Analytic solution for magnetohydrodynamic boundary layer flow of Casson fluid over a stretching/shrinking sheet with wall mass transfer

In this analysis,the magnetohydrodynamic boundary layer flow of Casson fluid over a permeable stretching/shrinking sheet in the presence of wall mass transfer is studied.Using similarity transformations,the governing equations are converted to an ordinary differential equation and then solved analytically.The introduction of a magnetic field changes the behavior of the entire flow dynamics in the shrinking sheet case and also has a major impact in the stretching sheet case.The similarity solution is always unique in the stretching case,and in the shrinking case the solution shows dual nature for certain values of the parameters.For stronger magnetic field,the similarity solution for the shrinking sheet case becomes unique.

Analytical Solution of Vibration Analysis on Fixed-Free Single-Walled Carbon Nanotube-Based Mass Sensor

Fixed-free single-walled carbon nanotubes (SWCNTs) have attracted a lot of interest in recent years due to their suitability for a wide range of applications, such as field emission and vacuum microelectronic devices, nanosensors, and nanoactuators. Based on a cantilever beam-bending model with a rigid mass at the free end and mode analysis, an analytical solution is developed in the present study to deal with the resonant frequency and mode shapes of a SWCNT- based mass sensor. The resonant frequency shift and mode shape of the fixed-free SWCNTs caused by the addition of a nanoscale particle to the beam tip are examined in order to explore the suitability of SWCNTs as a mass detector device. The simulation results reveal that the volume of the added particle has little effect on the first resonant frequency. In contrast, the second resonant frequency decreases with increasing the volume of the added particle. Furthermore, the resonant frequency shift of the first mode is very obvious for the amount of added mass, and the second resonant frequency decreases rapidly with increasing volume of added particle. Therefore, the first and second resonant frequencies can be used in the measurement of the mass of added particle and its volume, respectively.

MASS MOVEMENT IN THE GREAT WALL STATION AREA, ANTARCTICA

This paper deals with the mass movement processes on the Fildes Peninsula, King George Island. Based on numerous field investigation, the authors consider that the slope mass movement and periglacial form on the peninsula have an internal relationship in genesis, reflecting in there main aspects. 1, All patterns of mass movement are developed on the slope surface; 2, different -order mass movement and periglacial type show their space-time distribution rules (their development stages); 3, The slope mass movement are developed from the periglacio - geomorphic processes. More detailed works have been done, such as fixed reapeated surveying whose results are concord and with the typical characteristics above mentimed very well.

Mathematical Modelling of Mass Transfer and Free Convection Current Effects on Unsteady Viscous Flow with Ramped Wall Temperature

An exact analysis of the flow of an incompressible viscous fluid past an infinite vertical plate is conducted taking into account the presence of foreign mass or constant mass flux and ramped wall temperature. The dimensionless governing coupled linear partial differential equations are solved using the Laplace transform technique. Two different solutions for the fluid velocity are obtained–one valid for the fluids of Schmidt numbers different from unity, and the other for which the Schmidt number is unity. The effects of Prandtl number (Pr), Schmidt number (Sc), time (t) and mass to thermal buoyancy ratio parameter (N) for both aiding and opposing buoyancy effects on the velocity and skin-friction are studied. Also, the heat and mass transfer effects on the flow near a ramped temperature plate have been compared with the flow near a plate with constant temperature.

Effects of fluid recirculation on mass transfer from the arterial surface to flowing blood

The effect of disturbed flow on the mass trans- fer from arterial surface to flowing blood was studied nu- merically, and the results were compared with that of our previous work. The arterial wall was assumed to be vis- coelastic and the blood was assumed to be incompressible and non-Newtonian fluid, which is more close to human arte- rial system. Numerical results indicated that the mass trans- fer from the arterial surface to flowing blood in regions of disturbed flow is positively related with the wall shear rates and it is significantly enhanced in regions of disturbed flow with a local minimum around the reattachment point which is higher than the average value of the downstream. There- fore, it may be implied that the accumulation of cholesterol or lipids within atheromatous plaques is not caused by the reduced efflux of cholesterol or lipids, but by the infiltration of the LDL （low-density lipoprotein） from the flowing blood to the arterial wall.

Characteristics of Element Migration in the Process of Wall-Rock Alteration in the Shibangou Gold Deposit,Western Henan

Abstract The Shibangou gold deposit in western Henan is associated with irregular quartz veinlets occurring in altered shear zones dissecting a dioritic intrusion. The altered shear zones are characterized by silicification, pyritization, sericilization, chloritization and K-feldspar alteration. Zoning of altered rocks adjacent to the Au-bearing quartz veins is obviously exhibited. Fine-grained sulphides and quartz veinlets of different ages and small-scale fissures are widely distributed in the central part of the altered zones. Major mineralization types in this gold deposit are Au-bearing quartz veinlets and altered rocks in the shear zones. Samples were collected from drilling cores according to the alteration zoning and mineralization type and all samples were analyzed for major and trace elements. Mass balance, volume change (fv=97.3–71.9%) and major element variation sequences are studied in terms of major elements. The changes of mobile components (SiO2, K2O, Fe2O3) and CaO) and immobile component (Al2O3) in the wall-rock alteration are discussed. The gold mineralization is associated with the enrichment of As, Ag, Hg and Pb and depletion of Cu and Zn. The study of compositional variation of altered rocks proves to be a very efficient method for defining the extent of wall-rock alteration, fluid activity and mineralization and enrichment.

气体引射对临近空间升力体飞行器气动力热影响

针对临近空间高速飞行器的降热减阻需求,采用三维数值模拟手段研究了临近空间典型升力体飞行器气动力/热特性,分析了壁面气体质量引射对气动力/热特性的影响规律和作用机理。结果表明:壁面质量引射会略微增大激波脱体距离,对激波层和速度边界层有增厚作用,降低了边界层内的速度梯度,使得表面剪切力减小,从而具有较好的减阻效果。对于典型的升力体构型,在高度为60~70 km时,壁面质量引射减阻效率均不低于47.5%;在高度为80 km时,壁面质量引射减阻效率不低于10.2%;且壁面质量引射减阻效果随攻角增大而增强,随飞行高度升高而减弱。同时,壁面引射排出的低温气体对飞行器具有隔热保护作用,因此壁面质量引射能显著降低迎风面的热流,具有较好的降热效果。

内蒙古地区大体积混凝土挡墙施工温控分析

为降低多风干旱地区大体积混凝土挡墙早期开裂风险,确保其整体施工质量,以内蒙古某焦化厂煤堆取作业厂房混凝土挡墙为例,使用有限元方法,针对其有无布置冷水管,挡墙浇筑长度、高度和厚度进行参数化分析,得到混凝土浇筑后的温度场和应力场,并开展现场温度监测。结果表明:布置冷水管可以降低混凝土挡墙内部温度及里表温差;浇筑长度小于30 m时,收缩应力随浇筑长度增加而增大,大于30 m时,收缩应力无明显变化;浇筑高度超过4 m或墙体厚度超过1.5 m时,收缩应力值趋近于抗拉强度,开裂风险也随之增加;现场温度监测发现,冷水管作用下混凝土内部最大降温6.6℃,最大里表温差降低4.7℃。有限元模拟结果与实际监测结果相吻合。研究成果可为多风干旱地区的混凝土挡墙设计提供参考。

Non-Axisymmetric Mass Transfer Phenomenon behind an Orifice in a Curved Swirling Flow

The purpose of this paper is to understand the mechanism of non-axisymmetric wall-thinning that caused a pipe break in the pipeline of the Mihama nuclear power plant in 2004. The wall thinning was caused by the flow accelerated corrosion which affects low carbon steel pipelines. The mass transfer rate measurement of the wall thinning behind an office in a curved swirling flow is carried out in a closed-circuit water tunnel using a benzoic acid dissolution method. The experimental results indicate that the high mass transfer rate is observed on one side of the pipe behind the orifice, which is similar to the observation of the wall-thinning rate in the Mihama case. This result suggests that the influence of the secondary flow in the long elbow combined with the swirling flow can produce the non-axisymmetric mass transfer phenomenon behind the orifice.

地铁车站叠合墙内衬早龄期温度与应变演化规律

为探究叠合墙早龄期内衬温度与应变演化规律,依托地铁车站叠合墙工程开展早龄期内衬墙温度与应变现场监测,分析内衬墙的裂缝分布特征、温度与应变演化规律。结果表明:在早龄期,裂缝多从内衬墙的底部施工缝向上延伸,大部分裂缝为竖向裂缝,少量斜裂缝位于墙角;内衬墙的中部温度高于四周温度,而墙体中心的温度峰值与降温速率最大,表面温度峰值最小,并且墙体存在明显的里表温差;在早龄期,内衬墙存在明显的膨胀与收缩现象,并且不同方向上的应变演化规律存在明显的区别。

地铁车站大体积混凝土裂缝产生原因及解决措施分析

地铁建设近年来流行于各大中城市,地铁车站建设工程大体积混凝土施工比较普遍,在混凝土凝固过程中由于其体积收缩以及各种压力的作用,会造成大量的墙体裂缝;大面积的裂缝会导致建筑渗漏,给地铁车站带来了很大威胁。本文从荷载、位移、温度三个方面分析了地铁车站大体积混凝土结构的开裂成因;根据裂缝的大小、深度、成因等几个角度对裂缝进行了划分;从设计、材料、施工三个角度,对如何防止混凝土开裂进行了探讨。本文研究成果对保障地铁车站大体积混凝土施工质量有一定的参考意义。

南京仙新路长江大桥南锚碇基础施工关键技术

南京仙新路长江大桥为主跨1760 m的双塔地锚式悬索桥,南锚碇基础采用外径65 m、壁厚1.5 m的圆形地下连续墙结构,墙深60~63 m,且嵌入微风化砾岩3 m以上。为确保地下连续墙的成槽精度和质量,首先在地下连续墙施工前进行槽壁加固;然后分Ⅰ期槽和Ⅱ期槽施工地下连续墙,采用逆作法逐层开挖取土并逐层施工内衬,形成整体支护结构,直至开挖到设计标高;最后从基坑底部逐层往上浇筑底板、填芯和隔墙混凝土,完成锚碇施工。在南锚碇基础施工过程中,采用双轮铣深搅水泥土地下连续墙(SMC)工法进行槽壁加固,提高了深厚软土层条件下地下连续墙的成墙精度和防渗性能;通过对3种起重机进行比选,优化取土工艺,最终选择移动式抓斗起重机进行基坑取土,并搭建了“移动式抓斗起重机作业平台+装载车作业平台+卸土导向装置”的取土综合系统,提高了超深基坑的取土工效,保证了施工场地清洁环保;底板、填芯和隔墙大体积混凝土采用“塔式起重机+防离析导管+混凝土泵车”的施工技术,实现了深大基坑大体积混凝土的分层全过程快速浇筑。

石蜡@碳酸钙相变微胶囊在海藻纤维中的应用研究

使用石蜡作为相变的基础材料、碳酸钙为壁材,采用自组装法制备功能良好的相变微胶囊,后与海藻酸钠共混后经湿法纺丝制备具有调温功能的海藻纤维。文章通过对微胶囊制备过程中芯壁质量比、搅拌速率、乳化剂类型及配比等工艺参数优化设计,使用扫描电子显微镜、傅里叶红外光谱仪研究了微胶囊的表面形貌和结构,热重分析仪、差示扫描量热仪、红外热成像仪等分析了微胶囊和调温纤维的热性能。结果表明,当微胶囊芯壁质量比为1︰1、反应转速为1000 r/min、乳化剂为Span80+Tween80(1︰2)时,可得到粒径均匀、形貌良好、具有优异热性能的相变微胶囊;将其与4%的海藻酸钠、2%的PVA混合得到纺丝原液,经湿法纺丝可制备出良好调温功能的海藻纤维。

腹壁子宫内膜异位症一例

皮肤浅表包块是皮肤科门诊常见疾病,诊断需要超声协助,但有时超声作用有限,明确诊断主要通过组织病理活检。本文报道一例腹部包块的青年女性患者,超声提示低回声结节,CDFI可见少量血流信号,无明显提示意义。该包块位于剖宫产刀口附近,追问病史患者诉肿块大小与月经周期相关,遂转至产科诊疗,手术后病理结果提示为异位子宫腺体及间质,最终诊断为腹壁子宫内膜异位症。

氨基化-多壁碳纳米管QuEChERS-液相色谱-串联质谱法测定热带水果中110种农药及其代谢物残留量

建立基于氨基化-多壁碳纳米管(amino-functionalized multi-walled carbon nanotubes,NH2-MWCNTs)改进的QuEChERS净化方法,结合液相色谱-串联质谱(LC-MS/MS)测定3种热带水果中110种农药及其代谢物残留量。样品经乙腈提取,采用欧洲标准(EN.15662)萃取缓冲体系QuEChERS盐包提取,NH2-MWCNTs改良的分散固相萃取(d-SPE)净化管净化,多反应监测模式(MRM)分析,基质匹配标准曲线外标法定量。结果表明:在0.002~0.2 mg/L范围内110种农药及其代谢物具有良好的线性关系,决定系数(R2)均高于0.9902,定量限(LOQ)为0.005~0.05 mg/kg,添加回收率为61%~120%,相对标准偏差(RSD)为0.30%~15%(n=6)。该方法净化效果好,能在短时间内可靠地分析样品。灵敏度、正确度、精密度均满足日常检测定性、定量需求,适用于荔枝、龙眼和香蕉等热带水果中农药多残留的快速检测。

引江济淮船闸闸首施工期开裂风险与防裂分析

与混凝土坝相比,船闸闸首、泵站类薄壁大体积混凝土结构体型相对较小,但结构型式与受力复杂、约束明显且采用泵送高性能混凝土浇筑,早期混凝土放热量较常态混凝土大且发热快,施工期比大坝更易产生温度裂缝,其防裂设计成为施工质量控制的难点之一。结合在建的引江济淮枞阳船闸上闸首工程,采用三维有限元法仿真分析手段,模拟真实环境、材料、结构、温控措施的影响,分析结构施工期温度场、应力场以及开裂风险,并提出针对性的防裂措施。研究表明,输水廊道、墩墙、空箱及启闭机房周边大体积混凝土等功能性部位为高风险开裂部位,实现控温浇筑、通水冷却以及表面保温的多措并举且差异化控制,能够大大降低其开裂风险,可为引江济淮工程薄壁结构防裂设计提供参考。

高强防辐射大体积混凝土剪力墙施工技术探析

为保证高强防辐射剪力墙施工质量,文中以某质子辐照项目为例,提出了一种墙身不留孔洞、四道保证的模板支设方案及分组分层混凝土浇筑方案。结果表明,不切除拉螺杆、直接切割封堵两端,能够有效保证混凝土的防辐射性能;在混凝土浇筑中,四道保证体系的模板支撑方案中的材料刚度大、整体性好,可避免涨模,降低爆模风险;分组分层浇筑有效保证了混凝土的浇筑质量。

湿工况下带翼翅片管传热传质特性的数值研究

采用壁面反应原理建立冷凝传热模型,模拟研究平直翅片管、矩形翼翅片管以及弓形翼翅片管的通道内湿空气流动及传热传质特性。结果表明:当湿空气入口温度为328 K,水蒸气质量分数为11.2%时,矩形翼翅片管和弓形翼翅片管的传热因子相比于平直翅片管分别提高了24.9%—35.7%、26.7%—36.4%,传质因子分别提高了24.1%—35.4%、25.9%—38.3%,但矩形翼翅片管和弓形翼翅片管通道内工质的流动阻力系数分别增加了19.4%—25.3%、16.8%—22.9%,说明了矩形翼和弓形翼均可提高翅片管的传热传质特性,但也造成了阻力损失的增加。通过对综合传热性能评价因子的分析,矩形翼翅片管和弓形翼翅片管的综合传热性能评价因子值均>1,其综合传热性能均优于平直翅片管,且弓形翼翅片管综合传热性能最优。

深中通道西人工岛现浇隧道后浇筑墙体控裂技术研究及应用

深中通道西人工岛处于外海环境,岛上现浇隧道结构尺寸大,断面宽度及墙身高度呈渐变形式。施工过程中,为确保隧道主线临时通行需求,对敞开段隧道结构墙体进行部分预留,待交通转换后进行浇筑封闭。因其龄期间隔时间长,新老混凝土间易因收缩不同步造成结构开裂。为降低混凝土开裂风险,确保海工混凝土结构耐久性,对外海现浇隧道后浇筑墙体开展系统性控裂研究,通过采用有限元仿真模拟分析、研发智能温控系统、辅以温控硬件措施投入等综合控裂措施,实现后浇筑墙体控裂目标,有效避免了墙体有害裂缝的发生。

建筑外墙涂层的耐高温性能试验研究

为研究建筑外墙涂层的耐高温性能,文中对不同类型墙体涂层的耐高温腐蚀性能、高温老化性能、高温硬度以及隔热性能进行试验分析。结果表明,随着时间的增加,涂层试件的腐蚀质量呈现出不断增加的变化规律,涂层试件的背板温度表现为不断增加的变化规律;随着温度的增加,三种外墙涂层的硬度均表现为不断降低的变化规律。涂层具有良好的耐高温腐蚀性能、耐高温性能以及隔热性能。