Experimental determination of grain density function of AZ91/SiC composite with different mass fractions of SiC and undercoolings using heterogeneous nucleation model

The grain density,Nv,in the solid state after solidification of AZ91/SiC composite is a function of maximum undercooling,ΔT,of a liquid alloy.This type of function depends on the characteristics of heterogeneous nucleation sites and number of SiC present in the alloy.The aim of this paper was selection of parameters for the model describing the relationship between the grain density of primary phase and undercooling.This model in connection with model of crystallisation,which is based on chemical elements diffusion and grain interface kinetics,can be used to predict casting quality and its microstructure.Nucleation models have parameters,which exact values are usually not known and sometimes even their physical meaning is under discussion.Those parameters can be obtained after mathematical analysis of the experimental data.The composites with 0,1,2,3 and 4wt.% of SiC particles were prepared.The AZ91 alloy was a matrix of the composite reinforcement SiC particles.This composite was cast to prepare four different thickness plates.They were taken from the region near to the thermocouple,to analyze the undercooling for different composites and thickness plates and its influence on the grain size.The microstructure and thermal analysis gave set of values that connect mass fraction of SiC particles,and undercooling with grain size.These values were used to approximate nucleation model adjustment parameters.Obtained model can be very useful in modelling composites microstructure.

Planar System-Masses in an Equilateral Triangle:Numerical Study within Fractional Calculus

In this work,a system of three masses on the vertices of equilateral triangle is investigated.This system is known in the literature as a planar system.We first give a description to the system by constructing its classical Lagrangian.Secondly,the classical Euler-Lagrange equations(i.e.,the classical equations of motion)are derived.Thirdly,we fractionalize the classical Lagrangian of the system,and as a result,we obtain the fractional Euler-Lagrange equations.As the final step,we give the numerical simulations of the fractional model,a new model which is based on Caputo fractional derivative.

An Unsteady Oscillatory Flow of Generalized Casson Fluid with Heat and Mass Transfer:A Comparative Fractional Model

It is of high interest to study laminar flow with mass and heat transfer phenomena that occur in a viscoelastic fluid taken over a vertical plate due to its importance in many technological processes and its increased industrial applications.Because of its wide range of applications,this study aims at evaluating the solutions corresponding to Casson fluids’oscillating flow using fractional-derivatives.As it has a combined mass-heat transfer effect,we considered the fluid flow upon an oscillatory infinite vertical-plate.Furthermore,we used two new fractional approaches of fractional derivatives,named AB(Atangana–Baleanu)and CF(Caputo–Fabrizio),on dimensionless governing equations and then we compared their results.The Laplace transformation technique is used to get the most accurate solutions of oscillating motion of any generalized Casson fluid because of the Cosine oscillation passed over the infinite vertical-plate.We obtained and analyzed the distribution of concentration,expressions for the velocity-field and the temperature graphically,using various parameters of interest.We also analyzed the Nusselt number and the skin friction due to their important engineering usage.

Influence of Isothermal Treatment on Superelastic Behavior of Cu-13.8Al-4.0Ni(mass fraction) Single Crystals

The superelastic behaviors of different isothermal treated Cu-13.SAl-4.ONi (mass fraction) single crystals were studied by applying tensile stress along <001> of the d phase. The different isothermal specimens have different superelastic behavior due to the change of the ratio of stress-induced r1 and β1. The superelasticity of r1 phase tends to that of g; phase with cycling. Typical stabilization of stress-induced martensite above Ap results in residual deformation. Due to the reverse transformation of 7I, there is a deviation of pseudo-yield stress from linear relation with temperature at relatively low stress.

Peptidome profiling of human serum of uveal melanoma patients based on magnetic bead fractionation and mass spectrometry

AIM： To find new biomarkers for uveal melanoma （UM） by analyzing the serum peptidome profile. METHODS： Proteomic spectra in patients with UM before and after operation were analyzed and compared with those of healthy controls. Magnetic affinity beads were used to capture serum peptides and matrix-assisted laser desorption/ionization time-of-flight （MALDI-TOF） mass spectrometer were used to compile serum peptide profiles. RESULTS： A panel of 49 peptides were differentially expressed between UM patients and controls, of which 33 peptides were of higher intensities in patient group and 16 peptides were of higher intensities in control group. Based on combined use of these potential markers, peptides with mean molecular masses of 1467 and 9289.0 Da provide high sensitivity （83.3%）, specificity （100%） and accuracy rate （93.0%） together to differentiate melanoma patients from healthy controls. At the time point of 6mo postoperatively, the levels of many peptides differentially expressed before surgery showed no more statistical difference between the patients and the control group. Fibrinogen o-chain precursors were identified as potential UM markers. CONCLUSION： We have shown that a convenient and fast proteomic technique, affinity bead separation and MALDI- TOF analysis combined with bioinformatic software, facilitates the identification of novel biomarkers for UM.

Synthesis of biodegradable Mg-Zn alloy by mechanical alloying: Statistical prediction of elastic modulus and mass loss using fractional factorial design

Biodegradable Mg-Zn alloy was synthesized using mechanical alloying where a statistical model was developed using fractional factorial design to predict elastic modulus and mass loss of the bulk alloy.The effects of mechanical alloying parameters(i.e.,milling time,milling speed,ball-to-powder mass ratio and Zn content)and their interactions were investigated involving 4 numerical factors with 2 replicates,thus 16 runs of two-level fractional factorial design.Results of analysis of variance(ANOVA),regression analysis and R2 test indicated good accuracy of the model.The statistical model determined that the elastic modulus of biodegradable Mg-Zn alloy was between 40.18 and 47.88 GPa,which was improved and resembled that of natural bone(30-57 GPa).Corrosion resistance(mass loss of pure Mg,33.74 mg)was enhanced with addition of 3%-10%Zn(between 9.32 and 15.38 mg).The most significant independent variable was Zn content,and only the interaction of milling time and ball-to-powder mass ratio was significant as P-value was less than 0.05.Interestingly,mechanical properties(represented by elastic modulus)and corrosion resistance(represented by mass loss)of biodegradable Mg-Zn alloy can be statistically predicted according to the developed models.

Determination of Atomic Fractions of Isotopes Carbon-13 and Nitrogen-15 Directly in Glicine, L-Leucine, Isoleucine and Alanine

Using compounds modified by the isotopes carbon-13 and nitrogen-15 helps conduct research in various fields of science, such as medicine, pharmacology, pharmacokinetics, metabolism, agriculture, and others. In the case of the availability of reliable, express, and cheap methods, the area of their use will gradually expand. A determination of the atomic fraction of the isotopes carbon-13 and nitrogen-15 directly in glycine, leucine, isoleucine, and alanine is proposed;the modification concerns all centers or one or more identical carbon and nitrogen centers separately, as well as both isotopes at the same time. There are defined mass lines of the mass spectrum of each amino acid, through which the isotopic content of carbon and nitrogen is calculated. The processes that must be taken into account for the determination of the isotopic content are also established. Isotopic analysis of these compounds until now was carried out by transforming them into carbon oxide, dioxide, and molecular nitrogen, and determination of their content in individual centers was impossible.

沙粒质量分数对油气混输泵过流部件磨损的影响

为研究沙粒质量分数对油气混输泵过流部件磨损的影响规律,基于DPM模型对油气混输泵内部的沙粒运动进行数值计算,并采用Finnie磨蚀模型计算油气混输泵过流部件的磨蚀率.研究结果表明:在沙粒质量分数较小时,沙粒与流体介质混合均匀;随着沙粒质量分数的增大,增压单元内的沙粒局部质量浓度显著增大,沙粒集中在叶轮压力面及导叶流道中部;沙粒质量分数增大会使磨损区域和磨损率急剧增大;在叶轮域中,磨损首先发生在压力面出口处,吸力面则在进口外缘发生点状和条状磨损;在导叶域中,压力面的磨损主要发生在外缘处,吸力面的磨损主要发生在进口轮毂处;从定量分析看,叶轮叶片表面的磨蚀率普遍大于导叶叶片表面的磨蚀率,磨损最严重的位置为叶轮叶片进口靠近轮毂处.研究结果可为改善油气混输泵抗磨损性能以及提高油气混输泵实际运行寿命提供一定参考依据.

不同淹没水深下菹草对强辐射的响应

春末夏初菹草大批衰亡的原因一直是水体生态修复关注重点,强辐射被认为是最为重要的因素。为研究不同淹没水深下菹草对强辐射的抵御能力,通过模拟强辐射方式,用透明渔网将植株压迫至水下相应位置(10、20、30 cm),分别测定菹草形态、叶绿素质量分数及叶绿素荧光参数等变化,并与对照组(未压迫)比较。结果表明,压迫至水下20 cm处的植株在株高、叶面积、鲜物质量,以及叶绿素质量分数等指标均高于其他深度处理组,对照组各项指标最低;水下20 cm组PSⅡ中心活性最强,受强辐射中UV-B伤害最小,而对照组及水下10 cm处理组,受UV-B辐射后,其PSⅡ反应中心遭到破坏或可逆性失活,光能转换效率、光能传递能率以及电子传递速率下降;水下30 cm处理组,虽PSⅡ反应中心未遭到伤害,因光合有效辐射衰减,植株生长各项指标不及20 cm组。辐射对所有监测指标均有极显著影响,大部分指标同时受水深因素影响;株高、节间距、叶绿素质量分数及Fv/Fm、ϕPSⅡ、qP还受两者交互影响。该试验中,水下20 cm既可抵御有害辐射,光合有效辐射也能满足植株生长。因此,利用水体自身屏蔽作用,通过压迫方式可有效削减强辐射中有害辐射对菹草的伤害,是一种简单易行的方式,在自然水体中可参考UV-B生物有效光学深度来确定压迫深度。

酸分馏效应对GasBench-IRMS测定碳酸盐碳、氧同位素的影响

本文利用在线制样装置(GasBench)和稳定同位素比质谱仪(IRMS)测试一系列碳酸盐标准物质和现代海洋浮游有孔虫样品,在不同测试条件下,分析不同性状碳酸盐矿物的氧同位素分馏程度,计算氧同位素酸分馏系数,探讨酸分馏效应对不同碳酸盐矿物氧同位素测定的影响机制和控制因素,以及对氧同位素测试值(δ^(18)O_(m))的校正方法。结果表明,酸分馏效应对氧同位素值的影响主要是由于生成的CO_(2)气体与顶空瓶中气态水(高温时主要影响)或酸中游离态自由水(低温时主要影响)之间发生氧同位素交换引起的。不同性状碳酸盐标准物质的氧同位素酸分馏系数具有显著差异,且与氧同位素组成相关。δ^(18)O_(m)值发生偏移的程度与反应温度、样品量、磷酸含水量以及酸中游离态和气态水的氧同位素组成与样品氧同位素组成之间的差异等因素有关。氧同位素酸分馏效应与信号强度具有显著相关性。建议精确称量相同质量的标准物质和样品,遵循信号强度匹配的原则,并采用多种标准物质线性校正的方法有效校正氧同位素分馏现象。在较低的反应温度(25℃)下,氧同位素分馏程度较轻微,δ^(18)O分析精度更高,优于0.05‰。本方法为精确测定碳酸盐中碳、氧同位素组成提供了参考,可有效提高相关的测试精度。

液相色谱法测定纺织品中甾醇含量

通过确定植物甾醇3种主要成分(β-谷甾醇、菜油甾醇、豆甾醇)标准品的液相色谱分析条件,以特征保留时间确定各类甾醇相应的液相色谱指纹图谱。建立了纺织品中甾醇含量的测定方法:以相同液相色谱分析条件对纺织样品提取液进样分析,以各类甾醇标准品指纹图谱为基础,并以外标法求得纺织品中不同类别甾醇含量,最终获得纺织品中甾醇总的含量(质量分数)。测定方法精密度和回收率均满足相关标准要求,可用于纺织品中甾醇含量的检测。

贺兰山东、西坡群落植物叶N、P化学计量沿海拔梯度的格局及群落构建机制

为了研究贺兰山不同气候类型群落植物叶N、P化学计量沿海拔梯度的格局及群落构建机制,以贺兰山东、西坡沿不同海拔梯度的群落植物为研究对象,分析群落植物叶片N、P质量分数的加权平均值与海拔的关系,并通过构建零模型,探究沿海拔梯度贺兰山东、西坡植物群落构建机制。结果表明:贺兰山东坡植物叶片N质量分数和N、P质量分数比的群落加权平均值随着海拔的升高,呈现先增加后降低的趋势,并在海拔1600~2000 m处最高;东、西坡叶片P质量分数均随海拔升高逐渐增加。贺兰山东坡群落叶片N质量分数在中海拔(2000 m左右)处发散,在中高海拔(2600 m左右)处收敛;叶片P质量分数在中高海拔(2600 m左右)处最收敛,叶片N、P质量分数比在中低海拔(1700 m左右)处最发散。而贺兰山西坡植物叶片N质量分数在中高海拔(2600 m左右)处最发散,叶片P质量分数在中高海拔(2700 m左右)处最发散。环境因子不是贺兰山东坡群落构建的主要驱动因素,而是贺兰山西坡群落构建的主要驱动因素,其中,土壤N、P质量分数显著影响叶片N、P化学性状的群落加权方差。

再生细骨料残余浆体对混凝土流变性和强度的影响

文章开展再生细骨料残余浆体的定量表征实验、混凝土常规工作性能试验、流变性能试验和力学性能试验,研究不同残余浆体质量分数对再生细骨料混凝土流变性能和力学性能的影响。研究发现,再生骨料表面残余浆体的去除可以明显改善其基本性能,再生细骨料的使用会使新拌混凝土的坍落度和扩展度损失加快,屈服应力增大,塑性黏度降低。随着再生细骨料残余浆体质量分数的减少,用其制备出的再生混凝土的抗压强度和劈裂抗拉随之增大。当浆体质量分数为14.9%时,骨料水泥界面过渡区粘结紧密,再生细骨料混凝土的28 d抗压强度和劈裂抗拉强度分别为28.50、2.30 MPa,约为普通混凝土的89%、77%,表明较低残余浆体质量分数的再生细骨料可取代天然砂应用于混凝土中。

基于经典光学的透明溶液质量分数自动化测量

基于经典的折射和色散理论,设计了可使光路发生平移的棱柱形容器,并以此为基础搭建了自动化实时测量质量分数的装置.采用位移传感器替代传统的观察屏提高了光点位移测量的精确度,结合数据采集卡与LabVIEW软件实现了数据测量和处理的动态化、自动化和智能化.基于经典光学理论建立折射率-质量分数关系,实现多种透明溶液质量分数及混合溶液中各组分质量分数的实时测量.该装置可实现单一、混合以及流动透明溶液质量分数的实时自动化监测,实验结果均与理论符合良好.

稀土稳定同位素分析方法及在风化壳淋积型稀土矿研究中的应用展望

稀土元素因其特殊的化学性质和在地球科学研究中的重要价值而受到广泛关注。随着化学纯化方法的发展和质谱测定技术的提高,国内外对稀土稳定同位素体系开展了一系列探索。近年来,逐渐发展起来的稳定Ce和Nd同位素分析方法,为表生地质过程、氧化还原环境示踪以及生态环境演变等方面的研究提供了新的手段,也将为研究稀土矿提供直接证据。本文先系统介绍了稀土元素及其同位素体系的地球化学特征,总结稀土稳定同位素分析方法的发展历程与研究现状,并对其未来可能突破的方向进行评述。在此基础上,对稀土稳定同位素在风化壳淋积型稀土矿床研究中的应用前景进行了展望,指出稀土稳定同位素地球化学手段是深入了解风化壳淋积型稀土矿床形成过程与控矿机制的良好指标,其与稀土元素地球化学指标相结合有望在稀土矿化过程与机制方面取得新的认识。

N含量对S32750双相不锈钢中二次奥氏体析出行为的影响

随着行业对双相不锈钢品质及性能要求的提升,二次奥氏体已经成为影响S32750双相不锈钢应用的关键因素之一。二次奥氏体是“温度-冷却速率”共同作用的一种亚稳态产物,与铁素体相呈近K-S或N-W位向关系,且对N有富集作用,可按形貌将其分为针状二次奥氏体和孤岛状二次奥氏体。研究了N含量对二次奥氏体析出行为的影响。通过制备w[N]为0.02%、0.09%和0.17%的试验钢,并借助热模拟及EBSD检测可知,随着N含量增加,二次奥氏体由弯曲羽毛状向板条形针状转变,且奥氏体相的整体比例增加。经计算可知,奥氏体相的析出方式与本征吉布斯自由能相关,即受到成分与试验温度的影响。

具有板式基底结构的界面蒸发系统性能模拟

针对具有板式基底结构的太阳能界面蒸发系统建立三维数学模型,利用Ansys Fluent软件求解该系统的蒸发过程,研究板缝宽度及料液质量分数对界面蒸发过程的影响.结果表明:蒸发速率随板缝宽度和料液质量分数的增大而减小;当基底输水量小于蒸发需求时,蒸发界面出现干涸现象,干涸现象出现后蒸发速率显著降低;当板缝宽度为0.5 mm时,与最大蒸发速率对应的料液质量分数为3.5%~5.0%;当料液质量分数为3.5%时,与最大蒸发速率对应的板缝宽度为0.5~0.6 mm;系统能量利用率变化规律与蒸发速率基本一致.蒸发过程中蒸发量与料液供给量的匹配是影响板式基底结构的太阳能界面蒸发系统性能的重要因素.

垢对蜡沉积物强度及聚乙烯管道清管特性的影响

油井采出原油中含有泥沙、垢等颗粒物,在管输过程中颗粒物与原油中的蜡分子协同沉积,导致管道输量降低,严重时可能造成管道堵塞,影响原油管道安全输送。对掺垢蜡沉积物进行了屈服应力测试实验和显微特性实验;对室内聚乙烯管道进行了清管实验;基于清管实验结果,利用π定理建立了清管效率预测模型。结果表明,碳酸钙垢对蜡沉积物强度的影响存在临界垢质量分数;沉积物中含垢,会提高清管器的蜡层破坏力和清管效率;通过室内实验和第三方文献实验数据,验证了所建立的模型。

渗透剂对含瓦斯煤体置换效应实验研究

为研究渗透剂对含瓦斯煤体置换效应的变化规律,自主研制了一套高压吸附状态下解吸测试装置。选用聚乙二醇-4000和吐温-80两种非离子试剂,十二烷基苯磺酸钠和十二烷基硫酸钠两种阴离子试剂,及前者非离子与阴离子的混合试剂作为渗透剂。研究瓦斯煤体置换的全过程,分析渗透剂对瓦斯的置换量的影响,并在此基础上研究置换增幅规律。结果表明,在质量分数某一范围内,渗透剂的质量分数越高,置换瓦斯量随之增多。混合溶液的置换瓦斯能力强于阴离子溶液,阴离子溶液强于非离子溶液。

合成氨装置低温甲醇洗系统贫甲醇含水量升高的原因分析及对策

针对中国石油吉林石化公司30万t/a合成氨装置在新增合成气净化系统的工艺改造后,低温甲醇洗系统贫甲醇含水量(质量分数,下同)异常升高(高达2.6%)并超过设计指标值(1.5%),不得不降负荷运行的情况,排查了相关影响因素,分析了导致甲醇/水分离塔塔板筛孔堵塞的原因,并实施了相应的工艺优化措施。结果表明:工艺优化措施实施后,大幅改善了甲醇/水分离塔的分离效果,不仅使该装置低温甲醇洗系统负荷率由82%提升至100%,还使贫甲醇含水量降低至0.4%。