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1.
A pH-spectrophotometric study of the Ti-tiron complex in the presence of Ca ions revealed the existence of mixed compounds of Ca-Ti-tiron. These could account for the interference of Ca in the determination of Ti by tiron. The formation of these mixed compounds under varying concentrations of components and at varying pH is discussed. The absorbance of the Ti-tiron was likewise studied in the presence of many colorless salt solutions, but the behavior of Ca was found to be unique. Use was made of the color of the mixed compounds of Ca-Ti-tiron to develop a method for the identification of small amounts of Ca in the presence of large quantities of many common salts. 相似文献
2.
Summary The effect of variation of the rate of cooling on melt-crystallization of random copolymers of isotactic
polypropylene with low amount of either ethylene or 1-butene is evaluated using X-ray techniques, atomic
force microscopy, and calorimetry. Slow non-isothermal melt-crystallization mainly results in formation
of monoclinic α-crystals of lamellar geometry. The presence of comonomers leads to a decrease of
the degree of crystallinity, and of the thickness of lamellae. These changes are proportional to the
concentration of co-units, and are more distinct in propylene-ethylene copolymers. Rapid cooling of
propylene-1-butene copolymers leads to formation of non-lamellar mesomorphic domains, independent of
the concentration of co-units within the investigated range of concentrations. In quenched propylene-ethylene
copolymers, in contrast, the formation of mesomorphic structure partially is replaced by formation of
monoclinic α-crystals of still non-lamellar geometry. 相似文献
3.
V. A. Volkov E. L. Shchukina O. S. Egorova A. Amarlui I. V. Akesenova V. S. Skripnikova 《Fibre Chemistry》2011,42(4):249-253
A method of determining the contact angle of wetting of fibres in the capillaries of fabrics is proposed. A theoretical calculation
of the angles of wetting of cotton and blended fabric fibres with water was performed in the condition of formation of a uniform
hydrocarbon film on the surface of the fibres. The real contact angles of wetting of water-repellent fabrics were determined;
they differ from the angles of wetting of uniform hydrocarbon films by 10-12% due to the presence of hydrophilic molecules
of the emulsifiers in the modifying film. 相似文献
4.
A. V. Gal'yanov Yu. V. Laptev L. M. Fedorova 《Refractories and Industrial Ceramics》1988,29(7-8):494-500
Conclusions The DVKh-1000 mixer provides a completely satisfactory degree of uniformity of the chemical and grain size compositions of the material in production of electrical periclase powders. The optimum conditions are obtained with a weight of charged material of 1.4–1.6 tons and a mixing time of 20 min. The coefficient of averaging is 0.60–0.80 for the content of the impurity CaO and 0.64–0.86 for the grain size composition.With a change in the requirements of the standard for grain size composition of electrical periclase powders and also with a change in the method of their production the optimum operating conditions of the mixer may be established on the basis of special additional investigations.The use of methods of geometrization of quality criteria in mineral resources for evaluation of the degree of uniformity of a material in mixing made it possible to establish an effect consisting of the fact that such properties as plasticity and viscosity characteristics of the aggregate condition of a substance (solid, liquid, gaseous) are revealed in the geometric features of the change in quality criteria and physical and technical characteristics of the pulverized and bulk material. This effect explains the existence of some limit of uniformity in mixing of materials with a different degree of variability of its quality criteria. The numerical value of this limit is determined by the physical properties of the material and the design features of the mixing equipment. For the investigated material and type of mixer this limit is 0.06–0.08%.Translated from Ogneupory, No. 8, pp. 41–45, August, 1988. 相似文献
5.
Peter Wilding Peter J. Lillford Joe M. Regenstein 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1984,34(3):182-189
The measurement of functionality of protein food ingredients has developed somewhat haphazardly, probably due to the wide range of proteins used as ingredients and the diversity of foods. Studies of the physiochemical properties of proteins should enable prediction of a proteins response to process environments and prove more fruitful than many of the empirical measurements of functionality. The effects of pH, salt type and concentration on the phase behaviour of the oilseed globulin and arachin, demonstrates the complexity of protein solubility and the inadequacies of simple tests that have arisen. Studies of the effects of salts and conditioning on meat fibres, coupled with measurement of the location of water in pellets from water holding tests enable the latter to be applied with increased confidence. Comparison of the endothermic transitions observed on heating with the development of storage and loss moduli allow the contributions of domains of skeletal muscle myosin to gel structure to be investigated. 相似文献
6.
Experiments were conducted on computer modeling of the cross section of two-component yarn. The sensitivity of each of the
criteria of radial distribution of the fibres in the cross section of yarn made from a blend of chemical fibres was determined.
The area of application of each criterion was determined with consideration of the results of the computer experiments. 相似文献
7.
研究了7种轴向配位的萘酞菁硅配合物的激发态性质、产生单重态氧的能力及对几种氨基酸的光敏氧化能力.研究表明,对于相同浓度的不同配合物来说,随着轴向配位基团推电子能力的逐渐增强,激发三重态寿命降低,产生单重态氧的能力逐渐下降,而产生单重态氧的能力是光敏氧化氨基酸反应速率的决定因素,因此,其光敏氧化氨基酸的一级反应速率常数逐渐减小. 相似文献
8.
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10.
K. E. Perepelkin 《Fibre Chemistry》2000,32(6):389-401
The trends in the development of chemical fibre production processes are analyzed and the general characteristics of the change in their manufacture as a function of the fundamental determining factors are found. The characteristics of chemical fibre production processes and subsequent treatments are examined and the possibilities of optimizing and intensifying existing technologies and improving the properties of the fibres by physical and chemical modification are demonstrated. Fibre formation in nature and industry is compared. The possibilities of creating new fibre production technologies, using methods of bionics in particular, are demonstrated. The development of the raw-material base for chemical fibres, including finding new sources of raw materials, is evaluated. The development of alternative principles for spinning chemical fibres and new technologies and types of fibres should be expected: production of fibres of the Lyocell type by dissolving cellulose in organic solvents will solve the problem of development of hydrated cellulose fibres, which is important due to the gradual decrease in production of viscose fibres; creation of fibres based on synthetic polypeptides of the fibroin type and production of chemical fibres @mdash; close analogs of natural silk and cobwebs; use of the principles of bionics based on synthesis of regular block-copolymers of defined structure which allow regulating the properties of the fibres by their self-organization. Use of water as a solvent will allow creating @ldquo;environmentally clean@rdquo; fibre production processes. The development of polyvinyl alcohol fibre production is due to the creation of new methods of synthesis of polyvinyl alcohol. Water is also the basic component of solvents of synthetic polypeptides. New, alternative raw-material sources based on synthesis of monomers from atmospheric components (carbon dioxide, nitrogen) and water, biotechnological processes, growth of highly productive cellulose-containing crops, and others are becoming important for ensuring increasing chemical fibre production volumes. 相似文献
11.
D. S. Dvoretsky S. I. Dvoretsky S. V. Mishchenko G. M. Ostrovsky 《Theoretical Foundations of Chemical Engineering》2010,44(1):67-75
The problems of optimizing the design and operational (control) variables during the integrated design of flexible automated complexes of chemical engineering process (CEP)—automated control systems (ACS) under conditions of the uncertainty of physicochemical, engineering, and economic initial data have been formalized. The selection of the best available version of a flexible automated complex is performed by means of the pairwise comparison of alternative versions of automated complexes using criteria that take into account both the quality of the manufactured products and the characteristics of energy and resource saving, on one hand, and the quality of transient processes in the ACS, on the other hand. A two-stage problem of stoichastic optimization of flexible automated complexes with hard and soft constraints has been stated, and a new approach to its solution has been proposed. An example of the integrated design of a flexible continuous process of azo pigments synthesis and a system of the optimum stabilization of its conditions in the presence of an interval uncertainty of the kinetic coefficients of the chemical reaction and individual engineering variables has been shown. 相似文献
12.
悬浮态TiO_2光催化降解腐殖酸的影响因素研究 总被引:1,自引:0,他引:1
在悬浮态TiO2光催化体系中,探讨了光催化氧化降解腐殖酸的规律,考察了催化剂投加量、腐殖酸溶液初始浓度、初始pH值、光强、反应时间等因素对腐殖酸去除效果的影响。结果表明,光催化氧化法降解腐殖酸的效率比直接光解法有显著提高,腐殖酸的去除率从34.73%增加到65.61%(反应时间为3 h);TOC的去除率也大幅度提高,直接光解反应对TOC几乎无去除作用,而光催化氧化对TOC的去除率达37.5%;腐殖酸的初始浓度增加,初始pH值降低,光强增大,光照时间延长均能提高腐殖酸的降解率,其中pH值和光强的影响较为显著。另外,催化剂的投加量存在一个最佳值。 相似文献
13.
René Androsch 《Polymer》2008,49(21):4673-4679
The structure of the crystalline-amorphous interface of poly(R-3-hydroxybutyrate) (PHB) of different molar mass is evaluated by analysis of the rigid amorphous fraction and by analysis of the degree of reversible melting and crystallization. The rigid amorphous fraction of low-molar-mass PHB of 5 kDa is only 5-10%, and at best half of that of high-molar-mass PHB of almost 500 kDa, despite identical crystallinity. This result is paralleled by observation of distinctly larger degree of reversible melting and crystallization in PHB of high molar mass. The larger rigid amorphous fraction and higher degree of reversible melting and crystallization in PHB of high molar mass, consistently and independently, prove enhanced covalent coupling of crystals and amorphous structure, and/or de-coupling of segments of macromolecules which traverse between phases, respectively. The distinct isolation of crystals in PHB of low molar mass is discussed in terms of absence of wide loops/folds, long-chain cilia, and tie-molecules. 相似文献
14.
This article deals with the alkaline hydrolysis of ethyl acrylate–acrylonitrile–divinylbenzene copolymer beads. Chemical changes during hydrolysis were evaluated by means of determination of total weight exchange capacity and of infrared spectroscopy. The influence of reaction temperature, concentration of the hydrolytic agent, degree of copolymers crosslinking as well as the influence of particle size upon the rate of hydrolysis were studied as a function of time. The mathematical and statistical calculations of experimental data were carried out. With respect to time dependence of hydrolysis of the copolymer functional groups, the average values of reaction rate constants as well as the values of assumed diffusion coefficients were calculated. The analysis is based on partial linearization of experimental results by means of semilogarithmic transformation. The empirical relations expressing dependences of reaction rate constants and of diffusion coefficients on conditions of hydrolysis were determined. 相似文献
15.
V. S. Ermolaev V. Z. Mordkovich I. G. Solomonik 《Theoretical Foundations of Chemical Engineering》2010,44(5):660-664
A mathematical model of heat and mass transfer processes in the grain of the Fischer-Tropsch synthesis catalyst is presented
that takes into account the effect of the capillary condensation of the products of the synthesis in the pores of the catalyst.
The influence of capillary condensation on the processes of the diffusion transfer of heat and mass in the catalyst grain
is analyzed using the proposed model. Dependences of the efficiency factor of the grain on the pressure and temperature of
the process and the partial pressure of various components of a mixture are presented. The possibility of determining the
optimum pressure and temperature of carrying out the process for the catalyst of a certain structure is shown. 相似文献
16.
A. S. Belyi 《Catalysis in Industry》2010,2(1):48-54
The article summarizes the results of development of the scientific foundations of preparation of the catalysts, and of the
experimental development works on creation of the new technologies of their production with the use of physical models, which
were previously created on the basis of fundamental research. The results of the adoption of the new production technologies
of the reforming catalysts of the PR series at the domestic plants are presented. The adoption consisted in creation and approbation
of the fundamentally new technologies of production of the aluminum hydroxide (AHO) by means of the continuous method, modification
of AHO by the elements of IV group, plasticization and forming of AHO in the production of the support, application of H2PtCl6 using the reactions of the ligand substitution of C− by the functional groups of the support, and reduction and activation of the catalyst, which provide the optimal chemical
com- position. Their operation during the 15-year period is analyzed. The reasons of high selectivity (up to 90%) of the new
catalysts are found; the new technologies of the combined processing of mixture of C3-C4 alkanes with C5+ are developed and tested for the production of the high-octane catalysts with selectivity approaching 100%. The main effect
of the C5+ yield increase of the end products is achieved by the transformation of the C3-C4 alkanes into the more high-molecular aromatic hydrocarbons. New processes of the combined processing of the mixtures of C3-C4 and gasoline fractions can be considered to be an alternative technology, which solves the important task of broadening the
source of raw materials of the motor fuels by the inclusion of the C3-C4 alkanes of little value into the processing. 相似文献
17.
The early stage of velocity relaxation of a water drop in a flow behind a shock wave under conditions of drop deformation
and breakup is studied experimentally. The aerodynamic drag of the drop is measured on the basis of the dynamics of motion
of its leading edge, and a strong dependence of the drag on the observation time is demonstrated. These data are compared
with the drag obtained on the basis of the dynamics of the center of mass of the drop. The drag of the center of mass is shown
to be comparable with the drag of a solid sphere and to be substantially smaller than the value determined from the leading
edge motion. A possible physical mechanism of this effect is proposed, which is based on the delay of the beginning of motion
of the center of mass of the drop, owing to certain specific features of stabilization of external and internal flows at the
early stage of velocity relaxation.
__________
Translated from Fizika Goreniya i Vzryva, Vol. 45, No. 2, pp. 101–108, March–April, 2008. 相似文献
18.
E. I. Evtushenko O. K. Sysa I. Yu. Moreva O. V. Starodubtseva 《Refractories and Industrial Ceramics》2010,51(2):70-72
Atechnique of estimating the structural instability of substances is developed on the basis of studies on hydrothermal modification
of clay ores. It is suggested that estimation of the degree of perfection of the crystalline structure of mono- and poly-mineral
clays be performed on the basis of a determination of the strength of individual junctions in suspensions. 相似文献
19.
The effect of the structure of graphitized fibre materials (fabric, nonwoven, tricot), degree of compression, and direction
of current flow on their resistivity was investigated. It was shown that there are local minima of the resistivity of these
materials as a function of the direction of current flow. The resistivity decreases linearly as a function of the apparent
bulk density of the graphitized fibre material. The value of the resistivity of carbon-fibre composites is close to the resistivity
of a maximally compressed material. It was found that systems design methods can be used to optimize the engineering creation
of the electrodes of fuel elements made of carbon-carbon porous composites. 相似文献
20.
对于光催化氧化降解处理工业污水的工艺条件或因素的权重评价是达到优良处理效果的关键性技术之一。将模糊数学中的模糊综合评判法与信息工程学中的熵权结合而建立地熵权模糊综合评判法来对光催化氧化降解过程的影响因素权重进行评价,结果表明,该种方法的评价结果和参考文献中的评价结果基本吻合。因此,熵权模糊综合评判法在光催化降解因素分析中具有一定的可靠性和可参考价值。 相似文献