Separation of non-newtonian liquids by thermal diffusion

A transport equation has been derived for a mixture of non-Newtonian liquids showing power-law flow; the optimum separation conditions in a thermal-diffusion column in the presence of parasitic convection have been defined.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 36, No. 5, pp. 835–840, May, 1979.     

Measurement of ionic diffusion in lithium fluoride by nuclear magnetic resonance techniques

Rates of diffusion of ⁷Li and ¹⁹F were investigated in doped crystals of lithium fluoride using the technique of motional narrowing of nuclear magnetic resonance lines. Major doping elements were divalent Mg and Mn ions, present in amounts between 3 and 240 × 10^–6 cation site fraction. Extrinsic vacancies introduced by this doping increased Li ion diffusion and caused ⁷Li motional narrowing to begin at lower temperatures for greater impurity contents.Diffusivities were determined from the motional narrowing curves using a method of analysis which reduces uncertainties due to magnetic field inhomogeneity and other temperature independent contributions to line broadening. Resulting log D vs 1/T plots showed the expected intrinsic, free vacancy extrinsic, and divalent ion-vacancy association regions of Li ion diffusivity. Activation energies determined for these regions were 1.87±0.09, 0.66±0.03, and 0.91±0.05 eV, respectively. These values yielded the energy for motion of a cation vacancy as 0.66 eV and the energy of formation of a Schottky defect as 2.42 eV.Experimental results obtained earlier in powdered LiF: Mn samples are clarified, and indications concerning the effects of other impurities on Li ion diffusion are presented and discussed.     

Separation of fluoride from aqueous solution by electrodialysis: effect of process parameters and other ionic species

Removal of fluoride from aqueous solution by electrodialysis was studied. Applied voltage, feed flow rate, fluoride concentration in the solution and effect of the other anions as sulfate, chloride were investigated as experimental parameters on fluoride removal from aqueous solution. The separation performance was evaluated in terms of mass transfer and energy consumption. It was obtained that the separation performance increased when the initial concentration of fluoride in the feed solution increased. Percent removal of fluoride increased as the applied potential increased. However, the effect of feed flow rate was not apparent in the range of applied feed flow rate. Separation of fluoride was influenced by chloride but not by sulfate ions.     

Radiation damage test of barium fluoride scintillator

Small samples of BaF₂ scintillator have been irradiated in a high-energy proton beam with doses of up to 1.3 × 10⁷ rad. To the precision of our measurement there was no effect in the scintillation output and only a slight decrease in transmission was observed.     

Generalization of test data on resistance in tubes with ribbon swirlers

On the basis of identity of the mechanism of fluid motion in tubes with ribbon swirlers and in coils, criterial equations have been obtained for determining the resistance coefficient in a swirled flow in the laminar regime with macro-eddies and in the turbulent regime.     

Adsorption of fluoride from water by aligned carbon nanotubes

Aligned carbon nanotubes (ACNTs), a new type of carbon material, were prepared by catalytic decomposition of xylene using ferrocene as catalyst. The kinetics experiment of ACNTs shows that fluoride adsorption rate is fast in the first 60 min and the adsorption capacity reaches 3.0 mg/g rapidly, then it decreases and adsorption achieves equilibrium gradually in about 180 min. The fluoride adsorption of ACNTs depends slightly on the solution pH value. The highest adsorption capacity of ACNTs occurs at pH 7 and reaches 4.5 mg/g at equilibrium fluoride concentration of 15 mg/l. The experimental results indicate that ACNTs are promising candidate materials for fluoride removal.     

Thermoelastic stresses in tubes produced from a melt by Stepanov's method

Temperature fields and their corresponding thermoelastic stresses in tubes in the process of their growth from a melt by Stepanov's method are calculated. Results of the calculations are presented in the form of surfaces constructed above a longitudinal section of a tube. The behavior of the maximal stresses as a function of the tube length, the middle radius, and the wall thickness is investigated. The influence of the screen on the stress distribution is also taken into account.Notation T temperature - T _m ⁰ melting temperature - k_s thermal conductivity coefficient - _t thermal expansion coefficient - c_ps heat capacity - h_s heat-transfer coefficient - E Young's modulus - Poisson coefficient - V₀ growth rate - ₁, ₂ temperatures of the external medium - _m normal meridian stress - normal hoop stress - u, axial and radial travels of the middle surface - R₁, R₂ inner and outer radii of the tube - density Institute of Physics of Solids of the Russian Academy of Sciences, Chernogolovka. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 64, No. 4, pp. 469–476, April, 1993.     

Synthesis of ultrathin rhenium disulfide nanoribbons using nano test tubes

The synthesis of ultrathin rhenium disulfide(ReS₂)nanoribbons within single-walled carbon nanotubes(SWNTs)has been established.Dirhenium decacarbonyl complex is encapsulated into the SWNTs to provide a source of confined rhenium atoms,which readily react with iodine to form discrete nm-sized clusters of rhenium iodide[Re₆l₁₄]^2- embedded in the nanotubes.The final step of the synthesis is accomplished by admitting hydrogen sulfide gas into nano test tubes,yielding twisted nanoribbons of rhenium disulfide encapsulated in carbon nanotubes,ReS₂@SWNTs.The width,structure,and composition of rhenium disulfide nanoribbons are strictly controlled by the extreme confinement of the host-SWNT.A holistic analytical approach combining complementary imaging and analysis methods is used at each synthetic step to elucidate the structure and composition of the guest material and reveal the role of the SWNT contributing towards the electronic interactions with encapsulated inorganic structures.As ReS₂ nanoribbons are expected to retain the electronic properties of the bulk material,such as direct bandgap,the low dimensional form of this material can be of interest for use in nanoscale electronic devices.     

纳滤技术分离谷氨酸和盐混合液的研究

考察了五种纳滤膜在高盐浓度下对溶液的脱盐性能,选择NF270进一步考察了pH值、氯化钠浓度、膜通量、搅拌速度对纳滤膜分离性能的影响.实验结果表明,虽然高盐浓度对膜表面的电荷屏蔽作用严重,但随着pH值的增加,NF270对谷氨酸的截留率增加,膜的分离选择性也同时增加,而跨膜压力随着pH值的增加而减小.在选择合适的膜通量和搅拌速度时,NF270对谷氨酸的截留率达到95.0%,膜的分离选择性达到18.8,可以实现高盐浓度下谷氨酸溶液的脱盐.     

炭膜处理染料水溶液的研究

对多孔炭膜处理染料水溶液进行研究，结果发现，炭膜对染料与水有很好的分离效果，对所考究的几各染料，其截留率为９５－９９％，水的渗透速度介于６５－２００Ｌ（ｍ＾２．ｈ．ＭＰａ）之间。     

试验参数对不锈钢包壳管环向拉伸的影响

包壳管是反应堆内重要的安全屏障,其在服役环境下承受一定裂变气体内压,同时面临芯块和包壳间机械相互作用的考验.开展包壳管环向拉伸性能研究,对反应堆燃料组件设计和安全分析具有重要意义.奥氏体不锈钢是快中子反应堆包壳管重要候选材料,具有良好的高温力学性能.本文针对奥氏体不锈钢包壳管高温环向拉伸试验,研究了夹具、标距段宽度和润滑条件等试验参数对包壳管环向拉伸试验的影响.结果表明:三嵌块夹具可以避免试样标距段向内展平,且夹具和试样间摩擦力较小;标距段的宽度对包壳管环向拉伸强度影响不大,但是标距段宽度过大或者过小都会造成试样延伸率下降;夹具与试样间隙的摩擦会增加拉伸载荷,降低延伸率,使用石墨润滑可以有效减小摩擦力的影响.     

Theoretical assessment of the steady state diffusion cell test

The steady state diffusion cell test is often used to determine the chloride ion diffusion coefficient in cementitious materials. It involves the measurement of the flux of chloride ions through a specimen under near steady state conditions. It has been noted that such a test may also provide data which characterises the chloride binding capacity of the specimen. In this work a numerical model of chloride diffusion subject to the effects of chloride binding is used to assess the effect of deviations from the steady state on the data obtained from a diffusion cell test. It is noted that there will be a tendency to underestimate the diffusion coefficient, although good practice should limit this error. The predicted error in the chloride binding isotherm is smaller than that in the diffusion coefficient. Furthermore, the influence of errors in the effective porosity on model predictions is limited as the resulting effect on the values of the calculated parameters describing chloride diffusion and binding counteract each other.     

Automatic test of photomultiplier tubes for the ZEUS forward and rear calorimeters

Prior to use in the ZEUS calorimeter, we measured the performance of 4800 photomultiplier tubes of the R580-12 type. The measurements were carried out under computer control using an automatic test system in which 80 tubes were tested simultaneously. The tests were made regarding the dark current, gain, linearity, long-term stability and gain stability under different intensities of dc background light. The results were used to both select and classify the tubes. Almost all of the tubes were found to be satisfactory.     

Experimental research on the performance of the diffusion absorption refrigerator with mixed fluoride refrigerants

A diffusion absorption refrigerator (DAR) operating with mixed fluoride refrigerants was built to obtain low refrigerating temperature at low generating temperature. Two groups of mixed fluoride refrigerants, R23/R134a and R23/R32/R134a, were tested experimentally. The N,N-dimethylformamide (DMF) and helium were used as the absorbent and inert gas, respectively. For the DAR with R23/R134a, the refrigerating temperature was not obviously influenced by the concentration of R23 in the mixed refrigerant vapor or the amounts of helium. For the DAR with R23/R32/R134a, an optimal concentration of R32 in the mixed refrigerant vapor and an optimal pressure were both found to achieve the lowest refrigerating temperature which was −28.8 °C at a generating temperature of 106.9 °C, and a refrigerating temperature of −23.7 °C was obtained at an extraordinarily low generating temperature of 83.3 °C. It showed the promising potentials of DAR operating with mixed fluoride refrigerants in applications of low temperature refrigeration and efficient utilization of the low-grade thermal energy.