Planetary Defense team project: READI (Roadmap for EArth Defense Initiatives)

Planetary Defense is a complex problem, not well understood by policy makers and the general public. The recent Chelyabinsk incident in Russia created temporary international attention but has failed to effectively stimulate public action. The lack of long-term attention to cosmic hazards has resulted in limited funding to defend our planet. Hence, it is hard to realistically address this challenge and achieve the high test and operational readiness needed for an effective Planetary Defense strategy. To address this problem, we have created a set of recommendations for the development of a Planetary Defense Program, for the purpose of contributing to the protection of Earth from asteroids and comets. The SSP15 READI Project focused on threats for which there is only a short-term warning, specifically a warning of two years or less from detection of the object to impact. We have provided recommendations in five areas of Planetary Defense including detection and tracking, deflection techniques, global collaboration, outreach and education, and evacuation and recovery. We have applied this set of recommendations in a narrative scenario to make our report more impactful and engaging. We contrast optimistic and pessimistic outcomes for a comet threat, differing from each other in terms of the level of readiness achieved during the years leading up to the discovery of the threat. In our optimistic scenario, the deflection system has achieved high test and operational readiness. The world’s governments have realized the importance of being prepared against cosmic hazards and put in place all of the necessary measures for a successful defense, leading to a positive deflection of the comet. In contrast, in the pessimistic scenario no preparation is done before the detection, and the comet strikes a heavily populated area releasing energy equivalent to 80 times the most powerful nuclear bomb ever detonated. The recommendations that we have identified in this report constitute a roadmap to avoid this horrible outcome, and we believe they should be taken seriously and swiftly implemented

Bipartite Consensus of Heterogeneous Multiagent Systems Based on Distributed Event-Triggered Control

In this paper, the bipartite consensus problem of heterogeneous multiagent systems composed of first-order and second-order agents is considered by utilizing the event-triggered control scheme. Under structurally balanced directed topology, event-triggered bipartite consensus protocol is put forward, and event-triggering functions consisting of measurement error and threshold are designed. To exclude Zeno behavior, an exponential function is introduced in the threshold. The bipartite consensus problem is transformed into the corresponding stability problem by means of gauge transformation and model transformation. By virtue of Lyapunov method, sufficient conditions for systems without input delay are obtained to guarantee bipartite consensus. Furthermore, for the case with input delay, sufficient conditions which include an admissible upper bound of the delay are obtained to guarantee bipartite consensus. Finally, numerical simulations are provided to illustrate the effectiveness of the obtained theoretical results

Modeling and Analysis of the Noise Performance of the Capacitive Sensing Circuit with a Differential Transformer

Capacitive sensing is a key technique to measure the test mass movement with a high resolution for space-borne gravitational wave detectors, such as Laser Interferometer Space Antenna (LISA) and TianQin. The capacitance resolution requirement of TianQin is higher than that of LISA, as the arm length of TianQin is about 15 times shorter. In this paper, the transfer function and capacitance measurement noise of the circuit are modeled and analyzed. Figure-of-merits, including the product of the inductance L and the quality factor Q of the transformer, are proposed to optimize the transformer and the capacitance measurement resolution of the circuit. The LQ product improvement and the resonant frequency augmentation are the key factors to enhance the capacitance measurement resolution. We fabricated a transformer with a high LQ product over a wide frequency band. The evaluation showed that the transformer can generate a capacitance resolution of 0.11 aF/Hz1/2 at a resonant frequency of 200 kHz, and the amplitude of the injection wave would be 0.6 V. This result supports the potential application of the proposed transformer in space-borne gravitational wave detection and demonstrates that it could relieve the stringent requirements for other parameters in the TianQin mission

Research on Arc-grounding Overvoltage in the 10kV Distribution System

AbstractThe using rate of cable which causes the capacitance current raise up out of limits in the urban distribution system is growing up very fast during the past years. It threatens the security of power-supply. In this paper, the author made lots of works analyze many methods of grounding through the natural point. The author also made the simulation models with EMTP/ATP program in theory and combine the fault of single-phase grounding in practice

Effect of Uphill Quenching on Microstructure and Residual Stress Reduction of AZ31B Magnesium Alloy Plate

Residual stress may be generated during the deformation process; cold and hot treatments on magnesium alloy, causing deformation; cracking; and other effects. Reducing the residual stress of magnesium alloys is of great significance for its size stability and quality. In this paper, the residual stress in the AZ31B plate was compared with different uphill quenching processes: no uphill quenching (NUQ), liquid nitrogen–boiling water (100 °C) (LNB), liquid nitrogen–hot air (160 °C) (LNHA) and liquid nitrogen–water (25 °C) (LNR). Residual stresses with and without treatment were measured by X-ray diffraction. The effect of uphill quenching on hardness was discussed. The microstructure and diffraction pattern of the samples treated with different uphill quenching processes was investigated by EBSD and XRD. The results showed that the microstructure of magnesium alloy rolling plate was refined by the uphill quenching treatment, which can reduce the residual stress without decreasing the mechanical properties. The largest residual stress reduction rate was obtained by the liquid nitrogen–boiling water process. This treatment process can not only reduce the residual stress of the magnesium alloy rolling plates by 56% but also increase the hardness by 29%

Effect of Uphill Quenching on Microstructure and Residual Stress Reduction of AZ31B Magnesium Alloy Plate

Residual stress may be generated during the deformation process; cold and hot treatments on magnesium alloy, causing deformation; cracking; and other effects. Reducing the residual stress of magnesium alloys is of great significance for its size stability and quality. In this paper, the residual stress in the AZ31B plate was compared with different uphill quenching processes: no uphill quenching (NUQ), liquid nitrogen–boiling water (100 °C) (LNB), liquid nitrogen–hot air (160 °C) (LNHA) and liquid nitrogen–water (25 °C) (LNR). Residual stresses with and without treatment were measured by X-ray diffraction. The effect of uphill quenching on hardness was discussed. The microstructure and diffraction pattern of the samples treated with different uphill quenching processes was investigated by EBSD and XRD. The results showed that the microstructure of magnesium alloy rolling plate was refined by the uphill quenching treatment, which can reduce the residual stress without decreasing the mechanical properties. The largest residual stress reduction rate was obtained by the liquid nitrogen–boiling water process. This treatment process can not only reduce the residual stress of the magnesium alloy rolling plates by 56% but also increase the hardness by 29%

Effect of homogenization annealing on internal residual stress distribution and texture in ME21 magnesium alloy extruded plates

The distribution of residual stresses through thickness of 5 mm-thick ME21 magnesium alloy extruded plates was analyzed non-destructively using short-wavelength X-ray diffraction (SWXRD), and the effect of homogenization annealing before extrusion on the residual stress was discussed. The classic d0 method with an annealed stress-free reference specimen was employed to determine the residual stress of the extruded plates. The residual stress results showed that the gradient of residual stress in the transverse direction was larger than that of the extrusion direction. The homogenization process prior to extrusion weaken the formed sample's texture. The maximum residual stress of the as-extruded plate was reduced, and the residual stress distribution was homogenized. Key words: ME21 magnesium alloy, Homogenization annealing, Residual stress, Short-wavelength X-ray diffractio

Synergistic Utilization of Necrostatin-1 and Z-VAD-FMK Efficiently Promotes the Survival of Compression-Induced Nucleus Pulposus Cells via Alleviating Mitochondrial Dysfunction

We recently reported that necroptosis contributed to compression-induced nucleus pulposus (NP) cells death. In the current study, we investigated the regulative effect of necroptosis inhibitor Necrostatin-1 on NP cells apoptosis and autophagy. Necrostatin-1, autophagy inhibitor 3-Methyladenine and apoptosis inhibitor Z-VAD-FMK were employed, and NP cells were exposed to 1.0 MPa compression for 0, 24 and 36 h. Necroptosis-associated molecules were measured by Western blot and RT-PCR. Autophagy and apoptosis levels were evaluated by Western blot and quantified by flow cytometry after monodansylcadaverine and Annexin V-FITC/propidium iodide staining, respectively. The cell viability and cell death were also examined. Furthermore, we measured mitochondrial membrane potential (MMP), mitochondrial permeability transition pore (MPTP) and indices of oxidative stress to assess mitochondrial dysfunction. The results established that Necrostatin-1 blocked NP cells autophagy, and 3-Methyladenine had little influence on NP cells necroptosis. The Necrostatin-1+3-Methyladenine treatment exerted almost the same role as Necrostatin-1 in reducing NP cells death. Necrostatin-1 restrained NP cells apoptosis, while Z-VAD-FMK enhanced NP cells necroptosis. The Necrostatin-1+Z-VAD-FMK treatment provided more prominent role in blocking NP cells death compared with Necrostatin-1, consistent with increased MMP, reduced opening of MPTP and oxidative stress. In summary, the synergistic utilization of Necrostatin-1 and Z-VAD-FMK is a very worthwhile solution in preventing compression-mediated NP cells death, which might be largely attributed to restored mitochondrial function

Influence of combined exposure levels of total arsenic and inorganic arsenic on arsenic methylation capacity among university students: findings from Bayesian kernel machine regression analysis

The arsenic (As) methylation capacity is an important determinant of susceptibility to As-related diseases. Total As (TAs) or inorganic As (iAs) was reported to associated with As methylation capacity. We measured urinary concentrations of iAs, monomethylarsonic acid (MMA), and dimethylarsinic acid (DMA) by using HPLC-HG-AFS and calculated the primary methylation capacity index (PMI) and secondary methylation capacity index (SMI) in 209 university students in Hefei, China, a non-As endemic area. Volunteers were given a standardized questionnaire asking about their sociodemographic characteristics. Bayesian kernel machine regression (BKMR) analysis was used to estimate the association of lnTAs and lniAs levels with methylation indices (ln%MMA, ln%DMA, lnPMI, lnSMI). The median concentrations of iAs, MMA, and DMA were 1.22, 0.92, and 12.17 μg/L, respectively; the proportions of iAs, MMA, and DMA were 8.76%, 6.13%, and 84.84%, respectively. Females had higher %DMA and lower %MMA than males. The combined levels of lnTAs and lniAs showed a decrease in the changes in ln%DMA and lnSMI. With regard to the single exposure level, the lnTAs showed positive correlations with ln%DMA, lnPMI, and lnSMI when lniAs was set at a specific level, while lniAs showed negative correlations with ln%DMA, lnPMI, and lnSMI when lnTAs was set at a specific level; all the dose-response relationships were nonlinear. Our results suggested that combined levels of TAs and iAs play an important role in reducing As methylation capacity, especially iAs, and the reduction only occurs when TAs and iAs are present up to a certain combined level.</p