Brittle Fracture of Rounded V-Notches in Isostatic Graphite under Static Multiaxial Loading

While a large bulk of experimental results from cracked specimens of polycrystalline graphite under pure modes of loading, in particular under mode I loading, can be found in the literature, only a very limited number of tests have been carried out on notches. At the best of the author knowledge dealing with the specific case of V-notches under mixed mode loading (tension + torsion) no results can be found in the literature. With the aim to fill this lack, the problem of mixed mode (I + III) brittle fracture of polycrystalline graphite is investigated systematically here for the first time. The present study considers cylindrical specimens weakened by circumferential notches characterized by different acuities. A new complete set of experimental data is provided considering different geometrical configurations by varying the notch opening angle and the notch tip radius. The multiaxial static tests have been performed considering different values of the mode mixity ratio (i.e. the ratio between the nominal stress due to tension and that due to torsion loading). A criterion based on the local strain energy density previously applied by the same authors only to pure modes of loading is extended here to the case of tension and torsion loadings applied in combination. The proposed criterion allows a sound assessment of the fracture loads.     

石墨管涂覆-塞曼效应原子吸收法测定生物样品中微量钡

以钨盐涂覆石墨管提高测定生物样品中钡的灵敏度，以基体改进剂提高分析精度，显著延长石墨管使用寿命，方法简便快速，得到了较好的回怍率和精密度。     

倾斜壁面中Kelvin-Helmholtz不稳定性演化数值分析

基于FTM（Front Tracking Method）对倾斜壁面下的二维不混溶、不可压缩流体的Kelvin-Helmholtz（K-H）不稳定性进行数值模拟.研究壁面倾角,速度梯度层厚度以及理查德森数对K-H不稳定性发展的影响.研究表明,壁面倾角越大,K-H不稳定性发展越快,卷起的液体越多;倾斜壁面下速度梯度层厚度的增加对界面卷起表现出抑制作用.理查德森数重力项越大,界面卷起越缓慢,而理查德森数表面张力项对界面卷起高度的影响较小.     

电感耦合等离子体-原子发射光谱法测定石墨中的钙

用电感耦合等离子体-原子发射光谱法测定了石墨中的微量钙,并对测试条件等进行了考察,结果表明,在所选择的最佳仪器条件下,方法的检出限(LD)为0.3866μg/g,测定下限(LOD)为1.93μg/g,精密度(RSD,n=10)为0.347％-3.913％.经美国国家标准方法(ASTMC 560-2005)分析验证,电感...     

石墨管涂覆-塞曼效应石墨炉原子吸收法测定土壤和沉积物中钡

样品使用硝酸-氢氟酸-高氯酸湿法消解,在0.015 mol·L-1硝酸介质中,采用自制涂钨石墨管,塞曼效应背景校正技术石墨炉原子吸收法测定了土壤和沉积物中的钡。经涂钨处理的石墨管表面形成了稳定的碳化钨层,有效避免了在原子化过程中待测元素钡与石墨管直接接触形成难熔碳化物,大幅度提高了检测的灵敏度和精密度,显著延长了石墨管使用寿命。碳化钨为间充型碳化物,在高温下可以产生较强的还原性氛围,可在一定程度上避免土壤和沉积物中常见的高浓度基体成分在原子化阶段生成难熔的氧化物而干扰钡的测定。氢氧化钙分子带背景干扰可以通过稀释法消除。该法测定土壤和沉积物中钡操作简便, 快速;检出限为4.2×10-10 g·g-1。环境样品中钡测定的相对标准偏差范围为2.0％～6.5％, 测定标准土壤的相对偏差均小于5％。     

High-Temperature Superconductivity of Graphite Particles Incorporated in Polystyrene

JETP Letters - The dependences of the magnetic moment in the graphite-polystyrene composite on the temperature and magnetic field have been studied. It has been shown that the magnetic field...     

基于MATLAB的二元线性回归在小孔流速实验中的应用

利用MATLAB软件对相关物理量进行二元线性回归拟合,求出了拟合曲线的待定参数和置信区间,拟合曲线与实验测试数据点符合较好。总结出小孔流速的经验公式,并对减少实验误差的途径进行了讨论。     

Fracture Assessment of Notched Bainitic Functionally Graded Steels under Mixed Mode (I + II) Loading

The averaged value of the strain-energy density over a well-defined volume is one of the powerful criteria to assess the static strength of U- and V-notched specimens. This contribution is the first to investigate the effect of notch parameters (notch radius, notch depth and notch opening angle) for fracture assessment of specimens weakened by blunt V-notches made of bainitic functionally graded steels under mixed mode loading (I + II). A numerical method has been used to evaluate the boundary of the control volume, the mean value of the strain-energy density and the critical fracture load. Different values of the notch radius (0.5, 1.0, 1.5 and 2.0 mm), notch depth (5.5, 6.0 and 6.5 mm), notch opening angle (30°, 60° and 90°) and distance of the applied load from the notch bisector line (5 and 10 mm) have been considered. Moreover, this contribution shows that the mean value of the strain-energy density over the control volume can also be accurately determined from a coarse mesh for functionally graded steels.     

Two-Stage Evaporation of Silver Samples in a Graphite Atomizer

A study has been made of the process of separation of silver from the excess in a sample of alkali-earth chlorides and sulfates by two-stage evaporation from the wall of a graphite atomizer and by fractional condensation on its integrated platform. It has been shown that after the condensation on the platform at room temperature the influence of the salts on the signal of atomic absorption is two times higher than that in ordinary one-stage evaporation. The reason for this is the formation of a cloud of condensed salt particles preventing the silver atoms from depositing on the platform. The atoms are deposited on these particles and are removed from the atomizer together with them before the stage of measurement of an analytical signal.     

预烧－碱熔－分光光度法测定中碳石墨中二氧化硅

本文研究了预烧－碱熔－光度法测定中碳石墨中二氧化硅的条件，确定了高温灼烧排除主体成份碳的时间，在草－硫混酸介质中，用硫酸亚铁铵还原硅钼黄，波长８１０ｎｍ处，二氧化硅含量在０．０１－０．３２ｍｇ／１００ｍＬ范围内呈良好线性，用于测定中碳石墨中二氧化硅含量，结果满意。     

原子吸收光谱分析中石墨炉的原子化效率

本文评述了原子吸收光谱分析中石墨炉原子化效率的研究进展，叙述了基础理论、各种原子化效率公式以及βm,βi(exp),βi(cal)间的关系，讨论了原子化效率研究中需要进一步改善的问题。     

Observation of Persistent Currents in Finely Dispersed Pyrolytic Graphite

The trapped magnetic flux in the finely ground pyrolytic graphite sample annealed at 670 K in air has been observed. Flux trapping occurs on cooling of the sample from room temperature to 10 K in a magnetic field of 1 T. The magnitude and sign of the induced trapped moment remain unchanged when the applied magnetic field is varied within ±1 T at T K. The trapped magnetic flux is manifested in the displacement of the magnetization curve relative to that of the sample cooled in zero field. Displacement magnitude gradually decreases with the temperature increase up to 350 K, not reaching zero. The set of experimental observations probably reflects the presence in the sample of a granular high-temperature superconducting phase.     

Synthesis of Nano-Crystalline Graphite Films in Hollow Cathode Discharge

The results of experiments on the production of nano-crystalline graphite films in the hollow cathode discharge on Ni(111)/sapphire substrate are presented. The characteristics of the discharge for different gases and pressures are given. The emission spectra of the plasma have been measured. The layers of the deposited graphite have been characterized by the methods of Raman scattering and atomic force microscopy. The field emission of nano-crystalline graphite was also measured. The produced layers have good homogeneity and high value of the electron field emission. The presence of vertically growing graphene is revealed.     

X射线荧光光谱法测定高纯石墨中的硫

采用X射线荧光光谱法测定出口高纯石墨中的硫，代替传统的化学分析方法。原样品粉末直接压片，标准样品采用国际焦炭样品和淀粉按比例混匀经研磨后压片，采用散射线背景校正法校正基体的影响，效果良好，简便易行。本方法的精与准确度均较好。     

斜向磁化的YIG波导中静磁波传播特性

分析了斜向静磁场作用下磁光薄膜波导中传播的静磁正向体波特性,计算了YIG薄膜波导中静磁波传播常数以及与磁光耦合系数相联系的动态磁化强度对静磁波模数、频率和斜向场等的依赖关系.计算表明：静磁波频率f及模数m越大、磁场H_i及其偏角θ越小,静磁波传播常数K_s越大;零模静磁体波的（动态磁化强度）振幅远大于高模数的静磁体波振幅.在适当的静磁体波频率范围内,斜向偏置磁场可提高静磁体波的振幅,进而可以改善静磁波与导波光的相互作用特性和提高导波光的衍射效率. 关键词：     

Experimental Investigation of Natural Convection in Inclined Channel in Presence of Electrostatic Field

The influence of external electrohydrodynamic forces on natural convection from a flat plate has been studied. Temperature distribution in the aforementioned channel at α = 45°, 90°, and 150° angles in different 10-, 12-, and 15-kV electrostatic fields has been reviewed. Corona wind and the shape of the created vortex by electrohydrodynamics were detected. The results showed that heat transfer was enhanced by increasing the electrostatic field in all angles. In the presence of the field, enhancement of heat transfer of the plate at acute angles is better than for obtuse ones. The optimal angle in terms of heat transfer was 45°, noting heat transfer improvement by 61%.     

石墨狭缝中甲烷吸附的分子动力学模拟

用分子动力学模拟研究石墨狭缝中甲烷的吸附,考察狭缝宽度和温度对甲烷吸附的影响.模拟发现甲烷在石墨狭缝中出现分层现象,吸附层中甲烷具有类液特征,第一吸附层内甲烷中总有两个氢原子的连线与另外两个氢原子的连线分别位于平行于狭缝壁的两个平面内,游离层中甲烷呈现气体的特征;碳原子间的平均作用势说明吸附层中甲烷分子间结合能力大于游离层,吸附态是甲烷在石墨狭缝中的主要赋存形式之一;伦敦力以及由吸附层净电荷产生的电场力是甲烷吸附和分层的主要原因;甲烷的吸附量随狭缝宽度增大或温度升高而减少,当狭缝宽度小于16.46Å时,甲烷仅以吸附形态存在.甲烷在第一吸附层中的扩散能力最弱、游离层中最强,甲烷扩散系数随狭缝宽度的增大或温度的升高而增大.     

石墨炉原子吸收光谱法测定鼠肝脏中的铅

采用2mg/mL磷酸二氢铵-1mg/mL硝酸镁作为混合基体改进剂,电热石墨炉原子化系统和氘灯扣背景校正的原子吸收光谱仪测定鼠肝脏中的痕量铅.结果表明铅在0-100ng/mL呈良好线性关系,r=0.9994,平均回收率为97.6%,RSD=2.6%,检出限为0.40ng/mL.方法操作简便,重现性好、灵敏度高且结果准确.