8 research outputs found
A Mathematician Hussein Ryfky Tamani ibn Muhammad ibn Kyrym Ghazi »
No full textIn this article an attempt is made to open up and make the analysis of the creative work of one of the outstanding scholar-mathematician in the Ottoman Empire at the end of the 18th – beginning of the 19th centuries whose origin was from the Crimean Khanate – Hussein Ryfky Tamani ibn Muhammad ibn Kyrym Ghazi.
At the beginning of the 19th century, during 11 years, the scholar was a leader (bashkhoja) of the Ground forces military-engineering school (Muhendishane-i berry-i Humayun) in Istanbul.
The article provides a review of translations made by Hussein Ryfky into the Ottoman language of European scientists’ works, as well as of his own research works on Geometry, Engineering and Military science, Astronomy, Geography, and other disciplines. The author also presents the textbooks having for centuries become the basic textbooks in the Ottoman Empire for learning exact sciences in the military educational institutions.
The author provides the analysis of the pedagogical and public activity of the scientist during the period of reforms Nizam-i-Jedid, as well as the short description of his activities during the student years.
Hussein Ryfky Tamani made a synthesis of Western and Ottoman approaches to the science. His works became the corner-stone in the foundation of Ottoman Mathematical science at the beginning of the 19th century
Dated Muslim epigraphic monuments of the Solkhat/Kirim city and its environs
No full textPurpose of the study: Identification of patterns and heterogeneities in the chronological distribution of epigraphic monuments. An attempt to correlate dated material with certain events in the life of the medieval city of Solkhat/Kirim. Detection of chronological markers in the typology and design of lapidary monuments, on the basis of which it will be possible to give a chronological reference for monuments without dating.
Research materials: The article contains information about more than a hundred dated epigraphic monuments with Arabic inscriptions found at different times on the territory of the Golden Horde city of Solkhat/Kirim and in its environs. The data was collected on the basis of lapidary material stored in museum and private collections, including 26 monuments that are being introduced into scientific circulation for the first time. The information mentioned in the works of Evliya Celebi, domestic researchers of the 19th to the beginning of the 20th century was taken into account, the studies of O.N. Akchokrakly, diaries and drawings of U. Bodaninsky, and photographic materials of archaeological expeditions of the 1920s.
Research results: The work presents the distribution of dated monuments over the time period from the second half of the 13th century to the last quarter of the 15th century. Also presented are the results of the chronological distribution for some subtypes of grave monuments and the time frame for the use of the Turkic language on the epigraphic monuments of Solkhat/Kirim
Erratum to: Symmetric and Asymmetric Magnetic Tunnel Junctions with Embedded Nanoparticles: Effects of Size Distribution and Temperature on Tunneling Magnetoresistance and Spin Transfer Torque (Scientific Reports, (2017), 7, 1, (8357), 10.1038/s41598-017-08354-7)
No full text© 2018, The Author(s). A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has not been fixed in the paper
Erratum to: Symmetric and Asymmetric Magnetic Tunnel Junctions with Embedded Nanoparticles: Effects of Size Distribution and Temperature on Tunneling Magnetoresistance and Spin Transfer Torque (Scientific Reports, (2017), 7, 1, (8357), 10.1038/s41598-017-08354-7)
No full text© 2018, The Author(s). A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has not been fixed in the paper
Symmetric and Asymmetric Magnetic Tunnel Junctions with Embedded Nanoparticles: Effects of Size Distribution and Temperature on Tunneling Magnetoresistance and Spin Transfer Torque
No full text© 2017 The Author(s). The problem of the ballistic electron tunneling is considered in magnetic tunnel junction with embedded non-magnetic nanoparticles (NP-MTJ), which creates additional conducting middle layer. The strong temperature impact was found in the system with averaged NP diameter d av < 1.8 nm. Temperature simulation is consistent with experimental observations showing the transition between dip and classical dome-like tunneling magnetoresistance (TMR) voltage behaviors. The low temperature approach also predicts step-like TMR and quantized in-plane spin transfer torque (STT) effects. The robust asymmetric STT respond is found due to voltage sign inversion in NP-MTJs with barrier asymmetry. Furthermore, it is shown how size distribution of NPs as well as quantization rules modify the spin-current filtering properties of the nanoparticles in ballistic regime. Different quantization rules for the transverse component of the wave vector are considered to overpass the dimensional threshold (d av ≈ 1.8 nm) between quantum well and bulk-assisted states of the middle layer
Symmetric and Asymmetric Magnetic Tunnel Junctions with Embedded Nanoparticles: Effects of Size Distribution and Temperature on Tunneling Magnetoresistance and Spin Transfer Torque
No full text© 2017 The Author(s). The problem of the ballistic electron tunneling is considered in magnetic tunnel junction with embedded non-magnetic nanoparticles (NP-MTJ), which creates additional conducting middle layer. The strong temperature impact was found in the system with averaged NP diameter d av < 1.8 nm. Temperature simulation is consistent with experimental observations showing the transition between dip and classical dome-like tunneling magnetoresistance (TMR) voltage behaviors. The low temperature approach also predicts step-like TMR and quantized in-plane spin transfer torque (STT) effects. The robust asymmetric STT respond is found due to voltage sign inversion in NP-MTJs with barrier asymmetry. Furthermore, it is shown how size distribution of NPs as well as quantization rules modify the spin-current filtering properties of the nanoparticles in ballistic regime. Different quantization rules for the transverse component of the wave vector are considered to overpass the dimensional threshold (d av ≈ 1.8 nm) between quantum well and bulk-assisted states of the middle layer
Особенности измерения твёрдости металлической поверхности, модифицированной ультрадисперсными частицами минералов
No full textOne of the important characteristics of the surface properties of metal parts subjected to friction is hardness. Hardness measurements are important for determining the operational characteristics of parts and monitoring the technological regimes of surface modification. However, hardness measurements of thin modified layers made by different methods can lead to differences in measurement results. The aim of the article was to study the hardness of a metal surface modified with ultrafine particles of minerals by two different methods (instrumental indentation and Vickers hardness measurement) and a comparative analysis of the measurement results obtained by these methods.Standard Vickers hardness measurements at loads of 0.025, 0.1 and 0.5 kgf showed a qualitative difference between the hardness values of the two samples modified with different mixtures of ultrafine particles of minerals and a large heterogeneity of the hardness values over the area. By the method of instrumental hardness, standard measurements were performed without preliminary selection of the indentation site (at a load of 1.05 N) and measurements during indentation into even sections (at low loads of 10 mN).It is noted that the high precision of measurements implemented by instrumental indentation, due to the large roughness of the samples, leads to large values of the error in calculating the measurement results. An additional difference in the results of measurements performed by two methods at shallow indentation depths may be due to the fact that the object under study has a complex structure consisting of a metal matrix and particles distributed over the depth of the sample. A possible way out of the situation lies in the transition from the use of hardness measures when calibrating instruments to standard samples of properties for which the constancy of mechanical properties in the measured range of indentation depths will be ensured, but which are not yet available in research practice. Therefore, at present, when carrying out work related to the search for optimal conditions for obtaining thin wear-resistant layers on the surface of metals modified with ultrafine particles of minerals, comparative measurements performed by one measurement method are recommended.Одной из важных характеристик свойств поверхности металлических деталей, подвергающихся трению, является твёрдость. Измерения твёрдости важны для определения эксплуатационных характеристик деталей и контроле технологических режимов модификации поверхности. Однако измерения твёрдости тонких модифицированных слоёв, выполненные разными методами, могут приводить к различию результатов измерений. Целью данной работы являлось исследование твёрдости поверхности металла, модифицированной ультрадисперсными частицами минералов, двумя различными методами (инструментального индентирования и измерения твёрдости по Виккерсу) и сравнительный анализ результатов измерений, полученных этими методами.Стандартные измерения твёрдости по Виккерсу при нагрузках 0,025, 0,1 и 0,5 кгс показали качественное отличие значений твёрдости двух образцов, модифицированных разными смесями ультрадисперсных частиц минералов и большую неоднородность значений твёрдости по площади. Методом инструментальной твёрдости выполнены стандартные измерения без предварительного выбора места индентирования (при нагрузке 1,05 Н) и измерения при индентировании в ровные участки (при малых нагрузках 10 мН).Отмечено, что высокая прецизионность измерений, реализуемая методом инструментального индентирования, из-за большой шероховатости образцов приводит к большим значениям погрешности при расчёте результатов измерений. Дополнительную разницу результатов измерений, выполненных двумя методами на малых глубинах индентирования, может вносить то, что исследуемый объект имеет сложную структуру, состоящую из матрицы металла и частиц, распределённых по глубине образца. Возможный выход из ситуации заключается в переходе от использования мер твёрдости при калибровке приборов к стандартным образцам свойств, для которых будет обеспечено постоянство механических свойств в измеряемом диапазоне глубин индентирования, но которые пока отсутствуют в исследовательской практике. Поэтому в настоящее время при проведении работ, связанных с поиском оптимальных условий получения тонких износостойких слоёв на поверхности металлов, модифицированных ультрадисперсными частицами минералов, рекомендуются сравнительные измерения, выполненные одним методом измерения
Исследование износостойкости поверхности алюминиевого сплава, модифицированного минералами, методом склерометрии
No full textImproving the wear resistance of the surface of metal parts used in various industries is one of the relevant areas of materials science. The aim of this work was a comparative study of the wear resistance of a sample of an aluminum alloy (EN AW-2024, an aluminum alloy of the Al-Cu-Mg system) modified with ultrafine particles of minerals using the sclerometry method, which makes it possible to measure the physicomechanical properties of the material at the microscale, as well as determining some tribological parameters (hardness and elastic modulus) of a duralumin sample with a mineral coating.Wear resistance was measured using a NanoScan-4D scanning hardness tester using the multi-cycle friction method using a sapphire sphere with control of the pressing force and the deepening of the tip into the sample. The use of such a measurement system is especially important when testing thin modified layers, when the layer thickness is comparable with the surface roughness parameters and the influence of the substrate is excluded.The measurement results showed that the wear resistance of the surface of an aluminum alloy sample modified with ultrafine mineral particles increased by more than 12 times compared to the wear resistance of an aluminum alloy surface without modification. Also, measurements of the hardness and elastic modulus of the surface of the modified sample were performed taking into account the features of measuring the mechanical parameters of thin layers.The obtained parameters of the modified surface of the aluminum alloy can be further used to build models of the processes of friction and wear of the surface modified by ultrafine particles of minerals. The lack of an acceptable explanation of the nature of the special properties of the surface modified by particles of minerals of natural origin does not exclude the use of the observed effects to significantly increase the resource of various parts and mechanisms.Повышение износостойкости поверхности металлических деталей, используемых в различных отраслях промышленности, является одним из актуальных направлений материаловедения. Целью данной работы являлось сравнительное исследование износостойкости образца из алюминиевого сплава (EN AW-2024, алюминиевый сплав системы Al-Cu-Mg), модифицированного ультрадисперсными частицами минералов с использованием метода склерометрии, позволяющего измерить физикомеханические свойства материала в микромасштабе, а также определение некоторых трибологических параметров (твердости и модуля упругости) образца из дюралюминия с минеральным покрытием.Измерение износостойкости было выполнено с помощью сканирующего твердомера «НаноСкан4D» методом многоциклового трения сапфировой сферой с контролем силы прижима и углубления наконечника в образец. Использование такой системы измерения особенно важно при испытании тонких модифицированных слоев, когда толщина слоя сопоставима с параметрами шероховатости поверхности и исключено влияние подложки.Результаты измерений показали, что износостойкость поверхности образца из алюминиевого сплава, модифицированной ультрадисперсными частицами минералов, увеличилась более чем 12 раз по сравнению с износостойкостью поверхности из алюминиевого сплава без модификации. Также выполнены измерения твердости и модуля упругости поверхности модифицированного образца с учетом особенностей измерения механических параметров тонких слоев.Полученные параметры модифицированной поверхности алюминиевого сплава могут быть в дальнейшем использованы для построения моделей процессов трения и износа поверхности, модифицированной ультрадисперсными частицами минералов. Отсутствие в настоящее время приемлемого объяснения природы особых свойств поверхности, модифицированной частицами минералов природного происхождения, не исключает использования наблюдаемых эффектов для значительного повышения ресурса различных деталей и механизмов
