Публикации
Launched in March 2021, the 3U CubeSat nanosatellite was the first ever to use an ultra-lightweight harmonic diffractive lens for Earth remote sensing. We describe the CubeSat platform we used; our 10 mm diameter and 70 mm focal length lens synthesis, design, and manufacturing; a custom 3D-printed camera housing built from a zero-thermal-expansion metal alloy; and the on-Earth image post-processing with a convolutional neural network resulting in images comparable in quality to classical refractive optics used for remote sensing before.
Terahertz (THz, 0.3 − 3 THz) wireless access is nowadays considered as a major enabling technology for sixth generation (6G) cellular systems. To compensate for high prop- agation losses, these systems will utilize antenna arrays with extremely directional beams. The performance of such systems will thus be heavily affected by micromobility such as shakes and rotations of user equipment (UE) even when user is in stationary position. The ultimate impact of micromobility is spontaneous degradation of signal-to-noise (SNR) level leading to outages. In this paper, we measure and statistically investigate the micromobility process of various applications including video viewing, phone calling, virtual reality viewing and racing game. Particularly, we characterize occupancy distributions and first- passage time (FPT) to outage for various antenna configurations. We also assess the radial symmetry in micromobility patterns and characterize distance-dependent velocity and drift to the origin parameters. The obtained results are essential for developing mathematical models of micromobility patterns that needs to be further used in system-level analysis of THz cellular systems. To this end, we also illustrate that Markov models are only suitable for applications with low and purely random micromobility dynamics such as video viewing and phone calling. When a user is controlled by the application, as in the case of gaming, Markov models overestimate FPT to outage.
Проведено компьютерное моделирование глубинного хода поглощенной дозы в зависимости от энергии электронного облучения действующего в диапазоне 30-60 кэВ, и проведены расчеты коэффициента накопления дозы в этих условиях для полиэтилентерефталата, полиметилметакрилата, полистирола и полиэтилена низкой плотности, как модельных полимеров корпусов микроэлектронных устройств. Показано, что значения энергии электронов, соответствующие максимальному коэффициенту накопления дозы, зависят от плотности полимера.
Проведенные исследования позволяют с большой точностью определять проводимость пластиковых корпусов микроэлектронных устройств в условиях электронного облучения, что представляет особый интерес для исключения физической возможности возникновения электростатических разрядов, приводящих к отказам бортовой электроники космических аппаратов.