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Abstract: Abstract In a microgravity environment, the flow pattern, flow characteristics, and heat transfer characteristics of gas–liquid two-phase flow are different from those in a normal gravity environment. To study the influence of microgravity on the flow and heat-transfer characteristics in an evaporator, this study develops a flow and heat-transfer model in an evaporator based on a previously proposed microgravity solution where the refrigerant and lubricating oil are mixed. This work also examines the flow and heat-transfer characteristics of gas–liquid two-phase flow in an evaporator with gravity of 10–6-10−3 g and studies the influence of lubricating-oil content on the flow and heat-transfer characteristics of mixed two-phase flow in the evaporator. The results show that when gravity is equal to 10−3 g, the gas volume fraction at the outlet is between 0.6 and 0.7, and when gravity is decreased to 10–6 g, the gas volume fraction at the outlet of the evaporator, after gradually decreasing, comes close to a zero gravity-state. In addition, the gas volume fraction remains between 0.3 and 0.6. It can also be seen that when gravity increases, the heat-transfer coefficient increases nearly linearly and reaches a maximum value of 14.013 W/(m2·K) and 16.066 W/(m2·K) when the lubricating oil content is 2% for normal gravity, and 4.443 W/(m2·K) and 5.519 W/(m2·K) when the lubricating oil content is 2.5% for microgravity. PubDate: 2023-11-29
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Abstract: Abstract Traversing granular regolith, especially in reduced gravity environments, remains a potential challenge for wheeled rovers. Mitigating hazards for planetary exploration rovers requires testing in representative environments, but direct Earth-based testing fails to account for the effect of reduced gravity on the soil itself. Granular scaling laws (GSL) have been proposed in the literature to predict performance of a larger wheel based on tests with a smaller wheel, or to predict performance in one gravity level based on tests in another gravity level. However, this is the first work to experimentally validate GSL in reduced gravity. Here, an expanded version of existing GSL was evaluated experimentally by measuring performance of a single wheel driving through cohesionless lunar soil simulant GRC-1 aboard parabolic flights that reproduce the effects of lunar gravity, and comparing those results to scaled tests performed on the ground. This scaled-wheel testing achieved less than 10% prediction error on three measured output metrics: drawbar pull (i.e. net traction), sinkage, and power draw. Predictions also erred on the conservative side. Subsurface soil imaging revealed similar soil behavior between scaled tests. GSL thus offers an accurate and conservative method for predicting wheel performance in reduced gravity based on 1-g experiments, at least in cohesionless soil. PubDate: 2023-11-24
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Abstract: Abstract In this study, a gravity unloading method based on electrostatic adsorption is proposed to address the issue of large flexibility in membrane phased-array antennas. Through considering the gravity distribution of the antenna and the edge effect of the electrode system, the unloading efficiency and system robustness are improved using a grouping strategy and size optimization. The deformation equilibrium equation under both gravity and electrostatic fields is established, and the voltage optimization model of the electrode system is also formulated with the goal of complete compensation for gravity deformation. The advantages and effectiveness of the proposed method are demonstrated by comparing simulation and unloading experiment results with those obtained using the suspension method. Both results indicate that the electrostatic unloading method can achieve the same unloading effect as the suspension method. Moreover, without introducing in-plane deformations during unloading, this method enhances accuracy and provides valuable insights for optimizing the assembly and testing processes. PubDate: 2023-11-22
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Abstract: Abstract An experimental investigation was conducted to prepare and study the thermal conductivity performance of copper and diamond composite materials. Copper powder and diamond particles were used as fillers, epoxy resin was used as matrix, and composite materials were prepared by vacuum-assisted mechanical stirring. The thermal expansion coefficient of different composite materials was measured by a laser flash method, which can be used to calculate the thermal conductivity. The effect of the filling rate of copper powder, the morphology of copper powder, the filling rate of diamond, and the thermal conductivity of the particles on the thermal conductivity of composite materials was studied. The results showed that thermal conductivity of copper powder and diamond particles composite materials were 874% and 535% higher than that of the epoxy resin when their filling rates were 50.3 vol.% and 40.0 vol.%, respectively. For two-dimensional flake copper powder materials, the thermal conductivity could be effectively improved at a lower filling rate. However, the flake particles were easy to aggregate at a high filling rate, which maybe cause the composite materials to pulverize. PubDate: 2023-11-17
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Abstract: Abstract During the lunar surface activities of the manned lunar landing project, the design verification and driving training of the manned lunar rover system should be carried out according to the requirements of space mission verification and astronaut comprehensive operation training. In this case, it is difficult to conduct somatosensory simulation of human rover driving training in the lunar surface environment. To solve the above problems, first, the characteristics of astronaut motion sensing information reception were analyzed, the lunar surface environment was created in the virtual environment, the lunar gravity conditions were established, and the dynamics model of the man-vehicle-moon system was established for motion sensing simulation. Then, the parameters of the somatosensory model are provided by dynamics calculation, and the astronaut's attitude adjustment is considered to simulate and verify the somatosensory model. Finally, the motion characteristics of astronauts driving on the Moon are analyzed, which provides support for the design verification and driving operation training of manned lunar rovers. PubDate: 2023-11-03
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Abstract: Abstract Surface tension and viscosity of complex Ti-based industrial alloys are important for simulation of liquid assisted industrial processes such as casting, joining, crystal growth and infiltration. Modelling of the interface and mass transport during liquid-solid phase transition requires reliable surface tension and viscosity data. Therefore, to obtain accurate predictions of microstructural evolution during solidification related processes, only reliable input data are necessary. In the case of liquid Ti-Al alloys, the experimental difficulties related to high temperature measurements and reactivity of these alloys with supporting materials or containers as well as inevitable presence of oxygen may lead to data gaps including a complete lack of property data. An alternative for container-based methods are containerless processing techniques that offer a significant accuracy improvement and / or make possible to measure temperature and composition dependent thermophysical properties of metallic melts, as in the case of the Ti-Al-Cr-Nb system. Advanced mathematical models and computer simulations, developed in several theoretical frameworks, can be used to compensate the missing data; on the other side, for the validation of theoretical models, the experimental data are used. In the present work, an evaluation of the surface tension and viscosity of liquid Ti-Al-Cr-Nb alloys by means of the predictive models and a comparison to the available experimental data were done. The proposed methodology is a tool to assess the reliability of thermophysical properties data of multicomponent alloy systems. PubDate: 2023-10-26
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Abstract: Abstract Some serious errors exist in the above paper. Many concentration profiles are truncated and wrong. The local similarity method used is not correct. The dimensionless Hartmann number is dimensional and wrong. PubDate: 2023-10-19
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Abstract: Abstract Simulated microgravity (SMG) is an environmental condition that affects bone density in vertebrates. Ground-based studies typically use a random positioning machine in either a 2D or a 3D mode to assess the effects of SMG, however the meaning of these results is difficult to compare between studies due to different experimental parameters. Here, we exposed larval Danio rerio at 3dpf to 23 h of SMG using a 2D and a 3D mode of rotation, using the same experimental setup. Zebrafish larvae were anaesthetized during the experiment. Our results showed that anesthesia (MS222) did not affect the amount of ossification while SMG-2D treatment slightly reduced the amount of ossification compared with the controls. On the other hand, SMG-3D treatment significantly reduced the overall ossification level of the skeleton. Specifically, the anterior end of the notochord, the ceratobranchial-5, the lower jaw articulation, the pharyngeal teeth, and the operculum were affected compared with control treatments. Overall, these results indicate that SMG-3D produced a more effective SMG effect compared with the SMG-2D. This research provides valuable insight into how different external stimuli such as SMG can cause negative effects on ossification in the developing skeleton in zebrafish. PubDate: 2023-10-11
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Abstract: Abstract This paper presents a method to analyse multirotor unmanned aerial vehicles (MUAVs) as microgravity platforms. MUAVs can maintain a free-fall state and provide microgravity owing to their precise thrust control abilities. Moreover, MUAVs are affordable platforms that can be procured at low-cost. Although several MUAVs of various sizes and configurations exist, their capabilities as microgravity platforms are not readily available. Towards this, a framework is developed to estimate microgravity performance measures such as 0g-time, payload capacity, and 0g-quality for a given MUAV. The proposed estimation framework requires only the data provided by the MUAV manufacturer to compute all the microgravity performance measures. The performance as a microgravity platform of several existing MUAVs of various configurations, masses, sizes, and thrust capabilities is estimated by employing this framework. This analysis reveals that there exist MUAVs that can provide microgravity (of the order of \(10^{-2}g\) ) for more than 4 s 0g-time while carrying more than 1 kg payloads. On the other hand, it is also shown that some MUAVs can carry payloads heavier than 90 kgs and provide microgravity for 2 s, which is comparable to the capability of some of the drop tower facilities. PubDate: 2023-09-27
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Abstract: Abstract Thermocapillary convection of nanofluid with evaporating phase change interface occurs in a variety of industrial processes such as micro/nano fabrication, ink-jet printing, thin film coatings, etc. Previous studies have mostly focused on the phenomena of thermocapillary convection in pure fluids without phase change. This paper reports the first fundamental experimental work on the thermocapillary flow of a thin nanofluid layer under the effect of evaporation. This research focuses on the behavior of a volatile thin nanofluid layer in a rectangular test cell under the effects of horizontal temperature gradient. The buoyancy effect can be neglected inside this thin liquid layer as in microgravity conditions. HEE7200 and HFE7200-Al2O3 nanofluid are used as working fluids to analyze the effect of nanoparticle addition. The results indicate that the linear relationship between the thickness of the liquid layer and the duration of evaporation is not changed by nanoparticles. HFE7200-Al2O3 nanofluid always has a higher evaporation rate than its base fluid with the temperature ranging from 2.98 °C to 13.92 °C. The critical Marangoni number for the nanofluid is lower than that of the pure fluid, which indicates that the addition of nanoparticles promotes the flow pattern transition. PubDate: 2023-09-25
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Abstract: Abstract InxGa1−xSb single crystals have been grown by using a GaSb/InSb/GaSb-sandwich system onboard at the International Space Station (ISS) via vertical gradient freezing method (VGF). In order to investigate the effects of InSb geometry on the InGaSb crystal growth under microgravity and further optimize the future space experiment, two-dimensional axisymmetric numerical simulations were carried out with different thicknesses and diameters of the InSb crystals. Simulation results showed that enough solutes from feed through diffusion is necessary for the crystal growth process and the InSb thickness will affect the axial Ga concentration gradient and therefore affect the crystal growth rates under microgravity. In addition, results also showed that a larger diameter for the InSb crystal will increase the volume crystal growth rates with a flatter shape for the grown crystal interfaces. In summary, simulation suggests a 2 mm or 3 mm thickness and a 12 mm diameter as the geometry of InSb for future space experiments. PubDate: 2023-09-15 DOI: 10.1007/s12217-023-10072-x
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Abstract: Abstract We report on the design and the construction of a sounding rocket payload capable of performing atom interferometry with Bose-Einstein condensates of \(^{41}\) K and \(^{87}\) Rb. The apparatus is designed to be launched in two consecutive missions with a VSB-30 sounding rocket and is qualified to withstand the expected vibrational loads of 1.8 g root-mean-square in a frequency range between 20–2000 Hz and the expected static loads during ascent and re-entry of 25 g. We present a modular design of the scientific payload comprising a physics package, a laser system, an electronics system and a battery module. A dedicated on-board software provides a largely automated process of predefined experiments. To operate the payload safely in laboratory and flight mode, a thermal control system and ground support equipment has been implemented and will be presented. The payload presented here represents a cornerstone for future applications of matter wave interferometry with ultracold atoms on satellites. PubDate: 2023-09-07 DOI: 10.1007/s12217-023-10068-7
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Abstract: Abstract A key aspect of space application technology is the generation and control of multi–phase flows. The efficiency of mass and heat transfer can be significantly improved by adding bubbles or droplets into continuous phases. The effects of the ratio of amplitude to bubble diameter (A/D), Bond number (Bo), and different gravity levels (G/g) on bubble centroid motion and shape oscillation are fully analyzed using the VOF method to understand the bubble–centroid trajectory and shape–oscillation mechanism under low–frequency vibrations. The present studies show that A/D, Bo, and G/g have important effects on bubble trajectory and shape oscillation. There are two types of oscillations for bubble shape: regular oscillation and chaotic oscillation. As Bo and A/D increase, bubble oscillation in a gravity–free environment changes from regular to chaotic oscillation. For the present results, bubble oscillations at different gravity levels (except zero–gravity level) are chaotic oscillations. Three types are recognized for the bubble–centroid motion: levitation, rising and sinking. When both A/D and Bo are tiny, a bubble is hung in its initial position in a gravity–free environment. Bubble–centroid motion changes from sinking to rising with an increase in A/D and Bo. The higher the gravity level is, the shorter the time taken for the bubble to rise is. The change in the flow field seems to be mainly caused by the vibration of fluid particles, almost independent of the level of gravity. The flow field becomes more chaotic as A/D and Bo increase. PubDate: 2023-09-05 DOI: 10.1007/s12217-023-10073-w
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Abstract: Abstract In droplet actuation, Lamb waves are utilized to manipulate and control liquid droplets on solid surfaces. This paper presents an analytical model for driving droplets using Lamb waves (a type of surface acoustic wave) on a non-piezoelectric substrate. The driving of droplets is simulated using the level set two-phase flow method, and the obtained data are validated through corresponding experiments. The simulation and experimental data are therefore combined to calculate and verify the attenuation of Lamb waves in droplet actuation. The research findings indicate that the droplets absorb the maximum amount of Lamb wave energy when their volume is 50 µL, and at this point, the Lamb wave experiences the fastest attenuation. PubDate: 2023-09-05 DOI: 10.1007/s12217-023-10071-y
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Abstract: Abstract Depression induced by weightlessness exposure in spaceflight has seriously affected astronauts’ psychology and flight missions, but the preventive and treatment methods remain limited. Here, we used systems pharmacology to identify the potential bioactive compounds from Hippophae rhamnoides L. (HR) for treating depression caused by weightlessness. First, isorhamnetin was screened out as a potential drug in HR for treating depression. Further, the therapeutic effect of isorhamnetin was investigated in depression induced by weightlessness using the hindlimb unloading (HLU) rat model. We found that treatment with isorhamnetin notably shortened immobility time during forced swimming tests and tail suspension tests in HLU rats. The hematoxylin-eosin staining results revealed that isorhamnetin could ameliorate morphological damage to the hippocampus of HLU-induced rats. Moreover, exposure to HLU caused increased corticosterone (CORT) and adrenocorticotropic hormone (ACTH) concentrations in serum. Administration with isorhamnetin for four weeks reduced the ACTH and CORT content in HLU rats. The 5-hydroxytryptamine and dopamine content in hippocampus were reduced in HLU rats, which were increased after isorhamnetin-treatment. Conclusively, isorhamnetin can alleviate the depression and hippocampus damage induced by weightlessness. Our study identified that isorhamnetin could be a natural bioactive drug for depression. PubDate: 2023-08-31 DOI: 10.1007/s12217-023-10070-z
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Abstract: Abstract In this paper, we developed a lightweight, self-sensing electret-based dynamic vibration absorber (ESDVA) for micro-vibration suppressions. We modeled the electromechanical coupling procedure of the ESDVA based on the first principles and proposed a sensing model based on support vector regression machine (SVR). The SVR algorithm helps to linearize the original voltage generated by the electret for precise vibration sensing. A prototype of the ESDVA is fabricated, and the theoretical model and SVR algorithms are verified by experiments. According to experimental results, the ESDVA successfully reduced primary structure vibration amplitudes by up to 50% with a mass burden of 1.4% of the primary structure. The proposed sensing model achieve an accuracy rate of over 93.5% for vibration sensing and the robustness of the model was also assessed. Moreover, the advantages of the proposed electret-based sensing method over classical methods are discussed. PubDate: 2023-08-18 DOI: 10.1007/s12217-023-10069-6
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Abstract: Abstract The future of space exploration will be contingent upon the use of plants in bioregenerative life support systems. Unfortunately, the microgravity of space can cause stress in plants, which can reduce growth. The Random Positioning Machine, RPM, is a device designed to provide an analogue for the effects of microgravity on Earth by rotating specimens in three dimensions. In this study, we compare the results from experiments conducted on the International Space Station with those conducted using the RPM (in the 3D clinostat mode) on the ground. Seedlings of Arabidopsis thaliana wildtype and phytochrome mutants were grown in true microgravity and in the omnidirectional gravity on a rotating RPM on the ground. We found that the RPM treatment caused less stress in the seedlings than did true microgravity. We also report that phytochromes A and B play roles in phototropic responses to unilateral light and that these roles differ in the two gravitational environments. Finally, we conclude that while root phototropism in unilateral red and blue differs significantly between the microgravity and omnidirectional stimuli, the RPM can serve as a reasonable analogue of microgravity conditions for assessment of shoot phototropism. PubDate: 2023-08-14 DOI: 10.1007/s12217-023-10066-9
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Abstract: Abstract In this study, a one-dimensional, two-phase transient model has been developed to study the transient behavior of water transport in the porous gas diffusion layer (GDL) of a proton exchange membrane fuel cell PEM fuel cell. This model based on the numerical resolution of the mass transport of liquid water and oxygen in the porous GDL is used to gauge the effects of various design and operational parameters, namely, the current density, GDL thickness and GDL permeability, on the overall performance of the system. PubDate: 2023-08-09 DOI: 10.1007/s12217-023-10067-8
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Abstract: Abstract The ongoing research numerically examines the impact of the nanoparticle shape factor on the coupled Marangoni and buoyancy convection in a cylindrical porous annular region saturated with Ag-MgO/water hybrid nanofluid with magnetic effects. The internal wall of the annulus is considered to be hot, while the external wall is believed to be cold. The inner cylinder is fitted with a thin circular heated disc. To solve the non-dimensional governing equations, the finite difference approach with ADI, central differencing, and SOR technique is used. The major goal of the current study is to analyze the impact of the various shape factors on the Marangoni convection, magnetic field and nanoparticle volume fraction in the cylindrical annulus. The current study reveals that the spherical shaped nanoparticle outperforms in all the cases and \(\overline{Nu}\) hikes with the Marangoni number and declines with Hartmann number. PubDate: 2023-08-05 DOI: 10.1007/s12217-023-10065-w
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