Investigation of the Formation Process of Hazardous and Harmful Production Factors When Cutting a Stone for Construction Works

Stone cutting for construction work is carried out by disk diamond wheels the rotation speed of which, and, consequently, the cutting speed is 35-50 m/s. In view of the high intensity of the cutting process and intensive microchip formation, the process of stone cutting is accompanied by considerable dust formation, which can be both harmful and dangerous in the work.The greatest danger is represented by dust particles, which dimensions are 5 μm or less. These particles have the greatest pathogenic effect on the respiratory system of the human body. In addition, the settling time of these particles is measured in hours. Thus, even after the termination of work, the risk of dust exposure to the human body remains. Insignificant time of inhalation of these particles can lead a person to disability and death. Insurance payments in case of disability and compensation in case of death of an employee for these reasons all over the world amount to multibillion sums, which, even for this reason, makes the issue of combating this phenomenon very urgent.In this paper, the process of generation of hazardous and harmful production factors arising as a result of dust formation during the stone cutting, the regularity of dust distribution by fractions, quantitative indicators of the process for improving equipment, as well as individual and collective means of personnel protection are determined. The shape and dimensions of the cutting grains of the cutting discs are studied in the paper, depending on the grain material and the grain size of the cutting disc. Thecurvature radii of the cutting grains depend on the grain material and the grain size of the cutting disc. The actual number of grains participating in cutting and, consequently, in dust formation is shown.The dimensions of the dust particles depend on the graininess of the cutting discs and the processing regimes. Using the law of normal particle size distribution, the percentage of dust particles is determined depending on processing conditions. The rate of particle settling depends on their size and mass. The formation of a dust-air mixture and its probable concentration and chemical composition of dust depend on the chemical composition of the cutting materials.Regularities are obtained, which can give an opportunity to improve the individual and collective protection of workers from this harmful production factor

Analitic Investigation of the Regularities of Changing Dust Concentration During the Abrasive Decrease of Stone Structures

In the process of repair or restoration of building structures, it is often necessary to strengthen building structures from limestone-shell rock, concrete, reinforced concrete, hard materials-granite, basalt, etc. by cutting or making cuts of the required size with detachable circles of synthetic diamond and cubic boron nitride (CA and CBN)The cutting process is accompanied by considerable dust formation, which can be both harmful and dangerous factor in the work.The aim of the work is studying the process of dust sedimentation and the regularity of the change in dust concentration during the abrasive cutting of concrete and stone materials.Mathematical models have been developed – dust emission from under the wheel, speed of sedimentation of dust particles depending on their material, size and shape, and also depending on temperature, pressure and humidity, the concentration of dust in the working space and the concentration change during the cutting cycle are calculated.It is shown that the velocity of the sedimentation of particles depends significantly on the shape. The higher the sphericity, the higher the sedimentation rate. The ambient temperature has little effect on the sedimentation rate, in the temperature range (-20 → + 40 °C) at which the operation takes place.The sedimentation rate of dust particles generated by cutting the most common building stone materials also differs slightly. Almost the same sedimentation rate has dust particles obtained by cutting basalt and concrete. A bit higher is the sedimentation rate of particles from granite.The sedimentation rate of particles of generated dust is about 600-700 cm/h or 10-11 cm/min for particles measuring 6 μm. This means that at a production height of about 2 m (200 cm) during the operating cycle (about 3 min), the dust will remain at an altitude of about 1.5 m, i.е. practically remains in the working area. This gives grounds to assert about a high concentration of dust during the cutting cycle (about 4.8 108/m3)

Emittance growth mechanisms in the Tevatron beams

In this article we present results of emittance growth measurements in the Tevatron beams. Several mechanisms leading to transverse and longitudinal diffusions are analyzed and their contributions estimated.Comment: 7 p

On L2L^2 -functions with bounded spectrum

We consider the class $PW(\mathbb R^n)$ of functions in $L^2(\mathbb R^n)$, whose Fourier transform has bounded support. We obtain a description of continuous maps $\varphi : \mathbb R^m\rightarrow\mathbb R^n$ such that $f\circ\varphi\in PW(\mathbb R^m)$ for every function $f\in PW(\mathbb R^n)$. Only injective affine maps $\varphi$ have this property

Spatial statistics of passive scalar in two-dimensional shear flow with fluctuations

We examine statistical properties of the passive scalar field advected by the flow consisting of the regular shear flow and of irregular flow fluctuations. We consider the particular case of two-dimensional flow where the shear flow is dominating and the random flow is smooth. We examine both the decaying case and the case of the permanent supply of the passive scalar fluctuations. In both cases the passive scalar possesses strong intermittence, that can be characterized via the single-point moments and correlation functions, calculated in our work. We reveal features of the correlation functions related to the strong anisotropy of the flow. Our qualitative results are universal. Some quantitative results are obtained in the framework of the model where the flow fluctuations are short correlated in time.Comment: 14 pages, 2 figure

Age-dependent role of steroids in the regulation of growth of the hen follicular wall

<p>Abstract</p> <p>Background</p> <p>The ovaries are the primary targets of senescence effects in mammalian and avian species. In the present study, relationships between reproductive aging, sex steroids and the growth pattern of the pre-ovulatory follicle wall were investigated using young hens with long clutch (YLC), old hens with long clutch (OLC), old hens with short clutch (OSC), and old hens with interrupted long clutch (OILC).</p> <p>Methods</p> <p>Experiment 1: Hens were sacrificed 1.5 and 14.5 h after ovulation. Experiment 2: YLC and OILC hens were sacrificed 3.5 h after treatments with LH and/or aminoglutethimide (AG), an inhibitor of steroid synthesis. Volumes of pre-ovulatory follicles (F1-F5) and plasma concentrations of ovarian steroids were determined. Experiment 3: Granulosa and theca cells from F3 follicles of OSC and/or YLC hens were exposed in vitro to estradiol-17beta (E₂), testosterone (T) and LH and the proliferative activity of the cells was examined using CellTiter 96 Aqueous One Solution Assay.</p> <p>Results</p> <p>In YLC and OLC groups, the total volume of F1-F5 follicles rose between 1.5 and 14.5 h after ovulation (P < 0.01), negatively correlating with the plasma level of E₂(P < 0.01). There was no growth of pre-ovulatory follicles in the middle of the ovulatory cycle in the OSC group, with a positive correlation being present between E₂and the follicular volume (P < 0.05). In young hens, AG caused a rise in the total follicular volume. This rise was associated with a fall in E₂(r = -0.54, P < 0.05). E₂enhanced proliferation of granulosa cells from YLC and OSC groups. The proliferative activity of granulosa and theca cells of YLC hens depended on the interaction between T and LH (P < 0.01).</p> <p>Conclusions</p> <p>These data indicate for the first time that the growth pattern of pre-ovulatory follicles during the ovulatory cycle changes in the course of reproductive aging. E₂seems to play a dual role in this adjustment; it stimulates the growth of the follicular wall in reproductive aged hens, whereas it may inhibit this process in young birds. T and LH are apparently involved in the growth regulation during the pre-ovulatory surge in young hens.</p

Enhancement of energy efficiency of the vacuum oil distillation unit using pinch analysis

The actual task of the state is to increase the energy efficiency of the oil refinery. The object of research is a vacuum distillation unit, including a preheating unit for raw materials and a furnace for heating fuel oil before the column. Pinch analysis allows to analyze and optimize a large number of heat flows. In this study the analysis and enhancement of efficiency of the research object is carried out by enthalpy pinch analysis.  In order to reduce the heat load of the furnaces, the additional flows were introduced into the heat exchange system of the oil heating unit. Parametric optimization of the new heat exchange system was carried out. The minimum needs of the heat exchange system in external energy carriers are determined. An enthalpy cascade of the heat exchange system has been constructed, which clearly shows the distribution of heat between each heat flow of the system. In the analysis of the energy efficiency of a furnace, an important point is the determination of the optimal heat capacity of the combustion products. In this work, we have determined the optimal flow heat capacity, at which the heat loss with the exhaust gases is minimal. As a result of the studies carried out, the efficiency of the fuel oil preheating unit has been increased by maximizing heat recovery, and the cost of external energy carriers has been minimized. By reducing heat loss with flue gases, it was possible to increase the efficiency of the furnace

Universal profile of the vortex condensate in two-dimensional turbulence

An inverse turbulent cascade in a restricted two-dimensional periodic domain creates a condensate—a pair of coherent system-size vortices. We perform extensive numerical simulations of this system and carry out theoretical analysis based on momentum and energy exchanges between the turbulence and the vortices. We show that the vortices have a universal internal structure independent of the type of small-scale dissipation, small-scale forcing, and boundary conditions. The theory predicts not only the vortex inner region profile, but also the amplitude, which both perfectly agree with the numerical data

Особливості багатошарового наплавання з використанням модуляції параметрів дугового процесу

Особливості багатошарового наплавання з використанням модуляції параметрів дугового процесу = Characteristics of multi-layer deployment using modulation of arc process parameters / В. О. Лебедєв, В. О. Тищенко, В. В. Спіхтаренко, С. А. Лой // Shipbuilding & Marine Infrastructure. – 2022. – № 1 (16). – С. 15–23.Наплавлення застосовується в основному для відновлення вузлів, що вже перебували в експлуатації, і тим самим продовжують термін їх експлуатації. Серед способів наплавлення можна відзначити два основних напрямки, які реалізуються за рахунок імпульсних і модульованих алгоритмів впливу на дуговий процес. Це насамперед способи, що впливають роботу джерела зварювального струму з періодичною зміною вихідної напруги та системи подачі електродного дроту з можливістю управління струмом зварювання – наплавлення. Метою роботи є підвищення експлуатаційних характеристик наплавлення за рахунок реалізації імпульсних та модульованих методів на дуговий процес. У даній роботі наведено дослідження та аналіз характеристик металу в зоні між наплавленими валиками, а також у зоні багатошарового наплавлення з оцінкою їх впливу на експлуатаційні можливості вузлів та деталей при використанні наплавлення з модульованими режимами. Для проведення програми досліджень було обрано комплекс обладнання у складі автомата А-874Н з випрямлячем ВДУ-506. Модуляція параметрів режиму проводилася за допомогою дослідної приставки модулятора ОИ-10 – конструкції ІЕЗ ім. Є.О. Патона шляхом періодичної зміни частоти обертання валу приводного електродвигуна механізму подачі електродного дроту, або синхронізованого впливу на електричні ланцюги управління джерела живлення та електроприводу двигуна подачі електродного дроту. У модуляторі є два канали управління – для електроприводу механізму подачі електродного дроту, а також заданням рівнів максимальної та мінімальної вихідної напруги і максимальної та мінімальної частот обертання валу приводного електродвигуна і відповідно струму зварювання. Наплавлення дослідних зразків проводилося високолегованим порошковим самозахисним електродним дротом ПП-АН-140 діаметром 2,0 мм. Наплавлення виконували на стандартних зразках, виконаних з легованих конструкційних сталей, переважно матеріалів штампового інструменту. Наплавлений шар випробовувався на зносостійкість. Вивчалася мікротвердість та мікроструктура отриманого шару. Результати дослідження показали, що використання модульованого струму при наплавленні зносостійкого шару дозволяє збільшити показники зносостійкості, при цьому модуляція режимів дугового процесу дозволяє поліпшити показники зносостійкості, так і показники твердості.Surfacing is mainly used to restore units that have already been in operation and thereby extend their service life. Among the surfacing methods, two main directions can be noted, which are implemented due to pulsed and modulated algorithms for influencing the arc process. First of all, these are methods that affect the operation of the welding power source with a periodic change in the output voltage and the electrode wire supply system with the ability to control the welding current – surfacing. The purpose of the work is to improve the operational characteristics of surfacing through the implementation of pulsed and modulated methods of influencing the arc process. This paper presents studies and analysis of the characteristics of the metal in the zone between the deposited beads, as well as in the zone of multilayer surfacing with an assessment of their influence on the operational capabilities of units and parts when using surfacing with modulated modes. To carry out the research program, a set of equipment consisting of an A-874N automatic machine with a VDU-506 rectifier was chosen. The modulation of the mode parameters was carried out with the help of an experimental attachment modulator OI-10 – designed by the PWI. E.O. Paton by either periodically changing the rotational speed of the drive motor shaft of the electrode wire feed mechanism, or by synchronizing the effect on the electrical control circuits of the power source and the electric drive of the electrode wire feed motor. The modulator has two control channels – for the electric drive of the electrode wire feed mechanism, as well as for setting the levels of the maximum and minimum output voltage and the maximum and minimum speeds of the drive motor shaft and, accordingly, the welding current. Surfacing of prototypes was carried out with highly alloyed flux-cored self-shielding electrode wire PP-AN-140 with a diameter of 2.0 mm. Surfacing was performed on standard specimens made of tool steels, mainly from materials of stamping tools. The deposited layer was tested for wear resistance. The microhardness and microstructure of the obtained layer were studied. The results of the study showed that the use of modulated current when surfacing a wear-resistant layer makes it possible to increase the wear resistance indicators, while the modulation of the arc process modes improves both the wear resistance indicators and the hardness indicators

Who are you, Griselda? A replacement name for a new genus of the Asiatic short-tailed shrews (Mammalia, Eulipotyphla, Soricidae): molecular and morphological analyses with the discussion of tribal affinities

The first genetic study of the holotype of the Gansu short-tailed shrew, Blarinella griselda Thomas, 1912, is presented. The mitochondrial analysis demonstrated that the type specimen of B. griselda is close to several recently collected specimens from southern Gansu, northern Sichuan and Shaanxi, which are highly distinct from the two species of Asiatic short-tailed shrews of southern Sichuan, Yunnan, and Vietnam, >B. quadraticauda and B. wardi. Our analysis of four nuclear genes supported the placement of B. griselda as sister to B. quadraticauda / B. wardi, with the level of divergence between these two clades corresponding to that among genera of Soricinae. A new generic name, Parablarinella, is proposed for the Gansu short-tailed shrew. Karyotypes of Parablarinella griselda(2n = 49, NFa = 50) and B. quadraticauda (2n = 49, NFa = 62) from southern Gansu are described. The tribal affinities of Blarinellini and Blarinini are discussed.Copyright Anna A. Bannikova et al. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. The attached file is the published version of the article