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A new active suspension gravity compensation system (ASGCS) is developed to offload the gravity of spacecraft or satellites for ground verification. The ASGCS is of six degrees of freedom (6-DOF), including a compensation stage of...
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A new active suspension gravity compensation system (ASGCS) is developed to offload the gravity of spacecraft or satellites for ground verification. The ASGCS is of six degrees of freedom (6-DOF), including a compensation stage of 3-DOF translation and a gimbal of 3-DOF rotation. A buffer-assisted pinion-rack mechanism is developed to substitute the traditional cable suspension unit, which enables the proportion of gravity compensation is tunable. A new 3-DOF gimbal that is suitable for objects of various sizes and arbitrary shape is developed. Hence, the test object attached to the ASGCS can be free-floating as it is in the outer space. Furthermore, a prototype of the ASGCS is developed, and the dynamic model and kinematic model are derived. Experiments are conducted with the aid of a 6-DOF hybrid coordinate manipulator. The results demonstrate that the ASGCS successfully tracks 6-DOF trajectories of a typical docking task and compensates for 95% of the gravity. (C) 2018 Elsevier Ltd. All rights reserved.
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PK-4 is a multi-functional plasma discharge source. Two setups exist for operating plasma discharge experiments on parabolic flight campaigns as well as in laboratory. Another setup for use on the International Space Station ISS i...
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PK-4 is a multi-functional plasma discharge source. Two setups exist for operating plasma discharge experiments on parabolic flight campaigns as well as in laboratory. Another setup for use on the International Space Station ISS is planned. The plasma can be created by a dc-discharge as well as by rf-discharges, coupled inductively. There exist various possibilities to manipulate the introduced microparticles: mechanical (glass-nozzle), optical (high power laser), electrical (EM-pulse-electrode, rf-electrodes, polarity-switching) and thermal (heating coil) manipulation. Several different types of experiments have already been done with PK-4 in parabolic flights: Nozzle-Experiments (particle jets, transition between fluid and single particle behaviour), Lane-Formation (cloud collisions), Laser driven shear flow, Shock waves and solitons (excitation of shock waves applying electric pulses using the EM-electrode), String-Fluids (electro-rheological fluids), and many more.
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This paper aims to address attitude stabilization control of an underactuated post-capture combination and achieve test validation based on the magnetism-buoyancy hybrid micro-gravity experiment system (MBHMES). Using a precise re...
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This paper aims to address attitude stabilization control of an underactuated post-capture combination and achieve test validation based on the magnetism-buoyancy hybrid micro-gravity experiment system (MBHMES). Using a precise reduced model, a cascade control law is proposed to solve the issue theoretically. First, an advanced quaternion-based kinematic control law is proposed to stabilize the attitude of the non-symmetric post-capture combination. This control law can overcome the singularity brought about by the small initial attitude under the consideration of uncontrolled angular velocity. Then, considering the existence of multiple disturbances introduced by the fluid flow and electromagnetic force, an effective adaptive dynamic controller is proposed to meet the attitude requirement and reduce the negative effect of the multiple disturbances. For test demonstrations, a scenario of a base body capturing the target with robotics, to achieve attitude stabilization expectation, is described. Simulation results demonstrate the performance of the cascade control laws and test data show the effectiveness of the proposed method.
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In this paper, new perspectives and developments in applying a ground-based micro-gravimetric method to detect groundwater storage change in Waterloo Moraine are investigated. Four epochs of gravity survey were conducted using abs...
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In this paper, new perspectives and developments in applying a ground-based micro-gravimetric method to detect groundwater storage change in Waterloo Moraine are investigated. Four epochs of gravity survey were conducted using absolute gravimeter (FG5), two relative gravity meters (CG5) and two geodetic global positioning systems (GPS) in the Waterloo Moraine in May and August of 2010 and 2011, respectively. Data were processed using the parametric least-squares method and integrated with geological and hydrological studies. The gravity differences between May and August for 2010 and 2011 epochs were inverted to provide the estimated total water storage changes. Changes in soil water content obtained from land surface models of Ecological Assimilation of Land and Climate Observations (EALCO) and the Global Land Data Assimilation System (GLDAS) program were employed to estimate the groundwater storage change. The ratios between the estimated groundwater storage changes and measured water table changes (specific yields) were determined at a local monitoring well located in the survey area. The results showed that the estimates of specific yields between May and August of 2010 and 2011 were consistent at a significant confidence level and are also within the range of the specific yield from geological and hydrological studies. Therefore, the micro-gravimetric (absolute and relative gravity meters) technology has demonstrated the great potential in detecting groundwater storage change and specific yield for local scale aquifers such as Waterloo Moraine.
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This paper studies the phenomenon of thermodiffusion in a binary mixture (water/isopropanol 90:10 wt %) subjected to different gravity fields. A second-order finite-difference code based on the projection method has been developed...
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This paper studies the phenomenon of thermodiffusion in a binary mixture (water/isopropanol 90:10 wt %) subjected to different gravity fields. A second-order finite-difference code based on the projection method has been developed to solve the governing equations. Initially, by studying the optimized cell orientation, the effects of a static gravity field on the quality of the experiment have been investigated. Furthermore, the effects of purely-oscillatory forced vibration on the flow characteristics have been investigated for a wide range of frequencies and amplitudes of the oscillatory gravity. These values have been chosen to represent the range of experiments that have been performed in the IVIDIL projects on board the International Space Station. Flow characteristics including average velocity, temperature, and concentration fields are extracted and discussed in detail. It was shown that the negative effects of an oscillatory gravity field are intensified for lower frequencies and larger amplitudes of vibration. For both cases of residual and oscillatory gravity fields a threshold is determined in terms of non-dimensional numbers beyond which the diffusion process is affected by the induced flow field.
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To strengthen the heat dissipating capacity of a heat pipe used for integrated insulated gate bipolar transistors, as an extension of our earlier work, the effect of micro-groove dimension on the thermal performance of flat micro-...
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To strengthen the heat dissipating capacity of a heat pipe used for integrated insulated gate bipolar transistors, as an extension of our earlier work, the effect of micro-groove dimension on the thermal performance of flat micro-grooved gravity heat pipe was studied. Nine pipes with different depths (0.4 mm, 0.8 mm, 1.2 mm) and widths (0.4 mm, 0.8 mm, 1.2 mm) were fabricated and tested under a heating load range from 80 W to 180 W. The start-up time, temperature difference, relative thermal resistance and equivalent thermal conductivity were presented as performance indicators by comparison of flat gravity heat pipes with and without micro-grooves. Results reveal that the highest equivalent thermal conductivity of the flat micro-grooved gravity heat pipes is 2.55 times as that of the flat gravity heat pipe without micro-grooves. The flat gravity heat pipes with deeper and narrower micro-grooves show better thermal performance and the optimal rectangular micro-groove dimension among the selected options is determined to be 1.2 mm (depth) × 0.4 mm (width). Furthermore, the liquid–vapor phase behaviors were observed to verify the heat transfer effects and analyze the heat transfer mechanism of the flat micro-grooved heat pipes.
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The multi-phase solver interFoam within the open-source CFD software OpenFOAM is newly applied to rare experiments conducted beginning over 10 years ago aboard the International Space Station (ISS). The fluid physics of interest c...
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The multi-phase solver interFoam within the open-source CFD software OpenFOAM is newly applied to rare experiments conducted beginning over 10 years ago aboard the International Space Station (ISS). The fluid physics of interest concern large length scale passive capillary flows in a microgravity environment driven largely by surface tension, wetting conditions, and container or conduit geometry. Such flows are critical to orbiting and coast spacecraft liquid fuels, propellants, cryogens, thermal fluids, and aqueous streams for water management, recycling, and life support. The value of the simulations is assessed via quantitative comparisons to the ISS Capillary Flow Experiments (CFE) for a series of centimetric handheld test cells. Three representative flows are simulated as functions of geometric complexity: 1) bubble coalescence, 2) ullage migration, and 3) draining flow. The experimental data is newly digitized for the bench-marking effort. The favorable agreement between the simulations and experiments adds confidence for advanced applications of the native interFoam multi-phase solver of the OpenFOAM suite, where experimental data is scarce.
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Magnetic fields and magnetic materials have promising microfluidic applications. For example, magnetic micro-convection can enhance mixing considerably. However, previous studies have not explained increased effective diffusion du...
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Magnetic fields and magnetic materials have promising microfluidic applications. For example, magnetic micro-convection can enhance mixing considerably. However, previous studies have not explained increased effective diffusion during this phenomenon. Here we show that enhanced interface smearing comes from a gravity induced convective motion within a thin microfluidic channel, caused by a small density difference between miscible magnetic and non-magnetic fluids. This motion resembles diffusive behavior and can be described with an effective diffusion coefficient. We explain this with a theoretical model, based on a dimensionless gravitational Rayleigh number, and verify it by numerical simulations and experiments with different cell thicknesses. Results indicate the applicability and limitations for microfluidic applications of other colloidal systems. Residual magnetic micro-convection follows earlier predictions.
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Micro-gravity Laboratory of Japan (MGLAB) was established in order to provide researchers in Japan and abroad with inexpensive and readily usable facilities for micro- ties have several features for researchers to use it easily an...
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Micro-gravity Laboratory of Japan (MGLAB) was established in order to provide researchers in Japan and abroad with inexpensive and readily usable facilities for micro- ties have several features for researchers to use it easily and to do repetitive experiments. A unique technology is adopted for the braking system to reduce the braking G.
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