Feed aggregator

Abstract

The spherical radial basis function (SRBF) approach, widely used in gravity modeling, is theoretically surveyed from a viewpoint of random field theory. Let the gravity potential be a random field which is represented as an integral functional of another random field, namely an isotropic Gaussian random field (IGRF) on a sphere inside the Bjerhammar sphere with the SRBF as the integral kernel. When the integration is approximated by a discrete sum within a local region, one gets the widely applicable SRBF model. With this theoretical study, the following two findings are made. First, the IGRF implies a Gaussian prior on the spherical harmonic coefficients (SHCs) of the gravity potential; for this prior the SHCs are independent with each other and their variances are degree-only dependent. This should be reminiscent of two well-known priors, namely the power-law Kaula’s rule and the asymptotic power-law Tscherning-Rapp model. Second, the IGRF-SRBF representation is non-unique. Benefiting from this redundant representation, one can employ a simple IGRF, e.g., the simplest white field, and then design the SRBF accordingly to represent a potential with desired prior statistical properties. This can simplify the corresponding SRBF modeling significantly; to be more specific, the regularization matrix in parameter estimation of the SRBF modeling can be chosen to be a diagonal matrix, or even the naïve identity matrix.

Abstract

In recent years, coseismic velocity from high-rate global navigation satellite systems (GNSS) carrier phase data has been widely utilized to estimate instrumental seismic intensity, thereby guiding earthquake early warning and emergency response. However, using carrier phase data only yields displacement, displacement increment, and average velocity but not instantaneous velocity at the epoch level. In large earthquakes, using average velocity over a brief time span (e.g., 1 s) to quantify instantaneous coseismic velocity is less reliable for recovering accurate deformation dynamics, especially for the near-field region. In this study, we first introduce GNSS raw Doppler-based instantaneous velocity into seismology, expanding carrier phase-based traditional GNSS seismology. We also propose a new integrated GNSS velocity estimation method that employs a Kalman filter to integrate raw Doppler-based instantaneous velocity and carrier phase-based average velocity. The GNSS data from shake table experiments and two real-world earthquake events (i.e., the 2016 Mw 6.6 Norcia earthquake and the 2011 Mw 9.1 Tohoku-oki earthquake) are used to investigate the impact of high-rate GNSS raw Doppler on capturing coseismic velocity waveforms and predicting instrumental seismic intensity. The simulated sine wave experiment results indicate that the accuracy of instantaneous and average velocity for the 1 Hz sampling rate case is 1.20 cm/s and 12.67 cm/s, respectively. A similar case holds for the simulated quake wave experiment. The retrospective analysis of the ultra-high-rate (20 Hz) GNSS data for the Norcia earthquake shows the average velocities exhibit more aliasing and have a smaller peak ground velocity value than instantaneous velocities in all cases (i.e., 1, 2, 4, 5, 10, and 20 Hz). For the 2011 Mw 9.1 Tohoku-oki earthquake, results show that incorporating raw Doppler data enhances the consistency between the GNSS intensity map and the United States Geological Survey intensity map for near-field regions. Therefore, high-rate GNSS RD data as it becomes more widely available should be incorporated into data processing of high-rate GNSS seismology to capture more accurate instantaneous coseismic velocity waveforms and predict more realistic instrumental seismic intensity in future analyses.

Abstract

Global Navigation Satellite Systems (GNSS) applications require computation of the geometric range between the satellite vehicle at the time-of-signal transmission and the receiver antenna location at the time-of-signal reception. This computation requires attention to the frames of reference due to the rotation of the Earth-Centered Earth-Fixed (ECEF) frame during the time-of-signal propagation. Three range computation approaches are commonplace and will be discussed herein. The first is the Global Positioning System Interface Control Document recommendation to rotate the ECEF frames to a common reference time. The other two are forms of the Sagnac correction. The Sagnac derivations already in the literature are either limited to stationary receivers or lack the connection between the Earth-centered inertial (ECI) and ECEF frames. Neither form of the Sagnac correction exactly reproduces the geometric range. They are approximations. The literature does not currently contain an analysis of the error involved in using either form of the Sagnac correction. This article makes two contributions: (1) it presents derivations for both forms of the Sagnac correction that are valid for moving receivers and that maintain the connection between the ECI and ECEF frames; and (2) it analyzes the error of the Sagnac correction for orbits of different radius. The analysis shows that Sagnac corrections introduce range errors less than \(7.57\times 10^{-4}\) meters for GNSS satellites at medium Earth orbit.

Author(s): Gusten Isfeldt, Fredrik Lundell, and Jakob Wohlert

Motivated by the limitations of conventional coarse-grained molecular dynamics for simulation of large systems of nanoparticles and the challenges in efficiently representing general pair potentials for rigid bodies, we present a method for approximating general rigid body pair potentials based on a…

[Phys. Rev. E 110, 055305] Published Tue Nov 12, 2024

Abstract

We provide an overview of the isotopic signatures of presolar supernova grains, specifically focusing on 44Ti-containing grains with robustly inferred supernova origins and their implications for nucleosynthesis and mixing mechanisms in supernovae. Recent technique advancements have enabled the differentiation between radiogenic (from 44Ti decay) and nonradiogenic 44Ca excesses in presolar grains, made possible by enhanced spatial resolution of Ca-Ti isotope analyses with the Cameca NanoSIMS (Nano-scale Secondary Ion Mass Spectrometer) instrument. Within the context of presolar supernova grain data, we discuss (i) the production of 44Ti in supernovae and the impact of interstellar medium heterogeneities on the galactic chemical evolution of 44Ca/40Ca, (ii) the nucleosynthesis processes of neutron bursts and explosive H-burning in Type II supernovae, and (iii) challenges in identifying the progenitor supernovae for 54Cr-rich presolar nanospinel grains. Drawing on constraints and insights derived from presolar supernova grain data, we also provide an overview of our current understanding of the roles played by various supernova types – including Type II, Type Ia, and electron capture supernovae – in accounting for the diverse array of nucleosynthetic isotopic variations identified in bulk meteorites and meteoritic components. We briefly overview the potential mechanisms that have been proposed to explain these nucleosynthetic variations by describing the transport and distribution of presolar dust carriers in the protoplanetary disk. We highlight existing controversies in the interpretation of presolar grain data and meteoritic nucleosynthetic isotopic variations, while also outlining potential directions for future research.

16 ноября 2023 г. в актовом зале Института спектроскопии Российской академии наук (ИСАН) (ул. Физическая 5, Троицк, г. Москва) состоялись научная сессия Отделения физических наук Российской академии наук (ОФН РАН) и юбилейный семинар ИСАН, посвящённые 55-летию создания ИСАН. Повестка заседания содержала следующие доклады:

1. Мелентьев П.Н. (ИСАН, Троицк,  Москва) Оптическое одномолекулярное секвенирование молекул ДНК: физические основы, фундаментальные и технические ограничения, экспериментальная реализация.
2. Афанасьев А.Е. (ИСАН, Троицк, г. Москва) Атомный чип как источник атомов для квантовой сенсорики.
3. Карташов Я.В. (ИСАН, Троицк, г. Москва) Солитоны в топологических волноводных структурах.
4. Попова М.Н., Болдырев К.Н. (ИСАН, Троицк, г. Москва) Спектроскопия высокого разрешения функциональных материалов.
5. Ерёмчев И.Ю., Наумов А.В. (ИСАН, Троицк, г. Москва) Флуоресцентная спектромикроскопия одиночных квантовых излучателей.
6. Медведев В.В. (ИСАН, Троицк, г. Москва) Источники коротковолнового излучения на основе лазерной плазмы.
7. Колачевский Н.Н. (Физический институт им. П.Н. Лебедева РАН (ФИАН), г. Москва) Квантовые вычисления на оптических кудитах.
8. Розанов Н.Н. (Физико-технический институт (ФТИ) им. А.Ф. Иоффе РАН, г. Санкт-Петербург) К предельно коротким униполярным и электромагнитным импульсам.
9. Кулик С.П. (Московский государственный университет им. М.В. Ломоносова, г.  Москва) Квантовые технологии в Московском университете.
10. Никитов С.А., Кошелец В.П. (Институт радиоэлектроники (ИРЭ) РАН, г. Москва) Сверхпроводниковая электроника для приёма и обработки информации.
11. Калачёв А.А. (Казанский физико-технический институт им. Е.К. Завойского Казанского научного центра РАН, г. Казань) Источники света для квантовых повторителей.
12. Драчёв В.П. (Сколковский институт науки и технологии (Сколтех), г. Москва) Плазмонные структуры в кремниевой интегральной фотонике.

Обзоры и статьи, написанные на основе докладов 1—4, 7, 8, 10 и 12, публикуются далее в этом специальном номере журнала "Успехи физических наук" (УФН), посвящённом 55-летию ИСАН.

Author(s): K. D. Meaney, Y. Kim, N. M. Hoffman, Z. L. Mohamed, W. T. Taitano, H. W. Herrmann, H. Geppert-Kleinrath, M. P. Springstead, A. B. Zylstra, A. Leatherland, L. Wilson, V. Yu. Glebov, and C. Forrest

Diffusion-dominated mix in inertial confinement fusion (ICF) is characterized where the majority of the mix occurs in the immediate fuel-shell interface while hydrodynamic-dominated mix pulls shell material from farther away into the central fuel. A thin (150 nm) separated reactants ICF mix platform…

[Phys. Rev. E 110, 055203] Published Fri Nov 08, 2024

Abstract

Strong gravitational lensing at the galaxy scale is a valuable tool for various applications in astrophysics and cosmology. Some of the primary uses of galaxy-scale lensing are to study elliptical galaxies’ mass structure and evolution, constrain the stellar initial mass function, and measure cosmological parameters. Since the discovery of the first galaxy-scale lens in the 1980s, this field has made significant advancements in data quality and modeling techniques. In this review, we describe the most common methods for modeling lensing observables, especially imaging data, as they are the most accessible and informative source of lensing observables. We then summarize the primary findings from the literature on the astrophysical and cosmological applications of galaxy-scale lenses. We also discuss the current limitations of the data and methodologies and provide an outlook on the expected improvements in both areas in the near future.

Л.М. Зелёный, Е.Ю. Кильпио

Основой для данной статьи послужил одноимённый доклад, сделанный академиком Л.М. Зелёным на научной сессии Общего собрания Отделения физических наук РАН "300-летие Академии: успехи и достижения физических наук в ХХI веке" в мае 2024 года. Информация, представленная в докладе, была дополнена и расширена, но, несмотря на это, в рамках одной статьи оказалось более чем сложно описать всё, что было сделано за прошедшую четверть века в такой достаточно непростой области, как астрономия и науки о космосе, перечислить все достижения и всех наших учёных, благодаря которым эти достижения были получены. Однако мы надеемся, что на основе представленной выборки читатели смогут составить общее представление о значимости многих ярких академических исследований, выполнявшихся в России в достаточно непростой для науки период, и оценить масштабы её достижений. Под академическими мы понимаем ниже исследования, ведущиеся в институтах РАН, ведущих вузах и университетах и других организациях, находящихся под научно-методическим руководством РАН.

В.А. Матвеев

Настоящий обзор написан на основе доклада, сделанного 27 мая 2024 года на Научной сессии Общего собрания Отделения физических наук Российской академии наук (ОФН РАН) "300-летие Академии: успехи и достижения физических наук в ХХI веке". Доклад был посвящён важнейшим достижениям исследований в области фундаментальной ядерной физики за последние 25—30 лет и перспективам их дальнейшего развития. Основное внимание уделяется вкладу учёных и специалистов нашей страны в общемировые достижения последних десятилетий в исследовании фундаментальных проблем ядерной физики, включая физику элементарных частиц и физику высоких энергий, релятивистскую ядерную физику и физику тяжёлых ионов, физику нейтрино и нейтринную астрофизику, физику космических лучей ультравысоких энергий. И, конечно, нельзя не сказать о достижениях отечественных учёных в области теоретической физики и космологии, в значительной степени определяющих успехи в исследовании фундаментальных свойств материи. Кратко представлен вклад учёных и специалистов России в реализацию крупных международных проектов, в значительной степени определивших их достижения последних десятилетий, в частности открытие бозона Хиггса. Представлен краткий обзор нынешнего состояния и проектов развития исследовательской инфраструктуры отечественных научных организаций. Указывается на важную роль, которую играет развитие и совершенствование ускорительной науки и техники в исследовании фундаментальных проблем ядерной физики. Особое внимание уделено разработке и реализации на территории России крупных ядерно-физических проектов мегасайенс-класса, а также намечающимся сдвигам в стратегии развития фундаментальных физических исследований и опирающемуся на их достижения развитию инновационных технологий в интересах экономики, образования и здравоохранения.

И.А. Щербаков

Основой настоящей работы является мой доклад на научной сессии, состоявшейся 27 мая 2024 г. в рамках Общего собрания Отделения физических наук РАН. Представленные результаты касаются таких научных направлений, как физика конденсированного состояния и физическое материаловедение, оптика, лазерная физика и лазерные технологии, физика плазмы, физическая электроника, радиофизика и акустика. Эти направления активно развивались в последние десятилетия и не утратили своей актуальности и сегодня.

27 мая 2024 г. в Институте физических проблем (ИФП) им. П.Л. Капицы РАН состоялось Общее собрание и Научная сессия Отделения физических наук (ОФН) Российской академии наук (РАН).
Повестка Общего собрания и Научной сессии содержала следующие доклады и выступления:

• вступительное слово академика-секретаря ОФН РАН академика РАН В.В. Кведера;
• доклад "О деятельности Отделения физических наук РАН в 2023 году" (докладчик — академик-секретарь ОФН РАН академик РАН В.В. Кведер);
• доклад "О научно-организационной деятельности Отделения физических наук РАН в 2023 году" (докладчик — д.ф.-м.н. Н.Л. Истомина).

На Общем собрании прошло вручение государственных наград членам ОФН РАН и премий имени выдающихся учёных РАН.
Научная сессия Общего собрания ОФН РАН "300-летие Академии: успехи и достижения физических наук в ХХI веке" включала следующие доклады:

1. Щербаков И.А. (Институт общей физики им. А.М. Прохорова РАН, Москва, Российская Федерация). О некоторых результатах, полученных в институтах ОФН РАН за последние 25 лет.
2. Матвеев В.А. (Институт ядерных исследований РАН, Москва, Российская Федерация; Объединённый институт ядерных исследований, Дубна, Московская обл., Российская Федерация). Важнейшие достижения исследований фундаментальных проблем ядерной физики за последние 25 лет и их дальнейшие перспективы.
3. Зелёный Л.М. (Институт космических исследований РАН, Москва, Российская Федерация). ОФН РАН в XXI веке: космос и астрофизика.

Статьи, написанные на основе докладов 1, 2 и 3 на Научной сессии ОФН РАН, публикуются далее в этом номере журнала Успехи физических наук (УФН).

Author(s): Y. Ohno, A. Del Maestro, and T. I. Lakoba

We develop convergence acceleration procedures that enable a gradient descent-type iteration method to efficiently simulate Hartree-Fock equations for many particles interacting both with each other and with an external potential. Our development focuses on three aspects: (i) optimization of a param…

[Phys. Rev. E 110, 055304] Published Wed Nov 06, 2024

Abstract

The Juno spacecraft completed 35 successful orbits around Jupiter from orbit insertion in 2016 through the end of its prime mission phase in 2021. The Advanced Stellar Compass (ASC) and associated Camera Head Units (CHUs) comprise a dedicated attitude sensing system of the Magnetic Field Investigation (MAG), one of Juno’s scientific payloads. The CHU is a CCD-based camera and is inherently susceptible to ionizing radiation. An energetic charged particle penetrating the camera head electronics shielding will deposit its energy and liberate charges in the charge wells. These events will register as isolated bright pixels in the integrated star tracker source images, and are distinguishable from optical sources that illuminate a number of collocated pixels spanning the imager’s point spread function. By simply counting the number of such isolated bright pixels, an estimate of the number of charged particles penetrating the CCD can be established, eventually constraining the local external omnidirectional radiation flux (omniflux). The ASC performs the bright pixel count onboard and includes this count rate with the attitude telemetry, providing an energetic particle omniflux measurement at high time resolution. We describe here this additional functional capability of the ASC, including the filtering required to isolate the unbiased attitude cycles, the calibration required to circumvent count statistics effects, and the calibration of the sensor sensitivity, as well as the attenuation efficacy of the sensor shielding mass. Finally, we discuss the potential of the omniflux product for radiation field mapping as well as a proxy for investigating physical phenomena otherwise unattainable.

Abstract

As climate change continues, the likelihood of passing critical thresholds or tipping points increases. Hence, there is a need to advance the science for detecting such thresholds. In this paper, we assess the needs and opportunities for Earth Observation (EO, here understood to refer to satellite observations) to inform society in responding to the risks associated with ten potential large-scale ocean tipping elements: Atlantic Meridional Overturning Circulation; Atlantic Subpolar Gyre; Beaufort Gyre; Arctic halocline; Kuroshio Large Meander; deoxygenation; phytoplankton; zooplankton; higher level ecosystems (including fisheries); and marine biodiversity. We review current scientific understanding and identify specific EO and related modelling needs for each of these tipping elements. We draw out some generic points that apply across several of the elements. These common points include the importance of maintaining long-term, consistent time series; the need to combine EO data consistently with in situ data types (including subsurface), for example through data assimilation; and the need to reduce or work with current mismatches in resolution (in both directions) between climate models and EO datasets. Our analysis shows that developing EO, modelling and prediction systems together, with understanding of the strengths and limitations of each, provides many promising paths towards monitoring and early warning systems for tipping, and towards the development of the next generation of climate models.

Author(s): Q. Cauvet, B. Bernecker, and B. Canaud

The nonlinear evolution of bubble and spike fronts growing through the generalized Rayleigh-Taylor instability are studied by numerical simulations and by solving an extension of Alon's [Phys. Rev. E 48, 1008 (1993)] statistical model based on the asymptotic velocity of a single-mode bubble and the …

[Phys. Rev. E 110, 055201] Published Tue Nov 05, 2024

Author(s): J. Griff-McMahon, V. Valenzuela-Villaseca, S. Malko, G. Fiksel, M. J. Rosenberg, D. B. Schaeffer, and W. Fox

Proton radiography is a central diagnostic technique for measuring electromagnetic (EM) fields in high-energy-density, laser-produced plasmas. In this technique, protons traverse the plasma where they accumulate small EM deflections which lead to variations in the proton fluence pattern on a detecto…

[Phys. Rev. E 110, 055202] Published Tue Nov 05, 2024

Author(s): K. Uzawa and K. Hagino

The authors present a “shift-invert Lanczos” method that helps significantly reducing the computational cost of solving transport with a non-equilibrium Green’s function theory. They show examples of application in the case of a model Hamiltonian and a more realistic one used to describe nuclear fission.

[Phys. Rev. E 110, 055302] Published Mon Nov 04, 2024

Author(s): Amin Rahmat, Berk Altunkeyik, Mostafa Safdari Shadloo, and Tom Montenegro-Johnson

In this paper, we introduce a computational technique for modeling heterogeneous thermoresponsive hydrogels. The model resolves local fluid-solid interactions in hydrogel pores during the deswelling process. The model is a Lagrangian particle-based technique, which benefits from computational grids …

[Phys. Rev. E 110, 055303] Published Mon Nov 04, 2024

Abstract

Lunar rover operations present unique specificities compared to other spacecraft operations. Preparing for the 14-day surface exploration phase of the Rashid-1 rover mission required developing new concepts, designs and tools to enable the mission goals and maximize its scientific return. The Emirates Lunar Rover was set to demonstrate enabling scientific capabilities on the lunar surface by hosting scientific payloads on a small 10 kg platform. It possesses mobility and other operational capabilities to provide science teams with varied sampling, imaging, and sensing opportunities. The operation of the rover systems and the science payloads was to be performed in tandem within the Mohammed bin Rashid Space Centre mission control centre for rapid decision-making and maximizing lunar surface exploration around the landing site during the short mission duration. This paper focuses on the operational design and the mission rehearsals performed by the Emirates Lunar Rover team in preparation of the lunar landing. With the goal of maximizing the science outcome of the mission, we show how the operations processes were continuously improved against the issues and challenges encountered during the training process and long duration rehearsals performed as preparation for the actual operations. This paper discusses these processes and provides analysis, down to the command and telemetry level, on the performance of the operations team to share lessons learned to improve future lunar rover operations