Vacuum Space Research Articles

Analysis of Ionicity-Magnetism Competition in 2D-MX3 Halides towards a Low-Dimensional Materials Study Based on GPU-Enabled Computational Systems.

The acceleration of parallel high-throughput first-principle calculations in the context of 3D (three dimensional) periodic boundary conditions for low-dimensional systems, and particularly 2D materials, is an important issue for new material design. Where the scalability rapidly deflated due to the use of large void unit cells along with a significant number of atoms, which should mimic layered structures in the vacuum space. In this report, we explored the scalability and performance of the Quantum ESPRESSO package in the hybrid central processing unit - graphics processing unit (CPU-GPU) environment. The study carried out in the comparison to CPU-based systems for simulations of 2D magnets where significant improvement of computational speed was achieved based on the IBM ESSL SMP CUDA library. As an example of physics-related results, we have computed and discussed the ionicity-covalency and related ferro- (FM) and antiferro-magnetic (AFM) exchange competitions computed for some CrX compounds. Further, it has been demonstrated how this exchange interplay leads to high-order effects for the magnetism of the 1L-RuCl compound.

Excellent thermoelectric performances of the SiSe2 monolayer and layered bulk

The excellent thermoelectric performance of the SiSe2 monolayer and layered bulk is identified by employing the density functional theory and the semi-classical Boltzmann transport theory. The geometrical structures of the SiSe2 monolayer and bulk are fully relaxed, and the dynamic and thermal stabilities have been confirmed through phonon dispersions and ab initio molecular dynamics simulations. By introducing a method to avoid the vacuum space of the supercell influence on the volume of the monolayer, we have obtained the lattice thermal conductivity, the Seebeck coefficient, electrical conductivity, power factor, and electron thermal conductivity for both the monolayer and the bulk. The ZT relative to temperature and carrier concentration are obtained to evaluate the thermoelectric performance. For the SiSe2 monolayer, the maximum ZT can reach 4.84 at 700 K with the p-type carrier concentration of 9.60 × 1019 cm−3, while for the SiSe2 bulk, the maximum ZT can also attain 4.11 at 700 K with the n-type carrier concentration of 2.38 × 1019 cm−3 . Therefore, both the SiSe2 monolayer and bulk are favorable candidates for thermoelectric applications. The mechanism for the superior thermoelectric properties is also examined.

HIGH PERFORMANCE PROCESSING CLUSTER FOR REMOTE SENSING SPACECRAFTS

Recently, there has been a tendency to complicate real time control algorithms, to process a large amount of information from the satellite payload (optical, radar, communication systems) directly on board and to create highly informative communication lines with both ground stations and other satellites. The conditions of outer space (vacuum, radiation) impose significant restrictions on the computing capabilities of onboard equipment, which is used as an onboard digital computer complex, and lead to a significant increasing in the cost of space components. A high-performance and relatively cheap computing cluster structure of an on-board computer based on widely available single-board minicomputers is proposed, which allows distributing the computing load among several nodes and simultaneously backing up the system. As a component of a computing cluster, it is proposed to use a computing cluster system based on COTS (Commercial off-the-shelf) components, which increases performance by several orders while reducing cost. Calculations have shown that the introduction of redundancy and distribution of computational tasks makes it possible to achieve an MTBF of about 3 years, which is quite enough for the active existence of university satellites. The proposed structure of the onboard computer complex is installed on the university satellite for remote sensing of the Earth in the visible range with controlled optical magnification, after the launch of which it is planned to confirm the reliability of the results obtained in this work. An assessment of the performance and reliability of such a cluster system is given, which has shown the possibility of implementing such a system on a university satellite for Earth remote sensing.

Resistance investigation of diamond-like carbon coatings to cyclic temperature changes

Optical elements used in outer space must be designed considering the effects of such factors as space vacuum, atomic oxygen in low Earth orbit, solar and space radiation, large temperature drops, gas release of spacecraft materials and structural elements, space dust and debris. In order to harden and protect mirror surfaces of optical elements from external factors, it has been promisingly applied diamond-like carbon coatings on their surface. These coatings are characterized by high strength and wear-resistant properties, in particular, high hardness, low friction coefficient, high wear resistance and chemical inertness. This leads to their widespread use in various fields of science and technology, including optical instrumentation. This paper presents the results of testing an aluminum mirror with a diamondlike carbon coating under the effect of cyclic temperature changes for determining their ability to withstand a rapid cyclic ambient temperature change, and specifically, to maintain optical and mechanical properties.

Nanoscale Reciprocating Sliding Contact Behaviors of an Isosceles Trapezoid Textured Surface in Space Environment

Background: In the space environment, microgravity and vacuum influence the mechanical behaviors of the devices. In the microgravity environment, the mechanical components vibrate with a small amplitude once there is a disturbance. The vibration can be seen as a reciprocating sliding contact with a small amplitude. In addition to the vibration, adhesion effects are predominant in a vacuum, which will induce a high friction force. Objective: To reduce the friction force, textured surfaces are widely used in mechanical engineering on the earth, and nanoscale textures are also verified to be used to improve the frictional behaviors of components in the size of nanometers. Methods: In this paper, the adhesion effects are considered by using molecular dynamics (MD) simulation, and the microgravity induced vibration is simplified as a reciprocating sliding contact. Coupling MD simulation and the finite element method which is a multiscale method are used to investigate the frictional properties of nanoscale reciprocating sliding contact between rigid multiasperity tips and an isosceles trapezoid textured surface. Results: Average friction forces for the different tips are presented, and the friction processes are analyzed. A stable friction process is discovered for a specific case, and the average friction force is kept at two stable values corresponding to two sliding directions. Conclusion: Compared with the total average friction forces of a smooth surface, the textured surface can reduce the friction forces greatly. This work could contribute to the textured surface design to improve frictional properties in the space environment.

Decoupled Ion Transport in Protein-Based Solid Electrolyte through Ab Initio Calculations and Experiments

Decoupling the ion motion and segmental relaxation is significant for developing advanced solid polymer electrolytes with high ionic conductivity and high mechanical properties. Our previous work proposed a decoupled ion transport in a novel protein-based solid electrolyte. Herein, we investigate the detailed ion interaction/transport mechanisms through first-principles density functional theory (DFT) calculations in a vacuum space. Specifically, we study the important roles of charged amino acids from proteins. Our results show that the charged amino acids (i.e., Arg and Lys) can strongly lock anions (ClO4-). When locked at a proper position (determined from the molecular structure of amino acids), the anions can provide additional hopping sites and facilitate Li+ transport. The findings are supported from our experiments of two protein solid electrolytes, in which the soy protein (with plenty of charged amino acids) electrolyte shows much higher ionic conductivity and lower activation energy in comparison to the zein (lack of charged amino acids) electrolyte.

Cold Welding in Hold Down Points of Space Mechanisms Due to Fretting When Omitting Grease

Cold welding refers to an effect related to space (vacuum). The heavy vibrations during a launch subject interfaces (hold down points) to oscillating motions which may lead to formation of a kind of “friction weld”. If so, these mechanisms may get stuck, and deployment will be hindered. This may endanger the functionality of the mission (instruments) or even the whole spacecraft (if solar panels do not open). Several studies have been done to characterize material combinations (including coatings) for their ability to cold welding in space. Meanwhile, also during launch grease free contacts are demanded. If grease hat to be omitted, the risk of cold welding under fretting was found to increase (when testing in high vacuum). To rate this risk under launch conditions, the test method was recently extended for testing under launch conditions. The new tests procedure consists of fretting applied in the sequence in air, low vacuum and high vacuum. The paper shall present first results gained with this new method of testing in launch conditions and compare them to previous studies done in vacuum. Following the need of space industry on mechanisms for launch and in-orbit life, a first set of combinations of materials and coatings were selected for this new test sequence where fretting is now applied in a sequence of air, low vacuum and high vacuum. Under this sequence, the measured levels of adhesion and it’s evolvement was found to differ strongly from tests done formerly. The paper outlines these first results and compares them to existing data.

Free-space group-velocity dispersion induced in space-time wave packets by V-shaped spectra

The authors introduce a space-time wave-packet structure that propagates in free space with a group velocity fixed at the speed of light in vacuum and large anomalous dispersion in free space. This is a noteworthy addition to the family of known optical wave packets and could have applications in optical signal processing and nonlinear optics.

Development of method of calculation of width of conductors of circuit boards with the improved heat extraction working in the conditions of space vacuum

Development of method of calculation of width of conductors of circuit boards with the improved heat extraction working in the conditions of space vacuum

Boosting Efficient Ammonia Synthesis over Atomically Dispersed Co-Based Catalyst via the Modulation of Geometric and Electronic Structures

Boosting Efficient Ammonia Synthesis over Atomically Dispersed Co-Based Catalyst via the Modulation of Geometric and Electronic Structures

L’organisation de cooperation de Shanghai (OCS) dans la Nouvelle Asie: une generalisation d’apres-guerre?

This article analyzes the concept of «New Asia» and the role of the SCO on it. The emergence of the “Shanghai spirit” сconsidered in the context of a strategic change in the post-bipolar period. The purpose of the article is to demonstrate the main milestones in the formation and development of the SCO and to study its potential as a regional system that fills the strategic vacuum in the Eurasian space. Special attention paid to the expansion of the SCO, the role of its partners and observers. This analysis proves that a platform for discussion and common decision-making is being created. Article attempts to give a conceptual framework of the concept of “New Asia” in the context of an analysis of the process of searching and developing solutions of common interest throughout this global space. A study of the political results of the SCO development process reveals SCO has no hostile intentions, but on the contrary creates an Asian space for member states. The space where the process of regional construction of neighboring states, the construction of a sustainable one, with which one can count on the search for common solutions and the subsequent implementation of common tasks are underway. At the same time, cooperation with the structures created earlier is also developing. In Europe, regional cooperation began after the Second World War, in African countries after the process of decolonization, Latin America has been in search of regional identity for a century and a half since its decolonization. One of the conclusions of this article is that the new Sino-post-Soviet Asia after the Cold War has a common historical and political basis for the formation of the region. A particular institutional illustration of this process is seen through the influence of the SCO. The SCO confirms the emergence of New Asia within the existing conceptual and contextual framework and offers other hypotheses to designate a modern region beyond Asia. The article raises a controversial question – what effective evidence of a causal relationship between post-war regionalization and regionalization of recent decades can be cited? Key words: SCO, “New Asia”, regional construction, cooperation.

Preparation and Performance Evaluation of Platinum Barium Hexaaluminate Catalyst for Green Propellant Hydroxylamine Nitrate Thrusters.

Spacecraft have monopropellant thruster systems for attitude control in the vacuum of space. Hydroxylamine nitrate is a green propellant that has high performance and low toxicity. Owing to the high adiabatic decomposition temperature of the hydroxylamine nitrate propellant, it is necessary to develop a catalyst with high thermal stability. We used a platinum barium hexaaluminate catalyst for green propellant hydroxylamine nitrate thrusters. Barium hexaaluminate support was prepared by a wet impregnation method and heat treatment. Platinum, the active material, was coated on catalyst supports. The Brunauer–Emmett–Teller specific surface was also investigated. X-ray diffraction and scanning electron microscope imagery were used to confirm the formation of barium hexaaluminate. A hydroxylamine nitrate propellant blended with methanol was used for performance evaluation via firing tests of the thruster. The catalytic decomposition performance of each test was evaluated by calculating the characteristic velocity efficiency using the pressure of the chamber at the end of the catalyst bed and the mass flow rate of the propellant. As the catalyst bed was preheated to 350 °C, the characteristic velocity efficiency was 71.9%. Test results revealed that the platinum barium hexaaluminate catalyst is feasible for a hydroxylamine nitrate thruster.

The common origin of the family mass hierarchy and CP violation from flavor-dependent vacuum for quarks and leptons

We rewrite the Yukawa interactions of the Standard Model in terms of flavor-dependent vacuum structure to address the family mass hierarchy and CP violation in both the quark sector and lepton sector. It is realized that Yukawa terms only include the same number of degrees of freedom as phenomenological observables with no requirement of extra particle or any new symmetry. The quark and lepton mass hierarchy arises as a natural result of the close-to-flat vacuum in flavor space. The CP violations in CKM mixing and PMNS mixing are explained as general quantum phases between weak gauge eigenstates and Yukawa interaction states. The mechanism is proven by reproduction of all current quark/lepton mass data and the CKM/PMNS mixing parameters.

Design and Experimental Study of Space Continuous Robots Applied to Space Non-Cooperative Target Capture.

Space capture actuators face problems such as insufficient flexibility and electrical components that are vulnerable to extreme space environments. To address these problems, a centralized-driven flexible continuous robot based on a multiple scissor mechanism units is proposed in this study. The continuous robot body is composed of two scissor mechanism units coupled in series, and the base container’s three motors to drive the robot. The two scissor mechanism units ensure a wide range of flexible operations and the light weight of the robot. The centralized drive with three motors not only reduces the number of driving sources, but also ensures temperature control and protection of electrical components in the space environment. The kinematics and dynamics of the robot are analyzed, and the workspace and deformation performance of the robot are verified through experiments. Compared with other continuous robots, the proposed continuous robot retains the characteristics of continuous robots in a wide range of flexible operations. At the same time, the configuration is light and a small number of driving sources are used, which is suitable for extreme temperatures, vacuum, radiation, and strict resource-constrained environments in space.

MECHANISM OF ROTATION OF GEOSPHERES OF THE PLANET EARTH

In recent decades, a fundamentally new direction of scientific work has appeared in the field of natural sciences, associated with the study of the effect on matter of such physical factors as radiation, electromagnetic radiation, ultrasound, plasma, high pressure, space vacuum, gravity, etc., where the general criterion of extremeness exposure can be the emergence of intermediate highly active states of particles of matter, which ultimately leads to a qualitative change in the micro- and macro characteristics of the processed object, the emergence of new properties. One of the types of complex extreme exposure is the effect of a high-voltage electric discharge, which combines the simultaneous action on a substance of strong mechanical compression, powerful ultrasound, hard X-ray, UV and IR radiation. The electromagnetic fields generated in the course of the discharge also have a strong effect on both the discharge itself and the ionic processes occurring in the surrounding liquid. Under their influence, various physical changes and chemical reactions occur in the processed material.

Revival of Anhydrobiotic Cyanobacterium Biofilms Exposed to Space Vacuum and Prolonged Dryness: Implications for Future Missions beyond Low Earth Orbit.

Dried biofilms of Chroococcidiopsis sp. CCMEE 029 were revived after a 672-day exposure to space vacuum outside the International Space Station during the EXPOSE-R2 space mission. After retrieval, they were air-dried stored for 3.5 years. Space vacuum reduced cell viability and increased DNA damage compared to air-dried storage for 6 years under laboratory conditions. Long exposure times to space vacuum and extreme dryness decrease the changes of survival that ultimately depend on DNA damage repair upon rehydration, and hence, an in silico analysis of Chroococcidiopsis sp. CCMEE 029's genome was performed with a focus on DNA repair pathways. The analysis identified a high number of genes that encode proteins of the homologous recombination RecF pathway and base excision repair that were over-expressed during 1 and 6 h rehydration of space-vacuum exposed biofilms. This suggests that Chroococcidiopsis developed a survival strategy against desiccation, with DNA repair playing a key role, which allowed the revival of biofilms exposed to space vacuum. Unravelling how long anhydrobiotic cyanobacteria can persist under space vacuum followed by prolonged air-dried storage is relevant to future astrobiological experiments that use space platforms and might require prolonged air-dried storage of the exposed samples before retrieval to Earth.

The bi-conical vector model at 1/N

We study finite N aspects of the O(m) × O(N − m) vector model with quartic interactions in general 2 ≤ d ≤ 6 spacetime dimensions. This model has recently been shown [1, 2] to display the phenomenon of persistent symmetry breaking at a perturbative Wilson-Fisher-like fixed point in d = 4 − ϵ dimensions. The large rank limit of the biconical model displays a conformal manifold and a moduli space of vacua. We find a set of three double trace scalar operators that are respectively irrelevant, relevant and marginal deformations of the conformal manifold in general d. We calculate the anomalous dimensions of the single and multi-trace scalar operators to the first sub-leading order in the large rank expansion. The anomalous dimension of the marginal operator does not vanish in general, indicating that the conformal manifold is lifted at finite N . In the case of equal ranks we are able to derive explicitly the scaling dimensions of various operators as functions of only d.

On the D(\u20131)/D7-brane systems

We study non-perturbative effects in supersymmetric U(N) gauge theories in eight dimensions realized by means of D(–1)/D7-brane systems with non-trivial world-volume fluxes turned on. Using an explicit string construction in terms of vertex operators, we derive the action for the open strings ending on the D(–1)-branes and exhibit its BRST structure. The space of vacua for these open strings is shown to be in correspondence with the moduli space of generalized ADHM gauge connections which trigger the non-perturbative corrections in the eight-dimensional theory. These corrections are computed via localization and turn out to depend on the curved background used to localize the integrals on the instanton moduli space, and vanish in flat space. Finally, we show that for specific choices of the background the instanton partition functions reduce to weighted sums of the solid partitions of the integers.

Non perturbative spherical gravitational waves

It is well-known that there is no spherical/topologically spherical gravitational waves in vacuum space in general relativity. We show that a deviation from general relativity leads to exact vacuum spherical gravitational waves, no matter how tiny this deviation is. We also discuss the related topics, including Vaidya-like metric in f(R) gravity. We demonstrate that the existence of spherical gravitational wave is a non perturbative property for gravities. We investigate energy carried by this nonperturbative wave. We first find the wave solution from investigations of Vaidya-like metric in f(R) gravity, which has only one longitude polarization. We further extend it to a metric with two transverse polarizations by directly solving the field equation.

Collective spontaneous emission of two entangled atoms near an oscillating mirror

We consider the cooperative spontaneous emission of a system of two identical atoms interacting with the electromagnetic field in the vacuum state and in the presence of an oscillating mirror. We assume that the two atoms, one in the ground state and the other in the excited state, are prepared in a correlated (symmetric or antisymmetric) Bell-type state. We also suppose that the perfectly reflecting plate oscillates adiabatically, with the field modes satisfying the boundary conditions at the mirror surface at any given instant, so that the time dependence of the interaction Hamiltonian is entirely enclosed in the instantaneous atom-wall distance. Using time-dependent perturbation theory, we investigate the spectrum of the radiation emitted by the two-atom system, showing how the oscillation of the boundary modifies the features of the emitted spectrum, which exhibits two lateral peaks not present in the case of a static boundary. We also evaluate the transition rate to the collective ground state of the two-atom system in both cases of the superradiant (symmetric) and subradiant (antisymmetric) state. We show that it is modulated in time and that the presence of the oscillating mirror can enhance or inhibit the decay rate compared to the case of atoms in vacuum space or near a static boundary. Our results thus suggest that a dynamical (i.e., time-modulated) environment can offer further possibilities to control and manipulate radiative processes of atoms or molecules nearby, such as the cooperative decay, and strongly indicate a similar possibility for other radiative processes, for example, the resonance interaction and the energy transfer between atoms or molecules.