Toward a Cultural Framework of Internet Governance: Russia’s Great Power Identity and the Quest for a Multipolar Digital Order

CARGC Paper 13, “Toward a Cultural Framework of Internet Governance: Russia’s Great Power Identity and the Quest for a Multipolar Digital Order,” by CARGC Postdoctoral Fellow Stanislav Budnitsky was initially delivered as a CARGC Colloquium in 2018. As part of Budnitsky’s larger research project on the relationship between nationalism and global internet governance, CARGC Paper 13 considers the cultural logics underlying Russia’s global internet governance agenda. It argues that to understand Russia’s digital vision in the early twenty-first century and, by extension, the dynamics of global internet politics writ large, scholars must incorporate Russia’s historic self-identification as a great power into their analyses.https://repository.upenn.edu/cargc_papers/1013/thumbnail.jp

Электрохимическое полирование матричных стентов из стали 316LVM с использованием микросекундных импульсов

With the development of minimally invasive treatment technology, coronary stents made of corrosion-resistant steel are in demand for restoring the patency of blood vessels. The effectiveness of coronary stenting depends on various factors, but the quality of the surface of the stents is a major factor. The higher the quality of the surface of the stent is, the less negative the effect on the circulatory system, arterial walls, and the higher the biocompatibility of the stent is. The complex shape, small cross-section, size, and low rigidity of coronary stents are the main reasons for the inability to ensure high surface quality using mechanical finishing methods. Therefore, electrochemical methods are used to polish stents. For electrochemical polishing (ECP) of stents, an electric mode based on direct current is traditionally used. The disadvantages of direct current ECP are excessive metal removal and the need to use electrolytes of complex compositions, often containing toxic components. As an alternative to the traditional ECP with the use of direct current, we have proposed a method of pulsed ECP using pulses of microsecond duration for polishing stents. The use of pulsed current allows one to achieve a significant increase in the efficiency of the SEC process, when, due to the localization of the anodic dissolution, the smoothing speed of the microroughness of the treated surface, referred to the total metal removal, increases significantly. The paper presents a comparative analysis of ECP modes using direct and pulse current to change the surface roughness, removal, radius of curvature of the edges, and corrosion resistance on the example of stents made of the 316LVM stainless steel. Based on the results of the studies, technological regimes of pulsed ECP were established that provide the highest quality polishing of the stent surface with a small metal removal with a slight rounding of the edges.С развитием технологии малоинвазивного лечения коронарные стенты из коррозионностойких сталей получили широкое распространение при восстановлении проходимости кровеносных сосудов. Эффективность стентирования коронарных сосудов зависит от различных факторов, однако основным фактором является качество поверхности стентов. Чем выше качество поверхности стента, тем меньше негативное влияние оказывается на кровеносную систему, стенки артерий и тем выше биологическая совместимость стента. Сложная форма, малое сечение, размеры и низкая жесткость коронарных стентов являются основными причинами невозможности обеспечения высокого качества поверхности с использованием механических способов финишной обработки. Поэтому для полирования стентов применяются электрохимические методы. Для электрохимического полирования (ЭХП) стентов традиционно используется электрический режим, основанный на постоянном токе. Недостатками ЭХП на постоянном токе являются чрезмерный съем металла и необходимость использования электролитов сложных составов, часто содержащих токсичные компоненты. В качестве альтернативы традиционному ЭХП с применением постоянного тока нами для полирования стентов предложен метод импульсного ЭХП с использованием импульсов микросекундной длительности. Применение импульсного тока позволяет добиться существенного повышения эффективности процесса ЭХП, когда за счет локализации анодного растворения скорость сглаживания микронеровностей обрабатываемой поверхности, отнесенная к общему съему металла, значительно возрастает. Представлен сравнительный анализ режимов ЭХП с применением постоянного и импульсного тока на изменение шероховатости поверхности, съема, радиуса закругления кромок и коррозионной стойкости на примере стентов из коррозионностойкой стали 316LVM. По результатам выполненных исследований установлены технологические режимы импульсного ЭХП, обеспечивающие наиболее качественное полирование поверхности стентов при малом съеме металла с незначительным скруглением кромок

Chromium-Compensated GaAs Detector Material and Sensors

Results obtained from numerical calculations of and experimental studies on the pulse height distribution inherent in ionizing radiation gallium arsenide sensors as a function of the design features of the devices and electrophysical characteristics of the detector material are presented. It is shown that the pulse height distribution is defined by the distribution pattern of the nonequilibrium charge carrier lifetime and by the electric field profile in the bulk of the sensor. Investigations on the detector sensitivity to X-ray energies in the range between 40 and 150 keV were performed. The sensor polarization was found to produce only a marginal effect compensated by an increase in the bias voltage. Prototype pixel sensors measuring 256 × 256 and 512 × 768 pixels with a 55 μm pitch and a 500 μm thick sensitive layer were produced. The dependence of the photocurrent and count rate on the X-ray radiation intensity and bias voltage applied to the sensor was examined. In the 40–80 keV energy range, the maximum count rate amounted to 800 kHz/pixel for a negative sensor bias voltage of 800 V. The sensors are demonstrated to provide spatial resolution varying with the pixel pitch and to enable high-quality X-ray images to be obtained

Characterization of 4 inch GaAs:Cr wafers

Producing of large area matrix detectors based on semiconductor materials with high atomic number suitable for the registration of the synchrotron radiation of high intensity in the photon energy range 20–90 keV is a relevant technological challenge of our time. This will develop a fundamentally new experimental base of scientific research conducted at leading X-ray synchrotron centers with high luminosity beams. The paper analyzes the possibility of using 4 inch gallium arsenide wafers to create a high-resistive GaAs:Cr detector quality structures on their basis and detector arrays of large area

Characterization of 4 inch GaAs:Cr wafers

Producing of large area matrix detectors based on semiconductor materials with high atomic number suitable for the registration of the synchrotron radiation of high intensity in the photon energy range 20–90 keV is a relevant technological challenge of our time. This will develop a fundamentally new experimental base of scientific research conducted at leading X-ray synchrotron centers with high luminosity beams. The paper analyzes the possibility of using 4 inch gallium arsenide wafers to create a high-resistive GaAs:Cr detector quality structures on their basis and detector arrays of large area

GaAs structures for X-ray imaging detectors

A comparative analysis of characteristics of detector structures fabricated by means of technology of epitaxial growth of an undoped high-resistive GaAs layer as well as structures based on SI-GaAs compensated with Cr during a diffusion process is presented in this work. Advantages and disadvantages of the proposed methods of formation of high- resistive layers, their electrophysical characteristics and properties are examined. Limit parameters of the detector structures which can be achieved by using a combination of technological methods are analyzed