Reverse Gravity Research Articles

Modeling the Interactive Patterns of International Migration Network through a Reverse Gravity Approach

The international migration network, comprising the movements of people between countries, is one of the most important global systems of interaction, which can reflect the complex international relations of economics, cultures, and politics and has huge impacts on global sustainability. However, the conventional gravity model cannot model its complicated interactions accurately. In this article, we propose a novel reverse gravity model using genetic algorithm to reconstruct the complicated interaction patterns with high accuracy. To verify the feasibility of our method, it was applied to a series of international migration networks. We found that the derived node attractions were highly correlated with socioeconomic factors and network metrics, and the calculated node positions outperformed the geometric centers from the perspective of human migration that related to economy and demography. Our approach could be a preferred choice to investigate the spatial–temporal interactive patterns in geographical space, facilitating comprehension of the mechanisms underlying their generation and evolution.

Fabrication of a superhydrophobic cotton fabric with efficient antibacterial properties and asymmetric wettability via synergistic effect of quaternized chitosan/TiO2/Ag

A superhydrophobic cotton fabric with unidirectional moisture transfer ability, antibacterial, and oil-water separation capabilities was fabricated by combining a simple coating method and oxygen plasma etching. Polydimethylsiloxane (PDMS) was employed to impart low surface energy to the cotton fabric, thereby endowing it with hydrophobic characteristics. The synthesized quaternized chitosan/TiO2/Ag (CTA) compound was subsequently applied onto the cotton fabric surface to introduce a desirable level of surface roughness, thus enhancing its hydrophobic properties and conferring excellent antibacterial efficacy. The cotton was subsequently treated by oxygen plasma to trigger asymmetrical wetting on both sides. The experimental findings reveal that the optimally treated cotton fabric exhibits hydrophobic properties on the bottom surface, with a water contact angle (WCA) reaching 162.8°, while the upper surface displays hydrophilic behavior, establishing a wetting gradient along the thickness direction. Notably, even under the influence of reverse gravity, water droplets are capable of transferring from the back to the top surface within 2 s, while preventing reverse penetration of liquid. Moreover, the synthesized compound CTA endows the cotton fabric with efficient and long-lasting antibacterial properties through two modes (contact and release sterilization modes) and three sterilization mechanisms (electrostatic interaction, plasma surface resonance effect, and reactive oxygen species). Remarkably, within a time frame of only 1 h, the modified cotton fabric is able to achieve a kill rate exceeding 99% against Escherichia coli and Staphylococcus aureus. Moreover, the aforementioned properties demonstrate outstanding durability against repeated washing, continuous abrasion, exposure to strong acid/base, and ultraviolet radiation. Additionally, this modified cotton fabric exhibits remarkable efficiency in terms of oil-water separation, effectively separating both light and heavy oil from water. It is worth noting that the preparation process is cost-effective, environmentally friendly, and free from fluorine.

Complex gravity-acoustic impact on V-flame structure

Development of efficient and safe energy systems for space objects includes ensuring fire safety. This problem requires a deep understanding of influence of gravitational forces on combustion processes, which explains the importance of studying this issue. The paper analyzes the dynamics of inverted conical methane-air flame under conditions of normal and reverse gravitational force with external acoustic excitation. Applied frequencies of acoustic excitation could be parasitic or be produced during proper work of different technical systems of aircraft. High speed recording of flame chemiluminescence and PIV analysis were conducted. Decomposition of flow vector pictures into the modes was calculated using POD method. Energy contribution into the flow was analyzed for its separate elements at the different frequencies of excitation. At the high excitation frequencies vortex generation intensity in the shear layer with reverse gravity is about the same as it was observed in the experiments with normal gravity direction, that could indicate dominance of acoustic mechanism of the vortexes stimulation over the mechanism of shear instability. At external excitation frequency equals 240 Hz significant growth of shear vortex diameters and increasing of perpendicular oscillations amplitude of flame branches were obtained. Thereby in such experiment with 240 Hz external acoustic excitation the most intensive large scale instability of flow was observed.

Vortex zone dynamics in premixed flame under complex gravity and acoustic impact

An inverted conical, plane-symmetrical premixed methane–air flame stabilized by a bluff body under acoustic excitation and various gravity conditions was experimentally investigated. Recirculation zone characteristics were found by means of the phase-resolved particle image velocimetry method. An increase in the size of the longitudinal vortex zone was shown with an increase in both fuel concentration and flow velocity under normal and reverse gravity. The longitudinal size of the vortex zone is independent of frequency, regardless of the direction of gravity at low flow velocity (≤5 m/s) in a stoichiometric flame under the considered excitation frequency range (40–420 Hz). With a flow velocity increase, the size of the vortex zone becomes sensitive to the excitation frequency. An increase in the excitation frequency results in a length decrease in the vortex zone. In rich flames, an inverse relation of the longitudinal vortex zone size to the excitation frequency is observed at lower velocities (5 m/s) for normal gravity conditions. Whereas, under conditions of inverted gravity, the fuel air ratio increase does not lead to such a relation; the vortex zone has a constant length under various excitation frequencies. An external acoustic excitation causes a periodic change in the vortex zone longitudinal size, and for a stoichiometric mixture, the amplitude does not depend on the disturbance frequency. For a rich mixture, a frequency increase results in an amplitude decrease. For selected frequencies and flow velocities, desynchronization of the vortex zone oscillations with external disturbances is observed.

Application of Physics for Understanding the Earth’s Reverse Gravity

The prevalent view endorses that the force of gravitation of the earth is directed towards the centre of the planet, in consequence of which, temperature and pressure at the deepest part of the planet must be very high. This view leads to the conclusion that the inner core or deepest part of the planet, though constituted of iron through which magnetic lines of force emanate, cannot be magnetic. The author has shown that amongst the earth’s three geospheres, fluid outer core that occurs between mantle and inner core, is a void zone which, because of the association of some particles from the mantle, apparently shows fluid characteristics. Occurrence of a virtually void zone in the planet’s deep interior separated by a solid mantle and iron inner core would generate a reversely directed gravitational force due to which pressure and temperature at the deepest part of the earth would be sufficiently low. Hence, the earth’s solid inner core, constituted of iron, is a dipolar permanent magnet. The paper envisages that the concept of reverse gravity presented here needs to be validated by physicists since it is an original view. The concept put forward here, not only explains the cause of earth’s magnetic phenomena, but also elucidates continental drifting and several other features of the planet in a scientifically accepted manner, thereby refuting the possibility of occurrence of convection current in the mantle which is solid and rigid.

Inverted conical methane/air flame shape transformation under acoustic excitation: Gravity impact

In this paper it is shown that under certain conditions under reverse gravity, acoustics increase the stability of the flame in comparison with normal gravity. It is shown that there is a hysteresis in the V–M and M–V transitions under reverse gravity as well as under normal one. In contrast to normal gravity, the conditions for hysteresis degeneracy under reverse gravity are proven to be independent of the excitation frequency.

Gravity impact on inverted conical flame stability and dynamics

The paper studies experimentally the stability of an inverted conical plane-symmetrical premixed methane-air flame under normal and reversed gravity. The conical flame is stabilized by a thin transverse rod. Flow velocity is varied within the range of 1–8 m/s, fuel equivalence ratio— within the range of 0.8–1.4. It is shown that such a flame could be both V-shaped (attached only to the stabilization rod) and M-shaped (attached both to nozzle edge and stabilization rod) depending on the set of conditions. The transition between two modes is studied experimentally under normal and reversed gravity. The hysteresis properties for the M–V and V–M transitions under the normal gravity conditions and their absence under the reverse gravity ones are reported. The most unstable flames are observed under reversed gravity at the maximum burning velocity (φ ≈ 1.1 ±). For such conditions, periodical oscillations between M-shaped and V-shaped flames occur over a wide range of velocities. In the experiments under reverse gravity, the V shape prevails over the M shape. It is found that a reverse flow exists above the stabilizer at any velocity under normal gravity and at high velocities (>5 m/s) under reverse gravity. In both cases, a linear increase in the longitudinal size of the vortex zone with increasing velocity is observed. It is concluded that gravity noticeably contributes to rich flames stability.

Fabrication of a wearable directional moisture-transfer cotton by clean technology of wet plasma, without fluoride consumption

A cleaner wearable cotton which has the properties of one-way water transfer and resisting external liquid contamination was fabricated in this study. Wet plasma combined with fluorine-free hydrophobic agent (WP-FfHA) was used as an environmental-friendly technology in the preparation process. Other than the attribute of environmental protection, it was proved that wet plasma can not only reduce the consumption of water-repellent agent by 25 %, but also significantly improve the waterproofness of fabric through contact angle measurement. Water-drip test was used to determine the asymmetric wettability of the fabric. The results display that the water droplets were transferred from the undersurface to the top surface within less than 3 s through wicking zones, even under the condition of reverse gravity. Meanwhile, the liquids on the upper surface were not able to reverse-penetrate to the bottom. Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) were employed to analyze the micro-topography and chemical construction of the wicking and non-wicking areas on the fabric surface. Tests for fastness showed that the fabric maintained a contact angle of 145 ° after 5 times of regular soaping. Investigation of breathability and mechanical property confirmed that the wearability of the cleaner directional moisture-transfer fabric was not adversely affected by this novel modification approach.

Calculating Theme Parks’ Tourism Demand and Attractiveness Energy: A Reverse Gravity Model and Particle Swarm Optimization

This study proposes two new concepts/indices—tourism demand energy and tourism attractiveness energy—to measure origin-side tourism demand and destination attractiveness. Tourism demand energy and tourism attractiveness energy are estimated based on tourist visitation, travel distance, and visitor flow network relationships. A reverse gravity model was developed, and a particle swarm optimization design was adopted and revised for estimation. This study has a theme park context and uses data collected from 47,360 TripAdvisor reviews for 170 US theme parks. We determined theme park demand energy for each of 52 tourist source regions, and theme park attractiveness energy for each of the 170 theme parks. These two new concepts extend and improve measures of origin-side tourism demand and destination attractiveness. They also underscore the importance of travel distance in measuring origin-side tourism demand and destination attractiveness, offering a new perspective on the driving forces of tourism.

Electrohydrodynamics and boiling: Experiments, numerical calculation and modeling of Maxwell stress tensor and electric force acting on bubbles

Boiling dynamics on earth is heavily affected by gravity. The purpose of this work is to investigate the feasibility of a replacement of gravity when it lacks: an external electric field can promote an efficient and reliable bubble removal system for space applications. To this intent, different experiments running in normal gravity, reverse gravity and microgravity (via parabolic flights) have been performed. The experiments were executed in adiabatic conditions (injecting air through an orifice) and in quasi-static conditions. This option was chosen in order to investigate only the dynamics terms of momentum balance, neglecting, at this stage, all the terms involving heat and mass transfer (which are in turn promoted by the electric field, i.e.: electroconvection). An experimental electric force has been calculated, as the unbalanced component of the force balance, and, thanks to the FEM software COMSOL Multiphysics, compared to the numerical integration of Maxwell stress tensor. Furthermore, a simple model based on the electrohydrodynamics of an oblate ellipsoid (Landau and Lifšitz 1984) has been compared to the results of the three sets of experiments.

How do urban spatial structures evolution in the high-speed rail era? Case study of Yangtze River Delta, China

The construction of high-speed rail (HSR) networks is of great significance to researchers in the fields of regional development, regional structure, and regional integration. Whilst a large number of studies have estimated the impacts of HSR networks on regional economic development, accessibility, and commuting behavior, how urban spatial structures evolution in the HSR era remain largely unexplored. Thus, the purpose of this paper is to explore how the urban structures (urban hierarchical structure and urban physical structure) of cities in the Yangtze River Delta evolution by employing a reverse gravity model and a gravity deviation model in the HSR era. Our findings indicate that in the HSR network, the traffic attractiveness of cities in Pan-Yangtze River Delta showed an obvious hierarchical distribution (taking on a spindle shape), and that the first-tier cities comprised of Shanghai and Nanjing. We further found that the impacts of introducing a HSR network on urban land growth were greater in non-HSR cities than in cities with HSR. In addition, the growth rate of urban land was found to be higher in areas surrounding HSR stations than in the city at large. This shows that the introduction of HSR significantly stimulated the development of the cities making up the study area. More importantly, after the opening of the HSR network, the center of gravity of the urban areas of 75% cities that were connected to the HSR network was found to deviate towards the HSR station. Differences in the pattern and degree of deviation were identified, thus indicating the presence of individual differences in the effects of HSR on urban growth in different cities.

Experimental and Numerical Studies on the Vertical Flow of Variable Density Fluid in Different Directions

Injecting freshwater and pumping salt water are effective methods to restore the salt water in a coastal area. Based on a one-dimensional vertical experiment, the variable density flow is simulated under the condition of different injection directions and injection rates of fresh water. A one-dimensional mathematical model of variable density flow and solute transport is established. The mathematical models are solved using the implicit difference method. Fortran code is developed to simulate and verify the vertical flow of variable density flow in different directions. Through both numerical simulation and experimental studies, it is found that the variable density fluid in the direction of reverse gravity is different from that in the direction of gravity. On this basis, the most effective desalination model of salt water is further discussed. It provides a theoretical and technical method for the restoration of salt water in the vertical injection of freshwater. In order to improve the remediation efficiency and reduce the cost in the engineering application, the suitable water injection rate should be ensured, considering the suitable construction time and zone of a study area.

Numerical simulation of the flow distribution in a trap of a propellant tank with micro gravity

A trap device is defined as a closed structure which holds and provides a specific quantity of propellant using the surface tension forces. A trap in a vane-type PMD is investigated. The influence of the cone angle of the trap and flow distributions with different conditions in space are investigated. The VOF model could be used to simulate the flow distribution in a trap with zero or small gravity condition. The optimal angle for the trap is α=45° and it has the best result of expulsion efficiency of the propellant tank. The trap can be full filled with propellant after 21 second at zero gravity condition and 37 second at north-south insurance condition. A gas bubble left in the trap at the end of the refilling process. There is no flow distribution change in the trap when the trap is full filled at reverse gravity condition and sink condition.

Continental Drift and Plate Tectonics vis-a-vis Earth’s Expansion:Probing the Missing Links for Understanding the Total Earth System

Hypotheses like continental drift, plate tectonics or Earth’s expansion should not be considered as viable in view of solid and rigid state of mantle which, in contrast, would resist such phenomena. Based on Hilgenberg’s model of Earth’s expansion (1933), the author elucidates that before expansion when the Earth was small and devoid of oceans, its mantle must have been sufficiently fluid owing to association of ocean-forming water. Further, matching thickness of fluid outer core and extent of radial expansion of the Earth strongly support that the outer core was opened up as a void geosphere owing to planetary expansion. At the deep interior of the planet, owing to occurrence of a void or pseudo-fluid geosphere separating basaltic mantle and solid iron core, an additional force of reverse gravity would develop acting in opposite direction of normal inwardly directed force of gravity. This postulation leads us to consider that in the deep interior of the planet an upwardly directed force of gravitational attraction would act in a predominant manner, thereby sustaining sufficiently low temperature and pressure condition and magnetic nature of the inner core which completely agrees with observed features of terrestrial magnetism. Over the Earth’s surface the crustal layer was fragmented due to expansion while through the expansion cracks widespread incidences of magma emission occurred forming rudimentary ocean basins. With further expansion, these basins were expanded and filled up with water that degassed from the mantle associated with the process of magma emission while owing to desiccation, the mantle itself eventually turned into a rigid body. Before expansion of the planet when the iron core and the mantle were juxtaposed to each other, due to external magnetic influence the magnetic iron core was deflected causing major change in polar and equatorial disposition of the planet. Subsequently in younger geological period when due to expansion a major void geosphere was opened up between the iron core and mantle, external magnetic influences caused the magnetic core to execute smooth revolutions giving rise to new magnetic phenomena like pole reversal and polar wandering, documented over the planet’s younger strata. It may be noted that while due to expansion, the continental fragments would tend to move away from one another, owing to rotation of the planet along its axis of rotation some continental fragments came closer to each other or even collided to form mountain ranges.

Study on Surface Depression of Ti-6Al-4V with Ultrahigh-Frequency Pulsed Gas Tungsten Arc Welding

Molten pool surface depression was observed with the arc welding process that was caused by arc pressure. It was supposed to have a significant effect on fluid in the molten pool that was important for the microstructure and joint properties. The impact of arc force was recognized as the reason for the surface depression during arc welding. The mathematical distribution of arc force was produced with the exponent and parabola models. Different models showed different concentrations and attenuations. The comparison between them was discussed with the simulation results. The volume of fluid method was picked up with the arc force distribution model. The surface depression was caused by the arc force. The geometry of the surface depression was discussed with liquid metal properties. The welding process was carried out with different pulsed frequencies. The results indicated the forced depression exists in molten pool and the geometry of depression was hugely due to the arc force distribution. The previous work calculated the depression in the center with force balance at one point. The other area of gas shielding was resistant by the reverse gravity from the feedback of liquid metal that was squeezed out. The article discusses the pressure effect with free deformation that allowed resistance of liquid and was easy to compare with different distributions. The curve profiles were studied with the arc force distributions, and exponent model was supposed to be more accurate to the as-weld condition.

Reconstructing Gravitational Attractions of Major Cities in China from Air Passenger Flow Data, 2001–2008: A Particle Swarm Optimization Approach*

In contrast to the conventional gravity model that estimates flows between cities of given sizes, the reverse gravity model attempts to reconstruct the theoretical gravitational attractions of cities from network flow data. This article introduces the particle swarm optimization (PSO) method in solving the reverse gravity model. With comparison to the linear programming (LP) and the simplified algebraic method (SAM), the advantages of the PSO method include flexibility in the impedance function and better goodness of fit. The method is applied to the case study of air passenger transport in China. The results indicate that estimated nodal attractions in cities are generally in line with their population sizes, but there are significant discrepancies between them. A close examination of the discrepancies reveals that a better developed tertiary sector and higher tourism revenue per capita are associated with overestimated attractions in air transport, and stronger railway dominance influences their underestimation. The changes of gravitational attractions in major cities from 2001 to 2008 indicate the declining dominance of the largest cities and a move toward a more balanced development in the air transport system of China.

Imaging of premixed flames in microgravity

A laser schlieren system which uses video recording and digital images analysis has been developed and applied successfully to microgravity combustion experiments performed in a drop-tower. The optical system and the experiment are installed within a small package which is subjected to free-fall. The images are recorded on video tape and are digitized and analyzed by a computer-controlled image processor. The experimental results include laminar and turbulent premixed conical flames in microgravity, normal positive gravity (upward), and reverse gravity (downward). The procedures to extract frequency information from the digitized images are described. Many gross features of the effects of gravity on premixed conical flames are found. Flames that ignite easily in normal gravity fail to ignite in microgravity. Buoyancy driven instabilities associated with an interface formed between the hot products and the cold surrounding air is the mechanism through which gravity influences premixed laminar and turbulent flames. In normal gravity, this causes the flame to flicker. In reverse gravity, -g, and microgravity, μg, the interface is stable and flame flickering ceases. The flickering frequencies of +g flames vary with changing upstream boundary conditions. The absence of flame flickering in μg suggest that μg flames would be less sensitive to these changes.

Liquid hydrogen slosh waves excited by constant reverse gravity acceleration of geyser initiation

The requirement to settle or to position liquid fuel over the outlet end of the spacecraft propellant tank before main engine restart poses a microgravity fluid behavior problem. Resettlement or reorientation of liquid propellant can be accomplished by providing the optimal acceleration to the spacecraft such that the propellant is reoriented over the tank outlet. In this study slosh wave excitation induced by the resettling flowfield during the course of liquid reorientation with the initiation of geyser for liquid-filled levels of 30, 50, 65, 70, and 80 percent have been studied. Characteristics of slosh waves with various frequencies excited are discussed. Slosh wave excitations will affect the fluid stress distribution exerted on the container wall and shift the fluid mass distribution inside the container, which imposes the time-dependent variations in the moment of inertia of the container. This information is important for the spacecraft control during the course of liquid reorientation.

Excitation of slosh waves associated with low frequency impulsive reverse gravity acceleration of geyser initiation

The objective of the cryogenic fluid management of the spacecraft propulsion system is to develop the technology necessary for acquisition or positioning of liquid and vapor within a tank in reduced gravity to enable liquid outflow or vapor venting. The requirement to settle or to position liquid fuel over the outlet end of the spacecraft propellant tank prior to main engine restart poses a microgravity fluid behavior problem. The purpose of the present study is to investigate the stability of the most efficient technique for propellant resettling through the minimization of propellant usage and weight penalties. In this study slosh wave excitation induced by the resettling flow field activated by 0.1 Hz low frequency, impulsive reverse gravity acceleration, during reorientation with the initiation of geyser for liquid fill levels of 30, 50, 65, 70 and 80%, have been studied. Characteristics of slosh waves with various frequencies excited are discussed. Slosh wave excitations shift the fluid mass distribution in the container which impose time dependent variations in spacecraft moment of inertia. This information is important for the spacecraft control during the course of liquid reorientation.

Constant reverse thrust activated reorientation of liquid hydrogen with Geyser initiation

A key objective of the cryogenic fluid management of the spacecraft propulsion system is to develop the technology necessary for acquisition or positioning of liquid outflow or vapor venting. Numerical simulation of positive liquid acquisition is attempted by introducing reverse gravity acceleration, resulting from the propulsive thrust of auxiliary engines, which exceeds critical value for the initiation of geyser. Based on the computer simulation of flowfields during the course of fluid reorientation, six dimensionless parameters resulted in this study. It shows that these parameters hold near-constant values through the entire ranges of liquid filled levels, from 30-80 percent, during the course of fluid reorientation.