Supergravity separation of Pb and Sn from waste printed circuit boards at different temperatures

Printed circuit boards（PCBs） contain many toxic substances as well as valuable metals, e.g., lead（Pb） and tin（Sn）. In this study, a novel technology, named supergravity, was used to separate different mass ratios of Pb and Sn from Pb–Sn alloys in PCBs. In a supergravity field, the liquid metal phase can permeate from solid particles. Hence, temperatures of 200, 280, and 400°C were chosen to separate Pb and Sn from PCBs. The results depicted that gravity coefficient only affected the recovery rates of Pb and Sn, whereas it had little effect on the mass ratios of Pb and Sn in the obtained alloys. With an increase in gravity coefficient, the recovery values of Pb and Sn in each step of the separation process increased. In the single-step separation process, the mass ratios of Pb and Sn in Pb–Sn alloys were 0.55, 0.40, and 0.64 at 200, 280, and 400°C, respectively. In the two-step separation process, the mass ratios were 0.12 and 0.55 at 280 and 400°C, respectively. Further, the mass ratio was observed to be 0.76 at 400°C in the three-step separation process. This process provides an innovative approach to the recycling mechanism of Pb and Sn from PCBs.

Preparation of Nickel‑Cobalt/Carborundum Carbide Composite Coatings by Supergravity Field‑Enhanced Electrodeposition

Nickel-cobalt/silicon carbide(Ni-Co/SiC)composite coatings were fabricated by supergravity field-enhanced electrodeposition.The surface morphology and the distribution of the SiC particles in the coatings were examined by scanning electron microscope and energy dispersive X-ray spectrometry.The preferred orientations of the coatings were measured by X-ray diffractometry.The wear resistance and microhardness were measured by a reciprocating tribometer and a microhardness instrument,respectively.The results revealed that the use of the supergravity field enhanced the smoothness of the as-deposited Ni-Co/SiC coatings,and the SiC nanoparticles were uniformly distributed in comparison with that for conventional electrodeposition.When the rotation speed of the cathode,which provided the supergravity field,was 800 r/min,the SiC content in the coating reached a maximum of 8.1 wt%,which was a much higher content than the 2.2 wt%value obtained under conventional electrodeposition.The highest coating microhardness of 680 HV was also observed at this rotation speed.In addition,the wear resistance of the as-prepared Ni-Co/SiC coatings exhibited improved performance relative to that prepared under normal gravity.A minimum wear weight loss of 1.4 mg together with an average friction coefficient of 0.13 were also realized at a rotation speed of 800 r/min,values which were much lower than those for normal gravity.

Supergravity-induced interactions on thick branes

The gravity coupling of the symmetric space sigma model is studied in the solvable Lie algebra parametrization. The corresponding Einstein equations are derived and the energy-momentum tensor is calculated. The results are used to derive the dynamical equations of the warped five-dimensional （5D） geometry for localized bulk scalar interactions in the framework of thick brane world models. The Einstein and scalar field equations are derived for flat brane geometry in the context of minimal and non-minimal gravity-bulk scalar couplings.

Supergravity effects on flame propagation and structure in hydrogen/air mixtures

In the current work,we investigated hydrogen/air flame propagation under supergravity conditions.Results show that when gravity is in the same/opposite direction as flame propagation,it leads to acceleration/deceleration of the flame,and that such an effect could substantially modify the flame propagation and structure at high gravity levels.Furthermore,for the absolute and relative flame propagation speeds,the gravity-affected flame speed shows opposite trends as the absolute flame speed is more affected by the local induced flow field,while the relative flame speeds are controlled by the super-adiabatic or sub-adiabatic flame temperature.The gravity-affected thermal and chemical flame structures are also examined through the influence of the mixture equivalence ratio,pressure,and flame stretch.

Fundamental research on recovering metals from hot-dip Zn-Al-Mg dross by supergravity separation

The dross generated in the hot-dip Zn–Al–Mg coating process is a valuable co-product,since it contains high quantities of recyclable alloy.A new method to recover Zn–Al–Mg alloy from the industrial Zn–Al–Mg dross was proposed using supergravity separation.The separation efficiency was analyzed as a function of gravity coefficient(G),separation time,and separation temperature.The separation of Zn–Al–Mg alloy from the dross can be achieved at G>100.The alloy content in the dross decreased gradually with an increase in the gravity coefficient,the separation time,and the separation temperature.The alloy ratio in the enriched dross decreased almost linearly as the gravity coefficient increased,and the recovery of Zn–Al–Mg alloy from the dross exceeded 78%;these results were consistent with the results of the FactSage software calculation.The purified alloy can be in-situ used in the hot-dip Zn–Al–Mg bath for production.The feasibility of supergravity separation as a promising process for efficiently recovering Zn–Al–Mg alloy from Zn–Al–Mg dross was thus demonstrated.

Graded microstructures of Al-Li-Mg-Zn-Cu entropic alloys under supergravity

Investigating the microstructures and properties of gradient materials has been regarded as a promising way to accelerate the identification of optimal compositions for applications. Herein, a supergravity method is applied to prepare the graded entropic alloys Al-Zn-Li-Mg-Cu. Through carefully optimizing the experimental conditions, the graded microstructures and hardness values appear after the supergravity technique. The morphology of the alloy significantly changes from the bulk intermetallics to eutectic structures along the supergravity force direction, which results from the crushed and graded aluminum oxide combined with the extremelystrong force. The results show that with this supergravity method, a performance-enhanced alloy can potentially be achieved through the centrifugation in a short time span and thus it paves the way for designing and synthesizing entropic alloys with intriguing properties.

Degenerate black rings in D=5 minimal supergravity

We consider both gauged and ungauged minimal supergravities in five dimensions and analyse the charged rotating solutions with two equal angular momenta J.When the electric charge Q∼J^(2/3) with some specific coefficient,we find new extremal black objects emerge that are asymptotic to either Minkowski or global AdS spacetimes and can be best described as degenerate black rings.Their near-horizon geometry is locally AdS3×S^(2),where the periodic U(1)fibre coordinate in S 3 untwists and collapses to be the degenerate part of the AdS3 horizon.It turns out that there are two branches of extremal rotating black holes,starting as the extremal RN black holes of the same mass,but opposite charges.With the increasing of the angular momentum,they will join to become the same degenerate black ring,where the Gibbs free energies however are not continuous at the joining.For the same Q(J)relation,we find that there is in addition a rotating soliton whose mass is smaller than that of the degenerate black ring.

Phase field simulation of solidification under supergravity

In order to understand the influence of supergravity on the microstructure of materials,crystal nucleation,dendritic growth,and polycrystal solidification under supergravity are investigated by using the modified nucleation theory and phase field models.Firstly,supergravity is considered in the nucleation theory by using pressure-dependent Gibbs free energy.It is found that the critical radius decreases and the nucleation rate increases when supergravity rises.Secondly,anisotropic heat transport is proposed in the phase field model to investigate the influence of supergravity on dendritic growth.Phase field simulations show that supergravity promotes the secondary dendritic growth in the direction parallel to supergravity.Finally,a multiply phase field model with pressure-dependent interfacial energy is employed to simulate the polycrystalline solidification under supergravity.Due to the depth-dependent pressure by supergravity,crystal grains are significantly refined by high pressure.In addition,gradient distribution of grain size is obtained in the solidification morphology of polycrystalline,which is consistent with previous experimental observations.Results of this work suggest that supergravity can be used to tune the microstructures and properties of materials.

Supersymmetric AdS_4 vacua in N=3 gauged supergravity

We study the maximally supersymmetric AdS backgrounds of matter-coupled N=3 gauged supergravity in four dimensions. We find that to admit supersymmetric AdS vacua, the gauge group can only be of the form G0×H?SO(3,n) with G0=SO(3),SO(3,1) or SL(3,R) and H a compact group of dimension n+3-dim(G0). We also show that these AdS vacua have no moduli, namely they correspond to critical points in field space.

A Scenario for Asymmetric Genesis of Matter

A previous preon scenario for the standard model particles, based on unbroken supersymmetry, is applied to the problem of matter-antimatter asymmetry. Attention is paid to the fact that the asymmetric hydrogen atom—like all atoms—can be described in terms of symmetric preons. Preons are created in the early universe. The matter-antimatter asymmetry is caused by stochastic correlations in charge density fluctuations of preons and antipreons and by the subsequent preon combinatorial mechanism to form quarks and leptons, and finally the three lightest elements. A tentative gravitino mass estimate is given based on minimal interference with nucleosynthesis. With local supersymmetry the scenario can be extended to supergravity.

Three Kinds of Special Relativity via Inverse Wick Rotation

Since the special relativity can be viewed as the physics in an inverse Wick rotation of four-dimensional （4D） Euclid space, which is at almost equal footing with the 4D Riemann/Lobachevski space, there should be important physics in the inverse Wick rotation of 4D Riemann/Lobachevski space. Thus, there are three kinds of special relativity in de Sitter（dS）/Minkowski/anti-de Sitter（AdS） space at almost equal footing, respectively. There is an instanton tunnelling scenario in the Riemann-de Sitter case that may explain why A be positive and link with the multiverse.

Double Charm Decays of B Mesons in mSUGRA Model

Based on the low energy effective Hamiltonian with naive factorization, we calculate the branching ratios （BRs） and CP asymmetries （CPAs） for the twenty three double charm decays B/B8 → D（＊）D（＊） in both the standard （s） （s） model （SM） and the minimal supergravity （mSUGRA） model. Within the considered parameter space, we find that （a） the theoretical predictions for the BRs, CPAs and the polarization fractions in the SM and the mSUGRA model are all consistent with the currently available data within ±2σ errors; （b） For all the considered decays, the supersymmetric contributions in the mSUGRA model are very small, less than 7% numerically. It may be difficult to observe so small SUSY contributions even at LHC.

Temperature fluctuations and heat transport in partitioned supergravitational thermal turbulence

We report an experimental study of the local temperature fluctuationsδT and heat transport in a partitioned supergravitational turbulent convection system.Due to the dynamics of zonal flow in the normal system without partition walls,the probability density function(PDF)at a position in the mixing zone exhibits a downward bending shape,suggesting that the multi-plume clustering effect plays an important role.In partitioned system,zonal flow is suppressed and the PDFs indicate that the single-plume effect is dominant.Moreover,statistical analysis shows that the PDF ofδT is sensitive to supergravity.Additionally,the thermal spectra follow P(f)∼f^(-5) in the normal system,which is relevant to the zonal flow.The absolute value of the scaling exponent of P(f)and the scaling range become small in the partitioned system,which provides another evidence for the influence of zonal flow on the energy cascade.Further,heat transfer enhancement is found in the partitioned system,which may result from zonal flow being restricted and then facilitating the radial movement of thermal plumes to the opposite conducting cylinder.This work may provide insights into the flow and heat transport control of some engineering and geophysical flows.

Negative corrections to black hole entropy from string theory

We report for the first time that in heterotic string compactified on 4-torus or equivalently IIA string compactified on K3,the leading α′corrections to the rotating black string entropy at fixed conserved charges can be negative.This further implies that the correction to the mass of extremal rotating string is positive,opposite to the standard expectation from the weak gravity conjecture.Our result suggests that the validity of positivity of entropy shift due to higher order operators depends on other factors omitted previously in the effective field theory analysis.

Simple single field inflation models and the running of spectral index

The BICEP2 experiment confirms the existence of primordial gravitational wave with the tensor-to-scalar ratio r = 0 ruled out at 70- level. The consistency of this large value of r with the Planck data requires a large negative running n＇s of the scalar spectral index. Herein we propose two types of the single field inflation models with simple potentials to study the possibility of the consistency of the models with the BICEP2 and Planck observations. One type of model suggested herein is realized in the supergravity model building. These models fail to provide the needed n＇s even though both can fit the tensor-to-scalar ratio and spectral index.

Re-visiting supersymmetric Janus solutions: a perturbative construction

We construct holographic Janus solutions,which describe a conformal interface in the theory of M2-branes,in four-dimensional gauged supergravities using a perturbative method.In particular,we study three Einsteinscalar systems and their BPS equations,which are derived by Bobev,Pilch,and Warner(2014).The actions of our interest are all consistent truncations of D=11 supergravity,chosen to be invariant under SO(4)×SO(4),SU(3)×U(1)×U(1),and G2 symmetry subgroups of SO(8).The utility of our semi-analytic result is illustrated by the calculation of minimal area surface and the associated holographic entanglement entropy.

ELECTRIC PROPERTIES OF InSb CRYSTAL GROWING UNDER MICRO-AND SU PER-G RAVITY CONDITIONS

Ⅰ. INTRODUCTIONIn recent years, the growth of crystal at microgravity intrigues many scientists. In space microgravity environment, gravity-induced natural convection and buoyancy in melts diminish. The sedimentation of matters, which exists at normal gravity on earth owing to different density, is absent. It is much easier to control the process of mixing different