Casson Nanofluid Flow with Cattaneo-Christov Heat Flux and Chemical Reaction Past a Stretching Sheet in the Presence of Porous Medium

In the current work,inclined magnetic field,thermal radiation,and the Cattaneo-Christov heat flux are taken into account as we analyze the impact of chemical reaction on magneto-hydrodynamic Casson nanofluid flow on a stretching sheet.Modified Buongiorno’s nanofluid model has been used to model the flow governing equations.The stretching surface is embedded in a porousmedium.By using similarity transformations,the nonlinear partial differential equations are transformed into a set of dimensionless ordinary differential equations.The numerical solution of transformed dimensionless equations is achieved by applying the shooting procedure together with Rung-Kutta 4th-order method employing MATLAB.The impact of significant parameters on the velocity profile f(ζ),temperature distributionθ(ζ),concentration profileϕ(ζ),skin friction coefficient(Cf),Nusselt number(Nux)and Sherwood number(Shx)are analyzed and displayed in graphical and tabular formats.With an increase in Casson fluid 0.5<β<2,the motion of the Casson fluid decelerates whereas the temperature profile increases.As the thermal relation factor expands 0.1<γ1<0.4,the temperature reduces,and consequently thermal boundary layer shrinks.Additionally,by raising the level of thermal radiation 1<Rd<7,the temperature profile significantly improves,and an abrupt expansion has also been observed in the associated thermal boundary with raise thermal radiation strength.It was observed that higher permeability 0<K<4 hinders the acceleration of Casson fluid.Higher Brownian motion levels 0.2<Nb<0.6 correspond to lower levels of the Casson fluid concentration profile.Moreover,it is observed that chemical reaction 0.2<γ2<0.5 has an inverse relation with the concentration level of Casson fluid.The current model’s significant uses include heat energy enhancement,petroleum recovery,energy devices,food manufacturing processes,and cooling device adjustment,among others.Furthermore,present outcomes have been found in great agreementwith already publishedwork.

Heat and Mass Transfer in MHD Visco-Elastic Fluid Flow through a Porous Medium over a Stretching Sheet with Chemical Reaction

This paper presents the study of convective heat and mass transfer characteristics of an incompressible MHD visco-elastic fluid flow immersed in a porous medium over a stretching sheet with chemical reaction and thermal stratification effects. The resultant governing boundary layer equations are highly non-linear and coupled form of partial differential equations, and they have been solved by using fourth order Runge-Kutta integration scheme with Newton Raphson shooting method. Numerical computations are carried out for the non-dimensional physical parameters. Here a numerical has been carried out to study the effect of different physical parameters such as visco-elasticity, permeability of the porous medium, magnetic field, Grashof number, Schmidt number, heat source parameter and chemical reaction parameter on the flow, heat and mass transfer characteristics.

Fretting Wear Behavior of Medium Carbon Steel Modified by Low Temperature Gas Multi-component Thermo-chemical Treatment

The introduction of surface engineering is expected to be an effective strategy against fretting damage. A large number of studies show that the low gas multi-component （such as carbon, nitrogen, sulphur and oxygen, etc） thermo-chemical treatment（LTGMTT） can overcome the brittleness of nitriding process, and upgrade the surface hardness and improve the wear resistance and fatigue properties of the work-pieces significantly. However, there are few reports on the anti-fretting properties of the LTGMTT modified layer up to now, which limits the applications of fretting. So this paper discusses the fretting wear behavior of modified layer on the surface of LZ50 （0.48%C） steel prepared by low temperature gas multi-component thermo-chemical treatment （LTGMTT） technology. The fretting wear tests of the modified layer flat specimens and its substrate （LZ50 steel） against 52100 steel balls with diameter of 40 mm are carried out under normal load of 150 N and displacement amplitudes varied from 2 μm to 40 μm. Characterization of the modified layer and dynamic analyses in combination with microscopic examinations were performed through the means of scanning electron microscope（SEM）, optical microscope（OM）, X-ray diffraction（XRD） and surface profilometer. The experimental results showed that the modified layer with a total thickness of 60 μm was consisted of three parts, i.e., loose layer, compound layer and diffusion layer. Compared with the substrate, the range of the mixed fretting regime（MFR） of the LTGMTT modified layer diminished, and the slip regime（SR） of the modified layer shifted to the direction of smaller displacement amplitude. The coefficient of friction（COF） of the modified layer was lower than that of the substrate in the initial stage. For the modified layer, the damage in partial slip regime（PSR） was very slight. The fretting wear mechanism of the modified layer both in MFR and SR was abrasive wear and delamination. The modified layer presented better wear resistance than the substrate in PSR and MFR; however, in SR, the wear resistance of the modified layer decreased with the increase of the displacement amplitudes. The experimental results can provide some experimental bases for promoting industrial application of LTGMTT modified layer in anti-fretting wear.

MHD Heat and Mass Transfer of an Oscillatory Flow over a Vertical Permeable Plate in a Porous Medium with Chemical Reaction

The problem of magneto-hydro-dynamic (MHD) mass and heat transfer of an oscillatory fluid in two-dimensional viscous, electrically conducting over an infinite vertical permeable moving plate in a saturated porous medium with the presence of a transverse magnetic field and chemical reaction is analytically presented. The governing equations, momentum, energy, and concentration are solved. Various flow parameters effects on velocity, temperature and concentration fields are discussed. It is found that, the fluid velocity increases with increasing both the permeability and chemical reaction parameters. While, it increases with decreasing the magnetic field parameter. Furthermore, the concentration increases with increasing chemical reaction parameters.

Differences of Physiological and Biochemical Indexes of Upper Fresh Leaves and Post-growth Roots in Different Quality Stages

In order to explore the physiological and biochemical characteristics of fresh upper leaves and roots of different qualities of tobacco, the malonaldehyde （MDA）, superoxide dismutase （SOD） activity, chlorophyllase activity, amylase activity, medium trace element content, chemical component content, root fresh weight, dry weight and activity in the normal tobacco leaves, tobacco leaves rich in nutrients and premature grey tobacco leaves were studied. The results showed that compared with the normal tobacco leaves, the root fresh weight, dry weight and activity in the premature grey tobacco leaves decreased by 41.22%, 14.44% and 60.29% respectively, while malonaldehyde content increased by 34.82%, and chlorophyllase, α-amylase, β-amylase and SOD activity declined by 89.55%, 65.71%, 71.26% and 37.25% respectively. Chlorophyllase, co-amylase and 13-amylase activity in the tobacco leaves rich in nutrients decreased by 58.76%, 36.19% and 41.93% respectively. The content of medium trace elements in the tobacco leaves rich in nutrients and premature grey tobacco leaves was lower than that of the normal tobacco leaves. Starch, total sugar, reducing sugar and potassium content in the normal tobacco leaves were higher than that of the tobacco leaves rich in nutrients and premature grey tobacco leaves.

Methodology and Application for Health Risk Classification of Chemicals in Foods Based on Risk Matrix

The method has been developed to accurately identify the magnitude of health risks and provide scientific evidence for implementation of risk management in food safety.It combines two parameters including consequence and likelihood of adverse effects based on risk matrix.Score definitions and classification for the consequence and the likelihood of adverse effects are proposed.The risk score identifies the intersection of consequence and likelihood in risk matrix represents its health risk level with different colors：‘low＇,‘medium＇,‘high＇.Its use in an actual case is shown.

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.

Chemical short-range-order induced multiscale strengthening in refractory medium entropy alloys

High/medium entropy alloys(H/MEAs)are generally possible to exhibit chemical short-range order(SRO).However,the complex role of SRO on mechanical properties from nano-scale to meso-scale is still challenging so far.Here,we study the strengthening mechanism and deformation behavior in a model body-centered-cubic HfNbTa MEA by using atomic-scale molecular dynamics,micro-scale dislocation dynamics,and meso-scale crystal plasticity finite element.The SRO inhibits dislocation nucleation at the atomic scale,improving the flow stress.The SRO-induced ultrastrong local stress fluctuation greatly improves the micro-scale dislocation-based strength by the significant dislocation forest strengthening.Moreover,the Ta-rich locally ordered structure leads to an obvious heterogeneous strain and stress partitioning,which forms a strong strain gradient in the adjacent grain interiors and contributes to the strong back-stress-induced strain hardening.

Analysis of a Stagnation Point Flow with Hybrid Nanoparticles over a Porous Medium

The unsteady stagnation-point flow of a hybrid nanofluid over a stretching/shrinking sheet embedded in a porous medium with mass transpiration and chemical reactions is considered.The momentum and mass transfer problems are combined to form a system of partial differential equations,which is converted into a set of ordinary differential equations via similarity transformation.These ordinary differential equations are solved analytically to obtain the solution for velocity and concentration profiles in exponential and hypergeometric forms,respectively.The concentration profile is obtained for four different cases namely constant wall concentration,uniform mass flux,general power law wall con-centration and general power law mass flux.The effect of different physical parameters such as Darcy number Da^(1-1),mass transpiration parameter V_(C),stretching/shrinking parameter (d),chemical reaction parameter(β)and Schmidt number (Sc)on velocity and concentration profile is examined.Results show that,the axial velocity will decreases as the shrinking sheet parameter increases,regardless of whether the suction or injection case is examined.The concentration decreases with an increase in the shrinking sheet parameter and the chemical reaction rate parameter.

Joule Heating and Thermal Radiation Effects on MHD Boundary Layer Flow of a Nanofluid over an Exponentially Stretching Sheet in a Porous Medium

A numerical study on boundary layer flow behaviour, heat and mass transfer characteristics of a nanofluid over an exponentially stretching sheet in a porous medium is presented in this paper. The sheet is assumed to be permeable. The governing partial differential equations are transformed into coupled nonlinear ordinary differential equations by using suitable similarity transformations. The transformed equations are then solved numerically using the well known explicit finite difference scheme known as the Keller Box method. A detailed parametric study is performed to access the influence of the physical parameters on longitudinal velocity, temperature and nanoparticle volume fraction profiles as well as the local skin-friction coefficient, local Nusselt number and the local Sherwood number and then, the results are presented in both graphical and tabular forms.

在线激光打孔脉冲持续时间对中支卷烟理化指标及其稳定性的影响研究

【目的】为中支卷烟在线激光打孔参数设计提供参考。【方法】分别采用显微镜和3D显微镜表征中支卷烟接装纸在线打孔的孔形态特征,考察在线打孔脉冲持续时间对中支卷烟理化指标及其稳定性的影响。【结果】①脉冲持续时间过短(≤47µs),出现孔未打透的情况,脉冲持续时间过长(≥90µs),出现椭圆孔的情况。②脉冲持续时间与孔直径、孔面积均呈线性正相关关系。③在线打孔脉冲持续时间与卷烟吸阻、滤嘴通风率和总通风率呈二次函数关系,且决定系数R2均在0.99以上;在线打孔脉冲持续时间与卷烟各项化学指标呈线性函数关系,且决定系数R2主要在0.96以上;卷烟水分释放量与打孔持续时间呈二次函数关系,决定系数为0.9767。④随着孔面积的升高及打孔个数的减小,卷烟的吸阻变化较小,均能保持相对稳定,卷烟总粒相物、烟碱、焦油、CO等释放量的标准偏差在脉冲持续时间适中(50~60μs)时比较小。

产碱性蛋白酶地衣芽孢杆菌合成培养基筛选与优化

该研究对于产碱性蛋白酶地衣芽孢杆菌(Bacillus licheniformis)的合成培养基进行了系统的筛选与优化。基于豆粕成分分析及文献报道构建初始化学合成培养基CDM_(0),并通过单一组分移除实验,初步确定对菌体生长有显著影响(生长降低20%以上)的组分,包括3种碱基、4种维生素、11种氨基酸以及一些金属离子和无机盐。在此基础上进行了组分添加实验,分别添加单一组分移除实验从CDM_(0)中剔除的组分,进而筛选出对菌体生长具有20%以上促进作用的5种关键营养物质,并用全排列方法得到了26种组合添加方式,经实验确定了添加的最佳组合为(NH_(4))_(2)SO_(4)、腺嘌呤和天冬酰胺。此外,还研究了甘油、5种单糖和3种双糖对菌体生长及碱性蛋白酶合成的影响,最终以半乳糖为碳源确定了一种优化后的化学全合成培养基CDM_(3)。实验结果表明,与CDM_(0)相比,CDM_(3)显著提高了菌体的生长速率和碱性蛋白酶的产量,其中酶活力提升至10300.7 U/mL,提高了约2.5倍。该实验结果为今后研究该菌株的代谢特性奠定了基础。

精细化工中中碳链甘油三酯的研究进展

C8-C10脂肪酸甘油三酯俗称中链甘油三酯(medium-chain triglycerides,简称MCT),在日化、食品、保健品、医药等行业有着广泛功效性应用。随着行业的发展对功效性中碳链脂肪酸甘油三酯的需求日益增加,而目前主要来源以动植物为主,供应有限,且难以达到医美、医药行业的应用以及品质需求。因此人工合成制备甘油三酯的研究显得极为重要。文章主要简述中碳链脂肪酸甘油三酯的化学法和生物酶合成方法,以及其分离提纯手段。

Heat and mass transfer effects on MHD viscoelastic fluid over a stretching sheet through porous medium in presence of chemical reaction

An attempt has been made to study the heat and mass transfcr effects in a boundary layer flow through porous medtium of an electrically conducting viscoelastic fluid subject to transverse magnetic field in the presence of heat sourcelsink and chemical reaction.It has been considered the effects of radliation,viscous and Joule dissipations and intemal heat generation/absorption.Closed form solutions for the boundary layer equations of viscoelastic,second-grxle and Walters'B’fluid models are obtained.The method of solution involves similarity transformation.The ransfommed equations of thermal and mass transport are solved by applying Kummer's function.The solutions of temperature field for both prescribed surface temperature(PST)as well as prescribed surface heat flux(PHF)are obtained.It is important to remark that the interaction of magnetic field is found to be counterproductive in enhancing velocity and concentration distibution whereas the presence of chemical reaction as well as porous matrix with moderate values of magnetic parameter reduces the temperature and concentration fields at all points of flow domain.

孔隙—裂缝型岩溶热储热——流—化多场耦合作用机理

岩溶型热储开采过程中,储层孔隙内水岩反应会导致流动通道变形,忽略这一反应过程将导致热储产能预测偏差较大。为了揭示水岩作用下岩溶型热储孔隙和裂缝形态的演化特征,综合考虑了孔隙和裂缝内的水岩反应过程,搭建了孔隙—裂缝双重介质热—流—化多场耦合模型并验证了其准确性,进而分析了热—流—化多物理场与孔隙—裂缝形态的分布特征,探究了孔隙—裂缝内水岩反应对孔、缝变形和系统取热性能的影响。研究结果表明:(1)欠饱和注入条件下,注入井处发生溶解反应,生产30年时,裂缝开度增大了0.32%,孔隙度增大了75.76%;(2)生产30年时,考虑孔隙—裂缝内水岩反应案例的裂缝平均开度降低了0.05%,考虑裂缝而不考虑孔隙内水岩反应案例的裂缝平均开度增大了17.12%,二者呈现相反的变化趋势;(3)考虑孔隙—裂缝内水岩反应案例相比于仅考虑裂缝而不考虑孔隙内水岩反应的案例,生产30年时,生产温度相差不大,系统注采压差增大了1.57倍。结论认为:(1)岩溶型热储孔隙内水岩反应对孔、缝变形和取热性能影响显著,其改变了水岩反应对裂缝开度的作用机理,影响系统注采压差;(2)孔隙内的水岩反应不容忽视,在进行岩溶型热储产能的精确预测和经济评价时必须予以充分考虑;(3)该认识可为岩溶型热储开发方案设计和产能预测方面提供理论和技术参考。

磷矿中磷灰石及脉石与盐酸反应活性的研究

选用主要组分为磷灰石、石英、白云石的中低品位磷矿与盐酸溶液进行反应,考察了反应后的残渣质量、残渣中P2O5的含量以及残渣的X射线衍射图谱等。结果表明:原料磷矿与5%(体积分数,下同)盐酸溶液反应30 min后,白云石相基本消失,残渣中P2O5的质量分数由27.81%升至29.40%;采用10%的盐酸溶液,磷灰石开始参与反应;采用25%的盐酸溶液反应30 min后,残渣中P2O5的质量分数降至0.13%,磷灰石相基本消失。通过控制盐酸溶液体积分数,可选择性地使原料磷矿中的组分与盐酸溶液反应,达到酸法选矿、避免产生磷尾矿的目的。

中高成熟度页岩油地面工艺探索与认识

中高成熟度页岩油特性与常规原油在开发方式与生产规律等方面存在较大差异,采用传统的地面工程建设技术难以满足低成本、高效开发的要求,且不同类型页岩油差异较大,因此结合页岩油物性特点和生产规律,开展了针对页岩油地面工艺的研究。通过现场试验、分析,结合国内外页岩油地面工艺现状,探讨中高成熟度页岩油地面工艺技术,包括单管不加热混输或分输的集输工艺、多井轮回计量的计量工艺、加注破乳剂的加药工艺、两级热化学脱水的脱水工艺、管输和拉运的原油外输工艺、分子筛脱水+丙烷制冷的天然气处理工艺以及其他相关的地面建设,如橇装化、数字化和返排液处理工艺技术。并通过对地面工艺的分析,总结了页岩油地面工程与油藏工程、钻井工程、采油工程等开发专业协调优化的必要性,地上、地下一体化联动,滚动开发,降低地面工程投资;工艺技术采用密闭工艺、分质处理、分质销售,降低油气损耗,增加产品附加值,提高效益;建设方式采用橇装设备分列布置、数字化建设,适应快速建产、后期扩改建需要,提升管理水平;返排液处理采用循环复配回用的方式,实现注采平衡,绿色开发。

嗜热链球菌grx02化学限定增殖培养基及变温培养策略的研究

文章研究了能够促进嗜热链球菌grx02生长的化学限定培养基成分、浓度及其变温培养方法。通过单一成分扣除实验确定化学限定培养基的碳源、氨基酸、维生素矿物质等营养成分的组成,进一步通过单因素实验,对化学限定培养基组分浓度、变温培养方法进行优化,以提高嗜热链球菌grx02的活菌数。结果表明,嗜热链球菌grx02化学限定增殖培养基由1种碳水化合物、16种氨基酸、6种维生素、3种矿物质、4种无机盐、2种有机盐组成;培养初始温度、延滞末期及对数末期温度分别为39、37、39℃。最终嗜热链球菌grx02生物量达到1.40,较优化前提高了1.63倍,活菌数达到9.04 log CFU/mL。可为嗜热链球菌生产及其代谢与功能研究提供参考。

中厚板Q235B表面纵裂原因分析及控制

Q235B中厚板是敬业集团2022年的主流产品之一,但是自进入4月份以后,大批量Q235B板材表面出现纵裂缺陷,每月纵裂缺陷品占Q235B总产量的比例最高达到0.41%,造成了严重的经济损失。针对中厚板Q235B表面纵裂缺陷造成大量板材降级问题,通过跟踪Q235B板坯的炼钢连铸生产过程,对比纵裂缺陷品的工艺参数,研究了纵裂的原因并制定了相关控制措施。从钢水质量、浇注稳定性、铸坯凝固平衡性三方面入手,通过控制钢水冶炼成分碳含量0.15%~0.17%、硫含量小于0.012%,保证精炼软吹效果、减少钢中夹杂物,稳定铸坯拉速波动小于0.1 m/min,优化浇注工艺、水口插入深度115~125 mm,结晶器冷却制度、平衡铸坯宽窄面热流密度等措施,使Q235B板坯表面纵裂纹发生率得到明显控制,9月份纵裂缺陷品占比0.128%,较8月份减少0.283%。

基于FTIR与烷烃气碳同位素特征的中阶煤结构演化研究

煤变质作用过程存在多次阶跃点,并发生以热降解-热裂解作用为主形成烷烃气。为探究中阶煤结构演化特征,以西山煤田中阶煤为研究对象,采用傅里叶红外光谱测试分析方法对中阶煤化学结构演化特征及其与烷烃气碳同位素关系进行了研究。结果表明,煤层气碳同位素值位于-57.20‰~-31.41‰之间,乙烷与甲烷碳同位素值相比变化相对较弱。样品中羟基以自缔合氢键为主,芳香烃结构以苯环三取代为主,芳碳率在演化中变化较弱,芳环缩合度则出现增大—减小—增大的变化趋势,脂肪烃以亚甲基含量为主,支链化程度参数在演化中出现减小—急增—减小的阶段性变化。结合甲烷碳同位素特征分析认为,中阶煤阶段结构演化可划分为五个阶段,第一阶段(0.65%<Ro<1.10%)以热解作用为主导,δ13C1呈微弱减小的趋势;第二阶段(1.10%<Ro<1.30%)以热解与缩聚的叠合为主,δ13C1值开始变重;第三阶段(1.30%<Ro<1.50%)由煤的热解逐渐进入以缩聚作用为主,烷烃气大量生成,δ13C1值变重趋势减弱;第四阶段(1.50%<Ro<1.80%)以缩聚作用为主,第五阶段(1.80%<Ro<2.0%)则由芳环的缩聚为叠合阶段做准备,δ13C1值的减小或与纳米孔隙结构变化对甲烷吸附的差异有关。中阶煤化学结构演化和碳同位素变化关系的研究对指导煤层气勘探开发和煤炭资源清洁利用具有重要意义。