液滴尺寸与滴定管质量

接近滴定终点时,滴定剂要以"单滴"为单位缓慢加入被测溶液,这说明了滴定分析时"滴"的重要性。但是,现有主要教科书还没有讨论单一液滴体积对滴定管质量及对滴定分析的影响。文章讨论了液滴体积与滴定管质量、滴定准确度、指示剂变色敏锐程度等的关系,对深入理解"滴"在滴定分析中的重要性有启示作用。     

Mathematical simulation of the ejection of a gas suspension from a shock-tube channel under the action of a compressed gas

Results are presented of a numerical calculation of an unsteady two-dimensional axisymmetric wave flow of an inert monodispersed gas suspension from the channel of a shock tube into the surrounding gaseous space under the action of a gas compressed in a high-pressure chamber. The acceleration of dispersed particles inside the tube and in the submerged space behind the diffracting air shock-wave front is analyzed. The effect of the formation of a vortex dispersed ring during dispersion of a particle cloud is discussed. The influence of the governing parameters of the ejected gas suspension layer and the driving gas on the distance of dispersion of a dispersed particle cloud is investigated. Translated fromFizika Goreniya i Vzryva,. Vol. 34, No. 3, pp. 107–116, May–June 1998.     

Effect of a change in the temperature of the drying agent on the heat treatment of a material

The process of heat and substance transfer between phases in drying a material is considered and ways to in tensify the internal transfer are indicated. The nature of the dependence of the temperature of the drying agent and the moist material at various points chosen for calculation on the technological parameters of the process is discussed. The method gives the effect of the independent variables of the process on the temperature of the used-up drying agent and the moisture content of the moist material. A control system that allows for a change in the energy stored by the lining of the furnace and the gas duct for automatic optimum adjustment of the regulator of the temperature of the drying agent is described.     

Investigation of the dependence of the infrared absorptivity of a functional moiety on the molecular weight of a homopolymer

The subject of this investigation was the determination of the effect of molecular weight (MW) on the infrared absorptivity of a functional moiety in polystyrene homopolymer. It was found that no consistent dependence of infrared absorptivity on MW was found for two sharp absorptions of polystyrene across the MW range from 600 to 2 × 10⁶. It was shown that end group effects for the very-low-molecular-weight polymer fraction may be subtle and should be accounted for when using homopolymer calibration standrads in the study of the dependence of copolymer composition on MW.     

Electrophoresis of a spheroid along the axis of a cylindrical pore

The boundary effect in electrophoresis can play an important role in applications of practical significance; typical example includes the electrophoresis in a narrow space and that of a concentrated dispersion. This effect is investigated by analyzing the electrophoresis of a spheroid along the axis of an infinite non-conducting cylinder in this study for the case of low surface potential. In particular, the effects of particle aspect ratio, the ratio (linear size of particle/radius of pore), double layer thickness, and the charged conditions on particle surface on the electrophoretic behavior of a particle are discussed. Several interesting results are observed. For example, if the volume of a particle is fixed, its electrophoretic mobility has a local maximum as its aspect ratio varies. Also, if wall effect is important, the relative magnitudes of the electrophoretic mobility of a particle follow the order prolate < sphere < oblate, and the reverse is true if it is unimportant.     

Analysis of the Equations for the Flow of a Liquid Filtering through a Granular Medium

The Goldshtik equations for the flow of a liquid filtering through a granular medium are considered. It is shown that the additional nonlinear terms in these equations are insignificant in comparison with the flow resistance in pores. The flow patterns are estimated. Formulas for the filtration velocity are obtained.__________Translated from Teoreticheskie Osnovy Khimicheskoi Tekhnologii, Vol. 39, No. 4, 2005, pp. 373–378.Original Russian Text Copyright © 2005 by Shilyaev, Bogomolov.     

Approximate solutions for the ignition of a solid as a function of the Biot number

The ignition of a finite planar 1‐dimensional solid is addressed for constant applied radiant heat flux. An ignition temperature criterion is used, with constant properties, and linearized reradiation. An approximate integral analysis leads to analytic formulas to predict the ignition time in terms of Biot (Bi) number and heat flux. The accuracy of the integral solution is found to be good compared to the exact infinite series solution for the conduction equation. The integral model is then used to assess the accuracy of common ideal thick and thin formulas for ignition. There is a domain of heat flux and Bi where the ideal formulas are not accurate. An example is given where the integral model is accurately applied to ignition data to illustrate the range where the ideal formula is not accurate.     

Method for the intermittent optimization of the working of a block by a rotary excavator

Conclusions A method of periodically optimizing the treatment process of an excavated block, by a rotary excavator at the refractory raw materials quarries of the Ukraine, has been developed. The method can also be applied to other open-cast quarries after taking into account the design and uncontrollable production parameters and the range of controllable parameters at the particular quarry.Translated from Ogneupory, No. 4, pp. 29–33, April, 1982.     

Effect of the Density of a Microspherical Catalyst on the Operating Regimes of a Fluidized Bed

An experimental study is performed of a circulating fluidized bed of two types of finely dispersed Geldart A particles with different bulk densities. The first type of particles have bulk density ρ_b = 1200 kg/m³, while the bulk density of the second type of particles is ρ_b = 1300 kg/m³. The studies are performed on a test bench 0.7 m in diameter and 5.75 m tall at room temperature with air used as the fluidizing gas. The velocity of fluidization ranges from 0.1 to 0.75 m/s. The bed is sectioned along its height with a set of horizontal diffuser grids. The results from measuring the fluctuations, the average drops in pressure, and the pressure distribution along the height of the fluidized bed are used to estimate the effect produced by the density of particles on its operational regimes. Velocity of transition U_c, determined from the mean-square deviations of pressure drop fluctuations, is 0.40 m/s for lighter particles and 0.35 m/s for heavier particles. Velocity of transition U_c determined from the power of the energy spectrum of pressure fluctuations Е is 0.45 and 0.40 m/s for lighter and heavier particles, respectively. The results from pressure measurements along the bed height show a linear drop with increasing bed height, and this drop is faster for heavier particles than for lighter particles.