Development of Defining Equations for the Mathematical Theory of Concrete Corrosion Processes

2020 ◽  
pp. 15-27
Keyword(s):  
Solid Phase ◽  
Longitudinal Direction ◽  
Technical Condition ◽  
Moving Boundaries ◽  
Chemical Transformations ◽  
Layer Depth ◽  
Dissolution Reaction ◽  
Concrete Layer ◽  
Physical And Chemical ◽  
Active Substances

The fundamental difference of the developed defining equations is that they consider the dual system of porosity and kinetic laws of physical and chemical transformations to describe individual stages of corrosion processes. The dual porosity system comprises through capillaries (pores) of the longitudinal direction and adjacent capillaries of the transverse direction. During the reagent mass transfer in through capillaries (pores) there takes place their transfer to transverse ones, in which we can observe the neutralization (dissolution) reaction of chemically active substances in solid phase with the formation of the moving boundaries. The binding and release rate in case of leaching are determined from the respective boundary value problems and are similar in structure. In defining equations, all parameters are reduced to two generalized ones. Their values for forecasting the technical condition of operating structures are to be determined on the basis of concentration distribution of the aggressive component in concrete layer depth in the above-specified structures.

scholarly journals Accelerated physical and chemical transformations in ceramics processing

2019 ◽  
Vol 84 (10) ◽  
pp. 1055-1071
Author(s):  
Ernő Kiss ◽  
Sanja Panic
Keyword(s):  
Chemical Reactions ◽  
Material Science ◽  
Solid Phase ◽  
General Term ◽  
Chemical Transformations ◽  
Silicate Chemistry ◽  
Basic Concepts ◽  
Points Of View ◽  
Physical And Chemical ◽  
Phase Chemical

From economic and environmental points of view, solid phase chemical reactions are very important parts of modern chemistry and technology, enabling various processes to become cleaner, safer and easier to perform. This survey presents the basic concepts of solid-state transformations in ceramics processing, including notions and phenomena described in capital books on silicate chemistry, published more than 100 years ago, to the present day. During this period, scientists and practitioners in the field of ceramics processing used concepts related to the acceleration of phase transitions and chemical reactions. Today, the differences between various accelerating agents (flux agents, mineralizers and catalysts) in terms of their composition and mechanism of action are almost completely defined and clearly delimited. However, in ceramics processing, a more general term additive is preferably used instead of the previously mentioned ones. The aim of this work is to show that all accelerating agents are equally important to researchers in the field of catalysis and material science, emphasizing that the used terminology could be interpreted from different perspectives.

Skin exposure: requirements to methods determining active ingredient of pesticides in washings

2019 ◽  
pp. 43-48
Author(s):  
V. N. Rakitskii ◽  
N. E. Fedorova ◽  
I. V. Bereznyak ◽  
N. G. Zavolokina ◽  
L. P. Muhina
Keyword(s):  
Lower Limit ◽  
Limit Of Detection ◽  
Solid Phase ◽  
Absorbed Dose ◽  
Ambient Air ◽  
Safety Coefficient ◽  
Limit Value ◽  
Calculated Risk ◽  
Nature Studies ◽  
Active Substances

The article presents results of studies exemplified by diquat on analysis concerning influence of lower limit value of quantitative assessment in washing sample for safety coefficient in exposure and in absorbed dose, if acting substance is absent in workplace ambient air samples and in dermal washings of workers. To control diquat in dermal washings, there is a method based on ion-pair liquid chromatography with ultraviolet detection (working wavelength 310 nm). To concentrate sample, cartridges for solid-phase extraction, containing ion exchange sorbent (Oasis MCX 6cc/500 mg), are used. Lower limit of assessment in washing sample — 0,15 micrograms. Experimentally set washing completeness is within range of 80–92%, standard deviation of repetition is 7,0% at most. The method created was tested in nature studies determining dermal exposure in workers subjected to 5 various preparations based on diquat dibromide when used for surface spraying from tractor and from aircraft. For lower limit of detection in washing sample (0,15 micrograms/washing), calculated risk value of exposure varied within 0,26–0,36; risk of absorbed dose was low — 0,23 (the allowable one ≤1). Findings are that present measuring methods which provide lower limit of detection 1 and 5 micrograms in washing sample could result in unallowable risk establishment even with absence of the substance in all samples of workplace air and dermal washings. The calculation formula suggested enables to give theoretic basis for requirements to lower limit of detecting active substances in dermal washing samples for evaluating risk of pesticides use in agriculture.

scholarly journals Adsorption of Copper in Soil and its Dependence on Physical and Chemical Properties

2018 ◽  
Vol 66 (1) ◽  
pp. 219-224 ◽  
Author(s):  
Vítězslav Vlček ◽  
Miroslav Pohanka
Keyword(s):  
Soil Properties ◽  
Solid Phase ◽  
Chemical Properties ◽  
Total Content ◽  
Exchange Capacity ◽  
Soil Reaction ◽  
Available Phosphorus ◽  
Copper Adsorption ◽  
Phosphorus And Potassium ◽  
Physical And Chemical

Soil samples (n = 11) were collected in the chernozem areas of the Czech Republic (the Central Europe) from the topsoil and used as representative samples. All sampling areas have been used for agricultural purposes (arable soil) and they were selected as typical representatives of agricultural soil. These samples represented the soil with same genesis (to reduction differencies between soil types) but with different soil properties (physical and chemical). Complete chemical and physical analyses were made for confirmation of copper adsorption on solid phase: we analysed the particle size distribution, content of oxidizable carbon (Cox), the cation exchange capacity (CEC), supply of exchange calcium, magnesium, sodium, phosphorus and potassium, soil reaction and the total supply of Fe, Al, Mn, Ca, Mg, K, P and N. The strongest simple correlation between analysed soil properties and copper concentration had content of available magnesium (r = 0.44) and available phosphorus (r = −0.51). In the case of multiple correlations (i. e. collective influence of multiple soil properties) had the strongest influence combination of clay, soil reaction, total content of phosphorus, available magnesium and available phosphorus. The main influence of phosphorus and magnesium is evident. We suppose that copper and phosphorus enter into specific complex. Influence of these five soil properties can explain 92.7 % (r = 0.927) changes in the content of copper changes in the experiment.

scholarly journals Changes in biologically active substances of stone fruits under the influence of low temperatures

2021 ◽  
Vol 34 ◽  
pp. 06017
Author(s):  
Irina Sobol ◽  
Ludmila Rodionova ◽  
Ludmila Donchenko ◽  
Artem Stepovoy
Keyword(s):  
Low Temperatures ◽  
Beta Carotene ◽  
Biologically Active Substances ◽  
Biologically Active ◽  
Carotene Content ◽  
Plum Varieties ◽  
Physical And Chemical ◽  
Active Substances ◽  
Acid Reduction ◽  
Pectin Substances

Sufficient consumption of natural biologically active substances (BAS) – vitamins, dietary fiber, mineral compounds – reduces the risk of developing diseases associated with negative external factors. A large number of BAS are contained in the cherry plum fruits. Cherry plum is characterized by storage short term, during which quality changes are possible. Studies have been conducted on the low temperatures effect the change of BAS in cherry plum fruits. Studied objects were five cherry plum varieties grown in the Russian southern regions – Dinnaya, Zhemchuzhina, Obilnaya, Puteshestvennitsa, Neberdzhayskaya ranyaya. It was found that during storage, the physical and chemical parameters change slightly, the dry substances content decreases (within 1.3-3.2 %), sugars (5.5-7.0 %), the total acids content increases (2.8 3.3 %). The BAS content slight decrease during storage does not significantly affect the nutritional value of cherry plum fruits. The ascorbic acid reduction is 9.8-17.3 %, the anthocyanins content decreases on average from 16.9 to 19.7 %, the beta-carotene content decreases by 8.7-14.8 %, the reduction level of pectin substances is 15.75-22.2 %. Thus, the freezing method application allows to preserve valuable BAS in cherry plum fruits and use them in the future as a basis for the production of functional food products.

Suspension Plasma Spraying (SPS) of Cobalt Spinel

1997 ◽  
Author(s):  
G. Schiller ◽  
M. Müller ◽  
F. Gitzhofer ◽  
M.I. Boulos ◽  
R.B. Heimann
Keyword(s):  
Plasma Spraying ◽  
Inductively Coupled Plasma ◽  
Solid Phase ◽  
Spinel Phase ◽  
Rf Plasma ◽  
Dry Powders ◽  
Inductively Coupled ◽  
Cobalt Spinel ◽  
Chemical Conditions ◽  
Physical And Chemical

Abstract Fine (median size 6 μm and 0.3 μm) cobalt spinel (Co3O4) powders were processed suspended in a suitable liquid phase. Suspensions exceeding 50 wt.% solid phase content were successfully injected into an inductively coupled plasma. Spheroidized powders with large particle size (up to 80 μm) were prepared, and cobalt oxide coatings were produced by this novel RF-SPS method. The microstructural features of the coatings can be controlled by parameter optimization similarly to plasma spraying of dry powders. Numerous variations of the physical and chemical conditions of the process were performed in an attempt to overcome the main disadvantage of the process, i.e. the decomposition of the spinel phase to CoO. So far, the spinel phase could be reestablished only by a post-treatment of the deposited coatings with atomic oxygen in the RF plasma.

Physical and chemical characteristics of cryoconites, sampled from glaciers of the Central Caucasus (Russia).

2021 ◽  
Author(s):  
Ivan Kushnov ◽  
Evgeny Abakumov ◽  
Rustam Tembotov ◽  
Viacheslav Polyakov
Keyword(s):  
Particle Size ◽  
Organic Carbon ◽  
Particle Size Distribution ◽  
Solid Phase ◽  
Basal Respiration ◽  
Chemical Characteristics ◽  
Significant Similarity ◽  
Physical And Chemical Characteristics ◽  
Central Caucasus ◽  
Physical And Chemical

<p>Cryoconites are a dark-colored granular sediments found in glacial landscapes. Cryoconites are known as a dark colored accumulation of various origin material in superficial holed of the glaciers which formed in polar and mountain regions of the Earth. They can significantly accelerate glacier retreating by reducing the albedo of the glacier and play a significant role in the colonization of the territory after its retreat, being an "oasis" for development of microorganisms on an uninhabited glacier surface. The understanding of key cryoconites properties is necessary to understand their impact on the mountain glaciers of the Central Caucasus, especially taking into account their recent rapid retreat.</p><p>The aim of this research is to study the physical and chemical characteristics of various cryoconites and cryoconite derived periglacial soils of the Central Caucasus. Eight cryoconite samples and eight soil samples from three soil sections were selected. The following characteristics of the samples were determined in laboratory conditions: total organic carbon (TOC), basal respiration level, pH H<sub>2</sub>O and exchangeable soil acidity, solid phase density and particle size distribution.</p><p>The results of the analyses showed both differences and some similarities in the physical and chemical characteristics of the cryoconites and soils of periglacial zone which were studied. Cryoconites, on average, are characterized by lower values of basal respiration than more developed soils from this region. The total organic carbon content in most samples was relatively low, but its values increase significantly soils investigated due to accumulation of carbon in fine earth under the influence of primary vegetation. The water extractable acidity values showed a significant similarity between the studied cryoconites and soils, they vary from slightly acidic to slightly alkaline in both groups. At the same time, the variation of exchangeable acidity values between cryoconite samples is significantly greater than in developed soils. Moreover, the density of the solid phase of the studied cryoconites varies in a larger range of values than that of the studied soils due to variety of sources of cryoconite materials. However, the analysis of particle size distribution showed a significant similarity of the studied objects: in almost all samples there is a significant dominance of the sand fraction (d=1-0.05 mm). The obtained data indicate both the difference in the physical and chemical properties of the studied cryoconites among themselves, and the probable influence of cryoconites on soil formation in this region.</p><p>This work was supported by Russian Foundation for Basic Research, project No <strong>19-05-50107</strong>  “The role of microparticles of organic carbon in degradation of ice cover of polar regions of the Earths and in the process of soil-like bodies formation”.</p>

PERBANDINGAN PELARUT ETANOL DAN AIR PADA PEMBUATAN EKSTRAK UMBI BAWANG TIWAI (Eleutherine americana Merr) MENGGUNAKAN METODE MASERASI

2017 ◽  
Vol 1 (2) ◽  
pp. 149
Author(s):  
Hayatus Sa'adah ◽  
Henny Nurhasnawati
Keyword(s):  
Medicinal Plant ◽  
Chemical Properties ◽  
Physical And Chemical Properties ◽  
Phytochemical Screening ◽  
Water As Solvent ◽  
Physical And Chemical ◽  
Eleutherine Americana ◽  
Solvent Optimization ◽  
Active Substances ◽  
And Chemical Properties

Bawang tiwai (Eleutherine americana Merr) is one kind of medicinal plant. To obtain an active substances with good physical and chemical properties, it is needs to do optimization of making extracts, one with solvent optimization. Type of solvent will determine the types of extracted substances in accordance with the polarity. On this research, extraction of bawang tiwai bulbs simplicia by maceration method using ethanol and water as solvent. This research is an experimental research with varying ethanol and water in a three comparison solvent that is water, ethanol, and mixture of water-etanol, then the yields is calculated. Furthermore, the data were analyzed statistically using ANOVA program to determine significant differences in the three yields. In each extract was conducted phytochemical screening to determine the content of secondary metabolites. The results showed significant differences in the yield of bawang tiwai extract with three treatments and two repetitions. The results of average yields using water as solvent is 8.75%, ethanol 5.3%; and water-etanol 8.31%

scholarly journals Comparative Analysis of Gearboxes Wear in Excavators and Mining Trucks

2020 ◽  
Vol 174 ◽  
pp. 03017
Author(s):  
Andrey Kudrevatykh ◽  
Andrey Ashcheulov ◽  
Alena Ashcheulova ◽  
Kumis Urazbaeva
Keyword(s):  
Comparative Analysis ◽  
Mining Industry ◽  
Technical Condition ◽  
Used Oil ◽  
Dump Trucks ◽  
Wear Products ◽  
High Level ◽  
Physical And Chemical ◽  
Metallic Impurities

The primary task of all enterprises in mining industry is to increase the durability and reliability of the mining complex. These very indicators provide nonstop minerals mining, and as a result, productivity increases. Indicators maintaining at high level can be achieved by different ways, but the most effective method is repair-in-place diagnosis of the actual technical condition of the main units and assemblies of equipment, as it is less costly and the most informative. To identify gear malfunctions, the physical and chemical analysis of the used oil is used to determine metallic impurities. A comparative analysis of wear products accumulation in rotary gears of mining excavators and gearboxes of the motor-wheel of dump trucks revealed the similarity of mathematical models for the determination of metallic impurities in used oil. The “universal” mathematical model is given in the paper; it allows to determine the actual technical condition of gearboxes for various equipment with a few assumptions. Moreover, the model takes into account various indicators of the environment, used oil, as well as the operating parameters of the equipment.

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