bluuebunny/crossref_metadata_2025 huggingface dataset:
Two-stage repair of the intrathoracic portion of a left subclavian artery aneurysm after previous coronary artery bypass surgery
Authors: Zlatanović Petar , Dragaš Marko , Cvetić Vladimir , Radmili Oliver , Vujčić Aleksandra , Trailović Ranko , Petrović Filip , Davidović Lazar
Published: May 2021

Introduction: We present a case of a 70-year-old patient who underwent successful two-stage repair of an intrathoracic left subclavian artery aneurysm (SAA) and who had previously undergone CABG. Case presentation: The patient had previously undergone three-vessel coronary artery bypass graft (CABG) repair with the use of the left internal mammary artery (LIMA) to the left anterior descending artery (LAD). Percutaneous coronary intervention (PCI) was performed as a backup option in case of potential intra-operative LIMA-LAD bypass occlusion. Owing to the impossibility of hybrid repair due to a short proximal landing zone and aortic arch anomaly (bovine type), the vascular surgery review board decided to perform two-stage open surgery. Firstly, the patient underwent a left carotid-subclavian (C-S) bypass with the Dacron graft, with the application of the standard supraclavicular approach. After a few days, the second procedure, through the left posterolateral thoracotomy was performed. The left subclavian artery (SA) was ligated distally to the SAA but proximally to the origin of the LIMA. The distal aortic arch at the site of the left SAA was clamped partially and the aneurysm was excised. The defect of the aortic arch was sutured and reinforced with a felt patch. Postoperatively, the patient had a good recovery, without any signs of myocardial injury or any surgery-related issues. Conclusion: Careful planning and two-stage open surgical treatment of the left SAA, first with a left carotid-subclavian bypass, followed by aneurysm exclusion and suture of the outer aortic arch curvature may be a treatment option for patients not amenable to hybrid treatment.
Experimental Technique for the Determination of Forces Acting on a Sailboat Rigging
Authors: Fossati F. , Moschini G. , Vitalone D.
Published: May 2021

In the present paper a complete procedure which provides a rapid and low cost method for load evaluation in each rigging element of a sailboat like stays in the fore and aft direction, shrouds in the athwartship, sheets, halyards, and running back stays, will be described. Some results obtained using the proposed method will be shown relevant to an arbitrary chosen cruising sailing yacht.
An Investigation of the Structural Dynamics of a Racing Yacht
Authors: Louarn Frederic , Temarel Pandeli
Published: May 2021

The dynamic behaviour of a WOR 60 is investigated using three dimensional hydroelasticity theory. Global structural responses (e.g. stresses) in waves are obtained corresponding to the upright as well as to the more realistic heeled sailing configurations, revealing the connection between the ballast keel and the hull as being a critical area of the structure.

For the "dry hull" analysis, a global finite element model has been developed, incorporating the hull and deck shell, the internal structure, the ballast keel and the rig together with rigging loads. The modular nature of the model has been used to assess the relative influence of each of the aforementioned components upon the required characteristic dynamic properties (e.g. natural frequencies and principal mode shapes).

Regarding the "wet hull" analysis, a three dimensional Green's function technique, using pulsating sources distributed over the wetted surface, provides a numerical solution to the case of the yacht sailing in regular waves at arbitrary heading. Principal coordinates for the rigid body motions and flexible distortions of interest are evaluated and the latter are used to obtain the dynamic stresses in waves using modal summation.

This paper will describe the modelling techniques used and discuss the applicability / limitations of hydroelasticity theory regarding this type of structures in the light of the results obtained for the upright and heeled operational conditions, as well as from the point of view of design aspects such as "L" and "T" keel configurations. The ABS design criteria will provide a practical reference for comparing the results from the dynamic analysis.
On the Application of RANS Simulation for Downwind Sail Aerodynamics
Authors: Lasher William
Published: May 2021

At the present time technology does not exist for accurately determining force coefficients for downwind sailing. Reynolds-Averaged Navier Stokes (RANS) simulation offers the potential of being a useful tool to help solve this problem. The basis of RANS is reviewed, and the results of computations for two-dimensional blocked flow normal to a flat plate are presented. Both quasi-steady and transient computations were performed. The quasi-steady computations provide excellent prediction of the effects of blockage on drag, while the transient simulations do a very good job of predicting the actual value of the drag. The application of the technology to realistic downwind sail configurations is discussed.
The Re-Righting of Sailing Yachts in Waves - A Comparison of Different Hull Forms
Authors: Renilson Martin , Binns Jonathan R. , Tuite Andrew
Published: May 2021

The re-righting performance of three yacht hulls has been assessed experimentally. The three hulls are considered to be representative of modern racing yachts. It has been shown that two different experimental techniques provide the same relative results between the three hulls, leading to the same conclusions. Correlation of re-righting performance with basic hydrostatic parameters has been shown for these three hulls, however a simple case when this correlation is non-existent is noted.
International America's Cup Class Yacht Design Using Viscous Flow CFD
Authors: Jones Paul , Korpus Rich
Published: May 2021

The Computational Fluid Dynamics (CFD) tools needed to incorporate viscous effects into design trade­off studies have finally matured to the point where practical guidance can be provided within design cycle tum-around times. The required techniques are known as Reynolds-Averaged Navier-Stokes (RANS) solvers, and saw their first practical application to yacht design during America's Cup XXX. The team of America One, for example, utilized RANS for upwind sail design and VPP aerodynamic force predictions. RANS was also used in the keel design process, and to provide "virtual prototyping" for investigating new concepts before building them. This paper presents some of these groundbreaking applications, and demonstrates the types of guidance available to the designer using RANS.
PCSAIL, A Velocity Prediction Program for a Home Computer
Authors: Martin David E. , Beck Robert F.
Published: May 2021

An Excel Velocity Prediction Program has been developed to allow for rapid evaluation of yacht performance at the initial design stage. The required input consists of only the basic hull and sail dimensions. Empirical equations, based on these basic dimensions, are used for initial estimates of required hull parameters. As the design progresses the user can easily replace these default values with refined estimates or actual values. Because of its simplicity, and short turn around time, the program has been used as a teaching aid at the University of Michigan. Reconstruction of the program, PCSAIL, may be made with equations and other information provided in the Appendix.

The Excel "Solver" has been found to be a reliable means of finding the equilibrium boat speed and heel angle. It seeks the maximum boat speed by adjusting the sail flattening factor, F, and reef, R, and the lateral location of the "movable crew." In the case of a hinged centerboard, or dagger- board, it will also adjust the draft for maximum boat speed.

For sloop rigs the program will also take in the jib and set the spinnaker, at the appropriate wind angle, in order to gain maximum boat speed. The program plots the speed "polar," and velocity made-good, and determines the tacking angles.
Sailing Performance of "Naniwa-maru" - A Full Scale Reconstruction of a Sailing Trader of Japanese Heritage
Authors: Nomoto Kensaku , Masuyama Yutaka , Sakurai Akira
Published: May 2021

"Naniwa-maru" is a reconstruction of a sailing trader that used to ply between Osaka and Edo, today's Tokyo, in the 18th to the mid-19th century. The rig was simple; single mast with a huge square sail. It was of totally wooden construction in a genuine Japanese manner. The present paper relates to her sailing sea-trial results compared with performance prediction based upon tank tests and wind tunnel studies. According to the trial the ship could reach as high as 70° to weather on her track and the speed then was some 30% of the true wind velocity in a fair sailing breeze. She was swiftest on a broad reach, achieving more than 40% of the wind speed. The said prediction proved to explain the test results fairly well.
Prácticas universitarias innovadoras sobre las ventajas educativas y desventajas de los entornos MOOC
Authors: Vázquez-Cano Esteban , López-Meneses Eloy , Gómez-Galán José , Parra-González María Elena
Published: May 2021

Las tecnologías de la información y la comunicación han revolucionado el mundo tal como lo conocíamos antes de su uso y aplicabilidad a la vida diaria. Este uso también se ha trasladado al campo educativo y ha transformado la forma en que se aprende y se enseña hoy. En medio de este panorama, los cursos abiertos masivos en línea emergen como una oportunidad disponible para que todos puedan aprender, lo que ha causado muchos cambios en el campo educativo. Este estudio se presenta como una investigación sobre prácticas universitarias innovadoras para analizar las ventajas y desventajas de estos MOOC en el entorno de la educación superior. Entre las principales ventajas analizadas, destacamos su gratuidad, el establecimiento de redes de colaboración y la flexibilidad horaria, mientras que entre las desventajas podemos destacar el abandono, que algunos cursos no están adaptados o disponibles para dispositivos fáciles o falta de seguimiento. La idea principal es que una vez que se conocen las ventajas y desventajas de los MOOC, se debe alentar a los primeros, dados los grandes beneficios que conllevan para la educación; y, a su vez, tratar de resolver las desventajas que se han visto que conducen al uso de MOOC, a fin de promover la efectividad de su uso.

Information and communication technologies have revolutionized the world as we knew it before its use and applicability to daily life. This use has also moved to the educational field and has transformed the way it is learned and taught today. In the midst of this panorama, Massive Online Open Courses emerge as an opportunity available for everyone to learn, which has caused many changes in the educational field. This study is presented as an investigation into innovative university practices to analyze the advantages and disadvantages of these MOOCs in the Higher Education environment. Among the main advantages analyzed, we highlight its gratuity, the establishment of collaboration networks and time flexibility, while among the disadvantages we can highlight the abandonment, that some courses are not adapted or available for easy devices or lack of follow-up. The main idea is that once the advantages and disadvantages of MOOCs are known, the former should be encouraged, given the great benefits they entail for education; and in turn try to solve the disadvantages that have been seen that lead to the use of MOOCs, in order to promote the effectiveness of their use.
Análisis crítico del concepto “aprendizaje ubicuo” a través de la Cartografía Conceptual
Authors: Velázquez Gatica Belén , López Martínez Rocío Edith
Published: May 2021

El concepto “aprendizaje ubicuo” se ha criticado por su carácter tecnocéntrico, debido a que enfatiza los aspectos tecnológicos por encima de los educativos. No obstante, una vez que el aprendizaje ubicuo evolucione hacia un concepto educativo, sus aportes podrán alcanzar mayor relevancia y pertinencia en el marco de la ubicuidad y sus aplicaciones en el aprendizaje. Por tal motivo, el objetivo del presente trabajo fue realizar una revisión documental sobre el término aprendizaje ubicuo, para elaborar un análisis crítico que apoye en su desarrollo. Para ello, se utilizó el método de Cartografía Conceptual, a través de un procedimiento en cuatro fases: 1) Búsqueda de documentos pertinentes a la investigación; 2) Definición de criterios de inclusión y exclusión de documentos; 3) Análisis de datos con categorías analíticas (Noción, Caracterización, Categorización, Diferenciación, Clasificación y Vinculación); 4) Interpretación de resultados. El resultado principal sugiere que el aprendizaje ubicuo maduró conceptualmente, debido a la incorporación de dos enfoques: el aprendizaje continuo y el personalizado. No obstante, estos enfoques se basan en ideales del aprendizaje, por lo que es necesario precisar conceptos que apoyen la perspectiva del aprendizaje ubicuo a la hora de establecer prácticas educativas concretas.

The concept of “ubiquitous learning” has been criticized due to its technocentric nature, which emphasizes technological aspects over educational ones. However, once ubiquitous learning evolves into an educational concept, its contributions may become more relevant and pertinent in the context of ubiquity and its applications in learning. For this reason, the objective of this work was to carry out a documentary review on the term ubiquitous learning, to make a critical analysis that supports its development. The Conceptual Cartography method was used, through a four-phase procedure: 1) Search for documents relevant to the research; 2) Definition of inclusion and exclusion criteria for documents; 3) Data analysis with analytical categories (Notion, Characterization, Categorization, Differentiation, Classification and Linkage); 4) Interpretation of results. The main result suggests that ubiquitous learning matured conceptually, due to the incorporation of two approaches: continuous and personalized learning. However, these approaches are based on learning ideals, so it is necessary to specify concepts that support the ubiquitous learning perspective when establishing concrete educational practices.
Compromiso, motivación y persistencia de participantes en xMOOC
Authors: Guajardo-Leal Brenda Edith , Gallardo Córdova Katherina Edith
Published: May 2021

Los cursos masivos y abiertos en línea (MOOC, por sus siglas en inglés Massive, Open Online Courses) se presentan como una modalidad educativa innovadora, económica y de fácil acceso, que ofrece la oportunidad de democratizar la educación en nuestro tiempo. Si bien el interés en estos cursos está en aumento, la tasa de participación de los estudiantes disminuye significativamente a medida que avanzan en las actividades, por lo que la eficiencia terminal suele ser baja. Este estudio cualitativo con diseño de caso múltiple estudió el compromiso, la motivación y la persistencia de los participantes de xMOOC a través del análisis de voces detalladas y descripción profunda de las perspectivas de los participantes, para comprender mejor las formas en las participan de esta modalidad educativa. Los hallazgos revelaron diferencias entre los grupos de alto, medio y bajo rendimiento en las distintas dimensiones del compromiso y persistencia, así como semejanzas en las necesidades psicológicas básicas de competencia, autonomía y relación. Aunque la muestra fue pequeña, fue posible hacer recomendaciones para la toma de medidas específicas con respecto al diseño, la política, la práctica, la teoría y la investigación posterior en cursos en línea masivos y abiertos.

Massive Open Online Courses (MOOC) are presented as an innovative, affordable and easily accessible educational modality, offering the opportunity to democratize education in our time. While interest in these courses is on the rise, the participation rate of students decreases significantly as they progress through activities, so terminal efficiency is often low. This qualitative study with multiple case design studied the engagement, motivation and persistence of xMOOC participants through detailed voice analysis and in-depth description of participants' perspectives, to better understand the ways in which they participate in this educational modality. The findings revealed differences between the high, medium and low performance groups in the different dimensions of engagement and persistence, as well as similarities in the basic psychological needs of competence, autonomy and relationship. Although the sample was considered small, it was possible to make recommendations for specific actions regarding design, policy, practice, theory, and subsequent research in massive open online courses.
Saberes digitales en el profesorado universitario. Estudio en una escuela mexicana.
Authors: Lara Rivera José Alejandro , Cabero Almenara Julio
Published: May 2021

Se presenta una investigación empírica que evalúa los saberes digitales en profesores de educación superior, los datos fueron recopilados en una institución mexicana ubicada en el noroeste del país.  La muestra es probabilística aleatoria simple compuesta por 224 profesores clasificados desde las variables Edad, Grado académico y Género, ya que, se trabajó con el hipotético de que los conocimientos tecnológicos están relacionados con estos factores. Con la finalidad de buscar relación estadística en el agrupamiento de los datos, se realizó un factorial exploratorio por Kaiser-Meyer-Olkin (KMO) y prueba de esfericidad de Bartlett con el método de extracción de componentes principales y rotación varimax. Se aceptaron solo los factores con un autovalor superior a 1 y un peso factorial por ítem superior al 0.40. Posteriormente se realizaron pruebas estadísticas no paramétricas para identificar relaciones desde las variables de cruce.  Los hallazgos dan cuenta de que la Edad de los profesores es un factor diferenciador para la apropiación de saberes digitales.

An empirical research is presented that assesses digital knowledge in higher education teachers, the data was collected in a Mexican institution located in the northwest of the country. The sample is simple random probabilistic composed of 224 teachers classified according to the variables Age, Academic Degree and Gender, since the hypothetical was worked on that technological knowledge is related to these factors. In order to find a statistical relationship in the grouping of data, an exploratory factorial was performed by Kaiser-Meyer-Olkin (KMO) and Bartlett's sphericity test with the principal component extraction method and varimax rotation. Only factors with an eigenvalue greater than 1 and a factorial weight per item greater than 0.40 were accepted. Subsequently, non-parametric statistical tests were performed to identify relationships from the crossover variables. The findings show that the age of the teachers is a differentiating factor for the appropriation of digital knowledge.
IMPROVEMENT OF METHOD FOR PRODUCING CHEMICAL ABSORBER OF AMMONIA AND HYDROGEN SULFIDE
Authors: Tsukanova Anzhelika N. , Farberova Elena A. , Khodyashev Nikolay B. , Kuzʼminykh Konstantin G. , Kazantsev Akeksandr L. , Limonov Nikolay V.
Published: May 2021

The method of obtaining a chemical adsorbent of ammonia and hydrogen sulfide is proposed to be modified to improve sorption characteristics. The dependence of the kinetics of the process was studied - crystallization of solutions of copper (II) sulfate with a concentration of 2.19 mol/dm3 and 2.38 mol/dm3 depending on the method of preparation of the impregnating solution: thermal with heating to a temperature of 80 - 90 °C, using ultrasonic oscillations with a frequency of 22 kHz and an intensity of 3.5 W/cm2, and the dependence of the studied thermal method with the additional introduction of 0.01% surfactants into the solution with nonionic, anionic and cationogenic properties. Crystallization of copper sulfate was performed using a probe video microscopy system. The formation of smaller crystals is observed upon cooling of the solutions subjected to ultrasound. The introduction of surfactants did not affect the size of the crystals of copper (II) sulfate. The dependence of the physicochemical properties of a solution of copper (II) sulfate at a concentration of 1.17 mol/dm3 and 2.26 mol/dm3 on the introduction of 0.01% surfactant and a change in the temperature of the solution was studied. It was found that the introduction of a surfactant can effectively reduce the surface tension of the solution at a temperature of 80 °C and reduce the contact angle of the solution of activated carbon granules. Impregnating solutions of copper (II) sulfate are prepared using the above methods and samples of a chemical adsorbent of ammonia and hydrogen sulfide are made by impregnating granular activated carbon with the obtained solutions. It is proved that the use of surfactants and ultrasonic vibrations during the preparation of an impregnating solution allows to increase the amount of active form of copper on the surface of the carrier during impregnation, which helps to increase the dynamic capacity of chemisorbents.
EFFECT ON DEGREE OF PHOSPHORIC ACID NEUTRALIZATION ON PROPERTIES OF NITRATE-CONTAINING NITROGEN-PHOSPHORUS-POTASSIUM FERTILIZERS
Authors: Kolpakov Viacheslav M. , Norov Andrey M. , Pagaleshkin Denis A. , Fedotov Pavel S. , Kochetova Inna M. , Petropavlovskiy Igor’ A.
Published: May 2021

Основной задачей данной работы является обоснование оптимального технологического режима производства нитроаммофоски с уравновешенным содержанием питательных веществ.  В статье на примере азотно-фосфорно-калийного удобрения марки 17:17:17 представлены результаты исследования зависимости химического и фазового состава, а также структуры и физико-механических характеристик гранулированных образцов от степени нейтрализации промышленной экстракционной фосфорной кислоты аммиаком, выраженной значением мольного отношения [NH3]:[H3PO4]. Приведены методики синтеза, гранулирования и изучения свойств образцов удобрений. Отмечены особенности процесса гранулирования удобрений, полученных с различной степенью нейтрализации: образцы с мольным отношением от 1,0 до 1,2 налипают на стенки гранулятора, образуя крупные агломераты из отдельных гранул; при увеличении мольного отношения более 1,2 и выше наблюдается стабилизация процесса гранулирования, образуются гранулы близкой к сферичной формы; при значениях мольного отношения более 1,6 полученные гранулы начинают интенсивно истираться между собой в тарелке гранулятора. Определены значения статической прочности и среднего диаметра гранул, слеживаемости и коэффициента гигроскопичности образцов удобрений. Предложено объяснение полиэкстремального характера зависимостей свойств удобрений от степени нейтрализации. Выполнен количественный рентгенофазовый анализ кристаллической фазы при различной степени нейтрализации. Описана зависимость изменения фазового состава кристаллической части удобрений при увеличении степени нейтрализации. Показано влияние примесей, вносимых с экстракционной фосфорной кислотой, на коэффициент гигроскопичности удобрений, измельченных до состояния порошка. Представлены микрофотографии сколов гранул. Предложены оптимальные значения мольного отношения [NH3]:[H3PO4] при получении наиболее востребованных удобрений марки 17:17:17.
AN INNOVATE METHOD OF THERMOGRAVIMETRIC DATA ANALYSIS
Authors: Mal’ko Mihail V. , Vasilevich Sergej V. , Mitrofanov Andrey V. , Mizonov Vadim E.
Published: May 2021

The objective of the study is to examine the Coats-Redfern approximation and to propose an innovative kinetic calculation method for the complex process of the heavy tar thermal decomposition under non-isothermal process. The thermal decomposition process was examined using the thermogravimetric analysis. There are several kinetic models proposed to analyze pyrolysis mechanism in terms of the formal reaction. In this manner, the kinetic parameters of the pyrolysis process can be evaluated based on total mass loss (thermogravimetric analysis –TGA). The TGA procedures can be conducted with isothermal or non-isothermal conditions, but the experimental data obtained according to this procedure have to be transformed into appropriate correlation. The obtained results have shown that the reaction takes place within temperature range of 540 K to 700 K and the inductive period of the process is about 224 min. Kinetic parameters were estimated with using of the conventional Coats-Redfern method. A new kinetic calculation method has been designed to provide a less laboriousness of identifications procedures compared with Coats-Redfern approximation and to take into account an induction time of the process. As the outcome of this study, it was shown that the kinetic parameters estimated with using of the proposed model-fitted method gives the more appropriate correlation in comparison with the conventional Coats-Redfern method. The proposed method uses the Coats-Redfern algorithm for evaluation of the reaction mechanism, but the value of the constant rate is defined directly from experimental data on the conversion rate.
ELECTROCHEMICAL SYNTHESIS OF DISPERSED BARIUM FERRITE USING ANODIC DISSOLUTION OF METAL
Authors: Grigoryeva Irina O. , Dresvyannikov Alexander F.
Published: May 2021

The process of anodic dissolution of iron (purity not less than 99%) in aqueous solutions of barium chloride, barium nitrate and binary electrolytes under galvanostatic conditions and by registration of potentiodynamic polarization curves was investigated. The influence of solution composition and concentration and the value of applied direct current on the intensity of anodic oxidation of iron was shown. It was revealed that the oxidation rate of metal in binary electrolytes containing barium chloride and barium nitrate is comparable with the intensity of anodic dissolution in a solution based on barium chloride. It was found that anodic polarization curve in solutions containing BaCl2 and Ba(NO3)2 has a complex form typical of passivated metals. There is a clear maximum of anodic oxidation current on this curve, as well as in barium nitrate solution, however the peak height is much higher (50-150 times). A method for the synthesis of dispersed barium ferrite, based on the anodic oxidation of iron in aqueous barium chloride and barium nitrate solutions with subsequent thermal treatment of the product of electrochemical dissolution was suggested. The phase and elemental composition and structural characteristics of obtained precursor and ferrite samples were examined using X-ray phase analysis. The influence of the heat treatment mode on the phase composition of the synthesized samples is shown. It is found that electrolysis with a soluble iron electrode using direct anode current in 0.05M BaCl2 + 0.5M Ba(NO3)2 solution and subsequent thermal treatment of the dissolution product at 1200 ° C provide the formation of dispersed system, whose phase composition is predominantly Ba0.87Fe11.08O17.15 (74%) and BaFe2O4 (17%).
THERMOGRAVIMETRIC AND KINETIC STUDY OF FUEL PELLETS FROM BIOMASS OF HERACLEUM SOSNOWSKYI MANDEN
Authors: Polina Irina N. , Mironov Mikhail V. , Belyy Vladimir A.
Published: May 2021

The comprehensive study of the process of thermal decomposition of fuel pellets from Heracleum Sosnowskyi biomass was carried out. Kinetic parameters of the process were determined based on thermo-gravimetric analysis in comparison with a sample of wood pellets from coniferous wood. The biomass of heracleum Sosnowskyi was collected in the village of Vylgort, Komi Republic, dried to atmospheric-dry state, ground to mean diameter dm<0.25 mm. The elemental composition, the content of the main components, the value of the thermal effect of the initial plant raw materials are determined. The features of the thermal decomposition of samples are established. Kinetic studies of samples pressed at 10 kN were carried out in air environment at heating rate of 5, 10 and 15 °C/min in the temperature range from 25 to 1000 °C using differential methods of Friedman and Ozawa-Flyn-Wall. Comparative analysis of softwood pellets and fuel pellets of hogweed Sosnowskyi confirmed the possibility of using the latter as an independent energy fuel, and as an additive to pellets without significantly reducing their quality characteristics. The results of the presented studies can be used to develop technology and equipment for burning fuel pellets for the purpose of rational extraction of thermal energy.

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MASS CONDUCTIVITY FOR DRYING NUCLEI AND SEED SUNFLOWER SHELLS
Authors: Rudobashta Stanislav P. , Kochetkov Vadim N. , Zueva Galina A. , Dmitriev Vyacheslav M.
Published: May 2021

The mass-conduction (diffusion) properties of sunflower seeds of the "MAS 95 OL" variety were experimentally investigated. From the experimental drying curves obtained in the intradiffusion kinetic mode at two temperatures of the drying agent (air), the coefficients of mass conductivity (moisture diffusion) were calculated by the zonal method, which are presented as dependences on the moisture content of the core and shell, respectively. It is shown that the coefficients of mass conductivity of nuclei and shells depend on the moisture content of the material and differ significantly both in magnitude and in the nature of the concentration dependences. The coefficient of mass conductivity of nuclei in different areas of moisture content is 15-25 times higher than that of shells, this is explained by differences in the structure of these materials. In the area of moisture content less than 0.5 kg / (kg of dry materiall), both dependences have the same character of concave functions increasing with moisture content, this is a consequence of the same mechanism of mass transfer dominating in this area of moisture content, which is osmotic mass transfer. In seed kernels, the area of moisture content of more than 0.5 kg / (kg of dry material) is absent, but in seed shells it is present and vapor diffusion dominates in it. The data on the coefficient of mass conductivity for seed shells were compared with the coefficient of mass conductivity of another capillary-porous colloidal material with a similar structure - wood. The nature of the concentration dependences for both materials is the same, which is explained by the similarity of the morphological structure of wood and seed shells, which have a tree-like structure. The coefficient of mass conductivity of the seed kernel was compared with the coefficients of mass conductivity of other capillary-porous colloidal materials of plant and animal origin. Comparison showed that they have the same order of mass conductivity coefficient: 10-9 m2/s. This is explained by the identical structure of these materials, which have a cellular structure, and, probably, by the same mechanisms of mass transfer at the corresponding moisture content. The obtained data on the coefficients of mass conductivity of the kernel and shell of sunflower seed can be used for the kinetic calculation of the process of convective drying of this material based on the solution of the differential equations of internal heat and mass transfer A.V. Lykov with the representation of the seed as a two-layer body.
SYNTHESIS OF CHROME TANNING AGENT IN PRESENCE OF OLIGO - AND POLYSACCHARIDES
Authors: Chursin Vyacheslav I. , Zaitseva Alena O.
Published: May 2021

The conditions for the synthesis of chrome tanning agent during the reduction of sodium dichromate with oligo - and polysaccharides have been investigated. The synthesis of the tanning agent is based on the reduction of hexavalent chromium Cr (VI) in the form of sodium dichromate with reducing agents from the class of vegetable oligo- and polysaccharides with a different sequence of their introduction into the reaction mixture in the presence of sulfuric acid. The introduction of sulfuric acid was carried out gradually to avoid overheating and splashing of the reaction mixture, since the reduction reaction is accompanied by a significant thermal effect. Glucose, maltodextrin and pectin were used as reducing agents. The properties of the obtained products were evaluated by spectrophotometry, conductometry, and analytical methods. It has been shown that the use of native pectin leads to the formation of a gel like mass due to the coordination of the functional groups of galacturonic acid, which is part of the pectin, with chromium atoms. Pretreatment of pectin with a citric acid solution and optimization of synthesis conditions made it possible to obtain a chromium tanning agent that does not contain unreduced chromium. The influence of oligosaccharides on the properties of chromium tanning agents, including their ability to dissolve, is considered. It is shown that the reduction of sodium dichromate with maltodextrin during the reaction results in the formation of incomplete oxidation products of the oligosaccharide, which cause the masking effect of the chromium complex and increase in the resistance of the tanning agent to the action of alkaline reagents used to increase in the basicity during tanning. Experimental samples of chrome tanning agent in dry form were obtained and their leatherprocessing characteristics were studied. The results of technological tests have confirmed the theoretical propositions, according to which the high hydrothermal stability of the leather semifinished product, the almost complete depletion of the processing solution and the required physical and mechanical properties of the finished leather are achieved by introducing the products of incomplete oxidation of oligosaccharides into the inner sphere of the chromium complex.
MULTI-OBJECTIVE OPTIMIZATION OF SOLUTION’S COMPOSITION ON THE BASE OF NICKEL COMPLEXES WITH GLYCINE AND SUCCINIC ACID FOR ELECTROLESS DEPOSITION OF Ni-P ALLOY
Authors: Mukhametova Gulnaz M. , Burukhina Tatiana F. , Vasil’ev Vladimir V. , Vinokurov Evgeny G. , Scopintsev Vladimir D.
Published: May 2021

In this paper the effect of parameters such as concentration of glycine, succinic acid and bath pH on the technological parameters of the electroless deposition of nickel-phosphorus alloy coatings (deposition rate, specific pH change during deposition), the composition of the coatings and their properties (microhardness after heat treatment) was studied. Experimental design of 23 central composite design (CCD) was used to evaluate the appearance of coating, rate, specific pH change, the chemical composition of alloys, and microhardness, as well as to optimize the electroless process of the alloy using Response Surface Methodology (RSM) associated with experimental design. The microhardness of the deposited coatings was 4.6 - 6.8 GPa and after heat treatment at 400 °C for 0.5 h increased to 9.7-11.6 GPa, which corresponds to hard chromium coatings obtained by electrodeposition from solutions of chromic acid. The Harrington desirability function was applied for optimization. The optimal composition of bath (in mol/l) and electroless conditions are proposed: NiSO4·6H2O – 0.12, NaH2PO2·H2O– 0.36, NH2CH2COOH – 0.30, (CH2)2(COOH)2 – 0.20, Pb(CH3COO)2 - 10-5; pH – 5.8. Temperature – 70 – 96 ºС. An acceptable rate deposition of 8 (70 ºС) and 34 (95 ºС) mg/(cm2∙h) was observed for an alloy obtained under optimal conditions from an solution of optimal composition. Under these conditions, the coating contained 6 wt.% of phosphorus. Therefore, the results of this work show the importance of using optimization techniques to obtain metallic coatings with controlled properties for different types of applications.
COMPARISON OF L-ASPARAGINE INTERACTIONS WITH PYRIDINE DERIVATIVES, PYRIDOXAL- 5'-PHOSPHATE AND PYRIDOXINE, IN AQUEOUS SOLUTIONS: THERMODYNAMIC ASPECTS
Authors: Tyunina Elena Yu. , Krutova Olga N. , Lytkin Alexandr I.
Published: May 2021

Interactions of proteins with various biologically active substances (hormones, drugs, enzymes, etc.) underlie many biochemical processes in the body. As part of the long-term task to studying various aspects of the interaction between model protein compounds and heterocyclic compounds that are into the structure of many enzymes and drugs, the thermochemical study of aqueous solutions containing aspartic acid amide (L-asparagine) and peridoxal-5¢-phosphate was carried out. Calorimetric measurements of the enthalpy of L-asparagine dissolution in an aqueous solution with pyridoxal-5¢-phosphate additives were performed on an ampoule-type isoperibolic dissolution calorimeter at 298.15 K. The error of measuring single heat effects was below 0.2%. The relative combined uncertainty in the measurements of the enthalpies of dissolution was not more than 0.7%. Based on the obtained experimental data and the using the HEAT computer program, the binding constants and thermodynamic parameters (lgK, ΔcG, ΔcH, ΔcS) of the complex formation between the reagents under study were calculated. A comparison of the affinity of amino acids to interaction with pyridoxal-5¢-phosphate and pyridoxine was carried out. The features of their behavior in an aqueous solution are revealed. It is shown that the interaction of L-asparagine with pyridoxine leads to the formation of a more stable complex than with peridoxal-5¢-phosphate. This fact may be explained in terms of a bulky phosphate group that hinders apparently the interaction of POP with aspartic acid amide. In addition, the peridoxal-5¢-phosphate molecule contains intramolecular hydrogen bonds between aldehyde CHO and phenolic OH groups, which must be destroyed by the interaction of peridoxal-5' - phosphate with an amino acid, which requires additional energy expenses. Thus, the selectivity of the interaction and the stability of the formed complexes are mainly regulated by the factors of structural and energy complementarity.
ANALYSIS OF ENERGY CONSUMPTION OF EXTRACTIVE DISTILLATION FLOWSHEETS OF FOUR-COMPONENT SOLVENT MIXTURE
Authors: Ryzhkin Dmitry A. , Raeva Valentina M.
Published: May 2021

A comparative analysis of energy consumption for extractive distillation flowsheets was carried out. This was done by the example of methanol - ethanol - acetonitrile - mixture. These solvents are used in pharmaceutical industries. The basic system methanol - ethanol - acetonitrile - water contains four binary and one ternary minimum-boiling azeotropes. Pressure change has almost no effect on the location of separatric surfaces. Therefore, extractive distillation should be used to separate solvents mixtures of any composition. Industrial entrainers dimethyl sulfoxide and glycerol are considered as selective agents. The effect of entrainer on vapor-liquid equilibrium at 30 and 101.32 kPa was evaluated by the relative volatility of the components forming azeotropes and the selectivity of the agents. The simulation was carried out on the Aspen Plus V.10.0 program environment. Two extractive distillation flosheets for the methanol - ethanol - acetonitrile - water separation are investigated. Both schemes include a two-column complex for the extractive distillation of the base mixture: in the first column, organic solvents are separated from water, and in the second column, the agent is regenerated. For subsequent separation of acetonitrile, extractive distillation with dimethyl sulfoxide or glycerol is also used. But separation of methanol-ethanol - entrainert zeotropic mixtures differs in the order of separation of components in schemes I and II. In scheme I, regeneration of the agent and further separation of the alcohol mixture is provided, in scheme II, methanol is first isolated, and then ethanol is separated from the agent. The optimized results for both schemes at columns pressures 30 and 101.32 kPa are performed. Different sets of selective agents introduced into extractive distillation columns are considered. The concept of an effective set of entrainers is introduced. The evaluation of the design alternatives need the assessment of energy demands. Total energy consumption for separation (reboiler duty) for the scheme II at 35-38% higher than values for scheme I. On the criterion of the minimum total energy consumption for the separation the scheme I was recommended: pressure columns 30 kPa, effective set of entrainers: glycerol for dehydration of the base mixture and dimethyl sulfoxide for acetonitrile isolation.
EXTRACTION OF RUBBER FROM LATEX BY HYBRID COAGULANT BASED ON POLYDIMETHYLDIALLYLAMMONIUM CHLORIDE AND VISCOSE FIBER
Authors: Nikulina Nadezhda S. , Pugacheva Inna N. , Misin Vyacheslav M. , Verezhnikov Viktor N. , Sannikova Natalia Yu. , Nikulin Sergey S.
Published: May 2021

In the proposed work, the possibility of using a hybrid coagulant based on a polymer cationic electrolyte-VPK – 402 (poly-N,N-dimethyl-N, N-diallylammonium chloride) in combination with viscose fiber in the technological process of separating SKS-30 ark rubber from latex is considered. The influence of the consumption of a hybrid coagulating agent, viscose fiber and its dosage, as well as the process temperature on the reduction of the aggregate stability of styrene-butadiene latex is considered. The influence of viscose fiber on the physical and mechanical properties of vulcanizates is established. At the same time, a number of features were noted consisting in a decrease in the aggregate stability of latex butadiene-styrene rubber during its coagulation with a hybrid coagulant. It was found that the use of a hybrid coagulant can reduce the consumption of cationic polyelectrolyte by up to 30%. It is shown that in the multicomponent system under consideration, several processes can occur simultaneously, which lead to the destabilization of latex dispersions. The use of a hybrid coagulant, including cationic polyelectrolyte, provides a combined effect of the bridging and neutralization mechanisms of violation of the aggregate stability of the dispersion. The presence of viscose fiber in the dispersed phase leads to an additional coagulating effect-adagulation, which is a kind of heterocoagulation. This may be due to the difference in surface potentials between the latex globules and the fiber additive. It is established that the temperature regime of the process of isolation of rubber from latex does not significantly affect the completeness of the extraction of rubber from latex. A decrease in the content of components of the emulsion system in wastewater discharged from the shops producing rubbers by emulsion polymerization was noted. According to the main physical and mechanical parameters, rubbers, rubber mixtures and vulcanizates prepared on their basis meet the requirements.
OXIDATION KINETIC AND ANODIC BEHAVIOR OF Zn22Al ALLOY DOPED WITH NICKEL
Authors: Khakimov Iskandar B. , Rakhimov Firuz A. , Ganiev Izatullo N. , Obidov Ziyodullo R.
Published: May 2021

The article presents the results of the study of the oxidation kinetics and the anodic behavior of the zinc-aluminum alloy Zn22Al, doped with nickel, in various corrosive environments. The kinetic and energy parameters of the process of high-temperature oxidation of alloys are determined. It is shown that the process of high-temperature oxidation of samples of Zn22Al-Ni alloys is characterized by a monotonic decrease in the true oxidation rate and an increase in the effective activation energy at the content of the alloying component in the initial Zn0.5Al alloy up to 0.5 wt.%. It was found that nickel additives within the studied concentration (0.01-0.5 wt.% ) slightly increases the oxidability of the base alloy Zn22Al at temperatures of 523, 573 and 623 K. It is shown that the dependence of the corrosion potential of zinc-aluminum alloys on the nickel content in them is of the same type, i.e. the additives of the alloying component contribute to the displacement of the corrosion potential in the region of positive values. The influence of the aggressiveness of the corrosive medium on the anodic behavior of alloys when comparing concentrated electrolytes with the increasing concentration of chloride ions in the sodium chloride solution is established. It is determined that the potentials of pitting formation and repassivation of the initial alloys shift to a more positive region with an increase in the nickel concentration in the alloys. The greatest shift of these potentials to the positive region is observed when alloying alloys containing small nickel additives. It is shown that the corrosion products of the studied alloys consist of a mixture of protective oxide films Al2O3, ZnO, NiO, Al2O3·ZnO and Al2O3·Ni2O3. It was found that the alloying of zinc-aluminum alloys with nickel (in the range of 0.01–0.05 wt.%) reduces the corrosion rate of the base alloy by 2-3 times. The proposed alloy compositions can be used as an anode coating for corrosion protection of steel products and structures.
DEPENDENCE OF PHYSICAL PROPERTIES OF PIEZOELECTRIC ALUMINUM-SCANDIUM NITRIDE ON SCANDIUM CONCENTRATION
Authors: Zhukov Vladlen V. , Shcherbakov Denis A. , Sorokin Pavel B. , Sorokin Boris P.
Published: May 2021

In this work the physical properties of the piezoelectric aluminum-scandium nitride (ASN) solid solution as a function of scandium concentration were studied using the density functional theory and experimental methods. The phase transition from the wurtzite phase to the rock salt phase at a Sc concentration of 43% was shown. The barriers of transformation from the wurtzite phase to the rock salt phase for various Sc concentrations were obtained. The behavior of the ASN piezoelectric constant d33 calculated by the piezoelectric constants e33, e31, and e15 shows a sharp increase with increasing Sc concentration compared to aluminum nitride AlN. The relationship between the increase in the piezoelectric response of ASN and the softening of the lattice, accompanied by a decrease in the main elastic constants C11, C33, C44 and C66, as well as a decrease in the c/a ratio with increasing Sc concentration, is shown. ASN films with a predominance of the crystal orientation (00·2) were obtained experimentally by magnetron sputtering. The structural properties of the films were studied by X-ray diffraction analysis. A comparison of the experimentally obtained dependence of the c/a ratio on the Sc concentration with the theoretical values showed a good correspondence. Studies of the physical properties of ASN thin films were performed using microwave multi-overtone composite resonators on diamond substrates with a longitudinal bulk acoustic wave (BAW) as the operating mode in the range of 0.5 – 20 GHz. The frequency dependences of the Q-factor of BAW-resonators with different ASN films were obtained, and the frequency dependences of the square of the modulus of the form factor as |m|2 were calculated. The dependences of the elastic constant С33 and the piezoelectric constant e33 for the ASN films with different Sc concentrations were calculated. The calculated and measured values of these constants are agreed within the experimental error.
Ultrasonic Pulse Velocities And Dynamic Elastic Constants Of Sandstones From The Semanggol Formation, Beris Dam, Kedah Darul Aman
Authors: K. Raj John
Published: May 2021

The main Beris Dam is founded on a sequence of thick bedded conglomerates and pebbly to fine grained sandstones with minor mudstone mapped as the Semanggol Formation of Triassic age. Ultrasonic pulse measurements show velocities of compressional and shear waves through the sandstones to increase with decreasing grain size; the pebbly sandstone with velocities of 2.210, and 5.171, km/s, and the coarse grained sandstone with velocities of 2.477, and 5.612, km/s, respectively. The medium grained sandstones have compressional and shear wave velocities of 2.457, and 5.793, km/s and the fine grained sandstones, velocities of 2.572, and 5.867 km/s, respectively. Dynamic elastic constants computed from the ultrasonic velocities also increase in values with decreasing grain size; Poisson’s ratio varying from 0.36 to 0.39, the modulus of elasticity from 35.076 to 48.210 GPa, the bulk modulus from 52.260 to 67.362 GPa and the modulus of rigidity from 12.637 to 17.468 GPa. Increasing velocities and elastic constants with decreasing grain size are considered to result from a denser arrangement of constituent grains as shown by increasing dry unit weights. Comparison with the results of an unconfined compression test on a fine grained sandstone indicate that the ultrasonic elastic constants are good approximations of static elastic constants.