160 research outputs found

    Black Hole Shadows: How to Fix the Extended Gravity Theory

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    The first images of black hole shadows open new possibilities to develop modern extended gravity theories. We discuss the shadow calculations in non-rotating case both when g11=g001g_{11} = - g_{00}^{-1} and g11g001g_{11} \neq - g_{00}^{-1}. We demonstrate the application to few different models: Horndesky theory with Gauss-Bonnet invariant, loop quantum gravity and conformal gravity. The difference of these theories from shadow models with the theory of general relativity is shown. In addition we show that when the rotation is taken into account the requirements to the observational accuracy decrease

    Obtaining Experimental Values of the Uniformity of Seed Distribution by Multivariate Regression Analysis

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    One of the key factors affecting agricultural productivity is the availability of technical means that include machine and tractor units of agricultural enterprises. The production volume of the plant growing industry depends on high yields that can be achieved by high-quality sowing, which implies the optimal seed placement and sowing depth. Thus, the modernization of existing seeding machines and the creation of new ones that ensure the optimal seed placement is an urgent task. This study aimed to develop a coulter for uniform seed distribution along the furrow length. The object of the study was uniform sowing patterns for grain crops based on the optimal parameters of the proposed working unit of the seeding machine obtained by multivariate regression analysis. A symmetric orthogonal compositional plan of the second order was chosen as a model. The criterion for optimization of the geometric parameters of the developed coulter was the uniformity of seed distribution along the furrow length. The following parameters of the proposed coulter were changed: the cut length of the outer side of the rectilinear profile of the lower edge of the rack varied within 20–80 mm (L), and the approach angle in the horizontal plane (α) and the roll angle in the vertical plane (β) varied within 3–28 deg. The study yielded the regression equation for constructing the response surfaces. The analysis of the response surfaces showed that the optimal parameters for uniform seed distribution along the furrow length can be achieved at the approach angle α=250, the roll angle β=150, and the cut length of the lower edge of the rack L=50 mm. Keywords: Coulter, sowing, grain, quality, distribution uniformity, multivariate experimen

    Border Carbon Adjustment: Implications for Russian Companies and Regions in the Context of the Russia Sanctions (the case of Magnitogorsk Iron and Steel Works and Chelyabinsk region)

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    Relevance. There are at least two serious challenges that Russian exporting companies are now facing: first, in 2021, the EU introduced the carbon border adjustment mechanism (CBAM), which will come into force in 2026, and, second, since February 2022, many exporters have been subject to the EU sanctions as part of the Russia sanctions regime. There is much uncertainty surrounding the duration of the current sanctions episode as well as the introduction of the carbon tax in the Middle Eastern and Asian countries. Research objective. The study aims to assess potential economic losses resulting from the CBAM introduction and the pressure of sanctions on the Russian exporters of metallurgical products and their home regions. The study focuses on the case of Magnitogorsk Iron and Steel Works (MMK) and Chelyabinsk region.Data and methods. Methodologically, the study relies on scenario analysis. Two scenarios are considered: the EU sanctions against Russian steel companies will be lifted after 2024–2025 and the sanctions will not be lifted in the near future. For each scenario, two variations are analyzed and the annual economic losses are calculated both for MMK and for Chelyabinsk region. The data for the study was taken from ММК official reports.Results. If the EU sanctions are lifted in the nearest future, at the initial stages of the carbon tax introduction, the economic consequences for Russian exporters will be insignificant.  In the future, however, carbon regulation can create serious threats to the financial condition of such enterprises even if exports account for a small share of their revenue. If the EU sanctions stay in place, Russian enterprises are likely to search for trade partners in the Middle East and Asia. If the latter introduce a carbon tax, Russian companies can enjoy a competitive edge due to the comparatively low carbon intensity.Conclusions. To ensure Russian steel companies’ competitive edge, it is necessary to stimulate them to reduce their carbon footprint and create a national carbon regulation system. Not only will this measure help to reduce the loss of export income and regional governments’ tax revenues but it will also enable companies to stay competitive and deal more effectively with the sanctions pressure

    Modeling of temperature fields of details during laser hardening using the method of polyargument systems

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    Представлено дані математичного моделювання теплового стану ріжучого інструменту в умовах лазерного загартування. Розглядаються особливості реалізації методу поліаргументних систем для розв’язання тривимірної задачі теплопереносу з локалізованим рухомим джерелом лазерного нагріву. Наводяться дані числових досліджень щодо встановлення закономірностей впливу радіуса плями нагріву на температурний режим зміцнюваного інструменту. Показано, що варіювання даного параметра може використовуватися як ефективний спосіб впливу на тепловий стан ріжучого інструменту в процесі його загартування променем лазера. Представлено результати моделювання температурних режимів інструмента в широкому практично важливому діапазоні зміни його кута заточки.The data of mathematical modeling of the thermal state of a cutting tool under conditions of laser hardening are presented. The features of the implementation of the method of polyargument systems for solving the three-dimensional heat transfer problem with a localized movable laser heating source are considered. The data of numerical studies to establish patterns of the influence of the radius of the heating spot on the temperature regime of the hardened tool are presented. It is shown that varying this parameter can be used as an effective way of influencing the thermal state of a cutting tool during its hardening by a laser beam. The results of modeling the temperature conditions of the tool in a wide practically important range of changes in its sharpening angle are presented.Представлены данные математического моделирования теплового состояния режущего инструмента в условиях лазерной закалки. Рассматриваются особенности реализации метода полиаргументных систем для решения трехмерной задачи теплопереноса с локализованным подвижным источником лазерного нагрева. Приводятся данные численных исследований по установлению закономерностей влияния радиуса пятна нагрева на температурный режим упрочняемого инструмента. Показано, что варьирование данного параметра может использоваться в качестве эффективного способа воздействия на тепловое состояние режущего инструмента в процессе его закалки лучом лазера. Представлены результаты моделирования температурных режимов инструмента в широком практически важном диапазоне изменения его угла заточки

    ДОСЛІДЖЕННЯ ОРТОПОЛІФОСФАТНОГО ПРЕПАРАТУ “SEA QUEST LIQUID” ДЛЯ АНТИКОРОЗІЙНОЇ ТА СТАБІЛІЗАЦІЙНОЇ ОБРОБКИ ВОДИ

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    Most water supply systems operating in Ukraine are made of steel or cast iron, which are subject to corrosion. The Institute of Water Problems and Land Reclamation of the National Academy of Sciences of Ukraine carried out the experimental studies on the effect of an orthophosphate corrosion inhibitor on the quality of drinking water and the rate of corrosion as a result of its appliance in various doses in the water supply network. The water supply system of Obolon district of the city of Kiev was selected as the object of research. A characteristic feature of this water supply system is the use of various sources of water supply - groundwater and surface waters of the Desna and Dnieper rivers. The results of the calculation of water corrosivity carried out at the Institute based on the chemical analysis of the quality of water taken from 29 wells at the research object showed that the Langelier indices obtained using the calculation formulas for all sampling points are in the range from 0,89 to 1,77, which indicates the continuous and significant corrosive activity of water at all sampling point. The Risner index in all samples was in the range from 7.8 to 8.8, which indicates the significant pipeline corrosion. That is especially typical for the water from the well № 232, the Rizner index of which is 9.58, which indicates very intensive corrosion of the pipeline. Indicators rH2, for all samples, calculated both by F.U. Clarke and by the formula of A.I. Trufanov, indicate that the studied aquatic environment is very favorable for the vital activity of iron bacteria in general, and the pH - Eh zone of water samples indicates that there is an active vital activity of various strains: Leptothrix, Gallionella , Thiobacillus thiooxcidans or their combined activity. All the studied factors indicate that the most likely there is a complex genesis of corrosion processes in water supply networks, which combines both physicochemical and biological processes. This combination usually contributes to the processes of active secondary water pollution by the products of pipeline corrosion. Indicators rH2, for all samples, calculated by the formulas of F.U. Clark and of A.I. Trufanov, indicate that the studied aquatic environment is very favorable for the activity of iron bacteria in general, and the pH - Eh zone of water samples indicates that there is a rather high activity of different strains: Leptothrix, Gallionella, Thiobacillus thiooxcidans or their combined activity. The results of the research showed that for all ways to use of "SeaQuest Liquid" spicemen in the water of all sampling points there were no deviations from the standards of basic physicochemical parameters: the average pH of water was 7,67 ± 0.01, total water hardness was 4,3 ± 0,03, total alkalinity - 4,4 ± 0,05 mmol/dm,3 calcium content - 58,6 ± 0,7 mg/dm3, magnesium - 16,1 ± 0.2 mg/dm3, hydrocarbons - 261,4 ± 4,8 mg/dm3, manganese <0,01 mg/dm3, sulfates - 21,9 ± 1,2 mg/dm3, chlorides - 44,3 ± 1,4 mg/dm3, sodium and potassium - 44,0 ± 2,0 mg/dm3, residual chlorine - 0,35 ± 0,02 mg/dm3, ammonium - 0,2 ± 0.01 mg/dm3, permanganate oxidation - 2,3 ± 0,1 mgО2/dm3, nitrites - 0,09 ± 0,01 mg/dm3, nitrates - 1,53 ± 0,14 mg/dm3, total mineralization - 459,9 ± 15,1 mg/dm3. In some samples of water treated with “SeaQuest Liquid”, the iron content exceeded the hygienic standard (0,2 mg/dm3) and exceeded the maximum allowable level (1,0 mg/dm3). In drinking water samples, the levels of substances that are the part of "SeaQuest Liquid" specimen (polyphosphates, orthophosphates), varied at different sampling points but were within the normative values. The anticipated biological component of corrosion according to the calculated Rh2 index, was confirmed. In the presence of sulfate-reducing and thiobacteria in water, "SeaQuest Liquid" specimen increases the corrosion rate of steel by 2,9-7,2 times; subject to additional disinfection of water when treating with sodium hypochlorite, it reduces this indicator by 1,4-2,7 times. Under the action of "SeaQuest Liquid" in water treated with sodium hypochlorite, there was a decrease in the Langelier index: from -2,23 to -2,08 and from -1,79 to -1,70, indicating a decrease in its corrosive activity. In water untreated with sodium hypochlorite under the action of "SeaQuest Liquid" there was some increase in the Langelier index: from -1.80 to -1,95 and from -1,85 to -2,78; from -2,01 to -2,13, which indicates an increase in its corrosive aggressiveness.  Зазначено, що переважна більшість водопроводів діючих в Україні систем водопостачання виконані із сталі, або чавуну, які схильні до корозії. Встановлено, що одним із напрямків зниження корозійної агресивності питної води є застосування орто- поліфосфатного препарату "SeaQuest Liquid" (ТУ У 20.5-У 0502222-001:2017). Наведено результати досліджень впливу препарату “SeaQuest Liquid” на органолептичі та фізико-хімічні показники питної води. Визначено, що обробка водопровідної питної води препаратом “SeaQuest Liquid” не впливає на органолептичні показники, середні рівні яких упродовж 5-ти місяців спостережень практично не зазнавали суттєвих змін та знаходились в межах гігієнічних нормативів. У зразках води рівні речовин, що входять до складу препарату “SeaQuest Liquid” (поліфосфати, ортофосфати), перебували у межах нормативних значень. Якість води, обробленої ортополіфосфатним препаратом “SeaQuest Liquid”, за основними санітарно-хімічними показниками, окрім заліза, відповідає вимогам гігієнічних нормативів ДСанПіН 2.2.4.171-10. В окремих пробах води вміст заліза перевищував гігієнічний норматив (0,2 мг/дм3) та виходив за максимально допустимий рівень (1,0 мг/дм3). Під дією препарату “SeaQuest Liquid” у воді, яка оброблена гіпохлоритом натрію, спостерігалось зменшення індексу Ланжельє: з -2,23 до -2,08 і з -1,79 до -1,70, що свідчить про зниження її корозійної активності. У воді, не обробленій гіпохлоритом натрію, під впливом препарату  “SeaQuest Liquid” спостерігалось деяке зростання індексу Ланжельє: з -1,80 до -1,95  та з -1,85 до - 2,78;  з -2,01 до -2,13, що свідчить про зростання її корозійної агресивності. В умовах наявності у воді сульфатредукуючих  тіобактерій  препарат “SeaQuest Liquid” збільшує швидкість корозії сталі в 2,9-7,2 рази; за умови додаткового знезараження води гіпохлоритом натрію останній знижує цей показник в  1,4-2,7 рази

    Study of onion processing waste powder for potential use in food sector

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    The development of food products that contain value-added dietary fibre beside different classes of phytochemicals is of great interest nowadays. The present research aimed to evaluate the powder obtained from onion processing waste (OPW) for its potential use as a value-added by-product in food sector. Data on chemical and microbiological characterization of onion processing waste powder (OPWP) were obtained. The dietary fibre content and antioxidant activity were also determined. The results showed that the OPWP was a low-calorie natural source of insoluble fibres (60.52±0.13 g/100 g dw), total phenols (41.04±1.22 mg GAE/g dw), and total flavonoids (20.44±1.22 mg QE/g dw). Moreover, the OPWP could be considered as an important source of total fructans (9.04±0.28 g/100 g dw), fructooligosaccharides (2.76 g/100 g dw), and inulin (2.41±0.18 g/100 g dw). In conclusion, this OPWP could be used as a value-added and healthy food ingredient

    Application of scanning probe microscopy methods to control the synthesis technology of multilayer structures with Bi-substituted iron garnets

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    Authors present the synthesis technology in which a lower surface roughness of the layers in multilayer structure with Bi-substituted iron garnets can be achieved through simultaneous crystallization annealing of the bottom Bi-substituted iron garnet layer and the top layer of SiO2.The authors acknowledge support by the RF Ministry of Education and Science (project no.3.7126.2017)

    Magnetic force microscopy investigation of domain structure and magnetic recording patterns in high-coercive garnet films with low Curie temperature

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    Authors present the investigation of domain structures and thermomagnetic recording patterns in iron garnet thin films by magnetic force microscopy. Iron garnet films with low Curie temperature and high coercivity were designed for recording process. Magnetic pattern of PC floppy disc was recorded in iron garnet film by contact printing method. Topography and magnetic structure of floppy disc and iron garnet film before and after thermomagnetic recording process are presented. Accuracy of thermomagnetic recording and parameters, which are influence on it, are discussed.The authors from V.I. Vernadsky Crimean Federal University acknowledge support by the RF Ministry of Education and Science (project no. 3.7126.2017)
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