a semi-infinite vertical cylinder. Taking into account the buoyancy force effects, for the situation in which the surface temperature and are subjected to the power-law surface heat and mass flux as and . The governing equations are solved by an implicit finite difference scheme of Crank-Nicolson method. Numerical results for the velocity, temperature and concentration profiles as well as for the skin-friction, Nusselt and Sherwood numbers are obtained and reported graphically for various parametric conditions to show interesting aspects of the solution.

活性材料冲击压缩及反应行为模拟方法研究进展

近年来,以含能结构材料、含能非晶合金、含能高熵合金等为代表的活性材料受到广泛关注.由于兼具结构强度特性和冲击反应释能特性,活性材料在高效毁伤和防护领域有十分重要的应用前景.其中,活性材料的冲击压缩响应行为及反应释能特性是该类材料设计和应用中关注的重点,研究人员在考虑其冲击反应行为的数值模拟方法上开展了大量的研究工作.本文基于活性材料宏观反应行为受微/细观结构特性控制的特点,从不同时空尺度对活性材料的冲击压缩及反应行为数值模拟方法的研究现状进行了综述,系统梳理了分子动力学模拟、冲击压缩特性细观模拟、冲击反应行为跨尺度模拟、冲击压缩及反应行为宏观尺度模拟方法等4个方面的研究进展.总结认为,活性材料的冲击压缩动力学响应特性数值模拟及冲击反应特性宏−细观尺度关联机制的研究已取得了较大进展,考虑反应弛豫时间和非自持反应特性的点火模型在宏观尺度数值模拟中得到发展与应用.但是,目前数值模拟中关于反应诱发后活性材料动力学行为的描述主要基于火/炸药等典型含能材料的本构模型,仅能实现对活性材料冲击反应行为的表观呈现,而对活性毁伤元作用过程关键参数的精确预测仍存在一定差距.因此,建立准确描述活性材料撞击点火、反应发展、释能做功过程的全时域理论模型,基于此发展该类材料冲击反应行为高可靠性数值模拟技术,是实现活性材料冲击反应释能特性调控和工程化应用的关注焦点.

将立德树人融入《化学反应工程》课程,培养一流化工人才

加强专业课与思政课的结合,是习近平总书记提出的推动高校思想政治教育的重要渠道。基于《化学反应工程》课程特点,立足专业课程学术内涵,结合近代以来化工界涌现的诸多科学家所具有的优秀品格,在化学反应工程课堂上进行课程思政,从而使得《化学反应工程》课程和课程思政有机结合,达到立德树人的目的,为国家培养一流卓越化工人才。本文结合广西大学《化学反应工程》课堂上的尝试,进行课程思政教学的理论和实践进行初步探析,以期为化学工程与工艺专业课堂上进行课程思政带来新的思路和视角。

基于化学杂化和官能团相似耦合方法的RP-3航空煤油反应动力学简化模型构建

真实航空燃料通常包含几十至上百种组分,直接构建其化学反应动力学模型十分困难。本文利用官能团相似法(SCFG),结合实测RP-3航空煤油组分比例,提出了RP-3四组分模型替代物。利用流动反应器,获得了温度为550~1150K,压力为0.1 MPa下RP-3热解数据,基于化学杂化方法(Hybrid Chemistry),构建了以真实RP-3为单一原始组分的航空煤油化学反应动力学模型(XJTURP3-2021),模型得到宏观点火延迟、层流火焰速度以及微观组分浓度系统验证。基于误差传递的直接关系图法(DRGEP)和全局敏感性分析(FSSA)对模型进行简化,获得含41种组分、212个基元反应的RP-3简化模型(XJTURP3r-2021)。与详细模型和实验数据对比发现,XJTURP3r-2021能较好地复现热力边界对RP-3基础燃烧特征影响规律,为解决CFD仿真对反应源项初始组分数量约束和计算精度固有矛盾提供新思路。

气固流化床化学反应数值模拟中颗粒尺度模型研究进展

气固流化床由于其优良的气固接触效率和传热传质效率,已经被广泛应用于能源、矿冶、化工、制药等工业领域。本文针对颗粒流态化-反应系统数值模拟研究进行了综述,阐述了数值模拟的三个尺度:化学反应工程模型、双流体模型以及颗粒尺度模型。然后聚焦于基于CFD-DEM方法的变粒径颗粒流态化-化学反应过程模拟,梳理分析了6种颗粒反应模型,即均匀转化模型、缩粒反应模型、缩核反应模型、联合收缩模型、细颗粒反应模型和随机孔隙模型,并从颗粒性质变化、化学反应模型、不同尺度耦合三个角度探讨了不同的颗粒反应模型的优点和应用中的局限性,分析了跨尺度颗粒系统模拟方法的发展近况,最后讨论了CFD-DEM方法在气固流化床化学反应过程模拟的应用上未来可能的发展方向,包括颗粒尺度大规模高效计算算法、颗粒反应模型的精确化以及颗粒-气体信息传递的精细化描述方面。有助于气固流化床化学反应模拟领域的梳理和发展,尤其是可供颗粒尺度模拟领域的研究人员参考和借鉴。

基于化学反应速率理论的空气开关柜局部放电特征气体研究

空气开关柜局部放电的检测具有重要实际意义,气体检测法较传统检测方法有明显优势,而气体检测法的关键在于特征气体的选取。为给特征气体的选取提供理论依据,基于化学反应速率理论对局部放电下空气的分解机理进行研究。首先,利用Gaussian软件搭建气体分子的计算模型,并优化反应物和产物的分子构型,在此基础上搜索各反应路径的过渡态,进而得到相应的反应速率常数,并以此为依据分析不同放电情形下可能的气体产物;之后,对气体分子在开关柜材料的吸附性能进行研究,分析吸附作用对反应的影响,结合反应速率常数与开关柜对气体吸附的影响,选取气体分解产物中的NO_(2)、CO、O_(3)作为特征气体;最后,搭建实验平台模拟不同缺陷类型下的局部放电,并收集局部放电下3种特征气体的浓度,以此数据为基础验证特征气体选择的可行性,结果表明:选取NO_(2)、CO、O_(3)3种特征气体能够较好地反映空气开关柜局部放电的情况。

高超声速CO_(2)稀薄气体振动激发与DSMC方法实现

针对火星独特的CO_(2)稀薄气体环境以及探测器高超声速进入火星过程中的高温真实气体效应,研究了CO_(2)多振动模式的激发特性。采用非结构网格和直接模拟蒙特卡洛法(Direct Simulation Monte Carlo method, DSMC),基于非谐振子振动激发模型,通过将CO_(2)离解能均分到4种振动模态,进而限制各模态最高振动能级,模拟了含CO_(2)的5组分17反应的高温稀薄真实气体化学反应模型。计算了“火星探路者”在火星大气环境65 km高度、进入速度为7 453 m/s、攻角为0°下的高温化学非平衡效应流场。结果表明:CO_(2)在激波后大量分解并消耗大量能量;迎风面激波中各组分占比与探测器物面特性等均与文献结果相符,证明了本文对于CO_(2)振动激发处理方法的可行性。在此基础上加入N_2组分,模拟火星大气8组分44基元化学反应流场,通过改变来流密度与马赫数分析了流场特性的变化。结果表明:随着来流密度减小,流场温度呈现先增加后减小的趋势,物面热流密度增大;来流马赫数增加使得流场温度和压力上升,物面热流密度提高但是热流密度系数变化幅度很小。

案例教学法在“化学反应工程”教学中的应用探讨

为了使学生能够充分认识“反应器选型”在工业生产中的重要性,案例教学法被引入“化学反应工程”教学中。研究过程重视案例选题背景及教学应用情景,强化了案例教学问题导入式教学法。基于“反应器选型”这一知识点,以实际工业中微生物法生产丙烯酰胺工艺中反应器的发展历程为背景,详细介绍了案例的设计与实施过程。教学实践结果表明,案例教学法强化了学生对反应器选型这一知识点的理解和掌握。