Orbital States Research Articles

Transformation behavior and toxicity assessment of beaytlmethodeyammonNium chbride (BAC-12) disinfectant during hospital wastewater treatment.

This work focused on the transformation behavior of the emerging beaytlmethodeyammonium chbride (BAC-12) disinfectant existed in the treatment of medical sewage during its disinfection treatment. The degradation ability of ozone (O3) to BAC-12 was the best, followed by UV/NaOCl, UV, and NaOCl. The enhancement of BAC-12 in UV/NaOCl system is caused by the combined effect of UV photolysis, reactive chlorine species (RCS), and •OH. The transformation products of BAC-12 in the disinfection treatment were detected, and the chemical structure of products was rationalized by frontier molecular orbital and transition state theory methodologies. According to the ecological structure-activity relationship (ECOSAR) assessment, the intermediates of BAC-12 in UV, NaOCl, and UV/NaOCl treatments had lower half lethal concentration (LC50) and chronic toxicity (ChV) values with a higher ecotoxicity than BAC-12. O3 disinfection treatment of these toxic intermediates can significantly reduce the toxicity of the BAC-12 solution. This work provides necessary information on the potential environmental risks of BAC-12 arising from different disinfection methods in the treatment of medical wastewater.

An Integrity Monitoring Method for Navigation Satellites Based on Multi-Source Observation Links

The BeiDou-3 navigation satellite system (BDS-3) has officially provided positioning, navigation, and timing (PNT) services to global users since 31 July 2020. With the application of inter-satellite link technology, global integrity monitoring becomes possible. Nevertheless, the content of integrity monitoring is still limited by the communication capacity of inter-satellite links and the layout of ground monitoring stations. Low earth orbit (LEO) satellites have advantages in information-carrying rate and kinematic velocity and can be used as satellite-based monitoring stations for navigation satellites. Large numbers of LEO satellites can provide more monitoring data than ground monitoring stations and make it easier to obtain full-arc observation data. A new challenge of redundant data also arises. This study constructs multi-source observation links with satellite-to-ground, inter-satellite, and satellite-based observation data, proposes an integrity monitoring method with optimization of observation links, and verifies the performance of integrity monitoring with different observation links. The experimental results show four findings. (1) Based on the integrity status of BDS-3, the proposed system-level integrity mode can realize full-arc anomaly diagnosis in information and signals according to the observation conditions of the target satellite. Apart from basic navigation messages and satellite-based augmentation messages, autonomous messages and inter-satellite ranging data can be used to evaluate the state of the target satellite. (2) For a giant LEO constellation, only a small number of LEO satellites need to be selected to construct a minimum satellite-based observation unit that can realize multiple returns of navigation messages and reduce the redundancy of observation data. With the support of 12 and 30 LEO satellites, the minimum number of satellite-based observation links is 1 and 4, respectively, verifying that a small amount of LEO satellites could be used to construct a minimum satellite-based observation unit. (3) A small number of LEO satellites can effectively improve the observation geometry of the target satellite. An orbit determination observation unit, which consists of chosen satellite-to-ground and/or satellite-based observation links based on observation geometry, is proposed to carry out fast calculations of satellite orbit. If the orbit determination observation unit contains 6 satellite-to-ground monitoring links and 6/12/60 LEO satellites, the value of satellite position dilution of precision (SPDOP) is 38.37, 24.60, and 15.71, respectively, with a 92.95%, 95.49%, and 97.12% improvement than the results using 6 satellite-to-ground monitoring links only. (4) LEO satellites could not only expand the resolution of integrity parameters in real time but also augment the service accuracy of the navigation satellite system. As the number of LEO satellites increases, the area where UDRE parameters can be solved in real time is constantly expanding to a global area. The service accuracy is 0.93 m, 0.88 m, and 0.65 m, respectively, with augmentation of 6, 12, and 60 LEO satellites, which is an 8.9%, 13.7%, and 36.3% improvement compared with the results of regional service. LEO satellites have practical application values by improving the integrity monitoring of navigation satellites.

Ohmic contact mechanism and charge redistribution of MoS2/Mn+1XnO2 heterostructures

Abstract Several M n+1 X n O2 compounds exhibit work functions higher than those of three-dimensional metals, enabling the formation of Ohmic contact heterostructures with MoS2, which enhances the catalytic activity of MoS2 for the hydrogen evolution reaction. However, the Schottky barrier height (SBH) in these Ohmic contact heterostructures does not adhere to the Schottky-Mott limit, leaving the Ohmic contact mechanism between MoS2 and M n+ 1X n O2 unclear and hindering further investigations into these heterostructures. In this study, we investigate 22 MoS2/M n+ 1X n O2 heterostructures using the unfolding method. Among these, the eight M n+ 1X n O2 compounds—Cr2CO2, Mo2CO2, V2CO2, W2CO2, Cr2NO2, V2NO2, Ti3C2O2 and V4C3O2—form p-type Ohmic contacts with MoS2. In contrast, the twelve compounds—Hf2CO2, Nb2CO2, Ta2CO2, Ti2CO2, Zr2CO2, Mo2NO2, Ti2NO2, Ti3N2O2, Zr3C2O2, Nb4C3O2, Ta4C3O2 and Ti4N3O2—create p-type Schottky contacts, while Hf2NO2 and Zr2NO2 form n-type Schottky contacts with MoS2. In the Ohmic contact heterostructures, out-of-plane orbital states hybridize to form a splitting band, allowing the highest valence band of MoS2 to cross the Fermi level and achieve hole doping. This splitting band not only results in a SBH that does not conform to the Schottky–Mott limit but also redistributes charge density. Notably, the heterostructures formed by Cr2CO2, Mo2CO2, V2CO2, W2CO2, Cr2NO2, V2NO2, V4C3O2, and MoS2 exhibit charge polarity distribution, whereas MoS2/Ti3C2O2 does not demonstrate charge polarity distribution.

In-orbit validation of a ferrofluidic Thermal Switch in ISS microgravity

AbstractFerrofluids offer a wide range of applications by enabling wearless systems for future space missions. As part of the FARGO (Ferrofluid Application Research Goes Orbital) project, an active Thermal Switch using ferrofluid was developed and validated during a 26-day International Space Station (ISS) mission. This experiment was conducted as part of the Überflieger2 competition organized by the Space Agency within the German Aerospace Center (DLR). Thermal management of spacecraft (S/C) and satellites is a universal challenge. In the development of thermal management components, it is therefore essential to minimize or even eliminate stress/strain peaks and potential safety risks for S/C operation and payloads induced by thermal differences. The thermal management system shall be able to keep all components within their acceptable temperature ranges. This shall be achieved under all orbit conditions, for example, when solar irradiance heats one side of the S/C resulting in possibly unwanted temperature gradients toward the cold vacuum of space. An active Thermal Switch allows heat flows to be routed along different paths within the S/C depending on the prevailing conditions. Within project FARGO, an active Thermal Switch was tested during an ISS mission. Tests on the ground already verified a measurable difference in thermal conductivity depending on the state of the switch. Magnetically moving the ferrofluid allows the creation of a thermally isolating and conducting Thermal Switch state. The ferrofluid utilized for the FARGO experiment is EFH-1 with a thermal conductivity of $${0.19\,\mathrm{\text {W}\text {m}^{-1}\text {K}^{-1}}}$$ 0.19 Wm - 1 K - 1 . The Thermal Switch consists of two silver rods in line, acting as heat conductors, separated by an airgap. One side of the switch is heated, and the other one cooled by one thermoelectric cooler (TEC) each. The gap between the conductors can be bridged by ferrofluid moved via magnetic fields. As the EFH-1 has a higher thermal conductivity k than air, thermal conductive change is achieved by switching. The temperature difference between hot and cold side are measured in the ON state as well as the OFF state. From these measurements, the switching ratio as a performance characteristic is calculated. The switch was tested under various heat loads and switching times. Electropermanent magnets (EPMs) are magnets that can be magnetically switched on and off by a current pulse. Compared to conventional electromagnets, heat generation and power generation are significantly reduced. In addition, the switch remains reliably in the selected state, even if a failure of the control electronics occurs, making it bi-stable. Moreover, electric power is only required to switch the state of the EPM, but not to maintain it.

Optimizing Consider-Covariance Models for Realistic Orbit Errors and Application to Collision Avoidance

Precise knowledge about the orbit state vectors and the associated uncertainties are crucial for reliable conjunction assessment and efficient mitigation of on-orbit collision risks through collision avoidance maneuvers by active satellites. The decision-making process heavily relies on the orbit accuracy and the uncertainty realism of the encountering objects, primarily space debris, and the maneuvering satellite itself. The process of determining an orbit creates an estimate of the orbit state and its associated state covariance matrix. This estimate serves as the initial value for predicting the orbit’s uncertainty at the time of closest approach. To determine and numerically propagate realistic orbit errors, the uncertainties of the dynamic model must be taken into account. One method that fulfils this purpose is consider covariance propagation, provided that suitable consider parameters and their variances have been established. This paper presents a novel method for optimizing the consider covariance parameters from past mission data. Real orbit data from multiple low Earth orbit satellites controlled by the DLR, German Aerospace Center’s German Space Operations Center are used to calibrate and evaluate different error models, including covariance parameters and other error terms. The results demonstrate improved uncertainty realism in orbit predictions and subsequent benefits for collision avoidance. Finally, this paper presents the required steps for integrating the new method into the existing collision avoidance system, along with initial results from conjunction assessment.

Feasibility Study of a European Commercial Space Station in Low Earth Orbit

Feasibility Study of a European Commercial Space Station in Low Earth Orbit

Wear Calculation for a Shaft Lip Seal under Randomly Changing Temperature and Load

A stochastic model of the wear process of a shaft lip seal that takes into account random changes in the temperature and external load was described. The results of a numerical analysis of the process of seal wear in relation to the conditions of operation in open space at near-Earth orbital stations are presented. The importance of taking into account random changes in temperature and external load for predicting the seal durability was evaluated.

Ferromagnetic ferroelectricity due to the Kugel-Khomskii mechanism of orbital ordering assisted by atomic Hund's second rule effects

The exchange interactions in insulators depend on the orbital state of magnetic ions, obeying certain phenomenological principles, known as Goodenough-Kanamori-Anderson rules. Particularly, the ferro order of alike orbitals tends to stabilize antiferromagnetic interactions, while the antiferro order of unlike orbitals favors ferromagnetic interactions. The Kugel-Khomskii theory provides a universal view on such coupling between spin and orbital degrees of freedom, based on the superexchange processes: namely, for a given magnetic order, the occupied orbitals tend to arrange in a way to further minimize the exchange energy. Then, if two magnetic sites are connected by the spatial inversion, the antiferro orbital order should lead to the ferromagnetic coupling break the inversion symmetry. This constitutes the basic idea of our work, which provides a pathway for designing ferromagnetic ferroelectrics: the rare but fundamentally and practically important multiferroic materials. After illustrating the basic idea on toy-model examples, we propose that such behavior can be indeed realized in the van der Waals ferromagnet VI3, employing for this analysis the realistic model derived from first-principles calculations for magnetic 3d bands. We argue that the intra-atomic interactions responsible for Hund's second rule, acting against the crystal field, tend to restore the orbital degeneracy of the ionic d2 state in VI3 and, thus, provide a necessary flexibility for activating the Kugel-Khomskii mechanism of the orbital ordering. In the honeycomb lattice, this orbital ordering breaks the inversion symmetry, stabilizing the ferromagnetic-ferroelectric ground state. The symmetry breaking leads to the canting of magnetization, which can be further controlled by the magnetic field, producing a huge change of electric polarization. Published by the American Physical Society 2024

Interpretation of recently discovered single bottom baryons in the relativistic flux tube model

Following recent experimental progress in the study of bottom baryons, we systematically calculate the mass spectra of Λb, Ξb, Σb, Ξb′, and Ωb baryons with a quark-diquark picture in the framework of a relativistic flux tube model with spin-dependent interactions in the j-j coupling scheme. Furthermore, we calculate the strong decay width of bottom baryons decaying into a bottom baryon and a light pseudoscalar meson. Good agreement is found between the calculated masses and the experimentally available masses of singly bottom baryons. By analyzing both mass spectra and strong decay widths, we interpret Σb(6097) as a 1P(3/2−) state and Ξb(6100) as a 1P(1/2−) state of the Ξb baryon. The Ξb(6227) is identified to be an orbital excitation 1P of the Ξb′ baryon with JP=3/2−. Further, we determine Ξb(6327) and Ξb(6333) as a 1P(3/2−) state and 1P(5/2−) state, respectively, of Ξb′ baryon. From the obtained mass spectra, we construct the Regge trajectories in the (J,M2) plane, which are found to be essentially linear, parallel, and equidistant. Our predictions for higher orbital and radial excited states can help experimentalists identify missing excited states of singly bottom baryons. Published by the American Physical Society 2024

High‐Fidelity Information Transmission Through the Turbulent Atmosphere Utilizing Partially Coherent Cylindrical Vector Beams

As the demand for high‐capacity and high‐fidelity communication systems continues to increase, addressing the challenges posed by noise and atmospheric turbulence disturbances is imperative. This study introduces and experimentally implements a novel free‐space optical communication protocol. This protocol combines the advantages of reducing the spatial coherence of light at the source with the capabilities of convolutional neural networks at the receiver to encode and transmit optical images through a noisy link. Light beams that are robust against noise are generated and atmospheric turbulence is modeled in a laboratory setting by decreasing the degree of spatial coherence of the source. Eight orbital angular momentum states, four polarizations, and eight coherence states of a light source that generates partially coherent cylindrical vector beams are utilized. These elements are employed to achieve a 256‐ary encoding/decoding data transmission within our protocol. This study is expected to catalyze further research into the utilization of partially coherent light and neural networks in the realm of free‐space optical communications.

Molecular design of furanoacene-based singlet fission sensitizers combining diradical character and cross-substitution

Singlet fission (SF) suffers from the scarcity of available SF chromophores and sensitizers. Tetracene, pentacene and their derivatives, are two typical model systems for the study of SF photophysical phenomena. Herein, the analogues of polyacenes, furanoacenes and their derivatives, were evaluated as potential SF chromophores and sensitizers through a theoretical study. The primary photostability were evaluated by the frontier molecular orbital energy levels, diradical characters and SF relevant excited state energies according to the type-I and −II photodegradation mechanisms. The cross-substitutions by combining central substitutions with triple bonds and terminal substituents enhance photostability, tune the SF relevant excited states efficiently, and give more appropriate E(T1) to be SF sensitizers. This work helps to give better understanding of the electronic structures and SF capability of furanoacenes.

Additively manufactured conductive and dielectric 3D metasurfaces for independent manipulation of broadband orbital angular momentum

Recent developments in conductive and dielectric multi-material additive manufacturing have generated significant interest for their potential to enhance the performance of electronic devices. Lights-out digital manufacturing, a sophisticated multi-material printing technique, facilitates the seamless sintering of silver nanoparticles and acrylate inks, enabling the creation of functional electronic devices. In this study, the LDM process is utilized to prototype intricate 3D metasurface designs. A comprehensive analysis of the properties of the printed materials confirms the practicality of this multi-material printing approach. The research examines various element distributions within multi-metal layer structures, including carbon, phosphorus, oxygen, sulfur, and fluorine, to investigate the interfaces between conductive and dielectric structures. In addition, the conductivities of silver nanoparticle inks at different curing temperatures are studied to identify optimal printing conditions. Both the conductive and dielectric inks exhibit precisely controlled particle sizes and exceptional stability, which are critical for accurate additive manufacturing. Using this sophisticated printing solution, the paper presents a broadband 3D metasurface engineered to independently manipulate two distinct orbital angular momentum states in the V-band (60–70 GHz) and W-band (79–90 GHz), suitable for high-speed wireless communications. The integration of deep neural networks helps reduce the phase coupling between the frequency bands, enabling independent control of the OAM states. The structure of the dual-band metasurface features four distinct silver layers yet is fabricated on a single ultra-thin planar substrate, demonstrating its potential for applications in future wireless communication systems.

Optimal proposal particle filters for detecting anomalies and manoeuvres from two line element data

Detecting the manoeuvres of satellites is an important goal within the broader task of space situational awareness. Moreover, it is advantageous to be able to detect other anomalous behaviour from satellites arising from, for instance, collisions or malfunction. The Two Line Element (TLE) data published by NORAD is the only publicy-available comprehensive source of data for satellite orbits. This paper presents a filtering approach for detecting anomalies in satellite orbits from TLE data. Particle filters are deployed to track the state of the satellites’ orbits. New TLEs that are deemed sufficiently unlikely given one’s belief of the current orbital state are designated as anomalies. The change in the orbits over time is modelled using the SGP4 model. However, it is shown that this model can have large errors in certain elements in some instances. The structure of these errors is analysed and a suitable model uncertainty is derived. The optimal proposal filter is used to further reduce the impact of the errors in the SGP4 model. This strategy improves the proposal distribution from which the particles are drawn before re-weighting, so that the resulting weights are less degenerate. The proposed techniques are evaluated on a benchmark set of 15 satellites for which an externally-obtained ground truth is available, along with simulated orbital data with inserted manoeuvres. Although this benchmark is larger than the evaluation sets used in other published work, it cannot be representative of the full population of satellites and so more emphasis is placed on the simulated data. The proposed techniques are compared against a baseline, which is similar to many previously-proposed techniques for satellite manoeuvre detection. The particle filters are shown to be superior at detecting the subtle in-track and cross-track manoeuvres in the simulated dataset. However, on the benchmark dataset, a simple baseline that focusses on the mean motion can perform equivalently to the best filters. This simple technique is likely overfit to the benchmark.

A recurrent neural network-based approach for ballistic coefficient estimation of resident space objects in low earth orbit

Characterizing Resident Space Objects (RSOs) has become paramount for several Space Situational Awareness functions, such as accurate orbit prediction, collision avoidance and sensor tasking. Due to the huge and diverse amount of data to handle and fuse for this purpose, there is an increasing interest in Machine Learning (ML) approaches to retrieve physical parameters of RSOs in a cost-efficient manner. Among different ML architectures, Recurrent Neural Networks (RNNs) are particularly suitable to handle sequential or time-series data. In this context, this paper demonstrates the possibility to use Recurrent Neural Networks to estimate the ballistic coefficient of RSOs in Low Earth Orbit from time series of orbital elements. A particular RNN architecture has been adopted, i.e., the Gated Recurrent Unit, as it has been demonstrated to be cost efficient and to have good performance for the required application. The sensitivity of RNNs with respect to atmospheric model uncertainty has been analysed. The algorithm can handle unevenly spaced time-series data. The proposed neural network has been demonstrated to be robust with respect to orbital state errors. The applicability of the presented approach is tested and discussed using synthetic datasets generated with a high-accuracy numerical orbital propagator, reaching a mean percentage error of 10% in the estimation of the ballistic coefficient.

Role of Disorder in the Intrinsic Orbital Hall Effect.

The orbital Hall effect (OHE) has garnered much attention as a promising approach to realize highly efficient "orbitronic" devices with a wide range of materials. However, the existing theories that attempt to explain the experimental evidence focus on the intrinsic effect, neglecting the omnipresent disorder. Here, we formulate the impact of random defect scattering on the orbital Hall effect by a quantum Boltzmann equation and solve it for a generic two-band model including the in-scattering collision integral (vertex correction). In contrast to the common belief that the intrinsic OHE is robust against the disorder, we find that diffuse scattering by an arbitrarily weak disorder affects and can even fully suppress the intrinsic orbital Hall current, depending on the character of orbital states and the disorder.

Determination of International Space Station Orbit Correction Fuel Consumption with Progress Ship

The paper proposes a method for determining the required amount of fuel for correcting the orbit of the ISS by the spacecraft Progress and Soyuz.

Analytical Second-Order Extended Kalman Filter for Satellite Relative Orbit Estimation

This study considers a relative orbit estimation problem wherein an observing spacecraft navigates with respect to a target space object at a large separation distance (several kilometers) using only the bearing angles obtained by a single onboard camera. Generally, the extended Kalman filter (EKF), which is based on linear relative motion equations such as the Clohessy–Wiltshire equation, is used for the relative navigation of satellites. The EKF linearizes the estimation error around the current estimate and applies the Kalman filter equations to this linearized system. However, it has been shown that nonlinearities of the orbit determination problem can make the linearization assumption insufficient to represent the actual uncertainty. Therefore, an analytical second-order extended Kalman filter (ASEKF) for relative orbit estimation is proposed in this study. The ASEKF, to sequentially estimate the relative states of satellites and their associated uncertainties, is formulated based on a second-order analytic relative-motion equation under J2-perturbtation, which can overcome the deficiencies of existing approaches that mainly focus on applications in two-body, near-circular, and linearized orbit dynamics. Numerical results show that the proposed method provides superior robustness and mean-square error performance compared to linear estimators under the conditions considered.

Qudit-based variational quantum eigensolver using photonic orbital angular momentum states.

Solving the electronic structure problem is a notorious challenge in quantum chemistry and material science. Variational quantum eigensolver (VQE) is a promising hybrid classical-quantum algorithm for finding the lowest-energy configuration of a molecular system. However, it typically requires many qubits and quantum gates with substantial quantum circuit depth to accurately represent the electronic wave function of complex structures. Here, we propose an alternative approach to solve the electronic structure problem using VQE with a single qudit. Our approach exploits a high-dimensional orbital angular momentum state of a heralded single photon and notably reduces the required quantum resources compared to conventional multi-qubit-based VQE. We experimentally demonstrate that our single-qudit-based VQE can efficiently estimate the ground state energy of hydrogen (H2) and lithium hydride (LiH) molecular systems corresponding to two- and four-qubit systems, respectively. We believe that our scheme opens a pathway to perform a large-scale quantum simulation for solving more complex problems in quantum chemistry and material science.

Effects of microgravity on human iPSC-derived neural organoids on the International Space Station.

Research conducted on the International Space Station (ISS) in low-Earth orbit (LEO) has shown the effects of microgravity on multiple organs. To investigate the effects of microgravity on the central nervous system, we developed a unique organoid strategy for modeling specific regions of the brain that are affected by neurodegenerative diseases. We generated 3-dimensional human neural organoids from induced pluripotent stem cells (iPSCs) derived from individuals affected by primary progressive multiple sclerosis (PPMS)or Parkinson's disease (PD) and non-symptomatic controls, by differentiating them toward cortical and dopaminergic fates, respectively, and combined them with isogenic microglia. The organoids were cultured for a month using a novel sealed cryovial culture method on the International Space Station (ISS) and a parallel set that remained on Earth. Live samples were returned to Earth for analysis by RNA expression and histology and were attached to culture dishes to enable neurite outgrowth. Our results show that both cortical and dopaminergic organoids cultured in LEO had lower levels of genes associated with cell proliferation and higher levels of maturation-associated genes, suggesting that the cells matured more quickly in LEO. This study is continuing with several more missions in order to understand the mechanisms underlying accelerated maturation and to investigate other neurological diseases. Our goal is to make use of the opportunity to study neural cells in LEO to better understand and treat neurodegenerative disease on Earth and to help ameliorate potentially adverse neurological effects of space travel.

The Maintenance of Orbital States in a Floating Partial Space Elevator Using the Reinforcement Learning Method

A partial space elevator (PSE) is a multi-body tethered space system in which the main satellite, typically an ultra-large spacecraft or a space station in a higher orbit, is connected to a transport spacecraft in a lower orbit via a tether, maintaining orbital synchronization. One or more climbers can move along the tether driven by electric power, enabling cross-orbital payload transportation between the two spacecraft. The climbers’ motion significantly alters the main satellite’s orbital states, compromising its safe and stable operation. The dynamic coupling and nonlinearity of the PSE further exacerbate this challenge. This study aims to preliminarily address this issue by proposing a new mission planning strategy. This strategy utilizes reinforcement learning (RL) to select the waiting interval between two transfer missions, thereby maintaining the main satellite’s orbital motion in a stable state. Simulation results confirm the feasibility and effectiveness of the proposed mission-based method.